WorldWideScience

Sample records for atmosphere coronal heating

  1. Episodic coronal heating

    International Nuclear Information System (INIS)

    A study is made of the observational consequences of the hypothesis that there is no steady coronal heating, the solar corona instead being heated episodically, such that each short burst of heating is followed by a long period of radiative cooling. The form of the resulting contribution to the differential emission measure (DEM), and to a convenient related function (the differential energy flux, DEF) is calculated. Observational data for the quiet solar atmosphere indicate that the upper branch of the DEM, corresponding to temperatures above 100,000 K, can be interpreted in terms of episodic energy injection at coronal temperatures. 22 refs

  2. Episodic coronal heating

    Science.gov (United States)

    Sturrock, P. A.; Dixon, W. W.; Klimchuk, J. A.; Antiochos, S. K.

    1990-01-01

    A study is made of the observational consequences of the hypothesis that there is no steady coronal heating, the solar corona instead being heated episodically, such that each short burst of heating is followed by a long period of radiative cooling. The form of the resulting contribution to the differential emission measure (DEM), and to a convenient related function (the differential energy flux, DEF) is calculated. Observational data for the quiet solar atmosphere indicate that the upper branch of the DEM, corresponding to temperatures above 100,000 K, can be interpreted in terms of episodic energy injection at coronal temperatures.

  3. Mechanisms of Coronal Heating

    Indian Academy of Sciences (India)

    S. R. Verma

    2006-06-01

    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 corona. Recent observations show that Magnetic Carpet is a potential candidate for solar coronal heating.

  4. Characterisation of small-scale heating events in the solar atmosphere from 3D MHD simulations and their potential role in coronal heating

    Science.gov (United States)

    Haberreiter, M.; Guerreiro, N.; Hansteen, V. H.; Schmutz, W. K.

    2015-12-01

    The physical mechanism that heats the solar corona is one of the still open science questions in solar physics. One of the proposed mechanism for coronal heating are nanoflares. To investigate their role in coronal heating we study the properties of the small-scale heating events in the solar atmosphere using 3D MHD simulations. We present a method to identify and track these heating events in time which allows us to study their life time, energy, and spectral signatures. These spectal signatures will be compared with available spectrosopic observations obtained with IRIS and SUMER. Ultimately, these results will be important for the coordinated scientific exploitation of SPICE and EUI along with other instruments onboard Solar Orbiter to address the coronal heating problem.

  5. Recent advances in coronal heating

    CERN Document Server

    De Moortel, Ineke

    2015-01-01

    The solar corona, the tenuous outer atmosphere of the Sun, is orders of magnitude hotter than the solar surface. This 'coronal heating problem' requires the identification of a heat source to balance losses due to thermal conduction, radiation and (in some locations) convection. The review papers in this Theo Murphy meeting issue present an overview of recent observational findings, large- and small-scale numerical modelling of physical processes occurring in the solar atmosphere and other aspects which may affect our understanding of the proposed heating mechanisms. At the same time, they also set out the directions and challenges which must be tackled by future research. In this brief introduction, we summarize some of the issues and themes which reoccur throughout this issue.

  6. On Tripolar Magnetic Reconnection and Coronal Heating

    CERN Document Server

    Pandey, K; Lohani, N K; Pandey, Kumud; Narain, Udit

    2003-01-01

    Using recent data for the photosphere-chromosphere region of the solar atmosphere the magnetic reconnection in tripolar geometry has been investigated through the procedure of Sturrock (1999). Particular attention has been given to the width of the reconnecting region, wave number of the rapidly growing tearing mode, island length scales, frequency of MHD fluctuations, tearing mode growth rate, energy dissipation rate and minimum magnetic field strength required to heat chromospheric plasma to coronal temperatures. It is found that small length scales are formed in the upper chromosphere. The maximum growth rate of tearing mode instability coincides with the peak in the energy dissipation rate both of which occur in the upper chromosphere at the same height. It is realized that the distribution of magnetic field with height is essential for a better understanding of the coronal heating problem.

  7. Nonlinear Processes in Coronal Heating and Slow Solar Wind Acceleration

    CERN Document Server

    Rappazzo, A F

    2010-01-01

    This work consists of two parts: the first devoted to the study of the heating of the magnetically confined Solar Corona, and the second to the acceleration of the Slow Solar Wind. Direct 3D reduced MHD simulations are presented. They model the heating of coronal loops in the solar atmosphere via the tangling of coronal field lines by photospheric footpoints motions within the framework of the "Parker scenario". We have derived scalings of physical quantities with loop length, and the ratio of photospheric to coronal Alfven velocities. The development of a turbulent dynamics makes the dissipation rate independent of the Reynolds number. The dynamics in physical space are desribed by weak turbulence, which develops when an MHD system is embedded in a strong axial magnetic field. The slow wind originates in and around the coronal streamer belt. The LASCO instrument onboard the SOHO spacecraft has observed plasma density enhancements forming beyond the cusp of a helmet streamer. Previous theoretical models for t...

  8. Coronal heating in coupled photosphere-chromosphere-coronal systems: turbulence and leakage

    CERN Document Server

    Verdini, Andrea; Velli, Marco

    2011-01-01

    Coronal loops act as resonant cavities for low frequency fluctuations that are transmitted from the deeper layers of the solar atmosphere and are amplified in the corona, triggering nonlinear interactions. However trapping is not perfect, some energy leaks down to the chromosphere, thus limiting the turbulence development and the associated heating. We consider the combined effects of turbulence and leakage in determining the energy level and associated heating rate in models of coronal loops which include the chromosphere and transition region. We use a piece-wise constant model for the Alfven speed and a Reduced MHD - Shell model to describe the interplay between turbulent dynamics in the direction perpendicular to the mean field and propagation along the field. Turbulence is sustained by incoming fluctuations which are equivalent, in the line-tied case, to forcing by the photospheric shear flows. While varying the turbulence strength, we compare systematically the average coronal energy level (E) and dissi...

  9. Role of Magnetic Carpet in Coronal Heating

    Indian Academy of Sciences (India)

    S. R. Verma; Diksha Chaudhary

    2008-03-01

    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 heating mechanisms are at work in the solar corona. The separate kinds of coronal loops may also be heated by different mechanisms. Using data from instruments onboard the Solar and Heliospheric Observatory (SOHO) and from the more recent Transition Region and Coronal Explorer (TRACE) scientists have identified small regions of mixed polarity, termed magnetic carpet contributing to solar activity on a short time scale. Magnetic loops of all sizes rise into the solar corona, arising from regions of opposite magnetic polarity in the photosphere. Energy released when oppositely directed magnetic fields meet in the corona is one likely cause for coronal heating. There is enough energy coming up from the loops of the “magnetic carpet” to heat the corona to its known temperature.

  10. Coronal Fourier power spectra: implications for coronal seismology and coronal heating

    CERN Document Server

    Ireland, Jack; Inglis, Andrew R

    2014-01-01

    The dynamics of regions of the solar corona are investigated using Atmospheric Imaging Assembly (AIA) 171\\AA\\ and 193\\AA\\ data. The coronal emission from the quiet Sun, coronal loop footprints, coronal moss, and from above a sunspot is studied. It is shown that the mean Fourier power spectra in these regions can be described by a power law at lower frequencies that tails to flat spectrum at higher frequencies, plus a Gaussian-shaped contribution that varies depending on the region studied. This Fourier spectral shape is in contrast to the commonly-held assumption that coronal time-series are well described by the sum of a long time-scale background trend plus Gaussian-distributed noise, with some specific locations also showing an oscillatory signal. The implications of this discovery to the field of coronal seismology and the automated detections of oscillations are discussed. The power law contribution to the shape of the Fourier power spectrum is interpreted as being due to the summation of a distribution ...

  11. Stellar activity and coronal heating: an overview of recent results

    Science.gov (United States)

    Testa, Paola; Saar, Steven H.; Drake, Jeremy J.

    2015-01-01

    Observations of the coronae of the Sun and of solar-like stars provide complementary information to advance our understanding of stellar magnetic activity, and of the processes leading to the heating of their outer atmospheres. While solar observations allow us to study the corona at high spatial and temporal resolution, the study of stellar coronae allows us to probe stellar activity over a wide range of ages and stellar parameters. Stellar studies therefore provide us with additional tools for understanding coronal heating processes, as well as the long-term evolution of solar X-ray activity. We discuss how recent studies of stellar magnetic fields and coronae contribute to our understanding of the phenomenon of activity and coronal heating in late-type stars. PMID:25897087

  12. Stellar Activity and Coronal Heating: an overview of recent results

    CERN Document Server

    Testa, Paola; Drake, Jeremy

    2015-01-01

    Observations of the coronae of the Sun and of solar-like stars provide complementary information to advance our understanding of stellar magnetic activity, and of the processes leading to the heating of their outer atmospheres. While solar observations allow us to study the corona at high spatial and temporal resolution, the study of stellar coronae allows us to probe stellar activity over a wide range of ages and stellar parameters. Stellar studies therefore provide us with additional tools for understanding coronal heating processes, as well as the long-term evolution of solar X-ray activity. We discuss how recent studies of stellar magnetic fields and coronae contribute to our understanding of the phenomenon of activity and coronal heating in late-type stars.

  13. Microflares as Possible Sources for Coronal Heating

    Indian Academy of Sciences (India)

    Meera Gupta; Rajmal Jain; Jayshree Trivedi; A. P. Mishra

    2008-03-01

    We present a preliminary study of 27 microflares observed by Solar X-ray Spectrometer (SOXS) mission during July 2003 to August 2006. We found that all 27 microflares show the Fe-line feature peaking around 6.7 keV, which is an indicator of the presence of coronal plasma temperature ≥ 9 MK. On the other hand, the spectra of microflares showhybrid model of thermal and non-thermal emission, which further supports them as possible sources of coronal heating. Our results based on the analysis show that the energy relapsed by the microflares is good enough for heating of the active corona. We discuss our results in the light of the hybrid model of microflares production.

  14. Network Coronal Bright Points: Coronal Heating Concentrations Found in the Solar Magnetic Network

    Science.gov (United States)

    Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.

    1998-01-01

    We examine the magnetic origins of coronal heating in quiet regions by combining SOHO/EIT Fe xii coronal images and Kitt Peak magnetograms. Spatial filtering of the coronal images shows a network of enhanced structures on the scale of the magnetic network in quiet regions. Superposition of the filtered coronal images on maps of the magnetic network extracted from the magnetograms shows that the coronal network does indeed trace and stem from the magnetic network. Network coronal bright points, the brightest features in the network lanes, are found to have a highly significant coincidence with polarity dividing lines (neutral lines) in the network and are often at the feet of enhanced coronal structures that stem from the network and reach out over the cell interiors. These results indicate that, similar to the close linkage of neutral-line core fields with coronal heating in active regions (shown in previous work), low-lying core fields encasing neutral lines in the magnetic network often drive noticeable coronal heating both within themselves (the network coronal bright points) and on more extended field lines rooted around them. This behavior favors the possibility that active core fields in the network are the main drivers of the heating of the bulk of the quiet corona, on scales much larger than the network lanes and cells.

  15. Particle Heating Resulting from Coronal Mass Ejection

    Science.gov (United States)

    Paul, Suman; Sundar De, Syam; Guha, Gautam

    2016-07-01

    Coronal Mass Ejection (CME) is a continuous phenomena occurring from the entire solar coronal zone responsible for the outflow of solar masses, viz., protons, electrons, neutrons and solar wind in the form of plasma. These perturb the Earth's atmosphere via magnetopause. Very high temperature plasma generator in the solar atmosphere produces huge magnetic dipoles with intense magnetic field. It traps the energetic charged particles released from the solar corona. These particles gyrate along the magnetic field lines and are gradually elongated outwards from the Sun. Due to this, the field lines get detached at some critical limit thereby enhancing the magnetic reconnection with the interplanetary magnetic field releasing huge energy in the form of X-rays and γ-rays. This perturbs the Earth's atmosphere. In this work, the situation has been investigated by momentum balance equation, energy balance equation along with the equations of continuity and states. From the analyses, the dispersive nature of the thermospheric medium is studied. Variation of normalized electron temperature with dimensionless time has been critically contemplated. The altitude dependent electric field in the medium is also investigated.

  16. 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.

  17. Coronal Heating versus Solar Wind Acceleration

    OpenAIRE

    Cranmer, Steven R.

    2004-01-01

    Parker's initial insights from 1958 provided a key causal link between the heating of the solar corona and the acceleration of the solar wind. However, we still do not know what fraction of the solar wind's mass, momentum, and energy flux is driven by Parker-type gas pressure gradients, and what fraction is driven by, e.g., wave-particle interactions or turbulence. SOHO has been pivotal in bringing these ideas back to the forefront of coronal and solar wind research. This paper reviews our cu...

  18. Coronal Heating versus Solar Wind Acceleration

    CERN Document Server

    Cranmer, S R

    2004-01-01

    Parker's initial insights from 1958 provided a key causal link between the heating of the solar corona and the acceleration of the solar wind. However, we still do not know what fraction of the solar wind's mass, momentum, and energy flux is driven by Parker-type gas pressure gradients, and what fraction is driven by, e.g., wave-particle interactions or turbulence. SOHO has been pivotal in bringing these ideas back to the forefront of coronal and solar wind research. This paper reviews our current understanding of coronal heating in the context of the acceleration of the fast and slow solar wind. For the fast solar wind, a recent model of Alfven wave generation, propagation, and non-WKB reflection is presented and compared with UVCS, SUMER, radio, and in-situ observations at the last solar minimum. The derived fractions of energy and momentum addition from thermal and nonthermal processes are found to be consistent with various sets of observational data. For the more chaotic slow solar wind, the relative rol...

  19. Numerical Simulation of DC Coronal Heating

    Science.gov (United States)

    Dahlburg, Russell B.; Einaudi, G.; Taylor, Brian D.; Ugarte-Urra, Ignacio; Warren, Harry; Rappazzo, A. F.; Velli, Marco

    2016-05-01

    Recent research on observational signatures of turbulent heating of a coronal loop will be discussed. The evolution of the loop is is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. HYPERION calculates the full energy cycle involving footpoint convection, magnetic reconnection, nonlinear thermal conduction and optically thin radiation. The footpoints of the loop magnetic field are convected by random photospheric 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 non-uniformly distributed so that only a fraction of thecoronal mass and volume gets heated at any time. Temperature and density are highly structured at scales which, in the solar corona, remain observationally unresolved: the plasma of the simulated loop is multi thermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at sub-observational scales. Typical simulated coronal loops are 50000 km length and have axial magnetic field intensities ranging from 0.01 to 0.04 Tesla. To connect these simulations to observations the computed number densities and temperatures are used to synthesize the intensities expected in emission lines typically observed with the Extreme ultraviolet Imaging Spectrometer (EIS) on Hinode. These intensities are then employed to compute differential emission measure distributions, which are found to be very similar to those derived from observations of solar active regions.

  20. Quiet Sun coronal heating statistical model

    CERN Document Server

    Krasnoselskikh, V V; Lefebvre, B; Vilmer, N

    2002-01-01

    To describe statistical properties of solar coronal heating by microflares, nanoflares, and even smaller events, we consider a cellular automata model subject to uniform small scale driving and dissipation. The model consists of two elements, the magnetic field source supposed to be associated with the small scale hydrodynamic turbulence convected from the photosphere and local dissipation of small scale currents. The dissipation is assumed to be provided by either anomalous resistivity, when the current density exceeds a certain threshold value, or by the magnetic reconnection. The main problem considered is how the statistical characteristics of dissipated energy flow depend upon characteristics of the magnetic field source and on physical mechanism responsible for the magnetic field dissipation. As the threshold value of current is increased, we observe the transition from Gaussian statistics to power-law type. In addition, we find that the dissipation provided by reconnection results in stronger deviation...

  1. 3d Nonlinear-Wave Heating of Coronal Loops

    NARCIS (Netherlands)

    Poedts, S.; Goedbloed, J. P.

    1994-01-01

    The heating of solar coronal loops by the resonant absorption or phase-mixing of incident wave energy is investigated in the framework of 3D nonlinear magnetohydrodynamics (MHD) by means of numerical simulations.

  2. Turbulent Coronal Heating Mechanisms: Coupling of Dynamics and Thermodynamics

    CERN Document Server

    Dahlburg, R B; Rappazzo, A F; Velli, M

    2012-01-01

    Context. Photospheric motions shuffle the footpoints of the strong axial magnetic field that threads coronal loops giving rise to turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned current sheets where energy is deposited at small-scales and the heating occurs. Previous studies show that current sheets thickness is orders of magnitude smaller than current state of the art observational resolution (~700 km). Aim. In order to understand coronal heating and interpret correctly observations it is crucial to study the thermodynamics of such a system where energy is deposited at unresolved small-scales. Methods. Fully compressible three-dimensional magnetohydrodynamic simulations are carried out to understand the thermodynamics of coronal heating in the magnetically confined solar corona. Results. We show that temperature is highly structured at scales below observational resolution and nonhomogeneously distributed so that only a fraction of the coronal mass and ...

  3. Wave heating of the solar atmosphere.

    Science.gov (United States)

    Arregui, Iñigo

    2015-05-28

    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. PMID:25897091

  4. Wave heating of the solar atmosphere.

    Science.gov (United States)

    Arregui, Iñigo

    2015-05-28

    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.

  5. 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

  6. Evidence of Non-Thermal Particles in Coronal Loops Heated Impulsively by Nanoflares

    CERN Document Server

    Testa, Paola; Allred, Joel; Carlsson, Mats; Reale, Fabio; Daw, Adrian; Hansteen, Viggo; Martinez-Sykora, Juan; Liu, Wei; DeLuca, Ed; Golub, Leon; McKillop, Sean; Reeves, Kathy; Saar, Steve; Tian, Hui; Lemen, Jim; Title, Alan; Boerner, Paul; Hurlburt, Neal; Tarbell, Ted; Wuelser, J P; Kleint, Lucia; Kankelborg, Charles; Jaeggli, Sarah

    2014-01-01

    The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (about 20 to 60 seconds) of intensity and velocity on small spatial scales at the footpoints of hot dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of non-thermal electrons, which are generated in small impulsive heating events called "coronal nanoflares". The accelerated electrons deposit a sizable fraction of their energy in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.

  7. Parallel-cascade-based mechanisms for heating solar coronal loops: test against observations

    CERN Document Server

    Li, Bo; Li, Xing; Xia, Li-Dong

    2014-01-01

    The heating of solar coronal loops is at the center of the problem of coronal heating. Given that the origin of the fast solar wind has been tracked down to atmospheric layers with transition region or even chromospheric temperatures, it is worthy attempting to address whether the mechanisms proposed to provide the basal heating of the solar wind apply to coronal loops as well. We extend the loop studies based on a classical parallel-cascade scenario originally proposed in the solar wind context by considering the effects of loop expansion, and perform a parametric study to directly contrast the computed loop densities and electron temperatures with those measured by TRACE and YOHKOH/SXT. This comparison yields that with the wave amplitudes observationally constrained by SUMER measurements, while the computed loops may account for a significant fraction of SXT loops, they seem too hot when compared with TRACE loops. Lowering the wave amplitudes does not solve this discrepancy, introducing magnetic twist will ...

  8. On the relationship between photospheric footpoint motions and coronal heating in solar active regions

    International Nuclear Information System (INIS)

    Coronal heating theories can be classified as either direct current (DC) or alternating current (AC) mechanisms, depending on whether the coronal magnetic field responds quasi-statically or dynamically to the photospheric footpoint motions. In this paper we investigate whether photospheric footpoint motions with velocities of 1-2 km s–1 can heat the corona in active regions, and whether the corona responds quasi-statically or dynamically to such motions (DC versus AC heating). We construct three-dimensional magnetohydrodynamic models for the Alfvén waves and quasi-static perturbations generated within a coronal loop. We find that in models where the effects of the lower atmosphere are neglected, the corona responds quasi-statically to the footpoint motions (DC heating), but the energy flux into the corona is too low compared to observational requirements. In more realistic models that include the lower atmosphere, the corona responds more dynamically to the footpoint motions (AC heating) and the predicted heating rates due to Alfvén wave turbulence are sufficient to explain the observed hot loops. The higher heating rates are due to the amplification of Alfvén waves in the lower atmosphere. We conclude that magnetic braiding is a highly dynamic process.

  9. Closed Field Coronal Heating Models Inspired by Wave Turbulence

    Science.gov (United States)

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

    2013-12-01

    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 dissipation (WTD) phenomenology for the heating of closed coronal loops. To do so, we employ an implementation of non-WKB equations 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 equations in 1D for an idealized loop, and the relevance to a range of solar conditions is established by computing solutions for several 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 realistic heating scale heights and thermal non-equilibrium cycles is discussed, and preliminary 3D thermodynamic MHD simulations using this formulation are presented. Research supported by NASA and NSF.

  10. Coronal Heating and the Magnetic Flux Content of the Network

    Science.gov (United States)

    Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Previously, from analysis of SOHO/EIT coronal images in combination with Kitt Peak magnetograms (Falconer et al 1998, ApJ, 501, 386-396), we found that the quiet corona is the sum of two components: the e-scale corona and the coronal network. The large-scale corona consists of all coronal-temperature (T approx. 10(exp 6) K) structures larger than supergranules (>approx.30,000 km). The coronal network (1) consists of all coronal-temperature structures smaller than supergranules, (2) is rooted in and loosely traces the photospheric magnetic network, (3) has its brightest features seated on polarity dividing fines (neutral lines) in the network magnetic flux, and (4) produces only about 5% of the total coronal emission in quiet regions. The heating of the coronal network is apparently magnetic in origin. Here, from analysis of EIT coronal images of quiet regions in combination with magnetograms of the same quiet regions from SOHO/MDI and from Kitt Peak, we examine the other 95% of the quiet corona and its relation to the underlying magnetic network. We find: (1) Dividing the large-scale corona into its bright and dim halves divides the area into bright "continents" and dark "oceans" having spans of 2-4 supergranules. (2) These patterns are also present in the photospheric magnetograms: the network is stronger under the bright half and weaker under the dim half. (3) The radiation from the large-scale corona increases roughly as the cube root of the magnetic flux content of the underlying magnetic network. In contrast, Fisher et A (1998, ApJ, 508, 985-998) found that the coronal radiation from an active region increases roughly linearly with the magnetic flux content of the active region. We assume, as is widely held, that nearly all of the large-scale corona is magnetically rooted in the network. Our results, together with the result of Fisher et al (1999), suggest that either the coronal heating in quiet regions has a large non-magnetic component, or, if the heating

  11. COMBINING PARTICLE ACCELERATION AND CORONAL HEATING VIA DATA-CONSTRAINED CALCULATIONS OF NANOFLARES IN CORONAL LOOPS

    International Nuclear Information System (INIS)

    We model nanoflare heating of extrapolated active-region coronal loops via the acceleration of electrons and protons in Harris-type current sheets. The kinetic energy of the accelerated particles is estimated using semi-analytical and test-particle-tracing approaches. Vector magnetograms and photospheric Doppler velocity maps of NOAA active region 09114, recorded by the Imaging Vector Magnetograph, were used for this analysis. A current-free field extrapolation of the active-region corona was first constructed. The corresponding Poynting fluxes at the footpoints of 5000 extrapolated coronal loops were then calculated. Assuming that reconnecting current sheets develop along these loops, we utilized previous results to estimate the kinetic energy gain of the accelerated particles. We related this energy to nanoflare heating and macroscopic loop characteristics. Kinetic energies of 0.1-8 keV (for electrons) and 0.3-470 keV (for protons) were found to cause heating rates ranging from 10–6 to 1 erg s–1 cm–3. Hydrodynamic simulations show that such heating rates can sustain plasma in coronal conditions inside the loops and generate plasma thermal distributions that are consistent with active-region observations. We concluded the analysis by computing the form of X-ray spectra generated by the accelerated electrons using the thick-target approach. These spectra were found to be in agreement with observed X-ray spectra, thus supporting the plausibility of our nanoflare-heating scenario.

  12. Competition between shock and turbulent heating in coronal loop system

    Science.gov (United States)

    Matsumoto, Takuma

    2016-11-01

    2.5-dimensional magnetohydrodynamic (MHD) simulations are performed with high spatial resolution in order to distinguish between competing models of the coronal heating problem. A single coronal loop powered by Alfvén waves excited in the photosphere is the target of this study. The coronal structure is reproduced in our simulations as a natural consequence of the transportation and dissipation of Alfvén waves. Further, the coronal structure is maintained as the spatial resolution is changed from 25 to 3 km, although the temperature at the loop top increases with the spatial resolution. The heating mechanisms change gradually across the magnetic canopy at a height of 4 Mm. Below the magnetic canopy, both the shock and the MHD turbulence are dominant heating processes. Above the magnetic canopy, the shock heating rate reduces to less than 10 per cent of the total heating rate while the MHD turbulence provides significant energy to balance the radiative cooling and thermal conduction loss or gain. The importance of compressibility shown in this study would significantly impact on the prospects of successful MHD turbulence theory in the solar chromosphere.

  13. Competition between shock and turbulent heating in coronal loop system

    Science.gov (United States)

    Matsumoto, Takuma

    2016-08-01

    2.5-dimensional magnetohydrodynamic (MHD) simulations are performed with high spatial resolution in order to distinguish between competing models of the coronal heating problem. A single coronal loop powered by Alfvén waves excited in the photosphere is the target of the present study. The coronal structure is reproduced in our simulations as a natural consequence of the transportation and dissipation of Alfvén waves. Further, the coronal structure is maintained as the spatial resolution is changed from 25 to 3 km, although the temperature at the loop top increases with the spatial resolution. The heating mechanisms change gradually across the magnetic canopy at a height of 4 Mm. Below the magnetic canopy, both the shock and the MHD turbulence are dominant heating processes. Above the magnetic canopy, the shock heating rate reduces to less than 10 % of the total heating rate while the MHD turbulence provides significant energy to balance the radiative cooling and thermal conduction loss or gain. The importance of compressibility shown in the present study would significantly impact on the prospects of successful MHD turbulence theory in the solar chromosphere.

  14. Competition between shock and turbulent heating in coronal loop system

    CERN Document Server

    Matsumoto, Takuma

    2016-01-01

    2.5-dimensional magnetohydrodynamic (MHD) simulations are performed with high spatial resolution in order to distinguish between competing models of the coronal heating problem. A single coronal loop powered by Alfv\\'{e}n waves excited in the photosphere is the target of the present study. The coronal structure is reproduced in our simulations as a natural consequence of the transportation and dissipation of Alfv\\'{e}n waves. Further, the coronal structure is maintained as the spatial resolution is changed from 25 to 3 km, although the temperature at the loop top increases with the spatial resolution. The heating mechanisms change gradually across the magnetic canopy at a height of 4 Mm. Below the magnetic canopy, both the shock and the MHD turbulence are dominant heating processes. Above the magnetic canopy, the shock heating rate reduces to less than 10 % of the total heating rate while the MHD turbulence provides significant energy to balance the radiative cooling and thermal conduction loss or gain. The i...

  15. Closed-Field Coronal Heating Driven by Wave Turbulence

    CERN Document Server

    Downs, Cooper; Mikić, Zoran; Linker, Jon A; Velli, Marco

    2016-01-01

    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 traditiona...

  16. A new way to convert Alfven waves into heat in solar coronal holes - Intermittent magnetic levitation

    Science.gov (United States)

    Moore, R. L.; Hammer, R.; Musielak, Z. E.; Suess, S. T.; An, C.-H.

    1992-01-01

    In our recent analysis of Alfven wave reflection in solar coronal holes, we found evidence that coronal holes are heated by reflected Alfven waves. This result suggests that the reflection is inherent to the process that dissipates these Alfven waves into heat. We propose a novel dissipation process that is driven by the reflection, and that plausibly dominates the heating in coronal holes.

  17. An Impulsive Heating Model for the Evolution of Coronal Loops

    Institute of Scientific and Technical Information of China (English)

    Li Feng; Wei-Qun Gan

    2006-01-01

    It was suggested by Parker that the solar corona is heated by many small energy release events generally called microflares or nanoflares. More and more observations showed flows and intensity variations in nonflaring loops. Both theories and observations have indicated that the heating of coronal loops should actually be unsteady. Using SOLFTM (Solar Flux Tube Model), we investigate the hydrodynamics of coronal loops undergoing different manners of impulsive heating with the same total energy deposition. The half length of the loops is 110 Mm, a typical length of active region loops. We divide the loops into two categories: loops that experience catastrophic cooling and loops that do not. It is found that when the nanoflare heating sources are in the coronal part, the loops are in non-catastrophic-cooling state and their evolutions are similar. When the heating is localized below the transition region, the loops evolve in quite different ways. It is shown that with increasing number of heating pulses and inter-pulse time, the catastrophic cooling is weakened, delayed, or even disappears altogether.

  18. A data driven kinetic approach to coronal heating

    CERN Document Server

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

    2016-01-01

    Coronal heating through the explosive release of magnetic energy remains an open problem in solar physics. Several one-dimensional hydrodynamical models have been developed over the last decade, using simple approaches for the way energy is deposited and transported in the coronal plasma, namely by inserting 'nanoflares' in the form of 'hot spots' at random sites and times. Our aim in this work is to investigate the problem from a different perspective. With the help of a nonlinear force-free extrapolation method we reconstruct the coronal magnetic field of a well-studied solar active region using an observed photospheric vector magnetogram of the region as the required boundary condition. We then determine the locations, energy contents, and volumes of unstable areas within the active-region corona. These areas include strong gradients in the magnetic field and are naturally connected to three-dimensional current sheets. The statistical distributions of these volumes, their fractal structure and correspondin...

  19. Nonlinear Dynamics of the Parker Scenario for Coronal Heating

    CERN Document Server

    Rappazzo, A F; Einaudi, G; Dahlburg, R B

    2007-01-01

    The Parker or field line tangling model of coronal heating is studied comprehensively via long-time high-resolution simulations of the dynamics of a coronal loop in cartesian geometry within the framework of reduced magnetohydrodynamics (RMHD). Slow photospheric motions induce a Poynting flux which saturates by driving an anisotropic turbulent cascade dominated by magnetic energy. In physical space this corresponds to a magnetic topology where magnetic field lines are barely entangled, nevertheless current sheets (corresponding to the original tangential discontinuities hypothesized by Parker) are continuously formed and dissipated. Current sheets are the result of the nonlinear cascade that transfers energy from the scale of convective motions ($\\sim 1,000 km$) down to the dissipative scales, where it is finally converted to heat and/or particle acceleration. Current sheets constitute the dissipative structure of the system, and the associated magnetic reconnection gives rise to impulsive ``bursty'' heating ...

  20. Parametrization of coronal heating: spatial distribution and observable consequences

    CERN Document Server

    van Wettum, T; Peter, H

    2013-01-01

    We investigate the difference in the spatial distribution of the energy input for parametrizations of different mechanisms to heat the corona of the Sun and possible impacts on the coronal emission. We use a 3D MHD model of a solar active region as a reference and compare the Ohmic-type heating in this model to parametrizations for alternating current (AC) and direct current (DC) heating models, in particular, we use Alfven wave and MHD turbulence heating. We extract the quantities needed for these two parametrizations from the reference model and investigate the spatial distribution of the heat input in all three cases, globally and along individual field lines. To study differences in the resulting coronal emission we employ 1D loop models with a prescribed heat input based on the heating rate we extracted along a bundle of field lines. On average, all heating implementations show a roughly drop of the heating rate with height. This also holds for individual field lines. While all mechanism show a concentra...

  1. What can large-scale magnetohydrodynamic numerical experiments tell us about coronal heating?

    Science.gov (United States)

    Peter, H

    2015-05-28

    The upper atmosphere of the Sun is governed by the complex structure of the magnetic field. This controls the heating of the coronal plasma to over a million kelvin. Numerical experiments in the form of three-dimensional magnetohydrodynamic simulations are used to investigate the intimate interaction between magnetic field and plasma. These models allow one to synthesize the coronal emission just as it would be observed by real solar instrumentation. Large-scale models encompassing a whole active region form evolving coronal loops with properties similar to those seen in extreme ultraviolet light from the Sun, and reproduce a number of average observed quantities. This suggests that the spatial and temporal distributions of the heating as well as the energy distribution of individual heat deposition events in the model are a good representation of the real Sun. This provides evidence that the braiding of fieldlines through magneto-convective motions in the photosphere is a good concept to heat the upper atmosphere of the Sun.

  2. Nonlinear wave heating of solar coronal loops

    NARCIS (Netherlands)

    Poedts, S.; Goedbloed, J. P.

    1997-01-01

    The heating of magnetically closed structures (loops) in the solar corona by the resonant absorption of incident waves is studied by means of numerical simulations in the framework of nonlinear resistive magnetohydrodynamics (MHD). It is shown that the dynamics in the resonant layer is indeed very n

  3. Signatures of Steady Heating in Time Lag Analysis of Coronal Emission

    CERN Document Server

    Viall, Nicholeen M

    2016-01-01

    Among the many ways of investigating coronal heating, the time lag method of Viall & Klimchuk (2012) is becoming increasingly prevalent as an analysis technique complementary to those traditionally used. The time lag method cross correlates light curves at a given spatial location obtained in spectral bands that sample different temperature plasmas. It has been used most extensively with data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We have previously applied the time lag method to entire active regions and surrounding quiet Sun and create maps of the results (Viall & Klimchuk 2012; Viall & Klimchuk 2015). We find that the majority of time lags are consistent with the cooling of coronal plasma that has been impulsively heated. Additionally, a significant fraction of the map area has a time lag of zero. This does not indicate a lack of variability. Rather, strong variability must be present, and it must occur in phase in the different channels. We have shown previous...

  4. A Constrained Tectonics Model for Coronal Heating

    CERN Document Server

    Ng, C S; 10.1086/525518

    2011-01-01

    An analytical and numerical treatment is given of a constrained version of the tectonics model developed by Priest, Heyvaerts, & Title [2002]. We begin with an initial uniform magnetic field ${\\bf B} = B_0 \\hat{\\bf z}$ that is line-tied at the surfaces $z = 0$ and $z = L$. This initial configuration is twisted by photospheric footpoint motion that is assumed to depend on only one coordinate ($x$) transverse to the initial magnetic field. The geometric constraints imposed by our assumption precludes the occurrence of reconnection and secondary instabilities, but enables us to follow for long times the dissipation of energy due to the effects of resistivity and viscosity. In this limit, we demonstrate that when the coherence time of random photospheric footpoint motion is much smaller by several orders of magnitude compared with the resistive diffusion time, the heating due to Ohmic and viscous dissipation becomes independent of the resistivity of the plasma. Furthermore, we obtain scaling relations that su...

  5. Plasma Heating Suring a Coronal Mass Ejection Observed by SOHO

    CERN Document Server

    Murphy, N A; Korreck, K E

    2011-01-01

    We perform a time-dependent ionization analysis to constrain plasma heating requirements during a fast partial halo coronal mass ejection (CME) observed on 2000 June 28 by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO). We use two methods to derive densities from the UVCS measurements, including a density sensitive O V line ratio at 1213.85 and 1218.35 Angstroms, and radiative pumping of the O VI 1032,1038 doublet by chromospheric emission lines. The most strongly constrained feature shows cumulative plasma heating comparable to or greater than the kinetic energy, while features observed earlier during the event show cumulative plasma heating comparable to or less than the kinetic energy. SOHO Michelson Doppler Imager (MDI) observations are used to estimate the active region magnetic energy. We consider candidate plasma heating mechanisms and provide constraints when possible. Because this CME was associated with a relatively weak flare, the contribution b...

  6. Signatures of Steady Heating in Time Lag Analysis of Coronal Emission

    Science.gov (United States)

    Viall, Nicholeen M.; Klimchuk, James A.

    2016-09-01

    Among the multitude of methods used to investigate coronal heating, the time lag method of Viall & Klimchuk is becoming increasingly prevalent as an analysis technique that is complementary to those that are traditionally used. The time lag method cross correlates light curves at a given spatial location obtained in spectral bands that sample different temperature plasmas. It has been used most extensively with data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We have previously applied the time lag method to entire active regions and surrounding the quiet Sun and created maps of the results. We find that the majority of time lags are consistent with the cooling of coronal plasma that has been impulsively heated. Additionally, a significant fraction of the map area has a time lag of zero. This does not indicate a lack of variability. Rather, strong variability must be present, and it must occur in phase between the different channels. We have previously shown that these zero time lags are consistent with the transition region response to coronal nanoflares, although other explanations are possible. A common misconception is that the zero time lag indicates steady emission resulting from steady heating. Using simulated and observed light curves, we demonstrate here that highly correlated light curves at zero time lag are not compatible with equilibrium solutions. Such light curves can only be created by evolution.

  7. Alfven Wave Solar Model: Part 1, Coronal Heating

    CERN Document Server

    van der Holst, Bart; Meng, Xing; Jin, Meng; Manchester, Ward B; Toth, Gabor; Gombosi, Tamas I

    2013-01-01

    We present the new Alfven Wave Solar Model (AWSoM), a global model from the upper chromosphere to the corona and the heliosphere. The coronal heating and solar wind acceleration are addressed with low-frequency Alfven wave turbulence. The injection of Alfven wave energy at the inner boundary is such that the Poynting flux is proportional to the magnetic field strength. The three-dimensional magnetic field topology is simulated using data from photospheric magnetic field measurements. This model does not impose open-closed magnetic field boundaries; those develop self-consistently. The physics includes: (1) The model employs three different temperatures, namely the isotropic electron temperature and the parallel and perpendicular ion temperatures. The firehose, mirror, and ion-cyclotron instabilities due to the developing ion temperature anisotropy are accounted for. (2) The Alfven waves are partially reflected by the Alfven speed gradient and the vorticity along the field lines. The resulting counter-propagat...

  8. The Spatial and Temporal Dependence of Coronal Heating by Alfven Wave Turbulence

    CERN Document Server

    Asgari-Targhi, M; Cranmer, S R; DeLuca, E E

    2013-01-01

    The solar atmosphere may be heated by Alfven waves that propagate up from the convection zone and dissipate their energy in the chromosphere and corona. To further test this theory, we consider wave heating in an active region observed on 2012 March 7. A potential field model of the region is constructed, and 22 field lines representing observed coronal loops are traced through the model. Using a three-dimensional (3D) reduced magneto-hydrodynamics (MHD) code, we simulate the dynamics of Alfven waves in and near the observed loops. The results for different loops are combined into a single formula describing the average heating rate Q as function of position within the observed active region. We suggest this expression may be approximately valid also for other active regions, and therefore may be used to construct 3D, time-dependent models of the coronal plasma. Such models are needed to understand the role of thermal non-equilibrium in the structuring and dynamics of the Sun's corona.

  9. Numerical Simulations of Coronal Heating through Footpoint Braiding

    CERN Document Server

    Hansteen, Viggo; De Pontieu, Bart; Carlsson, Mats

    2015-01-01

    Advanced 3D radiative MHD simulations now reproduce many properties of the outer solar atmosphere. When including a domain from the convection zone into the corona, a hot chromosphere and corona are self-consistently maintained. Here we study two realistic models, with different simulated area, magnetic field strength and topology, and numerical resolution. These are compared in order to characterize the heating in the 3D-MHD simulations which self-consistently maintains the structure of the atmosphere. We analyze the heating at both large and small scales and find that heating is episodic and highly structured in space, but occurs along loop shaped structures, and moves along with the magnetic field. On large scales we find that the heating per particle is maximal near the transition region and that widely distributed opposite-polarity field in the photosphere leads to a greater heating scale height in the corona. On smaller scales, heating is concentrated in current sheets, the thicknesses of which are set ...

  10. The mystery of coronal heating%日冕反常加热之谜新解

    Institute of Scientific and Technical Information of China (English)

    谭宝林

    2016-01-01

    日冕加热之谜是当代天文学、天体物理学中的八大难题之一。自日冕高温发现七十多年以来,人们建立了许多模型试图解决这一难题,但到目前为止,现有的模型几乎都无法给出一个完整的解答。近年来,人们从观测上取得了一系列新的发现,如从光球到日冕的超精细磁通道中的快速上升热流、二型针状体、极紫外龙卷风等。这些发现给我们一个新的启示,即日冕的加热能量很可能是直接通过热物质上升并在日冕区域沉积而实现的。但是,这些上升热流又是如何形成的呢?鉴于太阳大气中普遍存在具有磁场梯度的磁通量管,作者最近提出了磁场梯度抽运机制(magnetic gradient pumping mechanism, MGP),每一磁通量管就像一个抽水机一般,将底层热分布的等离子体中的高能端粒子抽运到高层大气中沉积,并最终形成了高温的日冕大气。这一机制为我们探索日冕加热之谜提供了一个新的思路。%The problem of coronal heating is one the eight key mysteries in modern as-tronomy and astrophysics. Since the discovery of extremely hot corona more than 70 years ago, many theoretical models have attempted to explain this mystery. However, so far no model can ex-plain the coronal heating process perfectly. Recently, there have been several new discoveries, such as the observation of hot plasma ejections along the ultrafine magnetic channels from the so-lar surface upward to the corona, hot upflows of type II spicules, magnetic tornados, and EUV cy-clones, which imply that the hot corona may be heated by hot plasma upflows directly from the underlying atmosphere. But how do these hot upflows form? We notice the fact that the magnetic gradient is ubiquitous in the whole solar atmosphere, based on which we have proposed a new the-oretical model, the magnetic-gradient pumping mechanism, to explain the coronal heating pro-cess. In this

  11. 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.

  12. EUV flickering of solar coronal loops: a new diagnostic of coronal heating

    CERN Document Server

    Tajfirouze, E; Peres, G; Testa, P

    2016-01-01

    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 A and 335 A 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 A channel and, viceversa, from the top to the bottom in the 335 A channel. This prediction is confirmed by the observation of a set of aligned neighbouring pixels along a bright arc of an active region core. Maps of pixel fluctuations may therefore provide easy diagnostics of nano-flaring ...

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

    International Nuclear Information System (INIS)

    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–1 in the chromosphere and about 130 km s–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.

  14. OBSERVATION OF HEATING BY FLARE-ACCELERATED ELECTRONS IN A SOLAR CORONAL MASS EJECTION

    International Nuclear Information System (INIS)

    We report a Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observation of flare-accelerated electrons in the core of a coronal mass ejection (CME) and examine their role in heating the CME. Previous CME observations have revealed remarkably high thermal energies that can far surpass the CME's kinetic energy. A joint observation by RHESSI and the Atmospheric Imaging Assembly of a partly occulted flare on 2010 November 3 allows us to test the hypothesis that this excess energy is collisionally deposited by flare-accelerated electrons. Extreme ultraviolet (EUV) images show an ejection forming the CME core and sheath, with isothermal multifilter analysis revealing temperatures of ∼11 MK in the core. RHESSI images reveal a large (∼100 × 50 arcsec2) hard X-ray (HXR) source matching the location, shape, and evolution of the EUV plasma, indicating that the emerging CME is filled with flare-accelerated electrons. The time derivative of the EUV emission matches the HXR light curve (similar to the Neupert effect observed in soft and HXR time profiles), directly linking the CME temperature increase with the nonthermal electron energy loss, while HXR spectroscopy demonstrates that the nonthermal electrons contain enough energy to heat the CME. This is the most direct observation to date of flare-accelerated electrons heating a CME, emphasizing the close relationship of the two in solar eruptive events

  15. ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF CORONAL LOOPS: CROSS-FIELD TEMPERATURE DISTRIBUTIONS

    International Nuclear Information System (INIS)

    We construct revised response functions for the Atmospheric Imaging Assembly (AIA) using the new atomic data, ionization equilibria, and coronal abundances available in CHIANTI 7.1. We then use these response functions in multithermal analysis of coronal loops, which allows us to determine a specific cross-field temperature distribution without ad hoc assumptions. Our method uses data from the six coronal filters and the Monte Carlo solutions available from our differential emission measure (DEM) analysis. The resulting temperature distributions are not consistent with isothermal plasma. Therefore, the observed loops cannot be modeled as single flux tubes and must be composed of a collection of magnetic strands. This result is now supported by observations from the High-resolution Coronal Imager, which show fine-scale braiding of coronal strands that are reconnecting and releasing energy. Multithermal analysis is one of the major scientific goals of AIA, and these results represent an important step toward the successful achievement of that goal. As AIA DEM analysis becomes more straightforward, the solar community will be able to take full advantage of the state-of-the-art spatial, temporal, and temperature resolution of the instrument.

  16. Fast Collisionless Reconnection Condition and Self-Organization of Solar Coronal Heating

    CERN Document Server

    Uzdensky, Dmitri A

    2007-01-01

    I propose that solar coronal heating is a self-regulating process that keeps the coronal plasma roughly marginally collisionless. The self-regulating mechanism is based on the interplay of two effects. First, plasma density controls coronal energy release via the transition between the slow collisional Sweet--Parker regime and the fast collisionless reconnection regime. This transition takes place when the Sweet--Parker layer becomes thinner than the characteristic collisionless reconnection scale. I present a simple criterion for this transition in terms of the upstream plasma density and magnetic field and the global length of the reconnection layer. Second, coronal energy release by reconnection raises the ambient plasma density via chromospheric evaporation and this, in turn, temporarily inhibits subsequent reconnection involving the newly-reconnected loops. Over time, however, radiative cooling gradually lowers the density again below the critical value and fast reconnection again becomes possible. As a ...

  17. Neutral-Line Magnetic Shear and Enhanced Coronal Heating in Solar Active Regions

    Science.gov (United States)

    Falconer, D. A.; Moore, R. L.; Porter, J. G.; Gary, G. A.; Shimizu, T.

    1997-01-01

    By examining the magnetic structure at sites in the bright coronal interiors of active regions that are not flaring but exhibit persistent strong coronal heating, we establish some new characteristics of the magnetic origins of this heating. We have examined the magnetic structure of these sites in five active regions, each of which was well observed by both the Yohkoh SXT and the Marshall Space Flight Center Vector Magnetograph and showed strong shear in its magnetic field along part of at least one neutral line (polarity inversion). Thus, we can assess whether this form of nonpotential field structure in active regions is a characteristic of the enhanced coronal heating and vice versa. From 27 orbits' worth of Yohkoh SXT images of the five active regions, we have obtained a sample of 94 persistently bright coronal features (bright in all images from a given orbit), 40 long (greater than or approximately equals 20,000 km) neutral-line segments having strong magnetic shear throughout (shear angle greater than 45 deg), and 39 long neutral-line segments having weak magnetic shear throughout (shear angle less than 45 deg). From this sample, we find that: (1) all of our persistently bright coronal features are rooted in magnetic fields that are stronger than 150 G; (2) nearly all (95%) of these enhanced coronal features are rooted near neutral lines (closer than 10,000 km); (3) a great majority (80%) of the bright features are rooted near strong-shear portions of neutral lines; (4) a great majority (85%) of long strong-shear segments of neutral lines have persistently bright coronal features rooted near them; (5) a large minority (40%) of long weak-shear segments of neutral lines have persistently bright coronal features rooted near them; and (6) the brightness of a persistently bright Coronal feature often changes greatly over a few hours. From these results, we conclude that most persistent enhanced heating of coronal loops in active regions: (1) requires the

  18. Feel the Burn: What accounts for spatial variations in coronal heating?

    Science.gov (United States)

    Atwood, Shane; Kankelborg, Charles C.

    2016-05-01

    The coronal volume is filled with magnetic field, yet only part of that volume has sufficient heating to exhibit hot x-ray loops. How does the Sun decide where the heat goes? Using XRT and AIA images and HMI magnetograms, we identify footpoints of hot coronal loops, and magnetically similar regions underlying relatively unheated corona. We then use IRIS rasters and sit-and-stare observations to compare the spatial, temporal, and spectral structure of these relatively ``heated’’ and ``unheated’’ regions. We seek a signature of upward propagating energy that could be associated with hot active region loops.

  19. Coronal Heating Driven by Magnetic-gradient Pumping Mechanism in Solar Plasmas

    CERN Document Server

    Tan, Baolin

    2014-01-01

    The solar coronal heating is a longstanding mystery in astrophysics. Considering that the solar magnetic field is spatially inhomogeneous with considerable magnetic gradient from solar surface to the corona, this work proposes a magnetic gradient pumping (MGP) mechanism and try to explain the formation of hot plasma upflows, such as the hot type II spicules and hot plasma ejections, etc. In MGP mechanism, the magnetic gradients drive the energetic particles to move upwards from the underlying solar atmosphere and form hot upflows. These upflow energetic particles deposit in corona and make it becoming very hot. Roughly estimations indicate that the solar corona can be heated to above 1 million degrees, and the upflow velocity is about 40 km/s in chromosphere and about 130 km/s in the corona. The solar magnetic flux tubes act as pumpers to extract energetic particles from the underlying thermal photosphere, convey them and deposit in the corona. The deposition of energetic particles will make the corona become...

  20. Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling

    CERN Document Server

    Dahlburg, R B; Taylor, B D; Ugarte-Urra, I; Warren, H P; Rappazzo, A F; Velli, M

    2016-01-01

    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 non-uniformly 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 which, in the solar corona, remain observationally unresolved: the plasma of our simulated loop is multi-thermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at sub-observational scales. Numerical simulations of coronal loops of 50000 km length and axial magnetic field intensities ranging from 0.01...

  1. Modeling the Line-of-Sight Integrated Emission in the Corona: Implications for Coronal Heating

    CERN Document Server

    Viall, Nicholeen M

    2013-01-01

    One of the outstanding problems in all of space science is uncovering how the solar corona is heated to temperatures greater than 1 MK. Though studied for decades, one of the major difficulties in solving this problem has been unraveling the line-of-sight (LOS) effects in the observations. The corona is optically thin, so a single pixel measures counts from an indeterminate number (perhaps tens of thousands) of independently heated flux tubes, all along that pixel's LOS. In this paper we model the emission in individual pixels imaging the active region corona in the Extreme Ultraviolet. If LOS effects are not properly taken into account, erroneous conclusions regarding both coronal heating and coronal dynamics may be reached. We model the corona as a LOS integration of many thousands of completely independently heated flux tubes. We demonstrate that despite the superposition of randomly heated flux tubes, nanoflares leave distinct signatures in light curves observed with multi-wavelength and high time cadence...

  2. Spectroscopy at the Solar Limb: II. Are Spicules Heated to Coronal Temperatures?

    Science.gov (United States)

    Beck, C.; Rezaei, R.; Puschmann, K. G.; Fabbian, D.

    2016-10-01

    Spicules of the so-called type II were suggested to be relevant for coronal heating because of their ubiquity on the solar surface and their eventual extension into the corona. We investigate whether solar spicules are heated to transition-region or coronal temperatures and reach coronal heights ({≫} 6 Mm) using multiwavelength observations of limb spicules in different chromospheric spectral lines (Ca ii H, Hɛ, Hα, Ca ii IR at 854.2 nm, He i at 1083 nm) taken with slit spectrographs and imaging spectrometers. We determine the line width of spectrally resolved line profiles in individual spicules and throughout the field of view, and estimate the maximal height that different types of off-limb features reach. We derive estimates of the kinetic temperature and the non-thermal velocity from the line width of spectral lines from different chemical elements. We find that most regular, i.e. thin and elongated, spicules reach a height of at most about 6 Mm above the solar limb. The majority of features found at larger heights are irregularly shaped with a significantly larger lateral extension, of up to a few Mm, than spicules. Both individual and average line profiles in all spectral lines show a decrease in their line width with height above the limb with very few exceptions. The kinetic temperature and the non-thermal velocity decrease with height above the limb. We find no indications that the spicules in our data reach coronal heights or transition-region or coronal temperatures.

  3. Plasma Sloshing in Pulse-heated Solar and Stellar Coronal Loops

    Science.gov (United States)

    Reale, F.

    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.

  4. Plasma sloshing in pulse-heated solar and stellar coronal loops

    CERN Document Server

    Reale, F

    2016-01-01

    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 that the sound crossing time of the flaring loop. The reason is that the plasma has not enough time to reach pressure equilibrium during the 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 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.

  5. Suppression of heating of coronal loops rooted in opposite polarity sunspot umbrae

    Science.gov (United States)

    Tiwari, Sanjiv K.; Thalmann, Julia K.; Moore, Ronald L.; Panesar, Navdeep; Winebarger, Amy R.

    2016-05-01

    EUV observations of active region (AR) coronae reveal the presence of loops at different temperatures. To understand the mechanisms that result in hotter or cooler loops, we study a typical bipolar AR, near solar disk center, which has moderate overall magnetic twist and at least one fully developed sunspot of each polarity. From AIA 193 and 94 A images we identify many clearly discernible coronal loops that connect plage or a sunspot of one polarity to an opposite-polarity plage region. The AIA 94 A images show dim regions in the umbrae of the spots. To see which coronal loops are rooted in a dim umbral area, we performed a non-linear force-free field (NLFFF) modeling using photospheric vector magnetic field measurements obtained with the HMI onboard SDO. After validation of the NLFFF model by comparison of calculated model field lines and observed loops in AIA 193 and 94, we specify the photospheric roots of the model field lines. The model field then shows the coronal magnetic loops that arch from the dim umbral areas of the opposite polarity sunspots. Because these coronal loops are not visible in any of the coronal EUV and X-ray images of the AR, we conclude they are the coolest loops in the AR. This result suggests that the loops connecting opposite polarity umbrae are the least heated because the field in umbrae is so strong that the convective braiding of the field is strongly suppressed.We hypothesize that the convective freedom at the feet of a coronal loop, together with the strength of the field in the body of the loop, determines the strength of the heating. In particular, we expect the hottest coronal loops to have one foot in an umbra and the other foot in opposite-polarity penumbra or plage (coronal moss), the areas of strong field in which convection is not as strongly suppressed as in umbra. Many transient, outstandingly bright, loops in the AIA 94 movie of the AR do have this expected rooting pattern. We will also present another example of AR in

  6. CORONAL HEATING BY THE INTERACTION BETWEEN EMERGING ACTIVE REGIONS AND THE QUIET SUN OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jun; Zhang, Bin; Li, Ting; Yang, Shuhong; Zhang, Yuzong; Li, Leping [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Chen, Feng; Peter, Hardi, E-mail: zjun@nao.cas.cn, E-mail: liting@nao.cas.cn, E-mail: shuhongyang@nao.cas.cn, E-mail: yuzong@nao.cas.cn, E-mail: lepingli@nao.cas.cn, E-mail: chen@mps.mpg.de, E-mail: peter@mps.mpg.de [Max-Planck Institute for Solar System Research (MPS), D-37077, Göttingen (Germany)

    2015-02-01

    The question of what heats the solar corona remains one of the most important puzzles in solar physics and astrophysics. Here we report Solar Dynamics Observatory Atmospheric Imaging Assembly observations of coronal heating by the interaction between emerging active regions (EARs) and the surrounding quiet Sun (QS). The EARs continuously interact with the surrounding QS, resulting in dark ribbons which appear at the boundary of the EARs and the QS. The dark ribbons visible in extreme-ultraviolet wavelengths propagate away from the EARs with speeds of a few km s{sup −1}. The regions swept by the dark ribbons are brightening afterward, with the mean temperature increasing by one quarter. The observational findings demonstrate that uninterrupted magnetic reconnection between EARs and the QS occurs. When the EARs develop, the reconnection continues. The dark ribbons may be the track of the interface between the reconnected magnetic fields and the undisturbed QS’s fields. The propagating speed of the dark ribbons reflects the reconnection rate and is consistent with our numerical simulation. A long-term coronal heating which occurs in turn from nearby the EARs to far away from the EARs is proposed.

  7. CORONAL HEATING BY THE INTERACTION BETWEEN EMERGING ACTIVE REGIONS AND THE QUIET SUN OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY

    International Nuclear Information System (INIS)

    The question of what heats the solar corona remains one of the most important puzzles in solar physics and astrophysics. Here we report Solar Dynamics Observatory Atmospheric Imaging Assembly observations of coronal heating by the interaction between emerging active regions (EARs) and the surrounding quiet Sun (QS). The EARs continuously interact with the surrounding QS, resulting in dark ribbons which appear at the boundary of the EARs and the QS. The dark ribbons visible in extreme-ultraviolet wavelengths propagate away from the EARs with speeds of a few km s−1. The regions swept by the dark ribbons are brightening afterward, with the mean temperature increasing by one quarter. The observational findings demonstrate that uninterrupted magnetic reconnection between EARs and the QS occurs. When the EARs develop, the reconnection continues. The dark ribbons may be the track of the interface between the reconnected magnetic fields and the undisturbed QS’s fields. The propagating speed of the dark ribbons reflects the reconnection rate and is consistent with our numerical simulation. A long-term coronal heating which occurs in turn from nearby the EARs to far away from the EARs is proposed

  8. Resonant Heating of Ions by Parallel Propagating Alfvén Waves in Solar Coronal Holes

    Institute of Scientific and Technical Information of China (English)

    Tian-Xi Zhang; Jing-Xiu Wang; Chi-Jie Xiao

    2005-01-01

    Resonant heating of H, O+5, and Mg+9 by parallel propagating ioncyclotron Alfven waves in solar coronal holes at a heliocentric distance is studied using the heating rate derived from the quasilinear theory. It is shown that the particle-Alfven-wave interaction is a significant microscopic process. The temperatures of the ions are rapidly increased up to the observed order in only microseconds, which implies that simply inserting the quasilinear heating rate into the fluid/MHD energy equation to calculate the radial dependence of ion temperatures may cause errors as the time scales do not match. Different species ions are heated by Alfven waves with a power law spectrum in approximately a mass order.To heat O+5 over Mg+9 as measured by the Ultraviolet Coronagraph Spectrometer (UVCS) in the solar coronal hole at a region≥ 1.9R⊙, the energy density of Alfven waves with a frequency close to the O+5-cyclotron frequency must be at least double of that at the Mg+9-cyclotron frequency. With an appropriate wave-energy spectrum, the heating of H, O+5 and Mg+9 can be consistent with the UVCS measurements in solar coronal holes at a heliocentric distance.

  9. 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.

  10. Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling

    Science.gov (United States)

    Dahlburg, R. B.; Einaudi, G.; Taylor, B. D.; Ugarte-Urra, I.; Warren, H. P.; Rappazzo, A. F.; Velli, M.

    2016-01-01

    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.

  11. Effect of a Radiation Cooling and Heating Function on Standing Longitudinal Oscillations in Coronal Loops

    CERN Document Server

    Kumar, Sanjay; Moon, Y -J

    2016-01-01

    Standing long-period (with the periods longer than several minutes) oscillations in large hot (with the 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 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 modelling 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 generalised 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-c...

  12. Evidence of suppressed heating of coronal loops rooted in opposite polarity sunspot umbrae

    Science.gov (United States)

    Tiwari, Sanjiv K.; Thalmann, Julia K.; Winebarger, Amy R.; Panesar, Navdeep K.; Moore, Ronald

    2015-04-01

    Observations of active region (AR) coronae in different EUV wavelengths reveal the presence of various loops at different temperatures. To understand the mechanisms that result in hotter or cooler loops, we study a typical bipolar AR, near solar disk center, which has moderate overall magnetic twist and at least one fully developed sunspot of each polarity. From AIA 193 and 94 A images we identify many clearly discernible coronal loops that connect opposite-polarity plage or a sunspot to a opposite-polarity plage region. The AIA 94 A images show dim regions in the umbrae of the spots. To see which coronal loops are rooted in a dim umbral area, we performed a non-linear force-free field (NLFFF) modeling using photospheric vector magnetic field measurements obtained with the Heliosesmic Magnetic Imager (HMI) onboard SDO. After validation of the NLFFF model by comparison of calculated model field lines and observed loops in AIA 193 and 94 A, we specify the photospheric roots of the model field lines. The model field then shows the coronal magnetic loops that arch from the dim umbral area of the positive-polarity sunspot to the dim umbral area of a negative-polarity sunspot. Because these coronal loops are not visible in any of the coronal EUV and X-ray images of the AR, we conclude they are the coolest loops in the AR. This result suggests that the loops connecting opposite polarity umbrae are the least heated because the field in umbrae is so strong that the convective braiding of the field is strongly suppressed.From this result, we further hypothesize that the convective freedom at the feet of a coronal loop, together with the strength of the field in the body of the loop, determines the strength of the heating. In particular, we expect the hottest coronal loops to have one foot in an umbra and the other foot in opposite-polarity penumbra or plage (coronal moss), the areas of strong field in which convection is not as strongly suppressed as in umbrae. Many

  13. A new approach for modelling chromospheric evaporation in response to enhanced coronal heating: 1 the method

    CERN Document Server

    Johnston, C D; Cargill, P J; De Moortel, I

    2016-01-01

    We present a new computational approach that addresses the difficulty of obtaining the correct interaction between the solar corona and the transition region in response to rapid heating events. In the coupled corona, transition region and chromosphere system, an enhanced downward conductive flux results in an upflow (chromospheric evaporation). However, obtaining the correct upflow generally requires high spatial resolution in order to resolve the transition region. With an unresolved transition region, artificially low coronal densities are obtained because the downward heat flux jumps across the unresolved region to the chromosphere, underestimating the upflows. Here, we treat the lower transition region as a discontinuity that responds to changing coronal conditions through the imposition of a jump condition that is derived from an integrated form of energy conservation. To illustrate and benchmark this approach against a fully resolved one-dimensional model, we present field-aligned simulations of corona...

  14. Spectroscopy at the Solar Limb: II. Are Spicules Heated to Coronal Temperatures?

    Science.gov (United States)

    Beck, C.; Rezaei, R.; Puschmann, K. G.; Fabbian, D.

