WorldWideScience

Sample records for constraining coronal heating

  1. CONSTRAINING A MODEL OF TURBULENT CORONAL HEATING FOR AU MICROSCOPII WITH X-RAY, RADIO, AND MILLIMETER OBSERVATIONS

    International Nuclear Information System (INIS)

    Cranmer, Steven R.; Wilner, David J.; MacGregor, Meredith A.

    2013-01-01

    Many low-mass pre-main-sequence stars exhibit strong magnetic activity and coronal X-ray emission. Even after the primordial accretion disk has been cleared out, the star's high-energy radiation continues to affect the formation and evolution of dust, planetesimals, and large planets. Young stars with debris disks are thus ideal environments for studying the earliest stages of non-accretion-driven coronae. In this paper we simulate the corona of AU Mic, a nearby active M dwarf with an edge-on debris disk. We apply a self-consistent model of coronal loop heating that was derived from numerical simulations of solar field-line tangling and magnetohydrodynamic turbulence. We also synthesize the modeled star's X-ray luminosity and thermal radio/millimeter continuum emission. A realistic set of parameter choices for AU Mic produces simulated observations that agree with all existing measurements and upper limits. This coronal model thus represents an alternative explanation for a recently discovered ALMA central emission peak that was suggested to be the result of an inner 'asteroid belt' within 3 AU of the star. However, it is also possible that the central 1.3 mm peak is caused by a combination of active coronal emission and a bright inner source of dusty debris. Additional observations of this source's spatial extent and spectral energy distribution at millimeter and radio wavelengths will better constrain the relative contributions of the proposed mechanisms

  2. Coronal heating via nanoflares

    International Nuclear Information System (INIS)

    Poletto, G.; Kopp, R.

    1993-01-01

    It has been recently proposed that the coronae of single late-type main sequence stars represent the radiative output from a large number of tiny energy release events, the so-called nanoflares. Although this suggestion is attractive and order of magnitude estimates of the physical parameters involved in the process are consistent with available data, nanoflares have not yet been observed and theoretical descriptions of these phenomena are still very crude. In this paper we examine the temporal behavior of a magnetic flux tube subject to the repeated occurrence of energy release events, randomly distributed in time, and we show that an originally empty cool loop may, in fact, reach typical coronal density and temperature values via nanoflare heating. By choosing physical parameters appropriate to solar conditions we also explore the possibilities for observationally detecting nanoflares. Although the Sun is the only star where nanoflares might be observed, present instrumentation appears to be inadequate for this purpose

  3. A contemporary view of coronal heating.

    Science.gov (United States)

    Parnell, Clare E; De Moortel, Ineke

    2012-07-13

    Determining the heating mechanism (or mechanisms) that causes the outer atmosphere of the Sun, and many other stars, to reach temperatures orders of magnitude higher than their surface temperatures has long been a key problem. For decades, the problem has been known as the coronal heating problem, but it is now clear that 'coronal heating' cannot be treated or explained in isolation and that the heating of the whole solar atmosphere must be studied as a highly coupled system. The magnetic field of the star is known to play a key role, but, despite significant advancements in solar telescopes, computing power and much greater understanding of theoretical mechanisms, the question of which mechanism or mechanisms are the dominant supplier of energy to the chromosphere and corona is still open. Following substantial recent progress, we consider the most likely contenders and discuss the key factors that have made, and still make, determining the actual (coronal) heating mechanism (or mechanisms) so difficult.

  4. Mechanisms of Coronal Heating S. R. Verma

    Indian Academy of Sciences (India)

    Abstract. The Sun is a mysterious star. The high temperature of the chromosphere and corona present one of the most puzzling problems of solar physics. Observations show that the solar coronal heating problem is highly complex with many different facts. It is likely that different heating mechanisms are at work in solar ...

  5. Role of Magnetic Carpet in Coronal Heating

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... One of the fundamental questions in solar physics is how the solar corona maintains its high temperature of several million Kelvin above photosphere with a temperature of 6000 K. Observations show that solar coronal heating problem is highly complex with many different facts. It is likely that different ...

  6. Coronal Heating Observed with Hi-C

    Science.gov (United States)

    Winebarger, Amy R.

    2013-01-01

    The recent launch of the High-Resolution Coronal Imager (Hi-C) as a sounding rocket has offered a new, different view of the Sun. With approx 0.3" resolution and 5 second cadence, Hi-C reveals dynamic, small-scale structure within a complicated active region, including coronal braiding, reconnection regions, Alfven waves, and flows along active region fans. By combining the Hi-C data with other available data, we have compiled a rich data set that can be used to address many outstanding questions in solar physics. Though the Hi-C rocket flight was short (only 5 minutes), the added insight of the small-scale structure gained from the Hi-C data allows us to look at this active region and other active regions with new understanding. In this talk, I will review the first results from the Hi-C sounding rocket and discuss the impact of these results on the coronal heating problem.

  7. Coronal Heating: Testing Models of Coronal Heating by Forward-Modeling the AIA Emission of the Ansample of Coronal Loops

    Science.gov (United States)

    Malanushenko, A. V.

    2015-12-01

    We present a systemic exploration of the properties of coronal heating, by forward-modeling the emission of the ensemble of 1D quasi-steady loops. This approximations were used in many theoretical models of the coronal heating. The latter is described in many such models in the form of power laws, relating heat flux through the photosphere or volumetric heating to the strength of the magnetic field and length of a given field line. We perform a large search in the parameter space of these power laws, amongst other variables, and compare the resulting emission of the active region to that observed by AIA. We use a recently developed magnetic field model which uses shapes of coronal loops to guide the magnetic model; the result closely resembles observed structures by design. We take advantage of this, by comparing, in individual sub-regions of the active region, the emission of the active region and its synthetic model. This study allows us to rule out many theoretical models and formulate predictions for the heating models to come.

  8. Constraining reconnection region conditions using imaging and spectroscopic analysis of a coronal jet

    Science.gov (United States)

    Brannon, Sean; Kankelborg, Charles

    2017-08-01

    Coronal jets typically appear as thin, collimated structures in EUV and X-ray wavelengths, and are understood to be initiated by magnetic reconnection in the lower corona or upper chromosphere. Plasma that is heated and accelerated upward into coronal jets may therefore carry indirect information on conditions in the reconnection region and current sheet located at the jet base. On 2017 October 14, the Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) observed a series of jet eruptions originating from NOAA AR 12599. The jet structure has a length-to-width ratio that exceeds 50, and remains remarkably straight throughout its evolution. Several times during the observation bright blobs of plasma are seen to erupt upward, ascending and subsequently descending along the structure. These blobs are cotemporal with footpoint and arcade brightenings, which we believe indicates multiple episodes of reconnection at the structure base. Through imaging and spectroscopic analysis of jet and footpoint plasma we determine a number of properties, including the line-of-sight inclination, the temperature and density structure, and lift-off velocities and accelerations of jet eruptions. We use these properties to constrain the geometry of the jet structure and conditions in reconnection region.

  9. New Evidence that Magnetoconvection Drives Solar–Stellar Coronal Heating

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; Winebarger, Amy R. [NASA Marshall Space Flight Center, Mail Code ST 13, Huntsville, AL 35812 (United States); Thalmann, Julia K., E-mail: sanjivtiwari80@gmail.com [Institute of Physics/IGAM, University of Graz, Universittsplatz 5/II, A-8010 Graz (Austria)

    2017-07-10

    How magnetic energy is injected and released in the solar corona, keeping it heated to several million degrees, remains elusive. Coronal heating generally increases with increasing magnetic field strength. From a comparison of a nonlinear force-free model of the three-dimensional active region coronal field to observed extreme-ultraviolet loops, we find that (1) umbra-to-umbra coronal loops, despite being rooted in the strongest magnetic flux, are invisible, and (2) the brightest loops have one foot in an umbra or penumbra and the other foot in another sunspot’s penumbra or in unipolar or mixed-polarity plage. The invisibility of umbra-to-umbra loops is new evidence that magnetoconvection drives solar-stellar coronal heating: evidently, the strong umbral field at both ends quenches the magnetoconvection and hence the heating. Broadly, our results indicate that depending on the field strength in both feet, the photospheric feet of a coronal loop on any convective star can either engender or quench coronal heating in the loop’s body.

  10. Free Magnetic Energy and Coronal Heating

    Science.gov (United States)

    Winebarger, Amy; Moore, Ron; Falconer, David

    2012-01-01

    Previous work has shown that the coronal X-ray luminosity of an active region increases roughly in direct proportion to the total photospheric flux of the active region's magnetic field (Fisher et al. 1998). It is also observed, however, that the coronal luminosity of active regions of nearly the same flux content can differ by an order of magnitude. In this presentation, we analyze 10 active regions with roughly the same total magnetic flux. We first determine several coronal properties, such as X-ray luminosity (calculated using Hinode XRT), peak temperature (calculated using Hinode EIS), and total Fe XVIII emission (calculated using SDO AIA). We present the dependence of these properties on a proxy of the free magnetic energy of the active region

  11. PLASMA SLOSHING IN PULSE-HEATED SOLAR AND STELLAR CORONAL LOOPS

    Energy Technology Data Exchange (ETDEWEB)

    Reale, F., E-mail: fabio.reale@unipa.it [Dipartimento di Fisica and Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)

    2016-08-01

    There is evidence that coronal heating is highly intermittent, and flares are the high energy extreme. The properties of the heat pulses are difficult to constrain. Here, hydrodynamic loop modeling shows that several large amplitude oscillations (∼20% in density) are triggered in flare light curves if the duration of the heat pulse is shorter than the sound crossing time of the flaring loop. The reason for this is that the plasma does not have enough time to reach pressure equilibrium during heating, and traveling pressure fronts develop. The period is a few minutes for typical solar coronal loops, dictated by the sound crossing time in the decay phase. The long period and large amplitude make these oscillations different from typical magnetohydrodynamic (MHD) waves. This diagnostic can be applied both to observations of solar and stellar flares and to future observations of non-flaring loops at high resolution.

  12. CLOSED-FIELD CORONAL HEATING DRIVEN BY WAVE TURBULENCE

    Energy Technology Data Exchange (ETDEWEB)

    Downs, Cooper; Lionello, Roberto; Mikić, Zoran; Linker, Jon A [Predictive Science Incorporated, 9990 Mesa Rim Rd. Suite 170, San Diego, CA 92121 (United States); Velli, Marco, E-mail: cdowns@predsci.com [EPSS, UCLA, Los Angeles, CA 90095 (United States)

    2016-12-01

    To simulate the energy balance of coronal plasmas on macroscopic scales, we often require the specification of the coronal heating mechanism in some functional form. To go beyond empirical formulations and to build a more physically motivated heating function, we investigate the wave-turbulence-driven (WTD) phenomenology for the heating of closed coronal loops. Our implementation is designed to capture the large-scale propagation, reflection, and dissipation of wave turbulence along a loop. The parameter space of this model is explored by solving the coupled WTD and hydrodynamic evolution in 1D for an idealized loop. The relevance to a range of solar conditions is also established by computing solutions for over one hundred loops extracted from a realistic 3D coronal field. Due to the implicit dependence of the WTD heating model on loop geometry and plasma properties along the loop and at the footpoints, we find that this model can significantly reduce the number of free parameters when compared to traditional empirical heating models, and still robustly describe a broad range of quiet-Sun and active region conditions. The importance of the self-reflection term in producing relatively short heating scale heights and thermal nonequilibrium cycles is also discussed.

  13. HEATING OF FLARE LOOPS WITH OBSERVATIONALLY CONSTRAINED HEATING FUNCTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Jiong; Liu Wenjuan; Longcope, Dana W. [Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States)

    2012-06-20

    We analyze high-cadence high-resolution observations of a C3.2 flare obtained by AIA/SDO on 2010 August 1. The flare is a long-duration event with soft X-ray and EUV radiation lasting for over 4 hr. Analysis suggests that magnetic reconnection and formation of new loops continue for more than 2 hr. Furthermore, the UV 1600 Angstrom-Sign observations show that each of the individual pixels at the feet of flare loops is brightened instantaneously with a timescale of a few minutes, and decays over a much longer timescale of more than 30 minutes. We use these spatially resolved UV light curves during the rise phase to construct empirical heating functions for individual flare loops, and model heating of coronal plasmas in these loops. The total coronal radiation of these flare loops are compared with soft X-ray and EUV radiation fluxes measured by GOES and AIA. This study presents a method to observationally infer heating functions in numerous flare loops that are formed and heated sequentially by reconnection throughout the flare, and provides a very useful constraint to coronal heating models.

  14. Diagnostics of Coronal Heating in Solar Active Regions

    Science.gov (United States)

    Fludra, Andrzej; Hornsey, Christopher; Nakariakov, Valery

    2015-04-01

    We aim to develop a diagnostic method for the coronal heating mechanism in active region loops. Observational constraints on coronal heating models have been sought using measurements in the X-ray and EUV wavelengths. Statistical analysis, using EUV emission from many active regions, was done by Fludra and Ireland (2008) who studied power-law relationships between active region integrated magnetic flux and emission line intensities. A subsequent study by Fludra and Warren (2010) for the first time compared fully resolved images in an EUV spectral line of OV 63.0 nm with the photospheric magnetic field, leading to the identification of a dominant, ubiquitous variable component of the transition region EUV emission and a discovery of a steady basal heating, and deriving the dependence of the basal heating rate on the photospheric magnetic flux density. In this study, we compare models of single coronal loops with EUV observations. We assess to what degree observations of individual coronal loops made in the EUV range are capable of providing constraints on the heating mechanism. We model the coronal magnetic field in an active region using an NLFF extrapolation code applied to a photospheric vector magnetogram from SDO/HMI and select several loops that match an SDO/AIA 171 image of the same active region. We then model the plasma in these loops using a 1D hydrostatic code capable of applying an arbitrary heating rate as a function of magnetic field strength along the loop. From the plasma parameters derived from this model, we calculate the EUV emission along the loop in AIA 171 and 335 bands, and in pure spectral lines of Fe IX 17.1 nm and Fe XVI 33.5 nm. We use different spatial distributions of the heating function: concentrated near the loop top, uniform and concentrated near the footpoints, and investigate their effect on the modelled EUV intensities. We find a diagnostics based on the dependence of the total loop intensity on the shape of the heating function

  15. CONSTRAINING THE SOLAR CORONAL MAGNETIC FIELD STRENGTH USING SPLIT-BAND TYPE II RADIO BURST OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kishore, P.; Ramesh, R.; Hariharan, K.; Kathiravan, C. [Indian Institute of Astrophysics, 2nd Block, Koramangala, Bangalore—560034 (India); Gopalswamy, N., E-mail: kishore@iiap.res.in [Code 671, Solar Physics Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States)

    2016-11-20

    We report on low-frequency radio (85–35 MHz) spectral observations of four different type II radio bursts, which exhibited fundamental-harmonic emission and split-band structure. Each of the bursts was found to be closely associated with a whitelight coronal mass ejection (CME) close to the Sun. We estimated the coronal magnetic field strength from the split-band characteristics of the bursts, by assuming a model for the coronal electron density distribution. The choice of the model was constrained, based on the following criteria: (1) when the radio burst is observed simultaneously in the upper and lower bands of the fundamental component, the location of the plasma level corresponding to the frequency of the burst in the lower band should be consistent with the deprojected location of the leading edge (LE) of the associated CME; (2) the drift speed of the type II bursts derived from such a model should agree closely with the deprojected speed of the LE of the corresponding CMEs. With the above conditions, we find that: (1) the estimated field strengths are unique to each type II burst, and (2) the radial variation of the field strength in the different events indicate a pattern. It is steepest for the case where the heliocentric distance range over which the associated burst is observed is closest to the Sun, and vice versa.

  16. OSO 8 observational limits to the acoustic coronal heating mechanism

    Science.gov (United States)

    Bruner, E. C., Jr.

    1981-01-01

    An improved analysis of time-resolved line profiles of the C IV resonance line at 1548 A has been used to test the acoustic wave hypothesis of solar coronal heating. It is shown that the observed motions and brightness fluctuations are consistent with the existence of acoustic waves. Specific account is taken of the effect of photon statistics on the observed velocities, and a test is devised to determine whether the motions represent propagating or evanescent waves. It is found that on the average about as much energy is carried upward as downward such that the net acoustic flux density is statistically consistent with zero. The statistical uncertainty in this null result is three orders of magnitue lower than the flux level needed to heat the corona.

  17. Identification of coronal heating events in 3D simulations

    Science.gov (United States)

    Kanella, Charalambos; Gudiksen, Boris V.

    2017-07-01

    Context. The solar coronal heating problem has been an open question in the science community since 1939. One of the proposed models for the transport and release of mechanical energy generated in the sub-photospheric layers and photosphere is the magnetic reconnection model that incorporates Ohmic heating, which releases a part of the energy stored in the magnetic field. In this model many unresolved flaring events occur in the solar corona, releasing enough energy to heat the corona. Aims: The problem with the verification and quantification of this model is that we cannot resolve small scale events due to limitations of the current observational instrumentation. Flaring events have scaling behavior extending from large X-class flares down to the so far unobserved nanoflares. Histograms of observable characteristics of flares show powerlaw behavior for energy release rate, size, and total energy. Depending on the powerlaw index of the energy release, nanoflares might be an important candidate for coronal heating; we seek to find that index. Methods: In this paper we employ a numerical three-dimensional (3D)-magnetohydrodynamic (MHD) simulation produced by the numerical code Bifrost, which enables us to look into smaller structures, and a new technique to identify the 3D heating events at a specific instant. The quantity we explore is the Joule heating, a term calculated directly by the code, which is explicitly correlated with the magnetic reconnection because it depends on the curl of the magnetic field. Results: We are able to identify 4136 events in a volume 24 × 24 × 9.5 Mm3 (I.e., 768 × 786 × 331 grid cells) of a specific snapshot. We find a powerlaw slope of the released energy per second equal to αP = 1.5 ± 0.02, and two powerlaw slopes of the identified volume equal to αV = 1.53 ± 0.03 and αV = 2.53 ± 0.22. The identified energy events do not represent all the released energy, but of the identified events, the total energy of the largest events

  18. An observationally-driven kinetic approach to coronal heating

    Science.gov (United States)

    Moraitis, K.; Toutountzi, A.; Isliker, H.; Georgoulis, M.; Vlahos, L.; Chintzoglou, G.

    2016-11-01

    Aims: Coronal heating through the explosive release of magnetic energy remains an open problem in solar physics. Recent hydrodynamical models attempt an investigation by placing swarms of "nanoflares" at random sites and times in modeled one-dimensional coronal loops. We investigate the problem in three dimensions, using extrapolated coronal magnetic fields of observed solar active regions. Methods: We applied a nonlinear force-free field extrapolation above an observed photospheric magnetogram of NOAA active region (AR) 11 158. We then determined the locations, energy contents, and volumes of "unstable" areas, namely areas prone to releasing magnetic energy due to locally accumulated electric current density. Statistical distributions of these volumes and their fractal dimension are inferred, investigating also their dependence on spatial resolution. Further adopting a simple resistivity model, we inferred the properties of the fractally distributed electric fields in these volumes. Next, we monitored the evolution of 105 particles (electrons and ions) obeying an initial Maxwellian distribution with a temperature of 10 eV, by following their trajectories and energization when subjected to the resulting electric fields. For computational convenience, the length element of the magnetic-field extrapolation is 1 arcsec, or 725 km, much coarser than the particles' collisional mean free path in the low corona (0.1-1 km). Results: The presence of collisions traps the bulk of the plasma around the unstable volumes, or current sheets (UCS), with only a tail of the distribution gaining substantial energy. Assuming that the distance between UCS is similar to the collisional mean free path we find that the low active-region corona is heated to 100-200 eV, corresponding to temperatures exceeding 2 MK, within tens of seconds for electrons and thousands of seconds for ions. Conclusions: Fractally distributed, nanoflare-triggening fragmented UCS in the active-region corona can

  19. DATA-CONSTRAINED CORONAL MASS EJECTIONS IN A GLOBAL MAGNETOHYDRODYNAMICS MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Jin, M. [Lockheed Martin Solar and Astrophysics Lab, Palo Alto, CA 94304 (United States); Manchester, W. B.; Van der Holst, B.; Sokolov, I.; Tóth, G.; Gombosi, T. I. [Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Mullinix, R. E.; Taktakishvili, A.; Chulaki, A., E-mail: jinmeng@lmsal.com, E-mail: chipm@umich.edu, E-mail: richard.e.mullinix@nasa.gov, E-mail: Aleksandre.Taktakishvili-1@nasa.gov [Community Coordinated Modeling Center, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2017-01-10

    We present a first-principles-based coronal mass ejection (CME) model suitable for both scientific and operational purposes by combining a global magnetohydrodynamics (MHD) solar wind model with a flux-rope-driven CME model. Realistic CME events are simulated self-consistently with high fidelity and forecasting capability by constraining initial flux rope parameters with observational data from GONG, SOHO /LASCO, and STEREO /COR. We automate this process so that minimum manual intervention is required in specifying the CME initial state. With the newly developed data-driven Eruptive Event Generator using Gibson–Low configuration, we present a method to derive Gibson–Low flux rope parameters through a handful of observational quantities so that the modeled CMEs can propagate with the desired CME speeds near the Sun. A test result with CMEs launched with different Carrington rotation magnetograms is shown. Our study shows a promising result for using the first-principles-based MHD global model as a forecasting tool, which is capable of predicting the CME direction of propagation, arrival time, and ICME magnetic field at 1 au (see the companion paper by Jin et al. 2016a).

  20. Transition region, coronal heating and the fast solar wind

    Science.gov (United States)

    Li, Xing

    2003-07-01

    It is assumed that magnetic flux tubes are strongly concentrated at the boundaries of supergranule convection cells. A power law spectrum of high frequency Alfvén waves with a spectral index -1 originating from the sun is assumed to supply all the energy needed to energize the plasma flowing in such magnetic flux tubes. At the high frequency end, the waves are eroded by ions due to ion cyclotron resonance. The magnetic flux concentration is essential since it allows a sufficiently strong energy flux to be carried by high frequency ion cyclotron waves and these waves can be readily released at the coronal base by cyclotron resonance. The main results are: 1. The waves are capable of creating a steep transition region, a hot corona and a fast solar wind if both the wave frequency is high enough and the magnetic flux concentration is sufficiently strong in the boundaries of the supergranule convection zone. 2. By primarily heating alpha particles only, it is possible to produce a steep transition region, a hot corona and a fast solar wind. Coulomb coupling plays a key role in transferring the thermal energy of alpha particles to protons and electrons at the corona base. The electron thermal conduction then does the remaining job to create a sharp transition region. 3. Plasma species (even ions) may already partially lose thermal equilibrium in the transition region, and minor ions may already be faster than protons at the very base of the corona. 4. The model predicts high temperature alpha particles (Talpha ~ 2 x 107 K) and low proton temperatures (Tp solar radii, suggesting that hydrogen Lyman lines observed by UVCS above coronal holes may be primarily broadened by Alfvén waves in this range.

  1. Understanding Solar Coronal Heating through Atomic and Plasma Physics Experiments

    Science.gov (United States)

    Savin, Daniel Wolf; Arthanayaka, Thusitha; Bose, Sayak; Hahn, Michael; Beiersdorfer, Peter; Brown, Gregory V.; Gekelman, Walter; Vincena, Steve

    2017-08-01

    Recent solar observations suggest that the Sun's corona is heated by Alfven waves that dissipate at unexpectedly low heights in the corona. These observations raise a number of questions. Among them are the problems of accurately quantifying the energy flux of the waves and that of describing the physical mechanism that leads to the wave damping. We are performing laboratory experiments to address both of these issues.The energy flux depends on the electron density, which can be measured spectroscopically. However, spectroscopic density diagnostics have large uncertainties, because they depend sensitively on atomic collisional excitation, de-excitation, and radiative transition rates for multiple atomic levels. Essentially all of these data come from theory and have not been experimentally validated. We are conducting laboratory experiments using the electron beam ion trap (EBIT) at Lawrence Livermore National Laboratory that will provide accurate empirical calibrations for spectroscopic density diagnostics and which will also help to guide theoretical calculations.The observed rapid wave dissipation is likely due to inhomogeneities in the plasma that drive flows and currents at small length scales where energy can be more efficiently dissipated. This may take place through gradients in the Alfvén speed along the magnetic field, which causes wave reflection and generates turbulence. Alternatively, gradients in the Alfvén speed across the field can lead to dissipation through phase-mixing. Using the Large Plasma Device (LAPD) at the University of California Los Angeles, we are studying both of these dissipation mechanisms in the laboratory in order to understand their potential roles in coronal heating.

  2. Observations and Numerical Models of Solar Coronal Heating Associated with Spicules

    Energy Technology Data Exchange (ETDEWEB)

    Pontieu, B. De; Martinez-Sykora, J. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Org. A021S, Building 252, Palo Alto, CA 94304 (United States); Moortel, I. De [School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom); McIntosh, S. W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

    2017-08-20

    Spicules have been proposed as significant contributors to the mass and energy balance of the corona. While previous observations have provided a glimpse of short-lived transient brightenings in the corona that are associated with spicules, these observations have been contested and are the subject of a vigorous debate both on the modeling and the observational side. Therefore, it remains unclear whether plasma is heated to coronal temperatures in association with spicules. We use high-resolution observations of the chromosphere and transition region (TR) with the Interface Region Imaging Spectrograph and of the corona with the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to show evidence of the formation of coronal structures associated with spicular mass ejections and heating of plasma to TR and coronal temperatures. Our observations suggest that a significant fraction of the highly dynamic loop fan environment associated with plage regions may be the result of the formation of such new coronal strands, a process that previously had been interpreted as the propagation of transient propagating coronal disturbances. Our observations are supported by 2.5D radiative MHD simulations that show heating to coronal temperatures in association with spicules. Our results suggest that heating and strong flows play an important role in maintaining the substructure of loop fans, in addition to the waves that permeate this low coronal environment.

  3. Microflares as Possible Sources for Coronal Heating Meera Gupta ...

    Indian Academy of Sciences (India)

    around 6.7 keV, which is an indicator of the presence of coronal plasma tem- perature ≥ 9 MK. On the other ... Key words. Solar flares: ... Details of SOXS mission, in-flight performance, calibration, instrumental response and background are ...

  4. What Dominates the Coronal Emission Spectrum During the Cycle of Impulsive Heating and Cooling?

    Science.gov (United States)

    Bradshaw, Stephen J.; Klimchuk, James A.

    2011-01-01

    The smoking gun of small-scale, impulsive events heating the solar corona is expected to be the presence of a hot ( > 5 MK) plasma component. Evidence for this has been scarce, but has gradually begun to accumulate due to recent studies designed to constrain the high temperature part of the emission measure distribution. However, the detected hot component is often weaker than models predict and this is due in part to the common modeling assumption that the ionization balance remains in equilibrium. The launch of the latest generation of space-based observing instrumentation aboard Hinode and the Solar Dynamics Observatory (SDO) has brought the matter of the ionization state of the plasma firmly to the forefront. It is timely to consider exactly what emission current instruments would detect when observing a corona heated impulsively on small-scales by nanoflares. Only after we understand the full effects of nonequilibrium ionization can we draw meaningful conclusions about the plasma that is (or is not) present. We have therefore performed a series of hydrodynamic simulations for a variety of different nanoflare properties and initial conditions. Our study has led to several key conclusions. 1. Deviations from equilibrium are greatest for short-duration nanoflares at low initial coronal densities. 2. Hot emission lines are the most affected and are suppressed sometimes to the point of being invisible. 3. The emission detected in all of the SDO-AIA channels is generally dominated by warm, over-dense, cooling plasma. 4. It is difficult not to create coronal loops that emit strongly at 1.5 MK and in the range 2 to 5 MK, which are the most commonly observed kind, for a broad range of nanoflare scenarios. 5. The Fe XV (284.16 ) emission in most of our models is about 10 times brighter than the Ca XVII (192.82 ) emission, consistent with observations. Our overarching conclusion is that small-scale, impulsive heating inducing a nonequilibrium ionization state leads to

  5. EUV FLICKERING OF SOLAR CORONAL LOOPS: A NEW DIAGNOSTIC OF CORONAL HEATING

    Energy Technology Data Exchange (ETDEWEB)

    Tajfirouze, E.; Reale, F.; Peres, G. [Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 (Italy); Testa, P., E-mail: reale@astropa.unipa.it [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2016-02-01

    A previous work of ours found the best agreement between EUV light curves observed in an active region core (with evidence of super-hot plasma) and those predicted from a model with a random combination of many pulse-heated strands with a power-law energy distribution. We extend that work by including spatially resolved strand modeling and by studying the evolution of emission along the loops in the EUV 94 Å and 335 Å channels of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. Using the best parameters of the previous work as the input of the present one, we find that the amplitude of the random fluctuations driven by the random heat pulses increases from the bottom to the top of the loop in the 94 Å channel and from the top to the bottom in the 335 Å channel. This prediction is confirmed by the observation of a set of aligned neighboring pixels along a bright arc of an active region core. Maps of pixel fluctuations may therefore provide easy diagnostics of nanoflaring regions.

  6. OBSERVATIONAL SIGNATURES OF CORONAL LOOP HEATING AND COOLING DRIVEN BY FOOTPOINT SHUFFLING

    Energy Technology Data Exchange (ETDEWEB)

    Dahlburg, R. B.; Taylor, B. D. [LCP and FD, Naval Research Laboratory, Washington, DC 20375 (United States); Einaudi, G. [Berkeley Research Associates, Inc., Beltsville, MD 20705 (United States); Ugarte-Urra, I. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Warren, H. P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Rappazzo, A. F. [Advanced Heliophysics, Pasadena, CA 91106 (United States); Velli, M., E-mail: rdahlbur@lcp.nrl.navy.mil [EPSS, UCLA, Los Angeles, CA 90095 (United States)

    2016-01-20

    The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random motions. As a consequence, the magnetic field in the loop is energized and develops turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned current sheets: energy is deposited at small scales where heating occurs. Dissipation is nonuniformly distributed so that only a fraction of the coronal mass and volume gets heated at any time. Temperature and density are highly structured at scales that, in the solar corona, remain observationally unresolved: the plasma of our simulated loop is multithermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at sub-observational scales. Numerical simulations of coronal loops of 50,000 km length and axial magnetic field intensities ranging from 0.01 to 0.04 T are presented. To connect these simulations to observations, we use the computed number densities and temperatures to synthesize the intensities expected in emission lines typically observed with the Extreme Ultraviolet Imaging Spectrometer on Hinode. These intensities are used to compute differential emission measure distributions using the Monte Carlo Markov Chain code, which are very similar to those derived from observations of solar active regions. We conclude that coronal heating is found to be strongly intermittent in space and time, with only small portions of the coronal loop being heated: in fact, at any given time, most of the corona is cooling down.

  7. SCALING LAWS AND TEMPERATURE PROFILES FOR SOLAR AND STELLAR CORONAL LOOPS WITH NON-UNIFORM HEATING

    International Nuclear Information System (INIS)

    Martens, P. C. H.

    2010-01-01

    The bulk of solar coronal radiative loss consists of soft X-ray emission from quasi-static loops at the cores of active regions. In order to develop diagnostics for determining the heating mechanism of these loops from observations by coronal imaging instruments, I have developed analytical solutions for the temperature structure and scaling laws of loop strands for a set of temperature- and pressure-dependent heating functions that encompass heating concentrated at the footpoints, uniform heating, and heating concentrated at the loop apex. Key results are that the temperature profile depends only weakly on the heating distribution-not sufficiently to be of significant diagnostic value-and that the scaling laws survive for this wide range of heating distributions, but with the constant of proportionality in the Rosner-Tucker-Vaiana scaling law (P 0 L ∼ T 3 max ) depending on the specific heating function. Furthermore, quasi-static solutions do not exist for an excessive concentration of heating near the loop footpoints, a result in agreement with recent numerical simulations. It is demonstrated that a generalization of the results to a set of solutions for strands with a functionally prescribed variable diameter leads to only relatively small correction factors in the scaling laws and temperature profiles for constant diameter loop strands. A quintet of leading theoretical coronal heating mechanisms is shown to be captured by the formalism of this paper, and the differences in thermal structure between them may be verified through observations. Preliminary results from full numerical simulations demonstrate that, despite the simplifying assumptions, the analytical solutions from this paper are accurate and stable.

  8. Constraining Stellar Coronal Mass Ejections through Multi-wavelength Analysis of the Active M Dwarf EQ Peg

    Science.gov (United States)

    Crosley, M. K.; Osten, R. A.

    2018-03-01

    Stellar coronal mass ejections remain experimentally unconstrained, unlike their stellar flare counterparts, which are observed ubiquitously across the electromagnetic spectrum. Low-frequency radio bursts in the form of a type II burst offer the best means of identifying and constraining the rate and properties of stellar CMEs. CME properties can be further improved through the use of proposed solar-stellar scaling relations and multi-wavelength observations of CMEs through the use of type II bursts and the associated flares expected to occur alongside them. We report on 20 hr of observation of the nearby, magnetically active, and well-characterized M dwarf star EQ Peg. The observations are simultaneously observed with the Jansky Very Large Array at their P-band (230–470 MHz) and at the Apache Point observatory in the SDSS u‧ filter (λ = 3557 Å). Dynamic spectra of the P-band data, constructed to search for signals in the frequency-time domains, did not reveal evidence of drifting radio bursts that could be ascribed to type II bursts. Given the sensitivity of our observations, we are able to place limits on the brightness temperature and source size of any bursts that may have occurred. Using solar scaling rations on four observed stellar flares, we predict CME parameters. Given the constraints on coronal density and photospheric field strength, our models suggest that the observed flares would have been insufficient to produce detectable type II bursts at our observed frequencies. We consider the implications of these results, and other recent findings, on stellar mass loss.

  9. MULTIFRACTAL SOLAR EUV INTENSITY FLUCTUATIONS AND THEIR IMPLICATIONS FOR CORONAL HEATING MODELS

    Energy Technology Data Exchange (ETDEWEB)

    Cadavid, A. C.; Lawrence, J. K.; Christian, D. J. [Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330 (United States); Rivera, Y. J. [Department of Climate and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109-2143 (United States); Jennings, P. J. [5174 S. Slauson Avenue, Culver City, CA 90230 (United States); Rappazzo, A. F., E-mail: ana.cadavid@csun.edu [Department of Earth, Planetary and Space Sciences, University of California Los Angeles, Los Angeles, CA 90095 (United States)

    2016-11-10

    We investigate the scaling properties of the long-range temporal evolution and intermittency of Atmospheric Imaging Assembly/ Solar Dynamics Observatory intensity observations in four solar environments: an active region core, a weak emission region, and two core loops. We use two approaches: the probability distribution function (PDF) of time series increments and multifractal detrended fluctuation analysis (MF-DFA). Noise taints the results, so we focus on the 171 Å waveband, which has the highest signal-to-noise ratio. The lags between pairs of wavebands distinguish between coronal versus transition region (TR) emission. In all physical regions studied, scaling in the range of 15–45 minutes is multifractal, and the time series are anti-persistent on average. The degree of anti-correlation in the TR time series is greater than that for coronal emission. The multifractality stems from long-term correlations in the data rather than the wide distribution of intensities. Observations in the 335 Å waveband can be described in terms of a multifractal with added noise. The multiscaling of the extreme-ultraviolet data agrees qualitatively with the radiance from a phenomenological model of impulsive bursts plus noise, and also from ohmic dissipation in a reduced magnetohydrodynamic model for coronal loop heating. The parameter space must be further explored to seek quantitative agreement. Thus, the observational “signatures” obtained by the combined tests of the PDF of increments and the MF-DFA offer strong constraints that can systematically discriminate among models for coronal heating.

  10. Characterizing a Model of Coronal Heating and Solar Wind Acceleration Based on Wave Turbulence.

    Science.gov (United States)

    Downs, C.; Lionello, R.; Mikic, Z.; Linker, J.; Velli, M.

    2014-12-01

    Understanding the nature of coronal heating and solar wind acceleration is a key goal in solar and heliospheric research. While there have been many theoretical advances in both topics, including suggestions that they may be intimately related, the inherent scale coupling and complexity of these phenomena limits our ability to construct models that test them on a fundamental level for realistic solar conditions. At the same time, there is an ever increasing impetus to improve our spaceweather models, and incorporating treatments for these processes that capture their basic features while remaining tractable is an important goal. With this in mind, I will give an overview of our exploration of a wave-turbulence driven (WTD) model for coronal heating and solar wind acceleration based on low-frequency Alfvénic turbulence. Here we attempt to bridge the gap between theory and practical modeling by exploring this model in 1D HD and multi-dimensional MHD contexts. The key questions that we explore are: What properties must the model possess to be a viable model for coronal heating? What is the influence of the magnetic field topology (open, closed, rapidly expanding)? And can we simultaneously capture coronal heating and solar wind acceleration with such a quasi-steady formulation? Our initial results suggest that a WTD based formulation performs adequately for a variety of solar and heliospheric conditions, while significantly reducing the number of free parameters when compared to empirical heating and solar wind models. The challenges, applications, and future prospects of this type of approach will also be discussed.

  11. The Role Of Torsional Alfvén Waves in Coronal Heating

    Science.gov (United States)

    Antolin, P.; Shibata, K.

    2010-03-01

    In the context of coronal heating, among the zoo of magnetohydrodynamic (MHD) waves that exist in the solar atmosphere, Alfvén waves receive special attention. Indeed, these waves constitute an attractive heating agent due to their ability to carry over the many different layers of the solar atmosphere sufficient energy to heat and maintain a corona. However, due to their incompressible nature these waves need a mechanism such as mode conversion (leading to shock heating), phase mixing, resonant absorption, or turbulent cascade in order to heat the plasma. Furthermore, their incompressibility makes their detection in the solar atmosphere very difficult. New observations with polarimetric, spectroscopic, and imaging instruments such as those on board the Japanese satellite Hinode, or the Crisp spectropolarimeter of the Swedish Solar Telescope or the Coronal Multi-channel Polarimeter, are bringing strong evidence for the existence of energetic Alfvén waves in the solar corona. In order to assess the role of Alfvén waves in coronal heating, in this work we model a magnetic flux tube being subject to Alfvén wave heating through the mode conversion mechanism. Using a 1.5 dimensional MHD code, we carry out a parameter survey varying the magnetic flux tube geometry (length and expansion), the photospheric magnetic field, the photospheric velocity amplitudes, and the nature of the waves (monochromatic or white-noise spectrum). The regimes under which Alfvén wave heating produces hot and stable coronae are found to be rather narrow. Independently of the photospheric wave amplitude and magnetic field, a corona can be produced and maintained only for long (>80 Mm) and thick (area ratio between the photosphere and corona >500) loops. Above a critical value of the photospheric velocity amplitude (generally a few km s-1) the corona can no longer be maintained over extended periods of time and collapses due to the large momentum of the waves. These results establish several

  12. The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Van Ballegooijen, A. A. [5001 Riverwood Avenue, Sarasota, FL 34231 (United States); Asgari-Targhi, M.; Voss, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2017-11-01

    In this paper we further develop a model for the heating of coronal loops by Alfvén wave turbulence (AWT). The Alfvén waves are assumed to be launched from a collection of kilogauss flux tubes in the photosphere at the two ends of the loop. Using a three-dimensional magnetohydrodynamic model for an active-region loop, we investigate how the waves from neighboring flux tubes interact in the chromosphere and corona. For a particular combination of model parameters we find that AWT can produce enough heat to maintain a peak temperature of about 2.5 MK, somewhat lower than the temperatures of 3–4 MK observed in the cores of active regions. The heating rates vary strongly in space and time, but the simulated heating events have durations less than 1 minute and are unlikely to reproduce the observed broad differential emission measure distributions of active regions. The simulated spectral line nonthermal widths are predicted to be about 27 km s{sup −1}, which is high compared to the observed values. Therefore, the present AWT model does not satisfy the observational constraints. An alternative “magnetic braiding” model is considered in which the coronal field lines are subject to slow random footpoint motions, but we find that such long-period motions produce much less heating than the shorter-period waves launched within the flux tubes. We discuss several possibilities for resolving the problem of producing sufficiently hot loops in active regions.

  13. Heating of an Erupting Prominence Associated with a Solar Coronal Mass Ejection on 2012 January 27

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jin-Yi; Moon, Yong-Jae; Kim, Kap-Sung [Department of Astronomy and Space Science, Kyung Hee University, Yongin-si, Gyeonggi-do, 17104 (Korea, Republic of); Raymond, John C.; Reeves, Katharine K. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

    2017-07-20

    We investigate the heating of an erupting prominence and loops associated with a coronal mass ejection and X-class flare. The prominence is seen as absorption in EUV at the beginning of its eruption. Later, the prominence changes to emission, which indicates heating of the erupting plasma. We find the densities of the erupting prominence using the absorption properties of hydrogen and helium in different passbands. We estimate the temperatures and densities of the erupting prominence and loops seen as emission features using the differential emission measure method, which uses both EUV and X-ray observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and the X-ray Telescope on board Hinode . We consider synthetic spectra using both photospheric and coronal abundances in these calculations. We verify the methods for the estimation of temperatures and densities for the erupting plasmas. Then, we estimate the thermal, kinetic, radiative loss, thermal conduction, and heating energies of the erupting prominence and loops. We find that the heating of the erupting prominence and loop occurs strongly at early times in the eruption. This event shows a writhing motion of the erupting prominence, which may indicate a hot flux rope heated by thermal energy release during magnetic reconnection.

  14. EFFECT OF A RADIATION COOLING AND HEATING FUNCTION ON STANDING LONGITUDINAL OSCILLATIONS IN CORONAL LOOPS

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S.; Nakariakov, V. M.; Moon, Y.-J., E-mail: sanjaykumar@khu.ac.kr [School of Space Research, Kyung Hee University, Yongin, 446-701, Gyeonggi (Korea, Republic of)

    2016-06-10

    Standing long-period (with periods longer than several minutes) oscillations in large, hot (with a temperature higher than 3 MK) coronal loops have been observed as the quasi-periodic modulation of the EUV and microwave intensity emission and the Doppler shift of coronal emission lines, and they have been interpreted as standing slow magnetoacoustic (longitudinal) oscillations. Quasi-periodic pulsations of shorter periods, detected in thermal and non-thermal emissions in solar flares could be produced by a similar mechanism. We present theoretical modeling of the standing slow magnetoacoustic mode, showing that this mode of oscillation is highly sensitive to peculiarities of the radiative cooling and heating function. We generalized the theoretical model of standing slow magnetoacoustic oscillations in a hot plasma, including the effects of the radiative losses and accounting for plasma heating. The heating mechanism is not specified and taken empirically to compensate the cooling by radiation and thermal conduction. It is shown that the evolution of the oscillations is described by a generalized Burgers equation. The numerical solution of an initial value problem for the evolutionary equation demonstrates that different dependences of the radiative cooling and plasma heating on the temperature lead to different regimes of the oscillations, including growing, quasi-stationary, and rapidly decaying. Our findings provide a theoretical foundation for probing the coronal heating function and may explain the observations of decayless long-period, quasi-periodic pulsations in flares. The hydrodynamic approach employed in this study should be considered with caution in the modeling of non-thermal emission associated with flares, because it misses potentially important non-hydrodynamic effects.

  15. An Efficient Approximation of the Coronal Heating Rate for use in Global Sun-Heliosphere Simulations

    Science.gov (United States)

    Cranmer, Steven R.

    2010-02-01

    The origins of the hot solar corona and the supersonically expanding solar wind are still the subject of debate. A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a physically motivated way of specifying the coronal heating rate. Recent one-dimensional models have been found to reproduce many observed features of the solar wind by assuming the energy comes from Alfvén waves that are partially reflected, then dissipated by magnetohydrodynamic turbulence. However, the nonlocal physics of wave reflection has made it difficult to apply these processes to more sophisticated (three-dimensional) models. This paper presents a set of robust approximations to the solutions of the linear Alfvén wave reflection equations. A key ingredient of the turbulent heating rate is the ratio of inward-to-outward wave power, and the approximations developed here allow this to be written explicitly in terms of local plasma properties at any given location. The coronal heating also depends on the frequency spectrum of Alfvén waves in the open-field corona, which has not yet been measured directly. A model-based assumption is used here for the spectrum, but the results of future measurements can be incorporated easily. The resulting expression for the coronal heating rate is self-contained, computationally efficient, and applicable directly to global models of the corona and heliosphere. This paper tests and validates the approximations by comparing the results to exact solutions of the wave transport equations in several cases relevant to the fast and slow solar wind.

  16. Thermal responses in a coronal loop maintained by wave heating mechanisms

    Science.gov (United States)

    Matsumoto, Takuma

    2018-05-01

    A full 3-dimensional compressible magnetohydrodynamic (MHD) simulation is conducted to investigate the thermal responses of a coronal loop to the dynamic dissipation processes of MHD waves. When the foot points of the loop are randomly and continuously forced, the MHD waves become excited and propagate upward. Then, 1-MK temperature corona is produced naturally as the wave energy dissipates. The excited wave packets become non-linear just above the magnetic canopy, and the wave energy cascades into smaller spatial scales. Moreover, collisions between counter-propagating Alfvén wave packets increase the heating rate, resulting in impulsive temperature increases. Our model demonstrates that the heating events in the wave-heated loops can be nanoflare-like in the sense that they are spatially localized and temporally intermittent.

  17. CAN LARGE TIME DELAYS OBSERVED IN LIGHT CURVES OF CORONAL LOOPS BE EXPLAINED IN IMPULSIVE HEATING?

    International Nuclear Information System (INIS)

    Lionello, Roberto; Linker, Jon A.; Mikić, Zoran; Alexander, Caroline E.; Winebarger, Amy R.

    2016-01-01

    The light curves of solar coronal loops often peak first in channels associated with higher temperatures and then in those associated with lower temperatures. The delay times between the different narrowband EUV channels have been measured for many individual loops and recently for every pixel of an active region observation. The time delays between channels for an active region exhibit a wide range of values. The maximum time delay in each channel pair can be quite large, i.e., >5000 s. These large time delays make-up 3%–26% (depending on the channel pair) of the pixels where a trustworthy, positive time delay is measured. It has been suggested that these time delays can be explained by simple impulsive heating, i.e., a short burst of energy that heats the plasma to a high temperature, after which the plasma is allowed to cool through radiation and conduction back to its original state. In this paper, we investigate whether the largest observed time delays can be explained by this hypothesis by simulating a series of coronal loops with different heating rates, loop lengths, abundances, and geometries to determine the range of expected time delays between a set of four EUV channels. We find that impulsive heating cannot address the largest time delays observed in two of the channel pairs and that the majority of the large time delays can only be explained by long, expanding loops with photospheric abundances. Additional observations may rule out these simulations as an explanation for the long time delays. We suggest that either the time delays found in this manner may not be representative of real loop evolution, or that the impulsive heating and cooling scenario may be too simple to explain the observations, and other potential heating scenarios must be explored

  18. Coronal heating driven by a magnetic gradient pumping mechanism in solar plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Baolin, E-mail: bltan@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China)

    2014-11-10

    The heating of the solar corona is a longstanding mystery in astrophysics. Considering that the solar magnetic field is spatially inhomogeneous with a considerable magnetic gradient from the solar surface to the corona, this work proposes a magnetic gradient pumping (MGP) mechanism to try to explain the formation of hot plasma upflows, such as hot type II spicules and hot plasma ejections. In the MGP mechanism, the magnetic gradient may drive the energetic particles to move upward from the underlying solar atmosphere and form hot upflows. These upflow energetic particles are deposited in the corona, causing it to become very hot. Rough estimations indicate that the solar corona can be heated to above 1 million degrees, and the upflow velocity is about 40 km s{sup –1} in the chromosphere and about 130 km s{sup –1} in the corona. The solar magnetic flux tubes act as pumpers to extract energetic particles from the underlying thermal photosphere, convey them, and deposit them in the corona. The deposit of these energetic particles causes the corona to become hot, and the escape of such particles from the photosphere leaves it a bit cold. This mechanism can present a natural explanation to the mystery of solar coronal heating.

  19. Turbulence-driven coronal heating and improvements to empirical forecasting of the solar wind

    International Nuclear Information System (INIS)

    Woolsey, Lauren N.; Cranmer, Steven R.

    2014-01-01

    Forecasting models of the solar wind often rely on simple parameterizations of the magnetic field that ignore the effects of the full magnetic field geometry. In this paper, we present the results of two solar wind prediction models that consider the full magnetic field profile and include the effects of Alfvén waves on coronal heating and wind acceleration. The one-dimensional magnetohydrodynamic code ZEPHYR self-consistently finds solar wind solutions without the need for empirical heating functions. Another one-dimensional code, introduced in this paper (The Efficient Modified-Parker-Equation-Solving Tool, TEMPEST), can act as a smaller, stand-alone code for use in forecasting pipelines. TEMPEST is written in Python and will become a publicly available library of functions that is easy to adapt and expand. We discuss important relations between the magnetic field profile and properties of the solar wind that can be used to independently validate prediction models. ZEPHYR provides the foundation and calibration for TEMPEST, and ultimately we will use these models to predict observations and explain space weather created by the bulk solar wind. We are able to reproduce with both models the general anticorrelation seen in comparisons of observed wind speed at 1 AU and the flux tube expansion factor. There is significantly less spread than comparing the results of the two models than between ZEPHYR and a traditional flux tube expansion relation. We suggest that the new code, TEMPEST, will become a valuable tool in the forecasting of space weather.

  20. Turbulence-driven coronal heating and improvements to empirical forecasting of the solar wind

    Energy Technology Data Exchange (ETDEWEB)

    Woolsey, Lauren N.; Cranmer, Steven R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2014-06-01

    Forecasting models of the solar wind often rely on simple parameterizations of the magnetic field that ignore the effects of the full magnetic field geometry. In this paper, we present the results of two solar wind prediction models that consider the full magnetic field profile and include the effects of Alfvén waves on coronal heating and wind acceleration. The one-dimensional magnetohydrodynamic code ZEPHYR self-consistently finds solar wind solutions without the need for empirical heating functions. Another one-dimensional code, introduced in this paper (The Efficient Modified-Parker-Equation-Solving Tool, TEMPEST), can act as a smaller, stand-alone code for use in forecasting pipelines. TEMPEST is written in Python and will become a publicly available library of functions that is easy to adapt and expand. We discuss important relations between the magnetic field profile and properties of the solar wind that can be used to independently validate prediction models. ZEPHYR provides the foundation and calibration for TEMPEST, and ultimately we will use these models to predict observations and explain space weather created by the bulk solar wind. We are able to reproduce with both models the general anticorrelation seen in comparisons of observed wind speed at 1 AU and the flux tube expansion factor. There is significantly less spread than comparing the results of the two models than between ZEPHYR and a traditional flux tube expansion relation. We suggest that the new code, TEMPEST, will become a valuable tool in the forecasting of space weather.

  1. PLASMA HEATING INSIDE INTERPLANETARY CORONAL MASS EJECTIONS BY ALFVÉNIC FLUCTUATIONS DISSIPATION

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hui; Wang, Chi; Zhang, Lingqian [State Key Laboratory of Space Weather, National Space Science Center, CAS, Beijing, 100190 (China); He, Jiansen [School of Earth and Space Sciences, Peking University, Beijing, 100871 (China); Richardson, John D.; Belcher, John W. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA (United States); Tu, Cui, E-mail: hli@spaceweather.ac.cn [Laboratory of Near Space Environment, National Space Science Center, CAS, Beijing, 100190 (China)

    2016-11-10

    Nonlinear cascade of low-frequency Alfvénic fluctuations (AFs) is regarded as one of the candidate energy sources that heat plasma during the non-adiabatic expansion of interplanetary coronal mass ejections (ICMEs). However, AFs inside ICMEs were seldom reported in the literature. In this study, we investigate AFs inside ICMEs using observations from Voyager 2 between 1 and 6 au. It has been found that AFs with a high degree of Alfvénicity frequently occurred inside ICMEs for almost all of the identified ICMEs (30 out of 33 ICMEs) and for 12.6% of the ICME time interval. As ICMEs expand and move outward, the percentage of AF duration decays linearly in general. The occurrence rate of AFs inside ICMEs is much less than that in ambient solar wind, especially within 4.75 au. AFs inside ICMEs are more frequently presented in the center and at the boundaries of ICMEs. In addition, the proton temperature inside ICME has a similar “W”-shaped distribution. These findings suggest significant contribution of AFs on local plasma heating inside ICMEs.

  2. Exomoon habitability constrained by illumination and tidal heating.

    Science.gov (United States)

    Heller, René; Barnes, Rory

    2013-01-01

    The detection of moons orbiting extrasolar planets ("exomoons") has now become feasible. Once they are discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days much shorter than their orbital period around the star and have seasons, all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circumplanetary "habitable edge." We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons. If either planet hosted a satellite at a distance greater than 10 planetary radii, then this could indicate the presence of a habitable moon.

  3. Exomoon Habitability Constrained by Illumination and Tidal Heating

    Science.gov (United States)

    2013-01-01

    Abstract The detection of moons orbiting extrasolar planets (“exomoons”) has now become feasible. Once they are discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days much shorter than their orbital period around the star and have seasons, all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circumplanetary “habitable edge.” We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons. If either planet hosted a satellite at a distance greater than 10 planetary radii, then this could indicate the presence of a habitable moon. Key Words: Astrobiology—Extrasolar planets—Habitability—Habitable zone—Tides. Astrobiology 13, 18–46. PMID:23305357

  4. How can we constrain the amount of heat producing elements in the interior of Mars?

    Science.gov (United States)

    Grott, M.; Plesa, A.; Breuer, D.

    2013-12-01

    The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission to be launched in 2016 will study Mars' deep interior and help improving our knowledge about the interior structure and the thermal evolution of the planet - the latter is also directly linked to its volcanic history and atmospheric evolution. Measurements planned with the two main instruments, SEIS (Seismic Experiment for Interior Structure) and HP3 (Heat Flow and Physical Properties Package) aim to constrain the main structure of the planet, i.e. core, mantle and crust as well as the rate at which the planet loses the interior heat over its surface. Since the surface heat flow depends on the amount of radiogenic heat elements (HPE) present in the interior, it offers a measurable quantity which could constrain the heat budget. Being the principal agent regulating the heat budget which in turn influences partial melting in the interior, crustal and atmospheric evolution, the heat producing elements have a major impact on the entire the present temperature thermal history of the planet. To constrain the radiogenic heat elements of the planet from the surface heat flow is possible assuming that the urey number of the planet, which describes the contribution of internal heat production to the surface heat loss, is known. We have tested this assumption by calculating the thermal evolution of the planet with fully dynamical numerical simulations and by comparing the obtained present-day urey number for a set of different models/parameters (Fig. 1). For one-plate planets like Mars, numerical models show - in contrast to models for the Earth, where plate tectonics play a major role adding more complexity to the system - that the urey ratio is mainly sensitive to two effects: the efficiency of cooling due to the temperature-dependence of the viscosity and the mean half-life time of the long lived radiogenic isotopes. The temperature-dependence of the viscosity results in the

  5. Role of Magnetic Carpet in Coronal Heating S. R. Verma & Diksha ...

    Indian Academy of Sciences (India)

    It is likely that different heating mechanisms are at work in the solar corona. ... ity, termed magnetic carpet contributing to solar activity on a short time .... migrates to the boundaries of supergranule cells and moves along them, fragmenting,.

  6. Formation of Large-scale Coronal Loops Interconnecting Two Active Regions through Gradual Magnetic Reconnection and an Associated Heating Process

    Science.gov (United States)

    Du, Guohui; Chen, Yao; Zhu, Chunming; Liu, Chang; Ge, Lili; Wang, Bing; Li, Chuanyang; Wang, Haimin

    2018-06-01

    Coronal loops interconnecting two active regions (ARs), called interconnecting loops (ILs), are prominent large-scale structures in the solar atmosphere. They carry a significant amount of magnetic flux and therefore are considered to be an important element of the solar dynamo process. Earlier observations showed that eruptions of ILs are an important source of CMEs. It is generally believed that ILs are formed through magnetic reconnection in the high corona (>150″–200″), and several scenarios have been proposed to explain their brightening in soft X-rays (SXRs). However, the detailed IL formation process has not been fully explored, and the associated energy release in the corona still remains unresolved. Here, we report the complete formation process of a set of ILs connecting two nearby ARs, with successive observations by STEREO-A on the far side of the Sun and by SDO and Hinode on the Earth side. We conclude that ILs are formed by gradual reconnection high in the corona, in line with earlier postulations. In addition, we show evidence that ILs brighten in SXRs and EUVs through heating at or close to the reconnection site in the corona (i.e., through the direct heating process of reconnection), a process that has been largely overlooked in earlier studies of ILs.

  7. Coronal heating by the resonant absorption of Alfven waves - Importance of the global mode and scaling laws

    Science.gov (United States)

    Steinolfson, Richard S.; Davila, Joseph M.

    1993-01-01

    Numerical simulations of the MHD equations for a fully compressible, low-beta, resistive plasma are used to study the resonance absorption process for the heating of coronal active region loops. Comparisons with more approximate analytic models show that the major predictions of the analytic theories are, to a large extent, confirmed by the numerical computations. The simulations demonstrate that the dissipation occurs primarily in a thin resonance layer. Some of the analytically predicted features verified by the simulations are (a) the position of the resonance layer within the initial inhomogeneity; (b) the importance of the global mode for a large range of loop densities; (c) the dependence of the resonance layer thickness and the steady-state heating rate on the dissipation coefficient; and (d) the time required for the resonance layer to form. In contrast with some previous analytic and simulation results, the time for the loop to reach a steady state is found to be the phase-mixing time rather than a dissipation time. This disagreement is shown to result from neglect of the existence of the global mode in some of the earlier analyses. The resonant absorption process is also shown to behave similar to a classical driven harmonic oscillator.

  8. Alfvén Wave Turbulence as a Coronal Heating Mechanism: Simultaneously Predicting the Heating Rate and the Wave-induced Emission Line Broadening

    Energy Technology Data Exchange (ETDEWEB)

    Oran, R. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139 (United States); Landi, E.; Holst, B. van der; Sokolov, I. V.; Gombosi, T. I., E-mail: roran@mit.edu [Atmospheric, Oceanic and Atmospheric Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI, 48109 (United States)

    2017-08-20

    We test the predictions of the Alfvén Wave Solar Model (AWSoM), a global wave-driven magnetohydrodynamic (MHD) model of the solar atmosphere, against high-resolution spectra emitted by the quiescent off-disk solar corona. AWSoM incorporates Alfvén wave propagation and dissipation in both closed and open magnetic field lines; turbulent dissipation is the only heating mechanism. We examine whether this mechanism is consistent with observations of coronal EUV emission by combining model results with the CHIANTI atomic database to create synthetic line-of-sight spectra, where spectral line widths depend on thermal and wave-related ion motions. This is the first time wave-induced line broadening is calculated from a global model with a realistic magnetic field. We used high-resolution SUMER observations above the solar west limb between 1.04 and 1.34 R {sub ⊙} at the equator, taken in 1996 November. We obtained an AWSoM steady-state solution for the corresponding period using a synoptic magnetogram. The 3D solution revealed a pseudo-streamer structure transversing the SUMER line of sight, which contributes significantly to the emission; the modeled electron temperature and density in the pseudo-streamer are consistent with those observed. The synthetic line widths and the total line fluxes are consistent with the observations for five different ions. Further, line widths that include the contribution from the wave-induced ion motions improve the correspondence with observed spectra for all ions. We conclude that the turbulent dissipation assumed in the AWSoM model is a viable candidate for explaining coronal heating, as it is consistent with several independent measured quantities.

  9. Coronal Heating Topology: The Interplay of Current Sheets and Magnetic Field Lines

    Energy Technology Data Exchange (ETDEWEB)

    Rappazzo, A. F.; Velli, M. [Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA 90095 (United States); Matthaeus, W. H. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Servidio, S., E-mail: rappazzo@ucla.edu [Dipartimento di Fisica, Università della Calabria, Cosenza I-87036 (Italy)

    2017-07-20

    The magnetic topology and field line random walk (FLRW) properties of a nanoflare-heated and magnetically confined corona are investigated in the reduced magnetohydrodynamic regime. Field lines originating from current sheets form coherent structures, called current sheet connected (CSC) regions, which extend around them. CSC FLRW is strongly anisotropic, with preferential diffusion along the current sheets’ in-plane length. CSC FLRW properties remain similar to those of the entire ensemble but exhibit enhanced mean square displacements and separations due to the stronger magnetic field intensities in CSC regions. The implications for particle acceleration and heat transport in the solar corona and wind, and for solar moss formation are discussed.

  10. A Hydrodynamic Model of Alfvénic Wave Heating in a Coronal Loop and Its Chromospheric Footpoints

    Science.gov (United States)

    Reep, Jeffrey W.; Russell, Alexander J. B.; Tarr, Lucas A.; Leake, James E.

    2018-02-01

    Alfvénic waves have been proposed as an important energy transport mechanism in coronal loops, capable of delivering energy to both the corona and chromosphere and giving rise to many observed features of flaring and quiescent regions. In previous work, we established that resistive dissipation of waves (ambipolar diffusion) can drive strong chromospheric heating and evaporation, capable of producing flaring signatures. However, that model was based on a simplified assumption that the waves propagate instantly to the chromosphere, an assumption that the current work removes. Via a ray-tracing method, we have implemented traveling waves in a field-aligned hydrodynamic simulation that dissipate locally as they propagate along the field line. We compare this method to and validate against the magnetohydrodynamics code Lare3D. We then examine the importance of travel times to the dynamics of the loop evolution, finding that (1) the ionization level of the plasma plays a critical role in determining the location and rate at which waves dissipate; (2) long duration waves effectively bore a hole into the chromosphere, allowing subsequent waves to penetrate deeper than previously expected, unlike an electron beam whose energy deposition rises in height as evaporation reduces the mean-free paths of the electrons; and (3) the dissipation of these waves drives a pressure front that propagates to deeper depths, unlike energy deposition by an electron beam.

  11. Coronal Waves and Oscillations

    Directory of Open Access Journals (Sweden)

    Nakariakov Valery M.

    2005-07-01

    Full Text Available Wave and oscillatory activity of the solar corona is confidently observed with modern imaging and spectral instruments in the visible light, EUV, X-ray and radio bands, and interpreted in terms of magnetohydrodynamic (MHD wave theory. The review reflects the current trends in the observational study of coronal waves and oscillations (standing kink, sausage and longitudinal modes, propagating slow waves and fast wave trains, the search for torsional waves, theoretical modelling of interaction of MHD waves with plasma structures, and implementation of the theoretical results for the mode identification. Also the use of MHD waves for remote diagnostics of coronal plasma - MHD coronal seismology - is discussed and the applicability of this method for the estimation of coronal magnetic field, transport coefficients, fine structuring and heating function is demonstrated.

  12. CORONAL HEATING BY SURFACE ALFVEN WAVE DAMPING: IMPLEMENTATION IN A GLOBAL MAGNETOHYDRODYNAMICS MODEL OF THE SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Evans, R. M. [NASA Goddard Space Flight Center, Space Weather Lab, Greenbelt, MD 20771 (United States); Opher, M. [Astronomy Department, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 (United States); Oran, R.; Van der Holst, B.; Sokolov, I. V.; Frazin, R.; Gombosi, T. I. [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States); Vasquez, A., E-mail: Rebekah.e.frolov@nasa.gov [Instituto de Astronomia y Fisica del Espacio (CONICET-UBA) and FCEN (UBA), CC 67, Suc 28, Ciudad de Buenos Aires (Argentina)

    2012-09-10

    The heating and acceleration of the solar wind is an active area of research. Alfven waves, because of their ability to accelerate and heat the plasma, are a likely candidate in both processes. Many models have explored wave dissipation mechanisms which act either in closed or open magnetic field regions. In this work, we emphasize the boundary between these regions, drawing on observations which indicate unique heating is present there. We utilize a new solar corona component of the Space Weather Modeling Framework, in which Alfven wave energy transport is self-consistently coupled to the magnetohydrodynamic equations. In this solar wind model, the wave pressure gradient accelerates and wave dissipation heats the plasma. Kolmogorov-like wave dissipation as expressed by Hollweg along open magnetic field lines was presented in van der Holst et al. Here, we introduce an additional dissipation mechanism: surface Alfven wave (SAW) damping, which occurs in regions with transverse (with respect to the magnetic field) gradients in the local Alfven speed. For solar minimum conditions, we find that SAW dissipation is weak in the polar regions (where Hollweg dissipation is strong), and strong in subpolar latitudes and the boundaries of open and closed magnetic fields (where Hollweg dissipation is weak). We show that SAW damping reproduces regions of enhanced temperature at the boundaries of open and closed magnetic fields seen in tomographic reconstructions in the low corona. Also, we argue that Ulysses data in the heliosphere show enhanced temperatures at the boundaries of fast and slow solar wind, which is reproduced by SAW dissipation. Therefore, the model's temperature distribution shows best agreement with these observations when both dissipation mechanisms are considered. Lastly, we use observational constraints of shock formation in the low corona to assess the Alfven speed profile in the model. We find that, compared to a polytropic solar wind model, the wave

  13. Thermodynamic optimization of mixed refrigerant Joule- Thomson systems constrained by heat transfer considerations

    International Nuclear Information System (INIS)

    Hinze, J F; Klein, S A; Nellis, G F

    2015-01-01

    Mixed refrigerant (MR) working fluids can significantly increase the cooling capacity of a Joule-Thomson (JT) cycle. The optimization of MRJT systems has been the subject of substantial research. However, most optimization techniques do not model the recuperator in sufficient detail. For example, the recuperator is usually assumed to have a heat transfer coefficient that does not vary with the mixture. Ongoing work at the University of Wisconsin-Madison has shown that the heat transfer coefficients for two-phase flow are approximately three times greater than for a single phase mixture when the mixture quality is between 15% and 85%. As a result, a system that optimizes a MR without also requiring that the flow be in this quality range may require an extremely large recuperator or not achieve the performance predicted by the model. To ensure optimal performance of the JT cycle, the MR should be selected such that it is entirely two-phase within the recuperator. To determine the optimal MR composition, a parametric study was conducted assuming a thermodynamically ideal cycle. The results of the parametric study are graphically presented on a contour plot in the parameter space consisting of the extremes of the qualities that exist within the recuperator. The contours show constant values of the normalized refrigeration power. This ‘map’ shows the effect of MR composition on the cycle performance and it can be used to select the MR that provides a high cooling load while also constraining the recuperator to be two phase. The predicted best MR composition can be used as a starting point for experimentally determining the best MR. (paper)

  14. Thermal Profile of the Lunar Interior Constrained by Revised Estimates of Concentrations of Heat Producing Elements

    Science.gov (United States)

    Fuqua-Haviland, H.; Panovska, S.; Mallik, A.; Bremner, P. M.; McDonough, W. F.

