WorldWideScience

Sample records for sun magnetic fields

  1. Polar Magnetic Field Reversals of the Sun in Maunder Minimum

    Indian Academy of Sciences (India)

    V. I. Makarov; A. G. Tlatov

    2000-09-01

    A possible scenario of polar magnetic field reversal of the Sun during the Maunder Minimum (1645-1715) is discussed using data of magnetic field reversals of the Sun for 1880-1991 and the 14C content variations in the bi-annual rings of the pine-trees in 1600-1730 yrs.

  2. Convective intensification of magnetic fields in the quiet Sun

    CERN Document Server

    Bushby, P J; Proctor, M R E; Weiss, N O

    2008-01-01

    Kilogauss-strength magnetic fields are often observed in intergranular lanes at the photosphere in the quiet Sun. Such fields are stronger than the equipartition field $B_e$, corresponding to a magnetic energy density that matches the kinetic energy density of photospheric convection, and comparable with the field $B_p$ that exerts a magnetic pressure equal to the ambient gas pressure. We present an idealised numerical model of three-dimensional compressible magnetoconvection at the photosphere, for a range of values of the magnetic Reynolds number. In the absence of a magnetic field, the convection is highly supercritical and is characterised by a pattern of vigorous, time-dependent, ``granular'' motions. When a weak magnetic field is imposed upon the convection, magnetic flux is swept into the convective downflows where it forms localised concentrations. Unless this process is significantly inhibited by magnetic diffusion, the resulting fields are often much greater than $B_e$, and the high magnetic pressur...

  3. Interpretation of the coronal magnetic field configuration of the Sun

    Institute of Scientific and Technical Information of China (English)

    Bo Li; Xing Li; Hui Yu

    2012-01-01

    The origin of the heliospheric magnetic flux on the Sun,and hence the origin of the solar wind,is a topic of hot debate.While the prevailing view is that the solar wind originates from outside the coronal streamer helmets,there also exists the suggestion that the open magnetic field spans a far wider region.Without the definitive measurement of the coronal magnetic field,it is difficult to unambiguously resolve the conflict between the two scenarios.We present two 2-dimensional,Alfvénic-turbulence-based models of the solar corona and solar wind,one with and the other without a closed magnetic field region in the inner corona.The purpose of the latter model is to test whether it is possible to realize a picture suggested by polarimetric measurements of the corona using the Fe ⅩⅢ 10747(A) line,where open magnetic field lines seem to penetrate the streamer base.The boundary conditions at the coronal base are able to account for important observational constraints,especially those on the magnetic flux distribution.Interestingly,the two models provide similar polarized brightness (pB) distributions in the field of view (FOV) of SOHO/LASCO C2 and C3 coronagraphs.In particular,a dome-shaped feature is present in the C2 FOV even for the model without a closed magnetic field.Moreover,both models fit the Ulysses data scaled to 1 AU equally well.We suggest that:1) The pB observations cannot be safely taken as a proxy for the magnetic field topology,as is often implicitly assumed.2) The Ulysses measurements,especially the one showing a nearly uniform distribution with heliocentric latitude of the radial magnetic field,do not rule out the ubiquity of open magnetic fields on the Sun.

  4. The reversal of the Sun's magnetic field in cycle 24

    CERN Document Server

    Mordvinov, Alexander V; Bertello, Luca; Petrie, Gordon J D

    2016-01-01

    Analysis of synoptic data from the Vector Stokes Magnetograph (VSM) of the Synoptic Optical Long-term Investigations of the Sun (SOLIS) and the NASA/NSO Spectromagnetograph (SPM) at the NSO/Kitt Peak Vacuum Telescope facility shows that the reversals of solar polar magnetic fields exhibit elements of a stochastic process, which may include the development of specific patterns of emerging magnetic flux, and the asymmetry in activity between northern and southern hemispheres. The presence of such irregularities makes the modeling and prediction of polar field reversals extremely hard if possible. In a classical model of solar activity cycle, the unipolar magnetic regions (UMRs) of predominantly following polarity fields are transported polewards due to meridional flows and diffusion. The UMRs gradually cancel out the polar magnetic field of the previous cycle, and re-build the polar field of opposite polarity setting the stage for the next cycle. We show, however, that this deterministic picture can be easily a...

  5. Inference of magnetic fields in the very quiet Sun

    Science.gov (United States)

    Martínez González, M. J.; Pastor Yabar, A.; Lagg, A.; Asensio Ramos, A.; Collados, M.; Solanki, S. K.; Balthasar, H.; Berkefeld, T.; Denker, C.; Doerr, H. P.; Feller, A.; Franz, M.; González Manrique, S. J.; Hofmann, A.; Kneer, F.; Kuckein, C.; Louis, R.; von der Lühe, O.; Nicklas, H.; Orozco, D.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma, M.; Waldman, T.; Volkmer, R.

    2016-11-01

    Context. Over the past 20 yr, the quietest areas of the solar surface have revealed a weak but extremely dynamic magnetism occurring at small scales (data with high spatio-temporal resolution. Aims: We present high-precision spectro-polarimetric data with high spatial resolution (0.4'') of the very quiet Sun at 1.56 μm obtained with the GREGOR telescope to shed some light on this complex magnetism. Methods: We used inversion techniques in two main approaches. First, we assumed that the observed profiles can be reproduced with a constant magnetic field atmosphere embedded in a field-free medium. Second, we assumed that the resolution element has a substructure with either two constant magnetic atmospheres or a single magnetic atmosphere with gradients of the physical quantities along the optical depth, both coexisting with a global stray-light component. Results: Half of our observed quiet-Sun region is better explained by magnetic substructure within the resolution element. However, we cannot distinguish whether this substructure comes from gradients of the physical parameters along the line of sight or from horizontal gradients (across the surface). In these pixels, a model with two magnetic components is preferred, and we find two distinct magnetic field populations. The population with the larger filling factor has very weak ( 150 G) horizontal fields similar to those obtained in previous works. We demonstrate that the field vector of this population is not constrained by the observations, given the spatial resolution and polarimetric accuracy of our data. The topology of the other component with the smaller filling factor is constrained by the observations for field strengths above 250 G: we infer hG fields with inclinations and azimuth values compatible with an isotropic distribution. The filling factors are typically below 30%. We also find that the flux of the two polarities is not balanced. From the other half of the observed quiet-Sun area 50% are two

  6. Flux Transport and the Sun's Global Magnetic Field

    Science.gov (United States)

    Hathaway, David H.

    2010-01-01

    The Sun s global magnetic field is produced and evolved through the emergence of magnetic flux in active regions and its transport across the solar surface by the axisymmetric differential rotation and meridional flow and the non-axisymmetric convective flows of granulation, supergranulation, and giant cell convection. Maps of the global magnetic field serve as the inner boundary condition for space weather. The photospheric magnetic field and its evolution determine the coronal and solar wind structures through which CMEs must propagate and in which solar energetic particles are accelerated and propagate. Producing magnetic maps which best represent the actual field configuration at any instant requires knowing the magnetic field over the observed hemisphere as well as knowing the flows that transport flux. From our Earth-based vantage point we only observe the front-side hemisphere and each pole is observable for only six months of the year at best. Models for the surface magnetic flux transport can be used to provide updates to the magnetic field configuration in those unseen regions. In this presentation I will describe successes and failures of surface flux transport and present new observations on the structure, the solar cycle variability, and the evolution of the flows involved in magnetic flux transport. I find that supergranules play the dominant role due to their strong flow velocities and long lifetimes. Flux is transported by differential rotation and meridional flow only to the extent that the supergranules participate in those two flows.

  7. Structure of magnetic fields on the quiet sun

    Science.gov (United States)

    Wang, Haimin

    1988-01-01

    To obtain quantitative temporal and spatial information on the network magnetic fields, auto- and cross-correlation techniques are applied to the Big Bear videomagnetogram data. The average size of the network magnetic elements derived from the auto-correlation curve is about 5700 km. The distance between the primary and secondary peak in the auto-correlation curve is about 17,000 km, which is half of the size of the supergranule as determined from the velocity map. The canceling features and the emergence of ephemeral regions are the major sources for the loss and replenishment of magnetic flux on the quiet sun.

  8. Convectively driven sinks and magnetic fields in the quiet Sun

    CERN Document Server

    Requerey, Iker S; Rubio, Luis R Bellot; Pillet, Valentín Martínez; Solanki, Sami K; Schmidt, Wolfgang

    2016-01-01

    We study the relation between mesogranular flows, convectively driven sinks and magnetic fields using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board Sunrise. We obtain the horizontal velocity flow fields of two quiet-Sun regions (31.2 $\\times$ 31.2 Mm$^{2}$) via local correlation tracking. Mesogranular lanes and the central position of sinks are identified using Lagrange tracers. We find $6.7\\times10^{-2}$ sinks per Mm$^{2}$ in the two observed regions. The sinks are located at the mesogranular vertices and turn out to be associated with (1) horizontal velocity flows converging to a central point and (2) long-lived downdrafts. The spatial distribution of magnetic fields in the quiet Sun is also examined. The strongest magnetic fields are preferentially located at sinks. We find that 40 \\% of the pixels with longitudinal component of the magnetic field stronger than 500 G are located in the close neighborhood of sinks. In contrast, the small-scale ma...

  9. Scaling laws for magnetic fields on the quiet Sun

    CERN Document Server

    Stenflo, Jan O

    2012-01-01

    The Sun's magnetic field is structured over a range of scales that span approximately seven orders of magnitudes, four of which lie beyond the resolving power of current telescopes. Here we have used a Hinode SOT/SP deep mode data set for the quiet-sun disk center in combination with constraints from the Hanle effect to derive scaling laws that describe how the magnetic structuring varies from the resolved scales down to the magnetic diffusion limit, where the field ceases to be frozen-in. The focus of the analysis is a derivation of the magnetic energy spectrum, but we also discuss the scale dependence of the probability density function (PDF) for the flux densities and the role of the cancellation function for the average unsigned flux density. Analysis of the Hinode data set with the line-ratio method reveals a collapsed flux population in the form of flux tubes with a size distribution that is peaked in the 10-100 km range. Magnetic energy is injected into this scale range by the instability mechanism of ...

  10. Mapping Magnetic Field Lines between the Sun and Earth

    Science.gov (United States)

    Li, Bo; Cairns, Iver; Gosling, J. T.; Lobzin, Vasili; Steward, Graham; Neudegg, Dave; Owens, Mathew

    2016-07-01

    Magnetic field topologies between the Sun and Earth are important for the connectivity to Earth of solar suprathermal particles, e.g., solar energetic particles and the electrons in type III solar radio bursts. An approach is developed for mapping large-scale magnetic field lines in the solar equatorial plane, using near-Earth observations and a solar wind model with nonzero azimuthal magnetic field at the source surface. The predicted field line maps show that near both minimal and maximal solar activity the field lines are typically open and that loops with both ends either connected to or disconnected from the Sun occur sometimes. The open field lines, nonetheless, often do not closely follow the Parker spiral, being less or more tightly wound, or strongly azimuthally or radially oriented, or inverted. Assessments of the mapped field line configurations using time-varying suprathermal electron pitch angle distributions (PADs) observed by Wind show that the mapping predictions agree quantitatively (˜90%) with the PAD observations and outperform (by ˜20%) the predictions using the standard Parker spiral model. Application to a type III radio burst observed by Ulysses and Wind shows that the mapping prediction agrees well with the local magnetic field line traced by the type III source path, which covers heliocentric distances of ˜0.1--0.4 AU. Furthermore, applications to local field structures inferred from ACE observations demonstrate that the mapping can predict the majority (65-75%) of the local field line inversions for the multiple phases of the solar cycle.

  11. Interpretation of the coronal magnetic field configuration of the Sun

    CERN Document Server

    Li, Bo; Yu, Hui

    2012-01-01

    The origin of the heliospheric magnetic flux on the Sun, and hence the origin of the solar wind, is a topic of hot debate.While the prevailing view is that the solar wind originates from outside coronal streamer helmets, there also exists the suggestion that the open magnetic field spans a far wider region.Without the definitive measurement of the coronal magnetic field, it is difficult to resolve the conflict between the two scenarios without doubt.We present two 2-dimensional, Alfv\\'enic-turbulence-based models of the solar corona and solar wind, one with and the other without a closed magnetic field region in the inner corona.The purpose of the latter model is to test whether it is possible to realize a picture suggested by polarimetric measurements of the corona using the FeXIII 10747\\AA\\ line, where open magnetic field lines seem to penetrate the streamer base.The boundary conditions at the coronal base are able to account for important observational constraints, especially those on the magnetic flux dis...

  12. Seismology of the Sun : Inference of Thermal, Dynamic and Magnetic Field Structures of the Interior

    CERN Document Server

    Hiremath, K M

    2012-01-01

    Recent overwhelming evidences show that the sun strongly influences the Earth's climate and environment. Moreover existence of life on this Earth mainly depends upon the sun's energy. Hence, understanding of physics of the sun, especially the thermal, dynamic and magnetic field structures of its interior, is very important. Recently, from the ground and space based observations, it is discovered that sun oscillates near 5 min periodicity in millions of modes. This discovery heralded a new era in solar physics and a separate branch called helioseismology or seismology of the sun has started. Before the advent of helioseismology, sun's thermal structure of the interior was understood from the evolutionary solution of stellar structure equations that mimicked the present age, mass and radius of the sun. Whereas solution of MHD equations yielded internal dynamics and magnetic field structure of the sun's interior. In this presentation, I review the thermal, dynamic and magnetic field structures of the sun's inter...

  13. THE INTERSTELLAR MAGNETIC FIELD CLOSE TO THE SUN. II

    Energy Technology Data Exchange (ETDEWEB)

    Frisch, P. C. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Andersson, B-G [SOFIA Science Center, Universities Space Research Association, NASA Ames Research Center, M.S. N232-12 Moffett Field, CA 94035 (United States); Berdyugin, A.; Piirola, V. [Finnish Centre for Astronomy with ESO, University of Turku (Finland); DeMajistre, R. [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD (United States); Funsten, H. O. [Los Alamos National Laboratory, Los Alamos, NM (United States); Magalhaes, A. M.; Seriacopi, D. B. [Inst. de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo (Brazil); McComas, D. J. [Southwest Research Institute, San Antonio, TX (United States); Schwadron, N. A. [Space Science Center, University of New Hampshire, Durham, NH (United States); Slavin, J. D. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Wiktorowicz, S. J. [Department of Astronomy, University of California at Santa Cruz, Santa Cruz, CA (United States)

    2012-12-01

    The magnetic field in the local interstellar medium (ISM) provides a key indicator of the galactic environment of the Sun and influences the shape of the heliosphere. We have studied the interstellar magnetic field (ISMF) in the solar vicinity using polarized starlight for stars within 40 pc of the Sun and 90 Degree-Sign of the heliosphere nose. In Frisch et al. (Paper I), we developed a method for determining the local ISMF direction by finding the best match to a group of interstellar polarization position angles obtained toward nearby stars, based on the assumption that the polarization is parallel to the ISMF. In this paper, we extend the analysis by utilizing weighted fits to the position angles and by including new observations acquired for this study. We find that the local ISMF is pointed toward the galactic coordinates l, b =47 Degree-Sign {+-} 20 Degree-Sign , 25 Degree-Sign {+-} 20 Degree-Sign . This direction is close to the direction of the ISMF that shapes the heliosphere, l, b =33 Degree-Sign {+-} 4 Degree-Sign , 55 Degree-Sign {+-} 4 Degree-Sign , as traced by the center of the 'Ribbon' of energetic neutral atoms discovered by the Interstellar Boundary Explorer (IBEX) mission. Both the magnetic field direction and the kinematics of the local ISM are consistent with a scenario where the local ISM is a fragment of the Loop I superbubble. A nearby ordered component of the local ISMF has been identified in the region l Almost-Equal-To 0 Degree-Sign {yields} 80 Degree-Sign and b Almost-Equal-To 0 Degree-Sign {yields} 30 Degree-Sign , where PlanetPol data show a distance-dependent increase of polarization strength. The ordered component extends to within 8 pc of the Sun and implies a weak curvature in the nearby ISMF of {approx}0.{sup 0}25 pc{sup -1}. This conclusion is conditioned on the small sample of stars available for defining this rotation. Variations from the ordered component suggest a turbulent component of {approx}23 Degree-Sign . The

  14. Probing Solar Magnetic Field with the "Cosmic-Ray Shadow" of the Sun

    CERN Document Server

    Amenomori, M; Chen, D; Chen, T L; Chen, W Y; Cui, S W; Danzengluobu,; Ding, L K; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gou, Q B; Guo, Y Q; Hakamada, K; He, H H; He, Z T; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Jia, H Y; Jiang, L; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren,; Le, G M; Li, A F; Li, H J; Li, W J; Liu, C; Liu, J S; Liu, M Y; Lu, H; Meng, X R; Mizutani, K; Munakata, K; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ozawa, S; Qian, X L; Qu, X B; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Shao, J; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, H; Wu, H R; Xue, L; Yamamoto, Y; Yang, Z; Yasue, S; Yuan, A F; Yuda, T; Zhai, L M; Zhang, H M; Zhang, J L; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhang, Ying; Zhaxisangzhu,; Zhou, X X

    2013-01-01

    We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the Potential Field Source Surface (PFSS) model and the Current Sheet Source Surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun's shadow observed in the TeV cosmic-ray flux.

  15. Polar confinement of the Sun's interior magnetic field by laminar magnetostrophic flow

    CERN Document Server

    Wood, Toby S

    2010-01-01

    The global-scale interior magnetic field B_i needed to account for the Sun's observed differential rotation can be effective only if confined in the polar caps. Axisymmetric magnetohydrodynamic solutions are obtained showing that such confinement can be brought about by a very weak downwelling flow U~10^{-5}cm/s over each pole. Such downwelling is consistent with the helioseismic evidence. All three components of the magnetic field decay exponentially with altitude across a thin, laminar "magnetic confinement layer" located at the bottom of the tachocline. With realistic parameter values, the thickness of the confinement layer ~10^{-3} of the Sun's radius. Alongside baroclinic effects and stable thermal stratification, the solutions take into account the stable compositional stratification of the helium settling layer, if present as in today's Sun, and the small diffusivity of helium through hydrogen, chi. The small value of chi relative to magnetic diffusivity produces a double boundary-layer structure in wh...

  16. Quiet Sun Magnetic Field Measurements Based on Lines with Hyperfine Structure

    CERN Document Server

    Almeida, J Sanchez; Degl'Innocenti, E Landi; Berrilli, F

    2007-01-01

    The Zeeman pattern of MnI lines is sensitive to hyperfine structure (HFS) and, they respond to hG magnetic field strengths differently from the lines used in solar magnetometry. This peculiarity has been employed to measure magnetic field strengths in quiet Sun regions. However, the methods applied so far assume the magnetic field to be constant in the resolution element. The assumption is clearly insufficient to describe the complex quiet Sun magnetic fields, biasing the results of the measurements. We present the first syntheses of MnI lines in realistic quiet Sun model atmospheres. The syntheses show how the MnI lines weaken with increasing field strength. In particular, kG magnetic concentrations produce NnI 5538 circular polarization signals (Stokes V) which can be up to two orders of magnitude smaller than the weak magnetic field approximation prediction. Consequently, (1) the polarization emerging from an atmosphere having weak and strong fields is biased towards the weak fields, and (2) HFS features c...

  17. Near-Sun and 1 AU magnetic field of coronal mass ejections: A parametric study

    CERN Document Server

    Patsourakos, S

    2016-01-01

    Aims. The magnetic field of coronal mass ejections (CMEs) determines their structure, evolution, and energetics, as well as their geoeffectiveness. However, we currently lack routine diagnostics of the near-Sun CME magnetic field, which is crucial for determining the subsequent evolution of CMEs. Methods. We recently presented a method to infer the near-Sun magnetic field magnitude of CMEs and then extrapolate it to 1 AU. This method uses relatively easy to deduce observational estimates of the magnetic helicity in CME-source regions along with geometrical CME fits enabled by coronagraph observations. We hereby perform a parametric study of this method aiming to assess its robustness. We use statistics of active region (AR) helicities and CME geometrical parameters to determine a matrix of plausible near-Sun CME magnetic field magnitudes. In addition, we extrapolate this matrix to 1 AU and determine the anticipated range of CME magnetic fields at 1 AU representing the radial falloff of the magnetic field in t...

  18. Spectral Inversion of Multi-Line Full-Disk Observations of Quiet Sun Magnetic Fields

    CERN Document Server

    Balthasar, H

    2012-01-01

    Spectral inversion codes are powerful tools to analyze spectropolarimetric observations, and they provide important diagnostics of solar magnetic fields. Inversion codes differ by numerical procedures, approximations of the atmospheric model, and description of radiative transfer. Stokes Inversion based on Response functions (SIR) is an implementation widely used by the solar physics community. It allows to work with different atmospheric components, where gradients of different physical parameters are possible, e.g., magnetic field strength and velocities. The spectropolarimetric full-disk observations were carried out with the Stokesmeter of the Solar Telescope for Operative Predictions (STOP) at the Sayan Observatory on 3 February 2009, when neither an active region nor any other extended flux concentration was present on the Sun. In this study of quiet Sun magnetic fields, we apply the SIR code simultaneously to 15 spectral lines. A tendency is found that weaker magnetic field strengths occur closer to th...

  19. Toroidal vs. poloidal magnetic fields in Sun-like stars: a rotation threshold

    CERN Document Server

    Petit, P; Solanki, SK; Donati, J-F; Aurière, M; Lignières, F; Morin, J; Paletou, F; Ramírez, J; Catala, C; Fares, R

    2008-01-01

    From a set of stellar spectropolarimetric observations, we report the detection of surface magnetic fields in a sample of four solar-type stars, namely HD 73350, HD 76151, HD 146233 and HD 190771. Assuming that the observed variability of polarimetric signal is controlled by stellar rotation, we establish the rotation periods of our targets, with values ranging from 8.8 d (for HD 190771) to 22.7 d (for HD 146233). Apart from rotation, fundamental parameters of the selected objects are very close to the Sun's, making this sample a practical basis to investigate the specific impact of rotation on magnetic properties of Sun-like stars. We reconstruct the large-scale magnetic geometry of the targets as a low-order (l<10) spherical harmonics expansion of the surface magnetic field. From the set of magnetic maps, we draw two main conclusions. (a) The magnetic energy of the large-scale field increases with rotation rate. The increase of chromospheric emission with the mean magnetic field is flatter than observed ...

  20. ENSEMBLE EMPIRICAL MODE DECOMPOSITION OF THE MAGNETIC FIELD OF THE SUN AS A STAR

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, N. B. [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Qu, Z. N., E-mail: znqu@ynao.ac.cn [Department of Physics, School of Science, Sichuan University of Science and Engineering, Zigong 643000 (China)

    2016-03-15

    The ensemble empirical mode decomposition (EEMD) analysis is utilized to extract the intrinsic mode functions (IMFs) of the solar mean magnetic field (SMMF) observed at the Wilcox Solar Observatory of Stanford University from 1975 to 2014, and then we analyze the periods of these IMFs as well as the relation of IMFs (SMMF) with some solar activity indices. The two special rotation cycles of 26.6 and 28.5 days should be derived from different magnetic flux elements in the SMMF. The rotation cycle of the weak magnetic flux element in the SMMF is 26.6 days, while the rotation cycle of the strong magnetic flux element in the SMMF is 28.5 days. The two rotation periods of the structure of the interplanetary magnetic field near the ecliptic plane are essentially related to weak and strong magnetic flux elements in the SMMF, respectively. The rotation cycle of weak magnetic flux in the SMMF did not vary over the last 40 years because the weak magnetic flux element derived from the weak magnetic activity on the full disk is not influenced by latitudinal migration. Neither the internal rotation of the Sun nor the solar magnetic activity on the disk (including the solar polar fields) causes the annual variation of SMMF. The variation of SMMF at timescales of a solar cycle is more related to weak magnetic activity on the full solar disk.

  1. Dynamical systems for modeling evolution of the magnetic field of the Sun, stars and planets

    Science.gov (United States)

    Popova, E.

    2016-12-01

    The magnetic activity of the Sun, stars and planets are connected with a dynamo process based on the combined action of the differential rotation and the alpha-effect. Application of this concept allows us to get different types of solutions which can describe the magnetic activity of celestial bodies. We investigated the dynamo model with the meridional circulation by the low-mode approach. This approach is based on an assumption that the magnetic field can be described by non-linear dynamical systems with a relatively small number of parameters. Such non-linear dynamical systems are based on the equations of dynamo models. With this method dynamical systems have been built for media which contains the meridional flow and thickness of the spherical shell where dynamo process operates. It was shown the possibility of coexistence of quiasi-biennial oscillations, 22-year cycle, and grand minima of magnetic activity which is consistent with the observational data for the solar activity. We obtained different regimes (oscillations, vacillations, dynamo-bursts) depending on a value of the dynamo-number, the meridional circulation, and thickness of the spherical shell. We discuss features of these regimes and compare them with the observed features of the magnetic fields of the Sun, stars and Earth. We built theoretical paleomagnetic time scale and butterfly-diagrams for the helicity and toroidal magnetic field for different regimes.

  2. The magnetic field vector of the Sun-as-a-star

    CERN Document Server

    Vidotto, A A

    2016-01-01

    Direct comparison between stellar and solar magnetic maps are hampered by their dramatic differences in resolution. Here, we present a method to filter out the small-scale component of vector fields, in such a way that comparison between solar and stellar (large-scale) magnetic field vector maps can be directly made. Our approach extends the technique widely used to decompose the radial component of the solar magnetic field to the azimuthal and meridional components as well. For that, we self-consistently decompose the three-components of the vector field using spherical harmonics of different $l$ degrees. By retaining the low $l$ degrees in the decomposition, we are able to calculate the large-scale magnetic field vector. Using a synoptic map of the solar vector field at Carrington Rotation CR2109, we derive the solar magnetic field vector at a similar resolution level as that from stellar magnetic images. We demonstrate that the large-scale field of the Sun is not purely radial, as often assumed -- at CR210...

  3. How to infer the Sun's global magnetic field using the Hanle effect

    Science.gov (United States)

    Vieu, T.; Martínez González, M. J.; Pastor Yabar, A.; Asensio Ramos, A.

    2017-03-01

    We present a different approach to determine the characteristics of the global magnetic field of the Sun based on the study of the Hanle signals. The Hanle effect of a stellar dipole produces a surface asymmetric pattern of linear polarization that depends on the strength and geometry of this global field. Moreover, if the dipole is misaligned with respect to the rotation, the Hanle signals are modulated following the rotational period. We explore the possibility to retrieve those characteristics by comparing the computed theoretical signatures with actual observations. We show that this is possible, in the case of the Sr I line of the Sun, provided that the polarimetric sensitivity is of the order or below 10-5-10-6. The inference can be done either using the maps of resolved signals, in particular the spread of values obtained along different directions on the stellar disc, or using the disc-integrated signals.

  4. Quiet Sun Magnetic Field Evolution Observed with Hinode SOT and IRIS

    Science.gov (United States)

    Fischer, C. E.; Bello González, N.; Rezaei, R.

    2016-04-01

    We study two physical processes that can be commonly observed in the quiet sun and involve temporal evolution of the magnetic field: convective collapse and flux cancellation. The aim is to investigate the response of the chromosphere to the magnetic events in the photosphere below. We have calibrated and aligned a co-spatial and co-temporal 3 hour quiet sun time series observed with the Hinode SOT (Solar Optical Telescope) and the IRIS (Interface Region Imaging Spectrograph) satellites. Convective collapse events are identified in the photosphere by inverting spectropolarimetric data and searching for magnetic field intensification, preceded by a downflow and accompanied by the development of a bright point in Ca II H images. We find a corresponding downflow in the low chromosphere as deduced from IRIS Mg II k and h spectra and an ensuing oscillatory velocity pattern. We use magnetograms in the high photosphere to study pairs of magnetic elements involved in flux cancellation and find an increase in the entire quasi-continuum of the IRIS Mg II k and h spectrum following the flux cancellation process and indicating a substantial energy deposit into the lower atmosphere.

  5. NON-POTENTIAL FIELDS IN THE QUIET SUN NETWORK: EXTREME-ULTRAVIOLET AND MAGNETIC FOOTPOINT OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Chesny, D. L.; Oluseyi, H. M.; Orange, N. B. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)

    2013-11-20

    The quiet Sun (QS) magnetic network is known to contain dynamics which are indicative of non-potential fields. Non-potential magnetic fields forming ''S-shaped'' loop arcades can lead to the breakdown of static activity and have only been observed in high temperature X-ray coronal structures—some of which show eruptive behavior. Thus, analysis of this type of atmospheric structuring has been restricted to large-scale coronal fields. Here we provide the first identification of non-potential loop arcades exclusive to the QS supergranulation network. High-resolution Atmospheric Imaging Assembly data from the Solar Dynamics Observatory have allowed for the first observations of fine-scale ''S-shaped'' loop arcades spanning the network. We have investigated the magnetic footpoint flux evolution of these arcades from Heliospheric and Magnetic Imager data and find evidence of evolving footpoint flux imbalances accompanying the formation of these non-potential fields. The existence of such non-potentiality confirms that magnetic field dynamics leading to the build up of helicity exist at small scales. QS non-potentiality also suggests a self-similar formation process between the QS network and high temperature corona and the existence of self-organized criticality (SOC) in the form of loop-pair reconnection and helicity dissipation. We argue that this type of behavior could lead to eruptive forms of SOC as seen in active region (AR) and X-ray sigmoids if sufficient free magnetic energy is available. QS magnetic network dynamics may be considered as a coronal proxy at supergranular scales, and events confined to the network can even mimic those in coronal ARs.

  6. Strength distribution of solar magnetic fields in photospheric quiet Sun regions

    Science.gov (United States)

    Ramírez Vélez, J. C.; López Ariste, A.; Semel, M.

    2008-08-01

    Context: The magnetic topology of the solar photosphere in its quietest regions is hidden by the difficulties to disentangle magnetic flux through the resolution element from the field strength of unresolved structures. The observation of spectral lines with strong coupling with hyperfine structure, like the observed Mn i line at 553.7 nm, allows such differentiation. Aims: To analyse the distribution of field strengths in the network and intranetwork of the solar photosphere through inversion of the Mn i line at 553.7 nm. Methods: An inversion code for the magnetic field using the principal component analysis (PCA) has been developed. Statistical tests are run on the code to validate it. The code has to draw information from the small-amplitude spectral feature appearing in the core of the Stokes V profile of the observed line for field strengths below a certain threshold, coinciding with lower limit of the Paschen-Back effect in the fine structure of the involved atomic levels. Results: The inversion of the observed profiles, using the circular polarisation (V) and the intensity (I), shows the presence of magnetic fields strengths in a range from 0 to 2 kG, with predominant weak strength values. Mixed regions with mean strength field values of 1130 and 435 Gauss are found associated with the network and intranetwork, respectively. Conclusions: The Mn i line at 553 nm probes the field strength distribution in the quiet sun and shows the predominance of weak, hectoGauss fields in the intranetwork, and strong, kiloGauss fields in the network. It also shows that both network and intranetwork are to be understood at our present spatial resolutions as field distributions, of which we hint at the mean properties.

  7. Ubiquitous rotating network magnetic fields and EUV cyclones in the quiet Sun

    CERN Document Server

    Zhang, Jun

    2011-01-01

    We present the {\\it Solar Dynamics Observatory} (SDO) Atmospheric Imaging Assembly (AIA) observations of EUV cyclones in the quiet Sun. These cyclones are rooted in the Rotating Network magnetic Fields (RNFs). Such cyclones can last several to more than ten hours, and, at the later phase, they are found to be associated with EUV brightenings (microflares) and even EUV waves. SDO Helioseismic and Magnetic Imager (HMI) observations show an ubiquitous presence of the RNFs. Using HMI line-of-sight magnetograms on 2010 July 8, we find 388 RNFs in an area of 800$\\times$980 square arcseconds near the disk center where no active region is present. The sense of rotation shows a weak hemisphere preference. The unsigned magnetic flux of the RNFs is about 4.0$\\times10^{21}$ Mx, or 78% of the total network flux. These observational phenomena at small scale reported in this letter are consistent with those at large scale in active regions. The ubiquitous RNFs and EUV cyclones over the quiet Sun may suggest an effective way...

  8. Slow twists of solar magnetic flux tubes and the polar magnetic field of the sun

    Science.gov (United States)

    Hollweg, Joseph V.; Lee, Martin A.

    1989-01-01

    The solar wind model of Weber and Davis (1967) is generalized to compute the heliospheric magnetic field resulting from solar rotation or a steady axisymmetric twist including a geometrical expansion which is more rapid than spherical. The calculated increase in the ratio of the toroidal to poloidal field components with heliocentric radial distance r clarifies an expression derived recently by Jokipii and Kota (1989). Magnetic-field components transverse to r do not in general grow to dominate the radial component at large r. The analysis also yields expressions for the Poynting flux associated with the steady twists.

  9. Activity and Magnetic Field Structure of the Sun-Like Planet Hosting Star HD 1237

    CERN Document Server

    Alvarado-Gómez, J D; Grunhut, J; Fares, R; Donati, J -F; Alecian, E; Kochukhov, O; Oksala, M; Morin, J; Redfield, S; Cohen, O; Drake, J J; Jardine, M; Matt, S; Petit, P; Walter, F M

    2015-01-01

    We analyse the magnetic activity characteristics of the planet hosting Sun-like star, HD 1237, using HARPS spectro-polarimetric time-series data. We find evidence of rotational modulation of the magnetic longitudinal field measurements consistent with our ZDI analysis, with a period of 7 days. We investigate the effect of customising the LSD mask to the line depths of the observed spectrum and find that it has a minimal effect on shape of the extracted Stokes V profile but does result in a small increase in the S/N ($\\sim$ 7%). We find that using a Milne-Eddington solution to describe the local line profile provides a better fit to the LSD profiles in this slowly rotating star, which also impacts the recovered ZDI field distribution. We also introduce a fit-stopping criterion based on the information content (entropy) of the ZDI maps solution set. The recovered magnetic field maps show a strong (+90 G) ring-like azimuthal field distribution and a complex radial field dominating at mid latitudes ($\\sim$45 degr...

  10. Magnetic fields on young, moderately rotating Sun-like stars II. EK Draconis (HD 129333)

    CERN Document Server

    Waite, Ian; Carter, Brad; Petit, Pascal; Jeffers, Sandra; Morin, Julien; Vidotto, Aline; Donati, Jean-Francois

    2016-01-01

    The magnetic fields, activity and dynamos of young solar-type stars can be empirically studied using time-series of spectropolarimetric observations and tomographic imaging techniques such as Doppler imaging and Zeeman Doppler imaging. In this paper we use these techniques to study the young Sun-like star EK Draconis (Sp-Type: G1.5V, HD 129333) using ESPaDOnS at the Canada-France-Hawaii Telescope and NARVAL at the T\\`elescope Bernard Lyot. This multi-epoch study runs from late 2006 until early 2012. We measure high levels of chromospheric activity indicating an active, and varying, chromosphere. Surface brightness features were constructed for all available epochs. The 2006/7 and 2008 data show large spot features appearing at intermediate-latitudes. However, the 2012 data indicate a distinctive polar spot. We observe a strong, almost unipolar, azimuthal field during all epochs that is similar to that observed on other Sun-like stars. Using magnetic features, we determined an average equatorial rotational vel...

  11. Resolving Azimuth Ambiguity Using Vertical Nature of Solar Quiet-Sun Magnetic Fields

    CERN Document Server

    Gosain, Sanjay

    2012-01-01

    The measurement of solar magnetic fields using the Zeeman effect diagnostics has a fundamental 180 degree ambiguity in the determination of the azimuth angle of the transverse field component. There are several methods that are used in the community and each one has its merits and demerits. Here we present a disambiguation idea that is based on the assumption that most of the magnetic field on the sun is predominantly vertical. While the method is not applicable to penumbra or other features harboring predominantly horizontal fields like the sheared neutral lines, it is useful for regions where fields are predominantly vertical like network and plage areas. The method is tested with the full-disk solar vector magnetograms observed by the VSM/SOLIS instrument. We find that statistically about 60-85 % of the pixels in a typical full-disk magnetogram has field inclination in the range of 0-30 degrees with respect to the local solar normal, and thus can be successfully disambiguated by the proposed method. Due to...

  12. The Magnetic Sun from Different Views: A Comparison of the Mean and Background Magnetic Field Observations made in Different Observatories and in Different Spectral Lines

    Indian Academy of Sciences (India)

    M. L. Demidov

    2000-09-01

    A comparison is made of observational data on the mean magnetic field of the Sun from several observatories (a selection of published information and new measurements). Results of correlation and regression analyses of observations of background magnetic fields at the STOP telescope of the Sayan solar observatory in different spectral lines are also presented. Results obtained furnish an opportunity to obtain more unbiased information about large-scale magnetic fields of the Sun and, in particular, about manifestations of strong (kilogauss) magnetic fields in them.

  13. A WebGL Tool for Visualizing the Topology of the Sun's Coronal Magnetic Field

    Science.gov (United States)

    Duffy, A.; Cheung, C.; DeRosa, M. L.

    2012-12-01

    We present a web-based, topology-viewing tool that allows users to visualize the geometry and topology of the Sun's 3D coronal magnetic field in an interactive manner. The tool is implemented using, open-source, mature, modern web technologies including WebGL, jQuery, HTML 5, and CSS 3, which are compatible with nearly all modern web browsers. As opposed to the traditional method of visualization, which involves the downloading and setup of various software packages-proprietary and otherwise-the tool presents a clean interface that allows the user to easily load and manipulate the model, while also offering great power to choose which topological features are displayed. The tool accepts data encoded in the JSON open format that has libraries available for nearly every major programming language, making it simple to generate the data.

  14. Confinement of the Sun's interior magnetic field, with implications for lithium burning

    CERN Document Server

    Wood, Toby S

    2010-01-01

    The simplest interior magnetic field B_i that can explain the observed uniform rotation of the Sun's radiative envelope is an axial dipole stabilized by a deep toroidal field. It can explain the uniform rotation only if confined in the polar caps. The field must be prevented from diffusing up into the high-latitude convection zone, whose slower rotation must remain decoupled from the radiative interior. This paper describes new analytical and numerical solutions of the relevant magnetohydrodynamic equations showing that such confinement and decoupling is dynamically possible by means of a laminar "magnetic confinement layer" at the bottom of the tachocline. With realistic values of the microscopic diffusivities, a weak laminar downwelling flow U~10^{-5}cm/s over the poles is enough to enforce exponential decay of B_i with altitude, in a confinement layer only a fraction of a megameter thick. Downwelling in the polar tachocline is implied both by helioseismic observations, combined with elementary dynamics, an...

  15. Magnetic field and wind of Kappa Ceti: towards the planetary habitability of the young Sun when life arose on Earth

    CERN Document Server

    Nascimento, J -D do; Folsom, P Petit C; Castro, M; Marsden, S C; Morin, J; de Mello, G F Porto; Meibom, S; Jeffers, S V; Guinan, E; Ribas, I

    2016-01-01

    We report magnetic field measurements for Kappa1~Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic field to derive the magnetic environment, stellar winds and particle flux permeating the interplanetary medium around Kappa1~Cet. Our results show a closer magnetosphere and mass-loss rate of Mdot = 9.7 x 10^{-13} Msol/yr, i.e., a factor 50 times larger than the current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the planet's habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditions

  16. Relationship between EUV microflares and small-scale magnetic fields in the quiet Sun

    CERN Document Server

    Jiang, Fayu; Yang, Shuhong

    2015-01-01

    Microflares are small dynamic signatures observed in X-ray and extreme-ultraviolet channels. Because of their impulsive emission enhancements and wide distribution, they are thought to be closely related to coronal heating. By using the high resolution 171 {\\AA} images from the Atmospheric Imaging Assembly and the lines-of-sight magnetograms obtained by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we trace 10794 microflares in a quiet region near the disk center with a field of view of 960 arcsec $\\times$ 1068 arcsec during 24 hr. The microflares have an occurrence rate of 4.4 $\\times$ 10$^{3}$ hr$^{-1}$ extrapolated over the whole Sun. Their average brightness, size, and lifetime are 1.7 I$_{0}$(of the quiet Sun), 9.6 Mm$^{2}$, and 3.6 min, respectively. There exists a mutual positive correlation between the microflares' brightness, area and lifetime. In general, the microflares distribute uniformly across the solar disk, but form network patterns locally, which are similar t...

  17. Surface Evolution of the Sun's Magnetic Field: A Historical Review of the Flux-Transport Mechanism

    Directory of Open Access Journals (Sweden)

    Sheeley Jr. Neil R.

    2005-10-01

    Full Text Available This paper reviews our attempts to understand the transport of magnetic flux on the Sun from the Babcock and Leighton models to the recent revisions that are being used to simulate the field over many sunspot cycles. In these models, the flux originates in sunspot groups and spreads outward on the surface via supergranular diffusion; the expanding patterns become sheared by differential rotation, and the remnants are carried poleward by meridional flow. The net result of all of the flux eruptions during a sunspot cycle is to replace the initial polar fields with new fields of opposite polarity. A central issue in this process is the role of meridional flow, whose relatively low speed is near the limit of detection with Doppler techniques. A compelling feature of Leighton’s original model was that it reversed the polar fields without the need for meridional flow. Now, we think that meridional flow is central to the reversal and to the dynamo itself.

  18. The mean magnetic field of the sun - Method of observation and relation to the interplanetary magnetic field

    Science.gov (United States)

    Scherrer, P. H.; Wilcox, J. M.; Kotov, V.; Severnyi, A. B.; Howard, R.

    1977-01-01

    The mean solar magnetic field as measured in integrated light has been observed since 1968. Since 1970 it has been observed both at Hale Observatories and at the Crimean Astrophysical Observatory. The observing procedures at both observatories and their implications for mean field measurements are discussed. A comparison of the two sets of daily observations shows that similar results are obtained at both observatories. A comparison of the mean field with the interplanetary magnetic polarity shows that the IMF sector structure has the same pattern as the mean field polarity.

  19. Confinement of the Sun's interior magnetic field: some exact boundary-layer solutions

    CERN Document Server

    Wood, T S

    2007-01-01

    High-latitude laminar confinement of the Sun's interior magnetic field is shown to be possible, as originally proposed by Gough and McIntyre (1998) but contrary to a recent claim by Brun and Zahn (A&A 2006). Mean downwelling as weak as 2x10^-6cm/s -- gyroscopically pumped by turbulent stresses in the overlying convection zone and/or tachocline -- can hold the field in advective-diffusive balance within a confinement layer of thickness scale ~ 1.5Mm ~ 0.002 x (solar radius) while transmitting a retrograde torque to the Ferraro-constrained interior. The confinement layer sits at the base of the high-latitude tachocline, near the top of the radiative envelope and just above the `tachopause' marking the top of the helium settling layer. A family of exact, laminar, frictionless, axisymmetric confinement-layer solutions is obtained for uniform downwelling in the limit of strong rotation and stratification. A scale analysis shows that the flow is dynamically stable and the assumption of laminar flow realistic. T...

  20. The Sun's Global Photospheric and Coronal Magnetic Fields: Observations and Models

    Directory of Open Access Journals (Sweden)

    Duncan Mackay

    2012-11-01

    Full Text Available In this review, our present day understanding of the Sun’s global photospheric and coronal magnetic fields is discussed from both observational and theoretical viewpoints. Firstly, the large-scale properties of photospheric magnetic fields are described, along with recent advances in photospheric magnetic flux transport models. Following this, the wide variety of theoretical models used to simulate global coronal magnetic fields are described. From this, the combined application of both magnetic flux transport simulations and coronal modeling techniques to describe the phenomena of coronal holes, the Sun’s open magnetic flux and the hemispheric pattern of solar filaments is discussed. Finally, recent advances in non-eruptive global MHD models are described. While the review focuses mainly on solar magnetic fields, recent advances in measuring and modeling stellar magnetic fields are described where appropriate. In the final section key areas of future research are identified.

  1. Relationships between fluid vorticity, kinetic helicity and magnetic field at the small-scale (quiet-network) on the Sun

    CERN Document Server

    Sangeetha, C R

    2016-01-01

    We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). From these we calculate horizontal divergence, vertical component of vorticity, and kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and that between vorticity (kinetic helicity) and magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), and is consistent with earlier studies using local helioseismology. Further, we show that the magnetic fields cau...

  2. Variable magnetic field geometry of the young sun HN Peg (HD 206860)

    OpenAIRE

    2014-01-01

    The large-scale magnetic field of solar-type stars reconstructed from their spectropolarimetric observations provide important insight into their underlying dynamo processes.We aim to investigate the temporal variability of the large-scale surface magnetic field and chromospheric activity of a young solar analogue, the G0 dwarf HN Peg.The large-scale surface magnetic field topology is reconstructed using Zeeman Doppler Imaging at six observational epochs covering seven years.We also investiga...

  3. Relationships between Fluid Vorticity, Kinetic Helicity, and Magnetic Field on Small-scales (Quiet-Network) on the Sun

    Science.gov (United States)

    Sangeetha, C. R.; Rajaguru, S. P.

    2016-06-01

    We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. From these we calculate the horizontal divergence, the vertical component of vorticity, and the kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and between vorticity (kinetic helicity) and the magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), consistent with earlier studies using local helioseismology. Furthermore, we show that the magnetic fields cause transfer of vorticity from supergranular inflow regions to outflow regions, and that they tend to suppress the vortical motions around them when magnetic flux densities exceed about 300 G (from HMI). We also show that such an action of the magnetic fields leads to marked changes in the correlations between fluid divergence and vorticity. These results are speculated to be of importance to local dynamo action (if present) and to the dynamical evolution of magnetic helicity at the small-scale.

  4. Variable magnetic field geometry of the young sun HN Peg (HD 206860)

    CERN Document Server

    Saikia, S Boro; Petit, P; Marsden, S; Morin, J; Folsom, C P

    2014-01-01

    The large-scale magnetic field of solar-type stars reconstructed from their spectropolarimetric observations provide important insight into their underlying dynamo processes.We aim to investigate the temporal variability of the large-scale surface magnetic field and chromospheric activity of a young solar analogue, the G0 dwarf HN Peg.The large-scale surface magnetic field topology is reconstructed using Zeeman Doppler Imaging at six observational epochs covering seven years.We also investigated the chromospheric activity variations by measuring the flux in the line cores of the three chromospheric activity indicators: Ca II H&K, H alpha, and the Ca II IRT lines.The magnetic topology of HN Peg shows a complex and variable geometry. While the radial field exhibits a stable positive polarity magnetic region at the poles at each observational epoch, the azimuthal field is strongly variable in strength, where a strong band of positive polarity magnetic field is present at equatorial latitudes. This field disa...

  5. EFFECT OF HORIZONTALLY INHOMOGENEOUS HEATING ON FLOW AND MAGNETIC FIELD IN THE CHROMOSPHERE OF THE SUN

    Energy Technology Data Exchange (ETDEWEB)

    Song, P.; Vasyliūnas, V. M., E-mail: paul_song@uml.edu [Space Science Laboratory and Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States)

    2014-12-01

    The solar chromosphere is heated by damped Alfvén waves propagating upward from the photosphere at a rate that depends on magnetic field strength, producing enhanced heating at low altitudes in the extended weak-field regions (where the additional heating accounts for the radiative losses) between the boundaries of the chromospheric network as well as enhanced heating per particle at higher altitudes in strong magnetic field regions of the network. The resulting inhomogeneous radiation and temperature distribution produces bulk flows, which in turn affect the configuration of the magnetic field. The basic flow pattern is circulation on the spatial scale of a supergranule, with upward flow in the strong-field region; this is a mirror image in the upper chromosphere of photospheric/subphotospheric convection widely associated with the formation of the strong network field. There are significant differences between the neutral and the ionized components of the weakly ionized medium: neutral flow streamlines can form closed cells, whereas plasma is largely constrained to flow along the magnetic field. Stresses associated with this differential flow may explain why the canopy/funnel structures of the network magnetic field have a greater horizontal extent and are relatively more homogeneous at high altitudes than is expected from simple current-free models.

  6. Emergence of non-twisted magnetic fields in the Sun: Jets and atmospheric response

    CERN Document Server

    Syntelis, Petros; Gontikakis, Costis; Tsinganos, Kanaris

    2015-01-01

    Aims. We study the emergence of a non-twisted flux tube from the solar interior into the solar atmosphere. We investigate whether the length of the buoyant part of the flux tube (i.e. {\\lambda}) affects the emergence of the field and the dynamics of the evolving magnetic flux system. Methods. We perform three-dimensional (3D), time-dependent, resistive, compressible MHD simulations using the Lare3D code. Results. We find that there are considerable differences in the dynamics of the emergence of a magnetic flux tube when {\\lambda} is varied. In the solar interior, for larger values of {\\lambda}, the rising magnetic field emerges faster and expands more due to its lower magnetic tension. As a result, its field strength decreases and its emergence above the photosphere occurs later than in the smaller {\\lambda} case. However, in both cases, the emerging field at the photosphere becomes unstable in two places, forming two magnetic bipoles that interact dynamically during the evolution of the system. Most of the ...

  7. Roald Amundsen's contributions to our knowledge of the magnetic fields of the Earth and the Sun

    Directory of Open Access Journals (Sweden)

    A. Egeland

    2011-12-01

    Full Text Available Roald Amundsen (1872–1928 was known as one of the premier polar explorers in the golden age of polar exploration. His accomplishments clearly document that he has contributed to knowledge in fields as diverse as ethnography, meteorology and geophysics. In this paper we will concentrate on his studies of the Earth's magnetic field. With his unique observations at the polar station Gjøahavn (geographic coordinates 68°37'10'' N; 95°53'25'' W, Amundsen was first to demonstrate, without doubt, that the north magnetic dip-pole does not have a permanent location, but steadily moves its position in a regular manner. In addition, his carefully calibrated measurements at high latitudes were the first and only observations of the Earth's magnetic field in the polar regions for decades until modern polar observatories were established. After a short review of earlier measurements of the geomagnetic field, we tabulate the facts regarding his measurements at the observatories and the eight field stations associated with the Gjøa expedition. The quality of his magnetic observations may be seen to be equal to that of the late 20th century observations by subjecting them to analytical techniques showing the newly discovered relationship between the diurnal variation of high latitude magnetic observations and the direction of the horizontal component of the interplanetary magnetic field (IMF By. Indeed, the observations at Gjøahavn offer a glimpse of the character of the solar wind 50 yr before it was known to exist. Our motivation for this paper is to illuminate the contributions of Amundsen as a scientist and to celebrate his attainment of the South Pole as an explorer 100 yr ago.

