Sample records for solar dust corona

  1. Viking solar corona experiment

    Microsoft Academic Search

    G. LEONARD Tyler; Joseph P. Brenkle; Thomas A. Komarek; Arthur I. Zygielbaum

    1977-01-01

    The 1976 Mars solar conjunction resulted in complete occulations of the Viking spacecraft by the sun at solar minimum. During the conjunction period, coherent 3.5- and 13-cm wavelength radio waves from the orbiters passed through the solar corona and were received with the 64-m antennas of the NASA Deep Space Network. Data were obtained within at least 0.3 and 0.8

  2. The Solar Corona

    NSDL National Science Digital Library

    David Hathaway

    This site describes the corona of the sun from three different points of view. In the first case, the white-light corona is the sight that is visible during total eclipses of the sun as a pearly white crown surrounding the sun and displays a variety of features including streamers, plumes, and loops. The emission line corona is explained on the basis of the extreme heat of the corona and the X-ray corona is described in terms of past and present research projects designed to study it. The site also contains an image for each of the three parts.

  3. Solar corona electron density distribution

    Microsoft Academic Search

    P. B. Esposito; Peter Edenhofer; Ernst Lueneburg

    1980-01-01

    The paper discusses the three and one-half months of single-frequency time delay data which were acquired from the Helios 2 spacecraft around the time of its solar occultation. The excess time delay due to integrated effect of free electrons along the signal's ray path could be separated and modeled following the determination of the spacecraft trajectory. An average solar corona

  4. Turbulence in the Solar Corona

    E-print Network

    Steven R. Cranmer

    2007-06-19

    The solar corona has been revealed in the past decade to be a highly dynamic nonequilibrium plasma environment. Both the loop-filled coronal base and the extended acceleration region of the solar wind appear to be strongly turbulent, but direct observational evidence for a cascade of fluctuation energy from large to small scales is lacking. In this paper I will review the observations of wavelike motions in the corona over a wide range of scales, as well as the macroscopic effects of wave-particle interactions such as preferential ion heating. I will also present a summary of recent theoretical modeling efforts that seem to explain the time-steady properties of the corona (and the fast and slow solar wind) in terms of an anisotropic MHD cascade driven by the partial reflection of low-frequency Alfven waves propagating along the superradially expanding solar magnetic field. Complete theoretical models are difficult to construct, though, because many of the proposed physical processes act on a multiplicity of spatial scales (from centimeters to solar radii) with feedback effects not yet well understood. This paper is thus a progress report on various attempts to couple these disparate scales.

  5. Petrovay: Solar physics Chromosphere and corona THE SOLAR CHROMOSPHERE

    E-print Network

    Petrovay, Kristóf

    Petrovay: Solar physics Chromosphere and corona THE SOLAR CHROMOSPHERE Visible in eclipses as red brightness temperature at 10.7 cm: Tb 10 000 K. #12;Petrovay: Solar physics Chromosphere and corona Mean temperature profile: VAL model atmosphere, based on lines #12;Petrovay: Solar physics Chromosphere and corona

  6. The Viking solar corona experiment

    NASA Technical Reports Server (NTRS)

    Tyler, G. L.; Brenkle, J. P.; Komarek, T. A.; Zygielbaum, A. I.

    1977-01-01

    The 1976 Mars solar conjunction resulted in complete occultations of the Viking spacecraft by the sun at solar minimum. During the conjunction period, coherent 3.5- and 13-cm wavelength radio waves from the orbiters passed through the solar corona and were received with the 64-m antennas of the NASA Deep Space Network. Data were obtained within at least 0.3 and 0.8 R sub s of the photosphere at the 3.5- and 13-cm wavelengths, respectively. The data can be used to determine the plasma density integrated along the radio path, the velocity of density irregularities in the coronal plasma, and the spectrum of the density fluctuations in the plasma. Observations of integrated plasma density near the south pole of the sun generally agree with a model of the corona which has an 8:1 decrease in plasma density from the equator to the pole. Power spectra of the 3.5- and 13-cm signals at a heliocentric radial distance of about 2 R sub s have a 1/2 power width of several hundred hertz and vary sharply with proximate geometric miss distance. Spectral broadening indicates a marked progressive increase in plasma irregularities with decreasing ray altitude at scales between about 1 and 100 km.

  7. Dynamics of the quiescent solar corona

    Microsoft Academic Search

    R. Rosner; W. H. Tucker; G. S. Vaiana

    1978-01-01

    A model for the quiescent, inhomogeneous solar corona is developed, based upon the concept of loop structures as the basic structural element of the corona. The results, which are compared with observations obtained by the S-054 Skylab X-ray telescope, show that (a) hydrostatic solutions are stable only if the temperature maximum is located at the top of loop structures, and

  8. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    1997-01-01

    Under this contract, we have continued our investigations of the large scale structure of the solar corona and inner heliosphere using global magnetohydrodynamic (MHD) simulations. These computations have also formed the basis for studies of coronal mass ejections (CMES) using realistic coronal configurations. We have developed a technique for computing realistic magnetohydrodynamic (MHD) computations of the solar corona and inner heliosphere. To perform computations that can be compared with specific observations, it is necessary to incorporate solar observations into the boundary conditions. We have used the Wilcox Solar Observatory synoptic maps (collected during a solar rotation by daily measurements of the line-of-sight magnetic field at central meridian) to specify the radial magnetic field (B,) at the photosphere. For the initial condition, we use a potential magnetic field consistent with the specified distribution of B, at the lower boundary, and a wind solution consistent with the specified plasma density and temperature at the solar surface. Together this initial condition forms a (non-equilibrium) approximation of the state of the solar corona for the time-dependent MHD computation. The MHD equations are then integrated in time to steady state. Here we describe solutions relevant to a recent solar eclipse, as well as Ulysses observations. We have also developed a model configuration of solar minimum, useful for studying CME initiation and propagation.

  9. Seeing The Solar Corona in Three Dimensions

    E-print Network

    Vásquez, Alberto Marcos

    2015-01-01

    The large availability and rich spectral coverage of today's observational data of the solar corona, and the high spatial and temporal resolution of many instruments, has enabled the evolution of three-dimensional (3D) physical models to a great level of detail. However, the 3D information provided by the data is rather limited as every instrument observes from a single angle of vision, or two at the most in the case of the STEREO mission. Two powerful available observational techniques to infer detailed 3D information of the solar corona from empirical data are stereoscopy and tomography. In particular, the technique known as \\emph{differential emission measure tomography} (DEMT) allows determination of the 3D distribution of the coronal electron density and temperature in the inner corona. This paper summarizes the main technical aspects of DEMT, reviews all published work based on it, and comments its future development and applications.

  10. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    2001-01-01

    This report describes the progress made in the investigation of the solar corona using magnetohydrodynamic (MHD) simulations. Coronal mass ejections (CME) are believed to be the primary cause of nonrecurrent geomagnetic storms and these have been investigated through the use of three-dimensional computer simulation.

  11. Probing the Solar Corona with VLBI

    NASA Astrophysics Data System (ADS)

    Soja, Benedikt; Sun, Jing; Heinkelmann, Robert; Schuh, Harald; Böhm, Johannes

    2013-04-01

    Radio observations close to the Sun are sensitive to the dispersive effects of the Sun corona. This has been used to determine (among other parameters) the electron density in the corona during solar conjunctions with spacecrafts. Although geodetic Very Long Baseline Interferometry (VLBI) observations close to the Sun have already been performed before 2002 (but suspended afterwards) they have not yet been used for calculations of corona electron densities. Almost 10 years later the International VLBI Service for Geodesy and Astrometry (IVS) decided to schedule twelve 24 hours VLBI sessions in 2011 and 2012 including observations closer than 15 degrees to the heliocenter. Both the recent and the earlier sessions are analysed in order to determine electron densities of the Sun corona. Based on the ionospheric delay corrections derived from two-frequency VLBI measurements, other dispersive effects like instrumental biases and, most important of all, the Earth's ionosphere effects are estimated and then eliminated. The residual delays are used to successfully determine power-law parameters of the electron density of the Sun corona for several of these sessions. In some cases, scheduled observations close to the Sun had failed, making it impossible to derive meaningful results from them. Both, the successful and the lost observations were analysed including external information like Sunspot numbers and flare occurrences. The estimated electron densities were compared to previous models of the Sun corona derived by radio measurements to spacecrafts during solar conjunctions. Our investigations show that it is possible to use geodetic VLBI sessions with observations close to the Sun to determine electron densities of the corona. The success depends on the geometry, i.e. the source position with respect to the Sun, and on the schedule, which can be optimized for such investigations. Unpredictable disturbances at the Sun's surface, such as flares, play also a role. So far, the VLBI-derived corona parameters have lower quality than those derived from spacecraft-bound measurements. However, the advantage of VLBI is the possibility to monitor the electron density on a regular basis and to create a homogenous time series. This could improve our understanding of time dependent Sun processes.

  12. MASC: Magnetic Activity of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Auchere, Frederic; Fineschi, Silvano; Gan, Weiqun; Peter, Hardi; Vial, Jean-Claude; Zhukov, Andrei; Parenti, Susanna; Li, Hui; Romoli, Marco

    We present MASC, an innovative payload designed to explore the magnetic activity of the solar corona. It is composed of three complementary instruments: a Hard-X-ray spectrometer, a UV / EUV imager, and a Visible Light / UV polarimetric coronagraph able to measure the coronal magnetic field. The solar corona is structured in magnetically closed and open structures from which slow and fast solar winds are respectively released. In spite of much progress brought by two decades of almost uninterrupted observations from several space missions, the sources and acceleration mechanisms of both types are still not understood. This continuous expansion of the solar atmosphere is disturbed by sporadic but frequent and violent events. Coronal mass ejections (CMEs) are large-scale massive eruptions of magnetic structures out of the corona, while solar flares trace the sudden heating of coronal plasma and the acceleration of electrons and ions to high, sometimes relativistic, energies. Both phenomena are most probably driven by instabilities of the magnetic field in the corona. The relations between flares and CMEs are still not understood in terms of initiation and energy partition between large-scale motions, small-scale heating and particle acceleration. The initiation is probably related to magnetic reconnection which itself results magnetic topological changes due to e.g. flux emergence, footpoints motions, etc. Acceleration and heating are also strongly coupled since the atmospheric heating is thought to result from the impact of accelerated particles. The measurement of both physical processes and their outputs is consequently of major importance. However, despite its fundamental importance as a driver for the physics of the Sun and of the heliosphere, the magnetic field of our star’s outer atmosphere remains poorly understood. This is due in large part to the fact that the magnetic field is a very difficult quantity to measure. Our knowledge of its strength and orientation is primarily based on extrapolations from photospheric observations, not from direct measurements. These extrapolations require strong assumptions on critical but unobserved quantities and thus fail to accurately reproduce the complex topologies inferred from remote-sensing observations of coronal structures in white light, EUV, and X-rays. Direct measurements of the coronal magnetic field are also clearly identified by the international heliophysics community as a key element susceptible to lead to major breakthroughs in the understanding of our star. MASC is thus designed to answer the following top-level scientific questions: 1. What is the global magnetic field configuration in the corona? 2. What is the role of the magnetic field in the triggering of flares and CMEs? 3. What is the role of the magnetic field in the acceleration mechanisms of the solar winds? 4. What is the energy spectrum and in particular what are the highest energies to which charged particles can be accelerated in the solar corona? MASC will address these fundamental questions with a suite of instruments composed of an X-ray spectrometer, a UV / EUV imager, and a coronagraph working in the visible and at Lyman alpha. The spectrometer will provide information on the energetics of solar flares, in particular at very high energies of accelerated particles. The UV / EUV imager will provide constraints on the temperature of the flaring and non-flaring corona. The coronagraph will provide the number density of free electrons in the corona, maps of the outflow velocity of neutral hydrogen, and measurements of the coronal magnetic field, via the Hanle effect. These measurements will be performed at all steps of the flare-CME processes, thus providing a detailed picture of the solar coronal dynamics in the quiet and eruptive periods.

  13. The Equatorial Background Solar Corona during Solar Minimum

    Microsoft Academic Search

    R. Ramesh; H. S. Nataraj; C. Kathiravan; Ch. V. Sastry

    2006-01-01

    We report two-frequency (51 and 77 MHz) radio observations of the equatorial brightness distribution of the ``undisturbed'' solar corona, close to the minimum between sunspot cycles 22 and 23. The contributions from different discrete structures in the observed one-dimensional profiles were identified and removed through an iterative multi-Gaussian least-squares curve fitting technique, and the ``background'' corona was obtained for each

  14. Global MHD Modeling of the Solar Corona and Solar Wind

    Microsoft Academic Search

    A. Usmanov; M. Goldstein

    2004-01-01

    We present a global three-dimensional steady-state MHD model of the solar corona and solar wind that uses observations of the photospheric magnetic field in the prescription of boundary condition. As part of the boundary conditions, we also specify a flux of Alfvén waves that emanates from the Sun. The Alfvén waves provide additional acceleration for the coronal outflow in the

  15. Ion Heating in the Solar Corona and Solar Wind

    Microsoft Academic Search

    Steven Cranmer

    2009-01-01

    The solar corona is the hot, ionized outer atmosphere of the Sun that expands into interplanetary space as a supersonic solar wind. This tenuous medium is a unique laboratory for the study of magnetohydrodynamics (MHD) and plasma physics with ranges of parameters that are inaccessible on Earth. The last decade has seen significant progress toward identifying and characterizing the processes

  16. Observations of the White Light Corona from Solar Orbiter and Solar Probe Plus

    NASA Astrophysics Data System (ADS)

    Howard, R. A.; Thernisien, A. F.; Vourlidas, A.; Plunkett, S. P.; Korendyke, C. M.; Sheeley, N. R.; Morrill, J. S.; Socker, D. G.; Linton, M. G.; Liewer, P. C.; De Jong, E. M.; Velli, M. M.; Mikic, Z.; Bothmer, V.; Lamy, P. L.

    2011-12-01

    The SoloHI instrument on Solar Orbiter and the WISPR instrument on Solar Probe+ will make white light coronagraphic images of the corona as the two spacecraft orbit the Sun. The minimum perihelia for Solar Orbiter is about 60 Rsun and for SP+ is 9.5 Rsun. The wide field of view of the WISPR instrument (about 105 degrees radially) corresponds to viewing the corona from 2.2 Rsun to 20 Rsun. Thus the entire Thomson hemisphere is contained within the telescope's field and we need to think of the instrument as being a traditional remote sensing instrument and then transitioning to a local in-situ instrument. The local behavior derives from the fact that the maximum Thomson scattering will favor the electron plasma close to the spacecraft - exactly what the in-situ instruments will be sampling. SoloHI and WISPR will also observe scattered light from dust in the inner heliosphere, which will be an entirely new spatial regime for dust observations from a coronagraph, which we assume to arise from dust in the general neighborhood of about half way between the observer and the Sun. As the dust grains approach the Sun, they evaporate and do not contribute to the scattering. A dust free zone has been postulated to exist somewhere inside of 5 Rsun where all dust is evaporated, but this has never been observed. The radial position where the evaporation occurs will depend on the precise molecular composition of the individual grains. The orbital plane of Solar Orbiter will gradually increase up to about 35 degrees, enabling a very different view through the zodiacal dust cloud to test the models generated from in-ecliptic observations. In this paper we will explore some of the issues associated with the observation of the dust and will present a simple model to explore the sensitivity of the instrument to observe such evaporations.

  17. Variable Winds and Dust Formation in R Coronae Borealis Stars

    E-print Network

    Clayton, Geoffrey C; Zhang, Wanshu

    2013-01-01

    We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I 10830 lines of twelve R Coronae Borealis (RCB) stars over short (1 month) and long (3 year) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities ~400 km/s appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

  18. VARIABLE WINDS AND DUST FORMATION IN R CORONAE BOREALIS STARS

    SciTech Connect

    Clayton, Geoffrey C.; Zhang Wanshu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Geballe, T. R., E-mail: gclayton@fenway.phys.lsu.edu, E-mail: wzhan21@lsu.edu, E-mail: tgeballe@gemini.edu [Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720 (United States)

    2013-08-01

    We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I {lambda}10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities {approx}400 km s{sup -1} appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

  19. High Energy Particles in the Solar Corona

    E-print Network

    Widom, A; Larsen, L

    2008-01-01

    Collective Ampere law interactions producing magnetic flux tubes piercing through sunspots into and then out of the solar corona allow for low energy nuclear reactions in a steady state and high energy particle reactions if a magnetic flux tube explodes in a violent event such as a solar flare. Filamentous flux tubes themselves are vortices of Ampere currents circulating around in a tornado fashion in a roughly cylindrical geometry. The magnetic field lines are parallel to and largely confined within the core of the vortex. The vortices may thereby be viewed as long current carrying coils surrounding magnetic flux and subject to inductive Faraday and Ampere laws. These laws set the energy scales of (i) low energy solar nuclear reactions which may regularly occur and (ii) high energy electro-weak interactions which occur when magnetic flux coils explode into violent episodic events such as solar flares or coronal mass ejections.

  20. Green corona and solar sector structure

    NASA Technical Reports Server (NTRS)

    Antonucci, E.; Svalgaard, L.

    1974-01-01

    Analysis of the green-line corona for the interval 1947-1970 suggests the existence of large-scale organization of the emission. The green-line emission at high northern latitudes (approximately 40 to 60 deg) is correlated with the emission at high southern latitudes 6, 15, and 24 days later, while the low-latitude green corona seems to be correlated on both sides of the equator with no time lag. These coronal features are recurrent with a 27-day period at all latitudes between plus or minus 60 deg, and these large-scale structures are believed to be associated with the solar magnetic sector structure. The high correlation between northern and southern high-latitude emission at 15 days time lag is explained as a signature of a two-sector structure, while four sectors are associated with the 6- and 24-day peaks.

  1. Slow magnetoacoustic waves in the solar corona

    NASA Astrophysics Data System (ADS)

    Nakariakov, Valery

    2012-07-01

    Quasi-monochromatic propagating disturbances of EUV intensity emission are often detected in fan-like structures and in polar plumes of the solar corona. We demonstrate that the observed characteristics of these propagating disturbances, including the apparent blue-wind asymmetry of the emission line, are consistent with their interpretation in terms of slow magnetoacoustic waves. The propagating waves are well-described by a one-dimensional evolutionary equation that accounts for the effects of thermal conduction and stratification. Moreover, the waves are shown to be a genuine counterpart of 3-min oscillations in the chromospheric slow-magnetoacoustic resonator. It is also found that the leaky slow magnetoacoustic waves provide a link between oscillations in sunspots and quasi-periodic pulsations in a solar flare occurring nearby, suggesting that the waves can play a role of external triggering of the energy release.

  2. On the evolution of dust in the solar vicinity.

    PubMed

    Mann, I; Mukai, T; Okamoto, H

    1995-01-01

    The analysis of interplanetary dust shows that the majority of particles in out-of-ecliptic regions comes from comets and also that near solar dust, in the ecliptic regions, results most probably largely from comets. The intense radiation flux in the solar vicinity is expected to cause strong modifications in the material composition and surface structure of interplanetary dust particles and hence the analysis of near solar dust provides interesting insights into the evolution of meteoritic, especially cometary materials. Because of the lack of in-situ measurements our present knowledge concerning these processes derives from remote sensing, i.e. observations of the solar F-corona. In particular these are observations of albedo, polarization and colour temperature given in terms of average particle properties. For example the analysis of near infra-red F-corona data points to the existence of a strong component of irregularly structured silicate particles, most probably of cometary origin. The data may indicate a subsequent sublimation of different particles or different constituents of the particles. Here we compare particle properties derived from F-corona observations with model calculations of single particle properties and discuss perspectives of future analysis of cometary dust in the interplanetary cloud. PMID:11543534

  3. Magnetohydrodynamic Simulations of the Solar Corona and Solar Wind Using a Boundary Treatment to Limit Solar Wind Mass Flux

    Microsoft Academic Search

    Keiji Hayashi

    2005-01-01

    Magnetohydrodynamic simulations of the solar corona and solar wind are sensitive to conditions in the sub-Alfvénic plasma at the base of the solar corona because the structure of the simulated solar corona is determined by the pressure balance of the plasma and the magnetic field. Therefore, it is important to construct an adequate boundary treatment for the sub-Alfvénic surface, and

  4. Magnetohydrodynamic modeling of the solar corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1990-01-01

    The ideal and resistive magnetohydrodynamic (MHD) model is used to examine the dynamics and structure of the solar corona. When the coronal magnetic field is deformed by photospheric flow it can evolve to states that become unstable to ideal MHD modes. The nonlinear evolution of these instabilities can lead to the generation of current sheets, field line reconnection, and energy release. The disruption of an arcade field and the kinking of coronal loops is described. The braiding of the large-scale coronal field by convective photospheric motions develops fine-scale structure in the magnetic field and leads to the development of intense current filaments. The resistive dissipation of these currents can provide an efficient coronal heating mechanism.

  5. Electron Acceleration in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Mann, G.

    The solar corona is the source of a variety of energetic particles. Energetic electrons are of special interest, as they are the source of nonthermal radio, X-ray, and gamma-ray radiation and are generated by different mechanisms. They can be produced by the electric field in the reconnection site. Magnetic reconnection is considered as the basic process, in which magnetic energy is rapidly converted into plasma heating, mass motions (e. g. jets and coronal mass ejections (CMEs)), electromagnetic radiation, and energetic particles. Furthermore, electrons can be accelerated by shock waves produced either by the pressure impulse due to the initial energy release (flare) or driven ahead CMEs. All these processes are discussed and summarized with respect to their characteristic properties.

  6. Indian Solar mission to study inner solar corona: Aditya 1

    NASA Astrophysics Data System (ADS)

    Singh, Jagdev; Banerjee, Dipankar; Venkatakrishnan, Parameswaran; Kasiviswanathan, Sankarasubramanian; Prasad B, Raghavendra

    2012-07-01

    Aditya-I is India's first dedicated scientific mission to study the sun. This is a low-earth orbit (LEO) mission at an altitude of 800 km. A visible emission line space solar coronagraph (VELC) has been selected as a payload under the small-satellite program of ISRO. It will provide high time cadence sharp images of the solar corona in the Green and Red Emission lines. These images will be used to study the highly dynamic nature of the solar corona including the small-scale coronal loops and large-scale Coronal Mass Ejections (CMEs). The uniqueness of this payload compared to previously flown space instruments are: (a) Observations in the visible wavelength closer to the disk (down to 1.05 solar radii), (b) high time cadence capability (better than 2-images per second), and (c) Simultaneous observations of at least two spectral windows all the time and three spectral windows for short durations. I will update the current status of the project and will point out the complimentary role Aditya can play in conjunction with other solar big missions like SDO.

  7. Where no dust instrument has gone before: Dust science with Solar Probe Plus

    NASA Astrophysics Data System (ADS)

    Rodmann, Jens; Bothmer, Volker; Thernisien, Arnaud

    2015-04-01

    Solar Probe Plus will be a ground-breaking mission to explore the innermost regions of the solar system. By flying down to less than 10 solar radii (~0.05 AU), the mission will greatly enhance our knowledge of the Near-Sun dust environment. This region is governed by a poorly understood interplay of dust delivery by sungrazing comets and radiation forces, the destruction of dust by sublimation, and interactions of dust particles with the ambient coronal plasma. We will focus on two Solar Probe Plus instruments relevant for dust: (1) the Wide-field Imager for SolarPRobe (WISPR), a white-light heliospheric imager dedicated to study the solar wind, coronal mass ejections, and dust-plasma interactions; (2) the FIELDS Experiment aimed at electric and magnetic field measurements in the solar wind, that can also detect telltale voltage signatures of dust-particle impacts on the spacecraft. We will highlight recent simulations of the scattered-light emission from dust particles (F-corona) in order to assess the capabilities of the WISPR instrument to image the dust-free zone around the Sun. We will test whether dust density enhancements as predicted by dynamical simulations can be identified and resolved. Furthermore, we will discuss whether WISPR imagery will allow us to separate composition-dependent sublimation fronts, e.g. for silicates or carbonaceous dust. For FIELDS, we will present predictions for count rates and impact velocities of micron-sized dust particle hits expected over the 7-year mission.

  8. XUV observations of solar corona in the spirit experiment on board the coronas-F satellite

    Microsoft Academic Search

    I. Zhitnik; S. Kuzin; A. Afanas'ev; O. Bugaenko; A. Ignat'ev; V. Krutov; A. Mitrofanov; S. Oparin; A. Pertsov; V. Slemzin; N. Sukhodrev; A. Umov

    2003-01-01

    The images of the solar corona from the limb out to the distance of about 5 solar radii have been obtained for the firs time in the XUV narrow spectral bands and monochromatic lines in the current experiment SPIRIT (SPectroheliographIc soft X-Ray Imaging Telescope). This paper presents the examples of images for the Sun's “quiet” atmosphere as well as for

  9. New Images of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Gurman, Joseph B.; Thompson, Barbara J.; Newmark, Jeffrey A.; Deforest, Craig E.

    In 1.5 years of operation, The Extreme Ultraviolet Imaging Telescope (EIT) on SOHO has obtained over 40,000 images of the Sun in four wavebands between 171 Angstroms and 304 Angstroms, with spatial resolution limited only by the pixel scale of 2.59 arcsec. These images, and in particular compilations of time series of images into digital movies, have changed several of our ideas about the corona at temperatures of 0.9 - 2.5 MK. For the first time, we are able to see outflow in polar plumes and microjets inputting momentum into the high-speed, polar wind flow. For the first time, in conjunction with the LASCO coronagraphs and ground-based He I imagers, we have been able to see all the structures involved in coronal mass ejections (CMEs), from the surface of the Sun to 30 solar radii above it. In several cases, we have been able to observe directly the dramatic Moreton waves emanating from the active region where the CMEs originate, and radiating across virtually the entire visible hemisphere of the Sun. We interpret these large-scale coronal disturbances as fast-mode waves. Such events appear in the SOHO-LASCO coronagraphs as earthward-directed, and several have been detected by solar wind monitoring experiments on SOHO and other spacecraft. We have been able to view a variety of small-scale phenomena as well, including motions in prominences and filaments, macrospicular and polar microjet eruptions, and fine structures in the polar crown filament belt. The multi-wavelength capability of EIT makes it possible to determine the temperature of the coronal plasma and, here, too, we have been afforded a novel view: the heating in coronal active regions occurs over a considerably larger area than the high-density loops structures alone (i.e., bright features) would indicate.

  10. On Stellar Coronae and Solar Active Regions

    NASA Astrophysics Data System (ADS)

    Drake, Jeremy J.; Peres, Giovanni; Orlando, Salvatore; Laming, J. Martin; Maggio, Antonio

    2000-12-01

    Based on Yohkoh Soft X-Ray Telescope (SXT) observations of the Sun near peak activity level obtained on 1992 January 6, we search for coronal structures that have emission measure distributions EM(T) that match the observed stellar coronal emission measure distributions derived for the intermediate-activity stars ? Eri (K2 V) and ? Boo A (G8 V) from Extreme Ultraviolet Explorer spectroscopic observations. We find that the temperatures of the peaks of the observed stellar distributions EM(T), as well as their slopes in the temperature range 6.0<~logT<~6.5, are very similar to those obtained for the brightest of the solar active regions in the 1992 January 6 SXT images. The observed slopes correspond approximately to EM~T? with ?~4, which is much steeper than predicted by static, uniformly heated loop models. Plasma densities in the coronae of ? Eri and ? Boo A are also observed to be essentially the same as the plasma densities typical of solar active regions. These data provide the best observational support yet obtained for the hypothesis that solar-like stars up to the activity levels of ? Eri (K2 V) and ? Boo A are dominated by active regions similar to, though possibly considerably larger than, those observed on the Sun. The surface filling factor of bright active regions needed to explain the observed stellar emission measures is approximately unity. We speculate on the scenario in which small-scale ``nanoflares'' dominate the heating of active regions up to activity levels similar to those of ? Eri (K2 V) and ? Boo A. At higher activity levels still, the interactions of the active regions themselves may lead to increasing flaring on larger scales that is responsible for heating plasma to the observed coronal temperatures of T>~107 K on very active stars. Observations of X-ray and EUV light curves using more sensitive instruments than are currently available, together with determinations of plasma densities over the full range of coronal temperatures (106-107 K and higher), will be important to confirm flare heating hypotheses and to elicit further details concerning coronal structures at solar-like active region temperatures (T<~5×106 K) and the temperatures that characterize the most active stars (T>~107 K).

  11. MAGNETOHYDRODYNAMIC SIMULATIONS OF THE SOLAR CORONA AND SOLAR WIND USING A BOUNDARY TREATMENT TO LIMIT SOLAR WIND MASS FLUX

    E-print Network

    California at Berkeley, University of

    MAGNETOHYDRODYNAMIC SIMULATIONS OF THE SOLAR CORONA AND SOLAR WIND USING A BOUNDARY TREATMENT TO LIMIT SOLAR WIND MASS FLUX Keiji Hayashi W. W. Hansen Experimental Physics Laboratory, Stanford ABSTRACT Magnetohydrodynamic simulations of the solar corona and solar wind are sensitive to conditions

  12. The Extended Solar Cycle Tracked High into the Corona

    E-print Network

    Tappin, S J

    2012-01-01

    We present observations of the extended solar cycle activity in white-light coronagraphs, and compare them with the more familiar features seen in the Fe XIV green-line corona. We show that the coronal activity zones seen in the emission corona can be tracked high into the corona. The peak latitude of the activity, which occurs near solar maximum, is found to be very similar at all heights. But we find that the equatorward drift of the activity zones is faster at greater heights, and that during the declining phase of the solar cycle, the lower branch of activity (that associated with the current cycle) disappears at about 3 Ro. This implies that that during the declining phase of the cycle, the solar wind detected near Earth is likely to be dominated by the next cycle. The so-called "rush to the poles" is also seen in the higher corona. In the higher corona it is found to start at a similar time but at lower latitudes than in the green-line corona. The structure is found to be similar to that of the equatorw...

  13. The origins of hot plasma in the solar corona.

    PubMed

    De Pontieu, B; McIntosh, S W; Carlsson, M; Hansteen, V H; Tarbell, T D; Boerner, P; Martinez-Sykora, J; Schrijver, C J; Title, A M

    2011-01-01

    The Sun's outer atmosphere, or corona, is heated to millions of degrees, considerably hotter than its surface or photosphere. Explanations for this enigma typically invoke the deposition in the corona of nonthermal energy generated by magnetoconvection. However, the coronal heating mechanism remains unknown. We used observations from the Solar Dynamics Observatory and the Hinode solar physics mission to reveal a ubiquitous coronal mass supply in which chromospheric plasma in fountainlike jets or spicules is accelerated upward into the corona, with much of the plasma heated to temperatures between ~0.02 and 0.1 million kelvin (MK) and a small but sufficient fraction to temperatures above 1 MK. These observations provide constraints on the coronal heating mechanism(s) and highlight the importance of the interface region between photosphere and corona. PMID:21212351

  14. Wave dissipation by ion cyclotron resonance in the solar corona

    Microsoft Academic Search

    C.-Y. Tu; E. Marsch

    2001-01-01

    It has recently been suggested that small-scale reconnection occurring in the chromospheric network creates high-frequency Alfvén waves, and that these waves may represent the main energy source for the heating of the solar corona and generation of the solar wind. However, if these waves exist, they will be absorbed preferentially by the minor heavy ions with low gyrofrequencies, and thus

  15. Topological Structure of the Magnetic Solar Corona

    NASA Astrophysics Data System (ADS)

    Maclean, R. C.

    2007-12-01

    The solar corona is a highly complex and active plasma environment, containing many exotic phenomena such as solar flares, coronal mass ejections, prominences, coronal loops, and bright points. The fundamental element giving coherence to all this apparent diversity is the strong coronal magnetic field, the dominant force shaping the plasma there. In this thesis, I model the 3D magnetic fields of various coronal features using the techniques of magnetic charge topology (MCT) in a potential field. Often the real coronal field has departures from its potential state, but these are so small that the potential field method is accurate enough to pick out the essential information about the structure and evolution of the magnetic field. First I perform a topological analysis of the magnetic breakout model for an eruptive solar flare. Breakout is represented by a topological bifurcation that allows initially enclosed flux from the newly emerging region in my MCT model of a delta sunspot to reconnect out to large distances. I produce bifurcation diagrams showing how this behaviour can be caused by changing the strength or position of the emerging flux source, or the force-free parameter ?. I also apply MCT techniques to observational data of a coronal bright point, and compare the results to 3D numerical MHD simulations of the effects of rotating the sources that underlie the bright point. The separatrix surfaces that surround each rotating source are found to correspond to locations of high parallel electric field in the simulations, which is a signature of magnetic reconnection. The large-scale topological structure of the magnetic field is robust to changes in the method of deriving point magnetic sources from the magnetogram. Next, I use a Green's function expression for the magnetic field to relax the standard topological assumption of a flat photosphere and extend the concept of MCT into a spherical geometry, enabling it to be applied to the entire global coronal magnetic field. I perform a comprehensive study of quadrupolar topologies in this new geometry, producing several detailed bifurcation diagrams. These results are compared to the equivalent study for a flat photosphere. A new topological state is found on the sphere which has no flat photosphere analogue; it is named the dual intersecting state because of its twin separators joining a pair of magnetic null points. The new spherical techniques are then applied to develop a simple six-source topological model of global magnetic field reversal during the solar cycle. The evolution of the large-scale global magnetic field is modelled through one complete eleven-year cycle, beginning at solar minimum. Several distinct topological stages are exhibited: active region flux connecting across the equator to produce transequatorial loops; the dominance of first the leading and then the following polarities of the active regions; the magnetic isolation of the poles; the reversal of the polar field; the new polar field connecting back to the active regions; the polar flux regaining its dominance; and the disappearance of the transequatorial loops.

  16. THE 2008 AUGUST 1 ECLIPSE SOLAR-MINIMUM CORONA UNRAVELED

    SciTech Connect

    Pasachoff, J. M. [Department of Planetary Sciences, California Institute of Technology 150-21, Pasadena, CA 91126 (United States); Rusin, V.; Saniga, M.; Minarovjech, M. [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia); Druckmueller, M. [Faculty of Mechanical Engineering, Brno University of Technology, 616 69 Brno (Czech Republic); Aniol, P. [ASTELCO Systems GmbH, Fraunhoferstr. 14, D-82152 Martinsried (Germany)

    2009-09-10

    We discuss the results stemming from observations of the white-light and [Fe XIV] emission corona during the total eclipse of the Sun of 2008 August 1, in Mongolia (Altaj region) and in Russia (Akademgorodok, Novosibirsk, Siberia). Corresponding to the current extreme solar minimum, the white-light corona, visible up to 20 solar radii, was of a transient type with well pronounced helmet streamers situated above a chain of prominences at position angles 48 deg., 130 deg., 241 deg., and 322 deg. A variety of coronal holes, filled with a number of thin polar plumes, were seen around the poles. Furthering an original method of image processing, stars up to 12 mag, a Kreutz-group comet (C/2008 O1) and a coronal mass ejection (CME) were also detected, with the smallest resolvable structures being of, and at some places even less than, 1 arcsec. Differences, presumably motions, in the corona and prominences are seen even with the 19 minutes time difference between our sites. In addition to the high-resolution coronal images, which show the continuum corona (K-corona) that results from electron scattering of photospheric light, images of the overlapping green-emission-line (530.3 nm, [Fe XIV]) corona were obtained with the help of two narrow-passband filters (centered on the line itself and for the continuum in the vicinity of 529.1 nm, respectively), each with an FWHM of 0.15 nm. Through solar observations, on whose scheduling and details we consulted, with the Solar and Heliospheric Observatory, Hinode's XRT and SOT, Transition Region and Coronal Explorer, and STEREO, as well as Wilcox Solar Observatory and Solar and Heliospheric Observatory/Michelson Doppler Imager magnetograms, we set our eclipse observations in the context of the current unusually low and prolonged solar minimum.

  17. Probing the solar corona with very long baseline interferometry

    PubMed Central

    Soja, B.; Heinkelmann, R.; Schuh, H.

    2014-01-01

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on spacecraft tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun’s corona. The VLBI results agree well with previous models from spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike spacecraft tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial–temporal samplings over a complete solar cycle. PMID:24946791

  18. Probing the solar corona with very long baseline interferometry.

    PubMed

    Soja, B; Heinkelmann, R; Schuh, H

    2014-01-01

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on spacecraft tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun's corona. The VLBI results agree well with previous models from spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike spacecraft tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial-temporal samplings over a complete solar cycle. PMID:24946791

  19. Magnetohydrodynamic modeling of the solar corona during Whole Sun Month

    Microsoft Academic Search

    J. A. Linker; Z. Mikic; D. A. Biesecker; R. J. Forsyth; S. E. Gibson; A. J. Lazarus; A. Lecinski; P. Riley; A. Szabo; B. J. Thompson

    1999-01-01

    The Whole Sun Month campaign (August 10 to September 8, 1996) brought together a wide range of space-based and ground-based observations of the Sun and the interplanetary medium during solar minimum. The wealth of data collected provides a unique opportunity for testing coronal models. We develop a three-dimensional magnetohydrodynamic (MHD) model of the solar corona (from 1 to 30 solar

  20. Radio Remote Sensing of the Corona and the Solar Wind

    E-print Network

    Steven R. Spangler; Catherine A. Whiting

    2008-09-26

    Modern radio telescopes are extremely sensitive to plasma on the line of sight from a radio source to the antenna. Plasmas in the corona and solar wind produce measurable changes in the radio wave amplitude and phase, and the phase difference between wave fields of opposite circular polarization. Such measurements can be made of radio waves from spacecraft transmitters and extragalactic radio sources, using radio telescopes and spacecraft tracking antennas. Data have been taken at frequencies from about 80 MHz to 8000 MHz. Lower frequencies probe plasma at greater heliocentric distances. Analysis of these data yields information on the plasma density, density fluctuations, and plasma flow speeds in the corona and solar wind, and on the magnetic field in the solar corona. This paper will concentrate on the information that can be obtained from measurements of Faraday rotation through the corona and inner solar wind. The magnitude of Faraday rotation is proportional to the line of sight integral of the plasma density and the line-of-sight component of the magnetic field. Faraday rotation provides an almost unique means of estimating the magnetic field in this part of space. This technique has contributed to measurement of the large scale coronal magnetic field, the properties of electromagnetic turbulence in the corona, possible detection of electrical currents in the corona, and probing of the internal structure of coronal mass ejections (CMEs). This paper concentrates on the search for small-scale coronal turbulence and remote sensing of the structure of CMEs. Future investigations with the Expanded Very Large Array (EVLA) or Murchison Widefield Array (MWA) could provide unique observational input on the astrophysics of CMEs.

  1. A Spectroscopic Study of the Solar Corona from Norikura and SOHO data

    Microsoft Academic Search

    K. P. Raju; T. Sakurai; K. Ichimoto

    2001-01-01

    We report the results from a spectroscopic study of the solar corona, wherein, we examine some of the current problems in the corona, such as the plume-interplume differences in coronal holes, coronal loops in active regions and wave propagation in the corona. The distribution of emission line intensities, Doppler velocities and line widths in the corona were obtained from the

  2. Time-dependent heating of the solar corona

    Microsoft Academic Search

    R. W. Walsh; G. E. Bell; A. W. Hood

    1995-01-01

    The problem of how the corona is heated is of central importance in solar physics research. Here it is assumed that the heating occurs in a regular time-dependent manner and the response of the plasma is investigated. If the magnetic field is strong then the dynamics reduces to a one-dimensional problem along the field. In addition if the radiative time

  3. Gas-magnetic field interactions in the solar corona

    Microsoft Academic Search

    G. W. Pneuman; Roger A. Kopp

    1971-01-01

    It is evident from eclipse photographs that gas-magnetic field interactions are important in determining the structure and dynamical properties of the solar corona and interplanetary medium. Close to the Sun in regions of strong field, the coronal gas can be contained within closed loop structures. However, since the field in these regions decreases outward rapidly, the pressure and inertial forces

  4. On the formation of current sheets in the solar corona

    Microsoft Academic Search

    Judith T. Karpen; Spiro K. Antiochos; C. Richard Devore

    1990-01-01

    Several theoretical studies have proposed that, in response to photospheric footpoint motions, current sheets can be generated in the solar corona without the presence of a null point in the initial potential magnetic field. A fundamental assumption in these analyses, commonly referred to as the line-tying assumption, is that all coronal field lines are anchored to a boundary surface representing

  5. New Views of the Solar Corona from STEREO and SDO

    NASA Astrophysics Data System (ADS)

    Vourlidas, A.

    2012-01-01

    In the last few years, we have been treated to an unusual visual feast of solar observations of the corona in EUV wavelengths. The observations from the two vantage points of STEREO/SECCHI are now capturing the entire solar atmosphere simultaneously in four wavelengths. The SDO/AIA images provide us with arcsecond resolution images of the full visible disk in ten wavelengths. All these data are captured with cadences of a few seconds to a few minutes. In this talk, I review some intriguing results from our first attempts to deal with these observations which touch upon the problems of coronal mass ejection initiation and solar wind generation. I will also discuss data processing techniques that may help us recover even more information from the images. The talk will contain a generous portion of beautiful EUV images and movies of the solar corona.

  6. A study of the background corona near solar minimum

    Microsoft Academic Search

    Kuniji Saito; Arthur I. Poland; Richard H. Munro

    1977-01-01

    The white light coronagraph data from Skylab is used to investigate the equatorial and polarK andF coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R? during the period of observation (May 1973 to February 1974) lead to the conclusions that: (1) the equatorial corona

  7. Three-dimensional time-dependent MHD simulation model of the solar corona and solar wind

    Microsoft Academic Search

    K. Hayashi

    2006-01-01

    We will present the MHD simulation model for the solar corona and solar wind. The simulation utilizes the solar photospheric magnetic field measurement data as the boundary condition, and the obtained MHD solution is fully matching the given solar surface magnetic field distribution. In order that the simulated situation will be more realistic, the boundary treatment in our code is

  8. Development of three-dimensional magnetohydrodynamic model for solar corona and solar wind simulation

    Microsoft Academic Search

    Xingqiu Yuan; Larisa Trichtchenko; David Boteler

    2010-01-01

    Propagation of coronal mass ejections from solar surface to the Earth magnetosphere is strongly influenced by the conditions in solar corona and ambient solar wind. Thus, reliable simulation of the background solar wind is the primary task toward the development of numerical model for the transient events. In this paper we introduce a new numerical model which has been specifically

  9. Seeing the corona with the solar probe plus mission: the wide-field imager for solar probe+ (WISPR)

    NASA Astrophysics Data System (ADS)

    Vourlidas, Angelos; Howard, Russell A.; Plunkett, Simon P.; Korendyke, Clarence M.; Carter, Michael T.; Thernisien, Arnaud F. R.; Chua, Damien H.; Van Duyne, Peter; Socker, Dennis G.; Linton, Mark G.; Liewer, Paulett C.; Hall, Jeffrey R.; Morrill, Jeff S.; DeJong, Eric M.; Mikic, Zoran; Rochus, Pierre L. P. M.; Bothmer, Volker; Rodman, Jens; Lamy, Philippe

    2013-09-01

    The Solar Probe Plus (SPP) mission scheduled for launch in 2018, will orbit between the Sun and Venus with diminishing perihelia reaching as close as 7 million km (9.86 solar radii) from Sun center. In addition to a suite of in-situ probes for the magnetic field, plasma, and energetic particles, SPP will be equipped with an imager. The Wide-field Imager for the Solar PRobe+ (WISPR), with a 95° radial by 58° transverse field of view, will image the fine-scale coronal structure of the corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. Given the tight mass constrains of the mission, WISPR incorporates an efficient design of two widefield telescopes and their associated focal plane arrays based on novel large-format (2kx2k) APS CMOS detectors into the smallest heliospheric imaging package to date. The flexible control electronics allow WISPR to collect individual images at cadences up to 1 second at perihelion or sum several of them to increase the signal-to-noise during the outbound part of the orbit. The use of two telescopes minimizes the risk of dust damage which may be considerable close to the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first `local' imager providing a crucial link between the large scale corona and the in-situ measurements.

  10. SemiEmpirical 2-D MHD Model of the Solar corona and Solar Wind: Energy Flow in the Corona

    Microsoft Academic Search

    Ed Sittler; Madhullika Guhathakurta; Ruth Skoug

    2001-01-01

    We have developed a semi-empirical 2-D MHD model of the solar corona and solar wind for which the major data inputs are white\\u000a light coronagraph data and plasma and magnetic field data from the Ulysses spacecraft. With regard to the white light coronagraph data we have used data from Spartan 201-05 to construct our empirical\\u000a models of the electron density

  11. Kinetics of Electrons in the Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Vocks, C.; Mann, G.

    2003-09-01

    The velocity distribution functions (VDFs) of electrons as measured in the solar wind show pronounced deviations from a Maxwellian. They seem to be composed of a thermal core and energetic tails, called halo. These VDFs can be fitted very well by kappa distributions. The formation of the energetic tails in the corona or in the solar wind is investigated. The relaxation of a kappa distribution under the influence of Coulomb collisions in the coronal plasma is calculated. This allows an estimation if the energetic tails of the VDFs can be formed in the corona. Resonant interaction between the electrons and electron cyclotron waves is suggested as a mechanism for the generation of the energetic tails. A kinetic model for electrons is presented. Coulomb collisions and wave-particle interactions are considered. With this model, electron VDFs can be calculated from the transition region up into the solar wind.

  12. Rigid and differential rotation of the solar corona

    NASA Technical Reports Server (NTRS)

    Antonucci, E.; Svalgaard, L.

    1974-01-01

    The rotation of the solar corona has been studied using recurrence properties of the green coronal line (5303 A) for the interval from 1947 to 1970. Short-lived coronal activity is found to show the same differential rotation as short-lived photospheric magnetic field features. Long-lived recurrences show rigid rotation in the latitude interval of plus or minus 57.5 deg. It is proposed that at least part of the variability of rotational properties of the solar atmosphere may be understood as a consequence of coexistence of differential and rigid solar rotation.

  13. OBSERVATION OF ULTRAFINE CHANNELS OF SOLAR CORONA HEATING

    SciTech Connect

    Ji, Haisheng [Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, CAS, Nanjing 210008 (China); Cao, Wenda; Goode, Philip R. [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    2012-05-01

    We report the first direct observations of dynamical events originating in the Sun's photosphere and subsequently lighting up the corona. Continuous small-scale, impulsive events have been tracked from their origin in the photosphere on through to their brightening of the local corona. We achieve this by combining high-resolution ground-based data from the 1.6 m aperture New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), and satellite data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The NST imaging observations in helium I 10830 A reveal unexpected complexes of ultrafine, hot magnetic loops seen to be reaching from the photosphere to the base of the corona. Most of these ultrafine loops are characterized by an apparently constant, but surprisingly narrow diameter of about 100 km all along each loop, and the loops originate on the solar surface from intense, compact magnetic field elements. The NST observations detect the signature of upward injections of hot plasma that excite the ultrafine loops from the photosphere to the base of the corona. The ejecta have their individual footpoints in the intergranular lanes between the Sun's ubiquitous, convectively driven granules. In many cases, AIA/SDO detects cospatial and cotemporal brightenings in the overlying, million degree coronal loops in conjunction with the upward injections along the ultrafine loops. Segments of some of the more intense upward injections are seen as rapid blueshifted events in simultaneous H{alpha} blue wing images observed at BBSO. In sum, the observations unambiguously show impulsive coronal heating events from upward energy flows originating from intergranular lanes on the solar surface accompanied by cospatial mass flows.

  14. Coupling Between Chromosphere and Corona: Why it Matters for the Solar Wind

    Microsoft Academic Search

    Lie-Svendsen; V. H. Hansteen; E. Leer

    2001-01-01

    The solar wind is driven by energy input which must be deposited mainly in the corona. In some sense, therefore, the solar wind ``starts'' in the corona, and most solar wind models have their lower boundary here. However, the underlying chromosphere and transition region is not only a ``passive'' supplier of solar wind plasma. Energy must be supplied as well

  15. Observational capabilities of solar satellite "Coronas-Photon"

    NASA Astrophysics Data System (ADS)

    Kotov, Yu.

    Coronas-Photon mission is the third satellite of the Russian Coronas program on solar activity observation The main goal of the Coronas-Photon is the study of solar hard electromagnetic radiation in the wide energy range from UV up to high energy gamma-radiation sim 2000MeV Scientific payload for solar radiation observation consists of three type of instruments 1 monitors Natalya-2M Konus-RF RT-2 Penguin-M BRM Phoka Sphin-X Sokol for spectral and timing measurements of full solar disk radiation with timing in flare burst mode up to one msec Instruments Natalya-2M Konus-RF RT-2 will cover the wide energy range of hard X-rays and soft Gamma rays 15keV to 2000MeV and will together constitute the largest area detectors ever used for solar observations Detectors of gamma-ray monitors are based on structured inorganic scintillators with energy resolution sim 5 for nuclear gamma-line band to 35 for GeV-band PSD analysis is used for gamma neutron separation for solar neutron registration T 30MeV Penguin-M has capability to measure linear polarization of hard X-rays using azimuth are measured by Compton scattering asymmetry in case of polarization of an incident flux For X-ray and EUV monitors the scintillation phoswich detectors gas proportional counter CZT assembly and Filter-covered Si-diodes are used 2 Telescope-spectrometer TESIS for imaging solar spectroscopy in X-rays with angular resolution up to 1 in three spectral lines and RT-2 CZT assembly of CZT

  16. Magnetic fields and the structure of the solar corona

    Microsoft Academic Search

    Martin D. Altschuler; Gordon Newkirk

    1969-01-01

    Several different mathematical methods are described which use the observed line-of-sight component of the photospheric magnetic field to determine the magnetic field of the solar corona in the current-free (or potential-field) approximation. Discussed are (1) a monopole method, (2) a Legendre polynomial expansion assuming knowledge of the radial photospheric magnetic field, (3) a Legendre polynomial expansion obtained from the line-of-sight

  17. ESTIMATING THE ''DARK'' ENERGY CONTENT OF THE SOLAR CORONA

    SciTech Connect

    McIntosh, Scott W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); De Pontieu, Bart, E-mail: mscott@ucar.edu [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover St., Org. A021S, Bldg. 252, Palo Alto, CA 94304 (United States)

    2012-12-20

    The discovery of ubiquitous low-frequency (3-5 mHz) Alfvenic waves in the solar chromosphere (with Hinode/Solar Optical Telescope) and corona (with CoMP and SDO) has provided some insight into the non-thermal energy content of the outer solar atmosphere. However, many questions remain about the true magnitude of the energy flux carried by these waves. Here we explore the apparent discrepancy in the resolved coronal Alfvenic wave amplitude ({approx}0.5 km s{sup -1}) measured by the Coronal Multi-channel Polarimeter (CoMP) compared to those of the Hinode and the Solar Dynamics Observatory (SDO) near the limb ({approx}20 km s{sup -1}). We use a blend of observational data and a simple forward model of Alfvenic wave propagation to resolve this discrepancy and determine the Alfvenic wave energy content of the corona. Our results indicate that enormous line-of-sight superposition within the coarse spatio-temporal sampling of CoMP hides the strong wave flux observed by Hinode and SDO and leads to the large non-thermal line broadening observed. While this scenario has been assumed in the past, our observations with CoMP of a strong correlation between the non-thermal line broadening with the low-amplitude, low-frequency Alfvenic waves observed in the corona provide the first direct evidence of a wave-related non-thermal line broadening. By reconciling the diverse measurements of Alfvenic waves, we establish large coronal non-thermal line widths as direct signatures of the hidden, or ''dark'', energy content in the corona and provide preliminary constraints on the energy content of the wave motions observed.

  18. Weak compressible magnetohydrodynamic turbulence in the solar corona

    E-print Network

    Benjamin D. G. Chandran

    2005-11-21

    This Letter presents a calculation of the power spectra of weakly turbulent Alfven waves and fast magnetosonic waves ("fast waves") in low-beta plasmas. It is shown that three-wave interactions transfer energy to high-frequency fast waves and, to a lesser extent, high-frequency Alfven waves. MHD turbulence is thus a promising mechanism for producing the high-frequency waves needed to explain the anisotropic heating of minor ions in the solar corona.

  19. Collisional damping of surface waves in the solar corona

    NASA Technical Reports Server (NTRS)

    Gordon, B. E.; Hollweg, J. V.

    1982-01-01

    The damping of surface waves by viscosity and heat conduction is evaluated. For the solar corona, it is found that surface waves dissipate efficiently only if their periods are shorter than a few tens of seconds and only if the background magnetic field is less than about 10 Gauss. Heating of quiet coronal regions is possible if the coronal waves have short periods, but they cannot heat regions of strong magnetic field, such as coronal active region loops.

  20. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1998-01-01

    Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the period covered by this report we have published 17 articles in the scientific literature. These publications are listed in Section 4 of this report. In the Appendix we have attached reprints of selected articles.

  1. Alfvénic waves with sufficient energy to power the quiet solar corona and fast solar wind.

    PubMed

    McIntosh, Scott W; De Pontieu, Bart; Carlsson, Mats; Hansteen, Viggo; Boerner, Paul; Goossens, Marcel

    2011-07-28

    Energy is required to heat the outer solar atmosphere to millions of degrees (refs 1, 2) and to accelerate the solar wind to hundreds of kilometres per second (refs 2-6). Alfvén waves (travelling oscillations of ions and magnetic field) have been invoked as a possible mechanism to transport magneto-convective energy upwards along the Sun's magnetic field lines into the corona. Previous observations of Alfvénic waves in the corona revealed amplitudes far too small (0.5?km?s(-1)) to supply the energy flux (100-200?W?m(-2)) required to drive the fast solar wind or balance the radiative losses of the quiet corona. Here we report observations of the transition region (between the chromosphere and the corona) and of the corona that reveal how Alfvénic motions permeate the dynamic and finely structured outer solar atmosphere. The ubiquitous outward-propagating Alfvénic motions observed have amplitudes of the order of 20?km?s(-1) and periods of the order of 100-500?s throughout the quiescent atmosphere (compatible with recent investigations), and are energetic enough to accelerate the fast solar wind and heat the quiet corona. PMID:21796206

  2. A Technique for Measuring Electrical Currents in the Solar Corona

    E-print Network

    Steven R. Spangler

    2007-09-11

    A technique is described for measuring electrical currents in the solar corona. It uses radioastronomical polarization measurements of a spatially-extended radio source viewed through the corona. The observations yield the difference in the Faraday rotation measure between two closely-spaced lines of sight through the corona, a measurement referred to as {\\em differential Faraday rotation}. It is shown that the expression for differential Faraday rotation is proportional to the path integral $\\oint n \\vec{B}\\cdot \\vec{ds}$ where $n$ is the plasma density and $\\vec{B}$ is the coronal magnetic field. The integral is around a closed loop (Amperian Loop) in the corona. If the plasma density is assumed roughly constant, the differential Faraday rotation is proportional to the current within the loop, via Ampere's Law. The validity of the constant density approximation is discussed, and two test cases are presented in which the associated error in the inferred current is small, of order tens of percent or less. The method is illustrated with observations of the radio source 3C228 with the Very Large Array (VLA) in August, 2003. A measurement of a differential Faraday rotation ``event'' on August 16, 2003, yields an estimate of $2.5 \\times 10^9$ Amperes in the Amperian Loop. A smaller event on August 18 yields an enclosed current of $2.3 \\times 10^8$ Amperes. The implications of these currents for coronal heating are briefly discussed.

  3. Energy distribution of nanoflares in the quiet solar corona

    NASA Astrophysics Data System (ADS)

    Ulyanov, Artyom

    2012-07-01

    We present a detailed statistical analysis of flare-like events in low layer of solar corona detected with TESIS instrument onboard CORONAS-PHOTON satellite in 171 {Ĺ} during high-cadence (5 sec) time-series. The estimated thermal energies of these small events amount to 10^{23} - 10^{26} erg. According to modern classification flare-like events with such energies are usually referred to as nanoflares. The big number of registered events (above 2000) allowed us to obtain precise distributions of geometric and physical parameters of nanoflares, the most intriguing being energy distribution. Following Aschwanden et al. (2000) and other authors we approximated the calculated energy distribution with a single power law slope: N(E)dE ˜ N^{-?}dE. The power law index was derived to be ? = 2.4 ą 0.2, which is very close to the value reported by Krucker & Benz (1998): ? ? 2.3 - 2.4. The total energy input from registered events constitute about 10^4 erg \\cdot cm^{-2} \\cdot s^{-1}, which is well beyond net losses in quiet corona (3 \\cdot 10^5 erg \\cdot cm^{-2} \\cdot s^{-1}). However, the value of ? > 2 indicates that nanoflares with lower energies dominate over nanoflares with bigger energies and could contribute considerably to quiet corona heating.

  4. A view of solar magnetic fields, the solar corona, and the solar wind in three dimensions

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.; Wilcox, J. M.

    1978-01-01

    In the last few years it has been recognized that the solar corona and the solar wind are three-dimensional. The deviations from spherical or even cylindrical symmetry are first-order effects, which are important for a basic description and physical understanding of the coronal expansion. Models of coronal magnetic fields are considered along with the characteristics of large-scale solar structure, the interplanetary magnetic field, coronal holes, geomagnetic activity, cosmic rays, and polar fields of the sun. It is pointed out that the present understanding of coronal and interplanetary morphology is based on data acquired during the descending part and the minimum of the considered sunspot cycle.

  5. A naturally driven reconnection mechanism for the solar corona

    NASA Astrophysics Data System (ADS)

    Lapenta, G.; Knoll, D.

    2002-12-01

    Reconnection in the solar corona is believed to be important for a series of processes from flares and CMEs to coronal heating. However, theoretical understanding of the reconnection process still remains elusive. The reconnection rate predicted by the Sweet-Parker model is determined by resistivity and is very many orders of magnitude too small to explain the observations. A possible mechanism that can provide fast reconnection rate is driven reconnection, When external flows drive field lines together, the rate of reconnection is determined by the driving mechanism and is indipendent of resistivity. In related works applied to the Earth's magnetopause [1], it as been shown that a Kelvin Helmholtz instability (KHI) can cause local compressive motions that push field lines together and drive reconnection. We propose here that the same mechanism could conceivably be at work in the solar corona. We propose that photospheric motions cause torsional Alfven waves that propagate in the chromosphere and are amplified in the transition regions, emerging as sizabe velocity shears in the solar corona. Simulaiton works have proposed that such shear can be amplified to a good fraction (e.g. 0.3) of the Alfven speed [2]. The velocity shear injected in the corona can cause magnetic loops previously stressed by photospheric motions [3] to reconnect. We have conducted a series of simulation to prove this scenario and to observe the properties of the reconneciton process. We have shown that indeed reconnection can be achieved trough local compression driven by the KHI and that the reconnection rate in that case is not sensitive to resistivity. [1] Brackbill, J.U., Knoll, D.A., Phys. Rev. Lett., 86, 2329 (2001) [2] Kudoh, T., Shibata K., Ap. J., 514, 493 (1999) [3] Mikic, Z., Barnes, D.C., Schnack, D.D., Ap. J., 328, 830 (1988)

  6. Observaciones de la corona solar interior con un coronógrafo de espejo

    Microsoft Academic Search

    G. Stenborg; R. Schwenn; C. Francile; M. Rovira

    1999-01-01

    El plasma de la corona solar es un buen indicador de las líneas de fuerza del campo magnético. Por lo tanto, el análisis de estructuras coronales cuasiestacionarias en la corona da importante información sobre el campo magnético y la actividad asociada. Se trata de poner límites a los modelos teóricos existentes mediante el estudio de distintas estructuras en la corona

  7. Joule Heating and Anomalous Resistivity in the Solar Corona

    E-print Network

    Steven R. Spangler

    2008-12-22

    Recent radioastronomical observations of Faraday rotation in the solar corona can be interpreted as evidence for coronal currents, with values as large as $2.5 \\times 10^9$ Amperes (Spangler 2007). These estimates of currents are used to develop a model for Joule heating in the corona. It is assumed that the currents are concentrated in thin current sheets, as suggested by theories of two dimensional magnetohydrodynamic turbulence. The Spitzer result for the resistivity is adopted as a lower limit to the true resistivity. The calculated volumetric heating rate is compared with an independent theoretical estimate by Cranmer et al (2007). This latter estimate accounts for the dynamic and thermodynamic properties of the corona at a heliocentric distance of several solar radii. Our calculated Joule heating rate is less than the Cranmer et al estimate by at least a factor of $3 \\times 10^5$. The currents inferred from the observations of Spangler (2007) are not relevant to coronal heating unless the true resistivity is enormously increased relative to the Spitzer value. However, the same model for turbulent current sheets used to calculate the heating rate also gives an electron drift speed which can be comparable to the electron thermal speed, and larger than the ion acoustic speed. It is therefore possible that the coronal current sheets are unstable to current-driven instabilities which produce high levels of waves, enhance the resistivity and thus the heating rate.

  8. Release timescales of solar energetic particles in the low corona

    NASA Astrophysics Data System (ADS)

    Agueda, N.; Klein, K.-L.; Vilmer, N.; Rodríguez-Gasén, R.; Malandraki, O. E.; Papaioannou, A.; Subirŕ, M.; Sanahuja, B.; Valtonen, E.; Dröge, W.; Nindos, A.; Heber, B.; Braune, S.; Usoskin, I. G.; Heynderickx, D.; Talew, E.; Vainio, R.