    2017-12-01

    Constraining the heat producing element (HPE) concentrations of the Moon is important for understanding the thermal state of the interior. The lunar HPE budget is debated to be suprachondritic [1] to chondritic [2]. The Moon is differentiated, thus, each reservoir has a distinct HPE signature complicating this effort. The thermal profile of the lunar interior has been constructed using HPE concentrations of an ordinary chondrite (U = 0.0068 ppm; Th = 0.025 ppm; K = 17 ppm) which yields a conservative low estimate [2, 3, 4]. A later study estimated the bulk lunar mantle HPE concentrations (U = 0.039 ppm; Th = 0.15 ppm; K = 212 ppm) based on measurements of Apollo pyroclastic glasses [5] assuming that these glasses represent the least fractionated, near-primary lunar mantle melts, hence, are the best proxies for capturing mantle composition. In this study, we independently validate the revised estimate by using HPE concentrations [5] to construct a conductive lunar thermal profile, or selenotherm. We compare our conductive profile to the range of valid temperatures. We demonstrate the HPE concentrations reported by [5], when used in a simple 1D spherical thermal conduction equation, yield an impossibly hot mantle with temperatures in excess of 4,000 K (Fig 1). This confirms their revised estimate is not representative of the bulk lunar mantle, and perhaps only representative of a locally enriched mantle domain. We believe that their Low-Ti avg. source estimate (Th = 0.055 ppm, Th/U=4; K/U=1700), with the least KREEP assimilation is the closest representation of the bulk lunar mantle, producing 3E-12 W/kg of heat. This estimate is close to that of the Earth (5E-12 W/kg), indicating that the bulk Earth and lunar mantles are similar in their HPE constituents. We have used the lunar mantle heat production, in conjunction with HPE estimates of the Fe-Ti-rich cumulates (high Ti-source estimate from [5]) and measurements of crustal ferroan anorthite [6], to capture the

  15. Coronal magnetometry

    CERN Document Server

    Zhang, Jie; Bastian, Timothy

    2014-01-01

    This volume is a collection of research articles on the subject of the solar corona, and particularly, coronal magnetism. The book was motivated by the Workshop on Coronal Magnetism: Connecting Models to Data and the Corona to the Earth, which was held 21 - 23 May 2012 in Boulder, Colorado, USA. This workshop was attended by approximately 60 researchers. Articles from this meeting are contained in this topical issue, but the topical issue also contains contributions from researchers not present at the workshop. This volume is aimed at researchers and graduate students active in solar physics. Originally published in Solar Physics, Vol. 288, Issue 2, 2013 and Vol. 289, Issue 8, 2014.

  16. Extreme ion heating in the dayside ionosphere in response to the arrival of a coronal mass ejection on 12 March 2012

    Directory of Open Access Journals (Sweden)

    H. Fujiwara

    2014-07-01

    Full Text Available Simultaneous measurements of the polar ionosphere with the European Incoherent Scatter (EISCAT ultra high frequency (UHF radar at Tromsø and the EISCAT Svalbard radar (ESR at Longyearbyen were made during 07:00–12:00 UT on 12 March 2012. During the period, the Advanced Composition Explorer (ACE spacecraft observed changes in the solar wind which were due to the arrival of coronal mass ejection (CME effects associated with the 10 March M8.4 X-ray event. The solar wind showed two-step variations which caused strong ionospheric heating. First, the arrival of shock structures in the solar wind with enhancements of density and velocity, and a negative interplanetary magnetic field (IMF-Bz component caused strong ionospheric heating around Longyearbyen; the ion temperature at about 300 km increased from about 1100 to 3400 K over Longyearbyen while that over Tromsø increased from about 1050 to 1200 K. After the passage of the shock structures, the IMF-Bz component showed positive values and the solar wind speed and density also decreased. The second strong ionospheric heating occurred after the IMF-Bz component showed negative values again; the negative values lasted for more than 1.5 h. This solar wind variation caused stronger heating of the ionosphere in the lower latitudes than higher latitudes, suggesting expansion of the auroral oval/heating region to the lower latitude region. This study shows an example of the CME-induced dayside ionospheric heating: a short-duration and very large rise in the ion temperature which was closely related to the polar cap size and polar cap potential variations as a result of interaction between the solar wind and the magnetosphere.

  17. PONDEROMOTIVE ACCELERATION IN CORONAL LOOPS

    Energy Technology Data Exchange (ETDEWEB)

    Dahlburg, R. B.; Obenschain, K. [LCP and FD, Naval Research Laboratory, Washington, DC 20375 (United States); Laming, J. M. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Taylor, B. D. [AFRL Eglin AFB, Pensacola, FL 32542 (United States)

    2016-11-10

    Ponderomotive acceleration has been asserted to be a cause of the first ionization potential (FIP) effect, the well-known enhancement in abundance by a factor of 3–4 over photospheric values of elements in the solar corona with FIP less than about 10 eV. It is shown here by means of numerical simulations that ponderomotive acceleration occurs in solar coronal loops, with the appropriate magnitude and direction, as a “by-product” of coronal heating. The numerical simulations are performed with the HYPERION code, which solves the fully compressible three-dimensional magnetohydrodynamic equations including nonlinear thermal conduction and optically thin radiation. Numerical simulations of coronal loops with an axial magnetic field from 0.005 to 0.02 T and lengths from 25,000 to 75,000 km are presented. In the simulations the footpoints of the axial loop magnetic field are convected by random, large-scale motions. There is a continuous formation and dissipation of field-aligned current sheets, which act to heat the loop. As a consequence of coronal magnetic reconnection, small-scale, high-speed jets form. The familiar vortex quadrupoles form at reconnection sites. Between the magnetic footpoints and the corona the reconnection flow merges with the boundary flow. It is in this region that the ponderomotive acceleration occurs. Mirroring the character of the coronal reconnection, the ponderomotive acceleration is also found to be intermittent.

  18. PONDEROMOTIVE ACCELERATION IN CORONAL LOOPS

    International Nuclear Information System (INIS)

    Dahlburg, R. B.; Obenschain, K.; Laming, J. M.; Taylor, B. D.

    2016-01-01

    Ponderomotive acceleration has been asserted to be a cause of the first ionization potential (FIP) effect, the well-known enhancement in abundance by a factor of 3–4 over photospheric values of elements in the solar corona with FIP less than about 10 eV. It is shown here by means of numerical simulations that ponderomotive acceleration occurs in solar coronal loops, with the appropriate magnitude and direction, as a “by-product” of coronal heating. The numerical simulations are performed with the HYPERION code, which solves the fully compressible three-dimensional magnetohydrodynamic equations including nonlinear thermal conduction and optically thin radiation. Numerical simulations of coronal loops with an axial magnetic field from 0.005 to 0.02 T and lengths from 25,000 to 75,000 km are presented. In the simulations the footpoints of the axial loop magnetic field are convected by random, large-scale motions. There is a continuous formation and dissipation of field-aligned current sheets, which act to heat the loop. As a consequence of coronal magnetic reconnection, small-scale, high-speed jets form. The familiar vortex quadrupoles form at reconnection sites. Between the magnetic footpoints and the corona the reconnection flow merges with the boundary flow. It is in this region that the ponderomotive acceleration occurs. Mirroring the character of the coronal reconnection, the ponderomotive acceleration is also found to be intermittent.

  19. An observation-constrained multi-physics WRF ensemble for simulating European mega heat waves

    NARCIS (Netherlands)

    Stegehuis, A.I.; Vautard, R.; Ciais, P.; Teuling, A.J.; Gonzalez Miralles, D.; Wild, M.

    2015-01-01

    Many climate models have difficulties in properly reproducing climate extremes, such as heat wave conditions. Here we use the Weather Research and Forecasting (WRF) regional climate model with a large combination of different atmospheric physics schemes, in combination with the NOAH land-surface

  20. An observation-constrained multi-physics WRF ensemble for simulating European mega heat waves

    NARCIS (Netherlands)

    Stegehuis, A.I.; Vautard, R.; Ciais, P.; Teuling, A.J.; Miralles, D.G.; Wild, M.

    2015-01-01

    Many climate models have difficulties in properly reproducing climate extremes, such as heat wave conditions. Here we use the Weather Research and Forecasting (WRF) regional climate model with a large combination of different atmospheric physics schemes, in combination with the NOAH land-surface

  1. A new multi-objective reserve constrained combined heat and power dynamic economic emission dispatch

    International Nuclear Information System (INIS)

    Niknam, Taher; Azizipanah-Abarghooee, Rasoul; Roosta, Alireza; Amiri, Babak

    2012-01-01

    Combined heat and power units are playing an ever increasing role in conventional power stations due to advantages such as reduced emissions and operational cost savings. This paper investigates a more practical formulation of the complex non-convex, non-smooth and non-linear multi-objective dynamic economic emission dispatch that incorporates combined heat and power units. Integrating these types of units, and their power ramp constraints, require an efficient tool to cope with the joint characteristics of power and heat. Unlike previous approaches, the spinning reserve requirements of this system are clearly formulated in the problem. In this way, a new multi-objective optimisation based on an enhanced firefly algorithm is proposed to achieve a set of non-dominated (Pareto-optimal) solutions. A new tuning parameter based on a chaotic mechanism and novel self adaptive probabilistic mutation strategies are used to improve the overall performance of the algorithm. The numerical results demonstrate how the proposed framework was applied in real time studies. -- Highlights: ► Investigate a practical formulation of the DEED (Dynamic Economic Emission Dispatch). ► Consider combined heat and power units. ► Consider power ramp constraints. ► Consider the system spinning reserve requirements. ► Present a new multi-objective optimization firefly.

  2. An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection

    Energy Technology Data Exchange (ETDEWEB)

    Reeves, Katharine K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS 58, Cambridge, MA 02138 (United States); Freed, Michael S.; McKenzie, David E. [Montana State University, Bozeman, MT 59717 (United States); Savage, Sabrina L., E-mail: kreeves@cfa.harvard.edu [NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States)

    2017-02-10

    We perform a detailed analysis of the thermal structure of the region above the post-eruption arcade for a flare that occurred on 2011 October 22. During this event, a sheet of hot plasma is visible above the flare loops in the 131 Å bandpass of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory . Supra-arcade downflows (SADs) are observed traveling sunward through the post-eruption plasma sheet. We calculate differential emission measures using the AIA data and derive an emission measure weighted average temperature in the supra-arcade region. In areas where many SADs occur, the temperature of the supra-arcade plasma tends to increase, while in areas where no SADs are observed, the temperature tends to decrease. We calculate the plane-of-sky velocities in the supra-arcade plasma and use them to determine the potential heating due to adiabatic compression and viscous heating. Of the 13 SADs studied, 10 have noticeable signatures in both the adiabatic and the viscous terms. The adiabatic heating due to compression of plasma in front of the SADs is on the order of 0.1–0.2 MK/s, which is similar in magnitude to the estimated conductive cooling rate. This result supports the notion that SADs contribute locally to the heating of plasma in the supra-arcade region. We also find that in the region without SADs, the plasma cools at a rate that is slower than the estimated conductive cooling, indicating that additional heating mechanisms may act globally to keep the plasma temperature high.

  3. An Exploration of Heating Mechanisms in a Supra-arcade Plasma Sheet Formed after a Coronal Mass Ejection

    International Nuclear Information System (INIS)

    Reeves, Katharine K.; Freed, Michael S.; McKenzie, David E.; Savage, Sabrina L.

    2017-01-01

    We perform a detailed analysis of the thermal structure of the region above the post-eruption arcade for a flare that occurred on 2011 October 22. During this event, a sheet of hot plasma is visible above the flare loops in the 131 Å bandpass of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory . Supra-arcade downflows (SADs) are observed traveling sunward through the post-eruption plasma sheet. We calculate differential emission measures using the AIA data and derive an emission measure weighted average temperature in the supra-arcade region. In areas where many SADs occur, the temperature of the supra-arcade plasma tends to increase, while in areas where no SADs are observed, the temperature tends to decrease. We calculate the plane-of-sky velocities in the supra-arcade plasma and use them to determine the potential heating due to adiabatic compression and viscous heating. Of the 13 SADs studied, 10 have noticeable signatures in both the adiabatic and the viscous terms. The adiabatic heating due to compression of plasma in front of the SADs is on the order of 0.1–0.2 MK/s, which is similar in magnitude to the estimated conductive cooling rate. This result supports the notion that SADs contribute locally to the heating of plasma in the supra-arcade region. We also find that in the region without SADs, the plasma cools at a rate that is slower than the estimated conductive cooling, indicating that additional heating mechanisms may act globally to keep the plasma temperature high.

  4. Constraining the heat flux between Enceladus’ tiger stripes: numerical modeling of funiscular plains formation

    Science.gov (United States)

    Bland, Michael T.; McKinnon, William B; Schenk, Paul M.

    2015-01-01

    The Cassini spacecraft’s Composite Infrared Spectrometer (CIRS) has observed at least 5 GW of thermal emission at Enceladus’ south pole. The vast majority of this emission is localized on the four long, parallel, evenly-spaced fractures dubbed tiger stripes. However, the thermal emission from regions between the tiger stripes has not been determined. These spatially localized regions have a unique morphology consisting of short-wavelength (∼1 km) ridges and troughs with topographic amplitudes of ∼100 m, and a generally ropy appearance that has led to them being referred to as “funiscular terrain.” Previous analysis pursued the hypothesis that the funiscular terrain formed via thin-skinned folding, analogous to that occurring on a pahoehoe flow top (Barr, A.C., Preuss, L.J. [2010]. Icarus 208, 499–503). Here we use finite element modeling of lithospheric shortening to further explore this hypothesis. Our best-case simulations reproduce funiscular-like morphologies, although our simulated fold wavelengths after 10% shortening are 30% longer than those observed. Reproducing short-wavelength folds requires high effective surface temperatures (∼185 K), an ice lithosphere (or high-viscosity layer) with a low thermal conductivity (one-half to one-third that of intact ice or lower), and very high heat fluxes (perhaps as great as 400 mW m−2). These conditions are driven by the requirement that the high-viscosity layer remain extremely thin (≲200 m). Whereas the required conditions are extreme, they can be met if a layer of fine grained plume material 1–10 m thick, or a highly fractured ice layer >50 m thick insulates the surface, and the lithosphere is fractured throughout as well. The source of the necessary heat flux (a factor of two greater than previous estimates) is less obvious. We also present evidence for an unusual color/spectral character of the ropy terrain, possibly related to its unique surface texture. Our simulations demonstrate

  5. Nonlinear Propagation of Alfven Waves Driven by Observed Photospheric Motions: Application to the Coronal Heating and Spicule Formation

    Science.gov (United States)

    Matsumoto, Takuma; Shibata, Kazunari

    We have performed MHD simulations of Alfven wave propagation along an open ux tube in the solar atmosphere. In our numerical model, Alfven waves are generated by the photospheric granular motion. As the wave generator, we used a derived temporal spectrum of the photo-spheric granular motion from G-band movies of Hinode/SOT. It is shown that the total energy ux at the corona becomes larger and the transition region height becomes higher in the case when we use the observed spectrum rather than white/pink noise spectrum as the wave gener-ator. This difference can be explained by the Alfven wave resonance between the photosphere and the transition region. After performing Fourier analysis on our numerical results, we have found that the region between the photosphere and the transition region becomes an Alfven wave resonant cavity. We have conrmed that there are at least three resonant frequencies, 1, 3 and 5 mHz, in our numerical model. Alfven wave resonance is one of the most effective mechanisms to explain the dynamics of the spicules and the sufficient energy ux to heat the corona.

  6. Simultaneously constraining the astrophysics of reionisation and the epoch of heating with 21CMMC

    Science.gov (United States)

    Greig, Bradley; Mesinger, Andrei

    2018-05-01

    We extend our MCMC sampler of 3D EoR simulations, 21CMMC, to perform parameter estimation directly on light-cones of the cosmic 21cm signal. This brings theoretical analysis one step closer to matching the expected 21-cm signal from next generation interferometers like HERA and the SKA. Using the light-cone version of 21CMMC, we quantify biases in the recovered astrophysical parameters obtained from the 21cm power spectrum when using the co-eval approximation to fit a mock 3D light-cone observation. While ignoring the light-cone effect does not bias the parameters under most assumptions, it can still underestimate their uncertainties. However, significant biases (~few - 10 σ) are possible if all of the following conditions are met: (i) foreground removal is very efficient, allowing large physical scales (k ~ 0.1 Mpc-1) to be used in the analysis; (ii) theoretical modelling is accurate to ~10 per cent in the power spectrum amplitude; and (iii) the 21cm signal evolves rapidly (i.e. the epochs of reionisation and heating overlap significantly

  7. Trans-generational plasticity in response to immune challenge is constrained by heat stress.

    Science.gov (United States)

    Roth, Olivia; Landis, Susanne H

    2017-06-01

    Trans-generational plasticity (TGP) is the adjustment of phenotypes to changing habitat conditions that persist longer than the individual lifetime. Fitness benefits (adaptive TGP) are expected upon matching parent-offspring environments. In a global change scenario, several performance-related environmental factors are changing simultaneously. This lowers the predictability of offspring environmental conditions, potentially hampering the benefits of TGP. For the first time, we here explore how the combination of an abiotic and a biotic environmental factor in the parental generation plays out as trans-generational effect in the offspring. We fully reciprocally exposed the parental generation of the pipefish Syngnathus typhle to an immune challenge and elevated temperatures simulating a naturally occurring heatwave. Upon mating and male pregnancy, offspring were kept in ambient or elevated temperature regimes combined with a heat-killed bacterial epitope treatment. Differential gene expression (immune genes and DNA- and histone-modification genes) suggests that the combined change of an abiotic and a biotic factor in the parental generation had interactive effects on offspring performance, the temperature effect dominated over the immune challenge impact. The benefits of certain parental environmental conditions on offspring performance did not sum up when abiotic and biotic factors were changed simultaneously supporting that available resources that can be allocated to phenotypic trans-generational effects are limited. Temperature is the master regulator of trans-generational phenotypic plasticity, which potentially implies a conflict in the allocation of resources towards several environmental factors. This asks for a reassessment of TGP as a short-term option to buffer environmental variation in the light of climate change.

  8. Inverse problem to constrain the controlling parameters of large-scale heat transport processes: The Tiberias Basin example

    Science.gov (United States)

    Goretzki, Nora; Inbar, Nimrod; Siebert, Christian; Möller, Peter; Rosenthal, Eliyahu; Schneider, Michael; Magri, Fabien

    2015-04-01

    Salty and thermal springs exist along the lakeshore of the Sea of Galilee, which covers most of the Tiberias Basin (TB) in the northern Jordan- Dead Sea Transform, Israel/Jordan. As it is the only freshwater reservoir of the entire area, it is important to study the salinisation processes that pollute the lake. Simulations of thermohaline flow along a 35 km NW-SE profile show that meteoric and relic brines are flushed by the regional flow from the surrounding heights and thermally induced groundwater flow within the faults (Magri et al., 2015). Several model runs with trial and error were necessary to calibrate the hydraulic conductivity of both faults and major aquifers in order to fit temperature logs and spring salinity. It turned out that the hydraulic conductivity of the faults ranges between 30 and 140 m/yr whereas the hydraulic conductivity of the Upper Cenomanian aquifer is as high as 200 m/yr. However, large-scale transport processes are also dependent on other physical parameters such as thermal conductivity, porosity and fluid thermal expansion coefficient, which are hardly known. Here, inverse problems (IP) are solved along the NW-SE profile to better constrain the physical parameters (a) hydraulic conductivity, (b) thermal conductivity and (c) thermal expansion coefficient. The PEST code (Doherty, 2010) is applied via the graphical interface FePEST in FEFLOW (Diersch, 2014). The results show that both thermal and hydraulic conductivity are consistent with the values determined with the trial and error calibrations. Besides being an automatic approach that speeds up the calibration process, the IP allows to cover a wide range of parameter values, providing additional solutions not found with the trial and error method. Our study shows that geothermal systems like TB are more comprehensively understood when inverse models are applied to constrain coupled fluid flow processes over large spatial scales. References Diersch, H.-J.G., 2014. FEFLOW Finite

  9. MULTIDIMENSIONAL MODELING OF CORONAL RAIN DYNAMICS

    Energy Technology Data Exchange (ETDEWEB)

    Fang, X.; Xia, C.; Keppens, R. [Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, B-3001 Leuven (Belgium)

    2013-07-10

    We present the first multidimensional, magnetohydrodynamic simulations that capture the initial formation and long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host a chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes of physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into V-shaped features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views of blobs that evaporate in situ or are siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys of coronal rain showers in true multidimensional settings to connect parameterized heating prescriptions with rain statistics, ultimately allowing us to quantify the coronal heating input.

  10. MULTIDIMENSIONAL MODELING OF CORONAL RAIN DYNAMICS

    International Nuclear Information System (INIS)

    Fang, X.; Xia, C.; Keppens, R.

    2013-01-01

    We present the first multidimensional, magnetohydrodynamic simulations that capture the initial formation and long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host a chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes of physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into V-shaped features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views of blobs that evaporate in situ or are siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys of coronal rain showers in true multidimensional settings to connect parameterized heating prescriptions with rain statistics, ultimately allowing us to quantify the coronal heating input.

  11. Formation of coronal cavities

    International Nuclear Information System (INIS)

    An, C.H.; Suess, S.T.; Tandberg-Hanssen, E.; Steinolfson, R.S.

    1986-01-01

    A theoretical study of the formation of a coronal cavity and its relation to a quiescent prominence is presented. It is argued that the formation of a cavity is initiated by the condensation of plasma which is trapped by the coronal magnetic field in a closed streamer and which then flows down to the chromosphere along the field lines due to lack of stable magnetic support against gravity. The existence of a coronal cavity depends on the coronal magnetic field strength; with low strength, the plasma density is not high enough for condensation to occur. Furthermore, we suggest that prominence and cavity material is supplied from the chromospheric level. Whether a coronal cavity and a prominence coexist depends on the magnetic field configuration; a prominence requires stable magnetic support

  12. The physical structure of coronal holes

    International Nuclear Information System (INIS)

    Pneuman, G.W.

    1978-11-01

    The longitudinal geometrical structure of solar wind streams as observed at the orbit of earth is governed by two mechanisms - solar rotation and, most importantly, the geometry of the inner coronal magnetic fields. Here, we study the influence of the latter for the polar coronal hole observed by Skylab in 1973 and modeled by Munro and Jackson (1977). The influence of coronal heating on the properties of the solar wind in this geometry is also investigated. To do this, a crude exponentially damped heating function similar to that used by Kopp and Orrall (1976) is introduced into the solar wind equations. We find that increased heating produces higher temperatures in the inner corona but has little effect upon the temperature at 1 A.U. However, the density at 1 A.U. is increased significantly due to the increase in scale height. The most surprising consequence of coronal heating is its effect on the solar wind velocity, being that the velocity at 1 A.U. is actually decreased by heating in the inner corona. Physical reasons for this effect are discussed. (orig./WL) [de

  13. Critical Magnetic Field Strengths for Unipolar Solar Coronal Plumes In Quiet Regions and Coronal Holes?

    Science.gov (United States)

    Avallone, Ellis; Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; Winebarger, Amy

    2017-01-01

    Coronal plumes are bright magnetic funnels that are found in quiet regions and coronal holes that extend high into the solar corona whose lifetimes can last from hours to days. The heating processes that make plumes bright involve the magnetic field at the base of the plume, but their intricacies remain mysterious. Raouafi et al. (2014) infer from observation that plume heating is a consequence of magnetic reconnection at the base, whereas Wang et al. (2016) infer that plume heating is a result of convergence of the magnetic flux at the plume's base, or base flux. Both papers suggest that the base flux in their plumes is of mixed polarity, but do not quantitatively measure the base flux or consider whether a critical magnetic field strength is required for plume production. To investigate the magnetic origins of plume heating, we track plume luminosity in the 171 Å wavelength as well as the abundance and strength of the base flux over the lifetimes of six unipolar coronal plumes. Of these, three are in coronal holes and three are in quiet regions. For this sample, we find that plume heating is triggered when convergence of the base flux surpasses a field strength of approximately 300 - 500 Gauss, and that the luminosity of both quiet region and coronal hole plumes respond similarly to the strength of the magnetic field in the base.

  14. Coronal rain in magnetic bipolar weak fields

    Science.gov (United States)

    Xia, C.; Keppens, R.; Fang, X.

    2017-07-01

    Aims: We intend to investigate the underlying physics for the coronal rain phenomenon in a representative bipolar magnetic field, including the formation and the dynamics of coronal rain blobs. Methods: With the MPI-AMRVAC code, we performed three dimensional radiative magnetohydrodynamic (MHD) simulation with strong heating localized on footpoints of magnetic loops after a relaxation to quiet solar atmosphere. Results: Progressive cooling and in-situ condensation starts at the loop top due to radiative thermal instability. The first large-scale condensation on the loop top suffers Rayleigh-Taylor instability and becomes fragmented into smaller blobs. The blobs fall vertically dragging magnetic loops until they reach low-β regions and start to fall along the loops from loop top to loop footpoints. A statistic study of the coronal rain blobs finds that small blobs with masses of less than 1010 g dominate the population. When blobs fall to lower regions along the magnetic loops, they are stretched and develop a non-uniform velocity pattern with an anti-parallel shearing pattern seen to develop along the central axis of the blobs. Synthetic images of simulated coronal rain with Solar Dynamics Observatory Atmospheric Imaging Assembly well resemble real observations presenting dark falling clumps in hot channels and bright rain blobs in a cool channel. We also find density inhomogeneities during a coronal rain "shower", which reflects the observed multi-stranded nature of coronal rain. Movies associated to Figs. 3 and 7 are available at http://www.aanda.org

  15. Can coronal hole spicules reach coronal temperatures?

    Science.gov (United States)

    Madjarska, M. S.; Vanninathan, K.; Doyle, J. G.

    2011-08-01

    Aims: The present study aims to provide observational evidence of whether coronal hole spicules reach coronal temperatures. Methods: We combine multi-instrument co-observations obtained with the SUMER/SoHO and with the EIS/SOT/XRT/Hinode. Results: The analysed three large spicules were found to be comprised of numerous thin spicules that rise, rotate, and descend simultaneously forming a bush-like feature. Their rotation resembles the untwisting of a large flux rope. They show velocities ranging from 50 to 250 kms-1. We clearly associated the red- and blue-shifted emissions in transition region lines not only with rotating but also with rising and descending plasmas. Our main result is that these spicules although very large and dynamic, are not present in the spectral lines formed at temperatures above 300 000 K. Conclusions: In this paper we present the analysis of three Ca ii H large spicules that are composed of numerous dynamic thin spicules but appear as macrospicules in lower resolution EUV images. We found no coronal counterpart of these and smaller spicules. We believe that the identification of phenomena that have very different origins as macrospicules is due to the interpretation of the transition region emission, and especially the He ii emission, wherein both chromospheric large spicules and coronal X-ray jets are present. We suggest that the recent observation of spicules in the coronal AIA/SDO 171 Å and 211 Å channels probably comes from the existence of transition region emission there. Movie is available in electronic form at http://www.aanda.org

  16. Optimizing Global Coronal Magnetic Field Models Using Image-Based Constraints

    Science.gov (United States)

    Jones-Mecholsky, Shaela I.; Davila, Joseph M.; Uritskiy, Vadim

    2016-01-01

    The coronal magnetic field directly or indirectly affects a majority of the phenomena studied in the heliosphere. It provides energy for coronal heating, controls the release of coronal mass ejections, and drives heliospheric and magnetospheric activity, yet the coronal magnetic field itself has proven difficult to measure. This difficulty has prompted a decades-long effort to develop accurate, timely, models of the field, an effort that continues today. We have developed a method for improving global coronal magnetic field models by incorporating the type of morphological constraints that could be derived from coronal images. Here we report promising initial tests of this approach on two theoretical problems, and discuss opportunities for application.

  17. Solar wind acceleration in coronal holes

    International Nuclear Information System (INIS)

    Kopp, R.A.

    1978-01-01

    Past attempts to explain the large solar wind velocities in high speed streams by theoretical models of the expansion have invoked either extended nonthermal heating of the corona, heat flux inhibition, or direct addition of momentum to the expanding coronal plasma. Several workers have shown that inhibiting the heat flux at low coronal densities is probably not adequate to explain quantitatively the observed plasma velocities in high speed streams. It stressed that, in order to account for both these large plasma velocities and the low densities found in coronal holes (from which most high speed streams are believed to emanate), extended heating by itself will not suffice. One needs a nonthermal mechanism to provide the bulk acceleration of the high wind plasma close to the sun, and the most likely candidate at present is direct addition of the momentum carried by outward-propagating waves to the expanding corona. Some form of momentum addition appears to be absolutely necessary if one hopes to build quantitatively self-consistent models of coronal holes and high speed solar wind streams

  18. THE CORONAL LOOP INVENTORY PROJECT: EXPANDED ANALYSIS AND RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Schmelz, J. T. [USRA, 7178 Columbia Gateway Drive, Columbia, MD 21046 (United States); Christian, G. M.; Chastain, R. A., E-mail: jschmelz@usra.edu [Physics Department, University of Memphis, Memphis, TN 38152 (United States)

    2016-11-10

    We have expanded upon earlier work that investigates the relative importance of coronal loops with isothermal versus multithermal cross-field temperature distributions. These results are important for determining if loops have substructure in the form of unresolved magnetic strands. We have increased the number of loops targeted for temperature analysis from 19 to 207 with the addition of 188 new loops from multiple regions. We selected all loop segments visible in the 171 Å images of the Atmospheric Imaging Assembly (AIA) that had a clean background. Eighty-six of the new loops were rejected because they could not be reliably separated from the background in other AIA filters. Sixty-one loops required multithermal models to reproduce the observations. Twenty-eight loops were effectively isothermal, that is, the plasma emission to which AIA is sensitive could not be distinguished from isothermal emission, within uncertainties. Ten loops were isothermal. Also, part of our inventory was one small flaring loop, one very cool loop whose temperature distribution could not be constrained by the AIA data, and one loop with inconclusive results. Our survey can confirm an unexpected result from the pilot study: we found no isothermal loop segments where we could properly use the 171-to-193 ratio method, which would be similar to the analysis done for many loops observed with TRACE and EIT. We recommend caution to observers who assume the loop plasma is isothermal, and hope that these results will influence the direction of coronal heating models and the effort modelers spend on various heating scenarios.

  19. Simulating coronal condensation dynamics in 3D

    Science.gov (United States)

    Moschou, S. P.; Keppens, R.; Xia, C.; Fang, X.

    2015-12-01

    We present numerical simulations in 3D settings where coronal rain phenomena take place in a magnetic configuration of a quadrupolar arcade system. Our simulation is a magnetohydrodynamic simulation including anisotropic thermal conduction, optically thin radiative losses, and parametrised heating as main thermodynamical features to construct a realistic arcade configuration from chromospheric to coronal heights. The plasma evaporation from chromospheric and transition region heights eventually causes localised runaway condensation events and we witness the formation of plasma blobs due to thermal instability, that evolve dynamically in the heated arcade part and move gradually downwards due to interchange type dynamics. Unlike earlier 2.5D simulations, in this case there is no large scale prominence formation observed, but a continuous coronal rain develops which shows clear indications of Rayleigh-Taylor or interchange instability, that causes the denser plasma located above the transition region to fall down, as the system moves towards a more stable state. Linear stability analysis is used in the non-linear regime for gaining insight and giving a prediction of the system's evolution. After the plasma blobs descend through interchange, they follow the magnetic field topology more closely in the lower coronal regions, where they are guided by the magnetic dips.

  20. Nonlinear Force-free Coronal Magnetic Stereoscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chifu, Iulia; Wiegelmann, Thomas; Inhester, Bernd, E-mail: chifu@mps.mpg.de [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2017-03-01

    Insights into the 3D structure of the solar coronal magnetic field have been obtained in the past by two completely different approaches. The first approach are nonlinear force-free field (NLFFF) extrapolations, which use photospheric vector magnetograms as boundary condition. The second approach uses stereoscopy of coronal magnetic loops observed in EUV coronal images from different vantage points. Both approaches have their strengths and weaknesses. Extrapolation methods are sensitive to noise and inconsistencies in the boundary data, and the accuracy of stereoscopy is affected by the ability of identifying the same structure in different images and by the separation angle between the view directions. As a consequence, for the same observational data, the 3D coronal magnetic fields computed with the two methods do not necessarily coincide. In an earlier work (Paper I) we extended our NLFFF optimization code by including stereoscopic constrains. The method was successfully tested with synthetic data, and within this work, we apply the newly developed code to a combined data set from SDO /HMI, SDO /AIA, and the two STEREO spacecraft. The extended method (called S-NLFFF) contains an additional term that monitors and minimizes the angle between the local magnetic field direction and the orientation of the 3D coronal loops reconstructed by stereoscopy. We find that when we prescribe the shape of the 3D stereoscopically reconstructed loops, the S-NLFFF method leads to a much better agreement between the modeled field and the stereoscopically reconstructed loops. We also find an appreciable decrease by a factor of two in the angle between the current and the magnetic field. This indicates the improved quality of the force-free solution obtained by S-NLFFF.

  1. Solar Coronal Structure Study

    Science.gov (United States)

    Nitta, Nariaki; Bruner, Marilyn E.; Saba, Julia; Strong, Keith; Harvey, Karen

    2000-01-01

    The subject of this investigation is to study the physics of the solar corona through the analysis of the EUV and UV data produced by two flights (12 May 1992 and 25 April 1994) of the Lockheed Solar Plasma Diagnostics Experiment (SPDE) sounding rocket payload, in combination with Yohkoh and ground-based data. Each rocket flight produced both spectral and imaging data. These joint datasets are useful for understanding the physical state of various features in the solar atmosphere at different heights ranging from the photosphere to the corona at the time of the, rocket flights, which took place during the declining phase of a solar cycle, 2-4 years before the minimum. The investigation is narrowly focused on comparing the physics of small- and medium-scale strong-field structures with that of large-scale, weak fields. As we close th is investigation, we have to recall that our present position in the understanding of basic solar physics problems (such as coronal heating) is much different from that in 1995 (when we proposed this investigation), due largely to the great success of SOHO and TRACE. In other words, several topics and techniques we proposed can now be better realized with data from these missions. For this reason, at some point of our work, we started concentrating on the 1992 data, which are more unique and have more supporting data. As a result, we discontinued the investigation on small-scale structures, i.e., bright points, since high-resolution TRACE images have addressed more important physics than SPDE EUV images could do. In the final year, we still spent long time calibrating the 1992 data. The work was complicated because of the old-fashioned film, which had problems not encountered with more modern CCD detectors. After our considerable effort on calibration, we were able to focus on several scientific topics, relying heavily on the SPDE UV images. They include the relation between filaments and filament channels, the identification of hot

  2. Constraining Parameter Uncertainty in Simulations of Water and Heat Dynamics in Seasonally Frozen Soil Using Limited Observed Data

    Directory of Open Access Journals (Sweden)

    Mousong Wu

    2016-02-01

    Full Text Available Water and energy processes in frozen soils are important for better understanding hydrologic processes and water resources management in cold regions. To investigate the water and energy balance in seasonally frozen soils, CoupModel combined with the generalized likelihood uncertainty estimation (GLUE method was used. Simulation work on water and heat processes in frozen soil in northern China during the 2012/2013 winter was conducted. Ensemble simulations through the Monte Carlo sampling method were generated for uncertainty analysis. Behavioral simulations were selected based on combinations of multiple model performance index criteria with respect to simulated soil water and temperature at four depths (5 cm, 15 cm, 25 cm, and 35 cm. Posterior distributions for parameters related to soil hydraulic, radiation processes, and heat transport indicated that uncertainties in both input and model structures could influence model performance in modeling water and heat processes in seasonally frozen soils. Seasonal courses in water and energy partitioning were obvious during the winter. Within the day-cycle, soil evaporation/condensation and energy distributions were well captured and clarified as an important phenomenon in the dynamics of the energy balance system. The combination of the CoupModel simulations with the uncertainty-based calibration method provides a way of understanding the seasonal courses of hydrology and energy processes in cold regions with limited data. Additional measurements may be used to further reduce the uncertainty of regulating factors during the different stages of freezing–thawing.

  3. Coronal mass ejections and coronal structures

    International Nuclear Information System (INIS)

    Hildner, E.; Bassi, J.; Bougeret, J.L.

    1986-01-01

    Research on coronal mass ejections (CMF) took a variety of forms, both observational and theoretical. On the observational side there were: case studies of individual events, in which it was attempted to provide the most complete descriptions possible, using correlative observations in diverse wavelengths; statistical studies of the properties of CMEs and their associated activity; observations which may tell us about the initiation of mass ejections; interplanetary observations of associated shocks and energetic particles; observations of CMEs traversing interplanetary space; and the beautiful synoptic charts which show to what degree mass ejections affect the background corona and how rapidly (if at all) the corona recovers its pre-disturbance form. These efforts are described in capsule form with an emphasis on presenting pictures, graphs, and tables so that the reader can form a personal appreciation of the work and its results

  4. Temperature Structure of a Coronal Cavity

    Science.gov (United States)

    Kucera, T. A.; Gibson, S. E.; Schmit, D. J.

    2011-01-01

    we analyze the temperature structure of a coronal cavity observed in Aug. 2007. coronal cavities are long, low-density structures located over filament neutral lines and are often seen as dark elliptical features at the solar limb in white light, EUV and x-rays. when these structures erupt they form the cavity portions of CMEs. It is important to establish the temperature structure of cavities in order to understand the thermodynamics of cavities in relation to their three-dimensional magnetic structure. To analyze the temperature we compare temperature ratios of a series of iron lines observed by the Hinode/EUv Imaging spectrometer (EIS). We also use those lines to constrain a forward model of the emission from the cavity and streamer. The model assumes a coronal streamer with a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel lenth. Temperature and density can be varied as a function of altitude both in the cavity and streamer. The general cavity morphology and the cavity and streamer density have already been modeled using data from STEREO's SECCHI/EUVI and Hinode/EIS (Gibson et al 2010 and Schmit & Gibson 2011).

  5. Coronal Mass Ejections

    CERN Document Server

    Kunow, H; Linker, J. A; Schwenn, R; Steiger, R

    2006-01-01

    It is well known that the Sun gravitationally controls the orbits of planets and minor bodies. Much less known, however, is the domain of plasma fields and charged particles in which the Sun governs a heliosphere out to a distance of about 15 billion kilometers. What forces activates the Sun to maintain this power? Coronal Mass Ejections (CMEs) and their descendants are the troops serving the Sun during high solar activity periods. This volume offers a comprehensive and integrated overview of our present knowledge and understanding of Coronal Mass Ejections (CMEs) and their descendants, Interplanetary CMEs (ICMEs). It results from a series of workshops held between 2000 and 2004. An international team of about sixty experimenters involved e.g. in the SOHO, ULYSSES, VOYAGER, PIONEER, HELIOS, WIND, IMP, and ACE missions, ground observers, and theoreticians worked jointly on interpreting the observations and developing new models for CME initiations, development, and interplanetary propagation. The book provides...

  6. Long-period Intensity Pulsations in Coronal Loops Explained by Thermal Non-equilibrium Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Froment, C.; Auchère, F.; Bocchialini, K.; Buchlin, E.; Solomon, J. [Institut d’Astrophysique Spatiale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 121, F-91405 Orsay cedex (France); Aulanier, G. [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, F-92195 Meudon (France); Mikić, Z., E-mail: clara.froment@astro.uio.no [Predictive Science, Inc., San Diego, CA 92121 (United States)

    2017-02-01

    In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit us to strongly constrain heating scenarios. While TNE is currently the standard interpretation of coronal rain, the long-term periodic evolution predicted by simulations has never been observed. However, the detection of long-period intensity pulsations (periods of several hours) has been recently reported with the Solar and Heliospheric Observatory /EIT, and this phenomenon appears to be very common in loops. Moreover, the three intensity-pulsation events that we recently studied with the Solar Dynamics Observatory /Atmospheric Imaging Assembly (AIA) show strong evidence for TNE in warm loops. In this paper, a realistic loop geometry from linear force-free field (LFFF) extrapolations is used as input to 1D hydrodynamic simulations. Our simulations show that, for the present loop geometry, the heating has to be asymmetrical to produce TNE. We analyze in detail one particular simulation that reproduces the average thermal behavior of one of the pulsating loop bundle observed with AIA. We compare the properties of this simulation with those deduced from the observations. The magnetic topology of the LFFF extrapolations points to the presence of sites of preferred reconnection at one footpoint, supporting the presence of asymmetric heating. In addition, we can reproduce the temporal large-scale intensity properties of the pulsating loops. This simulation further strengthens the interpretation of the observed pulsations as signatures of TNE. This consequently provides important information on the heating localization and timescale for these loops.

  7. BAYESIAN MAGNETOHYDRODYNAMIC SEISMOLOGY OF CORONAL LOOPS

    International Nuclear Information System (INIS)

    Arregui, I.; Asensio Ramos, A.

    2011-01-01

    We perform a Bayesian parameter inference in the context of resonantly damped transverse coronal loop oscillations. The forward problem is solved in terms of parametric results for kink waves in one-dimensional flux tubes in the thin tube and thin boundary approximations. For the inverse problem, we adopt a Bayesian approach to infer the most probable values of the relevant parameters, for given observed periods and damping times, and to extract their confidence levels. The posterior probability distribution functions are obtained by means of Markov Chain Monte Carlo simulations, incorporating observed uncertainties in a consistent manner. We find well-localized solutions in the posterior probability distribution functions for two of the three parameters of interest, namely the Alfven travel time and the transverse inhomogeneity length scale. The obtained estimates for the Alfven travel time are consistent with previous inversion results, but the method enables us to additionally constrain the transverse inhomogeneity length scale and to estimate real error bars for each parameter. When observational estimates for the density contrast are used, the method enables us to fully constrain the three parameters of interest. These results can serve to improve our current estimates of unknown physical parameters in coronal loops and to test the assumed theoretical model.

  8. Energy released by the interaction of coronal magnetic fields

    International Nuclear Information System (INIS)

    Sheeley, N.R. Jr.

    1976-01-01

    Comparisons between coronal spectroheliograms and photospheric magnetograms are presented to support the idea that as coronal magnetic fields interact, a process of field line reconnection usually takes place as a natural way of preventing magnetic stresses from building up in the lower corona. This suggests that the energy which would have been stored in stressed fields in continuously released as kinetic energy of material being driven aside to make way for the reconnecting fields. However, this kinetic energy is negligible compared to the thermal energy of the coronal plasma. Therefore, it appears that these slow adjustments of coronal magnetic fields cannot account for even the normal heating of the corona, much less the energetic events associated with solar flares. (Auth.)

  9. Solar Coronal Jets: Observations, Theory, and Modeling

    Science.gov (United States)

    Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; Devore, C. R.; Archontis, V.; hide

    2016-01-01

    Chromospheric and coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of signicant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of nominal solar ares and Coronal Mass Ejections (CMEs), jets share many common properties with these major phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients closeor at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint to basic process for heating the corona and accelerating the solar wind; consequently their study gives us the opportunity to attack a broadrange of solar-heliospheric problems.

  10. Thermal instabilities in magnetically confined plasmas: Solar coronal loops

    International Nuclear Information System (INIS)

    Habbal, S.R.; Rosner, R.

    1979-01-01

    The thermal stability of confined solar coronal structures (''loops'') is investigated, following both normal mode and a new, global instability analysis. We demonstrate that: (a) normal mode analysis shows modes with size scales comparable to that of loops to be unstable, but to be strongly affected by the loop boundary conditions; (b) a global analysis, based upon variation of the total loop energy losses and gains, yields loop stability conditions for global modes dependent upon the coronal loop heating process, with magnetically coupled heating processes giving marginal stability. The connection between the present analysis and the minimum flux corona of Hearn is also discussed

  11. Statistical model of quiet Sun coronal heating (French Title: Modèle statistique de chauffage de la couronne solaire calme)

    Science.gov (United States)

    Podladchikova, O.

    2002-02-01

    The high temperature of the solar corona is still a puzzling problem of solar physics. However, the recent observations of satellites SoHO, Yohkoh or TRACE seem to indicate that the processes responsible for the heating of the closed regions are situated in the low corona or in the chromosphere, thus close to the sun surface, and are associated to the direct currents dissipation. Statistical data analysis suggest that the heating mechanisms result thus from numerous events of current layers dissipation of small scale and weak energy, on the resolution limit of modern instruments. We propose a statistical lattice model, resulting from an approach more physical than self-organized criticality, constituted by a magnetic energy source at small scales and by dissipation mechanisms of the currents, which can be associated either to magnetic reconnection or to anomalous resistivity. The various types of sources and mechanisms of dissipation allow to study their influence on the statistical properties of the system, in particular on the energy dissipation. With the aim of quantifying this behavior and allowing detailed comparisons between models and observations, analysis techniques little used in solar physics, such as the singular values decomposition, entropies, or Pearson technique of PDF classification are introduced and applied to the study of the spatial and temporal properties of the model. La température anormalement élevée de la couronne reste un des problèmes majeurs de la physique solaire. Toutefois, les observations récentes des satellites SoHO, Yohkoh ou TRACE semblent indiquer que les processus responsables du chauffage des régions fermées se situent dans la basse couronne ou dans la chromosphère, donc proches de la surface solaire, et sont associés à la dissipation de couches de courant continu. L'analyse statistique de données suggère que les mécanismes de chauffage résulteraient donc de nombreux événements de dissipation de couches de

  12. Evolving Coronal Holes and Interplanetary Erupting Stream ...

    Indian Academy of Sciences (India)

    prominences, have a significantly higher rate of occurrence in the vicinity of coronal .... coronal holes due to the birth of new holes or the growth of existing holes. .... Statistics of newly formed coronal hole areas (NFOCHA) associated with ...

  13. Fermi/LAT observations of dwarf galaxies highly constrain a dark matter interpretation of excess positrons seen in AMS-02, HEAT, and PAMELA

    Energy Technology Data Exchange (ETDEWEB)

    López, Alejandro [Michigan Center for Theoretical Physics, University of Michigan – Ann Arbor, 450 Church St., Ann Arbor (United States); Savage, Christopher [Nordita (Nordic Institute for Theoretical Physics), KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, Stockholm (Sweden); Spolyar, Douglas; Adams, Douglas Q., E-mail: aolopez@umich.edu, E-mail: chris@savage.name, E-mail: dspolyar@gmail.com, E-mail: doug.q.adams@gmail.com [Oskar Klein Centre for Cosmoparticle Physics, Stockholm University, Roslagstullsbacken 23, Roslagstullsbacken 21, Stockholm (Sweden)

    2016-03-01

    It is shown that a Weakly Interacting Massive dark matter Particle (WIMP) interpretation for the positron excess observed in a variety of experiments, HEAT, PAMELA, and AMS-02, is highly constrained by the Fermi/LAT observations of dwarf galaxies. In particular, this paper examines the annihilation channels that best fit the current AMS-02 data (Boudaud et al., 2014), specifically focusing on channels and parameter space not previously explored by the Fermi/LAT collaboration. The Fermi satellite has surveyed the γ-ray sky, and its observations of dwarf satellites are used to place strong bounds on the annihilation of WIMPs into a variety of channels. For the single channel case, we find that dark matter annihilation into (b b-bar ,e{sup +}e{sup -}, μ{sup +}μ{sup -}, τ{sup +}τ{sup -},4-e or 4-τ ) is ruled out as an explanation of the AMS positron excess (here b quarks are a proxy for all quarks, gauge and Higgs bosons). In addition, we find that the Fermi/LAT 2σ upper limits, assuming the best-fit AMS-02 branching ratios, exclude multichannel combinations into b b-bar and leptons. The tension between the results might relax if the branching ratios are allowed to deviate from their best-fit values, though a substantial change would be required. Of all the channels we considered, the only viable channel that survives the Fermi/LAT constraint and produces a good fit to the AMS-02 data is annihilation (via a mediator) to 4-μ, or mainly to 4-μ in the case of multichannel combinations.

  14. THE CONTRIBUTION OF CORONAL JETS TO THE SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Lionello, R.; Török, T.; Titov, V. S.; Mikić, Z.; Linker, J. A. [Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States); Leake, J. E.; Linton, M. G., E-mail: lionel@predsci.com [US Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375 (United States)

    2016-11-01

    Transient collimated plasma eruptions in the solar corona, commonly known as coronal (or X-ray) jets, are among the most interesting manifestations of solar activity. It has been suggested that these events contribute to the mass and energy content of the corona and solar wind, but the extent of these contributions remains uncertain. We have recently modeled the formation and evolution of coronal jets using a three-dimensional (3D) magnetohydrodynamic (MHD) code with thermodynamics in a large spherical domain that includes the solar wind. Our model is coupled to 3D MHD flux-emergence simulations, i.e., we use boundary conditions provided by such simulations to drive a time-dependent coronal evolution. The model includes parametric coronal heating, radiative losses, and thermal conduction, which enables us to simulate the dynamics and plasma properties of coronal jets in a more realistic manner than done so far. Here, we employ these simulations to calculate the amount of mass and energy transported by coronal jets into the outer corona and inner heliosphere. Based on observed jet-occurrence rates, we then estimate the total contribution of coronal jets to the mass and energy content of the solar wind to (0.4–3.0)% and (0.3–1.0)%, respectively. Our results are largely consistent with the few previous rough estimates obtained from observations, supporting the conjecture that coronal jets provide only a small amount of mass and energy to the solar wind. We emphasize, however, that more advanced observations and simulations (including parametric studies) are needed to substantiate this conjecture.

  15. Constrained consequence

    CSIR Research Space (South Africa)

    Britz, K

    2011-09-01

    Full Text Available their basic properties and relationship. In Section 3 we present a modal instance of these constructions which also illustrates with an example how to reason abductively with constrained entailment in a causal or action oriented context. In Section 4 we... of models with the former approach, whereas in Section 3.3 we give an example illustrating ways in which C can be de ned with both. Here we employ the following versions of local consequence: De nition 3.4. Given a model M = hW;R;Vi and formulas...

  16. Interpretation of coronal synoptic observations

    International Nuclear Information System (INIS)

    Munro, R.H.; Fisher, R.R.

    1986-01-01

    Three-dimensional reconstruction techniques used to determine coronal density distributions from synoptic data are complicated and time consuming to employ. Current techniques also assume time invariant structures and thus mix both temporal and spatial variations present in the coronal data. The observed distribution of polarized brightness, pB, and brightness, B, of coronal features observed either at eclipses or with coronagraphs depends upon both the three-dimensional distribution of electron density within the structure and the location of the feature with respect to the plane-of-the-sky. By theoretically studying the signature of various coronal structures as they would appear during a limb transit, it is possible to recognize these patterns in real synoptic data as well as estimate temporal evolutionary effects

  17. Constrained Vapor Bubble Experiment

    Science.gov (United States)

    Gokhale, Shripad; Plawsky, Joel; Wayner, Peter C., Jr.; Zheng, Ling; Wang, Ying-Xi

    2002-11-01

    Microgravity experiments on the Constrained Vapor Bubble Heat Exchanger, CVB, are being developed for the International Space Station. In particular, we present results of a precursory experimental and theoretical study of the vertical Constrained Vapor Bubble in the Earth's environment. A novel non-isothermal experimental setup was designed and built to study the transport processes in an ethanol/quartz vertical CVB system. Temperature profiles were measured using an in situ PC (personal computer)-based LabView data acquisition system via thermocouples. Film thickness profiles were measured using interferometry. A theoretical model was developed to predict the curvature profile of the stable film in the evaporator. The concept of the total amount of evaporation, which can be obtained directly by integrating the experimental temperature profile, was introduced. Experimentally measured curvature profiles are in good agreement with modeling results. For microgravity conditions, an analytical expression, which reveals an inherent relation between temperature and curvature profiles, was derived.

  18. Petrologically-constrained thermo-chemical modelling of cratonic upper mantle consistent with elevation, geoid, surface heat flow, seismic surface waves and MT data

    Science.gov (United States)

    Jones, A. G.; Afonso, J. C.

    2015-12-01

    The Earth comprises a single physio-chemical system that we interrogate from its surface and/or from space making observations related to various physical and chemical parameters. A change in one of those parameters affects many of the others; for example a change in velocity is almost always indicative of a concomitant change in density, which results in changes to elevation, gravity and geoid observations. Similarly, a change in oxide chemistry affects almost all physical parameters to a greater or lesser extent. We have now developed sophisticated tools to model/invert data in our individual disciplines to such an extent that we are obtaining high resolution, robust models from our datasets. However, in the vast majority of cases the different datasets are modelled/inverted independently of each other, and often even without considering other data in a qualitative sense. The LitMod framework of Afonso and colleagues presents integrated inversion of geoscientific data to yield thermo-chemical models that are petrologically consistent and constrained. Input data can comprise any combination of elevation, geoid, surface heat flow, seismic surface wave (Rayleigh and Love) data and receiver function data, and MT data. The basis of LitMod is characterization of the upper mantle in terms of five oxides in the CFMAS system and a thermal structure that is conductive to the LAB and convective along the adiabat below the LAB to the 410 km discontinuity. Candidate solutions are chosen from prior distributions of the oxides. For the crust, candidate solutions are chosen from distributions of crustal layering, velocity and density parameters. Those candidate solutions that fit the data within prescribed error limits are kept, and are used to establish broad posterior distributions from which new candidate solutions are chosen. Examples will be shown of application of this approach fitting data from the Kaapvaal Craton in South Africa and the Rae Craton in northern Canada. I

  19. Solar Coronal Plumes

    Directory of Open Access Journals (Sweden)

    Giannina Poletto

    2015-12-01

    Full Text Available Polar plumes are thin long ray-like structures that project beyond the limb of the Sun polar regions, maintaining their identity over distances of several solar radii. Plumes have been first observed in white-light (WL images of the Sun, but, with the advent of the space era, they have been identified also in X-ray and UV wavelengths (XUV and, possibly, even in in situ data. This review traces the history of plumes, from the time they have been first imaged, to the complex means by which nowadays we attempt to reconstruct their 3-D structure. Spectroscopic techniques allowed us also to infer the physical parameters of plumes and estimate their electron and kinetic temperatures and their densities. However, perhaps the most interesting problem we need to solve is the role they cover in the solar wind origin and acceleration: Does the solar wind emanate from plumes or from the ambient coronal hole wherein they are embedded? Do plumes have a role in solar wind acceleration and mass loading? Answers to these questions are still somewhat ambiguous and theoretical modeling does not provide definite answers either. Recent data, with an unprecedented high spatial and temporal resolution, provide new information on the fine structure of plumes, their temporal evolution and relationship with other transient phenomena that may shed further light on these elusive features.

  20. Coronal seismology waves and oscillations in stellar coronae

    CERN Document Server

    Stepanov, Alexander; Nakariakov, Valery M

    2012-01-01

    This concise and systematic account of the current state of this new branch of astrophysics presents the theoretical foundations of plasma astrophysics, magneto-hydrodynamics and coronal magnetic structures, taking into account the full range of available observation techniques -- from radio to gamma. The book discusses stellar loops during flare energy releases, MHD waves and oscillations, plasma instabilities and heating and charged particle acceleration. Current trends and developments in MHD seismology of solar and stellar coronal plasma systems are also covered, while recent p

  1. MHD modeling of coronal loops: the transition region throat

    Science.gov (United States)

    Guarrasi, M.; Reale, F.; Orlando, S.; Mignone, A.; Klimchuk, J. A.

    2014-04-01

    Context. The expansion of coronal loops in the transition region may considerably influence the diagnostics of the plasma emission measure. The cross-sectional area of the loops is expected to depend on the temperature and pressure, and might be sensitive to the heating rate. Aims: The approach here is to study the area response to slow changes in the coronal heating rate, and check the current interpretation in terms of steady heating models. Methods: We study the area response with a time-dependent 2D magnetohydrodynamic (MHD) loop model, including the description of the expanding magnetic field, coronal heating and losses by thermal conduction, and radiation from optically thin plasma. We run a simulation for a loop 50 Mm long and quasi-statically heated to about 4 MK. Results: We find that the area can change substantially with the quasi-steady heating rate, e.g., by ~40% at 0.5 MK as the loop temperature varies between 1 MK and 4 MK, and, therefore, affects the interpretation of the differential emission measure vs. temperature (DEM(T)) curves. The movie associated to Fig. 4 is available in electronic form at http://www.aanda.org

  2. Comparison of Two Coronal Magnetic Field Models to Reconstruct a Sigmoidal Solar Active Region with Coronal Loops

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Aiying; Zhang, Huai [Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing 100049 (China); Jiang, Chaowei [Institute of Space Science and Applied Technology, Harbin Institute of Technology, Shenzhen, 518055 (China); Hu, Qiang; Gary, G. Allen; Wu, S. T. [Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Cao, Jinbin, E-mail: duanaiying@ucas.ac.cn, E-mail: hzhang@ucas.ac.cn, E-mail: chaowei@hit.edu.cn [School of Space and Environment, Beihang University, Beijing 100191 (China)

    2017-06-20

    Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE–MHD–NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO /AIA. It is found that the CESE–MHD–NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ∼10°. This suggests that the CESE–MHD–NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (∼30°). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.

  3. Density Fluctuations in a Polar Coronal Hole

    Science.gov (United States)

    Hahn, Michael; D’Huys, Elke; Savin, Daniel Wolf

    2018-06-01

    We have measured the root-mean-square (rms) amplitude of intensity fluctuations, ΔI, in plume and interplume regions of a polar coronal hole. These intensity fluctuations correspond to density fluctuations. Using data from the Sun Watcher using the Active Pixel System detector and Image Processing on the Project for Onboard Autonomy (Proba2), our results extend up to a height of about 1.35 R ⊙. One advantage of the rms analysis is that it does not rely on a detailed evaluation of the power spectrum, which is limited by noise levels to low heights in the corona. The rms approach can be performed up to larger heights where the noise level is greater, provided that the noise itself can be quantified. At low heights, both the absolute ΔI, and the amplitude relative to the mean intensity, ΔI/I, decrease with height. However, starting at about 1.2 R ⊙, ΔI/I increases, reaching 20%–40% by 1.35 R ⊙. This corresponds to density fluctuations of Δn e/n e ≈ 10%–20%. The increasing relative amplitude implies that the density fluctuations are generated in the corona itself. One possibility is that the density fluctuations are generated by an instability of Alfvén waves. This generation mechanism is consistent with some theoretical models and with observations of Alfvén wave amplitudes in coronal holes. Although we find that the energy of the observed density fluctuations is small, these fluctuations are likely to play an important indirect role in coronal heating by promoting the reflection of Alfvén waves and driving turbulence.

  4. Coronal Mass Ejections An Introduction

    CERN Document Server

    Howard, Timothy

    2011-01-01

    In times of growing technological sophistication and of our dependence on electronic technology, we are all affected by space weather. In its most extreme form, space weather can disrupt communications, damage and destroy spacecraft and power stations, and increase radiation exposure to astronauts and airline passengers. Major space weather events, called geomagnetic storms, are large disruptions in the Earth’s magnetic field brought about by the arrival of enormous magnetized plasma clouds from the Sun. Coronal mass ejections (CMEs) contain billions of tons of plasma and hurtle through space at speeds of several million miles per hour. Understanding coronal mass ejections and their impact on the Earth is of great interest to both the scientific and technological communities. This book provides an introduction to coronal mass ejections, including a history of their observation and scientific revelations, instruments and theory behind their detection and measurement, and the status quo of theories describing...

  5. Observational Analysis of Coronal Fans

    Science.gov (United States)

    Talpeanu, D.-C.; Rachmeler, L; Mierla, Marilena

    2017-01-01

    Coronal fans (see Figure 1) are bright observational structures that extend to large distances above the solar surface and can easily be seen in EUV (174 angstrom) above the limb. They have a very long lifetime and can live up to several Carrington rotations (CR), remaining relatively stationary for many months. Note that they are not off-limb manifestation of similarly-named active region fans. The solar conditions required to create coronal fans are not well understood. The goal of this research was to find as many associations as possible of coronal fans with other solar features and to gain a better understanding of these structures. Therefore, we analyzed many fans and created an overview of their properties. We present the results of this statistical analysis and also a case study on the longest living fan.

  6. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    Energy Technology Data Exchange (ETDEWEB)

    Kramar, Maxim [Physics Department, The Catholic University of America, Washington, DC (United States); Airapetian, Vladimir [Department of Physics and Astronomy, George Mason University, Fairfax, VA (United States); NASA/Goddard Space Flight Center, Code 671, Greenbelt, MD (United States); Lin, Haosheng, E-mail: vladimir.airapetian@nasa.gov [College of Natural Sciences, Institute for Astronomy, University of Hawaii at Manoa, Pukalani, HI (United States)

    2016-08-09

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 R{sub ⊙} using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 Å band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below ~2.5 R{sub ⊙}. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  7. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    Directory of Open Access Journals (Sweden)

    Maxim Kramar

    2016-08-01

    Full Text Available Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131 to retrieve and analyze the three-dimensional (3D coronal electron density in the range of heights from $1.5$ to $4 R_odot$ using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 AA band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below $sim 2.5 R_odot$. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  8. A Bayesian Approach to Period Searching in Solar Coronal Loops

    Energy Technology Data Exchange (ETDEWEB)

    Scherrer, Bryan; McKenzie, David [Montana State University, P.O. Box 173840 Bozeman, MT 59717-3840 (United States)

    2017-03-01

    We have applied a Bayesian generalized Lomb–Scargle period searching algorithm to movies of coronal loop images obtained with the Hinode X-ray Telescope (XRT) to search for evidence of periodicities that would indicate resonant heating of the loops. The algorithm makes as its only assumption that there is a single sinusoidal signal within each light curve of the data. Both the amplitudes and noise are taken as free parameters. It is argued that this procedure should be used alongside Fourier and wavelet analyses to more accurately extract periodic intensity modulations in coronal loops. The data analyzed are from XRT Observation Program 129C: “MHD Wave Heating (Thin Filters),” which occurred during 2006 November 13 and focused on active region 10293, which included coronal loops. The first data set spans approximately 10 min with an average cadence of 2 s, 2″ per pixel resolution, and used the Al-mesh analysis filter. The second data set spans approximately 4 min with a 3 s average cadence, 1″ per pixel resolution, and used the Al-poly analysis filter. The final data set spans approximately 22 min at a 6 s average cadence, and used the Al-poly analysis filter. In total, 55 periods of sinusoidal coronal loop oscillations between 5.5 and 59.6 s are discussed, supporting proposals in the literature that resonant absorption of magnetic waves is a viable mechanism for depositing energy in the corona.

  9. Coronal ``Wave'': Magnetic Footprint of a Coronal Mass Ejection?

    Science.gov (United States)

    Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal

    2007-02-01

    We investigate the properties of two ``classical'' EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process.

  10. The Fate of Cool Material in the Hot Corona: Solar Prominences and Coronal Rain

    Science.gov (United States)

    Liu, Wei; Antolin, Patrick; Sun, Xudong; Vial, Jean-Claude; Berger, Thomas

    2017-08-01

    As an important chain of the chromosphere-corona mass cycle, some of the million-degree hot coronal mass undergoes a radiative cooling instability and condenses into material at chromospheric or transition-region temperatures in two distinct forms - prominences and coronal rain (some of which eventually falls back to the chromosphere). A quiescent prominence usually consists of numerous long-lasting, filamentary downflow threads, while coronal rain consists of transient mass blobs falling at comparably higher speeds along well-defined paths. It remains puzzling why such material of similar temperatures exhibit contrasting morphologies and behaviors. We report recent SDO/AIA and IRIS observations that suggest different magnetic environments being responsible for such distinctions. Specifically, in a hybrid prominence-coronal rain complex structure, we found that the prominence material is formed and resides near magnetic null points that favor the radiative cooling process and provide possibly a high plasma-beta environment suitable for the existence of meandering prominence threads. As the cool material descends, it turns into coronal rain tied onto low-lying coronal loops in a likely low-beta environment. Such structures resemble to certain extent the so-called coronal spiders or cloud prominences, but the observations reported here provide critical new insights. We will discuss the broad physical implications of these observations for fundamental questions, such as coronal heating and beyond (e.g., in astrophysical and/or laboratory plasma environments).

  11. The dynamics of coronal magnetic structures

    International Nuclear Information System (INIS)

    Weber, W.

    1978-01-01

    An analysis is made of the evolution of coronal magnetic fields due to the interaction with the solar wind. An analysis of the formation of coronal streamers, arising as a result of the stretching of bipolar fields, is given. Numerical simulations of the formation of coronal streamers are presented. Fast-mode shocks as triggers of microturbulence in the solar corona are discussed

  12. Dynamics of Coronal Hole Boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Higginson, A. K.; Zurbuchen, T. H. [Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Antiochos, S. K.; DeVore, C. R. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wyper, P. F. [Universities Space Research Association, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)

    2017-03-10

    Remote and in situ observations strongly imply that the slow solar wind consists of plasma from the hot, closed-field corona that is released onto open magnetic field lines. The Separatrix Web theory for the slow wind proposes that photospheric motions at the scale of supergranules are responsible for generating dynamics at coronal-hole boundaries, which result in the closed plasma release. We use three-dimensional magnetohydrodynamic simulations to determine the effect of photospheric flows on the open and closed magnetic flux of a model corona with a dipole magnetic field and an isothermal solar wind. A rotational surface motion is used to approximate photospheric supergranular driving and is applied at the boundary between the coronal hole and helmet streamer. The resulting dynamics consist primarily of prolific and efficient interchange reconnection between open and closed flux. The magnetic flux near the coronal-hole boundary experiences multiple interchange events, with some flux interchanging over 50 times in one day. Additionally, we find that the interchange reconnection occurs all along the coronal-hole boundary and even produces a lasting change in magnetic-field connectivity in regions that were not driven by the applied motions. Our results show that these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the implications of our simulations for understanding the observed properties of the slow solar wind, with particular focus on the global-scale consequences of interchange reconnection.