    2016-08-01

    Spicules of the so-called type II were suggested to be relevant for coronal heating because of their ubiquity on the solar surface and their eventual extension into the corona. We investigate whether solar spicules are heated to transition-region or coronal temperatures and reach coronal heights ( {≫} 6 Mm) using multiwavelength observations of limb spicules in different chromospheric spectral lines (Ca uc(ii) H, H ɛ, H α, Ca uc(ii) IR at 854.2 nm, He uc(i) at 1083 nm) taken with slit spectrographs and imaging spectrometers. We determine the line width of spectrally resolved line profiles in individual spicules and throughout the field of view, and estimate the maximal height that different types of off-limb features reach. We derive estimates of the kinetic temperature and the non-thermal velocity from the line width of spectral lines from different chemical elements. We find that most regular, i.e. thin and elongated, spicules reach a height of at most about 6 Mm above the solar limb. The majority of features found at larger heights are irregularly shaped with a significantly larger lateral extension, of up to a few Mm, than spicules. Both individual and average line profiles in all spectral lines show a decrease in their line width with height above the limb with very few exceptions. The kinetic temperature and the non-thermal velocity decrease with height above the limb. We find no indications that the spicules in our data reach coronal heights or transition-region or coronal temperatures.

  15. THE HYDRODYNAMIC EVOLUTION OF IMPULSIVELY HEATED CORONAL LOOPS: EXPLICIT ANALYTICAL APPROXIMATIONS

    International Nuclear Information System (INIS)

    We derive simple analytical approximations (in explicit form) for the hydrodynamic evolution of the electron temperature T(s, t) and electron density n(s, t), for one-dimensional coronal loops that are subject to impulsive heating with subsequent cooling. Our analytical approximations are derived from first principles, using (1) the hydrodynamic energy balance equation, (2) the loop scaling laws of Rosner-Tucker-Vaiana and Serio, (3) the Neupert effect, and (4) the Jakimiec relationship. We compare our analytical approximations with 56 numerical cases of time-dependent hydrodynamic simulations from a parametric study of Tsiklauri et al., covering a large parameter space of heating rates, heating timescales, heating scale heights, loop lengths, for both footpoint and apex heating, mostly applicable to flare conditions. The average deviations from the average temperature and density values are typically ∼20% for our analytical expressions. The analytical approximations in explicit form provide an efficient tool to mimic time-dependent hydrodynamic simulations, to model observed soft X-rays and extreme-ultraviolet light curves of heated and cooling loops in the solar corona and in flares by forward fitting, to model microflares, to infer the coronal heating function from light curves of multi-wavelength observations, and to provide physical models of differential emission measure distributions for solar and stellar flares, coronae, and irradiance.

  16. Heating of Heavy Ions by Interplanetary Coronal Mass Ejection (ICME) Driven Collisionless Shocks

    CERN Document Server

    Korreck, K E; Lepri, S T; Raines, J M

    2006-01-01

    Shock heating and particle acceleration processes are some of the most fundamental physical phenomena of plasma physics with countless applications in laboratory physics, space physics, and astrophysics. This study is motivated by previous observations of non-thermal heating of heavy ions in astrophysical shocks (Korreck et al. 2004). Here, we focus on shocks driven by Interplanetary Coronal Mass Ejections (ICMEs) which heat the solar wind and accelerate particles. This study focuses specifically on the heating of heavy ions caused by these shocks. Previous studies have focused only on the two dynamically dominant species, H+ and He2+ . This study utilizes thermal properties measured by the Solar Wind Ion Composition Spectrometer (SWICS) aboard the Advanced Composition Explorer (ACE) spacecraft to examine heavy ion heating. This instrument provides data for many heavy ions not previously available for detailed study, such as Oxygen (O6+, O7+), Carbon (C5+, C6+), and Iron (Fe10+). The ion heating is found to d...

  17. Heating and cooling of coronal loops observed by SDO

    Science.gov (United States)

    Li, L. P.; Peter, H.; Chen, F.; Zhang, J.

    2015-11-01

    Context. One of the most prominent processes to have been suggested as heating the corona to well above 106 K builds on nanoflares, which are short bursts of energy dissipation. Aims: We compare observations to model predictions to test the validity of the nanoflare process. Methods: Using extreme UV data from AIA/SDO and HMI/SDO line-of-sight magnetograms, we study the spatial and temporal evolution of a set of loops in active region AR 11850. Results: We find a transient brightening of loops in emission from Fe xviii forming at about 7.2 MK, while at the same time these loops dim in emission from lower temperatures. This points to a fast heating of the loop that goes along with evaporation of material that we observe as apparent upward motions in the image sequence. After this initial phase lasting some 10 min, the loops brighten in a sequence of AIA channels that show progressively cooler plasma, indicating that this cooling of the loops lasts about one hour. A comparison to the predictions from a 1D loop model shows that this observation supports the nanoflare process in (almost) all aspects. In addition, our observations show that the loops get broader while getting brighter, which cannot be understood in a 1D model. Movie associated to Fig. 1 is available in electronic form at http://www.aanda.org

  18. Spectroscopy at the solar limb: II. Are spicules heated to coronal temperatures ?

    CERN Document Server

    Beck, C; Puschmann, K G; Fabbian, D

    2016-01-01

    Spicules of the so-called type II were suggested to be relevant for coronal heating because of their ubiquity on the solar surface and their eventual extension into the corona. We investigate whether solar spicules are heated to transition-region or coronal temperatures and reach coronal heights (>6 Mm) using multi-wavelength observations of limb spicules in different chromospheric spectral lines (Ca II H, Hepsilon, Halpha, Ca II IR at 854.2 nm, He I at 1083 nm). We determine the line width of individual spicules and throughout the field of view and estimate the maximal height that different types of off-limb features reach. We derive estimates of the kinetic temperature and the non-thermal velocity from the line width of spectral lines from different chemical elements. We find that most regular spicules reach a maximal height of about 6 Mm above the solar limb. The majority of features found at larger heights are irregularly shaped with a significantly larger lateral extension than spicules. Both individual ...

  19. Effect of a Radiation Cooling and Heating Function on Standing Longitudinal Oscillations in Coronal Loops

    Science.gov (United States)

    Kumar, S.; Nakariakov, V. M.; Moon, Y.-J.

    2016-06-01

    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.

  20. Can Large Time Delays Observed in Light Curves of Coronal Loops be Explained by Impulsive Heating?

    CERN Document Server

    Lionello, Roberto; Winebarger, Amy R; Linker, Jon A; Mikić, Zoran

    2015-01-01

    The light curves of solar coronal loops often peak first in channels associated with higher temperatures and then in those associated with lower. The time delays between the different narrowband EUV channels have been measured for many individual loops and recently for every pixel of an active region observation. Time delays between channels for an active region exhibit a wide range of values, with maxima $>$ 5,000\\,s. These large time delays make up 3-26\\% (depending on the channel pair) of the pixels where a significant, positive time delay is measured. It has been suggested that time delays can be explained by impulsive heating. 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 t...

  1. Heat flux in a non-Maxwellian plasma. [in realistic solar coronal loop

    Science.gov (United States)

    Ljepojevic, N. N.; Macneice, P.

    1989-01-01

    A hybrid numerical scheme is applied to solve the Landau equation for the electron distribution function over all velocity space. Evidence is presented for the first time of the degree and character of the failure of the classical Spitzer-Haerm heat flux approximation in a realistic solar coronal loop structure. In the loop model used, the failure is so severe at some points that the role of the heat flux in the plasma's energy balance is completely misinterpreted. In the lower corona the Spitzer-Haerm approximation predicts that the heat flux should act as an energy source, whereas the more accurate distribution functions calculated here show this to be an energy sink.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lionello, Roberto; Linker, Jon A.; Mikić, Zoran [Predictive Science, Inc., 9990 Mesa Rim Rd., Ste. 170, San Diego, CA 92121-3933 (United States); Alexander, Caroline E.; Winebarger, Amy R., E-mail: lionel@predsci.com, E-mail: linkerj@predsci.com, E-mail: mikicz@predsci.com, E-mail: caroline.e.alexander@nasa.gov, E-mail: amy.r.winebarger@nasa.gov [NASA Marshall Space Flight Center, ZP 13, Huntsville, AL 35805 (United States)

    2016-02-20

    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.

  3. The Coronal Solar Magnetism Observatory

    Science.gov (United States)

    Tomczyk, S.; Landi, E.; Zhang, J.; Lin, H.; DeLuca, E. E.

    2015-12-01

    Measurements of coronal and chromospheric magnetic fields are arguably the most important observables required for advances in our understanding of the processes responsible for coronal heating, coronal dynamics and the generation of space weather that affects communications, GPS systems, space flight, and power transmission. The Coronal Solar Magnetism Observatory (COSMO) is a proposed ground-based suite of instruments designed for routine study of coronal and chromospheric magnetic fields and their environment, and to understand the formation of coronal mass ejections (CME) and their relation to other forms of solar activity. This new facility will be operated by the High Altitude Observatory of the National Center for Atmospheric Research (HAO/NCAR) with partners at the University of Michigan, the University of Hawaii and George Mason University in support of the solar and heliospheric community. It will replace the current NCAR Mauna Loa Solar Observatory (http://mlso.hao.ucar.edu). COSMO will enhance the value of existing and new observatories on the ground and in space by providing unique and crucial observations of the global coronal and chromospheric magnetic field and its evolution. The design and current status of the COSMO will be reviewed.

  4. The Foggy EUV Corona and Coronal Heating by MHD Waves from Explosive Reconnection Events

    Science.gov (United States)

    Moore, Ron L.; Cirtain, Jonathan W.; Falconer, David A.

    2008-01-01

    In 0.5 arcsec/pixel TRACE coronal EUV images, the corona rooted in active regions that are at the limb and are not flaring is seen to consist of (1) a complex array of discrete loops and plumes embedded in (2) a diffuse ambient component that shows no fine structure and gradually fades with height. For each of two not-flaring active regions, found that the diffuse component is (1) approximately isothermal and hydrostatic and (2) emits well over half of the total EUV luminosity of the active-region corona. Here, from a TRACE Fe XII coronal image of another not-flaring active region, the large sunspot active region AR 10652 when it was at the west limb on 30 July 2004, we separate the diffuse component from the discrete loop component by spatial filtering, and find that the diffuse component has about 60% of the total luminosity. If under much higher spatial resolution than that of TRACE (e. g., the 0.1 arcsec/pixel resolution of the Hi-C sounding-rocket experiment proposed by J. W. Cirtain et al), most of the diffuse component remains diffuse rather being resolved into very narrow loops and plumes, this will raise the possibility that the EUV corona in active regions consists of two basically different but comparably luminous components: one being the set of discrete bright loops and plumes and the other being a truly diffuse component filling the space between the discrete loops and plumes. This dichotomy would imply that there are two different but comparably powerful coronal heating mechanisms operating in active regions, one for the distinct loops and plumes and another for the diffuse component. We present a scenario in which (1) each discrete bright loop or plume is a flux tube that was recently reconnected in a burst of reconnection, and (2) the diffuse component is heated by MHD waves that are generated by these reconnection events and by other fine-scale explosive reconnection events, most of which occur in and below the base of the corona where they are

  5. A new model for heating of Solar North Polar Coronal Hole

    CERN Document Server

    Devlen, E; Yardımcı, M; Pekünlü, E R

    2015-01-01

    This paper presents a new model of North Polar Coronal Hole (NPCH) to study dissipation/propagation of MHD waves. We investigate the effects of the isotropic viscosity and heat conduction on the propagation characteristics of the MHD waves in NPCH. We first model NPCH by considering the differences in radial as well as in the direction perpendicular to the line of sight (\\textit{los}) in temperature, particle number density and non-thermal velocities between plumes and interplume lanes for the specific case of \\ion{O}{VI} ions. This model includes parallel and perpendicular (to the magnetic field) heat conduction and viscous dissipation. Next, we derive the dispersion relations for the MHD waves in the case of absence and presence of parallel heat conduction. In the case of absence of parallel heat conduction, we find that MHD wave dissipation strongly depends on the viscosity for modified acoustic and Alfven waves. The energy flux density of acoustic waves varies between $10^{4.7}$ and $10^7 \\,erg\\,cm^{-2}\\,...

  6. Extraterrestrial Regolith Derived Atmospheric Entry Heat Shields

    Science.gov (United States)

    Hogue, Michael D.; Mueller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Rasky, Daniel J.

    2016-01-01

    High-mass planetary surface access is one of NASAs technical challenges involving entry, descent and landing (EDL). During the entry and descent phase, frictional interaction with the planetary atmosphere causes a heat build-up to occur on the spacecraft, which will rapidly destroy it if a heat shield is not used. However, the heat shield incurs a mass penalty because it must be launched from Earth with the spacecraft, thus consuming a lot of precious propellant. This NASA Innovative Advanced Concept (NIAC) project investigated an approach to provide heat shield protection to spacecraft after launch and prior to each EDL thus potentially realizing significant launch mass savings. Heat shields fabricated in situ can provide a thermal-protection system for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Regolith has extremely good insulating properties and the silicates it contains can be used in the fabrication and molding of thermal-protection materials. In this paper, we will describe three types of in situ fabrication methods for heat shields and the testing performed to determine feasibility of this approach.

  7. Atmospheric Heat Redistribution on Hot Jupiters

    CERN Document Server

    Perez-Becker, Daniel

    2013-01-01

    Infrared lightcurves of transiting hot Jupiters present a trend in which the atmospheres of the hottest planets are less efficient at redistributing the stellar energy absorbed on their daysides---and thus have a larger day-night temperature contrast---than colder planets. No predictive atmospheric model has been published that identifies which dynamical mechanisms determine the atmospheric heat redistribution efficiency on tidally locked exoplanets. Here we present a two-layer shallow water model of the atmospheric dynamics on synchronously rotating planets that explains the observed trend. Our model shows that planets with weak friction and weak irradiation exhibit a banded zonal flow with minimal day-night temperature differences, while models with strong irradiation and/or strong friction exhibit a day-night flow pattern with order-unity fractional day-night temperature differences. To interpret the model, we develop a scaling theory that shows that the timescale for gravity waves to propagate horizontall...

  8. 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.

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

    International Nuclear Information System (INIS)

    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.

  10. Turbulence-Driven Coronal Heating and Improvements to Empirical Forecasting of the Solar Wind

    CERN Document Server

    Woolsey, Lauren N

    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 Alfv\\'en waves on coronal heating and wind acceleration. The one-dimensional MHD code ZEPHYR self-consistently finds solar wind solutions without the need for empirical heating functions. Another 1D 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 ultim...

  11. Magnetic Influences on Turbulent Heating and Jet Production in Coronal Holes

    Science.gov (United States)

    Woolsey, L. N.; Cranmer, S. R.

    2015-12-01

    The heating of the solar wind from open-field regions in the corona is the subject of an ongoing body of work in the solar physics community. We present recent progress to understand the role of Alfvén-wave-driven turbulence in flux tubes open to the heliosphere. Our models use three-dimensional, time-dependent forms of the reduced magnetohydrodynamics equations to find the resulting properties of the solar wind. We use the BRAID model (van Ballegooijen et al., 2011) on open flux tubes that epitomize the most common magnetic structures in the corona: a polar coronal hole, an open flux tube on the boundary of an equatorial streamer, and one that neighbors a strong active region. Our results agree with prior work using the time-steady, one-dimensional ZEPHYR model (Cranmer et al., 2007; Woolsey and Cranmer, 2014). In addition, the time dependence in BRAID lets us explore the bursty, nanoflare-like nature of the heating in these flux tubes. We find that the transient heating can be captured into separate events with an average energy of 1022 erg, with a maximum energy of 1025 erg. The bursty heating lead us to pursue a better understanding of the physical processes responsible for the network jets seen in IRIS data (see e.g. Tian et al., 2014). We search for correlations between the supergranular magnetic field properties—using the Helioseismic and Magnetic Imager aboard SDO—and jet productivity to make better estimates of the mass and energy budget of these small-scale features and to find evidence of the mechanisms responsible for the network jets.

  12. Alfvén wave solar model (AWSoM): Coronal heating

    International Nuclear Information System (INIS)

    We present a new version of the Alfvén wave solar model, a global model from the upper chromosphere to the corona and the heliosphere. The coronal heating and solar wind acceleration are addressed with low-frequency Alfvén wave turbulence. The injection of Alfvén wave energy at the inner boundary is such that the Poynting flux is proportional to the magnetic field strength. The three-dimensional magnetic field topology is simulated using data from photospheric magnetic field measurements. This model does not impose open-closed magnetic field boundaries; those develop self-consistently. The physics include the following. (1) The model employs three different temperatures, namely the isotropic electron temperature and the parallel and perpendicular ion temperatures. The firehose, mirror, and ion-cyclotron instabilities due to the developing ion temperature anisotropy are accounted for. (2) The Alfvén waves are partially reflected by the Alfvén speed gradient and the vorticity along the field lines. The resulting counter-propagating waves are responsible for the nonlinear turbulent cascade. The balanced turbulence due to uncorrelated waves near the apex of the closed field lines and the resulting elevated temperatures are addressed. (3) To apportion the wave dissipation to the three temperatures, we employ the results of the theories of linear wave damping and nonlinear stochastic heating. (4) We have incorporated the collisional and collisionless electron heat conduction. We compare the simulated multi-wavelength extreme ultraviolet images of CR2107 with the observations from STEREO/EUVI and the Solar Dynamics Observatory/AIA instruments. We demonstrate that the reflection due to strong magnetic fields in the proximity of active regions sufficiently intensifies the dissipation and observable emission.

  13. Prolonged multiple excitation of large-scale Traveling Atmospheric Disturbances (TADs) by successive and interacting coronal mass ejections

    Science.gov (United States)

    Guo, Jianpeng; Wei, Fengsi; Feng, Xueshang; Forbes, Jeffrey M.; Wang, Yuming; Liu, Huixin; Wan, Weixing; Yang, Zhiliang; Liu, Chaoxu

    2016-03-01

    Successive and interacting coronal mass ejections (CMEs) directed earthward can have significant impacts throughout geospace. While considerable progress has been made in understanding their geomagnetic consequences over the past decade, elucidation of their atmospheric consequences remains a challenge. During 17-19 January 2005, a compound stream formed due to interaction of six successive halo CMEs impacted Earth's magnetosphere. In this paper, we report one atmospheric consequence of this impact, namely, the prolonged multiple excitation of large-scale (>˜1000 km) traveling atmospheric disturbances (TADs). The TADs were effectively excited in auroral regions by sudden injections of energy due to the intermittent southward magnetic fields within the stream. They propagated toward the equator at speeds near 800 m/s and produced long-duration (˜2.5 days) continuous large-scale density disturbances of order up ± 40% in the global thermosphere.

  14. Understanding coronal heating and solar wind acceleration: Case for in situ near-Sun measurements

    OpenAIRE

    McComas, D. J.; Velli, M.; Lewis, W. S.; Acton, L. W.; Balat-Pichelin, M.; V. Bothmer; Dirling, R. B., Jr.; Feldman, W. C.; G. Gloeckler; Habbal, S. R.; Hassler, D.M.; Mann, I.; Matthaeus, W. H.; McNutt, R. L., Jr.; Mewaldt, R.A

    2007-01-01

    The solar wind has been measured directly from 0.3 AU outward, and the Sun's atmosphere has been imaged from the photosphere out through the corona. These observations have significantly advanced our understanding of the influence of the Sun's varying magnetic field on the structure and dynamics of the corona and the solar wind. However, how the corona is heated and accelerated to produce the solar wind remains a mystery. Answering these fundamental questions requires in situ observations nea...

  15. Small Scale Dynamo Magnetism And the Heating of the Quiet Sun Solar Atmosphere.

    Science.gov (United States)

    Amari, T.

    2015-12-01

    The longstanding problem of the solar atmosphere heating has been addressed by many theoretical studies. Two specific mechanisms have been shown to play a key role in those : magnetic reconnection and waves. On the other hand the necessity of treating together chromosphere and corona has also been been stressed, with debates going on about the possibility of heating coronal plasma by energetic phenomena observed in the chromosphere,based on many key observations such as spicules, tornadoes…. We present some recent results about the modeling of quiet Sun heating in which magnetic fields are generated by a subphotospheric fluid dynamo which is connected to granulation. The model shows a topologically complex magnetic field of 160 G on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations.Those generated magnetic fields emerge into the chromosphere, providing the required energy flux and then small-scale eruptions releasing magnetic energy and driving sonic motions. Some of the more energetic eruptions can affect the very low corona only.It is also found that taking into account a vertical weak network magnetic field then allows to provide energy higher in the corona, while leaving unchanged the physics of chromospheric eruptions. The coronal heating mechanism rests on the eventual dissipation of Alfven waves generated inside the chromosphere and carrying upwards an adequate energy flux, while more energetic phenomena contribute only weakly to the heating of the corona.

  16. Coronal Holes

    Directory of Open Access Journals (Sweden)

    Steven R. Cranmer

    2009-09-01

    Full Text Available Coronal holes are the darkest and least active regions of the Sun, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. This paper reviews measurements of the plasma properties in coronal holes and how these measurements are used to reveal details about the physical processes that heat the solar corona and accelerate the solar wind. It is still unknown to what extent the solar wind is fed by flux tubes that remain open (and are energized by footpoint-driven wave-like fluctuations, and to what extent much of the mass and energy is input intermittently from closed loops into the open-field regions. Evidence for both paradigms is summarized in this paper. Special emphasis is also given to spectroscopic and coronagraphic measurements that allow the highly dynamic non-equilibrium evolution of the plasma to be followed as the asymptotic conditions in interplanetary space are established in the extended corona. For example, the importance of kinetic plasma physics and turbulence in coronal holes has been affirmed by surprising measurements from the UVCS instrument on SOHO that heavy ions are heated to hundreds of times the temperatures of protons and electrons. These observations point to specific kinds of collisionless Alfvén wave damping (i.e., ion cyclotron resonance, but complete theoretical models do not yet exist. Despite our incomplete knowledge of the complex multi-scale plasma physics, however, much progress has been made toward the goal of understanding the mechanisms ultimately responsible for producing the observed properties of coronal holes.

  17. Constraining a Model of Turbulent Coronal Heating for AU Microscopii with X-Ray, Radio, and Millimeter Observations

    CERN Document Server

    Cranmer, Steven R; 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 em...

  18. Comments on "The Coronal Heating Paradox" by M.J. Aschwanden, A. Winebarger, D. Tsiklauri and H. Peter [2007, Astrophys J., 659, 1673

    CERN Document Server

    Mahajan, Swadesh M

    2007-01-01

    We point out the priority of our paper (Mahajan et al. 2001, Phys. Plasmas, 8, 1340) over (Aschwanden et al. 2007, Astrophys J., 659, 1673) in introducing the term "Formation and primary heating of the solar corona" working out explicit models (theory as well as simulation) for coronal structure formation and heating. On analyzing the Aschwanden et al. (2007) scenario of coronal heating process (shifted to the chromospheric heating) we stress, that for efficient loop formation, the primary upflows of plasma in chromosphere/transition region should be relatively cold and fast (as opposed to hot). It is during trapping and accumulation in closed field structures, that the flows thermalize (due to the dissipation of the short scale flow energy) leading to a bright and hot coronal structure. The formation and primary heating of a closed coronal structure (loop at the end) are simultaneous and a process like the "filling of the empty coronal loop by hot upflows" is purely speculative and totally unlikely.

  19. Small-scale dynamo magnetism as the driver for heating the solar atmosphere

    Science.gov (United States)

    Amari, Tahar; Luciani, Jean-François; Aly, Jean-Jacques

    2015-06-01

    The long-standing problem of how the solar atmosphere is heated has been addressed by many theoretical studies, which have stressed the relevance of two specific mechanisms, involving magnetic reconnection and waves, as well as the necessity of treating the chromosphere and corona together. But a fully consistent model has not yet been constructed and debate continues, in particular about the possibility of coronal plasma being heated by energetic phenomena observed in the chromosphere. Here we report modelling of the heating of the quiet Sun, in which magnetic fields are generated by a subphotospheric fluid dynamo intrinsically connected to granulation. We find that the fields expand into the chromosphere, where plasma is heated at the rate required to match observations (4,500 watts per square metre) by small-scale eruptions that release magnetic energy and drive sonic motions. Some energetic eruptions can even reach heights of 10 million metres above the surface of the Sun, thereby affecting the very low corona. Extending the model by also taking into account the vertical weak network magnetic field allows for the existence of a mechanism able to heat the corona above, while leaving unchanged the physics of chromospheric eruptions. Such a mechanism rests on the eventual dissipation of Alfvén waves generated inside the chromosphere and that carry upwards the required energy flux of 300 watts per square metre. The model shows a topologically complex magnetic field of 160 gauss on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations, chromospheric features (contributing only weakly to the coronal heating) that can be identified with observed spicules and blinkers, and vortices that may be possibly associated with observed solar tornadoes.

  20. Small-scale dynamo magnetism as the driver for heating the solar atmosphere.

    Science.gov (United States)

    Amari, Tahar; Luciani, Jean-François; Aly, Jean-Jacques

    2015-06-11

    The long-standing problem of how the solar atmosphere is heated has been addressed by many theoretical studies, which have stressed the relevance of two specific mechanisms, involving magnetic reconnection and waves, as well as the necessity of treating the chromosphere and corona together. But a fully consistent model has not yet been constructed and debate continues, in particular about the possibility of coronal plasma being heated by energetic phenomena observed in the chromosphere. Here we report modelling of the heating of the quiet Sun, in which magnetic fields are generated by a subphotospheric fluid dynamo intrinsically connected to granulation. We find that the fields expand into the chromosphere, where plasma is heated at the rate required to match observations (4,500 watts per square metre) by small-scale eruptions that release magnetic energy and drive sonic motions. Some energetic eruptions can even reach heights of 10 million metres above the surface of the Sun, thereby affecting the very low corona. Extending the model by also taking into account the vertical weak network magnetic field allows for the existence of a mechanism able to heat the corona above, while leaving unchanged the physics of chromospheric eruptions. Such a mechanism rests on the eventual dissipation of Alfvén waves generated inside the chromosphere and that carry upwards the required energy flux of 300 watts per square metre. The model shows a topologically complex magnetic field of 160 gauss on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations, chromospheric features (contributing only weakly to the coronal heating) that can be identified with observed spicules and blinkers, and vortices that may be possibly associated with observed solar tornadoes.

  1. Heated-Atmosphere Airship for the Titan Environment: Thermal Analysis

    Science.gov (United States)

    Heller, R. S.; Landis, G. A.; Hepp, A. F.; Colozza, A. J.

    2012-01-01

    Future exploration of Saturn's moon Titan can be carried out by airships. Several lighter-than-atmosphere gas airships and passive drifting heated-atmosphere balloon designs have been studied, but a heated-atmosphere airship could combine the best characteristics of both. This work analyses the thermal design of such a heated-atmosphere vehicle, and compares the result with a lighter-than-atmosphere (hydrogen) airship design. A design tool was created to enable iteration through different design parameters of a heated-atmosphere airship (diameter, number of layers, and insulating gas pocket thicknesses) and evaluate the feasibility of the resulting airship. A baseline heated-atmosphere airship was designed to have a diameter of 6 m (outer diameter of 6.2 m), three-layers of material, and an insulating gas pocket thickness of 0.05 m between each layer. The heated-atmosphere airship has a mass of 161.9 kg. A similar mission making use of a hydrogen-filled airship would require a diameter of 4.3 m and a mass of about 200 kg. For a long-duration mission, the heated-atmosphere airship appears better suited. However, for a mission lifetime under 180 days, the less complex hydrogen airship would likely be a better option.

  2. The Influence of Coronal Mass Ejections on the Gas Dynamics of the Atmosphere of a "Hot~Jupiter" Exoplanet

    CERN Document Server

    Bisikalo, D V

    2016-01-01

    The results of three-dimensional numerical simulations of the gas dynamics of the atmosphere of a "hot Jupiter" exoplanet during the passage of a coronal mass ejection (CME) from the central star are presented. These computations assumed the parameters for the stellar wind and the CME to be typical of the solar values. The characteristic variations of the flow pattern are considered for quasi-closed and closed (but appreciably distorted by the gravitational influence of the star) gaseous envelopes of the exoplanet. It is shown that a typical CME is sufficient to tear off the outer part of an asymmetric envelope that is located beyond the Roche lobe and carry it away from the exoplanet. This leads to a substantial increase in the mass-loss rate from the exoplanet envelope during the passage of CMEs. The mass-loss rate grows by about a factor of 11 for a closed envelope, and by about a factor of 14 for a quasi-closed envelope. Possible evolutionary consequences of the loss of part of the atmosphere during the p...

  3. Multifractal Solar EUV Intensity Fluctuations and their Implications for Coronal Heating Models

    CERN Document Server

    Cadavid, Ana Cristina Cadavid; Lawrence, John K; Christian, Damian J; Jennings, Peter J; Rappazzo, A Franco

    2016-01-01

    We investigate the scaling properties of the long-range temporal evolution and intermittency of SDO/AIA intensity observations in four solar environments: 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 Angstrom 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 15-45 min is multifractal, and the time series are anti-persistent on the average. The degree of anti-correlation in the TR time series is greater than for coronal emission. The multifractality stems from long term correlations in the data rather than the wide distribution of intensities. Observations in the 335 Angstrom waveband can be described in terms of a multifractal with ...

  4. Investigation of Urban Heat Stress from Satellite Atmospheric Profiles

    Science.gov (United States)

    Hu, L.; Brunsell, N. A.

    2014-12-01

    Heat stress is the leading cause of weather-related human mortality in the United States and in many countries world-wide. Heat stress is usually enhanced by the urban heat island effect. Here, we investigate the ability to use remotely sensed atmospheric profiles to detect and monitor heat stress in the urban environment. MODIS atmospheric profiles at 5 km are used to quantify the spatial distribution of heat stress across Chicago during summer periods from 2003-2013. Four heat stress indices are investigated (Discomfort Index (DI), NWS Heat Index (HI), Humidex, and Simplified Wet Bulb Globe Temperature (SWBGT)) from the near-surface temperature and humidity observed at ground sites and retrieved from satellite atmospheric profiles. The heat stress climatology indicates that the urban effects are similar to the heat stress in top 5% hot days and 11 summers during the daytime. There is a lack of relationship between urban fraction and the heat stress on the warmest nights. The nighttime heat stress in the hottest 5% suggests a larger stress compared to the normal conditions during 11 summers. A case study of the heat wave in 2012 is assessed to identify the key pre-heat wave spatial patterns, which may potentially apply to predict future high heat-stress events. In addition, the role of the temporal persistence on the spatial dynamics of the heat wave is also examined. This research illustrates the spatial heat pattern under normal and heat wave conditions, which may help to make public heat health protection strategies. Also, the remotely sensed temperature and humidity information are invaluable to assess urban heat island impact spatially and temporally.

  5. MECHANICAL ENERGY FLUXES ASSOCIATED WITH SATURATED CORONAL HEATING IN M DWARFS: COMPARISON WITH PREDICTIONS OF A TURBULENT DYNAMO

    Energy Technology Data Exchange (ETDEWEB)

    Mullan, D. J. [Bartol Research Institute, Dept of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); MacDonald, J., E-mail: mullan@udel.edu [Dept of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2016-02-20

    Empirically, the X-ray luminosity L{sub X} from M dwarfs has been found to have an upper limit of about 0.2% of the bolometric flux L{sub bol}. In the limit where magnetic fields in M dwarfs are generated in equipartition with convective motions, we use stellar models to calculate the energy flux of Alfvén waves F{sub A} as a function of depth in the sub-surface convection zone. Since Alfvén waves have the optimal opportunity for wave modes to reach the corona, we suggest that F{sub A} sets an upper limit on the mechanical flux F{sub mech} which causes coronal heating. This suggestion accounts quantitatively for the “saturated” values of L{sub X}/L{sub bol} which have been reported empirically for M dwarfs.

  6. The Heating of the Solar Atmosphere: from the Bottom Up?

    Science.gov (United States)

    Winebarger, Amy

    2014-01-01

    The heating of the solar atmosphere remains a mystery. Over the past several decades, scientists have examined the observational properties of structures in the solar atmosphere, notably their temperature, density, lifetime, and geometry, to determine the location, frequency, and duration of heating. In this talk, I will review these observational results, focusing on the wealth of information stored in the light curve of structures in different spectral lines or channels available in the Solar Dynamic Observatory's Atmospheric Imaging Assembly, Hinode's X-ray Telescope and Extreme-ultraviolet Imaging Spectrometer, and the Interface Region Imaging Spectrograph. I will discuss some recent results from combined data sets that support the heating of the solar atmosphere may be dominated by low, near-constant heating events.

  7. Critical review of hydraulic modeling on atmospheric heat dissipation

    International Nuclear Information System (INIS)

    Objectives of this study were: to define the useful roles of hydraulic modeling in understanding the predicting atmospheric effects of heat dissipation systems; to assess the state-of-the-art of hydraulic modeling of atmospheric phenomena; to inventory potentially useful existing hydraulic modeling facilities both in the United States and abroad; and to scope hydraulic model studies to assist the assessment of atmospheric effects of nuclear energy centers

  8. Heating of Jupiter's upper atmosphere above the Great Red Spot

    Science.gov (United States)

    O'Donoghue, James; Moore, Luke; Stallard, Tom; Melin, Henrik

    2016-10-01

    Measured upper-atmospheric, mid-to-low latitude temperatures of the giant planets are hundreds of degrees warmer than simulations based on solar heating alone can explain. Modelling studies, focused on additional sources of heating, have been so far unable to resolve this significant model-data discrepancy. Equatorward transport of energy from the hot auroral regions was expected to heat low latitude regions; instead, models have demonstrated that auroral energy is trapped at high latitudes, a consequence of the strong Coriolis forces on these rapidly rotating planets. Wave heating, driven from below, represents another potential source of upper-atmospheric heating. Using data taken in 2012 by the ground-based NASA IRTF, we found through observations of the H3+ ion that the upper atmosphere above Jupiter's Great Red Spot (GRS) - the largest storm in the solar system - is hundreds of degrees hotter than anywhere else on the planet. Specifically, the result shows that the northern region of the spot was over 1600 K, and that background temperatures away from the spot are ~850 K. The hotspot, by process of elimination, must be heated from below, and this detection is therefore strong evidence for coupling between Jupiter's lower and upper atmospheres, likely the result of upward propagating acoustic and/or gravity waves. Our results indicate that the lower atmosphere may yet play an important role in resolving the giant planet 'energy crisis'.

  9. Heat flow vs. atmospheric greenhouse on early Mars

    Science.gov (United States)

    Fanale, F. P.; Postawko, S. E.

    1991-01-01

    Researchers derived a quantitative relationship between the effectiveness of an atmospheric greenhouse and internal heat flow in producing the morphological differences between earlier and later Martian terrains. The derivation is based on relationships previously derived by other researchers. The reasoning may be stated as follows: the CO2 mean residence time in the Martian atmosphere is almost certainly much shorter than the total time span over which early climate differences are thought to have been sustained. Therefore, recycling of previously degassed CO2 quickly becomes more important than the ongoing supply of juvenile CO2. If so, then the atmospheric CO2 pressure, and thereby the surface temperature, may be approximated mathematically as a function of the total degassed CO2 in the atmosphere plus buried material and the ratio of the atmospheric and regolith mean residence times. The latter ratio can also be expressed as a function of heat flow. Hence, it follows that the surface temperature may be expressed as a function of heat flow and the total amount of available CO2. However, the depth to the water table can simultaneously be expressed as a function of heat flow and the surface temperature (the boundary condition). Therefore, for any given values of total available CO2 and regolith conductivity, there exist coupled independent equations which relate heat flow, surface temperature, and the depth to the water table. This means we can now derive simultaneous values of surface temperature and the depth of the water table for any value of the heat flow. The derived relationship is used to evaluate the relative importance of the atmospheric greenhouse effect and the internal regolith thermal gradient in producing morphological changes for any value of the heat flow, and to assess the absolute importance of each of the values of the heat flow which are thought to be reasonable on independent geophysical grounds.

  10. Heating of Jupiter's upper atmosphere above the Great Red Spot.

    Science.gov (United States)

    O'Donoghue, J; Moore, L; Stallard, T S; Melin, H

    2016-08-11

    The temperatures of giant-planet upper atmospheres at mid- to low latitudes are measured to be hundreds of degrees warmer than simulations based on solar heating alone can explain. Modelling studies that focus on additional sources of heating have been unable to resolve this major discrepancy. Equatorward transport of energy from the hot auroral regions was expected to heat the low latitudes, but models have demonstrated that auroral energy is trapped at high latitudes, a consequence of the strong Coriolis forces on rapidly rotating planets. Wave heating, driven from below, represents another potential source of upper-atmospheric heating, though initial calculations have proven inconclusive for Jupiter, largely owing to a lack of observational constraints on wave parameters. Here we report that the upper atmosphere above Jupiter's Great Red Spot--the largest storm in the Solar System--is hundreds of degrees hotter than anywhere else on the planet. This hotspot, by process of elimination, must be heated from below, and this detection is therefore strong evidence for coupling between Jupiter's lower and upper atmospheres, probably the result of upwardly propagating acoustic or gravity waves. PMID:27462811

  11. Plasma-ion Induced Sputtering and Heating of Titan's Atmosphere

    Science.gov (United States)

    Johnson, R. E.; Tucker, O. J.

    2007-05-01

    Titan is unique among the outer solar system icy satellites in having an atmosphere with a column density about ten times that of the Earth's atmosphere and an atmospheric mass to solid mass ratio comparable to that of Venus. Atmospheres equivalent in size to that at Titan would have been removed from the icy Galilean satellites by the plasma trapped in the Jovian magnetosphere (Johnson 2004). Therefore, the use of Cassini data to determine the present erosion rate of Titan's atmosphere provides an important end point for studying the erosion and heating of planetary and satellite atmospheres by an ambient plasma. In this paper we describe the deposition of energy, the erosion and the expansion of the upper atmosphere of Titan using Direct Simulation Monte Carlo models (Shematovich et al. 2003; Michael et al. 2005; Michael and Johnson 2005). These calculations are used to calibrate semi-empirical models of atmospheric sputtering (Johnson 1994) that are used to interpret Cassini data at Titan. Using a number of plasma conditions, the temperature and density vs. altitude above the exobase and the rate of escape are calculated. References: Johnson, R.E. "Plasma-induced Sputtering of an Atmosphere" in Space Science Reviews 69 215-253 (1994). Johnson. R.E., " The magnetospheric plasmadriven evolution of satellite atmospheres" Astrophys. J. 609, L99-L102 (2004). Michael, M. and R.E. Johnson, "Energy deposition of pickup ions and heating of Titan's atmosphere", Planetary & Space Sci.53, 1510-1514 (2005). Michael M., R.E. Johnson, F. Leblanc, M. Liu, J.G. Luhmann, and V.I. Shematovich, "Ejection of nitrogen from Titan's atmosphere by magnetospheric ions and pick-up ions", Icarus 175, 263-267 (2005). Shematovich, V.I., R.E. Johnson, M. Michael, and J.G. Luhmann, "Nitrogen loss from Titan", JGR 108, No. E8, 5087, doi:10.1029/2003JE002094 (2003).

  12. 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.

  13. LARGE-SCALE CORONAL PROPAGATING FRONTS IN SOLAR ERUPTIONS AS OBSERVED BY THE ATMOSPHERIC IMAGING ASSEMBLY ON BOARD THE SOLAR DYNAMICS OBSERVATORY—AN ENSEMBLE STUDY

    International Nuclear Information System (INIS)

    This paper presents a study of a large sample of global disturbances in the solar corona with characteristic propagating fronts as intensity enhancement, similar to the phenomena that have often been referred to as Extreme Ultraviolet Imaging Telescope (EIT) waves or extreme-ultraviolet (EUV) waves. Now EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory provide a significantly improved view of these large-scale coronal propagating fronts (LCPFs). Between 2010 April and 2013 January, a total of 171 LCPFs have been identified through visual inspection of AIA images in the 193 Å channel. Here we focus on the 138 LCPFs that are seen to propagate across the solar disk, first studying how they are associated with flares, coronal mass ejections (CMEs), and type II radio bursts. We measure the speed of the LCPF in various directions until it is clearly altered by active regions or coronal holes. The highest speed is extracted for each LCPF. It is often considerably higher than EIT waves. We do not find a pattern where faster LCPFs decelerate and slow LCPFs accelerate. Furthermore, the speeds are not strongly correlated with the flare intensity or CME magnitude, nor do they show an association with type II bursts. We do not find a good correlation either between the speeds of LCPFs and CMEs in a subset of 86 LCPFs observed by one or both of the Solar and Terrestrial Relations Observatory spacecraft as limb events

  14. The role of turbulence in coronal heating and solar wind expansion.

    Science.gov (United States)

    Cranmer, Steven R; Asgari-Targhi, Mahboubeh; Miralles, Mari Paz; Raymond, John C; Strachan, Leonard; Tian, Hui; Woolsey, Lauren N

    2015-05-13

    Plasma in the Sun's hot corona expands into the heliosphere as a supersonic and highly magnetized solar wind. This paper provides an overview of our current understanding of how the corona is heated and how the solar wind is accelerated. Recent models of magnetohydrodynamic turbulence have progressed to the point of successfully predicting many observed properties of this complex, multi-scale system. However, it is not clear whether the heating in open-field regions comes mainly from the dissipation of turbulent fluctuations that are launched from the solar surface, or whether the chaotic 'magnetic carpet' in the low corona energizes the system via magnetic reconnection. To help pin down the physics, we also review some key observational results from ultraviolet spectroscopy of the collisionless outer corona.

  15. Atmospheric heat redistribution and collapse on tidally locked rocky planets

    CERN Document Server

    Wordsworth, Robin

    2014-01-01

    Atmospheric collapse is likely to be of fundamental importance to tidally locked rocky exoplanets but remains understudied. Here, general results on the heat transport and stability of tidally locked terrestrial-type atmospheres are reported. First, the problem is modeled with an idealized 3D general circulation model (GCM) with gray gas radiative transfer. It is shown that over a wide range of parameters the atmospheric boundary layer, rather than the large-scale circulation, is the key to understanding the planetary energy balance. Through a scaling analysis of the interhemispheric energy transfer, theoretical expressions for the day-night temperature difference and surface wind speed are created that reproduce the GCM results without tuning. Next, the GCM is used with correlated-k radiative transfer to study heat transport for two real gases (CO2 and CO). For CO2, empirical formulae for the collapse pressure as a function of planetary mass and stellar flux are produced, and critical pressures for atmospher...

  16. The impact of oceanic heat transport on the atmospheric circulation

    CERN Document Server

    Knietzsch, Marc-Andre; Lunkeit, Frank

    2014-01-01

    A general circulation model of intermediate complexity with an idealized earthlike aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is put on the Lorenz energy cycle and the atmospheric mean meridional circulation. The latter is analysed by means of the Kuo-Eliassen equation. The atmospheric heat transport compensates the imposed oceanic heat transport changes to a large extent in conjunction with significant modification of the general circulation. Up to a maximum about 3PW, an increase of the oceanic heat transport leads to an increase of the global mean near surface temperature and a decrease of its equator-to-pole gradient. For larger transports, the gradient is reduced further but the global mean remains approximately constant. This is linked to a cooling and a reversal of the temperature gradient in the tropics. A larger oceanic heat transport leads to a reduction of all reservoirs and conversions of the Lorenz energy cycl...

  17. The impact of oceanic heat transport on the atmospheric circulation

    Directory of Open Access Journals (Sweden)

    M.-A. Knietzsch

    2014-11-01

    Full Text Available A general circulation model of intermediate complexity with an idealized earthlike aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is put on the Lorenz energy cycle and the atmospheric mean meridional circulation. The latter is analysed by means of the Kuo–Eliassen equation. The atmospheric heat transport compensates the imposed oceanic heat transport changes to a large extent in conjunction with significant modification of the general circulation. Up to a maximum about 3 PW, an increase of the oceanic heat transport leads to an increase of the global mean near-surface temperature and a decrease of its equator-to-pole gradient. For larger transports, the gradient is reduced further but the global mean remains approximately constant. This is linked to a cooling and a reversal of the temperature gradient in the tropics. A larger oceanic heat transport leads to a reduction of all reservoirs and conversions of the Lorenz energy cycle but of different relative magnitude for the individual components. The available potential energy of the zonal mean flow and its conversion to eddy available potential energy are affected most. Both the Hadley and Ferrel cell show a decline for increasing oceanic heat transport, with the Hadley cell being more sensitive. Both cells exhibit a poleward shift of their maxima, and the Hadley cell broadens for larger oceanic transports. The partitioning, by means of the Kuo–Eliassen equation, reveals that zonal mean diabatic heating and friction are the most important sources for changes of the Hadley cell, while the behaviour of the Ferrell cell is mostly controlled by friction.

  18. Coronal bright points associated with minifilament eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Junchao; Jiang, Yunchun; Yang, Jiayan; Bi, Yi; Li, Haidong [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Yang, Bo; Yang, Dan, E-mail: hjcsolar@ynao.ac.cn [Also at Graduate School of Chinese Academy of Sciences, Beijing, China. (China)

    2014-12-01

    Coronal bright points (CBPs) are small-scale, long-lived coronal brightenings that always correspond to photospheric network magnetic features of opposite polarity. In this paper, we subjectively adopt 30 CBPs in a coronal hole to study their eruptive behavior using data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. About one-quarter to one-third of the CBPs in the coronal hole go through one or more minifilament eruption(s) (MFE(s)) throughout their lifetimes. The MFEs occur in temporal association with the brightness maxima of CBPs and possibly result from the convergence and cancellation of underlying magnetic dipoles. Two examples of CBPs with MFEs are analyzed in detail, where minifilaments appear as dark features of a cool channel that divide the CBPs along the neutral lines of the dipoles beneath. The MFEs show the typical rising movements of filaments and mass ejections with brightenings at CBPs, similar to large-scale filament eruptions. Via differential emission measure analysis, it is found that CBPs are heated dramatically by their MFEs and the ejected plasmas in the MFEs have average temperatures close to the pre-eruption BP plasmas and electron densities typically near 10{sup 9} cm{sup –3}. These new observational results indicate that CBPs are more complex in dynamical evolution and magnetic structure than previously thought.

  19. Coronal bright points associated with minifilament eruptions

    International Nuclear Information System (INIS)

    Coronal bright points (CBPs) are small-scale, long-lived coronal brightenings that always correspond to photospheric network magnetic features of opposite polarity. In this paper, we subjectively adopt 30 CBPs in a coronal hole to study their eruptive behavior using data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. About one-quarter to one-third of the CBPs in the coronal hole go through one or more minifilament eruption(s) (MFE(s)) throughout their lifetimes. The MFEs occur in temporal association with the brightness maxima of CBPs and possibly result from the convergence and cancellation of underlying magnetic dipoles. Two examples of CBPs with MFEs are analyzed in detail, where minifilaments appear as dark features of a cool channel that divide the CBPs along the neutral lines of the dipoles beneath. The MFEs show the typical rising movements of filaments and mass ejections with brightenings at CBPs, similar to large-scale filament eruptions. Via differential emission measure analysis, it is found that CBPs are heated dramatically by their MFEs and the ejected plasmas in the MFEs have average temperatures close to the pre-eruption BP plasmas and electron densities typically near 109 cm–3. These new observational results indicate that CBPs are more complex in dynamical evolution and magnetic structure than previously thought.

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

    Science.gov (United States)

    Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; DeVore, C. R.; Archontis, V.; Török, T.; Mason, H.; Curdt, W.; Meyer, K.; Dalmasse, K.; Matsui, Y.

    2016-07-01

    Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant 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 flares and coronal mass ejections (CMEs), jets share many common properties with these 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 close or 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 broad range of solar-heliospheric problems.

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

    CERN Document Server

    Raouafi, N E; Pariat, E; Young, P R; Sterling, A C; Savcheva, A; Shimojo, M; Moreno-Insertis, F; DeVore, C R; Archontis, V; Török, T; Mason, H; Curdt, W; Meyer, K; Dalmasse, K; Matsui, Y

    2016-01-01

    Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant 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 flares and coronal mass ejections (CMEs), jets share many common properties with these 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 close or 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 broad range of solar-heliospheric problems.

  2. Thermal and non-thermal emission from reconnecting twisted coronal loops

    CERN Document Server

    Pinto, R; Browning, P K; Vilmer, N

    2016-01-01

    Twisted magnetic fields should be ubiquitous in the solar corona. The magnetic energy contained in such twisted fields can be released during solar flares and other explosive phenomena. Reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops, and can be a viable alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. The goal of this study is to investigate the observational signatures of plasma heating and particle acceleration in kink-unstable twisted coronal loops using combination of MHD simulations and test-particle methods. The simulations describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD, and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us est...

  3. Is Magnetic Topology Important for Heating the Solar Atmosphere?

    CERN Document Server

    Parnell, C E; Threlfall, J; Edwards, S J

    2015-01-01

    Magnetic fields permeate the entire solar atmosphere weaving an extremely complex pattern on both local and global scales. In order to understand the nature of this tangled web of magnetic fields, its magnetic skeleton, which forms the boundaries between topologically distinct flux domains, may be determined. The magnetic skeleton consists of null points, separatrix surfaces, spines and separators. The skeleton is often used to clearly visualize key elements of the magnetic configuration, but parts of the skeleton are also locations where currents and waves may collect and dissipate. In this review, the nature of the magnetic skeleton on both global and local scales, over solar cycle time scales, is explained. The behaviour of wave pulses in the vicinity of both nulls and separators is discussed and so too is the formation of current layers and reconnection at the same features. Each of these processes leads to heating of the solar atmosphere, but collectively do they provide enough heat, spread over a wide e...

  4. Heating efficiency in hydrogen-dominated upper atmospheres

    CERN Document Server

    Shematovich, Valery I; Lammer, Helmut

    2014-01-01

    Context. The heating efficiency is defined as the ratio of the net local gas-heating rate to the rate of stellar radiative energy absorption. It plays an important role in thermal-escape processes from the upper atmospheres of planets that are exposed to stellar soft X-rays and extreme ultraviolet radiation (XUV). Aims. We model the thermal-escape-related heating efficiency of the stellar XUV radiation in the hydrogen-dominated upper atmosphere of the extrasolar gas giant HD 209458b. The model result is then compared with previous thermal-hydrogen-escape studies which assumed heating efficiency values between 10-100%. Methods. The photolytic and electron impact processes in the thermosphere were studied by solving the kinetic Boltzmann equation and applying a Direct Simulation Monte Carlo model. We calculated the energy deposition rates of the stellar XUV flux and that of the accompanying primary photoelectrons that are caused by electron impact processes in the H2 to H transition region in the upper atmosphe...

  5. Atmospheric electric field anomalies associated with solar flare/coronal mass ejection events and solar energetic charged particle "Ground Level Events"

    Directory of Open Access Journals (Sweden)

    E. A. Kasatkina

    2009-10-01

    Full Text Available We discuss the fair weather atmospheric electric field signatures of three major solar energetic charged particle events which occurred in on 15 April 2001, 18 April and 4 November, and their causative solar flares/coronal mass ejections (SF/CMEs. Only the 15 April 2001 shows clear evidence for Ez variation associated to SF/CME events and the other two events may support this hypothesis as well although for them the meteorological data were not available. All three events seem to be associated with relativistic solar protons (i.e. protons with energies >450 MeV of the Ground Level Event (GLE type. The study presents data on variations of the vertical component of the atmospheric electric field (Ez measured at the auroral station Apatity (geomagnetic latitude: 63.8°, the polar cap station Vostok (geomagnetic latitude: −89.3° and the middle latitude stations Voyeikovo (geomagnetic latitude: 56.1° and Nagycenk (geomagnetic latitude: 47.2°. A significant disturbance in the atmospheric electric field is sometimes observed close to the time of the causative solar flare; the beginning of the electric field perturbation at Apatity is detected one or two hours before the flare onset and the GLE onset. Atmospheric electric field records at Vostok and Voyeikovo show a similar disturbance at the same time for the 15 April 2001 event. Some mechanisms responsible for the electric field perturbations are considered.

  6. Atmospheric dynamics. Constrained work output of the moist atmospheric heat engine in a warming climate.

    Science.gov (United States)

    Laliberté, F; Zika, J; Mudryk, L; Kushner, P J; Kjellsson, J; Döös, K

    2015-01-30

    Incoming and outgoing solar radiation couple with heat exchange at Earth's surface to drive weather patterns that redistribute heat and moisture around the globe, creating an atmospheric heat engine. Here, we investigate the engine's work output using thermodynamic diagrams computed from reanalyzed observations and from a climate model simulation with anthropogenic forcing. We show that the work output is always less than that of an equivalent Carnot cycle and that it is constrained by the power necessary to maintain the hydrological cycle. In the climate simulation, the hydrological cycle increases more rapidly than the equivalent Carnot cycle. We conclude that the intensification of the hydrological cycle in warmer climates might limit the heat engine's ability to generate work.

  7. Is magnetic topology important for heating the solar atmosphere?

    Science.gov (United States)

    Parnell, Clare E.; Stevenson, Julie E. H.; Threlfall, James; Edwards, Sarah J.

    2015-04-01

    Magnetic fields permeate the entire solar atmosphere weaving an extremely complex pattern on both local and global scales. In order to understand the nature of this tangled web of magnetic fields, its magnetic skeleton, which forms the boundaries between topologically distinct flux domains, may be determined. The magnetic skeleton consists of null points, separatrix surfaces, spines and separators. The skeleton is often used to clearly visualize key elements of the magnetic configuration, but parts of the skeleton are also locations where currents and waves may collect and dissipate. In this review, the nature of the magnetic skeleton on both global and local scales, over solar cycle time scales, is explained. The behaviour of wave pulses in the vicinity of both nulls and separators is discussed and so too is the formation of current layers and reconnection at the same features. Each of these processes leads to heating of the solar atmosphere, but collectively do they provide enough heat, spread over a wide enough area, to explain the energy losses throughout the solar atmosphere? Here, we consider this question for the three different solar regions: active regions, open-field regions and the quiet Sun. We find that the heating of active regions and open-field regions is highly unlikely to be due to reconnection or wave dissipation at topological features, but it is possible that these may play a role in the heating of the quiet Sun. In active regions, the absence of a complex topology may play an important role in allowing large energies to build up and then, subsequently, be explosively released in the form of a solar flare. Additionally, knowledge of the intricate boundaries of open-field regions (which the magnetic skeleton provides) could be very important in determining the main acceleration mechanism(s) of the solar wind.

  8. Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere

    Science.gov (United States)

    Perez-Hoyos, Santiago; Sánchez-Lavega, A.

    2009-09-01

    We discuss here the solar downward net flux in the 0.25 - 2.5 µm range in the atmosphere of Jupiter and the associated heating rates under a number of vertical cloud structure scenarios focusing in the effect of clouds and hazes. Our numerical model is based in the doubling-adding technique to solve the radiative transfer equation and it includes gas absorption by CH4, NH3 and H2, in addition to Rayleigh scattering by a mixture of H2 plus He. Four paradigmatic Jovian regions have been considered (hot-spots, belts, zones and Polar Regions). The hot-spots are the most transparent regions with downward net fluxes of 2.5±0.5 Wm-2 at the 6 bar level. The maximum solar heating is 0.04±0.01 K/day and occurs above 1 bar. Belts and zones characterization result in a maximum net downward flux of 0.5 Wm-2 at 2 bar and 0.015 Wm-2 at 6 bar. Heating is concentrated in the stratospheric and tropospheric hazes. Finally, Polar Regions are also explored and the results point to a considerable stratospheric heating of 0.04±0.02 K/day. In all, these calculations suggest that the role of the direct solar forcing in the Jovian atmospheric dynamics is limited to the upper 1 - 2 bar of the atmosphere except in the hot-spot areas. Acknowledgments: This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07.

  9. Is magnetic topology important for heating the solar atmosphere?

    Science.gov (United States)

    Parnell, Clare E; Stevenson, Julie E H; Threlfall, James; Edwards, Sarah J

    2015-05-28

    Magnetic fields permeate the entire solar atmosphere weaving an extremely complex pattern on both local and global scales. In order to understand the nature of this tangled web of magnetic fields, its magnetic skeleton, which forms the boundaries between topologically distinct flux domains, may be determined. The magnetic skeleton consists of null points, separatrix surfaces, spines and separators. The skeleton is often used to clearly visualize key elements of the magnetic configuration, but parts of the skeleton are also locations where currents and waves may collect and dissipate. In this review, the nature of the magnetic skeleton on both global and local scales, over solar cycle time scales, is explained. The behaviour of wave pulses in the vicinity of both nulls and separators is discussed and so too is the formation of current layers and reconnection at the same features. Each of these processes leads to heating of the solar atmosphere, but collectively do they provide enough heat, spread over a wide enough area, to explain the energy losses throughout the solar atmosphere? Here, we consider this question for the three different solar regions: active regions, open-field regions and the quiet Sun. We find that the heating of active regions and open-field regions is highly unlikely to be due to reconnection or wave dissipation at topological features, but it is possible that these may play a role in the heating of the quiet Sun. In active regions, the absence of a complex topology may play an important role in allowing large energies to build up and then, subsequently, be explosively released in the form of a solar flare. Additionally, knowledge of the intricate boundaries of open-field regions (which the magnetic skeleton provides) could be very important in determining the main acceleration mechanism(s) of the solar wind.

  10. Tidal Heating of Young Super-Earth Atmospheres

    CERN Document Server

    Ginzburg, Sivan

    2016-01-01

    Short-period Earth to Neptune size exoplanets (super-Earths) with voluminous gas envelopes seem to be very common. These gas atmospheres are thought to have originated from the protoplanetary disk in which the planets were embedded during their first few Myr. The accretion rate of gas from the surrounding nebula is determined by the ability of the gas to cool and radiate away its gravitational energy. Here we demonstrate that heat from the tidal interaction between the star and the young (and therefore inflated) planet can inhibit the gas cooling and accretion. Quantitatively, we find that the growth of super-Earth atmospheres halts for planets with periods of about 10 days, provided that their initial eccentricities are of the order of 0.2. Thus, tidal heating provides a robust and simple mechanism that can simultaneously explain why these planets did not become gas giants and account for the deficit of low-density planets closer to the star, where the tides are even stronger. We suggest that tidal heating m...

  11. Geothermal heating enhances atmospheric asymmetries on synchronously rotating planets

    CERN Document Server

    Haqq-Misra, Jacob

    2014-01-01

    Earth-like planets within the liquid water habitable zone of M type stars may evolve into synchronous rotators. On these planets, the sub-stellar hemisphere experiences perpetual daylight while the opposing anti-stellar hemisphere experiences perpetual darkness. Because the night-side hemisphere has no direct source of energy, the air over this side of the planet is prone to freeze out and deposit on the surface, which could result in atmospheric collapse. However, general circulation models (GCMs) have shown that atmospheric dynamics can counteract this problem and provide sufficient energy transport to the anti-stellar side. Here we use an idealized GCM to consider the impact of geothermal heating on the habitability of synchronously rotating planets. Geothermal heating may be expected due to tidal interactions with the host star, and the effects of geothermal heating provide additional habitable surface area and may help to induce melting of ice on the anti-stellar hemisphere. We also explore the persisten...

  12. Energetic characterisation and statistics of solar coronal brightenings

    CERN Document Server

    Joulin, Vincent; Solomon, Jacques; Guennou, Chloé

    2016-01-01

    To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the largest contributors to the total energy dissipation in the corona. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. On the other hand, more detailed spectroscopic studies of structures such as coronal bright points do not provide enough statistical information to derive their total contribution to heating. We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel Extreme Ultra-Violet (EUV) data. To estimate the energies corresponding to heating events and deduce their distribution, we detect brightenings in five EUV channels of the Atmospheric Imaging Assembl...

  13. 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.

  14. Atmospheric heat transfer to the Arctic under main synoptic processes

    Science.gov (United States)

    Yurova, Alla; Gnatiuk, Natalia; Bobylev, Leonid; Zhu, Yali

    2016-04-01

    Arctic - mid-latitude teleconnections are operating in both ways and behind them are potentially some causes of the enhanced Arctic warming (e.g., through heat transfer from lower to higher latitudes) and the feedbacks from the Arctic climate to the mid-latitude weather patterns. In order to explain the variability of the surface air temperature in the Arctic, we aim to analyse the typical synoptic situations that, we hypothesize, are characterized by a specific patterns of heat exchange between the Arctic and mid-latitudes. According to classification of synoptic processes in the Arctic developed at the Arctic and Antarctic Research Institute (AARI) in St. Petersburg major typical groups of synoptic situations in the Arctic are few (six). They correspond to position and intensity of low- and high-pressure centres. Therefore, the whole data sample for the winter period for the entire period of instrumental observations (archive exists back to 1939) can be split into six groups that sub-sample each of six groups/types of synoptic situations. Then heat transfer to the Arctic can be estimated as the divergence of the horizontal (advective) heat flux (the product of wind speed and temperature gradient) within each vertical atmospheric layer, which is calculated based on the ERA Interim Reanalysis data for the winter season (1979-now). Mapping heat divergence fields will reveal the main mid-latitude sources of heat transported to the Arctic, average for the whole data sample and for each of the six main groups of synoptic situations. This work was supported by RFBR grants 16-55-53031

  15. Dynamical behaviour in coronal loops

    Science.gov (United States)

    Haisch, Bernhard M.

    1986-01-01

    Rapid variability has been found in two active region coronal loops observed by the X-ray Polychromator (XRP) and the Hard X-ray Imaging Spectrometer (HXIS) onboard the Solar Maximum Mission (SMM). There appear to be surprisingly few observations of the short-time scale behavior of hot loops, and the evidence presented herein lends support to the hypothesis that coronal heating may be impulsive and driven by flaring.

  16. On the structure of solar and stellar coronae - Loops and loop heat transport

    Science.gov (United States)

    Litwin, Christof; Rosner, Robert

    1993-01-01

    We discuss the principal constraints on mechanisms for structuring and heating the outer atmospheres - the coronae - of stars. We argue that the essential cause of highly localized heating in the coronae of stars like the sun is the spatially intermittent nature of stellar surface magnetic fields, and that the spatial scale of the resulting coronal structures is related to the spatial structure of the photospheric fields. We show that significant constraints on coronal heating mechanisms derive from the observed variations in coronal emission, and, in addition, show that the observed structuring perpendicular to coronal magnetic fields imposes severe constraints on mechanisms for heat dispersal in the low-beta atmosphere. In particular, we find that most of commonly considered mechanisms for heat dispersal, such as anomalous diffusion due to plasma turbulence or magnetic field line stochasticity, are much too slow to account for the observed rapid heating of coronal loops. The most plausible mechanism appears to be reconnection at the interface between two adjacent coronal flux bundles. Based on a model invoking hyperresistivity, we show that such a mechanism naturally leads to dominance of isolated single bright coronal loops and to bright coronal plasma structures whose spatial scale transverse to the local magnetic field is comparable to observed dimensions of coronal X-ray loops.