    2014-10-01

    Aims: We present a systematic study of the timing and duration of the release processes of near-relativistic (NR; >50 keV) electrons in the low corona. Methods: We analyze seven well-observed events using in situ measurements by both the ACE and Wind spacecraft and context electromagnetic observations in soft X-rays, radio, hard X-rays and white light. We make use of velocity dispersion analysis to estimate the release time of the first arriving electrons and compare with the results obtained by using a simulation-based approach, taking interplanetary transport effects into account to unfold the NR electron release time history from in situ measurements. Results: The NR electrons observed in interplanetary space appear to be released during either short (<30 min) or long (>2 h) periods. The observation of NR electron events showing beamed pitch-angle distributions (PADs) during several hours is the clearest observational signature of sustained release in the corona. On the other hand, the in situ observation of PADs isotropizing in less than a couple of hours is a clear signature of a prompt release of electrons in the low corona. Short release episodes appear to originate in solar flares, in coincidence with the timing of the observed type III radio bursts. Magnetic connectivity plays an important role. Only type III radio bursts reaching the local plasma line measured at 1 AU are found to be related with an associated release episode in the low corona. Other type III bursts may also have a release of NR electrons associated with them, but these electrons do not reach L1. Long release episodes appear associated with signatures of long acceleration processes in the low corona (long decay of the soft X-ray emission, type IV radio bursts, and time-extended microwave emission). Type II radio bursts are reported for most of the events and do not provide a clear discrimination between short and long release timescales.

  9. Diagnosing the Prominence-Cavity Connection in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Schmit, D. J.

    The energetic equilibrium of the corona is described by a balance of heating, thermal conduction, and radiative cooling. Prominences can be described by the thermal instability of coronal energy balance which leads to the formation of cool condensations. Observationally, the prominence is surrounded by a density depleted elliptical structure known as a cavity. In this dissertation, we use extreme ultraviolet remote sensing observations of the prominence-cavity system to diagnose the static and dynamic properties of these structures. The observations are compared with numerical models for the time-dependent coronal condensation process and the time-independent corona-prominence magnetic field. To diagnose the density of the cavity, we construct a three-dimensional structural model of the corona. This structural model allows us to synthesize extreme ultraviolet emission in the corona in a way that incorporates the projection effects which arise from the optically thin plasma. This forward model technique is used to constrain a radial density profile simultaneously in the cavity and the streamer. We use a ?2 minimization to find the density model which best matches a density sensitive line ratio (observed with Hinode/Extreme ultraviolet Imaging Spectrometer) and the white light scattered intensity (observed with Mauna Loa Solar Observatory MK4 coronagraph). We use extreme ultraviolet spectra and spectral images to diagnose the dynamics of the prominence and the surrounding corona. Based on the doppler shift of extreme ultraviolet coronal emission lines, we find that there are large regions of flowing plasma which appear to occur within cavities. These line of sight flows have speeds of 10 km/s-1 and projected spatial scales of 100 Mm. Using the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) dataset, we observe dynamic emission from the prominence-cavity system. The SDO/AIA dataset observes multiple spectral bandpasses with different temperature sensitivities. Time-dependent changes in the observed emission in these bandpass images represent changes in the thermodynamic properties of the emitting plasma. We find that the coronal region surrounding the prominence exhibits larger intensity variations (over tens of hours of observations) as compared to the streamer region. This variability is particularly strong in the cool coronal emission of the 171Ĺ bandpass. We identify the source of this variability as strong brightening events that resemble concave-up loop segments and extend from the cool prominence plasma. Magnetic field lines are the basic structural building block of the corona. Energy and pressure balance in the corona occur along magnetic field lines. The large-scale extreme ultraviolet emission we observe in the corona is a conglomerate of many coronal loops projected along a line of sight. In order to calculate the plasma properties at a particular point in the corona, we use one-dimensional models for energy and pressure balance along field lines. In order to predict the extreme ultraviolet emission along a particular line of sight, we project these one-dimensional models onto the three-dimensional magnetic configuration provided by a MHD model for the coronal magnetic field. These results have allowed us to the establish the first comprehensive picture on the magnetic and energetic interaction of the prominence and the cavity. While the originally hypothesis that the cavity supplies mass to the prominence proved inaccurate, we cannot simply say that these structures are not related. Rather our findings suggest that the prominence and the cavity are distinct magnetic substructures that are complementary regions of a larger whole, specifically a magnetic flux rope. (Abstract shortened by UMI.).

  10. Generalized similarity in magnetohydrodynamic turbulence as seen in the solar corona and solar wind

    Microsoft Academic Search

    S. C. Chapman; E. Leonardis; R. M. Nicol; C. Foullon

    2010-01-01

    A key property of turbulence is that it can be characterized and quantified in a robust and reproducible way in terms of the ensemble averaged statistical properties of fluctuations. Importantly, fluctuations associated with a turbulent field show similarity or scaling in their statistics and we test for this in observations of magnetohydrodynamic turbulence in the solar corona and solar wind

  11. Wave Energy Deposition in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Van Doorsselaere, Tom; Goossens, Marcel; Verth, Gary; Soler, Roberto; Gijsen, Stief; Andries, Jesse

    Recently, a significant amount of transverse wave energy has been estimated propagating along solar atmospheric magnetic fields. However, these estimates have been made with the classic bulk Alfven wave model which assumes a homogeneous plasma. In this talk, the kinetic, magnetic, and total energy densities and the flux of energy are first computed for transverse MHD waves in one-dimensional cylindrical flux tube models with a piecewise constant density profile. There are fundamental deviations from the properties for classic bulk Alfven waves. (1) There is no local equipartition between kinetic and magnetic energy. (2) The flux of energy and the velocity of energy transfer have, in addition to a component parallel to the magnetic field, components in the planes normal to the magnetic field. (3) The energy densities and the flux of energy vary spatially, contrary to the case of classic bulk Alfven waves. This last property is then used to connect the energy flux in such a simple model to the energy flux in multiple flux tube systems. We use the plasma filling factor f to derive an ad-hoc formula for estimating the energy that is propagated in bundles of loops. We find that the energy flux in kink waves is lower than the energy computed from a bulk Alfven wave interpretation, by a factor that is (approximately) between f and 2f. We consider some geometric models to quantify this correction factor.

  12. Radio sounding of the solar corona during 1995 solar conjunction of the Ulysses spacecraft

    NASA Technical Reports Server (NTRS)

    Bird, M. K.; Paetzold, M.; Karl, J.; Edenhofer, P.; Asmar, S. W.

    1995-01-01

    The Ulysses spacecraft will pass through superior solar conjunction on March 5 1995, a few days before its perihelion and passage through the ecliptic plane. Dual-frequency S/X-band ranging and Doppler observations will be conducted in support of the Ulysses Solar Corona Experiment (SCE) during a three-week interval centered on the conjunction. The occultation geometry is unique in the annals of interplanetary exploration. As viewed from Earth, the spacecraft will appear to cut diagonally through the southwest quadrant of the solar corona from the South Pole to the equator. The minimum proximate distance to the Sun of the radio ray path will be 21.6 solar radius. The entire latitude scan from pole to equator occurs for a limited range of solar offset distances (is less than 30 solar radius thus facilitating the separation of latitudinal from radial variations in the coronal density and associated parameters of interest.

  13. Current driven low-frequency electrostatic waves in the solar corona: Linear theory and nonlinear saturation

    Microsoft Academic Search

    Kuang Wu Lee; Jörg Büchner; Nina Elkina

    2007-01-01

    Important solar physical problems such as the heating of the corona, reconnection, and electron acceleration might be related to current-driven plasma waves, especially at low frequencies, where, perhaps, most of the wave power is concentrated. Since a direct observation of plasma waves in the solar corona is impossible, theoretical investigations are needed to clarify the possibilities of their excitation, of

  14. Solar Corona Sounders: A radio-science mission to the sun

    Microsoft Academic Search

    M. Pätzold; F. M. Neubauer; B. Häusler; W. Eidel; M. K. Bird

    1996-01-01

    The Solar Corona Sounders (SCS) mission proposal, a mission for radio sounding the inner solar corona, was submitted to ESA in response to the agency's call for new mission concepts. Two small identical spacecraft are placed at the “Anti-Earth” position with orbital elements slightly different from those of the Earth. As viewed from ground-based tracking stations, the two radially aligned

  15. The Soft XRay/Microwave Ratio of Solar and Stellar Flares and Coronae

    E-print Network

    Guedel, Manuel

    as thermal radiations of coronal plasmas. On the other hand, the microwave emission of stars and solar flares. Some coronae of active stars of late spectral type are detected microwave sources. The microwaveThe Soft X­Ray/Microwave Ratio of Solar and Stellar Flares and Coronae A. O. Benz Institute

  16. Interstellar Dust in the Solar System

    E-print Network

    Harald Krueger; Markus Landgraf; Nicolas Altobelli; Eberhard Gruen

    2007-06-21

    The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse almost perpendicular to the ecliptic plane (inclination 79 deg, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. The in-situ dust detector on board continuously measured interstellar dust grains with masses up to 10^-13 kg, penetrating deep into the solar system. The flow direction is close to the mean apex of the Sun's motion through the solar system and the grains act as tracers of the physical conditions in the local interstellar cloud (LIC). While Ulysses monitored the interstellar dust stream at high ecliptic latitudes between 3 and 5 AU, interstellar impactors were also measured with the in-situ dust detectors on board Cassini, Galileo and Helios, covering a heliocentric distance range between 0.3 and 3 AU in the ecliptic plane. The interstellar dust stream in the inner solar system is altered by the solar radiation pressure force, gravitational focussing and interaction of charged grains with the time varying interplanetary magnetic field. We review the results from in-situ interstellar dust measurements in the solar system and present Ulysses' latest interstellar dust data. These data indicate a 30 deg shift in the impact direction of interstellar grains w.r.t. the interstellar helium flow direction, the reason of which is presently unknown.

  17. Corongraphic Observations and Analyses of The Ultraviolet Solar Corona

    NASA Technical Reports Server (NTRS)

    Kohl, John L.

    2000-01-01

    The activities supported under NASA Grant NAG5-613 included the following: 1) reduction and scientific analysis of data from three sounding rocket flights of the Rocket Ultraviolet Coronagraph Spectrometer, 2) development of ultraviolet spectroscopic diagnostic techniques to provide a detailed empirical description of the extended solar corona, 3) extensive upgrade of the rocket instrument to become the Ultraviolet Coronal Spectrometer (UVCS) for Spartan 201,4) instrument scientific calibration and characterization, 5) observation planning and mission support for a series of five Spartan 201 missions (fully successful except for STS 87 where the Spartan spacecraft was not successfully deployed and the instruments were not activated), and 6) reduction and scientific analysis of the UVCS/Spartan 201 observational data. The Ultraviolet Coronal Spectrometer for Spartan 201 was one unit of a joint payload and the other unit was a White Light Coronagraph (WLC) provided by the High Altitude Observatory and the Goddard Space Flight Center. The two instruments were used in concert to determine plasma parameters describing structures in the extended solar corona. They provided data that could be used individually or jointly in scientific analyses. The WLC provided electron column densities in high spatial resolution and high time resolution. UVCS/Spartan provided hydrogen velocity distributions, and line of sight hydrogen velocities. The hydrogen intensities from UVCS together with the electron densities from WLC were used to determine hydrogen outflow velocities. The UVCS also provided O VI intensities which were used to develop diagnostics for velocity distributions and outflow velocities of minor ions.

  18. Coronagraphic observations and analyses of the ultraviolet solar corona

    NASA Technical Reports Server (NTRS)

    Kohl, John L.

    1994-01-01

    This status report for the period 1 October 1992 to 30 September 1994 covers the final preparation and first observations with the Spartan Ultraviolet Coronal Spectrometer on Spartan 201-1, and the preparation and second flight for Spartan 201-2. Both flights were fully successful and resulted in high quality spectroscopic observations of the extended solar corona out to 3.5 solar radii from Sun-center. The primary focus of this report is the results from Spartan 201-1. There is also a brief description of the evaluation of the quick look data from the second flight. Highlights from the first flight include a discovery that the proton velocity distribution in coronal holes is complex and consists of a central core with elevated high velocity wings compared to a Gaussian shape.

  19. Dust Accumulation on MER Solar Panels

    NASA Astrophysics Data System (ADS)

    Guinness, E. A.; Arvidson, R. E.; McEwen, A. S.; Cull, S.

    2011-12-01

    HiRISE acquired in March 2011 a color image of the Spirit Mars Exploration Rover from orbit that shows an exceptionally bright reflection from the rover solar panels. HiRISE data combined with laboratory measurements of MER solar cell reflectance provide a method for constraining the thickness of dust on the solar panels. Spirit is the brightest object in the HiRISE scene with a reflectance that is about 3 times higher at 500 nm and about 1.5 times higher at 700 and 850 nm than bright outcrop and soil near the rover. The rover is also less red than these nearby materials and less red than a typical Mars dust spectrum modeled with the same geometry and seen through similar atmospheric conditions as the HiRISE image. Lighting and viewing angles for the HiRISE image of Spirit are close to a specular reflection geometry when factoring in the rover orientation, the sun position, and the location of HiRISE during image acquisition. Laboratory photometric measurements of clean and dust-coated MER solar cells show a strong specular reflection for dust coating thicknesses up to at least 45 micrometers. The specular reflection was not present in the laboratory data when the solar cell was covered with about a 135 micrometer thick layer. The dust used in the experiments consisted of less than 10 micrometer sized particles derived from a palagonitic tephra from Mauna Kea that is spectrally similar to Mars dust. A survey of MER Pancam color images acquired by Spirit and Opportunity also shows several examples of specular reflections from the solar panels. These examples correspond to times when the solar cells were moderately clean to dusty as inferred from the amount of power generated by the cells. Specular reflections in Pancam images have been observed when the solar cell output was only 45% that of a dust-free cell. Spirit HiRISE data indicate that the rover was not covered by an optical thick layer of dust because some of the reflected light must have come from the underlying solar panels. The laboratory and HiRISE data suggest that the Spirit solar panels may have had a dust layer on the order of only 10s of micrometers thick. Further investigation of rover image data sets for the presence or absence of specular reflections as correlated with solar cell power output will yield more quantitative information on the amounts of atmospheric dust accumulation throughout the Spirit and Opportunity missions.

  20. A study of acoustic heating and forced convection in the solar corona

    NASA Technical Reports Server (NTRS)

    Foukal, P. V.

    1980-01-01

    The S055 EUV spectra was used to perform emission measure and line intensity ratio analyses of loop plasma conditions in a study on the thermodynamics of magnetic loops in the solar corona. The evidence that loops contain plasma hotter than the background corona, and thus, require enhanced local dissipation of magnetic or mechanical energy is discussed. The S055 EUV raster pictures were used to study physical conditions in cool ultraviolet absorbing clouds in the solar corona, and optical data were used to derive constraints on the dimension, time scales and optical depths in dark opaque clouds not seen in H alpha and CaK as filaments or prominences. Theoretical modelling of propagation of magnetically guided acoustic shocks in the solar chromosphere finds it still unlikely that high frequency acoustic shocks could reach the solar corona. Dynamic modelling of spicules shows that such guided slow mode shocks can explain the acceleration of cool spicular material seen high in the corona.

  1. Constant cross section of loops in the solar corona

    NASA Astrophysics Data System (ADS)

    Peter, H.; Bingert, S.

    2012-12-01

    Context. The corona of the Sun is dominated by emission from loop-like structures. When observed in X-ray or extreme ultraviolet emission, these million K hot coronal loops show a more or less constant cross section. Aims: In this study we show how the interplay of heating, radiative cooling, and heat conduction in an expanding magnetic structure can explain the observed constant cross section. Methods: We employ a three-dimensional magnetohydrodynamics (3D MHD) model of the corona. The heating of the coronal plasma is the result of braiding of the magnetic field lines through footpoint motions and subsequent dissipation of the induced currents. From the model we synthesize the coronal emission, which is directly comparable to observations from, e.g., the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (AIA/SDO). Results: We find that the synthesized observation of a coronal loop seen in the 3D data cube does match actually observed loops in count rate and that the cross section is roughly constant, as observed. The magnetic field in the loop is expanding and the plasma density is concentrated in this expanding loop; however, the temperature is not constant perpendicular to the plasma loop. The higher temperature in the upper outer parts of the loop is so high that this part of the loop is outside the contribution function of the respective emission line(s). In effect, the upper part of the plasma loop is not bright and thus the loop actually seen in coronal emission appears to have a constant width. Conclusions: From this we can conclude that the underlying field-line-braiding heating mechanism provides the proper spatial and temporal distribution of the energy input into the corona - at least on the observable scales. Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org

  2. Convective Instability Of The Solar Corona: Why The Solar Wind Blows

    Microsoft Academic Search

    Joseph Lemaire

    2010-01-01

    Chapman's conductive model of the solar corona is characterized by a temperature varying as r-2\\/7 with heliocentric distance r. The density distribution in this non-isothermal hydrostatic model has a minimum value at 123 RS, and increases with r above that altitude. It is shown that this hydrostatic model becomes convectively unstable above r = 35 RS, where the temperature lapse

  3. RADIO OBSERVATIONS OF WEAK ENERGY RELEASES IN THE SOLAR CORONA

    SciTech Connect

    Ramesh, R.; Kathiravan, C.; Barve, Indrajit V. [Indian Institute of Astrophysics, Bangalore 560 034 (India); Beeharry, G. K.; Rajasekara, G. N., E-mail: ramesh@iiap.res.i [University of Mauritius, Reduit (Mauritius)

    2010-08-10

    We report observations of weak, circularly polarized, structureless type III bursts from the solar corona in the absence of H{alpha}/X-ray flares and other related activity, during the minimum between the sunspot cycles 23 and 24. The spectral information about the event obtained with the CALLISTO spectrograph at Mauritius revealed that the drift rate of the burst is {approx}-30 MHz s{sup -1} is in the range 50-120 MHz. Two-dimensional imaging observations of the burst at 77 MHz obtained with the Gauribidanur radioheliograph indicate that the emission region was located at a radial distance of {approx}1.5 R{sub sun} in the solar atmosphere. The estimated peak brightness temperature of the burst at 77 MHz is {approx}10{sup 8} K. We derived the average magnetic field at the aforementioned location of the burst using the one-dimensional (east-west) Gauribidanur radio polarimeter at 77 MHz, and the value is {approx}2.5 {+-} 0.2 G. We also estimated the total energy of the non-thermal electrons responsible for the observed burst as {approx}1.1 x 10{sup 24} erg. This is low compared to the energy of the weakest hard X-ray microflares reported in the literature, which is about {approx}10{sup 26} erg. The present result shows that non-thermal energy releases that correspond to the nanoflare category (energy {approx}10{sup 24} erg) are taking place in the solar corona, and the nature of such small-scale energy releases has not yet been explored.

  4. The Expansion of Active Regions into the Extended Solar Corona

    NASA Astrophysics Data System (ADS)

    Morgan, Huw; Jeska, Lauren; Leonard, Drew

    2013-06-01

    Advanced image processing of Large Angle and Spectrometric Coronagraph Experiment (LASCO) C2 observations reveals the expansion of the active region closed field into the extended corona. The nested closed-loop systems are large, with an apparent latitudinal extent of 50°, and expanding to heights of at least 12 R ?. The expansion speeds are ~10 km s-1 in the AIA/SDO field of view, below ~20 km s-1 at 2.3 R ?, and accelerate linearly to ~60 km s-1 at 5 R ?. They appear with a frequency of one every ~3 hr over a time period of around three days. They are not coronal mass ejections (CMEs) since their gradual expansion is continuous and steady. They are also faint, with an upper limit of 3% of the brightness of background streamers. Extreme ultraviolet images reveal continuous birth and expansion of hot, bright loops from a new active region at the base of the system. The LASCO images show that the loops span a radial fan-like system of streamers, suggesting that they are not propagating within the main coronal streamer structure. The expanding loops brighten at low heights a few hours prior to a CME eruption, and the expansion process is temporarily halted as the closed field system is swept away. Closed magnetic structures from some active regions are not isolated from the extended corona and solar wind, but can expand to large heights in the form of quiescent expanding loops.

  5. Radio sounding of the solar corona during 1995 solar conjunction of the ULYSSES spacecraft

    Microsoft Academic Search

    M. K. Bird; M. Paetzold; J. Karl; P. Edenhofer; S. W. Asmar

    1995-01-01

    The Ulysses spacecraft will pass through superior solar conjunction on March 5 1995, a few days before its perihelion and passage through the ecliptic plane. Dual-frequency S\\/X-band ranging and Doppler observations will be conducted in support of the Ulysses Solar Corona Experiment (SCE) during a three-week interval centered on the conjunction. The occultation geometry is unique in the annals of

  6. Simultaneous Observation of High Temperature Plasma of Solar Corona By TESIS CORONAS-PHOTON and XRT Hinode.

    NASA Astrophysics Data System (ADS)

    Reva, A.; Kuzin, S.; Bogachev, S.; Shestov, S.

    2012-05-01

    The Mg XII spectroheliograph is a part of instrumentation complex TESIS (satellite CORONAS-PHOTON). This instrument builds monochromatic images of hot plasma of the solar corona (? = 8.42 Ĺ, T>5 MK). The Mg XII spectroheliograph observed hot plasma in the non-flaring active-region NOAA 11019 during nine days. We reconstructed DEM of this active region with the help of genetic algorithm (we used data of the Mg XII spectroheliograph, XRT and EIT). Emission measure of the hot component amounts 1 % of the emission measure of the cool component.

  7. Magnetic loops, downflows, and convection in the solar corona

    NASA Technical Reports Server (NTRS)

    Foukal, P.

    1978-01-01

    Optical and extreme-ultraviolet observations of solar loop structures show that flows of cool plasma from condensations near the loop apex are a common property of loops associated with radiations whose maximum temperature is greater than approximately 7000 K and less than approximately 3,000,000 K. It is suggested that the mass balance of these structures indicates reconnection by means of plasma motion across field lines under rather general circumstances (not only after flares). It is shown that the cool material has lower gas pressure than the surrounding coronal medium. The density structure of the bright extreme ultraviolet loops suggests that downflows of cool gas result from isobaric condensation of plasma that is either out of thermal equilibrium with the local energy deposition rate into the corona, or is thermally unstable. The evidence is thought to indicate that magnetic fields act to induce a pattern of forced convection.

  8. Clementine Observes the Moon, Solar Corona, and Venus

    NASA Technical Reports Server (NTRS)

    1997-01-01

    In 1994, during its flight, the Clementine spacecraft returned images of the Moon. In addition to the geologic mapping cameras, the Clementine spacecraft also carried two Star Tracker cameras for navigation. These lightweight (0.3 kg) cameras kept the spacecraft on track by constantly observing the positions of stars, reminiscent of the age-old seafaring tradition of sextant/star navigation. These navigation cameras were also to take some spectacular wide angle images of the Moon.

    In this picture the Moon is seen illuminated solely by light reflected from the Earth--Earthshine! The bright glow on the lunar horizon is caused by light from the solar corona; the sun is just behind the lunar limb. Caught in this image is the planet Venus at the top of the frame.

  9. The Magnetic Connection between the Solar Photosphere and the Corona

    NASA Astrophysics Data System (ADS)

    Schrijver, Carolus J.; Title, Alan M.

    2003-11-01

    The solar magnetic field that extends through the chromosphere into the corona is envisioned to fan out from strong flux concentrations located within the supergranular downflow lanes. That so-called network field appears to be surrounded by a mixed-polarity magnetic field with a scale comparable to that of the granulation. We argue that for an internetwork field with a magnitude of a few tens of Mx cm-2, as suggested by both observations and models, the commonly held notion of a wineglass-shaped magnetic canopy of network flux that fully encloses weakly magnetic regions below it is fundamentally wrong. We estimate that in the presence of such a relatively strong internetwork field, as much as half of the coronal field over very quiet Sun may be rooted in that mixed-polarity internetwork field throughout the supergranules rather than in the network flux concentrations, as assumed until now. A corresponding amount of flux forms collars of closed loops around the network concentrations, connecting network flux back down onto the internetwork field over distances of several thousand kilometers. Within such a geometry, the rapid evolution of the internetwork field may substantially affect coronal heating and the acceleration of the solar wind. We discuss the potential consequences of these interacting network and internetwork fields for atmospheric heating, for wave propagation and the formation of acoustic shadows, and for the appearance of the near-surface solar outer atmosphere.

  10. Observational Links Between Active Stellar Coronae and Solar Active Regions

    NASA Astrophysics Data System (ADS)

    Drake, Jeremy J.; Giovanni, Peres; Orlando, Salvatore; Laming, J. Martin; Maggio, Antonio

    1999-04-01

    Based on Yohkoh SXT observations of the Sun near peak activity level obtained on 6 January 1992, we search for coronal structures that have emission measure distributions EM(T) that match the observed stellar coronal emission measure distributions derived for the intermediate activity stars epsilon Eri (K2 V) and xi Boo A (G8 V) from EUVE spectroscopic observations. We find that the temperatures of the peaks of the observed stellar distributions EM(T), as well as their slopes in the temperature range 6.0 <= log T <= 6.5, are very similar to those obtained for the brightest of the solar active regions in the 6 January 1992 SXT images. The observed slopes correspond approximately to EM~ T(beta ) with beta ~ 4, which is much steeper than predicted by static, uniformly heated loop models. Plasma densities in the coronae of epsilon Eri and xi Boo A are also observed to be essentially the same as the plasma densities typical of solar active regions. These data provide the best observational support yet obtained for the hypothesis that solar-like stars up to the activity levels of epsilon Eri (K2 V) and xi Boo A are dominated by active regions similar to those observed on the Sun. The surface filling factors of bright active regions needed to explain the observed stellar emission measures is approximately unity. Based on these results, we speculate on the nature of coronal structure at still higher levels of activity.

  11. Electron beams generated by shock waves in the solar corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    2005-10-01

    Beams of energetic electrons can be generated by shock waves in the solar corona. At the Sun shock waves are produced either by flares and/or by coronal mass ejections (CMEs). They can be observed as type II bursts in the solar radio radiation. Shock accelerated electron beams appear as rapidly drifting emission stripes (so-called “herringbones”) in dynamic radio spectra of type II bursts. A large sample of type II bursts showing “herringbones” was statistically analysed with respect to their properties in dynamic radio spectra. The electron beams associated with the “herringbones” are considered to be generated by shock drift acceleration. Then, the accelerated electrons establish a shifted loss-cone distribution in the upstream region of the associated shock wave. Such a distribution causes plasma instabilities leading to the emission of radio waves observed as “herringbones”. Consequences of a shifted loss-cone distribution of the shock accelerated electrons are discussed in comparison with the observations of “herringbones” within solar type II radio bursts.

  12. Shock accelerated electron beams in the solar corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    2002-12-01

    In the solar corona shock waves can be produced by flares and/or coronal mass ejections. Type II radio bursts represent the signature of such shock waves in the solar radio radiation. Shock accelerated electron beams appear as rapidly drifting emission stripes (so-called "herringbones") within type II radio bursts. A large sample of "herringbones" and solar type III radio bursts is statistically analysed concerning their properties in dynamic radio spectra. Type III bursts are regarded as being associated with electron beams immediately generated by the flare process. The analysis shows that the drift rates of "herringbones" are significantly smaller (about one half) than those of type III bursts in the same frequency range. Thus, electron beams related to type III bursts have a higher velocity than those generated by coronal shock waves. The velocity of electron beams associated with "herringbones" is found to be about 30,000 km/s. These beams are considered to be produced by shock drift acceleration. Then, the accelerated electrons establish a shifted loss-cone distribution in the upstream region of the associated shock wave. Such a distribution leads to a plasma instabilities leading to the emission of radio waves as observed as "herringbones".

  13. THE SOLAR MINIMUM CORONA FROM DIFFERENTIAL EMISSION MEASURE TOMOGRAPHY

    SciTech Connect

    Vasquez, Alberto M. [Instituto de AstronomIa y Fisica del Espacio, CONICET-University of Buenos Aires, Ciudad de Buenos Aires, CC 67-Suc 28 (Argentina); Frazin, Richard A.; Manchester, Ward B., E-mail: albert@iafe.uba.a, E-mail: rfrazin@umich.ed [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

    2010-06-01

    We present results derived from a dual-spacecraft tomographic reconstruction of the solar corona's three-dimensional (3D) extreme ultraviolet (EUV) emissivity. We use simultaneously taken STEREO A and B spacecraft EUVI images from Carrington rotation 2077 (UT 2008 November 20 06:56 through UT December 17 14:34). During this period, the spacecraft view angles were separated by an average 85.{sup 0}4 which allowed for the reconstruction to be performed with data gathered in about 3/4 of a full solar rotational time. The EUV reconstructions provide the 3D emissivity in each of the three EUVI Fe bands, in the range of heights 1.00-1.25 R {sub s}. We use this information to perform local differential emission measure (LDEM) analysis. Taking moments of the so-derived LDEM distributions gives the 3D values of the electron density, temperature, and temperature spread. We determine relationships between the moments of the LDEM and the coronal magnetic field by making longitudinal averages of the moments, and relating them to the global-scale structures of a potential field source surface magnetic field model. In this way, we determine how the electron density, mean temperature, and temperature spread vary for different coronal structures. We draw conclusions about the relationship between the LDEM moments and the sources of the fast and slow solar winds, and the transition between the two regimes.

  14. Slow wind and magnetic topology in the solar minimum corona in 1996-1997

    Microsoft Academic Search

    E. Antonucci; L. Abbo; M. A. Dodero

    2005-01-01

    This study examines the physical conditions of the outer solar corona in order to identify the regions where the slow solar wind is accelerated and to investigate the latitudinal transition from slow to fast wind during the minimum of the solar cycle. The analysis is based on observations of six streamers obtained during the years of solar minimum, 1996 and

  15. A model of the Alfvén speed in the solar corona

    NASA Astrophysics Data System (ADS)

    Warmuth, A.; Mann, G.

    2005-06-01

    We present an analytic model of the Alfvén speed vA in the solar corona. The coronal magnetic field is modeled by a radial component representing the global field and by a dipole representing an active region. The free parameters of the model are constrained by actual observations of solar magnetic fields and coronal electron densities. The coronal magnetic field strength in the quiet Sun is determined by coronal seismology, using EIT waves as proxies for the fast magnetosonic speed vms, and thus for the magnetic field strength. Depending on the orientation of the dipole, we find local minima of vA (and vms) at the coronal base at distances of 0.2-0.3 solar radii from the center of the modelled active region (AR), as well as above the AR at comparable heights. For all dipole orientations, a global maximum is found at 3.5 solar radii. We apply our model to the study of the formation and propagation of coronal shock waves which are observed as flare waves and as type II radio bursts, using a sample of eight solar events. We find that flare waves are initially highly supermagnetosonic (with magnetosonic Mach numbers of Mms ? 2-3). During their propagation, they decelerate until Mms=1 is reached. This behavior can be explained by a strong shock or large-amplitude simple wave that decays to an ordinary fast magnetosonic wave. The observed starting frequencies and Mach numbers of the associated type II bursts are consistent with the predictions of the model.

  16. Interstellar Dust in the Solar System

    E-print Network

    Krueger, Harald; Altobelli, Nicolas; Gruen, Eberhard

    2007-01-01

    The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse almost perpendicular to the ecliptic plane (inclination 79 deg, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. The in-situ dust detector on board continuously measured interstellar dust grains with masses up to 10^-13 kg, penetrating deep into the solar system. The flow direction is close to the mean apex of the Sun's motion through the solar system and the grains act as tracers of the physical conditions in the local interstellar cloud (LIC). While Ulysses monitored the interstellar dust stream at high ecliptic latitudes between 3 and 5 AU, interstellar impactors were also measured with the in-situ dust detectors on board Cassini, Galileo and Helios, covering a heliocentric distance range between 0.3 and 3 AU in the ecliptic plane. The interstellar dust stream in the inner solar system is altered by the solar radiation pressure force, gravitational focussing and interaction of charged gr...

  17. VLTI observations of the dust geometry around R Coronae Borealis stars

    E-print Network

    Bright, S N; Clayton, G C; De Marco, O; Leăo, I C; Nordhaus, J; Gallagher, J S

    2011-01-01

    We are investigating the formation and evolution of dust around the hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars. We aim to determine the connection between the probable merger past of these stars and their current dust-production activities. We carried out high-angular resolution interferometric observations of three RCB stars, namely RY Sgr, V CrA, and V854 Cen with the mid-IR interferometer, MIDI on the VLTI, using two telescope pairs. The baselines ranged from 30 to 60 m, allowing us to probe the dusty environment at very small spatial scales (~ 50 mas or 400 stellar radii). The observations of the RCB star dust environments were interpreted using both geometrical models and one-dimensional radiative transfer codes. From our analysis we find that asymmetric circumstellar material is apparent in RY Sgr, may also exist in V CrA, and is possible for V854 Cen. Overall, we find that our observations are consistent with dust forming in clumps ejected randomly around the RCB star so tha...

  18. Dust around R Coronae Borealis stars: II. Infrared emission features in a H-poor environment

    E-print Network

    Garcia-Hernandez, D A; Lambert, D L

    2013-01-01

    Residual Spitzer/IRS spectra for a sample of 31 R Coronae Borealis (RCB) stars are presented and discussed in terms of narrow emission features superimposed on the quasi-blackbody continuous infrared emission. A broad ~6-10 um dust emission complex is seen in the RCBs showing an extreme H-deficiency. A secondary and much weaker ~11.5-15 um broad emission feature is detected in a few RCBs with the strongest ~6-10 um dust complex. The Spitzer infrared spectra reveal for the first time the structure within the ~6-10 um dust complex, showing the presence of strong C-C stretching modes at ~6.3 and 8.1 um as well as of other dust features at ~5.9, 6.9, and 7.3 um, which are attributable to amorphous carbonaceous solids with little or no hydrogen. The few RCBs with only moderate H-deficiencies display the classical 'unidentified infrared bands (UIRs)' and mid-infrared features from fullerene-related molecules. In general, the characteristics of the RCB infrared emission features are not correlated with the stellar a...

  19. Reconnection driven by natural flows in the solar corona

    NASA Astrophysics Data System (ADS)

    Knoll, D.; Lapenta, G.

    2003-12-01

    Reconnection in the solar corona is believed to be important for a series of processes from flares and CMEs to coronal heating. However, theoretical understanding of the reconnection process still remains elusive. The reconnection rate predicted by the Sweet-Parker model is determined by resistivity and is very many orders of magnitude too small to explain the observations. A possible mechanism that can provide fast reconnection rate is driven reconnection, When flows drive field lines together, the rate of reconnection is determined by the driving mechanism and is independent of resistivity. In the present work we consider two possibilities: converging flows created by the long term evolution of coronal structures and converging flows due to flow instabilities. While the first mechanism has been invoked in the flux rope model of coronal mass ejections (CME) [1], the second mechanism has been proposed recently in studies of the evolution of helmet streamer configurations in presence of velocity shears [2]. Velocity shear induces the onset of the Kelvin Helmhotlz instability that leads to the compression of field lines in localized zones. Localized compression, in turn, leads to reconnection driven by the flow. The presence of the Kelvin-Helmholtz instability can be due to superAlfvenic field aligned flows or even to subAlfvenic flows across the field lines. [1] T.G. Forbes, J. Geophys. Res. 95, 11919 (1990). [2] G. Lapenta, D.A. Knoll, Solar Phys., 214, 107 (2003)

  20. Latitudinal and Radial Variation of Solar Corona Rotation at Solar Minimum

    NASA Astrophysics Data System (ADS)

    Giordano, S.; Mancuso, S.; Romoli, M.

    2007-09-01

    The rotation of the solar corona at different heliolatitudes from 1.5 to 3.0 Rsolar from Sun center has been studied at solar minimum from the reconstructed intensity time series of the O VI 1032 Ĺ and H I Ly? l216 Ĺ spectral lines and visible light polarized brightness obtained by the observations of UVCS/SOHO instrument. The time period analyzed range from mid May 1996 to mid May 1997, when, at solar minimum, some features persist for several rotations, thus allowing to analyze the UV and visible emission as time series modulated at the period of the solar rotation. The coronal differential rotation rate significantly differs from that of the photospheric plasma. The estimated equatorial synodic rotation period of the corona at 1.5 Rsolar is 27.48+/-0.15 days. The study of the latitudinal variation shows that the UV corona decelerates towards the photospheric rates from the equator up to the poleward boundary of the mid-latitude streamers, reaching a peak of 28.16+/-0.20 days around +/-30° from the equator at 1.5 Rsolar, while a less evident peak is observed in the northern hemisphere, suggesting a real north-south rotational asymmetry, the northern hemisphere the rotation looks more solid-body-like and slower than in the southern hemisphere. The mid-latitude results are also confirmed by the visible light data available at 1.75 and 2.0 Rsolar. The study of the radial rotation profiles shows that the corona is rotating almost rigidly with height, but we find an abrupt increase by about half a days between 2.3 and 2.5 Rsolar. The larger radial and latitudinal gradients of the rotation rates are localized at the boundary between the open and closed field lines, suggesting that in these regions the differential rotation might be a source of magnetic stress and, consequently, of energy release.

  1. Observations from space of the solar corona\\/inner zodiacal light

    Microsoft Academic Search

    R. M. Macqueen; C. L. Ross; T. Mattingly

    1973-01-01

    Observations, from the Apollo 16 spacecraft, in lunar orbit, of the ; total radiance of the K + F corona, from 3 R\\/sub sub solar \\/ to 55 R\\/sub sub ; solar \\/ are presented and discussed. The logarithmic slope of the K + F coronal ; radiance, in the region r > 20 R\\/sub sub solar \\/, is found

  2. DUST AROUND R CORONAE BOREALIS STARS. I. SPITZER/INFRARED SPECTROGRAPH OBSERVATIONS

    SciTech Connect

    Anibal Garcia-Hernandez, D. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200 La Laguna (Spain); Kameswara Rao, N. [Indian Institute of Astrophysics, Bangalore 560 034 (India); Lambert, David L., E-mail: agarcia@iac.es, E-mail: nkrao@iiap.res.in, E-mail: dll@astro.as.utexas.edu [W. J. McDonald Observatory, University of Texas at Austin, 1 University Station, C1400, Austin, TX 78712-0259 (United States)

    2011-09-20

    Spitzer/infrared spectrograph (IRS) spectra from 5 to 37 {mu}m for a complete sample of 31 R Coronae Borealis stars (RCBs) are presented. These spectra are combined with optical and near-infrared photometry of each RCB at maximum light to compile a spectral energy distribution (SED). The SEDs are fitted with blackbody flux distributions and estimates are made of the ratio of the infrared flux from circumstellar dust to the flux emitted by the star. Comparisons for 29 of the 31 stars are made with the Infrared Astronomical Satellite (IRAS) fluxes from three decades earlier: Spitzer and IRAS fluxes at 12 {mu}m and 25 {mu}m are essentially equal for all but a minority of the sample. For this minority, the IRAS to Spitzer flux ratio exceeds a factor of three. The outliers are suggested to be stars where formation of a dust cloud or dust puff is a rare event. A single puff ejected prior to the IRAS observations may have been reobserved by Spitzer as a cooler puff at a greater distance from the RCB. RCBs which experience more frequent optical declines have, in general, a circumstellar environment containing puffs subtending a larger solid angle at the star and a quasi-constant infrared flux. Yet, the estimated subtended solid angles and the blackbody temperatures of the dust show a systematic evolution to lower solid angles and cooler temperatures in the interval between IRAS and Spitzer. Dust emission by these RCBs and those in the LMC is similar in terms of total 24 {mu}m luminosity and [8.0]-[24.0] color index.

  3. Dust around R Coronae Borealis stars: I. Spitzer/IRS observations

    E-print Network

    Garcia-Hernandez, D A; Lambert, David L

    2011-01-01

    Spitzer/IRS spectra from 5 to 37 um for a complete sample of 31 R Coronae Borealis stars (RCBs) are presented. These spectra are combined with optical and near-infrared photometry of each RCB at maximum light to compile a spectral energy distribution (SED). The SEDs are fitted with blackbody flux distributions and estimates made of the ratio of the infrared flux from circumstellar dust to the flux emitted by the star. Comparisons for 29 of the 31 stars are made with the IRAS fluxes from three decades earlier: Spitzer and IRAS fluxes at 12 um and 25 um are essentially equal for all but a minority of the sample. For this minority, the IRAS to Spitzer flux ratio exceeds a factor of three. The outliers are suggested to be stars where formation of a dust cloud or dust puff is a rare event. A single puff ejected prior to the IRAS observations may have been reobserved by Spitzer as a cooler puff at a greater distance from the RCB. RCBs which experience more frequent optical declines have, in general, a circumstellar...

  4. Dynamics of Solar System Dust

    NASA Technical Reports Server (NTRS)

    Dermott, Stanley F.

    2002-01-01

    The ongoing aim of the research is to investigate the dynamical and physical evolution of interplanetary dust particles in order to produce a detailed global model of the zodiacal cloud and its constituent components that is capable of predicting thermal fluxes in mid-infrared wave bands to an accuracy of 1% or better; with the additional aim of exploiting this research as a basis for predicting structure in exozodiacal clouds that may be signatures of unseen planets.

  5. Predicting the Structure of the Solar Corona During the December 4, 2002 Total Solar Eclipse

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran; Linker, Jon A.; Riley, Pete; Lionello, Roberto

    2003-01-01

    The solar magnetic field plays a key role in determining coronal. The principal input to MHD models is the observed solar magnetic field. 3D MHD models can be used to compare with eclipse and coronograph images, SOHO images (LOSCO, EIT), Ulysses and WIND spacecraft data, and interplanetary scintillation (IPS) measurements. MHD computations can tell us about the structure of the corona. Eclipses can help us to verify the accuracy of the models. 4 December, 2002 total eclipce: visible in the southern hemisphere (South Atlantic, southern Africa, Indian Ocean, and Australia). Total in center Angola is at 06:00 UT.

  6. On the formation of current sheets in the solar corona

    SciTech Connect

    Karpen, J.T.; Antiochos, S.K.; Devore, C.R. (Naval Research Laboratory, Washington, DC (USA))

    1990-06-01

    Several theoretical studies have proposed that, in response to photospheric footpoint motions, current sheets can be generated in the solar corona without the presence of a null point in the initial potential magnetic field. A fundamental assumption in these analyses, commonly referred to as the line-tying assumption, is that all coronal field lines are anchored to a boundary surface representing the top of the dense, gas pressure-dominated photosphere. It is shown here that line-typing cannot be applied indiscriminately to dipped coronal fields, and that the conclusions of the line-tied models are incorrect. To support the theoretical arguments, the response of a dipped potential magnetic field in a hydrostatic-equilibrium atmosphere to shearing motions of the footpoints is studied, using a 2.5-dimensional MHD code. The results show that, in the absence of artificial line-tying conditions, a current sheet indeed does not form at the location of the dip. Rather, the dipped magnetic field rises, causing upflows of photospheric and chromospheric plasma. 20 refs.

  7. Solar Wind Acceleration from the Upper Chromosphere to the Corona in Coronal Hole Regions

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1999-01-01

    Flow speeds derived in recent years from chromospheric/transition region and coronal observations suggest that the solar wind acceleration process might start at heights in the solar atmosphere much lower than previously imagined. The goal of the proposed investigation was to study atmospheric outflows in coronal hole regions from the chromosphere into the corona using observational and theoretical approaches. In addition to outflows, other plasma properties such as electron densities, and electron and ion temperatures were also included in the study. To investigate these plasma properties in the inner corona is important as they play a crucial role in placing limits on possible coronal heating and solar wind acceleration mechanisms.

  8. The Writhe of Helical Structures in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Toeroek, T.; Berger, M. A.; Kliem, B.

    2010-01-01

    Context. Helicity is a fundamental property of magnetic fields, conserved in ideal MHD. In flux rope topology, it consists of twist and writhe helicity. Despite the common occurrence of helical structures in the solar atmosphere, little is known about how their shape relates to the writhe, which fraction of helicity is contained in writhe, and how much helicity is exchanged between twist and writhe when they erupt. Aims. Here we perform a quantitative investigation of these questions relevant for coronal flux ropes. Methods. The decomposition of the writhe of a curve into local and nonlocal components greatly facilitates its computation. We use it to study the relation between writhe and projected S shape of helical curves and to measure writhe and twist in numerical simulations of flux rope instabilities. The results are discussed with regard to filament eruptions and coronal mass ejections (CMEs). Results. (1) We demonstrate that the relation between writhe and projected S shape is not unique in principle, but that the ambiguity does not affect low-lying structures, thus supporting the established empirical rule which associates stable forward (reverse) S shaped structures low in the corona with positive (negative) helicity. (2) Kink-unstable erupting flux ropes are found to transform a far smaller fraction of their twist helicity into writhe helicity than often assumed. (3) Confined flux rope eruptions tend to show stronger writhe at low heights than ejective eruptions (CMEs). This argues against suggestions that the writhing facilitates the rise of the rope through the overlying field. (4) Erupting filaments which are S shaped already before the eruption and keep the sign of their axis writhe (which is expected if field of one chirality dominates the source volume of the eruption), must reverse their S shape in the course of the rise. Implications for the occurrence of the helical kink instability in such events are discussed.

  9. Electron Temperature and Speed Measurements In the Low Solar Corona: Results from the June 2001 Eclipse

    Microsoft Academic Search

    N. L. Reginald; O. C. St. Cyr; J. M. Davila; J. W. Brosius

    2003-01-01

    The determination of the radial and latitudinal temperature and solar wind speed profiles of the solar corona is of immense importance in understanding the coronal heating mechanism and the dynamics of the coronal features. Cram (Sol. Phys, 48,3, 1976) provided the theory for the formation of the K-coronal spectrum and a method for determining the radial profile of the coronal

  10. Dust Accumulation and Cleaning of the MER Spirit Solar Array

    NASA Astrophysics Data System (ADS)

    Herman, J. A.; Lemmon, M. T.; Johnson, J. R.; Cantor, B. A.; Stella, P. M.; Chin, K. B.; Wood, E. G.

    2012-12-01

    The solar array of the NASA Mars Exploration Rover (MER) Spirit was expected to accumulate so much dust after ninety Martian days (sols) that it could no longer provide enough energy to guarantee continued surface operations. Instead, due in part to low dust accumulation rates and numerous dust cleaning events, Spirit carried out surface operations for over 2200 sols (over three Mars years). During this time period, the rover experienced four Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a tool to quantitatively estimate the loading and aeolian removal of dust from the solar array each sol. We will discuss the accumulation of dust on the solar panels as a proxy for dust movement at Gusev Crater over the course of the entire mission.

  11. Three-dimensional MHD modeling of the solar corona and solar wind: Comparison with the Wang-Sheeley model

    Microsoft Academic Search

    A. V. Usmanov; M. L. Goldstein

    2003-01-01

    We present simulation results from a tilted-dipole steady-state MHD model of the solar corona and solar wind and compare the output from our model with the Wang-Sheeley model which relates the divergence rate of magnetic flux tubes near the Sun (inferred from solar magnetograms) to the solar wind speed observed near Earth and at Ulysses. The boundary conditions in our

  12. Evidence for wave heating in the solar corona.

    PubMed

    Hahn, Michael

    2013-07-01

    The temperature of the Sun increases over a short distance from a few thousand degrees in the photosphere to over a million degrees in the corona. To understand coronal heating is one of the major problems in astrophysics. There is general agreement that the energy source is convective motion in and below the photosphere. It remains to determine how this mechanical energy is transported outward into the corona and then deposited as heat. Two classes of models have been proposed, namely those that rely on magnetic reconnection and those that rely on waves, particularly Alfvén waves. There is increasing evidence that waves are ubiquitous in the corona. However, a difficulty for wave-driven models has been that most theories predict Alfvén waves to be undamped in the corona, and therefore they cannot dissipate their energy into heat. Our research has shown unambiguous observational evidence that the waves do damp at sufficiently low heights in the corona to be important for coronal heating. PMID:23676178

  13. HERSCHEL/SCORE, imaging the solar corona in visible and EUV light: CCD camera characterization.

    PubMed

    Pancrazzi, M; Focardi, M; Landini, F; Romoli, M; Fineschi, S; Gherardi, A; Pace, E; Massone, G; Antonucci, E; Moses, D; Newmark, J; Wang, D; Rossi, G

    2010-07-01

    The HERSCHEL (helium resonant scattering in the corona and heliosphere) experiment is a rocket mission that was successfully launched last September from White Sands Missile Range, New Mexico, USA. HERSCHEL was conceived to investigate the solar corona in the extreme UV (EUV) and in the visible broadband polarized brightness and provided, for the first time, a global map of helium in the solar environment. The HERSCHEL payload consisted of a telescope, HERSCHEL EUV Imaging Telescope (HEIT), and two coronagraphs, HECOR (helium coronagraph) and SCORE (sounding coronagraph experiment). The SCORE instrument was designed and developed mainly by Italian research institutes and it is an imaging coronagraph to observe the solar corona from 1.4 to 4 solar radii. SCORE has two detectors for the EUV lines at 121.6 nm (HI) and 30.4 nm (HeII) and the visible broadband polarized brightness. The SCORE UV detector is an intensified CCD with a microchannel plate coupled to a CCD through a fiber-optic bundle. The SCORE visible light detector is a frame-transfer CCD coupled to a polarimeter based on a liquid crystal variable retarder plate. The SCORE coronagraph is described together with the performances of the cameras for imaging the solar corona. PMID:20428852

  14. Generalized similarity in magnetohydrodynamic turbulence as seen in the solar corona and solar wind

    NASA Astrophysics Data System (ADS)

    Chapman, S. C.; Leonardis, E.; Nicol, R. M.; Foullon, C.

    2010-12-01

    A key property of turbulence is that it can be characterized and quantified in a robust and reproducible way in terms of the ensemble averaged statistical properties of fluctuations. Importantly, fluctuations associated with a turbulent field show similarity or scaling in their statistics and we test for this in observations of magnetohydrodynamic turbulence in the solar corona and solar wind with both power spectra and Generalized Structure Functions. Realizations of turbulence that are finite sized are known to exhibit a generalized or extended self-similarity (ESS). ESS was recently demonstrated in magnetic field timeseries of Ulysses single point in-situ observations of fluctuations of quiet solar wind for which a single robust scaling function was found [1-2]. Flows in solar coronal prominences can be highly variable, with dynamics suggestive of turbulence. The Hinode SOT instrument provides observations (images) at simultaneous high spatial and temporal resolution which span several decades in both spatial and temporal scales. We focus on specific Calcium II H-line observations of solar quiescent prominences with dynamic, highly variable small-scale flows. We analyze these images from the perspective of a finite sized turbulent flow. We discuss this evidence of ESS in the SOT images and in Ulysses solar wind observations- is there a single universal scaling of the largest eddies in the finite range magnetohydrodynamic turbulent flow? [1] S. C. Chapman, R. M. Nicol, Generalized Similarity in Finite Range Solar Wind Magnetohydrodynamic Turbulence, Phys. Rev. Lett., 103, 241101 (2009) [2] S. C. Chapman, R. M. Nicol, E. Leonardis, K. Kiyani, V. Carbone, Observation of universality in the generalized similarity of evolving solar wind turbulence as seen by ULYSSES, Ap. J. Letters, 695, L185, (2009)

  15. Predicting the Structure of the Solar Corona for the Total Solar Eclipse of March 29,2006

    NASA Technical Reports Server (NTRS)

    Mikic, Z.; Linker, J. a.; Lionello, R.; Riley, P.; TItov, V.

    2007-01-01

    We describe the use of a three-dimensional MHD model to predict the s tructure of the corona prior to the total solar eclipse of March 29, 2006. The calculation uses the observed photospheric radial magnetic f ield as a boundary condition. We use a new version of our model that has an improved description of energy transport in the corona. The mo del allows us to predict the emission of X-ray and EUV radiation in t he corona. We compare the predicted polarization brightness in the co rona with four observations of the eclipse from Greece, Egypt, and Li bya, and we demonstrate that the model accurately predicts the largescale structure of the corona. We also compare X-ray emission from the model with GOES/SXI images.

  16. Development of shocks waves in the solar corona and the interplanetary space

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.; Aurass, H.; Classen, H. T.

    2003-09-01

    At the Sun shock waves are produced either by flares or by coronal mass ejections and are regarded to be the source of solar energetic particle events. The propagation of a disturbance away from an active region through the corona into the interplanetary space is considered by evaluating the radial behaviour of the Alfvén speed. The magnetic field of an active region is modelled by a magnetic dipole superimposed on that of the quiet Sun. Such a magnetic field structure leads to a local mimimum of the Alfvén speed in the middle of the corona and a maximum of 740 km/s at a radial distance of 6 solar radii from the center of the Sun. The occurrence of these extrema of the Alfvén speed has consequences for the formation and development of shock waves in the corona and interplanetary space.

  17. Research on dual spectrum solar-blind ultraviolet corona detection system

    NASA Astrophysics Data System (ADS)

    Yang, Feng; Gu, Yan; Sun, Jianning; Pan, Jingsheng; Zhu, Bo; Wang, Qi; Lu, Xiaoqing

    2015-04-01

    A dual spectrum solar-blind ultraviolet (UV) corona detection system is designed in this paper. A common optical axis using a dichroic mirror is applied to this system in order to make visible light and ultraviolet light spectroscopy to ultraviolet detector and visible detectors. A high speed circuit of image processing based on TMS320DM642 DSP and a circuit that is used into system control and power management based on microcontroller are designed for the presented system. On the basis of the multi-threaded programming ideas, real-time image acquisition of ultraviolet and visible detectors, ultraviolet image noise reduction, image registration, dual spectral integration, Characteristic superimposing, serial communication and image display are achieved by using the DSP image processing circuit. Experimental results show that the dual spectrum solar-blind ultraviolet corona detection system has a good performance of corona detection based on ultraviolet and visible image fusion.

  18. Origin of the ten degree Solar System dust bands

    Microsoft Academic Search

    K. Grogan; S. F. Dermott; S. Jayaraman; Y. L. Xu

    1997-01-01

    The Solar System dust bands discovered by IRAS are toroidal distributions of dust particles with common proper inclinations. It is impossible for particles with high eccentricity (approximately 0.2 or greater) to maintain a near constant proper inclination as they precess, and therefore the dust bands must be composed of material having a low eccentricity, pointing to an asteroidal origin. The

  19. A Dust Characterization Experiment for Solar Cells Operating on Mars

    NASA Technical Reports Server (NTRS)

    Jenkins, Phillip; Landis, Geoffrey A.; Krasowski, Michael; Greer, Lawrence; Wilt, David; Baraona, Cosmo; Scheiman, David; Lekki, John

    2001-01-01

    During the Viking and Pathfinder missions to Mars, significant amounts of dust accumulated on the spacecrafts. In Pathfinder's case, the dust obscured the solar panels on the lander and the rover degrading their output current. The material adherence experiment aboard the Pathfinder rover quantified the rate of decrease in short circuit current at 0.28% per day. This rate is unacceptably high for long duration missions. In response, NASA has developed the Dust Accumulation and Removal Technology (DART) experiment. DART has three instruments for characterizing dust settling out of the atmosphere and tests two methods to keep dust from settling on solar cells.

  20. Structure of the Solar System's Dust Disk: Influence of Massive Bodies

    Microsoft Academic Search

    S. F. Dermott; T. J. J. Kehoe

    2004-01-01

    Dust in the solar system is derived from two large reservoirs of collisionally evolved bodies: dust in the outer solar system originates from the Kuiper belt, while the solar system dust bands discovered by IRAS show that the asteroid belt is the dominant source of dust in the inner solar system. The rate of accretion of dust by the Earth

  1. Signatures of Slow Solar Wind Streams from Active Regions in the Inner Corona

    NASA Astrophysics Data System (ADS)

    Slemzin, V.; Harra, L.; Urnov, A.; Kuzin, S.; Goryaev, F.; Berghmans, D.

    2013-08-01

    The identification of solar-wind sources is an important question in solar physics. The existing solar-wind models ( e.g., the Wang-Sheeley-Arge model) provide the approximate locations of the solar wind sources based on magnetic field extrapolations. It has been suggested recently that plasma outflows observed at the edges of active regions may be a source of the slow solar wind. To explore this we analyze an isolated active region (AR) adjacent to small coronal hole (CH) in July/August 2009. On 1 August, Hinode/EUV Imaging Spectrometer observations showed two compact outflow regions in the corona. Coronal rays were observed above the active-region coronal hole (ARCH) region on the eastern limb on 31 July by STEREO-A/EUVI and at the western limb on 7 August by CORONAS- Photon/TESIS telescopes. In both cases the coronal rays were co-aligned with open magnetic-field lines given by the potential field source surface model, which expanded into the streamer. The solar-wind parameters measured by STEREO-B, ACE, Wind, and STEREO-A confirmed the identification of the ARCH as a source region of the slow solar wind. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere.

  2. Synoptic Solar Cycle 24 in Corona, Chromosphere, and Photosphere Seen by the Solar Dynamics Observatory

    NASA Astrophysics Data System (ADS)

    Benevolenskaya, E.; Slater, G.; Lemen, J.

    2014-09-01

    The Solar Dynamics Observatory provides multiwavelength imagery from extreme ultraviolet (EUV) to visible light as well as magnetic-field measurements. These data enable us to study the nature of solar activity in different regions of the Sun, from the interior to the corona. For solar-cycle studies, synoptic maps provide a useful way to represent global activity and evolution by extracting a central meridian band from sequences of full-disk images over a full solar Carrington rotation (? 27.3 days). We present the global evolution during Solar Cycle 24 from 20 May 2010 to 31 August 2013 (CR 2097 - CR 2140), using synoptic maps constructed from full-disk, line-of-sight magnetic-field imagery and EUV imagery (171 Ĺ, 193 Ĺ, 211 Ĺ, 304 Ĺ, and 335 Ĺ). The synoptic maps have a resolution of 0.1 degree in longitude and steps of 0.001 in sine of latitude. We studied the axisymmetric and non-axisymmetric structures of solar activity using these synoptic maps. To visualize the axisymmetric development of Cycle 24, we generated time-latitude (also called butterfly) images of the solar cycle in all of the wavelengths, by averaging each synoptic map over all longitudes, thus compressing it to a single vertical strip, and then assembling these strips in time order. From these time-latitude images we observe that during the ascending phase of Cycle 24 there is a very good relationship between the integrated magnetic flux and the EUV intensity inside the zone of sunspot activities. We observe a North-South asymmetry of the EUV intensity in high-latitudes. The North-South asymmetry of the emerging magnetic flux developed and resulted in a consequential asymmetry in the timing of the polar magnetic-field reversals.

  3. Coexistence of Self-Organized Criticality and Intermittent Turbulence in the Solar Corona

    Microsoft Academic Search

    Vadim M. Uritsky; Maya Paczuski; Joseph M. Davila; Shaela I. Jones

    2007-01-01

    An extended data set of extreme ultraviolet images of the solar corona provided by the SOHO spacecraft is analyzed using statistical methods common to studies of self-organized criticality (SOC) and intermittent turbulence (IT). The data exhibit simultaneous hallmarks of both regimes: namely, power-law avalanche statistics as well as multiscaling of structure functions for spatial activity. This implies that both SOC

  4. Co-existence of self-organized criticality and intermittent turbulence in the solar corona

    Microsoft Academic Search

    V. Uritsky; M. Paczuski; J. M. Davila; S. Jones

    2006-01-01

    Turbulence and self-organized criticality (SOC) represent two major paths of dynamical complexity in driven, extended nonlinear systems. We present direct observational evidence for co-existence of these phenomena in the magnetized plasma of the solar corona. Using an extended collection of SOHO EIT images, we apply two alternative numerical analysis methods - one for analyzing avalanche statistics of bursty dissipation events

  5. Formation and Development of Shock Waves In The Solar Corona and Interplanetary Space

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.; Aurass, H.; Classen, H.-T.

    At the Sun shock waves are produced either by flares or by coronal mass ejections and are regarded to be the source of solar energetic particle events. In the solar corona shock waves appear as type II radio bursts. The propagation of a disturbance away from an active region from the corona into the interplanetary space is considered by evaluating the radial behaviour of the Alfven speed. The magnetic field of an active region is modelled by a magnetic dipole superimposed on that of the quiet Sun. Such a magnetic field structure leads to a local minimum of the Alfvén speed in the middle of the corona and a maximum of 740 km/s at a distance of 3.8 solar radii from the center of the Sun. The occurrence of such a minimum and maximum has important consequences on the formation and development of shock waves in the corona and the interplanetary space and their ability to accelerate particles leading to a special temporal delay of the on-set of solar energetic particle events.