  8. Long-term magnetic field monitoring of the Sun-like star Ksi Boo A

    CERN Document Server

    Morgenthaler, A; Saar, S; Solanki, S K; Auriere, M; Dintrans, B; Fares, R; Gastine, T; Lanoux, J; Lignieres, F; Marsden, S C; Morin, J; Paletou, F; Velez, J C Ramirez; Theado, S; Van Grootel, V

    2011-01-01

    Aims. We aim at investigating the long-term temporal evolution of the magnetic field of the solar-type star Ksi Boo A, both from direct magnetic field measurements and from the simultaneous estimate of indirect activity indicators. Methods. We use 7 time-series of high-resolution, circularly-polarized spectra obtained with the NARVAL spectropolarimeter between 2007 and 2011, for a total of 76 spectra. Using about 6,100 photospheric spectral lines covering the visible domain, we employ a cross-correlation procedure to compute, from each spectrum, a mean polarized line profile. We model the large-scale photospheric magnetic field of the star by means of Zeeman-Doppler Imaging and follow the year-to-year evolution of the reconstructed magnetic topology. Simultaneously, we monitor the width of several magnetically-sensitive spectral lines, the radial velocity and line asymmetry of intensity line profiles and the chromospheric emission in the cores of the Ca II H and Halpha lines. Results. During the highest obser...

  9. Strength distribution of solar magnetic fields in photospheric quiet Sun regions

    CERN Document Server

    Velez, J C Ramirez; Semel, M

    2008-01-01

    The magnetic topology of the solar photosphere in its quietest regions is hidden by the difficulties to disentangle magnetic flux through the resolution element from the field strength of unresolved structures. The observation of spectral lines with strong coupling with hyperfine structure, like the observed MnI line at 553.7 nm, allows such differentiation. The main aim is to analyse the distribution of field strengths in the network and intranetwork of the solar photosphere through inversion of the MnI line at 553.7 nm. An inversion code for the magnetic field using the Principal Component Analysis (PCA) has been developed. Statistical tests are run on the code to validate it. The code has to draw information from the small-amplitude spectral feature oppearing in the core of the Stokes V profile of the observed line for field strengths below a certain threshold, coinciding with lower limit of the Paschen-Back effect in the fine structure of the involved atomic levels. The inversion of the observed profiles,...

  10. Connecting the surface of the Sun to the Heliosphere : wind speed and magnetic field geometry

    Science.gov (United States)

    Pinto, Rui

    2016-07-01

    The large-scale solar wind speed distribution varies in time in response to the cyclic variations of the strength and geometry of the magnetic field of the corona. Based on this idea, semi-empirical predictive laws for the solar wind speed (such as in the widely-used WSA law) use simple parameters describing the geometry of the coronal magnetic field. In practice, such scaling laws require ad-hoc corrections and empirical fits to in-situ spacecraft data, and a predictive law based solely on physical principles is still missing. I will discuss improvements to this kind of laws based on the analysis of very large samples of wind acceleration profiles in open flux-tubes (both from MHD simulations and potential-field extrapolations), and possible strategies for corona and heliosphere model coupling. I will, furthermore present an ongoing modelling effort to determine the magnetic connectivity, paths and propagation delays of any type of disturbance (slow/fast solar wind, waves, energetic particles, ballistic propagation) between the solar surface and any point in the interplanetary space at any time. This is a key point for the exploitation of data from Solar Orbiter and Solar Probe Plus, and more generally for establishing connections between remote and in-situ spacecraft data. This is work is supported by the FP7 project #606692 (HELCATS).

  11. Hierarchical analysis of the quiet Sun magnetism

    CERN Document Server

    Ramos, A Asensio

    2014-01-01

    Standard statistical analysis of the magnetic properties of the quiet Sun rely on simple histograms of quantities inferred from maximum-likelihood estimations. Because of the inherent degeneracies, either intrinsic or induced by the noise, this approach is not optimal and can lead to highly biased results. We carry out a meta-analysis of the magnetism of the quiet Sun from Hinode observations using a hierarchical probabilistic method. This model allows us to infer the statistical properties of the magnetic field vector over the observed field-of-view consistently taking into account the uncertainties in each pixel due to noise and degeneracies. Our results point out that the magnetic fields are very weak, below 275 G with 95% credibility, with a slight preference for horizontal fields, although the distribution is not far from a quasi-isotropic distribution.

  12. Wreathes of Magnetism in Rapidly Rotating Suns

    CERN Document Server

    Brown, Benjamin P; Brun, Allan Sacha; Toomre, Juri

    2009-01-01

    When our Sun was young it rotated much more rapidly than now. Observations of young, rapidly rotating stars indicate that many possess substantial magnetic activity and strong axisymmetric magnetic fields. We conduct simulations of dynamo action in rapidly rotating suns with the 3-D MHD anelastic spherical harmonic (ASH) code to explore the complex coupling between rotation, convection and magnetism. Here we study dynamo action realized in the bulk of the convection zone for two systems, rotating at three and five times the current solar rate. We find that substantial organized global-scale magnetic fields are achieved by dynamo action in these systems. Striking wreathes of magnetism are built in the midst of the convection zone, coexisting with the turbulent convection. This is a great surprise, for many solar dynamo theories have suggested that a tachocline of penetration and shear at the base of the convection zone is a crucial ingredient for organized dynamo action, whereas these simulations do not includ...

  13. New insight into Earth's weather through studies of Sun's magnetic fields

    Science.gov (United States)

    1990-01-01

    Solar Vector Magnetograph is used to predict solar flares, and other activities associated with sun spots. This research provides new understanding about weather on the Earth, and solar-related conditions in orbit.

  14. Solar magnetic field studies using the 12 micron emission lines. I - Quiet sun time series and sunspot slices

    Science.gov (United States)

    Deming, Drake; Boyle, Robert J.; Jennings, Donald E.; Wiedemann, Gunter

    1988-01-01

    The use of the extremely Zeeman-sensitive IR emission line Mg I, at 12.32 microns, to study solar magnetic fields. Time series observations of the line in the quiet sun were obtained in order to determine the response time of the line to the five-minute oscillations. Based upon the velocity amplitude and average period measured in the line, it is concluded that it is formed in the temperature minimum region. The magnetic structure of sunspots is investigated by stepping a small field of view in linear 'slices' through the spots. The region of penumbral line formation does not show the Evershed outflow common in photospheric lines. The line intensity is a factor of two greater in sunspot penumbrae than in the photosphere, and at the limb the penumbral emission begins to depart from optical thinness, the line source function increasing with height. For a spot near disk center, the radial decrease in absolute magnetic field strength is steeper than the generally accepted dependence.

  15. A Robust Method to Predict the Near-Sun and Interplanetary Magnetic Field Strength of Coronal Mass Ejections: Parametric and Case Studies

    Science.gov (United States)

    Patsourakos, Spiros; Georgoulis, Manolis K.

    2016-07-01

    Predicting the near-Sun, and particularly the Interplanetary (IP), magnetic field structure of Coronal Mass Ejections (CMEs) and interplanetary counterparts (ICMEs) is a topic of intense research activity. This is because Earth-directed CMEs with strong southward magnetic fields are responsible for the most powerful geomagnetic storms. We have recently developed a simple two-tier method to predict the magnetic field strength of CMEs in the outer corona and in the IP medium, using as input the magnetic-helicity budget of the source solar active region and stereoscopic coronagraphic observations. Near-Sun CME magnetic fields are obtained by utilizing the principle of magnetic helicity conservation of flux-rope CMEs for coronagraphic observations. Interplanetary propagation of the inferred values is achieved by employing power-law prescriptions of the radial evolution of the CME-ICME magnetic fields. We hereby present a parametric study of our method, based on the observed statistics of input parameters, to infer the anticipated range of values for the near-Sun and interplanetary CME-ICME magnetic fields. This analysis is complemented by application of our method to several well-observed major CME-ICME events.

  16. A new perspective on quiet Sun magnetism

    Institute of Scientific and Technical Information of China (English)

    LITES; Bruce; William

    2009-01-01

    The Hinode mission has provided us with a new, quantitative view of the magnetism of the quiet Sun. It has revealed that the quiet internetwork areas are blanketed by horizontal fields that appear at first sight to have more flux than the vertical fields resolved on the same 0.3 size scale. These measurements point to the possibility that the horizontal fields might be the primary source of the "hidden turbulent flux" of the quiet Sun anticipated from Hanle effect depolarization. In this paper, evidence is presented suggesting that the "seething" horizontal fields observed by Harvey in 2007 and the horizontal fields revealed by Hinode are the same phenomenon. Because the seething fields appear to be of uniform fluctuation over the whole disk, the phenomenon is most likely not associated with the dynamo source of solar activity. Thus, the small-scale "hidden turbulent flux" lends support to the notion of a local solar dynamo acting on granular sizes and time scales.

  17. Realistic Modeling of Interaction of Quiet-Sun Magnetic Fields with the Chromosphere

    Science.gov (United States)

    Kitiashvili, Irina; Kosovichev, Alexander G.; Mansour, Nagi N.; Wray, Alan A.

    2017-08-01

    High-resolution observations and 3D MHD simulations reveal intense interaction between the convection zone dynamics and the solar atmosphere on subarcsecond scales. To investigate processes of the dynamical coupling and energy exchange between the subsurface layers and the chromosphere we perform 3D radiative MHD modeling for a computational domain that includes the upper convection zone and the chromosphere, and investigate the structure and dynamics for different intensity of the photospheric magnetic flux. For comparison with observations, the simulation models have been used to calculate synthetic Stokes profiles of various spectral lines. The results show intense energy exchange through small-scale magnetized vortex tubes rooted below the photosphere, which provide extra heating of the chromosphere, initiate shock waves, and small-scale eruptions.

  18. Magnetic Patches in Internetwork Quiet Sun

    Science.gov (United States)

    De Wijn, Alfred; Lites, B.; Berger, T.; Shine, R.; Title, A.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Hinode Team

    2007-05-01

    We study strong flux elements in the quiet sun in the context of the nature of quiet-sun magnetism, its coupling to chromospheric, transition-region and coronal fields, and the nature of a local turbulent dynamo. Strong, kilogauss flux elements show up intermittently as small bright points in G-band and Ca II H images. Although bright points have been extensively studied in the magnetic network, internetwork magnetism has only come under scrutiny in recent years. A full spectrum of field strengths seems to be ubiquitously present in the internetwork at small spatial scales, with the stronger elements residing in intergranular lanes. De Wijn et al. (2005) found that bright points in quiet sun internetwork areas appear recurrently with varying intensity and horizontal motion within long-lived patches that outline cell patterns on mesogranular scales. They estimate that the "magnetic patches" have a mean lifetime of nine hours, much longer than granular timescales. We use multi-hour sequences of G-band and Ca II H images as well as magnetograms recorded by the Hinode satellite to follow up on their results. The larger field of view, the longer sequences, the addition of magnetograms, and the absence of atmospheric seeing allows us to better constrain the patch lifetime, to provide much improved statistics on IBP lifetime, to compare IBPs to network bright points, and to study field polarity of IBPs in patches and between nearby patches. Hinode is an international project supported by JAXA, NASA, PPARC and ESA. We are grateful to the Hinode team for all their efforts in the design, build and operation of the mission.

  19. The Earth's Magnetic Field

    OpenAIRE

    Edda Lína Gunnarsdóttir 1988

    2012-01-01

    The Earth's magnetic field is essential for life on Earth, as we know it, to exist. It forms a magnetic shield around the planet, protecting it from high energy particles and radiation from the Sun, which can cause damage to life, power systems, orbiting satellites, astronauts and spacecrafts. This report contains a general overview of the Earth's magnetic field. The different sources that contribute to the total magnetic field are presented and the diverse variations in the field are describ...

  20. A new perspective on quiet Sun magnetism

    Institute of Scientific and Technical Information of China (English)

    LITES Bruce William

    2009-01-01

    The Hinode mission has provided us with a new, quantitative view of the magnetism of the quiet Sun. It has revealed that the quiet internetwork areas are blanketed by horizontal fields that appear at first sight to have more flux than the vertical fields resolved on the same 0.3″ size scale. These measurements point to the possibility that the horizontal fields might be the primary source of the "hidden turbulent flux" of the quiet Sun anticipated from Hanle effect depolarization. In this paper, evidence is presented suggesting that the "seething" horizontal fields observed by Harvey in 2007 and the horizontal fields revealed by Hinode are the same phenomenon. Because the seething fields appear to be of uniform fluctuation over the whole disk, the phenomenon is most likely not associated with the dynamo source of solar activity. Thus, the small-scale "hidden turbulent flux" lends support to the notion of a local solar dynamo acting on granular sizes and time scales.

  1. Turbulent magnetic fields in the quiet Sun: implications of Hinode observations and small-scale dynamo simulations

    CERN Document Server

    Graham, Jonathan Pietarila; Schuessler, Manfred

    2008-01-01

    Using turbulent MHD simulations (magnetic Reynolds numbers up to 8000) and Hinode observations, we study effects of turbulence on measuring the solar magnetic field outside active regions. Firstly, from synthetic Stokes V profiles for the FeI lines at 630.1 and 630.2 nm, we show that a peaked probability distribution function (PDF) for observationally-derived field estimates is consistent with a monotonic PDF for actual vertical field strengths. Hence, the prevalence of weak fields is greater than would be naively inferred from observations. Secondly, we employ the fractal self-similar geometry of the turbulent solar magnetic field to derive two estimates (numerical and observational) of the true mean vertical unsigned flux density. We also find observational evidence that the scales of magnetic structuring in the photosphere extend at least down to an order of magnitude smaller than 200 km: the self-similar power-law scaling in the signed measure from a Hinode magnetogram ranges (over two decades in length s...

  2. Imaging convection and magnetism in the sun

    CERN Document Server

    Hanasoge, Shravan

    2015-01-01

    This book reviews the field of helioseismology and its outstanding challenges and also offers a detailed discussion of the latest computational methodologies. The focus is on the development and implementation of techniques to create 3-D images of convection and magnetism in the solar interior and to introduce the latest computational and theoretical methods to the interested reader. With the increasing availability of computational resources, demand for greater accuracy in the interpretation of helioseismic measurements and the advent of billion-dollar instruments taking high-quality observations, computational methods of helioseismology that enable probing the 3-D structure of the Sun have increasingly become central. This book will benefit students and researchers with proficiency in basic numerical methods, differential equations and linear algebra who are interested in helioseismology.

  3. Magnetic Bipoles in Emerging Flux Regions on the Sun

    Science.gov (United States)

    Barth, C. S.; Livi, S. H. B.

    1990-11-01

    ABSTRACT. We analyse magnetograms and H-alpha filtergrams of an Emerging Flux Region. Small bipoles have been observed on the magnetograms emerging between opposite polarities. Separation velocities of the opposite poles for 45 bipoles observed on June 9, 1985 have been measured and are in the range 0.5 contribuciones de los bipolos emergentes. Key words: SUN-CHROMOSPHERE - SUN-MAGNETIC FIELDS

  4. A Helicity-Based Method to Infer the CME Magnetic Field Magnitude in Sun and Geospace: Generalization and Extension to Sun-Like and M-Dwarf Stars and Implications for Exoplanet Habitability

    Science.gov (United States)

    Patsourakos, S.; Georgoulis, M. K.

    2017-07-01

    Patsourakos et al. ( Astrophys. J. 817, 14, 2016) and Patsourakos and Georgoulis ( Astron. Astrophys. 595, A121, 2016) introduced a method to infer the axial magnetic field in flux-rope coronal mass ejections (CMEs) in the solar corona and farther away in the interplanetary medium. The method, based on the conservation principle of magnetic helicity, uses the relative magnetic helicity of the solar source region as input estimates, along with the radius and length of the corresponding CME flux rope. The method was initially applied to cylindrical force-free flux ropes, with encouraging results. We hereby extend our framework along two distinct lines. First, we generalize our formalism to several possible flux-rope configurations (linear and nonlinear force-free, non-force-free, spheromak, and torus) to investigate the dependence of the resulting CME axial magnetic field on input parameters and the employed flux-rope configuration. Second, we generalize our framework to both Sun-like and active M-dwarf stars hosting superflares. In a qualitative sense, we find that Earth may not experience severe atmosphere-eroding magnetospheric compression even for eruptive solar superflares with energies {≈} 104 times higher than those of the largest Geostationary Operational Environmental Satellite (GOES) X-class flares currently observed. In addition, the two recently discovered exoplanets with the highest Earth-similarity index, Kepler 438b and Proxima b, seem to lie in the prohibitive zone of atmospheric erosion due to interplanetary CMEs (ICMEs), except when they possess planetary magnetic fields that are much higher than that of Earth.

  5. Magnetic fields in galaxies

    CERN Document Server

    Beck, Rainer

    2013-01-01

    Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic fie...

  6. Solar Magnetic Fields

    Indian Academy of Sciences (India)

    J. O. Stenflo

    2008-03-01

    Since the structuring and variability of the Sun and other stars are governed by magnetic fields, much of present-day stellar physics centers around the measurement and understanding of the magnetic fields and their interactions. The Sun, being a prototypical star, plays a unique role in astrophysics, since its proximity allows the fundamental processes to be explored in detail. The PRL anniversary gives us an opportunity to look back at past milestones and try to identify the main unsolved issues that will be addressed in the future.

  7. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced......he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics...... in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field...

  8. Tilt of Emerging Bipolar Magnetic Regions on the Sun

    Science.gov (United States)

    Kosovichev, A. G.; Stenflo, J. O.

    2008-12-01

    Magnetic fields emerging from the Sun's interior carry information about the physical processes of magnetic field generation and transport in the convection zone. A statistical analysis of variations of the tilt angle of bipolar magnetic regions during the emergence, observed from SOHO MDI, shows that the systematic tilt with respect to the equator (Joy's law) is established by the middle of the emergence period. This suggests that the tilt is most likely generated below the surface. However, the data do not show evidence of a dependence of the tilt angle on the amount of flux or a relaxation of the bipolar orientation toward the east-west direction, in contrast to the predictions of the rising magnetic flux rope theories.

  9. Molecules in Magnetic Fields

    Science.gov (United States)

    Berdyugina, Svetlana

    2015-08-01

    Molecules probe cool matter in the Universe and various astrophysical objects. Their ability to sense magnetic fields provides new insights into magnetic properties of these objects. During the past fifteen years we have carried out a theoretical study of molecular magnetic effects such as the Zeeman, Paschen-Back and Hanle effects and their applications for inferring magnetic structures and spatial inhomogeneities on the Sun, cool stars, brown dwarfs, and exoplanets from molecular spectro-polarimetry (e.g., Berdyugina 2011). Here, we present an overview of this study and compare our theoretical predictions with recent laboratory measurements of magnetic properties of some molecules. We present also a new web-based tool to compute molecular magnetic effects and polarized spectra which is supported by the ERC Advanced Grant HotMol.

  10. Sun

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Sun Microsystems, Inc. is committed to open standards,a standardization system, and sharing within the information tech nology field, focusing not only on technical innovation, but also on new ideas, practices and future development.

  11. Supersonic Magnetic Flows in the Quiet Sun

    CERN Document Server

    Borrero, J M; Schlichenmaier, R; Schmidt, W; Berkefeld, T; Solanki, S K; Bonet, J A; Iniesta, J C del Toro; Domingo, V; Barthol, P; Gandorfer, A

    2012-01-01

    In this contribution we describe some recent observations of high-speed magnetized flows in the quiet Sun granulation. These observations were carried out with the Imaging Magnetograph eXperiment (IMaX) onboard the stratospheric balloon {\\sc Sunrise}, and possess an unprecedented spatial resolution and temporal cadence. These flows were identified as highly shifted circular polarization (Stokes $V$) signals. We estimate the LOS velocity responsible for these shifts to be larger than 6 km s$^{-1}$, and therefore we refer to them as {\\it supersonic magnetic flows}. The average lifetime of the detected events is 81.3 s and they occupy an average area of about 23\\,000 km$^2$. Most of the events occur within granular cells and correspond therefore to upflows. However some others occur in intergranular lanes or bear no clear relation to the convective velocity pattern. We analyze a number of representative examples and discuss them in terms of magnetic loops, reconnection events, and convective collapse.

  12. Solar Magnetic Fields

    CERN Document Server

    Hood, Alan W

    2011-01-01

    This review provides an introduction to the generation and evolution of the Sun's magnetic field, summarising both observational evidence and theoretical models. The eleven year solar cycle, which is well known from a variety of observed quantities, strongly supports the idea of a large-scale solar dynamo. Current theoretical ideas on the location and mechanism of this dynamo are presented. The solar cycle influences the behaviour of the global coronal magnetic field and it is the eruptions of this field that can impact on the Earth's environment. These global coronal variations can be modelled to a surprising degree of accuracy. Recent high resolution observations of the Sun's magnetic field in quiet regions, away from sunspots, show that there is a continual evolution of a small-scale magnetic field, presumably produced by small-scale dynamo action in the solar interior. Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and disperse over a period of several days. Numerical simulation...

  13. Can the Solar Wind be Driven by Magnetic Reconnection in the Sun's Magnetic Carpet?

    CERN Document Server

    Cranmer, Steven R

    2010-01-01

    The physical processes that heat the solar corona and accelerate the solar wind remain unknown after many years of study. Some have suggested that the wind is driven by waves and turbulence in open magnetic flux tubes, and others have suggested that plasma is injected into the open tubes by magnetic reconnection with closed loops. In order to test the latter idea, we developed Monte Carlo simulations of the photospheric "magnetic carpet" and extrapolated the time-varying coronal field. These models were constructed for a range of different magnetic flux imbalance ratios. Completely balanced models represent quiet regions on the Sun and source regions of slow solar wind streams. Highly imbalanced models represent coronal holes and source regions of fast wind streams. The models agree with observed emergence rates, surface flux densities, and number distributions of magnetic elements. Despite having no imposed supergranular motions, a realistic network of magnetic "funnels" appeared spontaneously. We computed t...

  14. Surface Magnetic Flux Maintenance In Quiet Sun

    CERN Document Server

    Iida, Y

    2013-01-01

    We investigate surface processes of magnetic patches, namely merging, splitting, emergence, and cancellation, by using an auto-detection technique. We find that merging and splitting are locally predominant in the surface level, while the frequencies of the other two are less by one or two orders of magnitude. The frequency dependences on flux con- tent of surface processes are further investigated. Based on these observations, we discuss a possible whole picture of the maintenance. Our conclusion is that the photospheric magnetic field structure, especially its power-law nature, is maintained by the processes locally in the surface not by the interactions between different altitudes. We suggest a scenario of the flux maintenance as follows: The splitting and merging play a crucial role for the generation of the power-law distribution, not the emergence nor cancellation do. This power-law distribution results in another power-law one of the cancellation with an idea of the random convective transport. The can...

  15. Pair separation of magnetic elements in the quiet Sun

    CERN Document Server

    Giannattasio, F; Biferale, L; Del Moro, D; Sbragaglia, M; Rubio, L Bellot; Gosic, M; Suarez, D Orozco

    2014-01-01

    The dynamic properties of the quiet Sun photosphere can be investigated by analyzing the pair dispersion of small-scale magnetic fields (i.e., magnetic elements). By using $25$ hr-long Hinode magnetograms at high spatial resolution ($0".3$), we tracked $68,490$ magnetic element pairs within a supergranular cell near the disk center. The computed pair separation spectrum, calculated on the whole set of particle pairs independently of their initial separation, points out what is known as a super-diffusive regime with spectral index $\\gamma=1.55\\pm0.05$, in agreement with the most recent literature, but extended to unprecedented spatial and temporal scales (from granular to supergranular). Furthermore, for the first time, we investigated here the spectrum of the mean square displacement of pairs of magnetic elements, depending on their initial separation $r_0$. We found that there is a typical initial distance above (below) which the pair separation is faster (slower) than the average. A possible physical interp...

  16. Polar migration of prominences and the inversion of the polar magnetic field of the sun in the 11th and 12th solar cycles (1869 - 1885).

    Science.gov (United States)

    Makarov, V. I.

    The trajectories of the polar migration of prominences are calculated on the basis of spectroscopic observations of prominences during 1869 - 1885. The epoch of the polarity inversion of the polar magnetic field is determined. Three "waves" of migration of polar prominences were observed in the southern hemisphere in the 12th solar cycle whose velocities were 3.9, 7.0 and 8.3 m sec-1. In the northern hemisphere only one "wave" of migration was observed whose velocity was 4.0 m sec-1. The 12th solar cycle is similar to the 14th solar cycle from the point of view of polar migration of prominences.

  17. A theoretical study of the build-up of the Sun's polar magnetic field by using a 3D kinematic dynamo model

    CERN Document Server

    Hazra, Gopal; Miesch, Mark S

    2016-01-01

    We develop a three-dimensional kinematic self-sustaining model of the solar dynamo in which the poloidal field generation is from tilted bipolar sunspot pairs placed on the solar surface above regions of strong toroidal field by using the SpotMaker algorithm and then the transport of this poloidal field to the tachocline is primarily caused by turbulent diffusion. We obtain a dipolar solution within a certain range of parameters. We use this model to study the build-up of the polar magnetic field and show that some insights obtained from surface flux transport (SFT) models have to be revised. We present results obtained by putting a single bipolar sunspot pair in a hemisphere and two symmetrical sunspot pairs in two hemispheres. We find that the polar fields produced by them disappear due to subduction by the meridional circulation sinking underneath the surface in the polar region, which is not included in the SFT models. We also study the effect that a large sunspot pair violating Hale's polarity law would ...

  18. Magnetic Field Calculator

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Calculator will calculate the total magnetic field, including components (declination, inclination, horizontal intensity, northerly intensity,...

  19. Definition of Magnetic Monopole Numbers for SU(N) Lattice Gauge-Higgs Models

    CERN Document Server

    Hollands, S

    2001-01-01

    A geometric definition for a magnetic charge of Abelian monopoles in SU(N) lattice gauge theories with Higgs fields is presented. The corresponding local monopole number defined for almost all field configurations does not require gauge fixing and is stable against small perturbations. Its topological content is that of a 3-cochain. A detailed prescription for calculating the local monopole number is worked out. Our method generalizes a magnetic charge definition previously invented by Phillips and Stone for SU(2).

  20. Reconnection of Magnetic Fields

    Science.gov (United States)

    Birn, J.; Priest, E. R.

    2007-01-01

    Preface; Part I. Introduction: 1.1 The Sun E. R. Priest; 1.2 Earth's magnetosphere J. Birn; Part II. Basic Theory of MHD Reconnection: 2.1 Classical theory of two-dimensional reconnection T. G. Forbes; 2.2 Fundamental concepts G. Hornig; 2.3 Three-dimensional reconnection in the absence of magnetic null points G. Hornig; 2.4 Three-dimensional reconnection at magnetic null points D. Pontin; 2.5 Three-dimensional flux tube reconnection M. Linton; Part III. Basic Theory of Collisionless Reconnection: 3.1 Fundamentals of collisionless reconnection J. Drake; 3.2 Diffusion region physics M. Hesse; 3.3 Onset of magnetic reconnection P. Pritchett; 3.4 Hall-MHD reconnection A. Bhattacharjee and J. Dorelli; 3.5 Role of current-aligned instabilities J. Büchner and W. Daughton; 3.6 Nonthermal particle acceleration M. Hoshino; Part IV. Reconnection in the Magnetosphere: 4.1 Reconnection at the magnetopause: concepts and models J. G. Dorelli and A. Bhattacharjee; 4.2 Observations of magnetopause reconnection K.-H. Trattner; 4.3 On the stability of the magnetotail K. Schindler; 4.4 Simulations of reconnection in the magnetotail J. Birn; 4.5 Observations of tail reconnection W. Baumjohann and R. Nakamura; 4.6 Remote sensing of reconnection M. Freeman; Part V. Reconnection in the Sun's Atmosphere: 5.1 Coronal heating E. R. Priest; 5.2 Separator reconnection D. Longcope; 5.3 Pinching of coronal fields V. Titov; 5.4 Numerical experiments on coronal heating K. Galsgaard; 5.5 Solar flares K. Kusano; 5.6 Particle acceleration in flares: theory T. Neukirch; 5.7 Fast particles in flares: observations L. Fletcher; 6. Open problems J. Birn and E. R. Priest; Bibliography; Index.

  1. Magnetic non-potentiality on the quiet Sun and the filigree

    Institute of Scientific and Technical Information of China (English)

    Meng Zhao; Jing-Xiu Wang; Chun-Lan Jin; Gui-Ping Zhou

    2009-01-01

    From the observed vector magnetic fields by the Solar Optical Telescope/ Spectro-Polarimeter aboard the satellite Hinode, we have examined whether or not the quiet Sun magnetic fields are non-potential, and how the G-band filigrees and Ca Ⅱ net-work bright points (NBPs) are associated with the magnetic non-potentiality. A sizable quiet region in the disk center is selected for this study. The new findings by the study are as follows. (1) The magnetic fields of the quiet region are obviously non-potential. The region-average shear angle is 40°, the average vertical current is 0.016 A m-2, and the average free magnetic energy density, 2.7×102erg cm-3. The magnitude of these non-potential quantities is comparable to that in solar active regions. (2) There are over-all correlations among current helicity, free magnetic energy and longitudinal fields. The magnetic non-potentiality is mostly concentrated in the close vicinity of network elements which have stronger longitudinal fields. (3) The filigrees and NBPs are magnetically char-acterized by strong longitudinal fields, large electric helicity, and high free energy density. Because the selected region is away from any enhanced network, these new results can generally be applied to the quiet Sun. The findings imply that stronger network elements play a role in high magnetic non-potentiality in heating the solar atmosphere and in con-ducting the solar wind.

  2. Observing the sun a pocket field guide

    CERN Document Server

    Jenkins, Jamey L

    2013-01-01

    A comprehensive solar observing guide for use at the telescope by amateur astronomers at all three levels: beginning, intermediate, and advanced. Users will find invaluable information for identifying features through photos, charts, diagrams in a logical, orderly fashion and then interpreting the observations. Because the Sun is a dynamic celestial body in constant flux, astronomers rarely know for certain what awaits them at the eyepiece. All features of the Sun are transient and sometimes rather fleeting. Given the number of features and the complex life cycles of some solar features, it can be a challenging hobby, and this guide provides all of the guidance necessary to inform observers about the sights and events unfolding before their eyes on the most active and powerful member of our Solar System.

  3. Do the legs of magnetic clouds contain twisted flux-rope magnetic fields?

    OpenAIRE

    Owens, Mathew

    2016-01-01

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterised primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The tim...

  4. Inclinations of small quiet-Sun magnetic features based on a new geometric approach

    CERN Document Server

    Jafarzadeh, S; Lagg, A; Rubio, L R Bellot; van Noort, M; Feller, A; Danilovic, S

    2014-01-01

    High levels of horizontal magnetic flux have been reported in the quiet-Sun internetwork, often based on Stokes profile inversions. Here we introduce a new method for deducing the inclination of magnetic elements and use it to test magnetic field inclinations from inversions. We determine accurate positions of a set of small, bright magnetic elements in high spatial resolution images sampling different photospheric heights obtained by the Sunrise balloon-borne solar observatory. Together with estimates of the formation heights of the employed spectral bands, these provide us with the inclinations of the magnetic features. We also compute the magnetic inclination angle of the same magnetic features from the inversion of simultaneously recorded Stokes parameters. Our new, geometric method returns nearly vertical fields (average inclination of around 14 deg with a relatively narrow distribution having a standard deviation of 6 deg). In strong contrast to this, the traditionally used inversions give almost horizo...

  5. Cosmological Magnetic Fields

    CERN Document Server

    Kunze, Kerstin E

    2013-01-01

    Magnetic fields are observed on nearly all scales in the universe, from stars and galaxies upto galaxy clusters and even beyond. The origin of cosmic magnetic fields is still an open question, however a large class of models puts its origin in the very early universe. A magnetic dynamo amplifying an initial seed magnetic field could explain the present day strength of the galactic magnetic field. However, it is still an open problem how and when this initial magnetic field was created. Observations of the cosmic microwave background (CMB) provide a window to the early universe and might therefore be able to tell us whether cosmic magnetic fields are of primordial, cosmological origin and at the same time constrain its parameters. We will give an overview of the observational evidence of large scale magnetic fields, describe generation mechanisms of primordial magnetic fields and possible imprints in the CMB.

  6. Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observations

    CERN Document Server

    Anusha, L S; Hirzberger, Johann; Feller, Alex

    2016-01-01

    The evolution of small magnetic features in quiet regions of the Sun provides a unique window to probing solar magneto-convection. Here we analyze small scale magnetic features in the quiet Sun, using the high resolution, seeing-free observations from the Sunrise balloon borne solar observatory. Our aim is to understand the contribution of different physical processes, such as splitting, merging, emergence and cancellation of magnetic fields to the rearrangement, addition and removal of magnetic flux in the photosphere. We employ a statistical approach for the analysis and the evolution studies are carried out using a feature tracking technique. In this paper we provide a detailed description of the feature tracking algorithm that we have newly developed and we present the results of a statistical study of several physical quantities. The results on the fractions of the flux in the emergence, appearance, splitting, merging, disappearance and cancellation qualitatively agrees with other recent studies. To summ...

  7. Magnetic Field Grid Calculator

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Properties Calculator will computes the estimated values of Earth's magnetic field(declination, inclination, vertical component, northerly...

  8. Long-term variation in the Sun's activity caused by magnetic Rossby waves in the tachocline

    CERN Document Server

    Zaqarashvili, T V; Hanslmeier, A; Carbonell, M; Ballester, J L; Gachechiladze, T; Usoskin, I G

    2015-01-01

    Long-term records of sunspot number and concentrations of cosmogenic radionuclides (10Be and 14C) on the Earth reveal the variation of the Sun's magnetic activity over hundreds and thousands of years. We identify several clear periods in sunspot, 10Be, and 14C data as 1000, 500, 350, 200 and 100 years. We found that the periods of the first five spherical harmonics of the slow magnetic Rossby mode in the presence of a steady toroidal magnetic field of 1200-1300 G in the lower tachocline are in perfect agreement with the time scales of observed variations. The steady toroidal magnetic field can be generated in the lower tachocline either due to the steady dynamo magnetic field for low magnetic diffusivity or due to the action of the latitudinal differential rotation on the weak poloidal primordial magnetic field, which penetrates from the radiative interior. The slow magnetic Rossby waves lead to variations of the steady toroidal magnetic field in the lower tachocline, which modulate the dynamo magnetic field ...

  9. Recent Progress in Understanding the Sun's Magnetic Dynamo

    Science.gov (United States)

    Hathaway, David. H.

    2004-01-01

    100 years ago we thought that the Sun and stars shone as a result of slow gravitational contraction over a few tens of millions of years - putting astronomers at odds with geologists who claimed that the Earth was much, much older. That mystery was solved in the 1920s and 30s with the discovery of nuclear energy (proving that the geologists had it right all along). Other scientific mysteries concerning the Sun have come and gone but three major mysteries remain: 1) How does the Sun produce sunspots with an 11-year cycle? 2) What produces the huge explosions that result in solar flares, prominence eruptions, and coronal mass ejections? and 3) Why is the Sun's outer atmosphere, the corona, so darned hot? Recent progress in solar astronomy reveals a single key to understanding all three of these mysteries.The 11-year time scale for the sunspot cycle indicates the presence of a magnetic dynamo within the Sun. For decades this dynamo was though to operate within the Sun's convection zone - the outmost 30% of the Sun where convective currents transport heat and advect magnetic lines of force. The two leading theories for the dynamo had very different models for the dynamics of the convection zone. Actual measurements of the dynamics using the techniques of helioseismology showed that both of these models had to be wrong some 20 years ago. A thin layer of strongly sheared flow at the base of the convection zone (now called the tachocline) was then taken to be the seat of the dynamo. Over the last 10 years it has become apparent that a weak meridional circulation within the convection zone also plays a key role in the dynamo. This meridional circulation has plasma rising up from the tachocline in the equatorial regions, spreading out toward the poles at a top speed of about 10-20 m/s at the surface, sinking back down to the tachocline in the polar regions, and then flowing back toward the equator at a top speed of about 1-2 m/s in the tachocline itself. Recent dynamo

  10. Recent Progress in Understanding the Sun's Magnetic Dynamo

    Science.gov (United States)

    Hathaway, David. H.

    2004-01-01

    100 years ago we thought that the Sun and stars shone as a result of slow gravitational contraction over a few tens of millions of years - putting astronomers at odds with geologists who claimed that the Earth was much, much older. That mystery was solved in the 1920s and 30s with the discovery of nuclear energy (proving that the geologists had it right all along). Other scientific mysteries concerning the Sun have come and gone but three major mysteries remain: 1) How does the Sun produce sunspots with an 11-year cycle? 2) What produces the huge explosions that result in solar flares, prominence eruptions, and coronal mass ejections? and 3) Why is the Sun's outer atmosphere, the corona, so darned hot? Recent progress in solar astronomy reveals a single key to understanding all three of these mysteries.The 11-year time scale for the sunspot cycle indicates the presence of a magnetic dynamo within the Sun. For decades this dynamo was though to operate within the Sun's convection zone - the outmost 30% of the Sun where convective currents transport heat and advect magnetic lines of force. The two leading theories for the dynamo had very different models for the dynamics of the convection zone. Actual measurements of the dynamics using the techniques of helioseismology showed that both of these models had to be wrong some 20 years ago. A thin layer of strongly sheared flow at the base of the convection zone (now called the tachocline) was then taken to be the seat of the dynamo. Over the last 10 years it has become apparent that a weak meridional circulation within the convection zone also plays a key role in the dynamo. This meridional circulation has plasma rising up from the tachocline in the equatorial regions, spreading out toward the poles at a top speed of about 10-20 m/s at the surface, sinking back down to the tachocline in the polar regions, and then flowing back toward the equator at a top speed of about 1-2 m/s in the tachocline itself. Recent dynamo

  11. Can the Solar Wind be Driven by Magnetic Reconnection in the Sun's Magnetic Carpet?

    Science.gov (United States)

    Cranmer, Steven R.; van Ballegooijen, Adriaan A.

    2010-09-01

    The physical processes that heat the solar corona and accelerate the solar wind remain unknown after many years of study. Some have suggested that the wind is driven by waves and turbulence in open magnetic flux tubes, and others have suggested that plasma is injected into the open tubes by magnetic reconnection with closed loops. In order to test the latter idea, we developed Monte Carlo simulations of the photospheric "magnetic carpet" and extrapolated the time-varying coronal field. These models were constructed for a range of different magnetic flux imbalance ratios. Completely balanced models represent quiet regions on the Sun and source regions of slow solar wind streams. Highly imbalanced models represent coronal holes and source regions of fast wind streams. The models agree with observed emergence rates, surface flux densities, and number distributions of magnetic elements. Despite having no imposed supergranular motions in the models, a realistic network of magnetic "funnels" appeared spontaneously. We computed the rate at which closed field lines open up (i.e., recycling times for open flux), and we estimated the energy flux released in reconnection events involving the opening up of closed flux tubes. For quiet regions and mixed-polarity coronal holes, these energy fluxes were found to be much lower than that which is required to accelerate the solar wind. For the most imbalanced coronal holes, the energy fluxes may be large enough to power the solar wind, but the recycling times are far longer than the time it takes the solar wind to accelerate into the low corona. Thus, it is unlikely that either the slow or fast solar wind is driven by reconnection and loop-opening processes in the magnetic carpet.

  12. Magnetic Jam in the Corona of the Sun

    CERN Document Server

    Chen, F; Bingert, S; Cheung, M C M

    2015-01-01

    The outer solar atmosphere, the corona, contains plasma at temperatures of more than a million K, more than 100 times hotter that solar surface. How this gas is heated is a fundamental question tightly interwoven with the structure of the magnetic field in the upper atmosphere. Conducting numerical experiments based on magnetohydrodynamics we account for both the evolving three-dimensional structure of the atmosphere and the complex interaction of magnetic field and plasma. Together this defines the formation and evolution of coronal loops, the basic building block prominently seen in X-rays and extreme ultraviolet (EUV) images. The structures seen as coronal loops in the EUV can evolve quite differently from the magnetic field. While the magnetic field continuously expands as new magnetic flux emerges through the solar surface, the plasma gets heated on successively emerging fieldlines creating an EUV loop that remains roughly at the same place. For each snapshot the EUV images outline the magnetic field, bu...

  13. Magnetic flux transport and the sun's dipole moment - New twists to the Babcock-Leighton model

    Science.gov (United States)

    Wang, Y.-M.; Sheeley, N. R., Jr.

    1991-01-01

    The mechanisms that give rise to the sun's large-scale poloidal magnetic field are explored in the framework of the Babcock-Leighton (BL) model. It is shown that there are in general two quite distinct contributions to the generation of the 'alpha effect': the first is associated with the axial tilts of the bipolar magnetic regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the magnetic flux is dispersed over the surface. The general relationship between flux transport and the BL dynamo is discussed.

  14. Photometric magnetic-activity metrics tested with the Sun: application to Kepler M dwarfs

    Directory of Open Access Journals (Sweden)

    Mathur Savita

    2014-05-01

    Full Text Available The Kepler mission has been providing high-quality photometric data leading to many breakthroughs in the exoplanet search and in stellar physics. Stellar magnetic activity results from the interaction between rotation, convection, and magnetic field. Constraining these processes is important if we want to better understand stellar magnetic activity. Using the Sun, we want to test a magnetic activity index based on the analysis of the photometric response and then apply it to a sample of M dwarfs observed by Kepler. We estimate a global stellar magnetic activity index by measuring the standard deviation of the whole time series, Sph. Because stellar variability can be related to convection, pulsations or magnetism, we need to ensure that this index mostly takes into account magnetic effects. We define another stellar magnetic activity index as the average of the standard deviation of shorter subseries which lengths are determined by the rotation period of the star. This way we can ensure that the measured photometric variability is related to starspots crossing the visible stellar disc. This new index combined with a time-frequency analysis based on the Morlet wavelets allows us to determine the existence of magnetic activity cycles. We measure magnetic indexes for the Sun and for 34 M dwarfs observed by Kepler. As expected, we obtain that the sample of M dwarfs studied in this work is much more active than the Sun. Moreover, we find a small correlation between the rotation period and the magnetic index. Finally, by combining a time-frequency analysis with phase diagrams, we discover the presence of long-lived features suggesting the existence of active longitudes on the surface of these stars.

  15. Observations of Magnetic Evolution and Network Flares Driven by Photospheric Flows in the Quiet Sun

    Science.gov (United States)

    Attie, Raphael; Thompson, Barbara J.

    2017-08-01

    The quiet Sun may be the biggest laboratory to study physical elementary processes of fundamental importance to space plasma. The advantage is the continuous availability of small-scale events, carrying the hidden microphysics that is responsible for larger-scale phenomena. By small-scale events, we mean spatial dimensions of a few Mm at most, and durations of less than an hour. I present here an attempt to describe and understand the coupling between the photospheric flows, the photospheric magnetic flux, and small-scale energetic transient events. By adapting and improving the highly efficient Balltracking technique for Hinode/SOT data, we relate the fine structures of the supergranular flow fields with the magnetic flux evolution. For studying the dynamics of the latter, and more precisely, the magnetic flux cancellation at sites of energy releases, we applied a new feature tracking algorithm called "Magnetic Balltracking" -- which tracks photospheric magnetic elements -- to high-resolution magnetograms from Hinode/SOT.Using observations of the low corona in soft X-rays with Hinode/XRT, we analyse the triggering mechanism of small-scale network flares. By tracking both the flow fields on the one hand, and the magnetic motions on the other hand, we relate the flows with cancelling magnetic flux. We identify two patterns of horizontal flows that act as catalysts for efficient magnetic reconnection: (i) Funnel-shaped streamlines in which the magnetic flux is carried, and (ii) large-scale vortices (~10 Mm and above) at the network intersections, in which distant magnetic features of opposite polarities seem to be sucked in and ultimately vanish. The excess energy stored in the stressed magnetic field of the vortices is sufficient to power network flares.Prospects for determining the magnetic energy budget in the quiet sun are discussed.

  16. Spatial deconvolution of spectropolarimetric data: an application to quiet Sun magnetic elements

    Science.gov (United States)

    Quintero Noda, C.; Asensio Ramos, A.; Orozco Suárez, D.; Ruiz Cobo, B.

    2015-07-01

    Context. One of the difficulties in extracting reliable information about the thermodynamical and magnetic properties of solar plasmas from spectropolarimetric observations is the presence of light dispersed inside the instruments, known as stray light. Aims: We aim to analyze quiet Sun observations after the spatial deconvolution of the data. We examine the validity of the deconvolution process with noisy data as we analyze the physical properties of quiet Sun magnetic elements. Methods: We used a regularization method that decouples the Stokes inversion from the deconvolution process, so that large maps can be quickly inverted without much additional computational burden. We applied the method on Hinode quiet Sun spectropolarimetric data. We examined the spatial and polarimetric properties of the deconvolved profiles, comparing them with the original data. After that, we inverted the Stokes profiles using the Stokes Inversion based on Response functions (SIR) code, which allow us to obtain the optical depth dependence of the atmospheric physical parameters. Results: The deconvolution process increases the contrast of continuum images and makes the magnetic structures sharper. The deconvolved Stokes I profiles reveal the presence of the Zeeman splitting while the Stokes V profiles significantly change their amplitude. The area and amplitude asymmetries of these profiles increase in absolute value after the deconvolution process. We inverted the original Stokes profiles from a magnetic element and found that the magnetic field intensity reproduces the overall behavior of theoretical magnetic flux tubes, that is, the magnetic field lines are vertical in the center of the structure and start to fan when we move far away from the center of the magnetic element. The magnetic field vector inferred from the deconvolved Stokes profiles also mimic a magnetic flux tube but in this case we found stronger field strengths and the gradients along the line-of-sight are larger

  17. The Juno Magnetic Field Investigation

    DEFF Research Database (Denmark)

    Connerney, J. E. P.; Benn, Mathias; Bjarnø, Jonas Bækby

    2017-01-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter’s planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor ...

  18. Reconstruction of Open Solar Magnetic Flux and Interplanetary Magnetic Field in the 20Th Century

    Science.gov (United States)

    Ivanov, V. G.; Miletsky, E. V.

    2004-10-01

    We reconstruct mean magnitudes of the open solar magnetic field since 1915 using α magnetic synoptic charts of the Sun. The obtained series allows estimation of the interplanetary magnetic field. They also confirm the known conclusion about the secular increase of the solar open magnetic flux in the first half of the 20th century.

  19. The First Magnetic Fields

    CERN Document Server

    Widrow, Lawrence M; Schleicher, Dominik; Subramanian, Kandaswamy; Tsagas, Christos G; Treumann, Rudolf A

    2011-01-01

    We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early genera...

  20. Organic magnetic field sensor

    Energy Technology Data Exchange (ETDEWEB)

    McCamey, Dane; Boehme, Christoph

    2017-01-24

    An organic, spin-dependent magnetic field sensor (10) includes an active stack (12) having an organic material with a spin-dependence. The sensor (10) also includes a back electrical contact (14) electrically coupled to a back of the active stack (12) and a front electrical contact (16) electrically coupled to a front of the active stack (12). A magnetic field generator (18) is oriented so as to provide an oscillating magnetic field which penetrates the active stack (12).

  1. Magnetic jam in the corona of the Sun

    Science.gov (United States)

    Chen, F.; Peter, H.; Bingert, S.; Cheung, M. C. M.

    2015-06-01

    The outer solar atmosphere, the corona, contains plasma at temperatures of more than a million kelvin--more than 100 times hotter than the solar surface. How this gas is heated is a fundamental question tightly interwoven with the structure of the magnetic field. Together this governs the evolution of coronal loops, the basic building block prominently seen in X-rays and extreme ultraviolet (EUV) images. Here we present numerical experiments accounting for both the evolving three-dimensional structure of the magnetic field and its complex interaction with the plasma. Although the magnetic field continuously expands as new magnetic flux emerges through the solar surface, plasma on successive field lines is heated in succession, giving the illusion that an EUV loop remains roughly at the same place. For each snapshot the EUV images outline the magnetic field. However, in contrast to the traditional view, the temporal evolution of the magnetic field and the EUV loops can be quite different. This indicates that the thermal and the magnetic evolution in the outer atmosphere of a cool star should be treated together, and should not be simply separated as predominantly done so far.

  2. Probing deep photospheric layers of the quiet Sun with high magnetic sensitivity

    Science.gov (United States)

    Lagg, A.; Solanki, S. K.; Doerr, H.-P.; Martínez González, M. J.; Riethmüller, T.; Collados Vera, M.; Schlichenmaier, R.; Orozco Suárez, D.; Franz, M.; Feller, A.; Kuckein, C.; Schmidt, W.; Asensio Ramos, A.; Pastor Yabar, A.; von der Lühe, O.; Denker, C.; Balthasar, H.; Volkmer, R.; Staude, J.; Hofmann, A.; Strassmeier, K.; Kneer, F.; Waldmann, T.; Borrero, J. M.; Sobotka, M.; Verma, M.; Louis, R. E.; Rezaei, R.; Soltau, D.; Berkefeld, T.; Sigwarth, M.; Schmidt, D.; Kiess, C.; Nicklas, H.