  13. MHD aspects of coronal transients

    International Nuclear Information System (INIS)

    Anzer, U.

    1979-10-01

    If one defines coronal transients as events which occur in the solar corona on rapid time scales (< approx. several hours) then one would have to include a large variety of solar phenomena: flares, sprays, erupting prominences, X-ray transients, white light transients, etc. Here we shall focus our attention on the latter two phenomena. (orig.) 891 WL/orig. 892 RDG

  14. Endogenous Magnetic Reconnection in Solar Coronal Loops

    Science.gov (United States)

    Asgari-Targhi, M.; Coppi, B.; Basu, B.; Fletcher, A.; Golub, L.

    2017-12-01

    We propose that a magneto-thermal reconnection process occurring in coronal loops be the source of the heating of the Solar Corona [1]. In the adopted model, magnetic reconnection is associated with electron temperature gradients, anisotropic electron temperature fluctuations and plasma current density gradients [2]. The input parameters for our theoretical model are derived from the most recent observations of the Solar Corona. In addition, the relevant (endogenous) collective modes can produce high energy particle populations. An endogenous reconnection process is defined as being driven by factors internal to the region where reconnection takes place. *Sponsored in part by the U.S. D.O.E. and the Kavli Foundation* [1] Beafume, P., Coppi, B. and Golub, L., (1992) Ap. J. 393, 396. [2] Coppi, B. and Basu, B. (2017) MIT-LNS Report HEP 17/01.

  15. The Coronal Place; Why is It Special?

    Directory of Open Access Journals (Sweden)

    Azhar Alkazwini

    2017-10-01

    Full Text Available To prove the existence of arguments about the exact place that can bear the term ‘coronal’, it would be enough to check the explanatory dictionary’s entry. There are different arguments regarding the exact place of coronal. In this paper, some of the linguistic evidence regarding the coronal place shall be mentioned. Then, I shall discuss the classes of coronal that lend support to the fact that coronal place is believed to be special, and that is by discussing the different typologies of coronal consonants and giving their description.

  16. An equatorial coronal hole at solar minimum

    Science.gov (United States)

    Bromage, B. J. I.; DelZanna, G.; DeForest, C.; Thompson, B.; Clegg, J. R.

    1997-01-01

    The large transequatorial coronal hole that was observed in the solar corona at the end of August 1996 is presented. It consists of a north polar coronal hole called the 'elephant's trunk or tusk'. The observations of this coronal hole were carried out with the coronal diagnostic spectrometer onboard the Solar and Heliospheric Observatory (SOHO). The magnetic field associated with the equatorial coronal hole is strongly connected to that of the active region at its base, resulting in the two features rotating at almost the same rate.

  17. Coronal Seismology: The Search for Propagating Waves in Coronal Loops

    Science.gov (United States)

    Schad, Thomas A.; Seeley, D.; Keil, S. L.; Tomczyk, S.

    2007-05-01

    We report on Doppler observations of the solar corona obtained in the Fe XeXIII 1074.7nm coronal emission line with the HAO Coronal Multi-Channel Polarimeter (CoMP) mounted on the NSO Coronal One Shot coronagraph located in the Hilltop Facility of NSO/Sacramento Peak. The COMP is a tunable filtergraph instrument that records the entire corona from the edge of the occulting disk at approximately 1.03 Rsun out to 1.4 Rsun with a spatial resolution of about 4” x 4”. COMP can be rapidly scanned through the spectral line while recording orthogonal states of linear and circular polarization. The two dimensional spatial resolution allows us to correlate temporal fluctuations observed in one part of the corona with those seen at other locations, in particular along coronal loops. Using cross spectral analysis we find that the observations reveal upward propagating waves that are characterized by Doppler shifts with rms velocities of 0.3 km/s, peak wave power in the 3-5 mHz frequency range, and phase speeds 1-3 Mm/s. The wave trajectories are consistent with the direction of the magnetic field inferred from the linear polarization measurements. We discuss the phase and coherence of these waves as a function of height in the corona and relate our findings to previous observations. The observed waves appear to be Alfvenic in character. "Thomas Schad was supported through the National Solar Observatory Research Experiences for Undergraduate (REU) site program, which is co-funded by the Department of Defense in partnership with the National Science Foundation REU Program." Daniel Seeley was supported through the National Solar Observatory Research Experience for Teachers (RET) site program, which is funded by the National Science Foundation RET program.

  18. Geometric Model of a Coronal Cavity

    Science.gov (United States)

    Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.; hide

    2010-01-01

    We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities

  19. Investigating the Response of Loop Plasma to Nanoflare Heating Using RADYN Simulations

    Science.gov (United States)

    Polito, V.; Testa, P.; Allred, J.; De Pontieu, B.; Carlsson, M.; Pereira, T. M. D.; Gošić, Milan; Reale, Fabio

    2018-04-01

    We present the results of 1D hydrodynamic simulations of coronal loops that are subject to nanoflares, caused by either in situ thermal heating or nonthermal electron (NTE) beams. The synthesized intensity and Doppler shifts can be directly compared with Interface Region Imaging Spectrograph (IRIS) and Atmospheric Imaging Assembly (AIA) observations of rapid variability in the transition region (TR) of coronal loops, associated with transient coronal heating. We find that NTEs with high enough low-energy cutoff ({E}{{C}}) deposit energy in the lower TR and chromosphere, causing blueshifts (up to ∼20 km s‑1) in the IRIS Si IV lines, which thermal conduction cannot reproduce. The {E}{{C}} threshold value for the blueshifts depends on the total energy of the events (≈5 keV for 1024 erg, up to 15 keV for 1025 erg). The observed footpoint emission intensity and flows, combined with the simulations, can provide constraints on both the energy of the heating event and {E}{{C}}. The response of the loop plasma to nanoflares depends crucially on the electron density: significant Si IV intensity enhancements and flows are observed only for initially low-density loops (<109 cm‑3). This provides a possible explanation of the relative scarcity of observations of significant moss variability. While the TR response to single heating episodes can be clearly observed, the predicted coronal emission (AIA 94 Å) for single strands is below current detectability and can only be observed when several strands are heated closely in time. Finally, we show that the analysis of the IRIS Mg II chromospheric lines can help further constrain the properties of the heating mechanisms.

  20. Polarization of Coronal Forbidden Lines

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hao; Qu, Zhongquan [Yunnan Observatories, Chinese Academy of Sciences, Kunming, Yunnan 650011 (China); Landi Degl’Innocenti, Egidio, E-mail: sayahoro@ynao.ac.cn [Dipartimento di Astronomia e Scienza dello Spazio, Università di Firenze, Largo E. Fermi 2, I-50125 Firenze (Italy)

    2017-03-20

    Since the magnetic field is responsible for most manifestations of solar activity, one of the most challenging problems in solar physics is the diagnostics of solar magnetic fields, particularly in the outer atmosphere. To this end, it is important to develop rigorous diagnostic tools to interpret polarimetric observations in suitable spectral lines. This paper is devoted to analyzing the diagnostic content of linear polarization imaging observations in coronal forbidden lines. Although this technique is restricted to off-limb observations, it represents a significant tool to diagnose the magnetic field structure in the solar corona, where the magnetic field is intrinsically weak and still poorly known. We adopt the quantum theory of polarized line formation developed in the framework of the density matrix formalism, and synthesize images of the emergent linear polarization signal in coronal forbidden lines using potential-field source-surface magnetic field models. The influence of electronic collisions, active regions, and Thomson scattering on the linear polarization of coronal forbidden lines is also examined. It is found that active regions and Thomson scattering are capable of conspicuously influencing the orientation of the linear polarization. These effects have to be carefully taken into account to increase the accuracy of the field diagnostics. We also found that linear polarization observation in suitable lines can give valuable information on the long-term evolution of the magnetic field in the solar corona.

  1. Exploitation of the Phebus inquiry. Better qualifying fuel poverty situations: coldness, heating restrictions, payment difficulties of energy bills, constrained limited mobility

    International Nuclear Information System (INIS)

    Ambrosio, Giulia; Belaid, Fateh; Bair, Sabrine; Teissier, Olivier

    2015-01-01

    The object of the research consists in estimating situations of fuel poverty from the statistical analysis of Phebus database 2012. The analysis of thermal characteristics of housing crossed with the uses by cutting down of heating, restriction of mobility and difficulties of payment of energy bills will allow us to anticipate better the phenomenon and to bring adapted answers

  2. Solar Magnetic Carpet III: Coronal Modelling of Synthetic Magnetograms

    Science.gov (United States)

    Meyer, K. A.; Mackay, D. H.; van Ballegooijen, A. A.; Parnell, C. E.

    2013-09-01

    This article is the third in a series working towards the construction of a realistic, evolving, non-linear force-free coronal-field model for the solar magnetic carpet. Here, we present preliminary results of 3D time-dependent simulations of the small-scale coronal field of the magnetic carpet. Four simulations are considered, each with the same evolving photospheric boundary condition: a 48-hour time series of synthetic magnetograms produced from the model of Meyer et al. ( Solar Phys. 272, 29, 2011). Three simulations include a uniform, overlying coronal magnetic field of differing strength, the fourth simulation includes no overlying field. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. In particular, we study their dependence upon the evolution of the photospheric magnetic field and the strength of the overlying coronal field. We also consider where energy is stored and dissipated within the coronal field. The free magnetic energy built up is found to be more than sufficient to power small-scale, transient phenomena such as nanoflares and X-ray bright points, with the bulk of the free energy found to be stored low down, between 0.5 - 0.8 Mm. The energy dissipated is currently found to be too small to account for the heating of the entire quiet-Sun corona. However, the form and location of energy-dissipation regions qualitatively agree with what is observed on small scales on the Sun. Future MHD modelling using the same synthetic magnetograms may lead to a higher energy release.

  3. Chasing the Great American 2017 Total Solar Eclipse: Coronal Results from NASA's WB-57F High-Altitude Research Aircraft

    Science.gov (United States)

    Caspi, A.; Tsang, C.; DeForest, C. E.; Seaton, D. B.; Bryans, P.; Burkepile, J.; Casey, T. A.; Collier, J.; Darrow, D.; DeLuca, E.; Durda, D. D.; Gallagher, P.; Golub, L.; Judge, P. G.; Laurent, G. T.; Lewis, J.; Mallini, C.; Parent, T.; Propp, T.; Steffl, A.; Tomczyk, S.; Warner, J.; West, M. J.; Wiseman, J.; Zhukov, A.

    2017-12-01

    Total solar eclipses present rare opportunities to study the complex solar corona, down to altitudes of just a few percent of a solar radius above the surface, using ground-based and airborne observatories that would otherwise be dominated by the intense solar disk and high sky brightness. Studying the corona is critical to gaining a better understanding of physical processes that occur on other stars and astrophysical objects, as well as understanding the dominant driver of space weather that affects human assets at Earth and elsewhere. For example, it is still poorly understood how the corona is heated to temperatures of 1-2 MK globally and up to 5-10 MK above active regions, while the underlying chromosphere is 100 times cooler; numerous theories abound, but are difficult to constrain due to the limited sensitivities and cadences of prior measurements. The origins and stability of coronal fans, and the extent of their reach to the middle and outer corona, are also not well known, limited in large part by sensitivities and fields of view of existing observations. Airborne observations during the eclipse provide unique advantages; by flying in the stratosphere at altitudes of 50 kft or higher, they avoid all weather, the seeing quality is enormously improved, and additional wavelengths such as near- IR also become available due to significantly reduced water absorption. For an eclipse, an airborne observatory can also follow the shadow, increasing the total observing time by 50% or more. We present results of solar coronal measurements from airborne observations of the 2017 Great American Total Solar Eclipse using two of NASA's WB-57 high-altitude research aircraft, each equipped with two 8.7" telescopes feeding high-sensitivity visible (green-line) and medium-wave IR (3-5 μm) cameras operating at high cadence (30 Hz) with 3 arcsec/pixel platescale and ±3 R_sun fields of view. The aircraft flew along the eclipse path, separated by 110 km, to observe a summed 7

  4. Observable Signatures of Energy Release in Braided Coronal Loops

    Energy Technology Data Exchange (ETDEWEB)

    Pontin, D. I. [University of Dundee, Nethergate, Dundee, DD1 4HN (United Kingdom); Janvier, M. [Institut d’Astrophysique Spatiale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 121, F-91405, Orsay Cedex (France); Tiwari, S. K.; Winebarger, A. R.; Cirtain, J. W. [NASA Marshall Space Flight Center, ZP 13, Huntsville, AL 35812 (United States); Galsgaard, K. [Niels Bohr Institute, Geological Museum Østervoldgade 5-7, DK-1350, Copenhagen K (Denmark)

    2017-03-10

    We examine the turbulent relaxation of solar coronal loops containing non-trivial field line braiding. Such field line tangling in the corona has long been postulated in the context of coronal heating models. We focus on the observational signatures of energy release in such braided magnetic structures using MHD simulations and forward modeling tools. The aim is to answer the following question: if energy release occurs in a coronal loop containing braided magnetic flux, should we expect a clearly observable signature in emissions? We demonstrate that the presence of braided magnetic field lines does not guarantee a braided appearance to the observed intensities. Observed intensities may—but need not necessarily—reveal the underlying braided nature of the magnetic field, depending on the degree and pattern of the field line tangling within the loop. However, in all cases considered, the evolution of the braided loop is accompanied by localized heating regions as the loop relaxes. Factors that may influence the observational signatures are discussed. Recent high-resolution observations from Hi-C have claimed the first direct evidence of braided magnetic fields in the corona. Here we show that both the Hi-C data and some of our simulations give the appearance of braiding at a range of scales.

  5. OBSERVING THE FINE STRUCTURE OF LOOPS THROUGH HIGH-RESOLUTION SPECTROSCOPIC OBSERVATIONS OF CORONAL RAIN WITH THE CRISP INSTRUMENT AT THE SWEDISH SOLAR TELESCOPE

    International Nuclear Information System (INIS)

    Antolin, P.; Rouppe van der Voort, L.

    2012-01-01

    Observed in cool chromospheric lines, such as Hα or Ca II H, coronal rain corresponds to cool and dense plasma falling from coronal heights. Considered as a peculiar sporadic phenomenon of active regions, it has not received much attention since its discovery more than 40 years ago. Yet, it has been shown recently that a close relationship exists between this phenomenon and the coronal heating mechanism. Indeed, numerical simulations have shown that this phenomenon is most likely due to a loss of thermal equilibrium ensuing from a heating mechanism acting mostly toward the footpoints of loops. We present here one of the first high-resolution spectroscopic observations of coronal rain, performed with the CRisp Imaging Spectro Polarimeter (CRISP) instrument at the Swedish Solar Telescope. This work constitutes the first attempt to assess the importance of coronal rain in the understanding of the coronal magnetic field in active regions. With the present resolution, coronal rain is observed to literally invade the entire field of view. A large statistical set is obtained in which dynamics (total velocities and accelerations), shapes (lengths and widths), trajectories (angles of fall of the blobs), and thermodynamic properties (temperatures) of the condensations are derived. Specifically, we find that coronal rain is composed of small and dense chromospheric cores with average widths and lengths of ∼310 km and ∼710 km, respectively, average temperatures below 7000 K, displaying a broad distribution of falling speeds with an average of ∼70 km s –1 , and accelerations largely below the effective gravity along loops. Through estimates of the ion-neutral coupling in the blobs we show that coronal rain acts as a tracer of the coronal magnetic field, thus supporting the multi-strand loop scenario, and acts as a probe of the local thermodynamic conditions in loops. We further elucidate its potential in coronal heating. We find that the cooling in neighboring strands

  6. ON SUN-TO-EARTH PROPAGATION OF CORONAL MASS EJECTIONS

    International Nuclear Information System (INIS)

    Liu, Ying D.; Luhmann, Janet G.; Möstl, Christian; Bale, Stuart D.; Lin, Robert P.; Lugaz, Noé; Davies, Jackie A.

    2013-01-01

    We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts, and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs. Different from previous event studies, this work attempts to create a general picture for CME Sun-to-Earth propagation and compare different techniques for determining CME interplanetary kinematics. Key results are obtained concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be approximately formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the time of the maximum heating and radiation has elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs over a relatively short timescale following the acceleration phase; and (4) CME-CME interactions seem a common phenomenon close to solar maximum. Our comparison between different techniques (and data sets) has important implications for CME observations and their interpretations: (1) for the current cases, triangulation assuming a compact CME geometry is more reliable than triangulation assuming a spherical front attached to the Sun for distances below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the latter more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the

  7. Characteristics of polar coronal hole jets

    Science.gov (United States)

    Chandrashekhar, K.; Bemporad, A.; Banerjee, D.; Gupta, G. R.; Teriaca, L.

    2014-01-01

    Context. High spatial- and temporal-resolution images of coronal hole regions show a dynamical environment where mass flows and jets are frequently observed. These jets are believed to be important for the coronal heating and the acceleration of the fast solar wind. Aims: We studied the dynamics of two jets seen in a polar coronal hole with a combination of imaging from EIS and XRT onboard Hinode. We observed drift motions related to the evolution and formation of these small-scale jets, which we tried to model as well. Methods: Stack plots were used to find the drift and flow speeds of the jets. A toymodel was developed by assuming that the observed jet is generated by a sequence of single reconnection events where single unresolved blobs of plasma are ejected along open field lines, then expand and fall back along the same path, following a simple ballistic motion. Results: We found observational evidence that supports the idea that polar jets are very likely produced by multiple small-scale reconnections occurring at different times in different locations. These eject plasma blobs that flow up and down with a motion very similar to a simple ballistic motion. The associated drift speed of the first jet is estimated to be ≈27 km s-1. The average outward speed of the first jet is ≈171 km s-1, well below the escape speed, hence if simple ballistic motion is considered, the plasma will not escape the Sun. The second jet was observed in the south polar coronal hole with three XRT filters, namely, C-poly, Al-poly, and Al-mesh filters. Many small-scale (≈3″-5″) fast (≈200-300 km s-1) ejections of plasma were observed on the same day; they propagated outwards. We observed that the stronger jet drifted at all altitudes along the jet with the same drift speed of ≃7 km s-1. We also observed that the bright point associated with the first jet is a part of sigmoid structure. The time of appearance of the sigmoid and that of the ejection of plasma from the bright

  8. Using noble gases and 87Sr/86Sr to constrain heat sources and fluid evolution at the Los Azufres Geothermal Field, Mexico

    Science.gov (United States)

    Wen, T.; Pinti, D. L.; Castro, M. C.; Lopez Hernandez, A.; Hall, C. M.; Shouakar-Stash, O.; Sandoval-Medina, F.

    2017-12-01

    Geothermal wells and hot springs were sampled for noble gases' volume fraction and isotopic measurements and 87Sr/86Sr in the Los Azufres Geothermal Field (LAGF), Mexico, to understand the evolution of fluid circulation following three decades of exploitation and re-injection of used brines. The LAGF, divided into the Southern Production Zone (SPZ) and the Northern Production Zone (NPZ), is hosted in a Miocene to Pliocene andesitic volcanic complex covered by Quaternary rhyolitic-dacitic units. Air contamination corrected 3He/4He ratios (Rc) normalized to the atmospheric ratio (Ra=1.384 x 10-6), show a median value of 6.58 indicating a dominant mantle helium component. Contributions of crustal helium up to 53% and 18% are observed in NPZ and SPZ, respectively. Observations based on Rc/Ra and 87Sr/86Sr ratios points to the mixing of three magmatic sources supplying mantle helium to the LAGF: (1) a pure mantle He (Rc/Ra = 8) and Sr (87Sr/86Sr = 0.7035) source; (2) a pure mantle helium (Rc/Ra = 8) with some radiogenic Sr (87Sr/86Sr = 0.7049) source possibly resulting from Quaternary rhyolitic volcanism; and (3) a fossil mantle He component (Rc/Ra = 3.8) with some radiogenic Sr (87Sr/86Sr = 0.7038), corresponding possibly to the Miocene andesite reservoir. Intrusions within the last 50 kyrs from sources (1) and (2) are likely responsible for the addition of mantle volatiles and heat to the hydrothermal system of Los Azufres. He and Ar isotopes indicate that heat flow is transported by both convection and conduction. Atmospheric noble gas elemental ratios suggest that geothermal wells located closer to the western re-injection zone are beginning to be dominated by re-injection of used brines (injectate). The area affected by boiling in LAGF has further extended to the north and west since the last noble gas sampling campaign in 2009.

  9. On the Occurrence of Thermal Nonequilibrium in Coronal Loops

    Science.gov (United States)

    Froment, C.; Auchère, F.; Mikić, Z.; Aulanier, G.; Bocchialini, K.; Buchlin, E.; Solomon, J.; Soubrié, E.

    2018-03-01

    Long-period EUV pulsations, recently discovered to be common in active regions, are understood to be the coronal manifestation of thermal nonequilibrium (TNE). The active regions previously studied with EIT/Solar and Heliospheric Observatory and AIA/SDO indicated that long-period intensity pulsations are localized in only one or two loop bundles. The basic idea of this study is to understand why. For this purpose, we tested the response of different loop systems, using different magnetic configurations, to different stratifications and strengths of the heating. We present an extensive parameter-space study using 1D hydrodynamic simulations (1020 in total) and conclude that the occurrence of TNE requires specific combinations of parameters. Our study shows that the TNE cycles are confined to specific ranges in parameter space. This naturally explains why only some loops undergo constant periodic pulsations over several days: since the loop geometry and the heating properties generally vary from one loop to another in an active region, only the ones in which these parameters are compatible exhibit TNE cycles. Furthermore, these parameters (heating and geometry) are likely to vary significantly over the duration of a cycle, which potentially limits the possibilities of periodic behavior. This study also confirms that long-period intensity pulsations and coronal rain are two aspects of the same phenomenon: both phenomena can occur for similar heating conditions and can appear simultaneously in the simulations.

  10. AN MHD AVALANCHE IN A MULTI-THREADED CORONAL LOOP

    Energy Technology Data Exchange (ETDEWEB)

    Hood, A. W.; Cargill, P. J.; Tam, K. V. [School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife, KY16 9SS (United Kingdom); Browning, P. K., E-mail: awh@st-andrews.ac.uk [School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2016-01-20

    For the first time, we demonstrate how an MHD avalanche might occur in a multithreaded coronal loop. Considering 23 non-potential magnetic threads within a loop, we use 3D MHD simulations to show that only one thread needs to be unstable in order to start an avalanche even when the others are below marginal stability. This has significant implications for coronal heating in that it provides for energy dissipation with a trigger mechanism. The instability of the unstable thread follows the evolution determined in many earlier investigations. However, once one stable thread is disrupted, it coalesces with a neighboring thread and this process disrupts other nearby threads. Coalescence with these disrupted threads then occurs leading to the disruption of yet more threads as the avalanche develops. Magnetic energy is released in discrete bursts as the surrounding stable threads are disrupted. The volume integrated heating, as a function of time, shows short spikes suggesting that the temporal form of the heating is more like that of nanoflares than of constant heating.

  11. FIELD TOPOLOGY ANALYSIS OF A LONG-LASTING CORONAL SIGMOID

    International Nuclear Information System (INIS)

    Savcheva, A. S.; Van Ballegooijen, A. A.; DeLuca, E. E.

    2012-01-01

    We present the first field topology analysis based on nonlinear force-free field (NLFFF) models of a long-lasting coronal sigmoid observed in 2007 February with the X-Ray Telescope on Hinode. The NLFFF models are built with the flux rope insertion method and give the three-dimensional coronal magnetic field as constrained by observed coronal loop structures and photospheric magnetograms. Based on these models, we have computed horizontal maps of the current and the squashing factor Q for 25 different heights in the corona for all six days of the evolution of the region. We use the squashing factor to quantify the degree of change of the field line linkage and to identify prominent quasi-separatrix layers (QSLs). We discuss the major properties of these QSL maps and devise a way to pick out important QSLs since our calculation cannot reach high values of Q. The complexity in the QSL maps reflects the high degree of fragmentation of the photospheric field. We find main QSLs and current concentrations that outline the flux rope cavity and that become characteristically S-shaped during the evolution of the sigmoid. We note that, although intermittent bald patches exist along the length of the sigmoid during its whole evolution, the flux rope remains stable for several days. However, shortly after the topology of the field exhibits hyperbolic flux tubes (HFT) on February 7 and February 12 the sigmoid loses equilibrium and produces two B-class flares and associated coronal mass ejections (CMEs). The location of the most elevated part of the HFT in our model coincides with the inferred locations of the two flares. Therefore, we suggest that the presence of an HFT in a coronal magnetic configuration may be an indication that the system is ready to erupt. We offer a scenario in which magnetic reconnection at the HFT drives the system toward the marginally stable state. Once this state is reached, loss of equilibrium occurs via the torus instability, producing a CME.

  12. Comparison between two models of energy balance in coronal loops

    Science.gov (United States)

    Mac Cormack, C.; López Fuentes, M.; Vásquez, A. M.; Nuevo, F. A.; Frazin, R. A.; Landi, E.

    2017-10-01

    In this work we compare two models to analyze the energy balance along coronal magnetic loops. For the first stationary model we deduce an expression of the energy balance along the loops expressed in terms of quantities provided by the combination of differential emission measure tomography (DEMT) applied to EUV images time series and potential extrapolations of the coronal magnetic field. The second applied model is a 0D hydrodynamic model that provides the evolution of the average properties of the coronal plasma along the loops, using as input parameters the loop length and the heating rate obtained with the first model. We compare the models for two Carrington rotations (CR) corresponding to different periods of activity: CR 2081, corresponding to a period of minimum activity observed with the Extreme Ultraviolet Imager (EUVI) on board of the Solar Terrestrial Relations Observatory (STEREO), and CR 2099, corresponding to a period of activity increase observed with the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The results of the models are consistent for both rotations.

  13. The Prospect for Detecting Stellar Coronal Mass Ejections

    Science.gov (United States)

    Osten, Rachel A.; Crosley, Michael Kevin

    2018-06-01

    The astrophysical study of mass loss, both steady-state and transient, on the cool half of the HR diagram has implications bothfor the star itself and the conditions created around the star that can be hospitable or inimical to supporting life. Recent results from exoplanet studies show that planets around M dwarfs are exceedingly common, which together with the commonality of M dwarfs in our galaxy make this the dominant mode of star and planet configurations. The closeness of the exoplanets to the parent M star motivate a comprehensive understanding of habitability for these systems. Radio observations provide the most clear signature of accelerated particles and shocks in stars arising as the result of MHD processes in the stellar outer atmosphere. Stellar coronal mass ejections have not been conclusively detected, despite the ubiquity with which their radiative counterparts in an eruptive event (stellar flares) have. I will review some of the different observational methods which have been used and possibly could be used in the future in the stellar case, emphasizing some of the difficulties inherent in such attempts. I will provide a framework for interpreting potential transient stellar mass loss in light of the properties of flares known to occur on magnetically active stars. This uses a physically motivated way to connect the properties of flares and coronal mass ejections and provides a testable hypothesis for observing or constraining transient stellar mass loss. I will describe recent results using radio observations to detect stellar coronal mass ejections, and what those results imply about transient stellar mass loss. I will provide some motivation for what could be learned in this topic from space-based low frequency radio experiments.

  14. Space weather and coronal mass ejections

    CERN Document Server

    Howard, Tim

    2013-01-01

    Space weather has attracted a lot of attention in recent times. Severe space weather can disrupt spacecraft, and on Earth can be the cause of power outages and power station failure. It also presents a radiation hazard for airline passengers and astronauts. These ""magnetic storms"" are most commonly caused by coronal mass ejections, or CMES, which are large eruptions of plasma and magnetic field from the Sun that can reach speeds of several thousand km/s. In this SpringerBrief, Space Weather and Coronal Mass Ejections, author Timothy Howard briefly introduces the coronal mass ejection, its sc

  15. CORONAL DENSITY STRUCTURE AND ITS ROLE IN WAVE DAMPING IN LOOPS

    Energy Technology Data Exchange (ETDEWEB)

    Cargill, P. J. [Space and Atmospheric Physics, The Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom); De Moortel, I.; Kiddie, G., E-mail: p.cargill@imperial.ac.uk [School of Mathematics and Statistics, University of St Andrews, St Andrews, Scotland KY16 9SS (United Kingdom)

    2016-05-20

    It has long been established that gradients in the Alfvén speed, and in particular the plasma density, are an essential part of the damping of waves in the magnetically closed solar corona by mechanisms such as resonant absorption and phase mixing. While models of wave damping often assume a fixed density gradient, in this paper the self-consistency of such calculations is assessed by examining the temporal evolution of the coronal density. It is shown conceptually that for some coronal structures, density gradients can evolve in a way that the wave-damping processes are inhibited. For the case of phase mixing we argue that (a) wave heating cannot sustain the assumed density structure and (b) inclusion of feedback of the heating on the density gradient can lead to a highly structured density, although on long timescales. In addition, transport coefficients well in excess of classical are required to maintain the observed coronal density. Hence, the heating of closed coronal structures by global oscillations may face problems arising from the assumption of a fixed density gradient, and the rapid damping of oscillations may have to be accompanied by a separate (non-wave-based) heating mechanism to sustain the required density structuring.

  16. Coronal Magnetism and Forward Solarsoft Idl Package

    Science.gov (United States)

    Gibson, S. E.

    2014-12-01

    The FORWARD suite of Solar Soft IDL codes is a community resource for model-data comparison, with a particular emphasis on analyzing coronal magnetic fields. FORWARD may be used both to synthesize a broad range of coronal observables, and to access and compare to existing data. FORWARD works with numerical model datacubes, interfaces with the web-served Predictive Science Inc MAS simulation datacubes and the Solar Soft IDL Potential Field Source Surface (PFSS) package, and also includes several analytic models (more can be added). It connects to the Virtual Solar Observatory and other web-served observations to download data in a format directly comparable to model predictions. It utilizes the CHIANTI database in modeling UV/EUV lines, and links to the CLE polarimetry synthesis code for forbidden coronal lines. FORWARD enables "forward-fitting" of specific observations, and helps to build intuition into how the physical properties of coronal magnetic structures translate to observable properties.

  17. COMPOSITION OF CORONAL MASS EJECTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Zurbuchen, T. H.; Weberg, M.; Lepri, S. T. [Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI (United States); Von Steiger, R. [International Space Science Institute, Bern (Switzerland); Mewaldt, R. A. [California Institute of Technology, Pasadena, CA (United States); Antiochos, S. K. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    2016-07-20

    We analyze the physical origin of plasmas that are ejected from the solar corona. To address this issue, we perform a comprehensive analysis of the elemental composition of interplanetary coronal mass ejections (ICMEs) using recently released elemental composition data for Fe, Mg, Si, S, C, N, Ne, and He as compared to O and H. We find that ICMEs exhibit a systematic abundance increase of elements with first ionization potential (FIP) < 10 eV, as well as a significant increase of Ne as compared to quasi-stationary solar wind. ICME plasmas have a stronger FIP effect than slow wind, which indicates either that an FIP process is active during the ICME ejection or that a different type of solar plasma is injected into ICMEs. The observed FIP fractionation is largest during times when the Fe ionic charge states are elevated above Q {sub Fe} > 12.0. For ICMEs with elevated charge states, the FIP effect is enhanced by 70% over that of the slow wind. We argue that the compositionally hot parts of ICMEs are active region loops that do not normally have access to the heliosphere through the processes that give rise to solar wind. We also discuss the implications of this result for solar energetic particles accelerated during solar eruptions and for the origin of the slow wind itself.

  18. Evolutionary constrained optimization

    CERN Document Server

    Deb, Kalyanmoy

    2015-01-01

    This book makes available a self-contained collection of modern research addressing the general constrained optimization problems using evolutionary algorithms. Broadly the topics covered include constraint handling for single and multi-objective optimizations; penalty function based methodology; multi-objective based methodology; new constraint handling mechanism; hybrid methodology; scaling issues in constrained optimization; design of scalable test problems; parameter adaptation in constrained optimization; handling of integer, discrete and mix variables in addition to continuous variables; application of constraint handling techniques to real-world problems; and constrained optimization in dynamic environment. There is also a separate chapter on hybrid optimization, which is gaining lots of popularity nowadays due to its capability of bridging the gap between evolutionary and classical optimization. The material in the book is useful to researchers, novice, and experts alike. The book will also be useful...

  19. Introduction of hind foot coronal alignment view

    International Nuclear Information System (INIS)

    Moon, Il Bong; Jeon, Ju Seob; Yoon, Kang Cheol; Choi, Nam Kil; Kim, Seung Kook

    2006-01-01

    Accurate clinical evaluation of the alignment of the calcaneus relative to the tibia in the coronal plane is essential in the evaluation and treatment of hind foot pathologic condition. Previously described standard anteroposterior, lateral, and oblique radiographic methods of the foot or ankle do not demonstrate alignment of the tibia relation to the calcaneus in the coronal plane. The purpose of this study was to introduce hind foot coronal alignment view. Both feet were imaged simultaneously on an elevated, radiolucent foot stand equipment. Both feet stood on a radiolucent platform with equal weight on both feet. Both feet are located foot axis longitudinal perpendicular to the platform. Silhouette tracing around both feet are made, and line is then drawn to bisect the silhouette of the second toe and the outline of the heel. The x-ray beam is angled down approximately 15 .deg. to 20 .deg. This image described tibial axis and medial, lateral tuberosity of calcaneus. Calcaneus do not rotated. The view is showed by talotibial joint space. Although computed tomographic and magnetic resonance imaging techniques are capable of demonstrating coronal hind foot alignment, they lack usefulness in most clinical situations because the foot is imaged in a non-weight bearing position. But hind foot coronal alignment view is obtained for evaluating position changing of inversion, eversion of the hind foot and varus, valgus deformity of calcaneus

  20. The first coronation churches of medieval Serbia

    Directory of Open Access Journals (Sweden)

    Kalić Jovanka

    2017-01-01

    Full Text Available The medieval ceremony of coronation as a rule took place in the most important church of a realm. The sites of the coronation of Serbian rulers before the establishment of the Žiča monastery church as the coronation church of Serbian kings in the first half of the thirteenth century have not been reliably identified so far. Based on the surviving medieval sources and the archaeological record, this paper provides background information about the titles of Serbian rulers prior to the creation of the Nemanjić state, and proposes that Stefan, son of the founder of the Nemanjić dynasty, was crowned king (1217 in the church of St Peter in Ras.

  1. Wavelet library for constrained devices

    Science.gov (United States)

    Ehlers, Johan Hendrik; Jassim, Sabah A.

    2007-04-01

    The wavelet transform is a powerful tool for image and video processing, useful in a range of applications. This paper is concerned with the efficiency of a certain fast-wavelet-transform (FWT) implementation and several wavelet filters, more suitable for constrained devices. Such constraints are typically found on mobile (cell) phones or personal digital assistants (PDA). These constraints can be a combination of; limited memory, slow floating point operations (compared to integer operations, most often as a result of no hardware support) and limited local storage. Yet these devices are burdened with demanding tasks such as processing a live video or audio signal through on-board capturing sensors. In this paper we present a new wavelet software library, HeatWave, that can be used efficiently for image/video processing/analysis tasks on mobile phones and PDA's. We will demonstrate that HeatWave is suitable for realtime applications with fine control and range to suit transform demands. We shall present experimental results to substantiate these claims. Finally this library is intended to be of real use and applied, hence we considered several well known and common embedded operating system platform differences; such as a lack of common routines or functions, stack limitations, etc. This makes HeatWave suitable for a range of applications and research projects.

  2. DIRECT OBSERVATION OF SOLAR CORONAL MAGNETIC FIELDS BY VECTOR TOMOGRAPHY OF THE CORONAL EMISSION LINE POLARIZATIONS

    International Nuclear Information System (INIS)

    Kramar, M.; Lin, H.; Tomczyk, S.

    2016-01-01

    We present the first direct “observation” of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The vector tomographic inversion uses measurements of the Fe xiii 10747 Å Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and 3D coronal density and temperature derived from scalar tomographic inversion of Solar Terrestrial Relations Observatory (STEREO)/Extreme Ultraviolet Imager (EUVI) coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, we compared the tomography inverted coronal magnetic fields with those constructed by magnetohydrodynamic (MHD) simulations based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for several regions. Particularly, for one of the most noticeable regions, we found that the MHD simulation for CR 2113 predicted a model that more closely resembles the vector tomography inverted magnetic fields. In another case, our tomographic reconstruction predicted an open magnetic field at a region where a coronal hole can be seen directly from a STEREO-B/EUVI image. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments

  3. Exploring Constrained Creative Communication

    DEFF Research Database (Denmark)

    Sørensen, Jannick Kirk

    2017-01-01

    Creative collaboration via online tools offers a less ‘media rich’ exchange of information between participants than face-to-face collaboration. The participants’ freedom to communicate is restricted in means of communication, and rectified in terms of possibilities offered in the interface. How do...... these constrains influence the creative process and the outcome? In order to isolate the communication problem from the interface- and technology problem, we examine via a design game the creative communication on an open-ended task in a highly constrained setting, a design game. Via an experiment the relation...... between communicative constrains and participants’ perception of dialogue and creativity is examined. Four batches of students preparing for forming semester project groups were conducted and documented. Students were asked to create an unspecified object without any exchange of communication except...

  4. Choosing health, constrained choices.

    Science.gov (United States)

    Chee Khoon Chan

    2009-12-01

    In parallel with the neo-liberal retrenchment of the welfarist state, an increasing emphasis on the responsibility of individuals in managing their own affairs and their well-being has been evident. In the health arena for instance, this was a major theme permeating the UK government's White Paper Choosing Health: Making Healthy Choices Easier (2004), which appealed to an ethos of autonomy and self-actualization through activity and consumption which merited esteem. As a counterpoint to this growing trend of informed responsibilization, constrained choices (constrained agency) provides a useful framework for a judicious balance and sense of proportion between an individual behavioural focus and a focus on societal, systemic, and structural determinants of health and well-being. Constrained choices is also a conceptual bridge between responsibilization and population health which could be further developed within an integrative biosocial perspective one might refer to as the social ecology of health and disease.

  5. Radio emission from coronal and interplanetary shocks

    International Nuclear Information System (INIS)

    Cane, H.V.

    1987-01-01

    Observational data on coronal and interplanetary (IP) type II burst events associated with shock-wave propagation are reviewed, with a focus on the past and potential future contributions of space-based observatories. The evidence presented by Cane (1983 and 1984) in support of the hypothesis that the coronal (metric) and IP (kilometric) bursts are due to different shocks is summarized, and the fast-drift kilometric events seen at the same time as metric type II bursts (and designated shock-accelerated or shock-associated events) are characterized. The need for further observations at 0.5-20 MHz is indicated. 20 references

  6. Three-Dimensional Morphology of a Coronal Prominence Cavity

    Science.gov (United States)

    Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; hide

    2010-01-01

    We present a three-dimensional density model of coronal prominence cavities, and a morphological fit that has been tightly constrained by a uniquely well-observed cavity. Observations were obtained as part of an International Heliophysical Year campaign by instruments from a variety of space- and ground-based observatories, spanning wavelengths from radio to soft-X-ray to integrated white light. From these data it is clear that the prominence cavity is the limb manifestation of a longitudinally-extended polar-crown filament channel, and that the cavity is a region of low density relative to the surrounding corona. As a first step towards quantifying density and temperature from campaign spectroscopic data, we establish the three-dimensional morphology of the cavity. This is critical for taking line-of-sight projection effects into account, since cavities are not localized in the plane of the sky and the corona is optically thin. We have augmented a global coronal streamer model to include a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. We have developed a semi-automated routine that fits ellipses to cross-sections of the cavity as it rotates past the solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI) observations from the two Solar Terrestrial Relations Observatory (STEREO) spacecraft. This defines the morphological parameters of our model, from which we reproduce forward-modeled cavity observables. We find that cavity morphology and orientation, in combination with the viewpoints of the observing spacecraft, explains the observed variation in cavity visibility for the east vs. west limbs

  7. Constrained superfields in supergravity

    Energy Technology Data Exchange (ETDEWEB)

    Dall’Agata, Gianguido; Farakos, Fotis [Dipartimento di Fisica ed Astronomia “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)

    2016-02-16

    We analyze constrained superfields in supergravity. We investigate the consistency and solve all known constraints, presenting a new class that may have interesting applications in the construction of inflationary models. We provide the superspace Lagrangians for minimal supergravity models based on them and write the corresponding theories in component form using a simplifying gauge for the goldstino couplings.

  8. Minimal constrained supergravity

    Energy Technology Data Exchange (ETDEWEB)

    Cribiori, N. [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Dall' Agata, G., E-mail: dallagat@pd.infn.it [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Farakos, F. [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Porrati, M. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)

    2017-01-10

    We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  9. Minimal constrained supergravity

    Directory of Open Access Journals (Sweden)

    N. Cribiori

    2017-01-01

    Full Text Available We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  10. Minimal constrained supergravity

    International Nuclear Information System (INIS)

    Cribiori, N.; Dall'Agata, G.; Farakos, F.; Porrati, M.

    2017-01-01

    We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  11. Magnetic Untwisting in Jets that Go into the Outer Solar Corona in Polar Coronal Holes

    Science.gov (United States)

    Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David

    2014-06-01

    We present results from a study of 14 jets that were observed in SDO/AIA EUV movies to erupt in the Sun’s polar coronal holes. These jets were similar to the many other jets that erupt in coronal holes, but reached higher than the vast majority, high enough to be observed in the outer corona beyond 2 solar radii from Sun center by the SOHO/LASCO/C2 coronagraph. We illustrate the characteristic structure and motion of these high-reaching jets by showing observations of two representative jets. We find that (1) the speed of the jet front from the base of the corona out to 2-3 solar radii is typically several times the sound speed in jets in coronal holes, (2) each high-reaching jet displays unusually large rotation about its axis (spin) as it erupts, and (3) in the outer corona, many jets display lateral swaying and bending of the jet axis with an amplitude of a few degrees and a period of order 1 hour. From these observations we infer that these jets are magnetically driven, propose that the driver is a magnetic-untwisting wave that is basically a large-amplitude (non-linear) torsional Alfven wave that is put into the open magnetic field in the jet by interchange reconnection as the jet erupts, and estimate that the magnetic-untwisting wave loses most of its energy before reaching the outer corona. These observations of high-reaching coronal jets suggest that the torsional magnetic waves observed in Type-II spicules can similarly dissipate in the corona and thereby power much of the coronal heating in coronal holes and quiet regions. This work is funded by the NASA/SMD Heliophysics Division’s Living With a Star Targeted Research & Technology Program.

  12. Solar Wind Associated with Near Equatorial Coronal Hole M ...

    Indian Academy of Sciences (India)

    2015-05-25

    May 25, 2015 ... coronal hole and solar wind. For both the wavelength bands, we also com- pute coronal hole radiative energy near the earth and it is found to be of similar order as that of solar wind energy. However, for the wavelength. 193 Å, owing to almost similar magnitudes of energy emitted by coronal hole and ...

  13. Higher-speed coronal mass ejections and their geoeffectiveness

    Science.gov (United States)

    Singh, A. K.; Bhargawa, Asheesh; Tonk, Apeksha

    2018-06-01

    We have attempted to examine the ability of coronal mass ejections to cause geoeffectiveness. To that end, we have investigated total 571 cases of higher-speed (> 1000 km/s) coronal mass ejection events observed during the years 1996-2012. On the basis of angular width (W) of observance, events of coronal mass ejection were further classified as front-side or halo coronal mass ejections (W = 360°); back-side halo coronal mass ejections (W = 360°); partial halo (120°mass ejections were much faster and more geoeffective in comparison of partial halo and non-halo coronal mass ejections. We also inferred that the front-sided halo coronal mass ejections were 67.1% geoeffective while geoeffectiveness of partial halo coronal mass ejections and non-halo coronal mass ejections were found to be 44.2% and 56.6% respectively. During the same period of observation, 43% of back-sided CMEs showed geoeffectiveness. We have also investigated some events of coronal mass ejections having speed > 2500 km/s as a case study. We have concluded that mere speed of coronal mass ejection and their association with solar flares or solar activity were not mere criterion for producing geoeffectiveness but angular width of coronal mass ejections and their originating position also played a key role.

  14. Magnetic Topology of Coronal Hole Linkages

    Science.gov (United States)

    Titov, V. S.; Mikic, Z.; Linker, J. A.; Lionello, R.; Antiochos, S. K.

    2010-01-01

    In recent work, Antiochos and coworkers argued that the boundary between the open and closed field regions on the Sun can be extremely complex with narrow corridors of open ux connecting seemingly disconnected coronal holes from the main polar holes, and that these corridors may be the sources of the slow solar wind. We examine, in detail, the topology of such magnetic configurations using an analytical source surface model that allows for analysis of the eld with arbitrary resolution. Our analysis reveals three important new results: First, a coronal hole boundary can join stably to the separatrix boundary of a parasitic polarity region. Second, a single parasitic polarity region can produce multiple null points in the corona and, more important, separator lines connecting these points. Such topologies are extremely favorable for magnetic reconnection, because it can now occur over the entire length of the separators rather than being con ned to a small region around the nulls. Finally, the coronal holes are not connected by an open- eld corridor of finite width, but instead are linked by a singular line that coincides with the separatrix footprint of the parasitic polarity. We investigate how the topological features described above evolve in response to motion of the parasitic polarity region. The implications of our results for the sources of the slow solar wind and for coronal and heliospheric observations are discussed.

  15. Evolving Coronal Holes and Interplanetary Erupting Stream ...

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Coronal holes and interplanetary disturbances are important aspects of the physics of the Sun and heliosphere. Interplanetary disturbances are identified as an increase in the density turbulence compared with the ambient solar wind. Erupting stream disturbances are transient large-scale structures of ...

  16. On interplanetary coronal mass ejection identification at 1 AU

    International Nuclear Information System (INIS)

    Mulligan, T.; Russell, C.T.; Gosling, J.T.

    1999-01-01

    Coronal mass ejections are believed to be produced in the corona from closed magnetic regions not previously participating in the solar wind expansion. At 1 AU their interplanetary counterparts (ICMEs) generally have a number of distinct plasma and field signatures that distinguish them from the ambient solar wind. These include heat flux dropouts, bi-directional streaming, enhanced alpha particle events, times of depressed proton temperatures, intervals of distorted or enhanced magnetic field, and times of large magnetic field rotations characteristic of magnetic clouds. The first three of these signatures are phenomena that occur at some point within the ICME, but do not necessarily persist throughout the entire ICME. The large scale magnetic field rotations, distortions and enhancements, and the proton temperature depressions tend to mark more accurately the beginning and end of the ICME proper. We examine herein the reliability with which each of these markers identifies ICMEs utilizing ISEE-3 data from 1978 - 1980. copyright 1999 American Institute of Physics

  17. INTERCHANGE RECONNECTION AND CORONAL HOLE DYNAMICS

    International Nuclear Information System (INIS)

    Edmondson, J. K.; Antiochos, S. K.; DeVore, C. R.; Lynch, B. J.; Zurbuchen, T. H.

    2010-01-01

    We investigate the effect of magnetic reconnection between open and closed fields, often referred to as 'interchange' reconnection, on the dynamics and topology of coronal hole boundaries. The most important and most prevalent three-dimensional topology of the interchange process is that of a small-scale bipolar magnetic field interacting with a large-scale background field. We determine the evolution of such a magnetic topology by numerical solution of the fully three-dimensional MHD equations in spherical coordinates. First, we calculate the evolution of a small-scale bipole that initially is completely inside an open field region and then is driven across a coronal hole boundary by photospheric motions. Next the reverse situation is calculated in which the bipole is initially inside the closed region and driven toward the coronal hole boundary. In both cases, we find that the stress imparted by the photospheric motions results in deformation of the separatrix surface between the closed field of the bipole and the background field, leading to rapid current sheet formation and to efficient reconnection. When the bipole is inside the open field region, the reconnection is of the interchange type in that it exchanges open and closed fields. We examine, in detail, the topology of the field as the bipole moves across the coronal hole boundary and find that the field remains well connected throughout this process. Our results, therefore, provide essential support for the quasi-steady models of the open field, because in these models the open and closed flux are assumed to remain topologically distinct as the photosphere evolves. Our results also support the uniqueness hypothesis for open field regions as postulated by Antiochos et al. On the other hand, the results argue against models in which open flux is assumed to diffusively penetrate deeply inside the closed field region under a helmet streamer. We discuss the implications of this work for coronal observations.

  18. DARK JETS IN SOLAR CORONAL HOLES

    Energy Technology Data Exchange (ETDEWEB)

    Young, Peter R. [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

    2015-03-10

    A new solar feature termed a dark jet is identified from observations of an extended solar coronal hole that was continuously monitored for over 44 hr by the Extreme Ultraviolet Imaging Spectrometer on board the Hinode spacecraft in 2011 February 8–10 as part of Hinode Operation Plan No. 177 (HOP 177). Line of sight (LOS) velocity maps derived from the coronal Fe xii λ195.12 emission line, formed at 1.5 MK, revealed a number of large-scale, jet-like structures that showed significant blueshifts. The structures had either weak or no intensity signal in 193 Å filter images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, suggesting that the jets are essentially invisible to imaging instruments. The dark jets are rooted in bright points and occur both within the coronal hole and at the quiet Sun–coronal hole boundary. They exhibit a wide range of shapes, from narrow columns to fan-shaped structures, and sometimes multiple jets are seen close together. A detailed study of one dark jet showed LOS speeds increasing along the jet axis from 52 to 107 km s{sup −1} and a temperature of 1.2–1.3 MK. The low intensity of the jet was due either to a small filling factor of 2% or to a curtain-like morphology. From the HOP 177 sample, dark jets are as common as regular coronal hole jets, but their low intensity suggests a mass flux around two orders of magnitude lower.

  19. UNRAVELLING THE COMPONENTS OF A MULTI-THERMAL CORONAL LOOP USING MAGNETOHYDRODYNAMIC SEISMOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, S. Krishna; Jess, D. B. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast, BT7 1NN (United Kingdom); Klimchuk, J. A. [Heliophysics Division, NASA Goddard Space Flight Center, Greenbelt, MD, 20771 (United States); Banerjee, D., E-mail: krishna.prasad@qub.ac.uk [Indian Institute of Astrophysics, II Block Koramangala, Bengaluru 560034 (India)

    2017-01-10

    Coronal loops, constituting the basic building blocks of the active Sun, serve as primary targets to help understand the mechanisms responsible for maintaining multi-million Kelvin temperatures in the solar and stellar coronae. Despite significant advances in observations and theory, our knowledge on the fundamental properties of these structures is limited. Here, we present unprecedented observations of accelerating slow magnetoacoustic waves along a coronal loop that show differential propagation speeds in two distinct temperature channels, revealing the multi-stranded and multithermal nature of the loop. Utilizing the observed speeds and employing nonlinear force-free magnetic field extrapolations, we derive the actual temperature variation along the loop in both channels, and thus are able to resolve two individual components of the multithermal loop for the first time. The obtained positive temperature gradients indicate uniform heating along the loop, rather than isolated footpoint heating.

  20. Coronal heating by Alfven waves dissipation in compressible nonuniform media

    International Nuclear Information System (INIS)

    Malara, Francesco; Primavera, Leonardo; Veltri, Pierluigi

    1996-01-01

    The possibility to produce small scales and then to efficiently dissipate energy has been studied by Malara et al. [1992b] in the case of MHD disturbances propagating in an weakly dissipative incompressible and inhomogeneous medium, for a strictly 2D geometry. We extend this work to include both compressibility and the third component for vector quantities. Numerical simulations show that, when an Alfven wave propagates in a compressible nonuniform medium, the two dynamical effects responsible for the small scales formation in the incompressible case are still at work: energy pinching and phase-mixing. These effects give rise to the formation of compressible perturbations (fast and slow waves or a static entropy wave). Some of these compressive fluctuations are subject to the steepening of the wave front and become shock waves, which are extremely efficient in dissipating their energy, their dissipation being independent of the Reynolds number. Rough estimates of the typical times the various dynamical processes take to produce small scales show that these times are consistent with those required to dissipate inside the solar corona the energy of Alfven waves of photospheric origin

  1. Constrained noninformative priors

    International Nuclear Information System (INIS)

    Atwood, C.L.

    1994-10-01

    The Jeffreys noninformative prior distribution for a single unknown parameter is the distribution corresponding to a uniform distribution in the transformed model where the unknown parameter is approximately a location parameter. To obtain a prior distribution with a specified mean but with diffusion reflecting great uncertainty, a natural generalization of the noninformative prior is the distribution corresponding to the constrained maximum entropy distribution in the transformed model. Examples are given

  2. TWO-DIMENSIONAL CELLULAR AUTOMATON MODEL FOR THE EVOLUTION OF ACTIVE REGION CORONAL PLASMAS

    Energy Technology Data Exchange (ETDEWEB)

    López Fuentes, Marcelo [Instituto de Astronomía y Física del Espacio, CONICET-UBA, CC. 67, Suc. 28, 1428 Buenos Aires (Argentina); Klimchuk, James A., E-mail: lopezf@iafe.uba.ar [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)

    2015-02-01

    We study a two-dimensional cellular automaton (CA) model for the evolution of coronal loop plasmas. The model is based on the idea that coronal loops are made of elementary magnetic strands that are tangled and stressed by the displacement of their footpoints by photospheric motions. The magnetic stress accumulated between neighbor strands is released in sudden reconnection events or nanoflares that heat the plasma. We combine the CA model with the Enthalpy Based Thermal Evolution of Loops model to compute the response of the plasma to the heating events. Using the known response of the X-Ray Telescope on board Hinode, we also obtain synthetic data. The model obeys easy-to-understand scaling laws relating the output (nanoflare energy, temperature, density, intensity) to the input parameters (field strength, strand length, critical misalignment angle). The nanoflares have a power-law distribution with a universal slope of –2.5, independent of the input parameters. The repetition frequency of nanoflares, expressed in terms of the plasma cooling time, increases with strand length. We discuss the implications of our results for the problem of heating and evolution of active region coronal plasmas.

  3. 3D MHD MODELING OF TWISTED CORONAL LOOPS

    Energy Technology Data Exchange (ETDEWEB)

    Reale, F.; Peres, G. [Dipartimento di Fisica and Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Orlando, S. [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Guarrasi, M. [CINECA—Interuniversity consortium, via Magnanelli 6/3, I-40033, Casalecchio di Reno, Bologna (Italy); Mignone, A. [Dipartimento di Fisica Generale, Università di Torino, via Pietro Giuria 1, I-10125, Torino (Italy); Hood, A. W.; Priest, E. R., E-mail: fabio.reale@unipa.it [School of Mathematics and Statistics, University of St. Andrews, St. Andrews, KY16 9SS (United Kingdom)

    2016-10-10

    We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube in the solar atmosphere extending from the high- β chromosphere to the low- β corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ∼30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the flux tube is heated to active region temperatures (∼3 MK) after ∼2/3 hr. Upflows from the chromosphere up to ∼100 km s{sup −1} fill the core of the flux tube to densities above 10{sup 9} cm{sup −3}. More heating is released in the low corona than the high corona and is finely structured both in space and time.

  4. Analysis of coronal H I Lyman alpha measurements from a rocket flight on 1979 April 13

    International Nuclear Information System (INIS)

    Withbroe, G.L.; Kohl, J.L.; Weiser, H.; Noci, G.; Munro, R.H.

    1982-01-01

    Measurements of the profiles of resonantly scattered hydrogen Lyman-α coronal radiation have been used to determine hydrogen kinetic temperatures from 1.5 to 4 R/sub sun/ from Sun center in a quiet region of the corona. Proton temperatures derived from the line widths decrease with height from 2.6 x 10 6 K at r = 1.5 R/sub sun/ to 1.2 x 10 6 K at r = 4 R/sub sun/. These measurements combined with temperatures for lower heights determined from earlier Skylab and eclipse data suggest that there is a maximum in the quiet coronal proton temperature at about 1.5 R/sub sun/. Comparison of measured Lyman-α intensities with those calculated using a representative model for the radial variation of the coronal electron density provides information on the magnitude of the electron temperature gradient and suggests that the solar wind flow was subsonic for r<4 R/sub sun/ in the observed region. Comparison of the measured kinetic temperatures to the predictions of a simple two fluid model suggests that there is a small amount of proton heating and/or a nonthermal contribution to the motions of coronal protons between 1.5 and 4 R/sub sun/

  5. Production planning and coronal stop deletion in spontaneous speech

    Directory of Open Access Journals (Sweden)

    James Tanner

    2017-06-01

    Full Text Available Many phonological processes can be affected by segmental context spanning word boundaries, which often lead to variable outcomes. This paper tests the idea that some of this variability can be explained by reference to production planning. We examine coronal stop deletion (CSD, a variable process conditioned by preceding and upcoming phonological context, in a corpus of spontaneous British English speech, as a means of investigating a number of variables associated with planning: Prosodic boundary strength, word frequency, conditional probability of the following word, and speech rate. From the perspective of production planning, (1 prosodic boundaries should affect deletion rate independently of following context; (2 given the locality of production planning, the effect of the following context should decrease at stronger prosodic boundaries; and (3 other factors affecting planning scope should modulate the effect of upcoming phonological material above and beyond the modulating effect of prosodic boundaries. We build a statistical model of CSD realization, using pause length as a quantitative proxy for boundary strength, and find support for these predictions. These findings are compatible with the hypothesis that the locality of production planning constrains variability in speech production, and have practical implications for work on CSD and other variable processes.

  6. Interplanetary Coronal Mass Ejections detected by HAWC

    Science.gov (United States)

    Lara, Alejandro

    The High Altitude Water Cherenkov (HAWC) observatory is being constructed at the volcano Sierra Negra (4100 m a.s.l.) in Mexico. HAWC’s primary purpose is the study of both: galactic and extra-galactic sources of high energy gamma rays. HAWC will consist of 300 large water Cherenkov detectors (WCD), instrumented with 1200 photo-multipliers. The Data taking has already started while construction continues, with the completion projected for late 2014. The HAWC counting rate will be sensitive to cosmic rays with energies above the geomagnetic cutoff of the site (˜ 8 GV). In particular, HAWC will detect solar energetic particles known as Ground Level Enhancements (GLEs), and the effects of Coronal Mass Ejections on the galactic cosmic ray flux, known as Forbush Decreases. In this paper, we present a description of the instrument and its response to interplanetary coronal mass ejections, and other solar wind large scale structures, observed during the August-December 2013 period.

  7. Sinonasal polyposis: investigation by direct coronal CT

    International Nuclear Information System (INIS)

    Drutman, J.; Harnsberger, H.R.; Babbel, R.W.; Sonkens, J.W.; Braby, D.

    1994-01-01

    To demonstrate the typical clinical and CT features of sinonasal polyposis, we reviewed the clinical records and preoperative direct coronal CT scans of 35 patients with surgically proven disease. Symptoms included progressive nasal stuffiness (100 %), rhinorrhea (69 %), facial pain (60 %), headache (43 %) and anosmia (17 %). We found associations with rhinitis (46 %), asthma (29 %) and aspirin sensitivity (9 %). Coronal CT features included polypoid masses in the nasal cavity (91 %), partial or complete pansinus opacification (90 %), enlargement of infundibula (89 %), bony attenuation of the ethmoid trabeculae (63 %) and nasal septum (37 %), opacified ethmoid sinuses with convex lateral walls (51 %) and air-fluid levels (43 %). The latter feature correlated with symptoms and signs of acute sinusitis in only 40 % of patients. Recognition of sinonasal polyposis is important to the endoscopic surgeon since it can be the most troubling sinonasal inflammatory disease to manage due to its aggressive nature and tendency to recur despite appropriate treatment. (orig.)

  8. Fracture mechanism of coronal teenage dentin

    Science.gov (United States)

    Panfilov, P. E.; Kabanova, A. V.; Borodin, I. N.; Guo, J.; Zang, Z.

    2017-10-01

    The structure of coronal teenage dentin and the development of cracks in it are studied on microand nanolevels. The material is found to fail according to a ductile mechanism on a microlelvel and according to a ductile-brittle mechanism on a nanoscale. This behavior is similar to the failure of a polyethylene film and rubber, when significant elastic and irreversible deformation precedes crack growth. The viscoelastic behavior can be considered as the reaction of dentin to an applied mechanical load.

  9. Plasma Diagnostics of Coronal Dimming Events

    Science.gov (United States)

    Vanninathan, Kamalam; Veronig, Astrid M.; Dissauer, Karin; Temmer, Manuela

    2018-04-01

    Coronal mass ejections are often associated with coronal dimmings, i.e., transient dark regions that are most distinctly observed in Extreme Ultra-violet wavelengths. Using Atmospheric Imaging Assembly (AIA) data, we apply Differential Emission Measure diagnostics to study the plasma characteristics of six coronal dimming events. In the core dimming region, we find a steep and impulsive decrease of density with values up to 50%–70%. Five of the events also reveal an associated drop in temperature of 5%–25%. The secondary dimming regions also show a distinct decrease in density, but less strong, decreasing by 10%–45%. In both the core and the secondary dimming the density changes are much larger than the temperature changes, confirming that the dimming regions are mainly caused by plasma evacuation. In the core dimming, the plasma density reduces rapidly within the first 20–30 minutes after the flare start and does not recover for at least 10 hr later, whereas the secondary dimming tends to be more gradual and starts to replenish after 1–2 hr. The pre-event temperatures are higher in the core dimming (1.7–2.6 MK) than in the secondary dimming regions (1.6–2.0 MK). Both core and secondary dimmings are best observed in the AIA 211 and 193 Å filters. These findings suggest that the core dimming corresponds to the footpoints of the erupting flux rope rooted in the AR, while the secondary dimming represents plasma from overlying coronal structures that expand during the CME eruption.

  10. The transition region and coronal explorer (TRACE)

    Science.gov (United States)

    Title, Alan; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong, K.; Tarbell, Ted; Wolfson, C. Jacob; Golub, L.; Bookbinder, J.; Fisher, R.

    1995-01-01

    The transition region and coronal explorer (TRACE) NASA small explorer mission and instrument are presented. The TRACE scientific investigation explores the relationships between fine-scale magnetic fields and the associated solar plasma structures. The instrument collects images of solar plasmas at temperatures from 10(exp 4) to 10(exp 7) K with one arcsec spatial resolution. The design specifications of the trace instrument are presented.

  11. A SURVEY OF CORONAL CAVITY DENSITY PROFILES

    International Nuclear Information System (INIS)

    Fuller, J.; Gibson, S. E.

    2009-01-01

    Coronal cavities are common features of the solar corona that appear as darkened regions at the base of coronal helmet streamers in coronagraph images. Their darkened appearance indicates that they are regions of lowered density embedded within the comparatively higher density helmet streamer. Despite interfering projection effects of the surrounding helmet streamer (which we refer to as the cavity rim), Fuller et al. have shown that under certain conditions it is possible to use a Van de Hulst inversion of white-light polarized brightness (pB) data to calculate the electron density of both the cavity and cavity rim plasma. In this article, we apply minor modifications to the methods of Fuller et al. in order to improve the accuracy and versatility of the inversion process, and use the new methods to calculate density profiles for both the cavity and cavity rim in 24 cavity systems. We also examine trends in cavity morphology and how departures from the model geometry affect our density calculations. The density calculations reveal that in all 24 cases the cavity plasma has a flatter density profile than the plasma of the cavity rim, meaning that the cavity has a larger density depletion at low altitudes than it does at high altitudes. We find that the mean cavity density is over four times greater than that of a coronal hole at an altitude of 1.2 R sun and that every cavity in the sample is over twice as dense as a coronal hole at this altitude. Furthermore, we find that different cavity systems near solar maximum span a greater range in density at 1.2 R sun than do cavity systems near solar minimum, with a slight trend toward higher densities for systems nearer to solar maximum. Finally, we found no significant correlation of cavity density properties with cavity height-indeed, cavities show remarkably similar density depletions-except for the two smallest cavities that show significantly greater depletion.

  12. Forward Modeling of a Coronal Cavity

    Science.gov (United States)

    Kucera, T. A.; Gibson, S. E.; Schmit, D. J.

    2011-01-01

    We apply a forward model of emission from a coronal cavity in an effort to determine the temperature and density distribution in the cavity. Coronal cavities are long, low-density structures located over filament neutral lines and are often seen as dark elliptical features at the solar limb in white light, EUV and X-rays. When these structures erupt they form the cavity portions of CMEs The model consists of a coronal streamer model with a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. Temperature and density can be varied as a function of altitude both in the cavity and streamer. We apply this model to a cavity observed in Aug. 2007 by a wide array of instruments including Hinode/EIS, STEREO/EUVI and SOHO/EIT. Studies such as these will ultimately help us understand the the original structures which erupt to become CMEs and ICMES, one of the prime Solar Orbiter objectives.

  13. Solar origins of coronal mass ejections

    Science.gov (United States)

    Kahler, Stephen

    1987-01-01

    The large scale properties of coronal mass ejections (CMEs), such as morphology, leading edge speed, and angular width and position, have been cataloged for many events observed with coronagraphs on the Skylab, P-78, and SMM spacecraft. While considerable study has been devoted to the characteristics of the SMEs, their solar origins are still only poorly understood. Recent observational work has involved statistical associations of CMEs with flares and filament eruptions, and some evidence exists that the flare and eruptive-filament associated CMEs define two classes of events, with the former being generally more energetic. Nevertheless, it is found that eruptive-filament CMEs can at times be very energetic, giving rise to interplanetary shocks and energetic particle events. The size of the impulsive phase in a flare-associated CME seems to play no significant role in the size or speed of the CME, but the angular sizes of CMEs may correlate with the scale sizes of the 1-8 angstrom x-ray flares. At the present time, He 10830 angstrom observations should be useful in studying the late development of double-ribbon flares and transient coronal holes to yield insights into the CME aftermath. The recently available white-light synoptic maps may also prove fruitful in defining the coronal conditions giving rise to CMEs.