  6. MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2

    E-print Network

    Fornberg, Bengt

    MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy

  7. Reflection of Alfvén waves in the corona and solar wind: An impulse function approach

    Microsoft Academic Search

    Joseph V. Hollweg; P. A. Isenberg

    2007-01-01

    We consider the reflection of Alfvén waves in the corona and solar wind, using variables f and g which follow sunward and antisunward characteristics, respectively. We show that the basic equations for f and g have the same structure as the Klein-Gordon equation. Unlike previous studies which used a harmonic analysis, we emphasize the impulse response of the system. This

  8. Expansion of solar corona in the Sun's gravitational field and formation of the heliospheric current sheet

    Microsoft Academic Search

    I. M. Podgorny; A. I. Podgorny

    2005-01-01

    [1] Taking into account gravitation and the temperature gradient, three-dimensional MHD simulation of solar corona expansion in a dipole magnetic field was performed. Dissipation, compressibility, and anisotropy of thermal conductivity were taken into consideration. For calculations, the PERESVET code was used. It was been shown that a heliospheric current sheet having a normal component of magnetic field is formed. An

  9. THE CYCLING OF MATERIAL BETWEEN THE SOLAR CORONA AND CHROMOSPHERE

    SciTech Connect

    Guerreiro, N.; Hansteen, Viggo [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); De Pontieu, B., E-mail: n.m.r.guerreiro@astro.uio.no [Lockheed Martin Solar and Astrophysics Laboratory, Org. A021S, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

    2013-05-20

    Observations of transition region emission lines reveal the presence of redshifts in lines formed from the top of the chromosphere up to temperatures of about 2.5 Multiplication-Sign 10{sup 5} K and blueshifts for temperatures above that. However, it is doubtful that the apparent large downward flows in the lower transition region represents an emptying of the corona, so some mechanism must be responsible for maintaining the mass balance between the corona and the lower atmospheric layers. We use a three-dimensional magnetohydrodynamics code to study the cycling of mass between the corona, transition region, and chromosphere by adding a tracer fluid to the simulation in various temperature intervals in the transition region. We find that most of the material seen in transition region emission lines formed at temperatures below 3 Multiplication-Sign 10{sup 5} K is material that has been rapidly heated from chromospheric temperatures and thereafter is pushed down as it cools. This implies that the bulk of transition region material resides in small loops. In these loops, the density is high and radiative cooling is efficient.

  10. The Structure and Dynamics of the Solar Corona and Inner Heliosphere

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    2002-01-01

    This report covers technical progress during the second quarter of the first year of NASA Sun-Earth Connections Theory Program (SECTP) contract 'The Structure and Dynamics of the Solar Corona and Inner Heliosphere,' NAS5-99188, between NASA and Science Applications International Corporation. and covers the period November 16, 1999 to February 15, 2000. Under this contract SAIC and the University of California, Irvine (UCI) have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD (magnetohydrodynamic) model. The topics studied include: the effect of emerging flux on the stability of helmet streamers, coronal loops and streamers, the solar magnetic field, the solar wind, and open magnetic field lines.

  11. The flow of interstellar dust through the solar system: the role of dust charging

    SciTech Connect

    Sterken, V. J. [MPIK, Saupfercheckweg 1, D-69117 Heidelberg (Germany); TU Braunschweig, IGEP, Mendelssohnstr. 3, D-38106 Braunschweig (Germany); Altobelli, N.; Schwehm, G. [ESA-ESAC - P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Kempf, S. [LASP, University of Colorado, 1234 Innovation Dr, Boulder, CO, 80303-7814 (United States); TU Braunschweig, IGEP, Mendelssohnstr. 3, D-38106 Braunschweig (Germany); Srama, R. [MPIK, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Universitaet Stuttgart, IRS, Pfaffenwaldring 31, D-70569 Stuttgart (Germany); Strub, P. [MPS, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany); Gruen, E. [MPIK, Saupfercheckweg 1, D-69117 Heidelberg (Germany); LASP, University of Colorado, 1234 Innovation Dr, Boulder, CO, 80303-7814 (United States)

    2011-11-29

    Interstellar dust can enter the solar system through the relative motion of the Sun with respect to the Local Interstellar Cloud. The trajectories of the dust through the solar system are not only influenced by gravitation and solar radiation pressure forces, but also by the Lorentz forces due to the interaction of the interplanetary magnetic field with the charged dust particles. The interplanetary magnetic field changes on two major time scales: 25 days (solar rotation frequency) and 22 years (solar cycle). The short-term variability averages out for regions that are not too close (>{approx}2 AU) to the Sun. This interplanetary magnetic field variability causes a time-variability in the interstellar dust densities, that is correlated to the solar cycle.In this work we characterize the flow of interstellar dust through the solar system using simulations of the dust trajectories. We start from the simple case without Lorentz forces, and expand to the full simulation. We pay attention to the different ways of modeling the interplanetary magnetic field, and discuss the influence of the dust parameters on the resulting flow patterns. We also discuss the possibilities of using this modeling for prediction of dust fluxes for different space missions or planets, and we pay attention to where simplified models are justified, and where or when a full simulation, including all forces is necessary. One of the aims of this work is to understand measurements of spacecraft like Ulysses, Cassini and Stardust.

  12. Velocity Profiles in the Solar Corona from Multi-Instrument Observations

    E-print Network

    E. Quemerais; R. Lallement; D. Koutroumpa; P. Lamy

    2007-06-13

    We present a method to derive outflow velocities in the solar corona using different data sets including solar wind mass flux coming from the SWAN/SOHO instrument, electron density values from LASCO-C2 and interplanetary solar wind velocities derived from ground-based Interplanetary Scintillation Observations (IPS). In a first step, we combine the LASCO electron densities at 6 solar radii and the IPS velocities, and compare the product to the SWAN mass fluxes. It is found that this product represents the actual mass flux at 6 solar radii for the fast wind, but not for the slow wind. In regions dominated by the slow wind, the fluxes derived from SWAN are systematically smaller. This is interpreted as a proof that the fast solar wind has reached its terminal velocity at about 6 solar radii and expands with constant velocity beyond this distance. On the contrary, the slow solar wind has reached only half of its terminal value and is thus accelerated further out. In a second step, we combine the LASCO-C2 density profiles and the SWAN flux data to derive velocity profiles in the corona between 2.5 and 6 solar radii. Such profiles can be used to test models of the acceleration mechanism of the fast solar wind.

  13. SWAP Observations of the Long-Term, Large-Scale Evolution of the EUV Solar Corona

    E-print Network

    Seaton, Daniel B; Shearer, Paul; Berghmans, David; Nicula, Bogdan

    2013-01-01

    The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar telescope on board the Project for On-Board Autonomy 2 (PROBA2) spacecraft has been regularly observing the solar corona in a bandpass near 17.4 nm since February 2010. With a field-of-view of 54x54 arcmin, SWAP provides the widest-field images of the EUV corona available from the perspective of the Earth. By carefully processing and combining multiple SWAP images it is possible to produce low-noise composites that reveal the structure of the EUV corona to relatively large heights. A particularly important step in this processing was to remove instrumental stray light from the images by determining and deconvolving SWAP's point spread function (PSF) from the observations. In this paper we use the resulting images to conduct the first ever study of the evolution of the large-scale structure of the corona observed in the EUV over a three-year period that includes the complete rise phase of solar cycle 24. Of particular note is the persiste...

  14. Numerical simulations of self-consistently generated ? distributions in the solar wind and solar corona

    NASA Astrophysics Data System (ADS)

    Randol, B. M.; Christian, E. R.

    2014-12-01

    In a previous study (Randol and Christian, submitted to JGR, April 2014), numerical simulations of protons and anti-protons obeying Coulomb's law provided key insight into the self-consistent generation of ? distributions in space plasmas. In that study, the velocity distribution function (VDF) first formed a tail with the common spectral index of -5 and then gradually became a ?-r distribution, with ? = 1.5, corresponding to the common spectrum. The form of this distribution was found to relate to the electric field distribution function (EDF). These results were robust to a range of initialized densities and thermal speeds; however, this range of parameters did not include values close to those of the solar wind at 1 AU. Here we report on simulations of the same type but for a broader range of parameters, including those of the solar wind and corona. Our earliest findings indicate a lack of consistency in the VDF with the common spectrum, the cause of which again lies in the EDF. The results are instructive for understanding the solar wind ion VDF core and tail, as well as for ? distributed plasmas in general.

  15. Reoccurring Heavy Ion Dropouts in the Solar Wind: Rates, Locations, and Constraints on Magnetic Reconnection in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Weberg, M. J.; Zurbuchen, T.; Lepri, S. T.

    2012-12-01

    The abundance and charge state variations of heavy elements within the solar wind yield unique insight into processes occurring in the solar corona. Previously we have reported in-situ observations of heavy ion dropouts in the solar wind with depletion factors ranging from 2 - 25. Many of these dropouts exhibit mass-dependent fractionation in qualitative agreement with remote observations of gravitational settling in large, streamer belt coronal loops. We present here a robust statistical analysis pertaining to the occurrence rate and fractionation patterns of dropouts found in the ACE/SWICS data set between February 1998 and August 2011. In particular, we focus on dropouts which appear to reoccur over the course of multiple Carrington rotations. Such sequences of dropouts indicate source regions which are long lived structures in the solar corona and, as such, may provide important observational constraints on magnetic reconnection and magnetic diffusion processes at the edges of coronal holes.

  16. Magnetohydrodynamics of atmospheric transients. II - Two-dimensional numerical results for a model solar corona

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Han, S. M.; Dryer, M.; Nakagawa, Y.

    1978-01-01

    A systematic study of dynamic response of the inner solar corona is made within the context of two-dimensional, time-dependent plane hydromagnetics. The governing equations are written in r-phi coordinates (i.e., in the solar equatorial plane), and numerical solutions are obtained by introducing an impulsive temperature enhancement within a rectangular region (i.e., 'box') in an initially isothermal corona in magnetohydrostatic equilibrium. Effects of the magnetic field configuration are illustrated for initially open (radial) and closed (azimuthal) magnetic fields by comparison with the nonmagnetic response. The channeling or blocking effects by the magnetic fields on the mass motion of solar plasma as the consequence of the evolution of fast and slow mode MHD shock waves are demonstrated. Some physically significant applications of the results, useful for the interpretation of observations, are discussed. It is noted, for example, that coronal transients observed in white light probably occur within essentially radial field topologies.

  17. The temperature structure, mass, and energy flow in the corona and inner solar wind

    NASA Technical Reports Server (NTRS)

    Withbroe, George L.

    1988-01-01

    Remote-sensing and in situ data are used to constrain a radiative energy balance model in order to study the radial variations of coronal temperatures, densities, and outflow speeds in several types of coronal holes and in an unstructured quiet region of the corona. A one-fluid solar wind model is used which takes into account the effects of radiative and inward conductive losses in the low corona and the chromospheric-coronal transition region. The results show that the total nonradiative energy input in magnetically open coronal regions is 5 + or - 10 to the 5th ergs/sq cm, and that most of the energy heating the coronal plasma is dissipated within 2 solar radii of the solar surface.

  18. EIT: Solar corona synoptic observations from SOHO with an Extreme-ultraviolet Imaging Telescope

    NASA Technical Reports Server (NTRS)

    Delaboudiniere, J. P.; Gabriel, A. H.; Artzner, G. E.; Michels, D. J.; Dere, K. P.; Howard, R. A.; Catura, R.; Stern, R.; Lemen, J.; Neupert, W.

    1988-01-01

    The Extreme-ultraviolet Imaging Telescope (EIT) of SOHO (solar and heliospheric observatory) will provide full disk images in emission lines formed at temperatures that map solar structures ranging from the chromospheric network to the hot magnetically confined plasma in the corona. Images in four narrow bandpasses will be obtained using normal incidence multilayered optics deposited on quadrants of a Ritchey-Chretien telescope. The EIT is capable of providing a uniform one arc second resolution over its entire 50 by 50 arc min field of view. Data from the EIT will be extremely valuable for identifying and interpreting the spatial and temperature fine structures of the solar atmosphere. Temporal analysis will provide information on the stability of these structures and identify dynamical processes. EIT images, issued daily, will provide the global corona context for aid in unifying the investigations and in forming the observing plans for SOHO coronal instruments.

  19. Global Magnetic Topology and Large-Scale Dynamics of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Titov, Viacheslav; Linker, Jon; Mikic, Zoran; Riley, Pete; Lionello, Roberto; Downs, Cooper; Torok, Tibor

    We consider the global topology of the coronal magnetic field in relation to the large-scale dynamics of the solar corona. Our consideration includes recent results on the structural analysis of this field determined in two different approximations, namely, potential field source surface model and solar magnetohydrodynamic model. We identify similarities and differences between structural features of the magnetic field obtained in these two models and discuss their implications for understanding various large-scale phenomena in the solar corona. The underlying magnetic topology manifests itself in a variety of observed morphological features such as streamers, pseudo-streamers or unipolar streamers, EUV dimmings, flare ribbons, coronal holes, and jets. For each of them, the related magnetic configuration has specific structural features, whose presence has to be not only identified but also verified on its independence from the used field model in order to reliably predict the impact of such features on physical processes in the corona. Among them are magnetic null points and minima, bald patches, separatrix surfaces and quasi-separatrix layers, and open and closed separator field lines. These features form a structural skeleton of the coronal magnetic field and are directly involved through the ubiquitous process of magnetic reconnection in many solar dynamic phenomena such as coronal mass ejections, solar wind, acceleration and transport of energetic particles. We will pinpoint and elucidate in our overview some of such involvements that have recently received a considerable attention in our ongoing projects at Predictive Science.

  20. Global Multi-Fluid Solar Corona and Inner Heliosphere Model for Solar Probe Plus and Solar Orbite

    NASA Astrophysics Data System (ADS)

    van der Holst, B.; Sokolov, I.; Toth, G.; Gombosi, T. I.

    2014-12-01

    The mechanisms that heat and accelerate the fast and slow wind have not yet been conclusively identified, and their understanding is one of the major science goals of the Solar Orbiter (SO) and Solar Probe Plus (SPP) missions. Helium abundance and properties in the solar wind are critical tracers for both processes so that understanding them is key towards gaining insight in the solar wind phenomenon, and being able to model it and predict its properties. SO and SPP will carry critical instrumentation to measure the properties of Helium in the solar wind at distances between within 10 solar radii up to 1 AU. We present a generalization of the recently developed global solar corona and inner heliosphere model with low-frequency Alfvenic turbulence [van der Holst et al. (2014)] to include alpha-particle dynamics. This new multi-fluid model uses the stochastic heating mechanism to partition the turbulence dissipation into coronal heating of the electrons and ions. The momentum and energy exchange rates due to Coulomb collisions are accounted for. We discuss the feasibility for Alfvenic turbulence to simultaneously address the coronal heating and proton-alpha particle differential streaming.

  1. Solar wind magnetic field bending of Jovian dust trajectories.

    PubMed

    Zook, H A; Grün, E; Baguhl, M; Hamilton, D P; Linkert, G; Liou, J; Forsyth, R; Phillips, J L

    1996-11-29

    From September 1991 to October 1992, the cosmic dust detector on the Ulysses spacecraft recorded 11 short bursts, or streams, of dust. These dust grains emanated from the jovian system, and their trajectories were strongly affected by solar wind magnetic field forces. Analyses of the on-board measurements of these fields, and of stream approach directions, show that stream-associated dust grain masses are of the order of 10(-18) gram and dust grain velocities exceed 200 kilometers per second. These masses and velocities are, respectively, about 10(3) times less massive and 5 to 10 times faster than earlier reported. PMID:8929405

  2. Solar wind driven dust acoustic instability with Lorentzian kappa distribution

    NASA Astrophysics Data System (ADS)

    Arshad, Kashif; Ehsan, Zahida; Khan, S. A.; Mahmood, S.

    2014-02-01

    In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution function (Lorentzian or kappa), it is shown that a kinetic instability of dust-acoustic mode exists. The instability threshold is affected when such (quasineutral) plasma permeates through another static plasma. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust. In the limits of phase velocity of the waves larger and smaller than the thermal velocity of dust particles, the dispersion properties and growth rate of dust-acoustic mode are investigated analytically with validation via numerical analysis.

  3. Unified Models of Turbulence and Nonlinear Wave Evolution in the Extended Solar Corona and Solar Wind

    NASA Technical Reports Server (NTRS)

    Cranmer, Steven R.; Wagner, William (Technical Monitor)

    2003-01-01

    The PI (Cranmer) and Co-I (A. van Ballegooijen) made significant progress toward the goal of building a "unified model" of the dominant physical processes responsible for the acceleration of the solar wind. The approach outlined in the original proposal comprised two complementary pieces: (1) to further investigate individual physical processes under realistic coronal and solar wind conditions, and (2) to extract the dominant physical effects from simulations and apply them to a one-dimensional and time-independent model of plasma heating and acceleration. The accomplishments in the report period are thus divided into these two categories: 1a. Focused Study of Kinetic MHD Turbulence. We have developed a model of magnetohydrodynamic (MHD) turbulence in the extended solar corona that contains the effects of collisionless dissipation and anisotropic particle heating. A turbulent cascade is one possible way of generating small-scale fluctuations (easy to dissipate/heat) from a pre-existing population of low-frequency Alfven waves (difficult to dissipate/heat). We modeled the cascade as a combination of advection and diffusion in wavenumber space. The dominant spectral transfer occurs in the direction perpendicular to the background magnetic field. As expected from earlier models, this leads to a highly anisotropic fluctuation spectrum with a rapidly decaying tail in the parallel wavenumber direction. The wave power that decays to high enough frequencies to become ion cyclotron resonant depends on the relative strengths of advection and diffusion in the cascade. For the most realistic values of these parameters, though, there is insufficient power to heat protons and heavy ions. The dominant oblique waves undergo Landau damping, which implies strong parallel electron heating. We thus investigated the nonlinear evolution of the electron velocity distributions (VDFs) into parallel beams and discrete phase-space holes (similar to those seen in the terrestrial magnetosphere) which are an alternate means of heating protons via stochastic interactions similar to particle-particle collisions. 1b. Focused Study of the Multi-Mode Detailed Balance Formalism. The PI began to explore the feasibility of using the "weak turbulence," or detailed-balance theory of Tsytovich, Melrose, and others to encompass the relevant physics of the solar wind. This study did not go far, however, because if the "strong" MHD turbulence discussed above is a dominant player in the wind's acceleration region, this formalism is inherently not applicable to the corona. We will continue to study the various published approaches to the weak turbulence formalism, especially with an eye on ways to parameterize nonlinear wave reflection rates. 2. Building the Unified Model Code Architecture. We have begun developing the computational model of a time-steady open flux tube in the extended corona. The model will be "unified" in the sense that it will include (simultaneously for the first time) as many of the various proposed physical processes as possible, all on equal footing. To retain this generality, we have formulated the problem in two interconnected parts: a completely kinetic model for the particles, using the Monte Carlo approach, and a finite-difference approach for the self-consistent fluctuation spectra. The two codes are run sequentially and iteratively until complete consistency is achieved. The current version of the Monte Carlo code incorporates gravity, the zero-current electric field, magnetic mirroring, and collisions. The fluctuation code incorporates WKJ3 wave action conservation and the cascade/dissipation processes discussed above. The codes are being run for various test problems with known solutions. Planned additions to the codes include prescriptions for nonlinear wave steepening, kinetic velocity-space diffusion, and multi-mode coupling (including reflection and refraction).

  4. Discovery of Finely Structured Dynamic Solar Corona Observed in the Hi-C Telescope

    NASA Technical Reports Server (NTRS)

    Winebarger, A.; Cirtain, J.; Golub, L.; DeLuca, E.; Savage, S.; Alexander, C.; Schuler, T.

    2014-01-01

    In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore examine how the intensity scales from AIA resolution to Hi-C resolution. For each low-resolution pixel, we calculate the standard deviation in the contributing high-resolution pixel intensities and compare that to the expected standard deviation calculated from the noise. If these numbers are approximately equal, the corona can be assumed to be smoothly varying, i.e. have no evidence of substructure in the Hi-C image to within Hi-C's ability to measure it given its throughput and readout noise. A standard deviation much larger than the noise value indicates the presence of substructure. We calculate these values for each low-resolution pixel for each frame of the Hi-C data. On average, 70 percent of the pixels in each Hi-C image show no evidence of substructure. The locations where substructure is prevalent is in the moss regions and in regions of sheared magnetic field. We also find that the level of substructure varies significantly over the roughly 160 s of the Hi-C data analyzed here. This result indicates that the finely structured corona is concentrated in regions of heating and is highly time dependent.

  5. The Substructure of the Solar Corona Observed in the Hi-C Telescope

    NASA Technical Reports Server (NTRS)

    Winebarger, A.; Cirtain, J.; Golub, L.; DeLuca, E.; Savage, S.; Alexander, C.; Schuler, T.

    2014-01-01

    In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore calculate how the intensity scales from a low-resolution (AIA) pixels to high-resolution (Hi-C) pixels for both the dynamic events and "background" emission (meaning, the steady emission over the 5 minutes of data acquisition time). We find there is no evidence of substructure in the background corona; the intensity scales smoothly from low-resolution to high-resolution Hi-C pixels. In transient events, however, the intensity observed with Hi-C is, on average, 2.6 times larger than observed with AIA. This increase in intensity suggests that AIA is not resolving these events. This result suggests a finely structured dynamic corona embedded in a smoothly varying background.

  6. Estimating the contribution of Alfvén waves to the process of heating the quiet solar corona

    NASA Astrophysics Data System (ADS)

    González-Avilés, J. J.; Guzmán, F. S.

    2015-07-01

    We solve numerically the ideal magnetohydrodynamic equations with an external gravitational field in 2D in order to study the effects of impulsively generated linear and non-linear Alfvén waves into isolated solar arcades and coronal funnels. We analyse the region containing the interface between the photosphere and the corona. The main interest is to study the possibility that Alfvén waves triggers the energy flux transfer towards the quiet solar corona and heat it, including the case that two consecutive waves can occur. We find that in the case of arcades, short or large, the transferred fluxes by Alfvén waves are sufficient to heat the quiet corona only during a small lapse of time and in a certain region. In the case of funnels the threshold is achieved only when the wave is faster than 10 km s-1, which is extremely high. We conclude from our analysis, that Alfvén waves, even in the optimistic scenario of having two consecutive Alfvén wave pulses, cannot transport enough energy as to heat the quiet corona.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    We study 14 large solar jets observed in polar coronal holes. In EUV movies from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), each jet appears similar to most X-ray jets and EUV jets that erupt in coronal holes; but each is exceptional in that it goes higher than most, so high that it is observed in the outer corona beyond 2.2 RSun in images from the Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph (LASCO)/C2 coronagraph. From AIA He ii 304 Ĺ movies and LASCO/C2 running-difference images of these high-reaching jets, we find: (1) the front of the jet transits the corona below 2.2 RSun at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most of the jets display measureable swaying and bending of a few degrees in amplitude; in three jets the swaying is discernibly oscillatory with a period of order 1 hr. These characteristics suggest that the driver in these jets is a magnetic-untwisting wave that is basically a large-amplitude (i.e., nonlinear) torsional Alfvén wave that is put into the reconnected open field in the jet by interchange reconnection as the jet erupts. From the measured spinning and swaying, we estimate that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 RSun. We point out that the torsional waves observed in Type-II spicules might dissipate in the corona in the same way as the magnetic-untwisting waves in our big jets, and thereby power much of the coronal heating in coronal holes.

  8. Turbulent Alfven Waves as a Solar Wind Driver: Results from a new 4D model for the Solar Corona and Solar Wind

    Microsoft Academic Search

    R. Oran; I. Sokolov; I. I. Roussev; R. A. Frazin; T. I. Gombosi

    2009-01-01

    The mechanisms responsible for plasma heating in the solar corona and solar wind acceleration are still not well understood. Turbulent MHD waves have been suggested as a possible mechanism, which both heats the plasma via wave energy dissipation and accelerates it due to the wave pressure gradient force. In order to account for these processes, a self-consistent model of the

  9. Mapping the Solar Wind from its Source Region into the Outer Corona

    NASA Technical Reports Server (NTRS)

    Esser, Ruth; Wagner, William J. (Technical Monitor)

    2000-01-01

    The solar wind not only forms the space environment of Earth and other planets, but is also the cause of many phenomena observed in the Earth's atmosphere, such as aurorae. The expansion of the coronal plasma of the Sun is characteristic to many main sequence stars, and thus provides an example for understanding stellar winds as well. In spite of its importance for both space science and stellar physics, basic solar wind properties remain essentially unresolved. Since its discovery about 50 years ago, the complexity of the Sun corona - solar wind system has complicated the interpretation of observations. Recent progress in remote sensing observations as provided for example by YOHKOH, SOHO, SPARTAN and ULYSSES as well as some ground based techniques such as Interplanetary Scintillation observations, offer a compelling opportunity to unravel the 50 year old puzzle regarding the heat source or sources that cause the expansion of the solar corona. The new era of solar wind observations initiated by SOHO and ULYSSES, have also led to a wealth of new theoretical approaches. The goal of the proposed research was to carry out an integrated study of the coronal and solar wind plasma making use of the opportunities provided by the above spacecraft, as well as plasma emission calculations and new ideas on solar wind expansion theory.

  10. Skylab and solar exploration. [chromosphere-corona structure, energy production and heat transport processes

    NASA Technical Reports Server (NTRS)

    Von Puttkamer, J.

    1973-01-01

    Review of some of the findings concerning solar structure, energy production, and heat transport obtained with the aid of the manned Skylab space station observatory launched on May 14, 1973. Among the topics discussed are the observation of thermonuclear fusion processes which cannot be simulated on earth, the observation of short-wave solar radiation not visible to observers on earth, and the investigation of energy-transport processes occurring in the photosphere, chromosphere, and corona. An apparent paradox is noted in that the cooler chromosphere is heating the hotter corona, seemingly in defiance of the second law of thermodynamics, thus suggesting that a nonthermal mechanism underlies the energy transport. Understanding of this nonthermal mechanism is regarded as an indispensable prerequisite for future development of plasma systems for terrestrial applications.

  11. The Structure and Dynamics of the Solar Corona and Inner Heliosphere

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran; Grebowsky, J. (Technical Monitor)

    2001-01-01

    This report covers technical progress during the third quarter of the second year of NASA Sun-Earth Connections Theory Program (SECTP) contract 'The Structure and Dynamics of the Solar Corona and Inner Heliosphere,' NAS5-99188, between NASA and Science Applications International Corporation, and covers the period February 16, 2001 to May 15, 2001. Under this contract SAIC and the University of California, Irvine (UCI) have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model.In this report we summarize the accomplishments made by our group during the first seven quarters of our Sun-Earth Connection Theory Program contract. The descriptions are intended to illustrate our principal results. A full account can be found in the referenced publications.

  12. Coexistence of Self-Organized Criticality and Intermittent Turbulence in the Solar Corona

    Microsoft Academic Search

    Vadim M. Uritsky; Maya Paczuski; Joseph M. Davila; Shaela I. Jones

    2007-01-01

    An extended data set of extreme ultraviolet images of the solar corona\\u000aprovided by the SOHO spacecraft are analyzed using statistical methods common\\u000ato studies of self-organized criticality (SOC) and intermittent turbulence\\u000a(IT). The data exhibits simultaneous hallmarks of both regimes, namely power\\u000alaw avalanche statistics as well as multiscaling of structure functions for\\u000aspatial activity. This implies that both

  13. A dust characterization experiment for solar cells operating on Mars

    Microsoft Academic Search

    P. Jenkins; G. A. Landis; M. Krasowski; L. Greer; D. Wilt; C. Baraona; D. Scheiman; J. Lekki

    2000-01-01

    During the Viking and Pathfinder missions to Mars, significant amounts of dust accumulated on the spacecraft. In Pathfinder's case, the dust obscured the solar panels on the lander and the rover degrading their output current. The material adherence experiment aboard the Pathfinder rover quantified the rate of decrease in short circuit current at 0.28% per day. This rate is unacceptably

  14. Dust to planetesimals - Settling and coagulation in the solar nebula

    Microsoft Academic Search

    S. J. Weidenschilling

    1980-01-01

    The behavior of solid particles in a low-mass solar nebula during settling to the central plane and the formation of planetesimals is discussed. The gravitational instability in a dust layer and collisional accretion are examined as possible mechanisms of planetesimal formation. The shear between the gas and a dust layer is considered along with the differences in the planetesimal formation

  15. Spectroscopic measurements of element abundances in the solar corona: Variations on the FIP theme

    NASA Technical Reports Server (NTRS)

    Saba, J. L. R.

    1995-01-01

    Solar wind and solar energetic particle (SEP) data yield systematic differences between elemental abundances in the corona and in the photosphere related to the first ionization potential (FIP) of the elements: low-FIP elements are preferentially enhanced relative to high-FIP elements by about a factor of four. Spectroscopic studies of the inner corona show that such a pattern may apply on average but not in detail for coronal loops: substantial abundance differences occur between different types of coronal structures, and variations have been found from flare to flare, from one active region to another, and over time in the same region; further, in some flares, anomalies such as enhanced Ne:O ratios, distinctly at odds with the FIP pattern, show that a competing element selection mechanism sometimes operates. Details of the observed abundance variability -- such as the magnitude of the variations, the relevant temporal and spatial scales, and correlations with other properties of the given coronal structure -- may give important clues to the processes which supply and heat the corona, or they may reflect the changing physical conditions or locations where those processes take place. However, many such details remain to be established definitively. At present, abundance variability is primarily a major complication to data analysis and interpretation. However, once it is better understood, it may provide a new diagnostic tool for probing the lower layers of the solar atmosphere.

  16. Destruction of Sun-grazing comet C/2011 N3 (SOHO) within the low solar corona.

    PubMed

    Schrijver, C J; Brown, J C; Battams, K; Saint-Hilaire, P; Liu, W; Hudson, H; Pesnell, W D

    2012-01-20

    Observations of comets in Sun-grazing orbits that survive solar insolation long enough to penetrate into the Sun's inner corona provide information on the solar atmosphere and magnetic field as well as on the makeup of the comet. On 6 July 2011, the Solar Dynamics Observatory (SDO) observed the demise of comet C/2011 N3 (SOHO) within the low solar corona in five wavelength bands in the extreme ultraviolet (EUV). The comet penetrated to within 0.146 solar radius (~100,000 kilometers) of the solar surface before its EUV signal disappeared. Before that, material released into the coma--at first seen in absorption--formed a variable EUV-bright tail. During the final 10 minutes of observation by SDO's Atmospheric Imaging Assembly, ~6 × 10(8) to 6 × 10(10) grams of total mass was lost (corresponding to an effective nucleus diameter of ~10 to 50 meters), as estimated from the tail's deceleration due to interaction with the surrounding coronal material; the EUV absorption by the comet and the brightness of the tail suggest that the mass was at the high end of this range. These observations provide evidence that the nucleus had broken up into a family of fragments, resulting in accelerated sublimation in the Sun's intense radiation field. PMID:22267810

  17. Penetration of nearby supernova dust in the inner solar system

    NASA Astrophysics Data System (ADS)

    Athanassiadou, Themis; Fields, B. D.

    2011-07-01

    We investigate the method by which nearby supernovae - within a few tens of pc of the solar system - can penetrate the solar system and deposit live radioactivities on earth. The radioactive isotopic signatures that could potentially leave an observable geological imprint are in the form of refractory metals; consequently, it is likely they would arrive in the form of supernova-produced dust grains. Such grains can penetrate into the solar system more easily than the bulk supernova plasma, which gets stalled and deflected near the solar system due to the solar wind plasma pressure. We therefore examine the motion of charged grains as they decouple from the supernova plasma and are influenced by the solar magnetic, radiation, and gravitational fields. We characterize the dust trajectories with analytical approximations which display the roles of grain size, initial velocity, and surface voltage. These results are verified with full numerical simulations for wide ranges of dust properties. We find that supernova dust grains traverse the inner solar system nearly undeflected, if the incoming grain velocity - which we take to be that of the incident supernova remnant - is comparable to the solar wind speeds and much larger than the escape velocity at 1 AU. Consequently, the dust penetration to 1 AU has essentially 100% transmission probability and the dust capture onto the earth should have a geometric cross section. Our results cast in a new light the terrestrial deposition of radioisotopes from nearby supernovae in the geological past. For explosions beyond ˜10 pc from earth, dust grains can still deliver supernova ejecta to earth, and thus the amount of supernova material deposited is set by the efficiency of dust condensation and survival in supernovae. Turning the problem around, we use observations of live 60Fe in both deep-ocean and lunar samples to infer a conservative lower bound iron condensation efficiency of Mdust,Fe/ Mtot,Fe ? 4 × 10 -4 for the supernova which apparently produced these species 2-3 Myr ago.

  18. Dust acoustic instability driven by solar and stellar winds

    SciTech Connect

    Vranjes, J. [Belgian Institute for Space Aeronomy, Ringlaan 3, 1180 Brussels (Belgium)

    2011-11-29

    A quantitative analysis is presented of the dust acoustic wave instability driven by the solar or stelar wind. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion plasma propagates through another quasi-neutral plasma which contains dust, electrons and ions. The cometary dusty plasma in the solar wind appears to be practically always unstable.

  19. Solar activity and its evolution across the corona: recent advances

    NASA Astrophysics Data System (ADS)

    Zuccarello, Francesca; Balmaceda, Laura; Cessateur, Gael; Cremades, Hebe; Guglielmino, Salvatore L.; Lilensten, Jean; Dudok de Wit, Thierry; Kretzschmar, Matthieu; Lopez, Fernando M.; Mierla, Marilena; Parenti, Susanna; Pomoell, Jens; Romano, Paolo; Rodriguez, Luciano; Srivastava, Nandita; Vainio, Rami; West, Matt; Zuccarello, Francesco P.

    2013-04-01

    Solar magnetism is responsible for the several active phenomena that occur in the solar atmosphere. The consequences of these phenomena on the solar-terrestrial environment and on Space Weather are nowadays clearly recognized, even if not yet fully understood. In order to shed light on the mechanisms that are at the basis of the Space Weather, it is necessary to investigate the sequence of phenomena starting in the solar atmosphere and developing across the outer layers of the Sun and along the path from the Sun to the Earth. This goal can be reached by a combined multi-disciplinary, multi-instrument, multi-wavelength study of these phenomena, starting with the very first manifestation of solar active region formation and evolution, followed by explosive phenomena (i.e., flares, erupting prominences, coronal mass ejections), and ending with the interaction of plasma magnetized clouds expelled from the Sun with the interplanetary magnetic field and medium. This wide field of research constitutes one of the main aims of COST Action ES0803: Developing Space Weather products and services in Europe. In particular, one of the tasks of this COST Action was to investigate the Progress in Scientific Understanding of Space Weather. In this paper we review the state of the art of our comprehension of some phenomena that, in the scenario outlined above, might have a role on Space Weather, focusing on the researches, thematic reviews, and main results obtained during the COST Action ES0803.

  20. On Shock Accelerated Electron Beams In The Solar Corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    Electron beams accelerated at coronal shock waves appear as rapidly drifting emission stripes (so-called "herringbones") withih solar type II radio bursts. Such shock waves can be produced eihter by flares or by coronal masse ejections. A large sample of solar type III radio bursts and "herringbones" within solar type II radio bursts is statistically analyzed with respect to their properties in dynamic radio spectra. The analysis reveals that the drift rate of the "herringbones" are significanlty smaller (about one half) than those of type III bursts in the same frequency range. Consequently, the electron beams related to type III bursts have a higher velocity than those produced by coronal shock waves. The velocity of electromn beams assiciated with the "herringbones" is deduced to be 40,000 km/s. This result is discussed in terms of the different velocity distribution functions of electron beams associated to type III bursts and "herringbone" bursts.

  1. Multi-wavelength Analysis to Solar Corona Heating Events

    NASA Astrophysics Data System (ADS)

    Xu, YANG; Hai-sheng, JI; Hao-chuan, LI

    2015-01-01

    With the advent and successful operation of the 1.6 m aperture New Solar Telescope of Big Bear Solar Observatory (BBSO/NST), solar observation has entered the era of high resolution better than 0.1". This permits us to carry out the case studies of single coronal heating events, to provide the original high-resolution observational evidence for finally solving the problem of coronal heating. By combining the high-resolution Helium I 10830 Ĺ, TiO 7057 Ĺ, and Ha blue-wing (-0.7 Ĺ) imaging data from the NST with the imaging data of extreme ultraviolet and longitudinal magnetic field observed simultaneously by the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board of the Solar Dynamics Observatory (SDO), we have analyzed the evolution of magnetic field in two tiny dynamical events of coronal heating (brightening of magnetic loops) that originate from the solar intergranular lanes. It is found that the footpoints of both brightening magnetic loops were all located in the one side of nearby neutral line of magnetic fields, the footpoints of one magnetic loop were accompanied by the disappearance of a small longitudinal magnetic element and the newly formed connection between two granulations, while the footpoints of another magnetic loop were accompanied by a weak variation of longitudinal magnetic field and the breakdown of a granulation. The observed result tends to suggest that the low-temperature and high-temperature outflows were produced simultaneously by the magnetic reconnection occurred among the solar granulations in the low-layer atmosphere. Meanwhile, it is noted that the high-resolution and high-accuracy polarization measurement of photospheric magnetic field is crucial for finally solving the problem of coronal heating.

  2. Moon Dust Telescopes, Solar Concentrators, and Structures

    NASA Astrophysics Data System (ADS)

    Chen, Peter C.; Van Steenberg, M. E.; Oliversen, R. J.

    2008-05-01

    We report development of an ISRU (in situ resource utilization) process to fabricate large telescope mirrors, solar concentrators, and structures on the Moon. The Moon is an excellent site for a future space base and space astrophysics research. However transporting extremely large (10-50m) telescopes to the Moon, building up an observatory structure, and providing power for operation face the obstacles of high cost and logistical difficulties. We suggest a simple and novel approach to the problem. Large mirrors can be made by spincasting a liquid over or mixed with lunar surface soil (regolith). The liquid, which is a special vacuum stable cryogenic polymer, gradually solidifies while spun into a hard parabolic surface. Additives including carbon nanotubes and fibers can be used to increase tensile strength, reduce cure shrinkage, and enhance thermal conductivity. The process uses a single apparatus to make multiple mirrors. Large arrays of solar concentrators can be fabricated to provide power to a lunar base. For astronomy, the mirror surface can be polished or modified in situ with an ion beam like process taking advantage of the high vacuum of the lunar environment. Moreover, we have found that the simple process of mixing a small amount of polymer with lunar regolith yields after curing a material similar to cement in terms of strength, density, and consistency. This `lunar cement’ may be useful as building blocks for human habitats and telescope structures. We report on experiments carried out at GSFC to demonstrate feasibility of the concept. Mirrors and bricks have been made by curing a cryogenic polymer with added JSC-1A Fine lunar soil simulant and carbon nanotubes. Preliminary observations have been carried out using such `Moon dust’ mirrors.

  3. Generation of Suprathermal Electrons by Resonant Wave-Particle Interaction in the Solar Corona and Wind

    NASA Astrophysics Data System (ADS)

    Vocks, C.; Mann, G.

    2003-08-01

    Observations of solar wind electron velocity distribution functions (VDFs) reveal pronounced deviations from a Maxwellian with enhanced numbers of suprathermal electrons. It is shown that these suprathermal tails of the electron VDFs can originate from the solar corona. A model for the acceleration of suprathermal electrons based on resonant interaction with whistler waves is presented. Quasi-linear theory describes this interaction as pitch-angle diffusion in the reference frame of the waves. The waves are assumed to be generated below the coronal base and to propagate antisunward through the corona. Under plasma conditions with high whistler wave phase speeds, the resonant interaction causes electrons to be accelerated from relatively small sunward velocities parallel to the background magnetic field to high speeds perpendicular to the magnetic field. Such plasma conditions are found in the solar corona. A kinetic model is developed to study this acceleration mechanism and the evolution of an electron VDF from the coronal base up into interplanetary space. The kinetic model includes not only the resonant interaction with whistler waves but also Coulomb collisions and the mirror force the electrons experience in the opening magnetic structure of a coronal funnel. The wave absorption of the electrons is also considered to guarantee energy conservation. Kinetic results for the coronal funnel and solar wind are presented. The electron VDFs show deviations from a Maxwellian that are in coincidence with theoretical expectations. The whistler waves generate suprathermal electrons. Toward interplanetary space, the mirror force focuses the electrons toward a narrow ``strahl.'' A comparative study without whistler waves shows that the waves considerably enhance the suprathermal electron fluxes in interplanetary space at 1 AU, as they are observed in the solar wind.

  4. Influence of solar flares on the X-ray corona

    NASA Technical Reports Server (NTRS)

    Rust, D. M.; Batchelor, D. A.

    1986-01-01

    Sequences of X-ray images of solar flares, obtained with the Hard X-ray Imaging Spectrometer on the SMM spacecraft, reveal many dynamical phenomena. Movies of 20 flares recorded with 6-sec time resolution were examined. A preliminary analysis of the events as a group are presented, and some new aspects of the well-studied May 21, 1980 flare and a November 6, 1980 flare are discussed.

  5. Dust Measurements in the Outer Solar System by the Student Dust Counter

    NASA Astrophysics Data System (ADS)

    Szalay, Jamey; Horanyi, M.

    2013-10-01

    The Student Dust Counter (SDC) is an impact dust detector on board the New Horizons Mission to Pluto. SDC was designed to resolve the mass of dust grains in the range of 10^-12 < m < 10^-9 g, covering an approximate size range of 0.5-10 um in particle radius. The measurements can be directly compared to the prediction of a grain tracing trajectory model of dust originating from the Edgeworth-Kuiper Belt. SDC's results are compared to our model to derive estimates for the mass production rate and the ejecta mass distribution power law exponent. Through October 2013, the New Horizons spacecraft reached approximately 27.5 AU, enabling SDC to map the dust density distribution of the solar system farther than any previous dust detector.

  6. Semiempirical Two-dimensional Magnetohydrodynamic Model of the Solar Corona and Interplanetary Medium

    SciTech Connect

    Sittler, E.C. Jr.; Guhathakurta, M. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)] [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    1999-10-01

    We have developed a two-dimensional semiempirical MHD model of the solar corona and solar wind. The model uses empirically derived electron density profiles from white-light coronagraph data measured during the {ital Skylab} period and an empirically derived model of the magnetic field which is fitted to observed streamer topologies, which also come from the white-light coronagraph data. The electron density model comes from that developed by Guhathakurta and coworkers. The electron density model is extended into interplanetary space by using electron densities derived from the {ital Ulysses} plasma instrument. The model also requires an estimate of the solar wind velocity as a function of heliographic latitude and radial component of the magnetic field at 1 AU, both of which can be provided by the {ital Ulysses} spacecraft. The model makes estimates as a function of radial distance and latitude of various fluid parameters of the plasma such as flow velocity {bold {ital V}}, effective temperature T{sub eff}, and effective heat flux q{sub eff}, which are derived from the equations of conservation of mass, momentum, and energy, respectively. The term {open_quotes}effective{close_quotes} indicates that wave contributions could be present. The model naturally provides the spiral pattern of the magnetic field far from the Sun and an estimate of the large-scale surface magnetic field at the Sun, which we estimate to be {approximately}12{endash}15 G. The magnetic field model shows that the large-scale surface magnetic field is dominated by an octupole term. The model is a steady state calculation which makes the assumption of azimuthal symmetry and solves the various conservation equations in the rotating frame of the Sun. The conservation equations are integrated along the magnetic field direction in the rotating frame of the Sun, thus providing a nearly self-consistent calculation of the fluid parameters. The model makes a minimum number of assumptions about the physics of the solar corona and solar wind and should provide a very accurate empirical description of the solar corona and solar wind. Once estimates of mass density {rho}, flow velocity {bold {ital V}}, effective temperature T{sub eff}, effective heat flux q{sub eff}, and magnetic field {bold {ital B}} are computed from the model and waves are assumed unimportant, all other plasma parameters such as Mach number, Alfv{acute e}n speed, gyrofrequency, etc. can be derived as a function of radial distance and latitude from the Sun. The model can be used as a planning tool for such missions as {ital Solar Probe} and provide an empirical framework for theoretical models of the solar corona and solar wind. The model will be used to construct a semiempirical MHD description of the steady state solar corona and solar wind using the {ital SOHO} Large Angle Spectrometric Coronagraph (LASCO) polarized brightness white-light coronagraph data, {ital SOHO} Extreme Ultraviolet Imaging Telescope data, and {ital Ulysses} plasma data. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  7. Common observations of solar X-rays from SPHINX/CORONAS-PHOTON and XRS/MESSENGER

    NASA Astrophysics Data System (ADS)

    Kepa, Anna; Sylwester, Janusz; Sylwester, Barbara; Siarkowski, Marek; Mrozek, Tomasz; Gryciuk, Magdalena; Phillips, Kenneth

    SphinX was a soft X-ray spectrophotometer constructed in the Space Research Centre of Polish Academy of Sciences. The instrument was launched on 30 January 2009 aboard CORONAS-PHOTON satellite as a part of TESIS instrument package. SphinX measured total solar X-ray flux in the energy range from 1 to 15 keV during the period of very low solar activity from 20 February to 29 November 2009. For these times the solar detector (X-ray Spectrometer - XRS) onboard MESSENGER also observed the solar X-rays from a different vantage point. XRS measured the radiation in similar energy range. We present results of the comparison of observations from both instruments and show the preliminary results of physical analysis of spectra for selected flares.

  8. Induced emission of Alfvén waves in inhomogeneous streaming plasma: implications for solar corona heating and solar wind acceleration.

    PubMed

    Galinsky, V L; Shevchenko, V I

    2013-07-01

    The results of a self-consistent kinetic model of heating the solar corona and accelerating the fast solar wind are presented for plasma flowing in a nonuniform magnetic field configuration of near-Sun conditions. The model is based on a scale separation between the large transit or inhomogeneity scales and the small dissipation scales. The macroscale instability of the marginally stable particle distribution function compliments the resonant frequency sweeping dissipation of transient Alfvén waves by their induced emission in inhomogeneous streaming plasma that provides enough energy for keeping the plasma temperature decaying not faster than r(-1) in close agreement with in situ heliospheric observations. PMID:23863008

  9. Semiempirical Two-Dimensional Magnetohydrodynamic Model of the Solar Corona and Interplanetary Medium

    NASA Technical Reports Server (NTRS)

    Sittler, Edward C., Jr.; Guhathakurta, Madhulika

    1999-01-01

    We have developed a two-dimensional semiempirical MHD model of the solar corona and solar wind. The model uses empirically derived electron density profiles from white-light coronagraph data measured during the Skylub period and an empirically derived model of the magnetic field which is fitted to observed streamer topologies, which also come from the white-light coronagraph data The electron density model comes from that developed by Guhathakurta and coworkers. The electron density model is extended into interplanetary space by using electron densities derived from the Ulysses plasma instrument. The model also requires an estimate of the solar wind velocity as a function of heliographic latitude and radial component of the magnetic field at 1 AU, both of which can be provided by the Ulysses spacecraft. The model makes estimates as a function of radial distance and latitude of various fluid parameters of the plasma such as flow velocity V, effective temperature T(sub eff), and effective heat flux q(sub eff), which are derived from the equations of conservation of mass, momentum, and energy, respectively. The term effective indicates that wave contributions could be present. The model naturally provides the spiral pattern of the magnetic field far from the Sun and an estimate of the large-scale surface magnetic field at the Sun, which we estimate to be approx. 12 - 15 G. The magnetic field model shows that the large-scale surface magnetic field is dominated by an octupole term. The model is a steady state calculation which makes the assumption of azimuthal symmetry and solves the various conservation equations in the rotating frame of the Sun. The conservation equations are integrated along the magnetic field direction in the rotating frame of the Sun, thus providing a nearly self-consistent calculation of the fluid parameters. The model makes a minimum number of assumptions about the physics of the solar corona and solar wind and should provide a very accurate empirical description of the solar corona and solar wind Once estimates of mass density rho, flow velocity V, effective temperature T(sub eff), effective heat flux q(sub eff), and magnetic field B are computed from the model and waves are assumed unimportant, all other plasma parameters such as Mach number, Alfven speed, gyrofrequency, etc. can be derived as a function of radial distance and latitude from the Sun. The model can be used as a planning tool for such missions as Slar Probe and provide an empirical framework for theoretical models of the solar corona and solar wind The model will be used to construct a semiempirical MHD description of the steady state solar corona and solar wind using the SOHO Large Angle Spectrometric Coronagraph (LASCO) polarized brightness white-light coronagraph data, SOHO Extreme Ultraviolet Imaging Telescope data, and Ulysses plasma data.

  10. The Funnel Geometry of Open Flux Tubes in the Low Solar Corona Constrained by O VI and Ne VIII Outflow

    NASA Technical Reports Server (NTRS)

    Byhring, Hanne S.; Esser, Ruth; Lie-Svendsen, Oystein

    2008-01-01

    Model calculations show that observed outflow velocities of order 7-10 km/s of C IV and O VI ions, and 15-20 km/s of Ne VIII ions, are not only consistent with models of the solar wind from coronas holes, but also place unique constraints on the degree of flow tube expansion as well as the location of the expansion in the transition region/lower corona.

  11. Dual-frequency radio sounding of the solar corona during the 1995 conjunction of the Ulysses spacecraft

    Microsoft Academic Search

    M. Pätzold; M. K. Bird; P. Edenhofer; S. W. Asmar; T. P. McElrath

    1995-01-01

    The Ulysses Solar Corona Experiment was performed during the spacecraft's superior solar conjunction from 22 February to 14 March 1995, shortly before perihelion and the transit through the ecliptic plane. The high inclination of the Ulysses orbit resulted in an unusual occultation geometry for coronal radio sounding with the spacecraft's dual-frequency down-link signals. Viewed from Earth, the virtual position of

  12. Dual-frequency radio sounding of the solar corona during the 1995 conjunction of the Ulysses spacecraft

    Microsoft Academic Search

    M. Pätzold; M. K. Bird; P. Edenhofer; S. W. Asmar; T. P. McElrath

    1995-01-01

    The Ulysses Solar Corona Experiment was performed during the spacecraft’s superior solar conjunction from 22 February to 14 March 1995, shortly before perihelion and the transit through the ecliptic plane. The high inclination of the Ulysses orbit resulted in an unusual occultation geometry for coronal radio sounding with the spacecraft's dual-frequency downlink signals. Viewed from Earth, the virtual position of

  13. Acceleration of suprathermal electrons by resonant interaction with whistler waves in the solar corona and wind

    NASA Astrophysics Data System (ADS)

    Vocks, C.; Mann, G.

    2003-04-01

    Observations of solar wind electron velocity distribution functions (VDFs) show destinctive deviations from Maxwellian distributions. The number of suprathermal electrons is strongly enhanced. These electron VDFs can be fitted by kappa distributions, or are described as core and halo population. A model for the acceleration of suprathermal electrons is presented. It is based on resonant interaction between electrons and whistler waves. The wave-electron interaction is described within the framework of quasilinear theory and leads to pitch-angle diffusion of the electrons in the reference frame of the waves. Thus, it is possible to accelerate electrons from relatively small negative v\\| to high v_{perp. The higher the wave phase speed, estimated by the electron Alfvén speed, the more energy the electrons can gain. To study this mechanism in detail and to investigate the overall evolution of an electron VDF from the corona into the solar wind, a kinetic model for the electrons is developed. The geometry and plasma conditions of a coronal funnel and fast solar wind are used as a background for the kinetic calculations. Beside the wave-electron interaction, the model includes the effects of the inhomogenous background conditions, the gravitational and electric fields, and Coulomb collisions. From the variation of the Alfvén speed with height it follows that the electron acceleration mechanism should be most effective in the corona, while solar wind electrons hardly gain energy. A study of the relaxation process of an electron VDF with suprathermal tails under typical coronal conditions shows that a coronal origin of the suprathermal tails indeed is possible. Simulation results from the corona up into the interplanetary space and in the energy range of several keV are presented. At the lower bound of the simulation box, a power law spectrum of whistler waves enters the box and propagates anti-sunwards. The electron VDF shows deviations from a Maxwellian that are in coincidence with the pitch-angle diffusion in the wave frame as it is expected from theory. Towards interplanetary space, the mirror force in the opening magnetic field geometry focuses the electrons towards a narrow ``strahl''. The resonant absorption of the whistler waves in the corona results in a considerable enhancement of solar wind suprathermal electron fluxes, as they are observed. Simulations with an electron energy range expanded up to 100 keV are also discussed.

  14. Kinematic Properties of Globally-Propagating Waves in the Solar Corona

    E-print Network

    Long, David M

    2012-01-01

    Globally-propagating coronal bright fronts (CBFs) in the solar corona are among the most dramatic manifestations of solar activity, but are not well understood despite strong links with both solar flares and coronal mass ejections. Extreme UltraViolet (EUV) observations from the STEREO and SDO spacecraft are used here to study their kinematics and morphology. The first STEREO observations of a CBF are presented, with the pulse observed in all available EUV passbands (171, 195, 284 and for the first time, 304A). The pulse displayed similar kinematics in all passbands, although the derived pulse velocity and acceleration were found to be strongly influenced by the observing cadence, implying that previous kinematics may have been underestimated. Different techniques for identifying CBFs and deriving their true kinematics were tested, with traditional techniques shown to be prone to undefined user-dependent errors. This was overcome through the development of a statistically rigorous, semi-automated identificati...

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

    E-print Network

    Moore, Ronald L; Falconer, David A

    2015-01-01

    We study 14 large solar jets observed in polar coronal holes. In EUV movies from SDO/AIA, each jet appears similar to most X-ray jets and EUV jets that erupt in coronal holes, but each is exceptional in that it goes higher than most, so high that it is observed in the outer corona beyond 2.2 RSun in images from the SOHO/LASCO/C2 coronagraph. From AIA He II 304 {\\AA} movies and LASCO/C2 running-difference images of these high-reaching jets, we find: (1) the front of the jet transits the corona below 2.2 RSun at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most of the jets display measureable swaying and bending of a few degrees in amplitude; in three jets the swaying is discernibly oscillatory with a period of order 1 hour. These characteristics suggest that the driver in these jets is a magnetic-untwisting wave that is basically a large-amplitude (i.e., non-linear) torsional Alfven wave that is put into the ...

  16. Modelling Magnetic Reconnection and Nano-flare Heating in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Biggs, George; Asgari-Targhi, Mahboubeh

    2015-01-01

    Current models describing magnetic reconnection in the solar corona assume single reconnection events occurring at random crossings between magnetic flux tubes. However, in the avalanche model of magnetic reconnection, multiple reconnections are expected to occur. The purpose of this research is to first, calculate the point of the greatest stress between magnetic flux tubes and then to allow for dynamic evolution utilising the avalanche model. This represents a significant increase in sophistication over previous models. This undertaking is not purely theoretical since we compare the results of our modelling with HI-C data. Using key inputs from the HIC and AIA observations such as loop length and magnetic field strength, we predict the number of reconnection events likely to take place. As a single reconnection event cannot currently be directly observed, the distribution of flare events are recorded instead. The power law fit yielded as a result of our simulations is within the expected range given the observational evidence of flare distributions and temperature values in the corona. This provides further evidence to support the role of Nano-flares in the heating of the corona.

  17. Spatio - Temporal Organization of the Intermittent Irradiance in the Quiet Solar Corona

    NASA Astrophysics Data System (ADS)

    Uritsky, Vadim; Davila, Joseph

    2014-05-01

    Using data from the EUVI instrument on board the STEREO spacecraft, we show, for the first time, that energy release events in the quiet solar corona exhibit random occurrence times described by an exponential probability distribution of interevent intervals exceding the charateristic Alfven transit time, and the temporal correlation dimension equal to one. This random temporal behavior is accompanied by a pronounced spatial clustering of event locations which mimics the supergranulation pattern of the underling photospheric network. Random temporal organization of the quiet Sun revealed by two independent statistical techniques is in a sharp contrast with power-law interevent time distributions of flaring events in solar active regions reported in previous studies. We propose that quiet solar corona, which is believed to be responsible to the bulk coronal heating, operates as a critical avalanching system driven by spatially nonuniform injection of the photospheric magnetic flux. Graph analysis of nearly-simultaneous dissipation events suggests that quiet-Sun avalanches may involve spatially disconnected sympathetic brightenings interacting across vast coronal distances.

  18. SWAP Observations of the Long-term, Large-scale Evolution of the Extreme-ultraviolet Solar Corona

    NASA Astrophysics Data System (ADS)

    Seaton, Daniel B.; De Groof, Anik; Shearer, Paul; Berghmans, David; Nicula, Bogdan

    2013-11-01

    The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar telescope on board the Project for On-Board Autonomy 2 spacecraft has been regularly observing the solar corona in a bandpass near 17.4 nm since 2010 February. With a field of view of 54 × 54 arcmin, SWAP provides the widest-field images of the EUV corona available from the perspective of the Earth. By carefully processing and combining multiple SWAP images, it is possible to produce low-noise composites that reveal the structure of the EUV corona to relatively large heights. A particularly important step in this processing was to remove instrumental stray light from the images by determining and deconvolving SWAP's point-spread function from the observations. In this paper, we use the resulting images to conduct the first-ever study of the evolution of the large-scale structure of the corona observed in the EUV over a three year period that includes the complete rise phase of solar cycle 24. Of particular note is the persistence over many solar rotations of bright, diffuse features composed of open magnetic fields that overlie polar crown filaments and extend to large heights above the solar surface. These features appear to be related to coronal fans, which have previously been observed in white-light coronagraph images and, at low heights, in the EUV. We also discuss the evolution of the corona at different heights above the solar surface and the evolution of the corona over the course of the solar cycle by hemisphere.

  19. Dust to planetesimals - Settling and coagulation in the solar nebula

    NASA Technical Reports Server (NTRS)

    Weidenschilling, S. J.

    1980-01-01

    The behavior of solid particles in a low-mass solar nebula during settling to the central plane and the formation of planetesimals is discussed. The gravitational instability in a dust layer and collisional accretion are examined as possible mechanisms of planetesimal formation. The shear between the gas and a dust layer is considered along with the differences in the planetesimal formation mechanisms between the inner and outer nebula. A numerical model for computing simultaneous coagulation and settling is described.

  20. Coexistence of Self-Organized Criticality and Intermittent Turbulence in the Solar Corona

    SciTech Connect

    Uritsky, Vadim M.; Paczuski, Maya [Complexity Science Group, Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, T2N 1N4 (Canada); Davila, Joseph M. [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Jones, Shaela I. [University of Maryland, College Park, Maryland 20742 (United States)

    2007-07-13

    An extended data set of extreme ultraviolet images of the solar corona provided by the SOHO spacecraft is analyzed using statistical methods common to studies of self-organized criticality (SOC) and intermittent turbulence (IT). The data exhibit simultaneous hallmarks of both regimes: namely, power-law avalanche statistics as well as multiscaling of structure functions for spatial activity. This implies that both SOC and IT may be manifestations of a single complex dynamical process entangling avalanches of magnetic energy dissipation with turbulent particle flows.

  1. Observations of the brightness temperature distribution of the quiet solar corona at decametric wavelengths

    NASA Technical Reports Server (NTRS)

    Sastry, Ch. V.

    1987-01-01

    The brightness temperature distribution of the quiet solar corona at a wavelength of 8.9 meters is measured by two types of radio telescope: (1) a 'T' type array with a resolution of 26'X38', and (2) a fan beam interferometer with an E-W resolution of 3'. It is found that the persistent bright regions do not have any angular structure on scales of 6' or less. The daily variations of the brightness temperature of different regions are studied and the possible interpretation discussed.

  2. Coexistence of Self-Organized Criticality and Intermittent Turbulence in the Solar Corona

    E-print Network

    Uritsky, V M; Davila, J M; Jones, S I; Uritsky, Vadim M.; Paczuski, Maya; Davila, Joseph M.; Jones, Shaela I.

    2006-01-01

    An extended data set of extreme ultraviolet images of the solar corona provided by the SOHO spacecraft are analyzed using statistical methods common to studies of self-organized criticality (SOC) and to intermittent turbulence. The data exhibits simultaneous hallmarks of both regimes, namely power-law avalanche statistics as well as multiscaling of structure functions of spatial activity. This indicates that both SOC and intermittent turbulence may be manifestations of a single dynamical process in magnetized plasmas entangling avalanches of magnetic energy dissipation with turbulent particle flows.

  3. Formation and Reconnection of Three-Dimensional Current Sheets in the Solar Corona

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    Current-sheet formation and magnetic reconnection are believed to be the basic physical processes responsible for much of the activity observed in astrophysical plasmas, such as the Sun s corona. We investigate these processes for a magnetic configuration consisting of a uniform background field and an embedded line dipole, a topology that is expected to be ubiquitous in the corona. This magnetic system is driven by a uniform horizontal flow applied at the line-tied photosphere. Although both the initial field and the driver are translationally symmetric, the resulting evolution is calculated using a fully three-dimensional magnetohydrodynamic (3D MHD) simulation with adaptive mesh refinement that resolves the current sheet and reconnection dynamics in detail. The advantage of our approach is that it allows us to apply directly the vast body of knowledge gained from the many studies of 2D reconnection to the fully 3D case. We find that a current sheet forms in close analogy to the classic Syrovatskii 2D mechanism, but the resulting evolution is different than expected. The current sheet is globally stable, showing no evidence for a disruption or a secondary instability even for aspect ratios as high as 80:1. The global evolution generally follows the standard Sweet- Parker 2D reconnection model except for an accelerated reconnection rate at a very thin current sheet, due to the tearing instability and the formation of magnetic islands. An interesting conclusion is that despite the formation of fully 3D structures at small scales, the system remains close to 2D at global scales. We discuss the implications of our results for observations of the solar corona. Subject Headings: Sun: corona Sun: magnetic fields Sun: reconnection

  4. ON THE CONSTANCY OF THE ELECTRON TEMPERATURE IN THE EXPANDING CORONA THROUGHOUT SOLAR CYCLE 23

    SciTech Connect

    Habbal, Shadia Rifai; Morgan, Huw [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Druckmueller, Miloslav [Faculty of Mechanical Engineering, Brno University of Technology, 616 69 Brno (Czech Republic); Ding, Adalbert [Institute of Optics and Atomic Physics, Technische Universitaet Berlin and Institute of Technical Physics, Berlin (Germany)], E-mail: shadia@ifa.hawaii.edu

    2010-03-10

    A recent analysis of Fe emission lines observed during the total solar eclipses of 2006 March 29 and 2008 August 1 established the first empirical link between the electron temperature in the expanding corona and Fe charge states measured in interplanetary space. In this Letter, we use this link to infer this temperature throughout solar cycle 23 from in situ charge state measurements from the Solar Wind Ion Composition Spectrometer (SWICS) on the Advanced Composition Explorer (ACE) and on Ulysses. The distribution of the SWICS/ACE Fe charge states, which span cycle 23 from 1998 to 2009, is skewed with a peak centered on Fe{sup 8+}, Fe{sup 9+}, and Fe{sup 10+} and a tail spanning Fe{sup 12+} to Fe{sup 20+}. An iterative process based on this distribution and on the Fe ion fraction as a function of electron temperature yields a narrow peak at 1.1 x 10{sup 6} K. The tail in the measured charge state distribution is attributed to the sporadic release of material hotter than 2 x 10{sup 6} K from closed magnetic structures within the bulges of streamers. The Fe Ulysses charge state measurements between 1992 and 1997 from cycle 22 peaked at Fe{sup 11+}, indicative of a slightly higher temperature of 1.5 x 10{sup 6} K. The relative constancy of the electron temperature in the expanding corona throughout solar cycle 23 points to the presence of an unknown mechanism regulating the energy input to electrons in the acceleration region of the solar wind at all latitudes during this cycle.