    2016-11-01

    Context. Investigations of the magnetism of the quiet Sun are hindered by extremely weak polarization signals in Fraunhofer spectral lines. Photon noise, straylight, and the systematically different sensitivity of the Zeeman effect to longitudinal and transversal magnetic fields result in controversial results in terms of the strength and angular distribution of the magnetic field vector. Aims: The information content of Stokes measurements close to the diffraction limit of the 1.5 m GREGOR telescope is analyzed. We took the effects of spatial straylight and photon noise into account. Methods: Highly sensitive full Stokes measurements of a quiet-Sun region at disk center in the deep photospheric Fe i lines in the 1.56 μm region were obtained with the infrared spectropolarimeter GRIS at the GREGOR telescope. Noise statistics and Stokes V asymmetries were analyzed and compared to a similar data set of the Hinode spectropolarimeter (SOT/SP). Simple diagnostics based directly on the shape and strength of the profiles were applied to the GRIS data. We made use of the magnetic line ratio technique, which was tested against realistic magneto-hydrodynamic simulations (MURaM). Results: About 80% of the GRIS spectra of a very quiet solar region show polarimetric signals above a 3σ level. Area and amplitude asymmetries agree well with small-scale surface dynamo-magneto hydrodynamic simulations. The magnetic line ratio analysis reveals ubiquitous magnetic regions in the ten to hundred Gauss range with some concentrations of kilo-Gauss fields. Conclusions: The GRIS spectropolarimetric data at a spatial resolution of ≈0.̋4 are so far unique in the combination of high spatial resolution scans and high magnetic field sensitivity. Nevertheless, the unavoidable effect of spatial straylight and the resulting dilution of the weak Stokes profiles means that inversion techniques still bear a high risk of misinterpretating the data.

  3. Magnetic Evolution and the Disappearance of Sun-Like Activity Cycles

    Science.gov (United States)

    Metcalfe, Travis S.; van Saders, Jennifer

    2017-09-01

    After decades of effort, the solar activity cycle is exceptionally well characterized, but it remains poorly understood. Pioneering work at the Mount Wilson Observatory demonstrated that other Sun-like stars also show regular activity cycles, and suggested two possible relationships between the rotation rate and the length of the cycle. Neither of these relationships correctly describes the properties of the Sun, a peculiarity that demands explanation. Recent discoveries have started to shed light on this issue, suggesting that the Sun's rotation rate and magnetic field are currently in a transitional phase that occurs in all middle-aged stars. Motivated by these developments, we identify the manifestation of this magnetic transition in the best available data on stellar cycles. We propose a reinterpretation of previously published observations to suggest that the solar cycle may be growing longer on stellar evolutionary timescales, and that the cycle might disappear sometime in the next 0.8 - 2.4 Gyr. Future tests of this hypothesis will come from ground-based activity monitoring of Kepler targets that span the magnetic transition, and from asteroseismology with the Transiting Exoplanet Survey Satellite (TESS) mission to determine precise masses and ages for bright stars with known cycles.

  4. Opposite magnetic polarity of two photospheric lines in single spectrum of the quiet Sun

    CERN Document Server

    Rezaei, R; Schmidt, W; Steiner, O

    2007-01-01

    We study the structure of the photospheric magnetic field of the quiet Sun by investigating weak spectro-polarimetric signals. We took a sequence of Stokes spectra of the Fe I 630.15 nm and 630.25 nm lines in a region of quiet Sun near the disk center, using the POLIS spectro-polarimeter at the German VTT on Tenerife. The line cores of these two lines form at different heights in the atmosphere. The 3$\\sigma$ noise level of the data is about 1.8 $\\times 10^{-3} I_{c}$. We present co-temporal and co-spatial Stokes-$V$ profiles of the Fe I 630 nm line pair, where the two lines show opposite polarities in a single spectrum. We compute synthetic line profiles and reproduce these spectra with a two-component model atmosphere: a non-magnetic component and a magnetic component. The magnetic component consists of two magnetic layers with opposite polarity: the upper one moves upwards while the lower one moves downward. In-between, there is a region of enhanced temperature. The Stokes-$V$ line pair of opposite polarit...

  5. Magnetic Flux Ropes from the Sun to 1 AU*

    Science.gov (United States)

    Krall, J.; Yurchyshyn, V. B.; St. Cyr, O. C.; Chen, J.

    2004-12-01

    Any practical model of the dynamics of a coronal mass ejection (CME) and its interplanetary counterpart (ICME) must conform to available observational constraints from sun and to the earth; the upcoming STEREO mission will add significantly to those constraints. We present model/data comparisons for specific CME/ICME events near the sun (using coronagraph image data) and in the heliosphere (using in situ measurements) to show that the flux rope model of Chen and Krall[1-2] provides an accurate physics-based characterization of flux-rope CMEs over this range. We further show that quantitative results, such as the field energy required for eruption, depend on specific aspects of the flux rope geometry, such as the ratio (length/width) of the elliptical shape traced out by the flux-rope axis. It is this geometry that will be determined, for the first time, by STEREO. [1] Chen, J. 1996, JGR, 101, 27499 [2] Krall, J. et al., 2000, ApJ, 539, 964 *Work supported by ONR, NASA and NSF

  6. Magnetization reversal in ultrashort magnetic field pulses

    CERN Document Server

    Bauer, M; Fassbender, J; Hillebrands, B

    2000-01-01

    We report the switching properties of a thin magnetic film subject to an ultrashort, laterally localized magnetic field pulse, obtained by numerical investigations. The magnetization distribution in the film is calculated on a grid assuming Stoner-like coherent rotation within the grid square size. Perpendicularly and in-plane magnetized films exhibit a magnetization reversal due to a 4 ps magnetic field pulse. Outside the central region the pulse duration is short compared to the precession period. In this area the evolution of the magnetization during the field pulse does not depend strongly on magnetic damping and/or pulse shape. However, the final magnetization distribution is affected by the magnetic damping. Although the pulse duration is short compared to the precession period, the time needed for the relaxation of the magnetization to the equilibrium state is rather large. The influence of the different magnetic anisotropy contributions and the magnetic damping parameter enters into the magnetization ...

  7. Exploring the Origin and Dynamics of Solar Magnetic Fields

    CERN Document Server

    Hazra, Soumitra

    2016-01-01

    The Sun is a magnetically active star and is the source of the solar wind, electromagnetic radiation and energetic particles which affect the heliosphere and the Earths atmosphere. The magnetic field of the Sun is responsible for most of the dynamic activity of the Sun. This thesis research seeks to understand solar magnetic field generation and the role that magnetic fields play in the dynamics of the solar atmosphere. Specifically, this thesis focuses on two themes: in the first part, we study the origin and behaviour of solar magnetic fields using magnetohydrodynamic dynamo theory and modelling, and in the second part, utilizing observations and data analysis we study two major problems in solar physics, namely, the coronal heating problem and initiation mechanisms of solar flares.

  8. Estimation of the magnetic flux emergence rate in the quiet Sun from Sunrise data

    CERN Document Server

    Smitha, H N; Solanki, S K; Riethmueller, T

    2016-01-01

    The small-scale internetwork (IN) features are thought to be the major source of fresh magnetic flux in the quiet Sun. During its first science flight in 2009, the balloon-borne observatory Sunrise captured images of the magnetic fields in the quiet Sun at a high spatial resolution. Using these data we measure the rate at which the IN features bring magnetic flux to the solar surface. In a previous paper it was found that the lowest magnetic flux in small-scale features detected using the Sunrise observations is 9 x 10^14 Mx. This is nearly an order of magnitude smaller than the smallest fluxes of features detected in observations from Hinode satellite. In this paper, we compute the flux emergence rate (FER) by accounting for such small fluxes, which was not possible before Sunrise. By tracking the features with fluxes in the range 10^15-10^18 Mx, we measure an FER of 1100 Mx cm^-2 day^-1. The smaller features with fluxes less than or equal to 10^16 Mx are found to be the dominant contributors to the solar ma...

  9. Probing deep photospheric layers of the quiet Sun with high magnetic sensitivity

    CERN Document Server

    Lagg, A; Doerr, H -P; González, M J Martínez; Riethmüller, T; Vera, M Collados; Schlichenmaier, R; Suárez, D Orozco; Franz, M; Feller, A; Kuckein, C; Schmidt, W; Ramos, A Asensio; Yabar, A Pastor; von der Lühe, O; Denker, C; Balthasar, H; Volkmer, R; Staude, J; Hofmann, A; Strassmeier, K; Kneer, F; Waldmann, T; Borrero, J M; Sobotka, M; Verma, M; Louis, R E; Rezaei, R; Soltau, D; Berkefeld, T; Sigwarth, M; Schmidt, D; Kiess, C; Nicklas, H

    2016-01-01

    Context. Investigations of the magnetism of the quiet Sun are hindered by extremely weak polarization signals in Fraunhofer spectral lines. Photon noise, straylight, and the systematically different sensitivity of the Zeeman effect to longitudinal and transversal magnetic fields result in controversial results in terms of the strength and angular distribution of the magnetic field vector. Aims. The information content of Stokes measurements close to the diffraction limit of the 1.5 m GREGOR telescope is analyzed. We took the effects of spatial straylight and photon noise into account. Methods. Highly sensitive full Stokes measurements of a quiet-Sun region at disk center in the deep photospheric Fe I lines in the 1.56 {\\mu}m region were obtained with the infrared spectropolarimeter GRIS at the GREGOR telescope. Noise statistics and Stokes V asymmetries were analyzed and compared to a similar data set of the Hinode spectropolarimeter (SOT/SP). Simple diagnostics based directly on the shape and strength of the ...

  10. Dynamic Flaring Non-potential Fields on Quiet Sun Network Scales

    Science.gov (United States)

    Chesny, D. L.; Oluseyi, H. M.; Orange, N. B.

    2016-05-01

    We report on the identification of dynamic flaring non-potential structures on quiet Sun (QS) supergranular network scales. Data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory allow for the high spatial and temporal resolution of this diverse class of compact structures. The rapidly evolving non-potential events presented here, with lifetimes 100″) and micro-sigmoids (>10″) with lifetimes on the order of hours to days. The photospheric magnetic field environment derived from the Helioseismic and Magnetic Imager shows a lack of evidence for these flaring non-potential fields being associated with significant concentrations of bipolar magnetic elements. Of much interest to our events is the possibility of establishing them as precursor signatures of eruptive dynamics, similar to notions for AR sigmoids and micro-sigmoids, but associated with uneventful magnetic network regions. We suggest that the mixed network flux of QS-like magnetic environments, though unresolved, can provide sufficient free magnetic energy for flaring non-potential plasma structuring. The appearance of non-potential magnetic fields could be a fundamental process leading to self-organized criticality in the QS-like supergranular network and contribute to coronal heating, as these events undergo rapid helicial and vortical relaxations.

  11. Babcock Redux: An Ammendment of Babcock's Schematic of the Sun's Magnetic Cycle

    CERN Document Server

    Moore, Ronald L; Sterling, Alphonse C

    2016-01-01

    We amend Babcock's original scenario for the global dynamo process that sustains the Sun's 22-year magnetic cycle. The amended scenario fits post-Babcock observed features of the magnetic activity cycle and convection zone, and is based on ideas of Spruit and Roberts (1983) about magnetic flux tubes in the convection zone. A sequence of four schematic cartoons lays out the proposed evolution of the global configuration of the magnetic field above, in, and at the bottom of the convection zone through sunspot Cycle 23 and into Cycle 24. Three key elements of the amended scenario are: (1) as the net following-polarity field from the sunspot-region omega-loop fields of an ongoing sunspot cycle is swept poleward to cancel and replace the opposite-polarity polar-cap field from the previous sunspot cycle, it remains connected to the ongoing sunspot cycle's toroidal source-field band at the bottom of the convection zone; (2) topological pumping by the convection zone's free convection keeps the horizontal extent of t...

  12. Vector magnetic field in solar polar region

    Institute of Scientific and Technical Information of China (English)

    邓元勇; 汪景秀; 艾国祥

    1999-01-01

    By means of ’deep integration’ observations of a videomagnetograph the vector magnetic field was first systematically measured near the solar south polar region on April 12, 1997 when the Sun was in the minimal phase between the 22nd and 23rd solar cycle. It was found that the polar magnetic field deviated from the normal of solar surface by about 42.2°±3.2°, a stronger magnetic element may have smaller inclination, and that within the polar cap above heliolatitude of 50°, the unsigned and net flux densities were 7.8×10-4 T and -3.4×10-4 T, respectively, and consequently, the unsigned and net fluxes were about 5.5×1022 and -2.5×1022 Mx. The net magnetic flux, which belongs to the large-scale global magnetic field of the Sun, roughly approaches the order of the interplanetary magnetic field (IMF) measured at distance of 1 AU.

  13. The influence of the magnetic topology on the braking of sun-like stars

    CERN Document Server

    Réville, Victor; Matt, Sean; Strugarek, Antoine; Pinto, Rui

    2014-01-01

    Stellar winds are thought to be the main process responsible for the spin down of main-sequence stars. The extraction of angular momentum by a magnetized wind has been studied for decades, leading to several formulations for the resulting torque. However, previous studies generally consider simple dipole or split monopole stellar magnetic topologies. Here we consider in addition to a dipolar stellar magnetic field, both quadrupolar and octupolar configurations, while also varying the rotation rate and the magnetic field strength. 60 simulations made with a 2.5D, cylindrical and axisymmetric set-up and computed with the PLUTO code were used to find torque formulations for each topology. We further succeed to give a unique law that fits the data for every topology by formulating the torque in terms of the amount of open magnetic flux in the wind. We also show that our formulation can be applied to even more realistic magnetic topologies, with examples of the Sun in its minimum and maximum phase as observed at t...

  14. The influence of the magnetic topology on the wind braking of sun-like stars.

    Science.gov (United States)

    Réville, V.; Brun, A. S.; Matt, S. P.; Strugarek, A.; Pinto, R.

    2014-12-01

    Stellar winds are thought to be the main process responsible for the spin down of main-sequence stars. The extraction of angular momentum by a magnetized wind has been studied for decades, leading to several formulations for the resulting torque. However, previous studies generally consider simple dipole or split monopole stellar magnetic topologies. Here we consider in addition to a dipolar stellar magnetic field, both quadrupolar and octupolar configurations, while also varying the rotation rate and the magnetic field strength. 60 simulations made with a 2.5D, cylindrical and axisymmetric set-up and computed with the PLUTO code were used to find torque formulations for each topology. We further succeed to give a unique law that fits the data for every topology by formulating the torque in terms of the amount of open magnetic flux in the wind. We also show that our formulation can be applied to even more realistic magnetic topologies, with examples of the Sun in its minimum and maximum phase as observed at the Wilcox Solar Observatory, and of a young K-star (TYC-0486-4943-1) whose topology has been obtained by Zeeman-Doppler Imaging (ZDI).

  15. The Sun's Meridional Flow and Its Role in Magnetic Flux Transport and the Sunspot Cycle

    Science.gov (United States)

    Hathaway, D. H.; Upton, L.

    2014-12-01

    The Sun's meridional flow can be measured with a variety of measurement techniques including, but not limited to: direct Doppler, magnetic feature tracking, velocity feature tracking, time-distance helioseismology, and ring-diagram analysis. Direct Doppler gives information on the flow in the photosphere while the other measurement techniques provide information about the flow at some depth or range of depths in the Sun's convection zone. These various measurement methods now provide a converging (but not yet fully converged) picture of the meridional flow as a function of latitude, depth, and time. This converging picture has a flow which is poleward from the equator all the way to pole in the near surface layers, has an equatorward return flow beginning at a depth of about 50 Mm, and has another poleward branch deeper in the convection zone. The poleward flow in the near surface layers varies systematically in strength and latitudinal structure with the phase of the sunspot cycle and from one cycle to the next. This near surface meridional flow is observed to play a significant role in the poleward transport of the magnetic flux that emerges at the surface in the form of bipolar active regions. Variations in the strength and structure of the meridional flow introduce variations in the strength of the Sun's polar fields, which in turn introduce variations in the size of subsequent sunspot cycles. The polar fields at the end of cycle 23 (2008-2009) were much weaker than the polar fields at the end of the previous cycles. This led to the production of the weakest sunspot cycle in 100 years - cycle 24. Surprisingly, we find that the variations we observed in the meridional flow during cycle 23 led to stronger polar fields than would have been produced otherwise. This suggests that variations in the meridional flow can be one mechanism for modulating the sizes of sunspot cycles - helping to keep them from getting too big or too small.

  16. ISR Radial Field Magnet

    CERN Multimedia

    1983-01-01

    There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water

  17. THE STORAGE AND DISSIPATION OF MAGNETIC ENERGY IN THE QUIET SUN CORONA DETERMINED FROM SDO/HMI MAGNETOGRAMS

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, K. A.; Sabol, J.; Mackay, D. H. [School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Van Ballegooijen, A. A., E-mail: karen@mcs.st-and.ac.uk [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2013-06-20

    In recent years, higher cadence, higher resolution observations have revealed the quiet-Sun photosphere to be complex and rapidly evolving. Since magnetic fields anchored in the photosphere extend up into the solar corona, it is expected that the small-scale coronal magnetic field exhibits similar complexity. For the first time, the quiet-Sun coronal magnetic field is continuously evolved through a series of non-potential, quasi-static equilibria, deduced from magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, where the photospheric boundary condition which drives the coronal evolution exactly reproduces the observed magnetograms. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. We find that the free magnetic energy built up and stored within the field is sufficient to explain small-scale, impulsive events such as nanoflares. On comparing with coronal images of the same region, the energy storage and dissipation visually reproduces many of the observed features. The results indicate that the complex small-scale magnetic evolution of a large number of magnetic features is a key element in explaining the nature of the solar corona.

  18. Cosmic magnetic fields

    CERN Document Server

    Kronberg, Philipp P

    2016-01-01

    Magnetic fields are important in the Universe and their effects contain the key to many astrophysical phenomena that are otherwise impossible to understand. This book presents an up-to-date overview of this fast-growing topic and its interconnections to plasma processes, astroparticle physics, high energy astrophysics, and cosmic evolution. The phenomenology and impact of magnetic fields are described in diverse astrophysical contexts within the Universe, from galaxies to the filaments and voids of the intergalactic medium, and out to the largest redshifts. The presentation of mathematical formulae is accessible and is designed to add insight into the broad range of topics discussed. Written for graduate students and researchers in astrophysics and related disciplines, this volume will inspire readers to devise new ways of thinking about magnetic fields in space on galaxy scales and beyond.

  19. Measurements of Photospheric and Chromospheric Magnetic Fields

    Science.gov (United States)

    Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca

    2017-09-01

    The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space. Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution.

  20. Field Experience with 3-Sun Mirror Module Systems

    Energy Technology Data Exchange (ETDEWEB)

    Fraas, Dr. Lewis [JX Crystals, Inc.; Avery, James E. [JX Crystals, Inc.; Huang, H, [JX Crystals, Inc.; Minkin, Leonid M [ORNL; Fraas, J. X. [JX Crystals, Inc.; Maxey, L Curt [ORNL; Gehl, Anthony C [ORNL

    2008-01-01

    JX Crystals 3-sun PV mirror modules have now been operating in four separate systems in the field for up to 2 years. Two post-mounted 2-axis tracking arrays of 12 modules each were installed at the Shanghai Flower Park in April of 2006. Then 672 modules were installed in a 100 kW array on N-S horizontal beam trackers at the Shanghai Flower Port in November of 2006. Finally, sets of 4 modules were installed on azimuth-tracking carousels on buildings at the Oak Ridge National Lab and at the U. of Nevada in Las Vegas in late 2007. All of these modules in each of these systems are still operating at their initial power ratings. No degradation in performance has been observed. The benefit of these 3-sun PV mirror modules is that they use 1/3 of the silicon single-crystal cell material in comparison to traditional planar modules. Since aluminum mirrors are much cheaper than high-purity single-crystal silicon-cells, these modules and systems should be much lower in cost when manufactured in high volume.

  1. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  2. Magnetized Jets Driven By the Sun: The Structure of the Heliosphere Revisited

    Science.gov (United States)

    Opher, Merav

    2015-11-01

    The classic accepted view of the heliosphere is a quiescent, comet-like shape aligned in the direction of the Sun's travel through the interstellar medium (ISM) extending for thousands of astronomical units (AUs). Here, we show, based on magnetohydrodynamic (MHD) simulations, that the tension (hoop) force of the twisted magnetic field of the Sun confines the solar wind plasma beyond the termination shock and drives jets to the north and south very much like astrophysical jets. These jets are deflected into the tail region by the motion of the Sun through the ISM similar to bent galactic jets moving through the intergalactic medium. The interstellar wind blows the two jets into the tail but is not strong enough to force the lobes into a single comet-like tail, as happens to some astrophysical jets. Instead, the interstellar wind flows around the heliosphere and into the equatorial region between the two jets. As in some astrophysical jets that are kink unstable, we show here that the heliospheric jets are turbulent (due to large-scale MHD instabilities and reconnection) and strongly mix the solar wind with the ISM. The resulting turbulence has important implications for particle acceleration in the heliosphere. The two-lobe structure is consistent with the energetic neutral atom (ENA) images of the heliotail from IBEX where two lobes are visible in the north and south and the suggestion from the Cassini ENAs that the heliosphere is ``tailless.''

  3. Magnetized jets driven by the sun: the structure of the heliosphere revisited

    CERN Document Server

    Opher, M; Zieger, B; Gombosi, T I

    2014-01-01

    The classic accepted view of the heliosphere is a quiescent, comet-like shape aligned in the direction of the Sun's travel through the interstellar medium (ISM) extending for 1000's of AUs (AU: astronomical unit). Here we show, based on magnetohydrodynamic (MHD) simulations, that the twisted magnetic field of the sun confines the solar wind plasma and drives jets to the North and South very much like astrophysical jets. These jets are deflected into the tail region by the motion of the Sun through the ISM similar to bent galactic jets moving through the intergalactic medium. The interstellar wind blows the two jets into the tail but is not strong enough to force the lobes into a single comet-like tail, as happens to some astrophysical jets (Morsony et al. 2013). Instead, the interstellar wind flows around the heliosphere and into equatorial region between the two jets. While relativistic jets may be stable, non-relativistic astrophysical jets are kink unstable (Porth et al. 2014) and we show here that the hel...

  4. Small satellite attitude control for sun-oriented operations utilizing a momentum bias with magnetic actuators

    Science.gov (United States)

    Wolfe, Scott M.

    1995-03-01

    The feasibility of using a three axis control, momentum bias system with magnetic actuators for sun-oriented operations is explored. Relevant equations of motion are developed for a sun-oriented coordinate system and control laws are developed for initial spacecraft capture after launch vehicle separation; reorientation from Earth oriented to a sun oriented operations mode; sun-oriented attitude control; and momentum wheel control. Simulations demonstrating the stability and time responsiveness of the system are performed. Sensor noise input tests are performed to investigate the systems susceptibility to imperfect conditions. Cross product of inertia effects are also input to test for system instability.

  5. Slow mode shocks propagating in open and closed magnetic fields

    Institute of Scientific and Technical Information of China (English)

    吕建永; 魏奉思

    1999-01-01

    A 2-D MHD model is used to investigate the propagation of slow mode shocks in the open and closed magnetic fields of the meridional plane near the sun. The solutions demonstrate that a forward slow shock could retain its slow shock characteristics into interplanetary space in the magnetically open region; however, it can evolve into an intermediate shock through the helmet-type current sheet to the open magnetic field.

  6. Magnetic fields in diffuse media

    CERN Document Server

    Pino, Elisabete; Melioli, Claudio

    2015-01-01

    This volume presents the current knowledge of magnetic fields in diffuse astrophysical media. Starting with an overview of 21st century instrumentation to observe astrophysical magnetic fields, the chapters cover observational techniques, origin of magnetic fields, magnetic turbulence, basic processes in magnetized fluids, the role of magnetic fields for cosmic rays, in the interstellar medium and for star formation. Written by a group of leading experts the book represents an excellent overview of the field. Nonspecialists will find sufficient background to enter the field and be able to appreciate the state of the art.

  7. Coronal Magnetic Field Models

    Science.gov (United States)

    Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete

    2017-09-01

    Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.

  8. Global-scale consequences of magnetic-helicity injection and condensation on the sun

    Energy Technology Data Exchange (ETDEWEB)

    Mackay, Duncan H. [School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS (United Kingdom); DeVore, C. Richard [Naval Research Laboratory, Washington, DC 20375 (United States); Antiochos, Spiro K., E-mail: dhm@st-and.ac.uk [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-04-01

    In the recent paper of Antiochos, a new concept for the injection of magnetic helicity into the solar corona by small-scale convective motions and its condensation onto polarity inversion lines (PILs) was developed. We investigate this concept through global simulations of the Sun's photospheric and coronal magnetic fields, and compare the results with the hemispheric pattern of solar filaments. Assuming that the vorticity of the cells is predominantly counterclockwise/clockwise in the northern/southern hemisphere, the convective motions inject negative/positive helicity into each hemisphere. The simulations show that: (1) on a north-south oriented PIL, both differential rotation and convective motions inject the same sign of helicity, which matches that required to reproduce the hemispheric pattern of filaments. (2) On a high-latitude east-west oriented polar crown or subpolar crown PIL, the vorticity of the cells has to be approximately 2-3 times greater than the local differential-rotation gradient in order to overcome the incorrect sign of helicity injection from differential rotation. (3) In the declining phase of the cycle, as a bipole interacts with the polar field, in some cases, helicity condensation can reverse the effect of differential rotation along the east-west lead arm but not in all cases. The results show that this newly developed concept of magnetic helicity injection and condensation, in conjunction with the mechanisms used in Yeates et al., is a viable explanation for the hemispheric pattern of filaments. Future observational studies should focus on examining the vorticity component within convective motions to determine both its magnitude and latitudinal variation relative to the differential-rotation gradient on the Sun.

  9. Global-Scale Consequences of Magnetic-Helicity Injection and Condensation on the Sun

    Science.gov (United States)

    Mackay, Duncan H.; DeVore, C. Richard; Antiochos, Spiro K.

    2013-01-01

    In the recent paper of Antiochos, a new concept for the injection of magnetic helicity into the solar corona by small-scale convective motions and its condensation onto polarity inversion lines (PILs) has been developed. We investigate this concept through global simulations of the Sun's photospheric and coronal magnetic fields and compare the results with the hemispheric pattern of solar filaments. Assuming that the vorticity of the cells is predominately counter-clockwise/clockwise in the northern/southern hemisphere, the convective motions inject negative/positive helicity into each hemisphere. The simulations show that: (i) On a north-south orientated PIL, both differential rotation and convective motions inject the same sign of helicity which matches that required to reproduce the hemispheric pattern of filaments. (ii) On a high latitude east-west orientated polar crown or sub-polar crown PIL, the vorticity of the cells has to be approximately 2-3 times greater than the local differential rotation gradient in order to overcome the incorrect sign of helicity injection from differential rotation. (iii) In the declining phase of the cycle, as a bipole interacts with the polar field, in some cases helicity condensation can reverse the effect of differential rotation along the East-West lead arm, but not in all cases. The results show that this newly developed concept of magnetic helicity injection and condensation is a viable method to explain the hemispheric pattern of filaments in conjunction with the mechanisms used in Yeates et al. (2008). Future observational studies should focus on determining the vorticity component within convective motions to determine, both its magnitude and latitudinal variation relative to the differential rotation gradient on the Sun.

  10. Babcock Redux: An Amendment of Babcock's Schematic of the Sun's Magnetic Cycle

    Science.gov (United States)

    Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.

    2017-08-01

    We amend Babcock's original scenario for the global dynamo process that sustains the Sun's 22-year magnetic cycle. The amended scenario fits post-Babcock observed features of the magnetic activity cycle and convection zone, and is based on ideas of Spruit & Roberts (1983, Nature, 304, 401) about magnetic flux tubes in the convection zone. A sequence of four schematic cartoons lays out the proposed evolution of the global configuration of the magnetic field above, in, and at the bottom of the convection zone through sunspot Cycle 23 and into Cycle 24. Three key elements of the amended scenario are: (1) as the net following-polarity magnetic field from the sunspot-region Ω-loop fields of an ongoing sunspot cycle is swept poleward to cancel and replace the opposite-polarity polar-cap field from the previous sunspot cycle, it remains connected to the ongoing sunspot cycle's toroidal source-field band at the bottom of the convection zone; (2) topological pumping by the convection zone's free convection keeps the horizontal extent of the poleward-migrating following-polarity field pushed to the bottom, forcing it to gradually cancel and replace old horizontal field below it that connects the ongoing-cycle source-field band to the previous-cycle polar-cap field; (3) in each polar hemisphere, by continually shearing the poloidal component of the settling new horizontal field, the latitudinal differential rotation low in the convection zone generates the next-cycle source-field band poleward of the ongoing-cycle band. The amended scenario is a more-plausible version of Babcock's scenario, and its viability can be explored by appropriate kinematic flux-transport solar-dynamo simulations. A paper giving a full description of our dynamo scenario is posted on arXiv (http://arxiv.org/abs/1606.05371).This work was funded by the Heliophysics Division of NASA's Science Mission Directorate through the Living With a Star Targeted Research and Technology Program and the Hinode

  11. Magnetic Field Topology in Jets

    Science.gov (United States)

    Gardiner, T. A.; Frank, A.

    2000-01-01

    We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

  12. Magnetic field switchable dry adhesives.

    Science.gov (United States)

    Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

    2015-02-01

    A magnetic field controllable dry adhesive device is manufactured. The normal adhesion force can be increased or decreased depending on the presence of an applied magnetic field. If the magnetic field is present during the entire normal adhesion test cycle which includes both applying a preloading force and measuring the pulloff pressure, a decrease in adhesion is observed when compared to when there is no applied magnetic field. Similarly, if the magnetic field is present only during the preload portion of the normal adhesion test cycle, a decrease in adhesion is observed because of an increased stiffness of the magnetically controlled dry adhesive device. When the applied magnetic field is present during only the pulloff portion of the normal adhesion test cycle, either an increase or a decrease in normal adhesion is observed depending on the direction of the applied magnetic field.

  13. Magnetic fields of young solar twins

    CERN Document Server

    Rosén, L; Hackman, T; Lehtinen, J

    2016-01-01

    The goal of this work is to study the magnetic fields of six young solar-analogue stars both individually, and collectively, to search for possible magnetic field trends with age. If such trends are found, they can be used to understand magnetism in the context of stellar evolution of solar-like stars and, the past of the Sun and the solar system. This is also important for the atmospheric evolution of the inner planets, Earth in particular. We used Stokes IV data from two different spectropolarimeters, NARVAL and HARPSpol. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a modern Zeeman-Doppler imaging code in order to reconstruct the magnetic topology of all stars and the brightness distribution of one of our studied stars. Our results show a significant decrease in the magnetic field strength and energy as the stellar age increases from 100Myr to 250Myr while there is no significant age dependence of the mean magnetic field str...

  14. Limits for primordial magnetic fields

    CERN Document Server

    Caprini, Chiara

    2011-01-01

    A possible explanation for the origin of the magnetic fields observed today in matter structures is that they were generated in the primordial universe. After briefly revising the model of a primordial stochastic magnetic field and sketching the main features of its time evolution in the primordial plasma, we illustrate the current upper bounds on the magnetic field amplitude and spectral index from Cosmic Microwave Background observations and gravitational wave production. We conclude that a primordial magnetic field generated by a non-causal process such as inflation with a red spectrum seems to be favoured as a seed for the magnetic fields observed today in structures.

  15. Swarm: Recent Progress in Analysis of the Sun Induced Magnetic Disturbance

    DEFF Research Database (Denmark)

    Tøffner-Clausen, Lars; Lesur, Vincent; Brauer, Peter

    The ESA Earth Observation Magnetic Mission Swarm carries high precision vector and scalar magnetometers. Careful analyses have revealed s smaller, Sun driven magnetic disturbance of the vector magnetometer. This disturbance have been imperically mapped and corrected since mid 2015. This work...

  16. Swarm: Recent Progress in Analysis of the Sun Induced Magnetic Disturbance

    DEFF Research Database (Denmark)

    Tøffner-Clausen, Lars; Lesur, Vincent; Brauer, Peter

    The ESA Earth Observation Magnetic Mission Swarm carries high precision vector and scalar magnetometers. Careful analyses have revealed s smaller, Sun driven magnetic disturbance of the vector magnetometer. This disturbance have been imperically mapped and corrected since mid 2015. This work...

  17. Can the Solar Wind be Driven by Magnetic Reconnection in the Sun's Magnetic Carpet?

    OpenAIRE

    Cranmer, Steven R.; van Ballegooijen, Adriaan A.

    2010-01-01

    The physical processes that heat the solar corona and accelerate the solar wind remain unknown after many years of study. Some have suggested that the wind is driven by waves and turbulence in open magnetic flux tubes, and others have suggested that plasma is injected into the open tubes by magnetic reconnection with closed loops. In order to test the latter idea, we developed Monte Carlo simulations of the photospheric "magnetic carpet" and extrapolated the time-varying coronal field. These ...

  18. Superhorizon magnetic fields

    CERN Document Server

    Campanelli, Leonardo

    2015-01-01

    [Abridged] We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wavenumber $k$ evolves, after inflation, according to the values of $k\\eta_e$, $n_{\\mathbf{k}}$, and $\\Omega_k$, where $\\eta_e$ is the conformal time at the end of inflation, $n_{\\mathbf{k}}$ is the number density spectrum of inflation-produced photons, and $\\Omega_k$ is the phase difference between the two Bogolubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that $n_{\\mathbf{k}}^{-1} \\ll |k\\eta_e| \\ll 1$, and three evolutionary scenarios are possible: ($i$) $|\\Omega_k \\mp \\pi| = \\mathcal{O}(1)$, in which case the evolution of the magnetic spectrum $B_k(\\eta)$ is adiabatic, $a^2B_k(\\eta) = \\mbox{const}$, with $a$ being the expansion parameter; ($ii$) $|\\Omega_k \\mp \\pi| \\ll |k\\eta_e|$,...

  19. SCUPOL Magnetic Field Analysis

    CERN Document Server

    Poidevin, Frederick; Kowal, Grzegorz; Pino, Elisabete de Gouveia Dal; Magalhaes, Antonio-Mario

    2013-01-01

    We present an extensive analysis of the 850 microns polarization maps of the SCUPOL Catalog produced by Matthews et al. (2009), focusing exclusively on the molecular clouds and star-forming regions. For the sufficiently sampled regions, we characterize the depolarization properties and the turbulent-to-mean magnetic field ratio of each region. Similar sets of parameters are calculated from 2D synthetic maps of dust emission polarization produced with 3D MHD numerical simulations scaled to the S106, OMC-2/3, W49 and DR21 molecular clouds polarization maps. For these specific regions the turbulent MHD regimes retrieved from the simulations, as described by the turbulent Alfv\\`en and sonic Mach numbers, are consistent within a factor 1 to 2 with the values of the same turbulent regimes estimated from the analysis of Zeeman measurements data provided by Crutcher (1999). Constraints on the values of the inclination angle of the mean magnetic field with respect to the LOS are also given. The values obtained from th...

  20. MAGNETIZED JETS DRIVEN BY THE SUN: THE STRUCTURE OF THE HELIOSPHERE REVISITED

    Energy Technology Data Exchange (ETDEWEB)

    Opher, M. [Astronomy Department, Boston University, Boston, MA 02215 (United States); Drake, J. F. [Department of Physics and the Institute for Physical Science and Technology, University of Maryland, College Park, MD (United States); Zieger, B. [Center for Space Physics, Boston University, Boston, MA 02215 (United States); Gombosi, T. I., E-mail: mopher@bu.edu [University of Michigan, Ann Arbor, MI (United States)

    2015-02-20

    The classic accepted view of the heliosphere is a quiescent, comet-like shape aligned in the direction of the Sun’s travel through the interstellar medium (ISM) extending for thousands of astronomical units (AUs). Here, we show, based on magnetohydrodynamic (MHD) simulations, that the tension (hoop) force of the twisted magnetic field of the Sun confines the solar wind plasma beyond the termination shock and drives jets to the north and south very much like astrophysical jets. These jets are deflected into the tail region by the motion of the Sun through the ISM similar to bent galactic jets moving through the intergalactic medium. The interstellar wind blows the two jets into the tail but is not strong enough to force the lobes into a single comet-like tail, as happens to some astrophysical jets. Instead, the interstellar wind flows around the heliosphere and into the equatorial region between the two jets. As in some astrophysical jets that are kink unstable, we show here that the heliospheric jets are turbulent (due to large-scale MHD instabilities and reconnection) and strongly mix the solar wind with the ISM beyond 400 AU. The resulting turbulence has important implications for particle acceleration in the heliosphere. The two-lobe structure is consistent with the energetic neutral atom (ENA) images of the heliotail from IBEX where two lobes are visible in the north and south and the suggestion from the Cassini ENAs that the heliosphere is “tailless.”.

  1. Magnetic Fields: Visible and Permanent.

    Science.gov (United States)

    Winkeljohn, Dorothy R.; Earl, Robert D.

    1983-01-01

    Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

  2. Magnetic fields in early-type stars

    CERN Document Server

    Grunhut, Jason H

    2015-01-01

    For several decades we have been cognizant of the presence of magnetic fields in early-type stars, but our understanding of their magnetic properties has recently (over the last decade) expanded due to the new generation of high-resolution spectropolarimeters (ESPaDOnS at CFHT, Narval at TBL, HARPSpol at ESO). The most detailed surface magnetic field maps of intermediate-mass stars have been obtained through Doppler imaging techniques, allowing us to probe the small-scale structure of these stars. Thanks to the effort of large programmes (e.g. the MiMeS project), we have, for the first time, addressed key issues regarding our understanding of the magnetic properties of massive (M > 8 M_sun) stars, whose magnetic fields were only first detected about fifteen years ago. In this proceedings article we review the spectropolarimetric observations and statistics derived in recent years that have formed our general understanding of stellar magnetism in early-type stars. We also discuss how these observations have fu...

  3. Surface Flux Transport and the Evolution of the Sun's Polar Fields

    Science.gov (United States)

    Wang, Y.-M.

    2017-09-01

    The evolution of the polar fields occupies a central place in flux transport (Babcock-Leighton) models of the solar cycle. We discuss the relationship between surface flux transport and polar field evolution, focusing on two main issues: the latitudinal profile of the meridional flow and the axial tilts of active regions. Recent helioseismic observations indicate that the poleward flow speed peaks at much lower latitudes than inferred from magnetic feature tracking, which includes the effect of supergranular diffusion and thus does not represent the actual bulk flow. Employing idealized simulations, we demonstrate that flow profiles that peak at mid latitudes give rise to overly strong and concentrated polar fields. We discuss the differences between magnetic and white-light measurements of tilt angles, noting the large uncertainties inherent in the sunspot group measurements and their tendency to underestimate the actual tilts. We find no clear evidence for systematic cycle-to-cycle variations in Joy's law during cycles 21-23. Finally, based on the observed evolution of the Sun's axial dipole component and polar fields up to the end of 2015, we predict that cycle 25 will be similar in amplitude to cycle 24.

  4. Rotation Profiles of Solar-like Stars with Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We investigate the rotation profile of solar-like stars with magnetic fields. A diffu-sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 σ level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 M⊙, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.

  5. Dynamics of multi-cored magnetic structures in the quiet Sun

    CERN Document Server

    Requerey, Iker S; Rubio, Luis R Bellot; Pillet, Valentín Martínez; Solanki, Sami K; Schmidt, Wolfgang

    2015-01-01

    We report on the dynamical interaction of quiet-Sun magnetic fields and granular convection in the solar photosphere as seen by \\textsc{Sunrise}. We use high spatial resolution (0\\farcs 15--0\\farcs 18) and temporal cadence (33 s) spectropolarimetric Imaging Magnetograph eXperiment data, together with simultaneous CN and Ca\\,\\textsc{ii}\\,H filtergrams from \\textsc{Sunrise} Filter Imager. We apply the SIR inversion code to the polarimetric data in order to infer the line of sight velocity and vector magnetic field in the photosphere. The analysis reveals bundles of individual flux tubes evolving as a single entity during the entire 23 minute data set. The group shares a common canopy in the upper photospheric layers, while the individual tubes continually intensify, fragment and merge in the same way that chains of bright points in photometric observations have been reported to do. The evolution of the tube cores are driven by the local granular convection flows. They intensify when they are "compressed" by sur...

  6. On the spectrum of turbulent magnetic fields. [on solar surface

    Science.gov (United States)

    Knobloch, E.; Rosner, R.

    1981-01-01

    Theoretical power spectra of magnetic fields subject to turbulent fluid motions in the kinematic regime are presented, and previous theories are reviewed, with reference to magnetic fields on the sun. Magnetic field diffusion in turbulence with persistent eddies is predicted to be described by an effective negative magnetic diffusivity. It is found that observations cannot be explained on the basis of turbulent kinematic theories unless the turbulent motions are three-dimensional, and the effective diffusivities are larger than the molecular diffusivities. Lower bounds on the turbulent viscosity are derived, suggesting that dynamical processes controlling the magnetic field spectrum occur at least 15,000 km below the surface. The results, which remain consistent with the assumption that effective diffusivity is uniform, suggest that surface magnetic field observations can be used as a diagnostic for subsurface flows.

  7. Approach to Integrate Global-Sun Models of Magnetic Flux Emergence and Transport for Space Weather Studies

    Science.gov (United States)

    Mansour, Nagi N.; Wray, Alan A.; Mehrotra, Piyush; Henney, Carl; Arge, Nick; Godinez, H.; Manchester, Ward; Koller, J.; Kosovichev, A.; Scherrer, P.; Zhao, J.; Stein, R.; Duvall, T.; Fan, Y.

    2013-01-01

    The Sun lies at the center of space weather and is the source of its variability. The primary input to coronal and solar wind models is the activity of the magnetic field in the solar photosphere. Recent advancements in solar observations and numerical simulations provide a basis for developing physics-based models for the dynamics of the magnetic field from the deep convection zone of the Sun to the corona with the goal of providing robust near real-time boundary conditions at the base of space weather forecast models. The goal is to develop new strategic capabilities that enable characterization and prediction of the magnetic field structure and flow dynamics of the Sun by assimilating data from helioseismology and magnetic field observations into physics-based realistic magnetohydrodynamics (MHD) simulations. The integration of first-principle modeling of solar magnetism and flow dynamics with real-time observational data via advanced data assimilation methods is a new, transformative step in space weather research and prediction. This approach will substantially enhance an existing model of magnetic flux distribution and transport developed by the Air Force Research Lab. The development plan is to use the Space Weather Modeling Framework (SWMF) to develop Coupled Models for Emerging flux Simulations (CMES) that couples three existing models: (1) an MHD formulation with the anelastic approximation to simulate the deep convection zone (FSAM code), (2) an MHD formulation with full compressible Navier-Stokes equations and a detailed description of radiative transfer and thermodynamics to simulate near-surface convection and the photosphere (Stagger code), and (3) an MHD formulation with full, compressible Navier-Stokes equations and an approximate description of radiative transfer and heating to simulate the corona (Module in BATS-R-US). CMES will enable simulations of the emergence of magnetic structures from the deep convection zone to the corona. Finally, a plan

  8. Vestibular stimulation by magnetic fields

    Science.gov (United States)

    Ward, Bryan K.; Roberts, Dale C.; Della Santina, Charles C.; Carey, John P.; Zee, David S.

    2015-01-01

    Individuals working next to strong static magnetic fields occasionally report disorientation and vertigo. With the increasing strength of magnetic fields used for magnetic resonance imaging (MRI) studies, these reports have become more common. It was recently learned that humans, mice and zebrafish all demonstrate behaviors consistent with constant peripheral vestibular stimulation while inside a strong, static magnetic field. The proposed mechanism for this effect involves a Lorentz force resulting from the interaction of a strong static magnetic field with naturally occurring ionic currents flowing through the inner ear endolymph into vestibular hair cells. The resulting force within the endolymph is strong enough to displace the lateral semicircular canal cupula, inducing vertigo and the horizontal nystagmus seen in normal mice and in humans. This review explores the evidence for interactions of magnetic fields with the vestibular system. PMID:25735662

  9. Evolution of the cycles of magnetic activity of the Sun and Sun-like stars in time

    CERN Document Server

    Bruevich, E A; Artamonov, B P

    2016-01-01

    We applied the method of continuous wavelet-transform to the time-frequency analysis to the sets of observations of relative sunspot numbers, sunspot areas and to 6 Mount Wilson HK-project stars with well-defined magnetic cycles. Wavelet analysis of these data reveals the following pattern: at the same time there are several activity cycles whose periods vary widely from the quasi-biennial up to the centennial period for the Sun and vary significant during observations time of the HK-project stars. These relatively low-frequency periodic variations of the solar and stellar activity gradually change the values of periods of different cycles in time. This phenomenon can be observed in every cycles of activity

  10. Magnetic fields of young solar twins

    Science.gov (United States)

    Rosén, L.; Kochukhov, O.; Hackman, T.; Lehtinen, J.

    2016-09-01

    Aims: The goal of this work is to study the magnetic fields of six young solar-analogue stars both individually, and collectively, to search for possible magnetic field trends with age. If such trends are found, they can be used to understand magnetism in the context of stellar evolution of solar-like stars and to understand the past of the Sun and the solar system. This is also important for the atmospheric evolution of the inner planets, Earth in particular. Methods: We used Stokes IV data from two different spectropolarimeters, NARVAL and HARPSpol. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a modern Zeeman-Doppler imaging code in order to reconstruct the magnetic topology of all stars and the brightness distribution of one of our studied stars. Results: Our results show a significant decrease in the magnetic field strength and energy as the stellar age increases from 100 Myr to 250 Myr, while there is no significant age dependence of the mean magnetic field strength for stars with ages 250-650 Myr. The spread in the mean field strength between different stars is comparable to the scatter between different observations of individual stars. The meridional field component is weaker than the radial and azimuthal field components in 15 of the 16 magnetic maps. It turns out that 89-97% of the magnetic field energy is contained in l = 1 - 3. There is also no clear trend with age and distribution of field energy into poloidal/toroidal and axisymmetric/non-axisymmetric components within the sample. The two oldest stars in this study show an octupole component that is twice as strong as the quadrupole component. This is only seen in 1 of the 13 maps of the younger stars. One star, χ1 Ori, displays two field polarity switches during almost 5 yr of observations suggesting a magnetic cycle length of 2, 6, or 8 yr. Based on observations made with the HARPSpol instrument on the ESO 3.6 m

  11. Magnetic response to applied electrostatic field in external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)

    2014-04-15

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics. (orig.)

  12. Magnetic response to applied electrostatic field in external magnetic field

    CERN Document Server

    Adorno, T C; Shabad, A E

    2014-01-01

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to a simple example of a spherically-symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space, the pattern of lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

  13. Do the Legs of Magnetic Clouds Contain Twisted Flux-rope Magnetic Fields?

    Science.gov (United States)

    Owens, M. J.

    2016-02-01

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The time of flight of energetic particles, however, suggests shorter magnetic field line lengths than such a continuous twisted flux rope would produce. In this study, two simple models are compared with observed flux rope axis orientations of 196 MCs to show that the flux rope structure is confined to the MC leading edge. The MC “legs,” which magnetically connect the flux rope to the Sun, are not recognizable as MCs and thus are unlikely to contain twisted flux rope fields. Spacecraft encounters with these non-flux rope legs may provide an explanation for the frequent observation of non-MC ICMEs.

  14. DO THE LEGS OF MAGNETIC CLOUDS CONTAIN TWISTED FLUX-ROPE MAGNETIC FIELDS?

    Energy Technology Data Exchange (ETDEWEB)

    Owens, M. J. [Space and Atmospheric Electricity Group, Department of Meteorology, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB (United Kingdom)

    2016-02-20

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The time of flight of energetic particles, however, suggests shorter magnetic field line lengths than such a continuous twisted flux rope would produce. In this study, two simple models are compared with observed flux rope axis orientations of 196 MCs to show that the flux rope structure is confined to the MC leading edge. The MC “legs,” which magnetically connect the flux rope to the Sun, are not recognizable as MCs and thus are unlikely to contain twisted flux rope fields. Spacecraft encounters with these non-flux rope legs may provide an explanation for the frequent observation of non-MC ICMEs.

  15. The Number Of Magnetic Null Points In The Quiet Sun Corona

    CERN Document Server

    Longcope, D W

    2008-01-01

    The coronal magnetic field above a particular photospheric region will vanish at a certain number of points, called null points. These points can be found directly in a potential field extrapolation or their density can be estimated from Fourier spectrum of the magnetogram. The spectral estimate, which assumes that the extrapolated field is random, homogeneous and has Gaussian statistics, is found here to be relatively accurate for quiet Sun magnetograms from SOHO's MDI. The majority of null points occur at low altitudes, and their distribution is dictated by high wavenumbers in the Fourier spectrum. This portion of the spectrum is affected by Poisson noise, and as many as five-sixths of null points identified from a direct extrapolation can be attributed to noise. The null distribution above 1500 km is found to depend on wavelengths that are reliably measured by MDI in either its low-resolution or high-resolution mode. After correcting the spectrum to remove white noise and compensate for the modulation tran...

  16. Spacecraft attitude determination using the earth's magnetic field

    Science.gov (United States)

    Simpson, David G.

    1989-01-01

    A method is presented by which the attitude of a low-Earth orbiting spacecraft may be determined using a vector magnetometer, a digital Sun sensor, and a mathematical model of the Earth's magnetic field. The method is currently being implemented for the Solar Maximum Mission spacecraft (as a backup for the failing star trackers) as a way to determine roll gyro drift.

  17. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  18. The MAVEN Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2014-01-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a quantization uncertainty of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05%. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers - multiple rotations about the spacecraft x and z axes - to characterize spacecraft fields and/or instrument offsets in flight.

  19. Comparison Study of Two Different Sun-Tracking Methods in Optical Efficiency of Heliostat Field

    OpenAIRE

    K.-K. Chong; Tan, M.H.