  17. Atmospheric pressure thermospray ionization using a heated microchip nebulizer.

    Science.gov (United States)

    Keski-Rahkonen, Pekka; Haapala, Markus; Saarela, Ville; Franssila, Sami; Kotiaho, Tapio; Kostiainen, Risto; Auriola, Seppo

    2009-10-30

    When a standard atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization (APPI) ion source is used without applying the corona discharge or photoirradiation, atmospheric pressure thermospray ionization (APTSI) of various compounds can be achieved. Although largely ignored, this phenomenon has recently gained interest as an alternative ionization technique. In this study, this technique is performed for the first time on a miniaturized scale using a microchip nebulizer. Sample ionization with the presented microchip-APTSI (microAPTSI) is achieved by applying only heat and gas flow to a nebulizer chip, without any other methods to promote gas-phase ionization. To evaluate the performance of the described microAPTSI setup, ionization efficiency for a set of test compounds was monitored as the microchip positioning, temperature, nebulizer gas flow rate, sample solution composition, and solvent flow rate were varied. The microAPTSI mass spectra of the test compounds were also compared to those obtained with ESI and APCI. The microAPTSI produces ESI-like spectra with low background noise, favoring the formation of protonated or deprotonated molecules of compounds that are ionizable in solution. Multiple charging of peptides without in-source fragmentation was also observed. Unlike ESI, however, the microAPTSI source can tolerate the presence of mobile phase additives like trifluoroacetic acid (TFA) without significant ion suppression. The microAPTSI source can be used with standard mass spectrometer ion source hardware, being a unique alternative to the present interfacing techniques.

  18. The Transition Region Response to a Coronal Nanoflare: Forward Modeling and Observations in SDO/AIA

    Science.gov (United States)

    Viall, Nicholeen; Klimchuk, James A.

    2016-05-01

    The corona and transition region (TR) are fundamentally coupled through the processes of thermal conduction and mass exchange. Yet the temperature-dependent emissions from the two locations behave quite differently in the aftermath of an impulsive heating event such as a coronal nanoflare. In this presentation, we use results from the EBTEL hydrodynamics code to demonstrate that after a coronal nanoflare, the TR is multithermal and the emission at all temperatures responds in unison. This is in contrast to the coronal plasma, which cools sequentially, emitting first at higher temperatures and then at lower temperatures. We apply the time lag technique of Viall & Klimchuk (2012) to the simulated Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory emission and show that coronal plasma light curves exhibit post-nanoflare cooling time lags, while TR light curves show time lags of zero, as observed. We further demonstrate that time lags of zero, regardless of physical cause, do not indicate a lack of variability. Rather, strong variability must be present, and it must occur in unison in the different channels. Lastly, we show that the 'coronal' channels in AIA can be dominated by bright TR emission. When defined in a physically meaningful way, the TR reaches a temperature of roughly 60% the peak temperature in a flux tube. The TR resulting from impulsive heating can extend to 3 MK and higher, well within the range of the 'coronal' AIA channels.

  19. Evaluation of carbon diffusion in heat treatment of H13 tool steel under different atmospheric conditions

    OpenAIRE

    Maziar Ramezani; Timotius Pasang; Zhan Chen; Thomas Neitzert; Dominique Au

    2015-01-01

    Although the cost of the heat treatment process is only a minor portion of the total production cost, it is arguably the most important and crucial stage on the determination of material quality. In the study of the carbon diffusion in H13 steel during austenitization, a series of heat treatment experiments had been conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied, i.e., heat treatment without atmospheric contro...

  20. Energetic characterisation and statistics of solar coronal brightenings

    Science.gov (United States)

    Joulin, V.; Buchlin, E.; Solomon, J.; Guennou, C.

    2016-07-01

    Context. To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the largest contributors to the total energy dissipation in the corona. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. On the other hand, more detailed spectroscopic studies of structures such as coronal bright points do not provide enough statistical information to derive their total contribution to heating. Aims: We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel extreme ultraviolet (EUV) data. Methods: To estimate the energies corresponding to heating events and deduce their distribution, we detected brightenings in five EUV channels of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We combined the results of these detections and used maps of temperature and emission measure derived from the same observations to compute the energies. Results: We obtain distributions of areas, durations, intensities, and energies (thermal, radiative, and conductive) of events. These distributions are power laws and we also find power-law correlations between event parameters. Conclusions: The energy distributions indicate that the energy from a population of events like the ones we detect represents a small contribution to the total coronal heating, even when extrapolating to smaller scales. The main explanations for this are how heating events can be extracted from observational data, and the incomplete knowledge of the thermal structure and processes in the coronal plasma attainable from available observations. Two movies attached to Fig. 3 are available in electronic form at

  1. Experimental Modeling of Sterilization Effects for Atmospheric Entry Heating on Microorganisms

    Science.gov (United States)

    Schubert, Wayne W.; Spry, James A.; Ronney, Paul D.; Pandian, Nathan R.; Welder, Eric

    2012-01-01

    The objective of this research was to design, build, and test an experimental apparatus for studying the parameters of atmospheric entry heating, and the inactivation of temperature-resistant bacterial spores. The apparatus is capable of controlled, rapid heating of sample coupons to temperatures of 200 to 350 C and above. The vacuum chamber permits operation under vacuum or special atmospheric gas mixtures.

  2. Evaluation of carbon diffusion in heat treatment of H13 tool steel under different atmospheric conditions

    Directory of Open Access Journals (Sweden)

    Maziar Ramezani

    2015-04-01

    Full Text Available Although the cost of the heat treatment process is only a minor portion of the total production cost, it is arguably the most important and crucial stage on the determination of material quality. In the study of the carbon diffusion in H13 steel during austenitization, a series of heat treatment experiments had been conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied, i.e., heat treatment without atmospheric control, heat treatment with stainless steel foil wrapping, pack carburization heat treatment and vacuum heat treatment. The results showed that stainless steel foil wrapping could restrict decarburization process, resulting in a constant hardness profile as vacuum heat treatment does. However, the tempering characteristic between these two heat treatment methods is different. Results from the gas nitrided samples showed that the thickness and the hardness of the nitrided layer is independent of the carbon content in H13 steel.

  3. On the averaging of ratios of specific heats in a multicomponent planetary atmosphere

    Science.gov (United States)

    Dubisch, R.

    1974-01-01

    The use of adiabatic relations in the calculation of planetary atmospheres requires knowledge of the ratio of specific heats of a mixture of gases under various pressure and temperature conditions. It is shown that errors introduced by simple averaging of the ratio of specific heats in a multicomponent atmosphere can be roughly 0.4%. Therefore, the gamma-averaging error can become important when integrating through the atmosphere to a large depth.

  4. Formation and evolution of coronal rain observed by SDO/AIA on February 22, 2012

    CERN Document Server

    Vashalomidze, Z; Zaqarashvili, T V; Oliver, R; Shergelashvili, B; Ramishvili, G; Poedts, S; De Causmaecker, P

    2015-01-01

    The formation and dynamics of coronal rain are currently not fully understood. Coronal rain is the fall of cool and dense blobs formed by thermal instability in the solar corona towards the solar surface with acceleration smaller than gravitational free fall. We aim to study the observational evidence of the formation of coronal rain and to trace the detailed dynamics of individual blobs. We used time series of the 171 \\AA\\, and 304 \\AA\\, spectral lines obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) above active region AR 11420 on February 22, 2012. Observations show that a coronal loop disappeared in the 171 \\AA\\ channel and appeared in the 304 \\AA\\ line$\\text{}\\text{}$ more than one hour later, which indicates a rapid cooling of the coronal loop from 1 MK to 0.05 MK. An energy estimation shows that the radiation is higher than the heat input, which indicates so-called catastrophic cooling. The cooling was accompanied by the formation of coronal rain in the fo...

  5. Impulsively Generated Linear and Non-linear Alfven Waves in the Coronal Funnels

    CERN Document Server

    Chmielewski, P; Murawski, K; Musielak, Z E

    2014-01-01

    We present simulation results of the impulsively generated linear and non-linear Alfven waves in the weakly curved coronal magnetic flux-tubes (coronal funnels) and discuss their implications for the coronal heating and solar wind acceleration. We solve numerically the time-dependent magnetohydrodynamic equations to find the temporal signatures of the small and large-amplitude Alfven waves in the model atmosphere of open and expanding magnetic field configuration with a realistic temperature distribution. We compute the maximum transversal velocity of both linear and non-linear Alfven waves at different heights of the model atmosphere, and study their response in the solar corona during the time of their propagation. We infer that the pulse-driven non-linear Alfven waves may carry sufficient wave energy fluxes to heat the coronal funnels and also to power the solar wind that originates in these funnels. Our study of linear Alfven waves show that they can contribute only to the plasma dynamics and heating of t...

  6. The Local Atmosphere and the Turbulent Heat Transfer in the Eastern Himalayas

    Institute of Scientific and Technical Information of China (English)

    ZOU Han; LI Peng; MA Shupo; ZHOU Libo; ZHU Jinhuan

    2012-01-01

    To understand the local atmosphere and heat transfer and to facilitate the boundary-layer parameterization of numerical simulation and prediction,an observational campaign was conducted in the Eastern Himalayas in June 2010.The local atmospheric properties and near-surface turbulent heat transfers were analyzed.The local atmosphere in this region is warmer,more humid and less windy,with weaker solar radiation and surface radiate heating than in the Middle Himalayas.The near-surface turbulent heat transfer in the Eastern Himalayas is weaker than that in the Middle Himalayas.The total heat transfer is mainly contributed by the latent heat transfer with a Bowen ratio of 0.36,which is essentially different from that in the Middle Himalayas and the other Tibetan regions.

  7. EIT waves and coronal magnetic field diagnostics

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Magnetic field in the solar lower atmosphere can be measured by the use of the Zeeman and Hanle effects. By contrast, the coronal magnetic field well above the solar surface, which directly controls various eruptive phenomena, can not be precisely measured with the traditional techniques. Several attempts are being made to probe the coronal magnetic field, such as force-free extrapolation based on the photospheric magnetograms, gyroresonance radio emissions, and coronal seismology based on MHD waves in the corona. Compared to the waves trapped in the localized coronal loops, EIT waves are the only global-scale wave phenomenon, and thus are the ideal tool for the coronal global seismology. In this paper, we review the observations and modelings of EIT waves, and illustrate how they can be applied to probe the global magnetic field in the corona.

  8. Quiet Sun coronal heating analyzing large scale magnetic structures driven by different small-scale uniform sources

    CERN Document Server

    Podladchikova, O; Krasnoselskikh, V V; Lefebvre, B

    2002-01-01

    Recent measurements of quiet Sun heating events by Krucker and Benz (1998) give strong support to Parker's (1988) hypothesis that small scale dissipative events make the main contribution to the quiet heating. Moreover, combining their observations with the analysis by Priest et al. (2000), it can be concluded that the sources driving these dissipative events are also small scale sources, typically of the order of (or smaller than) 2000 km and the resolution of modern instruments. Thus arises the question of how these small scale events participate into the larger scale observable phenomena, and how the information about small scales can be extracted from observations. This problem is treated in the framework of a simple phenomenological model introduced in Krasnoselskikh et al. (2001), which allows to switch between various small scale sources and dissipative processes. The large scale structure of the magnetic field is studied by means of Singular Value Decomposition (SVD) and a derived entropy, techniques ...

  9. Investigating the reliability of coronal emission measure distribution diagnostics using 3D radiative MHD simulations

    CERN Document Server

    Testa, Paola; Martinez-Sykora, Juan; Hansteen, Viggo; Carlsson, Mats

    2012-01-01

    Determining the temperature distribution of coronal plasmas can provide stringent constraints on coronal heating. Current observations with the Extreme ultraviolet Imaging Spectrograph onboard Hinode and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory provide diagnostics of the emission measure distribution (EMD) of the coronal plasma. Here we test the reliability of temperature diagnostics using 3D radiative MHD simulations. We produce synthetic observables from the models, and apply the Monte Carlo Markov chain EMD diagnostic. By comparing the derived EMDs with the "true" distributions from the model we assess the limitations of the diagnostics, as a function of the plasma parameters and of the signal-to-noise of the data. We find that EMDs derived from EIS synthetic data reproduce some general characteristics of the true distributions, but usually show differences from the true EMDs that are much larger than the estimated uncertainties suggest, especially when structures with signif...

  10. Conservative modelling of the moisture and heat transfer in building components under atmospheric excitation

    DEFF Research Database (Denmark)

    Janssen, Hans; Blocken, Bert; Carmeliet, Jan

    2007-01-01

    While the transfer equations for moisture and heat in building components are currently undergoing standardisation, atmospheric boundary conditions, conservative modelling and numerical efficiency are not addressed. In a first part, this paper adds a comprehensive description of those boundary co...

  11. Missing bits of the solar jigsaw puzzle: small-scale, kinetic effects in coronal studies

    CERN Document Server

    Tsiklauri, David

    2009-01-01

    The solar corona, anomalously hot outer atmosphere of the Sun, is traditionally described by magnetohydrodynamic, fluid-like approach. Here we review some recent developments when, instead, a full kinetic description is used. It is shown that some of the main unsolved problems of solar physics, such as coronal heating and solar flare particle acceleration can be viewed in a new light when the small-scale, kinetic plasma description methods are used.

  12. Sugarcane Bagasse Pyrolysis in a Carbon Dioxide Atmosphere with Conventional and Microwave-Assisted Heating

    OpenAIRE

    Lin, Bo-Jhih; Chen, Wei-Hsin

    2015-01-01

    Pyrolysis is an important thermochemical method to convert biomass into bio-oil. In this study, the pyrolysis of sugarcane bagasse in a CO2 atmosphere under conventional and microwave-assisted heating is investigated to achieve CO2 utilization. In the microwave pyrolysis, charcoal is used as the microwave absorber to aid in pyrolysis reactions. The results indicate that the yields of pyrolysis products are greatly influenced by the heating modes. In the conventional heating, the prime product...

  13. Sugarcane bagasse pyrolysis in a carbon dioxide atmosphere with conventional and microwave-assisted heating

    OpenAIRE

    Bo-Jhih eLin; Wei-Hsin eChen

    2015-01-01

    Pyrolysis is an important thermochemical method to convert biomass into bio-oil. In this study, the pyrolysis of sugarcane bagasse in a CO2 atmosphere under conventional and microwave-assisted heating is investigated to achieve CO2 utilization. In the microwave pyrolysis, charcoal is used as the microwave absorber to aid in pyrolysis reactions. The results indicate that the yields of pyrolysis products are greatly influenced by the heating modes. In the conventional heating, the prime product...

  14. Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA

    CERN Document Server

    Tian, Hui; Habbal, Shadia Rifal; He, Jiansen

    2011-01-01

    Observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) reveal ubiquitous episodic outflows (jets) with an average speed around 120 km s-1 at temperatures often exceeding a million degree in plume-like structures, rooted in magnetized regions of the quiet solar atmosphere. These outflows are not restricted to the well-known plumes visible in polar coronal holes, but are also present in plume-like structures originating from equatorial coronal holes and quiet-Sun regions. Outflows are also visible in the "interplume" regions throughout the atmosphere. Furthermore, the structures traced out by these flows in both plume and inter-plume regions continually exhibit transverse (Alfvenic) motion. Our finding suggests that high-speed outflows originate mainly from the magnetic network of the quiet Sun and coronal holes, and that the plume flows observed are highlighted by the denser plasma contained therein. These outflows might be an efficient means to provide heated mas...

  15. Middle atmosphere heating by exothermic chemical reactions involving odd-hydrogen species

    Science.gov (United States)

    Mlynczak, Martin G.; Solomon, Susan

    1991-01-01

    The rate of heating which occurs in the middle atmosphere due to four exothermic reactions involving members of the odd-hydrogen family is calculated. The following reactions are considered: O + OH yields O2 + H; H + O2 + M yields HO2 + M; H + O3 yields OH + O2; and O + HO2 yields OH + O2. It is shown that the heating rates due to these reactions rival the oxygen-related heating rates conventionally considered in middle-atmosphere models. The conversion of chemical potential energy into molecular translational energy (heat) by these odd-hydrogen reactions is shown to be a significant energy source in the middle atmosphere that has not been previously considered.

  16. Mega-heatwave temperatures due to combined soil desiccation and atmospheric heat accumulation

    Science.gov (United States)

    Miralles, Diego G.; Teuling, Adriaan J.; van Heerwaarden, Chiel C.; Vilà-Guerau de Arellano, Jordi

    2014-05-01

    The recent European mega-heatwaves of 2003 and 2010 broke temperature records across Europe. Although events of this magnitude were unprecedented from a historical perspective, they are expected to become common by the end of the century. However, our understanding of extreme heatwave events is limited and their representation in climate models remains imperfect. Here we investigate the physical processes underlying recent mega-heatwaves using satellite and balloon measurements of land and atmospheric conditions from the summers of 2003 in France and 2010 in Russia, in combination with a soil-water-atmosphere model. We find that, in both events, persistent atmospheric pressure patterns induced land-atmosphere feedbacks that led to extreme temperatures. During daytime, heat was supplied by large-scale horizontal advection, warming of an increasingly desiccated land surface and enhanced entrainment of warm air into the atmospheric boundary layer. Overnight, the heat generated during the day was preserved in an anomalous kilometres-deep atmospheric layer located several hundred metres above the surface, available to re-enter the atmospheric boundary layer during the next diurnal cycle. This resulted in a progressive accumulation of heat over several days, which enhanced soil desiccation and led to further escalation in air temperatures. Our findings suggest that the extreme temperatures in mega-heatwaves can be explained by the combined multi-day memory of the land surface and the atmospheric boundary layer.

  17. The Impact of Oceanic Heat Transport on the Atmospheric Circulation: a Thermodynamic Perspective

    CERN Document Server

    Schröder, Alexander; Lunkeit, Frank

    2014-01-01

    The present study investigates how global thermodynamic properties of the climate system are affected by the changes in the intensity of the imposed oceanic heat transport in an atmospheric general circulation model in aqua-planet configuration. Increasing the poleward oceanic heat transport results in an overall increase in the surface temperature and a decrease in the equator-to-pole surface temperature difference as a result of the ice-albedo feedback. Following the classical ansatz by Stone, the atmospheric heat transport changes in such a way that the total poleward heat transport remains almost unchanged. We also find that the efficiency of the climate machine, the intensity of the Lorenz energy cycle and the material entropy production of the system decline with increased oceanic heat transport which suggests that the climate system becomes less efficient and turns into a state of reduced entropy production, as the enhanced oceanic transport performs a stronger large-scale mixing between geophysical fl...

  18. Formation of extreme surface turbulent heat fluxes from the ocean to the atmosphere in the North Atlantic

    Science.gov (United States)

    Tilinina, N. D.; Gulev, S. K.; Gavrikov, A. V.

    2016-01-01

    The role of extreme surface turbulent fluxes in total oceanic heat loss in the North Atlantic is studied. The atmospheric circulation patterns enhancing ocean-atmosphere heat flux in regions with significant contributions of the extreme heat fluxes (up to 60% of the net heat loss) are analyzed. It is shown that extreme heat fluxes in the Gulf Stream and the Greenland and Labrador Seas occur in zones with maximal air pressure gradients, i.e., in cyclone-anticyclone interaction zones.

  19. Dual Nature of Heat Flux in Stable Atmospheric Surface Layer

    Science.gov (United States)

    Srivastava, P.; Sharan, M.

    2015-12-01

    The behavior of heat flux (H) with respect to the stability parameter (ζ) in stable surface layer (SSL) is analyzed with in the framework of Monin-Obukhov similarity (MOS) theory. The analytical expressions of H are obtained as functions of wind speed (U) and wind shear (dU/dz) using the linear similarity functions and accordingly two cases, (i) U = δ (constant) and (ii) dU/dz = δ are considered. The mathematical analysis shows that the magnitude of H increases with ζ till it attains a maximum value at ζ =ζc and then starts decreasing with increasing stability suggesting the dual characteristic of heat flux with stability parameter. The point of maximum heat flux is found to be dependent on the roughness length (z0) as well as the height above the surface. An attempt has been made to analyze the sensitivity of this dual characteristic of H with ζ using the non-linear similarity functions. The analysis shows that the dual nature of H persists in the case of linear as well as non-linear similarity functions. However, the point of extremum appears to be dependent on the nature of the similarity functions. Turbulent data over a tropical site Ranchi (India) is analyzed to validate the observed nature of H with the theoretical nature as predicted by MOS. The analysis of observational data reveals the non-existence of any preferred stability state in SSL as speculated by Wang and Bras (2010, 2011) and supports the conclusions of Malhi 1995, Derbyshire 1999, van de Wiel et al. 2007, Basu et al. 2008, and van de Wiel et al. 2011. Thus, the non-uniqueness of MOS equations does not appear to be a mathematical artifact and it is consistent with the observations as far as the nature of heat flux with respect to stability parameter in SSL is concerned.

  20. Emission Measure and Temperature Analysis of the Upper Coronal Source of a Solar Flare

    Science.gov (United States)

    Ning, Z.; Li, D.; Zhang, Q. M.

    2016-08-01

    An X-ray coronal source is usually seen above the reconnection site located above flare loops, while a second source appears in between this site and the loops. The first source is called the upper coronal source, the second the loop-top source. Both sources are thought to be related to the outflows from the magnetic reconnection site above the flare loops. Previous observations have shown that the upper coronal source has both a thermal and nonthermal component. In this article, we explore the spatial appearance of the upper coronal source in a solar flare observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory (SDO/AIA) on 8 March 2011. This event occurred at the limb with completely occulted loop footpoints. Both the loop-top and the upper coronal sources are well observed by RHESSI in X-rays. The loop-top source emission covers a wide energy range up to 50 keV, while the upper coronal source emits below 25 keV. The upper coronal source appears later (about two minutes) than the loop-top source, and the RHESSI X-ray spectral analysis shows that both sources have a temperature of 30 MK. This temperature is confirmed by the differential emission measure (DEM) analysis from SDO/AIA data. AIA observations show the counterparts in the ultraviolet (UV), and bidirectional outflows appear between AIA brightenings. The loop-top source seems to be located at the top of a hot and dense loop system, which expands with a speed of 10 km s^{-1}, while the upper coronal source moves faster upward with a speed of about 32 km s^{-1} in the same time interval. The analysis of the spatial distribution of the emission measure and temperature indicates that the hot plasma itself or the heating region are possibly moving upward from the lower coronal region where the loop-top source appears. This is the reason that the upper coronal source appears later than the loop-top source.

  1. Emission Measure and Temperature Analysis of the Upper Coronal Source of a Solar Flare

    Science.gov (United States)

    Ning, Z.; Li, D.; Zhang, Q. M.

    2016-06-01

    An X-ray coronal source is usually seen above the reconnection site located above flare loops, while a second source appears in between this site and the loops. The first source is called the upper coronal source, the second the loop-top source. Both sources are thought to be related to the outflows from the magnetic reconnection site above the flare loops. Previous observations have shown that the upper coronal source has both a thermal and nonthermal component. In this article, we explore the spatial appearance of the upper coronal source in a solar flare observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory (SDO/AIA) on 8 March 2011. This event occurred at the limb with completely occulted loop footpoints. Both the loop-top and the upper coronal sources are well observed by RHESSI in X-rays. The loop-top source emission covers a wide energy range up to 50 keV, while the upper coronal source emits below 25 keV. The upper coronal source appears later (about two minutes) than the loop-top source, and the RHESSI X-ray spectral analysis shows that both sources have a temperature of 30 MK. This temperature is confirmed by the differential emission measure (DEM) analysis from SDO/AIA data. AIA observations show the counterparts in the ultraviolet (UV), and bidirectional outflows appear between AIA brightenings. The loop-top source seems to be located at the top of a hot and dense loop system, which expands with a speed of 10 km s^{-1}, while the upper coronal source moves faster upward with a speed of about 32 km s^{-1} in the same time interval. The analysis of the spatial distribution of the emission measure and temperature indicates that the hot plasma itself or the heating region are possibly moving upward from the lower coronal region where the loop-top source appears. This is the reason that the upper coronal source appears later than the loop-top source.

  2. Heating of Jupiter’s upper atmosphere above the Great Red Spot

    Science.gov (United States)

    O'Donoghue, J.; Moore, L.; Stallard, T. S.; Melin, H.

    2016-08-01

    The temperatures of giant-planet upper atmospheres at mid- to low latitudes are measured to be hundreds of degrees warmer than simulations based on solar heating alone can explain. Modelling studies that focus on additional sources of heating have been unable to resolve this major discrepancy. Equatorward transport of energy from the hot auroral regions was expected to heat the low latitudes, but models have demonstrated that auroral energy is trapped at high latitudes, a consequence of the strong Coriolis forces on rapidly rotating planets. Wave heating, driven from below, represents another potential source of upper-atmospheric heating, though initial calculations have proven inconclusive for Jupiter, largely owing to a lack of observational constraints on wave parameters. Here we report that the upper atmosphere above Jupiter’s Great Red Spot—the largest storm in the Solar System—is hundreds of degrees hotter than anywhere else on the planet. This hotspot, by process of elimination, must be heated from below, and this detection is therefore strong evidence for coupling between Jupiter’s lower and upper atmospheres, probably the result of upwardly propagating acoustic or gravity waves.

  3. The puzzling chemical composition of GJ 436b's atmosphere: influence of tidal heating on the chemistry

    CERN Document Server

    Agundez, M; Selsis, F; Iro, N

    2013-01-01

    The dissipation of the tidal energy deposited on eccentric planets may induce a heating of the planet that affects its atmospheric thermal structure. Here we study the influence of tidal heating on the atmospheric composition of the eccentric (e = 0.16) "hot Neptune" GJ 436b, for which inconclusive chemical abundances are retrieved from multiwavelength photometric observations carried out during primary transit and secondary eclipse. We build up a one-dimensional model of GJ 436b's atmosphere in the vertical direction and compute the pressure-temperature and molecular abundances profiles for various plausible internal temperatures of the planet (up to 560 K) and metallicities (from solar to 100 times solar), using a radiative-convective model and a chemical model which includes thermochemical kinetics, vertical mixing, and photochemistry. We find that the CO/CH4 abundance ratio increases with metallicity and tidal heating, and ranges from 1/20 to 1000 within the ranges of metallicity and internal temperature ...

  4. 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.

  5. Forward Modelling of Standing Kink Modes in Coronal Loops II. Applications

    CERN Document Server

    Yuan, Ding

    2016-01-01

    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 modelling) of the observables into the thermal and magnetic structures of the plasma. However, owing to the limited availability of observables, this is an ill-posed issue. Forward Modelling is 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 t...

  6. Heat and water transfer in bare topsoil and the lower atmosphere

    OpenAIRE

    ten Berge, H.F.M.

    1996-01-01

    This book describes an analysis of processes and factors that affect the energy balance of bare soil, and the associated exchange of heat and moisture at the surface. After a brief treatment of basic transport theory, the processes of soil-atmosphere interaction are expressed in a simulation algorithm. This algorithm provides an instrument to study the 'conditioning' effect of soil on the lower atmosphere, and vice versa. Examples of sensitivity analysis are presented, with emphasis on the be...

  7. Response of a stably stratified atmosphere to low-level heating - An application to the heat island problem

    Science.gov (United States)

    Baik, Jong-Jin

    1992-01-01

    Two-dimensional airflow characteristics past a heat island are investigated using both a linear analytic model and a nonlinear numerical model in the context of the response of a stably stratified atmosphere to specified low-level heating in a constant shear flow. Results from the steady-state, linear, analytic solutions exhibit typical flow response fields that gravity waves produce in response to the local heat source in the presence of environmental flow. The magnitude of the perturbation vertical velocity is shown to be much larger in the shear-flow case than in the uniform-flow case. Two distinct flow features are observed for larger heating amplitude (hence, larger nonlinearity factor): the gravity-wave-type response field on the upstream side of the heat island and the strong updraft circulation cell located on the downstream side. As the heating amplitude increases, the updraft circulation cell strengthens and shifts farther downwind. The strong updraft cell is believed to be partly responsible for precipitation enhancement observed on the downstream side of the heat island. It is found that the continuing downwind propagation of the updraft circulation cell is related to basic-state wind speed.

  8. Shortwave radiative heating rate profiles in hazy and clear atmosphere: a sensitivity study

    Science.gov (United States)

    Doppler, Lionel; Fischer, Jürgen; Ravetta, François; Pelon, Jacques; Preusker, René

    2010-05-01

    Aerosols have an impact on shortwave heating rate profiles (additional heating or cooling). In this survey, we quantify the impact of several key-parameters on the heating rate profiles of the atmosphere with and without aerosols. These key-parameters are: (1) the atmospheric model (tropical, midlatitude summer or winter, US Standard), (2) the integrated water vapor amount (IWV ), (3) the ground surface (flat and rough ocean, isotropic surface albedo for land), (4) the aerosol composition (dusts, soots or maritimes mixtures with respect to the OPAC-database classification), (5) the aerosol optical depth and (6) vertical postion, and (7) the single-scattering albedo (?o) of the aerosol mixture. This study enables us to evaluate which parameters are most important to take into account in a radiative energy budget of the atmosphere and will be useful for a future study: the retrieval of heating rates profiles from satellite data (CALIPSO, MODIS, MERIS) over the Mediterranean Sea. All the heating rates are computed by using the vector irradiances computed at each pressure level in the spectral interval 0.2 - 3.6μm (shortwave) by the 1D radiative transfer model for atmosphere and ocean: MOMO (Matrix-Operator MOdel) of the Institute for Space Science, FU Berlin 1

  9. Alfv\\'en Wave Turbulence as a Coronal Heating Mechanism: Simultaneously Predicting the Heating Rate and the Wave-Induced Emission Line Broadening

    CERN Document Server

    Oran, R; van der Holst, B; Sokolov, I V; Gombosi, T I

    2014-01-01

    In the present work, we test the predictions of the AWSoM model, a global extended-MHD model capable of calculating the propagation and turbulent dissipation of Alfv\\'en waves in any magnetic topology, against high resolution spectra of the quiescent off-disk solar corona. Wave dissipation is the only heating mechanism assumed in this model. Combining 3D model results with the CHIANTI atomic database, we were able to create synthetic line-of-sight spectra which include the effects of emission line broadening due to both thermal and wave-related non-thermal motions. To the best of our knowledge this is the first time a global model is used to obtain synthetic non-thermal line broadening. We obtained a steady-state solution driven by a synoptic magnetogram and compared the synthetic spectra with SUMER observations of a quiescent area above the solar west limb extending between 1.04 and 1.34 solar radii at the equator. Both the predicted line widths and the total line fluxes were consistent with the observations...

  10. Synoptic-scale characteristics and atmospheric controls of summer heat waves in China

    Science.gov (United States)

    Wang, Weiwen; Zhou, Wen; Li, Xiuzhen; Wang, Xin; Wang, Dongxiao

    2016-05-01

    Summer heat waves with persistent extreme high temperatures have been occurring with increasing frequency in recent decades. These extreme events have disastrous consequences for human health, economies, and ecosystems. In this study, we examine three summers with intense and protracted heat waves: the summers of 2003, 2006, and 2013, with high temperatures located mainly in southeastern, southwestern, and eastern China, respectively. The synoptic-scale characteristics of these heat waves and associated atmospheric circulation anomalies are investigated. In the early heat wave episode of 2003, a heat center was located in the southeast coastal provinces during the first 20 days of July. The maximum southward displacement of the East Asian jet stream (EAJS) induced anticyclonic anomalies to the south, associated with southwestward intensification of the western North Pacific subtropical high (WNPSH), and extreme high temperatures were found only to the south of the Yangtze River. In the later episode, a poleward displacement of the EAJS and an enhanced WNPSH over the midlatitudes of eastern China resulted in a "heat dome" over the region, and the heat wave extended northward to cover a larger area of eastern China. The coupling between the westward-enhanced WNPSH and poleward-displaced EAJS was found in the East China heat wave of 2013 as well. But the area of high temperatures reached far to the north in August 2013, with below-normal temperatures located in a small region of South China. In the 2006 southwestern drought and heat wave, extreme poleward displacement of the EAJS, associated with extraordinary westward extension of the WNSPH, resulted in further blocking of the moisture supply from the southwest monsoon. Large-scale moisture deficiencies, dry conditions, and downslope winds were common features of all investigated heat wave episodes. But in 2006, low-level heat lows associated with a well-mixed layer due to intensive daytime heating and atmospheric

  11. Phase transformations of a talc ore under heated chlorine atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Orosco, P., E-mail: porosco@unsl.edu.ar [Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET), Chacabuco y Pedernera, 5700 San Luis (Argentina); Ruiz, M. del C. [Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET), Chacabuco y Pedernera, 5700 San Luis (Argentina); Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); González, J. [Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET), Chacabuco y Pedernera, 5700 San Luis (Argentina); Instituto de Ciencias Básicas, Universidad Nacional de Cuyo, Mendoza (Argentina)

    2013-02-20

    Highlights: ► We studied the effect of Cl{sub 2} on minerals present in a talc of ultramafic origin. ► Isothermal and non-isothermal assays were performed in N{sub 2} and Cl{sub 2}–N{sub 2} atmospheres. ► The reagents and the products were analyzed by DTA, XRD, SEM, and EPMA. ► The chlorination produced protoenstatite at 800 °C. ► Calcination of a talc ore in Cl{sub 2} produces more enstatite than thermal treatment in N{sub 2}. - Abstract: The effect of Cl{sub 2} on the phase transformations of the minerals present in a talc (Mg{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}) unpurified with clinochlore (Mg{sub 5}Al{sub 2}Si{sub 3}O{sub 10}(OH){sub 8}), magnesite (MgCO{sub 3}), dolomite (MgCa(CO{sub 3}){sub 2}), hematite (Fe{sub 2}O{sub 3}) and pyrite (FeS{sub 2}) was studied with the purpose of deferricating the mineral and obtaining protoenstatite (MgSiO{sub 3}), which is the basic component of steatite ceramics. Isothermal and non-isothermal assays in N{sub 2} and Cl{sub 2}–N{sub 2} atmospheres were performed using a thermogravimetric device at temperatures between 600 and 980 °C. The reagents and the products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Results obtained showed that the following phenomena were produced in Cl{sub 2}: (a) The transformation of vitreous silica (SiO{sub 2}), from the chlorination reaction of talc, into enstatite (MgSiO{sub 3}) started at about 700 °C, being dolomite the mineral that favored this reaction. At 800 °C, more enstatite was formed as a result of the reaction between vitreous silica not transformed, MgCl{sub 2} and O{sub 2} derived from the chlorination of dolomite and magnesite; then, polymorphic transformation of enstatite into protoenstatite was produced. (b) At about 950 °C, CaCl{sub 2} produced as a result of dolomite chlorination led to the destruction of the protoenstatite

  12. The Transition Region Response to a Coronal Nanoflare: Forward Modeling and Observations in SDO/AIA

    Science.gov (United States)

    Viall-Kepko, Nicholeen M.; Klimchuk, James A.

    2015-01-01

    The corona and transition region (TR) are fundamentally coupled through the processes of thermal conduction and mass exchange. It is not possible to understand one without the other. Yet the temperature-dependent emissions from the two locations behave quite differently in the aftermath of an impulsive heating event such as a coronal nanoflare. Whereas the corona cools sequentially, emitting first at higher temperatures and then at lower temperatures, the TR is multithermal and the emission at all temperatures responds in unison. We have previously applied the automated time lag technique of Viall & Klimchuk to disk observations of an active region (AR) made by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. Lines of sight passing through coronal plasma show clear evidence for post-nanoflare cooling, while lines of sight intersecting the TR footpoints of coronal strands show zero time lag. In this paper, we use the EBTEL hydrodynamics code to demonstrate that this is precisely the expected behavior when the corona is heated by nanoflares. We also apply the time lag technique for the first time to off-limb observations of an AR. Since TR emission is not present above the limb, the occurrence of zero time lags is greatly diminished, supporting the conclusion that zero time lags measured on the disk are due to TR plasma. Lastly, we show that the "coronal" channels in AIA can be dominated by bright TR emission. When defined in a physically meaningful way, the TR reaches a temperature of roughly 60% the peak temperature in a flux tube. The TR resulting from impulsive heating can extend to 3 MK and higher, well within the range of the "coronal" AIA channels.

  13. Segmentation of Coronal Holes Using Active Contours Without Edges

    CERN Document Server

    Boucheron, L E; McAteer, R T J

    2016-01-01

    An application of active contours without edges is presented as an efficient and effective means of extracting and characterizing coronal holes. Coronal holes are regions of low-density plasma on the Sun with open magnetic field lines. As the source of the fast solar wind, the detection and characterization of these regions is important for both testing theories of their formation and evolution and from a space weather perspective. Coronal holes are detected in full disk extreme ultraviolet (EUV) images of the corona obtained with the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA). The proposed method detects coronal boundaries without determining any fixed intensity value in the data. Instead, the active contour segmentation employs an energy-minimization in which coronal holes are assumed to have more homogeneous intensities than surrounding active regions and quiet Sun. The segmented coronal holes tend to correspond to unipolar magnetic regions, are consistent with concurrent solar wind ...

  14. Tropical Ocean and Global Atmosphere (TOGA) heat exchange project: A summary report

    Science.gov (United States)

    Liu, W. T.; Niiler, P. P.

    1985-01-01

    A pilot data center to compute ocean atmosphere heat exchange over the tropical ocean is prposed at the Jet Propulsion Laboratory (JPL) in response to the scientific needs of the Tropical Ocean and Global Atmosphere (TOGA) Program. Optimal methods will be used to estimate sea surface temperature (SET), surface wind speed, and humidity from spaceborne observations. A monthly summary of these parameters will be used to compute ocean atmosphere latent heat exchanges. Monthly fields of surface heat flux over tropical oceans will be constructed using estimations of latent heat exchanges and short wave radiation from satellite data. Verification of all satellite data sets with in situ measurements at a few locations will be provided. The data center will be an experimental active archive where the quality and quantity of data required for TOGA flux computation are managed. The center is essential to facilitate the construction of composite data sets from global measurements taken from different sensors on various satellites. It will provide efficient utilization and easy access to the large volume of satellite data available for studies of ocean atmosphere energy exchanges.

  15. Heat and water transfer in bare topsoil and the lower atmosphere

    NARCIS (Netherlands)

    ten Berge, H.F.M.

    1996-01-01

    This book describes an analysis of processes and factors that affect the energy balance of bare soil, and the associated exchange of heat and moisture at the surface. After a brief treatment of basic transport theory, the processes of soil-atmosphere interaction are expressed in a simulation algorit

  16. Persistent unstable atmospheric boundary layer enhances sensible and latent heat loss in a tropical great lake: Lake Tanganyika

    Science.gov (United States)

    Verburg, Piet; Antenucci, Jason P.

    2010-06-01

    Energy fluxes across the surface of lakes regulate heat storage and affect the water balance. Sensible and latent heat fluxes are affected by atmospheric stability, especially for large lakes. We examined the effect of atmospheric stability on the heat fluxes on seasonal time scales at Lake Tanganyika, East Africa, by estimating hourly sensible and latent heat fluxes and net radiation using thermistor chains and meteorological stations. The atmosphere was almost always unstable, in contrast to the atmosphere above North American Great Lakes which is unstable in winter and stable in summer. Persistent atmospheric instability resulted in a 13% and 18% increase in the annual mean heat loss by latent and sensible heat fluxes, respectively, relative to conditions of neutral stability. The persistent unstable atmosphere is caused by a higher water surface temperature compared with air temperature, which we argue is the case in general in (sub)tropical lakes. Low humidity further enhanced the frequency of unstable conditions and enhanced the exchange of heat and vapor from the lake to the atmosphere. The estimated heat fluxes were sensitive to the temporal scale of data inputs and to the local values of parameters such as air density. To our knowledge this is the first paper that demonstrates and quantifies the effect of atmospheric stability on latent and sensible heat fluxes from a lake on an annual basis, using data collected from the lake surface.

  17. Heat treatment's effects on hydroxyapatite powders in water vapor and air atmosphere

    Science.gov (United States)

    Karabulut, A.; Baştan, F. E.; Erdoǧan, G.; Üstel, F.

    2015-03-01

    Hydroxyapatite (HA; Ca10(PO4)6(OH)2) is the main chemical constituent of bone tissue (~70%) as well as HA which is a calcium phosphate based ceramic material forms inorganic tissue of bone and tooth as hard tissues is used in production of prosthesis for synthetic bone, fractured and broken bone restoration, coating of metallic biomaterials and dental applications because of its bio compatibility. It is known that Hydroxyapatite decomposes with high heat energy after heat treatment. Therefore hydroxyapatite powders that heated in water vapor will less decomposed phases and lower amorphous phase content than in air atmosphere. In this study high purity hydroxyapatite powders were heat treated with open atmosphere furnace and water vapor atmosphere with 900, 1000, 1200 °C. Morphology of same powder size used in this process by SEM analyzed. Chemical structures of synthesized coatings have been examined by XRD. The determination of particle size and morphological structure of has been characterized by Particle Sizer, and SEM analysis, respectively. Weight change of sample was recorded by thermogravimetric analysis (TGA) during heating and cooling.

  18. METHODS TO DETECT ATMOSPHERIC AND SURFACE HEAT ISLANDS IN URBAN AREAS

    Directory of Open Access Journals (Sweden)

    I. HERBEL

    2015-10-01

    Full Text Available Intensification of the urbanization process and its associated climatic effects is nowadays a major problem of large cities worldwide. One of these climatic effects is the urban heat island (UHI, that implies increased air and surface temperature values in the city when compared to the nearby rural areas. This phenomenon threatens the health of the population, especially during heat waves, affects the quality of the environment and the quality of life, and also generates significant costs to ensure the inhabitants' thermal comfort. In this study we present a review of the UHI concept and three of the main methods used to detect the atmospheric and surface urban heat islands. Satellite image data analysis seems an easier and time-saving solution, but due to its limitations, we consider that a combination of both surfaces and lower atmospheric layer temperature data analysis is the best choice in order to get accurate results of the intensity and spatial extension of the UHI.

  19. Magnetospheric structure and atmospheric Joule heating of habitable planets orbiting M-dwarf stars

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, O.; Drake, J. J.; Garraffo, C.; Poppenhaeger, K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Glocer, A. [NASA/GSFC, Code 673, Greenbelt, MD 20771 (United States); Bell, J. M. [Center for Planetary Atmospheres and Flight Sciences, National Institute of Aerospace, Hampton, VA 23666 (United States); Ridley, A. J.; Gombosi, T. I. [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)

    2014-07-20

    We study the magnetospheric structure and the ionospheric Joule Heating of planets orbiting M-dwarf stars in the habitable zone using a set of magnetohydrodynamic models. The stellar wind solution is used to drive a model for the planetary magnetosphere, which is coupled with a model for the planetary ionosphere. Our simulations reveal that the space environment around close-in habitable planets is extreme, and the stellar wind plasma conditions change from sub- to super-Alfvénic along the planetary orbit. As a result, the magnetospheric structure changes dramatically with a bow shock forming in the super-Alfvénic sectors, while no bow shock forms in the sub-Alfvénic sectors. The planets reside most of the time in the sub-Alfvénic sectors with poor atmospheric protection. A significant amount of Joule Heating is provided at the top of the atmosphere as a result of the intense stellar wind. For the steady-state solution, the heating is about 0.1%-3% of the total incoming stellar irradiation, and it is enhanced by 50% for the time-dependent case. The significant Joule Heating obtained here should be considered in models for the atmospheres of habitable planets in terms of the thickness of the atmosphere, the top-side temperature and density, the boundary conditions for the atmospheric pressure, and particle radiation and transport. Here we assume constant ionospheric Pedersen conductance similar to that of the Earth. The conductance could be greater due to the intense EUV radiation leading to smaller heating rates. We plan to quantify the ionospheric conductance in future study.

  20. Can coronal hole spicules reach coronal temperatures?

    OpenAIRE

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

    2011-01-01

    We aim with the present study to provide observational evidences on whether coronal hole spicules reach coronal temperatures. We combine multi-instrument co-observations obtained with the SUMER/SoHO and with the EIS/SOT/XRT/Hinode. The analysed three large spicules were found to be comprised of numerous thin spicules which 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 2...

  1. MICA Observations of Coronal Transients

    Science.gov (United States)

    Stenborg, G.; Schwenn, R.; Srivastava, N.

    1999-10-01

    Dynamical processes are well known to occur in the inner solar atmosphere, many of them giving origin to spectacular eruptions known as coronal mass ejections. The projected velocity of propagation of these events ranges from less than 100 km/sec to greater than 1200 km/sec. In order to study the initial evolution of the faster processes it is necessary to image the inner corona at a very high cadence. Although ground-based observations of the corona are strongly affected by sky conditions they allow imaging at a high temporal resolution as compared to coronagraphic observations from space. In the recently inaugurated German-Argentinean Solar-Observatory at El Leoncito, San Juan, Argentina, a mirror coronagraph (MICA) daily images the inner solar corona with high temporal and spatial resolution in two spectral ranges: the well known green (~1.8 MK) and red (~1.0 MK) coronal lines at 5303 A and 6374 A respectively. It is essentially similar in design to LASCO-C1 on board SOHO, its field-of-view ranging from 1.05 to 2.0 solar radii from the sun center. Thus, it is ideally suited to observe the hot material and reveal the fast processes that occur in the coronal plasma. In the last year MICA has recorded several fast and not so fast green line transients at a high temporal resolution. In this work we will present observations of a few such events. This study would allow us to have a better understanding of the conditions that trigger the coronal mass ejections and their propagation in the inner solar corona.

  2. Ponderomotive Acceleration in Coronal Loops

    CERN Document Server

    Dahlburg, R B; Taylor, B D; Obenschain, K

    2016-01-01

    Ponderomotive acceleration has been asserted to be a cause of the First Ionization Potential (FIP) effect, the by now 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 "byproduct" 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 a coronal loops with an axial magnetic field from 0.005 Teslas to 0.02 Teslas and lengths from 25000 km to 75000 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...

  3. Atmospheric Diabatic Heating Distributions Derived from a Combination of Satellite Sensor Data

    Science.gov (United States)

    Olson, W. S.; L'Ecuyer, T. S.; Gu, G.; Grecu, M.; Bosilovich, M. G.

    2010-12-01

    Satellite estimates of atmospheric latent+eddy heating (Q1-QR) and radiative heating (QR) are combined to yield estimates of the large-scale diabatic heating, or apparent heat source (Q1). The latent+eddy and radiative heating estimates rely on cloud and precipitation information from TRMM Microwave Imager (TMI) data, with additional cloud information supplied by the TRMM Visible and Infrared Scanner (VIRS) and clear-air environmental properties from NCEP reanalyses. Comparisons of the diabatic heating estimates to those derived primarily from the TRMM Precipitation Radar (PR) and from rawinsonde diagnostic budgets are favorable, although some biases due to differences in sampling and the limited sensitivity of the TMI are noted. The addition of an approximate Q1-QR estimate for non-precipitating regions leads to mean heating from precipitating/non-precipitating Q1-QR and mean cooling from QR in the troposphere that are roughly balanced over the TRMM domain. Recently, an eleven-year database of diabatic heating has been constructed using TRMM observations from 1998-2008, as part of NASA’s Energy and Water cycle Study (NEWS) program. Initial applications of this dataset have been the delineation of the seasonal cycle in the tropics/subtropics, the distribution of heating anomalies associated with the phases of ENSO, and the progression of heating in the Madden Julian Oscillation. Preliminary comparisons of satellite heating estimates versus model-based heating and dynamical fields from the Modern Era Retrospective-Analysis for Research and Applications (MERRA) will be presented at the conference.

  4. Coronal Loops: Observations and Modeling of Confined Plasma

    Science.gov (United States)

    Reale, Fabio

    2014-07-01

    Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered and, therefore, topics such as loop oscillations and flaring loops (except for non-solar ones, which provide information on stellar loops) are not specifically addressed here. The observational section discusses the classification, populations, and the morphology of coronal loops, its relationship with the magnetic field, and the loop stranded structure. The section continues with the thermal properties and diagnostics of the loop plasma, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics, hot and cool flows, and waves are illustrated. In the modeling section, some basics of loop physics are provided, supplying fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are divided into those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. More specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC) and impulsive (DC) heating. Large-scale models including atmosphere boxes and the magnetic field are also discussed. Finally, a brief discussion about stellar coronal loops is followed by highlights and open questions.

  5. Coronal Loops: Observations and Modeling of Confined Plasma

    Directory of Open Access Journals (Sweden)

    Fabio Reale

    2014-07-01

    Full Text Available Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered and, therefore, topics such as loop oscillations and flaring loops (except for non-solar ones, which provide information on stellar loops are not specifically addressed here. The observational section discusses the classification, populations, and the morphology of coronal loops, its relationship with the magnetic field, and the loop stranded structure. The section continues with the thermal properties and diagnostics of the loop plasma, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics, hot and cool flows, and waves are illustrated. In the modeling section, some basics of loop physics are provided, supplying fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are divided into those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. More specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC and impulsive (DC heating. Large-scale models including atmosphere boxes and the magnetic field are also discussed. Finally, a brief discussion about stellar coronal loops is followed by highlights and open questions.

  6. EUV Coronal Dimming and its Relationship to Coronal Mass Ejections

    Science.gov (United States)

    Mason, James

    2016-05-01

    As a coronal mass ejection (CME) departs from the inner solar atmosphere, it leaves behind a void. This region of depleted plasma results in a corresponding decrease in coronal emissions that can be observed by instruments tuned to measure the extreme ultraviolet (EUV) part of the electromagnetic spectrum. These coronal dimmings can be observed with EUV imagers and EUV spectral irradiance instruments. Onboard the Solar Dynamics Observatory (SDO), the EUV Variability Experiment (EVE) and Atmospheric Imaging Assembly (AIA) provide complementary observations; together they can be used to obtain high spatial and spectral resolution. AIA provides information about the location, extent, and spatial evolution of the dimming while EVE data are important to understand plasma temperature evolution. Concurrent processes with similar timescales to mass-loss dimming also impact the observations, which makes a deconvolution method necessary for the irradiance time series in order to have a “clean” mass-loss dimming light curve that can be parameterized and compared with CME kinematics. This presentation will first provide background on these various physical processes and the deconvolution method developed. Two case studies will then be presented, followed by a semi-statistical study (~30 events) to establish a correlation between dimming and CME parameters. In particular, the slope of the deconvolved irradiance dimming light curve is representative of the CME speed, and the irradiance dimming depth can serve as a proxy for CME mass. Finally, plans and early results from a more complete statistical study of all dimmings in the SDO era, based on an automated detection routine using EVE data, will be described and compared with independently derived dimmings automatically detected with AIA data.

  7. The redshifted footpoints of coronal loops

    Directory of Open Access Journals (Sweden)

    I. E. Dammasch

    2008-10-01

    Full Text Available The physics of coronal loops holds the key to understanding coronal heating and the flow of mass and energy in the region. However, the energy source, structure maintenance and mass balance in coronal loops are not yet fully understood. Observations of blue- and redshifted emissions have repeatedly been used in the construction of loop models. But observations and interpretations of line shifts have been widely debated. Here we present detailed SUMER observations, which clearly show a steady downflow in both footpoints of coronal loops observed at transition region (TR and lower corona temperatures. We also show and quantify a correlation existing between this Doppler shift and the spectral radiance. Our results indicate a strong correlation which holds from the chromosphere to the lower corona. We suggest that the downflow in the footpoints may be a common phenomenon on all scales, which could explain, why on a statistical basis bright pixels tend to be more redshifted. We conclude by presenting interpretation of such results and their implications in the light of a viable coronal loop model. The observation of steady downflow in redshifted footpoints seems to be in conflict with impulsive heating.

  8. MHD Modelling of Coronal Loops: Injection of High-Speed Chromospheric Flows

    Science.gov (United States)

    Petralia, A.; Reale, F.; Orlando, S.; Klimchuk, J. A.

    2014-01-01

    Context. Observations reveal a correspondence between chromospheric type II spicules and bright upward-moving fronts in the corona observed in the extreme-ultraviolet (EUV) band. However, theoretical considerations suggest that these flows are probably not the main source of heating in coronal magnetic loops. Aims. We investigate the propagation of high-speed chromospheric flows into coronal magnetic flux tubes and the possible production of emission in the EUV band. Methods. We simulated the propagation of a dense 104 K chromospheric jet upward along a coronal loop by means of a 2D cylindrical MHD model that includes gravity, radiative losses, thermal conduction, and magnetic induction. The jet propagates in a complete atmosphere including the chromosphere and a tenuous cool (approximately 0.8 MK) corona, linked through a steep transition region. In our reference model, the jet initial speed is 70 km per second, its initial density is 10(exp 11) per cubic centimeter, and the ambient uniform magnetic field is 10 G. We also explored other values of jet speed and density in 1D and different magnetic field values in 2D, as well as the jet propagation in a hotter (approximately 1.5 MK) background loop. Results. While the initial speed of the jet does not allow it to reach the loop apex, a hot shock-front develops ahead of it and travels to the other extreme of the loop. The shock front compresses the coronal plasma and heats it to about 10(exp 6) K. As a result, a bright moving front becomes visible in the 171 Angstrom channel of the SDO/AIA mission. This result generally applies to all the other explored cases, except for the propagation in the hotter loop. Conclusions. For a cool, low-density initial coronal loop, the post-shock plasma ahead of upward chromospheric flows might explain at least part of the observed correspondence between type II spicules and EUV emission excess.

  9. Radiation and Heat Transfer in the Atmosphere: A Comprehensive Approach on a Molecular Basis

    Directory of Open Access Journals (Sweden)

    Hermann Harde

    2013-01-01

    Full Text Available We investigate the interaction of infrared active molecules in the atmosphere with their own thermal background radiation as well as with radiation from an external blackbody radiator. We show that the background radiation can be well understood only in terms of the spontaneous emission of the molecules. The radiation and heat transfer processes in the atmosphere are described by rate equations which are solved numerically for typical conditions as found in the troposphere and stratosphere, showing the conversion of heat to radiation and vice versa. Consideration of the interaction processes on a molecular scale allows to develop a comprehensive theoretical concept for the description of the radiation transfer in the atmosphere. A generalized form of the radiation transfer equation is presented, which covers both limiting cases of thin and dense atmospheres and allows a continuous transition from low to high densities, controlled by a density dependent parameter. Simulations of the up- and down-welling radiation and its interaction with the most prominent greenhouse gases water vapour, carbon dioxide, methane, and ozone in the atmosphere are presented. The radiative forcing at doubled CO2 concentration is found to be 30% smaller than the IPCC-value.

  10. 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

  11. Atmospheric Forcing of the Winter Air–Sea Heat Fluxes over the Northern Red Sea

    KAUST Repository

    Papadopoulos, Vassilis P.

    2013-03-01

    The influence of the atmospheric circulation on the winter air–sea heat fluxes over the northern Red Sea is investigated during the period 1985–2011. The analysis based on daily heat flux values reveals that most of the net surface heat exchange variability depends on the behavior of the turbulent components of the surface flux (the sum of the latent and sensible heat). The large-scale composite sea level pressure (SLP) maps corresponding to turbulent flux minima and maxima show distinct atmospheric circulation patterns associated with each case. In general, extreme heat loss (with turbulent flux lower than −400 W m−2) over the northern Red Sea is observed when anticyclonic conditions prevail over an area extending from the Mediterranean Sea to eastern Asia along with a recession of the equatorial African lows system. Subcenters of high pressure associated with this pattern generate the required steep SLP gradient that enhances the wind magnitude and transfers cold and dry air masses from higher latitudes. Conversely, turbulent flux maxima (heat loss minimization with values from −100 to −50 W m−2) are associated with prevailing low pressures over the eastern Mediterranean and an extended equatorial African low that reaches the southern part of the Red Sea. In this case, a smooth SLP field over the northern Red Sea results in weak winds over the area that in turn reduce the surface heat loss. At the same time, southerlies blowing along the main axis of the Red Sea transfer warm and humid air northward, favoring heat flux maxima.

  12. Enhanced apatite formation on Ti metal heated in PO2-controlled nitrogen atmosphere.

    Science.gov (United States)

    Hashimoto, Masami; Hayashi, Kazumi; Kitaoka, Satoshi

    2013-10-01

    The oxynitridation of biomedical titanium metal under a precisely regulated oxygen partial pressure (PO2) of 10(-14)Pa in nitrogen atmosphere at 973 K for 1 h strongly enhanced apatite formation compared with that on Ti heated in air. The factors governing the high apatite-forming ability are discussed from the viewpoint of the surface properties of Ti heated under a PO2 of 10(-14)Pa in nitrogen atmosphere determined from X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. Nitrogen (N)-doped TiO2 (interstitial N) was formed on pure Ti heated under a PO2 of 10(-14)Pa in nitrogen atmosphere at 973 K. The XPS O1s main peak shifted toward a lower binding energy upon heating under a PO2 of 10(-14)Pa. This shift may be due to the formation of oxygen vacancies. This Ti surface had a positive zeta potential of approximately 20 mV. According to time-of-flight secondary ion mass spectroscopy results, PO4(3-) ions were predominantly adsorbed on Ti soaked in simulated body fluid (SBF) after heat treatment, followed by calcium ions. It was concluded that the apatite formation kinetics can be described using the Avrami-Erofeev equation with an Avrami index of n=2, which implies the instantaneous nucleation of apatite on the surface of Ti soaked in SBF after heat treatment at 973 K under a PO2 of 10(-14)Pa. PMID:23910327

  13. Simulation of sea surface temperatures with the surface heat fluxes from an atmospheric circulation model

    OpenAIRE

    Karaca, Mehmet; MÜLLER, DETLEV

    2011-01-01

    The global fields of the surface heat fluxes for the December-February period are calculated with the UCLA atmospheric circulation model (ACM). This model operates on a global grid net. The planetary boundary layer (PBL), as the decisive subsystem for the surface fluxes, is parameterized in terms of its bulk properties. For several locations in the north Atlantic, the model heat fluxes are incorporated into the forcing of a simple ocean mixed-layer (OML) model. The OML-model uses a slight gen...

  14. Sunquake Generation by Coronal Magnetic Restructuring

    CERN Document Server

    Russell, Alexander J B; Leake, James E; Hudson, Hugh 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 letter explores a mechanism for sunquake generation by the magnetic field changes 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 Alfv\\'en-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 by the order of 10 degrees 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 tilt change are of secondary importance.

  15. SUMER Observations of Coronal-Hole Temperatures

    Science.gov (United States)

    Wilhelm, Klaus

    2012-11-01

    Observations of emission lines in the vacuum-ultraviolet spectral range with calibrated instrumentation provide crucial information on the prevailing plasma temperatures in the solar atmosphere. Coronal-hole temperatures measured by the SUMER spectrometer on SOHO will be presented in this contribution. Electron temperatures can be estimated from the formation temperatures of the observed emission lines. Line-ratio and emission-measure analyses, however, offer higher accuracies. Typical electron temperatures at altitudes of H<200 Mm in coronal holes are below 1 MK in bright structures—the coronal plumes—with higher values in darker areas—the inter-plume regions. Line-width measurements yield effective ion temperatures, which are much higher than the electron temperatures. Observations of line profiles emitted from species with different masses allow a separation of the effective temperatures into ion temperatures and unresolved non-thermal motions along the line of sight.

  16. Understanding the Atmospheric Response to Ocean Heat Transport: a Model Inter-Comparison

    Science.gov (United States)

    Rose, B.

    2012-12-01

    The oceans' contribution to poleward heat transport (1 to 2 PW) is dwarfed by the atmosphere, and yet ocean heat transport (OHT) exerts a powerful climatic influence by exciting various atmospheric feedbacks. OHT drives polar-amplified greenhouse warming through a dynamical redistribution of tropospheric water vapor, and helps set the strength and position of the ITCZ. These complex responses explicitly couple tropical and extra-tropical processes, and depend on interactions between large-scale dynamics and moist physics. Considerable insights have been drawn from recent idealized experiments with aquaplanet GCMs coupled to slab oceans with prescribed OHT convergence (q-flux). However sensitivity to uncertain model parameterizations pose a barrier to deeper understanding. I will introduce a new multi-institution collaboration called the Q-flux / Aquaplanet Model Inter-comparison Project (QAquMIP), designed to test the robustness of the climatic impact of OHT and its relationship to traditional climate sensitivity. A standardized set of GCM experiments, repeated across a broad range of models, are forced by a few simple analytical q-fluxes. Experimental controls include the meridional scale of poleward OHT, strength of inter-hemispheric OHT, and zonally asymmetric equatorial heating. I will compare robust spatial patterns of temperature and precipitation changes associated with OHT forcing to those driven by CO2, and discuss the underlying spatial pattern of atmospheric feedbacks. A recurring theme is the key role of moist convection in communicating sea surface heating signals throughout the atmosphere, with consequences for clouds, water vapor, radiation, and hydrology. QAquMIP will better constrain the possible role of the oceans in past warm climates, provide a standard framework for testing new parameterizations, and advance our fundamental understanding of the moist processes contributing to present-day climate sensitivity.

  17. Average Heating Rate of Hot Atmospheres in Distant Clusters by Radio AGN: Evidence for Continuous AGN Heating

    CERN Document Server

    Ma, C -J; Nulsen, P E J; Schaffer, R; Vikhlinin, A

    2011-01-01

    X-ray observations of nearby clusters and galaxies have shown that energetic feedback from active galactic nuclei (AGN) is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 - 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in...