  14. [Development of electroforming apparatus for coronal restoration].

    Science.gov (United States)

    Watanabe, M; Sawada, T; Ukiya, M

    1989-03-01

    As dental technologies become highly developed, techniques have been more diversified. From as aspect of prosthodontic practice, both esthetic and functional requirements are emphasized for coronal restoration and consequently, these should be considered in the routine procedure. In fabrication of coronal restorations, metal, porcelain and resin are commonly used, and there exists the various disadvantages for metal cast method due to complicated processes by using different dental materials. Therefore, an electroforming apparatus was developed by us to replace the conventional procedure by a cathode rotary system. It was applied for coronal restorations to allow an electroforming directly on a working model. An experiment was successfully conducted to apply for a veneer crown on abutment tooth of upper central incisor on plaster model. The results were obtained as follows, 1. It was become possible to construct a metal framework by the electroforming. 2. Metal framework can be constructed on the same working model without a duplication of it. 3. The combined system for cathode rotation and liquid circulation could shorten the electroposition time, and allows a high current density extending to 50 A/dm2.

  15. SUNQUAKE GENERATION BY CORONAL MAGNETIC RESTRUCTURING

    Energy Technology Data Exchange (ETDEWEB)

    Russell, A. J. B.; Mooney, M. K. [School of Science and Engineering, University of Dundee, Dundee DD1 4HN (United Kingdom); Leake, J. E. [Naval Research Laboratory, Washington, DC 20375 (United States); Hudson, H. S. [Space Sciences Lab, University of California Berkeley, Berkeley, CA 94720 (United States)

    2016-11-01

    Sunquakes are the surface signatures of acoustic waves in the Sun’s interior that are produced by some but not all flares and coronal mass ejections (CMEs). This paper explores a mechanism for sunquake generation by the changes in magnetic field that occur during flares and CMEs, using MHD simulations with a semiempirical FAL-C atmosphere to demonstrate the generation of acoustic waves in the interior in response to changing magnetic tilt in the corona. We find that Alfvén–sound resonance combined with the ponderomotive force produces acoustic waves in the interior with sufficient energy to match sunquake observations when the magnetic field angle changes of the order of 10° in a region where the coronal field strength is a few hundred gauss or more. The most energetic sunquakes are produced when the coronal field is strong, while the variation of magnetic field strength with height and the timescale of the change in tilt are of secondary importance.

  16. SUNQUAKE GENERATION BY CORONAL MAGNETIC RESTRUCTURING

    International Nuclear Information System (INIS)

    Russell, A. J. B.; Mooney, M. K.; Leake, J. E.; Hudson, H. S.

    2016-01-01

    Sunquakes are the surface signatures of acoustic waves in the Sun’s interior that are produced by some but not all flares and coronal mass ejections (CMEs). This paper explores a mechanism for sunquake generation by the changes in magnetic field that occur during flares and CMEs, using MHD simulations with a semiempirical FAL-C atmosphere to demonstrate the generation of acoustic waves in the interior in response to changing magnetic tilt in the corona. We find that Alfvén–sound resonance combined with the ponderomotive force produces acoustic waves in the interior with sufficient energy to match sunquake observations when the magnetic field angle changes of the order of 10° in a region where the coronal field strength is a few hundred gauss or more. The most energetic sunquakes are produced when the coronal field is strong, while the variation of magnetic field strength with height and the timescale of the change in tilt are of secondary importance.

  17. THE CORONAL ABUNDANCE ANOMALIES OF M DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Brian E.; Laming, J. Martin [Naval Research Laboratory, Space Science Division, Washington, DC 20375 (United States); Karovska, Margarita, E-mail: brian.wood@nrl.navy.mil [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)

    2012-07-01

    We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an 'inverse FIP effect' is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

  18. The Coronal Abundance Anomalies of M Dwarfs

    Science.gov (United States)

    Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

    2012-07-01

    We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an "inverse FIP effect" is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

  19. THE CORONAL ABUNDANCE ANOMALIES OF M DWARFS

    International Nuclear Information System (INIS)

    Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

    2012-01-01

    We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an 'inverse FIP effect' is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

  20. EIT Observations of Coronal Mass Ejections

    Science.gov (United States)

    Gurman, J. B.; Fisher, Richard B. (Technical Monitor)

    2000-01-01

    Before the Solar and Heliospheric Observatory (SOHO), we had only the sketchiest of clues as to the nature and topology of coronal mass ejections (CMEs) below 1.1 - 1.2 solar radii. Occasionally, dimmings (or 'transient coronal holes') were observed in time series of soft X-ray images, but they were far less frequent than CME's. Simply by imaging the Sun frequently and continually at temperatures of 0.9 - 2.5 MK we have stumbled upon a zoo of CME phenomena in this previously obscured volume of the corona: (1) waves, (2) dimmings, and (3) a great variety of ejecta. In the three and a half years since our first observations of coronal waves associated with CME's, combined Large Angle Spectroscopic Coronagraph (LASCO) and extreme ultra-violet imaging telescope (EIT) synoptic observations have become a standard prediction tool for space weather forecasters, but our progress in actually understanding the CME phenomenon in the low corona has been somewhat slower. I will summarize the observations of waves, hot (> 0.9 MK) and cool ejecta, and some of the interpretations advanced to date. I will try to identify those phenomena, analysis of which could most benefit from the spectroscopic information available from ultraviolet coronograph spectrometer (UVCS) observations.

  1. Ring-constrained Join

    DEFF Research Database (Denmark)

    Yiu, Man Lung; Karras, Panagiotis; Mamoulis, Nikos

    2008-01-01

    . This new operation has important applications in decision support, e.g., placing recycling stations at fair locations between restaurants and residential complexes. Clearly, RCJ is defined based on a geometric constraint but not on distances between points. Thus, our operation is fundamentally different......We introduce a novel spatial join operator, the ring-constrained join (RCJ). Given two sets P and Q of spatial points, the result of RCJ consists of pairs (p, q) (where p ε P, q ε Q) satisfying an intuitive geometric constraint: the smallest circle enclosing p and q contains no other points in P, Q...

  2. Evidence of thermal conduction depression in hot coronal loops

    Science.gov (United States)

    Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Provornikova, Elena; Davila, Joseph

    2015-08-01

    Slow magnetoacoustic waves were first detected in hot (>6 MK) flare loops by the SOHO/SUMER spectrometer as Doppler shift oscillations in Fe XIX and Fe XXI lines. These oscillations are identified as standing slow-mode waves because the estimated phase speeds are close to the sound speed in the loop and some cases show a quarter period phase shift between velocity and intensity oscillations. The observed very rapid excitation and damping of standing slow mode waves have been studied by many authors using theories and numerical simulations, however, the exact mechanisms remain not well understood. Recently, flare-induced longitudinal intensity oscillations in hot post-flare loops have been detected by SDO/AIA. These oscillations have the similar physical properties as SUMER loop oscillations, and have been interpreted as the slow-mode waves. The multi-wavelength AIA observations with high spatio-temporal resolution and wide temperature coverage allow us to explore the wave excitation and damping mechanisms with an unprecedented detail to develope new coronal seismology. In this paper, we present accurate measurements of the effective adiabatic index (γeff) in the hot plasma from the electron temperature and density wave signals of a flare-induced longitudinal wave event using SDO/AIA data. Our results strikingly and clearly reveal that thermal conduction is highly depressed in hot (˜10 MK) post-flare loops and suggest that the compressive viscosity is the dominant wave damping mechanism which allows determination of the viscosity coefficient from the observables by coronal seismology. This new finding challenges our current understanding of thermal energy transport in solar and stellar flares, and may provide an alternative explanation of long-duration events and enhance our understand of coronal heating mechanism. We will discuss our results based on non-ideal MHD theory and simulations. We will also discuss the flare trigger mechanism based on magnetic topology

  3. The acceleration of electrons at a spherical coronal shock in a streamer-like coronal field

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Xiangliang, E-mail: kongx@sdu.edu.cn; Chen, Yao, E-mail: yaochen@sdu.edu.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China); Guo, Fan, E-mail: guofan.ustc@gmail.com [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2016-03-25

    We study the effect of large-scale coronal magnetic field on the electron acceleration at a spherical coronal shock using a test-particle method. The coronal field is approximated by an analytical solution with a streamer-like magnetic field featured by partially open magnetic field and a current sheet at the equator atop the closed region. It shows that the closed field plays the role of a trapping agency of shock-accelerated electrons, allowing for repetitive reflection and acceleration, therefore can greatly enhance the shock-electron acceleration efficiency. It is found that, with an ad hoc pitch-angle scattering, electron injected in the open field at the shock flank can be accelerated to high energies as well. In addition, if the shock is faster or stronger, a relatively harder electron energy spectrum and a larger maximum energy can be achieved.

  4. Prominence Bubbles and Plumes: Thermo-magnetic Buoyancy in Coronal Cavity Systems

    Science.gov (United States)

    Berger, Thomas; Hurlburt, N.

    2009-05-01

    The Hinode/Solar Optical Telescope continues to produce high spatial and temporal resolution images of solar prominences in both the Ca II 396.8 nm H-line and the H-alpha 656.3 nm line. Time series of these images show that many quiescent prominences produce large scale (50 Mm) dark "bubbles" that "inflate" into, and sometimes burst through, the prominence material. In addition, small-scale (2--5 Mm) dark plumes are seen rising into many quiescent prominences. We show typical examples of both phenomena and argue that they originate from the same mechanism: concentrated and heated magnetic flux that rises due to thermal and magnetic buoyancy to equilibrium heights in the prominence/coronal-cavity system. More generally, these bubbles and upflows offer a source of both magnetic flux and mass to the overlying coronal cavity, supporting B.C. Low's theory of CME initiation via steadily increasing magnetic buoyancy breaking through the overlying helmut streamer tension forces. Quiescent prominences are thus seen as the lowermost parts of the larger coronal cavity system, revealing through thermal effects both the cooled downflowing "drainage" from the cavity and the heated upflowing magnetic "plasmoids" supplying the cavity. We compare SOT movies to new 3D compressible MHD simulations that reproduce the dark turbulent plume dynamics to establish the magnetic and thermal character of these buoyancy-driven flows into the corona.

  5. The First Ionization Potential Effect from the Ponderomotive Force: On the Polarization and Coronal Origin of Alfvén Waves

    Energy Technology Data Exchange (ETDEWEB)

    Laming, J. Martin, E-mail: laming@nrl.navy.mil [Space Science Division, Naval Research Laboratory, Code 7684, Washington, DC 20375 (United States)

    2017-08-01

    We investigate in more detail the origin of chromospheric Alfvén waves that give rise to the separation of ions and neutrals—the first ionization potential (FIP) effect—through the action of the ponderomotive force. In open field regions, we model the dependence of fractionation on the plasma upflow velocity through the chromosphere for both shear (or planar) and torsional Alfvén waves of photospheric origin. These differ mainly in their parametric coupling to slow mode waves. Shear Alfvén waves appear to reproduce observed fractionations for a wider range of model parameters and present less of a “fine-tuning” problem than do torsional waves. In closed field regions, we study the fractionations produced by Alfvén waves with photospheric and coronal origins. Waves with a coronal origin, at or close to resonance with the coronal loop, offer a significantly better match to observed abundances than do photospheric waves, with shear and torsional waves in such a case giving essentially indistinguishable fractionations. Such coronal waves are likely the result of a nanoflare coronal heating mechanism that, as well as heating coronal plasmas, releases Alfvén waves that can travel down to loop footpoints and cause FIP fractionation through the ponderomotive force as they reflect from the chromosphere back into the corona.

  6. The First Ionization Potential Effect from the Ponderomotive Force: On the Polarization and Coronal Origin of Alfvén Waves

    International Nuclear Information System (INIS)

    Laming, J. Martin

    2017-01-01

    We investigate in more detail the origin of chromospheric Alfvén waves that give rise to the separation of ions and neutrals—the first ionization potential (FIP) effect—through the action of the ponderomotive force. In open field regions, we model the dependence of fractionation on the plasma upflow velocity through the chromosphere for both shear (or planar) and torsional Alfvén waves of photospheric origin. These differ mainly in their parametric coupling to slow mode waves. Shear Alfvén waves appear to reproduce observed fractionations for a wider range of model parameters and present less of a “fine-tuning” problem than do torsional waves. In closed field regions, we study the fractionations produced by Alfvén waves with photospheric and coronal origins. Waves with a coronal origin, at or close to resonance with the coronal loop, offer a significantly better match to observed abundances than do photospheric waves, with shear and torsional waves in such a case giving essentially indistinguishable fractionations. Such coronal waves are likely the result of a nanoflare coronal heating mechanism that, as well as heating coronal plasmas, releases Alfvén waves that can travel down to loop footpoints and cause FIP fractionation through the ponderomotive force as they reflect from the chromosphere back into the corona.

  7. Detection of nanoflare-heated plasma in the solar corona by the FOXSI-2 sounding rocket

    Science.gov (United States)

    Ishikawa, Shin-nosuke; Glesener, Lindsay; Krucker, Säm; Christe, Steven; Buitrago-Casas, Juan Camilo; Narukage, Noriyuki; Vievering, Juliana

    2017-11-01

    The processes that heat the solar and stellar coronae to several million kelvins, compared with the much cooler photosphere (5,800 K for the Sun), are still not well known1. One proposed mechanism is heating via a large number of small, unresolved, impulsive heating events called nanoflares2. Each event would heat and cool quickly, and the average effect would be a broad range of temperatures including a small amount of extremely hot plasma. However, detecting these faint, hot traces in the presence of brighter, cooler emission is observationally challenging. Here we present hard X-ray data from the second flight of the Focusing Optics X-ray Solar Imager (FOXSI-2), which detected emission above 7 keV from an active region of the Sun with no obvious individual X-ray flare emission. Through differential emission measure computations, we ascribe this emission to plasma heated above 10 MK, providing evidence for the existence of solar nanoflares. The quantitative evaluation of the hot plasma strongly constrains the coronal heating models.

  8. DETERMINING HEATING RATES IN RECONNECTION FORMED FLARE LOOPS OF THE M8.0 FLARE ON 2005 MAY 13

    Energy Technology Data Exchange (ETDEWEB)

    Liu Wenjuan; Qiu Jiong; Longcope, Dana W. [Department of Physics, Montana State University, Bozeman, MT 59717-3840 (United States); Caspi, Amir [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States)

    2013-06-20

    We analyze and model an M8.0 flare on 2005 May 13 observed by the Transition Region and Coronal Explorer and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to determine the energy release rate from magnetic reconnection that forms and heats numerous flare loops. The flare exhibits two ribbons in UV 1600 A emission. Analysis shows that the UV light curve at each flaring pixel rises impulsively within a few minutes, and decays slowly with a timescale longer than 10 minutes. Since the lower atmosphere (the transition region and chromosphere) responds to energy deposit nearly instantaneously, the rapid UV brightening is thought to reflect the energy release process in the newly formed flare loop rooted at the footpoint. In this paper, we utilize the spatially resolved (down to 1'') UV light curves and the thick-target hard X-ray emission to construct heating functions of a few thousand flare loops anchored at the UV footpoints, and compute plasma evolution in these loops using the enthalpy-based thermal evolution of loops model. The modeled coronal temperatures and densities of these flare loops are then used to calculate coronal radiation. The computed soft X-ray spectra and light curves compare favorably with those observed by RHESSI and by the Geostationary Operational Environmental Satellite X-ray Sensor. The time-dependent transition region differential emission measure for each loop during its decay phase is also computed with a simplified model and used to calculate the optically thin C IV line emission, which dominates the UV 1600 A bandpass during the flare. The computed C IV line emission decays at the same rate as observed. This study presents a method to constrain heating of reconnection-formed flare loops using all available observables independently, and provides insight into the physics of energy release and plasma heating during the flare. With this method, the lower limit of the total energy used to heat the flare loops in

  9. Sharp spatially constrained inversion

    DEFF Research Database (Denmark)

    Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.

    2013-01-01

    We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes...... inversions are compared against classical smooth results and available boreholes. With the focusing approach, the obtained blocky results agree with the underlying geology and allow for easier interpretation by the end-user....

  10. Numerical simulations of flares on M dwarf stars. I - Hydrodynamics and coronal X-ray emission

    Science.gov (United States)

    Cheng, Chung-Chieh; Pallavicini, Roberto

    1991-01-01

    Flare-loop models are utilized to simulate the time evolution and physical characteristics of stellar X-ray flares by varying the values of flare-energy input and loop parameters. The hydrodynamic evolution is studied in terms of changes in the parameters of the mass, energy, and momentum equations within an area bounded by the chromosphere and the corona. The zone supports a magnetically confined loop for which processes are described including the expansion of heated coronal gas, chromospheric evaporation, and plasma compression at loop footpoints. The intensities, time profiles, and average coronal temperatures of X-ray flares are derived from the simulations and compared to observational evidence. Because the amount of evaporated material does not vary linearly with flare-energy input, large loops are required to produce the energy measured from stellar flares.

  11. Coronal Loops: Evolving Beyond the Isothermal Approximation

    Science.gov (United States)

    Schmelz, J. T.; Cirtain, J. W.; Allen, J. D.

    2002-05-01

    Are coronal loops isothermal? A controversy over this question has arisen recently because different investigators using different techniques have obtained very different answers. Analysis of SOHO-EIT and TRACE data using narrowband filter ratios to obtain temperature maps has produced several key publications that suggest that coronal loops may be isothermal. We have constructed a multi-thermal distribution for several pixels along a relatively isolated coronal loop on the southwest limb of the solar disk using spectral line data from SOHO-CDS taken on 1998 Apr 20. These distributions are clearly inconsistent with isothermal plasma along either the line of sight or the length of the loop, and suggested rather that the temperature increases from the footpoints to the loop top. We speculated originally that these differences could be attributed to pixel size -- CDS pixels are larger, and more `contaminating' material would be expected along the line of sight. To test this idea, we used CDS iron line ratios from our data set to mimic the isothermal results from the narrowband filter instruments. These ratios indicated that the temperature gradient along the loop was flat, despite the fact that a more complete analysis of the same data showed this result to be false! The CDS pixel size was not the cause of the discrepancy; rather, the problem lies with the isothermal approximation used in EIT and TRACE analysis. These results should serve as a strong warning to anyone using this simplistic method to obtain temperature. This warning is echoed on the EIT web page: ``Danger! Enter at your own risk!'' In other words, values for temperature may be found, but they may have nothing to do with physical reality. Solar physics research at the University of Memphis is supported by NASA grant NAG5-9783. This research was funded in part by the NASA/TRACE MODA grant for Montana State University.

  12. A multi-channel coronal spectrophotometer.

    Science.gov (United States)

    Landman, D. A.; Orrall, F. Q.; Zane, R.

    1973-01-01

    We describe a new multi-channel coronal spectrophotometer system, presently being installed at Mees Solar Observatory, Mount Haleakala, Maui. The apparatus is designed to record and interpret intensities from many sections of the visible and near-visible spectral regions simultaneously, with relatively high spatial and temporal resolution. The detector, a thermoelectrically cooled silicon vidicon camera tube, has its central target area divided into a rectangular array of about 100,000 pixels and is read out in a slow-scan (about 2 sec/frame) mode. Instrument functioning is entirely under PDP 11/45 computer control, and interfacing is via the CAMAC system.

  13. Evolution of coronal and interplanetary magnetic fields

    International Nuclear Information System (INIS)

    Levine, R.H.

    1980-01-01

    Numerous studies have provided the detailed information necessary for a substantive synthesis of the empirical relation between the magnetic field of the sun and the structure of the interplanetary field. The author points out the latest techniques and studies of the global solar magnetic field and its relation to the interplanetary field. The potential to overcome most of the limitations of present methods of analysis exists in techniques of modelling the coronal magnetic field using observed solar data. Such empirical models are, in principle, capable of establishing the connection between a given heliospheric point and its magnetically-connected photospheric point, as well as the physical basis for the connection. (Auth.)

  14. Solar radio bursts of spectral type II, coronal shocks, and optical coronal transients

    Science.gov (United States)

    Maxwell, A.; Dryer, M.

    1981-01-01

    An examination is presented of the association of solar radio bursts of spectral type II and coronal shocks with solar flare ejecta observed in H-alpha, the green coronal line, and white-light coronagraphs. It is suggested that fast-moving optical coronal transients should for the most part be identified with piston-type phenomena well behind the outward-traveling shock waves that generate type II radio bursts. A general model is presented which relates type II radio bursts and coronal shocks to optically observed ejecta and consists of three main velocity regimes: (1) a quasi-hemispherical shock wave moving outward from the flare at speeds of 1000-2000 km/sec and Alfven Mach number of about 1.5; (2) the velocity of the piston driving the shock, on the order of 0.8 that of the shock; and (3) the regime of the slower-moving H-alpha ejecta, with velocities of 300-500 km/sec.

  15. Evaluation of the Minifilament-Eruption Scenario for Solar Coronal Jets in Polar Coronal Holes

    Science.gov (United States)

    Baikie, Tomi K.; Sterling, Alphonse C.; Falconer, David; Moore, Ronald L.; Savage, Sabrina L.

    2016-01-01

    Solar coronal jets are suspected to result from magnetic reconnection low in the Sun's atmosphere. Sterling et al. (2015) looked as 20 jets in polar coronal holes, using X-ray images from the Hinode/X-Ray Telescope (XRT) and EUV images from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). They suggested that each jet was driven by the eruption of twisted closed magnetic field carrying a small-scale filament, which they call a 'minifilament', and that the jet was produced by reconnection of the erupting field with surrounding open field. In this study, we carry out a more extensive examination of polar coronal jets. From 180 hours of XRT polar coronal hole observations spread over two years (2014-2016), we identified 130 clearly-identifiable X-ray jet events and thus determined an event rate of over 17 jets per day per in the Hinode/XRT field of view. From the broader set, we selected 25 of the largest and brightest events for further study in AIA 171, 193, 211, and 304 Angstrom images. We find that at least the majority of the jets follow the minifilament-eruption scenario, although for some cases the evolution of the minifilament in the onset of its eruption is more complex than presented in the simplified schematic of Sterling et al. (2015). For all cases in which we could make a clear determination, the spire of the X-ray jet drifted laterally away from the jet-base-edge bright point; this spire drift away from the bright point is consistent with expectations of the minifilament-eruption scenario for coronal-jet production. This work was supported with funding from the NASA/MSFC Hinode Project Office, and from the NASA HGI program.

  16. Extreme ultraviolet observations of coronal holes. II

    International Nuclear Information System (INIS)

    Bohlin, J.D.; Sheeley, N.R. Jr.

    1978-01-01

    Extreme-ultraviolet Skylab and ground-based solar magnetic field data have been combined to study the origin and evolution of coronal holes. It is shown that holes exist only within the large-scale unipolar magnetic cells into which the solar surface is divided at any given time. A well-defined boundary zone usually exists between the edge of a hole and the neutral line which marks the edge of its magnetic cell. This boundary zone is the region across which a cell is connected by magnetic arcades with adjacent cells of opposite polarity. Three pieces of observational evidence are offered to support the hypothesis that the magnetic lines of force from a hole are open. Kitt Peak magnetograms are used to show that, at least on a relative scale, the average field strengths within holes are quite variable, but indistinguishable from the field strengths in other quiet parts of the Sun's surface. Finally it is shown that the large, equatorial holes characteristic of the declining phase of the last solar cycle during Skylab (1973-74) were all formed as a result of the mergence of bipolar magnetic regions (BMR's), confirming an earlier hypothesis by Timothy et al. (1975). Systematic application of this model to the different aspects of the solar cycle correctly predicts the occurrence of both large, equatorial coronal holes (the 'M-regions' which cause recurrent geomagnetic storms) and the polar cap holes. (Auth.)

  17. Plasma Evolution within an Erupting Coronal Cavity

    Science.gov (United States)

    Long, David M.; Harra, Louise K.; Matthews, Sarah A.; Warren, Harry P.; Lee, Kyoung-Sun; Doschek, George A.; Hara, Hirohisa; Jenkins, Jack M.

    2018-03-01

    Coronal cavities have previously been observed to be associated with long-lived quiescent filaments and are thought to correspond to the associated magnetic flux rope. Although the standard flare model predicts a coronal cavity corresponding to the erupting flux rope, these have only been observed using broadband imaging data, restricting an analysis to the plane-of-sky. We present a unique set of spectroscopic observations of an active region filament seen erupting at the solar limb in the extreme ultraviolet. The cavity erupted and expanded rapidly, with the change in rise phase contemporaneous with an increase in nonthermal electron energy flux of the associated flare. Hot and cool filamentary material was observed to rise with the erupting flux rope, disappearing suddenly as the cavity appeared. Although strongly blueshifted plasma continued to be observed flowing from the apex of the erupting flux rope, this outflow soon ceased. These results indicate that the sudden injection of energy from the flare beneath forced the rapid eruption and expansion of the flux rope, driving strong plasma flows, which resulted in the eruption of an under-dense filamentary flux rope.

  18. Early cosmology constrained

    Energy Technology Data Exchange (ETDEWEB)

    Verde, Licia; Jimenez, Raul [Institute of Cosmos Sciences, University of Barcelona, IEEC-UB, Martí Franquès, 1, E08028 Barcelona (Spain); Bellini, Emilio [University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Pigozzo, Cassio [Instituto de Física, Universidade Federal da Bahia, Salvador, BA (Brazil); Heavens, Alan F., E-mail: liciaverde@icc.ub.edu, E-mail: emilio.bellini@physics.ox.ac.uk, E-mail: cpigozzo@ufba.br, E-mail: a.heavens@imperial.ac.uk, E-mail: raul.jimenez@icc.ub.edu [Imperial Centre for Inference and Cosmology (ICIC), Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)

    2017-04-01

    We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter Ω{sub MR} < 0.006 and extra radiation parameterised as extra effective neutrino species 2.3 < N {sub eff} < 3.2 when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond ΛCDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is r {sub s} = 147.4 ± 0.7 Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to r {sub s} = 150 ± 5 Mpc.

  19. Evolution of coronal mass ejections and their heliospheric imprints

    International Nuclear Information System (INIS)

    Rollett, T.

    2014-01-01

    Coronal mass ejections (CMEs) are the most powerful eruptions on the Sun and can reach speeds up to more than 3000 km/s. CMEs are the most important drivers of space weather and can cause geomagnetic storms when interacting with the Earth magnetosphere.The evolution and propagation of CMEs in interplanetary space is still not well understood. Interactions with the solar wind as well as other CMEs make accurate forecasting of arrival times difficult. The Constrained Harmonic Mean (CHM) method combines remote sensing white light data of STEREO/HI with in situ data and offers the possibility to derive kinematical profiles for any segment along the CME front to study its evolution in interplanetary space. We studied the influence of the ambient solar wind flow on the propagation behavior for three CME events. The kinematics revealed by the CHM method were compared to the simulated background solar wind. We found that CMEs are highly dependent on speed variations of the ambient medium. The CHM method was tested by analyzing a simulated CME as observed by STEREO/HI. After applying the CHM method, the resulting CME kinematics were compared to the real kinematics of the simulated CME. We found that the CHM method works best for small separation angles between the spacecraft. A case study of a fast CME that has been remotely observed by both STEREO/HI and in situ measured by four spacecraft at different heliocentric distances is also presented. Using this high number of in situ detections and the two side views we derived different speed profiles for the two different segments of the same CME causing a deformation of the overall structure of the CME. The studies presented show the effects of different influences of the ambient solar wind on the CME evolution. Interaction of CMEs with the solar wind or other CMEs lead to disturbances of the speed as well as the shape of CMEs, affecting their arrival time and their geoeffectivity. (author) [de

  20. Mid-term periodicities and heliospheric modulation of coronal index ...

    Indian Academy of Sciences (India)

    PRITHVI RAJ SINGH

    2018-03-06

    Mar 6, 2018 ... long-term periodicity of ∼11 years, with different solar activities. The physical processes that occur inside the. Sun are reflected by a periodic character in terms of coronal index of coronal emission (Fe XIV 530.3 nm) during solar activity cycles. Recently, a link between the strength of photospheric magnetic ...

  1. Constraining neutrinoless double beta decay

    International Nuclear Information System (INIS)

    Dorame, L.; Meloni, D.; Morisi, S.; Peinado, E.; Valle, J.W.F.

    2012-01-01

    A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum-rules (MSR). We show how these theories may constrain the absolute scale of neutrino mass, leading in most of the cases to a lower bound on the neutrinoless double beta decay effective amplitude.

  2. Quality of coroner's post-mortems in a UK hospital.

    Science.gov (United States)

    Al Mahdy, Husayn

    2014-01-01

    The aim of this paper was, principally, to look at the coroner's post-mortem report quality regarding adult medical patients admitted to an English hospital; and to compare results with Royal College of Pathologists guidelines. Hospital clinical notes of adult medical patients dying in 2011 and who were referred to the coroner's office to determine the cause of death were scrutinised. Their clinical care was also reviewed. There needs to be a comprehensive approach to coroner's post-mortems such as routinely taking histological and microbiological specimens. Acute adult medical patient care needs to improve. Steps should be taken to ensure that comprehensive coroner's post-mortems are performed throughout the UK, including with routine histological and microbiological specimens examination. Additionally, closer collaboration between clinicians and pathologists needs to occur to improve emergency adult medical patient clinical care. The study highlights inadequacies in coroner's pathology services.

  3. Assessment of Coronal Radiographic Parameters of the Spine in the Treatment of Adolescent Idiopathic Scoliosis

    Directory of Open Access Journals (Sweden)

    Mohsen Karami

    2016-10-01

    Preoperative coronal balance is very important to make a balanced spine after surgery. Other parameters like Lenke classification or main thoracic overcorrection did not affect postoperative coronal decompensation.

  4. CHROMOSPHERIC AND CORONAL WAVE GENERATION IN A MAGNETIC FLUX SHEATH

    International Nuclear Information System (INIS)

    Kato, Yoshiaki; Hansteen, Viggo; Gudiksen, Boris; Wedemeyer, Sven; Carlsson, Mats; Steiner, Oskar

    2016-01-01

    Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab “pump” the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in the chromosphere and higher tends to oscillate with a period of ν ≈ 4 mHz. We conclude that this process of “magnetic pumping” is a most plausible mechanism for the direct generation of longitudinal chromospheric and coronal compressive waves within magnetic flux concentrations, and it may provide an important heat source in the chromosphere. It may also be responsible for certain types of dynamic fibrils.

  5. CHROMOSPHERIC AND CORONAL WAVE GENERATION IN A MAGNETIC FLUX SHEATH

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Yoshiaki; Hansteen, Viggo; Gudiksen, Boris; Wedemeyer, Sven; Carlsson, Mats [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Steiner, Oskar, E-mail: yoshiaki.kato@astro.uio.no [Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg (Germany)

    2016-08-10

    Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab “pump” the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in the chromosphere and higher tends to oscillate with a period of ν ≈ 4 mHz. We conclude that this process of “magnetic pumping” is a most plausible mechanism for the direct generation of longitudinal chromospheric and coronal compressive waves within magnetic flux concentrations, and it may provide an important heat source in the chromosphere. It may also be responsible for certain types of dynamic fibrils.

  6. Coronal Mass Ejections: Models and Their Observational Basis

    Directory of Open Access Journals (Sweden)

    P. F. Chen

    2011-04-01

    Full Text Available Coronal mass ejections (CMEs are the largest-scale eruptive phenomenon in the solar system, expanding from active region-sized nonpotential magnetic structure to a much larger size. The bulk of plasma with a mass of ∼10^11 – 10^13 kg is hauled up all the way out to the interplanetary space with a typical velocity of several hundred or even more than 1000 km s^-1, with a chance to impact our Earth, resulting in hazardous space weather conditions. They involve many other much smaller-sized solar eruptive phenomena, such as X-ray sigmoids, filament/prominence eruptions, solar flares, plasma heating and radiation, particle acceleration, EIT waves, EUV dimmings, Moreton waves, solar radio bursts, and so on. It is believed that, by shedding the accumulating magnetic energy and helicity, they complete the last link in the chain of the cycling of the solar magnetic field. In this review, I try to explicate our understanding on each stage of the fantastic phenomenon, including their pre-eruption structure, their triggering mechanisms and the precursors indicating the initiation process, their acceleration and propagation. Particular attention is paid to clarify some hot debates, e.g., whether magnetic reconnection is necessary for the eruption, whether there are two types of CMEs, how the CME frontal loop is formed, and whether halo CMEs are special.

  7. ANALYSIS OF CORONAL RAIN OBSERVED BY IRIS , HINODE /SOT, AND SDO /AIA: TRANSVERSE OSCILLATIONS, KINEMATICS, AND THERMAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Kohutova, P.; Verwichte, E., E-mail: p.kohutova@warwick.ac.uk [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2016-08-10

    Coronal rain composed of cool plasma condensations falling from coronal heights along magnetic field lines is a phenomenon occurring mainly in active region coronal loops. Recent high-resolution observations have shown that coronal rain is much more common than previously thought, suggesting its important role in the chromosphere-corona mass cycle. We present the analysis of MHD oscillations and kinematics of the coronal rain observed in chromospheric and transition region lines by the Interface Region Imaging Spectrograph (IRIS) , the Hinode Solar Optical Telescope (SOT), and the Solar Dynamics Observatory ( SDO) Atmospheric Imaging Assembly (AIA). Two different regimes of transverse oscillations traced by the rain are detected: small-scale persistent oscillations driven by a continuously operating process and localized large-scale oscillations excited by a transient mechanism. The plasma condensations are found to move with speeds ranging from few km s{sup −1} up to 180 km s{sup −1} and with accelerations largely below the free-fall rate, likely explained by pressure effects and the ponderomotive force resulting from the loop oscillations. The observed evolution of the emission in individual SDO /AIA bandpasses is found to exhibit clear signatures of a gradual cooling of the plasma at the loop top. We determine the temperature evolution of the coronal loop plasma using regularized inversion to recover the differential emission measure (DEM) and by forward modeling the emission intensities in the SDO /AIA bandpasses using a two-component synthetic DEM model. The inferred evolution of the temperature and density of the plasma near the apex is consistent with the limit cycle model and suggests the loop is going through a sequence of periodically repeating heating-condensation cycles.

  8. Modeling Coronal Mass Ejections with EUHFORIA: A Parameter Study of the Gibson-Low Flux Rope Model using Multi-Viewpoint Observations

    Science.gov (United States)

    Verbeke, C.; Asvestari, E.; Scolini, C.; Pomoell, J.; Poedts, S.; Kilpua, E.

    2017-12-01

    Coronal Mass Ejections (CMEs) are one of the big influencers on the coronal and interplanetary dynamics. Understanding their origin and evolution from the Sun to the Earth is crucial in order to determine the impact on our Earth and society. One of the key parameters that determine the geo-effectiveness of the coronal mass ejection is its internal magnetic configuration. We present a detailed parameter study of the Gibson-Low flux rope model. We focus on changes in the input parameters and how these changes affect the characteristics of the CME at Earth. Recently, the Gibson-Low flux rope model has been implemented into the inner heliosphere model EUHFORIA, a magnetohydrodynamics forecasting model of large-scale dynamics from 0.1 AU up to 2 AU. Coronagraph observations can be used to constrain the kinematics and morphology of the flux rope. One of the key parameters, the magnetic field, is difficult to determine directly from observations. In this work, we approach the problem by conducting a parameter study in which flux ropes with varying magnetic configurations are simulated. We then use the obtained dataset to look for signatures in imaging observations and in-situ observations in order to find an empirical way of constraining the parameters related to the magnetic field of the flux rope. In particular, we focus on events observed by at least two spacecraft (STEREO + L1) in order to discuss the merits of using observations from multiple viewpoints in constraining the parameters.

  9. Measurements of coronal Faraday rotation at 4.6 R ☉

    International Nuclear Information System (INIS)

    Kooi, Jason E.; Fischer, Patrick D.; Buffo, Jacob J.; Spangler, Steven R.

    2014-01-01

    Many competing models for the coronal heating and acceleration mechanisms of the high-speed solar wind depend on the solar magnetic field and plasma structure in the corona within heliocentric distances of 5 R ☉ . We report on sensitive Very Large Array (VLA) full-polarization observations made in 2011 August, at 5.0 and 6.1 GHz (each with a bandwidth of 128 MHz) of the radio galaxy 3C 228 through the solar corona at heliocentric distances of 4.6-5.0 R ☉ . Observations at 5.0 GHz permit measurements deeper in the corona than previous VLA observations at 1.4 and 1.7 GHz. These Faraday rotation observations provide unique information on the magnetic field in this region of the corona. The measured Faraday rotation on this day was lower than our a priori expectations, but we have successfully modeled the measurement in terms of observed properties of the corona on the day of observation. Our data on 3C 228 provide two lines of sight (separated by 46'', 33,000 km in the corona). We detected three periods during which there appeared to be a difference in the Faraday rotation measure between these two closely spaced lines of sight. These measurements (termed differential Faraday rotation) yield an estimate of 2.6-4.1 GA for coronal currents. Our data also allow us to impose upper limits on rotation measure fluctuations caused by coronal waves; the observed upper limits were 3.3 and 6.4 rad m –2 along the two lines of sight. The implications of these results for Joule heating and wave heating are briefly discussed.

  10. Constrained evolution in numerical relativity

    Science.gov (United States)

    Anderson, Matthew William

    The strongest potential source of gravitational radiation for current and future detectors is the merger of binary black holes. Full numerical simulation of such mergers can provide realistic signal predictions and enhance the probability of detection. Numerical simulation of the Einstein equations, however, is fraught with difficulty. Stability even in static test cases of single black holes has proven elusive. Common to unstable simulations is the growth of constraint violations. This work examines the effect of controlling the growth of constraint violations by solving the constraints periodically during a simulation, an approach called constrained evolution. The effects of constrained evolution are contrasted with the results of unconstrained evolution, evolution where the constraints are not solved during the course of a simulation. Two different formulations of the Einstein equations are examined: the standard ADM formulation and the generalized Frittelli-Reula formulation. In most cases constrained evolution vastly improves the stability of a simulation at minimal computational cost when compared with unconstrained evolution. However, in the more demanding test cases examined, constrained evolution fails to produce simulations with long-term stability in spite of producing improvements in simulation lifetime when compared with unconstrained evolution. Constrained evolution is also examined in conjunction with a wide variety of promising numerical techniques, including mesh refinement and overlapping Cartesian and spherical computational grids. Constrained evolution in boosted black hole spacetimes is investigated using overlapping grids. Constrained evolution proves to be central to the host of innovations required in carrying out such intensive simulations.

  11. A model for a stable coronal loop

    International Nuclear Information System (INIS)

    Hoven, G.V.; Chiuderi, C.; Giachetti, R.

    1977-01-01

    We present here a new plasma-physics model of a stable active-region arch which corresponds to the structure observed in the EUV. Pressure gradients are seen, so that the equilibrium magnetic field must depart from the force-free form valid in the surrounding corona. We take advantage of the data and of the approximate cylindrical symmetry to develop a modified form of the commonly assumed sheared-spiral structure. The dynamic MHD behavior of this new pressure/field model is then evaluated by the Newcomb criterion, taken from controlled-fusion physics, and the results show short-wavelength stability in a specific parameter range. Thus we demonstrate the possibility, for pressure profiles with widths of the order of the magnetic-field scale, that such arches can persist for reasonable periods. Finally, the spatial proportions and magnetic fields of a characteristic stable coronal loop are described

  12. Image-Optimized Coronal Magnetic Field Models

    Science.gov (United States)

    Jones, Shaela I.; Uritsky, Vadim; Davila, Joseph M.

    2017-01-01

    We have reported previously on a new method we are developing for using image-based information to improve global coronal magnetic field models. In that work we presented early tests of the method which proved its capability to improve global models based on flawed synoptic magnetograms, given excellent constraints on the field in the model volume. In this follow-up paper we present the results of similar tests given field constraints of a nature that could realistically be obtained from quality white-light coronagraph images of the lower corona. We pay particular attention to difficulties associated with the line-of-sight projection of features outside of the assumed coronagraph image plane, and the effect on the outcome of the optimization of errors in localization of constraints. We find that substantial improvement in the model field can be achieved with this type of constraints, even when magnetic features in the images are located outside of the image plane.

  13. Image-optimized Coronal Magnetic Field Models

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Shaela I.; Uritsky, Vadim; Davila, Joseph M., E-mail: shaela.i.jones-mecholsky@nasa.gov, E-mail: shaela.i.jonesmecholsky@nasa.gov [NASA Goddard Space Flight Center, Code 670, Greenbelt, MD 20771 (United States)

    2017-08-01

    We have reported previously on a new method we are developing for using image-based information to improve global coronal magnetic field models. In that work, we presented early tests of the method, which proved its capability to improve global models based on flawed synoptic magnetograms, given excellent constraints on the field in the model volume. In this follow-up paper, we present the results of similar tests given field constraints of a nature that could realistically be obtained from quality white-light coronagraph images of the lower corona. We pay particular attention to difficulties associated with the line-of-sight projection of features outside of the assumed coronagraph image plane and the effect on the outcome of the optimization of errors in the localization of constraints. We find that substantial improvement in the model field can be achieved with these types of constraints, even when magnetic features in the images are located outside of the image plane.

  14. EUV and radio spectrum of coronal holes

    Energy Technology Data Exchange (ETDEWEB)

    Chiuderi Drago, F [Osservatorio Astrofisico di Arcetri, Florence (Italy)

    1980-03-01

    From the intensity of 19 EUV lines whose formation temperature anti T ranges from 3 x 10/sup 4/ to 1.4 x 10/sup 6/, two different models of the transition region and corona for the cell-centre and the network are derived. It is shown that both these models give radio brightness temperatures systematically higher than the observed ones. An agreement with radio data can be found only with lines formed at low temperature (anti T < 8.5 x 10/sup 5/) by decreasing the coronal temperature and the emission measure. The possibility of resolving the discrepancy by using different ion abundances has also been investigated with negative results.

  15. Coronal mass ejections and large geomagnetic storms

    International Nuclear Information System (INIS)

    Gosling, J.T.; Bame, S.J.; McComas, D.J.; Phillips, J.L.

    1990-01-01

    Previous work indicates that coronal mass ejection (CME) events in the solar wind at 1 AU can be identified by the presence of a flux of counterstreaming solar wind halo electrons (above about 80 eV). Using this technique to identify CMEs in 1 AU plasma data, the authors find that most large geomagnetic storms during the interval surrounding the last solar maximum (Aug. 1978-Oct. 1982) were associated with Earth-passage of interplanetary disturbances in which the Earth encountered both a shock and the CME driving the shock. However, only about one CME in six encountered by Earth was effective in causing a large geomagnetic storm. Slow CMEs which did not interact strongly with the ambient solar wind ahead were particularly ineffective in a geomagnetic sense

  16. Determination of Coronal Magnetic Fields from Vector Magnetograms

    Science.gov (United States)

    Mikic, Zoran

    1997-01-01

    During the course of the present contract we developed an 'evolutionary technique' for the determination of force-free coronal magnetic fields from vector magnetograph observations. The method can successfully generate nonlinear force- free fields (with non-constant-a) that match vector magnetograms. We demonstrated that it is possible to determine coronal magnetic fields from photospheric measurements, and we applied it to vector magnetograms of active regions. We have also studied theoretical models of coronal fields that lead to disruptions. Specifically, we have demonstrated that the determination of force-free fields from exact boundary data is a well-posed mathematical problem, by verifying that the computed coronal field agrees with an analytic force-free field when boundary data for the analytic field are used; demonstrated that it is possible to determine active-region coronal magnetic fields from photospheric measurements, by computing the coronal field above active region 5747 on 20 October 1989, AR6919 on 15 November 1991, and AR7260 on 18 August 1992, from data taken with the Stokes Polarimeter at Mees Solar Observatory, University of Hawaii; started to analyze active region 7201 on 19 June 1992 using measurements made with the Advanced Stokes Polarimeter at NSO/Sac Peak; investigated the effects of imperfections in the photospheric data on the computed coronal magnetic field; documented the coronal field structure of AR5747 and compared it to the morphology of footpoint emission in a flare, showing that the 'high- pressure' H-alpha footpoints are connected by coronal field lines; shown that the variation of magnetic field strength along current-carrying field lines is significantly different from the variation in a potential field, and that the resulting near-constant area of elementary flux tubes is consistent with observations; begun to develop realistic models of coronal fields which can be used to study flare trigger mechanisms; demonstrated that

  17. PROMINENCE ACTIVATION BY CORONAL FAST MODE SHOCK

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Takuya [Department of Astronomy, Kyoto University, Sakyo, Kyoto, 606-8502 (Japan); Asai, Ayumi [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471 (Japan); Shibata, Kazunari, E-mail: takahashi@kwasan.kyoto-u.ac.jp [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471 (Japan)

    2015-03-01

    An X5.4 class flare occurred in active region NOAA11429 on 2012 March 7. The flare was associated with a very fast coronal mass ejection (CME) with a velocity of over 2500 km s{sup −1}. In the images taken with the Solar Terrestrial Relations Observatory-B/COR1, a dome-like disturbance was seen to detach from an expanding CME bubble and propagated further. A Type-II radio burst was also observed at the same time. On the other hand, in extreme ultraviolet images obtained by the Solar Dynamic Observatory/Atmospheric Imaging Assembly (AIA), the expanding dome-like structure and its footprint propagating to the north were observed. The footprint propagated with an average speed of about 670 km s{sup −1} and hit a prominence located at the north pole and activated it. During the activation, the prominence was strongly brightened. On the basis of some observational evidence, we concluded that the footprint in AIA images and the ones in COR1 images are the same, that is, the MHD fast mode shock front. With the help of a linear theory, the fast mode Mach number of the coronal shock is estimated to be between 1.11 and 1.29 using the initial velocity of the activated prominence. Also, the plasma compression ratio of the shock is enhanced to be between 1.18 and 2.11 in the prominence material, which we consider to be the reason for the strong brightening of the activated prominence. The applicability of linear theory to the shock problem is tested with a nonlinear MHD simulation.

  18. Magnetic Untwisting in Solar Jets that Go into the Outer Corona in Polar Coronal Holes

    Science.gov (United States)

    Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David A.

    2014-01-01

    We present results from 14 exceptionally high-reaching large solar jets observed in the polar coronal holes. EUV movies from SDO/AIA show that each jet is similar to many other similar-size and smaller jets that erupt in coronal holes, but each is exceptional in that it goes higher than most other jets, so high that it is observed in the outer corona beyond 2.2 R(sub Sun) in images from the SOHO/LASCO/C2 coronagraph. For these high-reaching jets, we find: (1) the front of the jet transits the corona below 2.2 R(sub Sun) at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most jets display oscillatory swaying having an amplitude of a few degrees and a period of order 1 hour. We conclude that these jets are magnetically driven, propose that the driver is a magnetic-untwisting wave that is grossly a large-amplitude (i.e., nonlinear) torsional Alfven wave that is put into the reconnected open magnetic field in the jet by interchange reconnection as the jet erupts, and estimate from the measured spinning and swaying that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 R(sub Sun). From these results for these big jets, we reason that the torsional magnetic waves observed in Type-II spicules should dissipate in the corona in the same way and could thereby power much of the coronal heating in coronal holes.

  19. Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection

    Science.gov (United States)

    Song, H.; Zhang, J.; Chen, Y.; Cheng, X.

    2014-12-01

    Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are results of eruptions of magnetic flux ropes (MFRs). However, a heated debate is on whether MFRs pre-exist before the eruptions or they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre existing MFR scenario. There is almost no reported observation about MFR formation during the eruption. In this presentation, we present an intriguing observation of a solar eruptive event with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows a detailed formation process of the MFR during the eruption. The process started with the expansion of a low lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly-formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved-in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~ 10 MK), presumably a MFR, producing a CME. We suggest that two spatially-separated magnetic reconnections occurred in this event, responsible for producing the flare and the hot blob (CME), respectively.

  20. DIRECT OBSERVATIONS OF MAGNETIC FLUX ROPE FORMATION DURING A SOLAR CORONAL MASS EJECTION

    International Nuclear Information System (INIS)

    Song, H. Q.; Chen, Y.; Zhang, J.; Cheng, X.

    2014-01-01

    Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are the results of eruptions of magnetic flux ropes (MFRs). However, there is heated debate on whether MFRs exist prior to the eruptions or if they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures, and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation of MFR formation during the eruption. In this Letter, we present an intriguing observation of a solar eruptive event that occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows the formation process of the MFR during the eruption in detail. The process began with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (∼10 MK), presumably an MFR, producing a CME. We suggest that two spatially separated magnetic reconnections occurred in this event, which were responsible for producing the flare and the hot blob (CME)

  1. DIRECT OBSERVATIONS OF MAGNETIC FLUX ROPE FORMATION DURING A SOLAR CORONAL MASS EJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Song, H. Q.; Chen, Y. [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China); Zhang, J. [School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, VA 22030 (United States); Cheng, X., E-mail: hqsong@sdu.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing, Jiangsu 210093 (China)

    2014-09-10

    Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are the results of eruptions of magnetic flux ropes (MFRs). However, there is heated debate on whether MFRs exist prior to the eruptions or if they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures, and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation of MFR formation during the eruption. In this Letter, we present an intriguing observation of a solar eruptive event that occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows the formation process of the MFR during the eruption in detail. The process began with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (∼10 MK), presumably an MFR, producing a CME. We suggest that two spatially separated magnetic reconnections occurred in this event, which were responsible for producing the flare and the hot blob (CME)

  2. Combined Multipoint Remote and In Situ Observations of the Asymmetric Evolution of a Fast Solar Coronal Mass Ejection

    OpenAIRE

    Rollett, T.; Moestl, C.; Temmer, M.; Frahm, R. A.; Davies, J. A.; Veronig, A. M.; Vrsnak, B.; Amerstorfer, U. V.; Farrugia, C. J.; Zic, T.; Zhang, T. L.

    2014-01-01

    We present an analysis of the fast coronal mass ejection (CME) of 2012 March 7, which was imaged by both STEREO spacecraft and observed in situ by MESSENGER, Venus Express, Wind and Mars Express. Based on detected arrivals at four different positions in interplanetary space, it was possible to strongly constrain the kinematics and the shape of the ejection. Using the white-light heliospheric imagery from STEREO-A and B, we derived two different kinematical profiles for the CME by applying the...

  3. Testing a Constrained MPC Controller in a Process Control Laboratory

    Science.gov (United States)

    Ricardez-Sandoval, Luis A.; Blankespoor, Wesley; Budman, Hector M.

    2010-01-01

    This paper describes an experiment performed by the fourth year chemical engineering students in the process control laboratory at the University of Waterloo. The objective of this experiment is to test the capabilities of a constrained Model Predictive Controller (MPC) to control the operation of a Double Pipe Heat Exchanger (DPHE) in real time.…

  4. Measurements of EUV coronal holes and open magnetic flux

    International Nuclear Information System (INIS)

    Lowder, C.; Qiu, J.; Leamon, R.; Liu, Y.

    2014-01-01

    Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in these holes, and compare the measurements with calculations by the potential field source surface (PFSS) model. It is shown that, from 1996 through 2010, the total area of coronal holes measured with EIT images varies between 5% and 17% of the total solar surface area, and the total unsigned open flux varies between (2-5)× 10 22 Mx. The solar cycle dependence of these measurements is similar to the PFSS results, but the model yields larger hole areas and greater open flux than observed by EIT. The AIA/EUVI measurements from 2010-2013 show coronal hole area coverage of 5%-10% of the total surface area, with significant contribution from low latitudes, which is under-represented by EIT. AIA/EUVI have measured much enhanced open magnetic flux in the range of (2-4)× 10 22 Mx, which is about twice the flux measured by EIT, and matches with the PFSS calculated open flux, with discrepancies in the location and strength of coronal holes. A detailed comparison between the three measurements (by EIT, AIA-EUVI, and PFSS) indicates that coronal holes in low latitudes contribute significantly to the total open magnetic flux. These low-latitude coronal holes are not well measured with either the He I 10830 line in previous studies, or EIT EUV images; neither are they well captured by the static PFSS model. The enhanced observations from AIA/EUVI allow a more accurate measure of these low-latitude coronal holes and their contribution to open magnetic flux.

  5. Measurements of EUV coronal holes and open magnetic flux

    Energy Technology Data Exchange (ETDEWEB)

    Lowder, C.; Qiu, J.; Leamon, R. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Liu, Y., E-mail: clowder@solar.physics.montana.edu [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2014-03-10

    Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in these holes, and compare the measurements with calculations by the potential field source surface (PFSS) model. It is shown that, from 1996 through 2010, the total area of coronal holes measured with EIT images varies between 5% and 17% of the total solar surface area, and the total unsigned open flux varies between (2-5)× 10{sup 22} Mx. The solar cycle dependence of these measurements is similar to the PFSS results, but the model yields larger hole areas and greater open flux than observed by EIT. The AIA/EUVI measurements from 2010-2013 show coronal hole area coverage of 5%-10% of the total surface area, with significant contribution from low latitudes, which is under-represented by EIT. AIA/EUVI have measured much enhanced open magnetic flux in the range of (2-4)× 10{sup 22} Mx, which is about twice the flux measured by EIT, and matches with the PFSS calculated open flux, with discrepancies in the location and strength of coronal holes. A detailed comparison between the three measurements (by EIT, AIA-EUVI, and PFSS) indicates that coronal holes in low latitudes contribute significantly to the total open magnetic flux. These low-latitude coronal holes are not well measured with either the He I 10830 line in previous studies, or EIT EUV images; neither are they well captured by the static PFSS model. The enhanced observations from AIA/EUVI allow a more accurate measure of these low-latitude coronal holes and their contribution to open magnetic flux.

  6. TEMPERATURE AND EXTREME-ULTRAVIOLET INTENSITY IN A CORONAL PROMINENCE CAVITY AND STREAMER

    Energy Technology Data Exchange (ETDEWEB)

    Kucera, T. A. [NASA/GSFC, Code 671, Greenbelt, MD 20771 (United States); Gibson, S. E.; Schmit, D. J. [HAO/NCAR, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Landi, E. [Department of Atmospheric, Oceanic and Space Science, Space Research Building, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143 (United States); Tripathi, D. [Inter-University Centre for Astronomy and Astrophysics, Post Bag-4, Ganeshkhind, Pune University Campus, Pune 411 007 (India)

    2012-09-20

    We analyze the temperature and EUV line emission of a coronal cavity and surrounding streamer in terms of a morphological forward model. We use a series of iron line ratios observed with the Hinode Extreme-ultraviolet Imaging Spectrograph (EIS) on 2007 August 9 to constrain temperature as a function of altitude in a morphological forward model of the streamer and cavity. We also compare model predictions to the EIS EUV line intensities and polarized brightness (pB) data from the Mauna Loa Solar Observatory (MLSO) Mark 4 K-coronameter. This work builds on earlier analysis using the same model to determine geometry of and density in the same cavity and streamer. The fit to the data with altitude-dependent temperature profiles indicates that both the streamer and cavity have temperatures in the range 1.4-1.7 MK. However, the cavity exhibits substantial substructure such that the altitude-dependent temperature profile is not sufficient to completely model conditions in the cavity. Coronal prominence cavities are structured by magnetism so clues to this structure are to be found in their plasma properties. These temperature substructures are likely related to structures in the cavity magnetic field. Furthermore, we find that the model overestimates the EUV line intensities by a factor of 4-10, without overestimating pB. We discuss this difference in terms of filling factors and uncertainties in density diagnostics and elemental abundances.

  7. Lightweight cryptography for constrained devices

    DEFF Research Database (Denmark)

    Alippi, Cesare; Bogdanov, Andrey; Regazzoni, Francesco

    2014-01-01

    Lightweight cryptography is a rapidly evolving research field that responds to the request for security in resource constrained devices. This need arises from crucial pervasive IT applications, such as those based on RFID tags where cost and energy constraints drastically limit the solution...... complexity, with the consequence that traditional cryptography solutions become too costly to be implemented. In this paper, we survey design strategies and techniques suitable for implementing security primitives in constrained devices....

  8. Case report: pre-eruptive intra-coronal radiolucencies revisited.

    LENUS (Irish Health Repository)

    Counihan, K P

    2012-08-01

    Pre-eruptive intra-coronal radiolucency (PEIR) describes a radiolucent lesion located in the coronal dentine, just beneath the enamel-dentine junction of unerupted teeth. The prevalence of this lesion varies depending on the type and quality of radiographic exposure and age of patients used for assessment. The aetiology of pre-eruptive intra-coronal radiolucent lesions is not fully understood, but published clinical and histological evidence suggest that these lesions are resorptive in nature. Issues around the diagnosis, treatment planning and clinical management of this lesion are explored using previously unreported cases.

  9. Mass and energy supply of a cool coronal loop near its apex

    Science.gov (United States)

    Yan, Limei; Peter, Hardi; He, Jiansen; Xia, Lidong; Wang, Linghua

    2018-03-01

    Context. Different models for the heating of solar corona assume or predict different locations of the energy input: concentrated at the footpoints, at the apex, or uniformly distributed. The brightening of a loop could be due to the increase in electron density ne, the temperature T, or a mixture of both. Aim. We investigate possible reasons for the brightening of a cool loop at transition region temperatures through imaging and spectral observation. Methods: We observed a loop with the Interface Region Imaging Spectrograph (IRIS) and used the slit-jaw images together with spectra taken at a fixed slit position to study the evolution of plasma properties in and below the loop. We used spectra of Si IV, which forms at around 80 000 K in equilibrium, to identify plasma motions and derive electron densities from the ratio of inter-combination lines of O IV. Additional observations from the Solar Dynamics Observatory (SDO) were employed to study the response at coronal temperatures (Atmospheric Imaging Assembly, AIA) and to investigate the surface magnetic field below the loop (Helioseismic and Magnetic Imager, HMI). Results: The loop first appears at transition region temperatures and later also at coronal temperatures, indicating a heating of the plasma in the loop. The appearance of hot plasma in the loop coincides with a possible accelerating upflow seen in Si IV, with the Doppler velocity shifting continuously from -70 km s-1 to -265 km s-1. The 3D magnetic field lines extrapolated from the HMI magnetogram indicate possible magnetic reconnection between small-scale magnetic flux tubes below or near the loop apex. At the same time, an additional intensity enhancement near the loop apex is visible in the IRIS slit-jaw images at 1400 Å. These observations suggest that the loop is probably heated by the interaction between the loop and the upflows, which are accelerated by the magnetic reconnection between small-scale magnetic flux tubes at lower altitudes. Before

  10. Fast Breakdown as Coronal/Ionization Waves?

    Science.gov (United States)

    Krehbiel, P. R.; Petersen, D.; da Silva, C. L.

    2017-12-01

    Studies of high-power narrow bipolar events (NBEs) have shown they are produced by a newly-recognized breakdown process called fast positive breakdown (FPB, Rison et al., 2016, doi:10.1038/ncomms10721). The breakdown was inferred to be produced by a system of positive streamers that propagate at high speed ( ˜3-6 x 107 m/s) due to occurring in a localized region of strong electric field. The polarity of the breakdown was determined from broadband interferometer (INTF) observations of the propagation direction of its VHF radiation, which was downward into the main negative charge region of a normally-electrified storm. Subsequent INTF observations being conducted in at Kennedy Space Center in Florida have shown a much greater incidence of NBEs than in New Mexico. Among the larger dataset have been clear-cut instances of some NBEs being produced by upward breakdown that would be of negative polarity. The speed and behavior of the negative breakdown is the same as that of the fast positive, leading to it being termed fast negative breakdown (FNB). The similarity (not too mention its occurrence) is surprising, given the fact that negative streamers and breakdown develops much differently than that of positive breakdown. The question is how this happens. In this study, we compare fast breakdown characteristics to well-known streamer properties as inferred from laboratory experiments and theoretical analysis. Additionally, we begin to explore the possibility that both polarities of fast breakdown are produced by what may be called coronal or ionization waves, in which the enhanced electric field produced by streamer or coronal breakdown of either polarity propagates away from the advancing front at the speed of light into a medium that is in a metastable condition of being at the threshold of hydrometeor-mediated corona onset or other ionization processes. The wave would develop at a faster speed than the streamer breakdown that gives rise to it, and thus would be

  11. Catastrophic cooling and cessation of heating in the solar corona

    Science.gov (United States)

    Peter, H.; Bingert, S.; Kamio, S.

    2012-01-01

    Context. Condensations in the more than 106 K hot corona of the Sun are commonly observed in the extreme ultraviolet (EUV). While their contribution to the total solar EUV radiation is still a matter of debate, these condensations certainly provide a valuable tool for studying the dynamic response of the corona to the heating processes. Aims: We investigate different distributions of energy input in time and space to investigate which process is most relevant for understanding these coronal condensations. Methods: For a comparison to observations we synthesize EUV emission from a time-dependent, one-dimensional model for coronal loops, where we employ two heating scenarios: simply shutting down the heating and a model where the heating is very concentrated at the loop footpoints, while keeping the total heat input constant. Results: The heating off/on model does not lead to significant EUV count rates that one observes with SDO/AIA. In contrast, the concentration of the heating near the footpoints leads to thermal non-equilibrium near the loop top resulting in the well-known catastrophic cooling. This process gives a good match to observations of coronal condensations. Conclusions: This shows that the corona needs a steady supply of energy to support the coronal plasma, even during coronal condensations. Otherwise the corona would drain very fast, too fast to even form a condensation. Movies are available in electronic form at http://www.aanda.org

  12. LONG-TERM TREND OF SOLAR CORONAL HOLE DISTRIBUTION FROM 1975 TO 2014

    Energy Technology Data Exchange (ETDEWEB)

    Fujiki, K.; Tokumaru, M.; Hayashi, K.; Satonaka, D. [Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Furo-cho, Chikusa, Nagoya Aichi 464-8601 (Japan); Hakamada, K., E-mail: fujiki@isee.nagoya-u.ac.jp [Department of Natural Science and Mathematics, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501 (Japan)

    2016-08-20

    We developed an automated prediction technique for coronal holes using potential magnetic field extrapolation in the solar corona to construct a database of coronal holes appearing from 1975 February to 2015 July (Carrington rotations from 1625 to 2165). Coronal holes are labeled with the location, size, and average magnetic field of each coronal hole on the photosphere and source surface. As a result, we identified 3335 coronal holes and found that the long-term distribution of coronal holes shows a similar pattern known as the magnetic butterfly diagram, and polar/low-latitude coronal holes tend to decrease/increase in the last solar minimum relative to the previous two minima.

  13. Coronal Magnetic Field Lines and Electrons Associated with Type III

    Indian Academy of Sciences (India)

    Coronal Magnetic Field Lines and Electrons Associated with Type III–V Radio Bursts in a Solar Flare ... velocities of the electron streams associated with the above two types of bursts indicate ... Journal of Astrophysics and Astronomy | News ...

  14. Coroner Autopsy Findings Among Children and Adolescents of ...

    African Journals Online (AJOL)

    year retrospective study of coroner autopsies carried out on children I adolescents aged between 0-19 years, evaluated the pattern, causes and demographic features of childhood deaths in Rivers state, Nigeria. Methods A retrospective remew of ...

  15. The X-ray signature of solar coronal mass

    Science.gov (United States)

    Harrison, R. A.; Waggett, P. W.; Bentley, R. D.; Phillips, K. J. H.; Bruner, M.

    1985-01-01

    The coronal response to six solar X-ray flares has been investigated. At a time coincident with the projected onset of the white-light coronal mass ejection associated with each flare, there is a small, discrete soft X-ray enhancement. These enhancements (precursors) precede by typically about 20 m the impulsive phase of the solar flare which is dominant by the time the coronal mass ejection has reached an altitude above 0.5 solar radii. Motions of hot X-ray emitting plasma, during the precursors, which may well be a signature of the mass ejection onsets, are identified. Further investigations have also revealed a second class of X-ray coronal transient, during the main phase of the flare. These appear to be associated with magnetic reconnection above post-flare loop systems.

  16. Cyclical Variation of the Quiet Corona and Coronal Holes

    Indian Academy of Sciences (India)

    tribpo

    Key words. Coronagraphs—solar activity cycle—solar corona—total ... can be divided into the quiet sun (including coronal holes) and active regions. The ... regions has attracted attention and is termed as 'the extended solar cycle'. Here the.

  17. Coronal Structures as Tracers of Sub-Surface Processes

    Indian Academy of Sciences (India)

    tribpo

    dramatic differences in appearance and physical processes, all these structures share a common ... mena that indicate a close relationship between coronal and sub-photo- spheric processes. .... 8) maintaining the same chirality. Large scale ...

  18. The nature of micro CMEs within coronal holes

    Science.gov (United States)

    Bothmer, Volker; Nistico, Giuseppe; Zimbardo, Gaetano; Patsourakos, Spiros; Bosman, Eckhard

    Whilst investigating the origin and characteristics of coronal jets and large-scale CMEs identi-fied in data from the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) instrument suites on board the two STEREO satellites, we discovered transient events that originated in the low corona with a morphology resembling that of typical three-part struc-tured coronal mass ejections (CMEs). However, the CMEs occurred on considerably smaller spatial scales. In this presentation we show evidence for the existence of small-scale CMEs from inside coronal holes and present quantitative estimates of their speeds and masses. We interprete the origin and evolution of micro CMEs as a natural consequence of the emergence of small-scale magnetic bipoles related to the Sun's ever changing photospheric magnetic flux on various scales and their interactions with the ambient plasma and magnetic field. The analysis of CMEs is performed within the framework of the EU Erasmus and FP7 SOTERIA projects.