  5. Observations of high-energy jets in the corona above the quiet sun, the heating of the corona, and the acceleration of the solar wind

    NASA Technical Reports Server (NTRS)

    Brueckner, G. E.; Bartoe, J.-D. F.

    1983-01-01

    High spatial resolution observations of the ultraviolet solar spectrum which reveal high-energy events in the quiet sun are presented. The tandem Wadsworth spectrograph used to make the observations is described along with the observing techniques, and a brief description of the characteristics of high-resolution transition zone spectra is given. The sizes, velocities, line profiles, time behavior, temperature range, differential emission measures, densities, masses, energies, and birthrates of turbulent events and jets in the quiet sun are derived from the observations and discussed. Possible accelerating mechanisms for these events are discussed, and the consequences of these events for the heating of the solar corona are discussed. A cloud model of the solar wind is proposed and possible correlations between the high-energy events and other solar fine-structure features are discussed.

  6. The proper motion of network bright points and the heating of the solar corona

    NASA Astrophysics Data System (ADS)

    Muller, R.; Roudier, Th.; Vigneau, J.; Auffret, H.

    1994-03-01

    Since it has been proved that acoustic waves are inefficient, it has been widely accepted that the solar corona is heated by waves which propagate along magnetic flux tubes and are generated by the turbulent granular motions. Such motions, however, may have yet been measured nor the involved energy evaluated. We present in this paper the first measurements of the proper motion of the footprints of magnetic flux tubes, at the photospheric level, outside active regions. For this purpose, we have used a high resolution granulation movie obtained at the Pic du Midi Observatory, in which we were able to identify many network bright points (NBPs). As they are associated to the magnetic flux tubes, we have used these tiny bright points as tracers of magnetic fields. Velocity histograms have been derived. They show that NBPs proper motion is turbulent in nature and that its mean speed is 1.4 km/s. Velocities as large as 3 km/s have been measured. Using then the number density of NBPs derived by Muller & Roudier (1984) 200/100 sec x 100 sec, it has been possible to calculate the energy flux which can be carried toward the corona, using an expression recently published by Choudhuri et al. (1993a). This flux appears to be about one order of magnitude larger than is necessary. Actually, the wave flux should even be much larger than that, if we keep in mind that the magnetic flux visible as NBPs, represents only a fraction of the total magnetic flux really present in the photosphere, outside active regions. We conclude that the solar corona may really be heated by waves which propagate along magnetic flux tubes rooted in the photosphere, and shaken by granular motions. The propagation of these waves along flux tubes needed however to be understood better.

  7. NASA Sun-Earth Connections Theory Program: The Structure and Dynamics of the Solar Corona and Inner Heliosphere

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran; Grebowsky, Joseph M. (Technical Monitor)

    2001-01-01

    This report covers technical progress during the fourth quarter of the second year of NASA Sun-Earth Connections Theory Program (SECTP) contract 'The Structure and Dynamics of the Solar Corona and Inner Heliosphere,' NAS5-99188, between NASA and Science Applications International Corporation, and covers the period May 16,2001 to August 15, 2001. Under this contract SAIC and the University of California, Irvine (UCI) have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model.

  8. The Convex-Hull Method for Solving Differential Emission Measures in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Weber, Mark A.

    2011-05-01

    The Differential Emission Measure (DEM) describes the temperature distribution of the solar corona, but the inversion of the observations through the instrument's temperature response functions is mathematically ill-posed and typically under-constrained. The most commonly used techniques (e.g., the EM Loci Method, forward-fitting iterators, etc.) each have their drawbacks, but most importantly, they do not guarantee the solution is the globally minimum chi-square solution nor provide a way to quantitatively explore the range of solutions in the neighborhood of the globally minimum solution, which is necessary for properly evaluating levels of confidence. The Convex-Hull Method surmounts the mathematical difficulties of the DEM inversion, providing a more accurate characterization of the solution space with which to evaluate physical models against observations. I demonstrate how this method can be used to constrain the set of temperature distributions observed in the solar corona. This work was supported under contract SP02H1701R from Lockheed-Martin to SAO, and under contract NNM07AB07C from NASA to SAO.

  9. Fast magnetoacoustic wave trains in magnetic funnels of the solar corona

    NASA Astrophysics Data System (ADS)

    Pascoe, David; Nakariakov, Valery; Kupriyanova, Elena

    Fast magnetoacoustic waves are highly dispersive in waveguides and so can generate quasi-periodic wave trains if a localised, impulsive driver is applied, such as flaring energy release. Wave trains have been observed propagating in the solar corona and may be of use as a seismological tool since they depend upon the plasma structuring perpendicular to the direction of propagation. We extend existing models of magnetoacoustic waveguides to consider the effects of an expanding magnetic field with a field-aligned density structure, responding to the recent discovery of fast wave trains of EUV intensity. We investigate the dependence of the wave train properties on variables such as the density contrast ratio, density stratification, and the spectral profile of the driver. The funnel geometry leads to novel wave behaviour, such as the formation of additional wave trains that propagate outside but along the density structure due to leakage and refraction. The results of our numerical simulations demonstrate properties similar to those of wave trains observed in the solar corona.

  10. The Effect of Proton Temperature Anisotropy on the Solar Minimum Corona and Wind

    E-print Network

    Alberto M. Vasquez; Adriaan A. van Ballegooijen; John C. Raymond

    2003-10-29

    A semi-empirical, axisymmetric model of the solar minimum corona is developed by solving the equations for conservation of mass and momentum with prescribed anisotropic temperature distributions. In the high-latitude regions, the proton temperature anisotropy is strong and the associated mirror force plays an important role in driving the fast solar wind; the critical point where the outflow velocity equals the parallel sound speed is reached already at 1.5 Rsun from Sun center. The slow wind arises from a region with open field lines and weak anisotropy surrounding the equatorial streamer belt. The model parameters were chosen to reproduce the observed latitudinal extent of the equatorial streamer in the corona and at large distance from the Sun. We find that the magnetic cusp of the closed-field streamer core lies at about 1.95 Rsun. The transition from fast to slow wind is due to a decrease in temperature anisotropy combined with the non-monotonic behavior of the non-radial expansion factor in flow tubes that pass near the streamer cusp. In the slow wind, the plasma beta is of order unity and the critical point lies at about 5 Rsun, well beyond the magnetic cusp. The predicted outflow velocities are consistent with OVI Doppler dimming measurements from UVCS/SOHO. We also find good agreement with polarized brightness (pB) measurements from LASCO/SOHO and HI Ly-alpha images from UVCS/SOHO.

  11. A study of line widths and kinetic parameters of ions in the solar corona

    E-print Network

    Zhao, G Q; Wang, C B

    2014-01-01

    Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO spectrometer, this paper investigates the relation between the line widths and kinetic parameters of ions. It is shown that there exists a strongly linear correlation between two variables $(\\sigma/\\lambda)^2$ and $M^{-1}$, where $\\sigma$, $\\lambda$ and $M$ are the half-width of the observed line profile at $1/\\sqrt{e}$, the wavelength and the ion mass, respectively. The Pearson product-moment correlation coefficients exceed 0.9. This finding tends to suggest that the ions from a given height of polar corona have a common temperature and a common non-thermal velocity in terms of existing equation. The temperature and non-thermal velocity are obtained by linear least-square fit. The temperature is around $2.8$ MK at heights of 57$''$ and 102$''$. The non-thermal velocity is typical 21.6...

  12. Wave heating in astrophysical plasma - examples in the solar corona and in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Suzuki, Takeru K.

    2004-05-01

    It is widely known that hot plasma is ubiquitous in various astrophysical objects from stars to galaxy clusters. I have worked on the wave dissipation which play a role in the momentum and energy transfer in the plasma. In this article, I firstly introduce our results on the wave heating and acceleration in the solar corona. I show that two kinds of the solar winds, the high-speed wind and low-speed wind, can be explained by the dissipation of different types of the waves. Then, we apply the wave dissipation to the heating in galaxy clusters in collaboration with Yutaka Fujita and Keiichi Wada (NAOJ). We show that the wave heating could be an effective process in reducing the cooling flow.

  13. Generation of highly energetic electrons by shock waves in the solar corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Classen, H.-T.; Motschmann, U.

    2001-11-01

    In the solar corona, shock waves are generated by flares or coronal mass ejections. These shock waves are able to accelerate electrons up to high energies as observed by radio astronomical methods in terms of type II radio bursts and by extraterrestrial in situ measurements. A mechanism of electron acceleration acting at small spatial and temporal scales near the shock transition is presented and then compared with measurements of the Comprehensive Suprathermal and Energetic Particle Analyzer (COSTEP) instrument aboard the SOHO spacecraft during a particular solar event. A numerical hybrid simulation performed under typical coronal circumstances shows that strong magnetic field fluctuations appear immediately at the vicinity of the shock transition. Multiple encounters of electrons with such large-amplitude fluctuations lead to considerable acceleration up to high energies of about 1 MeV.

  14. The MHD simulation of the solar corona using the synoptic frame map of the solar photospheric magnetic field and the SOHO\\/EIT coronal temperature map

    Microsoft Academic Search

    K. Hayashi; X. P. Zhao; B. Benevolenskaya

    2006-01-01

    In simulation studies of the solar corona the synoptic map format data of the solar photospheric magnetic field have been used as the boundary value to specify the period of interest This approach successfully works however there remain two problems The first one is that the synoptic maps are constructed by collecting the data made at different date for example

  15. Charged Dust Dynamics in the Solar System

    Microsoft Academic Search

    Mihaly Horanyi

    1996-01-01

    In most space environments, dust particles are exposed to plasmas and UV radiation and, consequently, carry electrostatic charges. Their motion is influenced by electric and magnetic fields in addition to gravity, drag, and radiation pressure. On the surface of the Moon, in planetary rings, or at comets, for example, electromagnetic forces can shape the spatial and size distribution of micron-sized

  16. Direct imaging of a massive dust cloud around R Coronae Borealis

    E-print Network

    Jeffers, S V; Waters, L B F M; Canovas, H; Rodenhuis, M; Ovelar, M De Juan; Chies-Santos, A L; Keller, C U; 10.1051/0004-6361/201117138

    2012-01-01

    We present recent polarimetric images of the highly variable star R CrB using ExPo and archival WFPC2 images from the HST. We observed R CrB during its current dramatic minimum where it decreased more than 9 mag due to the formation of an obscuring dust cloud. Since the dust cloud is only in the line-of-sight, it mimics a coronograph allowing the imaging of the star's circumstellar environment. Our polarimetric observations surprisingly show another scattering dust cloud at approximately 1.3" or 2000 AU from the star. We find that to obtain a decrease in the stellar light of 9 mag and with 30% of the light being reemitted at infrared wavelengths (from R CrB's SED) the grains in R CrB's circumstellar environment must have a very low albedo of approximately 0.07%. We show that the properties of the dust clouds formed around R CrB are best fitted using a combination of two distinct populations of grains size. The first are the extremely small 5 nm grains, formed in the low density continuous wind, and the second...

  17. Dynamical response of the solar corona. III - Numerical simulation of the 1973 June 10 coronal transient

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Nakagawa, Y.

    1977-01-01

    A spherically symmetric adiabatic single-fluid model is outlined for simulating the nonlinear time-dependent response of the corona to solar events that are simulated by perturbations in the appropriate physical variables from their steady-state values at the coronal base. Several observed features of the coronal transient that occurred on June 10, 1973, are simulated by using a particular steady-state solar wind, a specific combination of density and temperature perturbations, and a particular time dependence of the perturbations. A different steady-state solar wind, a perturbation of shorter duration, and other perturbation combinations are also employed to simulate the same transient so that the effect of each quantity can be determined. It is found that the model cannot adequately simulate all the observational results for the investigated transient, that the steady-state solar wind is relatively unimportant in such numerical simulations, and that studies which attempt only to reproduce observed shock trajectories may lead to erroneous conclusions regarding the physics of the solar event that produced the transient.

  18. The time-dependent chemistry of cometary debris in the solar corona

    SciTech Connect

    Pesnell, W. D. [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States); Bryans, P. [ADNET Systems Inc., NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)

    2014-04-10

    Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.

  19. Astrophysical dust grains in stars, the interstellar medium, and the solar system

    NASA Technical Reports Server (NTRS)

    Gehrz, Robert D.

    1991-01-01

    Studies of astrophysical dust grains in circumstellar shells, the interstellar medium, and the solar system may provide information about stellar evolution and about physical conditions in the primitive solar nebula. The following subject areas are covered: (1) the cycling of dust in stellar evolution and the formation of planetary systems; (2) astrophysical dust grains in circumstellar environments; (3) circumstellar grain formation and mass loss; (4) interstellar dust grains; (5) comet dust and the zodiacal cloud; (6) the survival of dust grains during stellar evolution; and (7) establishing connections between stardust and dust in the solar system.

  20. EVOLUTION OF THE GLOBAL TEMPERATURE STRUCTURE OF THE SOLAR CORONA DURING THE MINIMUM BETWEEN SOLAR CYCLES 23 AND 24

    SciTech Connect

    Nuevo, Federico A.; Vasquez, Alberto M. [Instituto de Astronomia y Fisica del Espacio (CONICET-UBA) and FCEN (UBA), CC 67-Suc 28, Ciudad de Buenos Aires (Argentina); Huang Zhenguang; Frazin, Richard; Manchester, Ward B. IV; Jin Meng [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

    2013-08-10

    The combination of differential emission measure tomography with extrapolation of the photospheric magnetic field allows determination of the electron density and electron temperature along individual magnetic field lines. This is especially useful in quiet-Sun (QS) plasmas where individual loops cannot otherwise be identified. In Paper I, this approach was applied to study QS plasmas during Carrington rotation (CR) 2077 at the minimum between solar cycles (SCs) 23 and 24. In that work, two types of QS coronal loops were identified: ''up'' loops in which the temperature increases with height, and ''down'' loops in which the temperature decreases with height. While the first ones were expected, the latter ones were a surprise and, furthermore, were found to be ubiquitous in the low-latitude corona. In the present work, we extend the analysis to 11 CRs around the last solar minimum. We found that the ''down'' population, always located at low latitudes, was maximum at the time when the sunspot number was minimum, and the number of down loops systematically increased during the declining phase of SC-23 and diminished during the rising phase of SC-24. ''Down'' loops are found to have systematically larger values of {beta} than do ''up'' loops. These discoveries are interpreted in terms of excitation of Alfven waves in the photosphere, and mode conversion and damping in the low corona.

  1. The nature of the dust around R Coronae Borealis stars - Isolated amorphous carbon or graphite fractals

    SciTech Connect

    Hecht, J.H. (Aerospace Corp., Los Angeles, CA (USA))

    1991-02-01

    Wright (1989) has proposed that the R CrB phenomenon is caused by the occurrence of graphite fractal grains, each composed of numerous, less than 15-nm-radius graphite spheres. It is shown that both the observational data and models of dust formation are more in accord with an earlier model by Hecht et al. (1984): that the R CrB type dust is composed of isolated small (less than 100-nm-radius) glassy or amorphous carbon grains. It cannot be ruled out that a significant number of fractal grains exist, provided that they have dielectric properties different from bulk graphite and closer to amorphous carbon, and that the individual grains in the fractals are below 1 nm in size. However, the existence of such fractal grains around R CrB stars might be ruled out by the lack of a 2400-A feature in the interstellar extinction curve. 30 refs.

  2. Catastrophic Eruption of Magnetic Flux Rope in the Corona and Solar Wind With and Without Magnetic Reconnection

    Microsoft Academic Search

    Y. Chen; Y. Q. Hu; S. J. Sun

    2007-01-01

    It is generally believed that the magnetic free energy accumulated in the corona serves as a main energy source for solar explosions such as coronal mass ejections (CMEs). In the framework of the flux rope catastrophe model for CMEs, the energy may be abruptly released either by an ideal magnetohydrodynamic (MHD) catastrophe, which belongs to a global magnetic topological instability

  3. Interstellar Dust and the Organic Inventories of Early Solar Systems

    NASA Astrophysics Data System (ADS)

    Whittet, D. C. B.

    2004-06-01

    Interstellar dust grains are vectors for cosmic carbon and other biogenic chemical elements. They deliver carbon to protoplanetary disks in various refractory phases (amorphous, graphitic, etc.), and they are coated with icy mantles that contain organic molecules and water. The nature of the organics present in and on the dust appears to be closely related to physical conditions. Complex molecules may be synthesized when simple ices are irradiated. Astronomical observations show that this occurs in the vicinity of certain massive protostars, but it is not known whether our Solar System formed in such a region. Organic matter does not survive cycling though diffuse regions of interstellar space; any organics delivered to the early Earth must have originated in the parent molecular cloud, or in the solar nebula itself. A key question is thus identified: What was the star-formation environment of the Solar System? Possible constraints are briefly discussed.

  4. The Energetics of a Global Shock Wave in the Low Solar Corona

    NASA Astrophysics Data System (ADS)

    Long, David M.; Baker, Deborah; Williams, David R.; Carley, Eoin P.; Gallagher, Peter T.; Zucca, Pietro

    2015-02-01

    As the most energetic eruptions in the solar system, coronal mass ejections (CMEs) can produce shock waves at both their front and flanks as they erupt from the Sun into the heliosphere. However, the amount of energy produced in these eruptions, and the proportion of their energy required to produce the waves, is not well characterized. Here we use observations of a solar eruption from 2014 February 25 to estimate the energy budget of an erupting CME and the globally propagating "EIT wave" produced by the rapid expansion of the CME flanks in the low solar corona. The "EIT wave" is shown using a combination of radio spectra and extreme ultraviolet images to be a shock front with a Mach number greater than one. Its initial energy is then calculated using the Sedov-Taylor blast-wave approximation, which provides an approximation for a shock front propagating through a region of variable density. This approach provides an initial energy estimate of ?2.8 × 1031 erg to produce the "EIT wave," which is approximately 10% the kinetic energy of the associated CME (shown to be ?2.5 × 1032 erg). These results indicate that the energy of the "EIT wave" may be significant and must be considered when estimating the total energy budget of solar eruptions.

  5. Improved Constraints on the Preferential Heating and Acceleration of Oxygen Ions in the Extended Solar Corona

    E-print Network

    Steven R. Cranmer; Alexander V. Panasyuk; John L. Kohl

    2008-02-01

    We present a detailed analysis of oxygen ion velocity distributions in the extended solar corona, based on observations made with the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. Polar coronal holes at solar minimum are known to exhibit broad line widths and unusual intensity ratios of the O VI 1032, 1037 emission line doublet. The traditional interpretation of these features has been that oxygen ions have a strong temperature anisotropy, with the temperature perpendicular to the magnetic field being much larger than the temperature parallel to the field. However, recent work by Raouafi and Solanki suggested that it may be possible to model the observations using an isotropic velocity distribution. In this paper we analyze an expanded data set to show that the original interpretation of an anisotropic distribution is the only one that is fully consistent with the observations. It is necessary to search the full range of ion plasma parameters to determine the values with the highest probability of agreement with the UVCS data. The derived ion outflow speeds and perpendicular kinetic temperatures are consistent with earlier results, and there continues to be strong evidence for preferential ion heating and acceleration with respect to hydrogen. At heliocentric heights above 2.1 solar radii, every UVCS data point is more consistent with an anisotropic distribution than with an isotropic distribution. At heights above 3 solar radii, the exact probability of isotropy depends on the electron density chosen to simulate the line-of-sight distribution of O VI emissivity. (abridged abstract)

  6. SDO/AIA Observation of Kelvin-Helmholtz Instability in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Ofman, L.; Thompson, B. J.

    2011-01-01

    We present observations of the formation, propagation and decay of vortex-shaped features in coronal images from the Solar Dynamics Observatory (SDO) associated with an eruption starting at about 2:30UT on Apr 8, 2010. The series of vortices formed along the interface between an erupting (dimming) region and the surrounding corona. They ranged in size from several to ten arcseconds, and traveled along the interface at 6-14 km s-1. The features were clearly visible in six out of the seven different EUV wavebands of the Atmospheric Imaging Assembly (AIA). Based on the structure, formation, propagation and decay of these features, we identified these features as the first observations of the Kelvin- Helmholtz (KH) instability in the corona in EUV. The interpretation is supported by linear analysis and by MHD model of KH instability. We conclude that the instability is driven by the velocity shear between the erupting and closed magnetic field of the Coronal Mass Ejection (CME).

  7. SDO/AIA OBSERVATION OF KELVIN-HELMHOLTZ INSTABILITY IN THE SOLAR CORONA

    SciTech Connect

    Ofman, L. [Department of Physics, Catholic University of America, Washington, DC 20064 (United States); Thompson, B. J. [NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States)

    2011-06-10

    We present observations of the formation, propagation, and decay of vortex-shaped features in coronal images from the Solar Dynamics Observatory associated with an eruption starting at about 2:30 UT on 2010 April 8. The series of vortices were formed along the interface between an erupting (dimming) region and the surrounding corona. They ranged in size from several to 10 arcsec and traveled along the interface at 6-14 km s{sup -1}. The features were clearly visible in six out of the seven different EUV wave bands of the Atmospheric Imaging Assembly. Based on the structure, formation, propagation, and decay of these features, we identified the event as the first observation of the Kelvin-Helmholtz instability (KHI) in the corona in EUV. The interpretation is supported by linear analysis and by a nonlinear 2.5-dimensional magnetohydrodynamic model of KHI. We conclude that the instability is driven by the velocity shear between the erupting and closed magnetic field of the coronal mass ejection. The shear-flow-driven instability can play an important role in energy transfer processes in coronal plasma.

  8. A flux of EUV emission measured on-board the “CORONAS” artificial satellites near minimum and maximum of the 23rd cycle of solar activity

    Microsoft Academic Search

    A. A. Nusinov; T. V. Kazachevskaya; V. V. Katyushina

    2006-01-01

    The paper presents data on ionizing short-wave UV-emission of the Sun in a wave-range ??130nm measured on-board the CORONAS-I and CORONAS-F satellites. There were obtained absolute values of solar flux emission in the spectrum range ??130nm and the band near H L? hydrogen line on-board both satellites. Measurements on-board the CORONAS-I satellite coincided with a phase near the minimum of

  9. Formation and development of shock waves in the solar corona and the near-Sun interplanetary space

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.; Aurass, H.; Classen, H.-T.

    2003-03-01

    At the Sun, shock waves are produced either by flares and/or by coronal mass ejections (CMEs) and are regarded as the source of solar energetic particle events. They can be able to generate solar type II radio bursts. The non-radial propagation of a disturbance is considered away from an active region through the corona into the interplanetary space by evaluating the spatial behaviour of the Alfvén speed. The magnetic field of an active region is modelled by a magnetic dipole superimposed on that of the quiet Sun. Such a magnetic field structure leads to a local minimum of the Alfvén speed in the range 1.2-1.8 solar radii in the corona as well as a maximum of 740 km s-1 at a distance of 3.8 solar radii. The occurrence of such local extrema has important consequences for the formation and development of shock waves in the corona and the near-Sun interplanetary space and their ability to accelerate particles. It leads to a temporal delay of the onset of solar energetic particle events with respect to both the initial energy release (flare) and the onset of the solar type II radio burst.

  10. Electron acceleration by cascading reconnection in the solar corona I Magnetic gradient and curvature effects

    E-print Network

    Zhou, X; Barta, M; Gan, W; Liu, S

    2015-01-01

    Aims: We investigate the electron acceleration in convective electric fields of cascading magnetic reconnection in a flaring solar corona and show the resulting hard X-ray (HXR) radiation spectra caused by Bremsstrahlung for the coronal source. Methods: We perform test particle calculation of electron motions in the framework of a guiding center approximation. The electromagnetic fields and their derivatives along electron trajectories are obtained by linearly interpolating the results of high-resolution adaptive mesh refinement (AMR) MHD simulations of cascading magnetic reconnection. Hard X-ray (HXR) spectra are calculated using an optically thin Bremsstrahlung model. Results: Magnetic gradients and curvatures in cascading reconnection current sheet accelerate electrons: trapped in magnetic islands, precipitating to the chromosphere and ejected into the interplanetary space. The final location of an electron is determined by its initial position, pitch angle and velocity. These initial conditions also influ...

  11. Corona Discharge Treatment of TiO2 Electrode for Dye-Sensitized Solar Cells in Air

    NASA Astrophysics Data System (ADS)

    Teramoto, Yoshiyuki; Shiono, Taku; Ono, Ryo; Oda, Tetuji

    A nanoporous titanium oxide (TiO2) electrode of dye-sensitized solar cells (DSCs) is treated using pulsed corona discharge in room air condition. When the treatment time is 10 min with the discharge voltage of 30 kV, the short-circuit current and the energy conversion efficiency of the treated DSC are 10% higher than those of untreated DSC. This result indicates that the treatment of TiO2 electrode using a pulsed corona discharge in room air condition can enhance the energy conversion efficiency of DSCs.

  12. Periodicities in the X-ray emission from the solar corona

    SciTech Connect

    Chowdhury, Partha [University College of Science and Technology, Calcutta University, Kolkata 700 009 West Bengal (India); Jain, Rajmal; Awasthi, Arun K., E-mail: partha240@yahoo.co.in, E-mail: parthares@gmail.com, E-mail: rajmal@prl.res.in, E-mail: awasthi@prl.res.in [Physical Research Laboratory, Deptartment of Space, Government of India, Navrangpura, Ahmedabad 380 009 (India)

    2013-11-20

    We have studied the time series of full disk integrated soft and hard X-ray emission from the solar corona during 2004 January to 2008 December, covering the entire descending phase of solar cycle 23 from a global point of view. We employ the daily X-ray index derived from 1 s cadence X-ray observations from the Si and CZT detectors of the 'Solar X-ray Spectrometer' mission in seven different energy bands ranging between 6 and 56 keV. X-ray data in the energy bands 6-7, 7-10, 10-20, and 4-25 keV from the Si detector are considered, while 10-20, 20-30, and 30-56 keV high energy observations are taken from the CZT detector. The daily time series is subjected to power spectrum analysis after appropriate correction for noise. The Lomb-Scargle periodogram technique has shown prominent periods of ?13.5 days, ?27 days, and a near-Rieger period of ?181 days and ?1.24 yr in all energy bands. In addition to this, other periods like ?31, ?48, ?57, ?76, ?96, ?130, ?227, and ?303 days are also detected in different energy bands. We discuss our results in light of previous observations and existing numerical models.

  13. MHD Simulations of the Solar Corona in Early August 2010 Using the HMI Magnetic Field Data

    NASA Astrophysics Data System (ADS)

    Hayashi, Keiji; Zhao, X.; Liu, Y.; Sun, X.; Hoeksema, J.; HMI Team

    2011-05-01

    The HMI is observing the line-of-sight magnetic field, vector field and the Doppler plasma velocity. The full-disk magnetogram observation with high temporal and spatial resolution provides better global solar magnetic field map, in that the data gap is minimized and the noise level is quite low. To utilize the benefit of the HMI's magnetogram observation, we conducted the MHD simulation of the global solar corona using the HMI data. We chose a period around August 1st, 2010, to see how the magnetic field connectivity in the global scale had changed around the period: In early August period, the changes of the global coronal magnetic field seen at the entire Earth-side hemisphere seem to be well related with the emergence of the sunspot at the north-east part of the full disk images, though the dynamics involving both magnetic field and plasma will be retrieved by means of the MHD simulation models. We used the synchronic frame format to make the global solar surface magnetic field maps so that the magnetic field distribution at the time of interest will be better specified thus the simulated situation will be more realistic. In addition, we used the daily-updated global maps that are made by regularly replacing the portion of the global map with the meridional slip of the full-disk data on regular (daily) basis as well as the standard ones that are well low-nose dataset made with better-calibrated data.

  14. Formation and Development of Shock Waves in the Solar Corona and Near-Sun Interplanetary Space and Solar Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Mann, G. J.; Klassen, A.; Aurass, H.; Classen, H.; Bothmer, V.; Reiner, M. J.

    2001-12-01

    At the Sun shock waves are produced either by flares or by coronal mass ejections and are regarded as the source of solar energetic particle events. In the corona shock waves appear as solar type II radio bursts often associated with coronal transient (or EIT) waves. The propagation of a disturbance through the corona away from an active region into the interplanetary space is considered by evaluating the radial behaviour of the Alfven speed. The magnetic field of an active region is modelled by a magnetic dipole and is superimposed on that of the quiet Sun as deduced from the EIT wave analysis. Such a behaviour of the magnetic field leads to a local minimum of the Alfven speed in the range 1.2-1.8 solar radii in the corona as well as a maximum of 740 km/2 at a distance of 3.8 solar radii. The occurrence of such a minimum and maximum of the Alfven speed has important consequences to the formation and development of shock waves in the corona and near-Sun interplanetary space and to their ability to accelerate particles leading to a special temporal behaviour of solar energetic particle events.

  15. Validation of the Earth atmosphere models using the EUV solar occultation data from the CORONAS and PROBA 2 instruments

    NASA Astrophysics Data System (ADS)

    Slemzin, Vladimir; Kuzin, Sergey; Berghmans, David; Pertsov, Andrey; Dominique, Marie; Ulyanov, Artyom; Gaikovich, Konstantin

    Absorption in the atmosphere below 500 km results in attenuation of the solar EUV flux, variation of its spectra and distortion of solar images acquired by solar EUV instruments operating on LEO satellites even on solar synchronous orbits. Occultation measurements are important for planning of solar observations from these satellites, and can be used for monitoring the upper atmosphere as well as for studying its response to the solar activity. We present the results of the occultation measurements of the solar EUV radiation obtained by the CORONAS-F/SPIRIT telescope at high solar activity (2002), by the CORONAS-Photon/TESIS telescope at low activity (2009), and by the SWAP telescope and LYRA radiometer onboard the PROBA 2 satellite at moderate activity (2010). The measured attenuation profiles and the retrieved linear extinction coefficients at the heights 200-500 km are compared with simulations by the NRLMSIS-00 and DTM2013 atmospheric models. It was shown that the results of simulations by the DTM2013 model are well agreed with the data of measurements at all stages of solar activity and in presence of the geomagnetic storm, whereas the results of the NRLMSISE-00 model significantly diverge from the measurements, in particular, at high and low activity. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project ? 284461, www.eheroes.eu).

  16. MACS, an instrument, and a methodology for simultaneous and global measurements of the coronal electron temperature and the solar wind velocity on the solar corona

    Microsoft Academic Search

    Nelson Leslie Reginald

    2001-01-01

    The determination of the radial and latitudinal temperature and wind profiles of the solar corona is of great importance in understanding the coronal heating mechanism and the dynamics of coronal expansion. Cram (1976) presented the theory for the formation of the K- coronal spectrum and identified two important observations. He observed the existence of temperature sensitive anti-nodes at certain wavelengths

  17. MACS, An Instrument, and a Methodology for Simulations and Global Measurements of the Coronal Electron Temperature and the Solar Wind Velocity on the Solar Corona

    Microsoft Academic Search

    Nelson L. Reginald

    2000-01-01

    The determination of the radial and latitudinal temperature and wind profiles of the solar corona is of great importance in understanding the coronal heating mechanism and the dynamics of coronal expansion. Cram presented the theory for the formation of the K-coronal spectrum and identified two important observations. He observed the existence of temperature sensitive anti-nodes at certain wavelengths in the

  18. Tracing the magnetic connectivity between the solar surface, corona and inner heliosphere using combined X-ray and radio observations

    NASA Astrophysics Data System (ADS)

    Vilmer, Nicole; Maksimovic, Milan; Rackovic, Kristina

    On a few examples of flares observed with RHESSI at X-ray wavelengths and with the Nançay Radioheliograph (NRH) and WIND/WAVES at radio wavelengths, we shall illustrate how these combined observations allow to understand the link between energetic electrons interacting in the flare site and the escaping electrons which produce radio emissions at low frequencies in the high corona and in the interplanetary medium. While in some events, a close correspondence is observed between the timing and the fast variations of the HXR emissions and the radio emissions from electron beams in the high corona observed by Wind/Waves in the 1 to 14 MHz range suggesting a common acceleration/injection site for HXR and radio emitting electrons, in other cases there is a delay of the radio emissions in the high corona with respect to the onset of the HXR emission. We shall discuss in this contribution the input for a few events of the spatially resolved radio observations of the metric/decimetric emissions provided by the Nançay Radioheliograph to better understand the link between the X-ray emissions at the solar c surface and the radio bursts in the high corona. We shall also discuss the percentage of cases for which a close correspondance is observed. We shall also illustrate how these results may help the preparation of the observing modes of X-ray and radio bursts with STIX and RPW on Solar Orbiter.

  19. The Solar Helium Abundance in the Outer Corona Determined from Observations with SUMER/SOHO

    NASA Astrophysics Data System (ADS)

    Laming, J. M.; Feldman, U.

    2000-05-01

    At altitudes of about 1.05 solar radii or more, the corona above quiet solar regions becomes essentially isothermal. This obviates many of the difficulties associated with the inverse problem of determining emission measure distributions, and allows for fairly straightforward relative element abundance measurements. We present new values for the He abundance. The first is based on a reanalysis of the He/O ratio studied by previously by Feldman (1998) using data acquired by SUMER. We use a revised value of the O abundance, and a more thorough evaluation of the atomic physics for He II to derive an He/H abundance ratio of 0.092, (mass fraction, Y=0.27), with an error of ~ 17% coming mainly from the O abundance uncertainty. We demonstrate that this result may be affected by gravitational settling of O relative to He. We also derive an abundance for He by direct comparison to emission lines of the H I Lyman series, with the result He/H =0.083 +/- 10% (Y=0.25). Gravitational settling, if present, has the opposite effect on this result to that above. Combining the two measurements leads to a final result of He/H =0.084+/- 0.008. This work was supported by the NRL/ONR Solar Magnetism and the Earth's Environment 6.1 Research Option and by NASA Contract W19473. The SUMER project is financially supported by DARA, CNES, NASA and the ESA PRODEX program (Swiss contribution). SUMER is a part of SOHO, the Solar and Heliospheric Observatory, of ESA and NASA.

  20. The Solar Corona and a CME at the 2010 Total Eclipse

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Rusin, V.; Druckmüllerová, H.; Saniga, M.; Lu, M.; Malamut, C.; Seaton, D. B.; Golub, L.; Engell, A. J.; Hill, S. W.; Lucas, R.

    2011-05-01

    The 11 July 2010 total solar eclipse was observed on the ground from French Polynesia and, 83 minutes later, from Easter Island, and near-simultaneous images were made with spacecraft instruments including AIA/SDO, HMI/SDO, EUVI/STEREO, SWAP/PROBA2, EIT/SOHO, and LASCO/SOHO. We report on changes in the corona detectable with high-resolution image processing of the ground-based eclipse coronal imaging, including two CME's that were seen to evolve. We compare with the spacecraft images to give a complete depiction of coronal structure at the time of the eclipse, which corresponded to a low but rising phase of the solar-activity cycle. We acknowledge the support of NASA's MSFC NNX10AK47A, NSF REU AST-1005024 with DoD ASSURE, VEGA 2/0098/10 of the Slovak Acad. Sci, 205/09/1469 of the Czech Science Foundation, PRODEX C90345 of ESA/BELSPO, FP7/2007-2013/218816 SOTERIA, Lockheed Martin; for equipment: Nikon Professional Services, ASTELCO Systems GmbH (Germany), and National Geographic Society's Photographic Division; and colleagues Y.-M. Wang (NRL), S. Habbal (U. Hawaii), H. Lanteires (Tatakoto), and J. Kern (Carnegie Obs.).

  1. Development of the 3-D MHD model of the solar corona-solar wind combining system

    Microsoft Academic Search

    A. Nakamizo; T. Tanaka; Y. Kubo; S. Kamei; H. Shimazu; H. Shinagawa

    2009-01-01

    In the framework of integrated numerical space weather prediction, we have developed a 3-D MHD simulation model of the solar surface-solar wind system. We report the construction method of the model and its first results. By implementing a grid system with angularly unstructured and increasing radial spacing, we realized a spherical grid that has no pole singularity and realized a

  2. Rocket borne solar eclipse experiment to measure the temperature structure of the solar corona via lyman-. cap alpha. line profile observations

    SciTech Connect

    Argo, H.V.

    1981-01-01

    A rocket borne experiment to measure the temperature structure of the inner solar corona via the doppler broadening of the resonance hydrogen Lyman-..cap alpha.. (lambda1216A) radiation scattered by ambient neutral hydrogen atoms was attempted during the 16 Feb 1980 solar eclipse. Two Nike-Black Brant V sounding rockets carrying instrumented payloads were launched into the path of the advancing eclipse umbra from the San Marco satellite launch platform 3 miles off the east coast of Kenya.

  3. Dynamical behaviour of interstellar dust particles in the solar system

    NASA Astrophysics Data System (ADS)

    Kocifaj, Miroslav; Kla?ka, Jozef

    2004-11-01

    Motion and possible capture of interstellar dust particles (ISDPs) in the Solar System are investigated. Gravitational force of the Sun, solar electromagnetic and corpuscular radiation and interplanetary magnetic field are considered. The effect of solar electromagnetic radiation plays an important role in the sense that nonspherical ISDPs can be captured (and survive) much more effectively than spherical particles. It turns out that particles of effective radii ?0.4?m, moving initially near the solar equatorial plane and with impact parameter 400 RS?b? 500 RS (solar radii) exhibit a high probability of capture and survival in the Solar System. Only a very small number of spherical particles can be captured. Survived nonspherical ISDPs orbiting around the Sun are characterized by a quantity analogous to the Kepler's third law: /T, where T is orbital period and is time average of cubed solar distance over the period T. The value of the quantity /T is 0.673ą0.002[AU/year].

  4. MACS, An Instrument and a Methodology for Simultaneous and Global Measurements of the Coronal Electron Temperature and the Solar Wind Velocity on the Solar Corona

    NASA Technical Reports Server (NTRS)

    Reginald, Nelson L.

    2000-01-01

    In Cram's theory for the formation of the K-coronal spectrum he observed the existence of temperature sensitive anti-nodes, which were separated by temperature insensitive nodes, at certain wave-lengths in the K-coronal spectrum. Cram also showed these properties were remarkably independent of altitude above the solar limb. In this thesis Cram's theory has been extended to incorporate the role of the solar wind in the formation of the K-corona, and we have identified both temperature and wind sensitive intensity ratios. The instrument, MACS, for Multi Aperture Coronal Spectrometer, a fiber optic based spectrograph, was designed for global and simultaneous measurements of the thermal electron temperature and the solar wind velocity in the solar corona. The first ever experiment of this nature was conducted in conjunction with the total solar eclipse of 11 August 1999 in Elazig, Turkey. Here twenty fiber optic tips were positioned in the focal plane of the telescope to observe simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends were vertically stacked and placed at the primary focus of the spectrograph. By isolating the K-coronal spectrum from each fiber the temperature and the wind sensitive intensity ratios were calculated.

  5. Directivity of HXR Solar Flare Emission Obtained from Stereoscopic Observations by Mars Odyssey (HEND), RHESSI and CORONAS-F (SONG)

    Microsoft Academic Search

    Moisey Livshits; Dmitry Golovin; Igor Mitrofanov; S. Alexander Kozyrev; Maxim Litvak; Vladislav Tretyakov; Anton Sanin; William V. Boynton; Larisa Kashapova; Irina Myagkova; Andrey Bogomolov

    2010-01-01

    Two powerful X-Ray flares were observed on 2005, July 14 by three spacecrafts whose heliolon-gitudes were spaced on 39 degrees. The flares were observed, as projected on the solar disc by Mars Odyssey (HEND) and seeing almost directly on the limb by RHESSI and CORONAS-F. The most intensive hard X-ray and gamma-ray flare (up to 2 MeV) was observed by

  6. Corona Discharge Treatment of TiO2 Electrode for Dye-Sensitized Solar Cells in Air

    Microsoft Academic Search

    Yoshiyuki Teramoto; Taku Shiono; Ryo Ono; Tetuji Oda

    2010-01-01

    A nanoporous titanium oxide (TiO2) electrode of dye-sensitized solar cells (DSCs) is treated using pulsed corona discharge in room air condition. When the treatment time is 10 min with the discharge voltage of 30 kV, the short-circuit current and the energy conversion efficiency of the treated DSC are 10% higher than those of untreated DSC. This result indicates that the

  7. The eclipse corona: reality and possible research during the 1999 eclipse

    NASA Astrophysics Data System (ADS)

    Rusin, V.; Rybansky, M.

    1999-03-01

    Solar eclipses provide a unique opportunity to observe the solar corona and to solve many open questions in solar coronal physics, e.g., heating of the corona, small-scale structures, dust particles, formation and distribution of coronal structures around the solar surface with respect to the photospheric activity centers, polarization, dust vaporization near the Sun, formation and spatial orientation of solar wind streamers, etc. The forthcoming 1999 eclipse will pass across many countries in Europe, the Middle East and Asia. This event will provide a good opportunity to perform observations of the corona with 'bigger' equipment to obtain high-resolution. We propose to focus scientific experiments on the following targets: THE WHITE-LIGHT AND EMISSION CORONA: exact photometry of the corona with telescopes of focal length 1-3 m; in detail, photometry around the poles and/or above active regions with a minimum focal length of 5 m; photoelectric detection of oscillations; co-ordinated observations with `smaller' telescopes, of 1 m focal length, along the umbral path (dynamics and large-scale structure), polarization in emission corona, etc. SPECTRAL OBSERVATIONS: detection of short-term oscillations (less than 0.1 s) in individual spectral emission coronal lines or in the white-light corona; polarization in emission coronal lines (the Hanle effect - direction of coronal magnetic field lines); spectral observations with small-scale resolution: colour of the solar corona, large-scale resolution: profiles of emission lines; depth of absorption lines (F-corona), etc. Moreover, high-precision timing of eclipse contacts can help us to obtain more accurate parameters of the Moon's orbit around the Earth and to measure the diameter of the Sun. Comets, if any, should be studied in the close vicinity of the Sun. We are of the opinion that the most important problems in solar coronal research during the 1999 eclipse will be supported by coordinated ground-based and satellite observations.

  8. Set of instruments for solar EUV and soft X-ray monitoring onboard satellite Coronas-Photon

    NASA Astrophysics Data System (ADS)

    Kotov, Yury; Kochemasov, Alexey; Kuzin, Sergey; Kuznetsov, Vladimir; Sylwester, Janusz; Yurov, Vitaly

    Coronas-Photon mission is the third satellite of the Russian Coronas program on solar activity observation. The main goal of the "Coronas-Photon" is the study of solar hard electromagnetic radiation in the wide energy range from UV up to high energy gamma-radiation (2000MeV). Scientific payload for solar radiation observation consists of three types of instruments: Monitors (Natalya-2M, Konus-RF, RT-2, Penguin-M, BRM, PHOKA, Sphin-X, SOKOL spectral and timing measurements of full solar disk radiation have timing in flare/burst mode up to one msec. Instruments Natalya-2M, Konus-RF, RT-2 will cover the wide energy range of hard X-rays and soft gamma-rays (15keV to 2000MeV) and will together constitute the largest area detectors ever used for solar observations. Detectors of gamma-ray monitors are based on structured inorganic scintillators. For X-ray and EUV monitors the scintillation phoswich detectors, gas proportional counter, CdZnTe assembly and filter-covered Si-diodes are used. Telescope-spectrometer TESIS for imaging solar spectroscopy in X-rays has angular resolution up to 1arcsec in three spectral lines. Satellite platform and scientific payload is under construction to be launched in autumn 2008. Satellite orbit is circular with initial height 550km and inclination 82.5degrees. Accuracy of the spacecraft orientation to the Sun is better 3arcmin. In the report the capability of PHOKA, SphinX, SOKOL and TESIS as well as the observation program are described and discussed.

  9. Quasilinear relaxation of a beam with power law injected electrons propagating through solar corona

    NASA Astrophysics Data System (ADS)

    Khalilpour, H.

    2015-06-01

    It is assumed that the electron beam propagating thorough the Maxwellian solar corona plasma has a power law spectra. Using numerical simulations of the quasilinear equations, the effects of power law injected electrons on the generation of Langmuir waves are compared with a Maxwellian beam. It is found that the level of Langmuir waves increases in the presence of power law injected electrons. The average velocity of the beam propagation is constant for both Maxwellian and power law injected electrons but its value increases in the second case. The influence of the power law injected electrons on the evolution of gas-dynamical parameters such as the height of the plateau in the beam distribution function in velocity space, its upper and lower velocities boundary, and the local velocity of the beam and its spread is investigated. It is shown that the these parameters are dependent on the characteristics of the power law injected electrons, p (spectral index), and v 0 (the break speed). The upper boundary of plateau decreases (increases) with the p( v 0) but the lower boundary has inverse behavior. The height of plateau p( x, t) is a decreasing function of p and for a fixed value of p it has a maximum in a certain value of v 0 at a given time and position.

  10. Probing the Large Scale Plasma Structure of the Solar Corona with Faraday Rotation Measurements

    E-print Network

    Laura D. Ingleby; Steven R. Spangler; Catherine A. Whiting

    2007-01-18

    Faraday rotation measurements of the solar corona made with the Very Large Array (VLA) at frequencies of 1465 and 1665 MHz are reported. The measurements were made along 20 lines of sight to 19 extragalactic radio sources in March and April, 2005. The closest heliocentric distances of the lines of sight ranged from 9.7 to 5.6 $R_{\\odot}$. Measured rotation measures range from -25 to +61 rad/m$^2$. The purpose of these observations is to probe the three dimensional structure of the coronal plasma in the heliocentric distance range $5-10 R_{\\odot}$, and particularly the strength and structure of the coronal magnetic field. The measured rotation measures are compared with models for the coronal plasma structure. For the majority of the lines of sight, the observed rotation measures are reasonably well represented by the predictions from the models. However, 4 of the 20 lines of sight have large observed-model residuals, which do not seem associated with coronal mass ejections. The magnitude of the field necessary to reproduce the majority of the observations is in the range 46-120 milliGauss at $5 R_{\\odot}$, with a smaller, preferred range of 46-52 mG at $5 R_{\\odot}$.

  11. Excitation and damping of broadband kink waves in the solar corona

    NASA Astrophysics Data System (ADS)

    Pascoe, D. J.; Wright, A. N.; De Moortel, I.; Hood, A. W.

    2015-06-01

    Context. Observations such as those by the Coronal Multi-Channel Polarimeter (CoMP) have revealed that broadband kink oscillations are ubiquitous in the solar corona. Aims: We consider footpoint-driven kink waves propagating in a low ? coronal plasma with a cylindrical density structure. We investigate the excitation and damping of propagating kink waves by a broadband driver, including the effects of different spatial profiles for the driver. Methods: We employ a general spatial damping profile in which the initial stage of the damping envelope is approximated by a Gaussian profile and the asymptotic state by an exponential one. We develop a method of accounting for the presence of these different damping regimes and test it using data from numerical simulations. Results: Strongly damped oscillations in low density coronal loops are more accurately described by a Gaussian spatial damping profile than an exponential profile. The consequences for coronal seismology are investigated and applied to observational data for the ubiquitous broadband waves observed by CoMP. Current data cannot distinguish between the exponential and Gaussian profiles because of the levels of noise. We demonstrate the importance of the spatial profile of the driver on the resulting damping profile. Furthermore, we show that a small-scale turbulent driver is inefficient at exciting propagating kink waves.

  12. OBSERVATIONAL EVIDENCE OF RESONANTLY DAMPED PROPAGATING KINK WAVES IN THE SOLAR CORONA

    SciTech Connect

    Verth, G.; Goossens, M. [Centrum voor Plasma Astrofysica and Leuven Mathematical Modeling and Computational Science Centre, KU Leuven, Celestijnenlaan 200B, 3001 Heverlee (Belgium); Terradas, J., E-mail: gary.verth@wis.kuleuven.b, E-mail: marcel.goossens@wis.kuleuven.b, E-mail: jaume.terradas@uib.e [Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2010-08-01

    In this Letter, we establish clear evidence for the resonant absorption damping mechanism by analyzing observational data from the novel Coronal Multi-Channel Polarimeter. This instrument has established that in the solar corona there are ubiquitous propagating low-amplitude ({approx}1 km s{sup -1}) Alfvenic waves with a wide range of frequencies. Realistically interpreting these waves as the kink mode from magnetohydrodynamic wave theory, they should exhibit a frequency-dependent damping length due to resonant absorption, governed by the Terradas-Goossens-Verth relation showing that transverse plasma inhomogeneity in coronal magnetic flux tubes causes them to act as natural low-pass filters. It is found that the observed frequency dependence on damping length (up to about 8 mHz) can be explained by the kink wave interpretation; and furthermore, the spatially averaged equilibrium parameter describing the length scale of transverse plasma density inhomogeneity over a system of coronal loops is consistent with the range of values estimated from Transition Region and Coronal Explorer observations of standing kink modes.

  13. MAGNETIC FIELD TOPOLOGY AND THE THERMAL STRUCTURE OF THE CORONA OVER SOLAR ACTIVE REGIONS

    SciTech Connect

    Schrijver, Carolus J.; DeRosa, Marc L.; Title, Alan M., E-mail: schryver@lmsal.co [Lockheed Martin Advanced Technology Center, Palo Alto, CA 94304 (United States)

    2010-08-20

    Solar extreme ultraviolet (EUV) images of quiescent active-region coronae are characterized by ensembles of bright 1-2 MK loops that fan out from select locations. We investigate the conditions associated with the formation of these persistent, relatively cool, loop fans within and surrounding the otherwise 3-5 MK coronal environment by combining EUV observations of active regions made with TRACE with global source-surface potential-field models based on the full-sphere photospheric field from the assimilation of magnetograms that are obtained by the Michelson Doppler Imager (MDI) on SOHO. We find that in the selected active regions with largely potential-field configurations these fans are associated with (quasi-)separatrix layers (QSLs) within the strong-field regions of magnetic plage. Based on the empirical evidence, we argue that persistent active-region cool-loop fans are primarily related to the pronounced change in connectivity across a QSL to widely separated clusters of magnetic flux, and confirm earlier work that suggested that neither a change in loop length nor in base field strengths across such topological features are of prime importance to the formation of the cool-loop fans. We discuss the hypothesis that a change in the distribution of coronal heating with height may be involved in the phenomenon of relatively cool coronal loop fans in quiescent active regions.

  14. A tilted-dipole MHD model of the solar corona and solar wind

    Microsoft Academic Search

    A. V. Usmanov; M. L. Goldstein

    2003-01-01

    We simulate the three-dimensional structure of the heliosphere during solar activity minimum by specifying boundary conditions at the coronal base. We compare the output of the model with Ulysses observations obtained during the spacecraft's first fast latitude transition in 1994–1995. The polytropic MHD equations are solved for a steady coronal outflow that includes the addition of Alfvén wave momentum and

  15. A tilted-dipole MHD model of the solar corona and solar wind

    Microsoft Academic Search

    A. V. Usmanov; M. L. Goldstein

    2002-01-01

    We simulate the heliospheric structure during solar activity minimum as determined by boundary conditions at the coronal base and compare output from the model with Ulysses observations during its first fast latitude transition in 1994-1995. The polytropic MHD equations are solved for a steady coronal outflow and include Alfvén wave momentum and energy addition in the WKB approximation. A solution

  16. Low frequency turbulence in the solar corona and fundamental radiation of type III solar radio burst

    Microsoft Academic Search

    T. Takakura

    1979-01-01

    On the basis of the previous numerical simulations, a new mechanism for the emission of the fundamental radio waves of solar radio type III bursts is presented. This hypothesis is to attribute the fundamental radio emission to the coalescence of the plasma waves with the low frequency turbulence, whistler or ion acoustic waves, pre-existing on the way of the electron

  17. Study of the structure of streamer belts and chains in the solar corona

    Microsoft Academic Search

    V. G. Eselevich; V. G. Fainshtein; G. V. Rudenko

    1999-01-01

    A comparison is made of polarization brightness distributions of the white-light corona based on the data from Mark III (MLSO) with calculated magnetic configurations in the corona (a potential-field approximation) between adjacent coronal holes (or associated open magnetic tubes) with magnetic fields of single polarity. It is shown that in these coronal regions, which were referred to as ‘chains of

  18. Nonlinear evolution of magnetic and Kelvin-Helmholtz instabilities in the solar corona.

    NASA Astrophysics Data System (ADS)

    Einaudi, G.

    1999-03-01

    The linear and nonlinear evolution of two configurations of interest for the solar corona are presented. The first case examined refers to a cylindrically symmetric twisted magnetic flux tube which is intended to model a solar coronal loop which has evolved quasi-statically through sequences of equilibria with increasing twist due to the application of localized photospheric vortex flows. It is well known that when the twist exceeds a critical value that depends on its radial profile and on the loop length, the loop becomes kink-unstable. The nonlinear evolution of the instability is followed using a three-dimensional magnetohydrodynamic (MHD) code in cylindrical geometry in a magnetic field configuration where the net axial current is zero and radially confined, so that the magnetic field is an axial potential one in the external regions. It is shown that, during the nonlinear phase of the instability, loops develop current sheets and consequently their evolution becomes resistive with the occurrence of magnetic reconnection. The details of the reconnection phenomenon and the resistive dissipation mechanism are examined, along with the impact of the results in the understanding of coronal activity. The second case refers to a neutral sheet embedded in a plane fluid wake, which is a simplified representation of a streamer beyond the underlying coronal helmet. This wake-neutral sheet configuration is characterized by two parameters which vary with distance from the Sun: the ratio of the cross-stream velocity scale to the neutral sheet width and the ratio of the typical Alfvén velocity to the typical flow speed far from the neutral sheet. Depending on the values of these parameters, the linear theory predicts that three kinds of instability can develop when this system is perturbed: a tearing instability and two ideal fluid instabilities with different cross-stream symmetries.

  19. Effect of the Kelvin-Helmholtz Instability on Magnetic Reconnection on the Solar Corona: a 3D Resistive MHD Study.

    NASA Astrophysics Data System (ADS)

    Brackbill, J. U.; Knoll, Da; Lapenta, Giovanni

    2001-10-01

    For a typical configuration of Helmet Streamers in the Solar Corona, two possible instabilities are considered. First, the tearing instability can be considered a candidate for disrupting the equilibrium and for leading to Coronal Mass Ejections. An important conclusion regarding the resistive tearing instability is that its growth rate is negligible if the actual resistivity of the corona is used. Second, the likely presence of velocity shears induced by differential rotation and motion of the magnetic footpoints leads to the likely presence of the Kelvin-Helmholtz Instability (KHI). This instability, unlike the tearing instability does not require finite resistivity. Previous works (J.U. Brackbill, D.A. Knoll, Phys Rev. Lett. 86, 2329 2001) have suggested that the presence of the KHI changes the picture entirely. When reconnection happens in presence of the KHI, the growth rate is controlled by the KHI and not by the tearing instability. As a consequence, the reconnection rate becomes insensitive to resistivity and is primarily controlled by the velocity shear. In the present work, we explore the implications of the non-linear interaction of KHI and reconnection for the Solar Corona.

  20. GRAIN SORTING IN COMETARY DUST FROM THE OUTER SOLAR NEBULA

    SciTech Connect

    Wozniakiewicz, P. J.; Bradley, J. P.; Ishii, H. A. [Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Brownlee, D. E. [Department of Astronomy, University of Washington, Seattle, WA (United States); Kearsley, A. T. [Department of Mineralogy, Natural History Museum, London SW7 5BD (United Kingdom); Burchell, M. J.; Price, M. C., E-mail: P.Wozniakiewicz@kent.ac.uk [School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH (United Kingdom)

    2012-12-01

    Most young stars are surrounded by a disk of gas and dust. Close to the hot stars, amorphous dust grains from the parent molecular cloud are reprocessed into crystals that are then distributed throughout the accretion disk. In some disks, there is a reduction in crystalline grain size with heliocentric distance from the star. We investigated crystalline grain size distributions in chondritic porous (CP) interplanetary dust particles (IDPs) believed to be from small, icy bodies that accreted in outer regions of the solar nebula. The grains are Mg-rich silicates and Fe-rich sulfides, the two most abundant minerals in CP IDPs. We find that they are predominantly <0.25 {mu}m in radius with a mean grain size that varies from one CP IDP to another. We report a size-density relationship between the silicates and sulfides. A similar size-density relationship between much larger silicate and sulfide grains in meteorites from the asteroid belt is ascribed to aerodynamic sorting. Since the silicate and sulfide grains in CP IDPs are theoretically too small for aerodynamic sorting, their size-density relationship may be due to another process capable of sorting small grains.

  1. Development of a solar-cell dust opacity measurement instrument for Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey; Jenkins, Phillip P.

    1996-01-01

    The atmosphere of Mars has a considerable load of suspended dust. Over time, this dust is deposited out of the atmosphere. The mechanism and the temporal and geographical variation of this deposition are not well characterized. Measurements of settling rates and dust properties are of considerable scientific interest. Atmospheric dust affects the atmospheric solar absorption and thus the heat balance of Mars, as well as serving as nucleation sites for water and CO2 frost. Knowledge of dust properties is of critical interest to design and prediction of the lifetime and power output of solar arrays, and also to design of mechanical mechanisms and radiators. An instrument has been designed and fabricated to measure the dust accumulation during the course of the Mars Pathfinder rover mission. The solar-cell coverglass transmission experiment will measure the change in optical opacity of a transparent coverglass as dust settles on the surface, and a quartz crystal monitor will measure the mass deposited.

  2. The distant future of solar activity: A case study of Beta Hydri. III - Transition region, corona, and stellar wind

    NASA Technical Reports Server (NTRS)

    Dravins, D.; Linde, P.; Ayres, T. R.; Linsky, J. L.; Monsignori-Fossi, B.; Simon, T.; Wallinder, F.

    1993-01-01

    The paper investigates the secular decay of solar-type activity through a detailed comparison of the present sun with the very old solar-type star, Beta Hyi, taken as a proxy of the future sun. Analyses of successive atmospheric layers are presented, with emphasis of the outermost parts. The FUV emission lines for the transition zone are among the faintest so far seen in any solar-type star. The coronal soft X-ray spectrum was measured through different filters on EXOSAT and compared to simulated X-ray observations of the sun seen as a star. The flux from Beta Hyi is weaker than that from the solar corona and has a different spectrum. It is inferred that a thermally driven stellar wind can no longer be supported, which removes the mechanism from further rotational braking of the star through a magnetic stellar wind.

  3. Trapping of dust by coherent vortices in the solar nebula

    E-print Network

    Pierre-Henri Chavanis

    1999-12-06

    We develop the idea proposed by Barge & Sommeria (1995) and Tanga et al. (1996) that large-scale vortices present in the solar nebula can concentrate dust particles and facilitate the formation of planetesimals and planets. We introduce an exact vortex solution of the incompressible 2D Euler equation and study the motion of dust particles in that vortex. In particular, we derive analytical expressions for the capture time and the mass capture rate as a function of the friction parameter. Then, we study how small-scale turbulent fluctuations affect the motion of the particles in the vortex and determine their rate of escape by solving a problem of quantum mechanics. We apply these results to the solar nebula and find that the capture is optimum near Jupiter's orbit (as noticed already by Barge & Sommeria 1995) but also in the Earth region. This second optimum corresponds to the transition between the Epstein and the Stokes regime which takes place, for relevant particles, at the separation between telluric and giant planets (i.e near the asteroid belt). At these locations, the particles are efficiently captured and concentrated by the vortices and can undergo gravitational collapse to form the planetesimals.

  4. MAGNETIC FIELD STRENGTH IN THE UPPER SOLAR CORONA USING WHITE-LIGHT SHOCK STRUCTURES SURROUNDING CORONAL MASS EJECTIONS

    SciTech Connect

    Kim, R.-S.; Gopalswamy, N.; Cho, K.-S.; Yashiro, S. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Moon, Y.-J., E-mail: rok-soon.kim@nasa.gov [School of Space Research, Kyung Hee University, Yongin-shi 446-701 (Korea, Republic of)

    2012-02-20

    To measure the magnetic field strength in the solar corona, we examined 10 fast ({>=}1000 km s{sup -1}) limb coronal mass ejections(CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3-15 solar radii (R{sub s} ). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km s{sup -1} and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

  5. Generalized similarity observed in finite range magnetohydrodynamic turbulence in the corona and solar wind

    NASA Astrophysics Data System (ADS)

    Nicol, R.; Leonardis, E.; Chapman, S. C.; Foullon, C.