  18. Sensitivity of global ocean heat content from reanalyses to the atmospheric reanalysis forcing: A comparative study

    Science.gov (United States)

    Storto, Andrea; Yang, Chunxue; Masina, Simona

    2016-05-01

    The global ocean heat content evolution is a key component of the Earth's energy budget and can be consistently determined by ocean reanalyses that assimilate hydrographic profiles. This work investigates the impact of the atmospheric reanalysis forcing through a multiforcing ensemble ocean reanalysis, where the ensemble members are forced by five state-of-the-art atmospheric reanalyses during the meteorological satellite era (1979-2013). Data assimilation leads the ensemble to converge toward robust estimates of ocean warming rates and significantly reduces the spread (1.48 ± 0.18 W/m2, per unit area of the World Ocean); hence, the impact of the atmospheric forcing appears only marginal for the global heat content estimates in both upper and deeper oceans. A sensitivity assessment performed through realistic perturbation of the main sources of uncertainty in ocean reanalyses highlights that bias correction and preprocessing of in situ observations represent the most crucial component of the reanalysis, whose perturbation accounts for up to 60% of the ocean heat content anomaly variability in the pre-Argo period. Although these results may depend on the single reanalysis system used, they reveal useful information for the ocean observation community and for the optimal generation of perturbations in ocean ensemble systems.

  19. The Great Ice Age cycles associated with the variation of the atmospheric heat engine efficiency

    Institute of Scientific and Technical Information of China (English)

    汤懋苍; 郭维栋

    2000-01-01

    Investigating all the Great Ice Age events throughout the Earth’s history, each was found to follow a strong mountain-making process. Therefore, a hypothesis was put forward with its causality chain as: strong mountain-making process→great disparity in topography on the Earth surface→introducing efficient atmospheric circulation system (plateau monsoon)→increase in global atmospheric heat engine efficiency →generating more atmospheric kinetic energy → enhancing the planetary westerly (under the condition that the huge relief is longitudinal on the whole )→widening the temperature difference between the equator and the polar regions (restrained by the thermal wind law)→sharp cooling in high latitudes and the polars (supposing the solar radiation was approximately constant)→forming a Great Ice Age event.

  20. The Great Ice Age cycles associated with the variation of the atmospheric heat engine efficiency

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Investigating all the Great Ice Age events throughout the Earth's history, each was found to follow a strong mountain-making process. Therefore, a hypothesis was put forward with its causality chain as: strong mountain-making process→great disparity in topography on the Earth surface→introducing efficient atmospheric circulation system (plateau monsoon)→increase in global atmospheric heat engine efficiency→generating more atmospheric kinetic energy→enhancing the planetary westerly (under the condition that the huge relief is longitudinal on the whole )→widening the temperature difference between the equator and the polar regions (restrained by the thermal wind law)→sharp cooling in high latitudes and the polars (supposing the solar radiation was approximately constant)→forming a Great Ice Age event.

  1. The Fundamental Structure of Coronal Loops

    Science.gov (United States)

    Winebarger, Amy; Warren, Harry; Cirtain, Jonathan; Kobayashi, Ken; Korreck, Kelly; Golub, Leon; Kuzin, Sergey; Walsh, Robert; DePontieu, Bart; Title, Alan; Weber, Mark

    2012-01-01

    During the past ten years, solar physicists have attempted to infer the coronal heating mechanism by comparing observations of coronal loops with hydrodynamic model predictions. These comparisons often used the addition of sub ]resolution strands to explain the observed loop properties. On July 11, 2012, the High Resolution Coronal Imager (Hi ]C) was launched on a sounding rocket. This instrument obtained images of the solar corona was 0.2 ]0.3'' resolution in a narrowband EUV filter centered around 193 Angstroms. In this talk, we will compare these high resolution images to simultaneous density measurements obtained with the Extreme Ultraviolet Imaging Spectrograph (EIS) on Hinode to determine whether the structures observed with Hi ]C are resolved.

  2. Chemical characteristics and source apportionment of atmospheric particles during heating period in Harbin, China

    Institute of Scientific and Technical Information of China (English)

    Likun Huang; Guangzhi Wang

    2014-01-01

    Atmospheric particles (total suspended particles (TSPs); particulate matter (PM) with particle size below 10 μm,PM10; particulate matter with particle size below 2.5 μm,PM2.5)were collected and analyzed during heating and non-heating periods in Harbin.The sources of PM10 and PM2.5 were identified by the chemical mass balance (CMB) receptor model.Results indicated that PM2.5/TSP was the most prevalent and PM2.5 was the main component of PM10,while the presence of PM10-100 was relatively weak.SC42-and NO3-concentrations were more significant than other ions during the heating period.As compared with the non-heating period,Mn,Ni,Pb,S,Si,Ti,Zn,As,Ba,Cd,Cr,Fe and K were relatively higher during the heating period.In particular,Mn,Ni,S,Si,Ti,Zn and As in PM2.5 were obviously higher during the heating period.Organic carbon (OC) in the heating period was 2-5 times higher than in the non-heating period.Elemental carbon (EC) did not change much.OC/EC ratios were 8-11 during the heating period,which was much higher than in other Chinese cities (OC/EC:4-6).Results from the CMB indicated that 11 pollution sources were identified,of which traffic,coal combustion,secondary sulfate,secondary nitrate,and secondary organic carbon made the greatest contnbution.Before the heating period,dust and petrochemical industry made a larger contribution.In the heating period,coal combustion and secondary sulfate were higher.After the heating period,dust and petrochemical industry were highen Some hazardous components in PM2.5 were higher than in PM10,because PM2.5 has a higher ability to absorb toxic substances.Thus PM2.5 pollution is more significant regarding human health effects in the heating period.

  3. Can coronal hole spicules reach coronal temperatures?

    CERN Document Server

    Madjarska, M S; Doyle, J G

    2011-01-01

    We aim with the present study to provide observational evidences on whether coronal hole spicules reach coronal temperatures. We combine multi-instrument co-observations obtained with the SUMER/SoHO and with the EIS/SOT/XRT/Hinode. The analysed three large spicules were found to be comprised of numerous thin spicules which 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 km/s. We clearly associated the red- and blue-shifted emissions in transition region lines with rotating but also with rising and descending plasmas, respectively. Our main result is that these spicules although very large and dynamic, show no presence in spectral lines formed at temperatures above 300 000 K. The present paper brings out the analysis of three Ca II H large spicules which are composed of numerous dynamic thin spicules but appear as macrospicules in EUV lower resolution images. We found no coronal counte...

  4. Enhanced apatite formation on Ti metal heated in P{sub O2}-controlled nitrogen atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Masami, E-mail: masami@jfcc.or.jp; Hayashi, Kazumi, E-mail: k_hayashi@jfcc.or.jp; Kitaoka, Satoshi, E-mail: kitaoka@jfcc.or.jp

    2013-10-15

    The oxynitridation of biomedical titanium metal under a precisely regulated oxygen partial pressure (P{sub O2}) of 10{sup −14} Pa in nitrogen atmosphere at 973 K for 1 h strongly enhanced apatite formation compared with that on Ti heated in air. The factors governing the high apatite-forming ability are discussed from the viewpoint of the surface properties of Ti heated under a P{sub O2} of 10{sup −14} Pa in nitrogen atmosphere determined from X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. Nitrogen (N)-doped TiO{sub 2} (interstitial N) was formed on pure Ti heated under a P{sub O2} of 10{sup −14} Pa in nitrogen atmosphere at 973 K. The XPS O1s main peak shifted toward a lower binding energy upon heating under a P{sub O2} of 10{sup −14} Pa. This shift may be due to the formation of oxygen vacancies. This Ti surface had a positive zeta potential of approximately 20 mV. According to time-of-flight secondary ion mass spectroscopy results, PO{sub 4}{sup 3−} ions were predominantly adsorbed on Ti soaked in simulated body fluid (SBF) after heat treatment, followed by calcium ions. It was concluded that the apatite formation kinetics can be described using the Avrami–Erofeev equation with an Avrami index of n = 2, which implies the instantaneous nucleation of apatite on the surface of Ti soaked in SBF after heat treatment at 973 K under a P{sub O2} of 10{sup −14} Pa. - Highlights: • Nitrogen-doped TiO{sub 2} was formed on Ti heated under a P{sub O2} of 10{sup −14} Pa. • Oxygen vacancy was existed on the outermost layer of nitrogen-doped TiO{sub 2}. • This nitrogen-doped TiO{sub 2} surface had a positive zeta potential of 20 mV. • PO{sub 4}{sup 3−} ions were predominantly adsorbed on the nitrogen-doped TiO{sub 2} soaked in SBF.

  5. Stellar Coronal Response to Differential Rotation and Flux Emergence

    CERN Document Server

    Gibb, G P S; Jardine, M M; Yeates, A R

    2016-01-01

    We perform a numerical parameter study to determine what effect varying differential rotation and flux emergence has on a star's non-potential coronal magnetic field. In particular we consider the effects on the star's surface magnetic flux, open magnetic flux, mean azimuthal field strength, coronal free magnetic energy, coronal heating and flux rope eruptions. To do this, we apply a magnetic flux transport model to describe the photospheric evolution, and couple this to the non-potential coronal evolution using a magnetofrictional technique. A flux emergence model is applied to add new magnetic flux onto the photosphere and into the corona. The parameters of this flux emergence model are derived from the solar flux emergence profile, however the rate of emergence can be increased to represent higher flux emergence rates than the Sun's. Overall we find that flux emergence has a greater effect on the non-potential coronal properties compared to differential rotation, with all the aforementioned properties incr...

  6. Sugarcane bagasse pyrolysis in a carbon dioxide atmosphere with conventional and microwave-assisted heating

    Directory of Open Access Journals (Sweden)

    Bo-Jhih eLin

    2015-02-01

    Full Text Available Pyrolysis is an important thermochemical method to convert biomass into bio-oil. In this study, the pyrolysis of sugarcane bagasse in a CO2 atmosphere under conventional and microwave-assisted heating is investigated to achieve CO2 utilization. In the microwave pyrolysis, charcoal is used as the microwave absorber to aid in pyrolysis reactions. The results indicate that the yields of pyrolysis products are greatly influenced by the heating modes. In the conventional heating, the prime product is bio-oil and its yield is in the range of 51-54 wt%, whereas biochar is the major product in microwave-assisted heating and its yield ranges from 61 to 84 wt%. Two different absorber blending ratios of 0.1 and 0.3 are considered in the microwave pyrolysis. The solid yield decreases when the absorber blending ratio decreases from 0.3 to 0.1, while the gas and liquid yields increase. This is attributed to more energy consumed for bagasse pyrolysis at the lower blending ratio. Hydrogen is produced under the microwave pyrolysis and its concentration is between 2 and 12 vol%. This arises from the fact that the secondary cracking of vapors and the secondary decomposition of biochar in an environment with microwave irradiation is easier than those with conventional heating.

  7. Segmentation of Coronal Holes Using Active Contours Without Edges

    Science.gov (United States)

    Boucheron, L. E.; Valluri, M.; McAteer, R. T. J.

    2016-10-01

    An application of active contours without edges is presented as an efficient and effective means of extracting and characterizing coronal holes. Coronal holes are regions of low-density plasma on the Sun with open magnetic field lines. The detection and characterization of these regions is important for testing theories of their formation and evolution, and also from a space weather perspective because they are the source of the fast solar wind. Coronal holes are detected in full-disk extreme ultraviolet (EUV) images of the corona obtained with the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA). The proposed method detects coronal boundaries without determining any fixed intensity value in the data. Instead, the active contour segmentation employs an energy-minimization in which coronal holes are assumed to have more homogeneous intensities than the surrounding active regions and quiet Sun. The segmented coronal holes tend to correspond to unipolar magnetic regions, are consistent with concurrent solar wind observations, and qualitatively match the coronal holes segmented by other methods. The means to identify a coronal hole without specifying a final intensity threshold may allow this algorithm to be more robust across multiple datasets, regardless of data type, resolution, and quality.

  8. Segmentation of Coronal Holes Using Active Contours Without Edges

    Science.gov (United States)

    Boucheron, L. E.; Valluri, M.; McAteer, R. T. J.

    2016-09-01

    An application of active contours without edges is presented as an efficient and effective means of extracting and characterizing coronal holes. Coronal holes are regions of low-density plasma on the Sun with open magnetic field lines. The detection and characterization of these regions is important for testing theories of their formation and evolution, and also from a space weather perspective because they are the source of the fast solar wind. Coronal holes are detected in full-disk extreme ultraviolet (EUV) images of the corona obtained with the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA). The proposed method detects coronal boundaries without determining any fixed intensity value in the data. Instead, the active contour segmentation employs an energy-minimization in which coronal holes are assumed to have more homogeneous intensities than the surrounding active regions and quiet Sun. The segmented coronal holes tend to correspond to unipolar magnetic regions, are consistent with concurrent solar wind observations, and qualitatively match the coronal holes segmented by other methods. The means to identify a coronal hole without specifying a final intensity threshold may allow this algorithm to be more robust across multiple datasets, regardless of data type, resolution, and quality.

  9. Magnetospheric Structure and Atmospheric Joule Heating of Habitable Planets Orbiting M-dwarf Stars

    CERN Document Server

    Cohen, O; Glocer, A; Garraffo, C; Poppenhaeger, K; Bell, J M; Ridley, A J; Gombosi, T I

    2014-01-01

    We study the magnetospheric structure and the ionospheric Joule Heating of planets orbiting M-dwarf stars in the habitable zone using a set of magnetohydrodynamic (MHD) models. The stellar wind solution is used to drive a model for the planetary magnetosphere, which is coupled with a model for the planetary ionosphere. Our simulations reveal that the space environment around close-in habitable planets is extreme, and the stellar wind plasma conditions change from sub- to super-Alfvenic along the planetary orbit. As a result, the magnetospheric structure changes dramatically with a bow shock forming in the super-Alfvenic sectors, while no bow shock forms in the sub-Alfvenic sectors. The planets reside most of the time in the sub-Alfvenic sectors with poor atmospheric protection. A significant amount of Joule Heating is provided at the top of the atmosphere as a result of the planetary interaction with the stellar wind. For the steady-state solution, the heating is about 0.1-3\\% of the total incoming stellar ir...

  10. Oxidation Effect on Pool Boiling Heat Transfer in Atmospheric Saturated Water

    Energy Technology Data Exchange (ETDEWEB)

    Son, Hong Hyun; Jeong, Uiju; Seo, Gwang Hyeok; Jeun, Gyoodong; Kim, Sung Joong [Hanyang Univ., Seoul (Korea, Republic of)

    2014-10-15

    During the hypothesized severe accidents, however, the modified nature of the oxidized outer surface of RPV may act as a significant heat transfer variable to achieve In-Vessel Retention through External Reactor Vessel Cooling (IVR-ERVC) strategy, which is the one of important mitigation strategies of severe accident to delay occurrence of critical heat flux (CHF). As well understood, the CHF is mainly affected by the two distinctive conditions classified to thermal hydraulic behavior of fluid system and surface characteristics. In this regard, a CHF test considering oxidation effect on the pool boiling heat transfer of the RPV outer surface has been proposed to evaluate realistic thermal margin of IVR-ERVC strategy. In this study, pool boiling heat transfer experiment was conducted under the condition of atmospheric saturated water. Oxidized surface characteristics were quantitatively evaluated with measurement of contact angle and roughness. In this study, oxide layer formation on the heated surface was investigated and experimentally simulated to find out its effect on the pool boiling CHF. Several SS316L substrates were oxidized in the corrosive environment under the condition of high temperature with different oxidation periods. Local pitting corrosion was observed on the heating surface in 5 days of short-term oxidation but a fully oxidized surface with somewhat uniform thickness, 1. Pool boiling heat transfer tests with the bare and oxidized heaters were conducted and major findings are summarized as follows: 1. Wettability in terms of the receding angle of the oxidized surface is enhanced regardless of the oxidation period. 2. Average roughness between the oxidized surfaces is almost the same in the range of nano-scale. 3. Effect of wettability and surface roughness on the CHF was negligible in the locally oxidized surface, which may be attributed to the presence of the disconnected porous channel. Unlike the local oxidation, fully oxidized surface shows

  11. Observing coronal nanoflares in active region moss

    CERN Document Server

    Testa, Paola; Martinez-Sykora, Juan; DeLuca, Ed; Hansteen, Viggo; Cirtain, Jonathan; Winebarger, Amy; Golub, Leon; Kobayashi, Ken; Korreck, Kelly; Kuzin, Sergey; Walsh, Robert; DeForest, Craig; Title, Alan; Weber, Mark

    2013-01-01

    The High-resolution Coronal Imager (Hi-C) has provided Fe XII 193A images of the upper transition region moss at an unprecedented spatial (~0.3-0.4 arcsec) and temporal (5.5s) resolution. The Hi-C observations show in some moss regions variability on timescales down to ~15s, significantly shorter than the minute scale variability typically found in previous observations of moss, therefore challenging the conclusion of moss being heated in a mostly steady manner. These rapid variability moss regions are located at the footpoints of bright hot coronal loops observed by SDO/AIA in the 94A channel, and by Hinode/XRT. The configuration of these loops is highly dynamic, and suggestive of slipping reconnection. We interpret these events as signatures of heating events associated with reconnection occurring in the overlying hot coronal loops, i.e., coronal nanoflares. We estimate the order of magnitude of the energy in these events to be of at least a few $10^{23}rg, also supporting the nanoflare scenario. These Hi-C...

  12. Magnetohydrodynamic waves and coronal seismology: an overview of recent results.

    Science.gov (United States)

    De Moortel, Ineke; Nakariakov, Valery M

    2012-07-13

    Recent observations have revealed that magnetohydrodynamic (MHD) waves and oscillations are ubiquitous in the solar atmosphere, with a wide range of periods. We give a brief review of some aspects of MHD waves and coronal seismology that have recently been the focus of intense debate or are newly emerging. In particular, we focus on four topics: (i) the current controversy surrounding propagating intensity perturbations along coronal loops, (ii) the interpretation of propagating transverse loop oscillations, (iii) the ongoing search for coronal (torsional) Alfvén waves, and (iv) the rapidly developing topic of quasi-periodic pulsations in solar flares.

  13. Atmosphere expansion and mass loss of close-orbit giant exoplanets heated by stellar XUV: I. Modeling of hydrodynamic escape of upper atmospheric material

    CERN Document Server

    Shaikhislamov, I F; Sasunov, Yu L; Lammer, H; Kislyakova, K G; Erkaev, N V

    2015-01-01

    In the present series of papers we propose a consistent description of the mass loss process. To study the effects of intrinsic magnetic field of a close-orbit giant exoplanet (so-called Hot Jupiter) on the atmospheric material escape and formation of planetary inner magnetosphere in a comprehensive way, we start with a hydrodynamic model of an upper atmosphere expansion presented in this paper. While considering a simple hydrogen atmosphere model, we focus on selfconsistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to investigation of the role of specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free- and restricted- flow) are formed. Comparative study of different processes, such as XUV heating, material ionization and recombination, H3+ cooling, adiabatic and Lyman-alpha cooling, Lyman-alpha reabsorption is perf...

  14. Global Coronal Waves

    CERN Document Server

    Chen, P F

    2016-01-01

    After the {\\em Solar and Heliospheric Observatory} ({\\em SOHO}) was launched in 1996, the aboard Extreme Ultraviolet Imaging Telescope (EIT) observed a global coronal wave phenomenon, which was initially named "EIT wave" after the telescope. The bright fronts are immediately followed by expanding dimmings. It has been shown that the brightenings and dimmings are mainly due to plasma density increase and depletion, respectively. Such a spectacular phenomenon sparked long-lasting interest and debates. The debates were concentrated on two topics, one is about the driving source, and the other is about the nature of this wavelike phenomenon. The controversies are most probably because there may exist two types of large-scale coronal waves that were not well resolved before the {\\em Solar Dynamics Observatory} ({\\em SDO}) was launched: one is a piston-driven shock wave straddling over the erupting coronal mass ejection (CME), and the other is an apparently propagating front, which may correspond to the CME frontal...

  15. [Effects of temperature and heating time on armco iron spectral emissivity in atmospheric environment].

    Science.gov (United States)

    Yu, Kun; Wang, Wen-Bao; Zhang, Kai-Hua; Liu, Yu-Fang

    2014-09-01

    The spectral emissivity of pure iron at 1.55 μm was investigated systematically by using our self-designed reflective experimental apparatus based on the Kirchhoff's law, and the influences of temperature and heating time on the spectral emissivity of pure iron were also discussed. The experimental data showed that the spectral emissivity of pure iron increased with temperature rising and its peak value and valley value appeared at certain temperatures. By analyzing the emissivity model of metal with oxidation layer, the variation of the spectral emissivity of pure iron was illustrated. The influence of heating time on the spectral emissivity was different at different temperature. The research results will further enrich pure iron spectral emissivity data, and provide the experimental basis for its application in atmospheric environment.

  16. Numerical Simulation of the Self-Heating Effect Induced by Electron Beam Plasma in Atmosphere

    Institute of Scientific and Technical Information of China (English)

    邓永锋; 谭畅; 韩先伟; 谭永华

    2012-01-01

    For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo (MC) model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.

  17. Fabrication of thick W coatings by atmospheric plasma spraying and their transient high heat loading performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Zhangjian, E-mail: zhouzhj@mater.ustb.edu.c [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Song Shuxiang; Yao Weizhi [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Pintsuk, Gerald; Linke, Jochen [Forschungszentrum Juelich GmbH, EURATOM Association, Juelich D-52425 (Germany); Guo Shuangquan [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu (China); Ge Changchun [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2010-12-15

    Both tungsten coatings with or without a W/Cu graded interlayer on an oxygen-free copper substrate were fabricated by atmospheric plasma spraying. High purity argon gas was used for cooling the substrate and preventing the coating from oxidation. The thickness of both coatings is {approx}1 mm. XRD and EDS measurements of the coatings show that minimal oxidation occurred during the deposition process. Transient high heat load tests by electron beam with a pulse duration of 5 ms were performed on both coatings. The single pulse loading was applied on the virgin surfaces at several power densities (from 0.22 to 0.9 GW/m{sup 2}). Although the weight loss of the W/Cu FGM (functionally graded materials) based coating was slightly lower than that of the pure W coating, their transient high heat loading performances were quite similar.

  18. Heating effects of a non-equilibrium RF corona discharge in atmospheric air

    Energy Technology Data Exchange (ETDEWEB)

    Auzas, F; Makarov, M; Agneray, A [Technocentre Renault, 1 Avenue du Golf, 78288 Guyancourt (France); Tardiveau, P; Puech, V, E-mail: pierre.tardiveau@u-psud.f [Laboratoire de Physique des Gaz et des Plasmas, Bat 210, Universite Paris-Sud, 91405 Orsay Cedex (France)

    2010-12-15

    Electrical and thermal properties of a single electrode configuration corona discharge generated under radiofrequency high voltage inside an open air gap at pressures above 1 bar is investigated. Time-resolved imaging of the discharge shows a four-step development of the discharge at atmospheric pressure starting by streamers' inception and propagation, evolving in heating waves and stabilizing in a stationary regime until the power supply is switched off. The mean gas temperature reaches about 1700 K in tens of microseconds with electrical energy release around tens of millijoules. Heating has been attributed to ion collisions and excited species relaxation, promoted by the successive time periods of the power supply. At higher pressures, beyond 3 bar, this behaviour changes and heating occurs at the same time as the discharge propagates. It leads to hot channels which constrict near the electrode as long as the voltage pulse is applied. Temperature gets higher and saturates at 2600 K whatever the voltage and the pressure. Considering the change in the electrical energy density released within the plasma channels with pressure and voltage, temperature saturation seems to be an effect of heat confining within the channels due to pressure. The large and non-thermal plasma generated by the RF corona discharge is a very good candidate for car engine lean mixtures ignition issues.

  19. Heating effects of a non-equilibrium RF corona discharge in atmospheric air

    International Nuclear Information System (INIS)

    Electrical and thermal properties of a single electrode configuration corona discharge generated under radiofrequency high voltage inside an open air gap at pressures above 1 bar is investigated. Time-resolved imaging of the discharge shows a four-step development of the discharge at atmospheric pressure starting by streamers' inception and propagation, evolving in heating waves and stabilizing in a stationary regime until the power supply is switched off. The mean gas temperature reaches about 1700 K in tens of microseconds with electrical energy release around tens of millijoules. Heating has been attributed to ion collisions and excited species relaxation, promoted by the successive time periods of the power supply. At higher pressures, beyond 3 bar, this behaviour changes and heating occurs at the same time as the discharge propagates. It leads to hot channels which constrict near the electrode as long as the voltage pulse is applied. Temperature gets higher and saturates at 2600 K whatever the voltage and the pressure. Considering the change in the electrical energy density released within the plasma channels with pressure and voltage, temperature saturation seems to be an effect of heat confining within the channels due to pressure. The large and non-thermal plasma generated by the RF corona discharge is a very good candidate for car engine lean mixtures ignition issues.

  20. Spectroscopic Diagnostics of Polar Coronal Plumes

    CERN Document Server

    Wilhelm, K; Dwivedi, B N

    2009-01-01

    Polar coronal plumes seen during solar eclipses can now be studied with space-borne telescopes and spectrometers. We briefly discuss such observations from space with a view to understanding their plasma characteristics. Using these observations, especially from SUMER/SOHO, but also from EUVI/STEREO, we deduce densities, temperatures, and abundance anomalies in plumes and inter-plume regions, and discuss their implications for better understanding of these structures in the Sun's atmosphere.

  1. A self-consistent derivation of ion drag and Joule heating for atmospheric dynamics in the thermosphere

    Directory of Open Access Journals (Sweden)

    X. Zhu

    2005-11-01

    Full Text Available The thermosphere is subject to additional electric and magnetic forces, not important in the middle and lower atmosphere, due to its partially ionized atmosphere. The effects of charged particles on the neutral atmospheric dynamics are often parameterized by ion drag in the momentum equations and Joule heating in the energy equation. Presented in this paper are a set of more accurate parameterizations for the ion drag and Joule heating for the neutral atmosphere that are functions of the difference between bulk ion velocity and neutral wind. The parameterized expressions also depend on the magnetic field, the Pedersen and Hall conductivities, and the ratio of the ion cyclotron frequency to the ion-neutral collision frequency. The formal relationship between the electromagnetic energy, atmospheric kinetic energy, and Joule heating is illustrated through the conversion terms between these three types of energy. It is shown that there will always be an accompanying conversion of kinetic energy into Joule heating when electromagnetic energy is generated through the dynamo mechanism of the atmospheric neutral wind. Likewise, electromagnetic energy cannot be fully converted into kinetic energy without producing Joule heating in the thermosphere.

  2. Variability of Atlantic Ocean heat transport and its effects on the atmosphere

    Directory of Open Access Journals (Sweden)

    R. T. Sutton

    2003-06-01

    Full Text Available The variability of the Atlantic meridional Ocean Heat Transport (OHT has been diagnosed from a simulation of a coupled ocean-atmosphere general circulation model, and the mechanisms responsible for this variability have been elucidated. It has been demonstrated that the interannual variability in Atlantic OHT is dominated by windstress-driven Ekman fluctuations. In contrast, the decadal and multidecadal variability is associated with the fluctuations of the Thermohaline Circulation (THC, driven by the fluctuations in deep convection over the Greenland-Iceland-Norwegian (GIN Sea. The fluctuations of OHT induce Ocean Heat Content (OHC, and Sea Surface Temperature (SST anomalies over the tropical and subtropical North Atlantic. The SST anomalies, in turn, have an impact on the atmosphere. The lead-lag relationships between the fluctuations of THC-related OHT and those of OHC and SST raise the possibility that a knowledge of OHT fluctuations could be used to predict variations in Atlantic Sea surface temperatures, and perhaps aspects of climate, several years in advance. A comparison of results from a second, independent, coupled model simulation is also presented, and similar conclusions reached.

  3. Implementation of a boundary layer heat flux parameterization into the Regional Atmospheric Modeling System (RAMS

    Directory of Open Access Journals (Sweden)

    E. L. McGrath-Spangler

    2008-07-01

    Full Text Available The response of atmospheric carbon dioxide to a given amount of surface flux is inversely proportional to the depth of the boundary layer. Overshooting thermals that entrain free tropospheric air down into the boundary layer modify the characteristics and depth of the lower layer through the insertion of energy and mass. This alters the surface energy budget by changing the Bowen ratio and thereby altering the vegetative response and the surface boundary conditions. Although overshooting thermals are important in the physical world, their effects are unresolved in most regional models. A parameterization to include the effects of boundary layer entrainment was introduced into a coupled ecosystem-atmosphere model (SiB-RAMS. The parameterization is based on a downward heat flux at the top of the boundary layer that is proportional to the heat flux at the surface. Results with the parameterization show that the boundary layer simulated is deeper, warmer, and drier than when the parameterization is turned off. These results alter the vegetative stress factors thereby changing the carbon flux from the surface. The combination of this and the deeper boundary layer change the concentration of carbon dioxide in the boundary layer.

  4. Experimental Research on Water Boiling Heat Transfer on Horizontal Copper Rod Surface at Sub-Atmospheric Pressure

    Directory of Open Access Journals (Sweden)

    Li-Hua Yu

    2015-09-01

    Full Text Available In recent years, water (R718 as a kind of natural refrigerant—which is environmentally-friendly, safe and cheap—has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, the research on water boiling heat transfer at sub-atmospheric pressure has been an important issue. There are many research papers on the evaporation of water, but there is a lack of data on the characteristics at sub-atmospheric pressures, especially lower than 3 kPa (the saturation temperature is 24 °C. In this paper, the experimental research on water boiling heat transfer on a horizontal copper rod surface at 1.8–3.3 kPa is presented. Regression equations of the boiling heat transfer coefficient are obtained based on the experimental data, which are convenient for practical application.

  5. Standing Slow-Mode Waves in Hot Coronal Loops: Observations, Modeling, and Coronal Seismology

    CERN Document Server

    Wang, Tongjiang

    2010-01-01

    Strongly damped Doppler shift oscillations are observed frequently associated with flarelike events in hot coronal loops. In this paper, a review of the observed properties and the theoretical modeling is presented. Statistical measurements of physical parameters (period, decay time, and amplitude) have been obtained based on a large number of events observed by SOHO/SUMER and Yohkoh/BCS. Several pieces of evidence are found to support their interpretation in terms of the fundamental standing longitudinal slow mode. The high excitation rate of these oscillations in small- or micro-flares suggest that the slow mode waves are a natural response of the coronal plasma to impulsive heating in closed magnetic structure. The strong damping and the rapid excitation of the observed waves are two major aspects of the waves that are poorly understood, and are the main subject of theoretical modeling. The slow waves are found mainly damped by thermal conduction and viscosity in hot coronal loops. The mode coupling seems ...

  6. Thermal and non-thermal emission from reconnecting twisted coronal loops

    Science.gov (United States)

    Pinto, R. F.; Gordovskyy, M.; Browning, P. K.; Vilmer, N.

    2016-01-01

    Context. Twisted magnetic fields should be ubiquitous in the solar corona, particularly in flare-producing active regions where the magnetic fields are strongly non-potential. The magnetic energy contained in such twisted fields can be released during solar flares and other explosive phenomena. It has recently been shown that reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops. Hence, the magnetic reconnection and particle acceleration scenario involving magnetic helicity can be a viable alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. Aims: The key goal of this study is to investigate the links and observational signatures of plasma heating and particle acceleration in kink-unstable twisted coronal loops. Methods: We used a combination of magnetohydrodynamic (MHD) simulations and test-particle methods. These simulations describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us estimate thermal X-ray emission intensities. With the electric and magnetic fields we obtained, we calculated electron trajectories using the guiding-centre approximation. These trajectories combined with the MHD plasma density distributions let us deduce synthetic hard X-ray bremsstrahlung intensities. Results: Our simulations emphasise that the geometry of the emission patterns produced by hot plasma in flaring twisted coronal loops can differ from the actual geometry of the underlying magnetic fields. In particular, the twist angles revealed by the emission threads (soft X-ray thermal emission; SXR) are consistently lower than the field-line twist present at the onset of the

  7. Energy Transport Effects in Flaring Atmospheres Heated by Mixed Particle Beams

    Science.gov (United States)

    Zharkova, Valentina; Zharkov, Sergei; Macrae, Connor; Druett, Malcolm; Scullion, Eamon

    2016-07-01

    We investigate energy and particle transport in the whole flaring atmosphere from the corona to the photosphere and interior for the flaring events on the 1st July 2012, 6 and 7 September 2011 by using the RHESSI and SDO instruments as well as high-resolution observations from the Swedish 1-metre Solar Telescope (SST3) CRISP4 (CRisp Imaging Spectro-polarimeter). The observations include hard and soft X-ray emission, chromospheric emission in both H-alpha 656.3 nm core and continuum, as well as, in the near infra-red triplet Ca II 854.2 nm core and continuum channels and local helioseismic responses (sunquakes). The observations are compared with the simulations of hard X-ray emission and tested by hydrodynamic simulations of flaring atmospheres of the Sun heated by mixed particle beams. The temperature, density and macro-velocity variations of the ambient atmospheres are calculated for heating by mixed beams and the seismic response of the solar interior to generation of supersonic shocks moving into the solar interior. We investigate the termination depths of these shocks beneath the quiet photosphere levels and compare them with the parameters of seismic responses in the interior, or sunquakes (Zharkova and Zharkov, 2015). We also present an investigation of radiative conditions modelled in a full non-LTE approach for hydrogen during flare onsets with particular focus on Balmer and Paschen emission in the visible, near UV and near IR ranges and compare them with observations. The links between different observational features derived from HXR, optical and seismic emission are interpreted by different particle transport models that will allow independent evaluation of the particle transport scenarios.

  8. Parameter Study of Plasma-Induced Atmospheric Sputtering and Heating at Mars

    Science.gov (United States)

    Williamson, Hayley N.; Johnson, Robert E.; Leblanc, Francois

    2014-11-01

    Atoms and molecules in Mars’ upper atmosphere are lost predominately through sputtering, caused by the impact of ions into the exosphere, dissociative recombination, and thermal escape. While all three processes are thought to occur on Mars, a detailed understanding must ascertain the relative importance of each process, due to time variations in pick-up and solar wind ions. In this project, using case studies of an oxygen atmosphere modeled with Direct Simulation Monte Carlo techniques, we have endeavored to categorize when the momentum transfer or thermal escape is more likely to occur. To do this, we vary the incident plasma flux and energy based on models of the interaction of the solar wind with the Martian atmosphere. We first repeat the heating and sputtering rates due to a flux of pick-up O+ examined previously (Johnson et al. 2000; Michael and Johnson 2005; Johnson et al 2013). We have used multiple examples of particle fluxes for various solar wind conditions, from steady solar wind conditions (Luhmann et al. 1992; Chaufray et al. 2007) to more extreme cases (Fang et al. 2013; Wang et al. 2014), which are thought to increase escape by several orders of magnitude. The goal is to explore the escape parameter space in preparation for the expected data from MAVEN on hot atoms and molecules in the Martian exosphere.

  9. Observations of Fire-Atmosphere Interactions and Near-Surface Heat Transport on a Slope

    Science.gov (United States)

    Clements, Craig B.; Seto, Daisuke

    2015-03-01

    A simple field experiment was conducted to measure and quantify fire-atmosphere interactions during a grass fire spreading up a hill under a moderate cross-slope wind. The observed fire intensity measured by passive radiometers and calculated sensible heat fluxes ranged between 90 and 120 kW m. Observations from this experiment showed that convective heat generated from the fire front was transported downwind in the lowest 2 m and the highest plume temperatures remained in this shallow layer, suggesting the fire spread was driven primarily by the advection of near-ignition temperature gases, rather than by radiation of the tilted flame. Fire-induced circulations were present with upslope flows occurring during the fire-front passage helping to transport heat up the slope and perpendicular to the fire front. A decrease in atmospheric pressure of 0.4 hPa occurred at the fire front and coincided with a strong updraft core of nearly 8 m s. These observations provide evidence that, even under moderately windy conditions, the pressure minimum in the fire remains rather close to the combustion zone and plume. The turbulence associated with the fire front was characterized by isotropic behaviour at 12.0 m above the ground, while less isotropic conditions were found closer to the ground due to higher horizontal variances associated with fire-induced flow at the fire front. From analysis of the turbulence kinetic energy budget terms, it was found that buoyancy production, rather than shear generation, had a larger contribution to the generation of turbulence kinetic energy, even during a highly sheared and moderate ambient wind.

  10. Atmospheric Air –the Effective Source of Low-Grade Thermal Energy for Heat Pump Snow Melting Systems under Climatic Conditions of Moscow

    OpenAIRE

    Vasilyev G.P.; Leskov V.A.; Mitrofanova N.V.; Gornov V.F.; Kolesova M.V.; Yurchenko I.A.; Filippov M.D.

    2015-01-01

    The article presents the results of field experimental studies to evaluate effectiveness of heat pump snow melting systems use under climatic conditions of Moscow. The studies were conducted on a mock-up near-house heat pump snow melting site using low-grade atmospheric air heat. Experimental studies carried out in field conditions confirmed feasibility and efficiency of using atmospheric air as a source of low-grade heat for evaporators of heat pump snow melting systems under climatic condit...

  11. Forward Modelling of Standing Kink Modes in Coronal Loops I. Synthetic Views

    CERN Document Server

    Yuan, Ding

    2016-01-01

    Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this study, we synthesise the \\ion{Fe}{9} $\\lambda171.073$ emission of a coronal loop supporting a standing kink MHD mode. The kink MHD wave solution of a plasma cylinder is mapped into a semi-torus structure to simulate a curved coronal loop. We decompose the solution into a quasi-rigid kink motion and a quadrupole term, which dominate the plasma inside and outside the flux tube, respectively. At the loop edges, the line-of-sight integrates relatively more ambient plasma, and the background emission becomes significant. The plasma motion associated with the quadrupole term causes spectral line broadening and emission suppression. The periodic intensity suppression will modulate the integrated intensity and the effective loop width, which both exhibit oscillatory variations at half ...

  12. FORWARD MODELING OF STANDING KINK MODES IN CORONAL LOOPS. I. SYNTHETIC VIEWS

    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

    Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this study, we synthesize the Fe ix λ171.073 Å emission of a coronal loop supporting a standing kink MHD mode. The kink MHD wave solution of a plasma cylinder is mapped into a semi-torus structure to simulate a curved coronal loop. We decompose the solution into a quasi-rigid kink motion and a quadrupole term, which dominate the plasma inside and outside of the flux tube, respectively. At the loop edges, the line of sight integrates relatively more ambient plasma, and the background emission becomes significant. The plasma motion associated with the quadrupole term causes spectral line broadening and emission suppression. The periodic intensity suppression will modulate the integrated intensity and the effective loop width, which both exhibit oscillatory variations at half of the kink period. The quadrupole term can be directly observed as a pendular motion at the front view.

  13. 3D MHD modeling of twisted coronal loops

    CERN Document Server

    Reale, F; Guarrasi, M; Mignone, A; Peres, G; Hood, A W; Priest, E R

    2016-01-01

    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-beta chromosphere to the low-beta 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 fill the core of the flux tube to densities above 10^9 cm^-3. More heating is released in the low corona than the high corona and is finely ...

  14. 3D MHD modeling of twisted coronal loops

    Science.gov (United States)

    Reale, F.; Orlando, S.; Guarrasi, M.; Mignone, A.; Peres, G.; Hood, A. W.; Priest, E. R.

    2016-10-01

    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‑1 fill the core of the flux tube to densities above 109 cm‑3. More heating is released in the low corona than the high corona and is finely structured both in space and time.

  15. Observational constraints on atmospheric and oceanic cross-equatorial heat transports: revisiting the precipitation asymmetry problem in climate models

    Science.gov (United States)

    Loeb, Norman G.; Wang, Hailan; Cheng, Anning; Kato, Seiji; Fasullo, John T.; Xu, Kuan-Man; Allan, Richard P.

    2016-05-01

    Satellite based top-of-atmosphere (TOA) and surface radiation budget observations are combined with mass corrected vertically integrated atmospheric energy divergence and tendency from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Hemispheric contrasts in the energy budget terms are used to determine the radiative and combined sensible and latent heat contributions to the cross-equatorial heat transports in the atmosphere (AHTEQ) and ocean (OHTEQ). The contrast in net atmospheric radiation implies an AHTEQ from the northern hemisphere (NH) to the southern hemisphere (SH) (0.75 PW), while the hemispheric difference in sensible and latent heat implies an AHTEQ in the opposite direction (0.51 PW), resulting in a net NH to SH AHTEQ (0.24 PW). At the surface, the hemispheric contrast in the radiative component (0.95 PW) dominates, implying a 0.44 PW SH to NH OHTEQ. Coupled model intercomparison project phase 5 (CMIP5) models with excessive net downward surface radiation and surface-to-atmosphere sensible and latent heat transport in the SH relative to the NH exhibit anomalous northward AHTEQ and overestimate SH tropical precipitation. The hemispheric bias in net surface radiative flux is due to too much longwave surface radiative cooling in the NH tropics in both clear and all-sky conditions and excessive shortwave surface radiation in the SH subtropics and extratropics due to an underestimation in reflection by clouds.

  16. SOLAR JET–CORONAL HOLE COLLISION AND A CLOSELY RELATED CORONAL MASS EJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Ruisheng; Chen, Yao; Du, Guohui; Li, Chuanyang, E-mail: ruishengzheng@sdu.edu.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, 264209, Weihai (China)

    2016-03-10

    Jets are defined as impulsive, well-collimated upflows, occurring in different layers of the solar atmosphere with different scales. Their relationship with coronal mass ejections (CMEs), another type of solar impulsive events, remains elusive. Using high-quality imaging data from the Atmospheric Imaging Assembly/Solar Dynamics Observatory, we show a well-observed coronal jet event, in which the part of the jet with embedding coronal loops runs into a nearby coronal hole (CH) and gets bounced in the opposite direction. This is evidenced by the flat shape of the jet front during its interaction with the CH and the V-shaped feature in the time-slice plot of the interaction region. About a half-hour later, a CME with an initially narrow and jet-like front is observed by the LASCO C2 coronagraph propagating along the direction of the post-collision jet. We also observe some 304 Å dark material flowing from the jet–CH interaction region toward the CME. We thus suggest that the jet and the CME are physically connected, with the jet–CH collision and the large-scale magnetic topology of the CH being important in defining the eventual propagating direction of this particular jet–CME eruption.

  17. MAGNETIC FLUX SUPPLEMENT TO CORONAL BRIGHT POINTS

    Energy Technology Data Exchange (ETDEWEB)

    Mou, Chaozhou; Huang, Zhenghua; Xia, Lidong; Li, Bo; Fu, Hui; Jiao, Fangran; Hou, Zhenyong [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai, 264209 Shandong (China); Madjarska, Maria S., E-mail: z.huang@sdu.edu.cn [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom)

    2016-02-10

    Coronal bright points (BPs) are associated with magnetic bipolar features (MBFs) and magnetic cancellation. Here we investigate how BP-associated MBFs form and how the consequent magnetic cancellation occurs. We analyze longitudinal magnetograms from the Helioseismic and Magnetic Imager to investigate the photospheric magnetic flux evolution of 70 BPs. From images taken in the 193 Å passband of the Atmospheric Imaging Assembly (AIA) we dermine that the BPs’ lifetimes vary from 2.7 to 58.8 hr. The formation of the BP MBFs is found to involve three processes, namely, emergence, convergence, and local coalescence of the magnetic fluxes. The formation of an MBF can involve more than one of these processes. Out of the 70 cases, flux emergence is the main process of an MBF buildup of 52 BPs, mainly convergence is seen in 28, and 14 cases are associated with local coalescence. For MBFs formed by bipolar emergence, the time difference between the flux emergence and the BP appearance in the AIA 193 Å passband varies from 0.1 to 3.2 hr with an average of 1.3 hr. While magnetic cancellation is found in all 70 BPs, it can occur in three different ways: (I) between an MBF and small weak magnetic features (in 33 BPs); (II) within an MBF with the two polarities moving toward each other from a large distance (34 BPs); (III) within an MBF whose two main polarities emerge in the same place simultaneously (3 BPs). While an MBF builds up the skeleton of a BP, we find that the magnetic activities responsible for the BP heating may involve small weak fields.

  18. Coronal magnetic fields from multiple type II bursts

    Science.gov (United States)

    Honnappa, Vijayakumar; Raveesha, K. H.; Subramanian, K. R.

    Coronal magnetic fields from multiple type II bursts Vijayakumar H Doddamani1*, Raveesha K H2 and Subramanian3 1Bangalore University, Bangalore, Karnataka state, India 2CMR Institute of Technology, Bangalore, Karnataka state, India 3 Retd, Indian Institute of Astrophysics, Bangalore, Karnataka state, India Abstract Magnetic fields play an important role in the astrophysical processes occurring in solar corona. In the solar atmosphere, magnetic field interacts with the plasma, producing abundant eruptive activities. They are considered to be the main factors for coronal heating, particle acceleration and the formation of structures like prominences, flares and Coronal Mass Ejections. The magnetic field in solar atmosphere in the range of 1.1-3 Rsun is especially important as an interface between the photospheric magnetic field and the solar wind. Its structure and time dependent change affects space weather by modifying solar wind conditions, Cho (2000). Type II doublet bursts can be used for the estimation of the strength of the magnetic field at two different heights. Two type II bursts occur sometimes in sequence. By relating the speed of the type II radio burst to Alfven Mach Number, the Alfven speed of the shock wave generating type II radio burst can be calculated. Using the relation between the Alfven speed and the mean frequency of emission, the magnetic field strength can be determined at a particular height. We have used the relative bandwidth and drift rate properties of multiple type II radio bursts to derive magnetic field strengths at two different heights and also the gradient of the magnetic field in the outer corona. The magnetic field strength has been derived for different density factors. It varied from 1.2 to 2.5 gauss at a solar height of 1.4 Rsun. The empirical relation of the variation of the magnetic field with height is found to be of the form B(R) = In the present case the power law index ‘γ’ varied from -3 to -2 for variation of

  19. Wave-mean flow interaction and its relationship with the atmospheric energy cycle with diabatic heating

    Institute of Scientific and Technical Information of China (English)

    DUAN; Anmin

    2005-01-01

    Based on the traditional theory of wave mean flow interaction, an improved quasi-geostrophic Eliassen-Palm flux with diabatic heating included is deduced. It is shown that there exists an intrinsic relation between the atmospheric energy cycle derived by Lorenz and the wave energy transfer derived by Eliassen and Palm. From this relation it becomes clear that the energy propagation process of large-scale stationary wave is indeed a part of Lorenz energy cycle, and the energy transform from mean flow to wave equals the global mass integral of the divergence of local wave energy flux or the global integral of local wave energy. The diagnostic results by using NCEP/NCAR reanalysis data suggest that the classical adiabatic Eliassen-Palm flux relation can present only the wintertime wave energy transformation. For other seasons, however, the diabatic effect must be taken into account.

  20. Coronal Waves and Oscillations

    OpenAIRE

    Nakariakov Valery M.; Verwichte Erwin

    2005-01-01

    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 interactio...

  1. Sunquake Generation by Coronal Magnetic Restructuring

    Science.gov (United States)

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

    2015-12-01

    Solar flares and coronal mass ejections are powered by major restructurings of the coronal magnetic field, which appear to strongly perturb the magnetic field in the photosphere as well. Could the associated Lorentz forces generate sunquakes, as suggested by Hudson et al. 2008? Here, we present the first MHD simulations of sunquake generation by magnetic field perturbations, and explore the details of this mechanism. The downgoing magnetic field change is modelled as an Alfven wave, which propagates into the lower atmosphere. When it reaches the vicinity of the beta=1 layer (where the Alfven and sound speeds are equal), non-linear coupling excites a downgoing acoustic wave, which we interpret as a sunquake. The amplitude of the acoustic wave increases nonlinearly with the amplitude of the magnetic perturbation, reaching a limit where around 35% of the injected Poynting flux is transferred to the seismic wave - enough energy to match sunquake observations.

  2. Chemical Fractionation and Abundances in Coronal Plasma

    CERN Document Server

    Drake, J J

    2003-01-01

    Much of modern astrophysics is grounded on the observed chemical compositions of stars and the diffuse plasma that pervades the space between stars, galaxies and clusters of galaxies. X-ray and EUV spectra of the hot plasma in the outer atmospheres of stars have demonstrated that these environments are subject to chemical fractionation in which the abundances of elements can be enhanced and depleted by an order of magnitude or more. These coronal abundance anomalies are discussed and some of the physical mechanisms that might be responsible for producing them are examined. It is argued that coronal abundances can provide important new diagnostics on physical processes at work in solar and stellar coronae. It seems likely that other hot astrophysical plasmas will be subject to similar effects.

  3. Inferring heat recirculation and albedo for exoplanetary atmospheres: Comparing optical phase curves and secondary eclipse data

    CERN Document Server

    von Paris, P; Bordé, P; Selsis, F

    2015-01-01

    Basic atmospheric properties such as albedo and heat redistribution between day and nightside have been inferred for a number of planets using observations of secondary eclipses and thermal phase curves. Optical phase curves have not yet been used to constrain these atmospheric properties consistently. We re-model previously published phase curves of CoRoT-1b, TrES-2b and HAT-P-7b and infer albedos and recirculation efficiencies. These are then compared to previous estimates based on secondary eclipse data. We use a physically consistent model to construct optical phase curves. This model takes Lambertian reflection, thermal emission, ellipsoidal variations and Doppler boosting into account. CoRoT-1b shows a non-negligible scattering albedo (0.11

  4. THE EFFECTS OF IRRADIATION ON HOT JOVIAN ATMOSPHERES: HEAT REDISTRIBUTION AND ENERGY DISSIPATION

    Energy Technology Data Exchange (ETDEWEB)

    Perna, Rosalba [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Heng, Kevin [ETH Zuerich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Pont, Frederic [College of Engineering, Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

    2012-05-20

    Hot Jupiters, due to the proximity to their parent stars, are subjected to a strong irradiating flux that governs their radiative and dynamical properties. We compute a suite of three-dimensional circulation models with dual-band radiative transfer, exploring a relevant range of irradiation temperatures, both with and without temperature inversions. We find that, for irradiation temperatures T{sub irr} {approx}< 2000 K, heat redistribution is very efficient, producing comparable dayside and nightside fluxes. For T{sub irr} Almost-Equal-To 2200-2400 K, the redistribution starts to break down, resulting in a high day-night flux contrast. Our simulations indicate that the efficiency of redistribution is primarily governed by the ratio of advective to radiative timescales. Models with temperature inversions display a higher day-night contrast due to the deposition of starlight at higher altitudes, but we find this opacity-driven effect to be secondary compared to the effects of irradiation. The hotspot offset from the substellar point is large when insolation is weak and redistribution is efficient, and decreases as redistribution breaks down. The atmospheric flow can be potentially subjected to the Kelvin-Helmholtz instability (as indicated by the Richardson number) only in the uppermost layers, with a depth that penetrates down to pressures of a few millibars at most. Shocks penetrate deeper, down to several bars in the hottest model. Ohmic dissipation generally occurs down to deeper levels than shock dissipation (to tens of bars), but the penetration depth varies with the atmospheric opacity. The total dissipated Ohmic power increases steeply with the strength of the irradiating flux and the dissipation depth recedes into the atmosphere, favoring radius inflation in the most irradiated objects. A survey of the existing data, as well as the inferences made from them, reveals that our results are broadly consistent with the observational trends.

  5. Land surface and atmospheric conditions associated with heat waves over the Chickasaw Nation in the South Central United States

    Science.gov (United States)

    Lee, Eungul; Bieda, Rahama; Shanmugasundaram, Jothiganesh; Basara Richter, Heather

    2016-06-01

    Exposure to extreme heat was reconstructed based on regional land-atmosphere processes from 1979 to 2010 in the South Central U.S. The study region surrounds the Chickasaw Nation (CN), a predominantly Native American population with a highly prevalent burden of climate-sensitive chronic diseases. Land surface and atmospheric conditions for summer heat waves were analyzed during spring (March-April-May, MAM) and summer (June-July-August, JJA) based on the Climate and Ocean: Variability, Predictability, and Change maximum temperature definition for heat wave frequency (HWF). The spatial-temporal pattern of HWF was determined using empirical orthogonal function (EOF) analysis and the corresponding principle component time series of the first EOF of HWF. Statistically significant analyses of observed conditions indicated that sensible heat increased and latent heat fluxes decreased with high HWF in the South Central U.S. The largest positive correlations of sensible heat flux to HWF and the largest negative correlations of latent heat flux to HWF were specifically observed over the CN. This is a significantly different energy transfer regime due to less available soil moisture during the antecedent MAM and JJA. The higher sensible heat from dry soil could cause significant warming from the near surface (>2.0°C) to the lower troposphere (>1.5°C), and accumulated boundary layer heat could induce the significant patterns of higher geopotential height and enhance anticyclonic circulations (negative vorticity anomaly) at the midtroposphere. Results suggested a positive land-atmosphere feedback associated with heat waves and called attention to the need for region-specific climate adaptation planning.

  6. Atmospheric considerations regarding the impact of heat dissipation from a nuclear energy center

    International Nuclear Information System (INIS)

    Potential changes in climate resulting from a large nuclear energy center are discussed. On a global scale, no noticeable changes are likely, but on both a regional and a local scale, changes can be expected. Depending on the cooling system employed, the amount of fog may increase, the amount and distribution of precipitation will change, and the frequency or location of severe storms may change. Very large heat releases over small surface areas can result in greater atmospheric instability; a large number of closely spaced natural-draft cooling towers have this disadvantage. On the other hand, employment of natural-draft towers makes an increase in the occurrence of ground fog unlikely. The analysis suggests that the cooling towers for a large nuclear energy center should be located in clusters of four with at least 2.5-mile spacing between the clusters. This is equivalent to the requirement of one acre of land surface per each two megawatts of heat being rejected

  7. Solar coronal observations at high frequencies

    CERN Document Server

    Katsiyannis, A C; Phillips, K J H; Williams, D R; Keenan, F P

    2001-01-01

    The Solar Eclipse Coronal Imaging System (SECIS) is a simple and extremely fast, high-resolution imaging instrument designed for studies of the solar corona. Light from the corona (during, for example, a total solar eclipse) is reflected off a heliostat and passes via a Schmidt-Cassegrain telescope and beam splitter to two CCD cameras capable of imaging at 60 frames a second. The cameras are attached via SCSI connections to a purpose-built PC that acts as the data acquisition and storage system. Each optical channel has a different filter allowing observations of the same events in both white light and in the green line (Fe XIV at 5303 A). Wavelet analysis of the stabilized images has revealed high frequency oscillations which may make a significant contribution on the coronal heating process. In this presentation we give an outline of the instrument and its future development.

  8. Atmospheric Heating by Saharan Dust and Its Implication on the Temperature Profiles over the Tropical Cyclone Main Development Region

    Science.gov (United States)

    Wong, S.; Dessler, A. E.; Mahowald, N.; Yang, P.; Feng, Q.

    2007-12-01

    We have investigated anomalies in atmospheric temperature profiles that are associated with Saharan dust over the tropical cyclone main development region (10°-20°N, 20°-30°W), using temperature data from Atmospheric Infrared Sounder (AIRS) and aerosol data from Moderate Resolution Imaging Spectroradiometer (MODIS). We find that Saharan dust is associated with a vertical temperature structure that has a warm anomaly lying above the marine boundary layer (~850 hPa) and a cold anomaly throughout the middle troposphere (~350-600 hPa). We then estimate dynamical and dust radiative heating of the atmospheric column. The dynamical heating is estimated using wind and temperature data from NCEP reanalysis, while the dust radiative heating is computed using the NASA/GSFC CLIRAD radiative transfer model for both shortwave and longwave. Dust particle size distributions and vertical concentration profiles for use in the radiative transfer calculations are prescribed according to the simulation of the MATCH dust transport model. The warm anomaly in the lower tropsphere can be explained by the dynamical and dust radiative heating. For air columns with aerosol optical thickness greater than one, the dust heating rate is at least 20% of the dynamical heating rate in the lower troposphere. The cold anomaly in the middle troposphere cannot be explained by dynamical or radiative heating. Suppression of deep convection probably plays an essential role in cooling the middle troposphere over the dust layer by reduction of latent heat release. We will also investigate the sensitivity of dust radiative heating rate using assumed particle shapes for dust.

  9. Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath

    Science.gov (United States)

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

    2016-08-01

    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.

  10. The Asian monsoon's role in atmospheric heat transport responses to orbital and millennial-scale climate change

    Science.gov (United States)

    McGee, D.; Green, B.; Donohoe, A.; Marshall, J.

    2015-12-01

    Recent studies have provided a framework for understanding the zonal-mean position of the tropical rain belt by documenting relationships between rain belt latitude and atmospheric heat transport across the equator (Donohoe et al., 2013). Modern seasonal and interannual variability in globally-averaged rain belt position (often referred to as 'ITCZ position') reflects the interhemispheric heat balance, with the rain belt's displacement toward the warmer hemisphere directly proportional to atmospheric heat transport into the cooler hemisphere. Model simulations suggest that rain belt shifts are likely to have obeyed the same relationship with interhemispheric heat transport in response to past changes in orbital parameters, ice sheets, and ocean circulation. This relationship implies that even small (±1 degree) shifts in the mean rain belt require large changes in hemispheric heat budgets, placing tight bounds on mean rain belt shifts in past climates. This work has primarily viewed tropical circulation in two dimensions, as a pair of zonal-mean Hadley cells on either side of the rain belt that are displaced north and south by perturbations in hemispheric energy budgets, causing the atmosphere to transport heat into the cooler hemisphere. Here we attempt to move beyond this zonal-mean perspective, motivated by arguments that the Asian monsoon system, rather than the zonal-mean circulation, plays the dominant role in annual-mean heat transport into the southern hemisphere in the modern climate (Heaviside and Czaja, 2012; Marshall et al., 2014). We explore a range of climate change experiments, including simulations of North Atlantic cooling and mid-Holocene climate, to test whether changes in interhemispheric atmospheric heat transport are primarily driven by the mean Hadley circulation, the Asian monsoon system, or other regional-scale atmospheric circulation changes. The scalings that this work identifies between Asian monsoon changes and atmospheric heat

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

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, Sanjiv K.; Moore, Ronald L.; Winebarger, Amy R. [NASA Marshall Space Flight Center, Mail Code ZP 13, Huntsville, AL 35812 (United States); Alpert, Shane E., E-mail: sanjiv.k.tiwari@nasa.gov [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States)

    2016-01-10

    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.

  12. Magnetic Configurations Related to the Coronal Heating and Solar Wind Generation I. Twist and Expansion Profiles of Magnetic Loops Produced by Flux Emergence

    CERN Document Server

    Lee, Hwanhee

    2014-01-01

    The generation of outflows from the Sun known as solar winds is coupled with the heating of the solar corona, and both processes are operated in magnetic structures formed on the Sun. To study the magnetic configuration responsible for these processes, we use three-dimensional magnetohydrodynamic simulations to reproduce magnetic structures via flux emergence and investigate their configurations. We focus on two key quantities characterizing a magnetic configuration: the force-free parameter alpha and the flux expansion rate fex, the former of which represents how much a magnetic field is twisted while the latter represents how sharply a magnetic field expands. We derive distributions of these quantities in an emerging flux region. Our result shows that an emerging flux region consists of outer part where a magnetic loop takes a large flux expansion rate but a small value of alpha at their photospheric footpoints, and inner part occupied by those loops where a strong electric current flows. We also investigat...

  13. Solar jet-coronal hole collision and a related coronal mass ejection

    CERN Document Server

    Zheng, Ruisheng; Du, Guohui; Li, Chuanyang

    2016-01-01

    Jets are defined as impulsive, well-collimated upflows, occurring in different layers of the solar atmosphere with different scales. Their relationship with coronal mass ejections (CMEs), another type of solar impulsive events, remains elusive. Using the high-quality imaging data of AIA/SDO, here we show a well-observed coronal jet event, in which part of the jets, with the embedding coronal loops, runs into a nearby coronal hole (CH) and gets bounced towards the opposite direction. This is evidenced by the flat-shape of the jet front during its interaction with the CH and the V-shaped feature in the time-slice plot of the interaction region. About a half-hour later, a CME initially with a narrow and jet-like front is observed by the LASCO C2 coronagraph, propagating along the direction of the post-collision jet. We also observe some 304 A dark material flowing from the jet-CH interaction region towards the CME. We thus suggest that the jet and the CME are physically connected, with the jet-CH collision and t...

  14. Variance Method to Determine Turbulent Fluxes of Momentum And Sensible Heat in The Stable Atmospheric Surface Layer

    NARCIS (Netherlands)

    Debruin, H.A.R.; Hartogensis, O.K.

    2005-01-01

    Evidence is presented that in the stable atmospheric surface layer turbulent fluxes of heat and momentum can be determined from the standard deviations of longitudinal wind velocity and temperature, ¿u and ¿T respectively, measured at a single level. An attractive aspect of this method is that it yi

  15. Recent VLA Observations of Coronal Faraday Rotation

    Science.gov (United States)

    Kooi, Jason E.; Fischer, P. D.; Buffo, J. J.; Spangler, S. R.