  19. MHD Simulations of the Eruption of Coronal Flux Ropes under Coronal Streamers

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Yuhong, E-mail: yfan@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, 3080 Center Green Drive, Boulder, CO 80301 (United States)

    2017-07-20

    Using three-dimensional magnetohydrodynamic (MHD) simulations, we investigate the eruption of coronal flux ropes underlying coronal streamers and the development of a prominence eruption. We initialize a quasi-steady solution of a coronal helmet streamer, into which we impose at the lower boundary the slow emergence of a part of a twisted magnetic torus. As a result, a quasi-equilibrium flux rope is built up under the streamer. With varying streamer sizes and different lengths and total twists of the flux rope that emerges, we found different scenarios for the evolution from quasi-equilibrium to eruption. In the cases with a broad streamer, the flux rope remains well confined until there is sufficient twist such that it first develops the kink instability and evolves through a sequence of kinked, confined states with increasing height until it eventually develops a “hernia-like” ejective eruption. For significantly twisted flux ropes, prominence condensations form in the dips of the twisted field lines due to runaway radiative cooling. Once formed, the prominence-carrying field becomes significantly non-force-free due to the weight of the prominence, despite having low plasma β . As the flux rope erupts, the prominence erupts, showing substantial draining along the legs of the erupting flux rope. The prominence may not show a kinked morphology even though the flux rope becomes kinked. On the other hand, in the case with a narrow streamer, the flux rope with less than one wind of twist can erupt via the onset of the torus instability.

  20. Calcium K-line network in coronal holes

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, K A [Hale Observatories, Pasadena, Calif. (USA)

    1977-05-01

    Microphotometry of calcium K-line photographs in the regions of polar coronal holes shows that the chromospheric network exterior to a hole has a slightly broader intensity distribution than that inside the hole itself, a fact which can be attributed to a greater number of bright network elements outside the hole. These bright elements presumably represent the enhanced network resulting from the dispersal of magnetic flux from old active regions, a hypothesis which is consistent with current ideas of coronal hole formation.

  1. Photospheric Driving of Non-Potential Coronal Magnetic Field Simulations

    Science.gov (United States)

    2016-09-19

    synthesize observable emission . In future, the computational speed of the MF model makes it a potential avenue for near- real time and/or ensemble...AFRL-AFOSR-UK-TR-2016-0030 PHOTOSPHERIC DRIVING OF NON-POTENTIAL CORONAL MAGNETIC FIELD SIMULATIONS Anthony Yeates UNIVERSITY OF DURHAM Final Report...Final 3. DATES COVERED (From - To)  15 Sep 2014 to 14 Sep 2017 4. TITLE AND SUBTITLE PHOTOSPHERIC DRIVING OF NON-POTENTIAL CORONAL MAGNETIC FIELD

  2. Culex coronator in coastal Georgia and South Carolina.

    Science.gov (United States)

    Moulis, Robert A; Russell, Jennifer D; Lewandowski, Henry B; Thompson, Pamela S; Heusel, Jeffrey L

    2008-12-01

    In 2007, adult Culex coronator were collected in Chatham County, Georgia, and Jasper County, South Carolina, during nuisance and disease vector surveillance efforts. A total of 75 specimens of this species were collected at 8 widely separated locations in Chatham County, Georgia, and 4 closely situated sites in Jasper County, South Carolina. These represent the first Atlantic coastal records of this species in Georgia and the first confirmed records of Cx. coronator in South Carolina.

  3. Reconstructing the Morphology of an Evolving Coronal Mass Ejection

    Science.gov (United States)

    2009-01-01

    694, 707 Wood, B. E., Howard, R. A ., Thernisien, A ., Plunkett, S. P., & Socker, D. G. 2009b, Sol. Phys., 259, 163 Wood, B. E., Karovska , M., Chen, J...Reconstructing the Morphology of an Evolving Coronal Mass Ejection B. E. Wood, R. A . Howard, D. G. Socker Naval Research Laboratory, Space Science...mission, we empirically reconstruct the time-dependent three-dimensional morphology of a coronal mass ejection (CME) from 2008 June 1, which exhibits

  4. Active Longitude and Coronal Mass Ejection Occurrences

    International Nuclear Information System (INIS)

    Gyenge, N.; Kiss, T. S.; Erdélyi, R.; Singh, T.; Srivastava, A. K.

    2017-01-01

    The spatial inhomogeneity of the distribution of coronal mass ejection (CME) occurrences in the solar atmosphere could provide a tool to estimate the longitudinal position of the most probable CME-capable active regions in the Sun. The anomaly in the longitudinal distribution of active regions themselves is often referred to as active longitude (AL). In order to reveal the connection between the AL and CME spatial occurrences, here we investigate the morphological properties of active regions. The first morphological property studied is the separateness parameter, which is able to characterize the probability of the occurrence of an energetic event, such as a solar flare or CME. The second morphological property is the sunspot tilt angle. The tilt angle of sunspot groups allows us to estimate the helicity of active regions. The increased helicity leads to a more complex buildup of the magnetic structure and also can cause CME eruption. We found that the most complex active regions appear near the AL and that the AL itself is associated with the most tilted active regions. Therefore, the number of CME occurrences is higher within the AL. The origin of the fast CMEs is also found to be associated with this region. We concluded that the source of the most probably CME-capable active regions is at the AL. By applying this method, we can potentially forecast a flare and/or CME source several Carrington rotations in advance. This finding also provides new information for solar dynamo modeling.

  5. Active Longitude and Coronal Mass Ejection Occurrences

    Energy Technology Data Exchange (ETDEWEB)

    Gyenge, N.; Kiss, T. S.; Erdélyi, R. [Solar Physics and Space Plasmas Research Centre (SP2RC), School of Mathematics and Statistics, University of Sheffield Hounsfield Road, Hicks Building, Sheffield S3 7RH (United Kingdom); Singh, T.; Srivastava, A. K., E-mail: n.g.gyenge@sheffield.ac.uk [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi (India)

    2017-03-20

    The spatial inhomogeneity of the distribution of coronal mass ejection (CME) occurrences in the solar atmosphere could provide a tool to estimate the longitudinal position of the most probable CME-capable active regions in the Sun. The anomaly in the longitudinal distribution of active regions themselves is often referred to as active longitude (AL). In order to reveal the connection between the AL and CME spatial occurrences, here we investigate the morphological properties of active regions. The first morphological property studied is the separateness parameter, which is able to characterize the probability of the occurrence of an energetic event, such as a solar flare or CME. The second morphological property is the sunspot tilt angle. The tilt angle of sunspot groups allows us to estimate the helicity of active regions. The increased helicity leads to a more complex buildup of the magnetic structure and also can cause CME eruption. We found that the most complex active regions appear near the AL and that the AL itself is associated with the most tilted active regions. Therefore, the number of CME occurrences is higher within the AL. The origin of the fast CMEs is also found to be associated with this region. We concluded that the source of the most probably CME-capable active regions is at the AL. By applying this method, we can potentially forecast a flare and/or CME source several Carrington rotations in advance. This finding also provides new information for solar dynamo modeling.

  6. Active Longitude and Coronal Mass Ejection Occurrences

    Science.gov (United States)

    Gyenge, N.; Singh, T.; Kiss, T. S.; Srivastava, A. K.; Erdélyi, R.

    2017-03-01

    The spatial inhomogeneity of the distribution of coronal mass ejection (CME) occurrences in the solar atmosphere could provide a tool to estimate the longitudinal position of the most probable CME-capable active regions in the Sun. The anomaly in the longitudinal distribution of active regions themselves is often referred to as active longitude (AL). In order to reveal the connection between the AL and CME spatial occurrences, here we investigate the morphological properties of active regions. The first morphological property studied is the separateness parameter, which is able to characterize the probability of the occurrence of an energetic event, such as a solar flare or CME. The second morphological property is the sunspot tilt angle. The tilt angle of sunspot groups allows us to estimate the helicity of active regions. The increased helicity leads to a more complex buildup of the magnetic structure and also can cause CME eruption. We found that the most complex active regions appear near the AL and that the AL itself is associated with the most tilted active regions. Therefore, the number of CME occurrences is higher within the AL. The origin of the fast CMEs is also found to be associated with this region. We concluded that the source of the most probably CME-capable active regions is at the AL. By applying this method, we can potentially forecast a flare and/or CME source several Carrington rotations in advance. This finding also provides new information for solar dynamo modeling.

  7. Guided flows in coronal magnetic flux tubes

    Science.gov (United States)

    Petralia, A.; Reale, F.; Testa, P.

    2018-01-01

    Context. There is evidence that coronal plasma flows break down into fragments and become laminar. Aims: We investigate this effect by modelling flows confined along magnetic channels. Methods: We consider a full magnetohydrodynamic (MHD) model of a solar atmosphere box with a dipole magnetic field. We compare the propagation of a cylindrical flow perfectly aligned with the field to that of another flow with a slight misalignment. We assume a flow speed of 200 km s-1 and an ambient magnetic field of 30 G. Results: We find that although the aligned flow maintains its cylindrical symmetry while it travels along the magnetic tube, the misaligned one is rapidly squashed on one side, becoming laminar and eventually fragmented because of the interaction and back-reaction of the magnetic field. This model could explain an observation made by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory of erupted fragments that fall back onto the solar surface as thin and elongated strands and end up in a hedge-like configuration. Conclusions: The initial alignment of plasma flow plays an important role in determining the possible laminar structure and fragmentation of flows while they travel along magnetic channels. Movies are available in electronic form at http://www.aanda.org

  8. ANATOMY OF DEPLETED INTERPLANETARY CORONAL MASS EJECTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kocher, M.; Lepri, S. T.; Landi, E.; Zhao, L.; Manchester, W. B. IV, E-mail: mkocher@umich.edu [Department of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143 (United States)

    2017-01-10

    We report a subset of interplanetary coronal mass ejections (ICMEs) containing distinct periods of anomalous heavy-ion charge state composition and peculiar ion thermal properties measured by ACE /SWICS from 1998 to 2011. We label them “depleted ICMEs,” identified by the presence of intervals where C{sup 6+}/C{sup 5+} and O{sup 7+}/O{sup 6+} depart from the direct correlation expected after their freeze-in heights. These anomalous intervals within the depleted ICMEs are referred to as “Depletion Regions.” We find that a depleted ICME would be indistinguishable from all other ICMEs in the absence of the Depletion Region, which has the defining property of significantly low abundances of fully charged species of helium, carbon, oxygen, and nitrogen. Similar anomalies in the slow solar wind were discussed by Zhao et al. We explore two possibilities for the source of the Depletion Region associated with magnetic reconnection in the tail of a CME, using CME simulations of the evolution of two Earth-bound CMEs described by Manchester et al.

  9. A Catalog of Coronal "EIT Wave" Transients

    Science.gov (United States)

    Thompson, B. J.; Myers, D. C.

    2009-01-01

    Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT) data have been visually searched for coronal "EIT wave" transients over the period beginning from 1997 March 24 and extending through 1998 June 24. The dates covered start at the beginning of regular high-cadence (more than one image every 20 minutes) observations, ending at the four-month interruption of SOHO observations in mid-1998. One hundred and seventy six events are included in this catalog. The observations range from "candidate" events, which were either weak or had insufficient data coverage, to events which were well defined and were clearly distinguishable in the data. Included in the catalog are times of the EIT images in which the events are observed, diagrams indicating the observed locations of the wave fronts and associated active regions, and the speeds of the wave fronts. The measured speeds of the wave fronts varied from less than 50 to over 700 km s(exp -1) with "typical" speeds of 200-400 km s(exp -1).

  10. A CATALOG OF CORONAL 'EIT WAVE' TRANSIENTS

    International Nuclear Information System (INIS)

    Thompson, B. J.; Myers, D. C.

    2009-01-01

    Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT) data have been visually searched for coronal 'EIT wave' transients over the period beginning from 1997 March 24 and extending through 1998 June 24. The dates covered start at the beginning of regular high-cadence (more than 1 image every 20 minutes) observations, ending at the four-month interruption of SOHO observations in mid-1998. One hundred and seventy six events are included in this catalog. The observations range from 'candidate' events, which were either weak or had insufficient data coverage, to events which were well defined and were clearly distinguishable in the data. Included in the catalog are times of the EIT images in which the events are observed, diagrams indicating the observed locations of the wave fronts and associated active regions, and the speeds of the wave fronts. The measured speeds of the wave fronts varied from less than 50 to over 700 km s -1 with 'typical' speeds of 200-400 km s -1 .

  11. Evidence linking coronal mass ejections with interplanetary magnetic clouds

    International Nuclear Information System (INIS)

    Wilson, R.M.; Hildner, E.

    1983-12-01

    Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking. Six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients

  12. THE CORONAL ABUNDANCES OF MID-F DWARFS

    International Nuclear Information System (INIS)

    Wood, Brian E.; Laming, J. Martin

    2013-01-01

    A Chandra spectrum of the moderately active nearby F6 V star π 3 Ori is used to study the coronal properties of mid-F dwarfs. We find that π 3 Ori's coronal emission measure distribution is very similar to those of moderately active G and K dwarfs, with an emission measure peak near log T = 6.6 seeming to be ubiquitous for such stars. In contrast to coronal temperature, coronal abundances are known to depend on spectral type for main sequence stars. Based on this previously known relation, we expected π 3 Ori's corona to exhibit an extremely strong ''first ionization potential (FIP) effect'', a phenomenon first identified on the Sun where elements with low FIP are enhanced in the corona. We instead find that π 3 Ori's corona exhibits a FIP effect essentially identical to that of the Sun and other early G dwarfs, perhaps indicating that the increase in FIP bias toward earlier spectral types stops or at least slows for F stars. We find that π 3 Ori's coronal characteristics are significantly different from two previously studied mid-F stars, Procyon (F5 IV-V) and τ Boo (F7 V). We believe π 3 Ori is more representative of the coronal characteristics of mid-F dwarfs, with Procyon being different because of luminosity class, and τ Boo being different because of the effects of one of two close companions, one stellar (τ Boo B: M2 V) and one planetary.

  13. FORWARD MODELING OF STANDING KINK MODES IN CORONAL LOOPS. II. APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Ding; Doorsselaere, Tom Van, E-mail: DYuan2@uclan.ac.uk [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium)

    2016-04-15

    Magnetohydrodynamic waves are believed to play a significant role in coronal heating, and could be used for remote diagnostics of solar plasma. Both the heating and diagnostic applications rely on a correct inversion (or backward modeling) of the observables into the thermal and magnetic structures of the plasma. However, due to the limited availability of observables, this is an ill-posed issue. Forward modeling is designed to establish a plausible mapping of plasma structuring into observables. In this study, we set up forward models of standing kink modes in coronal loops and simulate optically thin emissions in the extreme ultraviolet bandpasses, and then adjust plasma parameters and viewing angles to match three events of transverse loop oscillations observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We demonstrate that forward models could be effectively used to identify the oscillation overtone and polarization, to reproduce the general profile of oscillation amplitude and phase, and to predict multiple harmonic periodicities in the associated emission intensity and loop width variation.

  14. Using coronal loops to reconstruct the magnetic field of an active region before and after a major flare

    Energy Technology Data Exchange (ETDEWEB)

    Malanushenko, A. [Department of Physics, Montana State University, Bozeman, MT (United States); Schrijver, C. J.; DeRosa, M. L. [Lockheed Martin Advanced Technology Center, Palo Alto, CA (United States); Wheatland, M. S. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Redfern, NSW (Australia)

    2014-03-10

    The shapes of solar coronal loops are sensitive to the presence of electrical currents that are the carriers of the non-potential energy available for impulsive activity. We use this information in a new method for modeling the coronal magnetic field of active region (AR) 11158 as a nonlinear force-free field (NLFFF). The observations used are coronal images around the time of major flare activity on 2011 February 15, together with the surface line-of-sight magnetic field measurements. The data are from the Helioseismic and Magnetic Imager and Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The model fields are constrained to approximate the coronal loop configurations as closely as possible, while also being subject to the force-free constraints. The method does not use transverse photospheric magnetic field components as input and is thereby distinct from methods for modeling NLFFFs based on photospheric vector magnetograms. We validate the method using observations of AR 11158 at a time well before major flaring and subsequently review the field evolution just prior to and following an X2.2 flare and associated eruption. The models indicate that the energy released during the instability is about 1 × 10{sup 32} erg, consistent with what is needed to power such a large eruptive flare. Immediately prior to the eruption, the model field contains a compact sigmoid bundle of twisted flux that is not present in the post-eruption models, which is consistent with the observations. The core of that model structure is twisted by ≈0.9 full turns about its axis.

  15. New techniques for the characterisation of dynamical phenomena in solar coronal images

    Science.gov (United States)

    Robbrecht, E.

    2007-02-01

    ) was an important step on the way to subarcsecond telescopes. It allows a spatial resolution of 1" in the EUV and UV bands and, simultaneously, a temporal resolution of the order of a few seconds. Coronal physics studies are dominated by two major and interlinked problems: coronal heating and solar wind acceleration. Above the chromosphere there is a thin transition layer in which the temperature suddenly increases and density drops. How can the temperature of the solar corona be three orders of magnitude higher than the temperature of the photosphere? In order for this huge temperature gradient to be stationary, non-thermal energy must be transported from below the photosphere towards the chromosphere and corona and converted into heat to balance the radiative and conductive losses. This puzzle of origin, transport and conversion of energy is referred to as the "coronal heating problem". Due to its fundamental role in the structuring of the corona, the magnetic field is supposed to play an important role in the heating. In this dissertation we describe two aspects of solar coronal dynamics: waves in coronal loops (Part I) and coronal mass ejections (Part II). We investigate the influence of (semi-) automated techniques on solar coronal research. This is a timely discussion since the observation of solar phenomena is transitioning from manual detection to "Solar Image Processing". Our results are mainly based on images from the Extreme UV Imaging Telescope (EIT) and the Large Angle and Spectrometric Coronagraph (LASCO), two instruments onboard the satellite SOHO (Solar and Heliospheric Observatory) of which we recently celebrated its 11th anniversary. The high quality of the images together with the long timespan created a valuable database for solar physics research. Part I reports on the first detection of slow magnetoacoustic waves in transequatorial coronal loops observed in high cadence image sequences simultaneously produced by EIT and TRACE (Transition Region

  16. ON THE RELATIONSHIP BETWEEN THE CORONAL MAGNETIC DECAY INDEX AND CORONAL MASS EJECTION SPEED

    Energy Technology Data Exchange (ETDEWEB)

    Xu Yan; Liu Chang; Jing Ju; Wang Haimin, E-mail: yx2@njit.edu [Space Weather Research Lab, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Boulevard, Newark, NJ 07102-1982 (United States)

    2012-12-10

    Numerical simulations suggest that kink and torus instabilities are two potential contributors to the initiation and prorogation of eruptive events. A magnetic parameter called the decay index (i.e., the coronal magnetic gradient of the overlying fields above the eruptive flux ropes) could play an important role in controlling the kinematics of eruptions. Previous studies have identified a threshold range of the decay index that distinguishes between eruptive and confined configurations. Here we advance the study by investigating if there is a clear correlation between the decay index and coronal mass ejection (CME) speed. Thirty-eight CMEs associated with filament eruptions and/or two-ribbon flares are selected using the H{alpha} data from the Global H{alpha} Network. The filaments and flare ribbons observed in H{alpha} associated with the CMEs help to locate the magnetic polarity inversion line, along which the decay index is calculated based on the potential field extrapolation using Michelson Doppler Imager magnetograms as boundary conditions. The speeds of CMEs are obtained from the LASCO C2 CME catalog available online. We find that the mean decay index increases with CME speed for those CMEs with a speed below 1000 km s{sup -1} and stays flat around 2.2 for the CMEs with higher speeds. In addition, we present a case study of a partial filament eruption, in which the decay indices show different values above the erupted/non-erupted part.

  17. Wave heating of the solar atmosphere

    Science.gov (United States)

    Arregui, Iñigo

    2015-04-01

    Magnetic waves are a relevant component in the dynamics of the solar atmosphere. Their significance has increased because of their potential as a remote diagnostic tool and their presumed contribution to plasma heating processes. We discuss our current understanding of coronal heating by magnetic waves, based on recent observational evidence and theoretical advances. The discussion starts with a selection of observational discoveries that have brought magnetic waves to the forefront of the coronal heating discussion. Then, our theoretical understanding of the nature and properties of the observed waves and the physical processes that have been proposed to explain observations are described. Particular attention is given to the sequence of processes that link observed wave characteristics with concealed energy transport, dissipation and heat conversion. We conclude with a commentary on how the combination of theory and observations should help us to understand and quantify magnetic wave heating of the solar atmosphere.

  18. Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations

    Science.gov (United States)

    Dzifčáková, E.; Dudík, J.; Mackovjak, Š.

    2016-05-01

    Context. Coronal heating is currently thought to proceed via the mechanism of nanoflares, small-scale and possibly recurring heating events that release magnetic energy. Aims: We investigate the effects of a periodic high-energy electron beam on the synthetic spectra of coronal Fe ions. Methods: Initially, the coronal plasma is assumed to be Maxwellian with a temperature of 1 MK. The high-energy beam, described by a κ-distribution, is then switched on every period P for the duration of P/ 2. The periods are on the order of several tens of seconds, similar to exposure times or cadences of space-borne spectrometers. Ionization, recombination, and excitation rates for the respective distributions are used to calculate the resulting non-equilibrium ionization state of Fe and the instantaneous and period-averaged synthetic spectra. Results: Under the presence of the periodic electron beam, the plasma is out of ionization equilibrium at all times. The resulting spectra averaged over one period are almost always multithermal if interpreted in terms of ionization equilibrium for either a Maxwellian or a κ-distribution. Exceptions occur, however; the EM-loci curves appear to have a nearly isothermal crossing-point for some values of κs. The instantaneous spectra show fast changes in intensities of some lines, especially those formed outside of the peak of the respective EM(T) distributions if the ionization equilibrium is assumed. Movies 1-5 are available in electronic form at http://www.aanda.org

  19. The Longitudinal Evolution of Equatorial Coronal Holes

    Science.gov (United States)

    Krista, Larisza D.; McIntosh, Scott W.; Leamon, Robert J.

    2018-04-01

    In 2011, three satellites—the Solar-Terrestrial RElations Observatory A & B, and the Solar Dynamics Observatory (SDO)—were in a unique spatial alignment that allowed a 360° view of the Sun. This alignment lasted until 2014, the peak of solar cycle 24. Using extreme ultraviolet images and Hovmöller diagrams, we studied the lifetimes and propagation characteristics of coronal holes (CHs) in longitude over several solar rotations. Our initial results show at least three distinct populations of “low-latitude” or “equatorial” CHs (below 65^\\circ latitude). One population rotates in retrograde direction and coincides with a group of long-lived (over sixty days) CHs in each hemisphere. These are typically located between 30° and 55^\\circ , and display velocities of ∼55 m s‑1 slower than the local differential rotation rate. A second, smaller population of CHs rotate prograde, with velocities between ∼20 and 45 m s‑1. This population is also long-lived, but observed ±10° from the solar equator. A third population of CHs are short-lived (less than two solar rotations), and they appear over a wide range of latitudes (±65°) and exhibit velocities between ‑140 and 80 m s‑1. The CH “butterfly diagram” we developed shows a systematic evolution of the longer-lived holes; however, the sample is too short in time to draw conclusions about possible connections to dynamo-related phenomena. An extension of the present work to the 22 years of the combined SOHO–SDO archives is necessary to understand the contribution of CHs to the decadal-scale evolution of the Sun.

  20. Coronal mass ejections and solar radio bursts

    International Nuclear Information System (INIS)

    Kundu, M.R.

    1990-01-01

    The properties of coronal mass ejection (CME) events and their radio signatures are discussed. These signatures are mostly in the form of type II and type IV burst emissions. Although type II bursts are temporally associated with CMEs, it is shown that there is no spatial relationship between them. Type II's associated with CMEs have in most cases a different origin, and they are not piston-driven by CMEs. Moving type IV and type II bursts can be associated with slow CMEs with speeds as low as 200 km/s, contrary to the earlier belief that only CMEs with speeds >400 km/s are associated with radio bursts. A specific event has been discussed in which the CME and type IV burst has nearly the same speed and direction, but the type II burst location was behind the CME and its motion was transverse. The speed and motion of the type II burst strongly suggest that the type II shock was decoupled from the CME and was probably due to a flare behind the limb. Therefore only the type IV source could be directly associated with the slow CME. The electrons responsble for the type IV emission could be produced in the flare or in the type II and then become trapped in a plasmoid associated with the CME. The reconnected loop could then move outwards as in the usual palsmoid model. Alternatively, the type IV emission could be interpreted as due to electrons produced by acceleration in wave turbulence driven by currents in the shock front driven by the CME. The lower-hybrid model Lampe and Papadopoulos (1982), which operates at both fast and slow mode shocks, could be applied to this situation. (author). 31 refs., 12 figs

  1. CME Interaction with Coronal Holes and Their Interplanetary Consequences

    Science.gov (United States)

    Gopalswamy, N.; Makela, P.; Xie, H.; Akiyama, S.; Yashiro, S.

    2008-01-01

    A significant number of interplanetary (IP) shocks (-17%) during cycle 23 were not followed by drivers. The number of such "driverless" shocks steadily increased with the solar cycle with 15%, 33%, and 52% occurring in the rise, maximum, and declining phase of the solar cycle. The solar sources of 15% of the driverless shocks were very close the central meridian of the Sun (within approx.15deg), which is quite unexpected. More interestingly, all the driverless shocks with their solar sources near the solar disk center occurred during the declining phase of solar cycle 23. When we investigated the coronal environment of the source regions of driverless shocks, we found that in each case there was at least one coronal hole nearby suggesting that the coronal holes might have deflected the associated coronal mass ejections (CMEs) away from the Sun-Earth line. The presence of abundant low-latitude coronal holes during the declining phase further explains why CMEs originating close to the disk center mimic the limb CMEs, which normally lead to driverless shocks due to purely geometrical reasons. We also examined the solar source regions of shocks with drivers. For these, the coronal holes were located such that they either had no influence on the CME trajectories. or they deflected the CMEs towards the Sun-Earth line. We also obtained the open magnetic field distribution on the Sun by performing a potential field source surface extrapolation to the corona. It was found that the CMEs generally move away from the open magnetic field regions. The CME-coronal hole interaction must be widespread in the declining phase, and may have a significant impact on the geoeffectiveness of CMEs.

  2. Space- and Ground-based Coronal Spectro-Polarimetry

    Science.gov (United States)

    Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan; Capobianco, Gerardo

    This presentation gives an overview of the near-future perspectives of ultraviolet and visible-light spectro-polarimetric instrumentation for probing coronal magnetism from space-based and ground-based observatories. Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter - has been recently installed on the Lomnicky Peak Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag will be presented. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include the capability of imaging polarimetry of the HI Lyman-alpha, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. This presentation will describe how in future re-flights SCORE could observe the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.

  3. Constraining walking and custodial technicolor

    DEFF Research Database (Denmark)

    Foadi, Roshan; Frandsen, Mads Toudal; Sannino, Francesco

    2008-01-01

    We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level-custodial technicolor-and argue that these models...

  4. The Large-scale Coronal Structure of the 2017 August 21 Great American Eclipse: An Assessment of Solar Surface Flux Transport Model Enabled Predictions and Observations

    Science.gov (United States)

    Nandy, Dibyendu; Bhowmik, Prantika; Yeates, Anthony R.; Panda, Suman; Tarafder, Rajashik; Dash, Soumyaranjan

    2018-01-01

    On 2017 August 21, a total solar eclipse swept across the contiguous United States, providing excellent opportunities for diagnostics of the Sun’s corona. The Sun’s coronal structure is notoriously difficult to observe except during solar eclipses; thus, theoretical models must be relied upon for inferring the underlying magnetic structure of the Sun’s outer atmosphere. These models are necessary for understanding the role of magnetic fields in the heating of the corona to a million degrees and the generation of severe space weather. Here we present a methodology for predicting the structure of the coronal field based on model forward runs of a solar surface flux transport model, whose predicted surface field is utilized to extrapolate future coronal magnetic field structures. This prescription was applied to the 2017 August 21 solar eclipse. A post-eclipse analysis shows good agreement between model simulated and observed coronal structures and their locations on the limb. We demonstrate that slow changes in the Sun’s surface magnetic field distribution driven by long-term flux emergence and its evolution governs large-scale coronal structures with a (plausibly cycle-phase dependent) dynamical memory timescale on the order of a few solar rotations, opening up the possibility for large-scale, global corona predictions at least a month in advance.

  5. Nanoflares and Heating of the Solar Corona

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Coronal heating by nanoflares is presented by using observational, analytical, numerical simulation and statistical results. Numerical simulations show the formation of numerous current sheets if the magnetic field is sheared and bipoles have unequal pole strengths. This fact supports the generation of ...

  6. Coronal Loop Evolution Observed with AIA and Hi-C

    Science.gov (United States)

    Mulu-Moore, Fana; Winebarger, A.; Cirtain, J.; Kobayashi, K.; Korreck, K.; Golub, L.; Kuzin. S.; Walsh, R.; DeForest, C.; DePontieu, B.; hide

    2012-01-01

    Despite much progress toward understanding the dynamics of the solar corona, the physical properties of coronal loops are not yet fully understood. Recent investigations and observations from different instruments have yielded contradictory results about the true physical properties of coronal loops. In the past, the evolution of loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this poster we discuss the first results of loop analysis comparing AIA and Hi-C data. We find signatures of cooling in a pixel selected along a loop structure in the AIA multi-filter observations. However, unlike previous studies, we find that the cooling time is much longer than the draining time. This is inconsistent with previous cooling models.

  7. Examining the Properties of Jets in Coronal Holes

    Science.gov (United States)

    Gaulle, Owen; Adams, Mitzi L.; Tennant, A. F.

    2012-01-01

    We examined both X-ray and Magnetic field data in order to determine if there is a correlation between emerging magnetic flux and the production of Coronal jets. It was proposed that emerging flux can be a trigger to a coronal jet. The jet is thought to be caused when local bipoles reconnect or when a region of magnetic polarity emerges through a uniform field. In total we studied 15 different jets that occurred over a two day period starting 2011-02-27 00:00:00 UTC and ending 2011-02-28 23:59:55 UTC. All of the jets were contained within a coronal hole that was centered on the disk. Of the 15 that we studied 6 were shown to have an increase of magnetic flux within one hour prior to the creation of the jet and 10 were within 3 hours before the event.

  8. Influence of coronal holes on CMEs in causing SEP events

    International Nuclear Information System (INIS)

    Shen Chenglong; Yao Jia; Wang Yuming; Ye Pinzhong; Wang Shui; Zhao Xuepu

    2010-01-01

    The issue of the influence of coronal holes (CHs) on coronal mass ejections (CMEs) in causing solar energetic particle (SEP) events is revisited. It is a continuation and extension of our previous work, in which no evident effects of CHs on CMEs in generating SEPs were found by statistically investigating 56 CME events. This result is consistent with the conclusion obtained by Kahler in 2004. We extrapolate the coronal magnetic field, define CHs as the regions consisting of only open magnetic field lines and perform a similar analysis on this issue for 76 events in total by extending the study interval to the end of 2008. Three key parameters, CH proximity, CH area and CH relative position, are involved in the analysis. The new result confirms the previous conclusion that CHs did not show any evident effect on CMEs in causing SEP events. (research papers)

  9. The origin of coronal lines in Seyfert galaxies

    International Nuclear Information System (INIS)

    Korista, K.T.; Ferland, G.J.

    1989-01-01

    This paper examines the possibility that the coronal line region in Seyfert galaxies may be the result of an interstellar medium (ISM) exposed to, and subsequently photoionized by, a 'bare' Seyfert nucleus. It is shown that a 'generic' AGN continuum illuminating the warm-phase of the ISM of a spiral galaxy can produce the observed emission. In this picture the same UV-radiation cone that is responsible for the high-excitation extended narrow-line emission clouds observed out to 1-2 kpc or farther from the nuclei of some Seyfert galaxies also produces the coronal lines. Soft X-rays originating in the nucleus are Compton-scattered off the ISM, thus producing extended soft X-ray emission, as observed in NGC 4151. The results of the calculations show a basic insensitivity to the ISM density, which explains why similar coronal line spectra are found in many Seyfert galaxies of varying physical environments. 60 refs

  10. CORONAL MASS EJECTION INDUCED OUTFLOWS OBSERVED WITH HINODE/EIS

    International Nuclear Information System (INIS)

    Jin, M.; Ding, M. D.; Chen, P. F.; Fang, C.; Imada, S.

    2009-01-01

    We investigate the outflows associated with two halo coronal mass ejections (CMEs) that occurred on 2006 December 13 and 14 in NOAA 10930, using the Hinode/EIS observations. Each CME was accompanied by an EIT wave and coronal dimmings. Dopplergrams in the dimming regions are obtained from the spectra of seven EIS lines. The results show that strong outflows are visible in the dimming regions during the CME eruption at different heights from the lower transition region to the corona. It is found that the velocity is positively correlated with the photospheric magnetic field, as well as the magnitude of the dimming. We estimate the mass loss based on height-dependent EUV dimmings and find it to be smaller than the CME mass derived from white-light observations. The mass difference is attributed partly to the uncertain atmospheric model, and partly to the transition region outflows, which refill the coronal dimmings.

  11. Trends in PDE constrained optimization

    CERN Document Server

    Benner, Peter; Engell, Sebastian; Griewank, Andreas; Harbrecht, Helmut; Hinze, Michael; Rannacher, Rolf; Ulbrich, Stefan

    2014-01-01

    Optimization problems subject to constraints governed by partial differential equations (PDEs) are among the most challenging problems in the context of industrial, economical and medical applications. Almost the entire range of problems in this field of research was studied and further explored as part of the Deutsche Forschungsgemeinschaft (DFG) priority program 1253 on “Optimization with Partial Differential Equations” from 2006 to 2013. The investigations were motivated by the fascinating potential applications and challenging mathematical problems that arise in the field of PDE constrained optimization. New analytic and algorithmic paradigms have been developed, implemented and validated in the context of real-world applications. In this special volume, contributions from more than fifteen German universities combine the results of this interdisciplinary program with a focus on applied mathematics.   The book is divided into five sections on “Constrained Optimization, Identification and Control”...

  12. TRANSITION-REGION/CORONAL SIGNATURES AND MAGNETIC SETTING OF SUNSPOT PENUMBRAL JETS: HINODE (SOT/FG), Hi-C, AND SDO/AIA OBSERVATIONS

    International Nuclear Information System (INIS)

    Tiwari, Sanjiv K.; Moore, Ronald L.; Winebarger, Amy R.; Alpert, Shane E.

    2016-01-01

    Penumbral microjets (PJs) are transient narrow bright features in the chromosphere of sunspot penumbrae, first characterized by Katsukawa et al. using the Ca ii H-line filter on Hinode's Solar Optical Telescope (SOT). It was proposed that the PJs form as a result of reconnection between two magnetic components of penumbrae (spines and interspines), and that they could contribute to the transition region (TR) and coronal heating above sunspot penumbrae. We propose a modified picture of formation of PJs based on recent results on the internal structure of sunspot penumbral filaments. Using data of a sunspot from Hinode/SOT, High Resolution Coronal Imager, and different passbands of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we examine whether PJs have signatures in the TR and corona. We find hardly any discernible signature of normal PJs in any AIA passbands, except for a few of them showing up in the 1600 Å images. However, we discovered exceptionally stronger jets with similar lifetimes but bigger sizes (up to 600 km wide) occurring repeatedly in a few locations in the penumbra, where evidence of patches of opposite-polarity fields in the tails of some penumbral filaments is seen in Stokes-V images. These tail PJs do display signatures in the TR. Whether they have any coronal-temperature plasma is unclear. We infer that none of the PJs, including the tail PJs, directly heat the corona in active regions significantly, but any penumbral jet might drive some coronal heating indirectly via the generation of Alfvén waves and/or braiding of the coronal field

  13. THERMAL PROPERTIES OF A SOLAR CORONAL CAVITY OBSERVED WITH THE X-RAY TELESCOPE ON HINODE

    Energy Technology Data Exchange (ETDEWEB)

    Reeves, Katharine K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS 58, Cambridge, MA 02138 (United States); Gibson, Sarah E. [HAO/NCAR, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Kucera, Therese A. [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States); Hudson, Hugh S. [Space Sciences Laboratories, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Kano, Ryouhei, E-mail: kreeves@cfa.harvard.edu [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2012-02-20

    Coronal cavities are voids in coronal emission often observed above high latitude filament channels. Sometimes, these cavities have areas of bright X-ray emission in their centers. In this study, we use data from the X-ray Telescope (XRT) on the Hinode satellite to examine the thermal emission properties of a cavity observed during 2008 July that contains bright X-ray emission in its center. Using ratios of XRT filters, we find evidence for elevated temperatures in the cavity center. The area of elevated temperature evolves from a ring-shaped structure at the beginning of the observation, to an elongated structure two days later, finally appearing as a compact round source four days after the initial observation. We use a morphological model to fit the cavity emission, and find that a uniform structure running through the cavity does not fit the observations well. Instead, the observations are reproduced by modeling several short cylindrical cavity 'cores' with different parameters on different days. These changing core parameters may be due to some observed activity heating different parts of the cavity core at different times. We find that core temperatures of 1.75 MK, 1.7 MK, and 2.0 MK (for July 19, July 21, and July 23, respectively) in the model lead to structures that are consistent with the data, and that line-of-sight effects serve to lower the effective temperature derived from the filter ratio.

  14. Correlation of Coronal Plasma Properties and Solar Magnetic Field in a Decaying Active Region

    Science.gov (United States)

    Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren, Harry P.; Ugarte-Urra, Ignacio

    2016-01-01

    We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a basal state (at 1.5 x 10(exp 6) K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.

  15. Temperature and EUV Intensity in a Coronal Prominence Cavity and Streamer

    Science.gov (United States)

    Kucera, T. A.; Gibson, S.E.; Schmit, D. J.; Landi, E.; Tripathi, D.

    2012-01-01

    We analyze the temperature and EUV line emission of a coronal cavity and surrounding streamer in terms of a morphological forward model. We use a series of iron line ratios observed with the Hinode Extreme-ultraviolet Imaging Spectrograph (EIS) on 2007 Aug. 9 to constrain temperature as a function of altitude in a morphological forward model of the streamer and cavity. We also compare model prediction of the EIS EUV line intensities and polarized brightness (pB) data from the Mauna Loa Solar Observatory (MLSO) MK4. This work builds on earlier analysis using the same model to determine geometry of and density in the same cavity and streamer. The fit to the data with altitude dependent temperature profiles indicates that both the streamer and cavity have temperatures in the range 1.4-1.7 MK. However, the cavity exhibits substantial substructure such that the altitude dependent temperature profile is not sufficient to completely model conditions in the cavity. Coronal prominence cavities are structured by magnetism so clues to this structure are to be found in their plasma properties. These temperature substructures are likely related to structures in the cavity magnetic field. Furthermore, we find that the model overestimates the line intensities by a factor of 4-10, while overestimating pB data by no more than a factor of 1.4. One possible explanation for this is that there may be a significant amount of material at temperatures outside of the range log T(K) approximately equals 5.8 - 6.7 in both the cavity and the streamer.

  16. Magnus: A New Resistive MHD Code with Heat Flow Terms

    Science.gov (United States)

    Navarro, Anamaría; Lora-Clavijo, F. D.; González, Guillermo A.

    2017-07-01

    We present a new magnetohydrodynamic (MHD) code for the simulation of wave propagation in the solar atmosphere, under the effects of electrical resistivity—but not dominant—and heat transference in a uniform 3D grid. The code is based on the finite-volume method combined with the HLLE and HLLC approximate Riemann solvers, which use different slope limiters like MINMOD, MC, and WENO5. In order to control the growth of the divergence of the magnetic field, due to numerical errors, we apply the Flux Constrained Transport method, which is described in detail to understand how the resistive terms are included in the algorithm. In our results, it is verified that this method preserves the divergence of the magnetic fields within the machine round-off error (˜ 1× {10}-12). For the validation of the accuracy and efficiency of the schemes implemented in the code, we present some numerical tests in 1D and 2D for the ideal MHD. Later, we show one test for the resistivity in a magnetic reconnection process and one for the thermal conduction, where the temperature is advected by the magnetic field lines. Moreover, we display two numerical problems associated with the MHD wave propagation. The first one corresponds to a 3D evolution of a vertical velocity pulse at the photosphere-transition-corona region, while the second one consists of a 2D simulation of a transverse velocity pulse in a coronal loop.

  17. Nested Sampling with Constrained Hamiltonian Monte Carlo

    OpenAIRE

    Betancourt, M. J.

    2010-01-01

    Nested sampling is a powerful approach to Bayesian inference ultimately limited by the computationally demanding task of sampling from a heavily constrained probability distribution. An effective algorithm in its own right, Hamiltonian Monte Carlo is readily adapted to efficiently sample from any smooth, constrained distribution. Utilizing this constrained Hamiltonian Monte Carlo, I introduce a general implementation of the nested sampling algorithm.

  18. A Long Look at MCG-5-23-16 with NuSTAR . I. Relativistic Reflection and Coronal Properties

    Energy Technology Data Exchange (ETDEWEB)

    Zoghbi, Abderahmen; Miller, J. M. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Matt, G. [Dipartimento di Matematica e Fisica, Universita degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Lohfink, A. M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Walton, D. J.; Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); García, J. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koss, M. J. [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Harrison, F. A. [Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Boggs, S. E.; Craig, W. [Space Science Laboratory, University of California, Berkeley, California 94720 (United States); Christensen, F. E. [DTU Space. National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027 (United States); Zhang, W. W., E-mail: abzoghbi@umich.edu [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)

    2017-02-10

    MCG-5-23-16 was targeted in early 2015 with a half mega-second observing campaign using NuSTAR . Here we present the spectral analysis of these data sets along with an earlier observation and study the relativistic reflection and the primary coronal source. The data show strong reflection features in the form of both narrow and broad iron lines plus a Compton reflection hump. A cutoff energy is significantly detected in all exposures. The shape of the reflection spectrum does not change in the two years spanned by the observations, suggesting a stable geometry. A strong positive correlation is found between the cutoff energy and both the hard X-ray flux and spectral index. The measurements imply that the coronal plasma is not at the runaway electron–positron pair limit, and instead contains mostly electrons. The observed variability in the coronal properties is driven by a variable optical depth. A constant heating-to-cooling ratio is measured, implying that there is a feedback mechanism in which a significant fraction of the photons cooling the corona are due to reprocessed hard X-rays.

  19. A Long Look at MCG-5-23-16 with NuSTAR. I. Relativistic Reflection and Coronal Properties

    Science.gov (United States)

    Zoghbi, Abderahmen; Matt, G.; Miller, J. M.; Lohfink, A. M.; Walton, D. J.; Ballantyne, D. R.; Garcia, J. A.; Stern, D.; Koss, M. J.; Farrah, D.; hide

    2017-01-01

    MCG-5-23-16 was targeted in early 2015 with a half mega-second observing campaign using NuSTAR. Here we present the spectral analysis of these data sets along with an earlier observation and study the relativistic reflection and the primary coronal source. The data show strong reflection features in the form of both narrow and broad iron lines plus a Compton reflection hump. A cutoff energy is significantly detected in all exposures. The shape of the reflection spectrum does not change in the two years spanned by the observations, suggesting a stable geometry. A strong positive correlation is found between the cutoff energy and both the hard X-ray flux and spectral index. The measurements imply that the coronal plasma is not at the runaway electron-positron pair limit, and instead contains mostly electrons. The observed variability in the coronal properties is driven by a variable optical depth. A constant heating-to-cooling ratio is measured, implying that there is a feedback mechanism in which a significant fraction of the photons cooling the corona are due to reprocessed hard X-rays.

  20. REFLECTION OF PROPAGATING SLOW MAGNETO-ACOUSTIC WAVES IN HOT CORONAL LOOPS: MULTI-INSTRUMENT OBSERVATIONS AND NUMERICAL MODELING

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Sudip; Banerjee, Dipankar; Pant, Vaibhav [Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Yuan, Ding; Fang, Xia; Doorsselaere, Tom Van, E-mail: sudip@iiap.res.in, E-mail: xia.fang@wis.kuleuven.be [Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, bus 2400, 3001, Leuven (Belgium)

    2016-09-10

    Slow MHD waves are important tools for understanding coronal structures and dynamics. In this paper, we report a number of observations from the X-Ray Telescope (XRT) on board HINODE and Solar Dynamic Observatory /Atmospheric Imaging Assembly (AIA) of reflecting longitudinal waves in hot coronal loops. To our knowledge, this is the first report of this kind as seen from the XRT and simultaneously with the AIA. The wave appears after a micro-flare occurs at one of the footpoints. We estimate the density and temperature of the loop plasma by performing differential emission measure (DEM) analysis on the AIA image sequence. The estimated speed of propagation is comparable to or lower than the local sound speed, suggesting it to be a propagating slow wave. The intensity perturbation amplitude, in every case, falls very rapidly as the perturbation moves along the loop and eventually vanishes after one or more reflections. To check the consistency of such reflection signatures with the obtained loop parameters, we perform a 2.5D MHD simulation, which uses the parameters obtained from our observation as inputs, and perform forward modeling to synthesize AIA 94 Å images. Analyzing the synthesized images, we obtain the same properties of the observables as for the real observation. From the analysis we conclude that a footpoint heating can generate a slow wave which then reflects back and forth in the coronal loop before fading. Our analysis of the simulated data shows that the main agent for this damping is anisotropic thermal conduction.

  1. More Macrospicule Jets in On-Disk Coronal Holes

    Science.gov (United States)

    Adams, M. L.; Sterling, A. C.; Moore, R. L.

    2015-01-01

    We examine the magnetic structure and dynamics of multiple jets found in coronal holes close to or on disk center. All data are from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO). We report on observations of about ten jets in an equatorial coronal hole spanning 2011 February 27 and 28. We show the evolution of these jets in AIA 193 A, examine the magnetic field configuration and flux changes in the jet area, and discuss the probable trigger mechanism of these events. We reported on another jet in this same coronal hole on 2011 February 27, (is) approximately 13:04 UT (Adams et al 2014, ApJ, 783: 11). That jet is a previously-unrecognized variety of blowout jet, in which the base-edge bright point is a miniature filament-eruption flare arcade made by internal reconnection of the legs of the erupting field. In contrast, in the presently-accepted 'standard' picture for blowout jets, the base-edge bright point is made by interchange reconnection of initially-closed erupting jet-base field with ambient open field. This poster presents further evidence of the production of the base-edge bright point in blowout jets by internal reconnection. Our observations suggest that most of the bigger and brighter EUV jets in coronal holes are blowout jets of the new-found variety.

  2. Magnetic Source Regions of Coronal Mass Ejections Brigitte ...

    Indian Academy of Sciences (India)

    2003) or two rows of opposite polarity field extending to ... sional Alfvén waves which bring up helicity from the sub-photospheric part of the flux tube ... Figure 1. Loss of equilibrium model: sketches of coronal field lines showing ... lines of the quadrupolar reconnection before the flare, (bottom left): TRACE observations of the.

  3. Automated coronal hole identification via multi-thermal intensity segmentation

    Science.gov (United States)

    Garton, Tadhg M.; Gallagher, Peter T.; Murray, Sophie A.

    2018-01-01

    Coronal holes (CH) are regions of open magnetic fields that appear as dark areas in the solar corona due to their low density and temperature compared to the surrounding quiet corona. To date, accurate identification and segmentation of CHs has been a difficult task due to their comparable intensity to local quiet Sun regions. Current segmentation methods typically rely on the use of single Extreme Ultra-Violet passband and magnetogram images to extract CH information. Here, the coronal hole identification via multi-thermal emission recognition algorithm (CHIMERA) is described, which analyses multi-thermal images from the atmospheric image assembly (AIA) onboard the solar dynamics observatory (SDO) to segment coronal hole boundaries by their intensity ratio across three passbands (171 Å, 193 Å, and 211 Å). The algorithm allows accurate extraction of CH boundaries and many of their properties, such as area, position, latitudinal and longitudinal width, and magnetic polarity of segmented CHs. From these properties, a clear linear relationship was identified between the duration of geomagnetic storms and coronal hole areas. CHIMERA can therefore form the basis of more accurate forecasting of the start and duration of geomagnetic storms.

  4. Magnetic Field in the Gravitationally Stratified Coronal Loops B. N. ...

    Indian Academy of Sciences (India)

    field for the longest (L = 406 Mm) coronal loops. The magnetic fields Bstr and Babs also increase with the number density, if the loop length does not vary much. The increment in the magnetic field due to gravitational stratification is small at the lower number densities, however, it is large at the higher number densities.

  5. Initiation and Propagation of Coronal Mass Ejections P. F. Chen

    Indian Academy of Sciences (India)

    Introduction. Coronal mass ejections (CMEs) have been observed for over 30 years. They keep being an intriguing research topic, not only because they are now realized to be the major driver for space weather disturbances, which are intimately connected to human activities, but also because they themselves are full of ...

  6. Photometric Variability of Four Coronally Active Stars J. C. Pandey ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    ray surveys with the Einstein and the ROSAT observatories and found to be associated with bright late- type stars. Many of these stars have not been studied in detail for their chromospheric and coronal activity, and their nature is not fully ...

  7. RADIOLOGICAL TIPS Coronal views of the paediatric mandibular ...

    African Journals Online (AJOL)

    imaging. None of the cases subsequently revealed any evidence of traumatic brain injury on CTB but they all demonstrated mandibular condyle fractures best appreciated on coronal views. Axial (Fig. 1) ... T Peedikayil, MB ChB. Department of Radiology, Red Cross War Memorial Children's Hospital, Cape Town.

  8. Automated Identification of Coronal Holes from Synoptic EUV Maps

    Science.gov (United States)

    Hamada, Amr; Asikainen, Timo; Virtanen, Ilpo; Mursula, Kalevi

    2018-04-01

    Coronal holes (CHs) are regions of open magnetic field lines in the solar corona and the source of the fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195 Å/193 Å, 171 Å and 304 Å) measured by the Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instruments. The two datasets are first homogenized by scaling the SDO/AIA data to the SOHO/EIT level by means of histogram equalization. We then develop a novel automated method to identify CHs from these homogenized maps by determining the intensity threshold of CH regions separately for each synoptic map. This is done by identifying the best location and size of an image segment, which optimally contains portions of coronal holes and the surrounding quiet Sun allowing us to detect the momentary intensity threshold. Our method is thus able to adjust itself to the changing scale size of coronal holes and to temporally varying intensities. To make full use of the information in the three wavelengths we construct a composite CH distribution, which is more robust than distributions based on one wavelength. Using the composite CH dataset we discuss the temporal evolution of CHs during the Solar Cycles 23 and 24.

  9. Standing Slow MHD Waves in Radiatively Cooling Coronal Loops ...

    Indian Academy of Sciences (India)

    The standing slow magneto-acoustic oscillations in cooling coronal loops ... turbation and, eventually, reduces the MHD equations to a 1D system modelling ..... where the function Q is expanded in power series with respect to ǫ, i.e.,. Q = Q0 + ...

  10. OBSERVATIONAL SIGNATURES OF THE CORONAL KINK INSTABILITY WITH THERMAL CONDUCTION

    International Nuclear Information System (INIS)

    Botha, G. J. J.; Arber, T. D.; Srivastava, Abhishek K.

    2012-01-01

    It is known from numerical simulations that thermal conduction along magnetic field lines plays an important role in the evolution of the kink instability in coronal loops. This study presents the observational signatures of the kink instability in long coronal loops when parallel thermal conduction is included. The three-dimensional nonlinear magnetohydrodynamic equations are solved numerically to simulate the evolution of a coronal loop that is initially in an unstable equilibrium. The loop has length 80 Mm, width 8 Mm, and an initial maximum twist of Φ = 11.5π, where Φ is a function of the radius. The initial loop parameters are obtained from a highly twisted loop observed in the Transition Region and Coronal Explorer (TRACE) 171 Å wave band. Synthetic observables are generated from the data. These observables include spatial and temporal averaging to account for the resolution and exposure times of TRACE images. Parallel thermal conduction reduces the maximum local temperature by up to an order of magnitude. This means that different spectral lines are formed and different internal loop structures are visible with or without the inclusion of thermal conduction. However, the response functions sample a broad range of temperatures. The result is that the inclusion of parallel thermal conductivity does not have as large an impact on observational signatures as the order of magnitude reduction in the maximum temperature would suggest; the net effect is a blurring of internal features of the loop structure.

  11. Coronal Activity in the R CrA T Association

    Science.gov (United States)

    Patten, Brian M.; Oliversen, Ronald J. (Technical Monitor)

    2005-01-01

    Brian Patten is the Principal Investigator of the NASA ROSS-ADP project Coronal Activity in the R CrA T Association. For this project we have extracted net counts and variability information for all of the X-ray sources found in 23 archival ROSAT PSPC and HRI images in the region of the R CrA T association. These data have been merged with an extensive database of optical and near-infrared photometry, optical spectroscopy, and parallax data. These data have been used to (1) identify new association members and clarify the membership status of a number of previously suspected members of the association, and (2) derive, for the first time, an accurate coronal luminosity function for the T Tauri members of this T association and make direct comparisons between the coronal luminosity functions for other T associations and those of large clusters. We have used our survey data to assess (a) the importance of the star-formation environment in initial coronal activity levels, (b) the effects of PMS evolution on dynamo activity as a function of mass and age, and (c) the level of contamination by field post-T Tauri stars on association membership surveys.

  12. Analysis of Solar Coronal Holes with Synoptic Magnetogram Data

    Science.gov (United States)

    Canner, A.; Kim, T. K.; Pogorelov, N.; Yalim, M. S.

    2017-12-01

    Coronal holes are regions in which the magnetic field of the Sun is open with high magnetic flux and low plasma density. Because of the low plasma beta in these regions, the open field lines transport plasma from the Sun throughout the heliosphere. Coronal hole area is closely related to the expansion factor of the magnetic flux tube, as demonstrated by Tokumaru et al. (2017). Following the approach of Tokumaru et al. (2017), we employ a potential field source surface model to identify the open field regions on the photosphere and estimate the area and expansion factor for each coronal hole. While Tokumaru et al. (2017) analyzed synoptic maps from Kitt Peak National Observatory for the period 1995-2011, we use different magnetograph observations with higher spatial resolution (e.g., SOHO-MDI) for the same time period. We compare the coronal hole area - expansion factor relationship with the original results of Tokumaru et al (2017). This work was supported by the NSF-funded Research Experience for Undergraduates program "Solar and Heliospheric Physics at UAH and MSFC" run by the University of Alabama in Huntsville in partnership with the Marshall Space Flight Center through grant AGS-1460767.

  13. Merging of coronal and heliospheric numerical two dimensional MHD models

    Czech Academy of Sciences Publication Activity Database

    Odstrčil, Dušan; Linker, J. A.; Lionello, R.; Mikic, Z.; Riley, P.; Pizzo, J. V.; Luhmann, J. G.

    2002-01-01

    Roč. 107, A12 (2002), s. SSH14-1 - SSH14-11 ISSN 0148-0227 R&D Projects: GA AV ČR IAA3003003 Institutional research plan: CEZ:AV0Z1003909 Keywords : coronal mass ejection * interplanetary shock * numerical MHD simulation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.245, year: 2002

  14. Solar wind heavy ions from energetic coronal events

    International Nuclear Information System (INIS)

    Bame, S.J.

    1978-01-01

    Ions heavier than those of He can be resolved in the solar wind with electrostatic E/q analyzers when the local thermal temperatures are low. Ordinarily this condition prevails in the low speed solar wind found between high speed streams, i.e. the interstream, IS, solar wind. Various ions of O, Si and Fe are resolved in IS heavy ion spectra. Relative ion peak intensities indicate that the O ionization state is established in the IS coronal source regions at approx. 2.1 x 10 6 K while the state of Fe is frozen in at approx. 1.5 x 10 6 K farther out. Occasionally, anomalous spectra are observed in which the usually third most prominent ion peak, O 8+ , is depressed as are the Fe peaks ranging from Fe 12+ to Fe 7+ . A prominent peak in the usual Si 8+ position of IS spectra is self-consistently shown to be Fe 16+ . These features demonstrate that the ionization states were frozen in at higher than usual coronal temperatures. The source regions of these hot heavy ion spectra are identified as energetic coronal events including flares and nonflare coronal mass ejections. 24 references

  15. Constrained minimization in C ++ environment

    International Nuclear Information System (INIS)

    Dymov, S.N.; Kurbatov, V.S.; Silin, I.N.; Yashchenko, S.V.

    1998-01-01

    Based on the ideas, proposed by one of the authors (I.N.Silin), the suitable software was developed for constrained data fitting. Constraints may be of the arbitrary type: equalities and inequalities. The simplest of possible ways was used. Widely known program FUMILI was realized to the C ++ language. Constraints in the form of inequalities φ (θ i ) ≥ a were taken into account by change into equalities φ (θ i ) = t and simple inequalities of type t ≥ a. The equalities were taken into account by means of quadratic penalty functions. The suitable software was tested on the model data of the ANKE setup (COSY accelerator, Forschungszentrum Juelich, Germany)

  16. Coherent states in constrained systems

    International Nuclear Information System (INIS)

    Nakamura, M.; Kojima, K.

    2001-01-01

    When quantizing the constrained systems, there often arise the quantum corrections due to the non-commutativity in the re-ordering of constraint operators in the products of operators. In the bosonic second-class constraints, furthermore, the quantum corrections caused by the uncertainty principle should be taken into account. In order to treat these corrections simultaneously, the alternative projection technique of operators is proposed by introducing the available minimal uncertainty states of the constraint operators. Using this projection technique together with the projection operator method (POM), these two kinds of quantum corrections were investigated

  17. The size of coronal hard X-ray sources in solar flares: How big are they?

    Science.gov (United States)

    Effenberger, F.; Krucker, S.; Rubio da Costa, F.

    2017-12-01

    Coronal hard X-ray sources are considered to be one of the key signatures of non-thermal particle acceleration and heating during the energy release in solar flares. In some cases, X-ray observations reveal multiple components spatially located near and above the loop top and even further up in the corona. Here, we combine a detailed RHESSI imaging analysis of near-limb solar flares with occulted footpoints and a multi-wavelength study of the flare loop evolution in SDO/AIA. We connect our findings to different current sheet formation and magnetic break-out scenarios and relate it to particle acceleration theory. We find that the upper and usually fainter emission regions can be underestimated in their size due to the majority of flux originating from the lower loops.

  18. Studying electron distributions using the time-resolved free-bound spectra from coronal plasmas

    International Nuclear Information System (INIS)

    Matthews, D.L.; Kauffman, R.L.; Kilkenny, J.D.; Lee, R.W.

    1982-11-01

    Absorption of laser light in a plasma by inverse bremsstrahlung, I.B., can lead to a non-Maxwellian velocity distribution provided the electron-elecron collision frequency is too low to equilibrate the velocity distribution in the coronal plasma region of a laser heated aluminum disk by measuring the radiation recombination continuum. The experiments are performed using lambda/sub L/ = 0.532 μm laser light at intensities of approx. 10 16 W/cm 2 . Such parameters are predicted to produce conditions suitable for a non-thermal electron distribution. The shape of the K-shell recombination radiation has been measured using a time-resolved x-ray spectrograph. The electron distribution can be determined from deconvolution of the recombination continuum shape

  19. RESOLVING THE ξ BOO BINARY WITH CHANDRA, AND REVEALING THE SPECTRAL TYPE DEPENDENCE OF THE CORONAL 'FIP EFFECT'

    International Nuclear Information System (INIS)

    Wood, Brian E.; Linsky, Jeffrey L.

    2010-01-01

    On 2008 May 2, Chandra observed the X-ray spectrum of ξ Boo (G8 V+K4 V), resolving the binary for the first time in X-rays and allowing the coronae of the two stars to be studied separately. With the contributions of ξ Boo A and B to the system's total X-ray emission now observationally established (88.5% and 11.5%, respectively), consideration of mass loss measurements for GK dwarfs of various activity levels (including one for ξ Boo) leads to the surprising conclusion that ξ Boo B may dominate the wind from the binary, with ξ Boo A's wind being very weak despite its active corona. Emission measure (EM) distributions and coronal abundances are computed for both stars and compared with Chandra measurements of other moderately active stars with G8-K5 spectral types, all of which exhibit a narrow peak in EM near log T = 6.6, indicating that the coronal heating process in these stars has a strong preference for this temperature. As is the case for the Sun and many other stars, our sample of stars shows coronal abundance anomalies dependent on the first ionization potential (FIP) of the element. We see no dependence of the degree of 'FIP effect' on activity, but there is a dependence on spectral type, a correlation that becomes more convincing when moderately active main-sequence stars with a broader range of spectral types are considered. This clear dependence of coronal abundances on spectral type weakens if the stellar sample is allowed to be contaminated by evolved stars, interacting binaries, or extremely active stars with log L X >29, explaining why this correlation has not been recognized in the past.

  20. Resolving the xi Boo Binary with Chandra, and Revealing the Spectral Type Dependence of the Coronal "Fip Effect"

    Science.gov (United States)

    Wood, Brian E.; Linsky, Jeffrey L.

    2010-01-01

    On 2008 May 2, Chandra observed the X-ray spectrum of xi Boo (G8 V+K4 V), resolving the binary for the first time in X-rays and allowing the coronae of the two stars to be studied separately. With the contributions of ξ Boo A and B to the system's total X-ray emission now observationally established (88.5% and 11.5% respectively), consideration of mass loss measurements for GK dwarfs of various activity levels (including one for xi Boo) leads to the surprising conclusion that xi Boo B may dominate the wind from the binary, with xi Boo A's wind being very weak despite its active corona. Emission measure (EM) distributions and coronal abundances are computed for both stars and compared with Chandra measurements of other moderately active stars with G8-K5 spectral types, all of which exhibit a narrow peak in EM near log T = 6.6, indicating that the coronal heating process in these stars has a strong preference for this temperature. As is the case for the Sun and many other stars, our sample of stars shows coronal abundance anomalies dependent on the first ionization potential (FIP) of the element. We see no dependence of the degree of FIP effect on activity, but there is a dependence on spectral type, a correlation that becomes more convincing when moderately active main-sequence stars with a broader range of spectral types are considered. This clear dependence of coronal abundances on spectral type weakens if the stellar sample is allowed to be contaminated by evolved stars, interacting binaries or extremely active stars with logLX 29, explaining why this correlation has not been recognized in the past.

  1. Coronal holes and high-speed wind streams

    International Nuclear Information System (INIS)

    Zirker, J.B.

    1977-01-01

    Coronal holes low have been identified as Bartel's M regions, i.e., sources of high-speed wind streams that produce recurrent geomagnetic variations. Throughout the Skylab period the polar caps of the Sun were coronal holes, and at lower latitudes the most persistent and recurrent holes were equatorial extensions of the polar caps. The holes rotated 'rigidly' at the equatorial synodic rate. They formed in regions of unipolar photospheric magnetic field, and their internal magnetic fields diverged rapidly with increasing distance from the sun. The geometry of the magnetic field in the inner corona seems to control both the physical properties of the holes and the global distribution of high-speed wind streams in the heliosphere. The latitude variation of the divergence of the coronal magnetic field lines produces corresponding variations in wind speed.During the years of declining solar activity the global field of the corona approximates a perturbed dipole. The divergence of field lines in each hemisphere produces a high-speed wind near the poles and low-speed wind in a narrow belt that coincides with the magnetic neutral sheet. The analysis of electron density measurements within a polar hole indicates that solar wind is accelerated principally in the region between 2 and 5 R/sub s/ and that mechanical wave pressure (possibly Alfven wave) may be responsible for the accleration of the wind. Phenomenological models for the birth and decay of coronal holes have been proposed. Attempts to explain the birth and rigid rotation of holes through dynamo action have been only partially successful. The 11-year variation of cosmic ray intensities at the earth may result from cyclic variation of open field regions associated with coronal holes

  2. FAST CONTRACTION OF CORONAL LOOPS AT THE FLARE PEAK

    International Nuclear Information System (INIS)

    Liu Rui; Wang Haimin

    2010-01-01

    On 2005 September 8, a coronal loop overlying the active region NOAA 10808 was observed in TRACE 171 A to contract at ∼100 km s -1 at the peak of an X5.4-2B flare at 21:05 UT. Prior to the fast contraction, the loop underwent a much slower contraction at ∼6 km s -1 for about 8 minutes, initiating during the flare preheating phase. The sudden switch to fast contraction is presumably corresponding to the onset of the impulsive phase. The contraction resulted in the oscillation of a group of loops located below, with the period of about 10 minutes. Meanwhile, the contracting loop exhibited a similar oscillatory pattern superimposed on the dominant downward motion. We suggest that the fast contraction reflects a suddenly reduced magnetic pressure underneath due either to (1) the eruption of magnetic structures located at lower altitudes or to (2) the rapid conversion of magnetic free energy in the flare core region. Electrons accelerated in the shrinking trap formed by the contracting loop can theoretically contribute to a late-phase hard X-ray burst, which is associated with Type IV radio emission. To complement the X5.4 flare which was probably confined, a similar event observed in SOHO/EIT 195 A on 2004 July 20 in an eruptive, M8.6 flare is briefly described, in which the contraction was followed by the expansion of the same loop leading up to a halo coronal mass ejection. These observations further substantiate the conjecture of coronal implosion and suggest coronal implosion as a new exciter mechanism for coronal loop oscillations.

  3. Features of solar wind streams on June 21-28, 2015 as a result of interactions between coronal mass ejections and recurrent streams from coronal holes

    Science.gov (United States)

    Shugay, Yu. S.; Slemzin, V. A.; Rod'kin, D. G.

    2017-11-01

    Coronal sources and parameters of solar wind streams during a strong and prolonged geomagnetic disturbance in June 2015 have been considered. Correspondence between coronal sources and solar wind streams at 1 AU has been determined using an analysis of solar images, catalogs of flares and coronal mass ejections, solar wind parameters including the ionic composition. The sources of disturbances in the considered period were a sequence of five coronal mass ejections that propagated along the recurrent solar wind streams from coronal holes. The observed differences from typical in magnetic and kinetic parameters of solar wind streams have been associated with the interactions of different types of solar wind. The ionic composition has proved to be a good additional marker for highlighting components in a mixture of solar wind streams, which can be associated with different coronal sources.