    2011-12-01

    Fluctuations associated with fully developed magnetohydrodynamic (MHD) turbulent flows in an infinite medium are characterized by non-Gaussian statistics which are scale invariant; this implies power law power spectra and multiscaling for the Generalized Structure Functions (GSFs). Given an observable f(r,t) and assuming statistical stationary, the p'th order moment of the GSF of the fluctuating differences <|f(r+L)-f(r)|p> scales as Lzeta(p), where L is the observation scale and ? (p) are the scaling exponents. For turbulence in a system that is of finite size, or that is not fully developed, the statistical property of scale invariance is replaced by a generalized scale invariance, or extended self- similarity (ESS), for which the various moments of the GSF have a power-law dependence on an initially unknown functions, G, such that <|f(r+L)-f(r)|p ˜ G(L)? (p). We have demonstrated [1] ESS in Ulysses in-situ observations of magnetic field fluctuations of the fast, quiet solar polar wind, and shoe that there is a single robust scaling function, G, which is anticipated to be a universal property of finite range MHD turbulent flows. However these are purely temporal observations at a single point in space. We therefore for the first time test ESS on direct measurements of the intensity field, I(r,t), associated with an imaged solar Quiescent Prominence (QP). The Solar Optical Telescope (SOT) on board Hinode provides suitable long time intervals of observation of the solar corona via images at a very high spatial and temporal resolution simultaneously. We focus on specific Ca II H-line observations of a QP which exhibits small scale up-flows with a high degree of variability suggestive of turbulence. We test self-similar properties and power-law scaling behaviour of spatio-temporal intensity fluctuations in the prominence plasma by applying GSF and ESS. We first verify that the statistics of the spatial variations of the intensity measurements are non-Gaussian. We then find power-law power spectra and evidence of ESS. By using ESS we calculate ratios of the scaling exponents ? (p), which we find are consistent with a multifractal field. Finally, we recover the dependence of the 3rd moment of the GSF for the spatial fluctuations on a function G(L) as anticipated for finite range turbulence. [1] S. C. Chapman, R. M. Nicol, Generalized Similarity in Finite Range Solar Wind Magnetohydrodynamic Turbulence, Phys. Rev. Lett. 103, 241101 (2009); S. C. Chapman, R. M. Nicol, E. Leonardis, K. Kiyani, V. Carbone, Observation of universality in the generalized similarity of evolving solar wind turbulence as seen by ULYSSES, Ap. J. Letters, 695, L185, (2009)

  6. Energy Buildup, Flux Confinement and Helicity Accumulation in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Hu, You-Qiu; Li, Wen

    2006-02-01

    Starting from a dipole field and a given distribution of footpoint displacement of field lines on the photosphere, we find axisymmetric, force-free field solutions in spherical coordinates that have the same distribution of normal field on the photosphere and magnetic topology as the dipole field. A photospheric shear is introduced in the azimuthal direction in a region that strides across the equator and ends at latitude ?s. The footpoint displacement has a sine distribution in latitude and a peak amplitude of varphim. The magnetic energy E, azimuthal flux Fvarphi, and magnetic helicity HT in the solar corona are then calculated for each force-free field solution. It is found that for a given shear region range ?s, all of the three quantities increase monotonically with increasing varphim. In particular, both Fvarphi and HT have a linear dependence on varphim. When varphim reaches a certain critical value varphimc, the force-free field loses equilibrium, leading to a partial opening of the field and the appearance of a current sheet in the equatorial plane. At this point, E, Fvarphi and HT reach their maximum values, Ec, Fvarphic and HTc. Ec increases, and Fvarphic and HTc decrease with decreasing ?s. It is found that Ec is always smaller than the open field energy, in agreement with the Aly conjecture. Of the three critical parameters, Ec has the weakest dependence on ?s. Therefore, if one is interested in the transition of a magnetic configuration from a stable state to a dynamic one, the magnetic energy is probably the most appropriate marker of the transition.

  7. Ion Temperatures in the Low Solar Corona: Polar Coronal Holes at Solar Minimum

    E-print Network

    Enrico Landi; Steven R. Cranmer

    2008-09-30

    In the present work we use a deep-exposure spectrum taken by the SUMER spectrometer in a polar coronal hole in 1996 to measure the ion temperatures of a large number of ions at many different heights above the limb between 0.03 and 0.17 solar radii. We find that the measured ion temperatures are almost always larger than the electron temperatures and exhibit a non-monotonic dependence on the charge-to-mass ratio. We use these measurements to provide empirical constraints to a theoretical model of ion heating and acceleration based on gradually replenished ion-cyclotron waves. We compare the wave power required to heat the ions to the observed levels to a prediction based on a model of anisotropic magnetohydrodynamic turbulence. We find that the empirical heating model and the turbulent cascade model agree with one another, and explain the measured ion temperatures, for charge-to-mass ratios smaller than about 0.25. However, ions with charge-to-mass ratios exceeding 0.25 disagree with the model; the wave power they require to be heated to the measured ion temperatures shows an increase with charge-to-mass ratio (i.e., with increasing frequency) that cannot be explained by a traditional cascade model. We discuss possible additional processes that might be responsible for the inferred surplus of wave power.

  8. MHD Waves and Instabilities of a Temperature-Anisotropic Plasma in the Solar Corona As a Source of Its Heating

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. D.; Dzhalilov, N. S.

    2012-04-01

    A strong interaction of MHD waves propagating against the direction of the thermal flux is established to exist in the temperature-anisotropic collisionless plasma with thermal fluxes. Such conditions are typical of the lower corona, where the thermal flux is directed downward, and waves propagate upward from the lower atmosphere. We have shown that aperiodic mirror instabilities of slow MHD waves can develop under solar coronal conditions for weak magnetic fields (B< 1 G), and periodic ion-acoustic instabilities can develop for strong magnetic fields (B> 10 G). It is supposed that the instabilities under consideration can play an important role in the energy balance of the corona and may be considered a large-scale energy source of the wave mechanism of coronal heating. In the process, a self-maintained heating mechanism is formed, i.e., the waves dissipate due to the thermal counter flow, and the downward directed thermal flux itself arises, in turn, because of the plasma heating due to wave dissipation. The growth rates and spatial scales of unstable modes are given for the conditions of the lower corona.

  9. Field Lines Twisting in a Noisy Corona: Implications for Energy Storage and Release, and Initiation of Solar Eruptions

    NASA Astrophysics Data System (ADS)

    Rappazzo, A. F.; Velli, M.; Einaudi, G.

    2013-07-01

    We present simulations modeling closed regions of the solar corona threaded by a strong magnetic field where localized photospheric vortical motions twist the coronal field lines. The linear and nonlinear dynamics are investigated in the reduced magnetohydrodynamic regime in Cartesian geometry. Initially the magnetic field lines get twisted and the system becomes unstable to the internal kink mode, confirming and extending previous results. As typical in this kind of investigations, where initial conditions implement smooth fields and flux-tubes, we have neglected fluctuations and the fields are laminar until the instability sets in. However, previous investigations indicate that fluctuations, excited by photospheric motions and coronal dynamics, are naturally present at all scales in the coronal fields. Thus, in order to understand the effect of a photospheric vortex on a more realistic corona, we continue the simulations after kink instability sets in, when turbulent fluctuations have already developed in the corona. In the nonlinear stage the system never returns to the simple initial state with ordered twisted field lines, and kink instability does not occur again. Nevertheless, field lines get twisted, although in a disordered way, and energy accumulates at large scales through an inverse cascade. This energy can subsequently be released in micro-flares or larger flares, when interaction with neighboring structures occurs or via other mechanisms. The impact on coronal dynamics and coronal mass ejections initiation is discussed.

  10. FIELD LINES TWISTING IN A NOISY CORONA: IMPLICATIONS FOR ENERGY STORAGE AND RELEASE, AND INITIATION OF SOLAR ERUPTIONS

    SciTech Connect

    Rappazzo, A. F. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, DE 19716 (United States); Velli, M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Einaudi, G., E-mail: rappazzo@udel.edu [Berkeley Research Associates, Inc., 6537 Mid Cities Avenue, Beltsville, MD 20705 (United States)

    2013-07-10

    We present simulations modeling closed regions of the solar corona threaded by a strong magnetic field where localized photospheric vortical motions twist the coronal field lines. The linear and nonlinear dynamics are investigated in the reduced magnetohydrodynamic regime in Cartesian geometry. Initially the magnetic field lines get twisted and the system becomes unstable to the internal kink mode, confirming and extending previous results. As typical in this kind of investigations, where initial conditions implement smooth fields and flux-tubes, we have neglected fluctuations and the fields are laminar until the instability sets in. However, previous investigations indicate that fluctuations, excited by photospheric motions and coronal dynamics, are naturally present at all scales in the coronal fields. Thus, in order to understand the effect of a photospheric vortex on a more realistic corona, we continue the simulations after kink instability sets in, when turbulent fluctuations have already developed in the corona. In the nonlinear stage the system never returns to the simple initial state with ordered twisted field lines, and kink instability does not occur again. Nevertheless, field lines get twisted, although in a disordered way, and energy accumulates at large scales through an inverse cascade. This energy can subsequently be released in micro-flares or larger flares, when interaction with neighboring structures occurs or via other mechanisms. The impact on coronal dynamics and coronal mass ejections initiation is discussed.

  11. Solar Heating of Suspended Particles and the Dynamics of Martian Dust Devils

    NASA Technical Reports Server (NTRS)

    Fuerstenau, Stephen D.

    2006-01-01

    The heat input to Martian dust devils due to solar warming of suspended particles is assessed based on a prior estimate of dust loading and from an analysis of shadows cast by dust devils in images taken from orbit. Estimated values for solar heating range from 0.12 to 0.57 W/m3 with associated temperature increases of 0.011 to 0.051(deg)C per second. These warming rates are comparable to the adiabatic cooling rate expected for a gas parcel rising on Mars with a vertical velocity of 10 m/s. Solar warming of suspended dust serves to maintain buoyancy in a rising dust plume and may be one cause for the large scale of dust devils observed on Mars.

  12. Time delay occultation data of the Helios spacecraft for probing the electron density distribution in the solar corona

    NASA Technical Reports Server (NTRS)

    Edenhofer, P.; Lueneburg, E.; Esposito, P. B.; Martin, W. L.; Zygielbaum, A. I.; Hansen, R. T.; Hansen, S. F.

    1978-01-01

    S-band time delay measurements were collected from the spacecraft Helios A and B during three solar occultations in 1975/76 within heliocentric distances of about 3 and 215 earth radius in terms of range, Doppler frequency shift, and electron content. Characteristic features of measurement and data processing are described. Typical data sets are discussed to probe the electron density distribution near the sun (west and east limb as well) including the outer and extended corona. Steady-state and dynamical aspects of the solar corona are presented and compared with earth-bound-K-coronagraph measurements. Using a weighted least squares estimation, parameters of an average coronal electron density profile are derived in a preliminary analysis to yield electron densities at r = 3, 65, 215 earth radius. Transient phenomena are discussed and a velocity of propagation v is nearly equal to 900 km/s is determined for plasma ejecta from a solar flare observed during an extraordinary set of Helios B electron content measurements.

  13. SIMULTANEOUS OBSERVATIONS OF A LARGE-SCALE WAVE EVENT IN THE SOLAR ATMOSPHERE: FROM PHOTOSPHERE TO CORONA

    SciTech Connect

    Shen, Yuandeng; Liu, Yu, E-mail: ydshen@ynao.ac.cn [Yunnan Astronomical Observatory, Chinese Academy of Sciences, Kunming 650011 (China)

    2012-06-20

    For the first time, we report a large-scale wave that was observed simultaneously in the photosphere, chromosphere, transition region, and low corona layers of the solar atmosphere. Using the high temporal and high spatial resolution observations taken by the Solar Magnetic Activity Research Telescope at Hida Observatory and the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory, we find that the wave evolved synchronously at different heights of the solar atmosphere, and it propagated at a speed of 605 km s{sup -1} and showed a significant deceleration (-424 m s{sup -2}) in the extreme-ultraviolet (EUV) observations. During the initial stage, the wave speed in the EUV observations was 1000 km s{sup -1}, similar to those measured from the AIA 1700 A (967 km s{sup -1}) and 1600 A (893 km s{sup -1}) observations. The wave was reflected by a remote region with open fields, and a slower wave-like feature at a speed of 220 km s{sup -1} was also identified following the primary fast wave. In addition, a type-II radio burst was observed to be associated with the wave. We conclude that this wave should be a fast magnetosonic shock wave, which was first driven by the associated coronal mass ejection and then propagated freely in the corona. As the shock wave propagated, its legs swept the solar surface and thereby resulted in the wave signatures observed in the lower layers of the solar atmosphere. The slower wave-like structure following the primary wave was probably caused by the reconfiguration of the low coronal magnetic fields, as predicted in the field-line stretching model.

  14. Neutral solar wind generated by lunar exospheric dust at the terminator

    Microsoft Academic Search

    Michael R. Collier; Timothy J. Stubbs

    2009-01-01

    We calculate the flux of neutral solar wind observed on the lunar surface at the terminator due to solar wind protons penetrating exospheric dust grains with (1) radii greater than 0.1 ?m and (2) radii greater than 0.01 ?m. For grains with radii larger than 0.1 ?m, the ratio of the neutral solar wind flux produced by exospheric dust to

  15. MHD waves and instabilities of a temperature-anisotropic plasma in the solar corona as a source of its heating

    NASA Astrophysics Data System (ADS)

    Dzhalilov, N. S.; Kuznetsov, V. D.

    2011-09-01

    The MHD instabilities of a temperature-anisotropic coronal plasma are considered. We show that aperiodic mirror instabilities of slow MHD waves can develop under solar coronal conditions for weak magnetic fields ( B < 1 G) and periodic ion-acoustic instabilities can develop for strong magnetic fields ( B > 10 G). We have found the instability growth rates and estimated the temporal and spatial scales of development and decay of the periodic instability. We show that the instabilities under consideration can play a prominent role in the energy balance of the corona and may be considered as a large-scale energy source of the wave coronal heating mechanism.

  16. Plasma Flows in the Chromosphere-Corona Transition Region of the Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Ptitsyna, Olga; Somov, Boris

    For various plasma flux velocities specified on the lower boundary of the chromosphere-corona transition region, we find temperature dependencies of plasma concentration, velocity and pressure along magnetic tube with one end immersed in the chromosphere and the other end located in the corona. We also obtain stationary temperature distributions along magnetic tube. At each point of the distribution, there is a balance between the heating by the classical heat flux, the energy losses through the radiation of optically thin plasma and the energy transport associated with plasma flow. We then determine: the range of velocities at the lower boundary of the chromosphere-corona transition region for which generation of shock waves in the transition region is possible; the range of velocities at the lower boundary of the chromosphere-corona transition region, for which transition region can be cousidered in the classical collisional approximation, and the range of velocities at the lower boundary of the chromosphere-corona transition region, for which the heating regime is close to p = const and computed radiation values are consistent with the results of satellite observations of extreme ultraviolet (EUV) radiation from the transition region.

  17. THE DUST PROPERTIES OF TWO HOT R CORONAE BOREALIS STARS AND A WOLF-RAYET CENTRAL STAR OF A PLANETARY NEBULA: IN SEARCH OF A POSSIBLE LINK

    SciTech Connect

    Clayton, Geoffrey C.; Gallagher, J. S.; Freeman, W. R.; Camp, K. A., E-mail: gclayton@fenway.phys.lsu.edu, E-mail: wfreem2@lsu.edu, E-mail: kcamp5@tigers.lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States)

    2011-08-15

    We present new Spitzer/IRS spectra of two hot R Coronae Borealis (RCB) stars, one in the Galaxy, V348 Sgr, and one lying in the Large Magellanic Cloud, HV 2671. These two objects may constitute a link between the RCB stars and the late Wolf-Rayet ([WCL]) class of central stars of planetary nebulae (CSPNe), such as CPD -56{sup 0} 8032, that has little or no hydrogen in their atmospheres. HV 2671 and V348 Sgr are members of a rare subclass that has significantly higher effective temperatures than most RCB stars, but shares the traits of hydrogen deficiency and dust formation that define the cooler RCB stars. The [WC] CSPN star, CPD -56{sup 0} 8032, displays evidence of dual-dust chemistry showing both polycyclic aromatic hydrocarbons (PAHs) and crystalline silicates in its mid-IR spectrum. HV 2671 shows strong PAH emission but no sign of having crystalline silicates. The spectrum of V348 Sgr is very different from that of CPD -56{sup 0} 8032 and HV 2671. The PAH emission seen strongly in the other two stars is not present. Instead, the spectrum is dominated by a broad emission centered at about 8.2 {mu}m. This feature is not identified with either PAHs or silicates. Several other cool RCB stars, novae, and post-asymptotic giant branch stars show similar features in their IR spectra. The mid-IR spectrum of CPD -56{sup 0} 8032 shows emission features that may be associated with C{sub 60}. The other two stars do not show evidence of C{sub 60}. The different nature of the dust around these stars does not help us in establishing further links that may indicate a common origin. HV 2671 has also been detected by Herschel/PACS and SPIRE. V348 Sgr and CPD -56{sup 0} 8032 have been detected by AKARI/Far-Infrared Surveyor. These data were combined with Spitzer, IRAS, Two Micron All Sky Survey, and other photometry to produce their spectral energy distributions (SEDs) from the visible to the far-IR. Monte Carlo radiative transfer modeling was used to study the circumstellar dust around these stars. HV 2671 and CPD -56{sup 0} 8032 require both a flared inner disk with warm dust and an extended diffuse envelope with cold dust to fit their SEDs. The SED of V348 Sgr can be fit with a much smaller disk and envelope. The cold dust in the extended diffuse envelopes inferred around HV 2671 and CPD -56{sup 0} 8032 may consist of interstellar medium swept up during mass-loss episodes.

  18. Electron Temperatures and Flow Speeds of the Low Solar Corona: MACS Results from the Total Solar Eclipse of 29 March 2006 in Libya

    NASA Technical Reports Server (NTRS)

    Reginald, Nelson L.; Davila, Joseph M.; SaintCyr, O.; Rabin, Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M.; Gashut, Hadi

    2011-01-01

    An experiment was conducted in conjunction with the total solar eclipse on 29 March 2006 in Libya to measure both the electron temperature and its flow speed simultaneously at multiple locations in the low solar corona by measuring the visible K-coronal spectrum. Coronal model spectra incorporating the effects of electron temperature and its flow speed were matched with the measured K-coronal spectra to interpret the observations. Results show electron temperatures of (1.10 +/- 0.05) MK, (0.70 +/- 0.08) MK, and (0.98 +/- 0.12) MK, at 1.1 Solar Radius from Sun center in the solar north, east and west, respectively, and (0.93 +/- 0.12) MK, at 1.2 Solar Radius from Sun center in the solar west. The corresponding outflow speeds obtained from the spectral fit are (103 +/- 92) km/s, (0 + 10) km/s, (0+10) km/s, and (0+10) km/s. Since the observations were taken only at 1.1 Solar Radius and 1.2 Solar Radius from Sun center, these speeds, consistent with zero outflow, are in agreement with expectations and provide additional confirmation that the spectral fitting method is working. The electron temperature at 1.1 Solar Radius from Sun center is larger at the north (polar region) than the east and west (equatorial region).

  19. The Corona at Solar Maximum as Imaged during the Total Solar Eclipses of 2012 November 13-14 and 2013 November 3-4

    NASA Astrophysics Data System (ADS)

    Habbal, Shadia R.; Druckmuller, Miloslav; Emmanouilides, Constantinos; Morgan, Huw

    2015-01-01

    The total solar eclipses of 2012 November 13-14 and 2013 November 3-4 coincided with peaks of activity in solar cycle 24. Despite challenging observing conditions due to weather patterns in both Australia and central Africa, respectively for these two eclipses, white light images were successfully obtained from groups stationed at different sites along the path of totality on both occasions. We show here how the corona during these two eclipses was remarkable in many ways. In 2012, a prominence eruption reflecting a classic example of a current sheet, with a linear extension of almost 0.25 Rs, ending in a bubble-shaped cavity, was captured in white light. In 2013, two plasmoids were observed at more than a solar radius above the solar limb, both associated with filament eruptions, and one ending in a classic CME bubble. In addition, the intricate complexity of the corona at these two eclipses, revealed by state-of-the art image processing, reflected the ubiquitous presence of large expanding loops, and the fingerprints of plasma instabilities in the form of twisted helical structures and vortex rings.

  20. The influence of absorbed solar radiation by Saharan dust on hurricane genesis

    NASA Astrophysics Data System (ADS)

    Bretl, Sebastian; Reutter, Philipp; Raible, Christoph C.; Ferrachat, Sylvaine; Poberaj, Christina Schnadt; Revell, Laura E.; Lohmann, Ulrike

    2015-03-01

    To date, the radiative impact of dust and the Saharan air layer (SAL) on North Atlantic hurricane activity is not yet known. According to previous studies, dust stabilizes the atmosphere due to absorption of solar radiation but thus shifts convection to regions more conducive for hurricane genesis. Here we analyze differences in hurricane genesis and frequency from ensemble sensitivity simulations with radiatively active and inactive dust in the aerosol-climate model ECHAM6-HAM. We investigate dust burden and other hurricane-related variables and determine their influence on disturbances which develop into hurricanes (developing disturbances, DDs) and those which do not (nondeveloping disturbances, NDDs). Dust and the SAL are found to potentially have both inhibiting and supporting influences on background conditions for hurricane genesis. A slight southward shift of DDs is determined when dust is active as well as a significant warming of the SAL, which leads to a strengthening of the vertical circulation associated with the SAL. The dust burden of DDs is smaller in active dust simulations compared to DDs in simulations with inactive dust, while NDDs contain more dust in active dust simulations. However, no significant influence of radiatively active dust on other variables in DDs and NDDs is found. Furthermore, no substantial change in the DD and NDD frequency due to the radiative effects of dust can be detected.

  1. Structure of the Solar System's Dust Disk: Influence of Massive Bodies

    NASA Astrophysics Data System (ADS)

    Dermott, S. F.; Kehoe, T. J. J.

    2004-12-01

    Dust in the solar system is derived from two large reservoirs of collisionally evolved bodies: dust in the outer solar system originates from the Kuiper belt, while the solar system dust bands discovered by IRAS show that the asteroid belt is the dominant source of dust in the inner solar system. The rate of accretion of dust by the Earth inferred from the microcratering record on LDEF is shown to be consistent with an asteroidal source and we use this rate to assess the rate of accretion of dust by the other planets, and hence to discuss the probability of transporting dust from the Kuiper belt to the inner solar system. The structure of the zodiacal cloud is determined by an interplay Between the gravitational and drag forces acting on particles in the cloud, which in turn depends upon the size of the particles. Observed asymmetries of the zodiacal cloud include: the warping of the mean plane of symmetry of the cloud due to planets in inclined orbits; an offset of the center of the cloud from the Sun due to planets in eccentric orbits; and clumping due to resonant trapping of particles by planets. The injection of dust into the zodiacal cloud is a stochastic process and large variations in the optical depth of the cloud are produced by the total disruption of both large asteroids and large comets. The catastrophic fragmentation and dispersal of the large asteroids that were the precursors of the Hirayama asteroid families produced numerous smaller asteroids that, with low probability, may have eventually impacted the Earth. However, these colossal, family-producing collisional events would have also given rise to waves of dust that would have swept through the inner solar system on timescales of tens of thousands to millions of years. The Earth could not have avoided these waves of dust and it is of interest to speculate on the possible climatic consequences of this interaction.

  2. Current-less solar wind driven dust acoustic instability in cometary plasma

    NASA Astrophysics Data System (ADS)

    Vranjes, J.

    2011-08-01

    A quantitative analysis is presented of the dust acoustic wave instability driven by the solar and stellar winds. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion wind plasma in its propagation penetrates through another quasi-neutral plasma which contains dust, electrons, and ions.

  3. The Dust Properties of Two Hot R Coronae Borealis Stars and a Wolf-Rayet Central Star of a Planetary Nebula: in Search of a Possible Link

    E-print Network

    Clayton, Geoffrey C; Whitney, B A; Babler, B; Gallagher, J S; Nordhaus, J; Speck, A K; Wolff, M J; Freeman, W R; Camp, K A; Lawson, W A; Roman-Duval, J; Misselt, K A; Meade, M; Sonneborn, G; Matsuura, M; Meixner, M

    2011-01-01

    We present new Spitzer/IRS spectra of two hot R Coronae Borealis (RCB) stars, one in the Galaxy,V348 Sgr, and one lying in the LMC, HV 2671. These two objects may constitute a link between the RCB stars and the late Wolf-Rayet ([WCL]) class of central stars of planetary nebula (CSPNe) such as CPD -56 8032 that has little or no hydrogen in their atmospheres. HV 2671 and V348 Sgr are members of a rare subclass that has significantly higher effective temperatures than most RCB stars, but sharing the traits of hydrogen deficiency and dust formation that define the cooler RCB stars. The [WC] CSPNe star, CPD -56 8032, displays evidence for dual-dust chemistry showing both PAHs and crystalline silicates in its mid-IR spectrum. HV 2671 shows strong PAH emission but shows no sign of having crystalline silicates. The spectrum of V348 Sgr is very different from those of CPD -56 8032 and HV 2671. The PAH emission seen strongly in the other two stars is not present. Instead, the spectrum is dominated by a broad emission c...

  4. Evolution of dust particle orbits under the influence of solar wind outflow asymmetries and the formation of the zodiacal dust cloud

    Microsoft Academic Search

    M. Banaszkiewicz; H. J. Fahr; K. Scherer

    1994-01-01

    The secular orbital evolution of zodiacal dust particles is mainly influenced by the electromagnetic and the plasma Poynting-Robertson effects. Whereas the first effect is radially symmetric, the second one, caused by the dynamical friction of the dust particles in the ambient solar wind flow, depends on heliographic latitude. This is because the solar wind appears to have pronounced mass and

  5. Solar flare track densities in interplanetary dust particles The determination of an asteroidal versus cometary source of the zodiacal dust cloud

    Microsoft Academic Search

    S Sandford

    1986-01-01

    The possibility is explored whether an IDP (interplanetary dust particle) is cometary or asteroidal from measurements of the solar flare track density within its constituent mineral grains. Dust particles that are larger than 1 micron, when injected into the Solar System from comets and asteroids, will spiral into the sun due to the Poynting-Robertson effect. During the process of spiraling

  6. Solar heating of suspended particles and the dynamics of Martian dust devils

    Microsoft Academic Search

    Stephen D. Fuerstenau

    2006-01-01

    for solar heating range from 0.12 to 0.57 W\\/m3 with associated temperature increases of 0.011 to 0.051? C per second. These warming rates are comparable to the adiabatic cooling rate expected for a gas parcel rising on Mars with a vertical velocity of 10 m\\/s. Solar warming of suspended dust serves to maintain buoyancy in a rising dust plume and

  7. Interstellar and Solar System Organic Matter Preserved in Interplanetary Dust

    NASA Technical Reports Server (NTRS)

    Messenger, Scott; Nakamura-Messenger, Keiko

    2015-01-01

    Interplanetary dust particles (IDPs) collected in the Earth's stratosphere derive from collisions among asteroids and by the disruption and outgassing of short-period comets. Chondritic porous (CP) IDPs are among the most primitive Solar System materials. CP-IDPs have been linked to cometary parent bodies by their mineralogy, textures, C-content, and dynamical histories. CP-IDPs are fragile, fine-grained (less than um) assemblages of anhydrous amorphous and crystalline silicates, oxides and sulfides bound together by abundant carbonaceous material. Ancient silicate, oxide, and SiC stardust grains exhibiting highly anomalous isotopic compositions are abundant in CP-IDPs, constituting 0.01 - 1 % of the mass of the particles. The organic matter in CP-IDPs is isotopically anomalous, with enrichments in D/H reaching 50x the terrestrial SMOW value and 15N/14N ratios up to 3x terrestrial standard compositions. These anomalies are indicative of low T (10-100 K) mass fractionation in cold molecular cloud or the outermost reaches of the protosolar disk. The organic matter shows distinct morphologies, including sub-um globules, bubbly textures, featureless, and with mineral inclusions. Infrared spectroscopy and mass spectrometry studies of organic matter in IDPs reveals diverse species including aliphatic and aromatic compounds. The organic matter with the highest isotopic anomalies appears to be richer in aliphatic compounds. These materials also bear similarities and differences with primitive, isotopically anomalous organic matter in carbonaceous chondrite meteorites. The diversity of the organic chemistry, morphology, and isotopic properties in IDPs and meteorites reflects variable preservation of interstellar/primordial components and Solar System processing. One unifying feature is the presence of sub-um isotopically anomalous organic globules among all primitive materials, including IDPs, meteorites, and comet Wild-2 samples returned by the Stardust mission.

  8. The Dust Properties of Hot R Coronae Borealis Stars and a Wolf-Rayet Central Star of a Planetary Nebula: In Search of the Missing Link

    NASA Technical Reports Server (NTRS)

    Clayton, Geoffrey C.; De Marco, O.; Whitney, B. A.; Babler, B.; Gallagher, J. S.; Nordhaus, J.; Speck, A. K.; Wolff, M. J.; Freeman, W. R.; Camp, K. A.; Lawson, W. A.; Roman-Duval, J.; Misselt, K. A.; Meade, M.; Sonneborn, G.; Matsuura, M.; Meixner, M.

    2012-01-01

    We present new Spitzer IIRS spectra of two hot R Coronae Borealis (RCB) stars, one in the Galaxy,V348 Sgr, and one lying in the Large Magellanic Cloud, HV 2671. These two objects constitute a link between the RCB stars and the [WCL] class of central stars of planetary nebula (CSPNe) that has little or no hydrogen in their atmospheres such as CPD -560 8032. HV 2671 and V348 Sgr are members of a rare subclass that has significantly higher effective temperatures than most RCB stars, but sharing the traits of hydrogen deficiency and dust formation that define the cooler RCB stars. The [WC] CSPNe star, CPD -560 8032, displays evidence for dual-dust chemistry showing both PAHs and crystalline silicates in its mid-IR spectrum. HV 2671 shows strong PAH emission but shows no sign of having crystalline silicates. The spectrum of V348 Sgr is very different from those of CPD -56deg 8032 and HV 2671. The PAH emission seen strongly in the other two stars is only weakly present. Instead, the spectrum is dominated by a broad emission centered at about 8.5 microns. This feature is not identified with either PAHs or silicates. Several other novae and post-asymptotic giant branch stars show similar features in their IR spectra. The mid-IR spectrum of CPD -56deg 8032 shows emission features associated with C60 . The other two stars do not show evidence for C60. The nature of the dust around these stars does not help us in establishing further links that may indicate a common origin.

  9. THE TEMPERATURE AND DENSITY STRUCTURE OF THE SOLAR CORONA. I. OBSERVATIONS OF THE QUIET SUN WITH THE EUV IMAGING SPECTROMETER ON HINODE

    SciTech Connect

    Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Brooks, David H. [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

    2009-07-20

    Measurements of the temperature and density structure of the solar corona provide critical constraints on theories of coronal heating. Unfortunately, the complexity of the solar atmosphere, observational uncertainties, and the limitations of current atomic calculations, particularly those for Fe, all conspire to make this task very difficult. A critical assessment of plasma diagnostics in the corona is essential to making progress on the coronal heating problem. In this paper, we present an analysis of temperature and density measurements above the limb in the quiet corona using new observations from the EUV Imaging Spectrometer (EIS) on Hinode. By comparing the Si and Fe emission observed with EIS we are able to identify emission lines that yield consistent emission measure distributions. With these data we find that the distribution of temperatures in the quiet corona above the limb is strongly peaked near 1 MK, consistent with previous studies. We also find, however, that there is a tail in the emission measure distribution that extends to higher temperatures. EIS density measurements from several density sensitive line ratios are found to be generally consistent with each other and with previous measurements in the quiet corona. Our analysis, however, also indicates that a significant fraction of the weaker emission lines observed in the EIS wavelength ranges cannot be understood with current atomic data.

  10. MAPPING THE DISTRIBUTION OF ELECTRON TEMPERATURE AND Fe CHARGE STATES IN THE CORONA WITH TOTAL SOLAR ECLIPSE OBSERVATIONS

    SciTech Connect

    Habbal, S. Rifai; Morgan, H.; Scholl, I. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Druckmueller, M. [Faculty of Mechanical Engineering, Brno University of Technology, 616 69 Brno (Czech Republic); Daw, A. [Appalachian State University, Boone, NC 28608 (United States); Johnson, J. [Electricon, Boulder, CO 80204 (United States); Ding, A. [Institute of Optics and Atomic Physics, Technische Universitaet Berlin and Institute of Technical Physics, Berlin (Germany); Arndt, M. [Bridgewater State College, Bridgewater, MA 02325 (United States); Esser, R. [University of Tromsoe (Norway); Rusin, V., E-mail: shadia@ifa.hawaii.ed [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia)

    2010-01-10

    The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 August 1 eclipse observations of a number of Fe emission lines yield an empirical value for a distance, which we call R{sub t} , where the emission changes from being collisionally to radiatively dominated. R{sub t} ranges from 1.1 to 2.0 R{sub sun}, depending on the charge state and the underlying coronal density structures. Beyond that distance, the intensity of the emission reflects the distribution of the corresponding Fe ion charge states. These observations thus yield the two-dimensional distribution of electron temperature and charge state measurements in the corona for the first time. The presence of the Fe X 637.4 nm and Fe XI 789.2 nm emission in open magnetic field regions below R{sub t} , such as in coronal holes and the boundaries of streamers, and the absence of Fe XIII 1074.7 nm and Fe XIV 530.3 nm emission there indicate that the sources of the solar wind lie in regions where the electron temperature is less than 1.2 x 10{sup 6} K. Beyond R{sub t} , the extent of the Fe X [Fe{sup 9+}] and Fe XI emission [Fe{sup 10+}], in comparison with Fe XIII [Fe{sup 12+}] and Fe XIV [Fe{sup 13+}], matches the dominance of the Fe{sup 10+} charge states measured by the Solar Wind Ion Composition Spectrometer, SWICS, on Ulysses, at -43{sup 0} latitude at 4 AU, in March-April 2006, and Fe{sup 9+} and Fe{sup 10+} charge states measured by SWICS on the Advanced Composition Explorer, ACE, in the ecliptic plane at 1 AU, at the time of both eclipses. The remarkable correspondence between these two measurements establishes the first direct link between the distribution of charge states in the corona and in interplanetary space.

  11. A NUMERICAL METHOD FOR THE VISUALIZATION OF THE Fe XIV EMISSION IN THE SOLAR CORONA USING BROADBAND FILTERS

    SciTech Connect

    Martisek, K.; Druckmuellerova, H., E-mail: kmartisek@email.cz [Institute of Mathematics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, 616 69 Brno (Czech Republic)

    2011-12-01

    The goal of this article is to demonstrate how the emission from the Fe XIV 530.3 nm coronal emission line, also known as the green line, can be extracted from images taken during total solar eclipses with commercially available color cameras. This concept is technically feasible because Fe XIV is the brightest optical emission line in the inner corona, and because the sensors of these cameras are retrofitted with a standard Bayer mask, namely, a square grid of spectrally broad (about 100 nm) green, blue, and red filters in the ratio of 2:1:1. The technique presented here, and developed for this purpose, yields qualitatively accurate Fe XIV images, as tested by comparing with Fe XIV eclipse images taken with a 0.15 nm narrow-bandpass filter. While this approach cannot replace narrow-bandpass Fe XIV images for quantitative studies of the corona, it provides a simple and affordable tool for studying the morphology of coronal structures emitting preferentially at the peak ionization temperature of Fe XIV, namely, 1.8 Multiplication-Sign 10{sup 6} K.

  12. Investigations of Solar X-ray flares from quiet Sun by instrument "PENGUIN-M" onboard satellite "CORONAS-PHOTON"

    NASA Astrophysics Data System (ADS)

    Glyanenko, Alexander; Kotov, Yury; Dergachev, Valentin; Yurov, Vitaly; Savchenko, Mikhail; Lazutkov, Vadim; Matveev, Gennady; Arkhangelsky, Andrey; Skorodumov, Dmitry; Pyatigorsky, Aleksei; Kruglov, Evgeny

    Hard X-rays spectrometer and polarimeter PENGUIN-M was launched in January, 31 2009 onboard CORONAS-PHOTON satellite. PENGUIN-M has two energy ranges: -1,8-20 keV (13 energy channels), 18-450 keV (40 energy channels). From the end of February, 2009 up to December, 1, 2009, more then 100 small Solar flares with classes A and B (GOES classification) and a dozen flares of C-class it was registered. Light profiles and data on fluxes in 1,8 -20 keV range were used for statistical study of these flares parameters. Time profiles have resolution 0,2 -1 sec. For flares of B and C-classes we calculate main physical parameters for flaring plasma properties (plasma temperature -T and Emission Measure -EM) using mono-thermal model for emitting region with time resolution 2 -10 sec. The result of statistical analysis of flare characteristics are discussed.

  13. Constraints on Nonlinear and Stochastic Growth Theories for Type 3 Solar Radio Bursts from the Corona to 1 AU

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Robinson, P. A.

    1998-01-01

    Existing, competing theories for coronal and interplanetary type III solar radio bursts appeal to one or more of modulational instability, electrostatic (ES) decay processes, or stochastic growth physics to preserve the electron beam, limit the levels of Langmuir-like waves driven by the beam, and produce wave spectra capable of coupling nonlinearly to generate the observed radio emission. Theoretical constraints exist on the wavenumbers and relative sizes of the wave bandwidth and nonlinear growth rate for which Langmuir waves are subject to modulational instability and the parametric and random phase versions of ES decay. A constraint also exists on whether stochastic growth theory (SGT) is appropriate. These constraints are evaluated here using the beam, plasma, and wave properties (1) observed in specific interplanetary type III sources, (2) predicted nominally for the corona, and (3) predicted at heliocentric distances greater than a few solar radii by power-law models based on interplanetary observations. It is found that the Langmuir waves driven directly by the beam have wavenumbers that are almost always too large for modulational instability but are appropriate to ES decay. Even for waves scattered to lower wavenumbers (by ES decay, for instance), the wave bandwidths are predicted to be too large and the nonlinear growth rates too small for modulational instability to occur for the specific interplanetary events studied or the great majority of Langmuir wave packets in type III sources at arbitrary heliocentric distances. Possible exceptions are for very rare, unusually intense, narrowband wave packets, predominantly close to the Sun, and for the front portion of very fast beams traveling through unusually dilute, cold solar wind plasmas. Similar arguments demonstrate that the ES decay should proceed almost always as a random phase process rather than a parametric process, with similar exceptions. These results imply that it is extremely rare for modulational instability or parametric decay to proceed in type III sources at any heliocentric distance: theories for type III bursts based on modulational instability or parametric decay are therefore not viable in general. In contrast, the constraint on SGT can be satisfied and random phase ES decay can proceed at all heliocentric distances under almost all circumstances. (The contrary circumstances involve unusually slow, broad beams moving through unusually hot regions of the Corona.) The analyses presented here strongly justify extending the existing SGT-based model for interplanetary type III bursts (which includes SGT physics, random phase ES decay, and specific electromagnetic emission mechanisms) into a general theory for type III bursts from the corona to beyond 1 AU. This extended theory enjoys strong theoretical support, explains the characteristics of specific interplanetary type III bursts very well, and can account for the detailed dynamic spectra of type III bursts from the lower corona and solar wind.

  14. Heating of the quiet solar corona from measurements of the FET/TESIS instrument on-board the KORONAS-FOTON satellite

    NASA Astrophysics Data System (ADS)

    Rybák, J.; Gömöry, P.; Benz, A.; Bogachev, P.; Brajša, R.

    2010-12-01

    The paper presents the first results of the observations of time evolution of the quiet solar corona brightenings obtained due to very rapid photography of the corona with full-disk EUV telescopes of the FET/TESIS instrument onboard the KORONA FOTON satellite. The measurements were performed simultaneously in the emission of the Fe IX / X 17.1 and Fe VIII 13.1 spectral lines with 10 second temporal cadence and spatial scale of 1.7 arc seconds within one hour. This test observation, carried out on 15 July 2009, was analyzed in order to determine whether this type of observation can be used to identify individual microevents in the solar corona heating that are above the tresholds of spatial and temporal resolutions of the observations of non-active regions in the solar atmosphere. For this purpose, a simple method was used involving cross-correlation of the plasma emission time evolution at different temperatures, each time from observations of identical elements. The results obtained are confronted with the expected observable manifestations of the corona heating via nanoflares. TESIS is a set of instruments for the Sun photography developed in the Lebedev Physics Institute of the Russian Academy of Sciences that was launched into orbit in January 2009.

  15. Multiscale filamentary structures in the solar corona and their implications for the origin and evolution of the solar wind

    Microsoft Academic Search

    Richard Woo; S. Rifai Habbal

    1998-01-01

    A change in the paradigm of coronal structure has emerged as a result of definitive measurements made with radio occultation, white-light (SOHOLASCO), ultraviolet (SOHO\\/WCS), and soft X-ray (Yohkoh) measurements. The new paradigm is a direct result of measurements with unprecedented capabilities for detecting the faint, low-contrast, and small-scale raylike structures (striations, filamentary structures, flux tubes) that pervade the entire corona.

  16. Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System

    E-print Network

    Hahn, Joseph M.

    Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System Joseph the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal solar radii to the orbit of Venus. The averaged ecliptic surface brightness of the zodiacal light falls

  17. The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona

    E-print Network

    Hayashi, Keiji; Liu, Yang; Bobra, Monica G; Sun, Xudong D; Norton, Aimee A

    2015-01-01

    Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic Magnetic Imager (HMI) full-disk magnetogram data. With the assumption of polytropic gas with specific heat ratio of 1.05, three types of simulation products are currently generated: i) simulation data with medium spatial resolution using the definitive calibrated synoptic map of the magnetic field with a cadence of one Carrington rotation, ii) data with low spatial resolution using the definitive version of the synchronic frame format of the magnetic field, with a cadence of one day, and iii) low-resolution data using near-real-time (NRT) synchronic format of the magnetic field on daily basis. The MHD data available in the JSOC database are three-dimen...

  18. Validation of Spherically Symmetric Inversion by Use of a Tomographically Reconstructed Three-Dimensional Electron Density of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Wang, Tongjiang; Davila, Joseph M.

    2014-01-01

    Determining the coronal electron density by the inversion of white-light polarized brightness (pB) measurements by coronagraphs is a classic problem in solar physics. An inversion technique based on the spherically symmetric geometry (spherically symmetric inversion, SSI) was developed in the 1950s and has been widely applied to interpret various observations. However, to date there is no study of the uncertainty estimation of this method. We here present the detailed assessment of this method using a three-dimensional (3D) electron density in the corona from 1.5 to 4 solar radius as a model, which is reconstructed by a tomography method from STEREO/COR1 observations during the solar minimum in February 2008 (Carrington Rotation, CR 2066).We first show in theory and observation that the spherically symmetric polynomial approximation (SSPA) method and the Van de Hulst inversion technique are equivalent. Then we assess the SSPA method using synthesized pB images from the 3D density model, and find that the SSPA density values are close to the model inputs for the streamer core near the plane of the sky (POS) with differences generally smaller than about a factor of two; the former has the lower peak but extends more in both longitudinal and latitudinal directions than the latter. We estimate that the SSPA method may resolve the coronal density structure near the POS with angular resolution in longitude of about 50 deg. Our results confirm the suggestion that the SSI method is applicable to the solar minimum streamer (belt), as stated in some previous studies. In addition, we demonstrate that the SSPA method can be used to reconstruct the 3D coronal density, roughly in agreement with the reconstruction by tomography for a period of low solar activity (CR 2066). We suggest that the SSI method is complementary to the 3D tomographic technique in some cases, given that the development of the latter is still an ongoing research effort.

  19. The Early Stages of Formation of a Solar System Dust Band

    NASA Astrophysics Data System (ADS)

    Espy, Ashley J.; Dermott, S. F.; Kehoe, T. J. J.

    2009-09-01

    A solar system dust band is formed as the dust released in the catastrophic disruption of an asteroid in the main belt decays under the effects of radiation forces and is sculpted by gravitational perturbations. There are currently known to be at least three full dust band pairs (Low et al., 1984) and these have been associated with several-million-year-old asteroidal disruptions (Dermott et al., 2002; Nesvorny et al., 2003; 2008). A method of coadding the IRAS data set to increase the signal-to-noise ratio revealed the existence of an additional, very faint, partially-formed dust band at 17 degrees inclination (Espy et al., 2009), likely a confirmation of the M/N pair suggested by Sykes (1988). Partial dust bands represent a very early stage of the dynamical evolution of the dust released in the catastrophic disruption of a parent asteroid. We build a model of the formation of this partial band, in order to determine the main dynamical mechanisms controlling dust band formation. Comparison of this model to the coadded IRAS observations also allows us to put strong constraints on the node, semi-major axis, inclination and age of the source body, as well as the cross-sectional area and size-distribution of dust in the band. Because of the young age of partial dust bands, typically much less than a million years old, collisions have not yet begun to play an important role and the size-distribution is closer to that created in the original disruption. Additionally, less of the dust produced in the disruption has been lost to removal by P-R drag than in the older, fully-formed dust bands. These factors imply that partial dust bands provide important information about the dust originally produced in the catastrophic disruption of an asteroid.

  20. OBSERVATIONS OF FIVE-MINUTE SOLAR OSCILLATIONS IN THE CORONA USING THE EXTREME ULTRAVIOLET SPECTROPHOTOMETER (ESP) ON BOARD THE SOLAR DYNAMICS OBSERVATORY EXTREME ULTRAVIOLET VARIABILITY EXPERIMENT (SDO/EVE)

    SciTech Connect

    Didkovsky, L.; Judge, D.; Wieman, S. [Space Sciences Center, University of Southern California, Los Angeles, CA 90089 (United States); Kosovichev, A. G. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Woods, T., E-mail: leonid@usc.edu [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO 80301 (United States)

    2011-09-01

    We report on the detection of oscillations in the corona in the frequency range corresponding to five-minute acoustic modes of the Sun. The oscillations have been observed using soft X-ray measurements from the Extreme Ultraviolet Spectrophotometer (ESP) of the Extreme Ultraviolet Variability Experiment on board the Solar Dynamics Observatory. The ESP zeroth-order channel observes the Sun as a star without spatial resolution in the wavelength range of 0.1-7.0 nm (the energy range is 0.18-12.4 keV). The amplitude spectrum of the oscillations calculated from six-day time series shows a significant increase in the frequency range of 2-4 mHz. We interpret this increase as a response of the corona to solar acoustic (p) modes and attempt to identify p-mode frequencies among the strongest peaks. Due to strong variability of the amplitudes and frequencies of the five-minute oscillations in the corona, we study how the spectrum from two adjacent six-day time series combined together affects the number of peaks associated with the p-mode frequencies and their amplitudes. This study shows that five-minute oscillations of the Sun can be observed in the corona in variations of the soft X-ray emission. Further investigations of these oscillations may improve our understanding of the interaction of the oscillation modes with the solar atmosphere, and the interior-corona coupling, in general.

  1. Mapping the Solar Wind from its Source Region into the Outer Corona

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1998-01-01

    Knowledge of the radial variation of the plasma conditions in the coronal source region of the solar wind is essential to exploring coronal heating and solar wind acceleration mechanisms. The goal of the present proposal is to determine as many plasma parameters in that region as possible by coordinating different observational techniques, such as Interplanetary Scintillation Observations, spectral line intensity observations, polarization brightness measurements and X-ray observations. The inferred plasma parameters are then used to constrain solar wind models.

  2. Mapping the Solar Wind from its Source Region into the Outer Corona

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1997-01-01

    Knowledge of the radial variation of the plasma conditions in the coronal source region of the solar wind is essential to exploring coronal heating and solar wind acceleration mechanisms. The goal of the proposal was to determine as many plasma parameters in the solar wind acceleration region and beyond as possible by coordinating different observational techniques, such as Interplanetary Scintillation Observations, spectral line intensity observations, polarization brightness measurements and X-ray observations. The inferred plasma parameters were then used to constrain solar wind models.

  3. The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona

    NASA Astrophysics Data System (ADS)

    Hayashi, K.; Hoeksema, J. T.; Liu, Y.; Bobra, M. G.; Sun, X. D.; Norton, A. A.

    2015-05-01

    Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of the Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic and Magnetic Imager (HMI) full-disk magnetogram data. With the assumption of a polytropic gas with specific-heat ratio of 1.05, three types of simulation products are currently generated: i) simulation data with medium spatial resolution using the definitive calibrated synoptic map of the magnetic field with a cadence of one Carrington rotation, ii) data with low spatial resolution using the definitive version of the synchronic frame format of the magnetic field, with a cadence of one day, and iii) low-resolution data using near-real-time (NRT) synchronic format of the magnetic field on a daily basis. The MHD data available in the JSOC database are three-dimensional, covering heliocentric distances from 1.025 to 4.975 solar radii, and contain all eight MHD variables: the plasma density, temperature, and three components of motion velocity, and three components of the magnetic field. This article describes details of the MHD simulations as well as the production of the input magnetic-field maps, and details of the products available at the JSOC database interface. To assess the merits and limits of the model, we show the simulated data in early 2011 and compare with the actual coronal features observed by the Atmospheric Imaging Assembly (AIA) and the near-Earth in-situ data.

  4. A Resolved Ring of Debris Dust Around the Solar Analog HD 107146

    E-print Network

    S. A. Corder; J. M. Carpenter; A. I. Sargent; B. A. Zauderer; M. C. H. Wright; S. White; D. P. Woody; P. Teuben; S. L. Scott; M. W. Pound; R. L. Plambeck; J. W. Lamb; J. Koda; M. W. Hodges; D. W. Hawkins; D. C. -J. Bock

    2008-12-09

    We present resolved images of the dust continuum emission from the debris disk around the young (80-200 Myr) solar-type star HD 107146 with CARMA at $\\lambda$1.3 mm and the CSO at $\\lambda$350 $\\mu$m. Both images show that the dust emission extends over an $\\sim$10\\arcsec diameter region. The high resolution (3\\arcsec) CARMA image further reveals that the dust is distributed in a partial ring with significant decrease in flux inward of 97 AU. Two prominent emission peaks appear within the ring separated by $\\sim$140 degrees in position angle. The morphology of the dust emission is suggestive of dust captured into a mean motion resonance, which would imply the presence of a planet at an orbital radius of $\\sim$45-75 AU.

  5. Neutral Solar Wind Generated by Lunar Exospheric Dust at the Terminator

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Stubbs, Timothy J.

    2007-01-01

    We calculate the flux of neutral solar wind observed on the lunar surface at the terminator due to solar wind protons penetrating exospheric dust with: (1) grains larger that 0.1 microns and (2) grains larger than 0.01 microns. For grains larger than 0.1 microns, the ratio of the neutral solar wind to solar wind flux is estimated to be approx.10(exp -4)-10(exp -3) at solar wind speeds in excess of 800 km/s, but much lower (less than 10(exp -5) at average to low solar wind speeds. However, when the smaller grain sizes are considered, the ratio of the neutral solar wind flux to solar wind flux is estimated to be greater than or equal to 10(exp -5) at all speeds and at speeds in excess of 700 km/s reaches 10(exp -3)-10(exp -2). These neutral solar wind fluxes are easily measurable with current low energy neutral atom instrumentation. Observations of neutral solar wind from the surface of the Moon could provide a very sensitive determination of the distribution of very small dust grains in the lunar exosphere and would provide data complementary to optical measurements at ultraviolet and visible wavelengths. Furthermore, neutral solar wind, unlike its ionized counterpart, is .not held-off by magnetic anomalies, and may contribute to greater space weathering than expected in certain lunar locations.

  6. The evolution of the zodiacal dust cloud under plasma drag and lorentz forces in the latitudinally asymmetric solar wind

    Microsoft Academic Search

    H. J. Fahr; K. Scherer; M. Banaszkiewicz

    1995-01-01

    Orbital evolutions of zodiacal dust particles are mainly influenced by electromagnetic and by plasma Poynting-Robertson effects. Whereas the first effect acts radially symmetric, the second one depends on heliographic latitude caused by the dynamical friction of the dust particles in the ambient asymmetric solar wind flow. The solar wind mass and momentum flows vary with heliographic latitude by about 50%

  7. On cyclotron wave heating and acceleration of solar wind ions in the outer corona

    Microsoft Academic Search

    C.-Y. Tu; E. Marsch

    2001-01-01

    The preferential heating and acceleration of O+5 ions, as observed by Ultraviolet Coronagraph Spectrometer (UVCS) on Solar and Heliospheric Observatory (SOHO) [Kohl et al., 1998] in the solar coronal holes have been interpreted and modeled by invoking wave-particle cyclotron resonance [Cranmer et al., 1999a, 1999b]. However, in the model of Cranmer et al. [1999a, 1999b] and in other subsequent models

  8. Solar Flux and Spectrum Measurements in the EUV Spectral Region on Board Coronas-I Satellite

    Microsoft Academic Search

    T. V. Kazachevskaya; S. I. Avdushin; D. A. Gonukh; A. I. Lomovsky; A. A. Nusinov; P. M. Svidsky; Yu. N. Tsigelnitsky; V. N. Oraevsky; I. M. Kopaev; S. I. Boldirev

    1998-01-01

    There are presented data on solar emission variations in the extreme ultraviolet rangelinebreak (? -2 s-1, the La line intensity was~ (3.3 –3.7) × 1011 photon cm-2 s-1 and the Heii (30.4 nm) line intensity was (6–7.5) × 109 photon cm-2 s-1. Intensive solar flares were not registered during the period of observation. During the flare of B4.5 X-ray class

  9. LADEE UVS Observations of Solar Occulation by Exospheric Dust above the Lunar Limb

    NASA Technical Reports Server (NTRS)

    Wooden, Diane; Cook, Amanda Marie; Colaprete, A.; Shirley, M. H.; Vargo, K. E.; Elphic, R. C.; Stubbs, T. J.; Glenar, D. A.

    2014-01-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) is a lunar orbiter launched in September 2012 that investigates the composition and temporal variation of the tenuous lunar exosphere and dust environment. The primary goals of the mission are to characterize the pristine gas and dust exosphere prior to future lunar exploration activities, which may alter the lunar environment. To address this goal, the LADEE instrument suite includes an Ultraviolet/ Visible Spectrometer (UVS), which searches for dust, Na, K, and trace gases such as OH, H2O, Si, Al, Mg, Ca, Ti, Fe, as well as other previously undetected species. UVS has two sets of optics: a limb-viewing telescope, and a solar viewing telescope. The solar viewer is equipped with a diffuser (see Figure 1a) that allows UVS to stare directly at the solar disk as the Sun starts to set (or rise from) behind the lunar limb. Solar viewer measurements generally have very high signal to noise (SNR>500) for 20-30 ms integration times. The 1-degree solar viewer field of view subtends a diameter of 8 km at a distance of 400-450 km

  10. Deflection of the local interstellar dust flow by solar radiation pressure

    NASA Technical Reports Server (NTRS)

    Landgraf, M.; Augustsson, K.; Grun, E.; Gustafson, B. A.

    1999-01-01

    Interstellar dust grains intercepted by the dust detectors on the Ulysses and Galileo spacecrafts at heliocentric distances from 2 to 4 astronomical units show a deficit of grains with masses from 1 x 10(-17) to 3 x 10(-16) kilograms relative to grains intercepted outside 4 astronomical units. To divert grains out of the 2- to 4-astronomical unit region, the solar radiation pressure must be 1.4 to 1.8 times the force of solar gravity. These figures are consistent with the optical properties of spherical or elongated grains that consist of astronomical silicates or organic refractory material. Pure graphite grains with diameters of 0.2 to 0.4 micrometer experience a solar radiation pressure force as much as twice the force of solar gravity.

  11. INFLUENCE OF SOLAR WIND HEATING FORMULATIONS ON THE PROPERTIES OF SHOCKS IN THE CORONA

    SciTech Connect

    Pomoell, J.; Vainio, R., E-mail: jens.pomoell@helsinki.fi [Department of Physics, University of Helsinki (Finland)

    2012-02-01

    One of the challenges in constructing global magnetohydrodynamic (MHD) models of the inner heliosphere for, e.g., space weather forecasting purposes, is to correctly capture the acceleration and expansion of the solar wind. In current models, various ad hoc heating prescriptions are introduced in order to obtain a realistic steady-state solar wind solution. In this work, we demonstrate, by performing MHD simulations of erupting coronal mass ejections (CMEs) on identical solar wind solutions employing different heating formulations, that the dynamics and properties of the CME-driven shocks are significantly altered depending on the applied heating prescription. Furthermore, we show how two popular heating formulations can be altered so as to yield shock properties consistent with theory and available coronal shock observations.

  12. ANALYTIC APPROXIMATE SEISMOLOGY OF PROPAGATING MAGNETOHYDRODYNAMIC WAVES IN THE SOLAR CORONA

    SciTech Connect

    Goossens, M.; Soler, R. [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven (Belgium); Arregui, I. [Instituto de Astrofisica de Canarias, Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Terradas, J., E-mail: marcel.goossens@wis.kuleuven.be [Solar Physics Group, Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2012-12-01

    Observations show that propagating magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. The technique of MHD seismology uses the wave observations combined with MHD wave theory to indirectly infer physical parameters of the solar atmospheric plasma and magnetic field. Here, we present an analytical seismological inversion scheme for propagating MHD waves. This scheme uses the observational information on wavelengths and damping lengths in a consistent manner, along with observed values of periods or phase velocities, and is based on approximate asymptotic expressions for the theoretical values of wavelengths and damping lengths. The applicability of the inversion scheme is discussed and an example is given.

  13. Extreme ultraviolet spectra of solar flares from the extreme ultraviolet spectroheliograph SPIRIT onboard the CORONAS-F satellite

    SciTech Connect

    Shestov, S.; Kuzin, S. [Lebedev Physical Institute, Russian Academy of Sciences, 119991, Moscow (Russian Federation); Reva, A., E-mail: sshestov@gmail.com [Moscow Institute of Physics and Technology (State University), Russia. (Russian Federation)

    2014-01-01

    We present detailed extreme ultraviolet (EUV) spectra of four large solar flares: M5.6, X1.3, X3.4, and X17 classes in the spectral ranges 176-207 Ĺ and 280-330 Ĺ. These spectra were obtained by the slitless spectroheliograph SPIRIT onboard the CORONAS-F satellite. To our knowledge, these are the first detailed EUV spectra of large flares obtained with a spectral resolution of ?0.1 Ĺ. We performed a comprehensive analysis of the obtained spectra and provide identification of the observed spectral lines. The identification was performed based on the calculation of synthetic spectra (the CHIANTI database was used), with simultaneous calculations of the differential emission measure (DEM) and density of the emitting plasma. More than 50 intense lines are present in the spectra that correspond to a temperature range of T = 0.5-16 MK; most of the lines belong to Fe, Ni, Ca, Mg, and Si ions. In all the considered flares, intense hot lines from Ca XVII, Ca XVIII, Fe XX, Fe XXII, and Fe XXIV are observed. The calculated DEMs have a peak at T ? 10 MK. The densities were determined using Fe XI-Fe XIII lines and averaged 6.5 × 10{sup 9} cm{sup –3}. We also discuss the identification, accuracy, and major discrepancies of the spectral line intensity prediction.

  14. Understanding Coronal Mass Ejections and Associated Shocks in the Solar Corona by Merging Multiwavelength Observations

    NASA Astrophysics Data System (ADS)

    Zucca, P.; Pick, M.; Démoulin, P.; Kerdraon, A.; Lecacheux, A.; Gallagher, P. T.

    2014-11-01

    Using multiwavelength imaging observations, in EUV, white light and radio, and radio spectral data over a large frequency range, we analyzed the triggering and development of a complex eruptive event. This one includes two components, an eruptive jet and a coronal mass ejection (CME), which interact during more than 30 minutes, and can be considered as physically linked. This was an unusual event. The jet is generated above a typical complex magnetic configuration that has been investigated in many former studies related to the build-up of eruptive jets; this configuration includes fan-field lines originating from a corona null point above a parasitic polarity, which is embedded in one polarity region of a large active region. The initiation and development of the CME, observed first in EUV, does not show usual signatures. In this case, the eruptive jet is the main actor of this event. The CME appears first as a simple loop system that becomes destabilized by magnetic reconnection between the outer part of the jet and the ambient medium. The progression of the CME is closely associated with the occurrence of two successive type II bursts from a distinct origin. An important part of this study is the first radio type II burst for which the joint spectral and imaging observations were allowed: (1) to follow, step by step, the evolution of the spectrum and of the trajectory of the radio burst, in relationship with the CME evolution and (2) to obtain, without introducing an electronic density model, the B field and the Alfvén speed.