    2014-01-01

    Proposed mechanisms for coronal heating and acceleration of the fast solar wind, such as Joule heating by coronal currents or dissipation of Alfvén waves, depend on the magnetic field structure and plasma characteristics of the corona within heliocentric distances of 5 solar radii. Faraday rotation observations can provide unique information on the magnetic field in this region of the corona. We report on sensitive full-polarization observations of the radio galaxy 3C228 through the solar corona at heliocentric distances of 4.6 - 5.0 solar radii. The observations were made with the VLA in August of 2011. We performed these observations at 5.0 and 6.1 GHz (each with a bandwidth of 128 MHz), permitting measurements deeper in the corona than previous VLA observations at 1.4 and 1.7 GHz. While the measured Faraday rotation was lower than our a priori expectations, we can understand the magnitude of the observed Faraday rotation in terms of observed properties of the corona on the day of observation. For coronal remote sensing, an advantage of using extended extragalactic radio sources such as 3C228 is that such observations provide multiple lines of sight through the corona. Our data provide two lines of sight (separated by 46″, 33,000 km in the corona), one to a northern hotspot and the other to a southern hotspot with fractional polarizations of 14% and 8% respectively. We detected three periods over the eight-hour observing session during which there appeared to be a difference in the Faraday rotation between these two closely spaced lines of sight. These measurements yield an estimate of 2 - 4 GA for coronal currents. We did not directly detect rotation measure fluctuations. Our data impose upper limits on rotation measure fluctuations caused by coronal waves. The observed upper limits were 3.3 and 6.4 rad/m2 and are comparable to and not inconsistent with some models for Alfvén wave heating. This research was supported at the University of Iowa by grants ATM09

  16. Observational features of equatorial coronal hole jets

    OpenAIRE

    Nisticò, G.; V. Bothmer; S. Patsourakos; Zimbardo, G.

    2010-01-01

    Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet e...

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

    CERN Document Server

    Jones, Shaela I; Uritsky, Vadim M

    2015-01-01

    The coronal magnetic field directly or indirectly affects a majority of the phenomena studied in space physics. It provides energy for coronal heating, controls the release of coronal mass ejections (CMEs), 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 which could be derived from coronal images. Here we report promising initial tests of this approach on two theoretical problems, and discuss opportunities for application.

  18. The Contribution of Coronal Jets To The Solar Wind

    CERN Document Server

    Lionello, R; Titov, V S; Leake, J E; MikiĆ, Z; Linker, J A; Linton, M G

    2016-01-01

    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 j...

  19. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    Science.gov (United States)

    Cuntz, Manfred; Suess, Steven T.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    We investigate the height of shock formation in coroner plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory/Ultraviolet Coronagraph Spectrometer (SOHO/UVCS). Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 solar radius, depending on the model parameters. The shock formation is calculated using the well-established wave breaking condition given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although slow magnetosonic waves are most likely not a solely operating energy supply mechanism.

  20. Development of a Model for Water and Heat Exchange Between the Atmosphere and a Water Body

    Institute of Scientific and Technical Information of China (English)

    SUN Shufen; YAN Jinfeng; XIA Nan; SUN Changhai

    2007-01-01

    A model for studying the heat and mass exchange between the atmosphere and a water body is developed,in which the phase change process of water freezing in winter and melting in summer and the function of the convective mixing process are taken into consideration. The model uses enthalpy rather than temperature as the predictive variable. It helps to set up governing equations more concisely, to deal with the phase change process more easily, and make the numerical scheme simpler. The model is verified by observed data from Lake Kinneret for a non-frozen lake in summer time, and Lake Lower Two Medicine for a frozen lake in winter time. Reasonably good agreements between the model simulations and observed data indicate that the model can serve as a component for a water body in a land surface model. In order to more efficiently apply the scheme in a climate system model, a sensitivity study of various division schemes with less layers in the vertical direction in the water body is conducted. The results of the study show that the division with around 10 vertical layers could produce a prediction accuracy that is comparable to the fine division with around 40 layers.

  1. Chromospheric Nanoflares as a Source of Coronal Plasma: II. Repeating Nanoflares

    CERN Document Server

    Bradshaw, Stephen J

    2016-01-01

    The million degree plasma of the solar corona must be supplied by the underlying layers of the atmosphere. The mechanism and location of energy release, and the precise source of coronal plasma, remain unresolved. In earlier work we pursued the idea that warm plasma is supplied to the corona via direct heating of the chromosphere by nanoflares, contrary to the prevailing belief that the corona is heated in-situ and the chromosphere is subsequently energized and ablated by thermal conduction. We found that single (low-frequency) chromospheric nanoflares could not explain the observed intensities, Doppler-shifts, and red/blue asymmetries in Fe XII and XIV emission lines. In the present work we follow up on another suggestion that the corona could be powered by chromospheric nanoflares that repeat on a timescale substantially shorter than the cooling/draining timescale. That is, a single magnetic strand is re-supplied with coronal plasma before the existing plasma has time to cool and drain. We perform a series ...

  2. 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.

  3. Atmosphere expansion and mass loss of close-orbit giant exoplanets heated by stellar XUV. I. Modeling of hydrodynamic escape of upper atmospheric material

    Energy Technology Data Exchange (ETDEWEB)

    Shaikhislamov, I. F. [Institute of Laser Physics SB RAS, Novosibirsk (Russian Federation); Khodachenko, M. L.; Sasunov, Yu. L.; Lammer, H.; Kislyakova, K. G. [Space Research Institute, Austrian Acad. Sci., Graz (Austria); Erkaev, N. V., E-mail: maxim.khodachenko@oeaw.ac.at [Institute of Computational Modelling, SB RAS, Krasnoyarsk (Russian Federation)

    2014-11-10

    In the present series of papers we propose a consistent description of the mass loss process. To study in a comprehensive way the effects of the intrinsic magnetic field of a close-orbit giant exoplanet (a so-called hot Jupiter) on atmospheric material escape and the formation of a planetary inner magnetosphere, we start with a hydrodynamic model of an upper atmosphere expansion in this paper. While considering a simple hydrogen atmosphere model, we focus on the self-consistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to an investigation of the role of the specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free and restricted flow) are formed. A comparative study is performed of different processes, such as X-ray and ultraviolet (XUV) heating, material ionization and recombination, H{sub 3}{sup +} cooling, adiabatic and Lyα cooling, and Lyα reabsorption. We confirm the basic consistency of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we determine that, under the typical conditions of an orbital distance of 0.05 AU around a Sun-type star, a hot Jupiter plasma envelope may reach maximum temperatures up to ∼9000 K with a hydrodynamic escape speed of ∼9 km s{sup –1}, resulting in mass loss rates of ∼(4-7) · 10{sup 10} g s{sup –1}. In the range of the considered stellar-planetary parameters and XUV fluxes, that is close to the mass loss in the energy-limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the follow-up paper (Paper II).

  4. Ocean-Atmosphere Heat Exchange: Limitations of Currently Available Datasets and Potential for Future Progress (Solicited Talk)

    Science.gov (United States)

    Josey, Simon

    2016-04-01

    The flux of heat between the ocean and the atmosphere is a key element of the global climate system, central to variations in the ocean heat budget and variations in surface temperature. Factors determining the heat exchange will be discussed using models and observations with an emphasis on the period 1990-2015. This period include changes associated with the potential warming hiatus and more recently the major El Nino event that developed in 2015. The ability of leading datasets to reliably estimate surface flux changes is limited by a number of factors and these will be discussed in the context of variations in other components of the climate system. Progress towards obtaining more reliable climatological estimates of the heat exchange will also be considered with reference to recent developments using residual techniques and ocean reanalyses in addition to atmospheric reanalysis, remote sensing and ship based datasets. In addition, use of surface meteorological fields to generate ocean model forcing will be examined together with recent developments using high resolution coupled ocean-atmosphere models. Finally, the potential for significant advances in regions of major uncertainty using the growing network of surface flux buoys will be discussed with a focus on two moorings now in place in the Southern Ocean.

  5. Coronal Mass Ejections: Observations

    Directory of Open Access Journals (Sweden)

    David F. Webb

    2012-06-01

    Full Text Available Solar eruptive phenomena embrace a variety of eruptions, including flares, solar energetic particles, and radio bursts. Since the vast majority of these are associated with the eruption, development, and evolution of coronal mass ejections (CMEs, we focus on CME observations in this review. CMEs are a key aspect of coronal and interplanetary dynamics. They inject large quantities of mass and magnetic flux into the heliosphere, causing major transient disturbances. CMEs can drive interplanetary shocks, a key source of solar energetic particles and are known to be the major contributor to severe space weather at the Earth. Studies over the past decade using the data sets from (among others the SOHO, TRACE, Wind, ACE, STEREO, and SDO spacecraft, along with ground-based instruments, have improved our knowledge of the origins and development of CMEs at the Sun and how they contribute to space weather at Earth. SOHO, launched in 1995, has provided us with almost continuous coverage of the solar corona over more than a complete solar cycle, and the heliospheric imagers SMEI (2003 – 2011 and the HIs (operating since early 2007 have provided us with the capability to image and track CMEs continually across the inner heliosphere. We review some key coronal properties of CMEs, their source regions and their propagation through the solar wind. The LASCO coronagraphs routinely observe CMEs launched along the Sun-Earth line as halo-like brightenings. STEREO also permits observing Earth-directed CMEs from three different viewpoints of increasing azimuthal separation, thereby enabling the estimation of their three-dimensional properties. These are important not only for space weather prediction purposes, but also for understanding the development and internal structure of CMEs since we view their source regions on the solar disk and can measure their in-situ characteristics along their axes. Included in our discussion of the recent developments in CME

  6. Analytical Solutions to the Near-Neutral Atmospheric Surface Energy Balance with and without Heat Storage for Urban Climatological Studies.

    Science.gov (United States)

    Tso, C. P.; Chan, B. K.; Hashim, M. A.

    1991-04-01

    Analytical solutions are presented to the near-neutral atmospheric surface energy balance with the new approach of including the participation of heat storage in the building substrate. Analytical solutions are also presented for the first time for the case without heat storage effect. By a linearization process, the governing equations are simplified to a set of time-dependent, linear, first-order equations from which explicit solutions are readily obtainable. The results compare well with those obtained by numerical solutions upon the set without linearization when applied to the tropical city of Kuala Lumpur, Malaysia.

  7. On the estimation of heating effects in the atmosphere because of seismic activities

    Science.gov (United States)

    Meister, Claudia-Veronika; Hoffmann, Dieter H. H.

    2014-05-01

    The dielectric model for waves in the Earth's ionosphere is further developed and applied to possible electro-magnetic phenomena in seismic regions. In doing so, in comparison to the well-known dielectric wave model by R.O. Dendy [Plasma dynamics, Oxford University Press, 1990] for homogeneous systems, the stratification of the atmosphere is taken into account. Moreover, within the frame of many-fluid magnetohydrodynamics also the momentum transfer between the charged and neutral particles is considered. Discussed are the excitation of Alfvén and magnetoacoustic waves, but also their variations by the neutral gas winds. Further, also other current driven waves like Farley-Buneman ones are studied. In the work, models of the altitudinal scales of the plasma parameters and the electromagnetic wave field are derived. In case of the electric wave field, a method is given to calculate the altitudinal scale based on the Poisson equation for the electric field and the magnetohydrodynamic description of the particles. Further, expressions are derived to estimate density, pressure, and temperatur changes in the E-layer because of the generation of the electromagnetic waves. Last not least, formulas are obtained to determine the dispersion and polarisation of the excited electromagnetic waves. These are applied to find quantitative results for the turbulent heating of the ionospheric E-layer. Concerning the calculation of the dispersion relation, in comparison to a former work by Meister et al. [Contr. Plasma Phys. 53 (4-5), 406-413, 2013], where a numerical double-iteration method was suggested to obtain results for the wave dispersion relations, now further analytical calculations are performed. In doing so, different polynomial dependencies of the wave frequencies from the wave vectors are treated. This helped to restrict the numerical calculations to only one iteration process.

  8. Theoretical studies of the physics of the solar atmosphere

    Science.gov (United States)

    Hollweg, Joseph V.

    1992-01-01

    Significant advances in our theoretical basis for understanding several physical processes related to dynamical phenomena on the sun were achieved. We have advanced a new model for spicules and fibrils. We have provided a simple physical view of resonance absorption of MHD surface waves; this allowed an approximate mathematical procedure for obtaining a wealth of new analytical results which we applied to coronal heating and p-mode absorption at magnetic regions. We provided the first comprehensive models for the heating and acceleration of the transition region, corona, and solar wind. We provided a new view of viscosity under coronal conditions. We provided new insights into Alfven wave propagation in the solar atmosphere. And recently we have begun work in a new direction: parametric instabilities of Alfven waves.

  9. Reflection of Propagating Slow Magneto-acoustic Waves in Hot Coronal Loops: Multi-instrument Observations and Numerical Modeling

    Science.gov (United States)

    Mandal, Sudip; Yuan, Ding; Fang, Xia; Banerjee, Dipankar; Pant, Vaibhav; Van Doorsselaere, Tom

    2016-09-01

    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.

  10. Study of the recurring dimming region detected at AR 11305 using the Coronal Dimming Tracker (CoDiT)

    OpenAIRE

    Krista, Larisza D.; Reinard, Alysha A.

    2013-01-01

    We present a new approach to coronal dimming detection using the COronal DImming Tracker tool (CODIT), which was found to be successful in locating and tracking multiple dimming regions. This tool, an extension of a previously developed coronal hole tracking software, allows us to study the prop- erties and the spatial evolution of dimming regions at high temporal and spatial cadence from the time of their appearance to their disappearance. We use the Solar Dynamics Observatory/Atmospheric Im...

  11. 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

  12. The Nature of CME-Flare Associated Coronal Dimming

    CERN Document Server

    Cheng, J X

    2016-01-01

    Coronal mass ejections (CMEs) are often accompanied by coronal dimming 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 properties of CMEs in the early phase of its eruption. In this study, we analyze the event of flare, CME, and coronal dimming on December 26, 2011. We use the data from the Atmospheric Imaging Assembly (AIA) on Solar Dynamics Observatories (SDO) for disk observations of the dimming, and analyze images taken by EUVI, COR1, and COR2 onboard the Solar Terrestrial Relations Observatories to obtain the height and velocity of the associated CMEs observed at the limb. We also measure magnetic reconnection rate from flare observations. Dimming occurs in a few locations next to the flare ribbons,...

  13. Coronal Response to an EUV Wave from DEM Analysis

    Science.gov (United States)

    Vanninathan, K.; Veronig, A. M.; Dissauer, K.; Madjarska, M. S.; Hannah, I. G.; Kontar, E. P.

    2015-10-01

    Extreme-Ultraviolet (EUV) waves are globally propagating disturbances that have been observed since the era of the Solar and Heliospheric Observatory/Exteme-ultraviolet Imaging Telescope instrument. Although the kinematics of the wave front and secondary wave components have been widely studied, there is not much known about the generation and plasma properties of the wave. In this paper we discuss the effect of an EUV wave on the local plasma as it passes through the corona. We studied the EUV wave, generated during the 2011 February 15 X-class flare/coronal mass ejection event, using Differential Emission Measure diagnostics. We analyzed regions on the path of the EUV wave and investigated the local density and temperature changes. From our study we have quantitatively confirmed previous results that during wave passage the plasma visible in the Atmospheric Imaging Assembly (AIA) 171 Å channel is getting heated to higher temperatures corresponding to AIA 193 and 211 Å channels. We have calculated an increase of 6%-9% in density and 5%-6% in temperature during the passage of the EUV wave. We have compared the variation in temperature with the adiabatic relationship and have quantitatively demonstrated the phenomenon of heating due to adiabatic compression at the wave front. However, the cooling phase does not follow adiabatic relaxation but shows slow decay indicating slow energy release being triggered by the wave passage. We have also identified that heating is taking place at the front of the wave pulse rather than at the rear. Our results provide support for the case that the event under study here is a compressive fast-mode wave or a shock.

  14. Heat engines and heat pumps in a hydrostatic atmosphere: How surface pressure and temperature control wind power output and circulation cell size

    CERN Document Server

    Makarieva, A M; Nefiodov, A V; Sheil, D; Nobre, A D; Shearman, P L; Li, B -L

    2015-01-01

    The gross spatial features of the atmospheric kinetic energy budget are analytically investigated. Kinetic energy generation is evaluated in a hydrostatic atmosphere where the axisymmetric circulation cells are represented by Carnot cycles. The condition that kinetic energy generation is positive in the lower atmosphere is shown to limit the poleward cell extension via a relationship between the meridional differences in surface pressure and temperature $\\Delta p_s$ and $\\Delta T_s$: an upper limit to cell size exists when $\\Delta p_s$ increases sublinearly with $\\Delta T_s$. This is the case for the Hadley cells as demonstrated here using data from MERRA re-analysis. The limited cell size necessitates the appearance of heat pumps -- circulation cells with negative work output where the low-level air moves towards colder areas. These cells consume the positive work output of heat engines -- cells where the low-level air moves towards the warmer areas -- and can in principle drive the global efficiency of atmo...

  15. On the Sensitivity of Atmospheric Model Implied Ocean Heat Transport to the Dominant Terms of the Surface Energy Balance

    Energy Technology Data Exchange (ETDEWEB)

    Gleckler, P J

    2004-11-03

    The oceanic meridional heat transport (T{sub o}) implied by an atmospheric General Circulation Model (GCM) can help evaluate a model's readiness for coupling with an ocean GCM. In this study we examine the T{sub o} from benchmark experiments of the Atmospheric Model Intercomparison Project, and evaluate the sensitivity of T{sub o} to the dominant terms of the surface energy balance. The implied global ocean TO in the Southern Hemisphere of many models is equatorward, contrary to most observationally-based estimates. By constructing a hybrid (model corrected by observations) T{sub o}, an earlier study demonstrated that the implied heat transport is critically sensitive to the simulated shortwave cloud radiative effects, which have been argued to be principally responsible for the Southern Hemisphere problem. Systematic evaluation of one model in a later study suggested that the implied T{sub o} could be equally as sensitive to a model's ocean surface latent heat flux. In this study we revisit the problem with more recent simulations, making use of estimates of ocean surface fluxes to construct two additional hybrid calculations. The results of the present study demonstrate that indeed the implied T{sub o} of an atmospheric model is very sensitive to problems in not only the surface net shortwave, but the latent heat flux as well. Many models underestimate the shortwave radiation reaching the surface in the low latitudes, and overestimate the latent heat flux in the same region. The additional hybrid transport calculations introduced here could become useful model diagnostic tests as estimates of implied ocean surface fluxes are improved.

  16. Role of atmospheric heat source/sink over the Qinghai- Xizang Plateau in quasi-4- year oscillation of atmosphere- land-ocean interaction

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using 1961-1995 monthly atmospheric apparent heat source/sink over the Qinghai-Xizang Plateau (QXP) and reanalysis data of NCEP/NCAR, and 1961-1994 monthly SST of UK/GISST2, the statistical study is undertaken on the QXP heat source/sink in relation to both atmospheric circulation in Asia and El Ni?o/La Ni?a events. It is discovered that there exists noticeable interaction in a quasi-4-year period among the of the QXP, low-level me-ridional winds east of the QXP, low-level zonal winds in the equatorial Pacific, SST in the equatorial eastern Pacific, and the circulation at mid and high latitudes north of the QXP. They have difference in phase. The cold source intensity of the QXP in winter favours a low-level meridional wind anomaly to prevail in the mainland of China and its coast east of the QXP and to last until the subsequent autumn. The wind anomaly can induce a low-level zonal wind anomaly of the tropic Pacific that finally affects an El Ni?o/La Ni?a event in the autumn and subsequent winter. The event in autumn/winter has effect on the deep trough position and cold air track of East Asia in next winter that influences the intensity of the QXP winter cold source.

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

    Science.gov (United States)

    Robbrecht, E.

    2007-02-01

    During a total solar eclipse, a narrow strip of the Earth's surface is shielded completely by the Moon from the disk of the Sun. In this strip, the corona appears crown-like around the shade of the Moon. It was uncertain until the middle of the 20th century whether the corona was a solar phenomenon or if it was related to the Moon or whether it represented an artifact produced by the Earth's atmosphere. The answer to this question was provided by Grotrian (1939) and Edlèn (1942). Based on studies of iron emission lines, they suggested that the surface of the Sun is surrounded by a hot tenuous gas having a temperature of million degrees Kelvin and thus in a state of high ionization. This discovery was a result from spectroscopy, a field of research which started in 1666 with Sir Isaac Newton's observations of sunlight, dispersed by a prism. It is now clear that the hot solar corona is made of a low density plasma, highly structured by the magnetic field on length scales ranging from the Sun's diameter to the limit of angular resolution (e.g. Démoulin and Klein 2000). The need to resolve and study the corona down to such scales has determined a vigorous scientific and technological impulse toward the development of solar Ultraviolet (UV) and X-ray telescopes with high spatial and temporal resolution. With the advent of the satellite SOHO (Solar and Heliospheric Observatory, see chapter 1), the picture of a quiet corona was definitely sent to the past. EUV (Extreme UV) image sequences of the lower solar corona revealed a finely structured medium constantly agitated by a wide variety of transients (e.g. Harrison 1998). Active regions consisting of large magnetic loops with enhanced temperature and density are observed, as well as "quiet" areas, coronal holes and numerous structures of different scales such as plumes, jets, spicules, X-ray bright points, blinkers, all structured by magnetic fields. Launched in 1998, the Transition Region And Coronal Explorer (TRACE

  18. Property changes of powdery polyacrylonitrile synthesized by aqueous suspension polymerization during heat-treatment process under air atmosphere.

    Science.gov (United States)

    Zhao, Ya-qi; Wang, Cheng-guo; Bai, Yu-jun; Chen, Guo-wen; Jing, Min; Zhu, Bo

    2009-01-01

    High molecular weight powdery polyacrylonitrile (PAN) polymers were prepared by aqueous suspension polymerization employing itaconic acid (IA) as comonomer and alpha,alpha(')-azobisisobutyronitrile (AIBN) as initiator at 60 degrees C. PAN polymers obtained with different monomer ratios were characterized by EA, DSC, FTIR and XRD. It is investigated that the oxygen element content in PAN polymers increased with the increase of required IA amounts in the feed and heat-treatment temperatures. DSC curves of PAN copolymers exhibited the triplet character, owing to the exothermic cyclization and oxidative reactions during heat-treatment process. Introduction of IA in the feed relaxed exothermic reactions of PAN polymers under air atmosphere. Structure and crystallinity changes were affected by required IA amounts in the feed and enhancement of heat-treatment temperatures. The characteristic functional groups (including C[triple bond]N, C=O, CH(2)) presented in FTIR spectra of PAN polymers indicated copolymerization reaction of AN and IA. Existence of some organic groups (C-O, C=C and/or C=N) indicated formation of ladderlike structure during heat-treatment process. PAN homopolymer had the better crystallinity (mainly peak intensity and peak area around 2theta = 17 degrees) than most RT-PAN copolymers. When heat-treatment temperature is around 210 degrees C, peak intensity, peak area, L(c) and CI of HT-PAN polymers corresponding to samples 1# and 2# got maxima, while crystallinity became weak at higher heat-treatment temperatures. PMID:18922543

  19. Damping of Slow Magnetoacoustic Waves in an Inhomogeneous Coronal Plasma

    Indian Academy of Sciences (India)

    Nagendra Kumar; Pradeep Kumar; Shiv Singh; Anil Kumar

    2008-03-01

    We study the propagation and dissipation of slow magnetoacoustic waves in an inhomogeneous viscous coronal loop plasma permeated by uniform magnetic field. Only viscosity and thermal conductivity are taken into account as dissipative processes in the coronal loop. The damping length of slow-mode waves exhibit varying behaviour depending upon the physical parameters of the loop in an active region AR8270 observed by TRACE. The wave energy flux associated with slow magnetoacoustic waves turns out to be of the order of 106 erg cm-2 s-1 which is high enough to replace the energy lost through optically thin coronal emission and the thermal conduction belowto the transition region. It is also found that only those slow-mode waves which have periods more than 240 s provide the required heating rate to balance the energy losses in the solar corona. Our calculated wave periods for slow-mode waves nearly match with the oscillation periods of loop observed by TRACE.

  20. Atmospheric Chemistry of Six Methyl-perfluoroheptene-ethers Used as Heat Transfer Fluid Replacement Compounds: Measured OH Radical Reaction Rate Coefficients, Atmospheric Lifetimes, and Global Warming Potentials

    Science.gov (United States)

    Jubb, A. M.; Gierczak, T.; Baasandorj, M.; Waterland, R. L.; Burkholder, J. B.

    2013-12-01

    Mixtures of methyl-perfluoroheptene-ethers (C7F13OCH3, MPHEs) are currently in use as a replacement for perfluorinated alkane (PFC) and polyether mixtures (both persistent greenhouse gases with atmospheric lifetimes >1000 years) used as heat transfer fluids. Currently, the atmospheric fate of the MPHE isomers are not well characterized, however, reaction with the OH radical is expected to be a dominant tropospheric loss process for these compounds. In order to assess the atmospheric lifetimes and environmental implications of MPHE use, rate coefficients for MPHE isomers' reaction with OH radicals are desired. In the work presented here, rate coefficients, k, for the gas-phase reaction of the OH radical with six MPHEs commonly used in commercial mixtures (isomers and stereoisomers) and their deuterated analogs (d3-MPHE) were determined at 296 K using a relative rate method with combined gas-chromatography/IR spectroscopy detection. A range of OH rate coefficient values was observed, up to a factor of 20× different, between the MPHE isomers with the (E)-stereoisomers exhibiting the greatest reactivity. The measured OH reaction rate coefficients for the d3-MPHE isomers were lower than the observed MPHE values although a large range of k values between isomers was still observed. The reduction in reactivity with deuteration signifies that the MPHE + OH reaction proceeds via both addition to the olefinic C=C bond and H-abstraction from the methyl ester group. OH addition to the C=C bond was determined to be the primary reaction channel. Atmospheric lifetimes with respect to the OH reaction for the six MPHE isomers were found to be in the range of days to months. The short lifetimes indicate that MPHE use will primarily impact tropospheric local and regional air quality. A MPHE atmospheric degradation mechanism will be presented. As part of this work, radiative efficiencies and global warming potentials (GWPs) for the MPHE isomers were estimated based on measured

  1. 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.

  2. Spectral Characteristics of Large-Scale Radio Emission Areas in Coronal Holes

    CERN Document Server

    Prosovetsky, D V; Kochanov, A A

    2013-01-01

    The spectra of the coronal hole radio emission in solar cycles 23 and 24 have been studied based on RATAN-600 data in the 4-16.5 GHz range at frequencies of 5.7 and 17 GHz and 327 MHz. It has been found that bright features of coronal hole microwave emission at 17 GHz and dark features at 5.7 GHz can exist in coronal holes when the spectral index is 1.25-1.5 in the 6.5-16.5 GHz range; the radio spectrum in this range is flat when coronal holes are indiscernible against the background of a quiet Sun. The possible vertical scale of the solar atmosphere over coronal holes is discussed.

  3. Effect of coronal temperature on the scale of solar chromospheric jets

    CERN Document Server

    Iijima, H

    2015-01-01

    We investigate the effect of coronal temperature on the formation process of solar chromospheric jets using two-dimensional magnetohydrodynamic simulations of the region from the upper convection zone to the lower corona. We develop a new radiative magnetohydrodynamic code for the dynamic modeling of the solar atmosphere, employing a LTE equation of state, optically thick radiative loss in the photosphere, optically thin radiative loss in the chromosphere and the corona, and thermal conduction along the magnetic field lines. Many chromospheric jets are produced in the simulations by shock waves passing through the transition region. We find that these jets are projected farther outward when the coronal temperature is lower (similar to that in coronal holes) and shorter when the coronal temperature is higher (similar to that in active regions). When the coronal temperature is high, the deceleration of the chromospheric jets is consistent with the model in which deceleration is determined by the periodic chromo...

  4. Decay of Activity Complexes, Formation of Unipolar Magnetic Regions and Coronal Holes in their Causal Relation

    CERN Document Server

    Golubeva, Elena

    2016-01-01

    North-south asymmetry of sunspot activity resulted in an asynchronous reversal of the Sun's polar fields in the current cycle. The asymmetry is also observed in the formation of polar coronal holes. A stable coronal hole was first formed at the South Pole, despite the later polar-field reversal there. The aim of this study is to understand processes making this situation possible. Synoptic magnetic maps from the Global Oscillation Network Group and corresponding coronal-hole maps from the Extreme ultraviolet Imaging Telescope aboard the Solar and Heliospheric Observatory and the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory are analyzed here to study a causal relationship between the decay of activity complexes, evolution of large-scale magnetic fields, and formation of coronal holes. Ensembles of coronal holes associated with decaying active regions and activity complexes are presented. These ensembles take part in global rearrangements of the Sun's open magnetic flux. In particular, the...

  5. 太阳光球磁亮点的基本特征研究及其对日冕加热的贡献%Studies of Magnetic Bright Points in the Photosphere and Their Contribution to the Coronal Heating

    Institute of Scientific and Technical Information of China (English)

    刘艳霄; 林隽; 吴宁

    2014-01-01

    在太阳光球表面出现的磁亮点是目前观测手段能够分辨的最小磁结构,也被认为是日冕中的磁绳在光球足点运动的可靠示踪者。磁亮点的尺度约为100∼300 km,寿命从几分钟到几十分钟。磁亮点被观测到不仅具有漩涡运动现象,还有很强的振荡现象。磁亮点是在磁通量管的对流坍缩过程中形成的,这已被观测和数值模拟所验证;磁亮点的运动导致其所在的磁通量管产生振荡,或者与其他磁通量管发生扭绞。理论上认为,这些振荡会以波的形式向色球和日冕传送能量,而磁通量管之间的扭绞会在色球和日冕中发生磁重联并释放能量,从而加热色球和日冕。为了解开日冕加热和色球加热等未解之谜,对磁亮点的研究显示出它特殊的重要性。对磁亮点的基本特征、形成原理、观测证据、光球磁亮点和太阳大气其他亮点之间的关系,以及磁亮点对日冕加热贡献等方面进行了介绍和讨论。%Magnetic bright points in the photosphere are the smallest structures that the present observational technique could resolve. They are regarded as a reliable tracer of footpoints of the coronal magnetic field in the photosphere. The energy conversion and transportation caused by the motion of these footpoints is considered as one of the most important energy source of heating the chromosphere and the corona by waves or magnetic reconnection through twist magnetic tubes. Currently, we have known some important facts about the elementary structures and the basic features of magnetic bright points. For example, magnetic bright points have sizes about 100∼300 km and their lifetimes range from several to tens of minutes. Furthermore, their velocities are around 1∼2 km·s-1 on average in the horizontal direction. Especially, some magnetic bright points whirl along a logarithm path in granulation lanes, which can trace large scales swirling down

  6. Combining Satellite Microwave Radiometer and Radar Observations to Estimate Atmospheric Latent Heating Profiles

    Science.gov (United States)

    Grecu, Mircea; Olson, William S.; Shie, Chung-Lin; L'Ecuyer, Tristan S.; Tao, Wei-Kuo

    2009-01-01

    In this study, satellite passive microwave sensor observations from the TRMM Microwave Imager (TMI) are utilized to make estimates of latent + eddy sensible heating rates (Q1-QR) in regions of precipitation. The TMI heating algorithm (TRAIN) is calibrated, or "trained" using relatively accurate estimates of heating based upon spaceborne Precipitation Radar (PR) observations collocated with the TMI observations over a one-month period. The heating estimation technique is based upon a previously described Bayesian methodology, but with improvements in supporting cloud-resolving model simulations, an adjustment of precipitation echo tops to compensate for model biases, and a separate scaling of convective and stratiform heating components that leads to an approximate balance between estimated vertically-integrated condensation and surface precipitation. Estimates of Q1-QR from TMI compare favorably with the PR training estimates and show only modest sensitivity to the cloud-resolving model simulations of heating used to construct the training data. Moreover, the net condensation in the corresponding annual mean satellite latent heating profile is within a few percent of the annual mean surface precipitation rate over the tropical and subtropical oceans where the algorithm is applied. Comparisons of Q1 produced by combining TMI Q1-QR with independently derived estimates of QR show reasonable agreement with rawinsonde-based analyses of Q1 from two field campaigns, although the satellite estimates exhibit heating profile structure with sharper and more intense heating peaks than the rawinsonde estimates. 2

  7. Interannual Variability of Heat Wave in South Korea and theirs Connection with Large-Scale Atmospheric Circulation Pattern

    Science.gov (United States)

    Lee, Woo-Seop; Lee, Myong-In

    2016-04-01

    This study investigates the interannual variation of heat wave frequency (HWF) in South Korea during the past 42 years (1973-2014) and examines its connection with large-scale atmospheric circulation changes. Korean heat waves tend to develop most frequently in late summer during July and August. The leading Empirical Orthogonal Function (EOF) accounting for 50% of the total variance shows a mono-signed pattern over South Korea, suggesting that the dominant mechanisms responsible for the heat wave are linked in a spatial scale much larger than the nation. It also exhibits a regional variation with more occurrences in the southeastern inland area. The regression of the leading principal component (PC) time series of HWF with large-scale atmospheric circulation identifies a north-south dipole pattern between the South China Sea and Northeast Asia. When this large-scale circulation mode facilitates deep convection in South China Sea, it tends to weaken moisture transport from the South China Sea to Northeast Asia. Enhanced deep convection in the South China Sea triggers a source of Rossby wave train along southerly wind that generates positive geopotential height anomalies around Korea. The anomalous high pressure pattern is accompanied by large-scale subsidence in Korea, thereby providing a favorable condition for extreme hot and dry days in Korea. This study highlights that there is a decadal change of the relationship between Korean heat waves and large-scale atmospheric circulation patterns. The tropical forcing tends to be weakened in the recent decade, with more influences from the Arctic variability from the mid-1990s.

  8. Unresolved fine-scale structure in solar coronal loop-tops

    Energy Technology Data Exchange (ETDEWEB)

    Scullion, E.; Van der Voort, L. Rouppe; Wedemeyer, S. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); Antolin, P., E-mail: scullie@tcd.ie [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2014-12-10

    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer substructures within coronal loop cross-sections, in order to understand the nature of the solar corona. Here, we push this lower limit further to search for the finest coronal loop substructures, through taking advantage of the resolving power of the Swedish 1 m Solar Telescope/CRisp Imaging Spectro-Polarimeter (CRISP), together with co-observations from the Solar Dynamics Observatory/Atmospheric Image Assembly (AIA). High-resolution imaging of the chromospheric Hα 656.28 nm spectral line core and wings can, under certain circumstances, allow one to deduce the topology of the local magnetic environment of the solar atmosphere where its observed. Here, we study post-flare coronal loops, which become filled with evaporated chromosphere that rapidly condenses into chromospheric clumps of plasma (detectable in Hα) known as a coronal rain, to investigate their fine-scale structure. We identify, through analysis of three data sets, large-scale catastrophic cooling in coronal loop-tops and the existence of multi-thermal, multi-stranded substructures. Many cool strands even extend fully intact from loop-top to footpoint. We discover that coronal loop fine-scale strands can appear bunched with as many as eight parallel strands within an AIA coronal loop cross-section. The strand number density versus cross-sectional width distribution, as detected by CRISP within AIA-defined coronal loops, most likely peaks at well below 100 km, and currently, 69% of the substructure strands are statistically unresolved in AIA coronal loops.

  9. INTERANNUAL VARIATIONS OF ATMOSPHERIC HEAT SOURCES AND MOISTURE SINKS OVER THE EQUATORIAL PACIFIC AND THEIR RELATIONS TO THE SST ANOMALIES

    Institute of Scientific and Technical Information of China (English)

    蓝光东; 温之平; 贺海晏

    2004-01-01

    The interannual variations of atmospheric heat sources and moisture sinks over the Equatorial Pacific and their relations with the SST anomalies are studied using ECMWF reanalysis data from 1979 to 1993. It is found by singular value decomposition (SVD) analysis that the region in the tropical Pacific with high positive correlation between the vertically integrated heat source anomaly and the SST anomaly, and between the vertically integrated moisture sink anomaly and the SST anomaly, is mainly located in a long and narrow belt to the east of 170 (E between 5 (S and 5 (N. The analysis of the vertical structure of atmospheric heat sources and moisture sinks shows that the interannual variations of Q1, Q2 and SST in the equatorial central and eastern Pacific are strongly and positively correlated in the whole troposphere except the bottom (962.5 hPa) and the top (85 hPa) layers. However, in the western Pacific, the interannual variations of Q1 below 850 hPa is negatively related to the SST. The correlation coefficient at the level 962.5 hPa reaches even -0.59. In other layers the positive correlation between the interannual variations of Q1, Q2 and the SST are weak in the western Pacific.

  10. Coronal Seismology: Inferring Magnetic Fields and Exploring Damping Mechanisms

    Science.gov (United States)

    McAteer, R. T. James; Ireland, Jack

    2015-08-01

    Recent observations in extreme ultra-violet wavelengths have shown that the solar corona oscillates at many different spatial sizes and temporal size scales. However, much remains unknown about many of these oscillations; they are intermittent for unknown reasons, appear on some coronal features and not on other, similar, neighboring features, and may (or may not) be magnetohydrodynamic (MHD) wave modes. Definitive causes of the structure and origins of these oscillations are still largely lacking. Here, we use automated oscillation detection routines to study a large sample of oscillations, inferring physical mechanisms as to how and why the corona varies.First, we measure the oscillation content of different physical regions on the Sun in SDO AIA data, using two different automated oscillation detection algorithms. This shows a power-law distribution in oscillatory frequency, disagreeing with strong historical assumptions about the nature of coronal heating and coronal seismology. We show how such disagreements can be reconciled by using a power-law background for oscillatory signals.Second we use coronal seismology to provide a means to infer coronal plasma parameters and to differentiate between potential damping mechanisms. Recent sets of kink-mode observations (usually 5-8 loops) have come insights into how the coronal is structured and how it evolves. We present a complex set of flare-induced, off-limb, coronal kink-mode oscillations of almost 100 loops. These display a spread of periods, amplitudes, and damping times, allowing us to probe the spatial distribution of these parameters for the first time. Both Fourier and Wavelet routines are used to automatically extract and characterize these oscillations. An initial period of P~500s, results in an inferred coronal magnetic field of B~20G. The decrease in the oscillation period of the loop position corresponds to a drop in number density inside the coronal loop, as predicted by MHD. As the the period drops

  11. A Moreton Wave and its Coronal Counterparts

    Science.gov (United States)

    Francile, Carlos N.; Mandrini, Cristina H.; Long, David; Cremades, Hebe; Lopez, Fernando M.; Luoni, Maria Luisa

    2016-07-01

    On 29 March 2014, a Moreton wave was detected in AR 12017 with the Halpha Solar Telescope for Argentina (HASTA) in association with an X1 flare. Several phenomena took place in various regimes in connection with this event, such as low coronal waves and a coronal mass ejection (CME). We investigate their role and relationship with the Moreton wave to shed light on issues so far under debate. We analyze its connection with waves observed in the low corona with the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory (SDO/AIA), as well as with the ensuing CME, via kinematics analyses. We build stack plots from sequences of images obtained at different wavelengths to track wave fronts along several directions and find links between the features observed in the chromosphere and low corona, as well as in the associated CME. We also derive the shock front properties. We propose a geometrical model of the wave to explain the observed wave fronts as the photospheric and chromospheric traces of an expanding and outward-traveling bubble intersecting the Sun.

  12. Kinematics and amplitude evolution of global coronal extreme ultraviolet waves

    Institute of Scientific and Technical Information of China (English)

    Ting Li; Jun Zhang; Shu-Hong Yang; Wei Liu

    2012-01-01

    With the observations of the Solar-Terrestrial Relations Observatory (STEREO) and the Solar Dynamics Observatory (SDO),we analyze in detail the kinematics of global coronal waves together with their intensity amplitudes (so-called "perturbation profiles").We use a semi-automatic method to investigate the perturbation profiles of coronal waves.The location and amplitude of the coronal waves are calculated over a 30° sector on the sphere,where the wave signal is strongest.The position with the strongest perturbation at each time is considered as the location of the wave front.In all four events,the wave velocities vary with time for most of their lifetime,up to 15 min,while in the event observed by the Atmospheric Imaging Assembly there is an additional early phase with a much higher velocity.The velocity varies greatly between different waves from 216 to 440 km s-1.The velocity of the two waves initially increases,subsequently decreases,and then increases again.Two other waves show a deceleration followed by an acceleration.Three categories of amplitude evolution of global coronal waves are found for the four events.The first is that the amplitude only shows a decrease.The second is that the amplitude initially increases and then decreases,and the third is that the amplitude shows an orderly increase,a decrease,an increase again and then a decrease.All the extreme ultraviolet waves show a decrease in amplitude while propagating farther away,probably because the driver of the global coronal wave (coronal mass ejection) is moving farther away from the solar surface.

  13. 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...

  14. METHODS TO DETECT ATMOSPHERIC AND SURFACE HEAT ISLANDS IN URBAN AREAS

    OpenAIRE

    I. HERBEL; A. E. CROITORU; A. M. IMBROANE; D. PETREA

    2015-01-01

    Intensification of the urbanization process and its associated climatic effects is nowadays a major problem of large cities worldwide. One of these climatic effects is the urban heat island (UHI), that implies increased air and surface temperature values in the city when compared to the nearby rural areas. This phenomenon threatens the health of the population, especially during heat waves, affects the quality of the environment and the quality of life, and also generates significant costs to...

  15. Extension of the MURaM radiative MHD code for coronal simulations

    CERN Document Server

    Rempel, Matthias

    2016-01-01

    We present a new version of the MURaM radiative MHD code that allows for simulations spanning from the upper convection zone into the solar corona. We implemented the relevant coronal physics in terms of optically thin radiative loss, field aligned heat conduction and an equilibrium ionization equation of state. We artificially limit the coronal Alfv{\\'e}n and heat conduction speeds to computationally manageable values using an approximation to semi-relativistic MHD with an artificially reduced speed of light (Boris correction). We present example solutions ranging from quiet to active Sun in order to verify the validity of our approach. We quantify the role of numerical diffusivity for the effective coronal heating. We find that the (numerical) magnetic Prandtl number determines the ratio of resistive to viscous heating and that owing to the very large magnetic Prandtl number of the solar corona, heating is expected to happen predominantly through viscous dissipation. We find that reasonable solutions can be...

  16. Absorption of solar energy heats up our planet's surface and the atmosphere and makes life for us po

    Science.gov (United States)

    2002-01-01

    Credit: Image courtesy Barbara Summey, NASA Goddard Visualization Analysis Lab, based upon data processed by Takmeng Wong, CERES Science Team, NASA Langley Research Center Satellite: Terra Sensor: CERES Image Date: 09-30-2001 VE Record ID: 11546 Description: Absorption of solar energy heats up our planet's surface and the atmosphere and makes life for us possible. But the energy cannot stay bound up in the Earth's environment forever. If it did then the Earth would be as hot as the Sun. Instead, as the surface and the atmosphere warm, they emit thermal longwave radiation, some of which escapes into space and allows the Earth to cool. This false-color image of the Earth was produced on September 30, 2001, by the Clouds and the Earth's Radiant Energy System (CERES) instrument flying aboard NASA's Terra spacecraft. The image shows where more or less heat, in the form of longwave radiation, is emanating from the top of Earth's atmosphere. As one can see in the image, the thermal radiation leaving the oceans is fairly uniform. The blue swaths across the central Pacific represent thick clouds, the tops of which are so high they are among the coldest places on Earth. In the American Southwest, which can be seen in the upper righthand corner of the globe, there is often little cloud cover to block outgoing radiation and relatively little water to absorb solar energy. Consequently, the amount of outgoing radiation in the American Southwest exceeds that of the oceans. Also, that region was experiencing an extreme heatwave when these data were acquired. Recently, NASA researchers discovered that incoming solar radiation and outgoing thermal radiation increased in the tropics from the 1980s to the 1990s. (Click to read the press release .) They believe that the reason for the unexpected increase has to do with an apparent change in circulation patterns around the globe, which effectively reduced the amount of water vapor and cloud cover in the upper reaches of the atmosphere

  17. Effect of Microstructure on Atmospheric-Induced Corrosion of Heat-treated Grade 2205 and 2507 Duplex Stainless Steels

    OpenAIRE

    Cem Örnek, Amina H. Ahmed, Dirk Engelberg

    2012-01-01

    Atmospheric-induced corrosion tests under MgCl2 salt deposits were carried out on duplex stainless steel grade 2205 and 2507. As-received and 750°C heat-treated material conditions were investigated, and selected micro-structural sites targeted with salt-laden deposits to determine their corrosion response. Deposits were wetted under controlled climatic conditions at 80°C and 40% relative humidity. Observations of micro-structural attack indicated the presence of net anodic and net cathodic s...

  18. Heat flux to the helium cryogenic system elements in the case of incidental vacuum vessel ventilation with atmospheric air

    CERN Document Server

    CERN. Geneva

    2016-01-01

    The selection process for size in safety equipment for cold vessels or process pipes in cryogenic systems should take into consideration the incidental ventilation of the vacuum vessel with atmospheric air. In this case, a significant heat input toward the cold elements of the system can be expected. A number of experimental investigations have been done for the elements at liquid helium temperature which have been covered with 10 layers of MLI. The typical values of the heat flux were measured in a range of 3.7 to 5.0 kW/m2 of the element surface. The helium temperature parts are typically surrounded by thermal shields that are kept in a temperature range of 50-80K. On the external side, the thermal shields are covered with 30-40 layers of MLI while on the internal side, the shields are bare. The theoretical calculations of heat flux to the thermal shield, with respect to the possibility of air condensation and freezing on the bare side of the thermal shield, show that the heat flux to the thermal shield can...

  19. Characteristics of Atmospheric Heat Sources over Asia in Summer:Comparison of Results Calculated Using Multiple Reanalysis Datasets

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bo; CHEN Longxun; HE Jinhai; ZHU Congwen; LI Wei

    2009-01-01

    Using 1979-2000 daily NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data (version 1, hereafter referred to as NCEP1; version 2, hereafter referred to as NCEP2), ECMWF (European Center for Medium-range Weather Forecasts) reanalysis data (ERA), and the Global Asian Monsoon Experiment (GAME) reanalysis data in summer 1998, the vertically integrated heat source (Q1) in summer is calculated, and results obtained using different datasets are com-pared. The distributions of (Q1) calculated by using NCEP1 are in good agreement with rainfall observations over the Arabian Sea/Indian Peninsula, the Bay of Bengal (BOB), and East China. The distributions of (Q1)revealed by using NCEP2 are unrealistic in the southern Indian Peninsula, the BOB, and the South China Sea. Using ERA, the heat sources over the tropical Asia are in accordance with the summer precipitation,however, the distributions of (Q1) in East China are unreasonable. In the tropical region, the distributions of the summer heat source given by NCEP1 and ERA seem to be more accurate than those revealed by NCEP2. The NCEP1 and NCEP2 data are better for calculating heat sources over the subtropical and eastern regions of mainland China.

  20. A Solar Coronal Jet Event Triggers A Coronal Mass Ejection

    CERN Document Server

    Liu, Jiajia; Shen, Chenglong; Liu, Kai; Pan, Zonghao; Wang, S

    2015-01-01

    We present the multi-point and multi-wavelength observation and analysis on a solar coronal jet and coronal mass ejection (CME) event in this paper. Employing the GCS model, we obtained the real (three-dimensional) heliocentric distance and direction of the CME and found it propagate in a high speed over 1000 km/s . The jet erupted before and shared the same source region with the CME. The temporal and spacial relation- ship between them guide us the possibility that the jet triggered the CME and became its core. This scenario could promisingly enrich our understanding on the triggering mechanism of coronal mass ejections and their relations with coronal large-scale jets. On the other hand, the magnetic field configuration of the source region observed by the SDO/HMI instrument and the off- limb inverse Y-shaped configuration observed by SDO/AIA 171 A passband, together provide the first detailed observation on the three-dimensional reconnection process of large-scale jets as simulated in Pariat et al. 2009. ...

  1. Effects of Coronal Mass Ejections on Distant Coronal Streamers

    CERN Document Server

    Filippov, B; Srivastava, A K; Martsenyuk, O

    2014-01-01

    The effects of a large coronal mass ejection (CME) on a solar coronal streamer located roughly 90 degrees from the main direction of the CME propagation observed on January 2, 2012 by the SOHO/LASCO coronagraph are analyzed. Radial coronal streamers undergo some bending when CMEs pass through the corona, even at large angular distances from the streamers. The phenomenon resembles a bending wave traveling along the streamer. Some researchers interpret these phenomena as the effects of traveling shocks generated by rapid CMEs, while others suggest they are waves excited inside the streamers by external impacts. The analysis presented here did not find convincing arguments in favor of either of these interpretations. It is concluded that the streamer behavior results from the effect of the magnetic field of a moving magnetic rope associated with the coronal ejection. The motion of the large-scale magnetic rope away from the Sun changes the surrounding magnetic field lines in the corona, and these changes resembl...

  2. Tutorial models of the climate and habitability of Proxima Centauri b: a thin atmosphere is sufficient to distribute heat given low stellar flux

    CERN Document Server

    Goldblatt, Colin

    2016-01-01

    Proxima Centauri b, an Earth-size planet in the habitable zone of our nearest stellar neighbour, has just been discovered. A theoretical framework of synchronously rotating planets, in which the risk of a runaway greenhouse on the sunlight side and atmospheric collapse on the reverse side are mutually ameliorated via heat transport is discussed. This is developed via simple (tutorial) models of the climate. These show that lower incident stellar flux means that less heat transport, so less atmospheric mass, is required. The incident stellar flux at Proxima Centauri b is indeed low, which may help enhance habitability if it has suffered some atmospheric loss or began with a low volatile inventory.

  3. Analysis of the solar coronal green line profiles from eclipse observations

    CERN Document Server

    Prabhakar, Maya; Chandrasekhar, T

    2013-01-01

    Analysis of the solar coronal green line profiles reveals information regarding the physical conditions of the solar corona like temperature, density, Doppler velocity, non-thermal velocity etc. It provides insights to the unresolved problems like the coronal heating and the acceleration of the solar winds. Recent studies have reported excess blueshifts in the coronal line profiles and are interpreted as due to nanoflare heating, type II spicules and nascent solar wind flow. We have analyzed a time series of Fabry-Perot interferograms of the solar corona obtained during the total solar eclipse of 2001 June 21 from Lusaka, Zambia. The spatial behavior of the coronal green line profiles were examined and variations in intensity, linewidth, Doppler velocity and line asymmetry were obtained. Several line profiles showed asymmetry indicating the presence of multicomponents. Such line profiles were fitted with double Gaussian curves. It has been found that 42% of the line profiles were single components, 34% were b...

  4. Coronal seismology of flare-excited longitudinal slow magnetoacoustic waves in hot coronal loops

    Science.gov (United States)

    Wang, T.; Ofman, L.; Sun, X.; Provornikova, E. A.; Davila, J. M.

    2015-12-01

    The flare-excited longitudinal intensity oscillations in hot flaring loops have been recently detected by SDO/AIA in 94 and 131 bandpasses. These oscillations show similar physical properties (such as period, decay time, and trigger) as those slow-mode standing waves previously detected by the SOHO/SUMER spectrometer in Doppler shift of flare lines formed above 6 MK. The multi-wavelength AIA observations with high spatio-temporal resolution and wide temperature coverage enable us to measure both thermal and wave properties of the oscillating hot plasma with unprecedented accuracy. These new measurements can be used to diagnose the complicated energy transport processes in flare plasma by a technique called coronal seismology based on the combination of observations and MHD wave theory. From a detailed case study we have found evidence for thermal conduction suppression in hot loops by measuring the polytropic index and analyzing the phase relationship between the temperature and density wave signals. This result is not only crucial for better understanding the wave dissipation mechanism but also provides an alternative mechanism to explain the puzzles of long-duration events and X-ray loop-top sources which show much slower cooling than expected by the classical Spitzer conductive cooling. This finding may also shed a light on the coronal heating problem because weak thermal conductivity implies slower cooling of hot plasma in nanoflares, so increasing the average coronal temperature for the same heating rate. We will discuss the effects of thermal conduction suppression on the wave damping and loop cooling based on MHD simulations.

  5. Influence of leads widths distribution on turbulent heat transfer between the ocean and the atmosphere

    Directory of Open Access Journals (Sweden)

    S. Marcq

    2011-10-01

    Full Text Available Leads are linear-like structures of open water within the sea ice cover that develop as the result of fracturing due to divergence or shear. Through leads, air and water come into contact and directly exchange latent and sensible heat through convective processes driven by the large temperature and moisture differences between them. In the central Arctic, leads only cover 1 to 2% of the ocean during winter, but account for more than 80% of the heat fluxes. Furthermore, narrow leads (several meters are more than twice as efficient at transmitting turbulent heat than larger ones (several hundreds of meters. We show that lead widths are power law distributed, P(X~X−a with a>1, down to very small spatial scales (20 m or below. This implies that the open water fraction is by far dominated by very small leads. Using two classical formulations, which provide first order turbulence closure for the fetch-dependence of heat fluxes, we find that the mean heat fluxes (sensible and latent over open water are up to 55 % larger when considering the lead width distribution obtained from a SPOT satellite image of the ice cover, compared to the situation where the open water fraction constitutes one unique large lead and the rest of the area is covered by ice, as it is usually considered in climate models at the grid scale. This difference may be even larger if we assume that the power law scaling of lead widths extents down to smaller (~1 m scales. Such estimations may be a first step towards a subgrid scale parameterization of the spatial distribution of open water for heat fluxes calculations in ocean/sea ice coupled models.

  6. Exploring Coronal Structures with SOHO

    Indian Academy of Sciences (India)

    Μ. Karovska; Β. Wood; J. Chen; J. Cook; R. Howard

    2000-09-01

    We applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

  7. Convectively Forced Gravity Waves and their Sensitivity to Heating Profile and Atmospheric Structure

    Science.gov (United States)

    Halliday, Oliver; Parker, Douglas; Griffiths, Stephen; Vosper, Simon; Stirling, Alison

    2016-04-01

    It has been known for some time that convective heating is communicated to its environment by gravity waves. Despite this, the radiation of gravity waves in macro-scale models, which are typically forced at the grid-scale by meso-scale parameterization schemes, is not well understood. We present here theoretical work directed toward improving our fundamental understanding of convectively forced gravity wave effects at the meso-scale, in order to begin to address this problem. Starting with the hydrostatic, non-rotating, 2D, Boussinesq equations in a slab geometry, we find a radiating, analytical solution to prescribed sensible heat forcing for both the vertical velocity and potential temperature response. Both Steady and pulsed heating with adjustable horizontal structure is considered. From these solutions we construct a simple model capable of interrogating the spatial and temporal sensitivity to chosen heating functions of the remote forced response in particular. By varying the assumed buoyancy frequency, the influence of the model stratosphere on the upward radiation of gravity waves, and in turn, on the tropospheric response can be understood. Further, we find that the macro-scale response to convection is highly dependent on the radiation characteristics of gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and upper boundary condition of the domain.

  8. Low-frequency variability and heat transport in a low-order nonlinear coupled ocean-atmosphere model

    CERN Document Server

    Vannitsem, Stéphane; De Cruz, Lesley; Ghil, Michael

    2014-01-01

    We formulate and study a low-order nonlinear coupled ocean-atmosphere model with an emphasis on the impact of radiative and heat fluxes and of the frictional coupling between the two components. This model version extends a previous 24-variable version by adding a dynamical equation for the passive advection of temperature in the ocean, together with an energy balance model. The bifurcation analysis and the numerical integration of the model reveal the presence of low-frequency variability (LFV) concentrated on and near a long-periodic, attracting orbit. This orbit combines atmospheric and oceanic modes, and it arises for large values of the meridional gradient of radiative input and of frictional coupling. Chaotic behavior develops around this orbit as it loses its stability; this behavior is still dominated by the LFV on decadal and multi-decadal time scales that is typical of oceanic processes. Atmospheric diagnostics also reveals the presence of predominant low- and high-pressure zones, as well as of a su...

  9. A Model for Stealth Coronal Mass Ejections

    Science.gov (United States)

    Lynch, Benjamin J.; Masson, Sophie; Li, Yan; DeVore, C. Richard; Luhmann, Janet; Antiochos, Spiro K.; Fisher, George H.

    2016-05-01

    Stealth coronal mass ejections (CMEs) are events in which there are almost no observable signatures of the CME eruption in the low corona but often a well-resolved slow flux rope CME observed in the coronagraph data. We present results from a three-dimensional numerical magnetohydrodynamics (MHD) simulation of the 2008 June 1-2 slow streamer blowout CME that Robbrecht et al. [2009] called “the CME from nowhere.” We model the global coronal structure using a 1.4 MK isothermal solar wind and a low-order potential field source surface representation of the Carrington Rotation 2070 magnetogram synoptic map. The bipolar streamer belt arcade is energized by simple shearing flows applied in the vicinity of the helmet streamer’s polarity inversion line. The slow expansion of the energized helmet-streamer arcade results in the formation of a radial current sheet. The subsequent onset of expansion-driven flare reconnection initiates the stealth CME while gradually releasing ~1.5E+30 erg of stored magnetic energy over the 20+ hour eruption duration. We show the energy flux available for flare heating and flare emission during the eruption is approximately two orders of magnitude below the energy flux required to heat the ambient background corona, thus confirming the “stealth” character of the 2008 June 1-2 CME’s lack of observable on disk signatures. We also present favorable comparisons between our simulation results and the multi-viewpoint SOHO-LASCO and STEREO-SECCHI coronagraph observations of the pre-eruption streamer structure and the initiation and evolution of the stealth streamer blowout CME.

  10. 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.

  11. Gas Nonideality at One Atmosphere Revealed through Speed of Sound Measurements and Heat Capacity Determinations

    Science.gov (United States)

    Halpern, Arthur M.; Liu, Allen

    2008-01-01

    Using an easy-to-make cylindrical resonator, students can measure the speed of sound in a gas, u, with sufficiently high precision (by locating standing-wave Lissajous patterns on an oscilloscope) to observe real gas properties at one atmosphere and 300 K. For CO[subscript 2] and SF[subscript 6], u is found to be 268.83 and 135.25 m s[superscript…

  12. The Estimation of Surface Latent Heat Flux over the Ocean and its Relationship to Marine Atmospheric Boundary Layer (MABL) Structure

    Science.gov (United States)

    Palm, Stephen P.; Schwemmer, Geary K.; Vandemark, Doug; Evans, Keith; Miller, David O.; Demoz, Belay B.; Starr, David OC. (Technical Monitor)

    2001-01-01

    A new technique combining active and passive remote sensing instruments for the estimation of surface latent heat flux over the ocean is presented. This synergistic method utilizes aerosol lidar backscatter data, multi-channel infrared radiometer data, and microwave scatterometer data acquired onboard the NASA P-313 research aircraft during an extended field campaign over the Atlantic ocean in support of the Lidar In-space Technology Experiment (LITE) in September of 1994. The 10 meter wind speed derived from scatterometers and lidar-radiometer inferred near-surface moisture are used to obtain an estimate of the surface flux of moisture via a bulk aerodynamic formula. The results are compared with the Special Sensor Microwave Imager (SSM/I) daily average latent heat flux and show reasonable agreement. However, the SSM/I values are biased low by about 15 W/sq m. In addition, the Marine Atmospheric Boundary Layer (MABL) height, entrainment zone thickness and integrated lidar backscatter intensity are computed from the lidar data and compared with the magnitude of the surface fluxes. The results show that the surface latent heat flux is most strongly correlated with entrainment zone depth, MABL height and the integrated MABL lidar backscatter, with corresponding correlation coefficients of 0.39, 0.43 and 0.71, respectively.

  13. Heat and momentum transfer from an atmospheric argon hydrogen plasma jet to spherical particles

    International Nuclear Information System (INIS)

    In this thesis the author describes the energy and momentum transfer from the plasma jet to the spray particles. This is done both experimentally and theoretically. Also the internal energy process of the recombining plasma is discussed. All elastic and inelastic collisional and radiative processes, as well as transport effects within the plasma are considered. In the next section, the so called passive spectroscopy is treated. It describes the diagnostics of electron density and temperature measurement, as well as the investigation on heat content of the particles. Spatially resolved electron density and temperature profiles are presented. Next, the active spectroscopy, i.e. the laser Doppler anemometer is dealt with. With this diagnostic, axial spray-particle velocities inside the plasma jet were determined. The author also presents heat and momentum transfer modelling of the plasma, related to the plasma particle interaction. Finally, a one dimensional model verification is made, using the experimentally determined particle velocity and plasma temperature profiles. (Auth.)

  14. Simulating the Formation and Evolution of Solar Prominences in Coronal Cavities

    Science.gov (United States)

    Xia, C.; Keppens, R.

    2015-12-01

    The physical mechanism responsible for the formation and the mass cycling of solar prominences has been uncertain for decades, because of the difficulty of knowing the three-dimensional (3D) magnetic field hosting prominences and the mass supply from chromosphere to prominences. Here we report comprehensive 3D simulations which demonstrate that the chromospheric evaporation and the coronal condensation in a magnetic flux rope lead to the formation of a quiescent prominence with complex internal fluid dynamics. First, we simulate the formation of a stable magnetic flux rope in the corona starting from a sheared magnetic bipolar arcade driven by shearing and converging flows at the bottom, using isothermal magnetohydrodynamics (MHD) modeling including gravity. Second, we fill the magnetic flux rope with hydrostatic plasma from chromosphere to corona and simulate a quiet sun in an equilibrium using full thermodynamic MHD with anisotropic thermal conduction, optically thin radiative losses, and parameterized heating. Then, we add extra strong heating localized in two circular regions covering chromospheric foot points of the flux rope. As the plasma is evaporated into corona, the lower part of the flux rope evolve into thermally unstable situation due to dominative radiative losses, where multiple blobs and threads of condensations form and move continuously mainly along local magnetic field. Some of the condensations fall down to chromosphere without support of magnetic dips near the foot region of the flux rope. Others linger in magnetic dips and descend slowly. Synthetic images of Solar Dynamics Observatory views with the Atmospheric Imaging Assembly shows many properties of quiescent prominences from real observations, such as, dynamics dark threads under elliptical coronal cavity.