  4. The Relation between Coronal Holes and Coronal Mass Ejections during the Rise, Maximum, and Declining Phases of Solar Cycle 23

    Science.gov (United States)

    Mohamed, A. A.; Gopalswamy, N; Yashiro, S.; Akiyama, S.; Makela, P.; Xie, H.; Jung, H.

    2012-01-01

    We study the interaction between coronal holes (CHs) and coronal mass ejections (CMEs) using a resultant force exerted by all the coronal holes present on the disk and is defined as the coronal hole influence parameter (CHIP). The CHIP magnitude for each CH depends on the CH area, the distance between the CH centroid and the eruption region, and the average magnetic field within the CH at the photospheric level. The CHIP direction for each CH points from the CH centroid to the eruption region. We focus on Solar Cycle 23 CMEs originating from the disk center of the Sun (central meridian distance =15deg) and resulting in magnetic clouds (MCs) and non-MCs in the solar wind. The CHIP is found to be the smallest during the rise phase for MCs and non-MCs. The maximum phase has the largest CHIP value (2.9 G) for non-MCs. The CHIP is the largest (5.8 G) for driverless (DL) shocks, which are shocks at 1 AU with no discernible MC or non-MC. These results suggest that the behavior of non-MCs is similar to that of the DL shocks and different from that of MCs. In other words, the CHs may deflect the CMEs away from the Sun-Earth line and force them to behave like limb CMEs with DL shocks. This finding supports the idea that all CMEs may be flux ropes if viewed from an appropriate vantage point.

  5. The structure of the coronal soft X-ray source associated with the dark filament disappearance of 1991 September 28 using the Yohkoh Soft X-ray Telescope

    Science.gov (United States)

    Mcallister, Alan; Uchida, Yutaka; Tsuneta, Saku; Strong, Keith T.; Acton, Loren W.; Hiei, Eijiro; Bruner, Marilyn E.; Watanabe, Takashi; Shibata, Kazunari

    1992-01-01

    The structure of the coronal soft X-ray source associated with the dark filament disappearance on September 28, 1991, observed with the Soft X-ray Telescope, is examined as a possible example of the 'eruption-reconnection' model of filament disappearance. The results suggest, however, that this model may not fit. There is a strong possibility that much of the dark filament mass remains in the heated unwinding axial field.

  6. PHYSICAL CONDITIONS OF CORONAL PLASMA AT THE TRANSIT OF A SHOCK DRIVEN BY A CORONAL MASS EJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Susino, R.; Bemporad, A.; Mancuso, S., E-mail: susino@oato.inaf.it [INAF–Turin Astrophysical Observatory, via Osservatorio 20, I-10025 Pino Torinese (Italy)

    2015-10-20

    We report here on the determination of plasma physical parameters across a shock driven by a coronal mass ejection using white light (WL) coronagraphic images and radio dynamic spectra (RDS). The event analyzed here is the spectacular eruption that occurred on 2011 June 7, a fast CME followed by the ejection of columns of chromospheric plasma, part of them falling back to the solar surface, associated with a M2.5 flare and a type-II radio burst. Images acquired by the Solar and Heliospheric Observatory/LASCO coronagraphs (C2 and C3) were employed to track the CME-driven shock in the corona between 2–12 R{sub ⊙} in an angular interval of about 110°. In this interval we derived two-dimensional (2D) maps of electron density, shock velocity, and shock compression ratio, and we measured the shock inclination angle with respect to the radial direction. Under plausible assumptions, these quantities were used to infer 2D maps of shock Mach number M{sub A} and strength of coronal magnetic fields at the shock's heights. We found that in the early phases (2–4 R{sub ⊙}) the whole shock surface is super-Alfvénic, while later on (i.e., higher up) it becomes super-Alfvénic only at the nose. This is in agreement with the location for the source of the observed type-II burst, as inferred from RDS combined with the shock kinematic and coronal densities derived from WL. For the first time, a coronal shock is used to derive a 2D map of the coronal magnetic field strength over intervals of 10 R{sub ⊙} altitude and ∼110° latitude.

  7. NuSTAR Detection of X-Ray Heating Events in the Quiet Sun

    Science.gov (United States)

    Kuhar, Matej; Krucker, Säm; Glesener, Lindsay; Hannah, Iain G.; Grefenstette, Brian W.; Smith, David M.; Hudson, Hugh S.; White, Stephen M.

    2018-04-01

    The explanation of the coronal heating problem potentially lies in the existence of nanoflares, numerous small-scale heating events occurring across the whole solar disk. In this Letter, we present the first imaging spectroscopy X-ray observations of three quiet Sun flares during the Nuclear Spectroscopic Telescope ARray (NuSTAR) solar campaigns on 2016 July 26 and 2017 March 21, concurrent with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. Two of the three events showed time lags of a few minutes between peak X-ray and extreme ultraviolet emissions. Isothermal fits with rather low temperatures in the range 3.2–4.1 MK and emission measures of (0.6–15) × 1044 cm‑3 describe their spectra well, resulting in thermal energies in the range (2–6) × 1026 erg. NuSTAR spectra did not show any signs of a nonthermal or higher temperature component. However, as the estimated upper limits of (hidden) nonthermal energy are comparable to the thermal energy estimates, the lack of a nonthermal component in the observed spectra is not a constraining result. The estimated Geostationary Operational Environmental Satellite (GOES) classes from the fitted values of temperature and emission measure fall between 1/1000 and 1/100 A class level, making them eight orders of magnitude fainter in soft X-ray flux than the largest solar flares.

  8. Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24

    Energy Technology Data Exchange (ETDEWEB)

    Hofmeister, Stefan J.; Veronig, Astrid; Reiss, Martin A.; Temmer, Manuela [University of Graz, Institute of Physics, IGAM-Kanzelhöhe Observatory, Graz (Austria); Vennerstrom, Susanne [National Space Institute, DTU Space (Denmark); Vršnak, Bojan [Hvar Observatory, Faculty of Geodesy, Zagreb (Croatia); Heber, Bernd, E-mail: stefan.hofmeister@uni-graz.at [Universität Kiel, Institut für Experimentelle und Angewandte Physik, Kiel (Germany)

    2017-02-01

    We investigate the statistics of 288 low-latitude coronal holes extracted from SDO /AIA-193 filtergrams over the time range of 2011 January 01–2013 December 31. We analyze the distribution of characteristic coronal hole properties, such as the areas, mean AIA-193 intensities, and mean magnetic field densities, the local distribution of the SDO /AIA-193 intensity and the magnetic field within the coronal holes, and the distribution of magnetic flux tubes in coronal holes. We find that the mean magnetic field density of all coronal holes under study is 3.0 ± 1.6 G, and the percentaged unbalanced magnetic flux is 49 ± 16%. The mean magnetic field density, the mean unsigned magnetic field density, and the percentaged unbalanced magnetic flux of coronal holes depend strongly pairwise on each other, with correlation coefficients cc > 0.92. Furthermore, we find that the unbalanced magnetic flux of the coronal holes is predominantly concentrated in magnetic flux tubes: 38% (81%) of the unbalanced magnetic flux of coronal holes arises from only 1% (10%) of the coronal hole area, clustered in magnetic flux tubes with field strengths >50 G (10 G). The average magnetic field density and the unbalanced magnetic flux derived from the magnetic flux tubes correlate with the mean magnetic field density and the unbalanced magnetic flux of the overall coronal hole (cc>0.93). These findings give evidence that the overall magnetic characteristics of coronal holes are governed by the characteristics of the magnetic flux tubes.

  9. Formal language constrained path problems

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, C.; Jacob, R.; Marathe, M.

    1997-07-08

    In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

  10. The quiet Sun extreme ultraviolet spectrum observed in normal incidence by the SOHO Coronal Diagnostic Spectrometer

    CERN Document Server

    Brooks, D H; Fludra, A; Harrison, R A; Innes, D E; Landi, E; Landini, M; Lang, J; Lanzafame, A C; Loch, S D; McWhirter, R W P; Summers, H P; Thompson, W T

    1999-01-01

    The extreme ultraviolet quiet Sun spectrum, observed at normal incidence by the Coronal Diagnostic Spectrometer on the SOHO spacecraft, is presented. The spectrum covers the wavelength ranges 308-381 AA and 513-633 AA and is based $9 on data recorded at various positions on the solar disk between October 1996 and February 1997. Datasets at twelve of these `positions' were judged to be free from active regions and data faults and selected for detailed study. A $9 constrained maximum likelihood spectral line fitting code was used to analyse the spectral features. In all over 200 spectrum lines have been measured and about 50 186584dentified. The line identification process consisted of a $9 number of steps. Firstly assignment of well known lines was made and used to obtain the primary wavelength calibration. Variations of wavelengths with position were used to assess the precision of calibration achievable. Then, an $9 analysis method first used in studies with the CHASE experiment, was applied to the new obser...

  11. Transition-Region/Coronal Signatures of Penumbral Microjets: Hi-C, SDO/AIA and Hinode (SOT/FG) Observations

    Science.gov (United States)

    Tiwari, Sanjiv K.; Alpert, Shane E.; Moore, Ronald L.; Winebarger, Amy R.

    2014-01-01

    Penumbral microjets are bright, transient features seen in the chromosphere of sunspot penumbrae. Katsuaka et al. (2007) noted their ubiquity and characterized them using the Ca II H-line filter on Hinode's Solar Optical Telescope (SOT). The jets are 1000{4000 km in length, 300{400 km in width, and last less than one minute. It was proposed that these penumbral microjets could contribute to the transition-region and coronal heating above sunspots. We examine whether these microjets appear in the transition-region (TR) and/or corona or are related{ temporally and spatially{ to similar brightenings in the TR and/or corona. First, we identify penumbral microjets with the SOT's Ca II H-line filter. The chosen sunspot is observed on July 11, 2012 from 18:50:00 UT to 20:00:00 UT at approx. 14 inches, -30 inches. We then examine the sunspot in the same field of view and at the same time in other wavelengths. We use the High Resolution Coronal Imager Telescope (Hi-C) at 193A and the 1600A, 304A, 171A, 193A, and 94A passbands of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory. We include examples of these jets and where they should appear in the other passbands, but find no signifcant association, except for a few jets with longer lifetimes and bigger sizes seen at locations in the penumbra with repeated stronger brightenings. We conclude that the normal microjets are not heated to transition-region/coronal temperatures, but the larger jets are.

  12. A model for radio emission from solar coronal shocks

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, G. Q.; Chen, L.; Wu, D. J., E-mail: djwu@pmo.ac.cn [Purple Mountain Observatory, CAS, Nanjing 210008 (China)

    2014-05-01

    Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.

  13. A model for radio emission from solar coronal shocks

    International Nuclear Information System (INIS)

    Zhao, G. Q.; Chen, L.; Wu, D. J.

    2014-01-01

    Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.

  14. Radio and white-light observations of coronal transients

    Science.gov (United States)

    Dulk, G. A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. In this paper the observed properties of coronal transients are reviewed, with concentration on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones nonthermal. The possible mechanisms involved in the radio bursts are then discussed and estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the field, provides a possible driving force for the coronal and interplanetary shock waves.

  15. Radio and white-light observations of coronal transients

    International Nuclear Information System (INIS)

    Dulk, G.A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. The author reviews the observed properties of coronal transients, concentrating on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones non-thermal. The possible mechanisms involved in the radio bursts are discussed and the estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the Sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the fields, provides a possible driving force for the coronal and interplanetary shock waves. (Auth.)

  16. Shear-induced inflation of coronal magnetic fields

    International Nuclear Information System (INIS)

    Klimchuk, J.A.

    1990-01-01

    Using numerical models of force-free magnetic fields, the shearing of footprints in arcade geometries leading to an inflation of the coronal magnetic field was examined. For each of the shear profiles considered, all of the field lines become elevated compared with the potential field. This includes cases where the shear is concentrated well away from the arcade axis, such that B(sub z), the component of field parallel to the axis, increases outward to produce an inward B(sub z) squared/8 pi magnetic pressure gradient force. These results contrast with an earlier claim, shown to be incorrect, that field lines can sometimes become depressed as a result of shear. It is conjectured that an inflation of the entire field will always result from the shearing of simple arcade configurations. These results have implications for prominence formation, the interplanetary magnetic flux, and possibly also coronal holes. 38 refs

  17. Swift X-ray monitoring of stellar coronal variability

    Science.gov (United States)

    Miller, Brendan; Hagen, Cedric; Gallo, Elena; Wright, Jason T.

    2018-01-01

    We used California Planet Search Ca II H and K core emission measurements to identify and characterize chromospheric activity cycles in a sample of main-sequence FGK stars. About a dozen of these with existing ROSAT archival data were targeted with Swift to obtain a current epoch X-ray flux. We find that coronal variability by a factor of several is common on decade-long timescales (we attempt to link to the chromospheric cycle phase) but can also occur on short timescales between Swift visits to a given target, presumably related to stellar rotation and coronal inhomogeneity or to small flares. Additionally, we present new Swift monitoring observations of two M dwarfs with known exoplanets: GJ 15A and GJ 674. GJ 15A b is around 5.3 Earth masses with an 11.4 day orbital period, while GJ 674 is around 11.1 Earth masses with a 4.7 day orbital period. GJ 15A was observed several times in late 2014 and then monitored at approximately weekly intervals for several months in early 2016, for a total exposure of 18 ks. GJ 674 was monitored at approximately weekly intervals for most of 2016, for a total exposure of 40 ks. We provide light curves and hardness ratios for both sources, and also compare to earlier archival X-ray data. Both sources show significant X-ray variability, including between consecutive observations. We quantify the energy distribution for coronal flaring, and compare to optical results for M dwarfs from Kepler. Finally, we discuss the implications of M dwarf coronal activity for exoplanets orbiting within the nominal habitable zone.

  18. Morphology and physical properties of solar coronal holes

    International Nuclear Information System (INIS)

    Rozelot, J.P.

    1983-01-01

    By their peculiar characteristics, coronal holes induce on Earth climatic variations and cyclic effects, not well known nowadays. Because of low electronical density and very low temperature, study of these holes was neglected. The author presents the results of the observations from discovery in the fifteens. He gives some new results, a theoretical model and not well resolved questions which can conduct to new methods of searching [fr

  19. The evolution of coronal activity in main sequence cool stars

    International Nuclear Information System (INIS)

    Stern, R.A.

    1984-01-01

    Stars spend most of their lifetime and show the least amount of nuclear evolution on the main sequence. However, the x-ray luminosities of cool star coronas change by orders of magnitude as a function of main sequence age. Such coronal evolution is discussed in relation to our knowledge of the solar corona, solar and stellar flares, stellar rotation and binarity. The relevance of X-ray observations to current speculations on stellar dynamos is also considered

  20. PROJECTION EFFECTS IN CORONAL DIMMINGS AND ASSOCIATED EUV WAVE EVENT

    Energy Technology Data Exchange (ETDEWEB)

    Dissauer, K.; Temmer, M.; Veronig, A. M.; Vanninathan, K. [IGAM/Institute of Physics, University of Graz, Universitätsplatz 5/II, A-8010 Graz (Austria); Magdalenić, J., E-mail: karin.dissauer@uni-graz.at [Solar-Terrestrial Center of Excellence-SIDC, Royal Observatory of Belgium, Av. Circulaire 3, B-1180 Brussels (Belgium)

    2016-10-20

    We investigate the high-speed ( v > 1000 km s{sup −1}) extreme-ultraviolet (EUV) wave associated with an X1.2 flare and coronal mass ejection (CME) from NOAA active region 11283 on 2011 September 6 (SOL2011-09-06T22:12). This EUV wave features peculiar on-disk signatures; in particular, we observe an intermittent “disappearance” of the front for 120 s in Solar Dynamics Observatory ( SDO )/AIA 171, 193, 211 Å data, whereas the 335 Å filter, sensitive to hotter plasmas ( T ∼ 2.5 MK), shows a continuous evolution of the wave front. The eruption was also accompanied by localized coronal dimming regions. We exploit the multi-point quadrature position of SDO and STEREO-A , to make a thorough analysis of the EUV wave evolution, with respect to its kinematics and amplitude evolution and reconstruct the SDO line-of-sight (LOS) direction of the identified coronal dimming regions in STEREO-A . We show that the observed intensities of the dimming regions in SDO /AIA depend on the structures that are lying along their LOS and are the combination of their individual intensities, e.g., the expanding CME body, the enhanced EUV wave, and the CME front. In this context, we conclude that the intermittent disappearance of the EUV wave in the AIA 171, 193, and 211 Å filters, which are channels sensitive to plasma with temperatures below ∼2 MK is also caused by such LOS integration effects. These observations clearly demonstrate that single-view image data provide us with limited insight to correctly interpret coronal features.

  1. Unambiguous Evidence of Coronal Implosions during Solar Eruptions and Flares

    Science.gov (United States)

    Wang, Juntao; Simões, P. J. A.; Fletcher, L.

    2018-05-01

    In the implosion conjecture, coronal loops contract as the result of magnetic energy release in solar eruptions and flares. However, after almost two decades, observations of this phenomenon are still rare and most previous reports are plagued by projection effects so that loop contraction could be either true implosion or just a change in loop inclination. In this paper, to demonstrate the reality of loop contractions in the global coronal dynamics, we present four events with the continuously contracting loops in an almost edge-on geometry from the perspective of SDO/AIA, which are free from the ambiguity caused by the projection effects, also supplemented by contemporary observations from STEREO for examination. In the wider context of observations, simulations and theories, we argue that the implosion conjecture is valid in interpreting these events. Furthermore, distinct properties of the events allow us to identify two physical categories of implosion. One type demonstrates a rapid contraction at the beginning of the flare impulsive phase, as magnetic free energy is removed rapidly by a filament eruption. The other type, which has no visible eruption, shows a continuous loop shrinkage during the entire flare impulsive phase, which we suggest shows the ongoing conversion of magnetic free energy in a coronal volume. Corresponding scenarios are described that can provide reasonable explanations for the observations. We also point out that implosions may be suppressed in cases when a heavily mass-loaded filament is involved, possibly serving as an alternative account for their observational rarity.

  2. Macrospicule Jets in On-Disk Coronal Holes

    Science.gov (United States)

    Adams, M. L.; Sterling, A. C.; Moore, R. L.

    2014-01-01

    We examine the magnetic structure and dynamics of multiple jets found in coronal holes close to or on disk center. All data are from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO). We report on observations of six jets in an equatorial coronal hole spanning 2011 February 27 and 28. We show the evolution of these jets in AIA 193 A, examine the magnetic field configuration, and postulate the probable trigger mechanism of these events. We recently reported on another jet in the same coronal hole on 2011 February 27, approximately 13:04 Universal Time (Adams et al 2014, Astrophysical Journal, 783: 11); this jet is a previously-unrecognized variety of blowout jet. In this variety, the reconnection bright point is not made by interchange reconnection of initially-closed erupting field in the base of the jet with ambient open field. Instead, there is a miniature filament-eruption flare arcade made by internal reconnection of the legs of the erupting field.

  3. THE NATURE OF CME-FLARE-ASSOCIATED CORONAL DIMMING

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, J. X. [Key Laboratory of Planetary Sciences, Shanghai Astronomical Observatory, Shanghai 200030 (China); Qiu, J., E-mail: chengjx@shao.ac.cn [Department of Physics, Montana State University, Bozeman MT 59717-3840 (United States)

    2016-07-01

    Coronal mass ejections (CMEs) are often accompanied by coronal dimming that is evident in extreme ultraviolet (EUV) and soft X-ray observations. The locations of dimming are sometimes considered to map footpoints of the erupting flux rope. As the emitting material expands in the corona, the decreased plasma density leads to reduced emission observed in spectral and irradiance measurements. Therefore, signatures of dimming may reflect the properties of CMEs in the early phase of their eruption. In this study, we analyze the event of flare, CME, and coronal dimming on 2011 December 26. We use the data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory for disk observations of the dimming, and analyze images taken by EUVI, COR1, and COR2 on board the Solar Terrestrial Relations Observatory to obtain the height and velocity of the associated CMEs observed at the limb. We also measure the magnetic reconnection rate from flare observations. Dimming occurs in a few locations next to the flare ribbons, and it is observed in multiple EUV passbands. Rapid dimming starts after the onset of fast reconnection and CME acceleration, and its evolution tracks the CME height and flare reconnection. The spatial distribution of dimming exhibits cores of deep dimming with a rapid growth, and their light curves are approximately linearly scaled with the CME height profile. From the dimming analysis we infer the process of the CME expansion, and estimate properties of the CME.

  4. Do coronal holes influence cosmic ray daily harmonics

    International Nuclear Information System (INIS)

    Ahluwalia, H.S.

    1977-01-01

    Coronal holes are identified by their low emissivity in either EUV (Munro and Withrobe, 1973) or in X-rays (Krieger et al, 1973). They are seats of unidirectional magnetic fields. Also, high speed solar wind streams originate in them. Also, high speed solar wind streams originate in then (Krieger et al, 1973; Neupert and Pizzo, 1974; Nolte et al, 1976). Coronal holes often extend over a wide range of heliolatitudes (Timothy et al, 1975). Elsewhere in the Proceedings we have presented results on the long term changes observed in the amplitudes and the times of maximum of the diurnal, the semidiurnal and the tridiurnal variations of cosmic rays, at low (neutrons) and at high (underground muons) primary rigidities (Ahluwalia, 1977). We have shown that a dramatic shift to early hours is noticeable in the times of maxima of the harmonics during 1971-72 period. In this paper we examine the nature of the contributions of off-ecliptic cosmic rays of high enough rigidity, streaming under the influence of large scale ordered interplanetary magnetic field set up by the coronal holes, to the cosmic ray daily harmonics. Some models are presented and discussed in a preliminary fashion. (author)

  5. Numerically modelling the large scale coronal magnetic field

    Science.gov (United States)

    Panja, Mayukh; Nandi, Dibyendu

    2016-07-01

    The solar corona spews out vast amounts of magnetized plasma into the heliosphere which has a direct impact on the Earth's magnetosphere. Thus it is important that we develop an understanding of the dynamics of the solar corona. With our present technology it has not been possible to generate 3D magnetic maps of the solar corona; this warrants the use of numerical simulations to study the coronal magnetic field. A very popular method of doing this, is to extrapolate the photospheric magnetic field using NLFF or PFSS codes. However the extrapolations at different time intervals are completely independent of each other and do not capture the temporal evolution of magnetic fields. On the other hand full MHD simulations of the global coronal field, apart from being computationally very expensive would be physically less transparent, owing to the large number of free parameters that are typically used in such codes. This brings us to the Magneto-frictional model which is relatively simpler and computationally more economic. We have developed a Magnetofrictional Model, in 3D spherical polar co-ordinates to study the large scale global coronal field. Here we present studies of changing connectivities between active regions, in response to photospheric motions.

  6. Coronal Physics and the Chandra Emission Line Project

    Science.gov (United States)

    Brickhouse, N. S.; Drake, J. J.

    2000-01-01

    With the launch of the Chandra X-ray Observatory, high resolution X-ray spectroscopy of cosmic sources has begun. Early, deep observations of three stellar coronal sources Capella, Procyon, and HR 1099 are providing not only invaluable calibration data, but also benchmarks for plasma spectral models. These models are needed to interpret data from stellar coronae, galaxies and clusters of galaxies, supernova, remnants and other astrophysical sources. They have been called into question in recent years as problems with understanding low resolution ASCA and moderate resolution Extreme Ultraviolet Explorer Satellite (EUVE) data have arisen. The Emission Line Project is a collaborative effort, to improve the models, with Phase I being the comparison of models with observed spectra of Capella, Procyon, and HR 1099. Goals of these comparisons are (1) to determine and verify accurate and robust diagnostics and (2) to identify and prioritize issues in fundamental spectroscopy which will require further theoretical and/or laboratory work. A critical issue in exploiting the coronal data for these purposes is to understand the extent, to which common simplifying assumptions (coronal equilibrium, negligible optical depth) apply. We will discuss recent, advances in our understanding of stellar coronae, in this context.

  7. THE NATURE OF CME-FLARE-ASSOCIATED CORONAL DIMMING

    International Nuclear Information System (INIS)

    Cheng, J. X.; Qiu, J.

    2016-01-01

    Coronal mass ejections (CMEs) are often accompanied by coronal dimming that is evident in extreme ultraviolet (EUV) and soft X-ray observations. The locations of dimming are sometimes considered to map footpoints of the erupting flux rope. As the emitting material expands in the corona, the decreased plasma density leads to reduced emission observed in spectral and irradiance measurements. Therefore, signatures of dimming may reflect the properties of CMEs in the early phase of their eruption. In this study, we analyze the event of flare, CME, and coronal dimming on 2011 December 26. We use the data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory for disk observations of the dimming, and analyze images taken by EUVI, COR1, and COR2 on board the Solar Terrestrial Relations Observatory to obtain the height and velocity of the associated CMEs observed at the limb. We also measure the magnetic reconnection rate from flare observations. Dimming occurs in a few locations next to the flare ribbons, and it is observed in multiple EUV passbands. Rapid dimming starts after the onset of fast reconnection and CME acceleration, and its evolution tracks the CME height and flare reconnection. The spatial distribution of dimming exhibits cores of deep dimming with a rapid growth, and their light curves are approximately linearly scaled with the CME height profile. From the dimming analysis we infer the process of the CME expansion, and estimate properties of the CME.

  8. An Estimate of Solar Wind Velocity Profiles in a Coronal Hole and a Coronal Streamer Area (6-40 R(radius symbol)

    Science.gov (United States)

    Patzold, M.; Tsurutani, B. T.; Bird, M. K.

    1995-01-01

    Total electron content data obtained from the Ulysses Solar Corona Experiment (SCE) in 1991 were used to select two data sets, one associated with a coronal hole and the other with coronal streamer crossings. (This is largely equatorial data shortly after solar maximum.) The solar wind velocity profile is estimated for these areas.

  9. NO TRACE LEFT BEHIND: STEREO OBSERVATION OF A CORONAL MASS EJECTION WITHOUT LOW CORONAL SIGNATURES

    International Nuclear Information System (INIS)

    Robbrecht, Eva; Patsourakos, Spiros; Vourlidas, Angelos

    2009-01-01

    The availability of high-quality synoptic observations of the extreme-ultraviolet (EUV) and visible corona during the SOHO mission has advanced our understanding of the low corona manifestations of coronal mass ejections (CMEs). The EUV imager/white light coronagraph connection has been proven so powerful, it is routinely assumed that if no EUV signatures are present when a CME is observed by a coronagraph, then the event must originate behind the visible limb. This assumption carries strong implications for space weather forecasting but has not been put to the test. This paper presents the first detailed analysis of a frontside, large-scale CME that has no obvious counterparts in the low corona as observed in EUV and Hα wavelengths. The event was observed by the SECCHI instruments onboard the STEREO mission. The COR2A coronagraph observed a slow flux-rope-type CME, while an extremely faint partial halo was observed in COR2B. The event evolved very slowly and is typical of the streamer-blowout CME class. EUVI A 171 A images show a concave feature above the east limb, relatively stable for about two days before the eruption, when it rises into the coronagraphic fields and develops into the core of the CME. None of the typical low corona signatures of a CME (flaring, EUV dimming, filament eruption, waves) were observed in the EUVI B images, which we attribute to the unusually large height from which the flux rope lifted off. This interpretation is supported by the CME mass measurements and estimates of the expected EUV dimming intensity. Only thanks to the availability of the two viewpoints we were able to identify the likely source region. The event originated along a neutral line over the quiet-Sun. No active regions were present anywhere on the visible (from STEREO B) face of the disk. Leaving no trace behind on the solar disk, this observation shows unambiguously that a CME eruption does not need to have clear on-disk signatures. Also it sheds light on the

  10. Evolution of magnetohydrodynamic waves in low layers of a coronal hole

    International Nuclear Information System (INIS)

    Pucci, Francesco; Malara, Francesco; Onofri, Marco

    2014-01-01

    Although a coronal hole is permeated by a magnetic field with a dominant polarity, magnetograms reveal a more complex magnetic structure in the lowest layers, where several regions of opposite polarity of typical size of the order of 10 4 km are present. This can give rise to magnetic separatrices and neutral lines. MHD fluctuations generated at the base of the coronal hole by motions of the inner layer of the solar atmosphere may interact with such inhomogeneities, leading to the formation of small scales. This phenomenon is studied on a 2D model of a magnetic structure with an X-point, using 2D MHD numerical simulations. This model implements a method of characteristics for boundary conditions in the direction outer-pointing to Sun surface to simulate both wave injection and exit without reflection. Both Alfvénic and magnetosonic perturbations are considered, and they show very different phenomenology. In the former case, an anisotropic power-law spectrum forms with a dominance of perpendicular wavevectors at altitudes ∼10 4 km. Density fluctuations are generated near the X-point by Alfvén wave magnetic pressure and propagate along open fieldlines at a speed comparable to the local Alfvén velocity. An analysis of energy dissipation and heating caused by the formation of small scales for the Alfvénic case is presented. In the magnetosonic case, small scales form only around the X-point, where a phenomenon of oscillating magnetic reconnection is observed to be induced by the periodic deformation of the magnetic structure due to incoming waves.

  11. Observational Signatures of Transverse Magnetohydrodynamic Waves and Associated Dynamic Instabilities in Coronal Flux Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Antolin, P.; Moortel, I. De [School of Mathematics and Statistics, University of St. Andrews, St. Andrews, Fife KY16 9SS (United Kingdom); Doorsselaere, T. Van [Centre for mathematical Plasma Astrophysics, Mathematics Department, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium); Yokoyama, T., E-mail: patrick.antolin@st-andrews.ac.uk [Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2017-02-20

    Magnetohydrodynamic (MHD) waves permeate the solar atmosphere and constitute potential coronal heating agents. Yet, the waves detected so far may be but a small subset of the true existing wave power. Detection is limited by instrumental constraints but also by wave processes that localize the wave power in undetectable spatial scales. In this study, we conduct 3D MHD simulations and forward modeling of standing transverse MHD waves in coronal loops with uniform and non-uniform temperature variation in the perpendicular cross-section. The observed signatures are largely dominated by the combination of the Kelvin–Helmholtz instability (KHI), resonant absorption, and phase mixing. In the presence of a cross-loop temperature gradient, we find that emission lines sensitive to the loop core catch different signatures compared to those that are more sensitive to the loop boundary and the surrounding corona, leading to an out-of-phase intensity and Doppler velocity modulation produced by KHI mixing. In all of the considered models, common signatures include an intensity and loop width modulation at half the kink period, a fine strand-like structure, a characteristic arrow-shaped structure in the Doppler maps, and overall line broadening in time but particularly at the loop edges. For our model, most of these features can be captured with a spatial resolution of 0.″33 and a spectral resolution of 25 km s{sup −1}, although we do obtain severe over-estimation of the line width. Resonant absorption leads to a significant decrease of the observed kinetic energy from Doppler motions over time, which is not recovered by a corresponding increase in the line width from phase mixing and KHI motions. We estimate this hidden wave energy to be a factor of 5–10 of the observed value.

  12. Correlation of Coronal Plasma Properties and Solar Magnetic Field in a Decaying Active Region

    Science.gov (United States)

    Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren, Harry P.; Ugarte-Urra, Ignacio

    2016-01-01

    We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a basal state (at 1.5 x 10(exp 6) K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas <10 G) weakened to below 35 G, while the electron density continued to decrease with the weakening field. These physical properties are all positively correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.

  13. Order-constrained linear optimization.

    Science.gov (United States)

    Tidwell, Joe W; Dougherty, Michael R; Chrabaszcz, Jeffrey S; Thomas, Rick P

    2017-11-01

    Despite the fact that data and theories in the social, behavioural, and health sciences are often represented on an ordinal scale, there has been relatively little emphasis on modelling ordinal properties. The most common analytic framework used in psychological science is the general linear model, whose variants include ANOVA, MANOVA, and ordinary linear regression. While these methods are designed to provide the best fit to the metric properties of the data, they are not designed to maximally model ordinal properties. In this paper, we develop an order-constrained linear least-squares (OCLO) optimization algorithm that maximizes the linear least-squares fit to the data conditional on maximizing the ordinal fit based on Kendall's τ. The algorithm builds on the maximum rank correlation estimator (Han, 1987, Journal of Econometrics, 35, 303) and the general monotone model (Dougherty & Thomas, 2012, Psychological Review, 119, 321). Analyses of simulated data indicate that when modelling data that adhere to the assumptions of ordinary least squares, OCLO shows minimal bias, little increase in variance, and almost no loss in out-of-sample predictive accuracy. In contrast, under conditions in which data include a small number of extreme scores (fat-tailed distributions), OCLO shows less bias and variance, and substantially better out-of-sample predictive accuracy, even when the outliers are removed. We show that the advantages of OCLO over ordinary least squares in predicting new observations hold across a variety of scenarios in which researchers must decide to retain or eliminate extreme scores when fitting data. © 2017 The British Psychological Society.

  14. DISPELLING ILLUSIONS OF REFLECTION: A NEW ANALYSIS OF THE 2007 MAY 19 CORONAL 'WAVE' EVENT

    International Nuclear Information System (INIS)

    Attrill, Gemma D. R.

    2010-01-01

    A new analysis of the 2007 May 19 coronal wave-coronal mass ejection-dimmings event is offered employing base difference extreme-ultraviolet (EUV) images. Previous work analyzing the coronal wave associated with this event concluded strongly in favor of purely an MHD wave interpretation for the expanding bright front. This conclusion was based to a significant extent on the identification of multiple reflections of the coronal wave front. The analysis presented here shows that the previously identified 'reflections' are actually optical illusions and result from a misinterpretation of the running difference EUV data. The results of this new multiwavelength analysis indicate that two coronal wave fronts actually developed during the eruption. This new analysis has implications for our understanding of diffuse coronal waves and questions the validity of the analysis and conclusions reached in previous studies.

  15. Reconstruction of a Large-scale Pre-flare Coronal Current Sheet Associated with a Homologous X-shaped Flare

    Science.gov (United States)

    Jiang, Chaowei; Yan, Xiaoli; Feng, Xueshang; Duan, Aiying; Hu, Qiang; Zuo, Pingbing; Wang, Yi

    2017-11-01

    As a fundamental magnetic structure in the solar corona, electric current sheets (CSs) can form either prior to or during a solar flare, and they are essential for magnetic energy dissipation in the solar corona because they enable magnetic reconnection. However, the static reconstruction of a CS is rare, possibly due to limitations that are inherent in the available coronal field extrapolation codes. Here we present the reconstruction of a large-scale pre-flare CS in solar active region 11967 using an MHD-relaxation model constrained by the SDO/HMI vector magnetogram. The CS is associated with a set of peculiar homologous flares that exhibit unique X-shaped ribbons and loops occurring in a quadrupolar magnetic configuration.This is evidenced by an ’X’ shape, formed from the field lines traced from the CS to the photosphere. This nearly reproduces the shape of the observed flare ribbons, suggesting that the flare is a product of the dissipation of the CS via reconnection. The CS forms in a hyperbolic flux tube, which is an intersection of two quasi-separatrix layers. The recurrence of the X-shaped flares might be attributed to the repetitive formation and dissipation of the CS, as driven by the photospheric footpoint motions. These results demonstrate the power of a data-constrained MHD model in reproducing a CS in the corona as well as providing insight into the magnetic mechanism of solar flares.

  16. Coronal pulp biomarker: A lesser known age estimation modality

    Directory of Open Access Journals (Sweden)

    Smrithi D Veera

    2014-01-01

    Full Text Available Introduction: The evolving state of art digital technology currently available is opening new avenues in forensic odontology for age estimation methods which are subject to debate in terms of accuracy and precision. A study was carried to analyze efficacy and practical application for age estimation using digital panoramic radiographs on South Indian population. Aims and Objectives: 1. To study reduction of coronal pulp chamber using Tooth Coronal Index (TCI on panoramic radiographs and correlate with chronologic age. 2. To establish accuracy of digital panoramic radiographs as a simple, non-invasive tool. Materials and Methods: The study illustrates the potential value of a little known aging method. The study groups comprised a total of 100 subjects of both sexes in age range of 20 and 60 years each who were subjected to panoramic radiography. A panoramic radiographic examination using digital panoramic machine was conducted on selected individuals. The TCI was calibrated using AGFA computer software for accuracy and precision. The values obtained were subjected to regression analysis, results calculated and correlated with chronologic age. In the present study a population of known age was studied and subjected to digital panoramic radiographic examination. The correlation between reduction of coronal pulp cavity and chronological age was examined. TCI was computed for each tooth and regressed on real age. Statistical Analysis Used: Pearson correlation co-efficient was used to find the significance of relationship between age and TCI. Regression analysis has been used for predicting age using TCI for premolar and molar. Inaccuracy and bias have been determined to assess the precision of prediction equations. Results and Conclusion: Prediction potential of TCI comes down for ages above 50 years and is comfortably good below 50 years without much difference between premolars and molars. This study demonstrates the potential value of TCI for age

  17. Expansion and broadening of coronal loop transients: A theoretical explanation

    International Nuclear Information System (INIS)

    Mouschovias, T.C.; Poland, A.I.

    1978-01-01

    We explore the consequences of the assumption that a coronal loop transient (observed by the white-light coronagraph aboard Skylab) is a twisted rope of magnetic field lines expanding and broadening in the background coronal plasma and magnetic field. We show that the expansion (i.e., the outward motion of the loop top) can be accounted for by the azimuthal component of the field, B/sub az/; the observed broadening of the loop as it moves outward can be accounted for by the longitudinal component of the field, B/sub l/. In order to have a net outward force and at the same time avoid a classicial pinch (sausage) instability, the two components of the field must satisfy the inequality 1.41 B/sub l/>B/sub az/>B/sub l/.We predict that, as the loop rises, the width (h) of its top portion should vary proportionally with the distance (R) from the Sun's center. This is in good agreement with measurements that show hproportionalR/sup 0.8/. Our prediction, that the radius of curvature (R/sub c/) of the top portion of the loop should be proportional to R, differs from the measured variation R/sub c/proportionalR/sup 1.6/. The difference could be accounted for by a drag due to the background coronal field that flattens the loop's top. A statistical study that can test this possibility is suggested. We also calculate the magnetic field within the top section of the loop. It is approximately equal to 1 gauss at R=2 R/sub sun/ and varies somewhat more slowly than R -2 during expansion

  18. ON THE NATURE OF THE SOLAR WIND FROM CORONAL PSEUDOSTREAMERS

    International Nuclear Information System (INIS)

    Wang, Y.-M.; Sheeley, N. R. J.R.; Grappin, R.; Robbrecht, E.

    2012-01-01

    Coronal pseudostreamers, which separate like-polarity coronal holes, do not have current sheet extensions, unlike the familiar helmet streamers that separate opposite-polarity holes. Both types of streamers taper into narrow plasma sheets that are maintained by continual interchange reconnection with the adjacent open magnetic field lines. White-light observations show that pseudostreamers do not emit plasma blobs; this important difference from helmet streamers is due to the convergence of like-polarity field lines above the X-point, which prevents the underlying loops from expanding outward and pinching off. The main component of the pseudostreamer wind has the form of steady outflow along the open field lines rooted just inside the boundaries of the adjacent coronal holes. These flux tubes are characterized by very rapid expansion below the X-point, followed by reconvergence at greater heights. Analysis of an idealized pseudostreamer configuration shows that, as the separation between the underlying holes increases, the X-point rises and the expansion factor f ss at the source surface increases. In situ observations of pseudostreamer crossings indicate wind speeds v ranging from ∼350 to ∼550 km s –1 , with O 7+ /O 6+ ratios that are enhanced compared with those in high-speed streams but substantially lower than in the slow solar wind. Hydrodynamic energy-balance models show that the empirical v-f ss relation overestimates the wind speeds from nonmonotonically expanding flux tubes, particularly when the X-point is located at low heights and f ss is small. We conclude that pseudostreamers produce a 'hybrid' type of outflow that is intermediate between classical slow and fast solar wind.

  19. The COronal Solar Magnetism Observatory (COSMO) Large Aperture Coronagraph

    Science.gov (United States)

    Tomczyk, Steve; Gallagher, Dennis; Wu, Zhen; Zhang, Haiying; Nelson, Pete; Burkepile, Joan; Kolinksi, Don; Sutherland, Lee

    2013-04-01

    The COSMO is a facility dedicated to observing coronal and chromospheric magnetic fields. It will be located on a mountaintop in the Hawaiian Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will provide unique observations of the global coronal magnetic fields and its environment to enhance the value of data collected by other observatories on the ground (e.g. SOLIS, BBO NST, Gregor, ATST, EST, Chinese Giant Solar Telescope, NLST, FASR) and in space (e.g. SDO, Hinode, SOHO, GOES, STEREO, Solar-C, Solar Probe+, Solar Orbiter). COSMO will employ a fleet of instruments to cover many aspects of measuring magnetic fields in the solar atmosphere. The dynamics and energy flow in the corona are dominated by magnetic fields. To understand the formation of CMEs, their relation to other forms of solar activity, and their progression out into the solar wind requires measurements of coronal magnetic fields. The large aperture coronagraph, the Chromospheric and Prominence Magnetometer and the K-Coronagraph form the COSMO instrument suite to measure magnetic fields and the polarization brightness of the low corona used to infer electron density. The large aperture coronagraph will employ a 1.5 meter fuse silica singlet lens, birefringent filters, and a spectropolarimeter to cover fields of view of up to 1 degree. It will observe the corona over a wide range of emission lines from 530.3 nm through 1083.0 nm allowing for magnetic field measurements over a wide range of coronal temperatures (e.g. FeXIV at 530.3 nm, Fe X at 637.4 nm, Fe XIII at 1074.7 and 1079.8 nm. These lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the large aperture coronagraph to a preliminary design review state by the end of 2013. As with all data from Mauna Loa, the data products from COSMO will be available to the community via the Mauna Loa website: http://mlso.hao.ucar.edu

  20. Paraboloidal X-ray telescope mirror for solar coronal spectroscopy

    Science.gov (United States)

    Brown, W. A.; Bruner, E. C., Jr.; Acton, L. W.; Franks, A.; Stedman, M.; Speer, R. J.

    1979-01-01

    The telescope mirror for the X-ray Spectrograph Spectrometer Telescope System is a sixty degree sector of an extreme off-axis paraboloid of revolution. It was designed to focus a coronal region 1 by 10 arc seconds in size on the entrance slit of the spectrometer after reflection from the gold surface. This paper discusses the design, manufacture, and metrology of the mirror, the methods of precision mechanical metrology used to focus the system, and the mounting system which locates the mirror and has proven itself through vibration tests. In addition, the results of reflection efficiency measurements, alignment tolerances, and ray trace analysis of the effects of misalignment are considered.

  1. The Radiation, Interplanetary Shocks, and Coronal Sources (RISCS) Toolset

    Science.gov (United States)

    Zank, G. P.; Spann, James F.

    2014-01-01

    The goal of this project is to serve the needs of space system designers and operators by developing an interplanetary radiation environment model within 10 AU:Radiation, Interplanetary Shocks, and Coronal Sources (RISCS) toolset: (1) The RISCS toolset will provide specific reference environments for space system designers and nowcasting and forecasting capabilities for space system operators; (2) We envision the RISCS toolset providing the spatial and temporal radiation environment external to the Earth's (and other planets') magnetosphere, as well as possessing the modularity to integrate separate applications (apps) that can map to specific magnetosphere locations and/or perform the subsequent radiation transport and dosimetry for a specific target.

  2. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...... to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number...

  3. Heat pumps: heat recovery

    Energy Technology Data Exchange (ETDEWEB)

    Pielke, R

    1976-01-01

    The author firstly explains in a general manner the functioning of the heat pump. Following a brief look at the future heat demand and the possibilities of covering it, the various methods of obtaining energy (making use of solar energy, ground heat, and others) and the practical applications (office heating, swimming pool heating etc.) are explained. The author still sees considerable difficulties in using the heat pump at present on a large scale. Firstly there is not enough maintenance personnel available, secondly the electricity supply undertakings cannot provide the necessary electricity on a wide basis without considerable investments. Other possibilities to save energy or to use waste energy are at present easier and more economical to realize. Recuperative and regenerative systems are described.

  4. Does correction of preoperative coronal imbalance make a difference in outcomes of adult patients with deformity?

    Science.gov (United States)

    Daubs, Michael D; Lenke, Lawrence G; Bridwell, Keith H; Kim, Yongjung J; Hung, Man; Cheh, Gene; Koester, Linda A

    2013-03-15

    Retrospective study with prospectively collected outcomes data. Determine the significance of coronal balance on spinal deformity surgery outcomes. Sagittal balance has been confirmed as an important radiographic parameter correlating with adult deformity treatment outcomes. The significance of coronal balance on functional outcomes is less clear. Eighty-five patients with more than 4 cm of coronal imbalance who underwent reconstructive spinal surgery were evaluated to determine the significance of coronal balance on functional outcomes as measured with the Oswestry Disability Index (ODI) and Scoliosis Research Society outcomes questionnaires. Sixty-two patients had combined coronal (>4 cm) and sagittal imbalance (>5 cm), while 23 patients had coronal imbalance alone. Postoperatively, 85% of patients demonstrated improved coronal balance. The mean improvement in the coronal C7 plumb line was 26 mm for a mean correction of 42%. The mean preoperative sagittal C7 plumb line in patients with combined coronal and sagittal imbalance was 118 mm (range, 50-310 mm) and improved to a mean 49 mm. The mean preoperative and postoperative ODI scores were 42 (range, 0-90) and 27 (range, 0-78), for a mean improvement of 15 (36%) (P = 0.00001; 95% CI, 12-20). The mean Scoliosis Research Society scores improved by 17 points (29%) (P = 0.00). Younger age (P = 0.008) and improvement in sagittal balance (P = 0.014) were positive predictors for improved ODI scores. Improvement in sagittal balance (P = 0.010) was a positive predictor for improved Scoliosis Research Society scores. In patients with combined coronal and sagittal imbalance, improvement in sagittal balance was the most significant predictor for improved ODI scores (P = 0.009). In patients with preoperative coronal imbalance alone, improvement in coronal balance trended toward, but was not a significant predictor for improved ODI (P = 0.092). Sagittal balance improvement is the strongest predictor of improved outcomes in

  5. Towards constraining extreme temperature projections of the CMIP5 ensemble

    Science.gov (United States)

    Vogel, Martha-Marie; Orth, René; Isabelle Seneviratne, Sonia

    2016-04-01

    The frequency and intensity of heat waves is expected to change in future in response to global warming. Given the severe impacts of heat waves on ecosystems and society it is important to understand how and where they will intensify. Projections of extreme hot temperatures in the IPCC AR5 model ensemble show large uncertainties for projected changes of extreme temperatures in particular in Central Europe. In this region land-atmosphere coupling can contribute substantially to the development of heat waves. This coupling is also subject to change in future, while model projections display considerable spread. In this work we link projections of changes in extreme temperatures and of changes in land-atmosphere interactions with a particular focus on Central Europe. Uncertainties in projected extreme temperatures can be partly explained by different projected changes of the interplay between latent heat and temperature as well as soil moisture. Given the considerable uncertainty in land-atmosphere coupling representation already in the current climate, we furthermore employ observational data sets to constrain the model ensemble, and consequently the extreme temperature projections.

  6. Asymptotic Likelihood Distribution for Correlated & Constrained Systems

    CERN Document Server

    Agarwal, Ujjwal

    2016-01-01

    It describes my work as summer student at CERN. The report discusses the asymptotic distribution of the likelihood ratio for total no. of parameters being h and 2 out of these being are constrained and correlated.

  7. Constrained bidirectional propagation and stroke segmentation

    Energy Technology Data Exchange (ETDEWEB)

    Mori, S; Gillespie, W; Suen, C Y

    1983-03-01

    A new method for decomposing a complex figure into its constituent strokes is described. This method, based on constrained bidirectional propagation, is suitable for parallel processing. Examples of its application to the segmentation of Chinese characters are presented. 9 references.

  8. Mathematical Modeling of Constrained Hamiltonian Systems

    NARCIS (Netherlands)

    Schaft, A.J. van der; Maschke, B.M.

    1995-01-01

    Network modelling of unconstrained energy conserving physical systems leads to an intrinsic generalized Hamiltonian formulation of the dynamics. Constrained energy conserving physical systems are directly modelled as implicit Hamiltonian systems with regard to a generalized Dirac structure on the

  9. Client's Constraining Factors to Construction Project Management

    African Journals Online (AJOL)

    factors as a significant system that constrains project management success of public and ... finance for the project and prompt payment for work executed; clients .... consideration of the loading patterns of these variables, the major factor is ...

  10. CHROMOSPHERE TO 1 au SIMULATION OF THE 2011 MARCH 7th EVENT: A COMPREHENSIVE STUDY OF CORONAL MASS EJECTION PROPAGATION

    Energy Technology Data Exchange (ETDEWEB)

    Jin, M. [Lockheed Martin Solar and Astrophysics Lab, Palo Alto, CA 94304 (United States); Manchester, W. B.; Holst, B. van der; Sokolov, I.; Tóth, G.; Gombosi, T. I. [Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Vourlidas, A. [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 (United States); Koning, C. A. de, E-mail: jinmeng@lmsal.com, E-mail: chipm@umich.edu, E-mail: angelos.vourlidas@jhuapl.edu, E-mail: curt.a.dekoning@noaa.gov [Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2017-01-10

    We perform and analyze the results of a global magnetohydrodynamic simulation of the fast coronal mass ejection (CME) that occurred on 2011 March 7. The simulation is made using the newly developed Alfvén Wave Solar Model (AWSoM), which describes the background solar wind starting from the upper chromosphere and extends to 24 R {sub ⊙}. Coupling AWSoM to an inner heliosphere model with the Space Weather Modeling Framework extends the total domain beyond the orbit of Earth. Physical processes included in the model are multi-species thermodynamics, electron heat conduction (both collisional and collisionless formulations), optically thin radiative cooling, and Alfvén-wave turbulence that accelerates and heats the solar wind. The Alfvén-wave description is physically self-consistent, including non-Wentzel–Kramers–Brillouin reflection and physics-based apportioning of turbulent dissipative heating to both electrons and protons. Within this model, we initiate the CME by using the Gibson-Low analytical flux rope model and follow its evolution for days, in which time it propagates beyond STEREO A . A detailed comparison study is performed using remote as well as in situ observations. Although the flux rope structure is not compared directly due to lack of relevant ejecta observation at 1 au in this event, our results show that the new model can reproduce many of the observed features near the Sun (e.g., CME-driven extreme ultraviolet [EUV] waves, deflection of the flux rope from the coronal hole, “double-front” in the white light images) and in the heliosphere (e.g., shock propagation direction, shock properties at STEREO A ).

  11. ON THE FOURIER AND WAVELET ANALYSIS OF CORONAL TIME SERIES

    International Nuclear Information System (INIS)

    Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J.

    2016-01-01

    Using Fourier and wavelet analysis, we critically re-assess the significance of our detection of periodic pulsations in coronal loops. We show that the proper identification of the frequency dependence and statistical properties of the different components of the power spectra provides a strong argument against the common practice of data detrending, which tends to produce spurious detections around the cut-off frequency of the filter. In addition, the white and red noise models built into the widely used wavelet code of Torrence and Compo cannot, in most cases, adequately represent the power spectra of coronal time series, thus also possibly causing false positives. Both effects suggest that several reports of periodic phenomena should be re-examined. The Torrence and Compo code nonetheless effectively computes rigorous confidence levels if provided with pertinent models of mean power spectra, and we describe the appropriate manner in which to call its core routines. We recall the meaning of the default confidence levels output from the code, and we propose new Monte-Carlo-derived levels that take into account the total number of degrees of freedom in the wavelet spectra. These improvements allow us to confirm that the power peaks that we detected have a very low probability of being caused by noise.

  12. Examining the Properties of Jets in Coronal Holes

    Science.gov (United States)

    Gaulle, Owen; Adams, Mitzi L.; Tennant, A. F.

    2012-01-01

    Data from the Solar Dynamics Observatory (SDO) were used to look for triggers of jets in a coronal hole. It has been proposed that bright points affiliated with the jets are caused by either random collisions between magnetic elements or by magnetic flux emerging from the photosphere; either of which can give rise to magnetic reconnection. Images from the 193AA filter of the Atmospheric Imaging Assembly (AIA) were searched to identify and locate jets. Changes in the line-of-sight magnetic field prior to the time of the jet were sought in data from the Helioseismic Magnetic Imager (HMI). In total we studied 15 different jets that occurred over a two day period starting 2011-02-27 00:00:00 UTC and ending 2011-02-28 23:59:55 UTC. All of the jets were contained within a coronal hole that was close to disk center. Of the 15 that we studied 6 were shown to have an increase of the parameter B2 (where B is the line-of-sight component of the magnetic field), within one hour prior to the creation of the jet and 10 were within 3 hours before the event.

  13. Filament shape versus coronal potential magnetic field structure

    Science.gov (United States)

    Filippov, B.

    2016-01-01

    Solar filament shape in projection on disc depends on the structure of the coronal magnetic field. We calculate the position of polarity inversion lines (PILs) of coronal potential magnetic field at different heights above the photosphere, which compose the magnetic neutral surface, and compare with them the distribution of the filament material in Hα chromospheric images. We found that the most of the filament material is enclosed between two PILs, one at a lower height close to the chromosphere and one at a higher level, which can be considered as a height of the filament spine. Observations of the same filament on the limb by the Solar Terrestrial Relations Observatory spacecraft confirm that the height of the spine is really very close to the value obtained from the PIL and filament border matching. Such matching can be used for filament height estimations in on-disc observations. Filament barbs are housed within protruding sections of the low-level PIL. On the base of simple model, we show that the similarity of the neutral surfaces in potential and non-potential fields with the same sub-photospheric sources is the reason for the found tendency for the filament material to gather near the potential-field neutral surface.

  14. Posterior coronal plating for tibial fractures: technique and advantages

    Directory of Open Access Journals (Sweden)

    Montu Jain

    2014-04-01

    Full Text Available Objective:Tibial shaft fractures are straightforward to treat but when associated with soft tissue injury particularly at the nail entry/plate insertion site or there is significant comminution proximally or a large butterfly fragment/a second split component in the posterior coronal plane, it is a challenge to the treating surgeon. The aim of the present report is to describe the technique of posterior coronal plating in such a scenario and its advantages. Methods:Between July 2008 and June 2011, 12 patients were pro spectively treated by this approach using 4.5 mm broad dynamic compression plates. Results:The time of bony consolidation and full weight bearing averaged 21.7 weeks (range, 16-26 weeks. Patients were followed up for at least 24 months (range, 24-48 months. At 1 year postoper atively, no loss in reduction or alignment was observed. Mean Hospital for Lower Extremity Measurement Functional Score was 72.8 (range, 64-78. All patients were satisfied with their treatment outcomes. Conclusion:Direct posterior approach and fixation using prone position helps to visualise the fracture fragments and provide rigid fixation. The approach is simple and extensile easily, apart from advantages of less soft tissue and hardware problems compared to standard medial or lateral plating. Key words: Tibial fractures; Bone plates; Orthopedic procedures

  15. ON THE OBSERVATION AND SIMULATION OF SOLAR CORONAL TWIN JETS

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiajia; Wang, Yuming; Zhang, Quanhao [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, NO. 96, Jinzhai Road, Hefei, Anhui 230026 (China); Fang, Fang [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, 1234 Innovation Drive, Boulder, CO 80303 (United States); McIntosh, Scott W.; Fan, Yuhong [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

    2016-02-01

    We present the first observation, analysis, and modeling of solar coronal twin jets, which occurred after a preceding jet. Detailed analysis on the kinetics of the preceding jet reveals its blowout-jet nature, which resembles the one studied in Liu et al. However, the erupting process and kinetics of the twin jets appear to be different from the preceding one. Lacking detailed information on the magnetic fields in the twin jet region, we instead use a numerical simulation using a three-dimensional (3D) MHD model as described in Fang et al., and find that in the simulation a pair of twin jets form due to reconnection between the ambient open fields and a highly twisted sigmoidal magnetic flux, which is the outcome of the further evolution of the magnetic fields following the preceding blowout jet. Based on the similarity between the synthesized and observed emission, we propose this mechanism as a possible explanation for the observed twin jets. Combining our observation and simulation, we suggest that with continuous energy transport from the subsurface convection zone into the corona, solar coronal twin jets could be generated in the same fashion addressed above.

  16. Electron acceleration and radiation signatures in loop coronal transients

    International Nuclear Information System (INIS)

    Vlahos, L.; Gergely, T.E.; Papadopoulos, K.

    1982-01-01

    A model for electron aceleration in loop coronal transients is suggested. We propose that in these transients an erupting loop moves away from the solar surface, with a velocity greater than the local Alfven speed, pushing against the overlying magnetic fields and driving a shock in the front of the moving part of the loop. We suggest that lower hybrid waves are excited at the shock front and propagate radially toward the center of the loop with phase velocity along the magnetic field which exceeds the thermal velocity. The lower hybrid waves stochastically accelerate the tail of the electron distribution inside the loop. We discuss how the accelerated electrons are trapped in the moving loop and give a rough estimate of their radiation signature. We find that plasma radiation can explain the power observed in stationary and moving type IV bursts. We discuss some of the conditions under which moving or stationary type IV bursts are expected to be associated with loop coronal transients

  17. SAUSAGE WAVES IN TRANSVERSELY NONUNIFORM MONOLITHIC CORONAL TUBES

    Energy Technology Data Exchange (ETDEWEB)

    Lopin, I. [Ussuriisk astrophysical observatory, Russion Academy of Sciences (Russian Federation); Nagorny, I., E-mail: lopin78@mail.ru [Institute of Automation and Control Processes FEB RAS, Vladivostok (Russian Federation)

    2015-09-10

    We investigate fast sausage waves in a monolithic coronal magnetic tube, modeled as a local density inhomogeneity with a continuous radial profile. This work is a natural extension of our previous results, obtained for a slab loop model for the case of cylindrical geometry. Using Kneser’s oscillating theorem, we provided the criteria for the existence of trapped and leaky wave regimes as a function of the profile features. For a number of density profiles there are only trapped modes for the entire range of longitudinal wave numbers. The phase speed of these modes tends toward the external Alfvén speed in the long wavelength limit. The generalized results were supported by the analytic solution of the wave equation for the specific density profiles. The approximate Wentzel–Kramers–Brillouin solutions allowed us to obtain the desired dispersion relations and to study their properties as a function of the profile parameters. The multicomponent quasi-periodic pulsations in flaring loops, observed on 2001 May 2 and 2002 July 3, are interpreted in terms of the transversely fundamental trapped fast sausage mode with several longitudinal harmonics in a smooth coronal waveguide.

  18. Activity associated with the solar origin of coronal mass ejections

    Science.gov (United States)

    Webb, D. F.; Hundhausen, A. J.

    1987-01-01

    Solar coronal mass ejections (CMEs) observed in 1980 with the HAO Coronagraph/Polarimeter on the Solar Maximum Mission (SMM) satellite are compared with other forms of solar activity that might be physically related to the ejections. The solar phenomena checked and the method of association used were intentionally patterned after those of Munro et al.'s (1979) analysis of mass ejections observed with the Skylab coronagraph to facilitate comparison of the two epochs. Comparison of the results reveals that the types and degree of CME associations are similar near solar activity minimum and at maximum. For both epochs, most CMEs with associations had associated eruptive prominences, and the proportions of association of all types of activity were similar. A high percentage of association between SMM CMEs and X-ray long duration events is also found, in agreement with Skylab results. It is concluded that most CMEs are the result of the destabilization and eruption of a prominence and its overlying coronal structure, or of a magnetic structure capable of supporting a prominence.

  19. Cannabis, possible cardiac deaths and the coroner in Ireland.

    LENUS (Irish Health Repository)

    Tormey, W P

    2012-01-10

    BACKGROUND: The elevated risk of triggering a myocardial infarction by smoking cannabis is limited to the first 2 h after smoking. AIM: To examine the possible role of cannabis in cardiac deaths. CASES AND RESULTS: From 3,193 coroners\\' cases over 2 years, there were 13 cases where the clinical information was compatible with a primary cardiac cause of death. An inquest was held in three cases. Myocardial infarction was the primary cause of death in 54%. Other causes were sudden adult death syndrome, sudden death in epilepsy, and poisoning by alcohol and diazepam. Cannabis was mentioned once only on a death certificate, but not as a cause of death. Blood delta9-tetrahydrocannabinol-carboxylic acid was recorded in one case and in no case was plasma tetrahydrocannabinol (THC) measured. CONCLUSIONS: To attribute sudden cardiac death to cannabis, plasma THC should be measured in the toxicology screen in coroners\\' cases where urine cannabinoids are positive. A positive urine cannabinoids immunoassay alone is insufficient evidence in the linkage of acute cardiac death and cannabis.

  20. ON THE FOURIER AND WAVELET ANALYSIS OF CORONAL TIME SERIES

    Energy Technology Data Exchange (ETDEWEB)

    Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J., E-mail: frederic.auchere@ias.u-psud.fr [Institut d’Astrophysique Spatiale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 121, F-91405 Orsay (France)

    2016-07-10

    Using Fourier and wavelet analysis, we critically re-assess the significance of our detection of periodic pulsations in coronal loops. We show that the proper identification of the frequency dependence and statistical properties of the different components of the power spectra provides a strong argument against the common practice of data detrending, which tends to produce spurious detections around the cut-off frequency of the filter. In addition, the white and red noise models built into the widely used wavelet code of Torrence and Compo cannot, in most cases, adequately represent the power spectra of coronal time series, thus also possibly causing false positives. Both effects suggest that several reports of periodic phenomena should be re-examined. The Torrence and Compo code nonetheless effectively computes rigorous confidence levels if provided with pertinent models of mean power spectra, and we describe the appropriate manner in which to call its core routines. We recall the meaning of the default confidence levels output from the code, and we propose new Monte-Carlo-derived levels that take into account the total number of degrees of freedom in the wavelet spectra. These improvements allow us to confirm that the power peaks that we detected have a very low probability of being caused by noise.

  1. Steady three-fluid coronal expansion for nonspherical geometries

    International Nuclear Information System (INIS)

    Joselyn, J.; Holzer, T.E.

    1978-01-01

    A steady three-fluid model of the solar coronal expansionk in which 4 He ++ ions (alphas) are treated as a nonminor species, is developed for nonspherically symmetric flow geometries of the general sort thought to be characteristic of coronal holes. It is found that the very high mass fluxes in the low corona, which are associated with rapidly diverging flow geometries, lead to a locally enhanced frictional coupling between protons and alphas and consequently to a significant reduction of the He/H abundance ratio in the lower corona from that normally predicted by multifluid models. In the models considered, the frictional drag on the protons by the alphas (a process neglected in most studies) is found to play an important role near the sun. Heavy ions, other than alphas, are treated as minor species and are seen to exhibit varying responses to the rapidly diverging flow geometries, depending on the ion mass and charge. As for the protons, the frictional effect of the alphas on the heavier ions is found to be significant in the models considered

  2. Coronal Flux Rope Catastrophe Associated With Internal Energy Release

    Science.gov (United States)

    Zhuang, Bin; Hu, Youqiu; Wang, Yuming; Zhang, Quanhao; Liu, Rui; Gou, Tingyu; Shen, Chenglong

    2018-04-01

    Magnetic energy during the catastrophe was predominantly studied by the previous catastrophe works since it is believed to be the main energy supplier for the solar eruptions. However, the contribution of other types of energies during the catastrophe cannot be neglected. This paper studies the catastrophe of the coronal flux rope system in the solar wind background, with emphasis on the transformation of different types of energies during the catastrophe. The coronal flux rope is characterized by its axial and poloidal magnetic fluxes and total mass. It is shown that a catastrophe can be triggered by not only an increase but also a decrease of the axial magnetic flux. Moreover, the internal energy of the rope is found to be released during the catastrophe so as to provide energy for the upward eruption of the flux rope. As far as the magnetic energy is concerned, it provides only part of the energy release, or even increases during the catastrophe, so the internal energy may act as the dominant or even the unique energy supplier during the catastrophe.

  3. FORECASTING A CORONAL MASS EJECTION'S ALTERED TRAJECTORY: ForeCAT

    International Nuclear Information System (INIS)

    Kay, C.; Opher, M.; Evans, R. M.

    2013-01-01

    To predict whether a coronal mass ejection (CME) will impact Earth, the effects of the background on the CME's trajectory must be taken into account. We develop a model, ForeCAT (Forecasting a CME's Altered Trajectory), of CME deflection due to magnetic forces. ForeCAT includes CME expansion, a three-part propagation model, and the effects of drag on the CME's deflection. Given the background solar wind conditions, the launch site of the CME, and the properties of the CME (mass, final propagation speed, initial radius, and initial magnetic strength), ForeCAT predicts the deflection of the CME. Two different magnetic backgrounds are considered: a scaled background based on type II radio burst profiles and a potential field source surface (PFSS) background. For a scaled background where the CME is launched from an active region located between a coronal hole and streamer region, the strong magnetic gradients cause a deflection of 8.°1 in latitude and 26.°4 in longitude for a 10 15 g CME propagating out to 1 AU. Using the PFSS background, which captures the variation of the streamer belt (SB) position with height, leads to a deflection of 1.°6 in latitude and 4.°1 in longitude for the control case. Varying the CME's input parameters within observed ranges leads to the majority of CMEs reaching the SB within the first few solar radii. For these specific backgrounds, the SB acts like a potential well that forces the CME into an equilibrium angular position

  4. Determining coronal electron temperatures from observations with UVCS/SOHO

    Science.gov (United States)

    Fineschi, S.; Esser, R.; Habbal, S. R.; Karovska, M.; Romoli, M.; Strachan, L.; Kohl, J. L.; Huber, M. C. E.