  15. The Effects of Differential Rotation on the Magnetic Structure of the Solar Corona: MHD Simulations

    NASA Technical Reports Server (NTRS)

    Lionello, Roberto; Riley, Pete; Linker, Jon A.; Mikic, Zoran

    2004-01-01

    Coronal holes are magnetically open regions from which the solar wind streams. Magnetic reconnection has been invoked to reconcile the apparently rigid rotation of coronal holes with the differential rotation of magnetic flux in the photosphere. This mechanism might also be relevant to the formation of the slow solar wind, the properties of which seem to indicate an origin from the opening of closed magnetic field lines. We have developed a global MHD model to study the effect of differential rotation on the coronal magnetic field. Starting from a magnetic flux distribution similar to that of Wang et al., which consists of a bipolar magnetic region added to a background dipole field, we applied differential rotation over a period of 5 solar rotations. The evolution of the magnetic field and of the boundaries of coronal holes are in substantial agreement with the findings of Wang et al.. We identified examples of interchange reconnection and other changes of topology of the magnetic field. Possible consequences for the origin of the slow solar wind are also discussed.

  16. Measurements of solar system dust at R < 1 AU and R > 3 AU

    NASA Technical Reports Server (NTRS)

    Mann, Ingrid; Hanner, Martha

    1998-01-01

    In Situ experiments on space craft yield information about dust parameters such as velocity, flux and size, and mass of particles. In Situ experiments as well as brightness measurements in the inner solar system have been made with Helios from .3 to 1 AU in the ecliptic plane which reveal two different dust populations with different bulk densities and relative velocities to the spacecraft. Zodiacal light measurements from Helios 1 and 2 reveal a radial brightness gradient proportional to R(exp -2.3). Measurements of dust particles in the outer solar system have been made onboard the Pioneer 10 and 11 spacecraft and for the high latitude region with Ulysses. Pioneer 10 and 11 also carried a spin-scan photopolarimeter that was used to map the zodiacal light and background starlight during the cruise to Jupiter in two broad bandpasses centered at .44 and .64 micron. Details of these measurements are briefly discussed.

  17. On the Berkowski daguerreotype (Königsberg, 1851 July 28): the first correctly-exposed photograph of the solar corona

    NASA Astrophysics Data System (ADS)

    Schielicke, Reinhard; Wittmann, Axel D.

    The first correctly-exposed photograph of the solar corona was made during the total phase of the solar eclipse of 28 July 1851 at Königsberg (now Kaliningrad) by a local daguerreotypist named Berkowski. Berkowski observed at the Royal Observatory following a proposal by its director A. Busch. A small refracting telescope (D = 6.1 cm, f = 81.2 cm) was attached to the hour drive of the 15.8-cm Fraunhofer heliometer, and a 84-s exposure was taken shortly after the beginning of totality. After the eclipse, Busch (who did not observe the eclipse at Königsberg but at Rixhöft), published some details about the daguerreotype (without mentioning Berkowski's first name) and ordered a local artist (R. Trossin) to make an enlarged steel engraving from the daguerreotype plate. On the original plate the moon's diameter is 7.85 mm, and at least 5 prominences are well visible on the limb of the sun. Later Berkowski himself made some daguerreotype reproductions from his original plate. One of these is still preserved at Jena University Observatory, it has a moon diameter of 8.69 mm. In 1891 the Königsberg Astronomer C.F.W. Peters ordered photographic reproductions of the original daguerreotype (which then still existed) to be made, some of which have been published in astronomical textbooks. We have calculated the local circumstances, in particular the contact times, of the Königsberg eclipse and compared them with observations. We describe the Berkowski daguerreotype and some of its copies, and we report about the Jena copy of this famous daguerreotype.

  18. Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System

    Microsoft Academic Search

    Joseph M. Hahn; Herbert A. Zook; Bonnie Cooper; Bhaskar Sunkara

    2002-01-01

    Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3???30° from the Sun. This surface brightness map is then used to infer the spatial distribution of interplanetary dust over heliocentric distances of about 10 solar radii to the orbit of Venus. The averaged

  19. The Size–Frequency Distribution of the Zodiacal Cloud: Evidence from the Solar System Dust Bands

    Microsoft Academic Search

    Keith Grogan; Stanley F. Dermott; Daniel D. Durda

    2001-01-01

    Recent observations of the size–frequency distribution of zodiacal cloud particles obtained from the cratering record on the LDEF satellite are the latest evidence for a significant large particle population (100-?m diameter or greater) near 1 AU. Our previous modeling of the Solar System dust bands, features of the zodiacal cloud associated with the comminution of Hirayama family asteroids, has been

  20. Mode Conversion of Langmuir to Electromagnetic Waves with Parallel Inhomogeneity in the Solar Wind and the Corona

    SciTech Connect

    Kim, Eun-Hwa; Cairns, Iver H.; Robinson, Peter A.

    2008-06-09

    Linear mode conversion of Langmuir waves to radiation near the plasma frequency at density gradients is potentially relevant to multiple solar radio emissions, ionospheric radar experiments, laboratory plasma devices, and pulsars. Here we study mode conversion in warm magnetized plasmas using a numerical electron fluid simulation code with the density gradient parallel to the ambient magnetic field B0 for a range of incident Langmuir wavevectors. Our results include: (1) Both o- and x-mode waves are produced for ? ? (?L)1/3(?c/?) somewhat less than 1, contrary to previous ideas. Only o mode is produced for ? and somewhat greater than 1.5. Here ?c is the (angular) electron cyclotron frequency, ? the angular wave frequency, and L the length scale of the (linear) density gradient. (2) In the unmagnetized limit, equal amounts of o- and x-mode radiation are produced. (3) The mode conversion window narrows as ? increases. (4) As ? increases the total electromagnetic field changes from linear to circular polarization, with the o- and x- mode signals remaining circularly polarized. (5) The conversion efficiency to the x mode decreases monotonically as ? increases while the o-mode conversion efficiency oscillates due to an interference phenomenon between incoming and reflected Langmuir/z modes. (6) The total conversion efficiency for wave energy from the Langmuir/z mode to radiation is typically less than 10%, but the corresponding power efficiencies differ by the ratio of the group speeds for each mode and are of order 50 ? 70%. (7) The interference effect and the disappearance of the x mode at ? somewhat greater than 1 can be accounted for semiquantitatively using a WKB-like analysis. (8) Constraints on density turbulence are developed for the x mode to be generated and be able to propagate from the source. (9) Standard parameters for the corona and the solar wind near 1 AU suggest that linear mode conversion should produce both o- and x- mode radiation for solar and interplanetary radio bursts. It is therefore possible that linear mode conversion under these conditions might explain the weak total circular polarizations of type II and III solar radio bursts.

  1. Penetration of nearby supernova dust in the inner solar system

    Microsoft Academic Search

    Themis Athanassiadou; B. D. Fields

    2011-01-01

    We investigate the method by which nearby supernovae – within a few tens of pc of the solar system – can penetrate the solar system and deposit live radioactivities on earth. The radioactive isotopic signatures that could potentially leave an observable geological imprint are in the form of refractory metals; consequently, it is likely they would arrive in the form

  2. Reconnection in the Solar Corona: a study of the interaction of the 3-D Kelvin-Helmholtz instability and tearing instability

    NASA Astrophysics Data System (ADS)

    Lapenta, G.; Knoll, D. A.; Brackbill, J. U.

    2001-12-01

    For a typical configuration of magnetic field arcades in the Solar Corona, two instabilities are possible. First, in presence of velocity shear, which exists on the photospheric surface, the Kelvin-Helmholtz Instability (KHI) is excited. In 3-D, with differential rotation, The low speed shear KHI can drive magnetic reconnection [1]. The growth rate of the KHI is primarily controlled by the destabilizing effect of the velocity shear and by the stabilizing effect of a flow aligned magnetic field. However, the KHI is insensitive to the presence of resistivity. Second, the tearing instability can be considered a candidate for disrupting the equilibrium and for leading to Coronal Mass Ejections. Within a resistive MHD approach, the growth rate of the Tearing instability is negligible if the actual resistivity of the corona is used. Previous work [1] has suggested that when reconnection happens in presence of the KHI (in 3-D with differential rotation) the reconnection time scale is controlled by the KHI and not by the tearing instability. As a consequence, the reconnection rate becomes insensitive to resistivity and is primarily controlled by the velocity shear. In the present work, we explore the implications of the non-linear interaction of the 3-D KHI with differential rotation and reconnection for the Solar Corona. [1] J.U. Brackbill, D.A. Knoll, Phys Rev. Lett. 86, 2329, 2001

  3. Mean free path and energy loss of electrons in the solar corona and the inner heliosphere

    NASA Astrophysics Data System (ADS)

    Estel, C.; Mann, G.

    1999-05-01

    We have studied the mean free path of electrons in the solar atmosphere in dependence on their initial velocity and their starting height above the photosphere. The net pitch angle change results from the combined effects of Coulomb scattering and the decreasing field strength of the large-scale magnetic field. We show that above a certain velocity all electrons can travel a distance of at least five AU without deflection. This treshold velocity decreases with increasing starting height. Furthermore the loss of kinetic energy due to Coulomb collisions as a function of distance from the Sun has been calculated. At small distances, up to at least 1.5 Rsun (solar radius), the energy component parallel to the magnetic field (assumed as radial from the Sun) decreases but above 1.5 Rsun this component increases though the total particle energy decreases. If we assume that the injected electrons also have a velocity component perpendicular to the magnetic field (pitch angle theta >0), the radial velocity component will increase even at low coronal heights. The theoretical results are compared with observational data of solar type III radio bursts.

  4. MESSENGER soft X-ray observations of the quiet solar corona

    NASA Astrophysics Data System (ADS)

    Schwartz, Richard A.; Hudson, Hugh S.; Tolbert, Anne K; Dennis, Brian R.

    2014-06-01

    In a remarkable result from their "SphinX" experiment, Sylwester et al. (2012) found a non-varying base level of soft X-ray emission at the quietest times in 2009. We describe comparable data from the soft X-ray monitor on board MESSENGER (en route to Mercury) which had excellent coverage both in 2009 and during the true solar minimum of 2008. These observations overlap SphinX's and also are often exactly at Sun-MESSENGER-Earth conjunctions. During solar minimum the Sun-MESSENGER distance varied substantially, allowing us to use the inverse-square law to help distinguish the aperture flux (ie, solar X-rays) from that due to sources of background in the 2-5 keV range. The MESSENGER data show a non-varying background level for many months in 2008 when no active regions were present. We compare these data in detail with those from SphinX. Both sets of data reveal a different behavior when magnetic active regions are present on the Sun, and when they are not.Reference: Sylwester et al., ApJ 751, 111 (2012)

  5. THE FIRST MEASUREMENT OF THE ADIABATIC INDEX IN THE SOLAR CORONA USING TIME-DEPENDENT SPECTROSCOPY OF HINODE/EIS OBSERVATIONS

    SciTech Connect

    Van Doorsselaere, Tom; Wardle, Nick; Jansari, Kishan; Verwichte, Erwin; Nakariakov, Valery M. [CFSA, Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Del Zanna, Giulio, E-mail: Tom.VanDoorsselaere@wis.kuleuven.BE [DAMTP, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2011-02-01

    We use observations of a slow magnetohydrodynamic wave in the corona to determine for the first time the value of the effective adiabatic index, using data from the Extreme-ultraviolet Imaging Spectrometer on board Hinode. We detect oscillations in the electron density, using the CHIANTI atomic database to perform spectroscopy. From the time-dependent wave signals from multiple spectral lines the relationship between relative density and temperature perturbations is determined, which allows in turn to measure the effective adiabatic index to be {gamma}{sub eff} = 1.10 {+-} 0.02. This confirms that the thermal conduction along the magnetic field is very efficient in the solar corona. The thermal conduction coefficient is measured from the phase lag between the temperature and density, and is shown to be compatible with Spitzer conductivity.

  6. Ultra high resolution images of the solar chromosphere and corona using coordinated rocket and balloon observations

    NASA Technical Reports Server (NTRS)

    Walker, Arthur B. C., Jr.; Timothy, J. G.; Hoover, Richard B.; Barbee, Troy W., Jr.

    1993-01-01

    A discussion is presented of the scientific objectives that can be pursued by simultaneous coronal/chromospheric observation with the Multi-Spectral Solar Telescope Array (MSSTA), and a new balloon-borne observatory called the Ultra-High Resolution Vacuum Ultraviolet Spectroheliograph (UHRVS). Attention is given to the proposed UHRVS observatory, which will incorporate two instruments, a 65-cm aperture telescope with narrowband filters for high resolution photographic and photoelectric spectroheliograms, and a very high resolution spectrograph which uses a 40-cm aperture telescope. The capabilities of the MSSTA, and the joint UHRVS/MSSTA observing program that is envisioned are reviewed.

  7. Numerical Study on In-Situ Prominence Formation by Radiative Condensation in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Yokoyama, T.

    2015-06-01

    We propose an in situ formation model for inverse-polarity solar prominences and demonstrate it using self-consistent 2.5 dimensional MHD simulations, including thermal conduction along magnetic fields and optically thin radiative cooling. The model enables us to form cool dense plasma clouds inside a flux rope by radiative condensation, which is regarded as an inverse-polarity prominence. Radiative condensation is triggered by changes in the magnetic topology, i.e., formation of the flux rope from the sheared arcade field, and by thermal imbalance due to the dense plasma trapped inside the flux rope. The flux rope is created by imposing converging and shearing motion on the arcade field. Either when the footpoint motion is in the anti-shearing direction or when heating is proportional to local density, the thermal state inside the flux rope becomes cooling-dominant, leading to radiative condensation. By controlling the temperature of condensation, we investigate the relationship between the temperature and density of prominences and derive a scaling formula for this relationship. This formula suggests that the proposed model reproduces the observed density of prominences, which is 10–100 times larger than the coronal density. Moreover, the time evolution of the extreme ultraviolet emission synthesized by combining our simulation results with the response function of the Solar Dynamics Observatory Atmospheric Imaging Assembly filters agrees with the observed temporal and spatial intensity shift among multi-wavelength extreme ultraviolet emission during in situ condensation.

  8. Generation of Suprathermal Electrons by Resonant Interaction with Whistler Waves in the Solar Corona and Wind

    NASA Astrophysics Data System (ADS)

    Vocks, C.; Mann, G.

    2003-12-01

    Observations of solar wind electron velocity distribution functions (VDFs) show pronounced deviations from a Maxwellian. The number of suprathermal electrons is strongly enhanced even under quiet solar conditions. An assessment of the relaxation of a non-Maxwellian coronal electron VDF shows that a coronal origin of these suprathermal electrons is possible. A model for the acceleration of suprathermal electrons based on resonant interaction with whistler waves is presented. This interaction is characterized by pitch-angle diffusion of the electrons in the reference frame of the waves. In the plasma rest frame, this leads to a significant acceleration of electrons from small sunwards velocities parallel to the background magnetic field to high speeds perpendicular to it. A kinetic model is developed to study this mechanism in detail and to investigate the overall evolution of an electron VDF from the transition region into the interplanetary space. Simulation results for the open magnetic structure of a coronal funnel are presented. In the energy range of several keV, they show a focussing of the suprathermal electrons in interplanetary space towards a narrow "strahl" and a strong enhancement of suprathermal electron fluxes due to whistler waves. Simulation results for higher energies of several 10 keV are also presented, and effects of other wave modes than whistler waves on the electron VDF are discussed.

  9. Interaction of the lunar surface and dust grains with the solar wind and Earth magnetosphere

    NASA Astrophysics Data System (ADS)

    Vaverka, Jakub; Richterova, Ivana; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek

    2015-04-01

    Interaction of the lunar surface with the solar wind and Earth's magnetosphere leads to it charging by several processes as photoemission, a collection of primary particles, and secondary electron emission. The parameters of a plasma environment strongly influence the charging processes because the energy of electrons and ions is significantly higher in the magnetosphere than in the solar wind, while the particle density is lower in the magnetosphere. Dominant charging currents depend on a lunar position relative to the Earth as well as on the Solar Zenith Angle which influences mainly the current of photoelectrons. The lunar surface potential varies from slightly positive to large negative values with respect to the surrounding plasma. A presence of dust levitating above the surface has been observed by several spacecraft and by astronauts during Apollo missions in the terminator area. We present model calculations of a temporal evolution of the lunar surface potential as well as potentials of dust grains above the surface using by the ARTEMIS data through one crossing of the Earth magnetosphere tail. We show that the lunar surface and levitating dust can be charged to different potentials under the same plasma conditions and we discuss a possibility of the dust grain levitation above the charged surface.

  10. Observations of steady anomalous magnetic heating in thin current sheets. [of solar corona

    NASA Technical Reports Server (NTRS)

    Martens, P. C. H.; Van Den Oord, G. H. J.; Hoyng, P.

    1985-01-01

    The Hard X-ray Imaging Spectrometer of the Solar Maximum Mission has yielded observations of a faint, steadily emitting loop-like structure, which have allowed the thermal evolution of this loop over a period of about 15 hr to be followed. Only 0.1 percent of the volume of the loop appears to be steadily heated, at the large rate of 0.6 erg/cu cm sec; this suggests that the heating represents the dissipation of magnetic fields in thin current sheets. Ion-kinetic tearing, as proposed by Galeev et al. (1981), is noted to be especially consonant with these observations. The source of the present X-ray emission is identified with the H-alpha filament in the same region. The present findings are held to constitute the first direct evidence for the steady dissipation of coronal magnetic fields via enhanced thin current sheet resistivity.

  11. Core and Wing Densities of Asymmetric Coronal Spectral Profiles: Implications for the Mass Supply of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Patsourakos, S.; Klimchuk, J. A.; Young, P. R.

    2014-01-01

    Recent solar spectroscopic observations have shown that coronal spectral lines can exhibit asymmetric profiles, with enhanced emissions at their blue wings. These asymmetries correspond to rapidly upflowing plasmas at speeds exceeding approximately equal to 50 km per sec. Here, we perform a study of the density of the rapidly upflowing material and compare it with that of the line core that corresponds to the bulk of the plasma. For this task, we use spectroscopic observations of several active regions taken by the Extreme Ultraviolet Imaging Spectrometer of the Hinode mission. The density sensitive ratio of the Fe(sub XIV) lines at 264.78 and 274.20 Angstroms is used to determine wing and core densities.We compute the ratio of the blue wing density to the core density and find that most values are of order unity. This is consistent with the predictions for coronal nanoflares if most of the observed coronal mass is supplied by chromospheric evaporation driven by the nanoflares. However, much larger blue wing-to-core density ratios are predicted if most of the coronal mass is supplied by heated material ejected with type II spicules. Our measurements do not rule out a spicule origin for the blue wing emission, but they argue against spicules being a primary source of the hot plasma in the corona. We note that only about 40% of the pixels where line blends could be safely ignored have blue wing asymmetries in both Fe(sub XIV) lines. Anticipated sub-arcsecond spatial resolution spectroscopic observations in future missions could shed more light on the origin of blue, red, and mixed asymmetries.

  12. Core and wing densities of asymmetric coronal spectral profiles: Implications for the mass supply of the solar corona

    SciTech Connect

    Patsourakos, S. [Section of Astrogeophysics, Physics Department, University of Ioannina, Ioannina GR-45110 (Greece); Klimchuk, J. A. [NASA Goddard Space Flight Center, Solar Physics Lab., Code 671, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Young, P. R., E-mail: spatsour@cc.uoi.gr, E-mail: james.a.klimchuk@nasa.gov [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

    2014-02-01

    Recent solar spectroscopic observations have shown that coronal spectral lines can exhibit asymmetric profiles, with enhanced emissions at their blue wings. These asymmetries correspond to rapidly upflowing plasmas at speeds exceeding ?50 km s{sup –1}. Here, we perform a study of the density of the rapidly upflowing material and compare it with that of the line core that corresponds to the bulk of the plasma. For this task, we use spectroscopic observations of several active regions taken by the Extreme Ultraviolet Imaging Spectrometer of the Hinode mission. The density sensitive ratio of the Fe XIV lines at 264.78 and 274.20 Ĺ is used to determine wing and core densities. We compute the ratio of the blue wing density to the core density and find that most values are of order unity. This is consistent with the predictions for coronal nanoflares if most of the observed coronal mass is supplied by chromospheric evaporation driven by the nanoflares. However, much larger blue wing-to-core density ratios are predicted if most of the coronal mass is supplied by heated material ejected with type II spicules. Our measurements do not rule out a spicule origin for the blue wing emission, but they argue against spicules being a primary source of the hot plasma in the corona. We note that only about 40% of the pixels where line blends could be safely ignored have blue wing asymmetries in both Fe XIV lines. Anticipated sub-arcsecond spatial resolution spectroscopic observations in future missions could shed more light on the origin of blue, red, and mixed asymmetries.

  13. The Efficiency of Electrostatic Precipitators Under Conditions of Corona Quenching

    Microsoft Academic Search

    M. B. Awad; G. S. P. Castle

    1975-01-01

    The suppression of corona by particle space-charge is of considerable importance in electrostatic precipitators dealing with medium to high concentrations of particulates. However, the effect of the dust concentration on collection efficiency has found no direct answer in the literature. In addition to the expected reduction in corona current due to low mobility dust particles, the presence of these charged

  14. The solar corona as probed by comet Lovejoy (C/2011 W3)

    SciTech Connect

    Raymond, J. C.; McCauley, P. I.; Cranmer, S. R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Downs, C. [Predictive Sciences, Inc., 990 Mesa Rim Rd., Suite 170, San Diego, CA, 92121 (United States)

    2014-06-20

    Extreme-ultraviolet images of Comet Lovejoy (C/2011 W3) from the Atmospheric Imaging Assembly show striations related to the magnetic field structure in both open and closed magnetic regions. The brightness contrast implies coronal density contrasts of at least a factor of six between neighboring flux tubes over scales of a few thousand kilometers. These density structures imply variations in the Alfvén speed on a similar scale. They will drastically affect the propagation and dissipation of Alfvén waves, and that should be taken into account in models of coronal heating and solar wind acceleration. In each striation, the cometary emission moves along the magnetic field and broadens with time. The speed and the rate of broadening are related to the parallel and perpendicular components of the velocities of the cometary neutrals when they become ionized. We use a magnetohydrodynamic model of the coronal magnetic field and the theory of pickup ions to compare the measurements with theoretical predictions, in particular with the energy lost to Alfvén waves as the cometary ions isotropize.

  15. Numerical Simulation of Fast-mode Magnetosonic Waves Excited by Plasmoid Ejections in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Yang, Liping; Zhang, Lei; He, Jiansen; Peter, Hardi; Tu, Chuanyi; Wang, Linghua; Zhang, Shaohua; Feng, Xueshang

    2015-02-01

    The Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory has directly imaged the fast-propagating magnetosonic waves (FMWs) successively propagating outward along coronal magnetic funnels. In this study we perform a numerical investigation of the excitation of FMWs in the interchange reconnection scenario, with footpoint shearing flow being used to energize the system and drive the reconnection. The modeling results show that as a result of magnetic reconnection, the plasma in the current sheet is heated up by Joule dissipation to ~10 MK and is ejected rapidly, developing the hot outflows. Meanwhile, the current sheet is torn into plasmoids, which are shot quickly both upward and downward. When the plasmoids reach the outflow regions, they impact and collide with the ambient magnetic field there, which consecutively launches FMWs. The FMWs propagate outward divergently away from the impact regions, with a phase speed of the Alfvén speed of ~1000 km s-1. In the k - ? diagram of the Fourier wave power, the FMWs display a broad frequency distribution with a straight ridge that represents the dispersion relation. With the WKB approximation, at the distance of 15 Mm from the wave source region, we estimate the energy flux of FMWs to be E ~ 7.0 × 106 erg cm-2 s-1, which is ~50 times smaller than the energy flux related to the tube-channeled reconnection outflow. These simulation results indicate that energetically and dynamically the outflow is far more important than the waves.

  16. Numerical Study on In-Situ Prominence Formation by Radiative Condensation in the Solar Corona

    E-print Network

    Kaneko, Takafumi

    2015-01-01

    We propose an in-situ formation model for inverse-polarity solar prominence and demonstrate it using self-consistent 2.5-dimensional magnetohydrodynamics simulations, including thermal conduction along magnetic fields and optically thin radiative cooling. The model enables us to form cool dense plasma clouds inside a flux rope by radiative condensation, which is regarded as an inverse-polarity prominence. Radiative condensation is triggered by changes in the magnetic topology, i.e., formation of the flux rope from the sheared arcade field, and by thermal imbalance due to the dense plasma trapped inside the flux rope. The flux rope is created by imposing converging and shearing motion on the arcade field. Either when the footpoint motion is in the anti-shearing direction or when heating is proportional to local density, the thermal state inside the flux rope becomes cooling-dominant, leading to radiative condensation. By controlling the temperature of condensation, we investigate the relationship between the t...

  17. Solar System dynamics and global-scale dust storms on Mars

    NASA Astrophysics Data System (ADS)

    Shirley, James H.

    2015-05-01

    Global-scale dust storms occur during the southern summer season on Mars in some Mars years but not in others. We present an updated catalog of Mars years including such storms (n = 9) and Mars years without global-scale storms (n = 11) through the year 2013. A remarkable relationship links the occurrence and non-occurrence of global-scale dust storms on Mars with changes in the orbital angular momentum of Mars with respect to the Solar System barycenter (LMars). All of the global-scale dust storms became planet-encircling in both latitude and longitude during periods when LMars was increasing or near maxima. Statistical significance at the 1% level is obtained for the clustering tendency of LMars phases for the 5 mid-season storms with Ls ranging from 208° to 262° (1956, 1971, 1982, 1994, and 2007). The 11 Mars years without global-scale dust storms exhibit mainly decreasing and minimum values of LMars during the first half of the dust storm season; this tendency is statistically significant at the 5% level. A systematic progression is present in the phasing of the solar irradiance and LMars waveforms for the global-scale storm years. LMars phases for the early season global-scale storms of 1977 and 2001 are advanced in phase with respect to those of the mid-season storms, while the phase for the late season storm of 1973 is delayed with respect to those of the mid-season storms cluster. Factors internal to the Mars climate system, such as a spatial redistribution of surface dust from year to year, must be invoked to account for the non-occurrence of global-scale dust storms in five years (1986, 2003, 2005, 2009, and 2013) when the LMars phase was otherwise favorable. Our results suggest that the occurrence of increasing or peak values of LMars immediately prior to and during the Mars dust storm season may be a necessary-but-not-sufficient condition for the initiation of global-scale dust storms on Mars.

  18. Evolution and Activity in the Solar Corona: A Comparison of Coronal and Chromospheric Structures Seen in Soft X-Rays, White Light and H-Alpha Emission

    NASA Technical Reports Server (NTRS)

    Bagenal, Fran

    2001-01-01

    The work completed under this project, 'Evolution and Activity in the Solar Corona: A Comparison of Coronal and Chromospheric Structures Seen in Soft X-Rays, White Light and H-Alpha Emission', includes the following presentations: (1) Analysis of H-alpha Observations of High-altitude Coronal Condensations; (2) Multi-spectral Imaging of Coronal Activity; (3) Measurement and Modeling of Soft X-ray Loop Arcades; (4) A Study of the Origin and Dynamics of CMEs; and various poster presentations and thesis dissertations.

  19. Formation of fast shocks by magnetic reconnection in the solar corona

    SciTech Connect

    Hsieh, M. H. [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Space Science, National Central University, Jhongli 320, Taiwan (China); Tsai, C. L. [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Space Science, National Central University, Jhongli 320, Taiwan (China); Earth Dynamic System Research Center, National Cheng Kung University, Tainan 701, Taiwan (China); Ma, Z. W. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Lee, L. C. [Institute of Space Science, National Central University, Jhongli 320, Taiwan (China)

    2009-09-15

    Reconnections of magnetic fields over the solar surface are expected to generate abundant magnetohydrodynamic (MHD) discontinuities and shocks, including slow shocks and rotational discontinuities. However, the generation of fast shocks by magnetic reconnection process is relatively not well studied. In this paper, magnetic reconnection in a current sheet is studied based on two-dimensional resistive MHD numerical simulations. Magnetic reconnections in the current sheet lead to the formation of plasma jets and plasma bulges. It is further found that the plasma bulges, the leading part of plasma jets, in turn lead to the generation of fast shocks on flanks of the bulges. The simulation results show that during the magnetic reconnection process, the plasma forms a series of structures: plasma jets, plasma bulges, and fast shocks. As time increases, the bulges spread out along the current sheet ({+-}z direction) and the fast shocks move just ahead of the bulges. The effects of initial parameters {rho}{sub s}/{rho}{sub m}, {beta}{sub {infinity}}, and t{sub rec} on the fast shock generation are also examined, where {rho}{sub s}/{rho}{sub m} is the ratio of plasma densities on two sides of the initial current sheet, {beta}{sub {infinity}}=P{sub {infinity}}/(B{sub {infinity}}{sup 2}/2{mu}{sub 0}), P{sub {infinity}} is the plasma pressure and B{sub {infinity}} is the magnetic field magnitude far from the current sheet, and t{sub rec} is the reconnection duration. In the asymmetric case with {rho}{sub s}/{rho}{sub m}=2, {beta}{sub {infinity}}=0.01 and t{sub rec}=1000, the maximum Alfven Mach number of fast shocks (M{sub A1max}) is M{sub A1max} congruent with 1.1, where M{sub A1}=V{sub n1}/V{sub A1}, and V{sub n1} and V{sub A1} are, respectively, the normal upstream fluid velocity and the upstream Alfven speed in the fast shocks frame. As the density ratio {rho}{sub s}/{rho}{sub m} (=1-8) and plasma beta {beta}{sub {infinity}} (=0.0001-1) increase, M{sub A1max} varies slightly. For the case with a large plasma beta {beta}{sub {infinity}} (=5), the fast shock is very weak. As the reconnection duration t{sub rec} increases, the bulges lead to generation of fast shocks with a higher M{sub A1max}. The present results can be applied to the mechanism of coronal heating by fast shocks.

  20. Experimental study of parameters of X-ray radiation from solar flares using the PENGUIN-M instrument aboard the CORONAS-PHOTON spacecraft

    NASA Astrophysics Data System (ADS)

    Kotov, Yu. D.; Glyanenko, A. S.; Arkhangelsky, A. I.; Bessonov, M. V.; Buslov, A. S.; Yurov, V. N.; Dergachev, V. A.; Matveev, G. A.; Kruglov, E. M.; Lazutkov, V. P.; Savchenko, M. I.; Skorodumov, D. V.; Pyatigorsky, A. G.; Pyatigorsky, G. A.; Shishov, I. I.; Khilkevich, E. M.; Vasilyev, G. I.; Krutkov, S. Yu.

    2011-04-01

    The main characteristics of the PENGUIN-M instrument are given. The instrument has been operating aboard the CORONAS-PHOTON spacecraft (SC) launched into orbit on January 30, 2009. The instrument includes the PENGUIN-MD detector unit (PMD) and the PENGUIN-ME electronic unit (PMD). The purpose of the experiment is to measure the degree of linear polarization of X-ray radiation from solar flares in the energy range of 20-150 keV and to obtain energy spectra of X-ray radiation from solar flares in the energy range of 2-500 keV. The paper describes the instrument, calibration procedure, and in-flight adjustment, and contains the first results of measurements.

  1. Is it justified to assume that 'Everywhere in the sun's photosphere-corona domain the electric conductivity is HIGH?'; or, what drives the solar upper atmosphere?

    NASA Astrophysics Data System (ADS)

    Feldman, Uri

    1993-07-01

    For many years, solar scientists have recognized the extreme complexity of the upper solar atmosphere. However, in order to construct a valid theoretical model they have formulated a set of simplified assumptions governing the makeup of the sun's upper atmosphere. In previous papers a number of assumptions used to construct the models were shown not to be valid. In this Paper I bring evidence to question the validity of the last and most important of the assumptions, the assertion that 'Everywhere in the photosphere-corona domain the electric conductivity is HIGH'. The consequences of the finding are briefly discussed. A laboratory measurement of the electrical conductivity versus temperature in a gas with photospheric composition would resolve this important issue and seem to be feasible.

  2. In-situ dust detection as a tool to study dust-plasma interactions in the Solar System

    NASA Astrophysics Data System (ADS)

    Srama, R.; Hsu, H. W.; Moragas-Klostermeyer, G.; Postberg, F.; Kempf, S.

    2014-12-01

    The unique results of the Cassini Cosmic Dust Analyzer onboard Cassini revealed the potential of in-situ dust detection for the study of dust-plasma interactions. In-situ techniques are charge induction, impact ionization, momentum transfer, foil depolarization, light scattering or mass spectrometry. Modern instruments like dust telescopes or the Cosmic Dust Analyzer (CDA) onboard Cassini combine different methods in one sensor. This paper gives an overview about in-situ dust measurements in space using direct detection methods. A focus is given to charge induction and impact ionization and their measurement thresholds are described. Major CDA discoveries are summarized and new results of nano-dust stream measurements in the outer Saturnian system are presented. These data show periodicities related to Saturn and its moons, leading to a deeper understanding of nano-dust origins and dynamics in Saturn's magnetosphere.

  3. Equation of State and Constitutive Models for Numerical Simulations of Dust Impacts on the Solar Probe

    E-print Network

    Kerley, Gerald I

    2013-01-01

    This report presents new EOS and strength models for use in numerical hydrocode simulations of dust impacts on the NASA solar probe space vehicle. This spacecraft will be subjected to impact at velocities up to 300 km/s, producing pressures as high as 100 TPa and temperatures as high as 200 eV. Hence the material models must treat a variety of physical and chemical phenomena, including solid-solid transitions, melting and vaporization, chemical reactions, electronic excitation and ionization. The EOSPro code is used to develop tabular EOS that include these effects. The report discusses the theoretical methods used to create the new EOS tables and constitutive models for six materials--Al2O3, two porous carbon materials, fused SiO2, a silicone elastomer, and germanium--which will be used in the thermal protection shield (TPS) and solar cells, the components most vulnerable to dust impacts. It also presents the results of hydrocode simulations of dust impacts on the TPS and on glass targets. It discusses the i...

  4. Corona Borealis

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    (the Northern Crown; abbrev. CrB, gen. Coronae Borealis; area 179 sq. deg.) A northern constellation which lies between Boötes and Hercules, and culminates at midnight in mid-May. It represents the crown that in Greek mythology was made by Hephaestus, god of fire, and worn by Princess Ariadne of Crete. Its brightest stars were cataloged by Ptolemy (c. AD 100-175) in the Almagest....

  5. Magnetohydrodynamics of atmospheric transients. IV - Nonplane two-dimensional analyses of energy conversion and magnetic field evolution. [during corona following solar flare

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Nakagawa, Y.; Han, S. M.; Dryer, M.

    1982-01-01

    The evolution of the magnetic field and the manner of conversion of thermal energy into different forms in the corona following a solar flare are investigated by means of a nonplane magnetohydrodynamic (MHD) analysis. All three components of magnetic field and velocity are treated in a physically self-consistent manner, with all physical variables as functions of time (t) and two spatial coordinates (r, theta). The difference arising from the initial magnetic field, either twisted (force-free) or non-twisted (potential), is demonstrated. Consideration is given to two initial field topologies (open vs. closed). The results demonstrate that the conversion of magnetic energy is faster for the case of the initially twisted (force-free) field than for the initially untwisted (potential) field. In addition, the twisted field is found to produce a complex structure of the density enhancements.

  6. Relaxation of the loss-cone by quasi-linear diffusion of the electron-cyclotron maser instability in the solar corona

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.

    1990-01-01

    A self-consistent numeric two-dimensional code using kinetic-wave particle equations has been developed and applied to the maser dynamics of the solar corona. Time histories generated by the code reveal details of the evolution of the linear phase, the saturation and subsequent relaxation of the loss cone. Quantitative values are obtained for the saturation time, the amount of the converted free energy, the critical wave energy level for onset of maser diffusion, the velocity and pitch angle range of the resonant particles, and the relative importance of the different magnetoionic modes and harmonics. A wide range of initial conditions is covered by varying the loss-cone distribution and the ambient cold plasma parameters.

  7. MODELS OF THE LARGE-SCALE CORONA. I. FORMATION, EVOLUTION, AND LIFTOFF OF MAGNETIC FLUX ROPES

    E-print Network

    Mackay, Duncan

    and thread through the solar atmosphere. Observations show that within the solar corona, magnetic fields such eruptions, we need to determine how flux ropes are formed and evolve in the solar corona in additionMODELS OF THE LARGE-SCALE CORONA. I. FORMATION, EVOLUTION, AND LIFTOFF OF MAGNETIC FLUX ROPES D. H

  8. Microphysics of Waves and Instabilities in the Solar Wind and Their Macro Manifestations in the Corona and Interplanetary Space

    NASA Technical Reports Server (NTRS)

    Habbal, Shadia Rifai

    2005-01-01

    Investigations of the physical processes responsible for coronal heating and the acceleration of the solar wind were pursued with the use of our recently developed 2D MHD solar wind code and our 1D multifluid code. In particular, we explored: (1) the role of proton temperature anisotropy in the expansion of the solar (2) the role of plasma parameters at the coronal base in the formation of high (3) a three-fluid model of the slow solar wind (4) the heating of coronal loops (5) a newly developed hybrid code for the study of ion cyclotron resonance in wind, speed solar wind streams at mid-latitudes, the solar wind.

  9. Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

    PubMed Central

    Blum, Jürgen; Beitz, Eike; Bukhari, Mohtashim; Gundlach, Bastian; Hagemann, Jan-Hendrik; Heißelmann, Daniel; Kothe, Stefan; Schräpler, Rainer; von Borstel, Ingo; Weidling, René

    2014-01-01

    For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System. PMID:24962693

  10. Laboratory drop towers for the experimental simulation of dust-aggregate collisions in the early solar system.

    PubMed

    Blum, Jürgen; Beitz, Eike; Bukhari, Mohtashim; Gundlach, Bastian; Hagemann, Jan-Hendrik; Heißelmann, Daniel; Kothe, Stefan; Schräpler, Rainer; von Borstel, Ingo; Weidling, René

    2014-01-01

    For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System. PMID:24962693

  11. On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations

    NASA Astrophysics Data System (ADS)

    Otto, S.; Trautmann, T.; Wendisch, M.

    2010-11-01

    Realistic size equivalence and shape of Saharan mineral dust particles are derived from on in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10%. At the bottom of the atmosphere (BOA) the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA) depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal) forcing by 55/5% at the TOA over ocean/land and 15% at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20%. Large dust particles significantly contribute to all the radiative effects reported.

  12. Hybrid Simulations of Ion Cyclotron Waves in Non-uniform Magnetic Field: Application to the Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Russell, C. T.; Jian, L.; Isenberg, P. A.; Wei, H.

    2013-12-01

    The presence of ions with perpendicular temperature larger than parallel in the corona is expected to result in the generation of ion cyclotron waves. Spacecraft observations in the interplanetary medium provide evidence for the presence of ion cyclotron waves generated near the Sun. In this presentation we examine the possibility that the observed ion cyclotron waves are generated in the corona and propagate into the interplanetary medium. To this end, we perform 2.5-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations with non-uniform magnetic field. By initializing ions with perpendicular temperature larger than parallel in a finite region of space, we investigate the generation of ion cyclotron waves in the high magnetic field region and their propagation to larger radial distances with weaker magnetic field strength. Specifically, we examine the propagation properties of the waves and the extent to which they are impacted by the presence of non-uninform magnetic field and nonlinear processes. Results show that at least in some cases, wave propagation is coupled to the outward motion (along the magnetic field) of the ions responsible for the generation of the waves. In such cases, wave generation may be ongoing for regions much larger than the initial source region where ions with temperature anisotropy are initialized. In this study we examine how the properties of ion cyclotron waves (e.g. spectral power, polarization) and their radial dependence vary with changes in the magnetic field model, level of temperature anisotropy, the nature of source ions (e.g. O5+; He++) and relative speed between the various ion species.

  13. On a Transition from Solar-Like Coronae to Rotation-Dominated Jovian-Like Magnetospheres in Ultracool Main-Sequence Stars

    NASA Astrophysics Data System (ADS)

    Schrijver, Carolus J.

    2009-07-01

    For main-sequence stars beyond spectral type M5, the characteristics of magnetic activity common to warmer solar-like stars change into the brown-dwarf domain: the surface magnetic field becomes more dipolar and the evolution of the field patterns slows, the photospheric plasma is increasingly neutral and decoupled from the magnetic field, chromospheric and coronal emissions weaken markedly, and the efficiency of rotational braking rapidly decreases. Yet, radio emission persists, and has been argued to be dominated by electron-cyclotron maser emission instead of the gyrosynchrotron emission from warmer stars. These properties may signal a transition in the stellar extended atmosphere. Stars warmer than about M5 have a solar-like corona and wind-sustained heliosphere in which the atmospheric activity is powered by convective motions that move the magnetic field. Stars cooler than early-L, in contrast, may have a Jovian-like rotation-dominated magnetosphere powered by the star's rotation in a scaled-up analog of the magnetospheres of Jupiter and Saturn. A dimensional scaling relationship for rotation-dominated magnetospheres by Fan et al. is consistent with this hypothesis.

  14. ON A TRANSITION FROM SOLAR-LIKE CORONAE TO ROTATION-DOMINATED JOVIAN-LIKE MAGNETOSPHERES IN ULTRACOOL MAIN-SEQUENCE STARS

    SciTech Connect

    Schrijver, Carolus J. [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, CA 94304 (United States)], E-mail: schrijver@lmsal.com

    2009-07-10

    For main-sequence stars beyond spectral type M5, the characteristics of magnetic activity common to warmer solar-like stars change into the brown-dwarf domain: the surface magnetic field becomes more dipolar and the evolution of the field patterns slows, the photospheric plasma is increasingly neutral and decoupled from the magnetic field, chromospheric and coronal emissions weaken markedly, and the efficiency of rotational braking rapidly decreases. Yet, radio emission persists, and has been argued to be dominated by electron-cyclotron maser emission instead of the gyrosynchrotron emission from warmer stars. These properties may signal a transition in the stellar extended atmosphere. Stars warmer than about M5 have a solar-like corona and wind-sustained heliosphere in which the atmospheric activity is powered by convective motions that move the magnetic field. Stars cooler than early-L, in contrast, may have a Jovian-like rotation-dominated magnetosphere powered by the star's rotation in a scaled-up analog of the magnetospheres of Jupiter and Saturn. A dimensional scaling relationship for rotation-dominated magnetospheres by Fan et al. is consistent with this hypothesis.

  15. On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations

    NASA Astrophysics Data System (ADS)

    Otto, S.; Trautmann, T.; Wendisch, M.

    2011-05-01

    Realistic size equivalence and shape of Saharan mineral dust particles are derived from in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10 %. At the bottom of the atmosphere (BOA) the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA) depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal) forcing by 55/5 % at the TOA over ocean/land and 15 % at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20 %. Large dust particles significantly contribute to all the radiative effects reported. They strongly enhance the absorbing properties and forward scattering in the solar and increase predominantly, e.g., the total TOA forcing of the dust over land.

  16. Motion of cometary dust

    Microsoft Academic Search

    Marco Fulle

    2004-01-01

    On timescales of days to months, the motion of cometary dust is mainly affected by solar radiation pressure, which determines dust dynamics according to the particle-scattering crosssection. Within this scenario, the motion of the dust creates structures referred to as dust tails. Tail photometry, depending on the dust cross-section, allows us to infer from model runs the best available outputs

  17. Solar Wind Five

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (editor)

    1983-01-01

    Topics of discussion were: solar corona, MHD waves and turbulence, acceleration of the solar wind, stellar coronae and winds, long term variations, energetic particles, plasma distribution functions and waves, spatial dependences, and minor ions.

  18. The solar flare catalog in the low-energy gamma-ray range based on the AVS-F instrument data onboard the CORONAS-F satellite in 2001 2005

    Microsoft Academic Search

    I. V. Arkhangelskaja; A. I. Arkhangelsky; Yu. D. Kotov; S. N. Kuznetsov; A. S. Glyanenko

    2006-01-01

    The AVS-F apparatus onboard the CORONAS-F satellite (operated from July 31, 2001, to December 6, 2005) was intended for investigation of solar hard X-ray and gamma-ray radiation and for registration of gamma-ray bursts. The AVS-F apparatus constitutes a system for processing the data from two detectors: SONG-D (a CsI(Tl) scintillation detector 200 mm in diameter and 100 mm in height,

  19. Electric fields and field-aligned currents in polar regions of the solar corona: 3-D MHD consideration

    Microsoft Academic Search

    Yu. V. Pisanko

    1995-01-01

    The calculation of the solar rotation electro-dynamical effects in the near-the-Sun solar wind seems more convenient from the non-inertial corotating reference frame. This implies some modification of the 3-D MHD equations generally on the base of the General Theory of Relativity. The paper deals with the search of stationary (in corotating non-inertial reference frame) solutions of the modified 3-D MHD

  20. Aspects of the Mass Distribution of Interstellar Dust Grains in the Solar System from In-Situ Measurements

    E-print Network

    M. Landgraf; W. J. Baggaley; E. Grün; H. Krüger; G. Linkert

    1999-08-10

    The in-situ detection of interstellar dust grains in the Solar System by the dust instruments on-board the Ulysses and Galileo spacecraft as well as the recent measurements of hyperbolic radar meteors give information on the properties of the interstellar solid particle population in the solar vicinity. Especially the distribution of grain masses is indicative of growth and destruction mechanisms that govern the grain evolution in the interstellar medium. The mass of an impacting dust grain is derived from its impact velocity and the amount of plasma generated by the impact. Because the initial velocity and the dynamics of interstellar particles in the Solar System are well known, we use an approximated theoretical instead of the measured impact velocity to derive the mass of interstellar grains from the Ulysses and Galileo in-situ data. The revised mass distributions are steeper and thus contain less large grains than the ones that use measured impact velocities, but large grains still contribute significantly to the overall mass of the detected grains. The flux of interstellar grains with masses $> 10^{-14} {\\rm kg}$ is determined to be $1\\cdot 10^{-6} {\\rm m}^{-2} {\\rm s}^{-1}$. The comparison of radar data with the extrapolation of the Ulysses and Galileo mass distribution indicates that the very large ($m > 10^{-10} {\\rm kg}$) hyperbolic meteoroids detected by the radar are not kinematically related to the interstellar dust population detected by the spacecraft.

  1. Mode conversion of Langmuir to electromagnetic waves at magnetic field-aligned density inhomogeneities: Simulations, theory, and applications to the solar wind and the corona

    SciTech Connect

    Kim, Eun-Hwa; Cairns, Iver H.; Robinson, Peter A. [School of Physics, University of Sydney, New South Wales 2006 (Australia)

    2008-10-15

    Linear mode conversion of Langmuir waves to radiation near the plasma frequency at density gradients is potentially relevant to multiple solar radio emissions, ionospheric radar experiments, laboratory plasma devices, and pulsars. Here we study mode conversion in warm magnetized plasmas using a numerical electron fluid simulation code with the density gradient parallel to the ambient magnetic field B{sub 0} for a range of incident Langmuir wavevectors. Our results include: (1) both o- and x-mode waves are produced for {omega}=({omega}L/c){sup 1/3}({omega}{sub c}/{omega})(less-or-similar sign)1, contrary to previous ideas. Only the o mode is produced for {omega}(greater-or-similar sign)1.5. Here {omega}{sub c} is the (angular) electron cyclotron frequency, {omega} is the angular wave frequency, L is the length scale of the (linear) density gradient, and c is the speed of light. A WKB-style analysis accounts semiquantitatively for the production and relative conversion efficiencies of the o and x modes in the simulations. (2) In the unmagnetized limit, equal amounts of o- and x-mode radiation are produced. (3) The mode conversion window narrows as {omega} increases. (4) As {omega} increases the total electromagnetic field changes from linear to circular polarization, with the o- and x-mode signals remaining circularly polarized. (5) The conversion efficiency to the x mode decreases monotonically as {omega} increases while the o-mode conversion efficiency oscillates due to an interference phenomenon between incoming and reflected Langmuir/z modes. (6) The maximum total conversion efficiencies for wave power from the Langmuir/z mode to radiation are of order 50%-70%. They depend strongly on the wave frequency when close to the background plasma frequency but weakly on the electron temperature T{sub 0} and {beta}=T{sub 0}/mc{sup 2}. The corresponding energy conversion efficiencies are favored since they allow separation into o and x modes, use directly measured experimental quantities, and generalize easily for wave packets. The total energy conversion efficiency differs from the power conversion efficiency by the ratio of the group speeds for each mode, is less than 10% for the value of {beta}=0.01 simulated, and decreases linearly with {beta}. Since {beta}{approx_equal}10{sup -5}-10{sup -4} in the solar wind and corona, this {beta} dependence is important in applications. (7) The interference effect and the disappearance of the x mode at {omega}(greater-or-similar sign)1 can be accounted for semiquantitatively using a WKB-type analysis. (8) Constraints on density turbulence are developed for the x mode to be generated and be able to propagate from the source. (9) Standard parameters for the corona and the solar wind near 1 AU suggest that linear mode conversion should produce both o- and x-mode radiation for solar and interplanetary radio bursts. It is therefore possible that linear mode conversion under these conditions might explain the weak total circular polarizations of type II and III solar radio bursts.

  2. Laboratory Evidence That Line-Tied Toroidal Magnetic Fields Can Suppress Loss-of-Equilibrium Flux Rope Eruptions in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W. R., II; Jara-Almonte, J.

    2014-12-01

    Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (potential) and internal (plasma-generated) magnetic fields. We find that forces due to the line-tied toroidal magnetic field, which are not included in the basic torus instability theory, can play a major role in preventing eruptions. The dependence of these toroidal magnetic forces on various potential field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

  3. Height of Shock Formation in the Solar Corona Inferred from Observations of Type II Radio Bursts and Coronal Mass Ejections

    E-print Network

    Gopalswamy, N; Mäkelä, P; Yashiro, S; Akiyama, S; Srivastava, W Uddin A K; Joshi, N C; Chandra, R; Manoharan, P K; Mahalakshmi, K; Dwivedi, V C; Awasthi, R Jain A K; Nitta, N V; Aschwanden, M J; Choudhary, D P

    2013-01-01

    Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequ...

  4. THE DIGITAL SYSTEM ARTEMIS FOR REAL-TIME PROCESSING OF RADIO TRANSIENT EMISSIONS IN THE SOLAR CORONA

    E-print Network

    Athens, University of

    THE DIGITAL SYSTEM ARTEMIS FOR REAL-TIME PROCESSING OF RADIO TRANSIENT EMISSIONS IN THE SOLAR system named 'ARTEMIS' that was developed and constructed by the Space Research Department (DESPA time signals from multichannel receivers. This system is controlled by a multiprocessor computer based

  5. Plasma Properties and Magnetic Field Structure of the Solar Corona, Based on Coordinated Max '91 Observations from SERTS, the VLA, and Magnetographs

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffrey W. (Principal Investigator)

    1996-01-01

    The plasma properties and magnetic field structure of the solar corona were determined using coordinated observations obtained with NASA/GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and Kitt Peak photospheric longitudinal magnetograms. A problem was identified with the SERTS calibration as determined from laboratory measurements. A revised calibration curve was derived by requiring that the numerous available measured line intensity ratios agreed with their respective theoretical values. Densities were derived from line intensity ratios, and active region densities were found to typically exceed quiet Sun densities by factors of only about 2. The active region density was found to remain constant across the SERTS slit, despite the fact that the emission line intensities vary significantly. This indicates that the product of the path length and the volume filling factor must vary significantly from the active region outskirts to the central core. Filling factors were derived and found to range from much less than one to nearly unity. Wavelength shifts were examined along the SERTS slit in the spatially resolved spectra, but no evidence was found for significant Doppler shifts in active region 7563 or in the quiet Sun. The numerical procedure developed by Monsignori-Fossi and Landini was used to derive the active region and quiet sun differential emission measure (DEM) from the spatially averaged spectra. A DEM was estimated for each spatial pixel in the two dimensional active region images by scaling the averaged active region DEM based upon corresponding pixel intensities of SERTS Mg IX, Fe XV, and Fe XVI images. These results, along with density measurements, were used in an IDL computer code which calculated the temperature dependence of the coronal magnetic field in each spatial pixel by minimizing the difference between the observed and calculated 20 and 6 cm microwave brightness temperatures.

  6. Corona Discharge in Clouds

    NASA Astrophysics Data System (ADS)

    Sin'kevich, A. A.; Dovgalyuk, Yu. A.

    2014-04-01

    We present a review of the results of theoretical studies and laboratory modeling of corona discharge initiation in clouds. The influence of corona discharges on the evolution of the cloud microstructure and electrification is analyzed. It is shown that corona discharges are initiated when large-size hydrometeors approach each other, whereas in some cases, corona discharges from crystals, ice pellets, and hailstones can appear. The corona discharges lead to significant air ionization, charging of cloud particles, and separation of charges in clouds and initiate streamers and lightnings. The influence of corona discharges on changes in the phase composition of clouds is analyzed.

  7. DETECTION OF PLASMA FLUCTUATIONS IN WHITE-LIGHT IMAGES OF THE OUTER SOLAR CORONA: INVESTIGATION OF THE SPATIAL AND TEMPORAL EVOLUTION

    SciTech Connect

    Telloni, D.; Antonucci, E. [National Institute for Astrophysics (INAF), Astrophysical Observatory of Torino, Via Osservatorio 20, I-10025 Pino Torinese (Italy); Ventura, R.; Romano, P.; Spadaro, D. [National Institute for Astrophysics (INAF), Astrophysical Observatory of Catania, Via S. Sofia 78, I-95123 Catania (Italy)

    2013-04-20

    This work focuses on the first results from the identification and characterization of periodic plasma density fluctuations in the outer corona, observed in STEREO-A COR1 white-light image time series. A two-dimensional reconstruction of the spatial distribution and temporal evolution of the coronal fluctuation power has been performed over the whole plane of the sky, from 1.4 to 4.0 R{sub Sun }. The adopted diagnostic tool is based on wavelet transforms. This technique, with respect to the standard Fourier analysis, has the advantage of localizing non-persistent fluctuating features and exploring variations of the relating wavelet power in both space and time. The map of the variance of the coronal brightness clearly outlines intermittent spatially coherent fluctuating features, localized along, or adjacent to, the strongest magnetic field lines. In most cases, they do not correspond to the visible coronal structures in the brightness maps. The results obtained provide a scenario in which the solar corona shows quasi-periodic, non-stationary density variations characterized by a wide range of temporal and spatial scales and strongly confined by the magnetic field topology. In addition, structures fluctuating with larger power are larger in size and evolve more slowly. The characteristic periodicities of the fluctuations are comparable to their lifetimes. This suggests that plasma fluctuations lasting only one or two wave periods and initially characterized by a single dominant periodicity either rapidly decay into a turbulent mixed flow via nonlinear interactions with other plasma modes, or they are damped by thermal conduction. The periodic non-stationary coronal fluctuations outlined by the closed field lines at low and mid latitudes might be associated with the existence of slow standing magneto-acoustic waves excited by the convective supergranular motion. The fluctuating ray-like structures observed along open field lines appear to be linked either to the intermittent nature of the processes underlying the generation of magnetic reconnection in the polar regions or to the oscillatory transverse displacements of the coronal ray itself.

  8. Detection of Plasma Fluctuations in White-light Images of the Outer Solar Corona: Investigation of the Spatial and Temporal Evolution

    NASA Astrophysics Data System (ADS)

    Telloni, D.; Ventura, R.; Romano, P.; Spadaro, D.; Antonucci, E.

    2013-04-01

    This work focuses on the first results from the identification and characterization of periodic plasma density fluctuations in the outer corona, observed in STEREO-A COR1 white-light image time series. A two-dimensional reconstruction of the spatial distribution and temporal evolution of the coronal fluctuation power has been performed over the whole plane of the sky, from 1.4 to 4.0 R ?. The adopted diagnostic tool is based on wavelet transforms. This technique, with respect to the standard Fourier analysis, has the advantage of localizing non-persistent fluctuating features and exploring variations of the relating wavelet power in both space and time. The map of the variance of the coronal brightness clearly outlines intermittent spatially coherent fluctuating features, localized along, or adjacent to, the strongest magnetic field lines. In most cases, they do not correspond to the visible coronal structures in the brightness maps. The results obtained provide a scenario in which the solar corona shows quasi-periodic, non-stationary density variations characterized by a wide range of temporal and spatial scales and strongly confined by the magnetic field topology. In addition, structures fluctuating with larger power are larger in size and evolve more slowly. The characteristic periodicities of the fluctuations are comparable to their lifetimes. This suggests that plasma fluctuations lasting only one or two wave periods and initially characterized by a single dominant periodicity either rapidly decay into a turbulent mixed flow via nonlinear interactions with other plasma modes, or they are damped by thermal conduction. The periodic non-stationary coronal fluctuations outlined by the closed field lines at low and mid latitudes might be associated with the existence of slow standing magneto-acoustic waves excited by the convective supergranular motion. The fluctuating ray-like structures observed along open field lines appear to be linked either to the intermittent nature of the processes underlying the generation of magnetic reconnection in the polar regions or to the oscillatory transverse displacements of the coronal ray itself.

  9. QUASI-PERIODIC PROPAGATING SIGNALS IN THE SOLAR CORONA: THE SIGNATURE OF MAGNETOACOUSTIC WAVES OR HIGH-VELOCITY UPFLOWS?

    SciTech Connect

    De Pontieu, Bart [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Org. ADBS, Bldg. 252, Palo Alto, CA 94304 (United States); McIntosh, Scott W., E-mail: bdp@lmsal.co, E-mail: mscott@ucar.ed [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

    2010-10-20

    Since the discovery of quasi-periodic propagating oscillations with periods of order 3-10 minutes in coronal loops with TRACE and SOHO/EIT (and later with STEREO/EUVI and Hinode/EIS), they have been almost universally interpreted as evidence for propagating slow-mode magnetoacoustic waves in the low plasma {beta} coronal environment. Here we show that this interpretation is not unique, and that for coronal loops associated with plage regions (as opposed to sunspots), the presence of magnetoacoustic waves may not be the only cause for the observed quasi-periodicities. We focus instead on the ubiquitous, faint upflows at 50-150 km s{sup -1} that were recently discovered as blueward asymmetries of spectral line profiles in footpoint regions of coronal loops, and as faint disturbances propagating along coronal loops in EUV/X-ray imaging time series. These faint upflows are most likely driven from below and have been associated with chromospheric jets that are (partially) rapidly heated to coronal temperatures at low heights. These two scenarios (waves versus flows) are difficult to differentiate using only imaging data, but careful analysis of spectral line profiles indicates that faint upflows are likely responsible for some of the observed quasi-periodic oscillatory signals in the corona. We show that recent EIS measurements of intensity and velocity oscillations of coronal lines (which had previously been interpreted as direct evidence for propagating waves) are actually accompanied by significant oscillations in the line width that are driven by a quasi-periodically varying component of emission in the blue wing of the line. This faint additional component of blue-shifted emission quasi-periodically modulates the peak intensity and line centroid of a single Gaussian fit to the spectral profile with the same small amplitudes (respectively a few percent of background intensity and a few km s{sup -1}) that were previously used to infer the presence of slow-mode magnetoacoustic waves. Our results indicate that it is possible that a significant fraction of the quasi-periodicities observed with coronal imagers and spectrographs that have previously been interpreted as propagating magnetoacoustic waves are instead caused by these upflows. The different physical cause for coronal oscillations would significantly impact the prospects of successful coronal seismology using propagating disturbances in coronal loops.

  10. Catastrophic eruption of magnetic flux rope in the corona and solar wind with and without magnetic reconnection

    Microsoft Academic Search

    Y. Chen; Y. Q. Hu; S. J. Sun

    2007-01-01

    It is generally believed that the magnetic free energy accumulated in the\\u000acorona serves as a main energy source for solar explosions such as coronal mass\\u000aejections (CMEs). In the framework of the flux rope catastrophe model for CMEs,\\u000athe energy may be abruptly released either by an ideal magnetohydrodynamic\\u000a(MHD) catastrophe, which belongs to a global magnetic topological instability

  11. Space storm measurements of the July 2005 solar extreme events from the low corona to the Earth

    E-print Network

    Caroubalos, C; Mavromichalaki, H; Moussas, X; Papaioannou, A; Mitsakou, E; Hillaris, A; 10.1016/j.asr.2008.09.019

    2010-01-01

    The Athens Neutron Monitor Data Processing (ANMODAP) Center recorded an unusual Forbush decrease with a sharp enhancement of cosmic ray intensity right after the main phase of the Forbush decrease on 16 July 2005, followed by a second decrease within less than 12 h. This exceptional event is neither a ground level enhancement nor a geomagnetic effect in cosmic rays. It rather appears as the effect of a special structure of interplanetary disturbances originating from a group of coronal mass ejections (CMEs) in the 13-14 July 2005 period. The initiation of the CMEs was accompanied by type IV radio bursts and intense solar flares (SFs) on the west solar limb (AR 786); this group of energetic phenomena appears under the label of Solar Extreme Events of July 2005. We study the characteristics of these events using combined data from Earth (the ARTEMIS IV radioheliograph, the Athens Neutron Monitor (ANMODAP)), space (WIND/WAVES) and data archives. We propose an interpretation of the unusual Forbush profile in term...