    2012-01-01

    There are two sun-tracking methods widely used for the heliostat, which are conventional Azimuth-Elevation and revolutionary Spinning-Elevation methods. Following the previous study to compare the range of motion, a comparison study in optical efficiency of heliostat field for the two methods is further explored in this paper. A special algorithm using ray-tracing technique has also been developed to simulate the optical efficiency of heliostat field for both sun-tracking methods in different...

  20. Counting Magnetic Bipoles on the Sun by Polarity Inversion

    Science.gov (United States)

    Jones, Harrison P.

    2004-01-01

    This paper presents a simple and efficient algorithm for deriving images of polarity inversion from NSO/Kitt Peak magnetograms without use of contouring routines and shows by example how these maps depend upon the spatial scale for filtering the raw data. Smaller filtering scales produce many localized closed contours in mixed polarity regions while supergranular and larger filtering scales produce more global patterns. The apparent continuity of an inversion line depends on how the spatial filtering is accomplished, but its shape depends only on scale. The total length of the magnetic polarity inversion contours varies as a power law of the filter scale with fractal dimension of order 1.9. The amplitude but nut the exponent of this power-law relation varies with solar activity. The results are compared to similar analyses of areal distributions of bipolar magnetic regions.

  1. Magnetic fields in non-convective regions of stars

    CERN Document Server

    Braithwaite, J

    2015-01-01

    We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them, the solar cycle being one of the better known examples. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and...

  2. Stokes Diagnostics of Wave Propagation in the Magnetic Network on the Sun

    CERN Document Server

    Vigeesh, G; Hasan, S S

    2011-01-01

    The solar atmosphere is magnetically structured and highly dynamic. Owing to the dynamic nature of the regions in which these magnetic structures exist, waves can be excited in them. Numerical investigations of wave propagation in small-scale magnetic flux concentrations in the magnetic network on the Sun have shown, that the nature of the excited modes depends on the value of plasma beta (the ratio of gas to magnetic pressure) where the driving motion occurs. Considering that the properties of these waves should give rise to observable characteristic signatures, we have attempted a study of emergent spectra from our numerical simulations. We find that the signatures of wave propagation in magnetic elements can be detected when the spatial resolution is sufficiently high to clearly resolve magnetic concentrations, enabling observations in different regions within the flux concentrations. The possibility to probe various lines-of-sight around the flux concentration bears the potential to reveal different modes...

  3. Our Explosive Sun

    Science.gov (United States)

    Brown, D. S.

    2009-01-01

    The Sun's atmosphere is a highly structured but dynamic place, dominated by the solar magnetic field. Hot charged gas (plasma) is trapped on lines of magnetic force that can snap like an elastic band, propelling giant clouds of material out into space. A range of ground-based and space-based solar telescopes observe these eruptions, particularly…

  4. Influence of Fast Global Variations of Solar Magnetic Fields on Space Weather in Cycle 23

    Institute of Scientific and Technical Information of China (English)

    S. I. Molodykh; G.A. Zherebtsov; V.A. Kovalenko; J.X. Wang; V.I. Sidorov

    2005-01-01

    It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the global magnetic field. Periods of fast global changes on the Sun are accompanied by anomalous manifestations in the interplanetary space and in the geomagnetic field. There is a regular recurrence of these periods in each cycle of solar activity, and the periods are characterized by enhanced flaring activity that reflects fast changes in magnetic structures. Is demonstrated, that the fast changes have essential influencing on a condition of space weather, as most strong geophysical disturbances are connected to sporadic phenomena on the Sun. An explanation has been offered for the origin of anomalous geomagnetic disturbances that are unidentifiable in traditionally used solar activity indices. Is shown, main physical mechanism that leads to fast variations of the magnetic fields in the Sun's atmosphere is the reconnection process.

  5. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  6. Rotating superconductor magnet for producing rotating lobed magnetic field lines

    Science.gov (United States)

    Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.

    1978-01-01

    This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.

  7. Solar wind induced magnetic field around the unmagnetized Earth

    CERN Document Server

    Birk, G T; Konz, C

    2004-01-01

    The Earth is a planet with a dipolar magnetic field which is agitated by a magnetized plasma wind streaming from the Sun. The magnetic field shields the Earth's surface from penetrating high energy solar wind particles, as well as interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds of times over the last 400 million years. These polarity reversals correspond to drastic breakdowns of the dynamo action. The question arises what the consequences for the Earth's atmosphere, climate, and, in particular, biosphere are. It is shown by kinematic estimates and three-dimensional plasma-neutral gas simulations that the solar wind can induce very fast a magnetic field in the previously completely unmagnetized Earth's ionosphere that is strong enough to protect Earth from cosmic radiations comparable to the case of an intact magnetic dynamo.

  8. Low Cost Magnetic Field Controller

    CERN Document Server

    Malafronte, Alexandre A

    2005-01-01

    The Physics Institute of the University of São Paulo (IFUSP) is building a continuous wave (cw) racetrack microtron. This machine has several dipole magnets, like the first and second stage recirculators, and a number of smaller ones in the transport line. These magnets must produce very stable magnetic fields to allow the beam to recirculate along very precise orbits and paths. Furthermore, the fields must be reproducible with great accuracy to allow an easier setup of the machine, though the effects of hysteresis tend to jeopardize the reproducibility. If the magnetic field is chosen by setting the current in the coils, temperature effects over the magnet and power supply tend to change the field. This work describes an inexpensive magnetic field controller that allows a direct measure of the magnetic field through an Hall probe. It includes a microcontroller running a feedback algorithm to control the power supply, in order to keep the field stable and reproducible. The controller can also execu...

  9. Background magnetic fields during last three cycles of solar activity

    Science.gov (United States)

    Andryeyeva, O. A.; Stepanian, N. N.

    2008-07-01

    This paper describes our studies of evolution of the solar magnetic field with different sign and field strength in the range from -100 G to 100 G. The structure and evolution of large-scale magnetic fields on the Sun during the last 3 cycles of solar activity is investigated using magnetograph data from the Kitt Peak Solar Observatory. This analysis reveals two groups of the large-scale magnetic fields evolving differently during the cycles. The first group is represented by relatively weak background fields, and is best observed in the range of 3-10 Gauss. The second group is represented by stronger fields of 75-100 Gauss. The spatial and temporal properties of these groups are described and compared with the total magnetic flux. It is shown that the anomalous behaviour of the total flux during the last cycle can be found only in the second group

  10. Understanding solar and stellar magnetic fields through helio- and asteroseismology

    Science.gov (United States)

    Broomhall, Anne-Marie

    Global helioseismology uses the Sun’s natural acoustic oscillations to study the solar interior, where the solar magnetic field is generated. At any one time thousands of acoustic oscillations are trapped in different but overlapping regions of the solar interior. Therefore, by studying the properties of these oscillations, such as their frequency and amplitude, we can probe inside the Sun. Often models designed to describe the helioseismic oscillations are based on the assumption that no magnetic field is present. However, this is clearly a simplistic view: The properties of these acoustic oscillations are affected by the presence of a magnetic field. By studying variations in the oscillations through the solar cycle we can learn about the Sun’s internal magnetic field and can feedback into MHD models of the solar interior. Similar techniques can be used to study the magnetic activity cycles of stars other than the Sun (through asteroseismology), using data from, for example, NASA’s Kepler satellite. While studying the Sun’s magnetic cycle helps us to understand the magnetic activity observed on other stars, activity cycles on other stars could prove vital in unravelling the mysteries of the Sun’s magnetic activity cycle.

  11. Resonant magnetic fields from inflation

    CERN Document Server

    Byrnes, Christian T; Jain, Rajeev Kumar; Urban, Federico R

    2012-01-01

    We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of ${\\cal O}(10^{-15}\\, \\Gauss)$ today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

  12. Static magnetic fields enhance turbulence

    CERN Document Server

    Pothérat, Alban

    2015-01-01

    More often than not, turbulence occurs under the influence of external fields, mostly rotation and magnetic fields generated either by planets, stellar objects or by an industrial environment. Their effect on the anisotropy and the dissipative behaviour of turbulence is recognised but complex, and it is still difficult to even tell whether they enhance or dampen turbulence. For example, externally imposed magnetic fields suppress free turbulence in electrically conducting fluids (Moffatt 1967), and make it two-dimensional (2D) (Sommeria & Moreau 1982); but their effect on the intensity of forced turbulence, as in pipes, convective flows or otherwise, is not clear. We shall prove that since two-dimensionalisation preferentially affects larger scales, these undergo much less dissipation and sustain intense turbulent fluctuations. When higher magnetic fields are imposed, quasi-2D structures retain more kinetic energy, so that rather than suppressing forced turbulence, external magnetic fields indirectly enha...

  13. Microflaring in Low-Lying Core Fields and Extended Coronal Heating in the Quiet Sun

    Science.gov (United States)

    Porter, Jason G.; Falconer, D. A.; Moore, Ronald L.

    1999-01-01

    We have previously reported analyses of Yohkoh SXT data examining the relationship between the heating of extended coronal loops (both within and stemming from active regions) and microflaring in core fields lying along neutral lines near their footpoints (J. G. Porter, D. A. Falconer, and R. L. Moore 1998, in Solar Jets and Coronal Plumes, ed. T. Guyenne, ESA SP-421, and references therein). We found a surprisingly poor correlation of intensity variations in the extended loops with individual microflares in the compact heated areas at their feet, despite considerable circumstancial evidence linking the heating processes in these regions. Now, a study of Fe XII image sequences from SOHO EIT show that similar associations of core field structures with the footpoints of very extended coronal features can be found in the quiet Sun. The morphology is consistent with the finding of Wang et al. (1997, ApJ 484, L75) that polar plumes are rooted at sites of mixed polarity in the magnetic network. We find that the upstairs/downstairs intensity variations often follow the trend, identified in the active region observations, of a weak correspondence. Apparently much of the coronal heating in the extended loops is driven by a type of core field magnetic activity that is "cooler" than the events having the coronal signature of microflares, i.e., activity that results in little heating within the core fields themselves. This work was funded by the Solar Physics Branch of NASA's Office of Space Science through the SR&T Program and the SEC Guest Investigator Program.

  14. Origin of cosmic magnetic fields

    Science.gov (United States)

    Rees, M. J.

    2006-06-01

    The first significant cosmic fields, and the seed field for galactic dynamos probably developed after the formation of the first non-linear structures. The history of star formation and the intergalactic medium is controlled, at least in part, by how and when galaxies and their precursors acquired their fields. The amplification of fields behind shocks, and the diffusivity of the magnetic flux, are crucial to the interpretation of radio sources, gamma ray burst afterglows, and other energetic cosmic phenomena. The build-up of magnetic fields is an important aspect of the overall cosmogonic process.

  15. High speed magnetized flows in the quiet Sun

    CERN Document Server

    Noda, C Quintero; Suárez, D Orozco; Cobo, B Ruiz

    2014-01-01

    We have examined the spatial and polarimetric properties of these events using a variety of data from the Hinode spacecraft. We have also inferred the atmospheric stratification of the physical parameters by means of the inversion of the observed Stokes profiles employing the Stokes Inversion based on Response functions (SIR) code. Finally, we analyzed their evolution using a time series from the same instrument. Blue-shifted events tend to appear over bright regions at the edge of granules, while red-shifted events are seen predominantly over dark regions on intergranular lanes. Large linear polarization signals can be seen in the region that connects them. The magnetic structure inferred from the time series revealed that the structure corresponds to a $\\Omega$-loop, with one footpoint always over the edge of a granule and the other inside an intergranular lane. The physical parameters obtained from the inversions of the observed Stokes profiles in both events show an increase with respect to the Harvard-Sm...

  16. Magnetohydrodynamics of the sun

    CERN Document Server

    Priest, Eric

    2014-01-01

    Magnetohydrodynamics of the Sun is a completely new up-to-date rewrite from scratch of the 1982 book Solar Magnetohydrodynamics, taking account of enormous advances in understanding since that date. It describes the subtle and complex interaction between the Sun's plasma atmosphere and its magnetic field, which is responsible for many fascinating dynamic phenomena. Chapters cover the generation of the Sun's magnetic field by dynamo action, magnetoconvection and the nature of photospheric flux tubes such as sunspots, the heating of the outer atmosphere by waves or reconnection, the structure of prominences, the nature of eruptive instability and magnetic reconnection in solar flares and coronal mass ejections, and the acceleration of the solar wind by reconnection or wave-turbulence. It is essential reading for graduate students and researchers in solar physics and related fields of astronomy, plasma physics and fluid dynamics. Problem sets and other resources are available at www.cambridge.org/9780521854719.

  17. Measuring Earth's Magnetic Field Simply.

    Science.gov (United States)

    Stewart, Gay B.

    2000-01-01

    Describes a method for measuring the earth's magnetic field using an empty toilet paper tube, copper wire, clear tape, a battery, a linear variable resistor, a small compass, cardboard, a protractor, and an ammeter. (WRM)

  18. ISR split-field magnet

    CERN Multimedia

    1975-01-01

    The experimental apparatus used at intersection 4 around the Split-Field Magnet by the CERN-Bologna Collaboration (experiment R406). The plastic scintillator telescopes are used for precise pulse-height and time-of-flight measurements.

  19. What Are Electric and Magnetic Fields? (EMF)

    Science.gov (United States)

    ... take for granted. What are electric and magnetic fields? Electric and magnetic fields (EMF) are invisible lines of ... humans. AC electric power produces electric and magnetic fields that create weak electric currents in humans. Being exposed to some kinds ...

  20. The Juno Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Benn, M.; Bjarno, J. B.; Denver, T.; Espley, J.; Jorgensen, J. L.; Jorgensen, P. S.; Lawton, P.; Malinnikova, A.; Merayo, J. M.; Murphy, S.; Odom, J.; Oliversen, R.; Schnurr, R.; Sheppard, D.; Smith, E. J.

    2017-02-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter's planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor suites, each consisting of a tri-axial Fluxgate Magnetometer (FGM) sensor and a pair of co-located imaging sensors mounted on an ultra-stable optical bench. The imaging system sensors are part of a subsystem that provides accurate attitude information (to ˜20 arcsec on a spinning spacecraft) near the point of measurement of the magnetic field. The two sensor suites are accommodated at 10 and 12 m from the body of the spacecraft on a 4 m long magnetometer boom affixed to the outer end of one of 's three solar array assemblies. The magnetometer sensors are controlled by independent and functionally identical electronics boards within the magnetometer electronics package mounted inside Juno's massive radiation shielded vault. The imaging sensors are controlled by a fully hardware redundant electronics package also mounted within the radiation vault. Each magnetometer sensor measures the vector magnetic field with 100 ppm absolute vector accuracy over a wide dynamic range (to 16 Gauss = 1.6 × 106 nT per axis) with a resolution of ˜0.05 nT in the most sensitive dynamic range (±1600 nT per axis). Both magnetometers sample the magnetic field simultaneously at an intrinsic sample rate of 64 vector samples per second. The magnetic field instrumentation may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. The attitude determination system compares images with an on-board star catalog to provide attitude solutions (quaternions) at a rate of up to 4 solutions per second, and may be configured to acquire images of selected targets for science and engineering analysis. The system tracks and catalogs objects that pass through the imager field of

  1. The Juno Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Benna, M.; Bjarno, J. B.; Denver, T.; Espley, J.; Jorgensen, J. L.; Jorgensen, P. S.; Lawton, P.; Malinnikova, A.; Merayo, J. M.; hide

    2017-01-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter's planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor suites, each consisting of a tri-axial Fluxgate Magnetometer (FGM) sensor and a pair of co-located imaging sensors mounted on an ultra-stable optical bench. The imaging system sensors are part of a subsystem that provides accurate attitude information (to approx. 20 arcsec on a spinning spacecraft) near the point of measurement of the magnetic field. The two sensor suites are accommodated at 10 and 12 m from the body of the spacecraft on a 4 m long magnetometer boom affixed to the outer end of one of 's three solar array assemblies. The magnetometer sensors are controlled by independent and functionally identical electronics boards within the magnetometer electronics package mounted inside Juno's massive radiation shielded vault. The imaging sensors are controlled by a fully hardware redundant electronics package also mounted within the radiation vault. Each magnetometer sensor measures the vector magnetic field with 100 ppm absolute vector accuracy over a wide dynamic range (to 16 Gauss = 1.6 x 10(exp. 6) nT per axis) with a resolution of approx. 0.05 nT in the most sensitive dynamic range (+/-1600 nT per axis). Both magnetometers sample the magnetic field simultaneously at an intrinsic sample rate of 64 vector samples per second. The magnetic field instrumentation may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. The attitude determination system compares images with an on-board star catalog to provide attitude solutions (quaternions) at a rate of up to 4 solutions per second, and may be configured to acquire images of selected targets for science and engineering analysis. The system tracks and catalogs objects that pass through

  2. Magnetic-Field Hazards Bibliography.

    Science.gov (United States)

    1985-09-01

    produced during pulsed- magnetic-field therapy for non-union of the tibia." Med. Biol. Eng. Comput., Vol. 20, pp. 501-511 (1982). 32. Miller, D. A...Phenum Publishing Co. (1983). 40. Topper, R. F., "Electromagnetic shielding feasibility study," ASD -TDR-63-194 (Armour Research Foundation, Chicago...mammalian cells by strong magnetic fields (1976). 93. Malins, D. C., and Collier, T. K., "Xenobiotic interactions in aquatic organisms-effects on

  3. Mean Interplanetary Magnetic Field Measurement Using the ARGO-YBJ Experiment

    CERN Document Server

    Aielli, G; Bartoli, B; Bernardini, P; Bi, X J; Bleve, C; Branchini, P; Budano, A; Bussino, S; Melcarne, A K Calabrese; Camarri, P; Cao, Z; Cappa, A; Cardarelli, R; Catalanotti, S; Cattaneo, C; Celio, P; Chen, S Z; Chen, T L; Chen, Y; Creti, P; Cui, S W; Dai, B Z; Staiti, G D'Alí; Danzengluobu,; Dattoli, M; De Mitri, I; Piazzoli, B D'Ettorre; De Vincenzi, M; Di Girolamo, T; Ding, X H; Di Sciascio, G; Feng, C F; Feng, Z Y; Feng, Zhenyong; Galeazzi, F; Galeotti, P; Gargana, R; Gou, Q B; Guo, Y Q; He, H H; Hu, Haibing; Hu, Hongbo; Huang, Q; Iacovacci, M; Iuppa, R; James, I; Jia, H Y; Labaciren,; Li, H J; Li, J Y; Li, X X; Liberti, B; Liguori, G; Liu, C; Liu, C Q; Liu, M Y; Liu, J; Lu, H; Ma, X H; Mancarella, G; Mari, S M; Marsella, G; Martello, D; Mastroianni, S; Meng, X R; Montini, P; Ning, C C; Pagliaro, A; Panareo, M; Perrone, L; Pistilli, P; Qu, X B; Rossi, E; Ruggieri, F; Saggese, L; Salvini, P; Santonico, R; Shen, P R; Sheng, X D; Shi, F; Stanescu, C; Surdo, A; Tan, Y H; Vallania, P; Vernetto, S; Vigorito, C; Wang, B; Wang, H; Wu, C Y; Wu, H R; Yao, Z G; Xu, B; Xue, L; Yan, Y X; Yang, Q Y; Yang, X C; Yuan, A F; Zha, M; Zhang, H M; Zhang, JiLong; Zhang, JianLi; Zhang, L; Zhang, P; Zhang, X Y; Zhang, Y; Zhaxisangzhu,; Zhaxiciren,; Zhou, X X; Zhu, F R; Zhu, Q Q; Zizzi, G

    2011-01-01

    The sun blocks cosmic ray particles from outside the solar system, forming a detectable shadow in the sky map of cosmic rays detected by the ARGO-YBJ experiment in Tibet. Because the cosmic ray particles are positive charged, the magnetic field between the sun and the earth deflects them from straight trajectories and results in a shift of the shadow from the true location of the sun. Here we show that the shift measures the intensity of the field which is transported by the solar wind from the sun to the earth.

  4. Large-scale solar magnetic field mapping: I.

    Science.gov (United States)

    Schatten, Kenneth H

    2013-12-01

    This article focuses on mapping the Sun's large-scale magnetic fields. In particular, the model considers how photospheric fields evolve in time. Our solar field mapping method uses Netlogo's cellular automata software via algorithms to carry out the movement of magnetic field on the Sun via agents. This model's entities consist of two breeds: blue and red agents. The former carry a fixed amount of radially outward magnetic flux: 10(23) Mx, and the latter, the identical amount of inward directed flux. The individual agents are distinguished, for clarity, by various shades of blue and red arrows whose orientation indicates the direction the agents are moving, relative to the near-steady bulk fluid motions. The fluid motions generally advect the field with the well known meridional circulation and differential rotation. Our model predominantly focuses on spatial and temporal variations from the bulk fluid motions owing to magnetic interactions. There are but a few effects that agents have on each other: i) while at the poles, field agents are connected via the Babcock - Leighton (B - L) subsurface field to other latitudes. This allows them to undertake two duties there: A) the B - L subsurface field spawns the next generation of new magnetic field via new agents, and B) the B - L subsurface field attracts lower-latitude fields via the "long-range" magnetic stress tension; ii) nearby agents affect each other's motion by short-range interactions; and iii) through annihilation: when opposite field agents get too close to each other, they disappear in pairs. The behavior of the agents' long- and short-range magnetic forces is discussed within this paper as well as the model's use of internal boundary conditions. The workings of the model may be seen in the accompanying movies and/or by using the software available via SpringerPlus' website, or on the Netlogo (TM) community website, where help is readable available, and should all these fail, some help from the author.

  5. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  6. Nanometric alternating magnetic field generator.

    Science.gov (United States)

    Espejo, A P; Tejo, F; Vidal-Silva, N; Escrig, J

    2017-07-05

    In this work we introduce an alternating magnetic field generator in a cylindrical nanostructure. This field appears due to the rotation of a magnetic domain wall located at some position, generating a magnetic region that varies its direction of magnetization alternately, thus inducing an alternating magnetic flux in its vicinity. This phenomenon occurs due to the competition between a spin-polarized current and a magnetic field, which allows to control both the angular velocity and the pinning position of the domain wall. As proof of concept, we study the particular case of a diameter-modulated nanowire with a spin-polarized current along its axis and the demagnetizing field produced by its modulation. This inhomogeneous field allows one to control the angular velocity of the domain wall as a function of its position along the nanowire allowing frequencies in the GHz range to be achieved. This generator could be used in telecommunications for devices in the range of radiofrequencies or, following Faraday's induction law, could also induce an electromotive force and be used as a movable alternate voltage source in future nanodevices.

  7. History of Solar Magnetic Fields Since George Ellery Hale

    Science.gov (United States)

    Stenflo, J. O.

    2017-09-01

    As my own work on the Sun's magnetic field started exactly 50 years ago at Crimea in the USSR, I have been a participant in the field during nearly half the time span since Hale's discovery in 1908 of magnetic fields in sunspots. The present historical account is accompanied by photos from my personal slide collection, which show a number of the leading personalities who advanced the field in different areas: measurement techniques, from photographic to photoelectric and imaging methods in spectro-polarimetry; theoretical foundations of MHD and the origin of cosmic magnetic fields (birth of dynamo theory); the quest for increased angular resolution from national projects to international consortia (for instruments both on ground and in space); introduction of the Hanle effect in astrophysics and the Second Solar Spectrum as its playground; small-scale nature of the field, the fundamental resolution limit, and transcending it by resolution-independent diagnostics.

  8. History of Solar Magnetic Fields Since George Ellery Hale

    Science.gov (United States)

    Stenflo, J. O.

    2015-09-01

    As my own work on the Sun's magnetic field started exactly 50 years ago at Crimea in the USSR, I have been a participant in the field during nearly half the time span since Hale's discovery in 1908 of magnetic fields in sunspots. The present historical account is accompanied by photos from my personal slide collection, which show a number of the leading personalities who advanced the field in different areas: measurement techniques, from photographic to photoelectric and imaging methods in spectro-polarimetry; theoretical foundations of MHD and the origin of cosmic magnetic fields (birth of dynamo theory); the quest for increased angular resolution from national projects to international consortia (for instruments both on ground and in space); introduction of the Hanle effect in astrophysics and the Second Solar Spectrum as its playground; small-scale nature of the field, the fundamental resolution limit, and transcending it by resolution-independent diagnostics.

  9. History of Solar Magnetic Fields since George Ellery Hale

    CERN Document Server

    Stenflo, Jan

    2015-01-01

    As my own work on the Sun's magnetic field started exactly 50 years ago at Crimea in the USSR, I have been a participant in the field during nearly half the time span since Hale's discovery in 1908 of magnetic fields in sunspots. The present historical account is accompanied by photos from my personal slide collection, which show a number of the leading personalities who advanced the field in different areas: measurement techniques, from photographic to photoelectric and imaging methods in spectro-polarimetry; theoretical foundations of MHD and the origin of cosmic magnetic fields (birth of dynamo theory); the quest for increased angular resolution from national projects to international consortia (for instruments both on ground and in space); introduction of the Hanle effect in astrophysics and the Second Solar Spectrum as its playground; small-scale nature of the field, the fundamental resolution limit, and transcending it by resolution-independent diagnostics.

  10. The interplanetary magnetic field observed by Juno enroute to Jupiter

    Science.gov (United States)

    Gruesbeck, Jacob R.; Gershman, Daniel J.; Espley, Jared R.; Connerney, John E. P.

    2017-06-01

    The Juno spacecraft was launched on 5 August 2011 and spent nearly 5 years traveling through the inner heliosphere on its way to Jupiter. The Magnetic Field Investigation was powered on shortly after launch and obtained vector measurements of the interplanetary magnetic field (IMF) at sample rates from 1 to 64 samples/second. The evolution of the magnetic field with radial distance from the Sun is compared to similar observations obtained by Voyager 1 and 2 and the Ulysses spacecraft, allowing a comparison of the radial evolution between prior solar cycles and the current depressed one. During the current solar cycle, the strength of the IMF has decreased throughout the inner heliosphere. A comparison of the variance of the normal component of the magnetic field shows that near Earth the variability of the IMF is similar during all three solar cycles but may be less at greater radial distances.

  11. Comparison Study of Two Different Sun-Tracking Methods in Optical Efficiency of Heliostat Field

    Directory of Open Access Journals (Sweden)

    K.-K. Chong

    2012-01-01

    Full Text Available There are two sun-tracking methods widely used for the heliostat, which are conventional Azimuth-Elevation and revolutionary Spinning-Elevation methods. Following the previous study to compare the range of motion, a comparison study in optical efficiency of heliostat field for the two methods is further explored in this paper. A special algorithm using ray-tracing technique has also been developed to simulate the optical efficiency of heliostat field for both sun-tracking methods in different latitudes. With the new algorithm, comprehensive analysis to compare the optical efficiency of individual heliostat and the overall heliostat field for the two sun-tracking methods has been carried out.

  12. Magnetic Field Generation in Stars

    CERN Document Server

    Ferrario, Lilia; Zrake, Jonathan

    2015-01-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a ...

  13. SOLIS/VSM Polar Magnetic Field Data

    CERN Document Server

    Bertello, Luca

    2015-01-01

    The Vector Spectromagnetograph (VSM) instrument on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) telescope is designed to obtain high-quality magnetic field observations in both the photosphere and chromosphere by measuring the Zeeman-induced polarization of spectral lines. With 1$^{\\prime \\prime}$ spatial resolution (1.14$^{\\prime \\prime}$ before 2010) and 0.05\\AA\\ spectral resolution, the VSM provides, among other products, chromospheric full-disk magnetograms using the CaII 854.2 nm spectral line and both photospheric full-disk vector and longitudinal magnetograms using the FeI 630.15 nm line. Here we describe the procedure used to compute daily weighted averages of the photospheric radial polar magnetic field at different latitude bands from SOLIS/VSM longitudinal full-disk observations. Time series of these measurements are publicly available from the SOLIS website at http://solis.nso.edu/0/vsm/vsm\\_plrfield.html. Future plans include the calculation of the mean polar field strength fr...

  14. Magnetic field draping at the low-latitude magnetopause

    Science.gov (United States)

    Richard, R. L.; Lotko, W.

    1991-01-01

    Magnetohydrodynamic simulations are used to investigate the structure of the low-latitude magnetopause for interplanetary magnetic field conditions with a dominant southward component. The structure is self-consistently calculated as an initial-value problem in which the system is allowed to evolve into a quasi-steady state. All components of the 3D velocity and magnetic field as well as compressibility, resistivity, and viscosity are included in the 2D calculation. The simulation model shows that magnetic field draping can occur at the magnetopause boundary when magnetic merging takes place in the presence of a tangential shear flow. For 'normal' (positive Bx) draping, the higher-latitude portion of the field lines are curved toward the sun on the magnetospheric side of the magnetopause and away from the sun on the magnetosheath side. The thickness of the normal draping structure scales with the viscosity. The field-aligned current system that accompanies normal magnetic draping is consistent with the sense of the region 1 currents that flow into the dayside ionosphere.

  15. Indoor localization using magnetic fields

    Science.gov (United States)

    Pathapati Subbu, Kalyan Sasidhar

    Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing

  16. Magnetic Fields in Spiral Galaxies

    CERN Document Server

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15\\mu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the interg...

  17. Rcscarch on Small-Scale Solar Magnetic Fields and Activities

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; YANG Shuhong

    2011-01-01

    It has been known that there are different kinds of small-scale active phenomena on the Sun. They are classified into spicules, macrospicules, and H-alpha jets, X-ray jets, etc., according to their sizes, velocities, lifetimes, and so on. All these phenomena are related to small-scale magnetic fields. The problems of solar upper atmospheric heating and solar wind acceleration have never been solved. Small-scale magnetic fields and activities are considered to play key roles in heating upper atmosphere and in accelerating solar wind.

  18. Magnetic field of the Earth

    Science.gov (United States)

    Popov, Aleksey

    2013-04-01

    The magnetic field of the Earth has global meaning for a life on the Earth. The world geophysical science explains: - occurrence of a magnetic field of the Earth it is transformation of kinetic energy of movements of the fused iron in the liquid core of Earth - into the magnetic energy; - the warming up of a kernel of the Earth occurs due to radioactive disintegration of elements, with excretion of thermal energy. The world science does not define the reasons: - drift of a magnetic dipole on 0,2 a year to the West; - drift of lithospheric slabs and continents. The author offers: an alternative variant existing in a world science the theories "Geodynamo" - it is the theory « the Magnetic field of the Earth », created on the basis of physical laws. Education of a magnetic field of the Earth occurs at moving the electric charge located in a liquid kernel, at rotation of the Earth. At calculation of a magnetic field is used law the Bio Savara for a ring electric current: dB = . Magnetic induction in a kernel of the Earth: B = 2,58 Gs. According to the law of electromagnetic induction the Faradey, rotation of a iron kernel of the Earth in magnetic field causes occurrence of an electric field Emf which moves electrons from the center of a kernel towards the mantle. So of arise the radial electric currents. The magnetic field amplifies the iron of mantle and a kernel of the Earth. As a result of action of a radial electric field the electrons will flow from the center of a kernel in a layer of an electric charge. The central part of a kernel represents the field with a positive electric charge, which creates inverse magnetic field Binv and Emfinv When ?mfinv = ?mf ; ?inv = B, there will be an inversion a magnetic field of the Earth. It is a fact: drift of a magnetic dipole of the Earth in the western direction approximately 0,2 longitude, into a year. Radial electric currents a actions with the basic magnetic field of a Earth - it turn a kernel. It coincides with laws

  19. Bipolar Magnetic Regions on the Sun: Global Analysis of the SOHO/MDI Data Set

    Science.gov (United States)

    Stenflo, J. O.; Kosovichev, A. G.

    2012-02-01

    The magnetic flux that is generated by dynamo processes inside the Sun emerges in the form of bipolar magnetic regions. The properties of these directly observable signatures of the dynamo can be extracted from full-disk solar magnetograms. The most homogeneous, high-quality synoptic data set of solar magnetograms has been obtained with the Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory spacecraft during 1995-2011. We have developed an IDL program that has, when applied to the 73,838 magnetograms of the MDI data set, automatically identified 160,079 bipolar magnetic regions that span a range of scale sizes across nearly four orders of magnitude. The properties of each region have been extracted and statistically analyzed, in particular with respect to the polarity orientations of the bipolar regions, including their tilt-angle distributions and their violations of Hale's polarity law. The latitude variation of the average tilt angles (with respect to the E-W direction), which is known as Joy's law, is found to closely follow the relation 32fdg1 × sin (latitude). There is no indication of a dependence on region size that one may expect if the tilts were produced by the Coriolis force during the buoyant rise of flux loops from the tachocline region. A few percent of all regions have orientations that violate Hale's polarity law. We show explicit examples, from different phases of the solar cycle, where well-defined medium-size bipolar regions with opposite polarity orientations occur side by side in the same latitude zone in the same magnetogram. Such oppositely oriented large bipolar regions cannot be part of the same toroidal flux system, but different flux systems must coexist at any given time in the same latitude zones. These examples are incompatible with the paradigm of coherent, subsurface toroidal flux ropes as the source of sunspots, and instead show that fluctuations must play a major role at all scales for the

  20. Black holes with su(N) gauge field hair and superconducting horizons

    Science.gov (United States)

    Shepherd, Ben L.; Winstanley, Elizabeth

    2017-01-01

    We present new planar dyonic black hole solutions of the su(N) Einstein-Yang-Mills equations in asymptotically anti-de Sitter space-time, focussing on su(2) and su(3) gauge groups. The magnetic part of the gauge field forms a condensate close to the planar event horizon. We compare the free energy of a non-Abelian hairy black hole with that of an embedded Reissner-Nordström-anti-de Sitter (RN-AdS) black hole having the same Hawking temperature and electric charge. We find that the hairy black holes have lower free energy. We present evidence that there is a phase transition at a critical temperature, above which the only solutions are embedded RN-AdS black holes. At the critical temperature, an RN-AdS black hole can decay into a hairy black hole, and it is thermodynamically favourable to do so. Working in the probe limit, we compute the frequency-dependent conductivity, and find that enlarging the gauge group from su(2) to su(3) eliminates a divergence in the conductivity at nonzero frequency.

  1. Black holes with ${\\mathfrak {su}}(N)$ gauge field hair and superconducting horizons

    CERN Document Server

    Shepherd, Ben L

    2016-01-01

    We present new planar dyonic black hole solutions of the ${\\mathfrak {su}}(N)$ Einstein-Yang-Mills equations in asymptotically anti-de Sitter space-time, focussing on ${\\mathfrak {su}}(2)$ and ${\\mathfrak {su}}(3)$ gauge groups. The magnetic part of the gauge field forms a condensate close to the planar event horizon. We compare the free energy of a non-Abelian hairy black hole with that of an embedded Reissner-Nordstr\\"om-anti-de Sitter (RN-AdS) black hole having the same Hawking temperature and electric charge. We find that the hairy black holes have lower free energy. We present evidence that there is a phase transition at a critical temperature, above which the only solutions are embedded RN-AdS black holes. At the critical temperature, an RN-AdS black hole can decay into a hairy black hole, and it is thermodynamically favourable to do so. Working in the probe limit, we compute the frequency-dependent conductivity, and find that enlarging the gauge group from ${\\mathfrak {su}}(2)$ to ${\\mathfrak {su}}(3)$...

  2. Magnetic cycles of Sun-like stars with different levels of coronal and chromospheric activity — comparison with the Sun

    Science.gov (United States)

    Shimanovskaya, Elena; Bruevich, Vasiliy; Bruevich, Elena

    2016-09-01

    The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of F, G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycle, is different: it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of chromospheric and coronal activity confirms that the Sun belongs to stars with a low level of chromospheric activity and stands apart among these stars by its minimum level of coronal radiation and minimum level of variations in photospheric flux.

  3. Magnetic cycles of Sun-like stars with different levels of coronal and chromospheric activity -- comparison with the Sun

    CERN Document Server

    Bruevich, E A; Shimanovskaya, E V

    2016-01-01

    The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of F, G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycles, is different: it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of the chromospheric and coronal activity confirms that the Sun belongs to stars with the low level of the chromospheric activity and stands apart among these stars by the minimum level of its coronal radiation and the minimum level of its variations of the photospheric flux.

  4. Magnetic fields of neutron stars

    CERN Document Server

    Reisenegger, Andreas

    2013-01-01

    Neutron stars contain the strongest magnetic fields known in the Universe. In this paper, I discuss briefly how these magnetic fields are inferred from observations, as well as the evidence for their time-evolution. I show how these extremely strong fields are actually weak in terms of their effects on the stellar structure, as is also the case for magnetic stars on the upper main sequence and magnetic white dwarfs, which have similar total magnetic fluxes. I propose a scenario in which a stable hydromagnetic equilibrium (containing a poloidal and a toroidal field component) is established soon after the birth of the neutron star, aided by the strong compositional stratification of neutron star matter, and this state is slowly eroded by non-ideal magnetohydrodynamic processes such as beta decays and ambipolar diffusion in the core of the star and Hall drift and breaking of the solid in its crust. Over sufficiently long time scales, the fluid in the neutron star core will behave as if it were barotropic, becau...

  5. Magnetic fields during galaxy mergers

    CERN Document Server

    Rodenbeck, Kai

    2016-01-01

    Galaxy mergers are expected to play a central role for the evolution of galaxies, and may have a strong impact on their magnetic fields. We present the first grid-based 3D magneto-hydrodynamical simulations investigating the evolution of magnetic fields during merger events. For this purpose, we employ a simplified model considering the merger event of magnetized gaseous disks in the absence of stellar feedback and without a stellar or dark matter component. We show that our model naturally leads to the production of two peaks in the evolution of the average magnetic field strength within 5 kpc, within 25 kpc and on scales in between 5 and 25 kpc. The latter is consistent with the peak in the magnetic field strength reported by Drzazga et al. (2011) in a merger sequence of observed galaxies. We show that the peak on the galactic scale and in the outer regions is likely due to geometrical effects, as the core of one galaxy enters the outskirts of the other one. In addition, there is a physical enhancement of t...

  6. Zero magnetic field type magnetic field sensor. Reijikaigata jikai sensor

    Energy Technology Data Exchange (ETDEWEB)

    Sonoda, T.; Ueda, R. (Kyushu Institute of Technology, Fukuoka (Japan))

    1990-11-20

    It is shown in this paper that a new type of sensor with excellent characteristics can be made by demagnetizing the sensor core toward a zero field state and then detecting an unknown field to be detected by the demagnetizing current. The core operates equivalently in a zero magnetic field so that the detection sensitivity is determined by the coil constant including the number of turns of the solenoid for demagnetization required to offset the field to be detected. Therefore the detection sensitivity does not depend on its configuration and magnetization characteristics and does not depend on the temperature. It is thereby considered that these characteristics can largely reduce such problems at present as the aging deterioration of magnetic materials or the quality control accompanied by manufacturing. In addition, the following points have been clarified: (1) The upper limit of the detectable range does not exist in principle. (2) The accuracy of the detection is 0.02% to the full scale 20kA/m. (3) The magnetization property required to the core used as a sensor is that it has a rectangular B-H loop which is as sharp as possible. 14 refs., 13 figs., 2 tabs.

  7. The connection between stellar activity cycles and magnetic field topology

    CERN Document Server

    See, V; Vidotto, A A; Donati, J -F; Saikia, S Boro; Bouvier, J; Fares, R; Folsom, C P; Gregory, S G; Hussain, G; Jeffers, S V; Marsden, S C; Morin, J; Moutou, C; Nascimento, J D do; Petit, P; Waite, I A

    2016-01-01

    Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on ...

  8. Anomalous resistivity and the evolution of magnetic field topology

    Science.gov (United States)

    Parker, E. N.

    1993-01-01

    This paper explores the topological restructuring of a force-free magnetic field caused by the hypothetical sudden onset of a localized region of strong anomalous resistivity. It is shown that the topological complexity increases, with the primitive planar force-free field with straight field lines developing field lines that wrap half a turn around each other, evidently providing a surface of tangential discontinuity in the wraparound region. It is suggested that the topological restructuring contributes to the complexity of the geomagnetic substorm, the aurora, and perhaps some of the flare activity on the sun, or other star, and the Galactic halo.

  9. Energy buildup in sheared force-free magnetic fields

    Science.gov (United States)

    Wolfson, Richard; Low, Boon C.

    1992-01-01

    Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.

  10. Energy flux determines magnetic field strength of planets and stars.

    Science.gov (United States)

    Christensen, Ulrich R; Holzwarth, Volkmar; Reiners, Ansgar

    2009-01-08

    The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (the slowly rotating Sun generates its field through a different dynamo mechanism). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear. Here we report an extension of a scaling law derived from geodynamo models to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.

  11. Energy flux determines magnetic field strength of planets and stars

    Science.gov (United States)

    Christensen, Ulrich R.; Holzwarth, Volkmar; Reiners, Ansgar

    2009-01-01

    The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (the slowly rotating Sun generates its field through a different dynamo mechanism). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear. Here we report an extension of a scaling law derived from geodynamo models to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.

  12. Primordial Magnetic Fields and Causality

    CERN Document Server

    Durrer, R; Durrer, Ruth; Caprini, Chiara

    2003-01-01

    In this letter we discuss the implications of causality on a primordial magnetic field. We show that the residual field on large scales is much stronger suppressed than usually assumed and that a helical component is even suppressed even more than the parity even part. We show that due to this strong suppression, even maximal primordial fields generated at the electroweak phase transition can just marginally seed the fields in galaxies and clusters, but they cannot leave any detectable imprint on the cosmic microwave background.

  13. Magnetic fields around black holes

    Science.gov (United States)

    Garofalo, David A. G.

    Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our

  14. Paleomagnetism. Solar nebula magnetic fields recorded in the Semarkona meteorite.

    Science.gov (United States)

    Fu, Roger R; Weiss, Benjamin P; Lima, Eduardo A; Harrison, Richard J; Bai, Xue-Ning; Desch, Steven J; Ebel, Denton S; Suavet, Clément; Wang, Huapei; Glenn, David; Le Sage, David; Kasama, Takeshi; Walsworth, Ronald L; Kuan, Aaron T

    2014-11-28

    Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constraints on the intensity of these fields. Here we show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 microteslas. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the Sun. This implies that background magnetic fields in the terrestrial planet-forming region were likely 5 to 54 microteslas, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.

  15. Chiral transition with magnetic fields

    CERN Document Server

    Ayala, Alejandro; Mizher, Ana Julia; Rojas, Juan Cristobal; Villavicencio, Cristian

    2014-01-01

    We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses, taken as functions of the order parameter, can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling const...

  16. Magnetic Fields of Neutron Stars

    Indian Academy of Sciences (India)

    Sushan Konar

    2017-09-01

    This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.

  17. Tongues, bottles, and disconnected loops: The opening and closing of the interplanetary magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    McComas, D.J. [Los Alamos National Lab., NM (United States). Space and Atmospheric Sciences Group

    1994-06-01

    For years the field of Space Physics has had a problem, a really big problem for it occurs on the largest spatial scales in Space physics -- across the entire region under the Sun`s influence, the heliosphere. The problem is that the Sun appears to keep opening new magnetic flux into interplanetary space with no obvious way for this flux to close back off again. This state of affairs, without some previously unknown method for closing the open interplanetary magnetic field (IMF), leads to an ever growing amount of magnetic flux in interplanetary space: the magnetic flux catastrophe. Recently, considerable progress has been made in understanding why this catastrophic state is not the observed state of the heliosphere. This brief article paints the newly emerging picture of the opening and closing of the IMF and how these processes may account for the observed variation in the amount of magnetic flux in interplanetary space over the solar cycle.

  18. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  19. Primordial Magnetic Fields that Last?

    CERN Document Server

    Carroll, S M; Carroll, Sean M.; Field, George B.

    1998-01-01

    The magnetic fields we observe in galaxies today may have their origins in the very early universe. While a number of mechanisms have been proposed which lead to an appreciable field amplitude at early times, the subsequent evolution of the field is of crucial importance, especially whether the correlation length of the field can grow as large as the size of a protogalaxy. This talk is a report on work in progress, in which we consider the fate of one specific primordial field scenario, driven by pseudoscalar effects near the electroweak phase transition. We argue that such a scenario has a number of attractive features, although it is still uncertain whether a field of appropriate size can survive until late times.

  20. Magnetic Properties of Erbium Gallium Gallate under High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Zhang Xijuan; Cheng Haiying; Yang Cuihong; Wang Wei

    2004-01-01

    A theoretical investigation on the magnetic properties of rare-earth Er3+ in Er3 Ga5 O12 was reported. The average magnetic moments(M) for applied magnetic field H parallel to the [001 ], [ 100], [ 110], [ 111 ] direction was studied based on the quantum theory. Temperature dependence of the magnetic properties is analyzed for H applied parallel to the [ 100] and [ 111 ] crystallographic directions. The magnetization decreases with increasing temperature,showing good agreement with thermal effect. A strong anisotropy of the magnetization is found under high magnetic field, but when the magnetic field is small, M and H are proportional.

  1. Analysis of Self Similar Scaling in Kinetic and Magnetic Energy Density as a Function of Distance From Sun

    Science.gov (United States)

    Banerjee, A.; Coplan, M. A.

    2009-12-01

    We analyze solar wind and interplanetary magnetic field data to study scaling properties of kinetic and magnetic energy density as a function of solar cycle and distance from the sun. In his original theory on turbulence, Kolmogorov predicted that in the inertial range the fluctuations in velocity differences should be self-similar. Analysis of solar wind data showed this not to be the case. On the other hand B. Hnat et.al.(Geophys. Res. Lett., 29 (10), 1446, 2002) and J.J Podesta (J. Geophys. Res., 111, A09105, 2006) showed that fluctuations in kinetic and magnetic energy density are approximately self-similar. We extend this analysis using data from the SWE and MFI experiments on the WIND spacecraft (at 1AU) during solar minimum (2006) and solar maximum (2001) and VHM/FGM experiment on the Ulysses spacecraft (1AU to 5AU). We calculate the cumulative distribution function (CDF) of the time delayed differences in kinetic and magnetic energy density and present a method through which the scaling exponent can be reliably calculated from the CDFs, instead of using structure functions which are very sensitive to large fluctuations. We compare the scaling exponents derived from the CDFs to the ones calculated from structure functions and study the rescaling properties of CDFs.

  2. Modeling and analysis of magnetic dipoles in weak magnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The magnetic leakage field distribution resulting from linear defects of a tube sample in the geomagnetic field is modeled according to the magnetic dipole theory.The formula to compute the normal component of the weak magnetic field is deduced based on the spatial distribution of the magnetic dipole.The shape and characteristics of the zero line (an important criterion for magnetic memory testing) of the normal field is analyzed under different longitudinal magnetizations.Results show that the characteristics of the zero line should be considered when the metal magnetic memory testing method is used to find and locate the defect.

  3. Galactic and intergalactic magnetic fields

    CERN Document Server

    Klein, Ulrich

    2014-01-01

    This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible.In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later c

  4. The Sun and Earth

    Science.gov (United States)

    Gopalswamy, Natchimuthuk

    2012-01-01

    Thus the Sun forms the basis for life on Earth via the black body radiation it emits. The Sun also emits mass in the form of the solar wind and the coronal mass ejections (CMEs). Mass emission also occurs in the form of solar energetic particles (SEPs), which happens during CMEs and solar flares. Both the mass and electromagnetic energy output of the Sun vary over a wide range of time scales, thus introducing disturbances on the space environment that extends from the Sun through the entire heliosphere including the magnetospheres and ionospheres of planets and moons of the solar system. Although our habitat is located in the neutral atmosphere of Earth, we are intimately connected to the non-neutral space environment starting from the ionosphere to the magnetosphere and to the vast interplanetary space. The variability of the solar mass emissions results in the interaction between the solar wind plasma and the magnetospheric plasma leading to huge disturbances in the geospace. The Sun ionizes our atmosphere and creates the ionosphere. The ionosphere can be severely disturbed by the transient energy input from solar flares and the solar wind during geomagnetic storms. The complex interplay between Earth's magnetic field and the solar magnetic field carried by the solar wind presents varying conditions that are both beneficial and hazardous to life on earth. This seminar presents some of the key aspects of this Sun-Earth connection that we have learned since the birth of space science as a scientific discipline some half a century ago.

  5. Bright Hot Impacts by Erupted Fragments Falling Back on the Sun: Magnetic Channelling

    Science.gov (United States)

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

    2016-11-01

    Dense plasma fragments were observed to fall back on the solar surface by the Solar Dynamics Observatory after an eruption on 2011 June 7, producing strong extreme-ultraviolet brightenings. Previous studies investigated impacts in regions of weak magnetic field. Here we model the ˜ 300 km s-1 impact of fragments channelled by the magnetic field close to active regions. In the observations, the magnetic channel brightens before the fragment impact. We use a 3D-MHD model of spherical blobs downfalling in a magnetized atmosphere. The blob parameters are constrained from the observation. We run numerical simulations with different ambient densitie and magnetic field intensities. We compare the model emission in the 171 Å channel of the Atmospheric Imaging Assembly with the observed one. We find that a model of downfall channelled in an ˜1 MK coronal loop confined by a magnetic field of ˜10-20 G, best explains qualitatively and quantitatively the observed evolution. The blobs are highly deformed and further fragmented when the ram pressure becomes comparable to the local magnetic pressure, and they are deviated to be channelled by the field because of the differential stress applied by the perturbed magnetic field. Ahead of them, in the relatively dense coronal medium, shock fronts propagate, heat, and brighten the channel between the cold falling plasma and the solar surface. This study shows a new mechanism that brightens downflows channelled by the magnetic field, such as in accreting young stars, and also works as a probe of the ambient atmosphere, providing information about the local plasma density and magnetic field.

  6. Minimal Magnetic States of the Sun and the Solar Wind: Implications for the Origin of the Slow Solar Wind

    Science.gov (United States)

    Cliver, E. W.; von Steiger, R.