    1995-01-01

    The electron temperature is a fundamental physical parameter of the coronal plasma. Currently, there are no direct measurements of this quantity in the extended corona. Observations with the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the upcoming Solar and Heliospheric Observatory (SOHO) mission can provide the most direct determination of the electron kinetic temperature (or, more precisely, the electron velocity distribution along the line of sight). This measurement is based on the observation of the Thomson-scattered Lyman alpha (Ly-alpha) profile. This observation is made particularly challenging by the fact that the integrated intensity of the electron-scattered Ly-alpha line is about 10(exp 3) times fainter than that of the resonantly-scattered Ly-alpha component. In addition, the former is distributed across 50 A (FWHM), unlike the latter that is concentrated in 1 A. These facts impose stringent requirements on the stray-light rejection properties of the coronagraph/spectrometer, and in particular on the requirements for the grating. We make use of laboratory measurements of the UVCS Ly-alpha grating stray-light, and of simulated electron-scattered Ly-alpha profiles to estimate the expected confidence levels of electron temperature determination. Models of different structures typical of the corona (e.g., streamers, coronal holes) are used for this parameter study.

  5. AN IMAGING STUDY OF A COMPLEX SOLAR CORONAL RADIO ERUPTION

    Energy Technology Data Exchange (ETDEWEB)

    Feng, S. W.; Chen, Y.; Song, H. Q.; Wang, B.; Kong, X. L., E-mail: yaochen@sdu.edu.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China)

    2016-08-10

    Solar coronal radio bursts are enhanced radio emission excited by energetic electrons accelerated during solar eruptions. Studying these bursts is important for investigating the origin and physical mechanism of energetic particles and further diagnosing coronal parameters. Earlier studies suffered from a lack of simultaneous high-quality imaging data of the radio burst and the eruptive structure in the inner corona. Here we present a study on a complex solar radio eruption consisting of a type II burst and three reversely drifting type III bursts, using simultaneous EUV and radio imaging data. It is found that the type II burst is closely associated with a propagating and evolving CME-driven EUV shock structure, originated initially at the northern shock flank and later transferred to the top part of the shock. This source transfer is coincident with the presence of shock decay and enhancing signatures observed at the corresponding side of the EUV front. The electron energy accelerated by the shock at the flank is estimated to be ∼0.3 c by examining the imaging data of the fast-drifting herringbone structure of the type II burst. The reverse-drifting type III sources are found to be within the ejecta and correlated with a likely reconnection event therein. The implications for further observational studies and relevant space weather forecasting techniques are discussed.

  6. On the Observation and Simulation of Solar Coronal Twin Jets

    Science.gov (United States)

    Liu, Jiajia; Fang, Fang; Wang, Yuming; McIntosh, Scott W.; Fan, Yuhong; Zhang, Quanhao

    2016-02-01

    We present the first observation, analysis, and modeling of solar coronal twin jets, which occurred after a preceding jet. Detailed analysis on the kinetics of the preceding jet reveals its blowout-jet nature, which resembles the one studied in Liu et al. However, the erupting process and kinetics of the twin jets appear to be different from the preceding one. Lacking detailed information on the magnetic fields in the twin jet region, we instead use a numerical simulation using a three-dimensional (3D) MHD model as described in Fang et al., and find that in the simulation a pair of twin jets form due to reconnection between the ambient open fields and a highly twisted sigmoidal magnetic flux, which is the outcome of the further evolution of the magnetic fields following the preceding blowout jet. Based on the similarity between the synthesized and observed emission, we propose this mechanism as a possible explanation for the observed twin jets. Combining our observation and simulation, we suggest that with continuous energy transport from the subsurface convection zone into the corona, solar coronal twin jets could be generated in the same fashion addressed above.

  7. Cannabis, possible cardiac deaths and the coroner in Ireland.

    Science.gov (United States)

    Tormey, W P

    2012-12-01

    The elevated risk of triggering a myocardial infarction by smoking cannabis is limited to the first 2 h after smoking. To examine the possible role of cannabis in cardiac deaths. CASES AND RESULTS: From 3,193 coroners' cases over 2 years, there were 13 cases where the clinical information was compatible with a primary cardiac cause of death. An inquest was held in three cases. Myocardial infarction was the primary cause of death in 54%. Other causes were sudden adult death syndrome, sudden death in epilepsy, and poisoning by alcohol and diazepam. Cannabis was mentioned once only on a death certificate, but not as a cause of death. Blood delta9-tetrahydrocannabinol-carboxylic acid was recorded in one case and in no case was plasma tetrahydrocannabinol (THC) measured. To attribute sudden cardiac death to cannabis, plasma THC should be measured in the toxicology screen in coroners' cases where urine cannabinoids are positive. A positive urine cannabinoids immunoassay alone is insufficient evidence in the linkage of acute cardiac death and cannabis.

  8. Global Energetics in Solar Flares and Coronal Mass Ejections

    Science.gov (United States)

    Aschwanden, Markus J.

    2017-08-01

    We present a statistical study of the energetics of coronal mass ejections (CME) and compare it with the magnetic, thermal, and nonthermal energy dissipated in flares. The physical parameters of CME speeds, mass, and kinetic energies are determined with two different independent methods, i.e., the traditional white-light scattering method using LASCO/SOHO data, and the EUV dimming method using AIA/SDO data. We analyze all 860 GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the SDO mission. The new ingredients of our CME modeling includes: (1) CME geometry in terms of a self-similar adiabatic expansion, (2) DEM analysis of CME mass over entire coronal temperature range, (3) deceleration of CME due to gravity force which controls the kinetic and potentail CME energy as a function of time, (4) the critical speed that controls eruptive and confined CMEs, (5) the relationship between the center-of-mass motion during EUV dimming and the leading edge motion observed in white-light coronagraphs. Novel results are: (1) Physical parameters obtained from both the EUV dimming and white-light method can be reconciled; (2) the equi-partition of CME kinetic and thermal flare energy; (3) the Rosner-Tucker-Vaiana scaling law. We find that the two methods in EUV and white-light wavelengths are highly complementary and yield more complete models than each method alone.

  9. THE RELATION BETWEEN EIT WAVES AND CORONAL MASS EJECTIONS

    International Nuclear Information System (INIS)

    Chen, P. F.

    2009-01-01

    More and more evidence indicates that 'EIT waves' are strongly related to coronal mass ejections (CMEs). However, it is still not clear how the two phenomena are related to each other. We investigate a CME event on 1997 September 9, which was well observed by both the EUV Imaging Telescope (EIT) and the high-cadence Mark-III K-Coronameter at Mauna Loa Solar Observatory, and compare the spatial relation between the 'EIT wave' fronts and the CME leading loops. It is found that 'EIT wave' fronts are cospatial with the CME leading loops, and the expanding EUV dimmings are cospatial with the CME cavity. It is also found that the CME stopped near the boundary of a coronal hole, a feature common to observations of 'EIT waves'. It is suggested that 'EIT waves'/dimmings are the EUV counterparts of the CME leading loop/cavity, based on which we propose that, as in the case of 'EIT waves', CME leading loops are apparently moving density enhancements that are generated by successive stretching (or opening-up) of magnetic loops.

  10. On the origin of constrained superfields

    Energy Technology Data Exchange (ETDEWEB)

    Dall’Agata, G. [Dipartimento di Fisica “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy); Dudas, E. [Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay,F-91128 Palaiseau (France); Farakos, F. [Dipartimento di Fisica “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)

    2016-05-06

    In this work we analyze constrained superfields in supersymmetry and supergravity. We propose a constraint that, in combination with the constrained goldstino multiplet, consistently removes any selected component from a generic superfield. We also describe its origin, providing the operators whose equations of motion lead to the decoupling of such components. We illustrate our proposal by means of various examples and show how known constraints can be reproduced by our method.

  11. Statistical properties of solar flares and coronal mass ejections through the solar cycle

    International Nuclear Information System (INIS)

    Telloni, Daniele; Antonucci, Ester; Carbone, Vincenzo; Lepreti, Fabio

    2016-01-01

    Waiting Time Distributions (WTDs) of solar flares are investigated all through the solar cycle. The same approach applied to Coronal Mass Ejections (CMEs) in a previous work is considered here for flare occurrence. Our analysis reveals that flares and CMEs share some common statistical properties, which result dependent on the level of solar activity. Both flares and CMEs seem to independently occur during minimum solar activity phases, whilst their WTDs significantly deviate from a Poisson function at solar maximum, thus suggesting that these events are correlated. The characteristics of WTDs are constrained by the physical processes generating those eruptions associated with flares and CMEs. A scenario may be drawn in which different mechanisms are actively at work during different phases of the solar cycle. Stochastic processes, most likely related to random magnetic reconnections of the field lines, seem to play a key role during solar minimum periods. On the other hand, persistent processes, like sympathetic eruptions associated to the variability of the photospheric magnetism, are suggested to dominate during periods of high solar activity. Moreover, despite the similar statistical properties shown by flares and CMEs, as it was mentioned above, their WTDs appear different in some aspects. During solar minimum periods, the flare occurrence randomness seems to be more evident than for CMEs. Those persistent mechanisms generating interdependent events during maximum periods of solar activity can be suggested to play a more important role for CMEs than for flares, thus mitigating the competitive action of the random processes, which seem instead strong enough to weaken the correlations among flare event occurrence during solar minimum periods. However, it cannot be excluded that the physical processes at the basis of the origin of the temporal correlation between solar events are different for flares and CMEs, or that, more likely, more sophisticated effects are

  12. Why fast solar wind originates from slowly expanding coronal flux tubes

    International Nuclear Information System (INIS)

    Wang, Y.M.; Sheeley, N.R. Jr.

    1991-01-01

    Empirical studies indicate that the solar wind speed at earth is inversely correlated with the divergence rate of the coronal magnetic field. It is shown that this result is consistent with simple wind acceleration models involving Alfven waves, provided that the wave energy flux at the coronal base is taken to be roughly constant within open field regions. 9 refs

  13. Assessment of Coronal Radiographic Parameters of the Spine in the Treatment of Adolescent Idiopathic Scoliosis.

    Science.gov (United States)

    Karami, Mohsen; Maleki, Arash; Mazda, Keyvan

    2016-10-01

    To determine the most important preoperative factors that affect postoperative coronal parameters of scoliotic curves. All Adolescent Idiopathic Scoliosis (AIS) patients included in the study were classified according to Lenke and King Classification. The fusion levels were selected according to the rigidity of the existing curves (correction less than 50%), tilt of T1 and shoulders, sagittal angle of the curves and with considering stable and neutral end vertebra. The radiographic coronal parameters: shoulders tilt angle, iliolumbar angle and coronal balance were measured in all patients before, after, and in the last follow-up visit. One hundred twenty patients after mean of 25 months follow-up (18-40 months) were included in the study. Before operation, abnormal coronal balance (more than 2 cm shift) was noticed in 46 patents (38%) and in the last visit, was noted in 22 patients (18%). Multivariate regression analysis revealed a significant predictive value of the preoperative coronal balance on the last visit coronal balance ( P value=0.01). Preoperative coronal balance is very important to make a balanced spine after surgery. Other parameters like Lenke classification or main thoracic overcorrection did not affect postoperative coronal decompensation.

  14. Multidetector CT enteroclysis: comparison of the reading performance for axial and coronal views

    International Nuclear Information System (INIS)

    Schmidt, Sabine; Chalaron, Marc; Schnyder, Pierre; Denys, Alban; Chevallier, Patrick; Bessoud, Bertrand; Verdun, Francis R.; Frascarolo, Philippe

    2005-01-01

    The purpose of this study was to compare the diagnostic performance of axial and coronal views in multidetector CT enteroclysis (MDCTE). We retrospectively evaluated 48 patients with pathological correlation investigated by MDCTE for small bowel disorders. After nasojejunal administration of 2 l of 5% methylcellulose axial arterial and venous acquisition of MDCTE was followed by coronal reconstructions using equal slice thicknesses of 2.5 mm with 2 mm increments. Spatial resolution of both planes was evaluated by phantom. Three radiologists independently read axial and coronal images concerning 12 pathological features. The interobserver agreement and time of reading was calculated. Sensitivity and specificity resulted from comparison with histopathology (n=39) or follow-up (n=9). Phantom study revealed higher spatial resolution for axial than coronal views, whatever reconstruction interval was used. However, spatial frequency always remained high. Most pathological signs, such as bowel wall thickening (BWT), bowel wall enhancement (BWE) and intraperitoneal fluid (IPF), showed better interobserver agreement on axial than coronal views (BWT: 0.61 vs. 0.44; BWE: 0.56 vs. 0.5; IPF:0.53 vs. 0.43). The Wilcoxon signed-rank test revealed significantly higher sensitivity for axial than coronal views (P=0.0453); the time of reading was significantly shorter for the latter (P=0.0146). The diagnostic value of axial slices is superior to coronal reconstructions despite the reduced data volume and display of the physiological course of bowel loops on the coronal plane. (orig.)

  15. Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24

    DEFF Research Database (Denmark)

    Hofmeister, Stefan J.; Veronig, Astrid; Reiss, Martin A.

    2017-01-01

    We investigate the statistics of 288 low-latitude coronal holes extracted from SDO/AIA-193 filtergrams over the time range of 2011 January 01–2013 December 31. We analyze the distribution of characteristic coronal hole properties, such as the areas, mean AIA-193 intensities, and mean magnetic fie...

  16. Using observations of slipping velocities to test the hypothesis that reconnection heats the active region corona

    Science.gov (United States)

    Yang, Kai; Longcope, Dana; Guo, Yang; Ding, Mingde

    2017-08-01

    Numerous proposed coronal heating mechanisms have invoked magnetic reconnection in some role. Testing such a mechanism requires a method of measuring magnetic reconnection coupled with a prediction of the heat delivered by reconnection at the observed rate. In the absence of coronal reconnection, field line footpoints move at the same velocity as the plasma they find themselves in. The rate of coronal reconnection is therefore related to any discrepancy observed between footpoint motion and that of the local plasma — so-called slipping motion. We propose a novel method to measure this velocity discrepancy by combining a sequence of non-linear force-free field extrapolations with maps of photospheric velocity. We obtain both from a sequence of vector magnetograms of an active region (AR). We then propose a method of computing the coronal heating produced under the assumption the observed slipping velocity was due entirely to coronal reconnection. This heating rate is used to predict density and temperature at points along an equilibrium loop. This, in turn, is used to synthesize emission in EUV and SXR bands. We perform this analysis using a sequence of HMI vector magnetograms of a particular AR and compare synthesized images to observations of the same AR made by SDO. We also compare differential emission measure inferred from those observations to that of the modeled corona.

  17. Heat pipe heat storage performance

    Energy Technology Data Exchange (ETDEWEB)

    Caruso, A; Pasquetti, R [Univ. de Provence, Marseille (FR). Inst. Universitaire des Systemes; Grakovich, L P; Vasiliev, L L [A.V. Luikov Heat and Mass Transfer Inst. of the BSSR, Academy of Sciences, Minsk (BY)

    1989-01-01

    Heat storage offers essential thermal energy saving for heating. A ground heat store equipped with heat pipes connecting it with a heat source and to the user is considered in this paper. It has been shown that such a heat exchanging system along with a batch energy source meets, to a considerable extent, house heating requirements. (author).

  18. Identification of Low Coronal Sources of “Stealth” Coronal Mass Ejections Using New Image Processing Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Alzate, Nathalia; Morgan, Huw, E-mail: naa19@aber.ac.uk [Institute of Mathematics, Physics and Computer Science Prifysgol Aberystwyth Ceredigion, Cymru SY23 3BZ (United Kingdom)

    2017-05-10

    Coronal mass ejections (CMEs) are generally associated with low coronal signatures (LCSs), such as flares, filament eruptions, extreme ultraviolet (EUV) waves, or jets. A number of recent studies have reported the existence of stealth CMEs as events without LCSs, possibly due to observational limitations. Our study focuses on a set of 40 stealth CMEs identified from a study by D’Huys et al. New image processing techniques are applied to high-cadence, multi-instrument sets of images spanning the onset and propagation time of each of these CMEs to search for possible LCSs. Twenty-three of these events are identified as small, low-mass, unstructured blobs or puffs, often occurring in the aftermath of a large CME, but associated with LCSs such as small flares, jets, or filament eruptions. Of the larger CMEs, seven are associated with jets and eight with filament eruptions. Several of these filament eruptions are different from the standard model of an erupting filament/flux tube in that they are eruptions of large, faint flux tubes that seem to exist at large heights for a long time prior to their slow eruption. For two of these events, we see an eruption in Large Angle Spectrometric Coronagraph C2 images and the consequent changes at the bottom edge of the eruption in EUV images. All 40 events in our study are associated with some form of LCS. We conclude that stealth CMEs arise from observational and processing limitations.

  19. Reconstructed coronal views of CT and isotopic images of the pancreas

    International Nuclear Information System (INIS)

    Kasuga, Toshio; Kobayashi, Toshio; Nakanishi, Fumiko

    1980-01-01

    To compare functional images of the pancreas by scintigraphy with morphological views of the pancreas by CT, CT coronal views of the pancreas were reconstructed. As CT coronal views were reconstructed from the routine scanning, there was a problem in longitudinal spatial resolution. However, almost satisfactory total images of the pancreas were obtained by improving images adequately. In 27 patients whose diseases had been confirmed, it was easy to compare pancreatic scintigrams with pancreatic CT images by using reconstructed CT coronal views, and information which had not been obtained by original CT images could be obtained by using reconstructed CT coronal views. Especially, defects on pancreatic images and the shape of pancreas which had not been visualized clearly by scintigraphy alone could be visualized by using reconstructed CT coronal views of the pancreas. (Tsunoda, M.)

  20. Heat transfer

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Heat transfer. Heat conduction in solid slab. Convective heat transfer. Non-linear temperature. variation due to flow. HEAT FLUX AT SURFACE. conduction/diffusion.

  1. Heat Waves

    Science.gov (United States)

    Heat Waves Dangers we face during periods of very high temperatures include: Heat cramps: These are muscular pains and spasms due ... that the body is having trouble with the heat. If a heat wave is predicted or happening… - ...

  2. Heat Islands

    Science.gov (United States)

    EPA's Heat Island Effect Site provides information on heat islands, their impacts, mitigation strategies, related research, a directory of heat island reduction initiatives in U.S. communities, and EPA's Heat Island Reduction Program.

  3. 77 FR 24537 - Draft Standards and Best Practices for Interaction Between Medical Examiner/Coroner and Organ and...

    Science.gov (United States)

    2012-04-24

    ... Best Practices for Interaction Between Medical Examiner/Coroner and Organ and Tissue Procurement... Committee Standards and Best Practices for Interaction Between Medical Examiner/Coroner Offices and Organ... coroner/medical examiner office representatives, law enforcement agencies, organizations, and all other...

  4. The application of coronal scattering measurements to solar radio bursts

    International Nuclear Information System (INIS)

    Bradford, H.M.

    1980-01-01

    The interpretation of ground based observations of solar 'plasma frequency' radio bursts has been hampered in the past by an insufficient knowledge of coronal scattering by density inhomogeneities close to the Sun. Calculations based on measuurements of the angular broadening of natural radio sources, and Woo's 1975 measurement of the angular broadening of the telemetry carrier by Helios I near occultation (Woo, 1978), indicate that plasma frequency solar bursts should undergo considerable scattering, at least near the maximum of the sunspot cycle. The calculated displacements of the apparent positions of the bursts are about equal to the observed displacements which have been attributed to the bursts occurring in dense streamers. In order to obtain more scattering data close to the Sun, interferometer measurements of the angular broadening of spacecraft signals are planned, and the important contribution which could be made with large dishes is discussed. (Auth.)

  5. Latitudinal Dependence of the Radial IMF Component: Coronal Imprint

    Science.gov (United States)

    Suess, S. T.; Smith, E. J.

    1996-01-01

    Measurements by Ulysses have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, B(sub r,) of the interplanetary magnetic field. In the corona, the plasma, beta is much less than 1, except directly above streamers, so longitudinal and latitudinal gradients in field strength will relax due to the transverse magnetic pressure gradient force as the solar wind carries magnetic flux away from the Sun. This happens quickly enough so that the field is essentially uniform by 5 - 10 solar radius, apparently remaining so as it is carried to beyond 1 AU. Here, we illustrate the coronal relaxation with a qualitative physical argument and by reference to a detailed Magneto HydroDynamics (MHD) simulation.

  6. Changes in the subgingival biofilm composition after coronally positioned flap

    Directory of Open Access Journals (Sweden)

    Jadson Almeida Lima

    2011-02-01

    Full Text Available OBJECTIVES: This study evaluated the effects of coronally positioned flap (CPF on the subgingival biofilm composition. MATERIAL AND METHODS: Twenty-two subjects with gingival recessions were treated with CPF. Clinical parameters were assessed before and at 6 months after surgery. Subgingival biofilms were analyzed by checkerboard DNA-DNA hybridization technique for 40 bacterial species. RESULTS: Recession height, clinical attachment level and bleeding on probing improved significantly (p<0.05 at 6 months post-CPF. The proportions of 10 periodontal pathogens and the proportions of red and orange complexes decreased at 6 months. CONCLUSION: In conclusion, CPF can induce beneficial effects on the composition of the subgingival microbiota after 6 months.

  7. Electron acceleration and radiation signatures in loop coronal transients

    Science.gov (United States)

    Vlahos, L.; Gergely, T. E.; Papadopoulos, K.

    1982-01-01

    It is proposed that in loop coronal transients an erupting loop moves away from the solar surface, with a velocity exceeding the local Alfven speed, pushing against the overlying magnetic fields and driving a shock in the front of the moving part of the loop. Lower hybrid waves are excited at the shock front and propagate radially toward the center of the loop with phase velocity along the magnetic field that exceeds the thermal velocity. The lower hybrid waves stochastically accelerate the tail of the electron distribution inside the loop. The manner in which the accelerated electrons are trapped in the moving loop are discussed, and their radiation signature is estimated. It is suggested that plasma radiation can explain the power observed in stationary and moving type IV bursts.

  8. FAST DIFFERENTIAL EMISSION MEASURE INVERSION OF SOLAR CORONAL DATA

    Energy Technology Data Exchange (ETDEWEB)

    Plowman, Joseph; Kankelborg, Charles; Martens, Petrus [Montana State University, Bozeman, MT 59717 (United States)

    2013-07-01

    We present a fast method for reconstructing differential emission measures (DEMs) using solar coronal data. The method consists of a fast, simple regularized inversion in conjunction with an iteration scheme for removal of residual negative emission measure. On average, it computes over 1000 DEMs s{sup -1} for a sample active region observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory, and achieves reduced chi-squared of order unity with no negative emission in all but a few test cases. The high performance of this method is especially relevant in the context of AIA, which images of order one million solar pixels per second. This paper describes the method, analyzes its fidelity, compares its performance and results with other DEM methods, and applies it to an active region and loop observed by AIA and by the Extreme-ultraviolet Imaging Spectrometer on Hinode.

  9. Coronal Polarization of Pseudostreamers and the Solar Polar Field Reversal

    Science.gov (United States)

    Rachmeler, L. A.; Guennou, C.; Seaton, D. B.; Gibson, S. E.; Auchere, F.

    2016-01-01

    The reversal of the solar polar magnetic field is notoriously hard to pin down due to the extreme viewing angle of the pole. In Cycle 24, the southern polar field reversal can be pinpointed with high accuracy due to a large-scale pseudostreamer that formed over the pole and persisted for approximately a year. We tracked the size and shape of this structure with multiple observations and analysis techniques including PROBA2/SWAP EUV images, AIA EUV images, CoMP polarization data, and 3D tomographic reconstructions. We find that the heliospheric field reversed polarity in February 2014, whereas in the photosphere, the last vestiges of the previous polar field polarity remained until March 2015. We present here the evolution of the structure and describe its identification in the Fe XII 1074nm coronal emission line, sensitive to the Hanle effect in the corona.

  10. Solar radio bursts and their relation of coronal magnetic structures

    International Nuclear Information System (INIS)

    Kattenberg, A.

    1981-01-01

    Following a general introduction, chapters II and III describe a model for coronal flux tubes. The model tube is a cylindrically symmetric localized force free current, that is embedded in a potential field. In both chapters the growth rates and sizes of the kink mode instability are calculated by solving the linearized equation of motion. In chapters IV and V, observations of solar Type-I radio bursts are presented and analysed. The observations were gathered with the 60-channel radio spectrograph in Dwingeloo. Chapters VI, VII, VIII, IX and X are concerned with observations of solar microwave bursts. The observations, with high time resolution (0.1 s) and high one-dimensional angular resolution (max. 4'') were made with the Westerbork Synthesis Radio Telescope. (Auth.)

  11. Shear-induced opening of the coronal magnetic field

    Science.gov (United States)

    Wolfson, Richard

    1995-01-01

    This work describes the evolution of a model solar corona in response to motions of the footpoints of its magnetic field. The mathematics involved is semianalytic, with the only numerical solution being that of an ordinary differential equation. This approach, while lacking the flexibility and physical details of full MHD simulations, allows for very rapid computation along with complete and rigorous exploration of the model's implications. We find that the model coronal field bulges upward, at first slowly and then more dramatically, in response to footpoint displacements. The energy in the field rises monotonically from that of the initial potential state, and the field configuration and energy appraoch asymptotically that of a fully open field. Concurrently, electric currents develop and concentrate into a current sheet as the limiting case of the open field is approached. Examination of the equations shows rigorously that in the asymptotic limit of the fully open field, the current layer becomes a true ideal MHD singularity.

  12. An ice-cream cone model for coronal mass ejections

    Science.gov (United States)

    Xue, X. H.; Wang, C. B.; Dou, X. K.

    2005-08-01

    In this study, we use an ice-cream cone model to analyze the geometrical and kinematical properties of the coronal mass ejections (CMEs). Assuming that in the early phase CMEs propagate with near-constant speed and angular width, some useful properties of CMEs, namely the radial speed (v), the angular width (α), and the location at the heliosphere, can be obtained considering the geometrical shapes of a CME as an ice-cream cone. This model is improved by (1) using an ice-cream cone to show the near real configuration of a CME, (2) determining the radial speed via fitting the projected speeds calculated from the height-time relation in different azimuthal angles, (3) not only applying to halo CMEs but also applying to nonhalo CMEs.

  13. Exploring the fine structure at the limb in coronal holes

    Science.gov (United States)

    Karovska, Magarita; Blundell, Solon F.; Habbal, Shadia Rifai

    1994-01-01

    The fine structure of the solar limb in coronal holes is explored at temperatures ranging from 10(exp 4) to 10(exp 6) K. An image enhancement algorithm orignally developed for solar eclipse observations is applied to a number of simultaneous multiwavelength observations made with the Harvard Extreme Ultraviolet Spectrometer experiment on Skylab. The enhanced images reveal the presence of filamentary structures above the limb with a characteristic separation of approximately 10 to 15 sec . Some of the structures extend from the solar limb into the corona to at least 4 min above the solar limb. The brightness of these structures changes as a function of height above the limb. The brightest emission is associated with spiculelike structures in the proximity of the limb. The emission characteristic of high-temperature plasma is not cospatial with the emission at lower temperatures, indicating the presence of different temperature plasmas in the field of view.

  14. A NEW VIEW OF CORONAL WAVES FROM STEREO

    International Nuclear Information System (INIS)

    Ma, S.; Lin, J.; Zhao, S.; Li, Q.; Wills-Davey, M. J.; Attrill, G. D. R.; Golub, L.; Chen, P. F.; Chen, H.

    2009-01-01

    On 2007 December 7, there was an eruption from AR 10977, which also hosted a sigmoid. An EUV Imaging Telescope (EIT) wave associated with this eruption was observed by EUVI on board the Solar Terrestrial Relations Observatory (STEREO). Using EUVI images in the 171 A and the 195 A passbands from both STEREO A and B, we study the morphology and kinematics of this EIT wave. In the early stages, images of the EIT wave from the two STEREO spacecrafts differ markedly. We determine that the EUV fronts observed at the very beginning of the eruption likely include some intensity contribution from the associated coronal mass ejection (CME). Additionally, our velocity measurements suggest that the EIT wave front may propagate at nearly constant velocity. Both results offer constraints on current models and understanding of EIT waves.

  15. Einstein Observatory coronal temperatures of late-type stars

    Science.gov (United States)

    Schmitt, J. H. M. M.; Collura, A.; Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.

    1990-01-01

    The results are presented of a survey of the coronal temperatures of late-type stars using the Einstein Observatory IPC. The spectral analysis shows that the frequently found one- and two-temperature descriptions are mainly influenced by the SNR of the data and that models using continuous emission measure distributions can provide equally adequate and physically more meaningful and more plausible descriptions. Intrinsic differences in differential emission measure distributions are found for four groups of stars. M dwarfs generally show evidence for high-temperature gas in conjunction with lower-temperature material, while main-sequence stars of types F and G have the high-temperature component either absent or very weak. Very hot coronae without the lower-temperature component appearing in dwarf stars are evident in most of the giant stars studied. RS CVn systems show evidence for extremely hot coronae, sometimes with no accompanying lower-temperature material.

  16. Development of a serial order in speech constrained by articulatory coordination.

    Directory of Open Access Journals (Sweden)

    Hiroki Oohashi

    Full Text Available Universal linguistic constraints seem to govern the organization of sound sequences in words. However, our understanding of the origin and development of these constraints is incomplete. One possibility is that the development of neuromuscular control of articulators acts as a constraint for the emergence of sequences in words. Repetitions of the same consonant observed in early infancy and an increase in variation of consonantal sequences over months of age have been interpreted as a consequence of the development of neuromuscular control. Yet, it is not clear how sequential coordination of articulators such as lips, tongue apex and tongue dorsum constrains sequences of labial, coronal and dorsal consonants in words over the course of development. We examined longitudinal development of consonant-vowel-consonant(-vowel sequences produced by Japanese children between 7 and 60 months of age. The sequences were classified according to places of articulation for corresponding consonants. The analyses of individual and group data show that infants prefer repetitive and fronting articulations, as shown in previous studies. Furthermore, we reveal that serial order of different places of articulations within the same organ appears earlier and then gradually develops, whereas serial order of different articulatory organs appears later and then rapidly develops. In the same way, we also analyzed the sequences produced by English children and obtained similar developmental trends. These results suggest that the development of intra- and inter-articulator coordination constrains the acquisition of serial orders in speech with the complexity that characterizes adult language.

  17. Development of a serial order in speech constrained by articulatory coordination.

    Science.gov (United States)

    Oohashi, Hiroki; Watanabe, Hama; Taga, Gentaro

    2013-01-01

    Universal linguistic constraints seem to govern the organization of sound sequences in words. However, our understanding of the origin and development of these constraints is incomplete. One possibility is that the development of neuromuscular control of articulators acts as a constraint for the emergence of sequences in words. Repetitions of the same consonant observed in early infancy and an increase in variation of consonantal sequences over months of age have been interpreted as a consequence of the development of neuromuscular control. Yet, it is not clear how sequential coordination of articulators such as lips, tongue apex and tongue dorsum constrains sequences of labial, coronal and dorsal consonants in words over the course of development. We examined longitudinal development of consonant-vowel-consonant(-vowel) sequences produced by Japanese children between 7 and 60 months of age. The sequences were classified according to places of articulation for corresponding consonants. The analyses of individual and group data show that infants prefer repetitive and fronting articulations, as shown in previous studies. Furthermore, we reveal that serial order of different places of articulations within the same organ appears earlier and then gradually develops, whereas serial order of different articulatory organs appears later and then rapidly develops. In the same way, we also analyzed the sequences produced by English children and obtained similar developmental trends. These results suggest that the development of intra- and inter-articulator coordination constrains the acquisition of serial orders in speech with the complexity that characterizes adult language.

  18. Volumetric measurement of the maxillary sinus by coronal CT scan

    International Nuclear Information System (INIS)

    Ikeda, Atsuko

    1996-01-01

    The volume of the maxillary sinus was estimated by coronal CT scan. The purpose of this study was to compare the estimated volume of the normal maxillary sinus with that of the inflamed maxillary sinus. Patients were classified following evaluation by CT scan of the paranasal sinuses into 3 categories. Group A (n=12): Patients suffered from headache, facial pain and epistaxis, but CT scans of their nasal cavity and paranasal sinus were within normal limits without inflammatory change. Group B (n=69): Patients with bilateral chronic maxillary sinusitis, CT scans of whom showed inflammatory changes in both maxillary sinuses. All of the patients in this group underwent sinus surgery after coronal CT scans. Group C (n=14): Patients with unilateral chronic maxillary sinusitis, CT scans of whom showed inflammatory change in unilateral maxillary sinuses. CT scans of these patients were measured by Plannimeter to take the area of each image of the maxillary sinus. Consecutively imaged areas were summated by integral calculus to obtain an estimate of the sinus volume. The mean maxillary sinus volume in the affected sinuses was significantly smaller than those in the contralateral normal sinuses (p<0.05, Wilcoxon-test). The various volumes of the maxillary sinuses and the developmental cause were discussed. Comparison of groups A with B suggested three distinct patterns; the maxillary sinus volume has decreased due to inflammatory changes in the bone. The small sinuses have a tendency to develop chronic inflammatory change. The aeration in the maxillary sinus may be decreased when anatomic variations that may obstruct the ethmoid infundibulum exist. (K.H.)

  19. Volumetric measurement of the maxillary sinus by coronal CT scan

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, Atsuko [Tokyo Medical and Dental Univ. (Japan). School of Medicine

    1996-08-01

    The volume of the maxillary sinus was estimated by coronal CT scan. The purpose of this study was to compare the estimated volume of the normal maxillary sinus with that of the inflamed maxillary sinus. Patients were classified following evaluation by CT scan of the paranasal sinuses into 3 categories. Group A (n=12): Patients suffered from headache, facial pain and epistaxis, but CT scans of their nasal cavity and paranasal sinus were within normal limits without inflammatory change. Group B (n=69): Patients with bilateral chronic maxillary sinusitis, CT scans of whom showed inflammatory changes in both maxillary sinuses. All of the patients in this group underwent sinus surgery after coronal CT scans. Group C (n=14): Patients with unilateral chronic maxillary sinusitis, CT scans of whom showed inflammatory change in unilateral maxillary sinuses. CT scans of these patients were measured by Plannimeter to take the area of each image of the maxillary sinus. Consecutively imaged areas were summated by integral calculus to obtain an estimate of the sinus volume. The mean maxillary sinus volume in the affected sinuses was significantly smaller than those in the contralateral normal sinuses (p<0.05, Wilcoxon-test). The various volumes of the maxillary sinuses and the developmental cause were discussed. Comparison of groups A with B suggested three distinct patterns; the maxillary sinus volume has decreased due to inflammatory changes in the bone. The small sinuses have a tendency to develop chronic inflammatory change. The aeration in the maxillary sinus may be decreased when anatomic variations that may obstruct the ethmoid infundibulum exist. (K.H.)

  20. Towards weakly constrained double field theory

    Directory of Open Access Journals (Sweden)

    Kanghoon Lee

    2016-08-01

    Full Text Available We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.

  1. Continuation of Sets of Constrained Orbit Segments

    DEFF Research Database (Denmark)

    Schilder, Frank; Brøns, Morten; Chamoun, George Chaouki

    Sets of constrained orbit segments of time continuous flows are collections of trajectories that represent a whole or parts of an invariant set. A non-trivial but simple example is a homoclinic orbit. A typical representation of this set consists of an equilibrium point of the flow and a trajectory...... that starts close and returns close to this fixed point within finite time. More complicated examples are hybrid periodic orbits of piecewise smooth systems or quasi-periodic invariant tori. Even though it is possible to define generalised two-point boundary value problems for computing sets of constrained...... orbit segments, this is very disadvantageous in practice. In this talk we will present an algorithm that allows the efficient continuation of sets of constrained orbit segments together with the solution of the full variational problem....

  2. Constrained principal component analysis and related techniques

    CERN Document Server

    Takane, Yoshio

    2013-01-01

    In multivariate data analysis, regression techniques predict one set of variables from another while principal component analysis (PCA) finds a subspace of minimal dimensionality that captures the largest variability in the data. How can regression analysis and PCA be combined in a beneficial way? Why and when is it a good idea to combine them? What kind of benefits are we getting from them? Addressing these questions, Constrained Principal Component Analysis and Related Techniques shows how constrained PCA (CPCA) offers a unified framework for these approaches.The book begins with four concre

  3. Assessment of T2-Weighted Coronal Magnetic Resonance Images in the Investigation of Pituitary Lesions

    International Nuclear Information System (INIS)

    Yuksekkaya, Ruken; Aggunlu, Levent; Oner, Yusuf; Celik, Halil; Akpek, Sergin; Celikyay, Fatih

    2014-01-01

    Magnetic resonance imaging is the most important diagnostic method in the investigation of the pituitary lesions. Our aim is to determine whether T2-weighted coronal images may be helpful in the evaluation of the pituitary gland with suspected pituitary adenomas. One hundred and sixty-seven patients were examined prospectively with T2-weighted coronal and T1-weighted coronal images enhanced with intravenous contrast material. The images were evaluated for the presence, the size, the location, and the ancillary signs including sellar floor erosion or ballooning, infindibulary deviation, convexity of the superior border of the gland, diffuse enlargement of the gland, and the invasion of the cavenous sinuses on both images. In forty-six (28%) patients lesions were revealed on both sequences. In twenty-one (12%) patients the lesions that were revealed on the T1-weighted images were not detected on the T2-weighted images. Positive predictive value, negative predictive value, sensitivity, specificity, and diagnostic accuracy rates of T2-weighted coronal images on the detection of the presence of lesions were 100%, 17.4%, 68.7%, 100%, and 87.4%, respectively. Both T2-weighted coronal and T1-weighted coronal images enhanced with intravenous gadolinium-based contrast material are important in the diagnosis of pituitary adenomas. T2-weighted coronal images could be used as a screening tool for the primary evaluation of the pituitary gland

  4. VECTOR TOMOGRAPHY FOR THE CORONAL MAGNETIC FIELD. II. HANLE EFFECT MEASUREMENTS

    International Nuclear Information System (INIS)

    Kramar, M.; Inhester, B.; Lin, H.; Davila, J.

    2013-01-01

    In this paper, we investigate the feasibility of saturated coronal Hanle effect vector tomography or the application of vector tomographic inversion techniques to reconstruct the three-dimensional magnetic field configuration of the solar corona using linear polarization measurements of coronal emission lines. We applied Hanle effect vector tomographic inversion to artificial data produced from analytical coronal magnetic field models with equatorial and meridional currents and global coronal magnetic field models constructed by extrapolation of real photospheric magnetic field measurements. We tested tomographic inversion with only Stokes Q, U, electron density, and temperature inputs to simulate observations over large limb distances where the Stokes I parameters are difficult to obtain with ground-based coronagraphs. We synthesized the coronal linear polarization maps by inputting realistic noise appropriate for ground-based observations over a period of two weeks into the inversion algorithm. We found that our Hanle effect vector tomographic inversion can partially recover the coronal field with a poloidal field configuration, but that it is insensitive to a corona with a toroidal field. This result demonstrates that Hanle effect vector tomography is an effective tool for studying the solar corona and that it is complementary to Zeeman effect vector tomography for the reconstruction of the coronal magnetic field

  5. Recurring coronal holes and their rotation rates during the solar cycles 22-24

    Science.gov (United States)

    Prabhu, K.; Ravindra, B.; Hegde, Manjunath; Doddamani, Vijayakumar H.

    2018-05-01

    Coronal holes (CHs) play a significant role in making the Earth geo-magnetically active during the declining and minimum phases of the solar cycle. In this study, we analysed the evolutionary characteristics of the Recurring CHs from the year 1992 to 2016. The extended minimum of Solar Cycle 23 shows unusual characteristics in the number of persistent coronal holes in the mid- and low-latitude regions of the Sun. Carrington rotation maps of He 10830 Å and EUV 195 Å observations are used to identify the Coronal holes. The latitude distribution of the RCHs shows that most of them are appeared between ± 20° latitudes. In this period, more number of recurring coronal holes appeared in and around 100° and 200° Carrington longitudes. The large sized coronal holes lived for shorter period and they appeared close to the equator. From the area distribution over the latitude considered, it shows that more number of recurring coronal holes with area <10^{21} cm2 appeared in the southern latitude close to the equator. The rotation rates calculated from the RCHs appeared between ± 60° latitude shows rigid body characteristics. The derived rotational profiles of the coronal holes show that they have anchored to a depth well below the tachocline of the interior, and compares well with the helioseismology results.

  6. Relationship between coronal holes and high speed streams at L1: arrival times, durations, and intensities

    Science.gov (United States)

    Luo, B.; Bu, X.; Liu, S.; Gong, J.

    2017-12-01

    Coronal holes are sources of high-speed steams (HSS) of solar wind. When coronal holes appear at mid/low latitudes on the Sun, consequential HSSs may impact Earth and cause recurrent geospace environment disturbances, such as geomagnetic storms, relativistic electron enhancements at the geosynchronous orbit, and thermosphere density enhancements. Thus, it is of interests for space weather forecasters to predict when (arrival times), how long (time durations), and how severe (intensities) HSSs may impact Earth when they notice coronal holes on the sun and are anticipating their geoeffectiveness. In this study, relationship between coronal holes and high speed streams will be statistically investigated. Several coronal hole parameters, including passage times of solar central meridian, coronal hole longitudinal widths, intensities reflected by mean brightness, are derived using Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) images for years 2011 to 2016. These parameters will be correlated with in-situ solar wind measurements measured at the L1 point by the ACE spacecraft, which can give some results that are useful for space weather forecaster in predicting the arrival times, durations, and intensities of coronal hole high-speed streams in about 3 days advance.

  7. Two-phase Heating in Flaring Loops

    Science.gov (United States)

    Zhu, Chunming; Qiu, Jiong; Longcope, Dana W.

    2018-03-01

    We analyze and model a C5.7 two-ribbon solar flare observed by the Solar Dynamics Observatory, Hinode, and GOES on 2011 December 26. The flare is made of many loops formed and heated successively over one and half hours, and their footpoints are brightened in the UV 1600 Å before enhanced soft X-ray and EUV missions are observed in flare loops. Assuming that anchored at each brightened UV pixel is a half flaring loop, we identify more than 6700 half flaring loops, and infer the heating rate of each loop from the UV light curve at the footpoint. In each half loop, the heating rate consists of two phases: intense impulsive heating followed by a low-rate heating that is persistent for more than 20 minutes. Using these heating rates, we simulate the evolution of their coronal temperatures and densities with the model of the “enthalpy-based thermal evolution of loops.” In the model, suppression of thermal conduction is also considered. This model successfully reproduces total soft X-ray and EUV light curves observed in 15 passbands by four instruments GOES, AIA, XRT, and EVE. In this flare, a total energy of 4.9 × 1030 erg is required to heat the corona, around 40% of this energy is in the slow-heating phase. About two-fifths of the total energy used to heat the corona is radiated by the coronal plasmas, and the other three fifth transported to the lower atmosphere by thermal conduction.

  8. Heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, E L; Eisenmann, G; Hahne, E [Stuttgart Univ. (TH) (F.R. Germany). Inst. fuer Thermodynamik und Waermetechnik

    1976-04-01

    A survey is presented on publications on design, heat transfer, form factors, free convection, evaporation processes, cooling towers, condensation, annular gap, cross-flowed cylinders, axial flow through a bundle of tubes, roughnesses, convective heat transfer, loss of pressure, radiative heat transfer, finned surfaces, spiral heat exchangers, curved pipes, regeneraters, heat pipes, heat carriers, scaling, heat recovery systems, materials selection, strength calculation, control, instabilities, automation of circuits, operational problems and optimization.

  9. Portuguese pellets market: Analysis of the production and utilization constrains

    International Nuclear Information System (INIS)

    Monteiro, Eliseu; Mantha, Vishveshwar; Rouboa, Abel

    2012-01-01

    As opposite in Portugal, the wood pellets market is booming in Europe. In this work, possible reasons for this market behavior are foreseen according to the key indicators of biomass availability, costs and legal framework. Two major constrains are found in the Portuguese pellets market: the first one is the lack of an internal consumption, being the market based on exportations. The second one is the shortage of raw material mainly due to the competition with the biomass power plants. Therefore, the combination of the biomass power plants with pellet production plants seems to be the best option for the pellets production in the actual Portuguese scenario. The main constrains for pellets market has been to convince small-scale customers that pellets are a good alternative fuel, mainly due to the investment needed and the strong competition with natural gas. Besides some benefits in the acquisition of new equipment for renewable energy, they are insufficient to cover the huge discrepancy of the investment in pellets heating. However, pellets are already economic interesting for large utilizations. In order cover a large amount of households, additional public support is needed to cover the supplementary costs of the pellets heating systems. - Highlights: ► There is a lack of internal consumption being the pellets market based on exportation. ► The shortage of raw material is mainly due to the biomass power plants. ► Combining pellet plants with biomass power plants seems to be a wise solution. ► The tax benefits of renewable energy equipments are not enough to cover the higher investment. ► Pellets are already economic interesting for large utilizations in the Portuguese scenario.

  10. Two-zone model of coronal hole structure in the high corona

    International Nuclear Information System (INIS)

    Wang, Z.; Kundu, M.R.; Yoshimura, H.

    1988-01-01

    The two-zone coronal hole structure model presently proposed for the high corona at 1.5-1.7 solar radii emerges from a comparison of computation results for the potential magnetic fields of the corona and meter-decameter radio observations. The two zones of a coronal hole are defined by the configuration of magnetic field lines around a coronal hole: (1) the central hole of an open diverging magnetic field line system; and (2) the boundary zone between the central zone of the open field line system and the closed field line system or systems surrounding the open field line system. 19 references

  11. Non-adversarial justice and the coroner's court: a proposed therapeutic, restorative, problem-solving model.

    Science.gov (United States)

    King, Michael S

    2008-12-01

    Increasingly courts are using new approaches that promote a more comprehensive resolution of legal problems, minimise any negative effects that legal processes have on participant wellbeing and/or that use legal processes to promote participant wellbeing. Therapeutic jurisprudence, restorative justice, mediation and problem-solving courts are examples. This article suggests a model for the use of these processes in the coroner's court to minimise negative effects of coroner's court processes on the bereaved and to promote a more comprehensive resolution of matters at issue, including the determination of the cause of death and the public health and safety promotion role of the coroner.

  12. CORONAL MAGNETIC FIELDS DERIVED FROM SIMULTANEOUS MICROWAVE AND EUV OBSERVATIONS AND COMPARISON WITH THE POTENTIAL FIELD MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Miyawaki, Shun; Nozawa, Satoshi [Department of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Iwai, Kazumasa; Shibasaki, Kiyoto [Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Nagano 384-1305 (Japan); Shiota, Daikou, E-mail: shunmi089@gmail.com [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Aichi 464-8601 (Japan)

    2016-02-10

    We estimated the accuracy of coronal magnetic fields derived from radio observations by comparing them to potential field calculations and the differential emission measure measurements using EUV observations. We derived line-of-sight components of the coronal magnetic field from polarization observations of the thermal bremsstrahlung in the NOAA active region 11150, observed around 3:00 UT on 2011 February 3 using the Nobeyama Radioheliograph at 17 GHz. Because the thermal bremsstrahlung intensity at 17 GHz includes both chromospheric and coronal components, we extracted only the coronal component by measuring the coronal emission measure in EUV observations. In addition, we derived only the radio polarization component of the corona by selecting the region of coronal loops and weak magnetic field strength in the chromosphere along the line of sight. The upper limits of the coronal longitudinal magnetic fields were determined as 100–210 G. We also calculated the coronal longitudinal magnetic fields from the potential field extrapolation using the photospheric magnetic field obtained from the Helioseismic and Magnetic Imager. However, the calculated potential fields were certainly smaller than the observed coronal longitudinal magnetic field. This discrepancy between the potential and the observed magnetic field strengths can be explained consistently by two reasons: (1) the underestimation of the coronal emission measure resulting from the limitation of the temperature range of the EUV observations, and (2) the underestimation of the coronal magnetic field resulting from the potential field assumption.

  13. On Tree-Constrained Matchings and Generalizations

    NARCIS (Netherlands)

    S. Canzar (Stefan); K. Elbassioni; G.W. Klau (Gunnar); J. Mestre

    2011-01-01

    htmlabstractWe consider the following \\textsc{Tree-Constrained Bipartite Matching} problem: Given two rooted trees $T_1=(V_1,E_1)$, $T_2=(V_2,E_2)$ and a weight function $w: V_1\\times V_2 \\mapsto \\mathbb{R}_+$, find a maximum weight matching $\\mathcal{M}$ between nodes of the two trees, such that

  14. Constrained systems described by Nambu mechanics

    International Nuclear Information System (INIS)

    Lassig, C.C.; Joshi, G.C.

    1996-01-01

    Using the framework of Nambu's generalised mechanics, we obtain a new description of constrained Hamiltonian dynamics, involving the introduction of another degree of freedom in phase space, and the necessity of defining the action integral on a world sheet. We also discuss the problem of quantizing Nambu mechanics. (authors). 5 refs

  15. Client's constraining factors to construction project management ...

    African Journals Online (AJOL)

    This study analyzed client's related factors that constrain project management success of public and private sector construction in Nigeria. Issues that concern clients in any project can not be undermined as they are the owners and the initiators of project proposals. It is assumed that success, failure or abandonment of ...

  16. Hyperbolicity and constrained evolution in linearized gravity

    International Nuclear Information System (INIS)

    Matzner, Richard A.

    2005-01-01

    Solving the 4-d Einstein equations as evolution in time requires solving equations of two types: the four elliptic initial data (constraint) equations, followed by the six second order evolution equations. Analytically the constraint equations remain solved under the action of the evolution, and one approach is to simply monitor them (unconstrained evolution). Since computational solution of differential equations introduces almost inevitable errors, it is clearly 'more correct' to introduce a scheme which actively maintains the constraints by solution (constrained evolution). This has shown promise in computational settings, but the analysis of the resulting mixed elliptic hyperbolic method has not been completely carried out. We present such an analysis for one method of constrained evolution, applied to a simple vacuum system, linearized gravitational waves. We begin with a study of the hyperbolicity of the unconstrained Einstein equations. (Because the study of hyperbolicity deals only with the highest derivative order in the equations, linearization loses no essential details.) We then give explicit analytical construction of the effect of initial data setting and constrained evolution for linearized gravitational waves. While this is clearly a toy model with regard to constrained evolution, certain interesting features are found which have relevance to the full nonlinear Einstein equations

  17. A Dynamic Programming Approach to Constrained Portfolios

    DEFF Research Database (Denmark)

    Kraft, Holger; Steffensen, Mogens

    2013-01-01

    This paper studies constrained portfolio problems that may involve constraints on the probability or the expected size of a shortfall of wealth or consumption. Our first contribution is that we solve the problems by dynamic programming, which is in contrast to the existing literature that applies...

  18. A model for optimal constrained adaptive testing

    NARCIS (Netherlands)

    van der Linden, Willem J.; Reese, Lynda M.

    2001-01-01

    A model for constrained computerized adaptive testing is proposed in which the information on the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum

  19. A model for optimal constrained adaptive testing

    NARCIS (Netherlands)

    van der Linden, Willem J.; Reese, Lynda M.

    1997-01-01

    A model for constrained computerized adaptive testing is proposed in which the information in the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum

  20. Neutron Powder Diffraction and Constrained Refinement

    DEFF Research Database (Denmark)

    Pawley, G. S.; Mackenzie, Gordon A.; Dietrich, O. W.

    1977-01-01

    The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement is...

  1. Terrestrial Sagnac delay constraining modified gravity models

    Science.gov (United States)

    Karimov, R. Kh.; Izmailov, R. N.; Potapov, A. A.; Nandi, K. K.

    2018-04-01

    Modified gravity theories include f(R)-gravity models that are usually constrained by the cosmological evolutionary scenario. However, it has been recently shown that they can also be constrained by the signatures of accretion disk around constant Ricci curvature Kerr-f(R0) stellar sized black holes. Our aim here is to use another experimental fact, viz., the terrestrial Sagnac delay to constrain the parameters of specific f(R)-gravity prescriptions. We shall assume that a Kerr-f(R0) solution asymptotically describes Earth's weak gravity near its surface. In this spacetime, we shall study oppositely directed light beams from source/observer moving on non-geodesic and geodesic circular trajectories and calculate the time gap, when the beams re-unite. We obtain the exact time gap called Sagnac delay in both cases and expand it to show how the flat space value is corrected by the Ricci curvature, the mass and the spin of the gravitating source. Under the assumption that the magnitude of corrections are of the order of residual uncertainties in the delay measurement, we derive the allowed intervals for Ricci curvature. We conclude that the terrestrial Sagnac delay can be used to constrain the parameters of specific f(R) prescriptions. Despite using the weak field gravity near Earth's surface, it turns out that the model parameter ranges still remain the same as those obtained from the strong field accretion disk phenomenon.

  2. Chance constrained uncertain classification via robust optimization

    NARCIS (Netherlands)

    Ben-Tal, A.; Bhadra, S.; Bhattacharayya, C.; Saketha Nat, J.

    2011-01-01

    This paper studies the problem of constructing robust classifiers when the training is plagued with uncertainty. The problem is posed as a Chance-Constrained Program (CCP) which ensures that the uncertain data points are classified correctly with high probability. Unfortunately such a CCP turns out

  3. Integrating job scheduling and constrained network routing

    DEFF Research Database (Denmark)

    Gamst, Mette

    2010-01-01

    This paper examines the NP-hard problem of scheduling jobs on resources such that the overall profit of executed jobs is maximized. Job demand must be sent through a constrained network to the resource before execution can begin. The problem has application in grid computing, where a number...

  4. Neuroevolutionary Constrained Optimization for Content Creation

    DEFF Research Database (Denmark)

    Liapis, Antonios; Yannakakis, Georgios N.; Togelius, Julian

    2011-01-01

    and thruster types and topologies) independently of game physics and steering strategies. According to the proposed framework, the designer picks a set of requirements for the spaceship that a constrained optimizer attempts to satisfy. The constraint satisfaction approach followed is based on neuroevolution...... and survival tasks and are also visually appealing....

  5. Models of Flux Tubes from Constrained Relaxation

    Indian Academy of Sciences (India)

    tribpo

    J. Astrophys. Astr. (2000) 21, 299 302. Models of Flux Tubes from Constrained Relaxation. Α. Mangalam* & V. Krishan†, Indian Institute of Astrophysics, Koramangala,. Bangalore 560 034, India. *e mail: mangalam @ iiap. ernet. in. † e mail: vinod@iiap.ernet.in. Abstract. We study the relaxation of a compressible plasma to ...

  6. COMBINED MULTIPOINT REMOTE AND IN SITU OBSERVATIONS OF THE ASYMMETRIC EVOLUTION OF A FAST SOLAR CORONAL MASS EJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Rollett, T.; Möstl, C.; Temmer, M.; Veronig, A. M.; Amerstorfer, U. V. [IGAM-Kanzelhöhe Observatory, Institute of Physics, University of Graz, A-8010 Graz (Austria); Frahm, R. A. [Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238 (United States); Davies, J. A. [RAL Space, Rutherford Appleton Laboratory, Harwell Oxford, OX11 0QX (United Kingdom); Vršnak, B.; Žic, T. [Hvar Observatory, Faculty of Geodesy, University of Zagreb, 1000 Zagreb (Croatia); Farrugia, C. J. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Zhang, T. L., E-mail: tanja.rollett@gmx.at [Space Research Institute, Austrian Academy of Sciences, A-8042 Graz (Austria)

    2014-07-20

    We present an analysis of the fast coronal mass ejection (CME) of 2012  March 7, which was imaged by both STEREO spacecraft and observed in situ by MESSENGER, Venus Express, Wind, and Mars Express. Based on detected arrivals at four different positions in interplanetary space, it was possible to strongly constrain the kinematics and the shape of the ejection. Using the white-light heliospheric imagery from STEREO-A and B, we derived two different kinematical profiles for the CME by applying the novel constrained self-similar expansion method. In addition, we used a drag-based model to investigate the influence of the ambient solar wind on the CME's propagation. We found that two preceding CMEs heading in different directions disturbed the overall shape of the CME and influenced its propagation behavior. While the Venus-directed segment underwent a gradual deceleration (from ∼2700 km s{sup –1} at 15 R {sub ☉} to ∼1500 km s{sup –1} at 154 R {sub ☉}), the Earth-directed part showed an abrupt retardation below 35 R {sub ☉} (from ∼1700 to ∼900 km s{sup –1}). After that, it was propagating with a quasi-constant speed in the wake of a preceding event. Our results highlight the importance of studies concerning the unequal evolution of CMEs. Forecasting can only be improved if conditions in the solar wind are properly taken into account and if attention is also paid to large events preceding the one being studied.

  7. Trans trochanteric approach with coronal osteotomy of the great trochanter

    Directory of Open Access Journals (Sweden)

    Steffann Francois

    2015-01-01

    Full Text Available Several surgical approaches could be used in hip arthroplasty or trauma surgery: anterior, anterolateral, lateral, posterior (with or without trochanterotomy, using or not an orthopedic reduction table. Subtrochanteric and extra-capsular trochanteric fractures (ECTF are usually treated by internal fixation with mandatory restrictions on weight bearing. Specific complications have been widely described. Mechanical failures are particularly high in unstable fractures. Hip fractures are a major public health issue with a mortality rate of 12%–23% at 1 year. An alternative option is to treat ECTF by total hip arthroplasty (THA to prevent decubitus complications, to help rapid recovery, and to permit immediate weight bearing as well as quick rehabilitation. However, specific risks of THA have to be considered such as dislocation or cardiovascular failure. The classical approach (anterior or posterior requires the opening of the joint and capsule, weakening hip stability and the repair of the great trochanter is sometimes hazardous. For 15 years, we have been treating unstable ECTF by THA with cementless stem, dual mobility cup (DMC, greater trochanter (GT reattachment, and a new surgical approach preserving capsule, going through the fracture and avoiding joint dislocation. Bombaci first described a similar approach in 2008; our trans fractural digastric approach (medial gluteus and lateral vastus is different. A coronal GT osteotomy is performed when there is no coronal fracture line. It allows easy access to the femoral neck and acetabulum. The THA is implanted without femoral internal rotation to avoid extra bone fragment displacement. With pre-operative planning, cup implantation is easy and stem positioning is adjusted referring to the top of the GT after trial reduction and preoperative planning. The longitudinal osteotomy and trochanteric fracture are repaired with wires and the digastric incision is closed. This variant of Bombaci

  8. Fitting and Reconstruction of Thirteen Simple Coronal Mass Ejections

    Science.gov (United States)

    Al-Haddad, Nada; Nieves-Chinchilla, Teresa; Savani, Neel P.; Lugaz, Noé; Roussev, Ilia I.

    2018-05-01

    Coronal mass ejections (CMEs) are the main drivers of geomagnetic disturbances, but the effects of their interaction with Earth's magnetic field depend on their magnetic configuration and orientation. Fitting and reconstruction techniques have been developed to determine important geometrical and physical CME properties, such as the orientation of the CME axis, the CME size, and its magnetic flux. In many instances, there is disagreement between different methods but also between fitting from in situ measurements and reconstruction based on remote imaging. This could be due to the geometrical or physical assumptions of the models, but also to the fact that the magnetic field inside CMEs is only measured at one point in space as the CME passes over a spacecraft. In this article we compare three methods that are based on different assumptions for measurements by the Wind spacecraft for 13 CMEs from 1997 to 2015. These CMEs are selected from the interplanetary coronal mass ejections catalog on https://wind.nasa.gov/ICMEindex.php https://wind.nasa.gov/ICMEindex.php" TargetType="URL"/> because of their simplicity in terms of: 1) slow expansion speed throughout the CME and 2) weak asymmetry in the magnetic field profile. This makes these 13 events ideal candidates for comparing codes that do not include expansion or distortion. We find that for these simple events, the codes are in relatively good agreement in terms of the CME axis orientation for six of the 13 events. Using the Grad-Shafranov technique, we can determine the shape of the cross-section, which is assumed to be circular for the other two models, a force-free fitting and a circular-cylindrical non force-free fitting. Five of the events are found to have a clear circular cross-section, even when this is not a precondition of the reconstruction. We make an initial attempt at evaluating the adequacy of the different assumptions for these simple CMEs. The conclusion of this work strongly suggests that attempts

  9. A New Method for Coronal Magnetic Field Reconstruction

    Science.gov (United States)

    Yi, Sibaek; Choe, Gwang-Son; Cho, Kyung-Suk; Kim, Kap-Sung

    2017-08-01

    A precise way of coronal magnetic field reconstruction (extrapolation) is an indispensable tool for understanding of various solar activities. A variety of reconstruction codes have been developed so far and are available to researchers nowadays, but they more or less bear this and that shortcoming. In this paper, a new efficient method for coronal magnetic field reconstruction is presented. The method imposes only the normal components of magnetic field and current density at the bottom boundary to avoid the overspecification of the reconstruction problem, and employs vector potentials to guarantee the divergence-freeness. In our method, the normal component of current density is imposed, not by adjusting the tangential components of A, but by adjusting its normal component. This allows us to avoid a possible numerical instability that on and off arises in codes using A. In real reconstruction problems, the information for the lateral and top boundaries is absent. The arbitrariness of the boundary conditions imposed there as well as various preprocessing brings about the diversity of resulting solutions. We impose the source surface condition at the top boundary to accommodate flux imbalance, which always shows up in magnetograms. To enhance the convergence rate, we equip our code with a gradient-method type accelerator. Our code is tested on two analytical force-free solutions. When the solution is given only at the bottom boundary, our result surpasses competitors in most figures of merits devised by Schrijver et al. (2006). We have also applied our code to a real active region NOAA 11974, in which two M-class flares and a halo CME took place. The EUV observation shows a sudden appearance of an erupting loop before the first flare. Our numerical solutions show that two entwining flux tubes exist before the flare and their shackling is released after the CME with one of them opened up. We suggest that the erupting loop is created by magnetic reconnection between

  10. Heat Stress

    Science.gov (United States)

    ... Publications and Products Programs Contact NIOSH NIOSH HEAT STRESS Recommend on Facebook Tweet Share Compartir OSHA-NIOSH ... hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational ...

  11. Reconstructed frontal and coronal cuts in computed tomography of the trunk

    International Nuclear Information System (INIS)

    Fochem, K.; Klumair, J.

    1982-01-01

    A comparison between the original coronally cuts and the reconstructed coronal cuts yielded basic information on the loss of quality by computed reconstruction of images. As for the trunk, only comparisons between the conventional linear tomography and computed frontal of trunk cuts are possible. A few examples will demonstrate that despite a considerable loss of quality, computed frontal cuts will supply additional information in certain cases. It is also shown that the reconstructed frontal cuts cannot replace conventional tomography. (orig.) [de

  12. A search for the origins of a possible coronal mass ejection in the low corona

    Science.gov (United States)

    Neupert, Werner M.

    1988-01-01

    Evidence for coronal and chromospheric precursors of a hypothesized coronal mass ejection is sought in OSO-7 observations of a filament eruption and the subsequent flare. Large-scale changes in the corona above the active region were clearly present for at least several minutes before the flare, culminating in the activation and eruption of two widely separated filaments; the eruption of one of the preexisting filaments initiated magnetic reconnections and energy releases in the low corona, generating the observed chromospheric flare.

  13. Self consistent MHD modeling of the solar wind from coronal holes with distinct geometries

    Science.gov (United States)

    Stewart, G. A.; Bravo, S.

    1995-01-01

    Utilizing an iterative scheme, a self-consistent axisymmetric MHD model for the solar wind has been developed. We use this model to evaluate the properties of the solar wind issuing from the open polar coronal hole regions of the Sun, during solar minimum. We explore the variation of solar wind parameters across the extent of the hole and we investigate how these variations are affected by the geometry of the hole and the strength of the field at the coronal base.

  14. MAGNETIC FIELD STRUCTURES TRIGGERING SOLAR FLARES AND CORONAL MASS EJECTIONS

    International Nuclear Information System (INIS)

    Kusano, K.; Bamba, Y.; Yamamoto, T. T.; Iida, Y.; Toriumi, S.; Asai, A.

    2012-01-01

    Solar flares and coronal mass ejections, the most catastrophic eruptions in our solar system, have been known to affect terrestrial environments and infrastructure. However, because their triggering mechanism is still not sufficiently understood, our capacity to predict the occurrence of solar eruptions and to forecast space weather is substantially hindered. Even though various models have been proposed to determine the onset of solar eruptions, the types of magnetic structures capable of triggering these eruptions are still unclear. In this study, we solved this problem by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations. As a result, we determined that two different types of small magnetic structures favor the onset of solar eruptions. These structures, which should appear near the magnetic polarity inversion line (PIL), include magnetic fluxes reversed to the potential component or the nonpotential component of major field on the PIL. In addition, we analyzed two large flares, the X-class flare on 2006 December 13 and the M-class flare on 2011 February 13, using imaging data provided by the Hinode satellite, and we demonstrated that they conform to the simulation predictions. These results suggest that forecasting of solar eruptions is possible with sophisticated observation of a solar magnetic field, although the lead time must be limited by the timescale of changes in the small magnetic structures.

  15. Coronal mass ejections and their sheath regions in interplanetary space

    Science.gov (United States)

    Kilpua, Emilia; Koskinen, Hannu E. J.; Pulkkinen, Tuija I.

    2017-11-01

    Interplanetary coronal mass ejections (ICMEs) are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs.

  16. FORMATION OF CORONAL HOLES ON THE ASHES OF ACTIVE REGIONS

    International Nuclear Information System (INIS)

    Karachik, Nina V.; Pevtsov, Alexei A.; Abramenko, Valentyna I.

    2010-01-01

    We investigate the formation of isolated non-polar coronal holes (CHs) on the remnants of decaying active regions (ARs) at the minimum/early ascending phase of sunspot activity. We follow the evolution of four bipolar ARs and measure several parameters of their magnetic fields including total flux, imbalance, and compactness. As regions decay, their leading and following polarities exhibit different dissipation rates: loose polarity tends to dissipate faster than compact polarity. As a consequence, we see a gradual increase in flux imbalance inside a dissipating bipolar region, and later a formation of a CH in place of more compact magnetic flux. Out of four cases studied in detail, two CHs had formed at the following polarity of the decaying bipolar AR, and two CHs had developed in place of the leading polarity field. All four CHs contain a significant fraction of magnetic field of their corresponding AR. Using potential field extrapolation, we show that the magnetic field lines of these CHs were closed on the polar CH at the North, which at the time of the events was in imbalance with the polar CH at the South. This topology suggests that the observed phenomenon may play an important role in transformation of toroidal magnetic field to poloidal field, which is a key step in transitioning from an old solar cycle to a new one. The timing of this observed transition may indicate the end of solar cycle 23 and the beginning of cycle 24.