  12. How Common are Hot Magnetic Flux Ropes in the Low Solar Corona? A Statistical Study of EUV Observations

    E-print Network

    Nindos, A; Vourlidas, A; Tagikas, C

    2015-01-01

    We use data at 131, 171, and 304 A from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) to search for hot flux ropes in 141 M-class and X-class solar flares that occurred at solar longitudes equal to or larger than 50 degrees. Half of the flares were associated with coronal mass ejections (CMEs). The goal of our survey is to assess the frequency of hot flux ropes in large flares irrespective of their formation time relative to the onset of eruptions. The flux ropes were identified in 131 A images using morphological criteria and their high temperatures were confirmed by their absence in the cooler 171 and 304 A passbands. We found hot flux ropes in 45 of our events (32% of the flares); 11 of them were associated with confined flares while the remaining 34 were associated with eruptive flares. Therefore almost half (49%) of the eruptive events involved a hot flux rope configuration. The use of supplementary Hinode X-Ray Telescope (XRT) data indicates that these percentages sh...

  13. Global numerical modeling of energetic proton acceleration in a coronal mass ejection traveling through the solar corona

    SciTech Connect

    Kozarev, Kamen A.; Opher, Merav [Department of Astronomy, Boston University, Boston, MA 02215 (United States); Evans, Rebekah M. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Schwadron, Nathan A. [Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824-3525 (United States); Dayeh, Maher A. [Department of Space Science, Southwest Research Institute, San Antonio, TX (United States); Korreck, Kelly E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Van der Holst, Bart [Center for Space Environment Modeling, University of Michigan, Ann Arbor, MI 48109-2143 (United States)

    2013-11-20

    The acceleration of protons and electrons to high (sometimes GeV/nucleon) energies by solar phenomena is a key component of space weather. These solar energetic particle (SEP) events can damage spacecraft and communications, as well as present radiation hazards to humans. In-depth particle acceleration simulations have been performed for idealized magnetic fields for diffusive acceleration and particle propagation, and at the same time the quality of MHD simulations of coronal mass ejections (CMEs) has improved significantly. However, to date these two pieces of the same puzzle have remained largely decoupled. Such structures may contain not just a shock but also sizable sheath and pileup compression regions behind it, and may vary considerably with longitude and latitude based on the underlying coronal conditions. In this work, we have coupled results from a detailed global three-dimensional MHD time-dependent CME simulation to a global proton acceleration and transport model, in order to study time-dependent effects of SEP acceleration between 1.8 and 8 solar radii in the 2005 May 13 CME. We find that the source population is accelerated to at least 100 MeV, with distributions enhanced up to six orders of magnitude. Acceleration efficiency varies strongly along field lines probing different regions of the dynamically evolving CME, whose dynamics is influenced by the large-scale coronal magnetic field structure. We observe strong acceleration in sheath regions immediately behind the shock.

  14. Aspects of the Mass Distribution of Interstellar Dust Grains in the Solar System from In-Situ Measurements

    E-print Network

    Landgraf, M; Grün, E; Krüger, H; Linkert, G

    1999-01-01

    The in-situ detection of interstellar dust grains in the Solar System by the dust instruments on-board the Ulysses and Galileo spacecraft as well as the recent measurements of hyperbolic radar meteors give information on the properties of the interstellar solid particle population in the solar vicinity. Especially the distribution of grain masses is indicative of growth and destruction mechanisms that govern the grain evolution in the interstellar medium. The mass of an impacting dust grain is derived from its impact velocity and the amount of plasma generated by the impact. Because the initial velocity and the dynamics of interstellar particles in the Solar System are well known, we use an approximated theoretical instead of the measured impact velocity to derive the mass of interstellar grains from the Ulysses and Galileo in-situ data. The revised mass distributions are steeper and thus contain less large grains than the ones that use measured impact velocities, but large grains still contribute significant...

  15. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites.

    PubMed

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H; Ramasse, Quentin M; Hoppe, Peter; Nittler, Larry R

    2014-10-28

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight (15)N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C-O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C-O bonding environments and nanoglobular organics with dominant aromatic and C-N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  16. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites

    PubMed Central

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H.; Ramasse, Quentin M.; Hoppe, Peter; Nittler, Larry R.

    2014-01-01

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight 15N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C–O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C–O bonding environments and nanoglobular organics with dominant aromatic and C–N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  17. Interplanetary dust in the transmission electron microscope - Diverse materials from the early solar system

    NASA Technical Reports Server (NTRS)

    Fraundorf, P.

    1981-01-01

    An analytical electron microscope study of dispersed interplanetary dust aggregates collected in the earth's stratosphere shows that, in spite of their similarities, the aggregates exhibit significant differences in composition, internal morphology, and mineralogy. Of 11 chondritic particles examined, two consist mostly of a noncrystalline chondritic material with an atomic S/Fe ratio equal to or greater than 2 in places, one consists of submicron metal and reduced silicate 'microchondrules' and sulfide grains embedded in a carbonaceous matrix, and another consists of submicron magnetic-decorated unequilibrated silicate and sulfide grains with thick low-Z coatings. Although the particles are unmetamorphosed by criteria commonly applied for chondritic meteorites, the presence of reduced chemistries and the ubiquity of mafic, instead of hydrated, silicates confirm that they are not simply C1 or C2 chondrite matrix material. The observations indicate that portions of some particles have not been significantly altered by thermal or radiation processes since their assembly, and that the particles probably contain fine debris from diverse processes in the early solar system.

  18. MODELING MAGNETIC FIELD STRUCTURE OF A SOLAR ACTIVE REGION CORONA USING NONLINEAR FORCE-FREE FIELDS IN SPHERICAL GEOMETRY

    SciTech Connect

    Guo, Y.; Ding, M. D. [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Liu, Y.; Sun, X. D. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); DeRosa, M. L. [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, CA 94304 (United States); Wiegelmann, T., E-mail: guoyang@nju.edu.cn [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany)

    2012-11-20

    We test a nonlinear force-free field (NLFFF) optimization code in spherical geometry using an analytical solution from Low and Lou. Several tests are run, ranging from idealized cases where exact vector field data are provided on all boundaries, to cases where noisy vector data are provided on only the lower boundary (approximating the solar problem). Analytical tests also show that the NLFFF code in the spherical geometry performs better than that in the Cartesian one when the field of view of the bottom boundary is large, say, 20 Degree-Sign Multiplication-Sign 20 Degree-Sign . Additionally, we apply the NLFFF model to an active region observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory (SDO) both before and after an M8.7 flare. For each observation time, we initialize the models using potential field source surface (PFSS) extrapolations based on either a synoptic chart or a flux-dispersal model, and compare the resulting NLFFF models. The results show that NLFFF extrapolations using the flux-dispersal model as the boundary condition have slightly lower, therefore better, force-free, and divergence-free metrics, and contain larger free magnetic energy. By comparing the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the Atmospheric Imaging Assembly on board SDO, we find that the NLFFF performs better than the PFSS not only for the core field of the flare productive region, but also for large EUV loops higher than 50 Mm.

  19. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, D.´niel; Lauretta, Dante S.

    2014-02-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  20. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, Dániel; Lauretta, Dante S.

    2010-01-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  1. Search for Rapid Changes in the Visible-Light Corona during the 21 June 2001 Total Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Rudawy, P.; Phillips, K. J. H.; Buczylko, A.; Williams, D. R.; Keenan, F. P.

    2010-12-01

    Some 8000 images obtained with the Solar Eclipse Coronal Imaging System (SECIS) fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been analysed to search for short-period oscillations in intensity that could be a signature of solar coronal heating mechanisms by MHD wave dissipation. Images were taken in white-light and Fe xiv green-line (5303 Ĺ) channels over 205 seconds (frame rate 39 s-1), approximately the length of eclipse totality at this location, with a pixel size of four arcseconds square. The data are of considerably better quality than those that we obtained during the 11 August 1999 total eclipse (Rudawy et al.: Astron. Astrophys. 416, 1179, 2004), in that the images are much better exposed and enhancements in the drive system of the heliostat used gave a much improved image stability. Classical Fourier and wavelet techniques have been used to analyse the emission at 29 518 locations, of which 10 714 had emission at reasonably high levels, searching for periodic fluctuations with periods in the range 0.1 - 17 seconds (frequencies 0.06 - 10 Hz). While a number of possible periodicities were apparent in the wavelet analysis, none of the spatially and time-limited periodicities in the local brightness curves was found to be physically important. This implies that the pervasive Alfvén wave-like phenomena (Tomczyk et al.: Science 317, 1192, 2007) using polarimetric observations with the Coronal Multi-Channel Polarimeter (CoMP) instrument do not give rise to significant oscillatory intensity fluctuations.

  2. A search for high frequency waves in the visible-light corona during the 2001 total solar eclipse

    NASA Astrophysics Data System (ADS)

    Rudawy, Pawel; Phillips, Kenneth

    Some 8000 images obtained with the SECIS fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 2001 March 21 have been analyzed to search for short-period oscillations in intensity that could be a signature of solar coronal heating mecha-nisms. The images were taken in white-light and Fe xiv green-line (5303 A) channels over 205 s (frame rate 39 images per second), nearly the entire length of totality at this location. The pixel size is 4 arcseconds square. The data are of considerably better quality than the data obtained during the 1999 August 11 total eclipse, observed by us and already reported, in that the images are much better exposed and improvements in the drive system of the heliostat used gave a far better image stability. Of the 29800 locations in each image,. some 12740 had usable signal levels. Classical Fourier and wavelet techniques have been used to analyze the emission at these locations, only some of which were in recognizable coronal structures, searching for periodic uctuations in the range 0.06-10 Hz. While a number of possible periodicities were apparent in the wavelet analysis, none of the peaks in the Fourier spectra was found to be sig-nicant above the 4 level and so definitely attributable to the solar processes. This implies that the pervasive Alfven wave-like phenomena previously reported using polarimetric observations with the CoMP instrument do not give rise to signicant oscillatory intensity uctuations.

  3. Status of Knowledge after Ulysses and SOHO: Session 2: Investigate the Links between the Solar Surface, Corona, and Inner Heliosphere.

    NASA Technical Reports Server (NTRS)

    Suess, Steven

    2006-01-01

    As spacecraft observations of the heliosphere have moved from exploration into studies of physical processes, we are learning about the linkages that exist between different parts of the system. The past fifteen years have led to new ideas for how the heliospheric magnetic field connects back to the Sun and to how that connection plays a role in the origin of the solar wind. A growing understanding these connections, in turn, has led to the ability to use composition, ionization state, the microscopic state of the in situ plasma, and energetic particles as tools to further analyze the linkages and the underlying physical processes. Many missions have contributed to these investigations of the heliosphere as an integrated system. Two of the most important are Ulysses and SOHO, because of the types of measurements they make, their specific orbits, and how they have worked to complement each other. I will review and summarize the status of knowledge about these linkages, with emphasis on results from the Ulysses and SOHO missions. Some of the topics will be the global heliosphere at sunspot maximum and minimum, the physics and morphology of coronal holes, the origin(s) of slow wind, SOHO-Ulysses quadrature observations, mysteries in the propagation of energetic particles, and the physics of eruptive events and their associated current sheets. These specific topics are selected because they point towards the investigations that will be carried out with Solar Orbiter (SO) and the opportunity will be used to illustrate how SO will uniquely contribute to our knowledge of the underlying physical processes.

  4. Interstellar Dust: Contributed Papers

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M. (editor); Allamandola, Louis J. (editor)

    1989-01-01

    A coherent picture of the dust composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: dust in diffuse interstellar medium; overidentified infrared emission features; dust in dense clouds; dust in galaxies; optical properties of dust grains; interstellar dust models; interstellar dust and the solar system; dust formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.

  5. The TESIS experiment on the CORONAS-PHOTON spacecraft

    NASA Astrophysics Data System (ADS)

    Kuzin, S. V.; Zhitnik, I. A.; Shestov, S. V.; Bogachev, S. A.; Bugaenko, O. I.; Ignat'ev, A. P.; Pertsov, A. A.; Ulyanov, A. S.; Reva, A. A.; Slemzin, V. A.; Sukhodrev, N. K.; Ivanov, Yu. S.; Goncharov, L. A.; Mitrofanov, A. V.; Popov, S. G.; Shergina, T. A.; Solov'ev, V. A.; Oparin, S. N.; Zykov, A. M.

    2011-04-01

    On February 26, 2009, the first data was obtained in the TESIS experiment on the research of the solar corona using imaging spectroscopy. The TESIS is a part of the scientific equipment of the CORONAS-PHO-TON spacecraft and is designed for imaging the solar corona in soft X-ray and extreme ultraviolet regions of the spectrum with high spatial, spectral, and temporal resolutions at altitudes from the transition region to three solar radii. The article describes the main characteristics of the instrumentation, management features, and operation modes.

  6. 2.5D MHD Simulations of the Kelvin-Helmholtz Instability at CME-Boundaries in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Möstl, Ute; Temmer, Manuela; Veronig, Astrid

    2013-04-01

    We discuss the observation of a coronal mass ejection (CME) by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory from 2011 February 24. This CME with an embedded filament shows periodic vortex-like structures at the northern side of the filament boundary with a wavelength of approximately 14.4 Mm and a propagation speed of about 310 ą 20 km/s. The morphological analysis hints at structures produced by the Kelvin-Helmholtz (KH) instability on the boundary of the filament. We conduct 2.5D numerical simulations of the KH instability, whose results yield qualitative as well as quantitative agreements with the observations. Furthermore, we study the absence of KH vortex-like structures on the southern side of the filament boundary and find that a magnetic field component parallel to the boundary with a strength of about 20% of the total magnetic field has stabilizing effects resulting in an asymmetric development of the instability. This work receives funding from the Austrian Science Fund (FWF): P21051-N16, V195-N16 and P24092-N16.

  7. Micron-Sized Dust Particles Detected in the Outer Solar System by the Voyager 1 and 2 Plasma Wave Instruments

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Ansher, J. A.; Kurth, W. S.; Granroth, L. J.

    1997-01-01

    During the Voyager 1 and 2 flybys of the outer planets it has been demonstrated that the plasma wave instrument can detect small dust particles striking the spacecraft. In this paper, we examine the Voyager plasma wave data for dust impacts in the interplanetary medium at heliocentric radial distances ranging from 6 to 60 astronomical units (AU). The results show that a small but persistent level of dust impacts exists out to at least 30 to 50 AU. The average number density of these particles is about 2 x 10(exp -8)/cu m, and the average mass of the impacting particles is believed to be a few times 10(exp -11) g, which corresponds to particle diameters in the micron range. Possible sources of these particles are planets, moons, asteroids, comets, and the interstellar medium. Of these, comets appear to be the most likely source. The number densities are only weakly dependent on ecliptic latitude, which indicates that the particles probably do not originate from planets, moons, or asteroids. Comparisons with interstellar dust fluxes measured in the inner regions of the solar system by the Ulysses spacecraft indicate that the particles are not of interstellar origin.

  8. The solar flare catalog in the low-energy gamma-ray range based on the AVS-F instrument data onboard the CORONAS-F satellite in 2001–2005

    Microsoft Academic Search

    I. V. Arkhangelskaja; A. I. Arkhangelsky; Yu. D. Kotov; S. N. Kuznetsov; A. S. Glyanenko

    2006-01-01

    The AVS-F apparatus onboard the CORONAS-F satellite (operated from July 31, 2001, to December 6, 2005) was intended for investigation of solar hard X-ray and gamma-ray\\u000a radiation and for registration of gamma-ray bursts. The AVS-F apparatus constitutes a system for processing the data from\\u000a two detectors: SONG-D (a CsI(Tl) scintillation detector 200 mm in diameter and 100 mm in height,

  9. Mapping the Magnetic Structure of the Corona During the ULYSSES Fast-Latitude Scan

    Microsoft Academic Search

    J. A. Linker; Z. Mikic

    1997-01-01

    The coronal magnetic field defines the large-scale structure of the solar corona, the position of the heliospheric current sheet, and the regions of fast and slow solar wind. To understand the structure of the solar corona and inner heliophere, we must relate observations of the large-scale magnetic field at the photosphere to coronal and interplanetary observations. Global magnetohydrodynamic (MHD) models

  10. Identification and Characterization of Early Solar system Organic Matter Preserved in Chondritic Porous Interplanetary Dust Particles

    NASA Astrophysics Data System (ADS)

    Flynn, George; Wirick, Sue; Keller, Lindsay

    2015-04-01

    The chondritic porous interplanetary dust particles (CP IDPs), collected by NASA from the Earth's stratosphere, have experienced minimal aqueous or thermal alteration since their formation. These CP IDPs are the best preserved samples of the minerals and organic matter that was present in the primitive Solar Nebula that are currently available for laboratory analysis [1]. The ~10 ?m CP IDPs are aggregates of tens-of-thousands of mostly sub-micron grains of diverse compositions and mineralogies. Many of the individual mineral grains are coated by a 50 to 200 nm thick rims of carbonaceous material, and other carbonaceous material occurs as larger, discrete subunits within the particles [2]. We characterize this carbonaceous material using two high-resolution, synchrotron-based instruments: a Scanning Transmission X-ray Microscope (STXM) to locate and map the carbon and to identify its major functional groups by X-ray Absorption Near-Edge Structure (XANES) spectroscopy, and a micro-Fourier Transform Infrared (?-FTIR) spectrometer to further characterize the functional groups by mid-infrared spectroscopy. Carbon-XANES spectroscopy identifies the rims coating the individual grains in CP IDPs as organic matter, dominated by the C=C, likely C-rings, and the C=O functional groups [3]. This structure, with the organic rims being the contact surfaces between the grains, implies a 3-step formation sequence: grain condensation, organic rim emplacement, and, finally, aggregation of the grains to form the dust particles. This suggests these organic rims formed very early in the evolution of the Solar Nebula, after grain condensation but before grain aggregation [3]. These organic rims coat grains of diverse compositions, including silicates, sulfides, and carbonates, which is inconsistent with formation by Fischer-Tropsch-like, mineral-specific catalysis, one of the mechanisms suggested for the formation of primitive organic matter. Our observations are consistent with an alternate model where carbon-bearing ices condense on the surfaces of grains, the ices are irradiated by ionizing radiation, and subsequent heating removes the ices leaving more refractory organic matter on the grain surfaces, as described by Bernstein et al. [4]. In one case we obtained C-, N-, and O-XANES spectra on the rim material. The O-XANES confirmed the presence of C=O. We found high N:C and O:C ratios that plot on the extension of the N:C vs. O:C correlation line, found in analysis of meteoritic organic matter [5], towards even more primitive organic matter than found in any meteorite. The organic rims are too thin for ?-FTIR spectroscopy, which is diffraction limited to about the wavelength/2, or ~2 ?m for the aliphatic C-H stretching features. However, mid-infrared spectra obtained on CP IDPs show the presence of aliphatic C-H, C=O, C-C, and O-H, as well as crystalline and amorphous silicates [6]. Aromatic C-H is rarely detected in CP IDPs. Neither the organic rims nor the bulk organic matter in CP IDPs show the graphite exciton feature, whose strength in meteorite organic matter correlates with increasing parent body thermal metamorphism [7], indicating the organic matter in CP IDPs experienced minimal metamorphism after it formed. The spectra show variation in the aliphatic -C-H2- to -C-H3 and C=O to aliphatic C-H ratios from spot to spot on the same particle. C-XANES of ultramicrotome sections of CP IDPs also show significant variability, particularly in the C=O to C=C ratio. Variability in the C-XANES and the mid-infrared spectra indicates the organic matter in primitive CP IDPs consists of several compositionally distinct components. Our C-XANES and ?-FTIR results indicate the organic matter in CP IDPs is extremely primitive and that much of the pre-biotic organic matter of our Solar System formed early in the evolution of the Solar Nebula, by a process that preceded parent body aqueous processing. References: [1] Ishii, H. A. et al. (2008) Science, 319, 447-450. [2] Thomas, K. L. et al. (1996) ASP Conference Series, 104, 295-298. [3] Flynn, G. J

  11. Dust Interactions on Small Solar System Bodies and Technology Considerations for Exploration

    NASA Technical Reports Server (NTRS)

    Kobrick, Ryan,; Hoffman, Jeffrey; Pavone, Marco; Street, Kenneth; Rickman, Douglas

    2014-01-01

    Small-bodies such as asteroids and Mars' moons Phobos and Deimos have relatively unknown regolith environments. It is hypothesized that dust preserved in the regolith on the surfaces will have similar mechanical properties to lunar dust because of similar formation processes from micrometeorite bombardment, low relative gravity for slow settling times, and virtually no weathering because there is no atmosphere. This combination of processes infers that small-body dust particles will be highly angular and retain abrasive properties. The focus of this paper uses the mission architecture and engineering design for an asteroid hopper known as Hedgehog, a spherical spacecraft with several symmetric spikes used to aid with tumbling mobility in a low gravity environment. Dust abrasion considerations are highlighted throughout the paper relating to the lead authors' previous work, but act as an example of one of many important dust or regolith physical properties that need to be considered for future exploration. Measurable regolith properties are summarized in order to identify technologies that may be useful for exploration in terms of scientific return and spacecraft design. Previous instruments are summarized in this paper that could be used on the Hedgehog. Opportunities for hardware payloads are highlighted that include low mass solutions or dualpurpose instruments that can measure regolith or dust properties. Finally, dust mitigation suggestions are made for vehicles of this mobility profile.

  12. Fragmentation and Collapse in Coronae-Australis

    NASA Astrophysics Data System (ADS)

    Llewellyn, R.; Payne, P.; Sakellis, S.; Taylor, K. N. R.

    1981-07-01

    Observations of H I in the vicinity of the dust lane of Corona Austrinae reveal a region of almost complete conversion of H I to H2. The results suggest that about 103Msun of material may be in a state of collapse. The projected centre of this region coincides with a small dense cloud which may be the physical centre of the collapsing fragment, while the limits of the collapsing zone appear to be defined by an almost complete dust ring of diameter 1.3 pc.

  13. ON THE REMOTE DETECTION OF SUPRATHERMAL IONS IN THE SOLAR CORONA AND THEIR ROLE AS SEEDS FOR SOLAR ENERGETIC PARTICLE PRODUCTION

    SciTech Connect

    Laming, J. Martin; Moses, J. Daniel; Ko, Yuan-Kuen [Space Science Division, Naval Research Laboratory, Code 7684, Washington, DC 20375 (United States); Ng, Chee K. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Rakowski, Cara E.; Tylka, Allan J. [NASA/GSFC Code 672, Greenbelt, MD 20771 (United States)

    2013-06-10

    Forecasting large solar energetic particle (SEP) events associated with shocks driven by fast coronal mass ejections (CMEs) poses a major difficulty in the field of space weather. Besides issues associated with CME initiation, the SEP intensities are difficult to predict, spanning three orders of magnitude at any given CME speed. Many lines of indirect evidence point to the pre-existence of suprathermal seed particles for injection into the acceleration process as a key ingredient limiting the SEP intensity of a given event. This paper outlines the observational and theoretical basis for the inference that a suprathermal particle population is present prior to large SEP events, explores various scenarios for generating seed particles and their observational signatures, and explains how such suprathermals could be detected through measuring the wings of the H I Ly{alpha} line.

  14. Three-dimensional study of Mars upper thermosphere\\/ionosphere and hot oxygen corona: 1. General description and results at equinox for solar low conditions

    Microsoft Academic Search

    Arnaud Valeille; Valeriy Tenishev; Stephen W. Bougher; Michael R. Combi; Andrew F. Nagy

    2009-01-01

    Unlike Earth and Venus, Mars with a weak gravity allows an extended corona of hot species and the escape of its lighter constituents in its exosphere. Being the most important reaction, the dissociative recombination of O2+ is responsible for most of the production of hot atomic oxygen deep in the dayside thermosphere\\/ionosphere. The investigation of the Martian upper atmosphere is

  15. Laboratory and observational study of the interrelation of the carbonaceous component of interstellar dust and solar system materials

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Sanford, S. A.; Schutte, W. A.; Tielens, A. G. G. M.

    1991-01-01

    By studying the chemical and isotopic composition of interstellar ice and dust, one gains insight into the composition and chemical evolution of the solid bodies in the solar nebula and the nature of the material subsequently brought into the inner part of the solar system by comets and meteorites. It is now possible to spectroscopically probe the composition of interstellar ice and dust in the mid-infrared, the spectral range which is most diagnostic of fundamental molecular vibrations. We can compare these spectra of various astronomical objects (including the diffuse and dense interstellar medium, comets, and the icy outer planets and their satellites) with the spectra of analogs we produce in the laboratory under conditions which mimic those in these different objects. In this way one can determine the composition and abundances of the major constituents of the various ices and place general constraints on the types of organics coating the grains in the diffuse interstellar medium. In particular we have shown the ices in the dense clouds contain H2O, CH3OH, CO, perhaps some NH3 and H2CO, we well as nitriles and ketones or esters. Furthermore, by studying the photochemistry of these ice analogs in the laboratory, one gains insight into the chemistry which takes place in interstellar/precometary ices. Chemical and spectroscopic studies of photolyzed analogs (including deuterated species) are now underway. The results of some of these studies will be presented and implications for the evolution of the biogenic elements in interstellar dust and comets will be discussed.

  16. Electric Current Equilibrium in the Corona

    NASA Astrophysics Data System (ADS)

    Filippov, Boris

    2013-04-01

    A hyperbolic flux-tube configuration containing a null point below the flux rope is considered as a pre-eruptive state of coronal mass ejections that start simultaneously with flares. We demonstrate that this configuration is unstable and cannot exist for a long time in the solar corona. The inference follows from general equilibrium conditions and from analyzing simple models of the flux-rope equilibrium. A direct consequence of the stable flux-rope equilibrium in the corona are separatrices in the horizontal-field distribution in the chromosphere. They can be recognized as specific "herring-bone structures" in a chromospheric fibril pattern.

  17. Speaking Volumes about Dust

    NSDL National Science Digital Library

    2012-12-06

    This is a lesson about density. Learners will relate the concept of density to the density of dust in space. They will use mission data from the Student Dust Counter (SDC) interface to determine the density of dust grains in a volume of space in the Solar System in order to answer questions concerning the distribution of dust in the solar system. They will discover that space is much more sparsely populated with dust than they may have thought. Students discuss their findings with the class.

  18. The theory of magnetohydrodynamic wave generation by localized sources. III - Efficiency of plasma heating by dissipation of far-field waves. [in solar corona

    NASA Technical Reports Server (NTRS)

    Collins, William

    1992-01-01

    The fraction of radiation emitted by Alfven waves is calculated by using two separate methods to determine whether the Alfven flux generated in the photosphere is sufficient to heat the corona. One method employs a set of scaling laws for the fluxes as functions of plasma and source parameters; the second method consist of a procedure for calculating the flux in each waveband from the interaction of vector-harmonic components of an arbitrary applied forcing. Both methods indicate that the Alfven flux accounts roughly for half of the total emission. The need to reexamine estimates of the amount of Alfven flux reaching the corona based on observations of plasma disturbances in the photosphere is emphasized.

  19. Disease specific protein corona

    NASA Astrophysics Data System (ADS)

    Rahman, M.; Mahmoudi, M.

    2015-03-01

    It is now well accepted that upon their entrance into the biological environments, the surface of nanomaterials would be covered by various biomacromolecules (e.g., proteins and lipids). The absorption of these biomolecules, so called `protein corona', onto the surface of (nano)biomaterials confers them a new `biological identity'. Although the formation of protein coronas on the surface of nanoparticles has been widely investigated, there are few reports on the effect of various diseases on the biological identity of nanoparticles. As the type of diseases may tremendously changes the composition of the protein source (e.g., human plasma/serum), one can expect that amount and composition of associated proteins in the corona composition may be varied, in disease type manner. Here, we show that corona coated silica and polystyrene nanoparticles (after interaction with in the plasma of the healthy individuals) could induce unfolding of fibrinogen, which promotes release of the inflammatory cytokines. However, no considerable releases of inflammatory cytokines were observed for corona coated graphene sheets. In contrast, the obtained corona coated silica and polystyrene nanoparticles from the hypofibrinogenemia patients could not induce inflammatory cytokine release where graphene sheets do. Therefore, one can expect that disease-specific protein coronas can provide a novel approach for applying nanomedicine to personalized medicine, improving diagnosis and treatment of different diseases tailored to the specific conditions and circumstances.

  20. Skeletal Structures in the Images of Cosmic Dust Clouds and Solar System Planets

    Microsoft Academic Search

    Valentin A. Rantsev-Kartinov

    2007-01-01

    Multilevel dynamical contrasting of cosmic dust cloud images reveals the presence of skeletallike structures that are similar to those found in various electrical discharges and in space plasmas. These results, which are concentric cylinders in interstellar space, corroborate the discovery of interstellar neutral hydrogen (HI) emission spectra that are recorded in radio astronomy from low- and high-velocity intergalactic clouds in

  1. THE ROTATION OF THE WHITE LIGHT SOLAR CORONA AT HEIGHT 4 R{sub sun} FROM 1996 TO 2010: A TOMOGRAPHICAL STUDY OF LARGE ANGLE AND SPECTROMETRIC CORONAGRAPH C2 OBSERVATIONS

    SciTech Connect

    Morgan, Huw, E-mail: hmorgan@ifa.hawaii.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2011-09-10

    Solar rotational tomography is applied to Large Angle and Spectrometric Coronagraph (LASCO) C2/Solar and Heliospheric Observatory (SOHO) observations covering the period 1996-2010, resulting in a set of electron density maps at a height of 4 R{sub sun} from which rotation rates can be calculated. Large variation of rotation rates is measured. Rates are dominated by the Carrington rotation rate (14.18 deg d{sup -1} sidereal), but at times over the solar cycle, rates are measured between -3 and 3 deg d{sup -1} relative to the Carrington rotation rate. Rotation rates can vary considerably between latitudes, even between neighboring latitudes. They can remain relatively stable or change smoothly over long periods of times, or can change rather abruptly. There are periods for certain latitudes (for example, the equator at solar maximum) when the movement is dominated by rapid structural reconfiguration, not a coherent rotation. These results raise new questions regarding the link between the Sun and the corona, and provide fresh challenges to interpretations of the coronal structural evolution and the development of large-scale coronal models. In particular, can interchange reconnection provide an explanation of the considerable latitudinal differences in rotation rates, and what mechanism can explain abrupt changes in rotation rates?

  2. Dust in brown dwarfs and extra-solar planets. I. Chemical composition and spectral appearance of quasi-static cloud layers

    Microsoft Academic Search

    Ch. Helling; P. Woitke; W.-F. Thi

    2008-01-01

    Aims: Brown dwarfs are covered by dust cloud layers which cause inhomogeneous surface features and move below the observable tau = 1 level during the object's evolution. The cloud layers have a strong influence on the structure and spectral appearance of brown dwarfs and extra-solar planets, e.g. by providing high local opacities and by removing condensable elements from the atmosphere

  3. SIMBA observations of the R Corona Australis molecular cloud

    Microsoft Academic Search

    K. Kampgen; B. Reipurth; M. Albrecht; E. Kreysa; R. Lemke; M. Nielbock; L. A. Reichertz; A. Sievers; R. Zylka

    2003-01-01

    We have mapped the R Corona Australis molecular cloud at 1.2 mm with SIMBA on SEST and detected 25 distinct dust emission peaks. While 7 of them coincide with positions of previously known young stars, 18 are seemingly not associated with any known stellar object. We discuss the nature of individual sources and conclude that there are at least four

  4. Radiative properties and direct radiative effect of Saharan dust measured by the C-130 aircraft during SHADE: 1. Solar spectrum

    Microsoft Academic Search

    Jim Haywood; Pete Francis; Simon Osborne; Martin Glew; Norman Loeb; Eleanor Highwood; Didier Tanré; Gunnar Myhre; Paola Formenti; Edwin Hirst

    2003-01-01

    The physical and optical properties of Saharan dust aerosol measured by the Met Office C-130 during the Saharan Dust Experiment (SHADE) are presented. Additional radiation measurements enable the determination of the aerosol optical depth, tau aerlambda, and the direct radiative effect (DRE) of the mineral dust. The results suggest that the absorption by Saharan dust is significantly overestimated in the

  5. Dust Mitigation for Martian Exploration

    NASA Technical Reports Server (NTRS)

    Williams, Blakeley Shay

    2011-01-01

    One of the efforts of the In-Situ Resource Utilization project is to extract oxygen, fuel, and water from the Martian air. However, the surface of Mars is covered in a layer of dust, which is uploaded into the atmosphere by dust devils and dust storms. This atmospheric dust would be collected along with the air during the conversion process. Thus, it is essential to extract the dust from the air prior to commencing the conversion. An electrostatic precipitator is a commonly used dust removal technology on earth. Using this technology, dust particles that pass through receive an electrostatic charge by means of a corona discharge. The particles are then driven to a collector in a region of high electric field at the center of the precipitator. Experiments were conducted to develop a precipitator that will function properly in the Martian atmosphere, which has a very low pressure and is made up . of primarily carbon dioxide.

  6. The energy and pressure balance in the corona

    Microsoft Academic Search

    R. W. P. McWhirter; R. Wilson

    1976-01-01

    The paper presents a brief review of studies related to the energy balance in the solar atmosphere above the chromosphere. Processes discussed include heating of the outer corona by the dissipation of mechanical waves generated in the lower atmosphere, convective outflow of the atmosphere giving rise to the solar wind, thermal conductivity, and radiated power loss. Energy-balance models dealing primarily

  7. Optical and adhesive properties of dust deposits on solar mirrors and their effects on specular reflectivity and electrodynamic cleaning for mitigating energy-yield loss

    NASA Astrophysics Data System (ADS)

    Mazumder, Malay; Yellowhair, Julius; Stark, Jeremy; Heiling, Calvin; Hudelson, John; Hao, Fang; Gibson, Hannah; Horenstein, Mark

    2014-10-01

    Large-scale solar plants are mostly installed in semi-arid and desert areas. In those areas, dust layer buildup on solar collectors becomes a major cause for energy yield loss. Development of transparent electrodynamic screens (EDS) and their applications for self-cleaning operation of solar mirrors are presented with a primary focus on the removal dust particles smaller than 30 ľm in diameter while maintaining specular reflection efficiency < 90%. An EDS consists of thin rectangular array of parallel transparent conducting electrodes deposited on a transparent dielectric surface. The electrodes are insulated from each other and are embedded within a thin transparent dielectric film. The electrodes are activated using three-phase high-voltage pulses at low current (< 1 mA/m2 ). The three-phase electric field charges the deposited particles, lifts them form the substrate by electrostatic forces and propels the dust layer off of the collector's surface by a traveling wave. The cleaning process takes less than 2 minutes; needs energy less than 1 Wh/m2 without requiring any water or manual labor. The reflection efficiency can be restored > 95% of the original clean-mirror efficiency. We briefly present (1) loss of specular reflection efficiency as a function of particle size distribution of deposited dust, and (2) the effects of the electrode design and materials used for minimizing initial loss of specular reflectivity in producing EDS-integrated solar mirrors. Optimization of EDS by using a figure of merit defined by the ratio of dust removal efficiency to the initial loss of specular reflection efficiency is discussed.

  8. Star dust.

    PubMed

    Ney, E P

    1977-02-11

    Infrared astronomy has shown that certain classes of stars are abundant producers of refractory grains, which condense in their atmospheres and are blown into interstellar space by the radiation pressure of these stars. Metallic silicates of the kind that produce terrestrial planets are injected by the oxygen-rich stars and carbon and its refractories by carbon stars. Much of the interstellar dust may be produced by this mechanism. A number of "infrared stars" are completely surrounded by their own dust, and a few of these exhibit a unique morphology that suggests the formation of a planetary system or a stage in the evolution of a planetary nebula. Certain novae also condense grains, which are blown out in their shells. In our own solar system, comets are found to contain the same silicates that are present elsewhere in the galaxy, suggesting that these constituents were present in the primeval solar nebula. PMID:17732279

  9. Accretionary dust mantles in CM chondrites - Evidence for solar nebula processes

    Microsoft Academic Search

    K. Metzler; A. Bischoff; D. Stoeffler

    1992-01-01

    The origin of the various components of 14 carbonaceous chondrites of the CM group, and the evolution of their parent body (or bodies) were examined by studying the texture and the model composition of these chondrites. Evidence is presented for the existence of preaccretionary aqueous alteration of anhydrous primary products in the solar nebula. Based on the results of textural,

  10. Radio wave scattering observations of the solar corona First-order measurements of expansion velocity and turbulence spectrum using Viking and Mariner 10 spacecraft

    NASA Technical Reports Server (NTRS)

    Tyler, G. L.; Vesecky, J. F.; Plume, M. A.; Howard, H. T.; Barnes, A.

    1981-01-01

    Radio wave scattering data were collected at 3.6 and 13 cm wavelengths by means of the radio link between the Viking orbiters and the earth during the Nov. 25, 1976 solar conjunction of Mars, which occurred near the beginning of solar cycle 21; Mariner 10 solar activity observations during 1974 are also used. It is found that the temporal frequency variance spectrum of amplitude fluctuations is useful for characterizing the bulk motion of the plasma, and the spectral index of electron density turbulence is obtained. The measurements of solar wind velocity and spectral index cover 78 days for Viking and 49 days for Mariner 10 and show the combined effects of changing heliocentric distance, solar latitude, and solar longitude as well as solar activity. It is concluded that the observational velocity profile differs significantly from the theoretical profiles in two ways: (1) the theoretical profile does not show the abrupt change in velocity at about 15 solar radii, and (2) the observational profile shows acceleration at larger radial distances than the model profiles. The observational profiles indicate velocities of less than about 150 km/sec out to 15 solar radii.

  11. Persistent Doppler Shift Oscillations Observed with HINODE-EIS in the Solar Corona: Spectroscopic Signatures of Alfvenic Waves and Recurring Upflows

    NASA Technical Reports Server (NTRS)

    Tian, Hui; McIntosh, Scott W.; Wang, Tongjiang; Offman, Leon; De Pontieu, Bart; Innes, Davina E.; Peter, Hardi

    2012-01-01

    Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfv´en waves rather than flows. In a few cases, there seems to be a p/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfv´enic oscillations. In this scenario, the intensity oscillations associated with Alfv´enic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.

  12. Far-infrared observations of young clusters embedded in the R Coronae Australis and Rho Ophiuchi dark clouds

    NASA Technical Reports Server (NTRS)

    Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

    1985-01-01

    Multicolor far-infrared maps in two nearby dark clouds, R Coronae Australis and Rho Ophiuchi, have been made in order to investigate the individual contribution of low-mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low-mass stars has been detected in CrA and four in Rho Oph; their far-infrared luminosities range from 2 solar luminosities to 40 solar luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50 percent of the star's energy was radiated longward of 20 microns. Meaningful limits to the far-infrared luminosities of an additional 11 association members in CrA and two in Rho Oph were also obtained. The dust optical depth surrounding the star R CrA appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of these results for the cloud energetics and star formation efficiency in these two clouds are discussed.

  13. Cosmic Dust: The Ulysses perspective

    E-print Network

    Eberhard Gruen; Harald Krueger; Markus Landgraf

    2000-12-11

    The Ulysses spacecraft, launched in October 1990, orbits the Sun on a polar trajectory. The spacecraft is equipped with a highly sensitive impact- ionization dust detector which can in situ measure cosmic dust grains in the mass range 10^-9 to 10^-19 kg. With the Ulysses dust detector dust streams originating from Jupiter's volcanically active moon Io have been discovered as well as interstellar dust particles sweeping through the solar system. The distribution of interplanetary dust grains has been measured at high ecliptic latitudes with Ulysses for the first time. The Ulysses measurements of interplanetary dust, dust grains interacting electromagnetically with the magnetosphere of Jupiter and measurements of interstellar dust in the solar system are reviewed.

  14. Cosmic Dust The Ulysses perspective

    E-print Network

    Grün, E; Landgraf, M; Gruen, Eberhard; Krueger, Harald; Landgraf, Markus

    2000-01-01

    The Ulysses spacecraft, launched in October 1990, orbits the Sun on a polar trajectory. The spacecraft is equipped with a highly sensitive impact- ionization dust detector which can in situ measure cosmic dust grains in the mass range 10^-9 to 10^-19 kg. With the Ulysses dust detector dust streams originating from Jupiter's volcanically active moon Io have been discovered as well as interstellar dust particles sweeping through the solar system. The distribution of interplanetary dust grains has been measured at high ecliptic latitudes with Ulysses for the first time. The Ulysses measurements of interplanetary dust, dust grains interacting electromagnetically with the magnetosphere of Jupiter and measurements of interstellar dust in the solar system are reviewed.

  15. Evidence for compact structuring in the corona of active stars

    E-print Network

    F. Favata

    2000-11-27

    The ``current wisdom'' regarding the structuring of the X-ray emitting corona in active stars (i.e. a corona dominated by extended coronal structures) is briefly reviewed, followed by a review of a new approach to flare analysis and the analysis of a significant number of newly observed and previously published large flares, all leading to a much more compactly structured corona. Recent observations showing the polar location of the flaring plasma are then discussed, showing how the current evidence points toward a (flaring) corona composed of rather low-lying polar structures, also in agreement with some recent radio VLBI observational results and with starspot Doppler images. The resulting picture is significantly different from the solar case.

  16. Dust storm in Sudan

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A dust storm is carrying dust from Sudan, Africa, out over the Red Sea (right) in this Moderate Resolution Imaging Spectroradiometer Image from June 30, 2002. In the lower left quadrant of the image, the sinuous path of the Nile can be seen. Dust storms such as this reduce the amount of solar radiation that reaches the surface, and have a cooling effect on the area. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  17. Solar wind theory and modeling

    Microsoft Academic Search

    Viggo H. Hansteen

    1996-01-01

    tending out to eight solar radii. Be showed that the electron density profile determined by Baumbach [1937] is consistent with an electron-proton corona with a temperature of around a million degrees. The idea of a hot corona was gradually accepted, and mechanisms for heating the corona were suggested by Biermann [1946, 1948], Alfvgn [1947], and Schwarzschild [1948]. Chapman [1957] constructed

  18. Corona discharge and electrostatic precipitation in carbon dioxide under reduced pressure simulating Mars atmosphere

    Microsoft Academic Search

    Hai Long PANG; P. Atten; J.-L. Reboud

    2005-01-01

    The possibility of using electrostatic precipitation to clean the gas above solar panels on the surface of planet Mars is investigated. Results are presented on corona discharge in carbon dioxide gas under reduced pressure ranging from 5 to 10 mbar with different electrode configurations. The corona discharge inception voltage and the threshold of bipolar discharge have been measured for the

  19. Cloud, dust, and ozone vertical profiles from solar occultation measurements: Implications for dynamics

    NASA Technical Reports Server (NTRS)

    Chassefiere, E.; Blamont, J. E.

    1993-01-01

    An instrument was designed for solar occultation measurements of the martian atmosphere from the Phobos spacecraft. It was composed of three different dispersive systems working in the ultraviolet (UV: 0.22-0.32 microns) for the measurement of O3 and aerosols, in the near infrared (NIR: 0.76 microns, 0.94 microns) for the detection of O2 and H2O, and in the infrared (IR: 1.9 microns, 3.7 microns) where CO2 and H2O were measured. A detailed description of the instrument may be found in the special issue of Nature. Its principle objective is to measure from the Phobos orbit the spectrum of the Sun, modified by atmospheric extinction, during sunset. The UV-NIR spot has an angular diameter of 1 arcmin, or approximately 3 km vertical resolution, and is located near the center of the solar disk. The IR field is about twice as large and its line of sight is shifted by 8.5 arcmin, or approximately 20 km, relative to the previous one. It is therefore located near the edge of the solar disk. Sampling times are generally 0.5, 1, and 2 s for IR, UV, and NIR channels respectively, corresponding to vertical excursions of the line of sight of 1, 2, and 4 km respectively under nominal conditions. The instrument operated from February 8 to March 26 (the martian equinox occurred on February 17). The latitude of the intersection of the Sun-spacecraft axis with the surface of Mars varied from -11 to +20, the seasonal date L(sub s) being in the range 0 - 20. All measurements were therefore made near northern spring equinox in equatorial regions. Due to an error in the pointing system, only partial results were obtained, the region below approximately equals 30 km altitude being never sounded by the UV-NIR spectrometer. On the contrary, nine complete occultations were obtained in the IR channels, whose line of sight was fortunately approximately equals 20 km below the UV-NIR axis.

  20. Dust and Planetary Rings

    NASA Astrophysics Data System (ADS)

    Siddiqui, Muddassir

    ABSTRACT Space is not empty it has comic radiations (CMBR), dust etc. Cosmic dust is that type of dust which is composed of particles in space which vary from few molecules to 0.1micro metres in size. This type of dust is made up of heavier atoms born in the heart of stars and supernova. Mainly it contains dust grains and when these dust grains starts compacting then it turns to dense clouds, planetary ring dust and circumstellar dust. Dust grains are mainly silicate particles. Dust plays a major role in our solar system, for example in zodiacal light, Saturn's B ring spokes, planetary rings at Jovian planets and comets. Observations and measurements of cosmic dust in different regions of universe provide an important insight into the Universe's recycling processes. Astronomers consider dust in its most recycled state. Cosmic dust have radiative properties by which they can be detected. Cosmic dusts are classified as intergalactic dusts, interstellar dusts and planetary rings. A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in flat disc shape. All of the Jovian planets in our solar system have rings. But the most notable one is the Saturn's ring which is the brightest one. In March 2008 a report suggested that the Saturn's moon Rhea may have its own tenuous ring system. The ring swirling around Saturn consists of chunks of ice and dust. Most rings were thought to be unstable and to dissipate over course of tens or hundreds of millions of years but it now appears that Saturn's rings might be older than that. The dust particles in the ring collide with each other and are subjected to forces other than gravity of its own planet. Such collisions and extra forces tend to spread out the rings. Pluto is not known to have any ring system but some Astronomers believe that New Horizons probe might find a ring system when it visits in 2015.It is also predicted that Phobos, a moon of Mars will break up and form into a planetary ring. Many theories are present regarding the formation of rings for example when moons collide, when moon breaks up and due to dust formation in supernova. But the most important question is, that how they maintain their orbit and why they are present there.

  1. How the morphology of dusts influences packing density in small solar system bodies

    NASA Astrophysics Data System (ADS)

    Zangmeister, C.; Radney, J. G.; Zachariah, M. R.

    2014-12-01

    Large planetary seedlings, comets, and nanoscale soot particles are made from rigid, aggregated subunits that are compacted under low compression into larger structures spanning over 10 orders of magnitude in dimensional space. Here, we demonstrate that the packing density (?f) of compacted rigid aggregates is independent of spatial scale for systems under weak compaction, a regime that includes small solar system bodies. The ?f of rigid aggregated structures across 6 orders of magnitude were measured using nanoscale spherical soot aerosol composed of aggregates with ? 17 nm monomeric subunits and aggregates made from uniform monomeric 6 mm spherical subunits at the macroscale. We find ?f = 0.36 ą 0.02 at both the nano- and macroscale. These values are remarkably similar to qf observed for comet nuclei and measured values of other rigid aggregated systems across a wide variety of spatial and formative conditions. We present a packing model that incorporates the aggregate morphology and show that ?f is independent of both monomer and aggregate size. These observations suggest thatqf of rigid aggregates is independent of spatial dimension across varied formative conditions ranging from interstellar space to pharmaceutical manufacturing.

  2. Observations of the Profiles of Solar UV Emission Lines and Their Analysis in Terms of the Heating and Production of the Corona

    Microsoft Academic Search

    B. C. Boland; S. F. T. Engstrom; B. B. Jones; R. W. P. McWhirter; P. C. Thonemann; R. Wilson

    1972-01-01

    Observations of the solar spectrum have been made between 1200 2200 Ĺ with high spectral resolution. The results were obtained with an all-reflecting echelle spectrograph carried by a stabilized Skylark rocket launched in April 1970. Measurements of the profiles of a number of emission lines due to Si ii, C ii, Si iii and C iv formed in the temperature

  3. Three-dimensional study of Mars upper thermosphere\\/ionosphere and hot oxygen corona: 2. Solar cycle, seasonal variations, and evolution over history

    Microsoft Academic Search

    Arnaud Valeille; Michael R. Combi; Stephen W. Bougher; Valeriy Tenishev; Andrew F. Nagy

    2009-01-01

    The global dynamics of the flow of energetic particles through the Martian upper atmosphere is studied for different cases reflecting variations in solar cycle, seasons, and epochs over history. In this study, the combination of the new 3-D Direct Simulation Monte Carlo kinetic model and the modern 3-D Mars Thermosphere General Circulation Model is employed to describe self-consistently the Martian

  4. The Brownian Motion of Dust Particles in the Solar Nebula: An Experimental Approach to the Problem of Pre-planetary Dust Aggregation

    Microsoft Academic Search

    Jurgen Blum; Gerhard Wurm; Sascha Kempf; Thomas Henning

    1996-01-01

    Laboratory experiments were performed to study the Brownian motion of ?m-sized dust grains and small aggregates under pre-planetary nebula conditions, i.e., in a thin gas atmosphere (Epstein drag regime), in the ballistic limit, and under microgravity conditions. The results of these experiments, i.e., the grain diffusivities, are in quantitative agreement with theoretical predictions for single spherical grains. Deviations from particle

  5. Spirit Feels Dust Gust

    NASA Technical Reports Server (NTRS)

    2007-01-01

    On sol 1149 (March 28, 2007) of its mission, NASA's Mars Exploration Rover Spirit caught a wind gust with its navigation camera. A series of navigation camera images were strung together to create this movie. The front of the gust is observable because it was strong enough to lift up dust. From assessing the trajectory of this gust, the atmospheric science team concludes that it is possible that it passed over the rover. There was, however, no noticeable increase in power associated with this gust. In the past, dust devils and gusts have wiped the solar panels of dust, making it easier for the solar panels to absorb sunlight.

  6. Solar Activity Indices

    NASA Astrophysics Data System (ADS)

    Tapping, K.; Murdin, P.

    2000-11-01

    Solar activity is driven by the temporally and spatially varying distribution of magnetic flux in the photosphere, chromosphere and corona. It covers a range of phenomena at all levels in the solar atmosphere and time-scales ranging from seconds and minutes (SOLAR FLARES and SOLAR CORONAL MASS EJECTIONS), through months (the evolution of ACTIVE REGIONS and SOLAR ACTIVITY COMPLEXES), to the 11 (or...

  7. Dust Devil Dynamics

    NASA Astrophysics Data System (ADS)

    Couedel, L.; Escarguel, A.; Horton, W.; Benkadda, S.; Arnas, C.; PIIM, Aix-Marseille University Collaboration; Institute for Fusion Studies Team

    2013-10-01

    A self-consistent hydrodynamic model for the onset of a dust devil vortex is derived and analyzed. The toroidal flows and vertical velocity fields are driven by an instability that arises from the inversion of the mass density stratification from solar heating of the sandy surface soil. The nonlinear dynamics in the vertical/horizontal flows drives the toroidal flow through a parametric decay process. Methods developed for triboelectric charging of dust are used to estimate the charging of the sand particles. Elementary comparisons are made with the data from in dust devil observations and research. The parameters for a proposed Dust Devil laboratory experiment are given.

  8. Microparticle impact calibration of the Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) onboard the solar power sail demonstrator IKAROS

    NASA Astrophysics Data System (ADS)

    Hirai, Takayuki; Cole, Michael J.; Fujii, Masayuki; Hasegawa, Sunao; Iwai, Takeo; Kobayashi, Masanori; Srama, Ralf; Yano, Hajime

    2014-10-01

    The Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) is an array of polyvinylidene fluoride (PVDF) based dust detectors aboard the solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). The total sensor area of ALADDIN (0.54 m2) is the world's largest among the past PVDF-based dust detectors. IKAROS was launched in May 2010 and then ALADDIN measured cosmic dust impacts for 16 months while orbiting around between 0.7 and 1.1 AU. The main scientific objective of ALADDIN is to reveal number density of ?10-?m-sized dust in the zodiacal cloud with much higher time-space resolution than that achieved by any past in-situ measurements. The distribution of ?10-?m-sized dust can be also observed mainly with the light scattering by optical instruments. This paper gives the scientific objectives, the instrumental description, and the results of microparticle impact calibration of ALADDIN conducted in ground laboratories. For the calibration tests we used Van de Graaf accelerators (VdG), two-stage light gas guns (LGG), and a nano-second pulsed Nd:YAG laser (nsPL). Through these experiments, we obtained depolarization charge signal caused by hypervelocity impacts or laser irradiation using the flight spare of 20-?m-thick PVDF sensor and the electronics box of ALADDIN. In the VdG experiment we accelerated iron, carbon, and silver microparticles at 1-30 km/s, while in the LGG experiment we performed to shoot 100's-?m-sized particles of soda-lime glass and stainless steel at 3-7 km/s as single projectile. For interpolation to ?10-?m size, we irradiated infrared laser at the energy of 15-20 mJ directly onto the PVDF sensor. From the signal analysis, we developed a calibration law for estimation of masses of impacted dust particles. The dynamic range of ALADDIN corresponds from 9×10-14 kg to 2×10-10 kg (4-56 ?m in diameter at density of 2.0 g/cm3) at the expected impact velocity of 10 km/s at 1 AU on the IKAROS inbound orbit. It was found that ALADDIN has ability to measure spatial densities of interplanetary dust particles larger than 10 ?m in size by setting the sensor threshold to an output voltage of 1 V.

  9. Plasma properties and magnetic field structure of the solar corona, based on coordinated Max 1991 observations from SERTS, the VLA, and magnetographs

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffrey W.

    1995-01-01

    The purposes of this investigation are to use existing, calibrated, coaligned sets of coordinated multiwaveband observations of the Sun to determine the coronal magnetic field strength and structure, and interpret the collective observations in terms of a self-consistent model of the coronal plasma and magnetic field. This information is vital to understanding processes such as coronal heating, solar wind acceleration, pre-flare energy storage, and active region evolution. Understanding these processes is the central theme of Max '91, the NASA-supported series of solar observing campaigns under which the observations acquired for this work were obtained. The observations came from NASA/GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and magnetographs. The technique of calculating the coronal magnetic field is to establish the contributions to the microwave emission from the two main emission mechanisms: thermal bremsstrahlung and thermal gyroemission. This is done by using the EUV emission to determine values of the coronal plasma quantities needed to calculate the thermal bremsstrahlung contribution to the microwave emission. Once the microwave emission mechanism(s) are determined, the coronal magnetic field can be calculated. A comparison of the coronal magnetic field derived from the coordinated multiwaveband observations with extrapolations from photospheric magnetograms will provide insight into the nature of the coronal magnetic field.

  10. Shock accelerated electron beams in the corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    2003-04-01

    In the solar corona shock waves can be observed as type II radio bursts in dynamic spectra of the solar radio radiation. Some of these type II bursts show sub-structures, so-called "herringbones", which are regarded as signatures of electron beams produced by the associated shock waves. A sample of solar type II radio bursts with "herringbone" - structures has been investigated with respect to their properties in dynamic radio spectra. It is well-known, that the electrons accelerated by a quasi-perpendicular shock establish a shifted loss-cone velocity distribution. The resulting properties of such a distribution for the shock accelerated electrons is compared with the features of "herringbones" in dynamic radio spectra. This study shows that the "herringbones" are mainly produced by nearly perpendicular shocks. The rapid pitch angle diffusion in the velocity space leads to a limited life time of the electron beams associated with the "herringbones".

  11. Development of a Mars dust characterization instrument

    Microsoft Academic Search

    Geoffrey A. Landis; Phillip Jenkins; Joseph Flatico; Larry Oberle; Mike Krasowski; Steven Stevenson

    1996-01-01

    The atmosphere of Mars has a considerable load of suspended dust. Over time, this dust deposits out of the atmosphere. The mechanism and the temporal and geographical variation of this deposition are not well characterized. Measurements of settling rates and dust properties are of considerable scientific interest. Suspended dust affects the atmospheric solar absorption and thus the heat balance of

  12. R Coronae Australis: A Cosmic Watercolour

    NASA Astrophysics Data System (ADS)

    2010-06-01

    This magnificent view of the region around the star R Coronae Australis was created from images taken with the Wide Field Imager (WFI) at ESO's La Silla Observatory in Chile. R Coronae Australis lies at the heart of a nearby star-forming region and is surrounded by a delicate bluish reflection nebula embedded in a huge dust cloud. The image reveals surprising new details in this dramatic area of sky. The star R Coronae Australis lies in one of the nearest and most spectacular star-forming regions. This portrait was taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. The image is a combination of twelve separate pictures taken through red, green and blue filters. This image shows a section of sky that spans roughly the width of the full Moon. This is equivalent to about four light-years at the distance of the nebula, which is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The complex is named after the star R Coronae Australis, which lies at the centre of the image. It is one of several stars in this region that belong to the class of very young stars that vary in brightness and are still surrounded by the clouds of gas and dust from which they formed. The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength. These complex processes, determined by the physics of the interstellar medium and the properties of the stars, are responsible for the magnificent colours of nebulae. The light blue nebulosity seen in this picture is mostly due to the reflection of starlight off small dust particles. The young stars in the R Coronae Australis complex are similar in mass to the Sun and do not emit enough ultraviolet light to ionise a substantial fraction of the surrounding hydrogen. This means that the cloud does not glow with the characteristic red colour seen in many star-forming regions. The huge dust cloud in which the reflection nebula is embedded is here shown in impressively fine detail. The subtle colours and varied textures of the dust clouds make this image resemble an impressionist painting. A prominent dark lane crosses the image from the centre to the bottom left. Here the visible light emitted by the stars that are forming inside the cloud is completely absorbed by the dust. These objects could only be detected by observing at longer wavelengths, by using a camera that can detect infrared radiation. R Coronae Australis itself is not visible to the unaided eye, but the tiny, tiara-shaped constellation in which it lies is easily spotted from dark sites due to its proximity on the sky to the larger constellation of Sagittarius and the rich star clouds towards the centre of our own galaxy, the Milky Way. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

  13. High-cadence observations of CME initiation and plasma dynamics in the corona with TESIS on board CORONAS-Photon

    NASA Astrophysics Data System (ADS)

    Bogachev, Sergey; Kuzin, Sergey; Zhitnik, I. A.; Bugaenko, O. I.; Goncharov, A. L.; Ignatyev, A. P.; Krutov, V. V.; Lomkova, V. M.; Mitrofanov, A. V.; Nasonkina, T. P.; Oparin, S. N.; Petzov, A. A.; Shestov, S. V.; Slemzin, V. A.; Soloviev, V. A.; Suhodrev, N. K.; Shergina, T. A.

    The TESIS is an ensemble of space instruments designed in Lebedev Institute of Russian Academy of Sciences for spectroscopic and imaging investigation of the Sun in EUV and soft X-ray spectral range with high spatial, temporal and spectral resolution. From 2009 January, when TESIS was launched onboard the Coronas-Photon satellite, it provided about 200 000 new images and spectra of the Sun, obtained during one of the deepest solar minimum in last century. Because of the wide field of view (4 solar radii) and high sensitivity, TESIS provided high-quality data on the origin and dynamics of eruptive prominences and CMEs in the low and intermediate solar corona. TESIS is also the first EUV instrument which provided high-cadence observations of coronal bright points and solar spicules with temporal resolution of a few seconds. We present first results of TESIS observations and discuss them from a scientific point of view.

  14. Combining Linear Polarization Measurements of both Forbidden/Permitted Coronal Emission Lines for measuring the Vector Magnetic Field in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Dima, G. I.; Kuhn, J. R.; Mickey, D.

    2014-12-01

    Measuring the coronal vector magnetic field is still a major challenge in solar physics. This is due to the intrinsic weakness of the field (~4 G at a height of 0.1 Rsun above an active region) and the large thermal broadening of coronal emission lines. Current methods deduce either the direction of the magnetic field or the magnetic flux density. We propose using concurrent linear polarization measurements in the near IR of forbidden and permitted lines to calculate the coronal vector magnetic field. The effect of the magnetic field on the polarization properties of emitted light is encapsulated in the Hanle effect. In the unsaturated Hanle regime both the direction and strength of the magnetic field affect the linear polarization, while for saturated Hanle the polarization is insensitive to the strength of the field. Coronal forbidden lines are always in the saturated Hanle regime so the linear polarization holds no information on the strength of the field. By pairing measurements of both forbidden and permitted lines we would be able to obtain both the direction and strength of the field. The near-IR region of the spectrum offers the opportunity to study this problem from the ground. The FeXIII 1.075 um and SiX 1.431 um forbidden lines are strongly polarizable and are sufficiently bright over a large field of view (out to 1.5 Rsun). Measurements of both these lines can be paired up with the recently observed coronal HeI 1.083 um permitted line. The first data set used to test this technique was taken during the March 29, 2006 total solar eclipse and consisted of near-IR spectra covering the spectral region 0.9-1.8 um, with a field of view of 3 x 3 Rsun. The data revealed unexpectedly strong SiX emission compared to FeXIII. Using the HAO FORWARD suite of codes we produced simulated emission maps from a global HMD model for the day of the eclipse. Comparing the intensity variation of the measurements and the model we predict that SiX emission is more extended for this day that the model would suggest, further supporting the possible usefulness of SiX polarimetry. The development of this method and associated tools will be critical in interpreting the high spectral, spatial and temporal IR measurements that will be possible when the Daniel K. Inouye Solar Telescope (DKIST) is completed in a few years time.

  15. Accretion disk coronae

    NASA Technical Reports Server (NTRS)

    White, N. E.; Holt, S. S.