  15. Impact of atmospheric forcing on heat content variability in the sub-surface layer in the Japan/East Sea, 1948-2009

    Science.gov (United States)

    Stepanov, Dmitry; Gusev, Anatoly; Diansky, Nikolay

    2016-04-01

    Based on numerical simulations the study investigates impact of atmospheric forcing on heat content variability of the sub-surface layer in Japan/East Sea (JES), 1948-2009. We developed a model configuration based on a INMOM model and atmospheric forcing extracted from the CORE phase II experiment dataset 1948-2009, which enables to assess impact of only atmospheric forcing on heat content variability of the sub-surface layer of the JES. An analysis of kinetic energy (KE) and total heat content (THC) in the JES obtained from our numerical simulations showed that the simulated circulation of the JES is being quasi-steady state. It was found that the year-mean KE variations obtained from our numerical simulations are similar those extracted from the SODA reanalysis. Comparison of the simulated THC and that extracted from the SODA reanalysis showed significant consistence between them. An analysis of numerical simulations showed that the simulated circulation structure is very similar that obtained from the PALACE floats in the intermediate and abyssal layers in the JES. Using empirical orthogonal function analysis we studied spatial-temporal variability of the heat content of the sub-surface layer in the JES. Based on comparison of the simulated heat content variations with those obtained from natural observations an assessment of the atmospheric forcing impact on the heat content variability was obtained. Using singular value decomposition analysis we considered relationships between the heat content variability and wind stress curl as well as sensible heat flux in winter. It was established the major role of sensible heat flux in decadal variability of the heat content of the sub-surface layer in the JES. The research was supported by the Russian Foundation for Basic Research (grant N 14-05-00255) and the Council on the Russian Federation President Grants (grant N MK-3241.2015.5)

  16. A scenario of planet erosion by coronal radiation

    OpenAIRE

    Sanz-Forcada, J.; Ribas, I.; Micela, G.; Pollock, A.M.T.; Garcia-Alvarez, D.; Solano, E.; Eiroa, C.

    2010-01-01

    Context: According to theory, high-energy emission from the coronae of cool stars can severely erode the atmospheres of orbiting planets. No observational tests of the long term effects of erosion have yet been made. Aims: To analyze the current distribution of planetary mass with X-ray irradiation of the atmospheres in order to make an observational assessment of the effects of erosion by coronal radiation. Methods: We study a large sample of planet-hosting stars with XMM-Newton, Chandra and...

  17. Waves and Magnetism in the Solar Atmosphere (WAMIS)

    Science.gov (United States)

    Ko, Y. K.; Auchere, F.; Casini, R.; Fineschi, S.; Gibson, S. E.; Knoelker, M.; Korendyke, C.; Laming, J. M.; Mcintosh, S. W.; Moses, J. D.; Romoli, M.; Rybak, J.; Socker, D. G.; Strachan, L.; Tomczyk, S.; Vourlidas, A.; Wu, Q.

    2014-12-01

    Magnetic fields in the solar atmosphere provide the energy for most varieties of solar activity, including high-energy electromagnetic radiation, solar energetic particles, flares, and coronal mass ejections, as well as powering the solar wind. Despite the fundamental role of magnetic fields in solar and heliospheric physics, there exists only very limited measurements of the field above the base of the corona. What is needed are direct measurements of not only the strength and orientation of the magnetic field but also the signatures of wave motions in order to better understand coronal structure, solar activity and the role of MHD waves in heating and accelerating the solar wind. Fortunately, the remote sensing instrumentation used to make magnetic field measurements is also well suited for measuring the Doppler signature of waves in the solar structures. With this in mind, we are proposing the WAMIS (Waves and Magnetism in the Solar Atmosphere) investigation. WAMIS will take advantage of greatly improved infrared (IR) detectors, forward models, advanced diagnostic tools and inversion codes to obtain a breakthrough in the measurement of coronal magnetic fields and in the understanding of the interaction of these fields with space plasmas. This will be achieved with a high altitude balloon borne payload consisting of a coronagraph with an IR spectro-polarimeter focal plane assembly. The balloon platform provides minimum atmospheric absorption and scattering at the IR wavelengths in which these observations are made. Additionally, a NASA long duration balloon flight mission from the Antarctic can achieve continuous observations over most of a solar rotation, covering all of the key time scales for the evolution of coronal magnetic fields. With these improvements in key technologies along with experience gained from current ground-based instrumentation, WAMIS will provide a low-cost mission with a high technology readiness leve.

  18. Improvement of the rate performance of hydrogen storage alloys by heat treatments in Ar and H2/Ar atmosphere for high-power nickel–metal hydride batteries

    International Nuclear Information System (INIS)

    Highlights: • A novel method for heat treatment of MH alloys have been proposed for the improvement of the alloy rate performance. • Low-, room-temperature rate discharge and high-temperature rate charge performance of the alloy can be improved by heat treatment in H2/Ar atmosphere. • The low-, room-temperature rate charge and high-temperature rate discharge performance can be enhanced by heat treatment in Ar atmosphere. - Abstract: The high-rate charge/discharge performance of L3DC alloy is improved by heat treatment in pure Ar or 10% H2/Ar atmosphere at 300 °C and 400 °C. L3DC, a commercially available LaNi5-type alloy, is used as the negative electrode for high-power nickel–metal hydride batteries. The structural modification, morphology, and surface composition of the heat-treated alloys are examined through X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy dispersive spectrometry (EDS). Electrochemical performance of the alloy is also tested with an electrochemical workstation and a charge/discharge tester. Results show that the low- and room-temperature rate discharge performance and high-temperature rate charge performance of the alloy can be improved by heat treatment in 10% H2/Ar atmosphere. Moreover, the low- and room-temperature rate charge performance and high-temperature rate discharge performance can only be enhanced by heat treatment in pure Ar atmosphere. Heat treatment can affect not only the speed of proton transport in the solid phase, but also the hydrogen reaction on the alloy surface

  19. Heat transport in the marine atmospheric boundary layer during an intense cold air outbreak

    Science.gov (United States)

    Chou, Shu-Hsien; Zimmerman, Jeffrey

    1988-01-01

    The generation of the virtual heat flux in the convective MABL associated with the January 28, 1986 intense cold air airbreak offshore of the Carolinas is studied. A technique based on the joint frequency distribution of the virtual potential temperature and vertical motion (Mahrt and Paumier, 1984) is used. The results suggest that, if buoyancy is mainly driven by the temperature flux, the physical processes for generating buoyancy flux are about the same for boundary layers over land and ocean, even with different convective regimes.

  20. 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)

    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

  1. A satellite retrieval of the shortwave heating of the atmosphere and the surface - Relationship to the general circulation, interannual climate variability, and the cryosphere

    Science.gov (United States)

    Charlock, Thomas P.; Smith, G. L.; Rose, Fred G.

    1990-01-01

    Data from several Nimbus-7 instruments and monthly averaged, multilayer delta-Eddington radiative transfer calculations are used to estimate the full vertical profile of the SW heating in the surface and the atmosphere. The noontime physical profile of clouds, water vapor, and surface albedo is used to compute a daily, monthly averaged top-of-atmosphere albedo (TOA), which was produced with noontime Nimbus-7 data, and a profile of SW heating for the atmosphere and surface. The daily, monthly averaged TOA albedo for July 1983 is compared with the ERBE daily, monthly averaged TOA albedo for July 1985. The sensitivity of the vertical SW heating profiles to the retrieval input assumptions is shown.

  2. The Effects of Irradiation on Hot Jovian Atmospheres: Heat Redistribution and Energy Dissipation

    CERN Document Server

    Perna, Rosalba; Pont, Frederic

    2012-01-01

    Hot Jupiters, due to the proximity to their parent stars, are subjected to a strong irradiating flux which governs their radiative and dynamical properties. We compute a suite of 3D circulation models with dual-band radiative transfer, exploring a relevant range of irradiation temperatures (770K <~ Tirr <~ 3000K), both with and without temperature inversions. We find that, for irradiation temperatures Tirr <~ 2000K, heat redistribution is very efficient, producing comparable day- and night-side fluxes. For Tirr ~ 2200-2400K, redistribution starts to break down, resulting in a high day-night flux contrast. Our simulations support the physical intuition that the efficiency of heat transfer is primarily governed by the ratio of advective to radiative timescales. For the same Tirr, models with temperature inversions display a higher day-night contrast, but we find this opacity-driven effect to be secondary to irradiation. The hotspot offset from the substellar point is large when insolation is weak and r...

  3. Satellite-Observed Urbanization Characters in Shanghai, China: Aerosols, Urban Heat Island Effect, and Land–Atmosphere Interactions

    Directory of Open Access Journals (Sweden)

    Gary Pereira

    2011-01-01

    Full Text Available Urbanization reflects how human-activities affect natural climate system. Accurately assessing the urban system by comparing it with the nearby rural regions helps to identify the impacts of urbanization. This work uses the recent satellite observed aerosol, skin temperature, land cover, albedo, cloud fraction and water vapor measurements to reveal how the city of Shanghai, one of the biggest, dense urban areas in East Asia, affects land surface and atmosphere conditions. In addition, the National Aeronautics and Space Administration (NASA ground observations from AErosol RObotic NETwork (AERONET is also used to reveal diurnal, seasonal, and interannual variations of the heavy aerosol load over Shanghai region. Furthermore, Shanghai reduces surface albedo, total column water vapor, cloud fraction and increases land skin temperature than rural region. These observations prove that Shanghai significantly modifies local and regional land surface physical properties as well as physical processes, which lead to the urban heat island effect (UHI.

  4. Intrinsic Instability of Coronal Streamers

    CERN Document Server

    Chen, Y; Song, H Q; Shi, Q Q; Feng, S W; Xia, L D; 10.1088/0004-637X/691/2/1936

    2009-01-01

    Plasma blobs are observed to be weak density enhancements as radially stretched structures emerging from the cusps of quiescent coronal streamers. In this paper, it is suggested that the formation of blobs is a consequence of an intrinsic instability of coronal streamers occurring at a very localized region around the cusp. The evolutionary process of the instability, as revealed in our calculations, can be described as follows: (1) through the localized cusp region where the field is too weak to sustain the confinement, plasmas expand and stretch the closed field lines radially outward as a result of the freezing-in effect of plasma-magnetic field coupling; the expansion brings a strong velocity gradient into the slow wind regime providing the free energy necessary for the onset of a subsequent magnetohydrodynamic instability; (2) the instability manifests itself mainly as mixed streaming sausage-kink modes, the former results in pinches of elongated magnetic loops to provoke reconnections at one or many loc...

  5. A Model for Radio Emission from Solar Coronal Shocks

    CERN Document Server

    Zhao, G Q; 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 problem. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiations from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock excites first Alfv\\'en wave (AW) and 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 the ECM instability. Our results show that this model may have potential application to solar type II radio bursts.

  6. Spatial damping of propagating sausage waves in coronal cylinders

    CERN Document Server

    Guo, Ming-Zhe; Li, Bo; Xia, Li-Dong; Yu, Hui

    2015-01-01

    Sausage modes are important in coronal seismology. Spatially damped propagating sausage waves were recently observed in the solar atmosphere. We examine how wave leakage influences the spatial damping of sausage waves propagating along coronal structures modeled by a cylindrical density enhancement embedded in a uniform magnetic field. Working in the framework of cold magnetohydrodynamics, we solve the dispersion relation (DR) governing sausage waves for complex-valued longitudinal wavenumber $k$ at given real angular frequencies $\\omega$. For validation purposes, we also provide analytical approximations to the DR in the low-frequency limit and in the vicinity of $\\omega_{\\rm c}$, the critical angular frequency separating trapped from leaky waves. In contrast to the standing case, propagating sausage waves are allowed for $\\omega$ much lower than $\\omega_{\\rm c}$. However, while able to direct their energy upwards, these low-frequency waves are subject to substantial spatial attenuation. The spatial damping ...

  7. Effect of transient solar wind pulses on atmospheric heating at Jupiter

    CERN Document Server

    Yates, J N; Guio, P

    2013-01-01

    Previously, we have presented the first study to investigate the response of the Jovian thermosphere to transient variations in solar wind dynamic pressure, using a coupled, azimuthally symmetric global circulation model coupled with a simple magnetosphere model. This work (Yates et al., 2013, submitted) described the response of thermospheric flows, momentum sources, and the magnetosphere-ionosphere coupling currents to transient compressions and expansions in the magnetosphere. The present study describes the response of thermospheric heating, cooling and the auroral emissions to the aforementioned transient events. We find that transient compressions and expansions, on time scales = 25 K and a ~2000 TW increase in the total power dissipated in the thermosphere. In terms of auroral processes, transient compressions increase main oval UV emission by a factor of ~4.5 whilst transient expansions increase this main emission by a more modest 37%. Both types of transient event cause shifts in the position of the ...

  8. Effect of surface oxide film and atmosphere on microwave heating of compacted copper powder

    International Nuclear Information System (INIS)

    The microwave irradiation was performed using a compacted Cu powder under different oxygen partial pressures. After reaching about 600 K, an abrupt temperature rise and drop occurred. The abrupt temperature drop is caused by both sintering of Cu powder particles and growing of surface oxide film. The magnitude of the abrupt temperature drop decreased with increasing oxygen partial pressure. The temperature then remained constant (steady state), gradually increased or exhibited a secondary significant increase. The magnitude of the temperature rise after abrupt temperature drop increased with increasing oxygen partial pressure. The microwave heating behavior of the compacted Cu powder depended on the type and thickness of the surface oxide film and also on the type and volume fraction of the gas occupying the vacant spaces between the Cu powder particles.

  9. Behaviour of non-metallic inclusions during electric-arc heating in argon-hydrogen atmosphere

    International Nuclear Information System (INIS)

    Conditions of steel refining by a high-temperature hydrogen-containing gas are studied experimentally. Armco-iron with different content of silicon or aluminium served as a source mareterial as well as corrosion resistant steel 12Kh18N10T. It permits to have in metals inclusions of a definite type (Al2O3; SiO2; TiN and others). Growth of alloy refining by oxygen and deoxidation products during electric - arc heating, when hydrogen being introduced into the inerti gas, is shown to be mainly connected with intensity rise in metal melt mixing during hydrogen boiling in case of iron remelting, deoxidized by aluminium, and with chemical interaction with hydrogen in case of iron remelting deoxidized bu silicon

  10. Effects of orbital forcing on atmosphere and ocean heat transports in Holocene and Eemian climate simulations with a comprehensive Earth system model

    Directory of Open Access Journals (Sweden)

    N. Fischer

    2010-03-01

    Full Text Available Orbital forcing does not only exert direct insolation effects, but also alters climate indirectly through feedback mechanisms that modify atmosphere and ocean dynamics and meridional heat and moisture transfers. We investigate the regional effects of these changes by detailed analysis of atmosphere and ocean circulation and heat transports in a coupled atmosphere-ocean-sea ice-biosphere general circulation model (ECHAM5/JSBACH/MPI-OM. We perform long term quasi equilibrium simulations under pre-industrial, mid-Holocene (6000 years before present – yBP, and Eemian (125 000 yBP orbital boundary conditions. Compared to pre-industrial climate, Eemian and Holocene temperatures show generally warmer conditions at higher and cooler conditions at lower latitudes. Changes in sea-ice cover, ocean heat transports, and atmospheric circulation patterns lead to pronounced regional heterogeneity. Over Europe, the warming is most pronounced over the north-eastern part in accordance with recent reconstructions for the Holocene. We attribute this warming to enhanced ocean circulation in the Nordic Seas and enhanced ocean-atmosphere heat flux over the Barents Shelf in conduction with retreat of sea ice and intensified winter storm tracks over northern Europe.

  11. Thermally Induced Chemistry of Meteoritic Complex Organic Molecules: A New Heat-Diffusion Model for the Atmospheric Entry of Meteorites

    CERN Document Server

    Shingledecker, Christopher N

    2014-01-01

    Research over the past four decades has shown a rich variety of complex organic molecular content in some meteorites. This current study is an attempt to gain a better insight into the thermal conditions experienced by these molecules inside meteorites during atmospheric entry. In particular, we wish to understand possible chemical processes that can occur during entry and that might have had an effect on complex organic or prebiotic species that were delivered in this way to the early Earth. A simulation was written in Fortran to model heating by the shock generated during entry and the subsequent thermal diffusion inside the body of a meteorite. Experimental data was used for the thermal parameters of several types of meteorites, including iron-nickel and several classes of chondrites. A Sutton-Graves model of stagnation-point heating was used to calculate peak surface temperatures and an explicit difference formula was used to generate thermal diffusion profiles for both chondrites and iron-nickel type met...

  12. Pool Boiling Behavior and Critical Heat Flux on Zircaloy and SiC Claddings in Deionized Water under Atmospheric Pressure

    International Nuclear Information System (INIS)

    Recently several researches on SiC material as an alternative of the nuclear fuel cladding have been conducted. From a fundamental point of view, Snead et al. did an extensive investigation on SiC properties. Their work revealed non-irradiated and irradiated material properties. In addition to the existing literature data, they even added new data, particularly in the high-temperature irradiation regime. Moreover, Carpenter has studied performance of a SiC fuel cladding in his Ph. D. thesis. With extensive in-core tests at MITR-II, his works showed the effects of cladding design for monolith and triplex types. He concluded that manufacturing techniques of the SiC cladding affected corrosion rates and swelling behavior after irradiation. For more practical nuclear applications, oxidation rates of a SiC cladding was investigated with a comparison assessment of those of a zircaloy-4 cladding. Lee et al. adopted an oxidation process under the conditions of the Loss of Coolant Accidents (LOCA) in LWRs. They found that SiC oxidation rates were greatly lower than those of zircaloy-4. In order to demonstrate the superiority of SiC cladding in terms of thermal performance, in this study pool boiling heat transfer experiments were carried out in a pool of saturated deionized water (DI water) at atmospheric pressure. For a comparison study, zircaloy-4 claddings, which are current fuel claddings in LWRs, were used as a reference case. Not only measuring nucleate boiling heat transfer coefficient (NBHTC) and critical heat flux (CHF) but also observing boiling behavior of both the claddings were conducted. In this study, pool boiling heat transfer experiments with zircaloy and SiC heaters were carried out. Comparison of the CHF and nucleate boiling heat transfer of the zircaloy-4 and SiC cladding were compared. Specifically, sophisticated high-speed photographs of nucleate boiling, the CHF, and film boiling phenomena were captured. · Structural integrity of the SiC heaters was

  13. ON THE RELATIONSHIPS BETWEEN THE SUMMER RAINFALL IN CHINA AND THE ATMOSPHERIC HEAT SOURCES OVER THE EASTERN TIBETAN PLATEAU AND THE WESTERN PACIFIC WARM POOL

    Institute of Scientific and Technical Information of China (English)

    简茂球; 罗会邦; 乔云亭

    2004-01-01

    The relationships between the summer rainfall in China and the atmospheric heat sources over the eastern Tibetan Plateau and the western Pacific warm pool were analyzed comparatively, using the NCEP/NCAR reanalysis daily data. The strong (weak) heat source in summer over the eastern Tibetan Plateau will lead to abundant (scarce) summer rainfall in the Yangtze River basin, and scarce/abundant summer rainfall in the eastern part of Southern China. While the strong (weak) heat source in summer over the western Pacific warm pool will lead to another pattern of abundant (scarce) summer rainfall in the middle-lower reaches of the Yangtze River and scarce (abundant) summer rainfall in Southern China and in the region of northern Jiangsu to southern Shandong. Comparatively, the heat source over the eastern Tibetan Plateau affects a larger area of summer rainfall than the heat source over the western Pacific. In both cases of the heat source anomalies over the eastern Tibetan Plateau and over the western Pacific, there exist EAP-like teleconnection patterns in East Asia. The summer rainfall in China is influenced directly by the abnormal vertical motion, which is related closely to the abnormal heat sources in the atmosphere. The ridge line of the western Pacific High locates far south (north) in summer in the case of strong (weak) heat sources over the two areas mentioned above.

  14. Alfv\\'en Wave Driven High Frequency Waves in the Solar Atmosphere: Implications for Ion Heating

    CERN Document Server

    Kaghashvili, Edisher Kh

    2014-01-01

    This work is an extension of Kaghashvili [1999] where ion-cyclotron wave dissipation channel for Alfv\\'en waves was discussed. While our earlier study dealt with the mode coupling in the commonly discussed sense, here we study changes in the initial waveform due to interaction of the initial driver Alfv\\'en wave and the plasma inhomogeneity, which are implicitly present in the equations, but were not elaborated in Kaghashvili [1999]. Using a cold plasma approximation, we show how high frequency waves (higher than the initial driver Alfv\\'en wave frequency) are generated in the inhomogeneous solar plasma flow. The generation of the high frequency forward and backward propagating modified fast magnetosonic/whistler waves as well as the generation of the driven Alfv\\'en waves is discussed in the solar atmosphere. The generated high frequency waves have a shorter dissipation timescale, and they can also resonant interact with particles using both the normal cyclotron and anomalous cyclotron interaction channels. ...

  15. Low-latitude coronal holes, decaying active regions and global coronal magnetic structure

    CERN Document Server

    Petrie, Gordon

    2013-01-01

    We study the relationship between decaying active region magnetic fields, coronal holes and the global coronal magnetic structure using Global Oscillations Network Group (GONG) synoptic magnetograms, Solar Terrestrial RElations Observatory (STEREO) extreme ultra-violet (EUV) synoptic maps and coronal potential-field source-surface (PFSS) models. We analyze 14 decaying regions and associated coronal holes occurring between early 2007 and late 2010, four from cycle 23 and 10 from cycle 24. We investigate the relationship between asymmetries in active regions' positive and negative magnetic intensities, asymmetric magnetic decay rates, flux imbalances, global field structure and coronal hole formation. Whereas new emerging active regions caused changes in the large-scale coronal field, the coronal fields of the 14 decaying active regions only opened under the condition that the global coronal structure remained almost unchanged. This was because the dominant slowly-varying, low-order multipoles prevented opposin...

  16. Inferring the Coronal Density Irregularity from EUV Spectra

    CERN Document Server

    Hahn, Michael

    2016-01-01

    Understanding the density structure of the solar corona is important for modeling both coronal heating and the solar wind. Direct measurements are difficult because of line-of-sight integration and possible unresolved structures. We present a new method for quantifying such structure using density-sensitive EUV line intensities to derive a density irregularity parameter, a relative measure of the amount of structure along the line of sight. We also present a simple model to relate the inferred irregularities to physical quantities, such as the filling factor and density contrast. For quiet Sun regions and interplume regions of coronal holes, we find a density contrast of at least a factor of three to ten and corresponding filling factors of about 10-20%. Our results are in rough agreement with other estimates of the density structures in these regions. The irregularity diagnostic provides a useful relative measure of unresolved structure in various regions of the corona.

  17. Short-term fluctuations in the eddy heat flux and baroclinic stability of the atmosphere

    Science.gov (United States)

    Stone, P. H.; Ghan, S. J.; Spiegel, D.; Rambaldi, S.

    1982-01-01

    National Meteorological Center data from midlatitudes for three Januaries is used in calculating time series of the zonal mean meridional eddy heat flux and the zonal mean baroclinic stability, as measured by the difference between the zonal wind shear and the critical value of the shear in two-level models. Time-lagged correlations between the two series reveal a highly significant negative correlation for short time lags, peaking at approximately -0.4 when the stability parameter lags one half day behind the eddy flux. They also reveal that strongly unstable conditions are not followed by significant increases in the eddy flux. These results are seen as indicating that the synoptic variations of the zonal mean eddy flux are not closely related to the degree of baroclinic instability of the zonal mean flow. The autocorrelation of the eddy flux is then compared with those expected for autoregressive processes. A Bayesian information criterion suggests that the behavior is represented best by a damped oscillation, with a damping time of 0.8 day and a period of five days.

  18. Coronal Seismology and the Propagation of Acoustic Waves Along Coronal Loops

    CERN Document Server

    Klimchuk, J A; De Moortel, I

    2004-01-01

    We use a combination of analytical theory, numerical simulation, and data analysis to study the propagation of acoustic waves along coronal loops. We show that the intensity perturbation of a wave depends on a number of factors, including dissipation of the wave energy, pressure and temperature gradients in the loop atmosphere, work action between the wave and a flow, and the sensitivity properties of the observing instrument. In particular, the scale length of the intensity perturbation varies directly with the dissipation scale length (i.e., damping length) and the scale lengths of pressure, temperature, and velocity. We simulate wave propagation in three different equilibrium loop models and find that dissipation and pressure and temperature stratification are the most important effects in the low corona where the waves are most easily detected. Velocity effects are small, and cross-sectional area variations play no direct role for lines-of-sight that are normal to the loop axis. The intensity perturbation...

  19. Changes in the Intensity and Frequency of Atmospheric Blocking and Associated Heat Waves During Northern Summer Over Eurasia in the CMIP5 Model Simulations

    Science.gov (United States)

    Kim, Kyu-Myong; Lau, K. M.; Wu, H. T.; Kim, Maeng-Ki; Cho, Chunho

    2012-01-01

    The Russia heat wave and wild fires of the summer of 2010 was the most extreme weather event in the history of the country. Studies show that the root cause of the 2010 Russia heat wave/wild fires was an atmospheric blocking event which started to develop at the end of June and peaked around late July and early August. Atmospheric blocking in the summer of 2010 was anomalous in terms of the size, duration, and the location, which shifted to the east from the normal location. This and other similar continental scale severe summertime heat waves and blocking events in recent years have raised the question of whether such events are occurring more frequently and with higher intensity in a warmer climate induced by greenhouse gases. We studied the spatial and temporal distributions of the occurrence and intensity of atmospheric blocking and associated heat waves for northern summer over Eurasia based on CMIPS model simulations. To examine the global warming induced change of atmospheric blocking and heat waves, experiments for a high emissions scenario (RCP8.S) and a medium mitigation scenario (RCP4.S) are compared to the 20th century simulations (historical). Most models simulate the mean distributions of blockings reasonably well, including major blocking centers over Eurasia, northern Pacific, and northern Atlantic. However, the models tend to underestimate the number of blockings compared to MERRA and NCEPIDOE reanalysis, especially in western Siberia. Models also reproduced associated heat waves in terms of the shifting in the probability distribution function of near surface temperature. Seven out of eight models used in this study show that the frequency of atmospheric blocking over the Europe will likely decrease in a warmer climate, but slightly increase over the western Siberia. This spatial pattern resembles the blocking in the summer of 2010, indicating the possibility of more frequent occurrences of heat waves in western Siberia. In this talk, we will also

  20. Modeling the (upper) solar atmosphere including the magnetic field

    CERN Document Server

    Peter, H

    2007-01-01

    The atmosphere of the Sun is highly structured and dynamic in nature. From the photosphere and chromosphere into the transition region and the corona plasma-$\\beta$ changes from above to below one, i.e. while in the lower atmosphere the energy density of the plasma dominates, in the upper atmosphere the magnetic field plays the governing role -- one might speak of a ``magnetic transition''. Therefore the dynamics of the overshooting convection in the photosphere, the granulation, is shuffling the magnetic field around in the photosphere. This leads not only to a (re-)structuring of the magnetic field in the upper atmosphere, but induces also the dynamic reaction of the coronal plasma e.g. due to reconnection events. Therefore the (complex) structure and the interaction of various magnetic patches is crucial to understand the structure, dynamics and heating of coronal plasma as well as its acceleration into the solar wind. The present article will emphasize the need for three-dimensional modeling accounting fo...

  1. Plasma motions and non-thermal line broadening in flaring twisted coronal loops

    Science.gov (United States)

    Gordovskyy, M.; Kontar, E. P.; Browning, P. K.

    2016-05-01

    Context. Observation of coronal extreme ultra-violet (EUV) spectral lines sensitive to different temperatures offers an opportunity to evaluate the thermal structure and flows in flaring atmospheres. This, in turn, can be used to estimate the partitioning between the thermal and kinetic energies released in flares. Aims: Our aim is to forward-model large-scale (50-10 000 km) velocity distributions to interpret non-thermal broadening of different spectral EUV lines observed in flares. The developed models allow us to understand the origin of the observed spectral line shifts and broadening, and link these features to particular physical phenomena in flaring atmospheres. Methods: We use ideal magnetohydrodynamics (MHD) to derive unstable twisted magnetic fluxtube configurations in a gravitationally stratified atmosphere. The evolution of these twisted fluxtubes is followed using resistive MHD with anomalous resistivity depending on the local density and temperature. The model also takes thermal conduction and radiative losses in the continuum into account. The model allows us to evaluate average velocities and velocity dispersions, which would be interpreted as non-thermal velocities in observations, at different temperatures for different parts of the models. Results: Our models show qualitative and quantitative agreement with observations. Thus, the line-of-sight (LOS) velocity dispersions demonstrate substantial correlation with the temperature, increasing from about 20-30 km s-1 around 1 MK to about 200-400 km s-1 near 10-20 MK. The average LOS velocities also correlate with velocity dispersions, although they demonstrate a very strong scattering compared to the observations. We also note that near footpoints the velocity dispersions across the magnetic field are systematically lower than those along the field. We conclude that the correlation between the flow velocities, velocity dispersions, and temperatures are likely to indicate that the same heating

  2. Transition Region Abundance Measurements During Impulsive Heating Events

    Science.gov (United States)

    Warren, Harry P.; Brooks, David H.; Doschek, George A.; Feldman, Uri

    2016-06-01

    It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona, low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper we report on measurements of plasma composition made during impulsive heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O iv, v, and vi emission lines are enhanced relative to emission lines from Mg v, vi, and vii and Si vi and vii, and indicate a composition close to that of the photosphere. Long-lived coronal fan structures, in contrast, show an enrichment of low-FIP elements. We conjecture that the plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from the lower layers of the solar atmosphere and higher-frequency heating leading to long-lived structures and the accumulation of low-FIP elements in the corona.

  3. From Forbidden Coronal Lines to Meaningful Coronal Magnetic Fields

    CERN Document Server

    Judge, Philip G; Landi, Enrico

    2013-01-01

    We review methods to measure magnetic fields within the corona using the polarized light in magnetic-dipole (M1) lines. We are particularly interested in both the global magnetic-field evolution over a solar cycle, and the local storage of magnetic free energy within coronal plasmas. We address commonly held skepticisms concerning angular ambiguities and line-of-sight confusion. We argue that ambiguities are in principle no worse than more familiar remotely sensed photospheric vector-fields, and that the diagnosis of M1 line data would benefit from simultaneous observations of EUV lines. Based on calculations and data from eclipses, we discuss the most promising lines and different approaches that might be used. We point to the S-like [Fe {\\sc XI}] line (J=2 to J=1) at 789.2nm as a prime target line (for ATST for example) to augment the hotter 1074.7 and 1079.8 nm Si-like lines of [Fe {\\sc XIII}] currently observed by the Coronal Multi-channel Polarimeter (CoMP). Significant breakthroughs will be made possibl...

  4. The quiet Sun average Doppler shift of coronal lines up to 2 MK

    Science.gov (United States)

    Dadashi, N.; Teriaca, L.; Solanki, S. K.

    2011-10-01

    Context. The average Doppler shift shown by spectral lines formed from the chromosphere to the corona reveals important information on the mass and energy balance of the solar atmosphere, providing an important observational constraint to any models of the solar corona. Previous spectroscopic observations of vacuum ultra-violet (VUV) lines have revealed a persistent average wavelength shift of lines formed at temperatures up to 1 MK. At higher temperatures, the behaviour is still essentially unknown. Aims: Here we analyse combined SUMER (Solar Ultraviolet Measurements of Emitted Radiation)/SoHO (Solar and Heliospheric Observatory) and EIS (EUV Imaging Spectrometer)/Hinode observations of the quiet Sun around disk centre to determine, for the first time, the average Doppler shift of several spectral lines formed between 1 and 2 MK, where the largest part of the quiet coronal emission is formed. Methods: The measurements are based on a novel technique applied to EIS spectra to measure the difference in Doppler shift between lines formed at different temperatures. Simultaneous wavelength-calibrated SUMER spectra allow establishing the absolute value at the reference temperature of T ≈ 1 MK. Results: The average line shifts at 1 MK SUMER measurements), this translates into a maximum Doppler shift of (-4.4 ± 2.2) km s-1 around 1.8 MK. The measured value appears to decrease to about (-1.3 ± 2.6) km s-1 at the Fe xv formation temperature of 2.1 MK. Conclusions: The measured average Doppler shift between 0.01 and 2.1 MK, for which we provide a parametrisation, appears to be qualitatively and roughly quantitatively consistent with what foreseen by 3D coronal models where heating is produced by dissipation of currents induced by photospheric motions and by reconnection with emerging magnetic flux.

  5. EFFECT OF CORONAL TEMPERATURE ON THE SCALE OF SOLAR CHROMOSPHERIC JETS

    Energy Technology Data Exchange (ETDEWEB)

    Iijima; Yokoyama, T.H., E-mail: h.iijima@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-10-20

    We investigate the effect of coronal temperature on the formation process of solar chromospheric jets using two-dimensional magnetohydrodynamic simulations of the region from the upper convection zone to the lower corona. We develop a new radiative magnetohydrodynamic code for the dynamic modeling of the solar atmosphere, employing an LTE equation of state, optically thick radiative loss in the photosphere, optically thin radiative loss in the chromosphere and the corona, and thermal conduction along the magnetic field lines. Many chromospheric jets are produced in the simulations by shock waves passing through the transition region. We find that these jets are projected farther outward when the coronal temperature is lower (similar to that in coronal holes) and shorter when the coronal temperature is higher (similar to that in active regions). When the coronal temperature is high, the deceleration of the chromospheric jets is consistent with the model in which deceleration is determined by the periodic chromospheric shock waves. However, when the coronal temperature is low, the gravitational deceleration becomes more important and the chromospheric jets approach ballistic motion.

  6. Diagnostics of Coronal Magnetic Fields Through the Hanle Effect in UV and IR Lines

    CERN Document Server

    Raouafi, N E; Gibson, S; Fineschi, S; Solanki, S K

    2016-01-01

    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-$\\alpha$ and the He I 10830 {\\AA} 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 magne...

  7. 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.

  8. The Effect of Cumulus Cloud Field Anisotropy on Domain-Averaged Solar Fluxes and Atmospheric Heating Rates

    Science.gov (United States)

    Hinkelman, Laura M.; Evans, K. Franklin; Clothiaux, Eugene E.; Ackerman, Thomas P.; Stackhouse, Paul W., Jr.

    2006-01-01

    Cumulus clouds can become tilted or elongated in the presence of wind shear. Nevertheless, most studies of the interaction of cumulus clouds and radiation have assumed these clouds to be isotropic. This paper describes an investigation of the effect of fair-weather cumulus cloud field anisotropy on domain-averaged solar fluxes and atmospheric heating rate profiles. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of cloud scenes from a large eddy simulation. Progressively greater degrees of x-z plane tilting and horizontal stretching were imposed on each of these scenes, so that an ensemble of scenes was produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo radiative transfer model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. The mechanisms by which anisotropy interacts with solar fluxes were investigated by comparisons to independent pixel approximation and tilted independent pixel approximation computations for the same scenes. Cumulus anisotropy was found to most strongly impact solar radiative transfer by changing the effective cloud fraction, i.e., the cloud fraction when the field is projected on a surface perpendicular to the direction of the incident solar beam.

  9. The Nature of CME-flare-Associated Coronal Dimming

    Science.gov (United States)

    Cheng, J. X.; Qiu, J.

    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.

  10. Spatial damping of propagating sausage waves in coronal cylinders

    Science.gov (United States)

    Guo, Ming-Zhe; Chen, Shao-Xia; Li, Bo; Xia, Li-Dong; Yu, Hui

    2015-09-01

    Context. Sausage modes are important in coronal seismology. Spatially damped propagating sausage waves were recently observed in the solar atmosphere. Aims: We examine how wave leakage influences the spatial damping of sausage waves propagating along coronal structures modeled by a cylindrical density enhancement embedded in a uniform magnetic field. Methods: Working in the framework of cold magnetohydrodynamics, we solve the dispersion relation (DR) governing sausage waves for complex-valued, longitudinal wavenumber k at given real angular frequencies ω. For validation purposes, we also provide analytical approximations to the DR in the low-frequency limit and in the vicinity of ωc, the critical angular frequency separating trapped from leaky waves. Results: In contrast to the standing case, propagating sausage waves are allowed for ω much lower than ωc. However, while able to direct their energy upward, these low-frequency waves are subject to substantial spatial attenuation. The spatial damping length shows little dependence on the density contrast between the cylinder and its surroundings, and depends only weakly on frequency. This spatial damping length is of the order of the cylinder radius for ω ≲ 1.5vAi/a, where a and vAi are the cylinder radius and the Alfvén speed in the cylinder, respectively. Conclusions: If a coronal cylinder is perturbed by symmetric boundary drivers (e.g., granular motions) with a broadband spectrum, wave leakage efficiently filters out the low-frequency components.

  11. Coronal energy input and dissipation in a solar active region 3D MHD model

    CERN Document Server

    Bourdin, Philippe-A; Peter, Hardi

    2015-01-01

    Context. We have conducted a 3D MHD simulation of the solar corona above an active region in full scale and high resolution, which shows coronal loops, and plasma flows within them, similar to observations. Aims. We want to find the connection between the photospheric energy input by field-line braiding with the coronal energy conversion by Ohmic dissipation of induced currents. Methods. To this end we compare the coronal energy input and dissipation within our simulation domain above different fields of view, e.g. for a small loops system in the active region (AR) core. We also choose an ensemble of field lines to compare, e.g., the magnetic energy input to the heating per particle along these field lines. Results. We find an enhanced Ohmic dissipation of currents in the corona above areas that also have enhanced upwards-directed Poynting flux. These regions coincide with the regions where hot coronal loops within the AR core are observed. The coronal density plays a role in estimating the coronal temperatur...

  12. Blind Stereoscopy of the Coronal Magnetic Field

    CERN Document Server

    Aschwanden, Markus J; Malanushenko, Anna

    2015-01-01

    We test the feasibility of 3D coronal-loop tracing in stereoscopic EUV image pairs, with the ultimate goal of enabling efficient 3D reconstruction of the coronal magnetic field that drives flares and coronal mass ejections (CMEs). We developed an automated code designed to perform triangulation of coronal loops in pairs (or triplets) of EUV images recorded from different perspectives. The automated (or blind) stereoscopy code includes three major tasks: (i) automated pattern recognition of coronal loops in EUV images, (ii) automated pairing of corresponding loop patterns from two different aspect angles, and (iii) stereoscopic triangulation of 3D loop coordinates. We perform tests with simulated stereoscopic EUV images and quantify the accuracy of all three procedures. In addition we test the performance of the blind stereoscopy code as a function of the spacecraft-separation angle and as a function of the spatial resolution. We also test the sensitivity to magnetic non-potentiality. The automated code develo...

  13. Hot gaseous atmospheres in galaxy groups and clusters are both heated and cooled by X-ray cavities

    CERN Document Server

    Brighenti, Fabrizio; Temi, Pasquale

    2015-01-01

    Expanding X-ray cavities observed in hot gas atmospheres of many galaxy groups and clusters generate shock waves and turbulence that are primary heating mechanisms required to avoid uninhibited radiatively cooling flows which are not observed. However, we show here that the evolution of buoyant cavities also stimulates radiative cooling of observable masses of low-temperature gas. During their early evolution, radiative cooling occurs in the wakes of buoyant cavities in two locations: in thin radial filaments parallel to the buoyant velocity and more broadly in gas compressed beneath rising cavities. Radiation from these sustained compressions removes entropy from the hot gas. Gas experiencing the largest entropy loss cools first, followed by gas with progressively less entropy loss. Most cooling occurs at late times, $\\sim 10^8-10^9$ yrs, long after the X-ray cavities have disrupted and are impossible to detect. During these late times, slightly denser low entropy gas sinks slowly toward the centers of the h...

  14. Solar coronal loops associated with small-scale mixed polarity surface magnetic fields

    CERN Document Server

    Chitta, L P; Solanki, S K; Barthol, P; Gandorfer, A; Gizon, L; Hirzberger, J; Riethmueller, T L; van Noort, M; Rodriguez, J Blanco; Iniesta, J C Del Toro; Suarez, D Orozco; Schmidt, W; Pillet, V Martinez; Knoelker, M

    2016-01-01

    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 (IMaX) instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) 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 S...

  15. The Temperature-Dependent Nature of Coronal Dimmings

    CERN Document Server

    Robbrecht, Eva

    2010-01-01

    The opening-up of the magnetic field during solar eruptive events is often accompanied by a dimming of the local coronal emission. From observations of filament eruptions recorded with the Extreme-Ultraviolet Imager on STEREO during 2008-2009, it is evident that these dimmings are much more pronounced in 19.5 nm than in the lower-temperature line 17.1 nm, as viewed either on the disk or above the limb. We conclude that most of the cooler coronal plasma is not ejected but remains gravitationally bound when the loops open up. This result is consistent with Doppler measurements by Imada and coworkers, who found that the upflow speeds in a transient coronal hole increased dramatically above a temperature of 1 MK; it is also consistent with the quasistatic behavior of polar plumes, as compared with the hotter interplume regions that are the main source of the fast solar wind. When the open flux reconnects and closes down again, the trapped plasma is initially heated to such high temperatures that it is no longer v...

  16. Zoning of the territory of Russia by the effectiveness of low-potential heat of the ground and atmospheric air for heating buildings

    Science.gov (United States)

    Vasilyev, G. P.; Kolesova, M. V.; Gornov, V. F.; Yurchenko, I. A.

    2016-06-01

    The article represents the results of researches to zone the territory of Russia and Europe division into districts of by efficiency of using for the heat supply of buildings of low-potential thermal energy of ground and free air and their combination. While modeling the heat regime of geothermal HPS in climatic conditions of different regions of the territory of Russia, the influence of the long-term extraction of geothermal heat energy on the ground heat regime has been taken into account as well as the influence of phase transitions of pore moisture in ground on the efficiency of operation of geothermal heat-pump heat-supply systems. Also considered were the sinking of temperatures of ground massif by long-term extraction of the heat energy from the ground as calculation parameters of the heat energy from the ground, and as calculation parameters of ground massif temperatures.

  17. Climatic features of atmospheric heat source/sink over theQinghai-Xizang Plateau in 35 years and its relation torainfall in China

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Ping

    2001-01-01

    [1]Yeh, T. C., Gao, Y. X., The Meteorology of the Qinghai-Xizang Plateau (in Chinese), Beijing: Science Press, 1979, 2-59.[2]Ji, G. L., Yao, L. C., Yuan, F. M. et al., Characteristics of surface and atmospheric heating fields over Qinghai-Xizang Plateau during the winter in 1982, Science in China, Ser. B, 1986, 29(8): 876-888.[3]Chen. L. X., Reiter, E. R., Feng, Z. Q., The atmospheric heat source over the Tibetan plateau: May-August 1979. Mon.Wea. Rev., 1985, 113(10): 1771-1790.[4]Yanai, M., Li, C., Song, Z. S., Seasonal heating of the Tibetan plateau and its effects on the evolution of the Asian summer monsoon, Journal of the Meteorological Society of Japan, 1992, 70(1): 319-350.[5]Zhao, P., Chen, L. X., The climate characteristics of surface turbulent exchange coefficients and surface heat source over the Qinghai-Tibetan plateau, Acta Meteorologica Sinica, 2000, 14(1): 13-29.[6]Zhao, P., Chen, L. X., The calculation of solar albedo and radiation balance and the analysis of their climate characteristics over the Qinghai-Tibetan plateau, Advances in Atmospheric Sciences, 2000, 17(1): 140-156.[7]Fu, C. B., Wang, Q., The definition and detection of the abrupt climatic change, Scientia Atmospheria Sinica (in Chinese),1992. 16 (4): 482-493.

  18. Gas-Solid Interactions During Nonisothermal Heat Treatment of a High-Strength CrMnCN Austenitic Steel Powder: Influence of Atmospheric Conditions and Heating Rate on the Densification Behavior

    Science.gov (United States)

    Krasokha, Nikolaj; Weber, Sebastian; Huth, Stephan; Zumsande, Kathrin; Theisen, Werner

    2012-11-01

    This work deals with gas-solid interactions between a high-alloyed steel powder and the surrounding atmosphere during continuous heating. It is motivated by the recently developed corrosion-resistant CrMnCN austenitic cast steels. Here, powder metallurgical processing would be desirable to manufacture highly homogeneous parts and/or novel corrosion-resistant metal-matrix composites. However, the successful use of this new production route calls for a comprehensive investigation of interactions between the sintering atmosphere and the metallic powder to prevent undesirable changes to the chemical composition, e.g., degassing of nitrogen or evaporation of manganese. In this study, dilatometric measurements combined with residual gas analysis, high-temperature X-ray diffraction (XRD) measurements, and thermodynamic equilibrium calculations provided detailed information about the influence of different atmospheric conditions on the microstructure, constitution, and densification behavior of a gas-atomized CrMnCN steel powder during continuous heating. Intensive desorption of nitrogen led to the conclusion that a vacuum atmosphere is not suitable for powder metallurgical (PM) processing. Exposure to an N2-containing atmosphere resulted in the formation of nitrides and lattice expansion. Experimental findings have shown that the N content can be controlled by the nitrogen partial pressure. Furthermore, the reduction of surface oxides because of a carbothermal reaction at elevated temperatures and the resulting enhancement of the powder's densification behavior are discussed in this work.

  19. FORWARD: A toolset for multiwavelength coronal magnetometry

    Directory of Open Access Journals (Sweden)

    Sarah eGibson

    2016-03-01

    Full Text Available Determining the 3D coronal magnetic field is a critical, but extremely difficult problem to solve. Since different types of multiwavelength coronal data probe different aspects of the coronal magnetic field, ideally these data should be used together to validate and constrain specifications of that field. Such a task requires the ability to create observable quantities at a range of wavelengths from a distribution of magnetic field and associated plasma -- i.e., to perform forward calculations. In this paper we describe the capabilities of the FORWARD SolarSoft IDL package, a uniquely comprehensive toolset for coronal magnetometry. FORWARD is a community resource that may be used both to synthesize a broad range of coronal observables, and to access and compare synthetic observables to existing data. It enables forward fitting of specific observations, and helps to build intuition into how the physical properties of coronal magnetic structures translate to observable properties. FORWARD can also be used to generate synthetic test beds from MHD simulations in order to facilitate the development of coronal magnetometric inversion methods, and to prepare for the analysis of future large solar telescope data.

  20. Observational features of equatorial coronal hole jets

    Directory of Open Access Journals (Sweden)

    G. Zimbardo

    2010-03-01

    Full Text Available Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km s−1, while the deceleration rate appears to be about 0.11 km s−2, less than solar gravity. The average jet visibility time is about 30 min, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and equatorial coronal hole jets.

  1. 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

  2. Imaging solar coronal magnetic structures in 3D

    Science.gov (United States)

    Cartledge, N. P.

    The study of solar coronal structures and, in particular prominences, is a key part of understanding the highly complex physical mechanisms occurring in the Sun's atmosphere. Solar prominences are important in their own right and some of the most puzzling questions in solar theory have arisen through their study. For example, how do they form and how is their mass continuously replenished? How can the magnetic field provide their continuous support against gravity over time periods of several months? How can such cool, dense material exist in thermal equilibrium in the surrounding coronal environment? Why do they erupt? A study of their structure and that of the surrounding medium is important in determining the nature of the coronal plasma and magnetic field. Also, prominences are closely associated with other key phenomena such as coronal mass ejections and eruptive solar flares which occur as a prominence loses equilibrium and rises from the solar surface. Our current understanding of these fascinating structures is extremely limited and we know very little about their basic global structure. In fact, recent prominence observations have caused our basic paradigms to be challenged (Priest, 1996) and so we must set up new models in order to gain even a fundamental understanding. Prominences are highly nonlinear, three-dimensional structures. Large feet (or barbs) reach out from the main body of a prominence and reach down to the photosphere where the dense material continuously drains away. These provide a real clue to the three-dimensional nature of the coronal field and its relation to the photospheric field. It is important, therefore, to make stereographic observations of prominences in order to gain a basic understanding of their essentially three-dimensional nature and attempt to formulate new paradigms for their structure and evolution. There is no doubt that the study of prominences in three dimensions is a crucial exercise if we are to develop a better

  3. An East Asian land-sea atmospheric heat source difference index and its relation to general circulation and summer rainfall over China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Using a monthly precipitation dataset of 160 stations over China and a daily and monthly National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset from 1961 to 2006, we here define an East Asian land-sea atmospheric heat source difference index ILSQD and investigate its relationship to summer rainfall in China and East Asian general circulation. The results show that ILSQD more closely reflects the anomalous variations in summer monsoon phenomena; in the high-index (HI) cases, the strong low-level southerlies over East China and the strong high-level westerlies over middle latitudes indicate an active summer monsoon, and vice versa in the low-index (LI) cases. This index also reflects summer rainfall anomalies over East China; in the HI (LI) cases rainfall increases (decreases) over North China and at the same time decreases (increases) over the mid-lower Yangtze River valley and the southern Yangtze River. Hence, ILSQD can be utilized as a summer monsoon index. There is also remarkable correlation between ILSQD in March and the following summer rainfall over the mid-lower Yangtze River valley. Finally, the Community Atmospheric Model Version 3.1 (CAM3.1) of NCAR is used to run numerical experiments, which verify that the anomalous summer precipitation in simulations is similar to that of diagnosis analysis based on the anomalous summer atmospheric heating forcing. Similarly, the atmospheric heating rate in March can force summer rainfall anomalies in the simulations just as observed in the data.

  4. Study of the Dependence Effectiveness of Low-potential Heat of the Ground and Atmospheric Air for Heating Buildings from Climatic parameters

    Directory of Open Access Journals (Sweden)

    Vasilyev Gregory P.

    2016-01-01

    Full Text Available The article represents the results of researches for division into districts of the territory of Russia and Europe by efficiency of using for the heat supply of buildings of low-potential thermal energy of ground and free air and their combination. While modeling of the heat regime of geothermal HPS in climatic conditions of different regions of the territory of Russia, the influence has been taken into account of the long-term extraction of geothermal heat energy on the ground heat regime as well as the influence of phase transitions of pore moisture in ground on the efficiency of operation of geothermal heat-pump heat-supply systems. While realization of the division into districts, the sinking of temperatures of ground massive was been taken into account which has been called by long-term extraction of the heat energy from the ground, and as calculation parameters of the heat energy from the ground, and as calculation parameters of ground massive temperatures, the ground temperatures were used which are waited for the 5-th year of operation of geothermal HPS.

  5. Coronal Loops: Observations and Modeling of Confined Plasma

    Directory of Open Access Journals (Sweden)

    Fabio Reale

    2010-11-01

    Full Text Available Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered, and therefore topics such as loop oscillations and flaring loops (except for non-solar ones which provide information on stellar loops are not specifically addressed here. The observational section discusses loop classification and populations, and then describes the morphology of coronal loops, its relationship with the magnetic field, and the concept of loops as multi-stranded structures. The following part of this section is devoted to the characteristics of the loop plasma and of its thermal structure in particular, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics and flows are illustrated. In the modeling section some basics of loop physics are provided, supplying some fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are distinguished between those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. Then, more specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC and impulsive (DC heating. Finally, a brief discussion about stellar X-ray emitting structures related to coronal loops is included and followed by conclusions and open questions.

  6. Multidimensional modeling of coronal rain dynamics

    CERN Document Server

    Fang, X; Keppens, R

    2013-01-01

    We present the first multidimensional, magnetohydrodynamic simulations which capture the initial formation and the 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 chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match with modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into $V$-shaped like features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views on blobs which evaporate in situ, or get siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys o...

  7. Microwave Enhancement in Coronal Holes: Statistical Properties

    Indian Academy of Sciences (India)

    Ν. Gopalswamy; Κ. Shibasaki; Μ. Salem

    2000-09-01

    We report on the statistical properties of the microwave enhancement (brightness temperature, area, fine structure, life time and magnetic field strength) in coronal holes observed over a period of several solar rotations.

  8. MHD Waves in the coronal holes

    CERN Document Server

    Banerjee, D

    2015-01-01

    Coronal holes are the dark patches in the solar corona associated with relatively cool, less dense plasma and unipolar fields. The fast component of the solar wind emanates from these regions. Several observations reveal the presence of magnetohydrodynamic (MHD) waves in coronal holes which are believed to play a key role in the acceleration of fast solar wind. The recent advent of high-resolution instruments had brought us many new insights on the properties of MHD waves in coronal holes which are reviewed in this article. The advances made in the identification of compressive slow MHD waves in both polar and equatorial coronal holes, their possible connection with the recently discovered high- speed quasi-periodic upflows, their dissipation, and the detection of damping in Alfven waves from the spectral line width variation are discussed in particular.

  9. Study of the recurring dimming region detected at AR 11305 using the Coronal Dimming Tracker (CoDiT)

    CERN Document Server

    Krista, Larisza D

    2013-01-01

    We present a new approach to coronal dimming detection using the COronal DImming Tracker tool (CODIT), which was found to be successful in locating and tracking multiple dimming regions. This tool, an extension of a previously developed coronal hole tracking software, allows us to study the prop- erties and the spatial evolution of dimming regions at high temporal and spatial cadence from the time of their appearance to their disappearance. We use the Solar Dynamics Observatory/Atmospheric Imaging Assembly 193 A wavelength observations and Helioseismic and Magnetic Imager to study dimmings. As a demonstration of the detection technique we analyzed six recurrences of a dimming observed near AR 11305 between 2011 September 29 and October 2. The dimming repeatedly ap- peared and formed in a similar way, first expanding then shrinking and occasionally stabilizing in the same location until the next eruption. The dimming areas were studied in conjunction with the corre- sponding flare magnitudes and coronal mass e...

  10. Coronal structure and brightness profile of the total solar eclipse on August 1,2008

    Institute of Scientific and Technical Information of China (English)

    ZHAO HaiBin; LIN QiSheng; CHEN YiPing; JIN Sheng; GUAN ZhenBiao; HU Zhongwei

    2009-01-01

    Solar corona is the outermost part of the solar atmosphere.Coronal activities influence space environment between the Sun and the Earth,space weather and the Earth itself.The total solar eclipse (TSE) is the best opportunity to observe the solar corona on ground.During the TSE 2008,a series of images of the corona and partial eclipse of solar disk were obtained using telescope and CCD camera.After image processing,preliminary results of coronal structure are given,and radial brightness profiles of the corona in directions of pole and equator of the Sun are measured.Though in solar activity minimum,the shape and structure of the corona are not symmetry.The equatorial regions are more extent than the polar one,and there are also larger differences between the east and west equatorial regions and between the south and north polar regions.Coronal streamers on east side of the equator,particularly the largest one in east-south direction,are very obvious.The coronal plume in south polar region consists of more polar rays than that in north polar region.These structures are also shown in other observations and data of SOHO.The radial brightness profiles in directions of pole and equator are similar to those of the Van de Hulst model in solar minimum,but there are a few differences due to coronal activity,which is shown in the isophote map of the corona.

  11. CHARACTERISTICS OF ATMOSPHERIC HEAT SOURCE ASSOCIATED WITH THE SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA AND THE POSSIBLE MECHANISM RESPONSIBLE FOR ITS LATE OR EARLY ONSET

    Institute of Scientific and Technical Information of China (English)

    蓝光东; 温之平; 贺海晏

    2004-01-01

    The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon onset is defined by the atmospheric heat source. Applying this criterion to the 15-year (1979 - 1993) mean field, the onset of the SCS summer monsoon is found to occur in the fourth pentad of May. And this criterion can also give reasonable results for the onset time of the SCS summer monsoon on a year-to-year basis. In addition, pretty high correlation has been found between the onset time of the SCS summer monsoon and the zonal mean vertically integrated heat source at 40(S in April. The causes for the late or early onset of the SCS summer monsoon and the close relationship between the onset time and the zonal mean vertically integrated heat source at 40 (S in April might be explained by the variations in intensity of the Hadley circulation.

  12. Soft X-ray emission in flaring coronal loops

    CERN Document Server

    Pinto, R F; Brun, A S

    2014-01-01

    Solar flares are associated with intense soft X-ray emission generated by the hot flaring plasma in coronal magnetic loops. Kink unstable twisted flux-ropes provide a source of magnetic energy which can be released impulsively and account for the heating of the plasma in flares. We investigate the temporal, spectral and spatial evolution of the properties of the thermal X-ray emission produced in such kink-unstable magnetic flux-ropes using a series of MHD simulations. We deduce emission diagnostics and their temporal evolution and discuss the results of the simulations with respect to observations. The numerical setup used consists of a highly twisted loop embedded in a region of uniform and untwisted background coronal magnetic field. We let the kink instability develop, compute the evolution of the plasma properties in the loop (density, temperature) and deduce the X-ray emission properties of the plasma during the whole flaring episode. During the initial phase of the instability plasma heating is mostly ...

  13. Formation, levitation, and stability of prominences in the magnetized solar atmosphere

    Science.gov (United States)

    Drake, J. F.; Mok, Y.; Van Hoven, G.

    1993-01-01

    The dynamic formation of prominences in the initial magnetothermal equilibrium and their stability to sideward displacements are investigated focusing on the structure of the 2D solar atmosphere in the presence of coronal arcades or loops. A model based on 2D magnetohydrodynamic equations takes into account gravity, compressible flows, heating, radiation, anisotropic thermal conduction, and coupling to a deep chromosphere. It is found that prominences in simple arcades characterized by magnetic field with significant curvature at the apex are unstable to a lateral displacement.

  14. Observational features of equatorial coronal hole jets

    CERN Document Server

    Nistico', G; Patsourakos, S; Zimbardo, G

    2010-01-01

    Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km/s, while the deceleration rate appears to be about 0.11 km/s2, less than solar gravity. The average jet visibility time is about 30 minutes, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and eq...

  15. Probing Coronal Mass Ejections with Faraday Rotation

    Science.gov (United States)

    Spangler, Steven R.; Fischer, P. D.; Kooi, J. E.; Buffo, J. J.

    2013-07-01

    Coronal Mass Ejections (CMEs) are one of the most important solar phenomena in affecting conditions on Earth. There is not a consensus as to the physical mechanisms responsible for ejecting CME material from the solar atmosphere. Measurements that specify basic physical properties close to the Sun, when the CME is still evolving, should be useful in determining the correct theoretical model. One of the best observational techniques is that of Faraday rotation, a rotation in the plane of polarization of radio waves when propagating through a magnetized medium like the corona. The importance of Faraday rotation in determining the structure and evolutionary history of CMEs was discussed in Liu et al (ApJ 665, 1439, 2007). In this paper, we report Faraday rotation observations of ``constellations'' of background extragalactic radio sources near the Sun on three days in August, 2012, with the intention of observing a source occulted by a CME. Observations were made with the Jansky Very Large Array (VLA) of the National Radio Astronomy Observatory. We made polarization measurements at 6 frequencies between 1.31 and 1.94 GHz. On August 2, 2012, a CME clearly visible on the LASCO C3 coronagraph occulted a radio source from our sample, 0843+1547. Preliminary data analysis shows a Faraday rotation transient for 0843+1547 which appears to be associated with the CME. The Faraday rotation measure changes from nearly 0 before CME passage, to a value of about -12 radians/square-meter before declining after CME passage. We will discuss the interpretation of these data in terms of models for CME structure, as well as the status of our observations of other sources on August 2, and on other days. This work was supported at the University of Iowa by grant ATM09-56901.

  16. Non-inductive current driven by Alfvén waves in solar coronal loops

    Science.gov (United States)

    Elfimov, A. G.; de Azevedo, C. A.; de Assis, A. S.

    1996-08-01

    It has been shown that Alfvén waves can drive non-inductive current in solar coronal loops via collisional or collisionless damping. Assuming that all the coronal-loop density of dissipated wave power (W= 10-3 erg cm-3 s-1), which is necessary to keep the plasma hot, is due to Alfvén wave electron heating, we have estimated the axial current density driven by Alfvén waves to be ≈ 103 105 statA cm-2. This current can indeed support the quasi-stationary equilibrium and stability of coronal loops and create the poloidal magnetic field up to B θ≈1-5 G.

  17. Trigger Mechanism of Solar Subflares in a Braided Coronal Magnetic Structure

    CERN Document Server

    Tiwari, Sanjiv K; Winebarger, Amy R; Moore, Ronald L

    2014-01-01

    Fine-scale braiding of coronal magnetic loops by continuous footpoint motions may power coronal heating via nanoflares, which are spontaneous fine-scale bursts of internal reconnection. An initial nanoflare may trigger an avalanche of reconnection of the braids, making a microflare or larger subflare. In contrast to this internal triggering of subflares, we observe external triggering of subflares in a braided coronal magnetic field observed by the {\\it High-resolution Coronal Imager (Hi-C)}. We track the development of these subflares using 12 s cadence images acquired by {\\it SDO}/AIA in 1600, 193, 94 \\AA, and registered magnetograms of {\\it SDO}/HMI, over four hours centered on the {\\it Hi-C} observing time. These data show numerous recurring small-scale brightenings in transition-region emission happening on polarity inversion lines where flux cancellation is occurring. We present in detail an example of an apparent burst of reconnection of two loops in the transition region under the braided coronal fiel...

  18. The Global Coronal Structure Investigation

    Science.gov (United States)

    Golub, Leon

    1998-02-01

    During the past year we have completed the changeover from the NIXT program to the new TXI sounding rocket program. The NIXT effort, aimed at evaluating the viability of the remaining portions of the NIXT hardware and design, has been finished and the portions of the NIXT which are viable and flightworthy, such as filters, mirror mounting hardware, electronics and telemetry interface systems, are now part of the new rocket payload. The backup NIXT multilayer-coated x-ray telescope and its mounting hardware have been completely fabricated and are being stored for possible future use in the TXI rocket. The H-alpha camera design is being utilized in the TXI program for real-time pointing verification and control via telemetry. A new H-alpha camera has been built, with a high-resolution RS170 CCD camera output. Two papers, summarizing scientific results from the NIXT rocket program, have been written and published this year: 1. "The Solar X-ray Corona," by L. Golub, Astrophysics and Space Science, 237, 33 (1996). 2. "Difficulties in Observing Coronal Structure," Keynote Paper, Proceedings STEPWG1 Workshop on Measurements and Analyses of the Solar 3D Magnetic Field, Solar Physics, 174, 99 (1997).