    2017-09-01

    During the last decade it has been proposed that both the Sun and the solar wind have minimum magnetic states, lowest order levels of magnetism that underlie the 11-yr cycle as well as longer-term variability. Here we review the literature on basal magnetic states at the Sun and in the heliosphere and draw a connection between the two based on the recent deep 2008-2009 minimum between cycles 23 and 24. In particular, we consider the implications of the low solar activity during the recent minimum for the origin of the slow solar wind.

  7. Stress Field of Straight Edge Dislocation in Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-long; HU Hai-yun; FAN Tian-you

    2007-01-01

    To study the changes in mechanical properties of materials within magnetic fields and the motion of dislocations,stress fields of dislocation in magnetic field need to be calculated.The straight edge dislocation is of basic importance in various defects.The stress field of straight edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media.This reduces to the known stress field when the magnet field is zero.The results can be used for further study on the strain energy of dislocations and the interactions between dislocations in magnetic fields.

  8. Diagnosis of solar chromospheric magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Hongqi(张洪起)

    2002-01-01

    This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic fields. Some questions in the study of the chromospheric magnetic field are also presented.

  9. The HMI Magnetic Field Pipeline

    Science.gov (United States)

    Hoeksema, Jon Todd; Liu, Y.; Schou, J.; Scherrer, P.; HMI Science Team

    2009-05-01

    The Helioseismic and Magnetic Imager (HMI) will provide frequent full-disk magnetic field data after launch of the Solar Dynamics Observatory (SDO), currently scheduled for fall 2009. 16 megapixel line-of-sight magnetograms (Blos) will be recorded every 45 seconds. A full set of polarized filtergrams needed to determine the vector magnetic field requires 90 seconds. Quick-look data will be available within a few minutes of observation. Quick-look space weather and browse products must have identified users, and the list currently includes full disk magnetograms, feature identification and movies, 12-minute disambiguated vector fields in active region patches, time evolution of AR indices, synoptic synchronic frames, potential and MHD model results, and 1 AU predictions. A more complete set of definitive science data products will be offered about a day later and come in three types. "Pipeline” products, such as full disk vector magnetograms, will be computed for all data on an appropriate cadence. A larger menu of "On Demand” products, such as Non-Linear Force Free Field snapshots of an evolving active region, will be produced whenever a user wants them. Less commonly needed "On Request” products that require significant project resources, such as a high resolution MHD simulation of the global corona, will be created subject to availability of resources. Further information can be found at the SDO Joint Science Operations Center web page, jsoc.stanford.edu

  10. A Vorticity-Magnetic Field Dynamo Instability

    OpenAIRE

    1997-01-01

    We generalize the mean field magnetic dynamo to include local evolution of the mean vorticity in addition to the mean magnetic field. The coupled equations exhibit a general mean field dynamo instability that enables the transfer of turbulent energy to the magnetic field and vorticity on larger scales. The growth of the vorticity and magnetic field both require helical turbulence which can be supplied by an underlying global rotation. The dynamo coefficients are derived including the backreac...

  11. Magnetic fields in non-convective regions of stars

    Science.gov (United States)

    Braithwaite, Jonathan

    2017-01-01

    We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them; the solar cycle being one of the better known examples. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and their observational effects are examined. We look at possible dynamo mechanisms that run on differential rotation rather than convection. Finally, we turn to neutron stars with a discussion of the possible origins for their magnetic fields. PMID:28386410

  12. Magnetic field of a combined plasma trap

    Science.gov (United States)

    Kotenko, V. G.; Moiseenko, V. E.; Ågren, O.

    2012-06-01

    This paper presents numerical simulations performed on the structure of a magnetic field created by the magnetic system of a combined plasma trap. The magnetic system includes the stellarator-type magnetic system and one of the mirror-type. For the stellarator type magnetic system the numeric model contains a magnetic system of an l=2 torsatron with the coils of an additional toroidal magnetic field. The mirror-type magnetic system element is considered as being single current-carrying turn enveloping the region of existence of closed magnetic surfaces of the torsatron. The calculations indicate the existence of a vast area of the values of the additional magnetic field magnitude and magnetic field of the single turn where, in principle, the implementation of the closed magnetic surface configuration is quite feasible.

  13. ANALYTIC EXPRESSION OF MAGNETIC FIELD DISTRIBUTION OF RECTANGULAR PERMANENT MAGNETS

    Institute of Scientific and Technical Information of China (English)

    苟晓凡; 杨勇; 郑晓静

    2004-01-01

    From the molecular current viewpoint,an analytic expression exactly describing magnetic field distribution of rectangular permanent magnets magnetized sufficiently in one direction was derived from the Biot-Savart's law. This expression is useful not only for the case of one rectangular permanent magnet bulk, but also for that of several rectangular permanent magnet bulks. By using this expression,the relations between magnetic field distribution and the size of rectangular permanent magnets as well as the magnitude of magnetic field and the distance from the point in the space to the top (or bottom) surface of rectangular permanent magnets were discussed in detail. All the calculating results are consistent with experimental ones. For transverse magnetic field which is a main magnetic field of rectangular permanent magnets,in order to describe its distribution,two quantities,one is the uniformity in magnitude and the other is the uniformity in distribution of magnetic field,were defined. Furthermore, the relations between them and the geometric size of the magnet as well as the distance from the surface of permanent magnets were investigated by these formulas. The numerical results show that the geometric size and the distance have a visible influence on the uniformity in magnitude and the uniformity in distribution of the magnetic field.

  14. SUN-LIKE MAGNETIC CYCLES IN THE RAPIDLY ROTATING YOUNG SOLAR ANALOG HD 30495

    Energy Technology Data Exchange (ETDEWEB)

    Egeland, Ricky [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Metcalfe, Travis S. [Space Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301 (United States); Hall, Jeffrey C. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Henry, Gregory W., E-mail: egeland@ucar.edu [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209 (United States)

    2015-10-10

    A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial (∼2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, a ∼1 Gyr old G1.5 V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at ∼1.7 years and a long cycle of ∼12 years. We measure three individual long-period cycles and find durations ranging from 9.6 to 15.5 years. We find the short-term variability to be intermittent, but present throughout the majority of the time series, though its occurrence and amplitude are uncorrelated with the longer cycle. These essentially solar-like variations occur in a Sun-like star with more rapid rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence.

  15. Modeling the Sun’s Small-scale Global Photospheric Magnetic Field

    Science.gov (United States)

    Meyer, K. A.; Mackay, D. H.

    2016-10-01

    We present a new model for the Sun’s global photospheric magnetic field during a deep minimum of activity, in which no active regions emerge. The emergence and subsequent evolution of small-scale magnetic features across the full solar surface is simulated, subject to the influence of a global supergranular flow pattern. Visually, the resulting simulated magnetograms reproduce the typical structure and scale observed in quiet Sun magnetograms. Quantitatively, the simulation quickly reaches a steady state, resulting in a mean field and flux distribution that are in good agreement with those determined from observations. A potential coronal magnetic field is extrapolated from the simulated full Sun magnetograms to consider the implications of such a quiet photospheric magnetic field on the corona and inner heliosphere. The bulk of the coronal magnetic field closes very low down, in short connections between small-scale features in the simulated magnetic network. Just 0.1% of the photospheric magnetic flux is found to be open at 2.5 R ⊙, around 10-100 times less than that determined for typical Helioseismic and Magnetic Imager synoptic map observations. If such conditions were to exist on the Sun, this would lead to a significantly weaker interplanetary magnetic field than is currently observed, and hence a much higher cosmic ray flux at Earth.

  16. Sun-Like Magnetic Cycles in the Rapidly-Rotating Young Solar Analog HD 30495

    CERN Document Server

    Egeland, Ricky; Hall, Jeffrey C; Henry, Gregory W

    2015-01-01

    A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial ($\\sim$2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, an $\\sim$1 Gyr-old G1.5V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at $\\sim$1.7 years and a long cycle of $...

  17. Field and Thermal Characteristics of Magnetizing Fixture

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be obtained, the efficient design of magnetizer which produce desired magnet will be possible using our modeling. For field modeling finite-element analysis is used as part of the design and analysis process for magnetizing fixture. The thermal modeling method of magnetizing fixture resistor uses multi-lumped model with equivalent thermal resistance and thermal capacitance.

  18. Magnetic fields for fluid motion.

    Science.gov (United States)

    Weston, Melissa C; Gerner, Matthew D; Fritsch, Ingrid

    2010-05-01

    Three forces induced by magnetic fields offer unique control of fluid motion and new opportunities in microfluidics. This article describes magnetoconvective phenomena in terms of the theory and controversy, tuning by redox processes at electrodes, early-stage applications in analytical chemistry, mature applications in disciplines far afield, and future directions for micro total analysis systems. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html .).

  19. Sun, Earth and Sky

    Science.gov (United States)

    Lang, Kenneth R.

    1995-01-01

    The Sun is enveloped by a hot, tenuous million-degree corona that expands to create a continuous solar wind that sweeps past all the planets and fills the heliosphere. The solar wind is modulated by strong gusts that are initiated by powerful explosions on the Sun, including solar flares and coronal mass ejections. This dynamic, invisible outer atmosphere of the Sun is currently under observation with the soft X-ray telescope aboard the Yohkoh spacecraft, whose results are presented. We also show observations from the Ulysses spacecraft that is now passing over the solar pole, sampling the solar wind in this region for the first time. Two other spacecraft, Voyager 1 and 2, have recently detected the outer edge of the invisible heliosphere, roughly halfway to the nearest star. Magnetic solar activity, the total radiative output from the Sun, and the Earth's mean global surface temperature all vary with the 11-year sunspot cycle in which the total number of sunspots varies from a maximum to a minimum and back to a maximum again in about 11 years. The terrestrial magnetic field hollows out a protective magnetic cavity, called the magnetosphere, within the solar wind. This protection is incomplete, however, so the Sun feeds an unseen world of high-speed particles and magnetic fields that encircle the Earth in space. These particles endanger spacecraft and astronauts, and also produce terrestrial aurorae. An international flotilla of spacecraft is now sampling the weak points in this magnetic defense. Similar spacecraft have also discovered a new radiation belt, in addition to the familiar Van Allen belts, except fed by interstellar ions instead of electrons and protons from the Sun.

  20. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-03-01

    After the discovery that superconducting magnets could levitate diamagnetic objects,1,2 researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields,3-5 which was given the name "The Moses Effect."5 Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary were produced by superconducting magnets.

  1. First use of synoptic vector magnetograms for global nonlinear force free coronal magnetic field models

    CERN Document Server

    Tadesse, Tilaye; Gosain, S; MacNeice, P; Pevtsov, Alexei A

    2013-01-01

    The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Currently there are several modelling techniques being used to calculate three-dimension of the field lines into the solar atmosphere. For the first time, synoptic maps of photospheric vector magnetic field synthesized from Vector Spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) are used to model the coronal magnetic field and estimate free magnetic energy in the global scale. The free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. We solve the nonlinear force-free field equations using optimizatio...

  2. Eigenmodes of three-dimensional magnetic arcades in the Sun's corona

    CERN Document Server

    Jain, Bradley W Hindman Rekha

    2015-01-01

    We develop a model of coronal-loop oscillations that treats the observed bright loops as an integral part of a larger 3-D magnetic structure comprised of the entire magnetic arcade. We demonstrate that magnetic arcades within the solar corona can trap MHD fast waves in a 3-D waveguide. This is accomplished through the construction of a cylindrically symmetric model of a magnetic arcade with a potential magnetic field. For a magnetically dominated plasma, we derive a governing equation for MHD fast waves and from this equation we show that the magnetic arcade forms a 3-D waveguide if the Alfv\\'en speed increases monotonically beyond a fiducial radius. Both magnetic pressure and tension act as restoring forces, instead of just tension as is generally assumed in 1-D models. Since magnetic pressure plays an important role, the eigenmodes involve propagation both parallel and transverse to the magnetic field. Using an analytic solution, we derive the specific eigenfrequencies and eigenfunctions for an arcade posse...

  3. Passive Magnetic Shielding in Gradient Fields

    CERN Document Server

    Bidinosti, C P

    2013-01-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields clos...

  4. Probing Magnetic Fields with Square Kilometre Array and its Precursors

    Indian Academy of Sciences (India)

    Subhashis Roy; Sharanya Sur; Kandaswamy Subramanian; Arun Mangalam; T. R. Seshadri; Hum Chand

    2016-12-01

    Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has remained a problem for its study. The first phase of Square Kilometre Array (SKA-I), will have almost an order of magnitude higher sensitivity than the best existing radio telescope at GHz frequencies. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarization and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic mediums. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data (e.g., pitch angles in spirals) with models which consider various processes giving rise to field amplification and maintenance (e.g., various types of dynamo models) will then be possible. Such observations will also provide the coherence scale of the fields and its random component through RM structure function. Measuring the random component is important to characterize turbulence in the medium. Observations of FDs with redshift will provide important information on magnetic field evolution as a function of redshift. The background sources could also be used to probe magnetic fields and its coherent scale in galaxy clusters and in bridges formed between interacting galaxies. Other than FDs, sensitive observations of synchrotron emission from galaxies will provide complimentary information on their magnetic field strengths in the sky plane. The core shift measurements of AGNs can provide more precise measurements of magnetic field in the sub parsec region near the black hole and its evolution. The low band of SKA-I will also be useful to study circularly polarized emission from Sun and comparing various

  5. BIPOLAR MAGNETIC REGIONS ON THE SUN: GLOBAL ANALYSIS OF THE SOHO/MDI DATA SET

    Energy Technology Data Exchange (ETDEWEB)

    Stenflo, J. O. [Institute of Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Kosovichev, A. G., E-mail: stenflo@astro.phys.ethz.ch, E-mail: AKosovichev@solar.stanford.edu [W.W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2012-02-01

    The magnetic flux that is generated by dynamo processes inside the Sun emerges in the form of bipolar magnetic regions. The properties of these directly observable signatures of the dynamo can be extracted from full-disk solar magnetograms. The most homogeneous, high-quality synoptic data set of solar magnetograms has been obtained with the Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory spacecraft during 1995-2011. We have developed an IDL program that has, when applied to the 73,838 magnetograms of the MDI data set, automatically identified 160,079 bipolar magnetic regions that span a range of scale sizes across nearly four orders of magnitude. The properties of each region have been extracted and statistically analyzed, in particular with respect to the polarity orientations of the bipolar regions, including their tilt-angle distributions and their violations of Hale's polarity law. The latitude variation of the average tilt angles (with respect to the E-W direction), which is known as Joy's law, is found to closely follow the relation 32.{sup 0}1 Multiplication-Sign sin (latitude). There is no indication of a dependence on region size that one may expect if the tilts were produced by the Coriolis force during the buoyant rise of flux loops from the tachocline region. A few percent of all regions have orientations that violate Hale's polarity law. We show explicit examples, from different phases of the solar cycle, where well-defined medium-size bipolar regions with opposite polarity orientations occur side by side in the same latitude zone in the same magnetogram. Such oppositely oriented large bipolar regions cannot be part of the same toroidal flux system, but different flux systems must coexist at any given time in the same latitude zones. These examples are incompatible with the paradigm of coherent, subsurface toroidal flux ropes as the source of sunspots, and instead show that fluctuations must play a

  6. Construction of Solar-Wind-Like Magnetic Fields

    Science.gov (United States)

    Roberts, Dana Aaron

    2012-01-01

    Fluctuations in the solar wind fields tend to not only have velocities and magnetic fields correlated in the sense consistent with Alfven waves traveling from the Sun, but they also have the magnitude of the magnetic field remarkably constant despite their being broadband. This paper provides, for the first time, a method for constructing fields with nearly constant magnetic field, zero divergence, and with any specified power spectrum for the fluctuations of the components of the field. Every wave vector, k, is associated with two polarizations the relative phases of these can be chosen to minimize the variance of the field magnitude while retaining the\\random character of the fields. The method is applied to a case with one spatial coordinate that demonstrates good agreement with observed time series and power spectra of the magnetic field in the solar wind, as well as with the distribution of the angles of rapid changes (discontinuities), thus showing a deep connection between two seemingly unrelated issues. It is suggested that using this construction will lead to more realistic simulations of solar wind turbulence and of the propagation of energetic particles.

  7. Magnetized jets driven by the Sun: The structure of the heliosphere revisited—Updates

    Energy Technology Data Exchange (ETDEWEB)

    Opher, M., E-mail: mopher@bu.edu [Astronomy Department, Boston University, Boston, Massachusetts 02215 (United States); Drake, J. F.; Swisdak, M. [University of Maryland, College Park, Maryland 20742 (United States); Zieger, B. [Center for Space Physics, Boston University, Massachusetts 02215 (United States); Toth, G. [Department of Climate and Space, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2016-05-15

    As the solar system moves through the interstellar medium, the solar wind is deflected forming the heliosphere. The standard picture of the heliosphere is a comet-shape like structure with the tail extending for 1000s of astronomical units. This standard picture stems from a view where magnetic forces are negligible and the solar magnetic field is convected passively down the tail. Recently, we showed that the magnetic tension of the solar magnetic field plays a crucial role on organizing the solar wind in the heliosheath into two jet-like structures. The two jets are separated by the interstellar medium that flows between them. The heliosphere then has a “croissant”-like shape where the distance to the heliopause downtail is almost the same as towards the nose. This new view of the heliosphere is in agreement with the energetic neutral atoms maps taken by the Interstellar Boundary Explorer and INCA/CASSINI. We developed as well an analytic model of the heliosheath in the axisymmetric limit that shows how the magnetic tension force is the driver for the north and south jets. We confirmed that the formation of these jets with magnetohydrodynamic (MHD) simulations. The main reason why previous global MHD simulations did not see these jets is due to spurious magnetic dissipation that was present at the heliospheric current sheet. We instead kept the same polarity for the interplanetary (solar) magnetic field in both the northern and southern hemispheres, eliminating spurious magnetic dissipation effects at the heliospheric current sheet. In this paper, we extend these previous results to include additional cases where we used: (a) weaker solar magnetic field; (b) solar magnetic field that reverses polarity at the solar equator in the axisymmetric limit; and (c) slower motion through the interstellar system. We discuss as well future challenges regarding the structure of the heliosphere.

  8. Magnetized jets driven by the Sun: The structure of the heliosphere revisited—Updates

    Science.gov (United States)

    Opher, M.; Drake, J. F.; Zieger, B.; Swisdak, M.; Toth, G.

    2016-05-01

    As the solar system moves through the interstellar medium, the solar wind is deflected forming the heliosphere. The standard picture of the heliosphere is a comet-shape like structure with the tail extending for 1000s of astronomical units. This standard picture stems from a view where magnetic forces are negligible and the solar magnetic field is convected passively down the tail. Recently, we showed that the magnetic tension of the solar magnetic field plays a crucial role on organizing the solar wind in the heliosheath into two jet-like structures. The two jets are separated by the interstellar medium that flows between them. The heliosphere then has a "croissant"-like shape where the distance to the heliopause downtail is almost the same as towards the nose. This new view of the heliosphere is in agreement with the energetic neutral atoms maps taken by the Interstellar Boundary Explorer and INCA/CASSINI. We developed as well an analytic model of the heliosheath in the axisymmetric limit that shows how the magnetic tension force is the driver for the north and south jets. We confirmed that the formation of these jets with magnetohydrodynamic (MHD) simulations. The main reason why previous global MHD simulations did not see these jets is due to spurious magnetic dissipation that was present at the heliospheric current sheet. We instead kept the same polarity for the interplanetary (solar) magnetic field in both the northern and southern hemispheres, eliminating spurious magnetic dissipation effects at the heliospheric current sheet. In this paper, we extend these previous results to include additional cases where we used: (a) weaker solar magnetic field; (b) solar magnetic field that reverses polarity at the solar equator in the axisymmetric limit; and (c) slower motion through the interstellar system. We discuss as well future challenges regarding the structure of the heliosphere.

  9. Dynamical Behavior of Core 3 He Nuclear Reaction-Diffusion Systems and Sun's Gravitational Field

    Institute of Scientific and Technical Information of China (English)

    DU Jiulin; SHEN Hong

    2005-01-01

    The coupling of the sun's gravitational field with processes of diffusion and convection exerts a significant influence on the dynamical behavior of the core 3He nuclear reaction-diffusion system. Stability analyses of the system are made in this paper by using the theory of nonequilibrium dynamics. It is showed that, in the nuclear reaction regions extending from the center to about 0.38 times of the radius of the sun, the gravitational field enables the core 3He nuclear reaction-diffusion system to become unstable and, after the instability, new states to appear in the system have characteristic of time oscillation. This may change the production rates of both 7Be and 8B neutrinos.

  10. CONDITIONS FOR TRANSVERSE WAVES PROPAGATION ALONG THIN MAGNETIC FLUX TUBES ON THE SUN

    Energy Technology Data Exchange (ETDEWEB)

    Lopin, Igor [Ussuriisk Astrophysical Observatory, Russian Academy of Sciences, Ussuriisk (Russian Federation); Nagorny, Ivan, E-mail: lopin78@mail.ru [Institute of Automation and Control Processes FEB RAS, Vladivostok (Russian Federation)

    2013-09-10

    The propagation of kink waves in the thin gravity stratified flux tubes with a generalized magnetic field distribution model is considered in cylindrical geometry. The new kink wave equations for both wave variables are obtained. It is shown that the inclusion of the radial component of an unperturbed tube magnetic field sufficiently transforms the conditions for the propagation of transverse waves. It is demonstrated that, for the models of isothermal and polytropic atmosphere in the tube and its environment, the propagation of kink waves along thin magnetic flux tubes is cutoff-free.

  11. Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Mauel, M; Ryutov, D; Kesner, J

    2003-12-02

    In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.

  12. The effect of interplanetary magnetic field orientation on the solar wind flux impacting Mercury's surface

    CERN Document Server

    Varela, J; Moncuquet, M

    2016-01-01

    The aim of this paper is to study the plasma flows on the Mercury surface for different interplanetary magnetic field orientations on the day side of the planet. We use a single fluid MHD model in spherical coordinates to simulate the interaction of the solar wind with the Hermean magnetosphere for six solar wind realistic configurations with different magnetic field orientations: Mercury-Sun, Sun-Mercury, aligned with the magnetic axis of Mercury (Northward and Southward) and with the orbital plane perpendicular to the previous cases. In the Mercury-Sun (Sun-Mercury) simulation the Hermean magnetic field is weakened in the South-East (North-East) of the magnetosphere leading to an enhancement of the flows on the South (North) hemisphere. For a Northward (Southward) orientation there is an enhancement (weakening) of the Hermean magnetic field in the nose of the bow shock so the fluxes are reduced and drifted to the poles (enhanced and drifted to the equator). If the solar wind magnetic field is in the orbital...

  13. Bats respond to very weak magnetic fields.

    Directory of Open Access Journals (Sweden)

    Lan-Xiang Tian

    Full Text Available How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 μT; the lowest field strength tested here, the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT, despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05. Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years.

  14. Hybrid Shielding for Magnetic Fields

    Science.gov (United States)

    Mullins, David; Royal, Kevin

    2017-01-01

    Precision symmetry measurements such as the search for the electric dipole moment of the neutron require magnetic shielding rooms to reduce the ambient field to the pT scale. The massive mu-metal sheets and large separation between layers make these shield rooms bulky and expensive. Active field cancellation systems used to reduce the surrounding field are limited in uniformity of cancellation. A novel approach to reducing the space between shield layers and increasing the effectiveness of active cancellation is to combine the two systems into a hybrid system, with active and passive layers interspersed. We demonstrate this idea in a prototype with an active layer sandwiched between two passive layers of shielding.

  15. Manifestations of Magnetic Field Inhomogeneities

    Indian Academy of Sciences (India)

    Lawrence Rudnick

    2011-12-01

    Both observations and simulations reveal large inhomogeneities in magnetic field distributions in diffuse plasmas. Incorporating these inhomogeneities into various calculations can significantly change the inferred physical conditions. In extragalactic sources, e.g., these can compromise analyses of spectral ageing, which I will illustrate with some current work on cluster relics. I also briefly re-examine the old issue of how inhomogeneous fields affect particle lifetimes; perhaps not surprisingly, the next generation of radio telescopes are unlikely to find many sources that can extend their lifetimes from putting relativistic electrons into a low-field ‘freezer’. Finally, I preview some new EVLA results on the complex relic in Abell 2256, with implications for the interspersing of its relativistic and thermal plasmas.

  16. THE FORMATION AND ERUPTION OF A SMALL CIRCULAR FILAMENT DRIVEN BY ROTATING MAGNETIC STRUCTURES IN THE QUIET SUN

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bo; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Xu, Zhe, E-mail: boyang@ynao.ac.cn, E-mail: yjy@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

    2015-04-20

    We present the first observation of the formation and eruption of a small circular filament driven by a rotating network magnetic field (RNF) in the quiet Sun. In the negative footpoint region of an inverse J-shaped dextral filament, the RNF was formed by the convergence to supergranular junctions of several magnetic flux patches of the same polarity, and it then rotated counterclockwise (CCW) for approximately 11 hr and showed up as a CCW rotating EUV cyclone, during which time the filament gradually evolved into a circular filament that surrounded the cyclone. When the calculated convergence and vortex flows appeared around the RNF during its formation and rotation phases, the injected magnetic helicity calculation also showed negative helicity accumulation during the RNF rotation that was consistent with the dextral chirality of the filament. Finally, the RNF rotation stopped and the cyclone disappeared, and, probably due to an emerging bipole and its forced cancellation with the RNF, the closure filament underwent an eruption along its axis in the (clockwise) direction opposite to the rotation directions of the RNF and cyclone. These observations suggest that the RNFs might play an important role in the formation of nearby small-scale circular filaments as they transport and inject magnetic energy and helicity, and the formation of the EUV cyclones may be a further manifestation of the helicity injected into the corona by the rotation of the RNFs in the photosphere. In addition, the new emerging bipole observed before the filament eruption might be responsible for destabilizing the system and triggering the magnetic reconnection which proves useful for the filament eruption.

  17. The Formation and Eruption of a Small Circular Filament Driven by Rotating Magnetic Structures in the Quiet Sun

    Science.gov (United States)

    Yang, Bo; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Xu, Zhe

    2015-04-01

    We present the first observation of the formation and eruption of a small circular filament driven by a rotating network magnetic field (RNF) in the quiet Sun. In the negative footpoint region of an inverse J-shaped dextral filament, the RNF was formed by the convergence to supergranular junctions of several magnetic flux patches of the same polarity, and it then rotated counterclockwise (CCW) for approximately 11 hr and showed up as a CCW rotating EUV cyclone, during which time the filament gradually evolved into a circular filament that surrounded the cyclone. When the calculated convergence and vortex flows appeared around the RNF during its formation and rotation phases, the injected magnetic helicity calculation also showed negative helicity accumulation during the RNF rotation that was consistent with the dextral chirality of the filament. Finally, the RNF rotation stopped and the cyclone disappeared, and, probably due to an emerging bipole and its forced cancellation with the RNF, the closure filament underwent an eruption along its axis in the (clockwise) direction opposite to the rotation directions of the RNF and cyclone. These observations suggest that the RNFs might play an important role in the formation of nearby small-scale circular filaments as they transport and inject magnetic energy and helicity, and the formation of the EUV cyclones may be a further manifestation of the helicity injected into the corona by the rotation of the RNFs in the photosphere. In addition, the new emerging bipole observed before the filament eruption might be responsible for destabilizing the system and triggering the magnetic reconnection which proves useful for the filament eruption.

  18. Effects of magnetic field on fluidization properties of magnetic pearls

    Institute of Scientific and Technical Information of China (English)

    Maoming Fan; Zhenfu Luo; Yuemin Zhao; Qingru Chen; Daniel Tao; Xiuxiang Tao; Zhenqiang Chen

    2007-01-01

    An experimental study of the influence of external magnetic field on the fluidization behavior of magnetic pearls was carried out. Magnetic pearls are a magnetic form of iron oxide that mainly consists of Fe2O3 which are recovered from a high-volume power plant fly ash from pulverized coal combustion. Due to its abundance, low price and particular physical and chemical properties, magnetic pearls can be used as a heavy medium for minerals or solid waste dry separation based on density difference. This paper introduces the properties of magnetic pearls and compares the performance of magnetic pearls fluidised bed operation with or without an external magnetic field. Experimental results show that an external magnetic field significantly improves the fluidization performance of magnetic pearls such as uniformity and stability.

  19. Magnetic Helicity and Large Scale Magnetic Fields: A Primer

    CERN Document Server

    Blackman, Eric G

    2014-01-01

    Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. H...

  20. On radial heliospheric magnetic fields: Voyager 2 observation and model

    Science.gov (United States)

    Wang, C.; Richardson, J. D.; Burlaga, L. F.; Ness, N. F.

    2003-05-01

    The heliospheric magnetic field (HMF) direction, on average, conforms well to the Parker spiral. However, numerous examples of events where the HMF is oriented in near-radial directions for many hours have been reported on the basis of observations inside 5 AU from spacecraft such as ISEE-3 and Ulysses. The magnetic field data observed by Voyager 2 from launch in 1977 through the end of 1982 (i.e., between 1 and ˜10 AU) were searched for all instances of radial fields with durations of 6 hours or more. Radial fields of significant durations at large distances are unusual as the Parker spiral is very tightly wound. The radial HMF events in the inner heliosphere typically occur at times when the solar wind speed is declining gradually, while they tend to be associated with steady wind speeds at distances beyond ˜6 AU. The durations of these events appear to be independent of distance and solar cycle, with an average duration of ˜11 hours. They generally are not associated with interplanetary coronal mass ejections (ICMEs). Possible generation mechanisms of the radial field events related to speed variations near the Sun are investigated by use of a MHD model. We find that a noticeable low-speed plateau of limited duration in solar wind speed near the Sun can produce radial field events having durations of the order of 10 hours in the heliosphere as observed by Voyager 2.

  1. Interaction between two magnetic dipoles in a uniform magnetic field

    Directory of Open Access Journals (Sweden)

    J. G. Ku

    2016-02-01

    Full Text Available A new formula for the interaction force between two magnetic dipoles in a uniform magnetic field is derived taking their mutual magnetic interaction into consideration and used to simulate their relative motion. Results show that when the angle β between the direction of external magnetic field and the centerline of two magnetic dipoles is 0 ° or 90 °, magnetic dipoles approach each other or move away from each other in a straight line, respectively. And the time required for them to contact each other from the initial position is related to the specific susceptibility and the diameter of magnetic particles, medium viscosity and magnetic field strength. When β is between 0 ° and 90 °, magnetic dipole pair performs approximate elliptical motion, and the motion trajectory is affected by the specific susceptibility, diameter and medium viscosity but not magnetic field strength. However, time required for magnetic dipoles to complete the same motion trajectory is shorter when adopting stronger magnetic field. Moreover, the subsequent motion trajectory of magnetic dipoles is ascertained once the initial position is set in a predetermined motion trajectory. Additionally, magnetic potential energy of magnetic dipole pairs is transformed into kinetic energy and friction energy during the motion.

  2. Effective magnetic moment of neutrinos in strong magnetic fields

    CERN Document Server

    Pérez, A; Masood, S S; Gaitan, R; Rodríguez, S

    2002-01-01

    In this paper we compute the effective magnetic moment of neutrinos propagating in dense high magnetized medium. Taking typical values of magnetic field and densities of astrophysical objects (such as the cores of supernovae and neutron stars) we obtain an effective type of dipole magnetic moment in agreement with astrophysical and cosmological bounds. (Author)

  3. Unsteady wandering magnetic field lines, turbulence and laboratory flux ropes

    Science.gov (United States)

    Intrator, T.; Sears, J.; Weber, T.; Liu, D.; Pulliam, D.; Lazarian, A.

    2011-12-01

    We describe earth bound laboratory experiment investigations of patchy, unsteady, bursty, patchy magnetic field structures that are unifying features of magnetic reconnection and turbulence in helio, space and astro physics. Macroscopic field lines occupy cross sectional areas, fill up three dimensional (3D) volumes as flux tubes. They contain mass with Newtonian dynamics that follow magneto-hydro-dynamic (MHD) equations of motion. Flux rope geometry can be ubiquitous in laminar reconnection sheet geometries that are themselves unstable to formation of secondary "islands" that in 3D are really flux ropes. Flux ropes are ubiquitous structures on the sun and the rest of the heliosphere. Understanding the dynamics of flux ropes and their mutual interactions offers the key to many important astrophysical phenomena, including magnetic reconnection and turbulence. We describe laboratory investigations on RSX, where 3D interaction of flux ropes can be studied in great detail. We use experimental probes inside the the flux ropes to measure the magnetic and electric fields, current density, density, temperatures, pressure, and electrostatic and vector plasma potentials. Macroscopic magnetic field lines, unsteady wandering characteristics, and dynamic objects with structure down to the dissipation scale length can be traced from data sets in a 3D volume. Computational approaches are finally able to tackle simple 3D systems and we sketch some intriguing simulation results that are consistent with 3D extensions of typical 2D cartoons for magnetic reconnection and turbulence.

  4. Magnetic field penetration of erosion switch plasmas

    Science.gov (United States)

    Mason, Rodney J.; Jones, Michael E.; Grossmann, John M.; Ottinger, Paul F.

    1988-10-01

    Computer simulations demonstrate that the entrainment (or advection) of magnetic field with the flow of cathode-emitted electrons can constitute a dominant mechanism for the magnetic field penetration of erosion switch plasmas. Cross-field drift in the accelerating electric field near the cathode starts the penetration process. Plasma erosion propagates the point for emission and magnetic field injection along the cathode toward the load-for the possibility of rapid switch opening.

  5. Magnetic field reversals and galactic dynamos

    OpenAIRE

    2012-01-01

    We argue that global magnetic field reversals similar to those observed in the Milky Way occur quite frequently in mean-field galactic dynamo models that have relatively strong, random, seed magnetic fields that are localized in discrete regions. The number of reversals decreases to zero with reduction of the seed strength, efficiency of the galactic dynamo and size of the spots of the seed field. A systematic observational search for magnetic field reversals in a representative sample of spi...

  6. Measuring interstellar magnetic fields by radio synchrotron emission

    CERN Document Server

    Beck, Rainer

    2009-01-01

    Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. The total intensity traces the strength and distribution of total magnetic fields. Total fields in gas-rich spiral arms and bars of nearby galaxies have strengths of 20-30 $\\mu$Gauss, due to the amplification of turbulent fields, and are dynamically important. In the Milky Way, the total field strength is about 6 $\\mu$G near the Sun and several 100 $\\mu$G in filaments near the Galactic Center. -- The polarized intensity measures ordered fields with a preferred orientation, which can be regular or anisotropic fields. Ordered fields with spiral structure exist in grand-design, barred, flocculent and even in irregular galaxies. The strongest ordered fields are found in interarm regions, sometimes forming "magnetic spiral arms" between the optical arms. Halo fields are X-shaped, probably due to outflows. -- The Faraday rotation of the polarization vectors tr...

  7. Strong dipole magnetic fields in fast rotating fully convective stars

    Science.gov (United States)

    Shulyak, D.; Reiners, A.; Engeln, A.; Malo, L.; Yadav, R.; Morin, J.; Kochukhov, O.

    2017-08-01

    M dwarfs are the most numerous stars in our Galaxy, with masses between approximately 0.5 and 0.1 solar masses. Many of them show surface activity qualitatively similar to our Sun and generate flares, high X-ray fluxes and large-scale magnetic fields1,2,3,4. Such activity is driven by a dynamo powered by the convective motions in their interiors2,5,6,7,8. Understanding properties of stellar magnetic fields in these stars finds a broad application in astrophysics, including theory of stellar dynamos and environment conditions around planets that may be orbiting these stars. Most stars with convective envelopes follow a rotation-activity relationship where various activity indicators saturate in stars with rotation periods shorter than a few days2,6,8. The activity gradually declines with rotation rate in stars rotating more slowly. It is thought that, due to a tight empirical correlation between X-ray radiance and magnetic flux9, the stellar magnetic fields will also saturate, to values around 4 kG (ref. 10). Here we report the detection of magnetic fields above the presumed saturation limit in four fully convective M dwarfs. By combining results from spectroscopic and polarimetric studies, we explain our findings in terms of bistable dynamo models11,12: stars with the strongest magnetic fields are those in a dipole dynamo state, whereas stars in a multipole state cannot generate fields stronger than about 4 kG. Our study provides observational evidence that the dynamo in fully convective M dwarfs generates magnetic fields that can differ not only in the geometry of their large-scale component, but also in the total magnetic energy.

  8. Bright hot impacts by erupted fragments falling back on the Sun: magnetic channelling

    CERN Document Server

    Petralia, A; Orlando, S; Testa, P

    2016-01-01

    Dense plasma fragments were observed to fall back on the solar surface by the Solar Dynamics Observatory after an eruption on 7 June 2011, producing strong EUV brightenings. Previous studies investigated impacts in regions of weak magnetic field. Here we model the $\\sim~300$ km/s impact of fragments channelled by the magnetic field close to active regions. In the observations, the magnetic channel brightens before the fragment impact. We use a 3D-MHD model of spherical blobs downfalling in a magnetized atmosphere. The blob parameters are constrained from the observation. We run numerical simulations with different ambient density and magnetic field intensity. We compare the model emission in the 171\\AA~ channel of the Atmospheric Imaging Assembly with the observed one. We find that a model of downfall channelled in a $\\sim~1$MK coronal loop confined by a magnetic field of $\\sim~10-20$G, best explains qualitatively and quantitatively the observed evolution. The blobs are highly deformed, further fragmented, wh...

  9. The Stereo Electron Spikes and the Interplanetary Magnetic Field

    Science.gov (United States)

    Jokipii, J. R.; Sheeley, N. R., Jr.; Wang, Y. M.; Giacalone, J.

    2016-12-01

    A recent paper (Klassen etal, 2015) discussed observations of a spike event of 55-65 keV electrons which occurred very nearly simultaneously at STEREO A and STEREO B, which at the time were separated in longitude by 38 degrees. The authors associated the spikes with a flare at the Sun near the footpoint of the nominal Archimedean spiral magnetic field line passing through STEREO A. The spike at STEREO A was delayed by 2.2 minutes from that at STEREOB. We discuss the observations in terms of a model in which the electrons, accelerated at the flare, propagate without significant scattering along magnetic field lines which separate or diverge as a function of radial distance from the Sun. The near simultaneity of the spikes at the two spacecraft is a natural consequence of this model. We interpret the divergence of the magnetic field lines as a consequence of field-line random walk and flux-tube expansion. We show that the field-line random walk in the absence of flux-tube expansion produces an rms spread of field lines significantly less than that which is required to produce to observed divergence. We find that observations of the solar wind and its source region at the time of the event can account for the observations in terms of propagation along interplanetary magnetic field-lines. Klassen, A., Dresing, N., Gomez-Herrero, R, and Heber, B., A&A 580, A115 (2015) Financial support for NS and YMW was provided by NASA and CNR.

  10. Bipolar Magnetic Regions on the Sun: Global Analysis of the SOHO/MDI Data Set

    CERN Document Server

    Stenflo, J O

    2011-01-01

    The magnetic flux that is generated by dynamo inside the Sun emerges in the form of bipolar magnetic regions. We have analyzed the whole set of solar magnetograms obtained with the SOHO/MDI instrument in 1995-2011, and automatically identified 160,079 bipolar magnetic regions that span a range of scale sizes across nearly four orders of magnitude. Their properties have been statistically analyzed, in particular with respect to the polarity orientations of the bipolar regions, including their tilt angle distributions. The latitude variation of the average tilt angles (with respect to the E-W direction), known as Joy's law, is found to closely follow the relation 32.1*sin(latitude)[deg]. There is no indication of a dependence on region size that one may expect if the tilts were produced by the Coriolis force during the buoyant rise of flux loops from the tachocline region. A few percent of all regions have orientations that violate Hale's polarity law. We show examples, from different phases of the solar cycle,...

  11. Magnetic upflow events in the quiet-Sun photosphere. I. Observations

    CERN Document Server

    Jafarzadeh, S; Rodriguez, J de la Cruz

    2015-01-01

    Rapid magnetic upflows in the quiet-Sun photosphere were recently uncovered from both SUNRISE/IMaX and Hinode/SOT observations. Here, we study magnetic upflow events (MUEs) from high-quality, high (spatial, temporal, and spectral) resolution, and full Stokes observations in four photospheric magnetically sensitive Fe I lines centered at 525.021 nm, 617.334 nm, 630.151 nm, and 630.250 nm acquired with SST/CRISP. We detect MUEs by subtracting in-line Stokes V signals from those in far-blue-wing whose signal-to-noise ratio >= 7. We find a larger number of MUEs at any given time (0.02 per square arcsec), larger by one to two orders of magnitude, than previously reported. The MUEs appear to fall into four classes presenting different shapes of Stokes V profiles with (I) asymmetric double lobes, (II) single lobes, (III) double-humped (two same-polarity lobes), and (IV) three lobes (extra blue-shifted bump in addition to a double-lobes), from which, only less than half of them are single-lobed. We also find that MUE...

  12. Ultra-fine-scale filamentary structures in the Outer Corona and the Solar Magnetic Field

    Science.gov (United States)

    Woo, Richard

    2006-01-01

    Filamentary structures following magnetic field lines pervade the Sun's atmosphere and offer us insight into the solar magnetic field. Radio propagation measurements have shown that the smallest filamentary structures in the solar corona are more than 2 orders of magnitude finer than those seen in solar imaging. Here we use radio Doppler measurements to characterize their transverse density gradient and determine their finest scale in the outer corona at 20-30 R(circled dot operator), where open magnetic fields prevail. Filamentary structures overly active regions have the steepest gradient and finest scale, while those overlying coronal holes have the shallowest gradient and least finest scale. Their organization by the underlying corona implies that these subresolution structures extend radially from the entire Sun, confirming that they trace the coronal magnetic field responsible for the radial expansion of the solar wind. That they are rooted all over the Sun elucidates the association between the magnetic field of the photosphere and that of the corona, as revealed by the similarity between the power spectra of the photospheric field and the coronal density fluctuations. This association along with the persistence of filamentary structures far from the Sun demonstrate that subresolution magnetic fields must play an important role not only in magnetic coupling of the photosphere and corona, but also in coronal heating and solar wind acceleration through the process of small-scale magnetic reconnection. They also explain why current widely used theoretical models that extrapolate photospheric magnetic fields into the corona do not predict the correct source of the solar wind.

  13. The Sun's interior structure and dynamics, and the solar cycle

    CERN Document Server

    Broomhall, A -M; Howe, R; Norton, A A; Thompson, M J

    2014-01-01

    The Sun's internal structure and dynamics can be studied with helioseismology, which uses the Sun's natural acoustic oscillations to build up a profile of the solar interior. We discuss how solar acoustic oscillations are affected by the Sun's magnetic field. Careful observations of these effects can be inverted to determine the variations in the structure and dynamics of the Sun's interior as the solar cycle progresses. Observed variations in the structure and dynamics can then be used to inform models of the solar dynamo, which are crucial to our understanding of how the Sun's magnetic field is generated and maintained.

  14. The deflection of light induced by the Sun's gravitational field and measured with geodetic VLBI

    CERN Document Server

    Titov, O

    2015-01-01

    The Sun's gravitational field deflects the apparent positions of close objects in accordance with the formulae of general relativity. Optical astrometry is used to test the prediction, but only with the stars close to the Sun and only during total Solar eclipses. Geodetic Very Long Baseline Interferometry (VLBI) is capable of measuring the deflection of the light from distant radio sources anytime and across the whole sky. We show that the effect of light deflection is equivalent to the gravitational delay calculated during the reduction of VLBI data. All reference radio sources display an annual circular motion with the magnitude proportional to their ecliptic latitude. In particular, radio sources near the ecliptic pole draw an annual circle with magnitude of 4 mas. This effect could be easily measured with the current precision of the geodetic VLBI data.

  15. Near-Field Magnetic Dipole Moment Analysis

    Science.gov (United States)

    Harris, Patrick K.

    2003-01-01

    This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

  16. Magnetic Fields from the Electroweak Phase Transition

    CERN Document Server

    Törnkvist, O

    1998-01-01

    I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.

  17. Empirical Modeling of Radiative versus Magnetic Flux for the Sun-as-a-Star

    CERN Document Server

    Preminger, Dora; Chapman, Gary; Martens, Petrus C H; 10.1007/s11207-010-9560-1

    2010-01-01

    We study the relationship between full-disk solar radiative flux at different wavelengths and average solar photospheric magnetic-flux density, using daily measurements from the Kitt Peak magnetograph and other instruments extending over one or more solar cycles. We use two different statistical methods to determine the underlying nature of these flux-flux relationships. First, we use statistical correlation and regression analysis and show that the relationships are not monotonic for total solar irradiance and for continuum radiation from the photosphere, but are approximately linear for chromospheric and coronal radiation. Second, we use signal theory to examine the flux-flux relationships for a temporal component. We find that a well-defined temporal component exists and accounts for some of the variance in the data. This temporal component arises because active regions with high magnetic field strength evolve, breaking up into small-scale magnetic elements with low field strength, and radiative and magnet...

  18. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  19. Period ratios for standing kink and sausage modes in magnetized structures with siphon flow on the Sun

    Science.gov (United States)

    Yu, Hui; Chen, Shao-Xia; Li, Bo; Xia, Li-Dong

    2016-06-01

    Standing oscillations with multiple periods have been found in a number of atmospheric structures on the Sun. The ratio of the period of the fundamental to twice the one of its first overtone, P 1/2P 2, is important in applications of solar magneto-seismology. We examine how field-aligned flows impact P 1/2P 2 of standing modes in solar magnetic cylinders. For coronal loops, the flow effects are significant for both fast kink and sausage modes. For kink modes, they reduce P 1/2P 2 by up to 17% relative to the static case even when the density contrast between the loop and its surroundings approaches infinity. For sausage modes, the reduction in P 1/2P 2 due to flow is typically ≲ 5.5% compared with the static case. However, the threshold aspect ratio, only above which can trapped sausage modes be supported, may increase dramatically with the flow magnitude. For photospheric tubes, the flow effect on P 1/2P 2 is not as strong. However, when applied to sausage modes, introducing field-aligned flows offers more possibilities in interpreting the multiple periods that have recently been measured. We conclude that field-aligned flows should be taken into account to help better understand what causes the departure of P 1/2P 2 from unity.

  20. Polar Magnetic Fields Observed During the Last Four Solar Minima

    Science.gov (United States)

    Sun, X.; Liu, Y.; Hoeksema, J. T.

    2008-12-01

    The Sun's polar fields during the current minimum are the weakest in at least four solar cycles. The field strengths are fairly symmetric, unlike at least the two previous minima. We compare data from the Wilcox Solar Observatory (WSO) and Michelson Doppler Imager (MDI) to follow the polar field changes since 1976. The polar field is never observed well from Earth because the ecliptic lies near the Sun's equator, and each year the view of the north (south) is completely hidden for several months around March 7 (September 7). Analysis of the most favorably oriented MDI synoptic maps each year allows us to derive the fairly slowly evolving large-scale polar magnetic field pattern from 1996 to the present. We account for differential rotation and other geometric effects. The analysis allows us to provide a useful interpolated or extrapolated correction that can be smoothly incorporated into the global synoptic or synchronic maps above about 70 degrees latitude. The polar field is important in modeling the large-scale coronal and heliospheric field, particularly at minimum. Even though there has been extremely little solar activity over the last several months, at the current solar minimum the structure of the corona is much less equatorial than usual, in part because the polar fields are relatively weak.

  1. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

  2. Exploring Magnetic Fields with a Compass

    Science.gov (United States)

    Lunk, Brandon; Beichner, Robert

    2011-01-01

    A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

  3. Biological Effect of Magnetic Field in Mice

    Institute of Scientific and Technical Information of China (English)

    Zhao-Wei ZENG

    2005-01-01

    Objective: To study the biological effect of magnetic field in mice bodies. Method: With a piece of permanent magnet embeded in mice bodies beside the femoral artery and vein to measure the electrophoretic velocity(um/s). Result: The magnetic field in mice bodies on the experiment group that the electrophoretic velocity is faster more than control and free group.Conclusion:The magnetic field in animal's body can raise the negative electric charges on the surface of erythrocyte to improve the microcirculation, this is the biological effect of magnetic field.

  4. The Magnetic Field Effect on Planetary Nebulae

    Institute of Scientific and Technical Information of China (English)

    A. R. Khesali; K. Kokabi

    2006-01-01

    In our previous work on the 3-dimensional dynamical structure of planetary nebulae the effect of magnetic field was not considered. Recently Jordan et al. have directly detected magnetic fields in the central stars of some planetary nebulae. This discovery supports the hypothesis that the non-spherical shape of most planetary nebulae is caused by magnetic fields in AGB stars. In this study we focus on the role of initially weak toroidal magnetic fields embedded in a stellar wind in altering the shape of the PN. We found that magnetic pressure is probably influential on the observed shape of most PNe.

  5. Magnetic field concentrator for probing optical magnetic metamaterials.

    Science.gov (United States)

    Antosiewicz, Tomasz J; Wróbel, Piotr; Szoplik, Tomasz

    2010-12-06

    Development of all dielectric and plasmonic metamaterials with a tunable optical frequency magnetic response creates a need for new inspection techniques. We propose a method of measuring magnetic responses of such metamaterials within a wide range of optical frequencies with a single probe. A tapered fiber probe with a radially corrugated metal coating concentrates azimuthally polarized light in the near-field into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one. The active probe may be used in a future scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of metamaterials.