  17. Areas of Polar Coronal Holes from 1996 Through 2010

    Science.gov (United States)

    Webber, Hess S. A.; Karna, N.; Pesnell, W. D.; Kirk, M. S.

    2014-01-01

    Polar coronal holes (PCHs) trace the magnetic variability of the Sun throughout the solar cycle. Their size and evolution have been studied as proxies for the global magnetic field. We present measurements of the PCH areas from 1996 through 2010, derived from an updated perimeter-tracing method and two synoptic-map methods. The perimeter tracing method detects PCH boundaries along the solar limb, using full-disk images from the SOlar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT). One synoptic-map method uses the line-of-sight magnetic field from the SOHO/Michelson Doppler Imager (MDI) to determine the unipolarity boundaries near the poles. The other method applies thresholding techniques to synoptic maps created from EUV image data from EIT. The results from all three methods suggest that the solar maxima and minima of the two hemispheres are out of phase. The maximum PCH area, averaged over the methods in each hemisphere, is approximately 6 % during both solar minima spanned by the data (between Solar Cycles 22/23 and 23/24). The northern PCH area began a declining trend in 2010, suggesting a downturn toward the maximum of Solar Cycle 24 in that hemisphere, while the southern hole remained large throughout 2010.

  18. COMPARING CORONAL AND HELIOSPHERIC MAGNETIC FIELDS OVER SEVERAL SOLAR CYCLES

    Energy Technology Data Exchange (ETDEWEB)

    Koskela, J. S.; Virtanen, I. I.; Mursula, K., E-mail: jennimari.koskela@oulu.fi [University of Oulu, P.O. Box 3000, FI-90014 Oulu (Finland)

    2017-01-20

    Here we use the PFSS model and photospheric data from Wilcox Solar Observatory, SOHO /MDI, SDO/HMI, and SOLIS to compare the coronal field with heliospheric magnetic field measured at 1 au, compiled in the NASA/NSSDC OMNI 2 data set. We calculate their mutual polarity match and the power of the radial decay, p , of the radial field using different source surface distances and different number of harmonic multipoles. We find the average polarity match of 82% for the declining phase, 78%–79% for maxima, 76%–78% for the ascending phase, and 74%–76% for minima. On an average, the source surface of 3.25 R{sub S} gives the best polarity match. We also find strong evidence for solar cycle variation of the optimal source surface distance, with highest values (3.3 R{sub S}) during solar minima and lowest values (2.6 R{sub S}–2.7 R{sub S}) during the other three solar cycle phases. Raising the number of harmonic terms beyond 2 rarely improves the polarity match, showing that the structure of the HMF at 1 au is most of the time rather simple. All four data sets yield fairly similar polarity matches. Thus, polarity comparison is not affected by photospheric field scaling, unlike comparisons of the field intensity.

  19. KELVIN-HELMHOLTZ INSTABILITY OF A CORONAL STREAMER

    Energy Technology Data Exchange (ETDEWEB)

    Feng, L.; Gan, W. Q. [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210008 Nanjing (China); Inhester, B., E-mail: lfeng@pmo.ac.cn [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Str.2, D-37191 Katlenburg-Lindau (Germany)

    2013-09-10

    Shear-flow-driven instability can play an important role in energy transfer processes in coronal plasma. We present for the first time the observation of a kink-like oscillation of a streamer that is probably caused by the streaming kink-mode Kelvin-Helmholtz instability (KHI). The wave-like behavior of the streamer was observed by the Large Angle and Spectrometric Coronagraph Experiment C2 and C3 on board the SOlar and Heliospheric Observatory. The observed wave had a period of about 70-80 minutes, and its wavelength increased from 2 R{sub Sun} to 3 R{sub Sun} in about 1.5 hr. The phase speeds of its crests and troughs decreased from 406 {+-} 20 to 356 {+-} 31 km s{sup -1} during the event. Within the same heliocentric range, the wave amplitude also appeared to increase with time. We attribute the phenomena to the MHD KHI, which occurs at a neutral sheet in a fluid wake. The free energy driving the instability is supplied by the sheared flow and sheared magnetic field across the streamer plane. The plasma properties of the local environment of the streamer were estimated from the phase speed and instability threshold criteria.

  20. Sheath-accumulating Propagation of Interplanetary Coronal Mass Ejection

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Takuya; Shibata, Kazunari, E-mail: takahasi@kusastro.kyoto-u.ac.jp [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607–8471 (Japan)

    2017-03-10

    Fast interplanetary coronal mass ejections (ICMEs) are the drivers of strong space weather storms such as solar energetic particle events and geomagnetic storms. The connection between the space-weather-impacting solar wind disturbances associated with fast ICMEs at Earth and the characteristics of causative energetic CMEs observed near the Sun is a key question in the study of space weather storms, as well as in the development of practical space weather prediction. Such shock-driving fast ICMEs usually expand at supersonic speeds during the propagation, resulting in the continuous accumulation of shocked sheath plasma ahead. In this paper, we propose a “sheath-accumulating propagation” (SAP) model that describes the coevolution of the interplanetary sheath and decelerating ICME ejecta by taking into account the process of upstream solar wind plasma accumulation within the sheath region. Based on the SAP model, we discuss (1) ICME deceleration characteristics; (2) the fundamental condition for fast ICMEs at Earth; (3) the thickness of interplanetary sheaths; (4) arrival time prediction; and (5) the super-intense geomagnetic storms associated with huge solar flares. We quantitatively show that not only the speed but also the mass of the CME are crucial for discussing the above five points. The similarities and differences between the SAP model, the drag-based model, and the“snow-plow” model proposed by Tappin are also discussed.

  1. Spatially resolved X-ray spectra of coronal active regions

    International Nuclear Information System (INIS)

    Catura, R.C.; Acton, L.W.; Joki, E.G.; Rapley, C.G.; Culhane, J.L.

    1975-01-01

    X-ray spectra from a number of coronal active regions were obtained during ATM support rocket flights carried out by the Lockheed group on June 11 and December 19, 1973. Multi-grid collimators were used to provide fields of view of 40ins. diameter and 90ins. diameter for a number of scanning crystal spectrometers and a bent crystal spectrometer which employed a position sensitive proportional counter to register the diffracted spectrum. A solar image was produced on film and on a TV camera on board the rocket with the aid of a 1 A Hα filter. A small part of the X-ray collimator was used to generate a multiple spot diffraction pattern which was superimposed on the Hα image and the composite picture was transmitted to the ground. Pre-launch calibrations allowed the spot corresponding to the X-ray collimator axis to be identified and so the collimator pointing direction on the solar disc was controlled from the ground by means of commands sent to the rocket. (Auth.)

  2. Coronal mass ejections and their sheath regions in interplanetary space

    Directory of Open Access Journals (Sweden)

    Emilia Kilpua

    2017-11-01

    Full Text Available Abstract Interplanetary coronal mass ejections (ICMEs are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs.

  3. A numerical study of two interacting coronal mass ejections

    Directory of Open Access Journals (Sweden)

    J. M. Schmidt

    2004-06-01

    Full Text Available The interaction in the solar wind between two coronal mass ejections (CMEs is investigated using numerical simulations. We show that the nature of the interaction depends on whether the CME magnetic structures interact, but in all cases the result is an equilisation of the speed of the two CMEs. In the absence of magnetic interaction, the forward shock of the faster trailing CME interacts with the slow leading CME, and accelerates it. When the two CMEs have magnetic fields with the same sense of rotation, magnetic reconnection occurs between the two CMEs, leading to the formation of a single magnetic structure: in the most extreme cases, one CME "eats" the other. When the senses of rotation are opposite, reconnection does not occur, but the CMEs collide in a highly non-elastic manner, again forming a single structure. The possibility of enhanced particle acceleration in such processes is assessed. The presence of strong magnetic reconnection provides excellent opportunities for the acceleration of thermal particles, which then form a seed population for further acceleration at the CME shocks. The presence of a large population of seed particles will thus lead to an overall increase in energetic particle fluxes, as suggested by some observations.

  4. Sheath-accumulating Propagation of Interplanetary Coronal Mass Ejection

    International Nuclear Information System (INIS)

    Takahashi, Takuya; Shibata, Kazunari

    2017-01-01

    Fast interplanetary coronal mass ejections (ICMEs) are the drivers of strong space weather storms such as solar energetic particle events and geomagnetic storms. The connection between the space-weather-impacting solar wind disturbances associated with fast ICMEs at Earth and the characteristics of causative energetic CMEs observed near the Sun is a key question in the study of space weather storms, as well as in the development of practical space weather prediction. Such shock-driving fast ICMEs usually expand at supersonic speeds during the propagation, resulting in the continuous accumulation of shocked sheath plasma ahead. In this paper, we propose a “sheath-accumulating propagation” (SAP) model that describes the coevolution of the interplanetary sheath and decelerating ICME ejecta by taking into account the process of upstream solar wind plasma accumulation within the sheath region. Based on the SAP model, we discuss (1) ICME deceleration characteristics; (2) the fundamental condition for fast ICMEs at Earth; (3) the thickness of interplanetary sheaths; (4) arrival time prediction; and (5) the super-intense geomagnetic storms associated with huge solar flares. We quantitatively show that not only the speed but also the mass of the CME are crucial for discussing the above five points. The similarities and differences between the SAP model, the drag-based model, and the“snow-plow” model proposed by Tappin are also discussed.

  5. Regarding the detectability and measurement of coronal mass ejections

    Directory of Open Access Journals (Sweden)

    Howard Timothy A.

    2015-01-01

    Full Text Available In this review I discuss the problems associated with the detection and measurement of coronal mass ejections (CMEs. CMEs are important phenomena both scientifically, as they play a crucial role in the evolution of the solar corona, and technologically, as their impact with the Earth leads to severe space weather activity in the form of magnetic storms. I focus on the observation of CMEs using visible white light imagers (coronagraphs and heliospheric imagers, as they may be regarded as the binding agents between different datasets and different models that are used to reconstruct them. Our ability to accurately measure CMEs observed by these imagers is hampered by many factors, from instrumental to geometrical to physical. Following a brief review of the history of CME observation and measurement, I explore the impediments to our ability to measure them and describe possible means for which we may be able to mitigate those impediments. I conclude with a discussion of the claim that we have reached the limit of the information that we can extract from the current generation of white light imagers, and discuss possible ways forward regarding future instrument capabilities.

  6. Coronal and local thermodynamic equilibriums in a hollow cathode discharge

    International Nuclear Information System (INIS)

    Zheng Xutao

    2005-01-01

    A characteristic two-section profile of excited-state populations is observed in a hollow cathode discharge and is explained by coexistence of the coronal equilibrium (CE) and the local thermodynamic equilibrium (LTE). At helium pressure 0.1 Torr and cathode current 200-300 mA, vacuum ultraviolet radiations from He I 1snp 1 P (n=2-16) and He II np 2 P (n=2-14) are resolved with a 2.2-M McPherson spectrometer. Relative populations of these states are deduced from the discrete line intensities and are plotted against energy levels. For both the He I and He II series, as energy level increases, populations of high-n (n>10) states are found to decrease much more quickly than low-n (n<7) populations. While low-n populations are described with the CE dominated by direct electron-impact excitations, high-n populations are fitted with the LTE to calculate the population temperatures of gas atoms and ions. Validities of the CE and LTE in different n-ranges are considered on the competition between radiative decays of the excited states and their collisions with gas atoms. (author)

  7. GLOBAL ENERGETICS OF SOLAR FLARES. IV. CORONAL MASS EJECTION ENERGETICS

    International Nuclear Information System (INIS)

    Aschwanden, Markus J.

    2016-01-01

    This study entails the fourth part of a global flare energetics project, in which the mass m cme , kinetic energy E kin , and the gravitational potential energy E grav of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The model derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at r ≳ 2 R ⊙ , while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly onboard the SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs.

  8. Understanding the Physical Nature of Coronal "EIT Waves".

    Science.gov (United States)

    Long, D M; Bloomfield, D S; Chen, P F; Downs, C; Gallagher, P T; Kwon, R-Y; Vanninathan, K; Veronig, A M; Vourlidas, A; Vršnak, B; Warmuth, A; Žic, T

    2017-01-01

    For almost 20 years the physical nature of globally propagating waves in the solar corona (commonly called "EIT waves") has been controversial and subject to debate. Additional theories have been proposed over the years to explain observations that did not agree with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode wave interpretation was challenged by differing viewpoints from the twin Solar Terrestrial Relations Observatory spacecraft and data with higher spatial and temporal resolution from the Solar Dynamics Observatory . In this article, we reexamine the theories proposed to explain EIT waves to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that the so-called EIT waves are best described as fast-mode large-amplitude waves or shocks that are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona.

  9. FGFR2c-mediated ERK-MAPK activity regulates coronal suture development

    Science.gov (United States)

    Pfaff, Miles J.; Xue, Ke; Li, Li; Horowitz, Mark C.; Steinbacher, Derek M.; Eswarakumar, Jacob V.P.

    2017-01-01

    Fibroblast growth factor receptor 2 (FGFR2) signaling is critical for proper craniofacial development. A gain-of-function mutation in the 2c splice variant of the receptor’s gene is associated with Crouzon syndrome, which is characterized by craniosynostosis, the premature fusion of one or more of the cranial vault sutures, leading to craniofacial maldevelopment. Insight into the molecular mechanism of craniosynostosis has identified the ERK-MAPK signaling cascade as a critical regulator of suture patency. The aim of this study is to investigate the role of FGFR2c-induced ERK-MAPK activation in the regulation of coronal suture development. Loss-of-function and gain-of-function Fgfr2c mutant mice have overlapping phenotypes, including coronal synostosis and craniofacial dysmorphia. In vivo analysis of coronal sutures in loss-of-function and gain-of-function models demonstrated fundamentally different pathogenesis underlying coronal suture synostosis. Calvarial osteoblasts from gain-of-function mice demonstrated enhanced osteoblastic function and maturation with concomitant increase in ERK-MAPK activation. In vitro inhibition with the ERK protein inhibitor U0126 mitigated ERK protein activation levels with a concomitant reduction in alkaline phosphatase activity. This study identifies FGFR2c-mediated ERK-MAPK signaling as a key mediator of craniofacial growth and coronal suture development. Furthermore, our results solve the apparent paradox between loss-of-function and gain-of-function FGFR2c mutants with respect to coronal suture synostosis. PMID:27034231

  10. Additional merit of coronal STIR imaging for MR imaging of lumbar spine

    Directory of Open Access Journals (Sweden)

    Ranjana Gupta

    2015-01-01

    Full Text Available Introduction: Back pain is a common clinical problem and is the frequent complaint for referral of lumbar spine magnetic resonance imaging (MRI. Coronal short tau inversion recovery sequence (STIR can provide diagnostically significant information in small percentage of patients. Materials and Methods: MRI examinations of a total of 350 patients were retrospectively included in the study. MR sequences were evaluated in two settings. One radiologist evaluated sagittal and axial images only, while another radiologist evaluated all sequences, including coronal STIR sequence. After recording the diagnoses, we compared the MRI findings in two subsets of patients to evaluate additional merit of coronal STIR imaging. Results: With addition of coronal STIR imaging, significant findings were observed in 24 subjects (6.8%. Twenty-one of these subjects were considered to be normal on other sequences and in three subjects diagnosis was changed with the addition of coronal STIR. Additional diagnoses on STIR included sacroiliitis, sacroiliac joint degenerative disease, sacral stress/insufficiency fracture/Looser′s zones, muscular sprain and atypical appendicitis. Conclusion: Coronal STIR imaging can provide additional diagnoses in a small percentage of patients presenting for lumbar spine MRI for back pain. Therefore, it should be included in the routine protocol for MR imaging of lumbar spine.

  11. Diagnostics of Coronal Magnetic Fields through the Hanle Effect in UV and IR Lines

    Energy Technology Data Exchange (ETDEWEB)

    Raouafi, Nour E. [The John Hopkins University Applied Physics Laboratory, Laurel, MD (United States); Riley, Pete [Predictive Science Inc., San Diego, CA (United States); Gibson, Sarah [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO (United States); Fineschi, Silvano [The Astrophysical Observatory of Turin, National Institute for Astrophysics, Turin (Italy); Solanki, Sami K., E-mail: noureddine.raouafi@jhuapl.edu [Max-Planck-Institut für Sonnensystemforschung, Göttingen (Germany); School of Space Research, Kyung Hee University, Yongin, South (Korea, Republic of)

    2016-06-22

    The plasma thermodynamics in the solar upper atmosphere, particularly in the corona, are dominated by the magnetic field, which controls the flow and dissipation of energy. The relative lack of knowledge of the coronal vector magnetic field is a major handicap for progress in coronal physics. This makes the development of measurement methods of coronal magnetic fields a high priority in solar physics. The Hanle effect in the UV and IR spectral lines is a largely unexplored diagnostic. We use magnetohydrodynamic (MHD) simulations to study the magnitude of the signal to be expected for typical coronal magnetic fields for selected spectral lines in the UV and IR wavelength ranges, namely the H i Ly-α and the He i 10,830 Å lines. We show that the selected lines are useful for reliable diagnosis of coronal magnetic fields. The results show that the combination of polarization measurements of spectral lines with different sensitivities to the Hanle effect may be most appropriate for deducing coronal magnetic properties from future observations.

  12. Are interplanetary magnetic clouds manifestations of coronal transients at 1 AU

    International Nuclear Information System (INIS)

    Wilson, R.M.; Hildner, E.

    1984-01-01

    Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga (1982) and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected control periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients. (orig.)

  13. Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; Noort, M. van [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Rodríguez, J. Blanco [Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Iniesta, J. C. Del Toro; Suárez, D. Orozco [Instituto de Astrofísica de Andalucía (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain); Schmidt, W. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Pillet, V. Martínez [National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States); Knölker, M., E-mail: chitta@mps.mpg.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)

    2017-03-01

    How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite-polarity magnetic elements very close to the larger dominant polarity. These opposite-polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca ii H images obtained from the Sunrise Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.

  14. Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields

    International Nuclear Information System (INIS)

    Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; Noort, M. van; Rodríguez, J. Blanco; Iniesta, J. C. Del Toro; Suárez, D. Orozco; Schmidt, W.; Pillet, V. Martínez; Knölker, M.

    2017-01-01

    How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite-polarity magnetic elements very close to the larger dominant polarity. These opposite-polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca ii H images obtained from the Sunrise Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.

  15. Does Tibial Slope Affect Perception of Coronal Alignment on a Standing Anteroposterior Radiograph?

    Science.gov (United States)

    Schwartz, Adam J; Ravi, Bheeshma; Kransdorf, Mark J; Clarke, Henry D

    2017-07-01

    A standing anteroposterior (AP) radiograph is commonly used to evaluate coronal alignment following total knee arthroplasty (TKA). The impact of coronal alignment on TKA outcomes is controversial, perhaps due to variability in imaging and/or measurement technique. We sought to quantify the effect of image rotation and tibial slope on coronal alignment. Using a standard extramedullary tibial alignment guide, 3 cadaver legs were cut to accept a tibial tray at 0°, 3°, and 7° of slope. A computed tomography scan of the entire tibia was obtained for each specimen to confirm neutral coronal alignment. Images were then obtained at progressive 10° intervals of internal and external rotation up to 40° maximum in each direction. Images were then randomized and 5 blinded TKA surgeons were asked to determine coronal alignment. Continuous data values were transformed to categorical data (neutral [0], valgus [L], and varus [R]). Each 10° interval of external rotation of a 7° sloped tibial cut (or relative internal rotation of a tibial component viewed in the AP plane) resulted in perception of an additional 0.75° of varus. The slope of the proximal tibia bone cut should be taken into account when measuring coronal alignment on a standing AP radiograph. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Self-constrained inversion of potential fields

    Science.gov (United States)

    Paoletti, V.; Ialongo, S.; Florio, G.; Fedi, M.; Cella, F.

    2013-11-01

    We present a potential-field-constrained inversion procedure based on a priori information derived exclusively from the analysis of the gravity and magnetic data (self-constrained inversion). The procedure is designed to be applied to underdetermined problems and involves scenarios where the source distribution can be assumed to be of simple character. To set up effective constraints, we first estimate through the analysis of the gravity or magnetic field some or all of the following source parameters: the source depth-to-the-top, the structural index, the horizontal position of the source body edges and their dip. The second step is incorporating the information related to these constraints in the objective function as depth and spatial weighting functions. We show, through 2-D and 3-D synthetic and real data examples, that potential field-based constraints, for example, structural index, source boundaries and others, are usually enough to obtain substantial improvement in the density and magnetization models.

  17. Cosmogenic photons strongly constrain UHECR source models

    Directory of Open Access Journals (Sweden)

    van Vliet Arjen

    2017-01-01

    Full Text Available With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT’s IGRB, as long as their number density is not strongly peaked at recent times.

  18. A constrained supersymmetric left-right model

    Energy Technology Data Exchange (ETDEWEB)

    Hirsch, Martin [AHEP Group, Instituto de Física Corpuscular - C.S.I.C./Universitat de València, Edificio de Institutos de Paterna, Apartado 22085, E-46071 València (Spain); Krauss, Manuel E. [Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany); Institut für Theoretische Physik und Astronomie, Universität Würzburg,Emil-Hilb-Weg 22, 97074 Wuerzburg (Germany); Opferkuch, Toby [Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany); Porod, Werner [Institut für Theoretische Physik und Astronomie, Universität Würzburg,Emil-Hilb-Weg 22, 97074 Wuerzburg (Germany); Staub, Florian [Theory Division, CERN,1211 Geneva 23 (Switzerland)

    2016-03-02

    We present a supersymmetric left-right model which predicts gauge coupling unification close to the string scale and extra vector bosons at the TeV scale. The subtleties in constructing a model which is in agreement with the measured quark masses and mixing for such a low left-right breaking scale are discussed. It is shown that in the constrained version of this model radiative breaking of the gauge symmetries is possible and a SM-like Higgs is obtained. Additional CP-even scalars of a similar mass or even much lighter are possible. The expected mass hierarchies for the supersymmetric states differ clearly from those of the constrained MSSM. In particular, the lightest down-type squark, which is a mixture of the sbottom and extra vector-like states, is always lighter than the stop. We also comment on the model’s capability to explain current anomalies observed at the LHC.

  19. Coding for Two Dimensional Constrained Fields

    DEFF Research Database (Denmark)

    Laursen, Torben Vaarbye

    2006-01-01

    a first order model to model higher order constraints by the use of an alphabet extension. We present an iterative method that based on a set of conditional probabilities can help in choosing the large numbers of parameters of the model in order to obtain a stationary model. Explicit results are given...... for the No Isolated Bits constraint. Finally we present a variation of the encoding scheme of bit-stuffing that is applicable to the class of checkerboard constrained fields. It is possible to calculate the entropy of the coding scheme thus obtaining lower bounds on the entropy of the fields considered. These lower...... bounds are very tight for the Run-Length limited fields. Explicit bounds are given for the diamond constrained field as well....

  20. Communication Schemes with Constrained Reordering of Resources

    DEFF Research Database (Denmark)

    Popovski, Petar; Utkovski, Zoran; Trillingsgaard, Kasper Fløe

    2013-01-01

    This paper introduces a communication model inspired by two practical scenarios. The first scenario is related to the concept of protocol coding, where information is encoded in the actions taken by an existing communication protocol. We investigate strategies for protocol coding via combinatorial...... reordering of the labelled user resources (packets, channels) in an existing, primary system. However, the degrees of freedom of the reordering are constrained by the operation of the primary system. The second scenario is related to communication systems with energy harvesting, where the transmitted signals...... are constrained by the energy that is available through the harvesting process. We have introduced a communication model that covers both scenarios and elicits their key feature, namely the constraints of the primary system or the harvesting process. We have shown how to compute the capacity of the channels...

  1. Q-deformed systems and constrained dynamics

    International Nuclear Information System (INIS)

    Shabanov, S.V.

    1993-01-01

    It is shown that quantum theories of the q-deformed harmonic oscillator and one-dimensional free q-particle (a free particle on the 'quantum' line) can be obtained by the canonical quantization of classical Hamiltonian systems with commutative phase-space variables and a non-trivial symplectic structure. In the framework of this approach, classical dynamics of a particle on the q-line coincides with the one of a free particle with friction. It is argued that q-deformed systems can be treated as ordinary mechanical systems with the second-class constraints. In particular, second-class constrained systems corresponding to the q-oscillator and q-particle are given. A possibility of formulating q-deformed systems via gauge theories (first-class constrained systems) is briefly discussed. (orig.)

  2. Online constrained model-based reinforcement learning

    CSIR Research Space (South Africa)

    Van Niekerk, B

    2017-08-01

    Full Text Available Constrained Model-based Reinforcement Learning Benjamin van Niekerk School of Computer Science University of the Witwatersrand South Africa Andreas Damianou∗ Amazon.com Cambridge, UK Benjamin Rosman Council for Scientific and Industrial Research, and School... MULTIPLE SHOOTING Using direct multiple shooting (Bock and Plitt, 1984), problem (1) can be transformed into a structured non- linear program (NLP). First, the time horizon [t0, t0 + T ] is partitioned into N equal subintervals [tk, tk+1] for k = 0...

  3. Constraining supergravity models from gluino production

    International Nuclear Information System (INIS)

    Barbieri, R.; Gamberini, G.; Giudice, G.F.; Ridolfi, G.

    1988-01-01

    The branching ratios for gluino decays g tilde → qanti qΧ, g tilde → gΧ into a stable undetected neutralino are computed as functions of the relevant parameters of the underlying supergravity theory. A simple way of constraining supergravity models from gluino production emerges. The effectiveness of hadronic versus e + e - colliders in the search for supersymmetry can be directly compared. (orig.)

  4. Cosmicflows Constrained Local UniversE Simulations

    Science.gov (United States)

    Sorce, Jenny G.; Gottlöber, Stefan; Yepes, Gustavo; Hoffman, Yehuda; Courtois, Helene M.; Steinmetz, Matthias; Tully, R. Brent; Pomarède, Daniel; Carlesi, Edoardo

    2016-01-01

    This paper combines observational data sets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. The latter are excellent laboratories for studies of the non-linear process of structure formation in our neighbourhood. With measurements of radial peculiar velocities in the local Universe (cosmicflows-2) and a newly developed technique, we produce Constrained Local UniversE Simulations (CLUES). To assess the quality of these constrained simulations, we compare them with random simulations as well as with local observations. The cosmic variance, defined as the mean one-sigma scatter of cell-to-cell comparison between two fields, is significantly smaller for the constrained simulations than for the random simulations. Within the inner part of the box where most of the constraints are, the scatter is smaller by a factor of 2 to 3 on a 5 h-1 Mpc scale with respect to that found for random simulations. This one-sigma scatter obtained when comparing the simulated and the observation-reconstructed velocity fields is only 104 ± 4 km s-1, I.e. the linear theory threshold. These two results demonstrate that these simulations are in agreement with each other and with the observations of our neighbourhood. For the first time, simulations constrained with observational radial peculiar velocities resemble the local Universe up to a distance of 150 h-1 Mpc on a scale of a few tens of megaparsecs. When focusing on the inner part of the box, the resemblance with our cosmic neighbourhood extends to a few megaparsecs (<5 h-1 Mpc). The simulations provide a proper large-scale environment for studies of the formation of nearby objects.

  5. Dynamic Convex Duality in Constrained Utility Maximization

    OpenAIRE

    Li, Yusong; Zheng, Harry

    2016-01-01

    In this paper, we study a constrained utility maximization problem following the convex duality approach. After formulating the primal and dual problems, we construct the necessary and sufficient conditions for both the primal and dual problems in terms of FBSDEs plus additional conditions. Such formulation then allows us to explicitly characterize the primal optimal control as a function of the adjoint process coming from the dual FBSDEs in a dynamic fashion and vice versa. Moreover, we also...

  6. Statistical mechanics of budget-constrained auctions

    OpenAIRE

    Altarelli, F.; Braunstein, A.; Realpe-Gomez, J.; Zecchina, R.

    2009-01-01

    Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). Based on the cavity method of statistical mechanics, we introduce a message passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution,...

  7. Constraining neutron star matter with Quantum Chromodynamics

    CERN Document Server

    Kurkela, Aleksi; Schaffner-Bielich, Jurgen; Vuorinen, Aleksi

    2014-01-01

    In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount --- or even presence --- of quark matter inside the stars.

  8. FLUCTUATING ENERGY STORAGE AND NONLINEAR CASCADE IN AN INHOMOGENEOUS CORONAL LOOP

    International Nuclear Information System (INIS)

    Malara, F.; Nigro, G.; Onofri, M.; Veltri, P.

    2010-01-01

    The dynamics and the energy balance of large-scale fluctuations in a coronal loop are studied. The loop is represented by a simplified structure where the curvature is neglected and the background magnetic field is uniform. In a previous paper, we studied a similar model where a uniform background density was assumed. The present paper represents a generalization of the previous one and it has the purpose of investigating possible modifications to the large-scale energy balance and dynamics due to a more realistic longitudinally nonuniform density. Large-scale fluctuations are dominated by coherent eigenmodes that nonlinearly couple to produce an energy cascade to smaller scales. Eigenmodes properties are calculated by a simplified linear dissipative model, deriving an expression for the input energy flux that is not substantially modified by the presence of the density inhomogeneity and is independent of dissipation. For typical values of the parameters, the derived input energy flux is comparable with that required to heat the active region corona. Nonlinear couplings are dominated by coherence effects due to the symmetry properties of eigenmodes; the consequences are that the system is in a weakly nonlinear regime that produces fluctuating energy storage in the loop, and that the kinetic and magnetic nonlinear energy fluxes are of the same order, despite the dominance of magnetic energy at large scales. From the energy balance, an expression for the velocity fluctuation is derived, which is valid in the more general case of a nonuniform background density; this estimate is in agreement both with measures of nonthermal velocities in the solar corona and with previous numerical results.

  9. A New Approach to Observing Coronal Dynamics: MUSE, the Multi-Slit Solar Explorer

    Science.gov (United States)

    Tarbell, T. D.

    2017-12-01

    The Multi-Slit Solar Explorer is a Small Explorer mission recently selected for a Phase A study, which could lead to a launch in 2022. It will provide unprecendented observations of the dynamics of the corona and transition region using both conventional and novel spectral imaging techniques. The physical processes that heat the multi-million degree solar corona, accelerate the solar wind and drive solar activity (CMEs and flares) remain poorly known. A breakthrough in these areas can only come from radically innovative instrumentation and state-of-the-art numerical modeling and will lead to better understanding of space weather origins. MUSE's multi-slit coronal spectroscopy will exploit a 100x improvement in spectral raster cadence to fill a crucial gap in our knowledge of Sun-Earth connections; it will reveal temperatures, velocities and non-thermal processes over a wide temperature range to diagnose physical processes that remain invisible to current or planned instruments. MUSE will contain two instruments: an EUV spectrograph (SG) and EUV context imager (CI). Both have similar spatial resolution and leverage extensive heritage from previous high-resolution instruments such as IRIS and the HiC rocket payload. The MUSE investigation will build on the success of IRIS by combining numerical modeling with a uniquely capable observatory: MUSE will obtain EUV spectra and images with the highest resolution in space (1/3 arcsec) and time (1-4 s) ever achieved for the transition region and corona, along 35 slits and a large context FOV simultaneously. The MUSE consortium includes LMSAL, SAO, Stanford, ARC, HAO, GSFC, MSFC, MSU, ITA Oslo and other institutions.

  10. Constraining the mass of the Local Group

    Science.gov (United States)

    Carlesi, Edoardo; Hoffman, Yehuda; Sorce, Jenny G.; Gottlöber, Stefan

    2017-03-01

    The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging - its mass budget is dominated by dark matter that cannot be directly observed. To meet this end, the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed - the Λ cold dark matter model that is used to set up the simulations, and an LG model that encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted on to the Cosmicflows-2 data base of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different vtan choices affect the peak mass values up to a factor of 2, and change mass ratios of MM31 to MMW by up to 20 per cent; (b) constrained simulations yield more sharply peaked posterior distributions compared with the random ones; (c) LG mass estimates are found to be smaller than those found using the timing argument; (d) preferred Milky Way masses lie in the range of (0.6-0.8) × 1012 M⊙; whereas (e) MM31 is found to vary between (1.0-2.0) × 1012 M⊙, with a strong dependence on the vtan values used.

  11. Combined Ulysses Solar Wind and SOHO Coronal Observations of Several West Limb Coronal Mass Ejections. Appendix 8

    Science.gov (United States)

    Funsten, H. O.; Gosling, J. T.; Riley, P.; St.Cyr, O. C.; Forsyth, R. J.; Howard, R. A.; Schwenn, R.

    2001-01-01

    From October 1996 to January 1997, Ulysses was situated roughly above the west limb of the Sun as observed from Earth at a heliocentric distance of about 4.6 AU and a latitude of about 25 deg. This presents the first opportunity to compare Solar and Heliospheric Observatory (SOHO) limb observations of coronal mass ejections (CMEs) directly with their solar wind counterparts far from the Sun using the Ulysses data. During this interval, large eruptive events were observed above the west limb of the Sun by the Large Angle Spectrometric Coronagraph (LASCO) on SOHO on October 5, November 28, and December 21-25, 1996. Using the combined plasma and magnetic field data from Ulysses, the October 5 event was clearly identified by several distinguishing signatures as a CME. The November 28 event was also identified as a CME that trailed fast ambient solar wind, although it was identified only by an extended interval of counterstreaming suprathermal electrons. The December 21 event was apparently characterized by a six-day interval of nearly radial field and a plasma rarefaction. For the numerous eruptive events observed by the LASCO coronagraph during December 23-25, Ulysses showed no distinct, CMEs, perhaps because of intermingling of two or more of the eruptive events. By mapping the Ulysses observations back in time to the Sun assuming a constant flow speed, we have identified intervals of plasma that were accelerated or decelerated between the LASCO and Ulysses observations.

  12. Heat pumps

    CERN Document Server

    Macmichael, DBA

    1988-01-01

    A fully revised and extended account of the design, manufacture and use of heat pumps in both industrial and domestic applications. Topics covered include a detailed description of the various heat pump cycles, the components of a heat pump system - drive, compressor, heat exchangers etc., and the more practical considerations to be taken into account in their selection.

  13. Intermittent heating of the solar corona by MHD turbulence

    Directory of Open Access Journals (Sweden)

    É. Buchlin

    2007-10-01

    Full Text Available As the dissipation mechanisms considered for the heating of the solar corona would be sufficiently efficient only in the presence of small scales, turbulence is thought to be a key player in the coronal heating processes: it allows indeed to transfer energy from the large scales to these small scales. While Direct numerical simulations which have been performed to investigate the properties of magnetohydrodynamic turbulence in the corona have provided interesting results, they are limited to small Reynolds numbers. We present here a model of coronal loop turbulence involving shell-models and Alfvén waves propagation, allowing the much faster computation of spectra and turbulence statistics at higher Reynolds numbers. We also present first results of the forward-modelling of spectroscopic observables in the UV.

  14. Coronal Mass Ejections: a Summary of Recent Results

    Science.gov (United States)

    Gopalswamy, Nat; Davila, J. M.

    2010-01-01

    Coronal mass ejections (CMEs) have been recognized as the most energetic phenomenon in the heliosphere, deriving their energy from the stressed magnetic fields on the Sun. This paper highlights some of the recent results on CMEs obtained from the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) missions. The summary of the talk follows. SOHO observations revealed that the CME rate is almost a factor of two larger than previously thought and varied with the solar activity cycle in a complex way (e.g., high-latitude CMEs occurred in great abundance during the solar maximum years). CMEs were found to interact with other CMEs as well as with other large-scale structures (coronal holes), resulting in deflections and additional particle acceleration. STEREO observations have confirmed the three-dimensional nature of CMEs and the shocks surrounding them. The EUV signatures (flare arcades, corona) dimming, filament eruption, and EUV waves) associated with CMEs have become vital in the identification of solar sources from which CMEs erupt. CMEs with speeds exceeding the characteristic speeds of the corona and the interplanetary medium drive shocks, which produce type II radio bursts. The wavelength range of type II bursts depends on the CME kinetic energy: type II bursts with emission components at all wavelengths (metric to kilometric) are due to CMEs of the highest kinetic energy. Some CMEs, as fast as 1600 km/s do not produce type II bursts, while slow CMEs (400 km/s) occasionally produce type II bursts. These observations can be explained as the variation in the ambient flow speed (solar wind) and the Alfven speed. Not all CME-driven shocks produce type II bursts because either they are subcritical or do not have the appropriate geometry. The same shocks that produce type II bursts also produce solar energetic particles (SEPs), whose release near the Sun seems to be delayed with respect to the onset of type II bursts

  15. Ulysses' rapid crossing of the polar coronal hole boundary

    International Nuclear Information System (INIS)

    McComas, D.J.; Riley, P.; Gosling, J.T.; Balogh, A.; Forsyth, R.

    1998-01-01

    The Ulysses spacecraft crossed from the slow dense solar wind characteristic of the solar streamer belt into the fast, less dense flow from the northern polar coronal hole over a very short interval (several days) in late March 1995. The spacecraft, which was at 1.35 AU and ∼19 degree north heliographic latitude, moving northward in its orbit, remained in the fast solar wind from then through summer 1996. This boundary crossing is unique in that the combination of the spacecraft motion and rotation of the structure past the spacecraft caused Ulysses to move smoothly and completely from one regime into the other. In this study we examine this crossing in detail. The crossing is marked by a region of enhanced pressure, typical of stream interaction regions, which extends ∼2x10 7 km across. We find that the transition between the slow and fast regimes occurs on several temporal, and hence spatial, scales. On the shortest scale ( 4 km) the stream interface is a tangential discontinuity where the proton and core electron densities and ion and electron pressures all drop while the magnetic pressure jumps to maintain a rough pressure balance. The alpha to proton ratio also jumps across the stream interface to reach the comparatively constant polar hole value of ∼4.3%. On larger scales (a few x10 6 km) the proton and alpha temperatures rise to their high-speed wind values. Finally, on the largest scale (∼10 8 km) the solar wind speed ramps up from ∼400kms -1 to ∼750kms -1 , typical of polar hole flows. While it seems likely that the stream interface maps back to a sharp boundary near the Sun, the large region of increasing flow speed suggests that there is also an extended gradient in solar wind source speed close to the Sun. copyright 1998 American Geophysical Union

  16. Predicting Coronal Mass Ejections Using Machine Learning Methods

    Science.gov (United States)

    Bobra, M. G.; Ilonidis, S.

    2016-04-01

    Of all the activity observed on the Sun, two of the most energetic events are flares and coronal mass ejections (CMEs). Usually, solar active regions that produce large flares will also produce a CME, but this is not always true. Despite advances in numerical modeling, it is still unclear which circumstances will produce a CME. Therefore, it is worthwhile to empirically determine which features distinguish flares associated with CMEs from flares that are not. At this time, no extensive study has used physically meaningful features of active regions to distinguish between these two populations. As such, we attempt to do so by using features derived from (1) photospheric vector magnetic field data taken by the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager instrument and (2) X-ray flux data from the Geostationary Operational Environmental Satellite’s X-ray Flux instrument. We build a catalog of active regions that either produced both a flare and a CME (the positive class) or simply a flare (the negative class). We then use machine-learning algorithms to (1) determine which features distinguish these two populations, and (2) forecast whether an active region that produces an M- or X-class flare will also produce a CME. We compute the True Skill Statistic, a forecast verification metric, and find that it is a relatively high value of ∼0.8 ± 0.2. We conclude that a combination of six parameters, which are all intensive in nature, will capture most of the relevant information contained in the photospheric magnetic field.

  17. Intermittency in MHD turbulence and coronal nanoflares modelling

    Directory of Open Access Journals (Sweden)

    P. Veltri

    2005-01-01

    Full Text Available High resolution numerical simulations, solar wind data analysis, and measurements at the edges of laboratory plasma devices have allowed for a huge progress in our understanding of MHD turbulence. The high resolution of solar wind measurements has allowed to characterize the intermittency observed at small scales. We are now able to set up a consistent and convincing view of the main properties of MHD turbulence, which in turn constitutes an extremely efficient tool in understanding the behaviour of turbulent plasmas, like those in solar corona, where in situ observations are not available. Using this knowledge a model to describe injection, due to foot-point motions, storage and dissipation of MHD turbulence in coronal loops, is built where we assume strong longitudinal magnetic field, low beta and high aspect ratio, which allows us to use the set of reduced MHD equations (RMHD. The model is based on a shell technique in the wave vector space orthogonal to the strong magnetic field, while the dependence on the longitudinal coordinate is preserved. Numerical simulations show that injected energy is efficiently stored in the loop where a significant level of magnetic and velocity fluctuations is obtained. Nonlinear interactions give rise to an energy cascade towards smaller scales where energy is dissipated in an intermittent fashion. Due to the strong longitudinal magnetic field, dissipative structures propagate along the loop, with the typical speed of the Alfvén waves. The statistical analysis on the intermittent dissipative events compares well with all observed properties of nanoflare emission statistics. Moreover the recent observations of non thermal velocity measurements during flare occurrence are well described by the numerical results of the simulation model. All these results naturally emerge from the model dynamical evolution without any need of an ad-hoc hypothesis.

  18. Coronal Mass Ejection Data Clustering and Visualization of Decision Trees

    Science.gov (United States)

    Ma, Ruizhe; Angryk, Rafal A.; Riley, Pete; Filali Boubrahimi, Soukaina

    2018-05-01

    Coronal mass ejections (CMEs) can be categorized as either “magnetic clouds” (MCs) or non-MCs. Features such as a large magnetic field, low plasma-beta, and low proton temperature suggest that a CME event is also an MC event; however, so far there is neither a definitive method nor an automatic process to distinguish the two. Human labeling is time-consuming, and results can fluctuate owing to the imprecise definition of such events. In this study, we approach the problem of MC and non-MC distinction from a time series data analysis perspective and show how clustering can shed some light on this problem. Although many algorithms exist for traditional data clustering in the Euclidean space, they are not well suited for time series data. Problems such as inadequate distance measure, inaccurate cluster center description, and lack of intuitive cluster representations need to be addressed for effective time series clustering. Our data analysis in this work is twofold: clustering and visualization. For clustering we compared the results from the popular hierarchical agglomerative clustering technique to a distance density clustering heuristic we developed previously for time series data clustering. In both cases, dynamic time warping will be used for similarity measure. For classification as well as visualization, we use decision trees to aggregate single-dimensional clustering results to form a multidimensional time series decision tree, with averaged time series to present each decision. In this study, we achieved modest accuracy and, more importantly, an intuitive interpretation of how different parameters contribute to an MC event.

  19. Birth, life, and death of a solar coronal plume

    Energy Technology Data Exchange (ETDEWEB)

    Pucci, Stefano; Romoli, Marco [Department of Physics and Astronomy, University of Firenze, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Poletto, Giannina [INAF-Arcetri Astrophysical Observatory, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Sterling, Alphonse C., E-mail: stpucci@arcetri.astro.it [Space Science Office, NASA/MSFC, Huntsville, AL 35812 (United States)

    2014-10-01

    We analyze a solar polar-coronal-hole (CH) plume over its entire ≈40 hr lifetime, using high-resolution Solar Dynamic Observatory Atmospheric Imaging Assembly (AIA) data. We examine (1) the plume's relationship to a bright point (BP) that persists at its base, (2) plume outflows and their possible contribution to the solar wind mass supply, and (3) the physical properties of the plume. We find that the plume started ≈2 hr after the BP first appeared and became undetectable ≈1 hr after the BP disappeared. We detected radially moving radiance variations from both the plume and from interplume regions, corresponding to apparent outflow speeds ranging over ≈(30-300) km s{sup –1} with outflow velocities being higher in the 'cooler' AIA 171 Å channel than in the 'hotter' 193 Å and 211 Å channels, which is inconsistent with wave motions; therefore, we conclude that the observed radiance variations represent material outflows. If they persist into the heliosphere and plumes cover ≈10% of a typical CH area, these flows could account for ≈50% of the solar wind mass. From a differential emission measure analysis of the AIA images, we find that the average electron temperature of the plume remained approximately constant over its lifetime, at T {sub e} ≈ 8.5 × 10{sup 5} K. Its density, however, decreased with the age of the plume, being about a factor of three lower when the plume faded compared to when it was born. We conclude that the plume died due to a density reduction rather than to a temperature decrease.

  20. Differential Rotation via Tracking of Coronal Bright Points.

    Science.gov (United States)

    McAteer, James; Boucheron, Laura E.; Osorno, Marcy

    2016-05-01

    The accurate computation of solar differential rotation is important both as a constraint for, and evidence towards, support of models of the solar dynamo. As such, the use of Xray and Extreme Ultraviolet bright points to elucidate differential rotation has been studied in recent years. In this work, we propose the automated detection and tracking of coronal bright points (CBPs) in a large set of SDO data for re-evaluation of solar differential rotation and comparison to other results. The big data aspects, and high cadence, of SDO data mitigate a few issues common to detection and tracking of objects in image sequences and allow us to focus on the use of CBPs to determine differential rotation. The high cadence of the data allows to disambiguate individual CBPs between subsequent images by allowing for significant spatial overlap, i.e., by the fact that the CBPs will rotate a short distance relative to their size. The significant spatial overlap minimizes the effects of incorrectly detected CBPs by reducing the occurrence of outlier values of differential rotation. The big data aspects of the data allows to be more conservative in our detection of CBPs (i.e., to err on the side of missing CBPs rather than detecting extraneous CBPs) while still maintaining statistically larger populations over which to study characteristics. The ability to compute solar differential rotation through the automated detection and tracking of a large population of CBPs will allow for further analyses such as the N-S asymmetry of differential rotation, variation of differential rotation over the solar cycle, and a detailed study of the magnetic flux underlying the CBPs.

  1. PREDICTING CORONAL MASS EJECTIONS USING MACHINE LEARNING METHODS

    Energy Technology Data Exchange (ETDEWEB)

    Bobra, M. G.; Ilonidis, S. [W.W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2016-04-20

    Of all the activity observed on the Sun, two of the most energetic events are flares and coronal mass ejections (CMEs). Usually, solar active regions that produce large flares will also produce a CME, but this is not always true. Despite advances in numerical modeling, it is still unclear which circumstances will produce a CME. Therefore, it is worthwhile to empirically determine which features distinguish flares associated with CMEs from flares that are not. At this time, no extensive study has used physically meaningful features of active regions to distinguish between these two populations. As such, we attempt to do so by using features derived from (1) photospheric vector magnetic field data taken by the Solar Dynamics Observatory ’s Helioseismic and Magnetic Imager instrument and (2) X-ray flux data from the Geostationary Operational Environmental Satellite’s X-ray Flux instrument. We build a catalog of active regions that either produced both a flare and a CME (the positive class) or simply a flare (the negative class). We then use machine-learning algorithms to (1) determine which features distinguish these two populations, and (2) forecast whether an active region that produces an M- or X-class flare will also produce a CME. We compute the True Skill Statistic, a forecast verification metric, and find that it is a relatively high value of ∼0.8 ± 0.2. We conclude that a combination of six parameters, which are all intensive in nature, will capture most of the relevant information contained in the photospheric magnetic field.

  2. Methods of Temperature and Emission Measure Determination of Coronal Loops

    Science.gov (United States)

    Cirtain, J. W.; Schmelz, J. T.; Martens, P. C. H.

    2002-05-01

    Recent observational results from both SOHO-EIT and TRACE indicate that coronal loops are isothermal along their length (axially). These results are obtained from a narrowband filter ratio method that assumes that the plasma is isothermal along the line of sight (radially). However, these temperatures vary greatly from those derived from differential emission measure (DEM) curves produced from spectral lines recorded by SOHO-CDS. The DEM results indicate that the loops are neither axially nor radially isothermal. This discrepancy was investigated by Schmelz et al. (2001). They chose pairs of iron lines from the same CDS data set to mimic the EIT and TRACE loop results. Ratios of different lines gave different temperatures, indicating that the plasma was not radially isothermal. In addition the results indicated that the loop was axially isothermal, even though the DEM analysis of the same data showed this result to be false. Here we have analyzed the EIT data for the CDS loop published by Schmelz et al. (2001). We took the ratios of the 171-to-195 and 195-to-284 filter data, and made temperature maps of the loop. The results indicate that the loop is axially isothermal, but different temperatures were found for each pair of filters. Both ratio techniques force the resultant temperature to lie within the range where the response functions (for filters) or the emissivity functions (for lines) overlap; isothermal loops are therefore a byproduct of the analysis. This conclusion strengthens support for the idea that temperature and emission measure results from filter ratio methods may be misleading or even drastically wrong. This research was funded in part by the NASA/TRACE MODA grant for Montana State University. Solar physics research at the University of Memphis is supported by NASA grant NAG5-9783.

  3. Fault lines in forensic medical toxicology in Ireland exposed through replies of pathologists and coroners to anonymous questionnaires.

    Science.gov (United States)

    Tormey, William P; Borovickova, Ingrid; Moore, Tara M

    2014-01-01

    The attitudes and experiences of pathologists and coroners to the provision of biochemical forensic toxicology in the Republic of Ireland were determined using separate questionnaires to each group anonymously. Replies were received from 36/88 (41%) of pathologists and 19/71 (27%) of coroners. 37% of coroners considered that histopathologists give an adequate opinion in forensic toxicology yet 58% of pathologists reported that they did not have adequate access to expert medical interpretative toxicological opinion. For drug-drug interactions and metabolic diseases, 69% of pathologists were unhappy with the processes and 68% of coroner replies did not know if vitreous samples were used appropriately. There is a clear requirement for retraining of coroners and for the appointment of medical toxicology expertise to improve the quality of service for coroners.

  4. Constraining the volatile fraction of planets from transit observations

    Science.gov (United States)

    Alibert, Y.

    2016-06-01

    Context. The determination of the abundance of volatiles in extrasolar planets is very important as it can provide constraints on transport in protoplanetary disks and on the formation location of planets. However, constraining the internal structure of low-mass planets from transit measurements is known to be a degenerate problem. Aims: Using planetary structure and evolution models, we show how observations of transiting planets can be used to constrain their internal composition, in particular the amount of volatiles in the planetary interior, and consequently the amount of gas (defined in this paper to be only H and He) that the planet harbors. We first explore planets that are located close enough to their star to have lost their gas envelope. We then concentrate on planets at larger distances and show that the observation of transiting planets at different evolutionary ages can provide statistical information on their internal composition, in particular on their volatile fraction. Methods: We computed the evolution of low-mass planets (super-Earths to Neptune-like) for different fractions of volatiles and gas. We used a four-layer model (core, silicate mantle, icy mantle, and gas envelope) and computed the internal structure of planets for different luminosities. With this internal structure model, we computed the internal and gravitational energy of planets, which was then used to derive the time evolution of the planet. Since the total energy of a planet depends on its heat capacity and density distribution and therefore on its composition, planets with different ice fractions have different evolution tracks. Results: We show for low-mass gas-poor planets that are located close to their central star that assuming evaporation has efficiently removed the entire gas envelope, it is possible to constrain the volatile fraction of close-in transiting planets. We illustrate this method on the example of 55 Cnc e and show that under the assumption of the absence of

  5. Heat generated by knee prostheses.

    Science.gov (United States)

    Pritchett, James W

    2006-01-01

    Temperature sensors were placed in 50 knees in 25 patients who had one or both joints replaced. Temperature recordings were made before walking, after walking, and after cycling. The heat generated in healthy, arthritic, and replaced knees was measured. The knee replacements were done using eight different prostheses. A rotating hinge knee prosthesis generated a temperature increase of 7 degrees C in 20 minutes and 9 degrees C in 40 minutes. An unconstrained ceramic femoral prosthesis articulating with a polyethylene tibial prosthesis generated a temperature increase of 4 degrees C compared with a healthy resting knee. The other designs using a cobalt-chrome alloy and high-density polyethylene had temperature increases of 5 degrees-7 degrees C with exercise. Frictional heat generated in a prosthetic knee is not immediately dissipated and may result in wear, creep, and other degenerative processes in the high-density polyethylene. Extended periods of elevated temperature in joints may inhibit cell growth and perhaps contribute to adverse performance via bone resorption or component loosening. Prosthetic knees generate more heat with activity than healthy or arthritic knees. More-constrained knee prostheses generate more heat than less-constrained prostheses. A knee with a ceramic femoral component generates less heat than a knee with the same design using a cobalt-chromium alloy.

  6. Root canal adhesive filling in dogs' teeth with or without coronal restoration: a histopathological evaluation.

    Science.gov (United States)

    Leonardo, Mario Roberto; Barnett, Frederick; Debelian, Gilberto J; de Pontes Lima, Regina Karla; Bezerra da Silva, Léa Assed

    2007-11-01

    The purpose of this study was to evaluate in vivo the response of the periradicular tissues after endodontic treatment and root filling with Epiphany/Resilon (Penntron Clinical Technologies, LLC, Wallingford, CT) or gutta percha and new Sealapex (SybronEndo, Glendora, CA) in dogs' teeth with or without coronal restoration. Teeth without coronal restorations were used to assess the influence of continuous exposure to the oral environment on the periradicular tissues. Sixty root canals with vital pulps in three dogs were instrumented and obturated in a single session and randomly assigned to one of four groups as follows. group 1: root canal filling with Epiphany/Resilon with coronal restoration, group 2: root canal filling with Sealapex sealer and gutta percha with restoration, group 3: root canal filling with Epiphany/Resilon without restoration, and group 4: root canal filling with Sealapex sealer and gutta percha without coronal restoration. After 90 days, the animals were euthanized, and the maxillas and mandibles were removed and submitted for histologic processing. Longitudinal sections were obtained and stained with hematoxylin and eosin, Mallory's trichrome, and Brown and Brenn stains and examined under light microscopy. There were significant differences found between the four groups (p < 0.05). The results showed that roots canals filled with Epiphany/Resilon, with coronal restoration, had significantly less periradicular inflammation than roots canals filled with gutta percha and Sealapex, with coronal restoration (p = 0.021). No significant difference was observed in the intensity of inflammation between roots canals filled with Epiphany/Resilon with no restoration and roots filled with gutta percha and Sealapex with restoration (p = 0.269). Roots canals filled with gutta percha and Sealapex sealer without coronal restoration showed the greatest degree of periradicular inflammation.

  7. Decision-making in a death investigation: Emotion, families and the coroner.

    Science.gov (United States)

    Tait, Gordon; Carpenter, Belinda; Quadrelli, Carol; Barnes, Michael

    2016-03-01

    The role of the coroner in common law countries such as Australia, England, Canada and New Zealand is to preside over death investigations where there is uncertainty as to the manner of death, a need to identify the deceased, a death of unknown cause, or a violent or unnatural death. The vast majority of these deaths are not suspicious and thus require coroners to engage with grieving families who have been thrust into a legal process through the misfortune of a loved one's sudden or unexpected death. In this research, 10 experienced coroners discussed how they negotiated the grief and trauma evident in a death investigation. In doing so, they articulated two distinct ways in which legal officers engaged with emotions, which are also evident in the literature. The first engages the script of judicial dispassion, articulating a hierarchical relationship between reason and emotion, while the second introduces an ethic of care via the principles of therapeutic jurisprudence, and thus offers a challenge to the role of emotion in the personae of the professional judicial officer. By using Hochschild's work on the sociology of emotions, this article discusses the various ways in which coroners manage the emotion of a death investigation through emotion work. While emotional distance may be an understandable response by coroners to the grief and trauma experienced by families and directed at cleaner coronial decision-making, the article concludes that coroners may be better served by offering emotions such as sympathy, consideration and compassion directly to the family in those situations where families are struggling to accept, or are resistant to, coroners' decisions.

  8. Cascading Constrained 2-D Arrays using Periodic Merging Arrays

    DEFF Research Database (Denmark)

    Forchhammer, Søren; Laursen, Torben Vaarby

    2003-01-01

    We consider a method for designing 2-D constrained codes by cascading finite width arrays using predefined finite width periodic merging arrays. This provides a constructive lower bound on the capacity of the 2-D constrained code. Examples include symmetric RLL and density constrained codes...

  9. Operator approach to solutions of the constrained BKP hierarchy

    International Nuclear Information System (INIS)

    Shen, Hsin-Fu; Lee, Niann-Chern; Tu, Ming-Hsien

    2011-01-01

    The operator formalism to the vector k-constrained BKP hierarchy is presented. We solve the Hirota bilinear equations of the vector k-constrained BKP hierarchy via the method of neutral free fermion. In particular, by choosing suitable group element of O(∞), we construct rational and soliton solutions of the vector k-constrained BKP hierarchy.

  10. Remaking the medico-legal scene: a social history of the late-Victorian coroner in Oxford.

    Science.gov (United States)

    Hurren, Elizabeth T

    2010-04-01

    There have been wide-ranging debates about medicine and the law encapsulated in the figure of the coroner in Victorian England. Recently the historical literature on coroners has been enriched by macro-studies. Despite this important research, the social lives of coroners and their daily interactions remain relatively neglected in standard historical accounts. This article redresses that issue by examining the working life of the coroner for Oxford during the late-Victorian era. Edward Law Hussey kept very detailed records of his time in office as coroner. New research material makes it feasible to trace his professional background, from doctor of the sick poor, to hospital house surgeon and then busy coroner. His career trajectory, personal interactions, and professional disputes, provide an important historical prism illuminating contemporary debates that occupied coroners in their working lives. Hussey tried to improve his medico-legal reach and the public image of his coroner's office by reducing infanticide rates, converting a public mortuary, and acquiring a proper coroner's court. His campaigns had limited success because the social scene in which he worked was complicated by the dominance of health and welfare agencies that resented his role as an expanding arm of the Victorian information state.

  11. Feature and Pose Constrained Visual Aided Inertial Navigation for Computationally Constrained Aerial Vehicles

    Science.gov (United States)

    Williams, Brian; Hudson, Nicolas; Tweddle, Brent; Brockers, Roland; Matthies, Larry

    2011-01-01

    A Feature and Pose Constrained Extended Kalman Filter (FPC-EKF) is developed for highly dynamic computationally constrained micro aerial vehicles. Vehicle localization is achieved using only a low performance inertial measurement unit and a single camera. The FPC-EKF framework augments the vehicle's state with both previous vehicle poses and critical environmental features, including vertical edges. This filter framework efficiently incorporates measurements from hundreds of opportunistic visual features to constrain the motion estimate, while allowing navigating and sustained tracking with respect to a few persistent features. In addition, vertical features in the environment are opportunistically used to provide global attitude references. Accurate pose estimation is demonstrated on a sequence including fast traversing, where visual features enter and exit the field-of-view quickly, as well as hover and ingress maneuvers where drift free navigation is achieved with respect to the environment.

  12. Heat pumps

    CERN Document Server

    Brodowicz, Kazimierz; Wyszynski, M L; Wyszynski

    2013-01-01

    Heat pumps and related technology are in widespread use in industrial processes and installations. This book presents a unified, comprehensive and systematic treatment of the design and operation of both compression and sorption heat pumps. Heat pump thermodynamics, the choice of working fluid and the characteristics of low temperature heat sources and their application to heat pumps are covered in detail.Economic aspects are discussed and the extensive use of the exergy concept in evaluating performance of heat pumps is a unique feature of the book. The thermodynamic and chemical properties o

  13. Incomplete Dirac reduction of constrained Hamiltonian systems

    Energy Technology Data Exchange (ETDEWEB)

    Chandre, C., E-mail: chandre@cpt.univ-mrs.fr

    2015-10-15

    First-class constraints constitute a potential obstacle to the computation of a Poisson bracket in Dirac’s theory of constrained Hamiltonian systems. Using the pseudoinverse instead of the inverse of the matrix defined by the Poisson brackets between the constraints, we show that a Dirac–Poisson bracket can be constructed, even if it corresponds to an incomplete reduction of the original Hamiltonian system. The uniqueness of Dirac brackets is discussed. The relevance of this procedure for infinite dimensional Hamiltonian systems is exemplified.

  14. Capturing Hotspots For Constrained Indoor Movement

    DEFF Research Database (Denmark)

    Ahmed, Tanvir; Pedersen, Torben Bach; Lu, Hua

    2013-01-01

    Finding the hotspots in large indoor spaces is very important for getting overloaded locations, security, crowd management, indoor navigation and guidance. The tracking data coming from indoor tracking are huge in volume and not readily available for finding hotspots. This paper presents a graph......-based model for constrained indoor movement that can map the tracking records into mapping records which represent the entry and exit times of an object in a particular location. Then it discusses the hotspots extraction technique from the mapping records....

  15. Quantization of soluble classical constrained systems

    International Nuclear Information System (INIS)

    Belhadi, Z.; Menas, F.; Bérard, A.; Mohrbach, H.

    2014-01-01

    The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way

  16. Quantization of soluble classical constrained systems

    Energy Technology Data Exchange (ETDEWEB)

    Belhadi, Z. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Laboratoire de physique théorique, Faculté des sciences exactes, Université de Bejaia, 06000 Bejaia (Algeria); Menas, F. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Ecole Nationale Préparatoire aux Etudes d’ingéniorat, Laboratoire de physique, RN 5 Rouiba, Alger (Algeria); Bérard, A. [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France); Mohrbach, H., E-mail: herve.mohrbach@univ-lorraine.fr [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France)

    2014-12-15

    The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way.

  17. Future space missions and ground observatory for measurements of coronal magnetic fields

    Science.gov (United States)

    Fineschi, Silvano; Gibson, Sarah; Bemporad, Alessandro; Zhukov, Andrei; Damé, Luc; Susino, Roberto; Larruquert, Juan

    2016-07-01

    This presentation gives an overview of the near-future perspectives for probing coronal magnetism from space missions (i.e., SCORE and ASPIICS) and ground-based observatory (ESCAPE). Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter. The CorMag filter is part of the ESCAPE experiment to be based at the French-Italian Concordia base in Antarctica. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include new generation, high-efficiency UV polarizer with the capability of imaging polarimetry of the HI Lyman-α, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. The second lauch is scheduled in 2016. Proba-3 is the other future solar mission that would provide the opportunity of diagnosing the coronal magnetic field. Proba-3 is the first precision formation-flying mission to launched in 2019). A pair of satellites will fly together maintaining a fixed configuration as a 'large rigid

  18. SOFT CORONAL X-RAYS FROM {beta} PICTORIS

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, H. M.; Wolk, S. J.; Drake, J. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lisse, C. M. [Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Robrade, J.; Schmitt, J. H. M. M., E-mail: hguenther@cfa.harvard.edu [Hamburger Sternwarte, Universitaet Hamburg, Gojenbergsweg 112, 21029 Hamburg (Germany)

    2012-05-01

    A-type stars are expected to be X-ray dark, yet weak emission has been detected from several objects in this class. We present new Chandra/HRC-I observations of the A5 V star {beta} Pictoris. It is clearly detected with a flux of (9 {+-} 2) Multiplication-Sign 10{sup -4} counts s{sup -1}. In comparison with previous data this constrains the emission mechanism and we find that the most likely explanation is an optically thin, collisionally dominated, thermal emission component with a temperature around 1.1 MK. We interpret this component as a very cool and dim corona, with log L{sub X} /L{sub bol} = -8.2 (0.2-2.0 keV). Thus, it seems that {beta} Pictoris shares more characteristics with cool stars than previously thought.

  19. Evidence for the Magnetic Breakout Model in an Equatorial Coronal-hole Jet

    Science.gov (United States)

    Kumar, Pankaj; Karpen, Judith T.; Antiochos, Spiro K.; Wyper, Peter F.; DeVore, C. Richard; DeForest, Craig E.

    2018-02-01

    Small, impulsive jets commonly occur throughout the solar corona, but are especially visible in coronal holes. Evidence is mounting that jets are part of a continuum of eruptions that extends to much larger coronal mass ejections and eruptive flares. Because coronal-hole jets originate in relatively simple magnetic structures, they offer an ideal testbed for theories of energy buildup and release in the full range of solar eruptions. We analyzed an equatorial coronal-hole jet observed by the Solar Dynamics Observatory (SDO)/AIA on 2014 January 9 in which the magnetic-field structure was consistent with the embedded-bipole topology that we identified and modeled previously as an origin of coronal jets. In addition, this event contained a mini-filament, which led to important insights into the energy storage and release mechanisms. SDO/HMI magnetograms revealed footpoint motions in the primary minority-polarity region at the eruption site, but show negligible flux emergence or cancellation for at least 16 hr before the eruption. Therefore, the free energy powering this jet probably came from magnetic shear concentrated at the polarity inversion line within the embedded bipole. We find that the observed activity sequence and its interpretation closely match the predictions of the breakout jet model, strongly supporting the hypothesis that the breakout model can explain solar eruptions on a wide range of scales.

  20. Mode Conversion of a Solar Extreme-ultraviolet Wave over a Coronal Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Zong, Weiguo [Key Laboratory of Space Weather, National Center for Space Weather, China Meteorological Administration, Beijing 100081 (China); Dai, Yu, E-mail: ydai@nju.edu.cn [Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210023 (China)

    2017-01-10

    We report on observations of an extreme-ultraviolet (EUV) wave event in the Sun on 2011 January 13 by Solar Terrestrial Relations Observatory and Solar Dynamics Observatory in quadrature. Both the trailing edge and the leading edge of the EUV wave front in the north direction are reliably traced, revealing generally compatible propagation velocities in both perspectives and a velocity ratio of about 1/3. When the wave front encounters a coronal cavity near the northern polar coronal hole, the trailing edge of the front stops while its leading edge just shows a small gap and extends over the cavity, meanwhile getting significantly decelerated but intensified. We propose that the trailing edge and the leading edge of the northward propagating wave front correspond to a non-wave coronal mass ejection component and a fast-mode magnetohydrodynamic wave component, respectively. The interaction of the fast-mode wave and the coronal cavity may involve a mode conversion process, through which part of the fast-mode wave is converted to a slow-mode wave that is trapped along the magnetic field lines. This scenario can reasonably account for the unusual behavior of the wave front over the coronal cavity.