  19. Empirical relationships between summertime oceanic heat anomalies in the Nordic seas and large-scale atmospheric circulation in the following winter

    Science.gov (United States)

    Schlichtholz, Pawel

    2016-09-01

    A lagged regression analysis between an index of observed summertime Atlantic water temperature (AWT) variability at the entrance to the Barents Sea in the period 1982-2005 and year-round atmospheric (NCEP/NCAR) reanalysis data is used to show that subsurface oceanic heat anomalies in high latitudes are significant precursors of wintertime atmospheric variability in middle latitudes. In particular, positive AWT anomalies precede predominantly westerly wind anomalies in high latitudes and easterly wind anomalies in middle latitudes. The mid-latitude wind anomalies, while being generally equivalent barotropic in the upper troposphere, have a strong low-level baroclinic contribution over Eurasia. The near-surface easterly wind anomalies in this area are locally deflected southward, maintaining cold spots near orography. The summertime oceanic anomalies explain about 40 % of the variance in the surface air temperature averaged over Eurasia from 35° to 45°N and about 50 % of the variance in surface winds over the Far East Asia in the following winter. We suggest that the remote connections arise from reorganization of the mid-latitude storm tracks. The AWT anomalies explain about 60 % of the variance in the upper-tropospheric storm track activity averaged over the Pacific and Eurasia from 35° to 55°N and in the lower-tropospheric poleward synoptic eddy heat flux over western Eurasia. Finally, we show that the AWT-associated wintertime atmospheric anomalies appear in quadrature with the concurrent anomalies associated with the North Atlantic Oscillation. These findings suggest that oceanic heat anomalies in high latitudes may be a useful predictor of atmospheric variability.

  20. Unresolved fine-scale structure in solar coronal loop-tops

    CERN Document Server

    Scullion, Eamon; Wedemeyer, Sven; Antolin, Patrick

    2014-01-01

    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer sub-structures within coronal loop cross sections, in order to understand the nature of the solar corona. Here, we push this lower limit further to search for the finest coronal loop sub-structures, through taking advantage of the resolving power of the Swedish 1- m Solar Telescope (SST) / CRisp Imaging Spectro-Polarimeter (CRISP), together with co-observations from the Solar Dynamics Observatory (SDO) / Atmospheric Image Assembly (AIA). High resolution imaging of the chromospheric H-alpha 656.28 nm spectral line core and wings can, under certain circumstances, allow one to deduce the topology of the local magnetic environment of the solar atmosphere where its observed. Here, we study post-flare coronal loops, which become filled with evaporated chromosphere that rapidly condenses into chromospheric clumps of plasma (detectable in H-alpha...

  1. Transition-Region/Coronal Signatures and Magnetic Setting of Sunspot Penumbral Jets: {\\it Hinode} (SOT/FG), Hi-C and {\\it SDO}/AIA Observations

    CERN Document Server

    Tiwari, Sanjiv K; Winebarger, Amy R; Alpert, Shane E

    2015-01-01

    Penumbral microjets (PJs) are transient narrow bright features in the chromosphere of sunspot penumbrae, first characterized by Katsukawa et al (2007) using the \\CaII\\ H-line filter on {\\it Hinode}'s Solar Optical Telescope (SOT). It was proposed that the PJs form as a result of reconnection between two magnetic components of penumbra (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 internal structure of sunspot penumbral filaments. Using data of a sunspot from {\\it Hinode}/SOT, High Resolution Coronal Imager, and different passbands of the Atmospheric Imaging Assembly (AIA) onboard the {\\it 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 a few of them showing up in the 1600 \\AA\\ images. However, we discovered exceptionally stro...

  2. Role of atmospheric heating over the South China Sea and western Pacific regions in modulating Asian summer climate under the global warming background

    Science.gov (United States)

    He, Bian; Yang, Song; Li, Zhenning

    2016-05-01

    The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate.

  3. Solar Atmospheric Magnetic Energy Coupling: Radiative Redistribution Efficiency

    Science.gov (United States)

    Orange, N. Brice; Gendre, Bruce; Morris, David C.; Chesny, David

    2016-07-01

    Essential to many outstanding solar and stellar physics problems is elucidating the dynamic magnetic to radiative energy coupling of their atmospheres. Using three years of Solar Dynamics Observatory's Atmospheric Imaging Assembly and Heliosemic Magnetic Imager data of gross atmospheric feature classes, an investigation of magnetic and radiative energy redistribution is detailed. Self-consistent radiative to temperature distributions, that include magnetic weighting, of each feature class is revealed via utilizing the upper limit of thermodynamic atmospheric conditions provided by Active Region Cores (ARCs). Distinctly interesting is that our radiative energy distributions, though indicative to a linearly coupling with temperature, highlight the manifestation of diffuse ``unorganized" emission at upper transition region -- lower coronal regimes. Results we emphasize as correlating remarkably with emerging evidence for similar dependencies of magnetic energy redistribution efficiency with temperature, i.e., linearly with an embedded diffuse emitting region. We present evidence that our magnetic and radiative energy coupling descriptions are consistent with established universal scaling laws for large solar atmospheric temperature gradients and descriptions to the unresolved emission, as well as their insight to a potential origin of large variability in their previous reports. Finally, our work casts new light on the utility of narrowband observations as ad hoc tools for detailing solar atmospheric thermodynamic profiles, thus, presenting significant provisions to the field of solar and stellar physics, i.e., nature of coronae heating.

  4. Computation and Prediction of plasma drag on Orbiting Satellites due to Space Environmental Perturbation by Coronal Mass Ejections (CMEs)

    Science.gov (United States)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar

    2012-07-01

    Certain earth pointing Coronal Mass Ejections (CMEs) induce geomagnetic storms, which significantly affect human activities. Satellites orbiting earth are particularly vulnerable to blasts of solar energy resulting from this phenomenon. It is known that the huge amount of energetic ultraviolet radiation from this space environmental disturbance can heat up the outer atmosphere, causing it to expand. This can cause a significant drag on Earth-Orbiting satellites and even degrade the precision of Global Positioning Systems (GPS) measurements. However, CMEs are more damaging. They are more frequent during the active (solar maximum) Phase of the sun's approximately 11-year cycle. As we approach another maximum in 2012-2013, it is instructive to make an estimate of average daily production of energetic proton flux based on GOES data on earth-pointing CMEs in the past solar cycle. We also compute the drag on satellites due to atmospheric perturbations by CMEs and make predictions of how the existing satellite orbits could be affected near the peak of next solar cycle maximum.

  5. Ectopic folliculosebaceous units at the coronal sulcus.

    Science.gov (United States)

    Fernandez-Flores, Angel

    2014-12-01

    Tyson glands were described in the 17th century as modified sebaceous glands of the coronal sulcus of the penis. However, this description and other early texts supporting the existence of Tyson glands were not accompanied by illustrations. The existence of such glands has been passing through the literature without adequate graphical demonstration, which has contributed to controversial debates. Herein we present a case of a partial penectomy performed on a 65-year-old man with a squamous cell carcinoma of the penis. In this case we identified sebaceous glands as well as folliculosebaceous units in the coronal sulcus. We also comparatively examined 12 cases of partial penectomy to search for sebaceous glands or folliculosebaceous units in the coronal sulcus or the preputium. We found neither sebaceous glands nor folliculosebaceous units at the coronal sulcus or the mucosal aspect of the prepuce. We conclude that: (1) folliculosebaceous units are possible in the coronal sulcus, as the current case illustrates for the first time in literature and (2) the current case is an oddity, probably induced by the accompanying squamous cell carcinoma, and therefore it may represent an ectopic folliculosebaceous unit rather than an anatomic variation.

  6. Effect of axial heat transfer and atmospheric conditions on the energy performance of GSHP systems: A simulation-based analysis

    International Nuclear Information System (INIS)

    A range of analytical and numerical models is available to investigate the thermal behaviour of vertical ground heat exchangers, both in the short- and long-term. However, most of them ignore the thermal effects of weather at ground level that affect the upper part of boreholes. Furthermore, few models look at the integrated simulation of a ground source heat pump system for both the borehole field and heat pump. Consequently, a limited number of applications to real cases are available for designers. This paper shows a study to assess the effects of both axial heat transfer in boreholes and the weather at ground level on the fluid temperature in the boreholes, as well as on the energy efficiency of the heat pump. To this purpose, long-term analysis of two ground source heat pump systems was conducted over ten years by means of a detailed numerical simulation tool. The systems were for two office buildings with unbalanced load profiles in Canada and Italy. These case studies were analyzed as they were being designed, then the influence of the borehole arrangement and borehole length was also investigated. The simulation results show that axial heat transfer affects fluid temperature in the boreholes and the seasonal energy efficiency of the whole system more than the weather. Moreover, when the load profile is unbalanced, neglecting the effect of weather does not always ensure a conservative design of the borehole field. - Highlights: • Multi-year integrated simulations of two real GSHP systems are carried out. • The work focuses on the long-term energy efficiency of GSHP systems. • The simulation tool considers both the borehole field and the heat pump. • The axial heat transfer in the ground affects the energy efficiency of the system. • The weather at the ground level affects the fluid temperature in the boreholes

  7. Scaling laws of coronal loops compared to a 3D MHD model of an Active Region

    CERN Document Server

    Bourdin, Philippe-A; Peter, Hardi

    2016-01-01

    Context. The structure and heating of coronal loops are investigated since decades. Established scaling laws relate fundamental quantities like the loop apex temperature, pressure, length, and the coronal heating. Aims. We test such scaling laws against a large-scale 3D MHD model of the Solar corona, which became feasible with nowadays high-performance computing. Methods. We drive an active region simulation a with photospheric observations and found strong similarities to the observed coronal loops in X-rays and EUV wavelength. A 3D reconstruction of stereoscopic observations showed that our model loops have a realistic spatial structure. We compare scaling laws to our model data extracted along an ensemble of field lines. Finally, we fit a new scaling law that represents well hot loops and also cooler structures, which was not possible before only based on observations. Results. Our model data gives some support for scaling laws that were established for hot and EUV-emissive coronal loops. For the RTV scali...

  8. QUASI-PERIODIC OSCILLATION OF A CORONAL BRIGHT POINT

    Energy Technology Data Exchange (ETDEWEB)

    Samanta, Tanmoy; Banerjee, Dipankar [Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Tian, Hui, E-mail: tsamanta@iiap.res.in, E-mail: hui.tian@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2015-06-20

    Coronal bright points (BPs) are small-scale luminous features seen in the solar corona. Quasi-periodic brightenings are frequently observed in the BPs and are generally linked with underlying magnetic flux changes. We study the dynamics of a BP seen in the coronal hole using the Atmospheric Imaging Assembly images, the Helioseismic and Magnetic Imager magnetogram on board the Solar Dynamics Observatory, and spectroscopic data from the newly launched Interface Region Imaging Spectrograph (IRIS). The detailed analysis shows that the BP evolves throughout our observing period along with changes in underlying photospheric magnetic flux and shows periodic brightenings in different EUV and far-UV images. With the highest possible spectral and spatial resolution of IRIS, we attempted to identify the sources of these oscillations. IRIS sit-and-stare observation provided a unique opportunity to study the time evolution of one footpoint of the BP as the slit position crossed it. We noticed enhanced line profile asymmetry, enhanced line width, intensity enhancements, and large deviation from the average Doppler shift in the line profiles at specific instances, which indicate the presence of sudden flows along the line-of-sight direction. We propose that transition region explosive events originating from small-scale reconnections and the reconnection outflows are affecting the line profiles. The correlation between all these parameters is consistent with the repetitive reconnection scenario and could explain the quasi-periodic nature of the brightening.

  9. A Type II Radio Burst without a Coronal Mass Ejection

    CERN Document Server

    Su, W; Ding, M D; Chen, P F; Sun, J Q

    2015-01-01

    Type II radio bursts are thought to be a signature of coronal shocks. In this paper, we analyze a short-lived type II burst that started at 07:40 UT on 2011 February 28. By carefully checking white-light images, we find that the type II radio burst is not accompanied by a coronal mass ejection, only with a C2.4 class flare and narrow jet. However, in the extreme-ultraviolet (EUV) images provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO), we find a wave-like structure that propagated at a speed of $\\sim$ 600 km s$^{-1}$ during the burst. The relationship between the type II radio burst and the wave-like structure is in particular explored. For this purpose, we first derive the density distribution under the wave by the differential emission measure (DEM) method, which is used to restrict the empirical density model. We then use the restricted density model to invert the speed of the shock that produces the observed frequency drift rate in the dynamic spectrum. The ...

  10. A new instrumentation project for the Lomnicky stit coronal station

    Science.gov (United States)

    Rybak, J.

    1993-07-01

    A proposal of a new telescope/auxiliary instrumentation system for the solar coronal station at Lomnicky Stit (2632 m asl) is described in both the general concept and some particular technical details. The main aim of the system is to observe the near-limb photospheric and chromospheric layers of the solar atmosphere by the white-light and narrow-band imaging, as well as to perform the visible and near-infrared spectroscopy and spectropolarimetry of the parts of solar disk already mentioned. These sorts of data, measured simultaneously with the coronal emission line profiles which are regularly obtained at this time by coronagraph, could give us a great amount of physical information about the solar activity events (such as the height distribution of energy, mass, magnetic fields and their time evolution). The initial ideas and motivation of the project are explained. The parameters of the system components - refractors, narrow band filters, focal plane detectors and fibre optics positioners, telescope-spectrograph coupling via fiber optics, spectrographs, detectors and computers for the control of observations and the data acquisition - are discussed. TV CCD detectors connected with the advanced frame grabbers and the IBM PC computers are especially taken into account for the data acquisition. We also briefly mention advantages and disadvantages of the system as a whole. Finally, the future prospects of the project proposal are briefly described.

  11. The groundwater buffering effect on heat waves and precipitation: coupled groundwater-atmosphere simulations over Europe and North America with a WRF-LEAFHYDRO system.

    Science.gov (United States)

    Miguez-Macho, Gonzalo; Gómez, Breogán; Regueiro-Sanfiz, Sabela; Georgescu, Matei

    2016-04-01

    We present coupled atmosphere-hydrology simulations with the WRF regional climate model and the LEAFHYDRO LSM, including groundwater dynamics. Simulations are carried out for the coupled system for the growing season (February to October) over Europe at 2.5km resolution over land and 20km over the atmosphere. Initial conditions for the land surface, groundwater and rivers are from 10 year off-line simulations, performed continuously over the same domain and period, forced by atmospheric data from the Earth2Observe FP7 project. We show that the presence of a shallow water table over portions of the European continent enhances evapotranspiration in dry periods under increasing atmospheric demand. The impact of the coupling between groundwater and the soil vegetation system on land surface fluxes results in decreases in air temperature and an increase in low level mixing ratios, which under certain convective regimes induces more precipitation. We illustrate for the heat wave of 2003 that models that do not include this groundwater buffering effect may enhance significantly the intensity of such temperature extreme cases. The effect on precipitation is mostly seen over inland areas where warm season convection is important. We show with results of additional simulations over North America, where summer convection over the interior of the continent is very relevant, that the effect of groundwater-enhanced evapotranspiration may have a sizeable impact on climate at the global scale.

  12. Bulk transfer coefficients of the atmospheric momentum and sensible heat over desert and Gobi in arid climate region of Northwest China

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Qiang(张强); WEI; Guoan(卫国安); HUANG; Ronghui(黄荣辉); CAO; Xiaoyan(曹晓彦)

    2002-01-01

    By utilizing the data of the intensive observation period (May-June, 2000) of Dunhuang land-surface process field experiment that belongs to "Land-atmosphere Interactive Field Experiment over Arid Region of Northwest China", the bulk momentum transfer coefficient Cd and bulk sensible heat transfer coefficient Ch between surface and atmosphere over desert and Gobi in the arid region are determined according to three different methods. The result shows that, though these bulk transfer coefficients are different, they are in the same order. Especially, the means of Cd and Ch are close. Moreover, through analyzing the wind direction, the interference of the building near the observational station with the data is eliminated. From this, the relation between the bulk transfer coefficients and the bulk Richardson number and the range of the typical values of the bulk transfer coefficients over desert and Gobi in the typical arid region are obtained.

  13. Temporal and spatial changes in mixed layer properties and atmospheric net heat flux in the Nordic Seas

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, A; Alekseev, G [SI ' Arctic and Antarctic Research Institute' , St. Petersburg (Russian Federation); Korablev, A; Esau, I, E-mail: avsmir@aari.nw.r [Nansen Environmental and Remote Sensing Centre, Bergen (Norway)

    2010-08-15

    The Nordic Seas are an important area of the World Ocean where warm Atlantic waters penetrate far north forming the mild climate of Northern Europe. These waters represent the northern rim of the global thermohaline circulation. Estimates of the relationships between the net heat flux and mixed layer properties in the Nordic Seas are examined. Oceanographic data are derived from the Oceanographic Data Base (ODB) compiled in the Arctic and Antarctic Research Institute. Ocean weather ship 'Mike' (OWS) data are used to calculate radiative and turbulent components of the net heat flux. The net shortwave flux was calculated using a satellite albedo dataset and the EPA model. The net longwave flux was estimated by Southampton Oceanography Centre (SOC) method. Turbulent fluxes at the air-sea interface were calculated using the COARE 3.0 algorithm. The net heat flux was calculated by using oceanographic and meteorological data of the OWS 'Mike'. The mixed layer depth was estimated for the period since 2002 until 2009 by the 'Mike' data as well. A good correlation between these two parameters has been found. Sensible and latent heat fluxes controlled by surface air temperature/sea surface temperature gradient are the main contributors into net heat flux. Significant correlation was found between heat fluxes variations at the OWS 'Mike' location and sea ice export from the Arctic Ocean.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kramar, M. [Physics Department, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); Lin, H. [Institute for Astronomy, University of Hawaii at Manoa, 34 Ohia Ku Street, Pukalani, Maui, HI 96768 (United States); Tomczyk, S., E-mail: kramar@cua.edu, E-mail: lin@ifa.hawaii.edu, E-mail: tomczyk@ucar.edu [High Altitude Observatory, 3080 Center Green Drive, Boulder, CO 80301 (United States)

    2016-03-10

    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.

  15. Correlation analysis of the urban heat island effect and the spatial and temporal distribution of atmospheric particulates using TM images in Beijing.

    Science.gov (United States)

    Xu, L Y; Xie, X D; Li, S

    2013-07-01

    This study combines the methods of observation statistics and remote sensing retrieval, using remote sensing information including the urban heat island (UHI) intensity index, the normalized difference vegetation index (NDVI), the normalized difference water index (NDWI), and the difference vegetation index (DVI) to analyze the correlation between the urban heat island effect and the spatial and temporal concentration distributions of atmospheric particulates in Beijing. The analysis establishes (1) a direct correlation between UHI and DVI; (2) an indirect correlation among UHI, NDWI and DVI; and (3) an indirect correlation among UHI, NDVI, and DVI. The results proved the existence of three correlation types with regional and seasonal effects and revealed an interesting correlation between UHI and DVI, that is, if UHI is below 0.1, then DVI increases with the increase in UHI, and vice versa. Also, DVI changes more with UHI in the two middle zones of Beijing.

  16. Transition Region Abundance Measurements During Impulsive Heating Events

    CERN Document Server

    Warren, Harry P; Doschek, George A; Feldman, Uri

    2015-01-01

    It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona low-FIP elements, such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements, such as C, N, O, Ar, and Ne. In this paper we report on measurements of plasma composition made during impulsive heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O IV, V, and VI emission lines are enhanced relative to emission lines from Mg V, VI, and VII and Si VI and VII and indicate a composition close to that of the photosphere. Long-lived coronal fan structures, in contrast, show an enrichment of low-FIP elements. We conjecture that the plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from...

  17. Observing the formation of flare-driven coronal rain

    CERN Document Server

    Scullion, E; Antolin, P; Wedemeyer, S; Vissers, G; Kontar, E P; Gallagher, P

    2016-01-01

    Flare-driven coronal rain can manifest from rapidly cooled plasma condensations near coronal loop-tops in thermally unstable post-flare arcades. We detect 5 phases that characterise the post-flare decay: heating, evaporation, conductive cooling dominance for ~120 s, radiative / enthalpy cooling dominance for ~4700 s and finally catastrophic cooling occurring within 35-124 s leading to rain strands with s periodicity of 55-70 s. We find an excellent agreement between the observations and model predictions of the dominant cooling timescales and the onset of catastrophic cooling. At the rain formation site we detect co-moving, multi-thermal rain clumps that undergo catastrophic cooling from ~1 MK to ~22000 K. During catastrophic cooling the plasma cools at a maximum rate of 22700 K s-1 in multiple loop-top sources. We calculated the density of the EUV plasma from the DEM of the multi-thermal source employing regularised inversion. Assuming a pressure balance, we estimate the density of the chromospheric componen...

  18. An estimate of the coronal magnetic field near a solar coronal mass ejection from low-frequency radio observations

    Energy Technology Data Exchange (ETDEWEB)

    Hariharan, K.; Ramesh, R.; Kishore, P.; Kathiravan, C. [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034 (India); Gopalswamy, N., E-mail: khariharan@iiap.res.in [Solar Physics Laboratory, NASA/GSFC, Code 671, Greenbelt, MD (United States)

    2014-11-01

    We report ground-based, low-frequency (<100 MHz) radio imaging, spectral, and polarimeter observations of the type II radio burst associated with the solar coronal mass ejection (CME) that occurred on 2013 May 2. The spectral observations indicate that the burst has fundamental (F) and harmonic (H) emission components with split-band and herringbone structures. The imaging observations at 80 MHz indicate that the H component of the burst was located close to leading edge of the CME at a radial distance of r ≈ 2 R {sub ☉} in the solar atmosphere. The polarimeter observations of the type II burst, also at 80 MHz, indicate that the peak degree of circular polarization (dcp) corresponding to the emission generated in the corona ahead of and behind the associated MHD shock front are ≈0.05 ± 0.02 and ≈0.1 ± 0.01, respectively. We calculated the magnetic field B in the above two coronal regions by adopting the empirical relationship between the dcp and B for the harmonic plasma emission and the values are ≈(0.7-1.4) ± 0.2 G and ≈(1.4-2.8) ± 0.1 G, respectively.

  19. Forward Modeling of Synthetic EUV/SXR Emission from Solar Coronal Active Regions: Case of AR 11117

    CERN Document Server

    Airapetian, V S

    2014-01-01

    Recent progress in obtaining high spatial resolution images of the solar corona in the extreme-ultraviolet (EUV) with Hinode, TRACE, SDO and recent Hi-C missions and soft X-ray (SXR) bands opened a new avenue in understanding the solar coronal heating, the major goal of solar physics. The data from EUV/SXR missions suggest that solar corona is a non-uniform environment structured into active regions (AR) represented by bundles magnetic loops heated to temperatures exceeding 5 MK. Any viable coronal heating model should be capable of reproducing EUV and SXR emission from coronal active regions well as dynamic activity. Measurements of emission measures (EM) for ARs provide clues to time dependence of the heating mechanism: static versus impulsive. While static equilibrium coronal loop models are successful in reproducing SXR emission within an AR, they cannot adequately predict the bright EUV loops. Meantime, impulsive heating is capable in reproducing both EUV and SXR loop emission. The major goal of this pap...

  20. Coronal Fractures of the Scaphoid: A Review.

    Science.gov (United States)

    Slutsky, David J; Herzberg, Guillaume; Shin, Alexander Y; Buijze, Geert A; Ring, David C; Mudgal, Chaitanya S; Leung, Yuen-Fai; Dumontier, Christian

    2016-08-01

    Coronal (or frontal plane) fractures of the scaphoid are distinctly uncommon. There are few published reports of coronal fractures of the scaphoid. This fracture is often missed on the initial X-ray films. A high index of suspicion should exist when there is a double contour of the proximal scaphoid pole on the anteroposterior X-ray view. A computed tomography scan is integral in making the diagnosis. Early recognition is key in salvaging the scaphoid fracture and in preventing articular damage. Level of Evidence IV. Retrospective case series. PMID:27574573

  1. MAVEN observations of the response of Mars to an interplanetary coronal mass ejection.

    Science.gov (United States)

    Jakosky, B M; Grebowsky, J M; Luhmann, J G; Connerney, J; Eparvier, F; Ergun, R; Halekas, J; Larson, D; Mahaffy, P; McFadden, J; Mitchell, D F; Schneider, N; Zurek, R; Bougher, S; Brain, D; Ma, Y J; Mazelle, C; Andersson, L; Andrews, D; Baird, D; Baker, D; Bell, J M; Benna, M; Chaffin, M; Chamberlin, P; Chaufray, Y-Y; Clarke, J; Collinson, G; Combi, M; Crary, F; Cravens, T; Crismani, M; Curry, S; Curtis, D; Deighan, J; Delory, G; Dewey, R; DiBraccio, G; Dong, C; Dong, Y; Dunn, P; Elrod, M; England, S; Eriksson, A; Espley, J; Evans, S; Fang, X; Fillingim, M; Fortier, K; Fowler, C M; Fox, J; Gröller, H; Guzewich, S; Hara, T; Harada, Y; Holsclaw, G; Jain, S K; Jolitz, R; Leblanc, F; Lee, C O; Lee, Y; Lefevre, F; Lillis, R; Livi, R; Lo, D; Mayyasi, M; McClintock, W; McEnulty, T; Modolo, R; Montmessin, F; Morooka, M; Nagy, A; Olsen, K; Peterson, W; Rahmati, A; Ruhunusiri, S; Russell, C T; Sakai, S; Sauvaud, J-A; Seki, K; Steckiewicz, M; Stevens, M; Stewart, A I F; Stiepen, A; Stone, S; Tenishev, V; Thiemann, E; Tolson, R; Toublanc, D; Vogt, M; Weber, T; Withers, P; Woods, T; Yelle, R

    2015-11-01

    Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere.

  2. MAVEN observations of the response of Mars to an interplanetary coronal mass ejection.

    Science.gov (United States)

    Jakosky, B M; Grebowsky, J M; Luhmann, J G; Connerney, J; Eparvier, F; Ergun, R; Halekas, J; Larson, D; Mahaffy, P; McFadden, J; Mitchell, D F; Schneider, N; Zurek, R; Bougher, S; Brain, D; Ma, Y J; Mazelle, C; Andersson, L; Andrews, D; Baird, D; Baker, D; Bell, J M; Benna, M; Chaffin, M; Chamberlin, P; Chaufray, Y-Y; Clarke, J; Collinson, G; Combi, M; Crary, F; Cravens, T; Crismani, M; Curry, S; Curtis, D; Deighan, J; Delory, G; Dewey, R; DiBraccio, G; Dong, C; Dong, Y; Dunn, P; Elrod, M; England, S; Eriksson, A; Espley, J; Evans, S; Fang, X; Fillingim, M; Fortier, K; Fowler, C M; Fox, J; Gröller, H; Guzewich, S; Hara, T; Harada, Y; Holsclaw, G; Jain, S K; Jolitz, R; Leblanc, F; Lee, C O; Lee, Y; Lefevre, F; Lillis, R; Livi, R; Lo, D; Mayyasi, M; McClintock, W; McEnulty, T; Modolo, R; Montmessin, F; Morooka, M; Nagy, A; Olsen, K; Peterson, W; Rahmati, A; Ruhunusiri, S; Russell, C T; Sakai, S; Sauvaud, J-A; Seki, K; Steckiewicz, M; Stevens, M; Stewart, A I F; Stiepen, A; Stone, S; Tenishev, V; Thiemann, E; Tolson, R; Toublanc, D; Vogt, M; Weber, T; Withers, P; Woods, T; Yelle, R

    2015-11-01

    Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere. PMID:26542576

  3. Multiwavelength observations of a giant flare on CN Leonis III. Temporal evolution of coronal properties

    OpenAIRE

    Liefke, Carolin; Fuhrmeister, Birgit; Schmitt, Juergen H. M. M.

    2010-01-01

    Stellar flares affect all atmospheric layers from the photosphere over chromosphere and transition region up into the corona. Simultaneous observations in different spectral bands allow to obtain a comprehensive picture of the environmental conditions and the physical processes going on during different phases of the flare. We investigate the properties of the coronal plasma during a giant flare on the active M dwarf CN Leo observed simultaneously with the UVES spectrograph at the VLT and XMM...

  4. Magnetohydrodynamic Simulation of a Streamer Beside a Realistic Coronal Hole

    Science.gov (United States)

    Suess, S. T.; Wu, S. T.; Wang, A. H.; Poletto, G.

    1994-01-01

    Existing models of coronal streamers establish their credibility and act as the initial state for transients. The models have produced satisfactory streamer simulations, but unsatisfactory coronal hole simulations. This is a consequence of the character of the models and the boundary conditions. The models all have higher densities in the magnetically open regions than occur in coronal holes (Noci, et al., 1993).

  5. Heating status of the Tibetan Plateau from April to June and rainfall and atmospheric circulation anomaly over East Asia in midsummer

    Institute of Scientific and Technical Information of China (English)

    DUAN Anmin; LIU Yimin; WU Guoxiong

    2005-01-01

    Based on the 1958-1999 monthly averaged reanalysis data of the National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and the rainfall data of 160 Chinese surface stations, the relationship between rainfall and the atmospheric circulation anomaly over East Asia (EA) in July and the sensible heating (SH) over the Tibetan Plateau (TP) from April to June (AMJ) is investigated by using the rotational experimental orthogonal function (REOF) method. The results show that the TP is an isolated heating source in this period. The lagged correlation analysis between the first rotational principal component (RPC) of SH over the TP in May and rainfall of EA in July demonstrates that strong SH over the TP before July leads to a positive rainfall anomaly over the TP, the valley between the Yangtze River and Huaihe River, and the regions south and southeast of the TP, and the Sichuan Basin and Yunnan-Guizhou Plateau, but less rainfall anomaly over the regions north, northeast, and west of the TP. Such rainfall anomaly patterns are shown to be well coordinated with those of the circulation and vapor flux fields, and are explained by using the thermal adaptation theory and quasi-stationary large-scale vorticity equation. Therefore, the status of SH over the TP during AMJ can be used as a predictor for the rainfall anomaly over EA, especially in the valley between the Yangtze River and Huaihe River.

  6. 2D cellular automaton model for the evolution of active region coronal plasmas

    CERN Document Server

    Fuentes, Marcelo López

    2016-01-01

    We study a 2D 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 (EBTEL) model to compute the response of the plasma to the heating events. Using the known response of the XRT 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 t...

  7. Magnetohydrodynamic turbulent cascade of coronal loop magnetic fields.

    Science.gov (United States)

    Rappazzo, A F; Velli, M

    2011-06-01

    The Parker model for coronal heating is investigated through a high resolution simulation. An inertial range is resolved where fluctuating magnetic energy EMk[Please see symbol]) [Please see symbol] k[Please see symbol](-2.7) exceeds kinetic energy EK(k[Please see symbol])[Please see symbol]k[Please see symbol](-0.6). Increments scale as δbℓ ~/= ℓ(-0.85) and δuℓ ~/= ℓ(+0.2) with velocity increasing at small scales, indicating that magnetic reconnection plays a prime role in this turbulent system. We show that spectral energy transport is akin to standard magnetohydrodynamic (MHD) turbulence even for a system of reconnecting current sheets sustained by the boundary. In this new MHD turbulent cascade, kinetic energy flows are negligible while cross-field flows are enhanced, and through a series of "reflections" between the two fields, cascade more than half of the total spectral energy flow.

  8. The non-ohmic and dielectric behavior evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} after heat treatments in oxygen-rich atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Qiaoli [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou 450011 (China); Li Tao, E-mail: hnlt529@163.com [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Chen Zhenping; Xue Renzhong; Wang Yongqiang [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the percent of oxygen at grain boundaries of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the dielectric properties of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the non-ohmic behaviors of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can enhance the potential barrier of CCTO ceramics. Black-Right-Pointing-Pointer We have explained behavior between the permittivity and the non-ohmic characteristics of CCTO ceramics by the Schottky potential barrier theory. - Abstract: CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics pellets were prepared using the solid-state reaction method, and then they were heat-treated at different temperatures in oxygen-rich atmosphere. The effect of heat treatments on the non-ohmic behaviors and dielectric properties were investigated. EDS analysis results indicate that the percent of oxygen at grain boundaries of CCTO ceramics heat-treated in oxygen-rich atmosphere increases markedly with the rise of temperature and approaches saturation state at about 850 Degree-Sign C. The breakdown voltage and nonlinear coefficient also exhibit an increase trend with the rise of temperature. In addition, the calculated results manifest that the height of Schottky potential barrier is closely related to the oxygen content at the grain boundaries. The permittivity and dielectric loss of samples heat-treated present a relatively intense decrease with the rise of temperature. But the permittivity has a behavior just reverse to the non-ohmic characteristics, which can be explained by the Schottky potential barrier theory.

  9. Coronal Behavior Before the Large Flare Onset

    CERN Document Server

    Imada, Shinsuke; Kusano, Kanya

    2014-01-01

    Flares are a major explosive event in our solar system. They are often followed by coronal mass ejection that has a potential to trigger the geomagnetic storms. There are various studies aiming to predict when and where the flares are likely to occur. Most of these studies mainly discuss the photospheric and chromospheric activity before the flare onset. In this paper we study the coronal features before the famous large flare occurrence on December 13th, 2006. Using the data from Hinode/EUV Imaging Spectrometer (EIS), X-Ray Telescope (XRT), and Solar and Heliospheric Observatory (SOHO) /Extreme ultraviolet Imaging Telescope (EIT), we discuss the coronal features in the large scale (~ a few 100 arcsec) before the flare onset. Our findings are as follows: 1) The upflows in and around active region start growing from ~10 to 30 km /s a day before the flare. 2) The expanding coronal loops are clearly observed a few hours before the flare. 3) Soft X-ray and EUV intensity are gradually reduced. 4) The upflows are f...

  10. 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.

  11. On the Connection between Propagating Solar Coronal Disturbances and Chromospheric Footpoints

    Science.gov (United States)

    Bryans, P.; McIntosh, S. W.; De Moortel, I.; De Pontieu, B.

    2016-09-01

    The Interface Region Imaging Spectrograph (IRIS) provides an unparalleled opportunity to explore the (thermal) interface between the chromosphere, transition region, and the coronal plasma observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). The SDO/AIA observations of coronal loop footpoints show strong recurring upward propagating signals—“propagating coronal disturbances” (PCDs) with apparent speeds of the order of 100-120 km s-1. That signal has a clear signature in the slit-jaw images of IRIS in addition to identifiable spectral signatures and diagnostics in the Mg iih (2803 Å) line. In analyzing the Mg iih line, we are able to observe the presence of magnetoacoustic shock waves that are also present in the vicinity of the coronal loop footpoints. We see there is enough of a correspondence between the shock propagation in Mg iih, the evolution of the Si iv line profiles, and the PCD evolution to indicate that these waves are an important ingredient for PCDs. In addition, the strong flows in the jet-like features in the IRIS Si iv slit-jaw images are also associated with PCDs, such that waves and flows both appear to be contributing to the signals observed at the footpoints of PCDs.

  12. Hydrogen Lyman-alpha and Lyman-beta radiances and profiles in polar coronal holes

    CERN Document Server

    Tian, Hui; Curdt, Werner; Vial, Jean-Claude

    2009-01-01

    The hydrogen Lyman-alpha plays a dominant role in the radiative energy transport in the lower transition region, and is important for the stud- ies of transition-region structure as well as solar wind origin. We investigate the Ly-alpha profiles obtained by SUMER in coronal holes and quiet Sun. In a subset of these observations, also the Hi Lyman-beta, Si iii, and O vi lines were (quasi-) simultaneously recorded. We find that the distances between the two peaks of Ly-alpha profiles are larger in coronal holes than in the quiet Sun, indicating a larger opacity in coronal holes. This difference might result from the different magnetic structures or the different radiation fields in the two regions. Most of the Ly-beta profiles in the coronal hole have a stronger blue peak, in contrast to those in quiet-Sun regions. Whilst in both regions the Ly-alpha profiles are stronger in the blue peak. Although the asymmetries are likely to be produced by differential flows in the solar atmosphere, their detailed formation ...

  13. Characterisation of Off-Limb Coronal Bright Fronts Observed with SDO/AIA

    Science.gov (United States)

    Kozarev, Kamen; Kendrick, Alexander

    2015-04-01

    Shocks associated with Coronal Mass Ejections (CMEs) in interplanetary space are known to accelerate ions to multi-MeV/nuc energies, creating solar energetic particles (SEPs). In the last five years, there have been multiple EUV observations of coronal bright fronts (CBFs), which may be the coronal counterparts of interplanetary shocks. However, it is not presently known how efficient these low-coronal shocks are in accelerating particles to SEP energies. We investigate a number of CME events over a period from 2010-2014, using an automated algorithm to measure the kinematics of the associated CBFs in data by the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory, as well as ground-based radio observations. We focus on off-limb events, since they allow for better determination of the three-dimensional structure of CBFs. Using a new suite of analysis tools, we automatically compute velocities and accelerations of the observed CBFs. We perform analysis of shock evolution and particle acceleration efficiency using data-driven magnetic field observations and differential emission measure modeling.

  14. Reconnection-Driven Coronal-Hole Jets with Gravity and Solar Wind

    CERN Document Server

    Karpen, J T; Antiochos, S K; Pariat, E

    2016-01-01

    Coronal-hole jets occur ubiquitously in solar coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry, gravity, and solar wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagat...

  15. Using coronal seismology to estimate the magnetic field strength in a realistic coronal model

    CERN Document Server

    Chen, Feng

    2015-01-01

    Coronal seismology is extensively used to estimate properties of the corona, e.g. the coronal magnetic field strength are derived from oscillations observed in coronal loops. We present a three-dimensional coronal simulation including a realistic energy balance in which we observe oscillations of a loop in synthesised coronal emission. We use these results to test the inversions based on coronal seismology. From the simulation of the corona above an active region we synthesise extreme ultraviolet (EUV) emission from the model corona. From this we derive maps of line intensity and Doppler shift providing synthetic data in the same format as obtained from observations. We fit the (Doppler) oscillation of the loop in the same fashion as done for observations to derive the oscillation period and damping time. The loop oscillation seen in our model is similar to imaging and spectroscopic observations of the Sun. The velocity disturbance of the kink oscillation shows an oscillation period of 52.5s and a damping tim...

  16. Standing sausage modes in curved coronal slabs

    Science.gov (United States)

    Pascoe, D. J.; Nakariakov, V. M.

    2016-09-01

    Context. Magnetohydrodynamic waveguides such as dense coronal loops can support standing modes. The ratios of the periods of oscillations for different longitudinal harmonics depend on the dispersive nature of the waveguide and so may be used as a seismological tool to determine coronal parameters. Aims: We extend models of standing sausage modes in low β coronal loops to include the effects of loop curvature. The behaviour of standing sausage modes in this geometry is used to explain the properties of observed oscillations that cannot be accounted for using straight loop models. Methods: We perform 2D numerical simulations of an oscillating coronal loop, modelled as a dense slab embedded in a potential magnetic field. The loop is field-aligned and so experiences expansion with height in addition to being curved. Standing sausage modes are excited by compressive perturbations of the loop and their properties are studied. Results: The spatial profiles of standing sausage modes are found to be modified by the expanding loop geometry typical for flaring loops and modelled by a potential magnetic field in our simulations. Longitudinal harmonics of order n > 1 have anti-nodes that are shifted towards the loop apex and the amplitude of anti-nodes near the loop apex is smaller than those near the loop footpoints. Conclusions: We find that the observation of standing sausage modes by the Nobeyama Radioheliograph in a flaring coronal loop on 12 January 2000 is consistent with interpretation in terms of the global mode (n = 1) and third harmonic (n = 3). This interpretation accounts for the period ratio and spatial structure of the observed oscillations.

  17. Future projections of the surface heat and water budgets of the Mediterranean Sea in an ensemble of coupled atmosphere-ocean regional climate models

    Energy Technology Data Exchange (ETDEWEB)

    Dubois, C.; Somot, S.; Deque, M.; Sevault, F. [CNRM-GAME, Meteo-France, CNRS, Toulouse (France); Calmanti, S.; Carillo, A.; Dell' Aquilla, A.; Sannino, G. [ENEA, Rome (Italy); Elizalde, A.; Jacob, D. [Max Planck Institute for Meteorology, Hamburg (Germany); Gualdi, S.; Oddo, P.; Scoccimarro, E. [INGV, Bologna (Italy); L' Heveder, B.; Li, L. [Laboratoire de Meteorologie Dynamique, Paris (France)

    2012-10-15

    Within the CIRCE project ''Climate change and Impact Research: the Mediterranean Environment'', an ensemble of high resolution coupled atmosphere-ocean regional climate models (AORCMs) are used to simulate the Mediterranean climate for the period 1950-2050. For the first time, realistic net surface air-sea fluxes are obtained. The sea surface temperature (SST) variability is consistent with the atmospheric forcing above it and oceanic constraints. The surface fluxes respond to external forcing under a warming climate and show an equivalent trend in all models. This study focuses on the present day and on the evolution of the heat and water budget over the Mediterranean Sea under the SRES-A1B scenario. On the contrary to previous studies, the net total heat budget is negative over the present period in all AORCMs and satisfies the heat closure budget controlled by a net positive heat gain at the strait of Gibraltar in the present climate. Under climate change scenario, some models predict a warming of the Mediterranean Sea from the ocean surface (positive net heat flux) in addition to the positive flux at the strait of Gibraltar for the 2021-2050 period. The shortwave and latent flux are increasing and the longwave and sensible fluxes are decreasing compared to the 1961-1990 period due to a reduction of the cloud cover and an increase in greenhouse gases (GHGs) and SSTs over the 2021-2050 period. The AORCMs provide a good estimates of the water budget with a drying of the region during the twenty-first century. For the ensemble mean, he decrease in precipitation and runoff is about 10 and 15% respectively and the increase in evaporation is much weaker, about 2% compared to the 1961-1990 period which confirm results obtained in recent studies. Despite a clear consistency in the trends and results between the models, this study also underlines important differences in the model set-ups, methodology and choices of some physical parameters inducing

  18. Shear Photospheric Forcing and the Origin of Turbulence in Coronal Loops

    CERN Document Server

    Rappazzo, A F; Einaudi, G

    2010-01-01

    We present a series of numerical simulations aimed at understanding the nature and origin of turbulence in coronal loops in the framework of the Parker model for coronal heating. A coronal loop is studied via reduced magnetohydrodynamics simulations in Cartesian geometry. A uniform and strong magnetic field threads the volume between the two photospheric planes, where a velocity field in the form of a 1D shear flow pattern is present. Initially the magnetic field which developes in the coronal loop is a simple map of the photospheric velocity field. This initial configuration is unstable to a multiple tearing instability which develops islands with X and O points in the plane orthogonal to the axial field. Once the nonlinear stage sets in the system evolution is characterized by a regime of MHD turbulence dominated by magnetic energy. A well developed power law in energy spectra is observed and the magnetic field never returns to the simple initial state mapping the photospheric flow. The formation of X and O...

  19. Evidence for evaporation-incomplete condensation cycles in warm solar coronal loops

    CERN Document Server

    Froment, Clara; Bocchialini, Karine; Buchlin, Eric; Guennou, Chloé; Solomon, Jacques

    2015-01-01

    Quasi-constant heating at the footpoints of loops leads to evaporation and condensation cycles of the plasma: thermal non-equilibrium (TNE). This phenomenon is believed to play a role in the formation of prominences and coronal rain. However, it is often discarded to be involved in the heating of warm loops as the models do not reproduce observations. Recent simulations have shown that these inconsistencies with observations may be due to oversimplifications of the geometries of the models. In addition, our recent observations reveal that long-period intensity pulsations (several hours) are common in solar coronal loops. These periods are consistent with those expected from TNE. The aim of this paper is to derive characteristic physical properties of the plasma for some of these events to test the potential role of TNE in loop heating. We analyzed three events in detail using the six EUV coronal channels of SDO/AIA. We performed both a Differential Emission Measure (DEM) and a time-lag analysis, including a n...

  20. Three-Dimensional Structure and Energy Balance of a Coronal Mass Ejection

    Science.gov (United States)

    Lee, J.-Y.; Raymond, J. C.; Ko, Y.-K.; Kim, K.-S.

    2009-01-01

    UVCS observed Doppler-shifted material of a partial halo coronal mass ejection (CME) on 2001 December 13. The observed ratio of [O VJ/O V] is a reliable density diagnostic important for assessing the state of the plasma. Earlier UVCS observations of CMEs found evidence that the ejected plasma is heated long after the eruption. This paper investigated the heating rates, which represent a significant fraction of the CME energy budget. The parameterized heating and radiative and adiabatic cooling have been used to evaluate the temperature evolution of the CME material with a time-dependent ionization state model. Continuous heating is required to match the UVCS observations. To match the O VI bright knots, a higher heating rate is required such that the heating energy is greater than the kinetic energy.

  1. The Estimation Surface Latent Heat Flux Over the Ocean and its Relationship to Marine Atmospheric Boundary Layer (MABL) Structure

    Science.gov (United States)

    Palm, Stephen P.; Schwemmer, Geary K.; Vandemark, Doug; Evans, Keith; Miller, David O.

    1999-01-01

    A new technique combining active and passive remote sensing instruments for the estimation of surface latent heat flux over the ocean is presented. This synergistic method utilizes aerosol lidar backscatter data, multi-channel infrared radiometer data and microwave scatterometer data acquired onboard the NASA P-3B research aircraft during an extended field campaign over the Atlantic ocean in support of the Lidar In-space Technology Experiment (LITE) in September of 1994. The 10 meter wind speed derived from the scatterometers and the lidar-radiometer inferred near-surface moisture are used to obtain an estimate of the surface flux of moisture via bulk aerodynamic formulae. The results are compared with the Special Sensor Microwave Imager (SSM/I) daily average latent heat flux and show reasonable agreement. However, the SSM/I values are biased high by about 30 W/sq m. In addition, the MABL height, entrainment zone thickness and integrated lidar backscatter intensity are computed from the lidar data and compared with the magnitude of the surface fluxes. The results show that the surface latent heat flux is most strongly correlated with entrainment zone top, bottom and the integrated MABL lidar backscatter, with corresponding correlation coefficients of 0.62, 0.67 and 0.61, respectively.

  2. Periodic Variations in the Coronal Green Line Intensity and their Connection with the White-light Coronal Structures

    Indian Academy of Sciences (India)

    Milan Minarovjech; Milan Rybansky; Vojtech Rusin

    2000-09-01

    We present an analysis of short time-scale intensity variations in the coronal green line as obtained with high time resolution observations. The observed data can be divided into two groups. The first one shows periodic intensity variations with a period of 5 min. the second one does not show any significant intensity variations. We studied the relation between regions of coronal intensity oscillations and the shape of whitelight coronal structures. We found that the coronal green-line oscillations occur mainly in regions where open white-light coronal structures are located.

  3. Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma evokes distinct changes in morphology and integrity of spores.

    Science.gov (United States)

    van Bokhorst-van de Veen, Hermien; Xie, Houyu; Esveld, Erik; Abee, Tjakko; Mastwijk, Hennie; Nierop Groot, Masja

    2015-02-01

    Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity. PMID:25481059

  4. RADIO ACTIVE GALAXY NUCLEI IN GALAXY CLUSTERS: HEATING HOT ATMOSPHERES AND DRIVING SUPERMASSIVE BLACK HOLE GROWTH OVER COSMIC TIME

    International Nuclear Information System (INIS)

    We estimate the average radio active galactic nucleus (AGN, mechanical) power deposited into the hot atmospheres of galaxy clusters over more than three quarters of the age of the Universe. Our sample was drawn from eight major X-ray cluster surveys and includes 685 clusters in the redshift range 0.1 44 erg s–1 exceeds the X-ray luminosity of 44% of the clusters, indicating that the accumulation of radio-AGN energy is significant in these clusters. Integrating the AGN mechanical power to redshift z = 2.0, using simple models for its evolution and disregarding the hierarchical growth of clusters, we find that the AGN energy accumulated per particle in low luminosity X-ray clusters exceeds 1 keV per particle. This result represents a conservative lower limit to the accumulated thermal energy. The estimate is comparable to the level of energy needed to 'preheat' clusters, indicating that continual outbursts from radio-AGN are a significant source of gas energy in hot atmospheres. Assuming an average mass conversion efficiency of η = 0.1, our result implies that the supermassive black holes that released this energy did so by accreting an average of ∼109 M ☉ over time, which is comparable to the level of growth expected during the quasar era.

  5. Cold atmospheric pressure plasma jets: Interaction with plasmid DNA and tailored electron heating using dual-frequency excitation

    Science.gov (United States)

    Niemi, K.; O'Neill, C.; Cox, L. J.; Waskoenig, J.; Hyland, W. B.; McMahon, S. J.; Reuter, S.; Currell, F. J.; Graham, W. G.; O'Connell, D.; Gans, T.

    2012-05-01

    Recent progress in plasma science and technology has enabled the development of a new generation of stable cold non-equilibrium plasmas operating at ambient atmospheric pressure. This opens horizons for new plasma technologies, in particular in the emerging field of plasma medicine. These non-equilibrium plasmas are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. The effect of a cold radio frequency-driven atmospheric pressure plasma jet on plasmid DNA has been investigated. The formation of double strand breaks correlates well with the atomic oxygen density. Taken with other measurements, this indicates that neutral components in the jet are effective in inducing double strand breaks. Plasma manipulation techniques for controlled energy delivery are highly desirable. Numerical simulations are employed for detailed investigations of the electron dynamics, which determines the generation of reactive species. New concepts based on nonlinear power dissipation promise superior strategies to control energy transport for tailored technological exploitations.

  6. Geospatial Strategy for Adverse Impact of Urban Heat Island in upper atmospheres of the earth Mountain Areas using LANDSAT ETM+ Sensors

    Science.gov (United States)

    Kumar, Amit; Vandana, Vandana

    2016-07-01

    We are living in the age of the rapidly growing population and changing environmental conditions with advanced technical capacity. This has been resulting in widespread land cover change. Among several human-induced environmental and urban thermal problems are reported to be negatively affecting urban residents in many ways. Urban Heat Islands exist in many large cities especially metropolitan cities and can significantly affect the permafrost layer in mountain areas. The adverse effect of urban heat island has become the subject of numerous studies in recent decades and is reflected in many major mountain cities around the world. The built-up structures in urbanized areas considerably alter land cover thereby affecting thermal energy flow which leads to the development of elevated surface and air temperature. The phenomenon Urban Heat Island implies 'island' of high temperature in cities, surrounded by relatively lower temperature in rural areas. The Urban Heat Island for the temporal period is estimated using geospatial techniques which are then utilized for the impact assessment of the climate of the surrounding regions and how it reduce the sustainability of the natural resources like air, vegetation. The knowledge of surface temperature is important for the study of urban climate and human health. The rapid growth of industries in peri-urban areas results in excessive warming and variations in weather conditions. It leads to soil degradation in frozen areas due to high temperature which leads to melting of snow in mountain areas Remotely sensed data of thermal infrared band in the region of 10.4-12.5 µm of EMR spectrum, available from LANDSAT- ETM+ is proved to be very helpful to identify urban heat islands. Thermal infrared data acquired during the daytime and night time can be used to monitor the heat island associated with urban areas as well as atmospheric pollution. The present paper describes the methodology and resolution dynamic urban heat island

  7. Influence of temperature on flammability limits of heat treating atmosphere%温度对热处理气氛可燃极限的影响

    Institute of Scientific and Technical Information of China (English)

    Dwyer John; Hansel James G.; Philips Tom; Chen Wayne; 侯学涛

    2011-01-01

    讨论了热处理气氛中常用气体成分的可燃极限,分析了上下可燃极限与温度的关系。提出了一个应用CAFT理论推断气氛可燃极限的方法,同时解释了温度对热处理炉安全操作的影响。%The flammability limits of gas constituents commonly used in heat treating atmospheres were discussed.The upper and lower flammability limits,with respect to temperature,were analyzed.A method was described for determining these limits using CAFT theory.This temperature factor and its impact on safe furnace practices were addressed.

  8. Magnetic Topology of Coronal Hole Linkages

    CERN Document Server

    Titov, V S; 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 flux 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 field 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. It is known that such topologies are extremely favorable for magnetic reconnection, because they allow this process to occur over the entire length of the separators rather than being confined to a small region around the...

  9. Geometrical Properties of Coronal Mass Ejections

    Science.gov (United States)

    Cremades, Hebe; Bothmer, Volker

    Based on the SOHO/LASCO dataset, a collection of "structured" coronal mass ejections (CMEs) has been compiled within the period 1996-2002, in order to analyze their three-dimensional configuration. These CME events exhibit white-light fine structures, likely indicative of their possible 3D topology. From a detailed investigation of the associated low coronal and photospheric source regions, a generic scheme has been deduced, which considers the white-light topology of a CME projected in the plane of the sky as being primarily dependent on the orientation and position of the source region's neutral line on the solar disk. The obtained results imply that structured CMEs are essentially organized along a symmetry axis, in a cylindrical manner. The measured dimensions of the cylinder's base and length yield a ratio of 1.6. These CMEs seem to be better approximated by elliptic cones, rather than by the classical ice cream cone, characterized by a circular cross section.

  10. Sinonasal polyposis: investigation by direct coronal CT

    International Nuclear Information System (INIS)

    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.)

  11. Solar Energetic Particles: Sampling Coronal Abundances

    Science.gov (United States)

    Reames, Donald V.

    1998-05-01

    In the large solar energetic particle (SEP) events, coronal mass ejections (CMEs) drive shock waves out through the corona that accelerate elements of the ambient material to MeV energies in a fairly democratic, temperature-independent manner. These events provide the most complete source of information on element abundances in the corona. Relative abundances of 22 elements from H through Zn display the well-known dependence on the first ionization potential (FIP) that distinguishes coronal and photospheric material. For most elements, the main abundance variations depend upon the gyrofrequency, and hence on the charge-to-mass ratio, Q/A, of the ion. Abundance variations in the dominant species, H and He, are not Q/A dependent, presumably because of non-linear wave-particle interactions of H and He during acceleration. Impulsive flares provide a different sample of material that confirms the Ne:Mg:Si and He/C abundances in the corona.

  12. Damped transverse oscillations of interacting coronal loops

    CERN Document Server

    Soler, Roberto

    2015-01-01

    Damped transverse oscillations of magnetic loops are routinely observed in the solar corona. This phenomenon is interpreted as standing kink magnetohydrodynamic waves, which are damped by resonant absorption owing to plasma inhomogeneity across the magnetic field. The periods and damping times of these oscillations can be used to probe the physical conditions of the coronal medium. Some observations suggest that interaction between neighboring oscillating loops in an active region may be important and can modify the properties of the oscillations compared to those of an isolated loop. Here we theoretically investigate resonantly damped transverse oscillations of interacting non-uniform coronal loops. We provide a semi-analytic method, based on the T-matrix theory of scattering, to compute the frequencies and damping rates of collective oscillations of an arbitrary configuration of parallel cylindrical loops. The effect of resonant damping is included in the T-matrix scheme in the thin boundary approximation. ...

  13. Current Sheets in Stressed Coronal Magnetic Fields

    Science.gov (United States)

    Labonte, B. J.

    2003-12-01

    The extrapolation of magnetic fields into the solar corona generally assumes that the fields are fully relaxed - all possible reconnection has occurred. This assumption is in conflict with the low magnetic diffusivity in the corona. I will present initial results on extrapolation based on stressed magnetic fields - those for which no reconnection has occurred. As an opposite extreme to traditional methods, stressed fields offer a different view of coronal fields. The locations of current sheets between flux systems are directly determined. Observational evidence of coronal reconnection can test the completeness of the extrapolation, as the field lines spanning flux systems must be in contact prior to reconnection. This work is supported by NASA SEC GI grant NAG5-13020.

  14. GLOBAL CORONAL SEISMOLOGY IN THE EXTENDED SOLAR CORONA THROUGH FAST MAGNETOSONIC WAVES OBSERVED BY STEREO SECCHI COR1

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Ryun-Young; Kramar, Maxim; Wang, Tongjiang; Ofman, Leon [Department of Physics, Institute for Astrophysics and Computational Sciences, Catholic University of America, 620 Michigan Avenue, Washington, DC 20064 (United States); Davila, Joseph M. [NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771 (United States); Chae, Jongchul [Astronomy Program, Department of Physics and Astronomy, Seoul National University (Korea, Republic of); Zhang, Jie [School of Physics, Astronomy and Computational Sciences, George Mason University, 4400 University Drive, MSN 6A2, Fairfax, VA 22030 (United States)

    2013-10-10

    We present global coronal seismology for the first time, which allows us to determine inhomogeneous magnetic field strength in the extended corona. From the measurements of the propagation speed of a fast magnetosonic wave associated with a coronal mass ejection (CME) and the coronal background density distribution derived from the polarized radiances observed by the STEREO SECCHI COR1, we determined the magnetic field strengths along the trajectories of the wave at different heliocentric distances. We found that the results have an uncertainty less than 40%, and are consistent with values determined with a potential field model and reported in previous works. The characteristics of the coronal medium we found are that (1) the density, magnetic field strength, and plasma β are lower in the coronal hole region than in streamers; (2) the magnetic field strength decreases slowly with height but the electron density decreases rapidly so that the local fast magnetosonic speed increases while plasma β falls off with height; and (3) the variations of the local fast magnetosonic speed and plasma β are dominated by variations in the electron density rather than the magnetic field strength. These results imply that Moreton and EIT waves are downward-reflected fast magnetosonic waves from the upper solar corona, rather than freely propagating fast magnetosonic waves in a certain atmospheric layer. In addition, the azimuthal components of CMEs and the driven waves may play an important role in various manifestations of shocks, such as type II radio bursts and solar energetic particle events.

  15. Relationship of EUV Irradiance Coronal Dimming Slope and Depth to Coronal Mass Ejection Speed and Mass

    CERN Document Server

    Mason, James Paul; Webb, David F; Thompson, Barbara J; Colaninno, Robin C; Vourlidas, Angelos

    2016-01-01

    Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar flare, as is often the case, the flare component of the irradiance light curve in the cooler coronal emission can be isolated and removed using simultaneous measurements of warmer coronal lines. We apply this technique to 37 dimming events identified during two separate two-week periods in 2011, plus an event on 2010 August 7 analyzed in a previous paper, to parameterize dimming in terms of depth and slope. We provide statistics on which combination of wavelengths worked best for the flare-removal method, describe the fitting methods applied to t...

  16. The plasma structure of coronal hole solar wind: Origins and evolution

    Science.gov (United States)

    Borovsky, Joseph E.

    2016-06-01

    Whereas slow solar wind is known to be highly structured, the fast (coronal hole origin) wind is usually considered to be homogeneous. Using measurements from Helios 1 + 2, ACE, Wind, and Ulysses, structure in the coronal hole origin solar wind is examined from 0.3 AU to 2.3 AU. Care is taken to collect and analyze intervals of "unperturbed coronal hole plasma." In these intervals, solar wind structure is seen in the proton number density, proton temperature, proton specific entropy, magnetic field strength, magnetic field to density ratio, electron heat flux, helium abundance, heavy-ion charge-state ratios, and Alfvenicity. Typical structure amplitudes are factors of 2, far from homogeneous. Variations are also seen in the solar wind radial velocity. Using estimates of the motion of the solar wind origin footpoint on the Sun for the various spacecraft, the satellite time series measurements are converted to distance along the photosphere. Typical variation scale lengths for the solar wind structure are several variations per supergranule. The structure amplitude and structure scale sizes do not evolve with distance from the Sun from 0.3 to 2.3 AU. An argument is quantified that these variations are the scale expected for solar wind production in open magnetic flux funnels in coronal holes. Additionally, a population of magnetic field foldings (switchbacks, reversals) in the coronal hole plasma is examined: this population evolves with distance from the Sun such that the magnetic field is mostly Parker spiral aligned at 0.3 AU and becomes more misaligned with distance outward.

  17. Coronal Mass Ejections of Solar Cycle 23

    Indian Academy of Sciences (India)

    Nat Gopalswamy

    2006-06-01

    I summarize the statistical, physical, and morphological properties of coronal mass ejections (CMEs) of solar cycle 23, as observed by the Solar and Heliospheric Observatory (SOHO) mission. The SOHO data is by far the most extensive data, which made it possible to fully establish the properties of CMEs as a phenomenon of utmost importance to Sun–Earth connection as well as to the heliosphere. I also discuss various subsets of CMEs that are of primary importance for their impact on Earth.

  18. Physics of laser fusion. Vol. I. Theory of the coronal plasma in laser-fusion targets

    International Nuclear Information System (INIS)

    This monograph deals with the physics of the coronal region in laser fusion targets. The corona consists of hot plasma which has been evaporated from the initially solid target during laser heating. It is in the corona that the laser light is absorbed by the target, and the resulting thermal energy is conducted toward cold high-density regions, where ablation occurs. The topics to be discussed are theoretical mechanisms for laser light absorption and reflection, hot-electron production, and the physics of heat conduction in laser-produced plasmas. An accompanying monograph by H. Ahlstrom (Vol.II) reviews the facilities, diagnostics, and data from recent laser fusion experiments

  19. Momentum, Heat, and Neutral Mass Transport in Convective Atmospheric Pressure Plasma-Liquid Systems and Implications for Aqueous Targets

    CERN Document Server

    Lindsay, Alexander; Slikboer, Elmar; Shannon, Steven; Graves, David

    2015-01-01

    There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 $\\mu$m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results fro...