  6. Electrolytic tiltmeters inside magnetic fields: Some observations

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, J. [CIEMAT, Madrid (Spain); Arce, P. [CIEMAT, Madrid (Spain); Barcala, J.M. [CIEMAT, Madrid (Spain); Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A. [CIEMAT, Madrid (Spain)]. E-mail: antonio.ferrando@ciemat.es; Josa, M.I. [CIEMAT, Madrid (Spain); Luque, J.M. [CIEMAT, Madrid (Spain); Molinero, A. [CIEMAT, Madrid (Spain); Navarrete, J. [CIEMAT, Madrid (Spain); Oller, J.C. [CIEMAT, Madrid (Spain); Yuste, C. [CIEMAT, Madrid (Spain); Calderon, A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Garcia-Moral, L.A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gomez, G. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gonzalez-Sanchez, F.J. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Martinez-Rivero, C. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Matorras, F. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Rodrigo, T. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Ruiz-Arbol, P. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Scodellaro, L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Sobron, M. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Vila, I. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Virto, A.L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain)

    2007-04-21

    We present observations of the electrolytic clinometers behaviour inside magnetic field environments introducing phenomenological expressions to account for the measured output voltage variations as functions of field gradients and field strengths.

  7. From Inverse to Delayed Magnetic Catalysis in Strong Magnetic Field

    CERN Document Server

    Mao, Shijun

    2016-01-01

    We study magnetic field effect on chiral phase transition in a Nambu--Jona-Lasinio model. In comparison with mean field approximation containing quarks only, including mesons as quantum fluctuations in the model leads to a transition from inverse to delayed magnetic catalysis at finite temperature and delays the transition at finite baryon chemical potential. The location of the critical end point depends on the the magnetic field non-monotonously.

  8. Non-Perturbative Self-Consistent Model in SU(N Gauge Field Theory

    Directory of Open Access Journals (Sweden)

    Koshelkin A.V.

    2012-06-01

    Full Text Available Non-perturbative quasi-classical model in a gauge theory with the Yang-Mills (YM field is developed. The self-consistent solutions of the Dirac equation in the SU(N gauge field, which is in the eikonal approximation, and the Yang-Mills (YM equations containing the external fermion current are solved. It shown that the developed model has the self-consistent solutions of the Dirac and Yang-Mills equations at N ≥ 3. In this way, the solutions take place provided that the fermion and gauge fields exist simultaneously, so that the fermion current completely compensates the current generated by the gauge field due to self-interaction of it.

  9. Dynamic shielding of the magnetic fields

    Directory of Open Access Journals (Sweden)

    RAU, M.

    2010-11-01

    Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

  10. Field free line magnetic particle imaging

    CERN Document Server

    Erbe, Marlitt

    2014-01-01

    Marlitt Erbe provides a detailed introduction into the young research field of Magnetic Particle Imaging (MPI) and field free line (FFL) imaging in particular. She derives a mathematical description of magnetic field generation for FFL imaging in MPI. To substantiate the simulation studies on magnetic FFL generation with a proof-of-concept, the author introduces the FFL field demonstrator, which provides the world's first experimentally generated rotated and translated magnetic FFL field complying with the requirements for FFL reconstruction. Furthermore, she proposes a scanner design of consi

  11. Structure of the photospheric magnetic field during sector crossings of the heliospheric magnetic field

    Science.gov (United States)

    Getachew, Tibebu; Virtanen, Ilpo; Mursula, Kalevi

    2017-04-01

    The photospheric magnetic field is the source of the coronal and heliospheric magnetic fields (HMF), but their mutual correspondence is non-trivial and depends on the phase of the solar cycle. The photospheric field during the HMF sector crossings observed at 1 AU has been found to contain enhanced field intensities and definite polarity ordering, forming regions called Hale boundaries. Here we study the structure of the photospheric field during the HMF sector crossings during solar cycles 21-24, separately for the four phases of each solar cycle. We use a refined version of Svalgaard's list of major HMF sector crossings, mapped to the Sun using the solar wind speed observed at the Earth, and the daily level-3 magnetograms of the photospheric field measured at the Wilcox Solar Observatory in 1976-2014. We find that the structure of the photospheric field corresponding to the HMF sector crossings, and the existence and properties of the corresponding Hale bipolar regions varies significantly with solar cycle and with solar cycle phase. We find evidence for Hale boundaries in many, but not all ascending, maximum and declining phases of solar cycles but no minimum phase. The most clear Hale boundaries are found during the (+,-) HMF crossings in the northern hemisphere of odd cycles 21 and 23, but less systematically during the (+,-) crossings in the southern hemisphere of even cycles 22 and 24. We also find that the Hale structure of cycles 23 and 24 is more systematic than during cycles 21 and 22. This may be due to the weakening activity, which reduces the complexity of the photospheric field and clarifies the Hale pattern. The photospheric field distribution also depicts a larger area for the field of the northern hemisphere during the declining and minimum phases, in a good agreement with the bashful ballerina phenomenon. The HMF sector crossings observed at 1AU have only a partial correspondence to Hale boundaries in the photosphere, indicating that the two HMF

  12. Magnetized Jets Driven by the Sun, the Structure of the Heliosphere Revisited: Consequences for Draping of BISM ahead of the HP and Time Variability of ENAs

    Science.gov (United States)

    Opher, M.; Drake, J. F.; Zieger, B.; Michael, A.; Toth, G.; Swisdak, M.; Gombosi, T. I.

    2015-12-01

    Recently we proposed (Opher et al. 2015) that the structure of the heliosphere might be very different than we previously thought. The classic accepted view of the heliosphere is a quiescent, comet-like shape aligned in the direction of the Sun's travel through the interstellar medium (ISM) extending for thousands of astronomical units. We have shown, based on magnetohydrodynamic (MHD) simulations, that the tension force of the twisted magnetic field of the Sun confines the solar wind plasma beyond the termination shock and drives jets to the north and south very much like astrophysical jets. These heliospheric jets are deflected into the tail region by the motion of the Sun through the ISM. As in some astrophysical jets the interstellar wind blows the two jets into the tail but is not strong enough to force the lobes into a single comet-like tail. Instead, the interstellar wind flows around the heliosphere and into the equatorial region between the two jets. We show that the heliospheric jets are turbulent (due to large-scale MHD instabilities and reconnection) and strongly mix the solar wind with the ISM. The resulting turbulence has important implications for particle acceleration in the heliosphere. The two-lobe structure is consistent with the energetic neutral atom (ENA) images of the heliotail from IBEX where two lobes are visible in the north and south and the suggestion from the Cassini ENAs that the heliosphere is "tailless." The new structure of the heliosphere is supported by recent analytic work (Drake et al. 2015) that shows that even in high β heliosheath the magnetic field plays a crucial role in funneling the solar wind in two jets. Here we present these recent results and show that the heliospheric jets mediate the draping of the magnetic field and the conditions ahead of the heliopause. We show that reconnection between the interstellar and solar magnetic field both at the flanks of the jets and in between them twist the interstellar magnetic

  13. Solar axions as an energy source and modulator of the Earth magnetic field

    CERN Document Server

    Rusov, V D; Kudela, K; Mavrodiev, S Cht; Zelentsova, T N; Smolyar, V P; Merkotan, K K

    2010-01-01

    We show existence of strong negative correlation between the temporal variations of magnetic field toroidal component of the solar tachocline (the bottom of convective zone) and the Earth magnetic field (Y-component). The possibility that hypothetical solar axions, which can transform into photons in external electric or magnetic fields (the inverse Primakoff effect), can be the instrument by which the magnetic field of convective zone of the Sun modulates the magnetic field of the Earth is considered. We propose the axion mechanism of "solar dynamo-geodynamo" connection, where an energy of axions, which form in the Sun core, is modulated at first by the magnetic field of the solar tachocline zone (due to the inverse coherent Primakoff effect) and after that is absorbed in the liquid core of the Earth under influence of the terrestrial magnetic field, thereby playing the role of an energy source and a modulator of the Earth magnetic field. Within the framework of this mechanism new estimations of the strength...

  14. Magnetic field mapper based on rotating coils

    CERN Document Server

    AUTHOR|(CDS)2087244; Arpaia, Pasquale

    This thesis presents a magnetic field mapper based on rotating coils. The requirements, the architecture, the conceptual design, and the prototype for straight magnets were shown. The proposed system is made up of a rotating coil transducer and a train-like system for longitudinal motion and positioning inside magnet bore. The mapper allows a localized measurement of magnetic fields and the variation of the harmonic multipole content in the magnet ends. The proof-of-principle demonstration and the experimental characterization of the rotating-coil transducer specifically conceived for mapping validated the main objective of satisfying the magnetic measurement needs of the next generation of compact accelerators.

  15. Evolution of the magnetic field distribution of active regions

    Science.gov (United States)

    Dacie, S.; Démoulin, P.; van Driel-Gesztelyi, L.; Long, D. M.; Baker, D.; Janvier, M.; Yardley, S. L.; Pérez-Suárez, D.

    2016-12-01

    Aims: Although the temporal evolution of active regions (ARs) is relatively well understood, the processes involved continue to be the subject of investigation. We study how the magnetic field of a series of ARs evolves with time to better characterise how ARs emerge and disperse. Methods: We examined the temporal variation in the magnetic field distribution of 37 emerging ARs. A kernel density estimation plot of the field distribution was created on a log-log scale for each AR at each time step. We found that the central portion of the distribution is typically linear, and its slope was used to characterise the evolution of the magnetic field. Results: The slopes were seen to evolve with time, becoming less steep as the fragmented emerging flux coalesces. The slopes reached a maximum value of -1.5 just before the time of maximum flux before becoming steeper during the decay phase towards the quiet-Sun value of -3. This behaviour differs significantly from a classical diffusion model, which produces a slope of -1. These results suggest that simple classical diffusion is not responsible for the observed changes in field distribution, but that other processes play a significant role in flux dispersion. Conclusions: We propose that the steep negative slope seen during the late-decay phase is due to magnetic flux reprocessing by (super)granular convective cells.

  16. Magnetic Fields and Star Formation

    CERN Document Server

    Van Loo, S; Falle, S A E G

    2012-01-01

    Research performed in the 1950s and 1960s by Leon Mestel on the roles of magnetic fields in star formation established the framework within which he and other key figures have conducted subsequent investigations on the subject. This short tribute to Leon contains a brief summary of some, but not all, of his ground breaking contributions in the area. It also mentions of some of the relevant problems that have received attention in the last few years. The coverage is not comprehensive, and the authors have drawn on their own results more and touched more briefly on those of others than they would in a normal review. Theirs is a personal contribution to the issue honouring Leon, one of the truly great gentlemen, wits, and most insightful of astrophysicists.

  17. Clusters of small eruptive flares produced by magnetic reconnection in the sun

    CERN Document Server

    Archontis, V

    2015-01-01

    We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform magnetic flux sheet was injected into a fully developed convective layer. The gradual emergence of the field into the solar atmosphere results in a network of magnetic loops, which interact dynamically forming current layers at their interfaces. The formation and ejection of plasmoids out of the current layers leads to patchy reconnection and the spontaneous formation of several small (size ? 1-2Mm) flares. We find that these flares are short-lived (30 s - 3 min) bursts of energy in the range O(10^25 - 10^27) ergs, which is basically the nanoflare-microflare range. Their persistent formation and co-operative action and evolution leads to recurrent emission of fast EUV/X-ray jets and considerable plasma heating in the active corona.

  18. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

    1994-01-01

    A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

  19. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, D.K.; Rankin, R.A.; Morgan, J.P.

    1994-05-31

    A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.

  20. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  1. Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Ida, Tetsuya; Watasaki, Masahiro [Department of Electronic Control Engineering, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsakikamijima-cho, Toyota-gun, Hiroshima 725-0231 (Japan); Kimura, Yosuke [Kawasaki Heavy Industries, Ltd. Technical Institute System Technology Development Centre 1-1, Kawasaki-cho, Akashi-shi, Hyogo 673-8666 (Japan); Miki, Motohiro; Izumi, Mitsuru, E-mail: ida@hiroshima-cmt.ac.j [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan)

    2010-06-01

    For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

  2. Magnetic field evolution in tidal disruption events

    CERN Document Server

    Bonnerot, Clément; Lodato, Giuseppe; Rossi, Elena M

    2016-01-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to be transmitted to the debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of $\\sim 10$. However, this valu...

  3. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  4. Demagnetizing fields in active magnetic regenerators

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Bahl, Christian R.H.; Smith, Anders

    2014-01-01

    is in general both a function of the overall shape of the regenerator and its morphology (packed particles, parallel plates etc.) as well as the magnetization of the material. Due to the pronounced temperature dependence of the magnetization near the Curie temperature, the demagnetization field is also......A magnetic material in an externally applied magnetic field will in general experience a spatially varying internal magnetic field due to demagnetizing effects. When the performance of active magnetic regenerators (AMRs) is evaluated using numerical models the internal field is often assumed...... temperature dependent. We propose a relatively straightforward method to correct sufficiently for the demagnetizing field in AMR models. We discuss how the demagnetizing field behaves in regenerators made of packed spheres under realistic operation conditions....

  5. New knowledge of the Galactic magnetic fields

    CERN Document Server

    Han, J L

    2009-01-01

    The magnetic fields of our Milky Way galaxy are the main agent for cosmic rays to transport. In the last decade, much new knowledge has been gained from measurements of the Galactic magnetic fields. In the Galactic disk, from the RMs of a large number of newly discovered pulsars, the large-scale magnetic fields along the spiral arms have been delineated in a much larger region than ever before, with alternating directions in the arm and interarm regions. The toroidal fields in the Galactic halo were revealed to have opposite directions below and above the Galactic plane, which is an indication of an A0 mode dynamo operating in the halo. The strength of large-scale fields obtained from pulsar RM data has been found to increase exponentially towards the Galactic center. Compared to the steep Kolmogorov spectrum of magnetic energy at small scales, the large-scale magnetic fields show a shallow broken spatial magnetic energy spectrum.

  6. Behaviour of ferrocholesterics under external magnetic fields

    Science.gov (United States)

    Petrescu, Emil; Motoc, Cornelia

    2001-08-01

    The influence of an external magnetic field on the orientational behaviour of a ferrocholesteric with a positive magnetic anisotropy is investigated. Both the phenomena arising when the field was switched on or switched off are considered. It is found that the field needed for a ferrocholesteric-ferronematic transition BFC↑ is higher when compared to that obtained for the pure cholesteric ( BC↑). A similar result was obtained when estimating the critical field for the homeotropic ferronematic-ferrocholesteric (focal conic) transition, occurring when the magnetic field was decreased or switched off. We found that BFC↓> BC↓. These results are explained when considering that the magnetic moments of the magnetic powder are not oriented parallel to the liquid crystal molecular directors, therefore hindering their orientation under a magnetic field.

  7. Coulomb crystals in the magnetic field

    CERN Document Server

    Baiko, D A

    2009-01-01

    The body-centered cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields $B \\gtrsim 10^{14}$ G). The effect of the magnetic ...

  8. Period ratios for standing kink and sausage modes in magnetized structures with siphon flow on the Sun

    CERN Document Server

    Yu, Hui; Li, Bo; Xia, Li-Dong

    2016-01-01

    Standing oscillations with multiple periods were found in a number of atmospheric structures on the Sun. The ratio of the period of the fundamental to twice the one of its first overtone, $P_1/2P_2$, is important in applications of solar magneto-seismology. We examine how field-aligned flows impact $P_1/2P_2$ of standing modes in solar magnetic cylinders. For coronal loops, the flow effects are significant for both fast kink and sausage modes. For kink ones, they reduce $P_1/2P_2$ by up to 17\\% relative to the static case even when the density contrast between the loop and its surroundings approaches infinity. For sausage modes, the reduction in $P_1/2P_2$ due to flow is typically $\\lesssim 5.5\\%$ compared with the static case. However, the threshold aspect ratio, only above which can trapped sausage modes be supported, may increase dramatically with the flow magnitude. For photospheric tubes, the flow effect on $P_1/2P_2$ is not as strong. However, when applied to sausage modes, introducing field-aligned flo...

  9. Generating the optimal magnetic field for magnetic refrigeration

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Insinga, Andrea Roberto; Smith, Anders

    2016-01-01

    remanence distribution for any desired magnetic field. The method is based on the reciprocity theorem, which through the use of virtual magnets can be used to calculate the optimal remanence distribution. Furthermore, we present a method for segmenting a given magnet design that always results...

  10. Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane

    Science.gov (United States)

    Pant, Bharat B. (Inventor); Wan, Hong (Inventor)

    2001-01-01

    A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

  11. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    Science.gov (United States)

    Soto-Aquino, D.; Rinaldi, C.

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given.

  12. Beam Transport in Toroidal Magnetic Field

    CERN Document Server

    Joshi, N; Meusel, O; Ratzinger, U

    2016-01-01

    The concept of a storage ring with toroidal magnetic field was presented in the two previous EPAC conferences. Here we report the first results of experiments performed with beam transport in toroidal magnetic fields and details of the injection system. The beam transport experiments were carried out with 30 degree toroidal segments with an axial magnetic field of 0.6T. The multi turn injection system relies on a transverse injection coil together with an electric kicker system.

  13. Magnetic Upflow Events in the Quiet-Sun Photosphere. I. Observations

    Science.gov (United States)

    Jafarzadeh, S.; Rouppe van der Voort, L.; de la Cruz Rodríguez, J.

    2015-09-01

    Rapid magnetic upflows in the quiet-Sun photosphere were recently uncovered from both Sunrise/IMaX and Hinode/SOT observations. Here, we study magnetic upflow events (MUEs) from high-quality, high- (spatial, temporal, and spectral) resolution, and full Stokes observations in four photospheric magnetically sensitive Fe i lines centered at 5250.21, 6173.34, 6301.51, and 6302.50 Å acquired with the Swedish Solar Telescope (SST)/CRISP. We detect MUEs by subtracting in-line Stokes V signals from those in the far blue wing whose signal-to-noise ratio (S/N) ≥slant 7. We find a larger number of MUEs at any given time (2.0× {10}-2 arcsec-2), larger by one to two orders of magnitude, than previously reported. The MUEs appear to fall into four classes presenting different shapes of Stokes V profiles with (I) asymmetric double lobes, (II) single lobes, (III) double-humped (two same-polarity lobes), and (IV) three lobes (an extra blueshifted bump in addition to double lobes), of which less than half are single-lobed. We also find that MUEs are almost equally distributed in network and internetwork areas and they appear in the interior or at the edge of granules in both regions. Distributions of physical properties, except for horizontal velocity, of the MUEs (namely, Stokes V signal, size, line-of-sight velocity, and lifetime) are almost identical for the different spectral lines in our data. A bisector analysis of our spectrally resolved observations shows that these events host modest upflows and do not show a direct indication of the presence of supersonic upflows reported earlier. Our findings reveal that the numbers, types (classes), and properties determined for MUEs can strongly depend on the detection techniques used and the properties of the employed data, namely, S/Ns, resolutions, and wavelengths.

  14. Magnetically modified bioсells in constant magnetic field

    Science.gov (United States)

    Abramov, E. G.; Panina, L. K.; Kolikov, V. A.; Bogomolova, E. V.; Snetov, V. N.; Cherepkova, I. A.; Kiselev, A. A.

    2017-02-01

    Paper addresses the inverse problem in determining the area, where the external constant magnetic field captures the biological cells modified by the magnetic nanoparticles. Zero velocity isolines, in area where the modified cells are captured by the magnetic field were determined by numerical method for two locations of the magnet. The problem was solved taking into account the gravitational field, magnetic induction, density of medium, concentration and size of cells, and size and magnetization of nanoparticles attached to the cell. Increase in the number of the nanoparticles attached to the cell and decrease in the cell' size, enlarges the area, where the modified cells are captured and concentrated by the magnet. Solution is confirmed by the visible pattern formation of the modified cells Saccharomyces cerevisiae.

  15. Near-zero-field nuclear magnetic resonance

    OpenAIRE

    Ledbetter, Micah; Theis, Thomas; Blanchard, John; Ring, Hattie; Ganssle, Paul; Appelt, Stephan; Bluemich, Bernhard; Pines, Alex; Budker, Dmitry

    2011-01-01

    We investigate nuclear magnetic resonance (NMR) in near-zero-field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J-coupling). This is in stark contrast to the high field case, where heteronuclear J-couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectr...

  16. Minimizing magnetic fields for precision experiments

    CERN Document Server

    Altarev, I; Lins, T; Marino, M G; Nießen, B; Petzoldt, G; Reisner, M; Stuiber, S; Sturm, M; Singh, J T; Taubenheim, B; Rohrer, H K; Schläpfer, U

    2015-01-01

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  17. Magnetic field evolution in tidal disruption events

    Science.gov (United States)

    Bonnerot, Clément; Price, Daniel J.; Lodato, Giuseppe; Rossi, Elena M.

    2017-08-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to pervade its debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of ˜10. However, this value represents a lower limit since it increases with numerical resolution. For an initial field strength of 1 G, the magnetic field never becomes dynamically important. Instead, the disruption of a star with a strong 1 MG magnetic field produces a debris stream within which magnetic pressure becomes similar to gas pressure a few tens of hours after disruption. If the remnant of one or multiple partial disruptions is eventually fully disrupted, its magnetic field could be large enough to magnetically power the relativistic jet detected from Swift J1644+57. Magnetized streams could also be significantly thickened by magnetic pressure when it overcomes the confining effect of self-gravity.

  18. Activation of Schwann cells in vitro by magnetic nanocomposites via applied magnetic field

    Directory of Open Access Journals (Sweden)

    Liu Z

    2014-12-01

    Full Text Available Zhongyang Liu,1,* Liangliang Huang,1,* Liang Liu,1,* Beier Luo,2,* Miaomiao Liang,3 Zhen Sun,1 Shu Zhu,1 Xin Quan,1 Yafeng Yang,1 Teng Ma,1 Jinghui Huang,1 Zhuojing Luo1 1Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi’an, 2Department of Orthopaedics, Changhai Hospital, Second Military Medical University, Shanghai, 3Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi’an, People’s Republic of China *These authors contributed equally to this work Abstract: Schwann cells (SCs are attractive seed cells in neural tissue engineering, but their application is limited by attenuated biological activities and impaired functions with aging. Therefore, it is important to explore an approach to enhance the viability and biological properties of SCs. In the present study, a magnetic composite made of magnetically responsive magnetic nanoparticles (MNPs and a biodegradable chitosan–glycerophosphate polymer were prepared and characterized. It was further explored whether such magnetic nanocomposites via applied magnetic fields would regulate SC biological activities. The magnetization of the magnetic nanocomposite was measured by a vibrating sample magnetometer. The compositional characterization of the magnetic nanocomposite was examined by Fourier-transform infrared and X-ray diffraction. The tolerance of SCs to the magnetic fields was tested by flow-cytometry assay. The proliferation of cells was examined by a 5-ethynyl-2-deoxyuridine-labeling assay, a PrestoBlue assay, and a Live/Dead assay. Messenger ribonucleic acid of BDNF, GDNF, NT-3, and VEGF in SCs was assayed by quantitative real-time polymerase chain reaction. The amount of BDNF, GDNF, NT-3, and VEGF secreted from SCs was determined by enzyme-linked immunosorbent assay. It was found that magnetic nanocomposites containing 10% MNPs showed a cross-section diameter of 32.33±1.81 µm, porosity of 80.41%±0.72%, and

  19. Magnetic field screening effect in electroweak model

    CERN Document Server

    Bakry, A; Zhang, P M; Zou, L P

    2014-01-01

    It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of that phenomenon is conditioned by features of the electro-weak interaction, namely, there is mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease of magnetic solutions. Applying variational method we have found a magnetic field configuration with a topological azimuthal magnetic flux which minimizes the energy functional and possesses a total energy of order 1 TeV. We suppose that corresponding magnetic bound state exists in the electroweak theory and can be detected in experiment.

  20. Numerical Simulation of Level Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    According to Maxwell electromagnetic field theory and magnetic vector potential integral equation, a mathematical model of LMF (Level Magnetic Field) for EMBR (Electromagnetic brake) was proposed, and the reliable software for LMF calculation was developed. The distribution of magnetic flux density given by numerical simulation shows that the magnetic flux density is greater in the magnet and magnetic leakage is observed in the gap. The magnetic flux density is uniform in horizontal plane and a peak is observed in vertical plane. Furthermore, the effects of electromagnetic and structural parameters on magnetic flux density were discussed. The relationship between magnetic flux, electromagnetic parameters and structural parameters is obtained by dimensional analysis, simulation experiment and least square method.

  1. SOLAR CYCLE VARIATION OF THE INTER-NETWORK MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Chunlan; Wang, Jingxiu, E-mail: cljin@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2015-06-20

    The solar inter-network magnetic field is the weakest component of solar magnetism, but it contributes most of the solar surface magnetic flux. The study of its origin has been constrained by the inadequate tempospatial resolution and sensitivity of polarization observations. With dramatic advances in spatial resolution and detecting sensitivity, the solar spectropolarimetry provided by the Solar Optical Telescope on board Hinode in an interval from the solar minimum to maximum of cycle 24 opens an unprecedented opportunity to study the cyclic behavior of the solar inter-network magnetic field. More than 1000 Hinode magnetograms observed from 2007 January to 2014 August are selected in the study. It has been found that there is a very slight correlation between sunspot number and magnetic field at the inter-network flux spectrum. From solar minimum to maximum of cycle 24, the flux density of the solar inter-network field is invariant, at 10 ± 1 G. The observations suggest that the inter-network magnetic field does not arise from flux diffusion or flux recycling of solar active regions, thereby indicating the existence of a local small-scale dynamo. Combining the full-disk magnetograms observed by the Solar and Heliospheric Observatory/Michelson Doppler Imager and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager in the same period, we find that the area ratio of the inter-network region to the full disk of the Sun apparently decreases from solar minimum to maximum but always exceeds 60%, even in the phase of solar maximum.

  2. Rydberg EIT in High Magnetic Field

    Science.gov (United States)

    Ma, Lu; Anderson, David; Miller, Stephanie; Raithel, Georg

    2016-05-01

    We present progress towards an all-optical approach for measurements of strong magnetic fields using electromagnetically induced transparency (EIT) with Rydberg atoms in an atomic vapor. Rydberg EIT spectroscopy is a promising technique for the development of atom-based, calibration- and drift-free technology for high magnetic field sensing. In this effort, Rydberg EIT is employed to spectroscopically investigate the response of Rydberg atoms exposed to strong magnetic fields, in which Rydberg atoms are in the strong-field regime. In our setup, two neodymium block magnets are used to generate fields of about 0.8 Tesla, which strongly perturb the atoms. Information on the field strength and direction is obtained by a comparison of experimental spectra with calculated spectral maps. Investigations of magnetic-field inhomogeneities and other decoherence sources will be discussed.

  3. Optical fibers with composite magnetic coating for magnetic field sensing

    Energy Technology Data Exchange (ETDEWEB)

    Radojevic, V.; Nedeljkovic, D.; Talijan, N. E-mail: ntalijan@elab.tmf.bg.ac.yu; Trifunovic, D.; Aleksic, R

    2004-05-01

    The investigated system for optical fiber sensor was multi-mode optical fiber with magnetic composite coating. Polymer component of composite coating was poly (ethylene-co-vinyl acetate)-EVA, and the magnetic component was powder of SmCo{sub 5} permanent magnet in form of single domain particles. The influence of the applied external magnetic field on the change of intensity of the light signal propagated through optical fiber was investigated.

  4. Optical fibers with composite magnetic coating for magnetic field sensing

    Science.gov (United States)

    Radojevic, V.; Nedeljkovic, D.; Talijan, N.; Trifunovic, D.; Aleksic, R.

    2004-05-01

    The investigated system for optical fiber sensor was multi-mode optical fiber with magnetic composite coating. Polymer component of composite coating was poly (ethylene-co-vinyl acetate)-EVA, and the magnetic component was powder of SmCo5 permanent magnet in form of single domain particles. The influence of the applied external magnetic field on the change of intensity of the light signal propagated through optical fiber was investigated.

  5. Swarm: A constellation to study the Earth's magnetic field

    DEFF Research Database (Denmark)

    Friis-Christensen, Eigil; Luhr, H.; Hulot, G.

    2006-01-01

    The Swarm mission was selected as the 5th mission in ESA's Earth Explorer Programme in 2004. The mission will provide the best ever survey of the geomagnetic field and its temporal evolution that will lead to new insights into the Earth system by improving our understanding of the Earth's interior...... and its effect on Geospace, the vast region around the Earth where electrodynamic processes are influenced by the Earth's magnetic field. Scheduled for launch in 2010, the mission will comprise a constellation of three satellites, with two spacecraft flying side-by-side at lower attitude (450 km initial...... field measurements, will provide the necessary observations that are required to separate and model the various Sources of the geomagnetic field. This results in it unique "view" inside the Earth from space to study the composition and processes of its interior. It also allows analysing the Sun...

  6. Magnetic Energy and Helicity in Two Emerging Active Regions in the Sun

    Science.gov (United States)

    Liu, Y.; Schuck, P. W.

    2012-01-01

    The magnetic energy and relative magnetic helicity in two emerging solar active regions, AR 11072 and AR 11158,are studied. They are computed by integrating over time the energy and relative helicity fluxes across the photosphere. The fluxes consist of two components: one from photospheric tangential flows that shear and braid field lines (shear term), the other from normal flows that advect magnetic flux into the corona (emergence term). For these active regions: (1) relative magnetic helicity in the active-region corona is mainly contributed by the shear term,(2) helicity fluxes from the emergence and the shear terms have the same sign, (3) magnetic energy in the corona (including both potential energy and free energy) is mainly contributed by the emergence term, and(4) energy fluxes from the emergence term and the shear term evolved consistently in phase during the entire flux emergence course.We also examine the apparent tangential velocity derived by tracking field-line footpoints using a simple tracking method. It is found that this velocity is more consistent with tangential plasma velocity than with the flux transport velocity, which agrees with the conclusion by Schuck.

  7. Reducing Field Distortion in Magnetic Resonance Imaging

    Science.gov (United States)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  8. An Intergalactic Magnetic Field from Quasar Outflows

    CERN Document Server

    Furlanetto, S; Furlanetto, Steven; Loeb, Abraham

    2001-01-01

    Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function magnetic field strength at different redshifts. We find that by a redshift z ~ 3, about 5-80% of the IGM volume is filled by magnetic fields with an energy density > 10% of the mean thermal energy density of a photo-ionized IGM (at ~ 10^4 K). As massive galaxies and X-ray clusters condense out of the magnetized IGM, the adiabatic compression of the magnetic field could result in the fields observed in these systems without a need for further dynamo amplification.

  9. MDI Synoptic Charts of Magnetic Field: Interpolation of Polar Fields

    Science.gov (United States)

    Liu, Yang; Hoeksema, J. T.; Zhao, X.; Larson, R. M.

    2007-05-01

    In this poster, we compare various methods for interpolation of polar field for the MDI synoptic charts of magnetic field. By examining the coronal and heliospheric magnetic field computed from the synoptic charts based on a Potential Field Source Surface model (PFSS), and by comparing the heliospheric current sheets and footpoints of open fields with the observations, we conclude that the coronal and heliospheric fields calculated from the synoptic charts are sensitive to the polar field interpolation, and a time-dependent interpolation method using the observed polar fields is the best among the seven methods investigated.

  10. Relational and geometric approaches to justifying the magnetic fields of astrophysical objects

    Science.gov (United States)

    Babenko, I. A.

    We propose justification of the Sutherland hypotheses about origin of the magnetic fields of the Earth, Sun and other astrophysical objects as a part of the relational theory of space-time and interactions ("binary geometrophysics") and multidimensional geometrical models of physical interactions (like the Kaluza-Klein theories).

  11. Efficient magnetic fields for supporting toroidal plasmas

    CERN Document Server

    Landreman, Matt

    2016-01-01

    The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The properties of curl-free magnetic fields allow magnetic field distributions to be ranked in order of their difficulty of production from a distance. Plasma shapes with low curvature and spectral width may be difficult to support, whereas plasma shapes with sharp edges may be efficiently supported by distant coils. Two measures of difficulty, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally-produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix y...

  12. The Evolution of the Earth's Magnetic Field.

    Science.gov (United States)

    Bloxham, Jeremy; Gubbins, David

    1989-01-01

    Describes the change of earth's magnetic field at the boundary between the outer core and the mantle. Measurement techniques used during the last 300 years are considered. Discusses the theories and research for explaining the field change. (YP)

  13. The Physics of Attraction and Repulsion: Magnetism and Magnetic Fields

    Science.gov (United States)

    Nakotte, Heinz

    2001-11-01

    The development of new materials with improved magnetic properties completely changed the modern world in the past decades. Recent progress is predominantly due to a better understanding of magnetism that has gone far beyond compass needles rotating in a magnetic field and bar magnets attracting or repelling each other. New magnetic materials are used to build smaller and smaller read/write heads and hard disks with increased storage capacity, developments that are responsible the revolution in the computer industry. Another example is the field of magnetic levitation that became feasible for commercial applications with the discovery of new superconducting materials, and a prototype train is under development in Japan. In medicine, the development of magnetic resonance imaging (MRI) provides an alternative to other (destructive) radiation techniques.

  14. Assembly of magnetic spheres in strong homogeneous magnetic field

    Science.gov (United States)

    Messina, René; Stanković, Igor

    2017-01-01

    The assembly in two dimensions of spherical magnets in strong magnetic field is addressed theoretically. It is shown that the attraction and assembly of parallel magnetic chains is the result of a delicate interplay of dipole-dipole interactions and short ranged excluded volume correlations. Minimal energy structures are obtained by numerical optimization procedure as well as analytical considerations. For a small number of constitutive magnets Ntot ≤ 26, a straight chain is found to be the ground state. In the regime of larger Ntot ≥ 27, the magnets form two touching chains with equally long tails at both ends. We succeed to identify the transition from two to three touching chains at Ntot = 129. Overall, this study sheds light on the mechanisms of the recently experimentally observed ribbon formation of superparamagnetic colloids via lateral aggregation of magnetic chains in magnetic field (Darras et al., 2016).

  15. Evolution of Neutron Star Magnetic Fields

    Indian Academy of Sciences (India)

    Dipankar Bhattacharya

    2002-03-01

    This paper reviews the current status of the theoretical models of the evolution of the magnetic fields of neutron stars other than magnetars. It appears that the magnetic fields of neutron stars decay significantly only if they are in binary systems. Three major physical models for this, namely spindown-induced flux expulsion, ohmic evolution of crustal field and diamagnetic screening of the field by accreted plasma, are reviewed.

  16. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Soto-Aquino, D. [ERC Incorporated, Air Force Research Laboratory, 10 E. Saturn Blvd., Edwards AFB, CA 93524 (United States); Rinaldi, C., E-mail: carlos.rinaldi@bme.ufl.edu [J. Crayton Pruitt Family Department of Biomedical Engineering and Department of Chemical Engineering, University of Florida, PO Box 116131, Gainesville, FL 32611-6131 (United States)

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given. - Highlights: • Rosensweig's model for SAR was extended to high fields. • The MRSh relaxation equation was used to predict SAR at high fields. • Rotational Brownian dynamics simulations were used to predict SAR. • The results of these models were compared. • Predictions of effect of size and field conditions on SAR are presented.

  17. Two-axis magnetic field sensor

    Science.gov (United States)

    Jander, Albrecht (Inventor); Nordman, Catherine A. (Inventor); Qian, Zhenghong (Inventor); Smith, Carl H. (Inventor)

    2006-01-01

    A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

  18. Magnetic fields and rotation of spiral galaxies

    CERN Document Server

    Battaner, E; Florido, E

    1998-01-01

    We present a simplified model in which we suggest that two important galactic problems -the magnetic field configuration at large scales and the flat rotation curve- may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, stablishing a merging of extragalactic and galactic magnetic fields. The outer disc may then adquire a magnetic energy gradient very close to the gradient required to explain the rotation curve, without the hypothesis of galactic dark matter. Our model predicts symmetries of the galactic field in noticeable agreement with the large scale structure of our galaxy.

  19. Rotating artificial gauge magnetic and electric fields

    CERN Document Server

    Lembessis, V E; Alshamari, S; Siddig, A; Aldossary, O M

    2016-01-01

    We consider the creation of artificial gauge magnetic and electric fields created when a two-level atom interacts with an optical Ferris wheel light field.These fields have the spatial structure of the optical Ferris wheel field intensity profile. If this optical field pattern is made to rotate in space then we have the creation of artificial electromagnetic fields which propagate in closed paths. The properties of such fields are presented and discussed

  20. A Monte Carlo simulation of magnetic field line tracing in the solar wind

    Directory of Open Access Journals (Sweden)

    P. Pommois

    2001-01-01

    Full Text Available It is well known that the structure of magnetic field lines in solar wind can be influenced by the presence of the magnetohydrodynamic turbulence. We have developed a Monte Carlo simulation which traces the magnetic field lines in the heliosphere, including the effects of magnetic turbulence. These effects are modelled by random operators which are proportional to the square root of the magnetic field line diffusion coefficient. The modelling of the random terms is explained, in detail, in the case of numerical integration by discrete steps. Furthermore, a proper evaluation of the diffusion coefficient is obtained by a numerical simulation of transport in anisotropic magnetic turbulence. The scaling of the fluctuation level and of the correlation lengths with the distance from the Sun are also taken into account. As a consequence, plasma transport across the average magnetic field direction is obtained. An application to the propagation of energetic particles from corotating interacting regions to high heliographic latitudes is considered.

  1. Magnetic fields in Neutron Stars

    CERN Document Server

    Viganò, Daniele; Miralles, Juan A; Rea, Nanda

    2015-01-01

    Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

  2. Earth magnetism a guided tour through magnetic fields

    CERN Document Server

    Campbell, Wallace H

    2001-01-01

    An introductory guide to global magnetic field properties, Earth Magnetism addresses, in non-technical prose, many of the frequently asked questions about Earth''s magnetic field. Magnetism surrounds and penetrates our Earth in ways basic science courses can rarely address. It affects navigation, communication, and even the growth of crystals. As we observe and experience an 11-year solar maximum, we may witness spectacular satellite-destroying solar storms as they interact with our magnetic field. Written by an acknowledged expert in the field, this book will enrich courses in earth science, atmospheric science, geology, meteorology, geomagnetism, and geophysics. Contains nearly 200 original illustrations and eight pages of full-color plates.* Largely mathematics-free and with a wide breadth of material suitable for general readers* Integrates material from geomagnetism, paleomagnetism, and solar-terrestrial space physics.* Features nearly 200 original illustrations and 4 pages of colour plates

  3. Magnetic fields of HgMn stars

    DEFF Research Database (Denmark)

    Hubrig, S.; Gonzalez, J. F.; Ilyin, I.

    2012-01-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have fai...

  4. Ground Vehicle Navigation Using Magnetic Field Variation

    Science.gov (United States)

    Shockley, Jeremiah A.

    The Earth's magnetic field has been the bedrock of navigation for centuries. The latest research highlights the uniqueness of magnetic field measurements based on position due to large scale variations as well as localized perturbations. These observable changes in the Earth's magnetic field as a function of position provide distinct information which can be used for navigation. This dissertation describes ground vehicle navigation exploiting variation in Earth's magnetic field using a self-contained navigation system consisting of only a magnetometer and magnetic field maps. In order to achieve navigation, effective calibration enables repeatable magnetic field measurements from different vehicles and facilitates mapping of the observable magnetic field as a function of position. A new modified ellipsoid calibration technique for strapdown magnetometers in large vehicles is described, as well as analysis of position measurement generation comparing a multitude of measurement compositions using existing and newly developed likelihood techniques. Finally, navigation solutions are presented using both a position measurement and direct incorporation of the magnetometer measurements via a particle filter to demonstrate road navigation in three different environments. Emphatically, the results affirm that navigation using magnetic field variation in ground vehicles is viable and achieves adequate performance for road level navigation.

  5. Lattice Planar QED in external magnetic field

    CERN Document Server

    Cea, Paolo; Giudice, Pietro; Papa, Alessandro

    2011-01-01

    We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

  6. Helical Magnetic Fields in AGN Jets

    Indian Academy of Sciences (India)

    Y. J. Chen; G.-Y. Zhao; Z.-Q. Shen

    2014-09-01

    We establish a simple model to describe the helical magnetic fields in AGN jets projected on the sky plane and the line-of-sight. This kind of profile has been detected in the polarimetric VLBI observation of many blazar objects, suggesting the existence of helical magnetic fields in these sources.

  7. Magnetic Fields at the Center of Coils

    Science.gov (United States)

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-01-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = µ[subscript 0] (N/L) I, (1) where I is the current, N…

  8. Magnetic Fields in Stars: Origin and Impact

    CERN Document Server

    Langer, N

    2013-01-01

    Various types of magnetic fields occur in stars: small scale fields, large scale fields, and internal toroidal fields. While the latter may be ubiquitous in stars due to differential rotation, small scale fields (spots) may be associated with envelop convection in all low and high mass stars. The stable large scale fields found in only about 10 per cent of intermediate mass and massive stars may be understood as a consequence of dynamical binary interaction, e.g., the merging of two stars in a binary. We relate these ideas to magnetic fields in white dwarfs and neutron stars, and to their role in core-collapse and thermonuclear supernova explosions.

  9. Classical theory of electric and magnetic fields

    CERN Document Server

    Good, Roland H

    1971-01-01

    Classical Theory of Electric and Magnetic Fields is a textbook on the principles of electricity and magnetism. This book discusses mathematical techniques, calculations, with examples of physical reasoning, that are generally applied in theoretical physics. This text reviews the classical theory of electric and magnetic fields, Maxwell's Equations, Lorentz Force, and Faraday's Law of Induction. The book also focuses on electrostatics and the general methods for solving electrostatic problems concerning images, inversion, complex variable, or separation of variables. The text also explains ma

  10. Pair annihilation in superstrong magnetic fields

    Science.gov (United States)

    Daugherty, J. K.; Bussard, R. W.

    1980-01-01

    The kinematical and dynamical aspects of the annihilation processes in superstrong magnetic fields are studied. The feasibility and potential significance of detecting from magnetic neutron stars are discussed. The discussion proceeds from the derivation of the fully relativistic differential cross sections and annihilation rates for both one- and two-photon emission from a ground-state gas of electrons and positrons in a static, uniform magnetic field.

  11. Mechanics of magnetic fluid column in strong magnetic fields

    Science.gov (United States)

    Polunin, V. M.; Ryapolov, P. A.; Platonov, V. B.

    2017-06-01

    Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.

  12. The Sun

    CERN Document Server

    Golub, Leon

    2017-01-01

    Essential for life on earth and a major influence on our environment, the Sun is also the most fascinating object in the daytime sky. Every day we feel the effect of its coming and going – literally the difference between day and night. But figuring out what the Sun is, what it’s made of, why it glows so brightly, how old it is, how long it will last – all of these take thought and observation. Leon Golub and Jay M. Pasachoff offer an engaging and informative account of what scientists know about the Sun, and the history of these discoveries. Solar astronomers have studied the Sun over the centuries both for its intrinsic interest and in order to use it as a laboratory to reveal the secrets of other stars. The authors discuss the surface of the Sun, including sunspots and their eleven-year cycle, as well as the magnetism that causes them; the Sun’s insides, as studied mainly from seismic waves that astronomers record on its surface; the outer layers of the Sun that we see from Earth only at eclipses ...

  13. Delayed quarkonium formation in a magnetic field

    CERN Document Server

    Suzuki, Kei

    2016-01-01

    Formation time of heavy quarkonia in a homogeneous magnetic field is analyzed by using a phenomenological ansatz of the vector current correlator. Because the existence of a magnetic field mixes vector quarkonia ($J/\\psi$, $\\psi^\\prime$) and their pseudoscalar partners ($\\eta_c$, $\\eta_c^\\prime$), the properties of the quarkonia can be modified through such a spin mixing. This means that the formation time of quarkonia is also changed by the magnetic field. We show the formation time of vector quarkonia is delayed by an idealized constant magnetic field, where the formation time of the excited state becomes longer than that of the ground state. As a more realistic situation in heavy-ion collisions, effects by a time-dependent magnetic field are also discussed.

  14. Structure of magnetic fields in intracluster cavities

    CERN Document Server

    Gourgouliatos, Konstantinos Nektarios; Lyutikov, Maxim

    2010-01-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.

  15. Heliocentric distance dependence of the interplanetary magnetic field

    Science.gov (United States)

    Behannon, K. W.

    1978-01-01

    Numerous spacecraft measurements bearing on the heliocentric distance dependencies of both large- and small-scale properties of the interplanetary magnetic field (IMF) are assembled and compared. These data tend to indicate that the average of the radial field component varies as the inverse square of distance. However, the azimuthal component is rather strongly a function of time, being influenced by both the time-dependent solar wind speed and the evolution of the source field at the sun. Thus, unless the solar wind speed dependence is taken into account, individual sets of measurements by a single spacecraft give an azimuthal component gradient which is steeper than the inverse distance dependence predicted from the Parker spiral model. A least squares fit to the composite (five spacecraft) solar rotation average data set gives a result close to the inverse distance dependence. Preliminary Helios results suggest general consistency with the spiral model.

  16. Probing Magnetic Fields of Early Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-06-01

    How do magnetic fields form and evolve in early galaxies? A new study has provided some clever observations to help us answer this question.The Puzzle of Growing FieldsDynamo theory is the primary model describing how magnetic fields develop in galaxies. In this picture, magnetic fields start out as weak seed fields that are small and unordered. These fields then become ordered and amplified by large-scale rotation and turbulence in galaxy disks and halos, eventually leading to the magnetic fields we observe in galaxies today.Schematic showinghow to indirectly measure protogalactic magnetic fields. The measured polarization of a background quasar is altered by the fields in a foreground protogalaxy. Click for a closer look! [Farnes et al. 2017/Adolf Schaller/STSCI/NRAO/AUI/NSF]To test this model, we need observations of the magnetic fields in young protogalaxies. Unfortunately, we dont have the sensitivity to be able to measure these fields directly but a team of scientists led by Jamie Farnes (Radboud University in the Netherlands) have come up with a creative alternative.The key is to find early protogalaxies that absorb the light of more distant background objects. If a protogalaxy lies between us and a distant quasar, then magnetic fields of the protogalaxy if present will affect the polarization measurements of the background quasar.Observing Galactic Building BlocksTop: Redshift distribution for the background quasars in the authors sample. Bottom: Redshift distribution for the foreground protogalaxies the authors are exploring. [Farnes et al. 2017]Farnes and collaborators examined two types of foreground protogalaxies: Damped Lyman-Alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). They obtained polarimetric data for a sample of 114 distant quasars with nothing in the foreground (the control sample), 19 quasars with DLAs in the foreground, and 27 quasars with LLSs in the foreground. They then used statistical analysis techniques to draw conclusions about

  17. Formation of magnetically anisotropic composite films at low magnetic fields

    Science.gov (United States)

    Ghazi Zahedi, Maryam; Ennen, Inga; Marchi, Sophie; Barthel, Markus J.; Hütten, Andreas; Athanassiou, Athanassia; Fragouli, Despina

    2017-04-01

    We present a straightforward two-step technique for the fabrication of poly (methyl methacrylate) composites with embedded aligned magnetic chains. First, ferromagnetic microwires are realized in a poly (methyl methacrylate) solution by assembling iron nanoparticles in a methyl methacrylate solution under heat in an external magnetic field of 160 mT. The simultaneous thermal polymerization of the monomer throughout the wires is responsible for their permanent linkage and stability. Next, the polymer solution containing the randomly dispersed microwires is casted on a solid substrate in the presence of a low magnetic field (20–40 mT) which induces the final alignment of the microwires into long magnetic chains upon evaporation of the solvent. We prove that the presence of the nanoparticles assembled in the form of microwires is a key factor for the formation of the anisotropic films under low magnetic fields. In fact, such low fields are not capable of driving and assembling dispersed magnetic nanoparticles in the same type of polymer solutions. Hence, this innovative approach can be utilized for the synthesis of magnetically anisotropic nanocomposite films at low magnetic fields.

  18. Teaching Representation Translations with Magnetic Field Experiments

    Science.gov (United States)

    Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

    2017-01-01

    We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and measurement of the spatial variation of magnetic field components along a line near magnets. We describe the experimental tasks, various difficulties students have throughout, and ways this lab makes even their incorrect predictions better. We suggest that developing lab activities of this nature brings a new dimension to the ways students learn and interact with field concepts.

  19. Magnetic fields of HgMn stars

    DEFF Research Database (Denmark)

    Hubrig, S.; González, J. F.; Ilyin, I.

    2012-01-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have...... failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims. We re-analyse the available spectropolarimetric material...

  20. Warm inflation in presence of magnetic fields

    CERN Document Server

    Piccinelli, Gabriella; Ayala, Alejandro; Mizher, Ana Julia

    2013-01-01

    We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales, which rises the possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger proper time method.

  1. Turbulent Pumping of Magnetic Flux Reduces Solar Cycle Memory and thus Impacts Predictability of the Sun's Activity

    CERN Document Server

    Karak, Bidya Binay

    2012-01-01

    Prediction of the Sun's magnetic activity is important because of its effect on space environmental conditions and climate. However, recent efforts to predict the amplitude of the solar cycle have resulted in diverging forecasts with no consensus. It is understood that the dynamical memory of the solar dynamo mechanism governs predictability and this memory is different for advection- and diffusion-dominated solar convection zones. By utilizing stochastically forced, kinematic dynamo simulations, we demonstrate that the inclusion of downward turbulent pumping of magnetic flux reduces the memory of both advection- and diffusion-dominated solar dynamos to only one cycle; stronger pumping degrades this memory further. We conclude that reliable predictions for the maximum of solar activity can be made only at the preceding minimum and for more accurate predictions, sequential data assimilation would be necessary in forecasting models to account for the Sun's short memory.

  2. The solar magnetic field: from complexity to simplicity (and back)

    Science.gov (United States)

    Schüssler, Manfred

    2017-06-01

    The Sun is the only astrophysical object that permits a detailed study of the basic processes governing its magnetic field. Observations reveal stunning complexity due to the interaction with turbulent convection. Numerical simulations and observations strongly suggest that most of the small-scale field is generated by a process called small-scale dynamo action. The fundamental nature of this process makes it a candidate for magnetic field generation in a broad variety of astrophysical settings.On the other hand, the global nature of the 11-year cycle (as exhibited, for instance, by the polarity laws of sunspot groups and the regularly reversing axial dipole field) reveals a surprising simplicity. This suggests a description of the global dynamo process underlying the solar cycle in terms of relatively simple concepts. Insufficient knowledge about the structure of magnetic field and flows in the convection zone requires the introduction of a variety of free parameters (or even free functions), which severely impairs the explanatory power of most such models. However, during the last decades, surface observations of plasma flows and magnetic flux emergence, together with studies of magnetic flux transport, provided crucial information aboutthe workings of the dynamo process. They confirm the visionary approach proposed already in the 1960s by Babcock and Leighton. A recent update of their model permits a full study of the space spanned by the few remaining parameters in order to identify the regions with solar-like solutions.Observations of other cool stars show that the magnetic activity level decreases strongly with stellar rotation rate. The relatively slow rotation of the Sun puts it near to the threshold at which global dynamo action ceases. This suggests a further simplification of the dynamo model in terms of a generic normal form for a weakly nonlinear system. Including the inherent randomness brought about by the flux emergence process leads to a stochastic

  3. Field Mapping System for Solenoid Magnet

    Science.gov (United States)

    Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.

    2007-01-01

    A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.

  4. Magnetic-field-controlled reconfigurable semiconductor logic.

    Science.gov (United States)

    Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark

    2013-02-07

    Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices.

  5. Solar Force-free Magnetic Fields

    CERN Document Server

    Wiegelmann, Thomas

    2012-01-01

    The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundar...

  6. Magnetic monopole field exposed by electrons

    CERN Document Server

    Béché, A; Van Tendeloo, G; Verbeeck, J

    2013-01-01

    Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...

  7. External-field-free magnetic biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-03-24

    In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6 dB from one iron oxide magnetic nanoparticle with 8 nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200 nm × 200 nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3 dB is achieved for 30 μl magnetic nanoparticles suspension (30 nm iron oxide particles, 1 mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

  8. Interplanetary magnetic field and geomagnetic Dst variations.

    Science.gov (United States)

    Patel, V. L.; Desai, U. D.

    1973-01-01

    The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

  9. Polarized radiation diagnostics of stellar magnetic fields

    Science.gov (United States)

    Mathys, Gautier

    The main techniques used to diagnose magnetic fields in stars from polarimetric observations are presented. First, a summary of the physics of spectral line formation in the presence of a magnetic field is given. Departures from the simple case of linear Zeeman effect are briefly considered: partial Paschen-Back effect, contribution of hyperfine structure, and combined Stark and Zeeman effects. Important approximate solutions of the equation of transfer of polarized light in spectral lines are introduced. The procedure for disk-integration of emergent Stokes profiles, which is central to stellar magnetic field studies, is described, with special attention to the treatment of stellar rotation. This formalism is used to discuss the determination of the mean longitudinal magnetic field (through the photographic technique and through Balmer line photopolarimetry). This is done within the specific framework of Ap stars, which, with their unique large-scale organized magnetic fields, are an ideal laboratory for studies of stellar magnetism. Special attention is paid to those Ap stars whose magnetically split line components are resolved in high-dispersion Stokes I spectra, and to the determination of their mean magnetic field modulus. Various techniques of exploitation of the information contained in polarized spectral line profiles are reviewed: the moment technique (in particular, the determination of the crossover and of the mean quadratic field), Zeeman-Doppler imaging, and least-squares deconvolution. The prospects that these methods open for linear polarization studies are sketched. The way in which linear polarization diagnostics complement their Stokes I and V counterparts is emphasized by consideration of the results of broad band linear polarization measurements. Illustrations of the use of various diagnostics to derive properties of the magnetic fields of Ap stars are given. This is used to show the interest of deriving more physically realistic models of the

  10. Evolution of the Magnetic Field Distribution of Active Regions

    CERN Document Server

    Dacie, Sally; van Driel-Gesztelyi, Lidia; Long, David; Baker, Deb; Janvier, Miho; Yardley, Stephanie; Pérez-Suárez, David

    2016-01-01

    Aims. Although the temporal evolution of active regions (ARs) is relatively well understood, the processes involved continue to be the subject of investigation. We study how the magnetic field of a series of ARs evolves with time to better characterise how ARs emerge and disperse. Methods. We examine the temporal variation in the magnetic field distribution of 37 emerging ARs. A kernel density estimation plot of the field distribution was created on a log-log scale for each AR at each time step. We found that the central portion of the distribution is typically linear and its slope was used to characterise the evolution of the magnetic field. Results. The slopes were seen to evolve with time, becoming less steep as the fragmented emerging flux coalesces. The slopes reached a maximum value of ~ -1.5 just before the time of maximum flux before becoming steeper during the decay phase towards the quiet Sun value of ~ -3. This behaviour differs significantly from a classical diffusion model, which produces a slope...

  11. Scattering in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    David C. Carey

    2002-08-19

    The fixed target program at Fermilab has come to an end. New projects are in the planning stage. Among them is a muon storage ring. Up to the present, all storage rings in high-energy physics have carried stable particles, namely the electron and proton and their antiparticles. The muon is unstable and decays with a mean lifetime of 2.0 x 10{sup -6} sec. Two types of cooling have been used in the past. One is stochastic cooling where an electrode is used to detect the positions of the particles and send a signal to another position across the ring. Through successive applications of this technique, the phase space is ultimately greatly reduced and beams can be made to collide with a useful event rate. The second type of cooling is electron cooling. Here protons and electrons are made to travel together for a short distance. Equipartition causes transfer of transverse energy of the protons to that of the electrons. Neither of these methods is fast enough to allow acceleration of a sufficient number of muons up to maximum energy before they decay. A new method known as ionization cooling has been proposed.[1] The muons are cooled by passing them through a container of liquid hydrogen. The energy loss reduces both transverse and longitudinal momentum. The longitudinal momentum is restored with RF cavities. The net result is to maintain the longitudinal momentum while cooling the transverse momentum. To minimize the total travel distance of the muons the liquid hydrogen is placed inside the focusing solenoids. The question arises as to whether the presence of the solenoids influences the phase space occupied by the muons. After the muon scatters it has transverse momentum. In a constant longitudinal magnetic field the trajectory wraps around the field lines and coincides in momentum and position with a particle which scatters one cycle later. Here we calculate the change in emittance for both a drift space and a solenoid. We find that the presence of the solenoid does

  12. Compact low field magnetic resonance imaging magnet: Design and optimization

    Science.gov (United States)

    Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

    2000-03-01

    Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

  13. Hyperfine magnetic fields in substituted Finemet alloys

    Energy Technology Data Exchange (ETDEWEB)

    Brzózka, K., E-mail: k.brzozka@uthrad.pl [University of Technology and Humanities in Radom, Department of Physics (Poland); Sovák, P. [P.J. Šafárik University, Institute of Physics (Slovakia); Szumiata, T.; Gawroński, M.; Górka, B. [University of Technology and Humanities in Radom, Department of Physics (Poland)

    2016-12-15

    Transmission Mössbauer spectroscopy was used to determine the hyperfine fields of Finemet-type alloys in form of ribbons, substituted alternatively by Mn, Ni, Co, Al, Zn, V or Ge of various concentration. The comparative analysis of magnetic hyperfine fields was carried out which enabled to understand the role of added elements in as-quenched as well as annealed samples. Moreover, the influence of the substitution on the mean direction of the local hyperfine magnetic field was examined.

  14. Magnetic fields in Local Group dwarf irregulars

    CERN Document Server

    Chyzy, Krzysztof T; Beck, Rainer; Bomans, Dominik J

    2011-01-01

    We clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and what is the role of dwarf galaxies in the magnetization of the Universe. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100m Effelsberg telescope at 2.64 and 4.85GHz. Magnetic fields in LG dwarfs are three times weaker than in the normal spirals (6muG) are observed only in dwarfs of extreme characteristics while typical LG dwarfs are not suitable objects for efficient supply of magnetic fields to the intergalactic medium.

  15. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    Science.gov (United States)

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm.

  16. Instability of strong magnetic field and neutrino magnetic dipole moment

    CERN Document Server

    Lee, Hyun Kyu

    2016-01-01

    Vacuum instability of the strong electromagnetic field has been discussed since long time ago. The instability of the strong electric field due to creation of electron pairs is one of the examples, which is known as Schwinger process. What matters are the coupling of particles to the electromagnetic field and the mass of the particle to be produced. The critical electric field for electrons in the minimal coupling is ~ m^2/e . Spin 1/2 neutral particles but with magnetic dipole moments can interact with the electromagnetic field through Pauli coupling. The instability of the particular vacuum under the strong magnetic field can be formulated as the emergence of imaginary parts of the effective potential. In this talk, the development of the imaginary part in the effective potential as a function of the magnetic field strength is discussed for the configurations of the uniform magnetic field and the inhomogeneous magnetic field. Neutrinos are the lightest particle(if not photon or gluon) in the "standard model...

  17. The earth’'s electric field sources from sun to mud

    CERN Document Server

    Kelley, Michael C

    2013-01-01

    The Earth's Electric Field provides you with an integrated and comprehensive picture of the generation of the terrestrial electric fields, their dynamics and how they couple/propagate through the medium. The Earth's Electric Field provides basic principles of terrestrial electric field related topics, but also a critical summary of electric field related observations and their significance to the various related phenomena in the atmosphere. For the first time, Kelley brings together information on this topic in a coherent way, making it easy to gain a broad overview of the critical processes in an efficient way. If you conduct research in atmospheric science, physics, atmospheric chemistry, space plasma physics, and solar terrestrial physics, you will find this book to be essential reading. The only book on the physics of terrestrial electric fields and their generation mechanisms, propagation and dynamics-making it essential reading for scientists conducting research in upper atmospheric, ionospheric, magnet...

  18. Computation of magnetic fields in hysteretic media

    Energy Technology Data Exchange (ETDEWEB)

    Adly, A.A.; Mayergoyz, I.D.; Gomez, R.D.; Burke, E.R. (Univ. of Maryland, College Park, MD (United States))

    1993-11-01

    A newly developed vector Preisach-type model of hysteresis is applied to the computation of static magnetic fields in media with hysteresis. Time stepping technique is used to trace the time evolution of local magnetic fields which form the history of magnetizing process. At each time step, the magnetostatic problem is formulated in terms of an integral equation and an efficient iterative algorithm is employed for solving this problem. The technique has been used to simulate some magnetic recording processes. Sample results of these simulations are given in the paper.

  19. Efficient magnetic fields for supporting toroidal plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Landreman, Matt, E-mail: mattland@umd.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2016-03-15

    The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However, the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The efficiency of an externally generated magnetic field is a measure of the field's shaping component magnitude at the plasma compared to the magnitude near the coils; the efficiency of a plasma equilibrium can be measured using the efficiency of the required external shaping field. Counterintuitively, plasma shapes with low curvature and spectral width may have low efficiency, whereas plasma shapes with sharp edges may have high efficiency. Two precise measures of magnetic field efficiency, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix yields an efficiency ordered basis for the magnetic field distributions. Calculations are carried out for both tokamak and stellarator cases. For axisymmetric surfaces with circular cross-section, the SVD is calculated analytically, and the range of poloidal and toroidal mode numbers that can be controlled to a given desired level is determined. If formulated properly, these efficiency measures are independent of the coordinates used to parameterize the surfaces.

  20. Quark matter under strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Peres Menezes, Debora [Universidade Federal de Santa Catarina, Depto de Fisica - CFM, Florianopolis, SC (Brazil); Laercio Lopes, Luiz [Universidade Federal de Santa Catarina, Depto de Fisica - CFM, Florianopolis, SC (Brazil); Campus VIII, Centro Federal de Educacao Tecnologica de Minas Gerais, Varginha, MG (Brazil)

    2016-02-15

    We revisit three of the mathematical formalisms used to describe magnetized quark matter in compact objects within the MIT and the Nambu-Jona-Lasinio models and then compare their results. The tree formalisms are based on 1) isotropic equations of state, 2) anisotropic equations of state with different parallel and perpendicular pressures and 3) the assumption of a chaotic field approximation that results in a truly isotropic equation of state. We have seen that the magnetization obtained with both models is very different: while the MIT model produces well-behaved curves that are always positive for large magnetic fields, the NJL model yields a magnetization with lots of spikes and negative values. This fact has strong consequences on the results based on the existence of anisotropic equations of state. We have also seen that, while the isotropic formalism results in maximum stellar masses that increase considerably when the magnetic fields increase, maximum masses obtained with the chaotic field approximation never vary more than 5.5%. The effect of the magnetic field on the radii is opposed in the MIT and NJL models: with both formalisms, isotropic and chaotic field approximation, for a fixed mass, the radii increase with the increase of the magnetic field in the MIT bag model and decrease in the NJL, the radii of quark stars described by the NJL model being smaller than the ones described by the MIT model. (orig.)

  1. Alignment of magnetic uniaxial particles in a magnetic field: Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Golovnia, O.A., E-mail: golovnya@imp.uran.ru [Institute of Metal Physics, Str. S. Kovalevskoy, 18, 620990 Ekaterinburg (Russian Federation); Popov, A.G [Institute of Metal Physics, Str. S. Kovalevskoy, 18, 620990 Ekaterinburg (Russian Federation); Sobolev, A.N. [South Ural State University (National Research University), av. Lenina, 76, 454080 Chelyabinsk (Russian Federation); Hadjipanayis, G.C. [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States)

    2014-09-01

    The numerical investigations of the process of alignment of magnetically uniaxial Nd–Fe–B powders in an applied magnetic field were carried out using the discrete element method (DEM). It is shown that magnetic alignment of ensemble of spherical particles provides extremely high degree of alignment, which is achieved in low magnetic fields. A model of formation of anisotropic particles as a combination of spherical particles is suggested. The influence of the shape anisotropy and friction coefficient on the alignment degree was analyzed. The increase in the friction coefficient leads to a decrease in the alignment degree; the simulation results are in qualitative agreement with experimental dependences. It is shown that in magnetic fields higher than 5 T, the calculated field dependences of the alignment degree quantitatively render the experimental data. The increase of about 6% in the alignment degree in the experiments with addition of internal lubricant can be explained by the decrease of 14% in friction coefficient. - Highlights: • We simulate the magnetic alignment of ensemble of Nd–Fe–B spherical uniaxial particles. • Anisotropic particles as a combination of spherical particles are constructed. • Influence of the particle shape anisotropy and friction on the alignment is analyzed. • We compare calculated and experimental data on field dependence of magnetic alignment. • The results render the experimental dependence.

  2. Electric-field guiding of magnetic skyrmions

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyaya, Pramey; Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L.

    2015-10-01

    We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin magnetic films with broken inversion symmetry, where an electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology and micromagnetic simulations we show that this electric-field coupling, via renormalizing the micromagnetic energy, modifies the equilibrium properties of the skyrmion. This change, in turn, results in a significant alteration of the current-induced skyrmion motion. Particularly, the speed and direction of the skyrmion can be manipulated by designing a desired energy landscape electrically, which we describe within Thiele's analytical model and demonstrate in micromagnetic simulations including electric-field-controlled magnetic anisotropy. We additionally use this electric-field control to construct gates for controlling skyrmion motion exhibiting a transistorlike and multiplexerlike function. The proposed electric-field effect can thus provide a low-energy electrical knob to extend the reach of information processing with skyrmions.

  3. Magnetic field in the primitive solar nebula

    Science.gov (United States)

    Levy, E. H.

    1978-01-01

    Carbonaceous chondrites have apparently been magnetized in their early history in magnetic fields with intensities of 0.1 to 10 G, but the origin of the magnetizing field has remained obscured. It is suggested that the magnetic field recorded in the remanence of carbonaceous chondrites may have been produced by a self-excited hydromagnetic dynamo in the gaseous preplanetary nebula from which the solar system is thought to have formed. Recently computed models for the evolution of the preplanetary nebula, consisting of turbulent and differentially rotating gaseous disks with characteristic radial scales of several AU, are used to demonstrate the feasibility of this hypothesis. The maximum field intensity that might be realized by the dynamo production process is estimated to be as high as 1 to 10 G, taking into account two dynamical mechanisms that limit the strength of the field (the Coriolis force and ambipolar diffusion).

  4. Magnetic field evolution in neutron stars

    Science.gov (United States)

    Castillo, F.; Reisenegger, A.; Valdivia, J. A.

    2017-07-01

    Neutron stars contain the strongest magnetic fields known in the Universe. Using numerical simulations restricted to axially symmetric geometry, we study the long-term evolution of the magnetic field in the interior of an isolated neutron star under the effect of ambipolar diffusion, i.e. the drift of the magnetic field and the charged particles relative to the neutrons. We model the stellar interior as an electrically neutral fluid composed of neutrons, protons and electrons; these species can be converted into each other by weak interactions (beta decays), suffer binary collisions, and be affected by each other's macroscopic electromagnetic fields. We show that, in the restricted case of pure ambipolar diffusion, neglecting weak interactions, the magnetic fields evolves towards a stable MHD equilibria configuration, in the timescales analytically expected.

  5. Magnetic field induced optical vortex beam rotation

    CERN Document Server

    Shi, Shuai; Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen

    2015-01-01

    Light with orbital angular momentum (OAM) has drawn a great deal of attention for its important applications in the fields of precise optical measurements and high capacity optical communications. Here we adopt a method to study the rotation of a light beam, which is based on magnetic field induced circular birefringence in warm 87Rb atomic vapor. The dependence of the rotation angle to the intensity of the magnetic field makes it appropriate for weak magnetic field measurement. We derive a detail theoretical description that is in well agreement with the experimental observations. The experiment shows here provides a new method for precise measurement of magnetic field intensity and expands the application of OAM-carrying light.

  6. Quantum Electrodynamics in a Uniform Magnetic Field

    CERN Document Server

    Suzuki, J

    2005-01-01

    A systematic formalism for quantum electrodynamics in a classical uniform magnetic field is discussed. The first order radiative correction to the ground state energy of an electron is calculated. This then leads to the anomalous magnetic moment of an electron without divergent integrals. Thorough analyses of this problem are given for the weak magnetic field limit. A new expression for the radiative correction to the ground state energy is obtained. This contains only one integral with an additional summation with respect to each Landau level. The importance of this formalism is also addressed in order to deal with quantum electrodynamics in an intense external field.

  7. Hyperon Stars in Strong Magnetic Fields

    CERN Document Server

    Gomes, R O; Vasconcellos, C A Z

    2013-01-01

    We investigate the effects of strong magnetic fields on the properties of hyperon stars. The matter is described by a hadronic model with parametric coupling. The matter is considered to be at zero temperature, charge neutral, beta-equilibrated, containing the baryonic octet, electrons and muons. The charged particles have their orbital motions Landau-quantized in the presence of strong magnetic fields (SMF). Two parametrisations of a chemical potential dependent static magnetic field are considered, reaching $1-2 \\times 10^{18}\\,G$ in the center of the star. Finally, the Tolman-Oppenheimer-Volkov (TOV) equations are solved to obtain the mass-radius relation and population of the stars.

  8. Magnetic fields from second-order interactions

    CERN Document Server

    Osano, Bob

    2014-01-01

    It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-free approach, but could be done in the standard covariant indexed-approach.

  9. Dissipative charged fluid in a magnetic field

    Directory of Open Access Journals (Sweden)

    Navid Abbasi

    2016-05-01

    Full Text Available We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes here. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.

  10. Magnetic fields from second-order interactions

    OpenAIRE

    Osano, Bob

    2014-01-01

    It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-fre...

  11. Magnetic Field Control of Combustion Dynamics

    Science.gov (United States)

    Barmina, I.; Valdmanis, R.; Zake, M.; Kalis, H.; Marinaki, M.; Strautins, U.

    2016-08-01

    Experimental studies and mathematical modelling of the effects of magnetic field on combustion dynamics at thermo-chemical conversion of biomass are carried out with the aim of providing control of the processes developing in the reaction zone of swirling flame. The joint research of the magnetic field effect on the combustion dynamics includes the estimation of this effect on the formation of the swirling flame dynamics, flame temperature and composition, providing analysis of the magnetic field effects on the flame characteristics. The results of experiments have shown that the magnetic field exerts the influence on the flow velocity components by enhancing a swirl motion in the flame reaction zone with swirl-enhanced mixing of the axial flow of volatiles with cold air swirl, by cooling the flame reaction zone and by limiting the thermo-chemical conversion of volatiles. Mathematical modelling of magnetic field effect on the formation of the flame dynamics confirms that the electromagnetic force, which is induced by the electric current surrounding the flame, leads to field-enhanced increase of flow vorticity by enhancing mixing of the reactants. The magnetic field effect on the flame temperature and rate of reactions leads to conclusion that field-enhanced increase of the flow vorticity results in flame cooling by limiting the chemical conversion of the reactants.

  12. Magnetic field evolution of accreting neutron stars

    CERN Document Server

    Istomin, Ya N

    2016-01-01

    The flow of a matter, accreting onto a magnetized neutron star, is accompanied by an electric current. The closing of the electric current occurs in the crust of a neutron stars in the polar region across the magnetic field. But the conductivity of the crust along the magnetic field greatly exceeds the conductivity across the field, so the current penetrates deep into the crust down up to the super conducting core. The magnetic field, generated by the accretion current, increases greatly with the depth of penetration due to the Hall conductivity of the crust is also much larger than the transverse conductivity. As a result, the current begins to flow mainly in the toroidal direction, creating a strong longitudinal magnetic field, far exceeding an initial dipole field. This field exists only in the narrow polar tube of $r$ width, narrowing with the depth, i.e. with increasing of the crust density $\\rho$, $r\\propto \\rho^{-1/4}$. Accordingly, the magnetic field $B$ in the tube increases with the depth, $B\\propto...

  13. Small-scale Magnetic Field Diagnostics outside Sunspots: Comparison of Different Methods

    Indian Academy of Sciences (India)

    D. N. Rachkovsky; T. T. Tsap; V. G. Lozitsky

    2005-12-01

    We analyse different observational data related to the problem of intrinsic magnetic field strength in small-scale fluxtubes outside sunspots. We conclude that the kG range of fluxtube fields follows from not only classical line ratio method, but also from other old and new techniques. For the quiet regions on the Sun, the most probable mode of such fields has a magnetic field strength of 1.2–1.5 kG assuming the rectangular field profile. To best interpret the observations, a weak background field between fluxtubes should be assumed, and its magnetic field strength is expected to increase with the filling factor of fluxtubes. The alternative point of view about subkilogauss fluxtube fields is critically examined, and possible sources of different conclusions are presented.

  14. Hydraulic concentration of magnetic fields in the solar photosphere. II - Bernoulli effect

    Science.gov (United States)

    Parker, E. N.

    1974-01-01

    The magnetic filaments in the solar photosphere are subject to vigorous kneading and massaging by the convective turbulence at, and beneath, the visible surface. It is shown that the Bernoulli effect of the consequent surging of fluid up and down along the filaments is a major factor in concentrating the magnetic pressure of the filament (the mean square field). The mean field is also increased if the phase velocity of the external massaging exceeds the Alfven speed within the filament. The net observational magnetic result of the surging, then, depends upon the response of the observing instrument, and whether it essentially observes the mean field, the rms field, or whether there are saturation effects. It is suggested that the chromospheric mottles (spicules) seen in H alpha are in fact the intense magnetic filaments that carry most of the magnetic flux across the photospheric boundary of the sun.

  15. Dispersion of Magnetic Fields in Molecular Clouds

    CERN Document Server

    Hildebrand, Roger H; Dotson, Jessie L; Houde, Martin; Vaillancourt, John E

    2008-01-01

    We describe a method for determining the dispersion of magnetic field vectors about local mean fields in turbulent molecular clouds. The method is designed to avoid inaccurate estimates of MHD or turbulent dispersion - and hence to avoid inaccurate estimates of field strengths - due to large-scale, non-turbulent field structure when using the well-known method of Chandrasekhar and Fermi. Our method also provides accurate, independent estimates of the turbulent to mean magnetic field strength ratio. We discuss applications to the molecular clouds Orion, M17, and DR21.

  16. Reversals of the Earth's Magnetic Field

    Science.gov (United States)

    Champion, Duene E.

    J.A. Jacobs of Cambridge University has written a concise, authoritative, and up-todate text on reversals of the earth's magnetic field. Chapter 1 is a concise summary of the basic attributes of the geomagnetic field and its behavior in different time frames. It explains spherical harmonic analysis of the field and presents the history of acquisition of the data that best represent the recent field. Lastly, it includes a short summary of the origin and electrodynamics of the magnetic field, outlining the current theoretical basis for its generation.

  17. Magnetic field considerations in fusion power plant environs

    Energy Technology Data Exchange (ETDEWEB)

    Liemohn, H.B.; Lessor, D.L.; Duane, B.H.

    1976-09-01

    A summary of magnetic field production mechanisms and effects is given. Discussions are included on the following areas: (1) stray magnetic and electric fields from tokamaks, (2) methods for reducing magnetic fields, (3) economics of magnetic field reductions, (4) forces on magnetizable objects near magnetic confinement fusion reactors, (5) electric field transients in tokamaks, (6) attenuation and decay of electromagnetic fields, and (7) magnetic field transients from tokamak malfunctions.

  18. The sun and heliosphere at solar maximum.

    Science.gov (United States)

    Smith, E J; Marsden, R G; Balogh, A; Gloeckler, G; Geiss, J; McComas, D J; McKibben, R B; MacDowall, R J; Lanzerotti, L J; Krupp, N; Krueger, H; Landgraf, M

    2003-11-14

    Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes.

  19. Clear widens the field for observations of the Sun with multi-conjugate adaptive optics

    Science.gov (United States)

    Schmidt, Dirk; Gorceix, Nicolas; Goode, Philip R.; Marino, Jose; Rimmele, Thomas; Berkefeld, Thomas; Wöger, Friedrich; Zhang, Xianyu; Rigaut, François; von der Lühe, Oskar

    2017-01-01

    The multi-conjugate adaptive optics (MCAO) pathfinder Clear on the New Solar Telescope in Big Bear Lake has provided the first-ever MCAO-corrected observations of the Sun that show a clearly and visibly widened corrected field of view compared to quasi-simultaneous observations with classical adaptive optics (CAO) correction. Clear simultaneously uses three deformable mirrors, each conjugated to a different altitude, to compensate for atmospheric turbulence. While the MCAO correction was most effective over an angle that is approximately three times wider than the angle that was corrected by CAO, the full 53'' field of view did benefit from MCAO correction. We further demonstrate that ground-layer-only correction is attractive for solar observations as a complementary flavor of adaptive optics for observational programs that require homogenous seeing improvement over a wide field rather than diffraction-limited resolution. We show illustrative images of solar granulation and of a sunspot obtained on different days in July 2016, and present a brief quantitative analysis of the generalized Fried parameters of the images. The movies associated to Fig. 1 are available at http://www.aanda.org

  20. Magnetic fields in early protostellar disk formation

    CERN Document Server

    González-Casanova, Diego F; Lazarian, Alexander

    2016-01-01

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac (1999) model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called "magnetic braking catastrophe". In particular, we provide a detailed study of the dynamics of a 0.5 M$_\\odot$ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, "reconnection diffusion", removes the magnetic flux from the disk, the other involves the change of the magnetic field's topology, but does not change the a...

  1. Intergalactic Magnetic Fields from Quasar Outflows

    CERN Document Server

    Furlanetto, S; Furlanetto, Steven; Loeb, Abraham

    2001-01-01

    Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function of size and magnetic field strength at different redshifts. We generically find that by a redshift z=3, about 5-20% of the IGM volume is filled by magnetic fields with an energy density >10% of the mean thermal energy density of a photo-ionized IGM (at T=10^4 K). As massive galaxies and X-ray clusters condense out of the magnetized IGM, the adiabatic compression of the magnetic field could result in the field strength observed in these systems without a need for further dynamo amplification. The intergalactic magnetic field could also provide a nonthermal contribution to the pressure of the photo-ionized gas that may account for the claimed discrepancy between the simulated and observed Doppler width distributions of the Ly-al...

  2. The CMS Magnetic Field Map Performance

    CERN Document Server

    Klyukhin, VI; Sarycheva, L I; Klyukhin, V I; Ball, A; Gaddi, A; Amapane, N; Gerwig, H; Andreev, V; Cure, B; Mulders, M; Loveless, R; Karimaki, V; Popescu, S; Herve, A

    2010-01-01

    The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field ...

  3. Compact Electric- And Magnetic-Field Sensor

    Science.gov (United States)

    Winterhalter, Daniel; Smith, Edward

    1994-01-01

    Compact sensor measures both electric and magnetic fields. Includes both short electric-field dipole and search-coil magnetometer. Three mounted orthogonally providing triaxial measurements of electromagnetic field at frequencies ranging from near 0 to about 10 kHz.

  4. The continuum intensity as a function of magnetic field II. Local magnetic flux and convective flows

    CERN Document Server

    Kobel, P; Borrero, J M

    2014-01-01

    To deepen our understanding of the role of small-scale magnetic fields in active regions (ARs) and in the quiet Sun (QS) on the solar irradiance, it is fundamental to investigate the physical processes underlying their continuum brightness. Previous results showed that magnetic elements in the QS reach larger continuum intensities than in ARs at disk center, but left this difference unexplained. We use Hinode/SP disk center data to study the influence of the local amount of magnetic flux on the vigour of the convective flows and the continuum intensity contrasts. The apparent (i.e. averaged over a pixel) longitudinal field strength and line-of-sight (LOS) plasma velocity were retrieved by means of Milne-Eddington inversions (VFISV code). We analyzed a series of boxes taken over AR plages and the QS, to determine how the continuum intensity contrast of magnetic elements, the amplitude of the vertical flows and the box-averaged contrast were affected by the mean longitudinal field strength in the box (which sca...

  5. High Field Pulse Magnets with New Materials

    Science.gov (United States)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.

    2004-11-01

    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  6. Light Polarization Using Ferrofluids and Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Alberto Tufaile

    2017-01-01

    Full Text Available We are presenting an experimental setup based on polarized light, enabling the visualization of the magnetic field of magnetic assemblies using a Hele-Shaw cell filled with ferrofluids. We have simulated the observed patterns with hypergeometric polynomials.

  7. The magnetic field of zeta Orionis A

    CERN Document Server

    Blazère, A; Tkachenko, A; Bouret, J -C; Rivinius, Th

    2015-01-01

    Zeta Ori A is a hot star claimed to host a weak magnetic field, but no clear magnetic detection was obtained so far. In addition, it was recently shown to be a binary system composed of a O9.5I supergiant and a B1IV star. We aim at verifying the presence of a magnetic field in zeta Ori A, identifying to which of the two binary components it belongs (or whether both stars are magnetic), and characterizing the field.Very high signal-to-noise spectropolarimetric data were obtained with Narval at the Bernard Lyot Telescope (TBL) in France. Archival HEROS, FEROS and UVES spectroscopic data were also used. The data were first disentangled to separate the two components. We then analyzed them with the Least-Squares Deconvolution (LSD) technique to extract the magnetic information. We confirm that zeta Ori A is magnetic. We find that the supergiant component zeta Ori Aa is the magnetic component: Zeeman signatures are observed and rotational modulation of the longitudinal magnetic field is clearly detected with a per...

  8. Studies of Solar Vector Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG Jingxiu

    2011-01-01

    In this article, we report a few advances in the studies based on the solar vector magnetic field observations which were carried out mainly with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station in the 1990s. (1) We developed necessary methodology and concepts in vector magnetogram analysis (Wang et al. 1996). For the first time, we proposed to use the photospheric free magnetic energy to quantify the major flare productivity of solar active regions (ARs), and it had been proved to be the best parameter in representing the major flare activity. (2) We revealed that there was always a dominant sense of magnetic shear in a given AR (Wang 1994), which was taken as the premise of the helicity calculation in ARs; we made the first quantitative estimation of magnetic helicity evolution in ARs (Wang 1996). (3) We identified the first group of evidence of magnetic reconnection in the lower solar atmosphere with vector magnetic field observations and proposed a two-step reconnection flare model to interpret the observed association of flux cancellation and flares (Wang and Shi 1993). Efforts to quantify the major flare productivity of super active regions with vector magnetic field observations have been also taken.

  9. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker

    1975-01-01

    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...

  10. Zero modes in finite range magnetic fields

    CERN Document Server

    Adam, C; Nash, C

    2000-01-01

    We find a class of Fermion zero modes of Abelian Dirac operators in three dimensional Euclidean space where the gauge potentials and the related magnetic fields are nonzero only in a finite space region.

  11. Axion production from primordial magnetic fields

    Science.gov (United States)

    Kamada, Kohei; Nakai, Yuichiro

    2017-07-01

    Production of axionlike particles (ALPs) by primordial magnetic fields may have significant impacts on cosmology. We discuss the production of ALPs in the presence of the primordial magnetic fields. We find a region of the ALP mass and photon coupling which realizes the observed properties of the dark matter with appropriate initial conditions for the magnetic fields. This region may be interesting in light of recent indications for the 3.5 keV lines from galaxy clusters. For a small axion mass, a region of previously allowed parameter spaces is excluded by overproduction of ALPs as a hot/warm dark matter component. Since the abundance of ALPs strongly depends on the initial conditions of primordial magnetic fields, our results provide implications for scenarios of magnetogenesis.

  12. Compact muon solenoid magnet reaches full field

    CERN Multimedia

    2006-01-01

    Scientist of the U.S. Department of Energy in Fermilab and collaborators of the US/CMS project announced that the world's largest superconducting solenoid magnet has reached full field in tests at CERN. (1 apge)

  13. A Topology for the Penumbral Magnetic Fields

    CERN Document Server

    Almeida, J Sanchez

    2009-01-01

    We describe a scenario for the topology of the magnetic field in penumbrae that accounts for recent observations showing upflows, downflows, and reverse magnetic polarities. According to our conjecture, short narrow magnetic loops fill the penumbral photosphere. Flows along these arched field lines are responsible for both the Evershed effect and the convective transport. This scenario seems to be qualitatively consistent with most existing observations, including the dark cores in penumbral filaments reported by Scharmer et al. Each bright filament with dark core would be a system of two paired convective rolls with the dark core tracing the common lane where the plasma sinks down. The magnetic loops would have a hot footpoint in one of the bright filament and a cold footpoint in the dark core. The scenario fits in most of our theoretical prejudices (siphon flows along field lines, presence of overturning convection, drag of field lines by downdrafts, etc). If the conjecture turns out to be correct, the mild...

  14. Local Magnetic Field Role in Star Formation

    CERN Document Server

    Koch, Patrick M; Ho, Paul T P; Zhang, Qizhou; Girart, Josep M; Chen, Huei-Ru V; Lai, Shih-Ping; Li, Hua-bai; Li, Zhi-Yun; Liu, Hau-Yu B; Padovani, Marco; Qiu, Keping; Rao, Ramprasad; Yen, Hsi-Wei; Frau, Pau; Chen, How-Huan; Ching, Tao-Chung

    2015-01-01

    We highlight distinct and systematic observational features of magnetic field morphologies in polarized submm dust continuum. We illustrate this with specific examples and show statistical trends from a sample of 50 star-forming regions.

  15. Revisiting holographic superconductor with Magnetic Fields

    CERN Document Server

    Momeni, Davood

    2014-01-01

    We study the effect of the bulk magnetic field (charge) on scalar condensation using an analytical approach of matching. An AdS-magnetized black hole solution has been used as a probe solution of normal phase of a strongly coupled condensed matter system on boundary. In the zero temperature limit of the black hole and infinite temperature, we show that there exists a critical magnetic field and so, the Meissner's effect presented. We compare this analytical result with our previous variational approach. By studying the different between heat capacities of the normal and superconducting phases near the critical point, we show that this thermodynamic quantity becomes divergent as the Rutgers formula predicted. Mathematical pole of Rutgers formula gives us a maximum for magnetic field which at this value, the system backs to the normal phase. In zero temperature we investigate exact series solutions of the field equations using an appropriate boundary conditions set. We show that conformal dimension is fixed by ...

  16. A Holographic Bound on Cosmic Magnetic Fields

    CERN Document Server

    McInnes, Brett

    2015-01-01

    Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary) times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark-gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description. We show that holography imposes an upper bound on the intensity of magnetic fields (scaled by the squared temperature) in these circumstances, and that the values expected in some models of cosmic magnetism come close to attaining that bound.

  17. Magnetic Fields in Limb Solar Flares

    Science.gov (United States)

    Lozitsky, V. G.; Lozitska, N. I.; Botygina, O. A.

    2013-02-01

    Two limb solar flares, of 14 July 2005 and 19 July 2012, of importance X1.2 and M7.7, are analyzed at present work. Magnetic field strength in named flares are investigated by Stokes I±V profiles of Hα and D3 HeI lines. There are direct evidences to the magnetic field inhomogeneity in flares, in particular, non-paralelism of bisectors in I+V and I-V profiles. In some flare places, the local maximums of bisectors splitting were found in both lines. If these bisector splittings are interpreted as Zeeman effect manifestation, the following magnetic field strengths reach up to 2200 G in Hα and 1300 G in D3. According to calculations, the observed peculiarities of line profiles may indicate the existence of optically thick emissive small-scale elements with strong magnetic fields and lowered temperature.

  18. Construction of high magnetic field facilities approved

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ On 25 January, the National Development and Reform Commission gave the green light to a proposal to construct high magnetic field facilities for experimental use. The suggestion was jointly submitted by the Ministry of Education and CAS.

  19. The Magnetic Field of Helmholtz Coils

    Science.gov (United States)

    Berridge, H. J. J.

    1975-01-01

    Describes the magnetic field of Helmholtz coils qualitatively and then provides the basis for a quantitative expression. Since the mathematical calculations are very involved, a computer program for solving the mathematical expression is presented and explained. (GS)

  20. EIT waves and coronal magnetic field diagnostics

    Institute of Scientific and Technical Information of China (English)

    CHEN PengFei

    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.

  1. Typical Profiles and Distributions of Plasma and Magnetic Field Parameters in Magnetic Clouds at 1 AU

    Science.gov (United States)

    Rodriguez, L.; Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Zhukov, A. N.; Gulisano, A. M.; Mierla, M.; Kilpua, E.; West, M.; Lacatus, D.; Paraschiv, A.; Janvier, M.

    2016-08-01

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). They are important because of their simple internal magnetic field configuration, which resembles a magnetic flux rope, and because they represent one of the most geoeffective types of solar transients. In this study, we analyze their internal structure using a superposed epoch method on 63 events observed at L1 by the Advance Composition Explorer (ACE), between 1998 and 2006. In this way, we obtain an average profile for each plasma and magnetic field parameter at each point of the cloud. Furthermore, we take a fixed time-window upstream and downstream from the MC to also sample the regions preceding the cloud and the wake trailing it. We then perform a detailed analysis of the internal characteristics of the clouds and their surrounding solar wind environments. We find that the parameters studied are compatible with log-normal distribution functions. The plasma β and the level of fluctuations in the magnetic field vector are the best parameters to define the boundaries of MCs. We find that one third of the events shows a peak in plasma density close to the trailing edge of the flux ropes. We provide several possible explanations for this result and investigate if the density peak is of a solar origin ( e.g. erupting prominence material) or formed during the magnetic cloud travel from the Sun to 1 AU. The most plausible explanation is the compression due to a fast overtaking flow, coming from a coronal hole located to the east of the solar source region of the magnetic cloud.

  2. High-Field Superconducting Magnets Supporting PTOLEMY

    Science.gov (United States)

    Hopkins, Ann; Luo, Audrey; Osherson, Benjamin; Gentile, Charles; Tully, Chris; Cohen, Adam

    2013-10-01

    The Princeton Tritium Observatory for Light, Early Universe, Massive Neutrino Yield (PTOLEMY) is an experiment planned to collect data on Big Bang relic neutrinos, which are predicted to be amongst the oldest and smallest particles in the universe. Currently, a proof-of-principle prototype is being developed at Princeton Plasma Physics Laboratory to test key technologies associated with the experiment. A prominent technology in the experiment is the Magnetic Adiabatic Collimation with an Electrostatic Filter (MAC-E filter), which guides tritium betas along magnetic field lines generated by superconducting magnets while deflecting those of lower energies. B field mapping is performed to ensure the magnets produce a minimum field at the midpoint of the configuration of the magnets and to verify accuracy of existing models. Preliminary tests indicate the required rapid decrease in B field strength from the bore of the more powerful 3.35 T magnet, with the field dropping to 0.18 T approximately 0.5 feet from the outermost surface of the magnet.

  3. Magnetic Field Amplification in Young Galaxies

    CERN Document Server

    Schober, Jennifer; Klessen, Ralf S

    2013-01-01

    The Universe at present is highly magnetized, with fields of the order of a few 10^-5 G and coherence lengths larger than 10 kpc in typical galaxies like the Milky Way. We propose that the magnetic field was amplified to this values already during the formation and the early evolution of the galaxies. Turbulence in young galaxies is driven by accretion as well as by supernova (SN) explosions of the first generation of stars. The small-scale dynamo can convert the turbulent kinetic energy into magnetic energy and amplify very weak primordial magnetic seed fields on short timescales. The amplification takes place in two phases: in the kinematic phase the magnetic field grows exponentially, with the largest growth on the smallest non-resistive scale. In the following non-linear phase the magnetic energy is shifted towards larger scales until the dynamo saturates on the turbulent forcing scale. To describe the amplification of the magnetic field quantitatively we model the microphysics in the interstellar medium ...

  4. Split-Field Magnet facility upgraded

    CERN Multimedia

    1977-01-01

    The Split Field Magnet (SFM) was the largest spectrometer for particles from beam-beam collisions in the ISR. It could determine particle momenta in a large solid angle, but was designed mainly for the analysis of forward travelling particles.As the magnet was working on the ISR circulating beams, its magnetic field had to be such as to restore the correct proton orbit.The SFM, therefore, produced zero field at the crossing point and fields of opposite signs upstream and downstream of it and was completed by 2 large and 2 small compensator magnets. The gradient effects were corrected by magnetic channels equipped with movable flaps. The useful magnetic field volume was 28 m3, the induction in the median plane 1.14 T, the gap heigth 1.1 m, the length 10.5 m, the weight about 1000 ton. Concerning the detectors, the SFM was the first massive application of multiwire proportional chambers (about 70000 wires) which filled the main and the large compensator magnets. In 1976 an improved programme was started with tw...

  5. Magnetic fields and massive star formation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qizhou; Keto, Eric; Ho, Paul T. P.; Ching, Tao-Chung; Chen, How-Huan [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Qiu, Keping [School of Astronomy and Space Science, Nanjing University, 22 Hankou Road, Nanjing 210093 (China); Girart, Josep M.; Juárez, Carmen [Institut de Ciències de l' Espai, (CSIC-IEEC), Campus UAB, Facultat de Ciències, C5p 2, E-08193 Bellaterra, Catalonia (Spain); Liu, Hauyu; Tang, Ya-Wen; Koch, Patrick M.; Rao, Ramprasad; Lai, Shih-Ping [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China); Li, Zhi-Yun [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Frau, Pau [Observatorio Astronómico Nacional, Alfonso XII, 3 E-28014 Madrid (Spain); Li, Hua-Bai [Department of Physics, The Chinese University of Hong Kong, Hong Kong (China); Padovani, Marco [Laboratoire de Radioastronomie Millimétrique, UMR 8112 du CNRS, École Normale Supérieure et Observatoire de Paris, 24 rue Lhomond, F-75231 Paris Cedex 05 (France); Bontemps, Sylvain [OASU/LAB-UMR5804, CNRS, Université Bordeaux 1, F-33270 Floirac (France); Csengeri, Timea, E-mail: qzhang@cfa.harvard.edu [Max Planck Institute for Radioastronomy, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2014-09-10

    Massive stars (M > 8 M {sub ☉}) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 μm obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of ≲0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40° of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (≲ 10{sup 3} AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  6. Core Processes: Earth's eccentric magnetic field

    DEFF Research Database (Denmark)

    Finlay, Chris

    2012-01-01

    Earth’s magnetic field is characterized by a puzzling hemispheric asymmetry. Calculations of core dynamo processes suggest that lopsided growth of the planet’s inner core may be part of the cause.......Earth’s magnetic field is characterized by a puzzling hemispheric asymmetry. Calculations of core dynamo processes suggest that lopsided growth of the planet’s inner core may be part of the cause....

  7. Orbit stability in billiards in magnetic field

    CERN Document Server

    Kovács, Z

    1997-01-01

    We study the stability properties of orbits in dispersing billiards in a homogeneous magnetic field by using a modified formalism based on the Bunimovich-Sinai curvature (horocycle method). We identify simple periodic orbits that can be stabilized by the magnetic field in the four-disk model and the square-lattice Lorentz gas. The stable orbits can play a key role in determining the transport properties of these models.

  8. First Use of Synoptic Vector Magnetograms for Global Nonlinear, Force-Free Coronal Magnetic Field Models

    Science.gov (United States)

    Tadesse, T.; Wiegelmann, T.; Gosain, S.; MacNeice, P.; Pevtsov, A. A.

    2014-01-01

    Context. The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Currently, there are several modelling techniques being used to calculate three-dimensional field lines into the solar atmosphere. Aims. For the first time, synoptic maps of a photospheric-vector magnetic field synthesized from the vector spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) are used to model the coronal magnetic field and estimate free magnetic energy in the global scale. The free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. Methods. We solve the nonlinear force-free field equations using an optimization principle in spherical geometry. The resulting threedimensional magnetic fields are used to estimate the magnetic free energy content E(sub free) = E(sub nlfff) - E(sub pot), which is the difference of the magnetic energies between the nonpotential field and the potential field in the global solar corona. For comparison, we overlay the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the atmospheric imaging assembly (AIA) on board the Solar Dynamics Observatory (SDO). Results. For a single Carrington rotation 2121, we find that the global nonlinear force-free field (NLFFF) magnetic energy density is 10.3% higher than the potential one. Most of this free energy is located in active regions.

  9. Comparison of Sun-Induced Chlorophyll Fluorescence Estimates Obtained from Four Portable Field Spectroradiometers

    Directory of Open Access Journals (Sweden)

    Tommaso Julitta

    2016-02-01

    Full Text Available Remote Sensing of Sun-Induced Chlorophyll Fluorescence (SIF is a research field of growing interest because it offers the potential to quantify actual photosynthesis and to monitor plant status. New satellite missions from the European Space Agency, such as the Earth Explorer 8 FLuorescence EXplorer (FLEX mission—scheduled to launch in 2022 and aiming at SIF mapping—and from the National Aeronautics and Space Administration (NASA such as the Orbiting Carbon Observatory-2 (OCO-2 sampling mission launched in July 2014, provide the capability to estimate SIF from space. The detection of the SIF signal from airborne and satellite platform is difficult and reliable ground level data are needed for calibration/validation. Several commercially available spectroradiometers are currently used to retrieve SIF in the field. This study presents a comparison exercise for evaluating the capability of four spectroradiometers to retrieve SIF. The results show that an accurate far-red SIF estimation can be achieved using spectroradiometers with an ultrafine resolution (less than 1 nm, while the red SIF estimation requires even higher spectral resolution (less than 0.5 nm. Moreover, it is shown that the Signal to Noise Ratio (SNR plays a significant role in the precision of the far-red SIF measurements.

  10. Magnetic Field Measurement on a Refined Kicker

    CERN Document Server

    Fan, Tai-Ching; Lin, Fu-Yuan

    2005-01-01

    To prepare for the operation of top-up mode and increase the efficiency of injection at storage ring, National Synchrotron Radiation Research Center (NSRRC) has upgraded the kicker magnets and power supply. We have built up a new magnetic field measurement system to test the kicker. This system, including a search coil and a coil loop, can map the field and take the first integral of field automatically. We also simulate the trajectory of electron beam by pulsed wire method of field measurement. We analyze the performance of the kicker system in this paper.

  11. Biological systems in high magnetic field

    Science.gov (United States)

    Yamagishi, A.

    1990-12-01

    Diamagnetic orientation of biological systems have been investigated theoretically and experimentally. Fibrinogen, one of blood proteins, were polymerized in static high magnetic fields up to 8 T. Clotted gels composed of oriented fibrin fibers were obtained even in a field as low as 1 T. Red blood cells (RBC) show full orientation with their plane parallel to the applied field of 4 T. It is confirmed experimentally that the magnetic orientation of RBC is caused by diamagnetic anisotropy. Full orientation is also obtained with blood platelet in a field of 3 T.

  12. Cooling Curve of Strange Star in Strong Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Qin; LUO Zhi-Quan

    2008-01-01

    In this paper, firstly, we investigate the neutrino emissivity from quark Urca process in strong magnetic field. Then, we discuss the heat capacity of strange stars in strong magnetic field. Finally, we give the cooling curve in strong magnetic field. In order to make a comparison, we also give the corresponding cooling curve in the case of null magnetic field. It turns out that strange stars cool faster in strong magnetic field than that without magnetic field.

  13. Combustion instability mitigation by magnetic fields

    Science.gov (United States)

    Jocher, Agnes; Pitsch, Heinz; Gomez, Thomas; Bonnety, Jérôme; Legros, Guillaume

    2017-06-01

    The present interdisciplinary study combines electromagnetics and combustion to unveil an original and basic experiment displaying a spontaneous flame instability that is mitigated as the non-premixed sooting flame experiences a magnetic perturbation. This magnetic instability mitigation is reproduced by direct numerical simulations to be further elucidated by a flow stability analysis. A key role in the stabilization process is attributed to the momentum and thermochemistry coupling that the magnetic force, acting mainly on paramagnetic oxygen, contributes to sustain. The spatial local stability analysis based on the numerical simulations shows that the magnetic field tends to reduce the growth rates of small flame perturbations.