  20. Estimating sensible heat exchange between screen-covered canopies and the atmosphere using the surface renewal technique

    Science.gov (United States)

    Mekhmandarov, Yonatan; Achiman, Ori; Pirkner, Moran; Tanny, Josef

    2014-05-01

    Screenhouses and screen-covers are widely used in arid and semi-arid agriculture to protect crops from direct solar radiation and high wind speed, and to increase water use efficiency. However, accurate estimation of crop water use under screens is still a challenge. The most reliable method that directly measures evapotranspiration, the Eddy Covariance (EC), is both expensive and complex in data collection and processing. This renders it unfeasible for day to day use by farmers. A simpler alternative is the Surface Renewal (SR) technique which utilizes high frequency temperature readings of low-cost fine-wire thermocouples, to estimate the sensible heat flux. Assuming energy conservation and employing relatively cheap complementary measurements, the evapotranspiration can be estimated. The SR technique uses a structure function mathematical analysis that filters out noise and involves a time lag parameter to provide amplitude and time period of a ramp-like temperature signal. This behavior arises from the detachment of air parcels that have been heated or cooled near the surface and sequentially renewed by air parcels from above. While the SR technique is relatively simple to employ, it requires calibration against direct measurements. The aim of this research is to investigate the applicability of the SR technique in two different types of commonly used screenhouses in Israel. Two field campaigns were carried out: In the first campaign we studied a banana plantation grown in a shading screenhouse located in the coastal plain of northern Israel. The second campaign was located in the Jordan Valley region of eastern Israel, where a pepper plantation cultivated in an insect-proof screenhouse, with a much denser screen, was examined. In the two campaigns, SR sensible heat flux estimates were calibrated against simultaneous eddy covariance measurements. To optimize the SR operation, in each campaign fine-wire (50-76 μm) exposed T-type thermocouples were placed at

  1. A Mechanism for Coronal Hole Jets

    CERN Document Server

    Mueller, D A N

    2008-01-01

    Bald patches are magnetic topologies in which the magnetic field is concave up over part of a photospheric polarity inversion line. A bald patch topology is believed to be the essential ingredient for filament channels and is often found in extrapolations of the observed photospheric field. Using an analytic source-surface model to calculate the magnetic topology of a small bipolar region embedded in a global magnetic dipole field, we demonstrate that although common in closed-field regions close to the solar equator, bald patches are unlikely to occur in the open-field topology of a coronal hole. Our results give rise to the following question: What happens to a bald patch topology when the surrounding field lines open up? This would be the case when a bald patch moves into a coronal hole, or when a coronal hole forms in an area that encompasses a bald patch. Our magnetostatic models show that, in this case, the bald patch topology almost invariably transforms into a null point topology with a spine and a fa...

  2. 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.

  3. Optical coronal polarization and solar dust ring

    International Nuclear Information System (INIS)

    Observations of the outer solar corona on the Java island were carried out on June 11, 1983, at a 30-km altitude using a B-15 balloon. At 5325, 5965, 7200, and 8015 A, data on polarizations in a field of 5 deg x 5 deg centered nearly on the sun were obtained. Our contour maps of polarization are the first of the two-dimensional polarization distribution covering wide area. An excess of polarization at the four wavelengths was found in the ecliptic plane and at the location of a coronal streamer. High polarization at the coronal streamer is caused mainly by coronal electrons, but dust grains in the region out of the ecliptic plane contribute also in a few percent to the high polarization degree in this streamer. It is confirmed by additional data that there is a peak in the polarization excess in the ecliptic between 4(R solar) and 5(R solar) as already reported by Isobe et al. (1985; AAA 40.074.053). This excess is considered to be due to an enhanced distribution of dust in a ring or a thick wide band around the sun. (author)

  4. Potential effect of atmospheric warming on grapevine phenology and post-harvest heat accumulation across a range of climates

    Science.gov (United States)

    Hall, Andrew; Mathews, Adam J.; Holzapfel, Bruno P.

    2016-09-01

    Carbohydrates are accumulated within the perennial structure of grapevines when their production exceeds the requirements of reproduction and growth. The period between harvest and leaf-fall (the post-harvest period) is a key period for carbohydrate accumulation in relatively warmer grape-growing regions. The level of carbohydrate reserves available for utilisation in the following season has an important effect on canopy growth and yield potential and is therefore an important consideration in vineyard management. In a warming climate, the post-harvest period is lengthening and becoming warmer, evidenced through studies in wine regions worldwide that have correlated recent air temperature increases with changing grapevine phenology. Budbreak, flowering, veraison, and harvest have all been observed to be occurring earlier than in previous decades. Additionally, the final stage of the grapevine phenological cycle, leaf-fall, occurs later. This study explored the potential for increased post-harvest carbohydrate accumulation by modelling heat accumulation following harvest dates for the recent climate (1975-2004) and two warmer climate projections with mean temperature anomalies of +1.26 and +2.61 °C. Summaries of post-harvest heat accumulation between harvest and leaf-fall were produced for each of Australia's Geographical Indications (wine regions) to provide comparisons from the base temperatures to projected warmer conditions across a range of climates. The results indicate that for warmer conditions, all regions observe earlier occurring budbreak and harvest as well as increasing post-harvest growing degree days accumulation before leaf-fall. The level of increase varies depending upon starting climatic condition, with cooler regions experiencing the greatest change.

  5. 3D Reconstruction of Coronal Loops by the Principal Component Analysis

    Directory of Open Access Journals (Sweden)

    Erwin Verwichte

    2013-10-01

    Full Text Available Knowing the three dimensional structure of plasma filaments in the uppermost part of the solar atmosphere, known as coronal loops, and especially their length, is an important parameter in the wave-based diagnostics of this part of the Sun. The combination of observations of the Sun from different points of observations in space, thanks to the most recent missions, including the Solar Dynamics Observatory (SDO and the Solar TErrestrial RElations Observatory (STEREO, allows us to infer information about the geometrical shape of coronal loops in 3D space. Here, we propose a new method to reconstruct the loop shape starting from stereoscopically determined 3D points, which sample the loop length, by principal component analysis. This method is shown to retrieve in an easy way the main parameters that define the loop, e.g., the minor and major axes, the loop plane, the azimuthal and inclination angles, for the special case of a coplanar loop.

  6. Solar Mini-Dimming Kinematics and Their Positive Correlations with Coronal Mass Ejections and Prominence

    CERN Document Server

    Alipour, Nasibe

    2013-01-01

    Solar mini-dimmings can be detect in the Extreme Ultra-Violet coro- nal eruptions. Here, sequences of 171 A images taken by Solar Dynamic Observa- tory/Atmospheric Imaging Assembaly on 13 June 2010 are used. In this special day, both of coronal mass ejection and prominence were observed. The average velocities and accelerations of 500 mini-dimmings which were detected using on feature based classifier (Alipour et al 2012) are studied. The large number of mini-dimmings shows positive accelerations in the beginning times as similar as Coronal Mass Ejections. On the the start time of prominence eruptions, the number of mini-dimmings is increased to a maximum values. There is a positive correlation between the kinematics of mini- dimmings and both CME and prominences. This study can be extended to understand the exact relationship of CMEs and mini-dimmings.

  7. Modelling the Global Solar Corona II: Coronal Evolution and Filament Chirality Comparison

    CERN Document Server

    Yeates, A R; Van Ballegooijen, A A

    2007-01-01

    The hemispheric pattern of solar filaments is considered using newly-developed simulations of the real photospheric and 3D coronal magnetic fields over a 6-month period, on a global scale. The magnetic field direction in the simulation is compared directly with the chirality of observed filaments, at their observed locations. In our model the coronal field evolves through a continuous sequence of nonlinear force-free equilibria, in response to the changing photospheric boundary conditions and the emergence of new magnetic flux. In total 119 magnetic bipoles with properties matching observed active regions are inserted. These bipoles emerge twisted and inject magnetic helicity into the solar atmosphere. When we choose the sign of this active-region helicity to match that observed in each hemisphere, the model produces the correct chirality for up to 96% of filaments, including exceptions to the hemispheric pattern. If the emerging bipoles have zero helicity, or helicity of the opposite sign, then this percenta...

  8. Origin and Initial Evolution of Coronal Mass Ejections Observed by SDO, STEREO, and IRIS

    Science.gov (United States)

    Cheng, Xin

    2016-07-01

    Magnetic flux rope (MFR) is a coherent magnetic structure with all magnetic field lines wrapping around its central axis. It has been supposed to exist in various celestial circumstances like the magnetotail of the Earth, the ionosphere of Venus, the Nebula, and the black hole system. In the solar atmosphere, the MFR is even believed to be a fundamental structure of coronal mass ejections, existing prior to and driving the solar eruptions. In this talk, I will present the observational signature of MFR; discuss its origin through analyzing EUV images, 3D magnetic field configurations, and thermal structures of associated active regions. Furthermore, the kinematic evolution of MFR and its role in the early dynamic process of coronal mass ejections are also included.

  9. The Impact of Atmospheric Heat Sources over the Eastern Tibetan Plateau and the Tropical Western Pacific on the Summer Rainfall over the Yangtze-River Basin

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter (namely, mode station variance percentage) based on 1951-2000 summer rainfall data from 160 stations in China. Compared with mode variance friction, the mode station variance percentage not only reveals more localized characteristics of the variability of the summer rainfall, but also helps to distinguish the regions with a high degree of dominant EOF modes representing the analyzed observational variable.The atmospheric circulation diagnostic studies with the NCEP/NCAR reanalysis daily data from 1966 to 2000 show that in summer, abundant (scarce) rainfall in the belt-area from the upper-middle reaches of the Yangtze River northeastward to the Huaihe River basin is linked to strong (weak) heat sources over the eastern Tibetan Plateau, while the abundant (scarce) rainfall in the area to the south of the middle-lower reaches of the Yangtze River is closely linked to the weak (strong) heat sources over the tropical western Pacific.

  10. Fast-mode Coronal Wave Trains Detected by SDO/AIA: Recent Observational Progress

    Science.gov (United States)

    Liu, Wei; Downs, Cooper; Ofman, Leon

    2016-05-01

    Quasi-periodic Fast Propagating wave trains (QFPs) are a new observational phenomenon discovered by SDO/AIA in extreme ultraviolet (EUV). They are fast-mode magnetosonic waves, closely related to quasi-periodic pulsations in solar flare emission ranging from radio to X-ray wavelengths. The significance of QFPs lies in their diagnostic potential, because they can provide critical clues to flare energy release and serve as new tools for coronal seismology. In this presentation, we report recent advances in observing QFPs. In particular, using differential emission measure (DEM) inversion, we found clear evidence of heating and cooling cycles that are consistent with alternating compression and rarefaction expected for magnetosonic wave pulses. We also found that different local magnetic and plasma environments can lead to two distinct types of QFPs located in different spatial domains with respect to their accompanying coronal mass ejections (CMEs). Moreover, recent IRIS observations of QFP source regions revealed sawtooth-like flare ribbon motions, indicative of pulsed magnetic reconnection, that are correlated with QFP excitation. More interestingly, from a statistical survey of over 100 QFP events, we found a preferential association with eruptive flares rather than confined flares. We will discuss the implications of these results and the potential roles of QFPs in coronal heating, energy transport, and solar eruptions.

  11. Tracing the Chromospheric and Coronal Magnetic Field with AIA, IRIS, IBIS, and ROSA Data

    Science.gov (United States)

    Aschwanden, Markus J.; Reardon, Kevin; Jess, Dave B.

    2016-07-01

    The aim of this study is to explore the suitability of chromospheric images for magnetic modeling of active regions. We use high-resolution images (≈ 0\\buildrel{\\prime\\prime}\\over{.} 2{--}0\\buildrel{\\prime\\prime}\\over{.} 3), from the Interferometric Bidimensional Spectrometer in the Ca ii 8542 Å line, the Rapid Oscillations in the Solar Atmosphere instrument in the Hα 6563 Å line, the Interface Region Imaging Spectrograph in the 2796 Å line, and compare non-potential magnetic field models obtained from those chromospheric images with those obtained from images of the Atmospheric Imaging Assembly in coronal (171 Å, etc.) and in chromospheric (304 Å) wavelengths. Curvi-linear structures are automatically traced in those images with the OCCULT-2 code, to which we forward-fitted magnetic field lines computed with the Vertical-current Approximation Nonlinear Force Free Field code. We find that the chromospheric images: (1) reveal crisp curvi-linear structures (fibrils, loop segments, spicules) that are extremely well-suited for constraining magnetic modeling; (2) that these curvi-linear structures are field-aligned with the best-fit solution by a median misalignment angle of {μ }2≈ 4^\\circ –7° (3) the free energy computed from coronal data may underestimate that obtained from cromospheric data by a factor of ≈ 2–4, (4) the height range of chromospheric features is confined to h≲ 4000 km, while coronal features are detected up to h = 35,000 km; and (5) the plasma-β parameter is β ≈ {10}-5{--}{10}-1 for all traced features. We conclude that chromospheric images reveal important magnetic structures that are complementary to coronal images and need to be included in comprehensive magnetic field models, something that is currently not accomodated in standard NLFFF codes.

  12. Radio AGN in galaxy clusters: heating hot atmospheres and driving supermassive black hole growth over cosmic time

    CERN Document Server

    Ma, C -J; Nulsen, P E J

    2012-01-01

    We estimate the average radio-AGN (mechanical) power deposited into the hot atmospheres of galaxy clusters over more than three quarters of the age of the Universe. Our sample was drawn from eight major X-ray cluster surveys, and includes 685 clusters in the redshift range 0.1

  13. The Source of Alfven Waves That Heat the Solar Corona

    Science.gov (United States)

    Ruzmaikin, A.; Berger, M. A.

    1998-01-01

    We suggest a source for high-frequency Alfven waves invoked in coronal heating and acceleration of the solar wind. The source is associated with small-scale magnetic loops in the chromospheric network.

  14. Coronal extension of the MURaM radiative MHD code: From quiet sun to flare simulations

    Science.gov (United States)

    Rempel, Matthias D.; Cheung, Mark

    2016-05-01

    We present a new version of the MURaM radiative MHD code, which includes a treatment of the solar corona in terms of MHD, optically thin radiative loss and field-aligned heat conduction. In order to relax the severe time-step constraints imposed by large Alfven velocities and heat conduction we use a combination of semi-relativistic MHD with reduced speed of light ("Boris correction") and a hyperbolic formulation of heat conduction. We apply the numerical setup to 4 different setups including a mixed polarity quiet sun, an open flux region, an arcade solution and an active region setup and find all cases an amount of coronal heating sufficient to maintain a corona with temperatures from 1 MK (quiet sun) to 2 MK (active region, arcade). In all our setups the Poynting flux is self-consistently created by photospheric and sub-photospheric magneto-convection in the lower part of our simulation domain. Varying the maximum allowed Alfven velocity ("reduced speed of light") leads to only minor changes in the coronal structure as long as the limited Alfven velocity remains larger than the speed of sound and about 1.5-3 times larger than the peak advection velocity. We also found that varying details of the numerical diffusivities that govern the resistive and viscous energy dissipation do not strongly affect the overall coronal heating, but the ratio of resistive and viscous energy dependence is strongly dependent on the effective numerical magnetic Prandtl number. We use our active region setup in order to simulate a flare triggered by the emergence of a twisted flux rope into a pre-existing bipolar active region. Our simulation yields a series of flares, with the strongest one reaching GOES M1 class. The simulation reproduces many observed properties of eruptions such as flare ribbons, post flare loops and a sunquake.

  15. Simulating the Environment Around Planet-Hosting Stars - I. Coronal Structure

    CERN Document Server

    Alvarado-Gómez, J D; Cohen, O; Drake, J J; Garraffo, C; Grunhut, J; Gombosi, T I

    2016-01-01

    We present the results of a detailed numerical simulation of the circumstellar environment around three exoplanet-hosting stars. A state-of-the-art global magnetohydrodynamic (MHD) model is considered, including Alfv\\'en wave dissipation as a self-consistent coronal heating mechanism. This paper contains the description of the numerical set-up, evaluation procedure, and the simulated coronal structure of each system (HD 1237, HD 22049 and HD 147513). The simulations are driven by surface magnetic field maps, recovered with the observational technique of Zeeman Doppler Imaging (ZDI). A detailed comparison of the simulations is performed, where two different implementations of this mapping routine are used to generate the surface field distributions. Quantitative and qualitative descriptions of the coronae of these systems are presented, including synthetic high-energy emission maps in the Extreme Ultra-Violet (EUV) and Soft X-rays (SXR) ranges. Using the simulation results, we are able to recover similar trend...

  16. Shock Formation and Energy Dissipation of Slow Magnetosonic Waves in Coronal Plumes

    Science.gov (United States)

    Cuntz, M.; Suess, S. T.

    2003-01-01

    We study the shock formation and energy dissipation of slow magnetosonic waves in coronal plumes. The wave parameters and the spreading function of the plumes as well as the base magnetic field strength are given by empirical constraints mostly from SOHO/UVCS. Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 bun, depending on the model parameters. In addition, following analytical estimates, we show that scale height of energy dissipation by the shocks ranges between 0.15 and 0.45 Rsun. This implies that shock heating by slow magnetosonic waves is relevant at most heights, even though this type of waves is apparently not a solely operating energy supply mechanism.

  17. On the statistical detection of propagating waves in polar coronal hole

    CERN Document Server

    Gupta, G R; Banerjee, Dhruba; Popescu, M; Doyle, J G

    2009-01-01

    Waves are important for the heating of the solar corona and the acceleration of the solar wind. We have examined a long spectral time series of a southern coronal hole observed on the 25th February 1997, with the SUMER spectrometer on-board SoHO. The observations were obtained in a transition region N IV 765 A line and in a low coronal Ne VIII 770 A line. Our observations indicate the presence of compressional waves with periods of 18 min. We also find significant power in shorter periods. Using Fourier techniques, we measured the phase delays between intensity as well as velocity oscillations in the two chosen lines over a frequency domain. From this we are able to measure the travel time of the propagating oscillations and, hence, the propagation speeds of the waves producing the oscillations. As the measured propagation speeds are subsonic, we conclude that the detected waves are slow magneto-acoustic in nature.

  18. Anomalous Cooling of Coronal Loops with Turbulent Suppression of Thermal Conduction

    CERN Document Server

    Bian, Nicolas H; Kontar, Eduard P; Emslie, A Gordon

    2016-01-01

    We investigate the impact of turbulent suppression of parallel heat conduction on the cooling of post-flare coronal loops. Depending on the value of the mean free path $\\lambda_T$ associated with the turbulent scattering process, we identify four main cooling scenarios. The overall temperature evolution, from an initial temperature in excess of $10^7$~K, is modeled in each case, highlighting the evolution of the dominant cooling mechanism throughout the cooling process. Comparison with observed cooling times allows the value of $\\lambda_T$ to be constrained, and interestingly this range corresponds to situations where collision-dominated conduction plays a very limited role, or even no role at all, in the cooling of post-flare coronal loops.

  19. Flare plasma dynamics obseved with the YOHKOH Bragg crystal spectrometer. III. Spectral signatures of electron-beam-heated atmospheres.

    Science.gov (United States)

    Marriska, John. T.

    1995-05-01

    Using numerical simulations of an electon-beam-heated solar flare, we investigate the observational consequences of variations in the electron beam total energy flux and the low-energy cut off value for models with both low and high initial densities. To do this we use the evolution of the physical parameters of the simulated flares to synthesize the time evolution of the spectrum in the wavelength region surrounding tha Ca xix resonance line. These spectra are then summed over a 9 s time interval to simulate typical spectra from the Yohkoh Bragg crystal spectometer and the first three moments are computed for comparison with observational results. This comparison shows that no single low or high initial density model satisfies the observed average behavior of the Ca xix resonance line. Low initial density models produce too large a blue shift velocity, while high initial density model have lines that are too narrow. Comparison of these models with the Yohkok data suggests that the key problem for models of the impulsive phase ofa solar flare is producing significant amounts of stationary hot plasma early in the flare.

  20. The role of active region coronal magnetic field in determining coronal mass ejection propagation direction

    OpenAIRE

    Wang, Rui; Liu, Ying D.; Dai, Xinghua; Yang, Zhongwei; Huang, Chong; Hu, Huidong

    2015-01-01

    We study the role of the coronal magnetic field configuration of an active region in determining the propagation direction of a coronal mass ejection (CME). The CME occurred in the active region 11944 (S09W01) near the disk center on 2014 January 7 and was associated with an X1.2 flare. A new CME reconstruction procedure based on a polarimetric technique is adopted, which shows that the CME changed its propagation direction by around 28$^\\circ$ in latitude within 2.5 R$_\\odot$ and 43$^\\circ$ ...

  1. 3D Coronal Slow Modes: Towards 3D Seismology

    OpenAIRE

    Marsh, M. S.; Walsh, R. W.; Plunkett, S.

    2009-01-01

    On 2008 January 10, the twin Solar Terrestrial Relations Observatory (STEREO) A and B spacecraft conducted a high time cadence study of the solar corona with the Extreme UltraViolet Imager (EUVI) instruments with the aim of investigating coronal dynamics. Observations of the three-dimensional propagation of waves within active region coronal loops and a measurement of the true coronal slow mode speed are obtained. Intensity oscillations with a period of approximately 12 minutes are observed t...

  2. Development and Study of Hard-Facing Materials on the Base of Heat-Resisting High-Hardness Steels for Plasma-Jet Hard- Facing in Shielding-Doping Nitrogen Atmosphere

    Science.gov (United States)

    Malushin, N. N.; Kovalev, A. P.; Valuev, D. V.; Shats, E. A.; Borovikov, I. F.

    2016-08-01

    The authors develop hard-facing materials on the base of heat-resisting highhardness steels for plasma-jet hard-facing in nitrogen atmosphere for manufacturing parts of mining and metallurgic equipment which significantly simplify the production process and effect a saving when producing bimetallic parts and tools.

  3. MxCSM: A massively-multiplexed coronal spectropolarimetric magnetometer for spaced-based coronal magnetometry

    Science.gov (United States)

    Lin, Haosheng

    2016-07-01

    This paper presents the conceptual design of a new coronal spectropolarimeter that employs large-scale multiplexing strategy to enable small coronagraphs to perform high-sensitivity measurements of the polarizations of multiple coronal emission lines (CELs) of the whole corona. The massively multiplexed coronal spectropolarimetric magnetometer (mxCSM) is a 25 cm catadioptric off-axis Gregorian coronagraph equipped with two 3-wavelength, 100-slit spectrographs to measure the polarization of six CELs simultaneously at 100 slits over a 1.2 degree x 1.0 degree (2.4 Rsun x 2.0 Rsun ) field of view. The large multiplexing capability of this design allows small coronagraphs to perform high sensitivity spectropolarimetric observations over a large FOV that until now is possible only with large aperture telescopes. Therefore, this design is ideally suited for space missions in which payload size and weight are important considerations. Future space missions with multiple mxCSMs in circumsolar orbits can provide polarization measurements of CELs from multiple lines of sight to enable true tomographic inversion of the coronal magnetic fields.

  4. The role of active region coronal magnetic field in determining coronal mass ejection propagation direction

    CERN Document Server

    Wang, Rui; Dai, Xinghua; Yang, Zhongwei; Huang, Chong; Hu, Huidong

    2015-01-01

    We study the role of the coronal magnetic field configuration of an active region in determining the propagation direction of a coronal mass ejection (CME). The CME occurred in the active region 11944 (S09W01) near the disk center on 2014 January 7 and was associated with an X1.2 flare. A new CME reconstruction procedure based on a polarimetric technique is adopted, which shows that the CME changed its propagation direction by around 28$^\\circ$ in latitude within 2.5 R$_\\odot$ and 43$^\\circ$ in longitude within 6.5 R$_\\odot$ with respect to the CME source region. This significant non-radial motion is consistent with the finding of M$\\ddot{o}$stl et al. (2015). We use nonlinear force-free field (NLFFF) and potential field source surface (PFSS) extrapolation methods to determine the configurations of the coronal magnetic field. We also calculate the magnetic energy density distributions at different heights based on the extrapolations. Our results show that the active region coronal magnetic field has a strong ...

  5. 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.

  6. 大气温室效应的一维辐射传热分析%One Dimensional Radiative Heat Transfer Analysis of Atmosphere Greenhouse Effects

    Institute of Scientific and Technical Information of China (English)

    刘彬; 帅永; 谈和平

    2011-01-01

    大气中温室气体对地面长波热辐射的吸收和再发射导致了温室效应.计算了大气不同高度200~50000 cm-1(0.2~50 μm)光谱吸收系数,采用一维大气介质模型和射线踪迹-节点分析法(RTNAM)的多层模型对大气中二氧化碳及水蒸气不同浓度情况下的大气温度进行了计算.结果表明标准大气CO2浓度增加1倍,对流层的温度上升0.453°C,若水蒸气浓度降低,CO2的温室效应更加明显.%Greenhouse gases absorb the thermal radiation from earth surface and reemit part of energy back. This progress leads to the greenhouse effects. Absorption coefficients at different latitude were calculated form 200 cm-1 to 50000 cm- 1(0.2~50μm). Using a one-dimensional radiative heat transfer model for atmosphere combined with multilayered model by Ray-Tracing/Nodal-Analyzing Method (RTNAM), atmospheric temperature fields were calculated under different CO2 and/or H2O concentration conditions. The results show that temperature in troposphere rise 0.453℃ if doubling of CO2Concentration, and if the concentration of H2O is lower, greenhouse effects of CO2 become more obvious.

  7. Precipitation rates and atmospheric heat transport during the Cenomanian greenhouse warming in North America: Estimates from a stable isotope mass-balance model

    Science.gov (United States)

    Ufnar, David F.; Ludvigson, Greg A.; Gonzalez, L.; Grocke, D.R.

    2008-01-01

    correlate with a mean annual average heat loss of 48??W/m2 at 10??N paleolatitude (present, 8??W/m2 at 15??N). The increased precipitation flux and moisture surplus in the mid-latitudes corresponds to a mean average annual heat gain of 180??W/m2 at 50??N paleolatitude (present, 17??W/m2 at 50??N). The Cenomanian low-latitude moisture deficit is similar to that of the Albian, however the mid-latitude (40-60??N) precipitation flux values and precipitation rates are significantly higher (Albian: 2200??mm/yr at 45??N; Cenomanian: 3600??mm/yr at 45??N). Furthermore, the heat transferred to the atmosphere via latent heat of condensation was approximately 10.6?? that of the present at 50??N. The intensified hydrologic cycle of the mid-Cretaceous greenhouse warming may have played a significant role in the poleward transfer of heat and more equable global conditions. Paleoclimatological reconstructions from multiple time periods during the mid-Cretaceous will aid in a better understanding of the dynamics of the hydrologic cycle and latent heat flux during greenhouse world conditions.

  8. Relationship of EUV Irradiance Coronal Dimming Slope and Depth to Coronal Mass Ejection Speed and Mass

    Science.gov (United States)

    Mason, James Paul; Woods, Thomas N.; Webb, David F.; Thompson, Barbara J.; Colaninno, Robin C.; Vourlidas, Angelos

    2016-10-01

    Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar flare, as is often the case, the flare component of the irradiance light curve in the cooler coronal emission can be isolated and removed using simultaneous measurements of warmer coronal lines. We apply this technique to 37 dimming events identified during two separate two-week periods in 2011 plus an event on 2010 August 7, analyzed in a previous paper to parameterize dimming in terms of depth and slope. We provide statistics on which combination of wavelengths worked best for the flare-removal method, describe the fitting methods applied to the dimming light curves, and compare the dimming parameters with corresponding CME parameters of mass and speed. The best linear relationships found are \\begin{eqnarray*}{v}{CME} ≤ft[\\displaystyle \\frac{{km}}{{{s}}}\\right] & ≈ & 2.36× {10}6 ≤ft[\\displaystyle \\frac{{km}}{ % }\\right]× {s}\\dim ≤ft[\\displaystyle \\frac{ % }{{{s}}}\\right]\\ {m}{CME} [{{g}}] & ≈ & 2.59× {10}15≤ft[\\displaystyle \\frac{g}{ % }\\right]× \\sqrt{{d}\\dim } [ % ].\\end{eqnarray*} These relationships could be used for space weather operations of estimating CME mass and speed using near-real-time irradiance dimming measurements.

  9. Nonlinear Resonant Excitation of Fast Sausage Waves in Current-Carrying Coronal Loops

    Science.gov (United States)

    Mikhalyaev, B. B.; Bembitov, D. B.

    2014-11-01

    We consider a model of a coronal loop that is a cylindrical magnetic tube with two surface electric currents. Its principal sausage mode has no cut-off in the long-wavelength limit. For typical coronal conditions, the period of the mode is between one and a few minutes. The sausage mode of flaring loops could cause long-period pulsations observed in microwave and hard X-ray ranges. There are other examples of coronal oscillations: long-period pulsations of active-region quiet loops in the soft X-ray emission are observed. We assume that these can also be caused by sausage waves. The question arises of how the sausage waves are generated in quiet loops. We assume that they can be generated by torsional oscillations. This process can be described in the framework of the nonlinear three-wave interaction formalism. The periods of interacting torsional waves are similar to the periods of torsional oscillations observed in the solar atmosphere. The timescale of the sausage-wave excitation is not much longer than the periods of interacting waves, so that the sausage wave is excited before torsional waves are damped.

  10. Analysis of an Anemone-Type Eruption in an On-Disk Coronal Hole

    Science.gov (United States)

    Tennant, Allyn; Sterling, Alphonse; Adams, Mitzi; Alexander, Caroline; Moore, Ronald; Woolley, Robert

    2016-01-01

    We report on an eruption seen in a very small coronal hole (about 120 arcseconds across), beginning at approximately 19:00 Universal Time on March 3, 2016. The event was initially observed by an amateur astronomer (RW) in an H-alpha movie from the Global Oscillation Network Group (GONG); the eruption attracted the attention of the observer because there was no nearby active region. To examine the region in detail, we use data from the Solar Dynamics Observatory (SDO), provided by the Atmospheric Imaging Assembly (AIA) in wavelengths 193 angstroms, 304 angstroms, and 94 angstroms, and the Helioseismic and Magnetic Imager (HMI). Data analysis and calibration activities such as scaling, rotation so that north is up, and removal of solar rotation are accomplished with SunPy. The eruption in low-cadence HMI data begins with the appearance of a bipole in the location of the coronal hole, followed by (apparent) expansion outwards when the intensity of the AIA wavelengths brighten; as the event proceeds, the coronal hole disappears. From high-cadence data, we will present results on the magnetic evolution of this structure, how it is related to intensity brightenings seen in the various SDO/AIA wavelengths, and how this event compares with the standard-anemone picture.

  11. Spatially resolved observations of coronal type II radio bursts with multiple lanes

    Science.gov (United States)

    Zimovets, Ivan; Vilmer, Nicole; Sadykov, Viacheslav

    We have analyzed two coronal type II radio bursts occurred during solar flare and CME events of 3 November 2010 and 16 February 2011. Characteristic feature of both these bursts is a separation into three bands (lanes) of emission. Joint analysis of spatially-resolved observations made by the Nancay Radioheliograph and the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory have shown that in both cases all three lanes were most probably emitted from above the CMEs. Radio sources of the first and the second lanes of each burst were located very close to each other and it is difficult to say unambiguously whether they were emitted from slightly different parts of a hypothetical shock front or from its upstream and downstream regions. However, emission region of the third lane, at least of the type II burst on 16 February 2011, was significantly different from emission region of the first two lanes. This confirms an old idea that different parts of a spatially extended non-planar shock wave can emit radiowaves from its different parts interacting with different coronal structures. Properties of these coronal structures are discussed.

  12. A closer look at a coronal loop rooted in a sunspot umbra

    CERN Document Server

    Chitta, L P; Young, P R

    2015-01-01

    Extreme UV (EUV) and X-ray loops in the solar corona connect regions of enhanced magnetic activity, but usually they are not rooted in the dark umbrae of sunspots. This is because there the strong magnetic field suppresses convection and thus the Poynting flux of magnetic energy into the upper atmosphere is not significant within the umbra, as long as there are no light bridges, umbral dots. Here we report a rare observation of a coronal loop rooted in the dark umbra of a sunspot without any traces of light bridges or umbral dots. We used the slit-jaw images and spectroscopic data from the IRIS and concentrate on the line profiles of O IV and Si IV that show persistent strong redshifted components in the loop rooted in the umbra. Using the ratios of O IV, we can estimate the density and thus investigate the mass flux. The coronal context and temperature diagnostics of these observations is provided through the EUV channels of the AIA. The coronal loop, embedded within cooler downflows, is hosting supersonic d...

  13. Interplanetary Propagation of Coronal Mass Ejections

    Science.gov (United States)

    Gopalswamy, Nat

    2011-01-01

    Although more than ten thousand coronal mass ejections (CMEs) are produced during each solar cycle at the Sun, only a small fraction hits the Earth. Only a small fraction of the Earth-directed CMEs ultimately arrive at Earth depending on their interaction with the solar wind and other large-scale structures such as coronal holes and CMEs. The interplanetary propagation is essentially controlled by the drag force because the propelling force and the solar gravity are significant only near the Sun. Combined remote-sensing and in situ observations have helped us estimate the influence of the solar wind on the propagation of CMEs. However, these measurements have severe limitations because the remote-sensed and in-situ observations correspond to different portions of the CME. Attempts to overcome this problem are made in two ways: the first is to model the CME and get the space speed of the CME, which can be compared with the in situ speed. The second method is to use stereoscopic observation so that the remote-sensed and in-situ observations make measurements on the Earth-arriving part of CMEs. The Solar Terrestrial Relations Observatory (STEREO) mission observed several such CMEs, which helped understand the interplanetary evolution of these CMEs and to test earlier model results. This paper discusses some of these issues and updates the CME/shock travel time estimates for a number of CMEs.

  14. Energetics of Solar Coronal Mass Ejections

    CERN Document Server

    Subramanian, P; Subramanian, Prasad; Vourlidas, Angelos

    2007-01-01

    Aims: To investigate if solar coronal mass ejections are driven mainly by coupling to the ambient solar wind, or through the release of internal magnetic energy. Methods: We examine the energetics of 39 flux-rope like coronal mass ejections (CMEs) from the Sun using data in the distance range $\\sim$ 2--20 $R_{{\\o}dot}$ from the Large Angle Spectroscopic Coronograph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). This comprises a complete sample of the best examples of flux-rope CMEs observed by LASCO in 1996-2001. Results: We find that 69% of the CMEs in our sample experience a clearly identifiable driving power in the LASCO field of view. For these CMEs which are driven, we examine if they might be deriving most of their driving power by coupling to the solar wind. We do not find conclusive evidence in favor of this hypothesis. On the other hand, we find that their internal magnetic energy is a viable source of the required driving power. We have estimated upper and lower limits on the power th...

  15. SAUSAGE OSCILLATIONS OF CORONAL PLASMA STRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Nakariakov, V. M.; Hornsey, C. [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Melnikov, V. F., E-mail: V.Nakariakov@warwick.ac.uk [Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, 196140 St Petersburg (Russian Federation)

    2012-12-20

    The dependence of the period of sausage oscillations of coronal loops on length together with the depth and steepness of the radial profile are determined. We performed a parametric study of linear axisymmetric fast magnetoacoustic (sausage) oscillations of coronal loops modeled as a field-aligned low-{beta} plasma cylinder with a smooth inhomogeneity of the plasma density in the radial direction. The density decreases smoothly in the radial direction. Sausage oscillations are impulsively excited by a perturbation of the radial velocity, localized at the cylinder axis and with a harmonic dependence on the longitudinal coordinate. The initial perturbation results in either a leaky or a trapped sausage oscillation, depending upon whether the longitudinal wavenumber is smaller or greater than a cutoff value, respectively. The period of the sausage oscillations was found to always increase with increasing longitudinal wavelength, with the dependence saturating in the long-wavelength limit. Deeper and steeper radial profiles of the Alfven speed correspond to more efficient trapping of sausage modes: the cutoff value of the wavelength increases with the steepness and the density (or Alfven speed) contrast ratio. In the leaky regime, the period is always longer than the period of a trapped mode of a shorter wavelength in the same cylinder. For shallow density profiles and shorter wavelengths, the period increases with wavelength. In the long-wavelength limit, the period becomes independent of the wavelength and increases with the depth and steepness of the radial profile of the Alfven speed.

  16. Ultraviolet spectroscopy of narrow coronal mass ejections

    CERN Document Server

    Dobrzycka, D; Biesecker, D A; Li, J; Ciaravella, A

    2003-01-01

    We present Ultraviolet Coronagraph Spectrometer (UVCS) observations of 5 narrow coronal mass ejections (CMEs) that were among 15 narrow CMEs originally selected by Gilbert et al. (2001). Two events (1999 March 27, April 15) were "structured", i.e. in white light data they exhibited well defined interior features, and three (1999 May 9, May 21, June 3) were "unstructured", i.e. appeared featureless. In UVCS data the events were seen as 4-13 deg wide enhancements of the strongest coronal lines HI Ly-alpha and OVI (1032,1037 A). We derived electron densities for several of the events from the Large Angle Spectrometric Coronagraph (LASCO) C2 white light observations. They are comparable to or smaller than densities inferred for other CMEs. We modeled the observable properties of examples of the structured (1999 April 15) and unstructured (1999 May 9) narrow CMEs at different heights in the corona between 1.5 and 2 R(Sun). The derived electron temperatures, densities and outflow speeds are similar for those two ty...

  17. Plasma motions and non-thermal line broadening in flaring twisted coronal loops

    CERN Document Server

    Gordovskyy, Mykola; Browning, Philippa

    2015-01-01

    Observation of coronal EUV spectral lines offers an opportunity to evaluate the thermal structure and flows in flaring atmospheres. This, in turn, can be used to estimate the partitioning between the thermal and kinetic energies released in flares. Our aim is to forward-model large-scale (50-10000 km) velocity distributions in order to interpret non-thermal broadening of different spectral EUV lines observed in flares. The developed models allow us to understand the origin of the observed spectral line shifts and broadening, and link these features to particular physical phenomena in flaring atmospheres. We use ideal MHD to derive unstable twisted magnetic fluxtube configurations in a gravitationally-stratified atmosphere. The evolution of these twisted fluxtubes is followed using resistive MHD, with anomalous resistivity depending on the local density and temperature. The model also takes into account the thermal conduction and radiative losses. The model allows us to evaluate average velocities and velocity...

  18. Solar Wind Associated with Near Equatorial Coronal Hole

    Indian Academy of Sciences (India)

    M. Hegde; K. M. Hiremath; Vijayakumar H. Doddamani; Shashanka R. Gurumath

    2015-09-01

    Present study probes temporal changes in the area and radiative flux of near equatorial coronal hole associated with solar wind parameters such as wind speed, density, magnetic field and temperature. Using high temporal resolution data from SDO/AIA for the two wave-lengths 193 Å and 211 Å, area and radiative flux of coronal holes are extracted and are examined for the association with high speed solar wind parameters. We find a strong association between different parameters of coronal hole and solar wind. For both the wavelength bands, we also compute 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 energy due to solar wind, it is conjectured that solar wind might have originated around the same height where 193 Å line is formed in the corona.

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

    CERN Document Server

    Meyer, K A; van Ballegooijen, A A; Parnell, C E; 10.1007/s11207-013-0272-1

    2013-01-01

    This paper is the third in a series of papers 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 hr time series of synthetic magnetograms produced from the model of Meyer, Mackay, van Ballegooijen and Parnell, 2011, Solar Phys., 272, 29. 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 ...

  20. Observational Characteristics of CMEs without Low Coronal Signatures

    CERN Document Server

    D'Huys, E; Poedts, S; Berghmans, D

    2014-01-01

    Solar eruptions are usually associated with a variety of phenomena occurring in the low corona before, during, and after onset of eruption. Though easily visible in coronagraph observations, so-called stealth coronal mass ejections (CMEs) do not obviously exhibit any of these low-coronal signatures. The presence or absence of distinct low coronal signatures can be linked to different theoretical models to establish the mechanisms by which the eruption is initiated and driven. In this study, 40 CMEs without low coronal signatures, occurring in 2012, are identified. Their observational and kinematic properties are analyzed and compared to those of regular CMEs. Solar eruptions without clear on-disk or low coronal signatures can lead to unexpected space weather impacts, since many early warning signs for significant space weather activity are not present in these events. A better understanding of their initiation mechanism(s) will considerably improve the ability to predict such space weather events.

  1. Temporal and Spatial Relationship of Flare Signatures and the Force-free Coronal Magnetic Field

    Science.gov (United States)

    Thalmann, J. K.; Veronig, A.; Su, Y.

    2016-08-01

    We investigate the plasma and magnetic environment of active region NOAA 11261 on 2011 August 2 around a GOES M1.4 flare/CME (SOL2011-08-02T06:19). We compare coronal emission at the (extreme) ultraviolet and X-ray wavelengths, using SDO AIA and RHESSI images, in order to identify the relative timing and locations of reconnection-related sources. We trace flare ribbon signatures at ultraviolet wavelengths in order to pin down the intersection of previously reconnected flaring loops in the lower solar atmosphere. These locations are used to calculate field lines from three-dimensional (3D) nonlinear force-free magnetic field models, established on the basis of SDO HMI photospheric vector magnetic field maps. Using this procedure, we analyze the quasi-static time evolution of the coronal model magnetic field previously involved in magnetic reconnection. This allows us, for the first time, to estimate the elevation speed of the current sheet’s lower tip during an on-disk observed flare as a few kilometers per second. A comparison to post-flare loops observed later above the limb in STEREO EUVI images supports this velocity estimate. Furthermore, we provide evidence for an implosion of parts of the flaring coronal model magnetic field, and identify the corresponding coronal sub-volumes associated with the loss of magnetic energy. Finally, we spatially relate the build up of magnetic energy in the 3D models to highly sheared fields, established due to the dynamic relative motions of polarity patches within the active region.

  2. A Sharp Look at Coronal Rain with Hinode/SOT and SST/CRISP

    CERN Document Server

    Antolin, P; van der Voort, L Rouppe; Verwichte, E; Vissers, G

    2012-01-01

    The tropical wisdom that when it is hot and dense we can expect rain might also apply to the Sun. Indeed, observations and numerical simulations have shown that strong heating at footpoints of loops, as is the case for active regions, puts their coronae out of thermal equilibrium, which can lead to a phenomenon known as catastrophic cooling. Following local pressure loss in the corona, hot plasma locally condenses in these loops and dramatically cools down to chromospheric temperatures. These blobs become bright in H-alpha and Ca II H in time scales of minutes, and their dynamics seem to be subject more to internal pressure changes in the loop rather than to gravity. They thus become trackers of the magnetic field, which results in the spectacular coronal rain that is observed falling down coronal loops. In this work we report on high resolution observations of coronal rain with the Solar Optical Telescope (SOT) on Hinode and CRISP at the Swedish Solar Telescope (SST). A statistical study is performed in whic...

  3. Statistical Evidence for the Existence of Alfv\\'enic Turbulence in Solar Coronal Loops

    CERN Document Server

    Liu, Jiajia; De Moortel, Ineke; Threlfall, James; Bethge, Christian

    2014-01-01

    Recent observations have demonstrated that waves which are capable of carrying large amounts of energy are ubiquitous throughout the solar corona. However, the question of how this wave energy is dissipated (on which time and length scales) and released into the plasma remains largely unanswered. Both analytic and numerical models have previously shown that Alfv\\'enic turbulence may play a key role not only in the generation of the fast solar wind, but in the heating of coronal loops. In an effort to bridge the gap between theory and observations, we expand on a recent study [De Moortel et al., ApJL, 782:L34, 2014] by analyzing thirty-seven clearly isolated coronal loops using data from the Coronal Multi-channel Polarimeter (CoMP) instrument. We observe Alfv\\'enic perturbations with phase speeds which range from 250-750 km/s and periods from 140-270 s for the chosen loops. While excesses of high frequency wave-power are observed near the apex of some loops (tentatively supporting the onset of Alfv\\'enic turbu...

  4. The initiation of coronal mass ejections by magnetic flux emergence

    Science.gov (United States)

    Dubey, G.; van der Holst, B.; Poedts, S.

    2006-12-01

    Aims.The initiation of solar Coronal Mass Ejections (CMEs) is studied in the framework of computational Magneto-Hydro-Dynamics (MHD). Methods: .The initial configuration includes a magnetic flux rope that is embedded in a gravitationally stratified solar atmosphere with a background dipole magnetic field in spherical, axi-symmetric geometry. The flux rope is in equilibrium due to an image current below the photosphere. An emerging magnetic flux triggering mechanism is used to make this equilibrium configuration unstable. Results: . When the magnetic flux emerges within the filament below the flux rope this results in a catastrophic behavior similar to earlier, more simple models. As a result, the flux rope rises and a current sheet forms below it. It is shown that the magnetic reconnection in the current sheet below the flux rope in combination with the outward curvature forces results in a fast ejection of the flux rope as observed for solar CMEs. We have done a parameter study of the effect of the flux emergence rate on the velocity and the acceleration of the resulting CMEs.

  5. A Filament-Associated Halo Coronal Mass Ejection

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There are only a few observations published so far that show the initiation of a coronal mass ejection (CME) and illustrate the magnetic changes in the surface origin of a CME. Any attempt to connect a CME with its local solar activities is meaningful. In this paper we present a clear instance of a halo CME initiation. A careful analysis of magnetograms shows that the only obvious magnetic changes in the surface region of the CME is a magnetic flux cancellation underneath a quiescent filament. The early disturbance was seen as the slow upward motion in segments of the quiescent filament. Four hours later, the filament was accelerated to about 50 km s-1 and erupted. While a small part of the material in the filament was ejected into the upper corona, most of the mass was transported to a nearby region. About forty minutes later, the transported mass was also ejected partially to the upper corona. The eruption of the filament triggered a two-ribbon flare, with post-flare loops connecting the flare ribbons. A halo CME, which is inferred to be associated with the eruptive filament, was observed from LASCO/C2 and C3. The halo CME contained two CME events, each event corresponded to a partial mass ejection of the filament. We suggest that the magnetic reconnection at the lower atmosphere is responsible for the filament eruption and the halo CME.

  6. Solar velocity field determined tracking coronal bright points

    Science.gov (United States)

    Brajša, R.; Sudar, D.; Skokić, I.; Saar, S. H.; Žic, T.

    Preliminary data from Atmospheric Imaging Assembly (AIA) instrumenton board Solar Dynamics Observatory (SDO) satellite were used to determine solar differential rotation and related phenomena. A segmentation algorithm, which uses multiple AIA channels in search for intensity enhancements in EUV and X-ray parts of the spectrum compared to the background intensity, was applied to obtain positional information of coronal bright points (CBPs). More than 60000 position measurements of more than 10000 identified CBPs from the period 1 - 2 January 2011 were analyzed. Rotational and meridional velocities were determined by tracking identified CBPs and various filters were used to exclude erroneous results. Also, proper motions of CBPs were calculated from rotation velocity residuals and meridional velocities. Proper motions of CBPs were investigated using a random walk model and the diffusion constant was calculated. These results were compared with the previous ones obtained by other instruments and methods (especially with the SOHO-EIT and Hinode data) and a striking agreement of the obtained diffusion constant with results from other studies was found.

  7. 某常减压装置换热网络节能改造%Retrofit heat exchanger network of an oil refinery atmospheric-vacuum distillation unit

    Institute of Scientific and Technical Information of China (English)

    杨智勇; 姜涛; 尹兆明

    2013-01-01

    应用夹点技术对某炼油厂常减压蒸馏装置换热器网络的用能状况进行分析,找出其瓶颈所在,对整个网络进行调优,提高拔头油换热终温、网络可操作性和操作弹性,求得最小网络投资和操作费用.根据现有换热网络流程结构,收集、提取相关冷热流股的数据,按照问题表格法进行夹点计算,确定原换网的最小传热温差、夹点位置及相关用能信息.绘制原换热网络格子图进行用能诊断,分析其中存在的不合理用能问题,确定能量回收目标和节能潜力;依据夹点设计法基本原则,同时考虑到现行换热网络结构,分两步进行整体调优.优化连接方式、换热顺序,充分利用原有换热器,首先考虑夹点处物流的匹配,然后分别向两头进行物流间的匹配换热,重新匹配某些冷热流股,调整局部传热温差,使换热器的负荷及温差更趋于合理.制定出两套改造方案,计算了改造费用和投资回收期,分析了两方案的优劣.两方案均消除了原换热网络中违反夹点设计基本原则的不合理用能现象,节约了加热和冷却公用工程费用,在原生产换热网络的基础上,两方案分别将拔头原油的换热终温提高了12℃和17℃,同时提高了整套装置操作弹性.%The pinch technology was applied to analysis and study on Heat Exchanger Network (HEN) of an oil refinery atmospheric-vacuum distillation unit to find out the bottleneck of its energy utilization and optimize the entire network to improving topped oil heat temperature,network operation and flexibility,to achieve the minimum network investment and operation cost.Based on the existing heat exchanger networks structure,collection,extraction associated with hot and cold stream data,in accordance with the problem table Algorithm for pinch point of the HEN,the original exchange network's △Tmin,the pinch point position and related information was determined.Grid Diagram of original

  8. Spicules and their on-disk counterparts, the main driver for solar chromospheric heating?

    CERN Document Server

    Puschmann, Klaus Gerhard

    2016-01-01

    The question how the outer solar atmosphere is heated from solar photospheric temperatures of about 5800K up to solar chromospheric and coronal temperatures of about 20 000K and millions of degrees respectively, remained without any satisfying answer for centuries. On 4 May 2005, I recorded several time series of Halpha line scans with the GREGOR Fabry-Perot Interferometer, still deployed at the German Vacuum Tower Telescope (VTT), for different solar limb and on-disc positions as well for quiet sun at solar disk center. The spatially and temporally highly resolved time series of Halpha line parameters reveal the entire and detailed complexity as well as the overwhelming dynamics of spicules covering the entire solar disk, thus apparently confirming spicules as the potential driver for chromospheric heating of both the Sun and sun-like stars.

  9. 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.

  10. Measurements of coronal Faraday rotation at 4.6 R {sub ☉}

    Energy Technology Data Exchange (ETDEWEB)

    Kooi, Jason E.; Fischer, Patrick D.; Buffo, Jacob J.; Spangler, Steven R., E-mail: jason-kooi@uiowa.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52240 (United States)

    2014-03-20

    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 {sub ☉}. 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 {sub ☉}. 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{sup –2} along the two lines of sight. The implications of these results for Joule heating and wave heating are briefly discussed.

  11. CHARACTERISTIC LENGTH OF ENERGY-CONTAINING STRUCTURES AT THE BASE OF A CORONAL HOLE

    International Nuclear Information System (INIS)

    An essential parameter for models of coronal heating and fast solar wind acceleration that rely on the dissipation of MHD turbulence is the characteristic energy-containing length λ of the squared velocity and magnetic field fluctuations (u2 and b2) transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale directly defines the heating rate. We use a time series analysis of solar granulation and magnetic field measurements inside two CHs obtained with the New Solar Telescope at Big Bear Solar Observatory. A data set for transverse magnetic fields obtained with the Solar Optical Telescope/Spectro-Polarimeter on board the Hinode spacecraft was utilized to analyze the squared transverse magnetic field fluctuations bt2. Local correlation tracking was applied to derive the squared transverse velocity fluctuations u 2. We find that for u 2 structures, the Batchelor integral scale λ varies in a range of 1800-2100 km, whereas the correlation length sigmav and the e-folding length L vary between 660 and 1460 km. Structures for bt2 yield λ ≈ 1600 km, sigmav ≈ 640 km, and L ≈ 620 km. An averaged (over λ, sigmav, and L) value of the characteristic length of u 2 fluctuations is 1260 ± 500 km, and that of bt2 is 950 ± 560 km. The characteristic length scale in the photosphere is approximately 1.5-50 times smaller than that adopted in previous models (3-30 × 103 km). Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration

  12. Using Coronal Loops to Reconstruct the Magnetic Field of an Active Region Before and After a Major Flare

    CERN Document Server

    Malanushenko, A; DeRosa, M L; Wheatland, M S

    2013-01-01

    The shapes of solar coronal loops are sensitive to the presence of electrical currents that are the carriers of the nonpotential energy available for impulsive activity. We use this information in a new method for modeling the coronal magnetic field of AR 11158 as a nonlinear force-free field (NLFFF). The observations used are coronal images around time of major flare activity on 2011/02/15, together with the surface line-of-sight magnetic field measurements. The data are from the Helioseismic and Magnetic Imager and Atmospheric Imaging Assembly (HMI and AIA, respectively) onboard the Solar Dynamics Observatory (SDO). The model fields are constrained to approximate the coronal loop configurations as closely as possible, while also 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 t...

  13. Transverse flow deflections associated with fast coronal mass ejecta in interplanetary space

    International Nuclear Information System (INIS)

    Using a bidirectional electron heat flux signature to identify coronal mass ejections, CMEs, in the solar wind at 1 AU, we find that the fast CMEs which drive interplanetary shocks are preferentially deflected eastward in transit outward from the sun. A corresponding westward deflection usually occurs in the compressed ambient solar wind plasma ahead of these CMEs. We suggest that this preferential pattern of deflections is caused primarily by the asymmetrical draping of the ambient interplanetary magnetic field about fast CMEs. 10 refs., 7 figs

  14. Prebiotic chemistry and atmospheric warming of early Earth by an active young Sun

    Science.gov (United States)

    Airapetian, V. S.; Glocer, A.; Gronoff, G.; Hébrard, E.; Danchi, W.

    2016-06-01

    Nitrogen is a critical ingredient of complex biological molecules. Molecular nitrogen, however, which was outgassed into the Earth’s early atmosphere, is relatively chemically inert and nitrogen fixation into more chemically reactive compounds requires high temperatures. Possible mechanisms of nitrogen fixation include lightning, atmospheric shock heating by meteorites, and solar ultraviolet radiation. Here we show that nitrogen fixation in the early terrestrial atmosphere can be explained by frequent and powerful coronal mass ejection events from the young Sun--so-called superflares. Using magnetohydrodynamic simulations constrained by Kepler Space Telescope observations, we find that successive superflare ejections produce shocks that accelerate energetic particles, which would have compressed the early Earth’s magnetosphere. The resulting extended polar cap openings provide pathways for energetic particles to penetrate into the atmosphere and, according to our atmospheric chemistry simulations, initiate reactions converting molecular nitrogen, carbon dioxide and methane to the potent greenhouse gas nitrous oxide as well as hydrogen cyanide, an essential compound for life. Furthermore, the destruction of N2, CO2 and CH4 suggests that these greenhouse gases cannot explain the stability of liquid water on the early Earth. Instead, we propose that the efficient formation of nitrous oxide could explain a warm early Earth.

  15. Atmospheric heating due to black carbon aerosol during the summer monsoon period over Ballia: A rural environment over Indo-Gangetic Plain

    Science.gov (United States)

    Tiwari, S.; Dumka, U. C.; Hopke, P. K.; Tunved, P.; Srivastava, A. K.; Bisht, D. S.; Chakrabarty, R. K.

    2016-09-01

    Black carbon (BC) aerosols are one of the most uncertain drivers of global climate change. The prevailing view is that BC mass concentrations are low in rural areas where industrialization and vehicular emissions are at a minimum. As part of a national research program called the "Ganga Basin Ground Based Experiment-2014 under the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) Phase-III" of Ministry of Earth Sciences, Government of India, the continuous measurements of BC and particulate matter (PM) mass concentrations, were conducted in a rural environment in the highly-polluted Indo-Gangetic Plain region during 16th June to 15th August (monsoon period), 2014. The mean mass concentration of BC was 4.03 (± 0.85) μg m- 3 with a daily variability between 2.4 and 5.64 μg m- 3, however, the mean mass PM concentrations [near ultrafine (PM1.0), fine (PM2.5) and inhalable (PM10)] were 29.1(± 16.2), 34.7 (± 19.9) and 43.7 (± 28.3) μg m- 3, respectively. The contribution of BC in PM1.0 was approximately 13%, which is one of the highest being recorded. Diurnally, the BC mass concentrations were highest (mean: 5.89 μg m- 3) between 20:00 to 22:00 local time (LT) due to the burning of biofuels/biomass such as wood, dung, straw and crop residue mixed with dung by the local residents for cooking purposes. The atmospheric direct radiative forcing values due to the composite and BC aerosols were determined to be + 78.3, + 44.9, and + 45.0 W m- 2 and + 42.2, + 35.4 and + 34.3 W m- 2 during the months of June, July and August, respectively. The corresponding atmospheric heating rates (AHR) for composite and BC aerosols were 2.21, 1.26 and 1.26; and 1.19, 0.99 and 0.96 K day- 1 for the month of June, July and August, respectively, with a mean of 1.57 and 1.05 K day- 1 which was 33% lower AHR (BC) than for the composite particles during the study period. This high AHR underscores the importance of absorbing aerosols such as BC contributed by

  16. Decadal Relationship Between Atmospheric Heat Source and Winter-Spring Snow Cover over the Tibetan Plateau and Rainfall in East China

    Institute of Scientific and Technical Information of China (English)

    ZHU Yuxiang; DING Yihui; XU Huaigang

    2008-01-01

    By using a reverse computation method and the NCEP/NCAR daily reanalysis data from 1960 to 2004,the atmospheric heat source(AHS)was calculated and analyzed.The resuIts show that AHS over the Tibetan Plateau(TP)and its neighboring areas takes on a persistent downtrend in spring and summer during the foregone 50 years.especially the latest 20 years.Snow depth at 50 stations over the TP in winter and spring presents an increase,especially the spring Snow depth exhibits a sharp increase in the late 1970s.A close negative correlation exists between snow cover and AHS over the TP and its neighboring areas,as revealed by an SVD analysis,namely if there is more snow over the TP in winter and spring,then the weaker AHS would appear over the TP in spring and summer.The SVD analysis between AHS over the TP in spring and summer and rainfall at 160 stations indicates that the former has a negative correlation with summer precipitation in the middle and lower reaches of the Yangtze River,and a positive correlation with that in South China and North China.The SVD allalysis of both snow cover over the TP in winter and spring and rainfall at the same 160 stations indicates that the former has a marked positive correlation with precipitation in the middle and lower reaches of the Yangtze River,and a reversed correlation in South China and North China.On the decadal scale,the AHS and winter and spring snow cover over the TP have a close correlation with the decadal precipitation pattern shift(southern flood and northern drought)in East China.The mechanism on how the AHS over the TP influences rainfall in East China is discussed.The weakening of AHS over the TP in spring and summer reduces the thermodynamic diirerence between ocean and continent,leading to a weaker East Asian summer monsoon,which brings more water vapor to the Yangtze Rivet Valley and less water vapor to North China.Meanwhile.the weakening of AHS over the TP renders the position of the subtropical high further

  17. Relationship Between a Coronal Mass Ejection-Driven Shock and a Coronal Metric Type II Burst

    Science.gov (United States)

    Liu, Y.; Luhmann, J. G.; Bale, S. D.; Lin, R. P.

    2009-02-01

    It has been an intense matter of debate whether coronal metric type II bursts are generated by coronal mass ejection (CME)-driven shocks or flare blast waves. Using unprecedented high-cadence observations from STEREO/SECCHI, we investigate the relationship between a metric type II event and a shock driven by the 2007 December 31 CME. The existence of the CME-driven shock is indicated by the remote deflection of coronal structures, which is in good timing with the metric type II burst. The CME speed is about 600 km s-1 when the metric type II burst occurs, much larger than the Alfvén speed of 419-489 km s-1 determined from band splitting of the type II burst. A causal relationship is well established between the metric and decametric-hectometric type II bursts. The shock height-time curve determined from the type II bands is also consistent with the shock propagation obtained from the streamer deflection. These results provide unambiguous evidence that the metric type II burst is caused by the CME-driven shock.

  18. Coronal Mass Ejections: From Sun to Earth

    Science.gov (United States)

    Patsourakos, S.

    2016-06-01

    Coronal Mass Ejections (CMEs) are gigantic expulsions of magnetized plasmas from the solar corona into the interplanetary (IP) space. CMEs spawn ~ 1015 gr of mass and reach speeds ranging between several hundred to a few thousand km/s (e.g., Gopalswamy et al. 2009; Vourlidas et al. 2010). It takes 1-5 days for a CME to reach Earth. CMEs are one of the most energetic eruptive manifestations in the solar system and are major drivers of space weather via their magnetic fields and energetic particles, which are accelerated by CME-driven shocks. In this review we give a short account of recent, mainly observational, results on CMEs from the STEREO and SDO missions which include the nature of their pre-eruptive and eruptive configurations and the CME propagation from Sun to Earth. We conclude with a discussion of the exciting capabilities in CME studies that will soon become available from new solar and heliospheric instrumentation.

  19. Magnetic structure of Coronal Mass Ejections

    CERN Document Server

    Lyutikov, Maxim

    2012-01-01

    We present several models of the magnetic structure of solar coronal mass ejections (CMEs). First, we model CMEs as expanding force-free magnetic structures. While keeping the internal magnetic field structure of the stationary solutions, expansion leads to complicated internal velocities and rotation, while the field structures remain force-free. Second, expansion of a CME can drive resistive dissipation within the CME changing the ionization states of different ions. We fit in situ measurements of ion charge states to the resistive spheromak solutions. Finally, we consider magnetic field structures of fully confined stable magnetic clouds containing both toroidal and poloidal magnetic fields and having no surface current sheets. Expansion of such clouds may lead to sudden onset of reconnection events.

  20. Kinematical properties of coronal mass ejections

    CERN Document Server

    Temmer, Manuela

    2016-01-01

    Coronal mass ejections (CMEs) are the most dynamic phenomena in our solar system. They abruptly disrupt the continuous outflow of solar wind by expelling huge clouds of magnetized plasma into interplanetary space with velocities enabling to cross the Sun-Earth distance within a few days. Earth-directed CMEs may cause severe geomagnetic storms when their embedded magnetic fields and the shocks ahead compress and reconnect with the Earth's magnetic field. The transit times and impacts in detail depend on the initial CME velocity, size, and mass, as well as on the conditions and coupling processes with the ambient solar wind flow in interplanetary space. The observed CME parameters may be severly affected by projection effects and the constant changing environmental conditions are hard to derive. This makes it difficult to fully understand the physics behind CME evolution, preventing to do a reliable forecast of Earth-directed events. This short review focusing on observational data, shows recent methods which w...