  14. Solar physics. The crucial role of surface magnetic fields for the solar dynamo.

    Science.gov (United States)

    Cameron, Robert; Schüssler, Manfred

    2015-03-20

    Sunspots and the plethora of other phenomena occurring in the course of the 11-year cycle of solar activity are a consequence of the emergence of magnetic flux at the solar surface. The observed orientations of bipolar sunspot groups imply that they originate from toroidal (azimuthally orientated) magnetic flux in the convective envelope of the Sun. We show that the net toroidal magnetic flux generated by differential rotation within a hemisphere of the convection zone is determined by the emerged magnetic flux at the solar surface and thus can be calculated from the observed magnetic field distribution. The main source of the toroidal flux is the roughly dipolar surface magnetic field at the polar caps, which peaks around the minima of the activity cycle.

  15. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  16. Magnetic Field Apparatus (MFA) Hardware Test

    Science.gov (United States)

    Anderson, Ken; Boody, April; Reed, Dave; Wang, Chung; Stuckey, Bob; Cox, Dave

    1999-01-01

    The objectives of this study are threefold: (1) Provide insight into water delivery in microgravity and determine optimal germination paper wetting for subsequent seed germination in microgravity; (2) Observe the behavior of water exposed to a strong localized magnetic field in microgravity; and (3) Simulate the flow of fixative (using water) through the hardware. The Magnetic Field Apparatus (MFA) is a new piece of hardware slated to fly on the Space Shuttle in early 2001. MFA is designed to expose plant tissue to magnets in a microgravity environment, deliver water to the plant tissue, record photographic images of plant tissue, and deliver fixative to the plant tissue.

  17. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; DUAN, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  18. New electric field in asymmetric magnetic reconnection.

    Science.gov (United States)

    Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D

    2013-09-27

    We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site.

  19. Influence of magnetic domain walls and magnetic field on the thermal conductivity of magnetic nanowires.

    Science.gov (United States)

    Huang, Hao-Ting; Lai, Mei-Feng; Hou, Yun-Fang; Wei, Zung-Hang

    2015-05-13

    We investigated the influence of magnetic domain walls and magnetic fields on the thermal conductivity of suspended magnetic nanowires. The thermal conductivity of the nanowires was obtained using steady-state Joule heating to measure the change in resistance caused by spontaneous heating. The results showed that the thermal conductivity coefficients of straight and wavy magnetic nanowires decreased with an increase in the magnetic domain wall number, implying that the scattering between magnons and domain walls hindered the heat transport process. In addition, we proved that the magnetic field considerably reduced the thermal conductivity of a magnetic nanowire. The influence of magnetic domain walls and magnetic fields on the thermal conductivity of polycrystalline magnetic nanowires can be attributed to the scattering of long-wavelength spin waves mediated by intergrain exchange coupling.

  20. Investigation of Force-Freeness of Solar Emerging Magnetic Field via Application of the Virial Theorem to MHD Simulations

    CERN Document Server

    Kang, Jihye

    2014-01-01

    Force-freeness of a solar magnetic field is a key to reconstructing invisible coronal magnetic structure of an emerging flux region on the Sun where active phenomena such as flares and coronal mass ejections frequently occur. We have performed magnetohydrodynamic (MHD) simulations which are adjusted to investigate force-freeness of an emerging magnetic field by using the virial theorem. Our focus is on how the force-free range of an emerging flux region develops and how it depends on the twist of a pre-emerged magnetic field. As an emerging flux region evolves, the upper limit of the force-free range continuously increases while the lower limit is asymptotically reduced to the order of a photospheric pressure scale height above the solar surface. As the twist becomes small the lower limit increases and then seems to be saturated. We also discuss the applicability of the virial theorem to an evolving magnetic structure on the Sun.

  1. Where is magnetic anisotropy field pointing to?

    CERN Document Server

    Gutowski, Marek W

    2013-01-01

    The desired result of magnetic anisotropy investigations is the determination of value(s) of various anisotropy constant(s). This is sometimes difficult, especially when the precise knowledge of saturation magnetization is required, as it happens in ferromagnetic resonance (FMR) studies. In such cases we usually resort to `trick' and fit our experimental data to the quantity called \\emph{anisotropy field}, which is strictly proportional to the ratio of the searched anisotropy constant and saturation magnetization. Yet, this quantity is scalar, simply a number, and is therefore of little value for modeling or simulations of the magnetostatic or micromagnetic structures. Here we show how to `translate' the values of magnetic anisotropy constants into the complete vector of magnetic anisotropy field. Our derivation is rigorous and covers the most often encountered cases, from uniaxial to cubic anisotropy.

  2. Forward modeling of the corona of the sun and solarlike stars

    DEFF Research Database (Denmark)

    Hardi, Peter; Gudiksen, Boris V.; Nordlund, Å.

    2006-01-01

    Transition Region Lines, AB-Initio Approach; Nonequilibrium Inozation; Doppler Shifts; Emission-Lines; Quiet-Sun; Sumer Telescope; Atomic Database; Magnetic-Field; Thin Plasmas......Transition Region Lines, AB-Initio Approach; Nonequilibrium Inozation; Doppler Shifts; Emission-Lines; Quiet-Sun; Sumer Telescope; Atomic Database; Magnetic-Field; Thin Plasmas...

  3. Bootstrapping the Coronal Magnetic Field with STEREO

    Science.gov (United States)

    Aschwanden, Markus J.

    2010-05-01

    The 3D coronal magnetic field obtained from stereoscopically triangulated loops has been compared with standard photospheric magnetogram extrapolations. We found a large misalignment of 20-40 deg, depending on the complexity of an AR (Sandman et al. 2009; DeRosa et al. 2009). These studies prove that the magnetic field in the photosphere is not force-free and fundamentally cannot reproduce the coronal magnetic field. Bootstrapping with coronal loop 3D geometries are required to improve modeling of the coronal field. Such coronal field bootstrapping methods are currently developed using stereoscopically triangulated loops from STEREO/EUVI and preliminary results show already a significantly reduced misalignment of 10-20 deg.

  4. Critical Magnetic Field Determination of Superconducting Materials

    Energy Technology Data Exchange (ETDEWEB)

    Canabal, A.; Tajima, T.; /Los Alamos; Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

    2011-11-04

    Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

  5. Fast Reconnection of Weak Magnetic Fields

    Science.gov (United States)

    Zweibel, Ellen G.

    1998-01-01

    Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids.

  6. Growth of Czochralski silicon under magnetic field

    Institute of Scientific and Technical Information of China (English)

    XU Yuesheng; LIU Caichi; WANG Haiyun; ZHANG Weilian; YANG Qingxin; LI Yangxian; REN Binyan; LIU Fugui

    2004-01-01

    Growth of Czochralski (CZ) silicon crystals under the magnetic field induced by a cusp-shaped permanent magnet of NdFeB has been investigated. It is found that the mass transport in silicon melt was controlled by its diffusion while the magnetic intensity at the edge of a crucible was over 0.15 T. In comparison with the growth of conventional CZ silicon without magnetic field, the resistivity homogeneity of the CZ silicon under the magnetic field was improved. Furthermore, the Marangoni convection which has a significant influence on the control of oxygen concentration was observed on the surface of silicon melt. It is suggested that the crystal growth mechanism in magnetic field was similar to that in micro-gravity if a critical value was reached, named the growth of equivalent micro-gravity. The relationship of the equivalent micro-gravity and the magnetic intensity was derived as g=(v0/veff)g0. Finally, the orders of the equivalent micro-gravity corresponding to two crucibles with characteristic sizes were calculated.

  7. Dynamo magnetic field-induced angular momentum transport in protostellar nebulae - The 'minimum mass' protosolar nebula

    Science.gov (United States)

    Stepinski, T. F.; Levy, E. H.

    1990-01-01

    Magnetic torques can produce angular momentum redistribution in protostellar nebulas. Dynamo magnetic fields can be generated in differentially rotating and turbulent nebulas and can be the source of magnetic torques that transfer angular momentum from a protostar to a disk, as well as redistribute angular momentum within a disk. A magnetic field strength of 100-1000 G is needed to transport the major part of a protostar's angular momentum into a surrounding disk in a time characteristic of star formation, thus allowing formation of a solar-system size protoplanetary nebula in the usual 'minimum-mass' model of the protosolar nebula. This paper examines the possibility that a dynamo magnetic field could have induced the needed angular momentum transport from the proto-Sun to the protoplanetary nebula.

  8. Dynamo magnetic field-induced angular momentum transport in protostellar nebulae - The minimum mass protosolar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Stepinski, T.F.; Levy, E.H. (Arizona Univ., Tucson (USA))

    1990-02-01

    Magnetic torques can produce angular momentum redistribution in protostellar nebulas. Dynamo magnetic fields can be generated in differentially rotating and turbulent nebulas and can be the source of magnetic torques that transfer angular momentum from a protostar to a disk, as well as redistribute angular momentum within a disk. A magnetic field strength of 100-1000 G is needed to transport the major part of a protostar's angular momentum into a surrounding disk in a time characteristic of star formation, thus allowing formation of a solar-system size protoplanetary nebula in the usual minimum-mass model of the protosolar nebula. This paper examines the possibility that a dynamo magnetic field could have induced the needed angular momentum transport from the proto-Sun to the protoplanetary nebula. 32 refs.

  9. Simulating magnetic fields in the Antennae galaxies

    CERN Document Server

    Kotarba, H; Naab, T; Johansson, P H; Dolag, K; Lesch, H

    2009-01-01

    We present self-consistent high-resolution simulations of NGC4038/4039 (the "Antennae galaxies") including star formation, supernova feedback and magnetic fields performed with the N-body/SPH code Gadget, in which hydrodynamics and magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 1 nG to 1 muG. At the time of the best match with the central region of the Antennae system the magnetic field has been amplified by compression and shear flows to an equilibrium field of approximately 10 muG, independent of the initial seed field. This simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of r...

  10. Magnetic Field Transport in Accretion Disks

    Science.gov (United States)

    Jafari, Amir; Vishniac, Ethan

    2017-06-01

    The most plausible theories for launching astrophysical jets rely on strong magnetic fields at the inner parts of some accretion disks. An internal dynamo can in principle generate small scale magnetic fields in situ but generating a large scale field in a disk seems a difficult task in the dynamo theories. In fact, as far as numerous numerical experiments indicate, a dynamo-generated field in general would not be coherent enough over the large length scales of order the disk's radius. Instead, a large scale poloidal field dragged in from the environment, and compressed by the accretion, provides a more promising possibility. The difficulty in the latter picture, however, arises from the reconnection of the radial field component across the mid-plane which annihilates the field faster than it is dragged inward by the accretion. We suggest that a combination of different effects, including magnetic buoyancy and turbulent pumping, is responsible for the vertical transport of the field lines toward the surface of the disk. The radial component of the poloidal field vanishes at the mid-plane, which efficiently impedes reconnection, and grows exponentially toward the surface where it can become much larger than the vertical field component. This allows the poloidal field to be efficiently advected to small radii until the allowed bending angle drops to of order unity, and the field can drive a strong outflow.

  11. Superconductivity in Strong Magnetic Field (Greater Than Upper Critical Field)

    Energy Technology Data Exchange (ETDEWEB)

    Tessema, G.X.; Gamble, B.K.; Skove, M.J.; Lacerda, A.H.; Mielke, C.H.

    1998-08-22

    The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond H{sub c2} as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

  12. Study of marine magnetic field

    Digital Repository Service at National Institute of Oceanography (India)

    Bhattacharya, G.C.

    (COB) is again both a basic scientific requirement as well at some places is a requirement under the UNCLOS related Legal Continental Shelf demarcation purpose. In the oceanic areas, the marine magnetic studies are one of the essential tools... oceans increased, more and more deviations from this simplified model, such as propagating ridges and overlapping spreading centers were discovered. These observations enabled the study of new aspects of seafloor spreading process beyond the initial...

  13. Magnetic field amplification in turbulent astrophysical plasmas

    CERN Document Server

    Federrath, Christoph

    2016-01-01

    Magnetic fields play an important role in astrophysical accretion discs, and in the interstellar and intergalactic medium. They drive jets, suppress fragmentation in star-forming clouds and can have a significant impact on the accretion rate of stars. However, the exact amplification mechanisms of cosmic magnetic fields remain relatively poorly understood. Here I start by reviewing recent advances in the numerical and theoretical modelling of the 'turbulent dynamo', which may explain the origin of galactic and inter-galactic magnetic fields. While dynamo action was previously investigated in great detail for incompressible plasmas, I here place particular emphasis on highly compressible astrophysical plasmas, which are characterised by strong density fluctuations and shocks, such as the interstellar medium. I find that dynamo action works not only in subsonic plasmas, but also in highly supersonic, compressible plasmas, as well as for low and high magnetic Prandtl numbers. I further present new numerical simu...

  14. The Magnetic Field of Solar Spicules

    CERN Document Server

    Centeno, R; Ramos, A Asensio

    2009-01-01

    Determining the magnetic field of solar spicules is vital for developing adequate models of these plasma jets, which are thought to play a key role in the thermal, dynamic, and magnetic structure of the chromosphere. Here we report on magnetic spicule properties in a very quiet region of the off-limb solar atmosphere, as inferred from new spectropolarimetric observations in the HeI 10830 A triplet. We have used a novel inversion code for Stokes profiles caused by the joint action of atomic level polarization and the Hanle and Zeeman effects (HAZEL) to interpret the observations. Magnetic fields as strong as 40G were unambiguously detected in a very localized area of the slit, which may represent a possible lower value of the field strength of organized network spicules.

  15. QCD thermodynamics and magnetization in nonzero magnetic field

    CERN Document Server

    Tawfik, Abdel Nasser; Ezzelarab, Nada; Shalaby, Asmaa G

    2016-01-01

    In nonzero magnetic field, the magnetic properties and thermodynamics of the quantum-chromodynamic (QCD) matter is studied in the hadron resonance gas and the Polyakov linear-sigma models and compared with recent lattice calculations. Both models are fairly suited to describe the degrees of freedom in the hadronic phase. The partonic ones are only accessible by the second model. It is found that the QCD matter has paramagnetic properties, which monotonically depend on the temperature and are not affected by the hadron-quark phase-transition. Furthermore, raising the magnetic field strength increases the thermodynamic quantities, especially in the hadronic phase but reduces the critical temperature, i.e. inverse magnetic catalysis.

  16. The magnetic fields of Jupiter and Saturn

    Science.gov (United States)

    Ness, N. F.

    1981-01-01

    The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.

  17. Gauge-covariant decomposition and magnetic monopole for G(2) Yang-Mills field

    CERN Document Server

    Matsudo, Ryutaro

    2016-01-01

    We give a gauge-covariant decomposition of the Yang-Mills field with an exceptional gauge group $G(2)$, which extends the field decomposition invented by Cho, Duan-Ge, and Faddeev-Niemi for the $SU(N)$ Yang-Mills field. As an application of the decomposition, we derive a new expression of the non-Abelian Stokes theorem for the Wilson loop operator in an arbitrary representation of $G(2)$. The resulting new form is used to define gauge-invariant magnetic monopoles in the $G(2)$ Yang-Mills theory. Moreover, we obtain the quantization condition to be satisfied by the resulting magnetic charge. The method given in this paper is general enough to be applicable to any semi-simple Lie group other than $SU(N)$ and $G(2)$.

  18. Magnetizing a complex plasma without a magnetic field

    CERN Document Server

    Kählert, H; Bonitz, M; Löwen, H; Greiner, F; Piel, A

    2012-01-01

    We propose and demonstrate a concept that mimics the magnetization of the heavy dust particles in a complex plasma while leaving the properties of the light species practically unaffected. It makes use of the frictional coupling between a complex plasma and the neutral gas, which allows to transfer angular momentum from a rotating gas column to a well-controlled rotation of the dust cloud. This induces a Coriolis force that acts exactly as the Lorentz force in a magnetic field. Experimental normal mode measurements for a small dust cluster with four particles show excellent agreement with theoretical predictions for a magnetized plasma.

  19. Magnetic nanoparticles for applications in oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Peeraphatdit, Chorthip [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific

  20. Primordial magnetic fields from the string network

    Science.gov (United States)

    Horiguchi, Kouichirou; Ichiki, Kiyotomo; Sugiyama, Naoshi

    2016-08-01

    Cosmic strings are a type of cosmic defect formed by a symmetry-breaking phase transition in the early universe. Individual strings would have gathered to build a network, and their dynamical motion would induce scalar-, vector-, and tensor-type perturbations. In this paper, we focus on the vector mode perturbations arising from the string network based on the one scale model and calculate the time evolution and the power spectrum of the associated magnetic fields. We show that the relative velocity between photon and baryon fluids induced by the string network can generate magnetic fields over a wide range of scales based on standard cosmology. We obtain the magnetic field spectrum before recombination as aB(k,z)~4×10Gμ/1k)3.5 gauss on super-horizon scales, and aB(k,z)~2.4×10Gμ/1k)2.5 gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, and has a final amplitude of approximately B~10Gμ gauss at the k~1 Mpc scale today. This field might serve as a seed for cosmological magnetic fields.

  1. CBS 128 - A new magnetic degenerate with a 65 megagauss surface field

    Energy Technology Data Exchange (ETDEWEB)

    Saffer, R.A.; Liebert, J.; Wagner, R.M.; Sion, E.M.; Starrfield, S.G. (Steward Observatory, Tucson, AZ (USA); Ohio State Univ., Columbus (USA); Villanova Univ., PA (USA); Arizona State Univ., Tempe (USA))

    1989-08-01

    A new magnetic degenerate, CBS 128, has been discovered through follow-up spectroscopy of the Case Blue Star candidates (Wagner et al., 1988). The spectrum reveals Zeeman-shifted Balmer-line components in a 16,000 K DA atmosphere. The spectroscopic observations have been modeled with a synthetic, magnetically distorted spectrum of a star with a centered dipole field geometry (cf. Latter et al., 1987). The model-derived polar field strength for CBS 128 is 65 megagauss (MG), placing this star's field value between the 30 MG (or less) values of the majority of magnetics and the strong-field cases at or above 100 MG. CBS 128, like the vast majority of the magnetic white dwarfs, has small space motions with respect to the sun, a possible indication of youth and evolution from fairly massive progenitors. 21 refs.

  2. CBS 128 - A new magnetic degenerate with a 65 megagauss surface field

    Science.gov (United States)

    Saffer, Rex A.; Liebert, James; Wagner, R. Mark; Sion, Edward M.; Starrfield, Sumner G.

    1989-08-01

    A new magnetic degenerate, CBS 128, has been discovered through follow-up spectroscopy of the Case Blue Star candidates (Wagner et al., 1988). The spectrum reveals Zeeman-shifted Balmer-line components in a 16,000 K DA atmosphere. The spectroscopic observations have been modeled with a synthetic, magnetically distorted spectrum of a star with a centered dipole field geometry (cf. Latter et al., 1987). The model-derived polar field strength for CBS 128 is 65 megagauss (MG), placing this star's field value between the 30 MG (or less) values of the majority of magnetics and the strong-field cases at or above 100 MG. CBS 128, like the vast majority of the magnetic white dwarfs, has small space motions with respect to the sun, a possible indication of youth and evolution from fairly massive progenitors.

  3. Lightning Magnetic Field Measurements around Langmuir Laboratory

    Science.gov (United States)

    Stock, M.; Krehbiel, P. R.; Rison, W.; Aulich, G. D.; Edens, H. E.; Sonnenfeld, R. G.

    2010-12-01

    In the absence of artificial conductors, underground lightning transients are produced by diffusion of the horizontal surface magnetic field of a return stroke vertically downward into the conducting earth. The changing magnetic flux produces an orthogonal horizontal electric field, generating a dispersive, lossy transverse electromagnetic wave that penetrates a hundred meters or more into the ground according to the skin depth of the medium. In turn, the electric field produces currents that flow toward or away from the channel to ground depending on the stroke polarity. The underground transients can produce large radial horizontal potential gradients depending on the distance from the discharge and depth below the surface. In this study we focus on the surface excitation field. The goal of the work is to compare measurements of surface magnetic field waveforms B(t) at different distances from natural lightning discharges with simple and detailed models of the return stroke fields. In addition to providing input to the diffusion mechanism, the results should aid in further understanding return stroke field generation processes. The observational data are to be obtained using orthogonal sets of straightened Rogowski coils to measure magnetic field waveforms in N-S and E-W directions. The waveforms are sampled at 500 kS/s over 1.024 second time intervals and recorded directly onto secure digital cards. The instrument operates off of battery power for several days or weeks at a time in remote, unattended locations and measures magnetic field strengths of up to several tens of amperes/meter. The observations are being made in conjunction with collocated slow electric field change measurements and under good 3-D lightning mapping array (LMA) and fast electric field change coverage.

  4. Teaching Representation Translations with Magnetic Field Experiments

    Science.gov (United States)

    Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

    2017-01-01

    We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and…

  5. Galactic magnetic fields and hierarchical galaxy formation

    CERN Document Server

    Rodrigues, Luiz Felippe S; Fletcher, Andrew; Baugh, Carlton

    2015-01-01

    A framework is introduced for coupling the evolution of galactic magnetic fields sustained by the mean-field dynamo with the formation and evolution of galaxies in the cold dark matter cosmology. Estimates of the steady-state strength of the large-scale and turbulence magnetic fields from mean-field and fluctuation dynamo models are used together with galaxy properties predicted by semi-analytic models of galaxy formation for a population of spiral galaxies. We find that the field strength is mostly controlled by the evolving gas content of the galaxies. Thus, because of the differences in the implementation of the star formation law, feedback from supernovae and ram-pressure stripping, each of the galaxy formation models considered predicts a distribution of field strengths with unique features. The most prominent of them is the difference in typical magnetic fields strengths obtained for the satellite and central galaxies populations as well as the typical strength of the large-scale magnetic field in galax...

  6. A deep dynamo generating Mercury's magnetic field.

    Science.gov (United States)

    Christensen, Ulrich R

    2006-12-21

    Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's large iron core is the most probable cause. However, the low intensity of Mercury's magnetic field--about 1% the strength of the Earth's field--cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core-mantle boundary is subadiabatic, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet's slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury's surface magnetic field and makes predictions that are testable with space missions both presently flying and planned.

  7. Teaching Representation Translations with Magnetic Field Experiments

    Science.gov (United States)

    Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

    2017-01-01

    We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and…

  8. Nonperturbative Physics in a Magnetic Field

    CERN Document Server

    de la Incera, Vivian

    2010-01-01

    Non-Perturbative Quantum Field Theory has played an important role in the study of phenomena where a fermion condensate can appear under certain physical conditions. The familiar phenomenon of electric superconductivity, the color superconductivity of very dense quark matter, and the chiral symmetry breaking of low energy effective chiral theories are all examples of that sort. Often one is interested in the behavior of these systems in the presence of an external magnetic field. In this talk I will outline the effects of an external magnetic field on theories with either fermion-fermion or fermion-antifermion condensates.

  9. Hyperon bulk viscosity in strong magnetic fields

    CERN Document Server

    Sinha, Monika

    2008-01-01

    We study bulk viscosity in neutron star matter including $\\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\\Lambda$ hyperons and the direct Urca (dUrca) process are calculated here. In the presence of a strong magnetic field, bulk viscosity coefficients are enhanced when protons, electrons and muons are populated in their respective zeroth Landau levels compared with the field free cases. The enhancement of bulk viscosity coefficient is larger for the dUrca case.

  10. Opening the cusp. [using magnetic field topology

    Science.gov (United States)

    Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.

    1991-01-01

    This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the cusp to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

  11. String field theory solution corresponding to constant background magnetic field

    CERN Document Server

    Ishibashi, Nobuyuki; Takahashi, Tomohiko

    2016-01-01

    Following the method recently proposed by Erler and Maccaferri, we construct solutions to the equation of motion of Witten's cubic string field theory, which describe constant magnetic field background. We study the boundary condition changing operators relevant to such background and calculate the operator product expansions of them. We obtain solutions whose classical action coincide with the Born-Infeld action.

  12. Magnetohydrodynamic experiments on cosmic magnetic fields

    CERN Document Server

    Stefani, Frank; Gerbeth, Gunter

    2008-01-01

    It is widely known that cosmic magnetic fields, including the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying both effects in liquid metal experiments. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment. An MRI-like mode was found on the background of a turbulent spherical Couette flow at the University of Maryland. Evidence for MRI as the first instability of an hydrodynamica...

  13. Magnetic Field Amplification via Protostellar Disc Dynamos

    CERN Document Server

    Dyda, Sergei; Ustyugova, Galina V; Koldoba, Alexander V; Wasserman, Ira

    2015-01-01

    We model the generation of a magnetic field in a protostellar disc using an \\alpha-dynamo and perform axisymmetric magnetohydrodynamics (MHD) simulations of a T Tauri star. We find that for small values of the dimensionless dynamo parameter $\\alpha_d$ the poloidal field grows exponentially at a rate ${\\sigma} \\propto {\\Omega}_K \\sqrt{\\alpha_d}$ , before saturating to a value $\\propto \\sqrt{\\alpha_d}$ . The dynamo excites dipole and octupole modes, but quadrupole modes are suppressed, because of the symmetries of the seed field. Initial seed fields too weak to launch MHD outflows are found to grow sufficiently to launch winds with observationally relevant mass fluxes of order $10^{-9} M_{\\odot}/\\rm{yr}$ for T Tauri stars. For large values of $\\alpha_d$ magnetic loops are generated over the entire disc. These quickly come to dominate the disc dynamics and cause the disc to break up due to the magnetic pressure.

  14. A holographic bound on cosmic magnetic fields

    Directory of Open Access Journals (Sweden)

    Brett McInnes

    2015-03-01

    Full Text Available Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark–gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description in terms of a thermal asymptotically AdS black hole. We show that holography imposes an upper bound on the intensity of magnetic fields (≈3.6×1018gauss at the hadronization temperature in these circumstances; this is above, but not far above, the values expected in some models of cosmic magnetogenesis.

  15. Measuring vector magnetic fields in solar prominences

    CERN Document Server

    Suárez, D Orozco; Bueno, J Trujillo

    2012-01-01

    We present spectropolarimetric observations in the He I 1083.0 nm multiplet of a quiescent, hedgerow solar prominence. The data were taken with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope at the Observatorio del Teide (Tenerife; Canary Islands; Spain). The observed He I circular and linear polarization signals are dominated by the Zeeman effect and by atomic level polarization and the Hanle effect, respectively. These observables are sensitive to the strength and orientation of the magnetic field vector at each spatial point of the field of view. We determine the magnetic field vector of the prominence by applying the HAZEL inversion code to the observed Stokes profiles. We briefly discuss the retrieved magnetic field vector configuration.

  16. Magnetic fields during high redshift structure formation

    CERN Document Server

    Schleicher, Dominik R G; Schober, Jennifer; Schmidt, Wolfram; Bovino, Stefano; Federrath, Christoph; Niemeyer, Jens; Banerjee, Robi; Klessen, Ralf S

    2012-01-01

    We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \\sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \\sim10^{-5} G can be expected at number densities of \\sim5 cm^{-3}.

  17. Inference of magnetic fields in inhomogeneous prominences

    CERN Document Server

    Milic, Ivan; Atanackovic, Olga

    2016-01-01

    Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D...

  18. Nonrelativistic Fermions in Magnetic Fields a Quantum Field Theory Approach

    CERN Document Server

    Espinosa, Olivier R; Lepe, S; Méndez, F

    2001-01-01

    The statistical mechanics of nonrelativistic fermions in a constant magnetic field is considered from the quantum field theory point of view. The fermionic determinant is computed using a general procedure that contains all possible regularizations. The nonrelativistic grand-potential can be expressed in terms polylogarithm functions, whereas the partition function in 2+1 dimensions and vanishing chemical potential can be compactly written in terms of the Dedekind eta function. The strong and weak magnetic fields limits are easily studied in the latter case by using the duality properties of the Dedekind function.

  19. Magnetic fields in Local Group dwarf irregulars

    Science.gov (United States)

    Chyży, K. T.; Weżgowiec, M.; Beck, R.; Bomans, D. J.

    2011-05-01

    Aims: We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods: We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m Effelsberg telescope at 2.64 GHz. Three galaxies were detected. A higher frequency (4.85 GHz) was used to search for polarized emission in five dwarfs that are the most luminous ones in the infrared domain, of which three were detected. Results: Magnetic fields in LG dwarfs are weak, with a mean value of the total field strength of regulated mainly by the star-formation surface density (with the power-law exponent of 0.30 ± 0.04) or by the gas surface density (with the exponent 0.47 ± 0.09). In addition, we find systematically stronger fields in objects of higher global star-formation rate. The dwarf galaxies follow a similar far-infrared relationship (with a slope of 0.91 ± 0.08) to that determined for high surface brightness spiral galaxies. The magnetic field strength in dwarf galaxies does not correlate with their maximum rotational velocity, indicating that a small-scale rather than a large-scale dynamo process is responsible for producting magnetic fields in dwarfs. If magnetization of the Universe by galactic outflows is coeval with its metal enrichment, we show that more massive objects (such as Lyman break galaxies) can efficiently magnetize the intergalactic medium with a magnetic field strength of about 0.8 nG out to a distance of 160-530 kpc at redshifts 5-3, respectively. Magnetic fields that are several times weaker and shorter magnetization distances are expected for primordial dwarf galaxies. We also predict that most star-forming local dwarfs might have magnetized their surroundings up to a field strength about 0.1 μG within about a 5 kpc distance. Conclusions: Strong magnetic

  20. Near-zero-field nuclear magnetic resonance

    CERN Document Server

    Ledbetter, Micah; Blanchard, John; Ring, Hattie; Ganssle, Paul; Appelt, Stephan; Bluemich, Bernhard; Pines, Alex; Budker, Dmitry

    2011-01-01

    We investigate nuclear magnetic resonance (NMR) in near-zero-field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J-coupling). This is in stark contrast to the high field case, where heteronuclear J-couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with non-trivial spectra.

  1. Near-zero-field nuclear magnetic resonance.

    Science.gov (United States)

    Ledbetter, M P; Theis, T; Blanchard, J W; Ring, H; Ganssle, P; Appelt, S; Blümich, B; Pines, A; Budker, D

    2011-09-02

    We investigate nuclear magnetic resonance (NMR) in near zero field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J coupling). This is in stark contrast to the high-field case, where heteronuclear J couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with nontrivial spectra.

  2. Magnetic Fields in the Interstellar Medium

    Science.gov (United States)

    Clark, Susan

    2017-01-01

    The Milky Way is magnetized. Invisible magnetic fields thread the Galaxy on all scales and play a vital but still poorly understood role in regulating flows of gas in the interstellar medium and the formation of stars. I will present highlights from my thesis work on magnetic fields in the diffuse interstellar gas and in accretion disks. At high Galactic latitudes, diffuse neutral hydrogen is organized into an intricate network of slender linear features. I will show that these neutral hydrogen “fibers” are extremely well aligned with the ambient magnetic field as traced by both starlight polarization (Clark et al. 2014) and Planck 353 GHz polarized dust emission (Clark et al. 2015). The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. Because the orientation of neutral hydrogen is an independent predictor of the local dust polarization angle, our work provides a new tool in the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination. Magnetic fields also drive accretion in astrophysical disks via the magnetorotational instability (MRI). I analytically derive the behavior of this instability in the weakly nonlinear regime and show that the saturated state of the instability depends on the geometry of the background magnetic field. The analytical model describes the behavior of the MRI in a Taylor-Couette flow, a set-up used by experimentalists in the ongoing quest to observe MRI in the laboratory (Clark & Oishi 2016a, 2016b).

  3. Effects of static magnetic fields on plants.

    Science.gov (United States)

    Kuznetsov, O.

    In our recent experiment on STS-107 (MFA-Biotube) we took advantage of the magnetic heterogeneity of the gravity receptor cells of flax roots, namely stronger diamagnetism of starch-filled amyloplasts compared to cytoplasm (Δ ≊ HGMF, grad(H2/2) up to 109-1010 Oe2/cm) of the experimental chambers (MFCs) repelled amyloplasts from the zones of stronger field thus providing a directional stimulus for plant gravisensing system in microgravity, and causing the roots to react. Such reaction was observed in the video downlink pictures. Unfortunately, the ``Columbia'' tragedy caused loss of the plant material and most of the images, thus preventing us from detailed studies of the results. Currently we are looking for a possibility to repeat this experiment. Therefore, it is very important to understand, what other effects (besides displacing amyloplasts) static magnetic fields with intensities 0 to 2.5104 Oe, and with the size of the area of non-uniformity 10-3 to 1 cm. These effects were estimated theoretically and tested experimentally. No statistically significant differences in growth rates or rates of gravicurvature were observed in experiments with Linum, Arabidopsis, Hordeum, Avena, Ceratodon and Chara between the plants grown in uniform magnetic fields of various intensities (102 to 2.5104 Oe) and those grown in the Earth's magnetic field. Microscopic studies also did not detect any structural differences between test and control plants. The magnitudes of possible effects of static magnetic fields on plant cells and organs (including effects on ion currents, magneto-hydrodynamic effects in moving cytoplasm, ponderomotive forces on other cellular structures, effects on some biochemical reactions and biomolecules) were estimated theoretically. The estimations have shown, that these effects are small compared to the thermodynamic noise and thus are insignificant. Both theoretical estimations and control experiments confirm, that intracellular magnetophoresis of

  4. Inference of magnetic fields in inhomogeneous prominences

    Science.gov (United States)

    Milić, I.; Faurobert, M.; Atanacković, O.

    2017-01-01

    Context. Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. Aims: We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. Methods: We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D slab model. Results: We find that differences between input and the inferred magnetic field vector are non-negligible. Namely, we almost universally find that the inferred field is weaker and more horizontal than the input field. Conclusions: Spatial inhomogeneities and radiative transfer have a strong effect on scattering line polarization in the optically thick lines. In real-life situations, ignoring these effects could lead to a serious misinterpretation of spectropolarimetric observations of chromospheric objects such as prominences.

  5. Whistler modes with wave magnetic fields exceeding the ambient field.

    Science.gov (United States)

    Stenzel, R L; Urrutia, J M; Strohmaier, K D

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background.

  6. Dissipation function in a magnetic field (Review)

    Science.gov (United States)

    Gurevich, V. L.

    2015-07-01

    The dissipation function is introduced to describe the behavior of the system of harmonic oscillations interacting with the environment (thermostat). This is a quadratic function of generalized velocities, which determines the rate of dissipation of the mechanical energy in the system. It was assumed earlier (Landau, Lifshitz) that the dissipation function can be introduced only in the absence of magnetic field. In the present review based on the author's studies, it has been shown how the dissipation function can be introduced in the presence of a magnetic field B. In a magnetic field, both dissipative and nondissipative responses arise as a response to perturbation and are expressed in terms of kinetic coefficients. The matrix of nondissipative coefficients can be obtained to determine an additional term formally including it into the equations of motion, which still satisfy the energy conservation law. Then, the dissipative part of the matrix can be considered in exactly the same way as without magnetic field, i.e., it defines the dissipation loss. As examples, the propagation and absorption of ultrasound in a metal or a semiconductor in a magnetic field have been considered using two methods: (i) the method based on the phenomenological theory using the equations of the theory of elasticity and (ii) the method based on the microscopic approach by analyzing and solving the kinetic equation. Both examples are used to illustrate the approach with the dissipation function.

  7. Magnetic Fields and Massive Star Formation

    CERN Document Server

    Zhang, Qizhou; Girart, Josep M; Hauyu,; Liu,; Tang, Ya-Wen; Koch, Patrick M; Li, Zhi-Yun; Keto, Eric; Ho, Paul T P; Rao, Ramprasad; Lai, Shih-Ping; Ching, Tao-Chung; Frau, Pau; Chen, How-Huan; Li, Hua-Bai; Padovani, Marco; Bontemps, Sylvain; Csengeri, Timea; Juarez, Carmen

    2014-01-01

    Massive stars ($M > 8$ \\msun) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 $\\mu$m obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of $\\lsim$ 0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within $40^\\circ$ of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the ...

  8. Magnetic fields of the outer planets

    Science.gov (United States)

    Connerney, J. E. P.

    1993-01-01

    It is difficult to imagine a group of planetary dynamos more diverse than those visited by the Pioneer and Voyager spacecraft. The magnetic field of Jupiter is large in magnitude and has a dipole axis within 10 deg of its rotation axis, comfortably consistent with the paleomagnetic history of the geodynamo. Saturn's remarkable (zonal harmonic) magnetic field has an axis of symmetry that is indistinguishable from its rotation axis (mush less than 1 deg angular separation); it is also highly antisymmetric with respect to the equator plane. According to one hypothesis, the spin symmetry may arise from the differential rotation of an electrically conducting and stably stratified layer above the dynamo. The magnetic fields of Uranus and Neptune are very much alike, and equally unlike those of the other known magnetized planets. These two planets are characterized by a large dipole tilts (59 deg and 47 deg, respectively) and quadrupole moments (Schmidt-normalized quadrupole/dipole ratio approximately equal 1.0). These properties may be characteristic of dynamo generation in the relatively poorly conducting 'ice' interiors of Uranus and Neptune. Characteristics of these planetary magnetic fields are illustrated using contour maps of the field on the planet's surface and discussed in the context of planetary interiors and dynamo generation.

  9. Cosmic Magnetic Fields: Observations and Prospects

    CERN Document Server

    Beck, Rainer

    2011-01-01

    Synchrotron emission, its polarization and its Faraday rotation at radio frequencies of 0.2-10 GHz are powerful tools to study the strength and structure of cosmic magnetic fields. The observational results are reviewed for spiral, barred and flocculent galaxies, the Milky Way, halos and relics of galaxy clusters, and for the intergalactic medium. Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of cosmic magnetic fields and will help to understand their origin. At low frequencies, LOFAR (10-250 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies and galaxy clusters. Polarization at higher frequencies (1-10 GHz), as observed with the EVLA, ASKAP, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of nearby galaxies in unprecedented detail. Surveys of Faraday rotation measures of pulsars will map the Milky Way's magnetic field with high precision. All-sky sur...

  10. Magnetic fields in primordial accretion disks

    Science.gov (United States)

    Latif, M. A.; Schleicher, D. R. G.

    2016-01-01

    Magnetic fields are considered a vital ingredient of contemporary star formation and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations and are subsequently amplified by the small-scale dynamo, leading to a strong, tangled magnetic field. We explore how the magnetic field provided by the small-scale dynamo is further amplified via the α-Ω dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop. III star with 10M⊙ and an accretion rate of 10-3M⊙ yr-1, and a supermassive star with 105M⊙ and an accretion rate of 10-1M⊙ yr-1. For the 10M⊙ Pop. III star, we find that coherent magnetic fields can be produced on scales of at least 100 AU, which are sufficient to drive a jet with a luminosity of 100L⊙ and a mass outflow rate of 10-3.7M⊙ yr-1. For the supermassive star, the dynamical timescales in its environment are even shorter, implying smaller orbital timescales and an efficient magnetization out to at least 1000 AU. The jet luminosity corresponds to ~106.0L⊙ and a mass outflow rate of 10-2.1M⊙ yr-1. We expect that the feedback from the supermassive star can have a relevant impact on its host galaxy.

  11. Magnetic Field Strengths in Photodissociation Regions

    CERN Document Server

    Balser, Dana S; Jeyakumar, S; Bania, T M; Montet, Benjamin T; Shitanishi, J A

    2015-01-01

    We measure carbon radio recombination line (RRL) emission at 5.3 GHz toward four HII regions with the Green Bank Telescope (GBT) to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi (2007) suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic (MHD) waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B ~ 100-300 micro Gauss in W3 and NGC6334A. Our results for W49 and NGC6334D are less well constrained with total magnetic field strengths between B ~ 200-1000 micro Gauss. HI and OH Zeeman measurements of the line-of-sight magnetic field strength (B_los), taken from the literature, are between a facto...

  12. Magnetic field effect on spoke behaviour

    Science.gov (United States)

    Hnilica, Jaroslav; Slapanska, Marta; Klein, Peter; Vasina, Petr

    2016-09-01

    The investigations of the non-reactive high power impulse magnetron sputtering (HiPIMS) discharge using high-speed camera imaging, optical emission spectroscopy and electrical probes showed that plasma is not homogeneously distributed over the target surface, but it is concentrated in regions of higher local plasma density called spokes rotating above the erosion racetrack. Magnetic field effect on spoke behaviour was studied by high-speed camera imaging in HiPIMS discharge using 3 inch titanium target. An employed camera enabled us to record two successive images in the same pulse with time delay of 3 μs between them, which allowed us to determine the number of spokes, spoke rotation velocity and spoke rotation frequency. The experimental conditions covered pressure range from 0.15 to 5 Pa, discharge current up to 350 A and magnetic fields of 37, 72 and 91 mT. Increase of the magnetic field influenced the number of spokes observed at the same pressure and at the same discharge current. Moreover, the investigation revealed different characteristic spoke shapes depending on the magnetic field strength - both diffusive and triangular shapes were observed for the same target material. The spoke rotation velocity was independent on the magnetic field strength. This research has been financially supported by the Czech Science Foundation in frame of the project 15-00863S.

  13. Reducing blood viscosity with magnetic fields.

    Science.gov (United States)

    Tao, R; Huang, K

    2011-07-01

    Blood viscosity is a major factor in heart disease. When blood viscosity increases, it damages blood vessels and increases the risk of heart attacks. Currently, the only method of treatment is to take drugs such as aspirin, which has, however, several unwanted side effects. Here we report our finding that blood viscosity can be reduced with magnetic fields of 1 T or above in the blood flow direction. One magnetic field pulse of 1.3 T lasting ~1 min can reduce the blood viscosity by 20%-30%. After the exposure, in the absence of magnetic field, the blood viscosity slowly moves up, but takes a couple of hours to return to the original value. The process is repeatable. Reapplying the magnetic field reduces the blood viscosity again. By selecting the magnetic field strength and duration, we can keep the blood viscosity within the normal range. In addition, such viscosity reduction does not affect the red blood cells' normal function. This technology has much potential for physical therapy.

  14. The Magnetic Field of Planet Earth

    DEFF Research Database (Denmark)

    Hulot, G.; Finlay, Chris; Constable, C. G.

    2010-01-01

    The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks h...... yr) to the longest (virtually the age of the Earth) time scales are finally reviewed, underlining the respective roles of the magnetohydodynamics at work in the core, and of the slow dynamic evolution of the planet as a whole.......The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks...... observations have been made possible from space, leading to the possibility of observing the Earth’s magnetic field in much more details than was previously possible. The progressive increase in computer power was also crucial, leading to advanced ways of handling and analyzing this considerable corpus of data...

  15. Cosmological Magnetic Fields from Primordial Helical Seeds

    CERN Document Server

    Sigl, G

    2002-01-01

    Most early Universe scenarios predict negligible magnetic fields on cosmological scales if they are unprocessed during subsequent expansion of the Universe. We present a new numerical treatment of the evolution of primordial fields and apply it to weakly helical seeds as they occur in certain early Universe scenarios. We find that initial helicities not much larger than the baryon to photon number can lead to fields of about 10^{-13} Gauss with coherence scales slightly below a kilo-parsec today.

  16. Magnetic Field Observations at Purcell, Oklahoma Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Chi, P. J. [Univ. of California, Los Angeles, CA (United States); Gibson, J. P. [Univ. of Oklahoma, Norman, OK (United States)

    2017-05-01

    The campaign “Magnetic Field Observations at Purcell, Oklahoma” installed a ground-based magnetometer at Purcell’s U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility boundary installation at the Kessler Atmospheric and Ecological Field Station, University of Oklahoma, to measure local magnetic field variations. It is a part of the nine stations of the Mid-continent MAgnetoseismic Chain (McMAC) placed as close to the 330° magnetic longitude as possible. This is the meridian in the world where land covers the greatest continuous range in magnetic latitude. Figure 1 shows the map of the magnetometer stations along the 330th magnetic meridian, including the Purcell (PCEL) station. The main scientific objective of the campaign is to detect the field line resonance (FLR) frequencies of the magnetic field line connected to the Purcell station. This magnetic field line extends from Purcell to the outer space at distances as far as 2 Earth radii (RE). To accurately identify FLR frequencies, however, simultaneous measurements at slightly different latitudes along the same meridian are necessary to allow the use of the cross-phase technique. This consideration explains the arrangement to operate magnetometers at the Americus (AMER) and Richardson (RICH) stations nearby. The measured resonant frequency can infer the plasma mass density along the field line through the method of normal-mode magnetoseismology. The magnetometer at the Purcell station can detect many other types of magnetic field fluctuations associated with the changes in the electric currents in the ionosphere and the magnetosphere, which by large are affected by the solar activity. In other words, the magnetic field data collected by this campaign are also useful for understanding space weather phenomena. The magnetometer was installed at Purcell’s ARM boundary facility in March 27, 2006. The construction of the triaxial fluxgate magnetometer used by the

  17. Magnetic field flow phenomena in a falling particle receiver

    Science.gov (United States)

    Armijo, Kenneth M.; Ho, Clifford; Anderson, Ryan; Christian, Joshua; Babiniec, Sean; Ortega, Jesus

    2016-05-01

    Concentrating solar power (CSP) falling particle receivers are being pursued as a desired means for utilizing low-cost, high-absorptance particulate materials that can withstand high concentration ratios (˜1000 suns), operating temperatures above 700 °C, and inherent storage capabilities which can be used to reduce to levelized cost of electricity (LCOE)1. Although previous falling particle receiver designs have proven outlet temperatures above 800 °C, and thermal efficiencies between 80-90%, performance challenges still exist to operate at higher concentration ratios above 1000 suns and greater solar absorptance levels. To increase absorptance, these receivers will require enhanced particle residence time within a concentrated beam of sunlight. Direct absorption solid particle receivers that can enhance this residence time will have the potential to achieve heat-transfer media temperatures2 over 1000 °C. However, depending on particle size and external forces (e.g., external wind and flow due to convective heat losses), optimized particle flow can be severely affected, which can reduce receiver efficiency. To reduce particle flow destabilization and increase particle residence time on the receiver an imposed magnetic field is proposed based on a collimated design for two different methodologies. These include systems with ferromagnetic and charged particle materials. The approaches will be analytically evaluated based on magnetic field strength, geometry, and particle parameters, such as magnetic moment. A model is developed using the computational fluid dynamics (CFD) code ANSYS FLUENT to analyze these approaches for a ˜2 MWth falling particle receiver at Sandia National Laboratories5,6. Here, assessment will be made with respect to ferromagnetic particles such as iron-oxides, as well as charged particles. These materials will be parametrically assessed (e.g., type, size, dipole moment and geometry) over a range of magnetic permeability, μ values. Modeling

  18. High-field magnetization in transuranium compound

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, K. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan) and KYOKUGEN, Osaka University, Osaka 560-8531 (Japan)]. E-mail: sugiyama@phys.sci.osaka-u.ac.jp; Nakashima, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Aoki, D. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Ikeda, S. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Y. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Yamamoto, E. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Homma, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Shiokawa, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Kindo, K. [Institite of Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581 (Japan); Hagiwara, M. [KYOKUGEN, Osaka University, Osaka 560-8531 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan)

    2007-03-15

    We measured the high-field magnetization up to 55T and constructed a magnetic phase diagram for a transuranium antiferromagnet NpRhGa{sub 5} with the tetragonal structure. The magnetization at 4.2K for H(parallel) [100] indicates a sharp metamagnetic transition with a step at H{sub c}=26T and saturates above H{sub s}=38T, reaching 0.43{mu}{sub B}/Np. An ordered moment of 0.96{mu}{sub B}/Np at zero field, which was determined from the neutron scattering experiment, is found to be reduced to 0.43{mu}{sub B}/Np at H{sub s}, together with an orientation of the magnetic moment from the (001) plane to the (100) plane.

  19. Mechanism of magnetic field effect in cryptochrome

    CERN Document Server

    Solov'yov, Ilia A

    2011-01-01

    Creatures as varied as mammals, fish, insects, reptiles, and migratory birds have an intriguing `sixth' sense that allows them to distinguish north from south by using the Earth's intrinsic magnetic field. Yet despite decades of study, the physical basis of this magnetic sense remains elusive. A likely mechanism is furnished by magnetically sensitive radical pair reactions occurring in the retina, the light-sensitive part of the eyes. A photoreceptor, cryptochrome, has been suggested to endow birds with magnetoreceptive abilities as the protein has been shown to exhibit the biophysical properties required for an animal magnetoreceptor to operate properly. Here, we propose a concrete light-driven reaction cycle in cryptochrome that lets a magnetic field influence the signaling state of the photoreceptor. The reaction cycle ties together transient absorption and electron-spin-resonance observations with known facts on avian magnetoreception. Our analysis establishes the feasibility of cryptochrome to act as a g...

  20. Magnetic Field Experiment on Yinghuo-1 at Mars

    Science.gov (United States)

    Zhao, Hua

    Magnetic Field Experiment on Yinghuo-1 at Mars Hua Zhao, G. W. Zhu, J. D. Wang, M. F. Yu, L. Li, Y. Q. Sun, S. W. Chen, H. Z. Liao, and B. Zhou Center for Space Science and Applied Research (CSSAR), Chinese Academy of Sciences, Beijing, China Abstract: A micro-satellite, Yinghuo-1, would be launched with Phobos-Grunt in October, 2009 to investigate the space environment around Mars. YH-1 and Phobos-Grunt forms a twopoint measurement configuration in the Martian space environment, and equipped with similar magnetic field and plasma detecting payload on two spacecraft would give some coordinated exploration around Mars. YH-1 would orbit Mars with periapsis of 800 km above the Martian surface, and apoapsis about 80000 km to the center of Mars. The orbit inclination is in the range of 0—7o to the Martian equator. A flux-gate type magnetometer, with two sensors, is developed for YH-1 spacecraft. Two sensors are mounted on one-side of the deployable solar panel with a radial separation about 45 cm to function as a gradiometer to minimize the affects of platform remanence. The dynamic range of √ magnetometer is with a 16-bit ADC converter, and the the noise level is better than 0.01 nT/ Hz, to measure three-component magnetic field from DC to 10Hz. Flux-gate magnetometer would work together with the Plasma Package onboard of YH-1 to investigate the Martian bow shock, magnetosheath, magnetic pileup region (MPR). A detail description of the flux-gate magnetometer is presented in this paper, with some test and calibration results.