    1981-01-01

    Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains an ADC. The possible origin of an ADC is discussed and a simple hydrostatic evaporated ADC model is developed which, when applied to 4U1822-37, 4U2129+47 and Cyg X-3, can explain their temporal and spectral properties. The quasi-sinusoidal modulation of all three sources can be reconciled with the partial occultation of the ADC by a bulge at the edge of the accretion disk which is caused by the inflowing material. The height of this bulge is an order of magnitude larger than the hydrostatic disk height and is the result of turbulence in the outer region of the disk. The spectral properties of all three sources can be understood in terms of Compton scattering of the original source spectrum by the ADC. Spectral variations with epoch in Cyg X-3 are probably caused by changes in the optical depth of the corona. A consequence of our model is that any accreting neutron star X-ray source in a semi-detached binary system which is close to its Eddington limit most likely contains an optically thick ADC.

  16. Observations of the Sun–Earth system within the CORONAS-F mission (July 31, 2001 to December 6, 2005)

    Microsoft Academic Search

    V. D. Kuznetsov

    2008-01-01

    The results of the study of solar active phenomena and their manifestations in the near-Earth space observed in the declining phase of the current activity cycle within the CORONAS-F space mission are presented. During its orbital operation from July 31, 2001 to December 6, 2005, the CORONAS-F satellite recorded a series of outstanding solar events and associated effects in solar

  17. Ground-based observation of emission lines from the corona of a red-dwarf star.

    PubMed

    Schmitt, J H; Wichmann, R

    2001-08-01

    All 'solar-like' stars are surrounded by coronae, which contain magnetically confined plasma at temperatures above 106 K. (Until now, only the Sun's corona could be observed in the optical-as a shimmering envelope during a total solar eclipse.) As the underlying stellar 'surfaces'-the photospheres-are much cooler, some non-radiative process must be responsible for heating the coronae. The heating mechanism is generally thought to be magnetic in origin, but is not yet understood even for the case of the Sun. Ultraviolet emission lines first led to the discovery of the enormous temperature of the Sun's corona, but thermal emission from the coronae of other stars has hitherto been detectable only from space, at X-ray wavelengths. Here we report the detection of emission from highly ionized iron (Fe XIII at 3,388.1 A) in the corona of the red-dwarf star CN Leonis, using a ground-based telescope. The X-ray flux inferred from our data is consistent with previously measured X-ray fluxes, and the non-thermal line width of 18.4 km s-1 indicates great similarities between solar and stellar coronal heating mechanisms. The accessibility and spectral resolution (45,000) of the ground-based instrument are much better than those of X-ray satellites, so a new window to the study of stellar coronae has been opened. PMID:11484044

  18. Sub-arcsec X-Ray Telescope for Imaging The Solar Corona In the 0.25 - 1.2 keV Band

    NASA Technical Reports Server (NTRS)

    Gallagher, Dennis; Cash, Webster; Jelsma, Schuyler; Farmer, Jason

    1996-01-01

    We have developed an X-ray telescope that uses a new technique for focusing X-rays with grazing incidence optics. The telescope was built with spherical optics for all of its components, utilizing the high quality surfaces obtainable when polishing spherical (as opposed to aspherical) optics. We tested the prototype X-ray telescope in the 300 meter vacuum pipe at White Sands Missile Range, NM. The telescope features 2 degee graze angles with tungsten coatings, yielding a bandpass of 0.25-1.5 keV with a peak effective area of 0.8 sq cm at 0.83 keV. Results from X-ray testing at energies of 0.25 keV and 0.93 keV (C-K and Cu-L) verify 0.5 arcsecond performance at 0.93 keV. Results from modeling the X-ray telescope's response to the Sun show that the current design would be capable of recording 10 half arcsecond images of a solar active region during a 300 second NASA sounding rocket flight.

  19. Solar Wind Acceleration Models in SWMF

    Microsoft Academic Search

    O. Cohen; I. V. Sokolov; M. Velli; T. I. Gombosi

    2006-01-01

    The choice of the solar wind model in numerical simulations of the processes in the Solar Corona (SC), Inner Heliosphere (IH) and Outer Heliosphere (OH) is a matter of a crucial importance. Since the available theoretical models for the turbulent processes and turbulent heating in the solar corona do not provide a reliable and quantitatively accurate agreement with the observed

  20. AN XMM-NEWTON STUDY OF THE CORONAE OF 2 CORONAE BOREALIS

    E-print Network

    Audard, Marc

    AN XMM-NEWTON STUDY OF THE CORONAE OF 2 CORONAE BOREALIS Jin A. Suh and Marc Audard1 Columbia present results of XMM-Newton Guaranteed Time observations of the RS CVn binary 2 Coronae Borealis headinggs: stars: activity -- stars: coronae -- stars: flare -- stars: individual (2 Coronae Borealis

  1. Optical fiber sensing of corona discharges

    Microsoft Academic Search

    Gerry A. Woolsey; D. W. Lamb; M. C. Woerner

    1991-01-01

    Coronas are localized discharges which occur adjacent to high voltage points in gases at around atmospheric pressure. A corona may be in the form of a steady glow or it may be pulsing. Ions produced in the corona rapidly move away from the point, transfer momentum to the neutral gas molecules, and thus generate a corona wind with speeds of

  2. Ultraviolet corona detection sensor study

    NASA Technical Reports Server (NTRS)

    Schmitt, R. J.; MATHERN

    1976-01-01

    The feasibility of detecting electrical corona discharge phenomena in a space simulation chamber via emission of ultraviolet light was evaluated. A corona simulator, with a hemispherically capped point to plane electrode geometry, was used to generate corona glows over a wide range of pressure, voltage, current, electrode gap length and electrode point radius. Several ultraviolet detectors, including a copper cathode gas discharge tube and a UV enhanced silicon photodiode detector, were evaluated in the course of the spectral intensity measurements. The performance of both silicon target vidicons and silicon intensified target vidicons was evaluated analytically using the data generated by the spectroradiometer scans and the performance data supplied by the manufacturers.

  3. The Martian Hot Oxygen Corona at Ancient times

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Combi, M. R.; Tenishev, V.; Bougher, S. W.; Dong, C.; Pawlowski, D. J.

    2014-12-01

    The evaluation of the global atomic oxygen loss rate and its changes over geologic time is necessary for a better understanding of the evolution of the Martian atmosphere. The recent surface geomorphological evidence suggests that water has played a key role in forming the present atmospheric environment. Throughout the planet's history, the inventory of water has been affected in part by changing solar radiation and solar wind conditions. In this study, we investigate the evolution of the oxygen atom inventory by simulating the hot oxygen corona for solar conditions appropriate to about 2.5 Gyr ago (about 3 times the current solar EUV flux). Dissociative recombination of O2+ion is assumed to remain as the dominant source of hot atomic oxygen at ancient times. To describe ancient Mars, we present the 3D self-consistent simulations of the Martian hot oxygen corona by one-way coupling our Adaptive Mesh Particle Simulator (AMPS) with the ancient thermosphere and ionosphere as simulated by the 3D Mars Global Ionosphere Thermosphere Model (M-GITM), a newly developed atmospheric model. The structure and composition of the Martian upper atmosphere and the hot oxygen corona during early solar conditions are compared with those at the current epoch to study the evolution of the macroscopic parameters and their effects on the hot oxygen corona. The coupled framework provides the density and escape probabilities of hot oxygen and estimates the global atmospheric loss rates for the conditions considered. These results are also being used as input into calculations of the global solar wind interaction with Mars' atmosphere, ionosphere and exosphere.

  4. Mid-Infrared Variations of R Coronae Borealis Stars

    E-print Network

    Rao, N Kameswara

    2014-01-01

    Mid-infrared photometry of R Coronae Borealis stars obtained from various satellites from IRAS to WISE has been utilized in studying the variations of the circumstellar dust's contributions to the spectral energy distribution of these stars. The variation of the fractional coverage (R) of dust clouds and their blackbody temperatures (T$_d$) have been used in trying to understand the dust cloud evolution over the three decades spanned by the satellite observations. In particular, it is shown that a prediction R $ \\propto T_d^4$ developed in this paper is satisfied, especially by those stars for which a single collection of cloud dominates the IR fluxes. Correlations of R with photospheric abundance and luminosity of the stars are explored.

  5. STATISTICAL DESCRIPTION OF A MAGNETIZED CORONA ABOVE A TURBULENT ACCRETION DISK Dmitri A. Uzdensky and Jeremy Goodman

    E-print Network

    is represented by a statistical ensemble of loops tied to the disk. Each loop evolves under several physical holes are attributed to hot, tenuous, quasi-spherical plasmas called accretion disk coronae (hereafter ADCe) by analogy with the solar corona, although Compotonization rather than atomic lines

  6. What Is the Shell Around R Coronae Borealis?

    NASA Astrophysics Data System (ADS)

    Montiel, Edward J.; Clayton, Geoffrey C.; Marcello, Dominic C.; Lockman, Felix J.

    2015-07-01

    The hydrogen-deficient, carbon-rich R Coronae Borealis (RCB) stars are known for being prolific producers of dust which causes their large iconic declines in brightness. Several RCB stars, including R Coronae Borealis (R CrB), itself, have large extended dust shells seen in the far-infrared. The origin of these shells is uncertain but they may give us clues to the evolution of the RCB stars. The shells could form in three possible ways. (1) They are fossil Planetary Nebula (PN) shells, which would exist if RCB stars are the result of a final, helium-shell flash, (2) they are material left over from a white-dwarf (WD) merger event which formed the RCB stars, or (3) they are material lost from the star during the RCB phase. Arecibo 21 cm observations establish an upper limit on the column density of H I in the R CrB shell implying a maximum shell mass of ?0.3 M?. A low-mass fossil PN shell is still a possible source of the shell although it may not contain enough dust. The mass of gas lost during a WD merger event will not condense enough dust to produce the observed shell, assuming a reasonable gas-to-dust ratio. The third scenario where the shell around R CrB has been produced during the star’s RCB phase seems most likely to produce the observed mass of dust and the observed size of the shell. But this means that R CrB has been in its RCB phase for ?104 years.

  7. Self-Correlation Analysis of R Coronae Borealis Stars: A Pilot Project

    Microsoft Academic Search

    John R. Percy; Kaushala Bandara; J. Donald Fernie; P. L. Cottrell; Ljiljana Skuljan

    2004-01-01

    R. Coronae Borealis (RCB) stars are peculiar yellow supergiant stars which suddenly and unpredictably decrease in brightness by up to several magnitudes, then slowly return to normal. Most (perhaps all) RCB stars also pulsate, and the pulsations may be related to the ejection of the dust clouds which produce the fadings. As a pilot project, we have applied self-correlation analysis

  8. Topographic Corona Gravity Survey Results

    NASA Technical Reports Server (NTRS)

    Comstock, R. L.; Smrekar, S. E.; Anderson, F. S.

    2001-01-01

    We present estimates for elastic and crustal thickness obtained from a gravity survey of Venusian topographic coronae, and characterize advantages and disadvantages for generating spectral admittance. Additional information is contained in the original extended abstract.

  9. Study of sungrazing comets with space-based coronagraphs: new possibilities offered by METIS on boar Solar Orbiter

    NASA Astrophysics Data System (ADS)

    Bemporad, Alessandro

    Thanks to the launch of SOHO in the end of 1995 and to the continuous monitoring of the white light (WL) corona offered by the LASCO coronagraphs, it was discovered that sungrazing comets are much more common than previously thought. More than 2500 comets have been discovered over about 17 years, hence slightly less than a comet every 2 days is observed by coronagraphs. The white light emission seen by SOHO/LASCO and more recently also by the STEREO/SECCHI instruments provides information not only on the comet orbits (hence on its origin), but also on the dust-tail formation, dust-tail disconnection, occurrence of nucleus fragmentation and nucleus disintegration processes. Very interestingly, a few sungrazing comets have been also observed in the UV spectra by the SOHO UV Coronagraph Spectrometer (UVCS) and the strong emission observed in the H I Lyman-alpha lambda 1216 Ĺ line provided direct information also on the water outgassing rate, tail chemical composition, nucleus size and occurrence of nucleus fragmentations. Moreover, the UV cometary emission provides a new method to estimate physical parameters of the coronal plasma met by the comet (like electron density, proton temperature and solar wind velocity), in a way that these comets can be considered as “local probes” for the solar corona. Unique observations of comets will be provided in the next future by the METIS coronagraph on board the Solar Orbiter mission: METIS will contemporary observe the corona in WL and in UV (HI Lyman-alpha), hence will be a unique instrument to study at the same time the transiting comets and the solar corona being crossed by the comets. Previous results and new possibilities offered by METIS on these topics are summarized and discussed here.

  10. Water vapor in the middle atmosphere of Mars during the global dust storm in 2007

    NASA Astrophysics Data System (ADS)

    Fedorova, Anna; Bertaux, Jean-Loup; Montmessin, Franck; Korablev, Oleg; Dzuban, Ilya; Maltagliati, Luca; Clarke, John

    2015-04-01

    Recent observations of the Martian hydrogen corona in the UV H Ly-? emission by Hubble Space Telescope (HST) [Clarke et al., 2014] and the SPICAM UV spectrometer on Mars Express [Chaffin et al., 2014] reported its rapid change an order of magnitude for the short period of a few months in 2007 (MY 28), which is inconsistent with the existing models. One proposed explanation of observed decrease in coronal emission is that during the global dust storm water vapor can be transported to higher altitudes where the rate of photodissociation by near-UV sunlight increases, providing an additional source of hydrogen for the upper atmosphere. Since 2004 the SPICAM IR spectrometer on Mars-Express carries out measurements of the vertical distribution of water vapor in the 1.38 ľm band and aerosol properties in the middle atmosphere of Mars by means of solar occultations. We presents here vertical profiles of water vapor at Ls = 250-310° during the dust storm of MY28. SPICAM observations confirm the increase of the H2O content at 60 km from Ls=268° to Ls=285° an order of magnitude for the northern hemisphere and in 3-4 times for the southern hemisphere. Nevertheless, the photochemical modeling is required to estimate a contribution of observed water abundance to the hydrogen corona. The interannual variability of water vapor vertical distribution for the southern summer season will be also presented.

  11. Corona Discharge Influence on Moulds

    NASA Astrophysics Data System (ADS)

    Scholtz, Vladimir

    2004-09-01

    It is known that the electric discharge has bacteriocid effect. We are interesting on influence of corona discharge on moulds and searching for it's fungicide effect. In this work we study the mould penicillium digitatum by using an easy apparatus, where may be situated two measured samples. One in the burning corona discharge and one in the area with ozone generated by this corona only. We expose the spores of penicillium digitatum on a metal plate and on a cultivating medium on cca 0.01mA, 5kV corona discharge and on generated ozone only for time cca two days. It is the time needed for sprouting of spores and growing of they to a visible size. The pilot results show, that the ozone generated by the corona discharge has none or very low influence on the sprouting and growing of the spores. Direct corona discharge inhibit the sprouting only, but does not kill the spores. In next experiments we will try to find some minimum inhibit and killing concentration of ozone and try to expose the sprout inhibition.

  12. The Dust Environment of the Moon: Expectations for the Lunar Dust Experiment (LDEX)

    NASA Astrophysics Data System (ADS)

    Horanyi, M.; Sternovsky, Z.; Lankton, M.; James, D.; Szalay, J.; Drake, K.; Shu, A.; Colette, A.; Gruen, E.; Kempf, S.; Srama, R.; Mocker, A.

    2012-03-01

    The lunar dust exosphere is sustained by interplanetary dust bombardment and by electromagnetic effects induced by the solar wind and UV radiation. We present the expectations for the observations by LDEX to be launched onboard the LADEE mission.

  13. The solar and heliospheric imager (SoloHI) instrument for the solar orbiter mission

    NASA Astrophysics Data System (ADS)

    Howard, Russell A.; Vourlidas, Angelos; Korendyke, Clarence M.; Plunkett, Simon P.; Carter, Michael T.; Wang, Dennis; Rich, Nathan; McMullin, Donald R.; Lynch, Sean; Thurn, Adam; Clifford, Greg; Socker, Dennis G.; Thernisien, Arnaud F.; Chua, Damien; Linton, Mark G.; Keller, David; Janesick, James R.; Tower, John; Grygon, Mark; Hagood, Robert; Bast, William; Liewer, Paulett C.; DeJong, Eric M.; Velli, Marco M. C.; Mikic, Zoran; Bothmer, Volker; Rochus, Pierre; Halain, Jean-Philippe; Lamy, Philippe L.

    2013-09-01

    The SoloHI instrument for the ESA/NASA Solar Orbiter mission will track density fluctuations in the inner heliosphere, by observing visible sunlight scattered by electrons in the solar wind. Fluctuations are associated with dynamic events such as coronal mass ejections, but also with the "quiescent" solar wind. SoloHI will provide the crucial link between the low corona observations from the Solar Orbiter instruments and the in-situ measurements on Solar Orbiter and the Solar Probe Plus missions. The instrument is a visible-light telescope, based on the SECCHI/Heliospheric Imager (HI) currently flying on the STEREO mission. In this concept, a series of baffles reduce the scattered light from the solar disk and reflections from the spacecraft to levels below the scene brightness, typically by a factor of 1012. The fluctuations are imposed against a much brighter signal produced by light scattered by dust particles (the zodiacal light/F-corona). Multiple images are obtained over a period of several minutes and are summed on-board to increase the signal-to-noise ratio and to reduce the telemetry load. SoloHI is a single telescope with a 40? field of view beginning at 5° from the Sun center. Through a series of Venus gravity assists, the minimum perihelia for Solar Orbiter will be reduced to about 60 Rsun (0.28 AU), and the inclination of the orbital plane will be increased to a maximum of 35° after the 7 year mission. The CMOS/APS detector is a mosaic of four 2048 x 1930 pixel arrays, each 2-side buttable with 11 ?m pixels.

  14. Supernova Dust Factories

    NASA Astrophysics Data System (ADS)

    Gomez, Haley; Consortium, MESS; LCOGT

    2013-01-01

    The origin of interstellar dust in galaxies is poorly understood, particularly the relative contribution from supernovae. We present infrared and submillimeter photometry and spectroscopy from the Herschel Space Observatory of the Galactic remnants Tycho, Kepler and the Crab Nebula, taken as part of the Mass Loss from Evolved StarS program (MESS). Although we detect small amounts of dust surrounding Tycho and Kepler (the remnants of Type Ia supernovae), we show this is due to swept-up interstellar and circumstellar material respectively. The lack of dust grains in the ejecta suggests that Type Ia remnants do not produce substantial quantities of iron-rich dust grains and has important consequences for the ‘missing’ iron mass observed in ejecta. After carefully subtracting the synchrotron and line emission from the Crab, the remaining far-infrared continuum originates from 0.1-0.2 solar masses of dust. These observations suggest that the Crab Nebula has condensed most of the relevant refractory elements into dust and that these grains appear well set to survive their journey into the interstellar medium. In summary, our Herschel observations show that significantly less dust forms in the ejecta of Type Ia supernovae than in the remnants of core-collapse explosions, placing stringent constraints on the environments in which dust and molecules can form.

  15. Coronae of stars with supersolar elemental abundances

    NASA Astrophysics Data System (ADS)

    Peretz, Uria; Behar, Ehud; Drake, Stephen A.

    2015-05-01

    Coronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the first ionization potential (FIP). This study focuses on the coronal composition of stars with supersolar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, ? Hor, HR 7291, ? Boo, and ? Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances we measured were obtained using the line-resolved spectra of the Reflection Grating Spectrometer (RGS) in conjunction with the higher throughput EPIC-pn camera spectra onboard the XMM-Newton observatory. A collisionally ionized plasma model with two or three temperature components is found to represent the spectra well. All elements are found to be consistently depleted in the coronae compared to their respective photospheres. For 11 LMi and ? Boo no FIP effect is present, while ? Hor, HR 7291, and ? Cen A and B show a clear FIP trend. These conclusions hold whether the comparison is made with solar abundances or the individual stellar abundances. Unlike the solar corona, where low-FIP elements are enriched, in these stars the FIP effect is consistently due to a depletion of high-FIP elements with respect to actual photospheric abundances. A comparison with solar (instead of stellar) abundances yields the same fractionation trend as on the Sun. In both cases, a similar FIP bias is inferred, but different fractionation mechanisms need to be invoked.

  16. Infrared Observations of Comet Dust

    Microsoft Academic Search

    Michael S. Kelley; C. E. Woodward

    2006-01-01

    Comets are one of the best preserved reservoirs of material from the epoch of planet formation. The mineralogy of comet dust may be directly linked to the mineralogy of their formation zones in the early outer solar system. This thesis is an investigation of the properties of comet dust through analytical and observational techniques. To achieve this goal, we observed

  17. The corona of HD 223460 (HR 9024)

    NASA Astrophysics Data System (ADS)

    Gondoin, P.

    2003-10-01

    HD 223460 (HR 9024), a chromospherically active late-type giant with a high X-ray luminosity, was observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. Analysis results suggest a scenario where the corona of HD 223460 is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The surface area coverage of these active regions may approach up to 30%. A hypothesis is that the interaction of these structures themselves induces a flaring activity on a small scale not visible in the EPIC light curves that is responsible for heating HD 223460 plasma to coronal temperatures of T >=107 K. The intense X-ray activity of HD 223460 is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that its rotation will spin down in the future with the effect of decreasing its helicity-related, dynamo-driven activity and suppressing large-scale magnetic structures in its corona.

  18. The Structure and Dynamics of the Corona—Heliosphere Connection

    NASA Astrophysics Data System (ADS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Miki?, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2012-11-01

    Determining how the heliospheric magnetic field and plasma connect to the Sun's corona and photosphere is, perhaps, the central problem in solar and heliospheric physics. For much of the heliosphere, this connection appears to be well understood. It is now generally accepted that so-called coronal holes, which appear dark in X-rays and are predominantly unipolar at the photosphere, are the sources of quasi-steady wind that is generally fast, >500 km/s, but can sometimes be slow. However, the connection to the Sun of the slow, non-steady wind is far from understood and remains a major mystery. We review the existing theories for the sources of the non-steady wind and demonstrate that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory is described in which this wind originates from the continuous opening and closing of narrow open field corridors in the corona, which give rise to a web of separatrices (the S-Web) in the heliosphere. Note that in this theory the corona—heliosphere connection is intrinsically dynamic, at least for this type of wind. Support for the S-Web model is derived from MHD solutions for the corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona—heliosphere connection, in general.

  19. Insights into Corona Formation through Statistical Analyses

    NASA Technical Reports Server (NTRS)

    Glaze, L. S.; Stofan, E. R.; Smrekar, S. E.; Baloga, S. M.

    2002-01-01

    Statistical analysis of an expanded database of coronae on Venus indicates that the populations of Type 1 (with fracture annuli) and 2 (without fracture annuli) corona diameters are statistically indistinguishable, and therefore we have no basis for assuming different formation mechanisms. Analysis of the topography and diameters of coronae shows that coronae that are depressions, rimmed depressions, and domes tend to be significantly smaller than those that are plateaus, rimmed plateaus, or domes with surrounding rims. This is consistent with the model of Smrekar and Stofan and inconsistent with predictions of the spreading drop model of Koch and Manga. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occuring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronas are found predominantly as isolated features in the plains. Coronae at hotspot rises tend to be significantly larger than coronae in other settings, consistent with a hotter upper mantle at hotspot rises and their active state.

  20. Insights into corona formation through statistical analyses

    NASA Astrophysics Data System (ADS)

    Glaze, L. S.; Stofan, E. R.; Smrekar, S. E.; Baloga, S. M.

    2002-12-01

    Statistical analysis of an expanded database of coronae on Venus indicates that the populations of Type 1 (with fracture annuli) and 2 (without fracture annuli) corona diameters are statistically indistinguishable, and therefore we have no basis for assuming different formation mechanisms. Analysis of the topography and diameters of coronae shows that coronae that are depressions, rimmed depressions, and domes tend to be significantly smaller than those that are plateaus, rimmed plateaus, or domes with surrounding rims. This is consistent with the model of Smrekar and Stofan [1997] and inconsistent with predictions of the spreading drop model of Koch and Manga [1996]. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occurring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronae are found predominantly as isolated features in the plains. Coronae at hot spot rises tend to be significantly larger than coronae in other settings, consistent with a hotter upper mantle at hot spot rises and their active state.

  1. Plasma Outflows in the Corona as Observed With Hinode XRT

    NASA Astrophysics Data System (ADS)

    Sakao, T.; Kano, R.; Narukage, N.; Deluca, E. E.; Grigis, P.

    2008-12-01

    We present imaging observations of plasma outflows in the solar corona made with X-Ray Telescope (XRT) aboard Hinode satellite. The XRT employs a back-illuminated CCD as the focal-plane imaging device which enables us, together with an optimized set of analysis filters, to investigate, for the first time, dynamic behavior of relatively cool (1-2 MK, say) plasmas in the corona. The XRT revealed a clear pattern of continuous outflow of plasmas from the edge of an active region NOAA AR 10942 right adjacent to a coronal hole. Plasmas of temperature ~1 MK flowed out with a sub-sonic velocity of typically ~140 km/s along magnetic field lines that are most likely open towards the interplanetary space. These outflowing plasmas may constitute a fraction of the (slow) solar wind. In addition to this discovery, the XRT has so far identified rich patterns of continuous outflows including those from coronal hole boundaries and along fan-like field lines rooted inside coronal holes. XRT observations of such plasma outflows in the corona are presented and their possible implications to the solar wind discussed.

  2. Atmospheric Dust

    NSDL National Science Digital Library

    2014-09-14

    Atmospheric dust storms are common in many of the world's semi-arid and arid regions and can impact local, regional, and even global weather, agriculture, public health, transportation, industry, and ocean health. This module takes a multifaceted approach to studying atmospheric dust storms. The first chapter examines the impacts of dust storms, the physical processes involved in their life cycle, their source regions, and their climatology. The second chapter explores satellite products (notably dust RGBs) and dust models used for dust detection and monitoring, and presents a process for forecasting dust storms. The third and final chapter of the module examines the major types of dust storms: those that are synoptically forced, such as pre- and post-frontal dust storms and those induced by large-scale trade winds; and those caused by mesoscale systems such as downslope winds, gap flow, convection, and inversion downburst storms.

  3. Dust Devil Dynamics

    NASA Astrophysics Data System (ADS)

    Horton, W.; Miura, H.

    2008-11-01

    A dust devil is a rotating updraft, with coherent structures ranging from small (H/D ˜ 5m/1m) to large (H/D ˜ 1000 m/10 m). Common in west Texas and Arizona, dust devils are formed unstable stratification of the air by solar heating over a sandy floor. Unstable gravity waves grow exponentially in the low density, hot air, rising into the upper layer of stably stratified atmosphere creating the large, 3D vortex. Dust devils are common on Mars. On Earth radio noise and electrical fields greater than 100kV/m are inferred [Kok J. F., N. O. Renno (2006), Geophys. Res. Lett., 33, L19S10]. Dust devils pick up small dirt and dust particles. The whirling charged dust particles (30 -50 microns) create a magnetic field that fluctuates between 3 and 30 times each second. The electric fields created assist the vortices in lifting materials off the ground and into the atmosphere. We use the theory and simulation tools of fusion plasma physics to describe dust devils. The Grad-Shafranov equation governs the vorticity dynamics and gives a solution for steady axisymmetric flows. The high core velocity is limited by the vortex model with viscous dissipation. The Reynolds number is not large, so these structures are well represented with super computers, in contrast to collisionless plasmas. 1mm Research supported by NIFS, Japan and the NSF through ATM-0638480 at UT Austin.

  4. Far-infrared observations of a star-forming region in the Corona Australis dark cloud

    NASA Technical Reports Server (NTRS)

    Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

    1984-01-01

    A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

  5. Hot oxygen corona of Mars

    SciTech Connect

    Ip, W.H.

    1988-10-01

    Electron dissociative recombination of O2(+) ions in the Venus ionosphere, which may be an important source of suprathermal atomic oxygen, is presently considered as a factor in the Mars exosphere; due to the weaker surface gravitational attraction of Mars, a hot oxygen corona thus formed would be denser than that of Venus at altitudes greater than 2000 km despite Mars' lower ionospheric content. If such an extended oxygen corona does exist on Mars, its collisional interaction with Phobos would lead to the formation of an oxygen gas torus whose average number density is of the order of only 1-2/cu cm along the Phobos orbit. 51 references.

  6. High-resolution spectroscopy of the R Coronae Borealis and Other Hydrogen Deficient Stars

    E-print Network

    Rao, N Kameswara

    2010-01-01

    High-resolution spectroscopy is a very important tool for studying stellar physics, perhaps, particularly so for such enigmatic objects like the R Coronae Borealis and related Hydrogen deficient stars that produce carbon dust in addition to their peculiar abundances. Examples of how high-resolution spectroscopy is used in the study of these stars to address the two major puzzles are presented: (i) How are such rare H-deficient stars created? and (ii) How and where are the obscuring soot clouds produced around the R Coronae Borealis stars?

  7. WINDS IN CORONAE BOREALIS STARS Geoffrey Clayton,

    E-print Network

    Bianchi, Luciana

    WINDS IN CORONAE BOREALIS STARS Geoffrey Clayton, 1 Geballe, Luciana Bianchi Received February accepted 2003 ABSTRACT present spectroscopic observations the i #10830 line Coronae Borealis (RCB) stars R Coronae Borealis (RCB) stars small group of hydrogen­deficient, carbon­rich supergiants

  8. Pulsed periodic corona discharges for biological decontamination

    Microsoft Academic Search

    I. V. Timoshkin; M. Maclean; S. J. MacGregor; J. G. Anderson; M. P. Wilson; T. Wang; M. J. Given

    2011-01-01

    The present paper explores the possibilities of using impulsive and steady-state corona discharges for biodecontamination operations. A high tension tubular corona electrode was stressed with positive or negative DC voltage with magnitude up to 26 kV, and a grounded mesh was used as an opposite electrode. Different operational regimes of this corona generator were investigated for the production of ozone

  9. Mutual Event Observations of Io's Sodium Corona

    Microsoft Academic Search

    M. H. Burger; N. M. Schneider; I. de Pater; M. E. Brown; A. H. Bouchez; L. M. Trafton; Y. Sheffer; E. S. Barker; A. Mallama

    2001-01-01

    We have measured the column density profile of Io's sodium corona using 10 mutual eclipses between the Galilean satellites. This approach circumvents the problem of spatially resolving Io's corona directly from Io's bright continuum in the presence of atmospheric seeing and telescopic scattering. The primary goal is to investigate the spatial and temporal variations of Io's corona. Spectra from the

  10. The structure and heating of the chromosphere-corona transition region

    NASA Technical Reports Server (NTRS)

    Moore, R. L.

    1972-01-01

    The structure and heating (or energy balance) of the transition region and the role of the transition region in the structure and heating of the solar atmosphere as a whole are investigated. The features of the structure of the atmosphere and radiative energy losses of the atmosphere are summarized. A static, planar model of the solar temperature which has a temperature profile representative of the actual solar atmosphere is considered. Then a static, planar model of the transition region which is heated by thermal conduction from the corona and cooled by radiative losses is developed. A general conclusion is that the temperature profile of the transition region and lower corona results primarily from the energy balance of the corona, while the number density is determined by the energy balance of the transition region.

  11. Dust Storm

    Atmospheric Science Data Center

    2013-04-16

    article title:  Massive Dust Storm over Australia     View Larger Image ... and dry conditions caused a massive blanket of dust from Australia's Outback to spread eastward across Queensland and New South Wales. ...

  12. Evaluating the Uncertainties in the Electron Temperature and Radial Speed Measurements Using White Light Corona Eclipse Observations

    NASA Technical Reports Server (NTRS)

    Reginald, Nelson L.; Davilla, Joseph M.; St. Cyr, O. C.; Rastaetter, Lutz

    2014-01-01

    We examine the uncertainties in two plasma parameters from their true values in a simulated asymmetric corona. We use the Corona Heliosphere (CORHEL) and Magnetohydrodynamics Around the Sphere (MAS) models in the Community Coordinated Modeling Center (CCMC) to investigate the differences between an assumed symmetric corona and a more realistic, asymmetric one. We were able to predict the electron temperatures and electron bulk flow speeds to within +/-0.5 MK and +/-100 km s(exp-1), respectively, over coronal heights up to 5.0 R from Sun center.We believe that this technique could be incorporated in next-generation white-light coronagraphs to determine these electron plasma parameters in the low solar corona. We have conducted experiments in the past during total solar eclipses to measure the thermal electron temperature and the electron bulk flow speed in the radial direction in the low solar corona. These measurements were made at different altitudes and latitudes in the low solar corona by measuring the shape of the K-coronal spectra between 350 nm and 450 nm and two brightness ratios through filters centered at 385.0 nm/410.0 nm and 398.7 nm/423.3 nm with a bandwidth of is approximately equal to 4 nm. Based on symmetric coronal models used for these measurements, the two measured plasma parameters were expected to represent those values at the points where the lines of sight intersected the plane of the solar limb.

  13. Fundamental Physical Processes in Coronae: Waves, Turbulence, Reconnection, and Particle Acceleration

    E-print Network

    Aschwanden, Markus J

    2007-01-01

    Our understanding of fundamental processes in the solar corona has been greatly progressed based on the space observations of SMM, Yohkoh, Compton GRO, SOHO, TRACE, RHESSI, and STEREO. We observe now acoustic waves, MHD oscillations, turbulence-related line broadening, magnetic configurations related to reconnection processes, and radiation from high-energy particles on a routine basis. We review a number of key observations in EUV, soft X-rays, and hard X-rays that innovated our physical understanding of the solar corona, in terms of hydrodynamics, MHD, plasma heating, and particle acceleration processes.

  14. Ultraviolet Corona Discharge Detection Based on Photomultiplier

    NASA Astrophysics Data System (ADS)

    Yongli, Liao; Liming, Wang; Ke, Wang; Canlin, Wang; Zhicheng, Guan

    High voltage equipments, especially polymer insulators may be getting into aging conditions due to the existence of corona discharge on the surface after a long term of running, which would accelerate the deterioration of the surface insulation performance, and even make equipments step into calamity ultimately. So it is significant to detect corona discharge on surface to ensure insulators' stable running. This paper presents the development of a novel corona discharge detection system based on photomultiplier tube (PMT), which has good functions of distance detection for corona discharge in determined region from surface of high voltage equipment and corona characteristics data analysis. In the verification experiments, it was shown that UV corona light can be also taken as characteristic for detecting corona discharge, other than corona leakage current detection, and a linear relationship was shown between the light magnitude and the current magnitude. Furthermore, mean peak value and number of pulses whose peak value is above threshold are extracted from the basic data, which can be used to quantify the development of corona discharge. The results of investigation on polymer insulators suggested that detection of the region between metal end fitting and first shed should be emphasized. The measurements of corona discharge distribution along insulators can be used to learn about the degradation conditions. Detection of polymer insulators in lab and field inspection experience are both soundly verifying the usefulness of the corona detection system.

  15. Slingshot prominences above stellar X-ray coronae

    E-print Network

    M. Jardine; A. A. van Ballegooijen

    2005-06-10

    We present a new model for the coronal structure of rapidly rotating solar-type stars. The presence of prominences trapped in co-rotation 2 to 5 stellar radii above the stellar surface has been taken as evidence that the coronae of these stars must be very extended. The observed surface magnetic fields, however, cannot contain X-ray emitting gas out to these distances. We present an alternative model: that these prominences are trapped in long thin loops embedded not in the X-ray corona, but in the wind. Above coronal helmet streamers, oppositely-directed wind-bearing field lines reconnect to form closed loops which then fill up with gas that was originally part of the wind. We demonstrate that static equilibria exist for these loops at a range of pressures and temperatures. The maximum loop height falls as the rotation rate increases, but rises as the loop temperature decreases. For a solar-mass star with rotation period 0.5 days, whose X-ray corona extends 1stellar radius above the surface, loops at temperatures of 10, 000 K can extend out to 5 stellar radii.

  16. An XMM-Newton Study of the Coronae of $?^2$ Coronae Borealis

    E-print Network

    J. A. Suh; M. Audard; M. Guedel; F. B. S. Paerels

    2005-06-10

    (Abridged) We present results of XMM-Newton observations of the RS CVn binary $\\sigma^2$ Coronae Borealis. The RGS and EPIC MOS2 spectra were simultaneously fitted with collisional ionization equilibrium plasma models to determine coronal abundances of various elements. Contrary to the solar first ionization potential (FIP) effect in which elements with a low FIP are overabundant in the corona compared to the solar photosphere, and contrary to the ``inverse'' FIP effect observed in several active RS CVn binaries, coronal abundance ratios in $\\sigma^2$ CrB show a complex pattern as supported by similar findings in the Chandra HETGS analysis of $\\sigma^2$ CrB with a different methodology (Osten et al. 2003). Low-FIP elements ($<10$ eV) have their abundance ratios relative to Fe consistent with the solar photospheric ratios, whereas high-FIP elements have their abundance ratios increase with increasing FIP. We find that the coronal Fe abundance is consistent with the stellar photospheric value, indicating that there is no metal depletion in $\\sigma^2$ CrB. However, we obtain a higher Fe absolute abundance than in Osten et al. (2003). Except for Ar and S, our absolute abundances are about 1.5 times larger than those reported by Osten et al. (2003). However, a comparison of their model with our XMM-Newton data (and vice versa) shows that both models work adequately in general. We find, therefore, no preference for one methodology over the other to derive coronal abundances. Despite the systematic discrepancy in absolute abundances, our abundance ratios are very close to those obtained by Osten et al. (2003). Finally, we confirm the measurement of a low density in \\ion{O}{7} ($< 4 \\times 10^{10}$ cm$^{-3}$), but could not confirm the higher densities measured in spectral lines formed at higher temperatures.

  17. Dust Measurements by the Student Dust Counter (SDC) onboard the New Horizons Mission

    Microsoft Academic Search

    David James; Mihaly Horanyi; Andrew Poppe

    2008-01-01

    The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft is a dust impact detector designed to map the interplanetary dust distribution along the trajectory of the New Horizons spacecraft as it traverses our solar system. VSDC is the first student built instrument on a deep space mission and is currently operated by a small group of undergraduate

  18. Fractal dust grains around R Coronae Borealis stars

    SciTech Connect

    Wright, E.L. (California Univ., Los Angeles (USA))

    1989-11-01

    Discrete dipole approximation calculations of the optical properties of random fractal aggregates of graphite spheroids show a UV absorption feature that is too wide and centered at too long a wavelength to fit the observed interstellar 2200-A feature, but which is a good match to the 2400-A feature seen in the hydrogen-deficient R CrB stars reported by Hecht et al. (1984). Graphite fractal grains also match the UV bump and large long-wavelenvth extinction seen in laboratory studies of carbon smoke published by Bussoletti et al. (1987), which are usually attributed to amorphous carbon. 16 refs.

  19. The lunar dust environment

    NASA Astrophysics Data System (ADS)

    Grün, Eberhard; Horanyi, Mihaly; Sternovsky, Zoltan

    2011-11-01

    Each year the Moon is bombarded by about 10 6 kg of interplanetary micrometeoroids of cometary and asteroidal origin. Most of these projectiles range from 10 nm to about 1 mm in size and impact the Moon at 10-72 km/s speed. They excavate lunar soil about 1000 times their own mass. These impacts leave a crater record on the surface from which the micrometeoroid size distribution has been deciphered. Much of the excavated mass returns to the lunar surface and blankets the lunar crust with a highly pulverized and "impact gardened" regolith of about 10 m thickness. Micron and sub-micron sized secondary particles that are ejected at speeds up to the escape speed of 2300 m/s form a perpetual dust cloud around the Moon and, upon re-impact, leave a record in the microcrater distribution. Such tenuous clouds have been observed by the Galileo spacecraft around all lunar-sized Galilean satellites at Jupiter. The highly sensitive Lunar Dust Experiment (LDEX) onboard the LADEE mission will shed new light on the lunar dust environment. LADEE is expected to be launched in early 2013. Another dust related phenomenon is the possible electrostatic mobilization of lunar dust. Images taken by the television cameras on Surveyors 5, 6, and 7 showed a distinct glow just above the lunar horizon referred to as horizon glow (HG). This light was interpreted to be forward-scattered sunlight from a cloud of dust particles above the surface near the terminator. A photometer onboard the Lunokhod-2 rover also reported excess brightness, most likely due to HG. From the lunar orbit during sunrise the Apollo astronauts reported bright streamers high above the lunar surface, which were interpreted as dust phenomena. The Lunar Ejecta and Meteorites (LEAM) Experiment was deployed on the lunar surface by the Apollo 17 astronauts in order to characterize the lunar dust environment. Instead of the expected low impact rate from interplanetary and interstellar dust, LEAM registered hundreds of signals associated with the passage of the terminator, which swamped any signature of primary impactors of interplanetary origin. It was suggested that the LEAM events are consistent with the sunrise/sunset-triggered levitation and transport of charged lunar dust particles. Currently no theoretical model explains the formation of a dust cloud above the lunar surface but recent laboratory experiments indicate that the interaction of dust on the lunar surface with solar UV and plasma is more complex than previously thought.

  20. Comparison of Solar Source Regions of LASCO Coronal Streamers and Solar Wind Sampled by ACE and Ulysses near Solar Maximum

    Microsoft Academic Search

    P. C. Liewer; M. Neugebauer; D. Biesecker; D. Socker

    2001-01-01

    The highly inclined and distorted current sheet seen during the current solar maximum leaves a strong imprint on the solar corona as seen by SOHO LASCO and the solar wind sector structure as seen by Ulysses and ACE. Here we present results of studies to determine the solar source regions of (1) solar wind streams sampled in situ by Ulysses

  1. High-resolution spectroscopy of the R Coronae Borealis Star V Coronae Australis

    E-print Network

    N. Kameswara Rao; David L. Lambert

    2007-10-26

    Optical high-resolution spectra of the R Coronae Borealis star V CrA at light maximum and during minimum light arediscussed. Abundance analysis confirms previous results showing that V CrA has the composition of the small subclass of R Coronae Borealis (RCB) stars know as `minority' RCBs, i.e., the Si/Fe and S/Fe ratios are 100 times their solar values. A notable novel result for RCBs is the detection of the 1-0 Swan system $^{12}$C$^{13}$C bandhead indicating that $^{13}$C is abundant: spectrum synthesis shows that $^{12}$C/$^{13}$C is about 3 to 4. Absorption line profiles are variable at maximum light with some lines showing evidence of splitting by about 10 km s$^{-1}$. A spectrum obtained as the star was recovering from a deep minimum shows the presence of cool C$_2$ molecules with a rotational temperature of about 1200K, a temperature suggestive of gas in which carbon is condensing into soot. The presence of rapidly outflowing gas is shown by blue-shifted absorption components of the Na {\\sc i} D and K {\\sc i} 7698 \\AA resonance lines.

  2. Hot Carbon Corona in Mars’ Upper Thermosphere and Exosphere

    NASA Astrophysics Data System (ADS)

    Lee, Yuni; Combi, M.; Tenishev, V.; Bougher, S.

    2013-10-01

    The production of energetic particles results in the formation of the hot corona, where the most of the escape of neutral atoms occur, in the Martian upper atmosphere. In order to investigate the dynamics of these energetic neutral atoms, we have carried out a study that provides a self-consistent global description of the hot corona in the upper thermosphere and exosphere by employing a self-consistent global kinetic model coupled with a thermosphere/ionosphere model. In this work, we evaluate the carbon atom inventory by studying the production and distribution of energetic carbon atoms. The most important source reactions for hot atomic carbon are expected to be photodissociation of CO and dissociative recombination of CO+, which are highly sensitive to solar activity and occur mostly deep in the dayside of the thermosphere. The latest available branching ratios is adopted, and appropriate choices of the rate coefficient and the photodissociation frequencies are made. In this study, we simulate the variations of the hot carbon corona over the solar cycle and seasons. The spatial distributions and profiles of density and temperature, atmospheric loss rates are discussed for the cases considered. The total global escape of hot carbon from all dominant photochemical processes is computed and compared with those from other previous models. To describe self-consistently the upper thermosphere and exosphere, a combination of our 3D Direct Simulation Monte Carlo (DSMC) model [Valeille, A., Combi, M., Bougher, S., Tenishev, V., Nagy, A., 2009. J. Geophys. Res. 114, E11006. doi:10.1029/2009JE003389] and the 3D Mars Thermosphere General Circulation Model (MTGCM) [Bougher, S. W., Bell, J. M., Murphy, J. R., Lopez-Valverde, M. A., Withers, P. G., 2006. Geophys. Res. Lett. 32, doi: 10.1029/2005GL024059. L02203] is used. Finally, our computed global total escape rate of hot carbon ranges ~ (5.2 - 57.1) × 1023 s-1 for the aphelion solar low to perihelion solar high case.

  3. Nebula around R Corona Borealis

    E-print Network

    Rao, N Kameswara

    2011-01-01

    The star R Corona Borealis (R CrB) shows forbidden lines of [O II], [N II], and [S II] during the deep minimum when the star is fainter by about 8 to 9 magnitudes from normal brightness, suggesting the presence of nebular material around it. We present low and high spectral resolution observations of these lines during the ongoing deep minimum of R CrB, which started in July 2007. These emission lines show double peaks with a separation of about 170 km/s. The line ratios of [S II] and [O II] suggest an electron density of about 100 cm$^{-3}$. We discuss the physical conditions and possible origins of this low density gas. These forbidden lines have also been seen in other R Coronae Borealis stars during their deep light minima and this is a general characteristic of these stars, which might have some relevance to their origins.

  4. Dust World

    NSDL National Science Digital Library

    2011-02-23

    The increasing importance of understanding dust and its role in the Earth system is driving new research and an analysis of past data. This website offers research on the impact of dust forcings on the Earth system from dust storms. Analysis of dust from a whole Earth perspective incorporates connections and interconnections of dust in the atmospheres as well as how to mitigate the increase and severity of dust storms. This resource is sponsored by the Earth System Science Education Alliance (ESSEA), a NASA, NSF and NOAA-supported program implemented by the Institute for Global Environmental Strategies (IGES) to improve the quality of geoscience instruction for pre-service and in-service K-12 teachers.

  5. The morphology of streamer coronas

    SciTech Connect

    Vitello, P.A.; Penetrante, B.M.; Bardsley, J.N. [Lawrence Livermore National Lab., CA (United States)

    1992-12-01

    Streamer coronas are of interest due to their application to pollution control devices. A streamer coronal discharge produces energetic electrons which, through dissociation and ionization processes, generate active radicals that in turn react with toxic molecules. The morphology of streamer coronas determines the energy distribution of the electrons produced. Streamers propagate due to a highly non-linear space charge driven ionization wave. Because of the complexity of the equations describing streamer dynamics, most of the numerical simulations have been restricted to one (longitudinal) spatial dimension. Some low resolution 2-D simulations have been previously performed, but so far have been restricted to plane-parallel electrode configurations. The authors have developed multi-dimensional streamer models that can be applied to arbitrarily shaped electrode structures. Their models have generated the first multi-dimensional fully resolved streamers which form self-consistent radial structure. They have applied these codes to study some of the issues related to finding the optimum working conditions for streamer corona reactors. Their results show that the radial components of the electron flow and the space charge field are very important in providing an accurate picture of the streamer morphology, especially near the highly stressed electrode.

  6. Atmospheric dust

    NSDL National Science Digital Library

    University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

    2003-01-01

    What is the purpose of dust in the atmosphere? On this activity page, part of an interactive laboratory series for grades 8-12, students read about the need for dust in the atmosphere as an agent for condensation. The addition of dust particles to the atmosphere by airplanes introduces students to the concept of cloud seeding and influencing the chance of rain in an area. Copyright 2005 Eisenhower National Clearinghouse

  7. Tectonics of Neyterkob corona on Venus

    NASA Technical Reports Server (NTRS)

    Kauhanen, K.

    1993-01-01

    Neyterkob double corona (50 deg N 202 deg) presents an area of corona-related interfering tectonic patterns which are formed in different phases of evolution of the corona and modified by regional stresses. Analyzing the patterns can reveal something about the coronal formation. Tectonic features form distinct units on topographic depressions, slopes, and volcanic flows extending over one radius of the corona. A remarkable amount of compressional features were found near the rim and related to interaction between adjacent coronae. Radial extension was mainly observed on a peculiar NE-SW trending high crossing the corona. Concentric fractures were found to the east partly connected to the lithospheric flexure. Tectonic features indicate movements of volcanic activity and modification of the area by more regional stresses.

  8. Active dust control and mitigation technology for lunar and Martian exploration

    Microsoft Academic Search

    C. I. Calle; C. R. Buhler; M. R. Johansen; M. D. Hogue; S. J. Snyder

    2011-01-01

    Mars is covered with a layer of dust that has been homogenized by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is the dominant weather phenomenon on Mars. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover

  9. Laser interferometry of SF6 coronas

    Microsoft Academic Search

    D W Lamb; G A Woolsey

    1995-01-01

    Radial profiles of gas density have been measured in positive and negative SF6 coronas at 101.3 kPa using optical interferometry. The results show that, in DC SF6 coronas, the electrical power input is confined to a small volume around the point electrode and energy transfer by the corona wind efficiently dissipates the heat generated there throughout the discharge chamber. Consequently,

  10. Solar

    NSDL National Science Digital Library

    Iowa Public Television. Explore More Project

    2004-01-01

    What part does solar energy play in satisfying energy demands? This informational piece, part of a series about the future of energy, introduces students to solar energy. Here students read about the uses, benefits, and active and passive methods of solar energy. Information is also presented about limitations, geographical considerations of solar power in the United States, and current uses of solar energy around the world. Thought-provoking questions afford students chances to reflect on what they've read about the uses of solar energy. Articles and information about a solar power plant in the Mohave Desert, the use of solar energy in Iowa, and statistics about solar energy are provided in a sidebar.

  11. Volatiles in interplanetary dust particles: a review.

    PubMed

    Gibson, E K

    1992-03-25

    The paper presents a review of the volatiles found within interplanetary dust particles. These particles have been shown to represent primitive material from early in the solar system's formation and also may contain records of stellar processes. The organogenic elements (i.e., H, C, N, O, and S) are among the most abundant elements in our solar system, and their abundances, distributions, and isotopic compositions in early solar system materials permit workers to better understand the processes operating early in the evolutionary history of solar system materials. Interplanetary dust particles have a range of elemental compositions, but generally they have been shown to be similar to carbonaceous chondrites, the solar photosphere, Comet Halley's chondritic cores, and matrix materials of chondritic chondrites. Recovery and analysis of interplanetary dust particles have opened new opportunities for analysis of primitive materials, although interplanetary dust particles represent major challenges to the analyst because of their small size. PMID:11537855

  12. Solar Wind: Manifestations of Solar Activity E N CYC LO PE D IA O F AS T R O N O MY AN D AS T R O PHYS I C S Solar Wind: Manifestations of Solar

    E-print Network

    Webb, David F.

    Solar Wind: Manifestations of Solar Activity E N CYC LO PE D IA O F AS T R O N O MY AN D AS T R O PHYS I C S Solar Wind: Manifestations of Solar Activity The Sun's outer atmosphere, the corona, is continually heated and expands to create the solar wind. Solar activity waxes and wanes with the 11 yr cycle

  13. OBSERVATIONAL CONSEQUENCES OF A MAGNETIC FLUX ROPE EMERGING INTO THE CORONA S. E. Gibson,1

    E-print Network

    Demoulin, Pascal

    OBSERVATIONAL CONSEQUENCES OF A MAGNETIC FLUX ROPE EMERGING INTO THE CORONA S. E. Gibson,1 Y. Fan,1 predicts solar structures and dynamics consistent with observations. We first consider the structure twisting motions along the magnetic flux surfaces. Observations of rotating sunspots may provide better

  14. Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure

    NASA Technical Reports Server (NTRS)

    Tiwari, S. K.; Alexander, C. E.; Winebarger, A.; Moore, R. L.

    2014-01-01

    The solar corona is much hotter (>=10(exp 6) K) than its surface (approx 6000 K), puzzling astrophysicists for several decades. Active region (AR) corona is again hotter than the quiet Sun (QS) corona by a factor of 4-10. The most widely accepted mechanism that could heat the active region corona is the energy release by current dissipation via reconnection of braided magnetic field structure, first proposed by E. N. Parker three decades ago. The first observational evidence for this mechanism has only recently been presented by Cirtain et al. by using High-resolution Coronal Imager (Hi-C) observations of an AR corona at a spatial resolution of 0.2 arcsec, which is required to resolve the coronal loops, and was not available before the rocket flight of Hi-C in July 2012. The Hi-C project is led by NASA/MSFC. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. We are currently investigating the changes taking place in photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. For this purpose, we are also using SDO/AIA data of +/- 2 hours around the 5 minutes Hi-C flight. In the present talk, I will first summarize some of the results of the Hi-C observations and then present some results from our recent analysis on what photospheric processes feed the magnetic energy that dissipates into heat in coronal loops.

  15. Outflow structure of the quiet sun corona probed by spacecraft radio scintillations in strong scattering

    SciTech Connect

    Imamura, Takeshi; Ando, Hiroki; Toda, Tomoaki; Nakamura, Masato [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Tokumaru, Munetoshi; Shiota, Daikou [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 484-8601 (Japan); Isobe, Hiroaki; Asai, Ayumi [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471, Japan. (Japan); Miyamoto, Mayu [Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Häusler, Bernd [Institut für Raumfahrttechnik, Universität der Bundeswehr München, D-85577 Neubiberg (Germany); Pätzold, Martin [Rheinisches Institut für Umweltforschung, Department Planetenforschung, Universität zu Köln, Aachener Strasse 209, D-50931 Köln (Germany); Nabatov, Alexander [The Institute of Radio Astronomy, National Academy of Science of Ukraine, Chervonoprapornaya, Strasse 4, Kharkov 61002 (Ukraine); Yaji, Kentaro [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Yamada, Manabu, E-mail: imamura.takeshi@jaxa.jp [Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba 275-0016 (Japan)

    2014-06-20

    Radio scintillation observations have been unable to probe flow speeds in the low corona where the scattering of radio waves is exceedingly strong. Here we estimate outflow speeds continuously from the vicinity of the Sun to the outer corona (heliocentric distances of 1.5-20.5 solar radii) by applying the strong scattering theory to radio scintillations for the first time, using the Akatsuki spacecraft as the radio source. Small, nonzero outflow speeds were observed over a wide latitudinal range in the quiet-Sun low corona, suggesting that the supply of plasma from closed loops to the solar wind occurs over an extended area. The existence of power-law density fluctuations down to the scale of 100 m was suggested, which is indicative of well-developed turbulence which can play a key role in heating the corona. At higher altitudes, a rapid acceleration typical of radial open fields is observed, and the temperatures derived from the speed profile show a distinct maximum in the outer corona. This study opened up a possibility of observing detailed flow structures near the Sun from a vast amount of existing interplanetary scintillation data.

  16. Atmospheric Dust

    NSDL National Science Digital Library

    Millions of tons of dust are lifted from deserts annually, suspended in the atmosphere, and released to fall on the oceans, but scientists are a long way from understanding the impact of atmospheric dust on the climate and weather systems of Earth or on marine organisms. This radio broadcast explains how the nitrogen, phosphorus and iron released from dust boosts the growth of phytoplankton, which also soak up carbon dioxide and release more gases into the atmosphere. Better monitoring and more sophisticated sensors are giving us a more accurate picture of the dust in the atmosphere; the broadcast reports on investigations of dust from ice cores and on computer simulations of the connections between dust and climate. But the unpredictable nature of dust events makes it extremely difficult to determine their impact on the natural systems of Earth. There are discussions with geographers, oceanographers, environmentalists and climate modelers about atmospheric dust, one of the least understood and most contradictory components of the atmosphere. The broadcast is 28 minutes in length.

  17. Distribution of Dust from Kuiper Belt Objects

    NASA Technical Reports Server (NTRS)

    Gorkavyi, Nick N.; Ozernoy, Leonid; Taidakova, Tanya; Mather, John C.; Fisher, Richard (Technical Monitor)

    2000-01-01

    Using an efficient computational approach, we have reconstructed the structure of the dust cloud in the Solar system between 0.5 and 100 AU produced by the Kuiper belt objects. Our simulations offer a 3-D physical model of the 'kuiperoidal' dust cloud based on the distribution of 280 dust particle trajectories produced by 100 known Kuiper belt objects; the resulting 3-D grid consists of 1.9 x 10' cells containing 1.2 x 10" particle positions. The following processes that influence the dust particle dynamics are taken into account: 1) gravitational scattering on the eight planets (neglecting Pluto); 2) planetary resonances; 3) radiation pressure; and 4) the Poynting-Robertson (P-R) and solar wind drags. We find the dust distribution highly non-uniform: there is a minimum in the kuiperoidal dust between Mars and Jupiter, after which both the column and number densities of kuiperoidal dust sharply increase with heliocentric distance between 5 and 10 AU, and then form a plateau between 10 and 50 AU. Between 25 and 45 AU, there is an appreciable concentration of kuiperoidal dust in the form of a broad belt of mostly resonant particles associated with Neptune. In fact, each giant planet possesses its own circumsolar dust belt consisting of both resonant and gravitationally scattered particles. As with the cometary belts simulated in our related papers, we reveal a rich and sophisticated resonant structure of the dust belts containing families of resonant peaks and gaps. An important result is that both the column and number dust density are more or less flat between 10 and 50 AU, which might explain the surprising data obtained by Pioneers 10 & 11 and Voyager that the dust number density remains approximately distance-independent in this region. The simulated kuiperoidal dust, in addition to asteroidal and cometary dust, might represent a third possible source of the zodiacal light in the Solar system.

  18. Andromeda's dust

    SciTech Connect

    Draine, B. T.; Aniano, G. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544-1001 (United States); Krause, Oliver; Groves, Brent; Sandstrom, Karin; Klaas, Ulrich; Linz, Hendrik; Rix, Hans-Walter; Schinnerer, Eva; Schmiedeke, Anika; Walter, Fabian [Max-Planck-Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg (Germany); Braun, Robert [CSIRO—Astronomy and Space Science, P.O. Box 76, Epping, NWS 1710 (Australia); Leroy, Adam, E-mail: draine@astro.princeton.edu, E-mail: ganiano@ias.u-psud.fr [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

    2014-01-10

    Spitzer Space Telescope and Herschel Space Observatory imaging of M31 is used, with a physical dust model, to construct maps of dust surface density, dust-to-gas ratio, starlight heating intensity, and polycyclic aromatic hydrocarbon (PAH) abundance, out to R ? 25 kpc. The global dust mass is M {sub d} = 5.4 × 10{sup 7} M {sub ?}, the global dust/H mass ratio is M {sub d}/M {sub H} = 0.0081, and the global PAH abundance is (q {sub PAH}) = 0.039. The dust surface density has an inner ring at R = 5.6 kpc, a maximum at R = 11.2 kpc, and an outer ring at R ? 15.1 kpc. The dust/gas ratio varies from M {sub d}/M {sub H} ? 0.026 at the center to ?0.0027 at R ? 25 kpc. From the dust/gas ratio, we estimate the interstellar medium metallicity to vary by a factor ?10, from Z/Z {sub ?} ? 3 at R = 0 to ?0.3 at R = 25 kpc. The dust heating rate parameter (U) peaks at the center, with (U) ? 35, declining to (U) ? 0.25 at R = 20 kpc. Within the central kiloparsec, the starlight heating intensity inferred from the dust modeling is close to what is estimated from the stars in the bulge. The PAH abundance reaches a peak q {sub PAH} ? 0.045 at R ? 11.2 kpc. When allowance is made for the different spectrum of the bulge stars, q {sub PAH} for the dust in the central kiloparsec is similar to the overall value of q {sub PAH} in the disk. The silicate-graphite-PAH dust model used here is generally able to reproduce the observed dust spectral energy distribution across M31, but overpredicts 500 ?m emission at R ? 2-6 kpc, suggesting that at R = 2-6 kpc, the dust opacity varies more steeply with frequency (with ? ? 2.3 between 200 and 600 ?m) than in the model.

  19. What is the Shell Around R Coronae Borealis?

    E-print Network

    Montiel, Edward J; Marcello, Dominic C; Lockman, Felix J

    2015-01-01

    The hydrogen-deficient, carbon-rich R Coronae Borealis (RCB) stars are known for being prolific producers of dust which causes their large iconic declines in brightness. Several RCB stars, including R CrB, itself, have large extended dust shells seen in the far-infrared. The origin of these shells is uncertain but they may give us clues to the evolution of the RCB stars. The shells could form in three possible ways. 1) they are fossil Planetary Nebula (PN) shells, which would exist if RCB stars are the result of a final, helium-shell flash, 2) they are material left over from a white-dwarf merger event which formed the RCB stars, or 3) they are material lost from the star during the RCB phase. Arecibo 21-cm observations establish an upper limit on the column density of H I in the R CrB shell implying a maximum shell mass of $\\lesssim$0.3 M$_{\\odot}$. A low-mass fossil PN shell is still a possible source of the shell although it may not contain enough dust. The mass of gas lost during a white-dwarf merger even...

  20. White dwarf mergers and the origin of R Coronae Borealis stars

    E-print Network

    Lorén-Aguilar, P; José, J; García-Berro, E; Althaus, L G; Isern, J

    2011-01-01

    We present a nucleosynthesis study of the merger of a 0.4 solar masses helium white dwarf with a 0.8 solar masses carbon-oxygen white dwarf, coupling the thermodynamic history of Smoothed Particle Hydrodynamics particles with a post-processing code. The resulting chemical abundance pattern, particularly for oxygen and fluorine, is in qualitative agreement with the observed abundances in R Coronae Borealis stars.

  1. Dust Devils Seen by Spirit

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1 Annotated

    At the Gusev site recently, skies have been very dusty, and on its 421st sol (March 10, 2005) NASA's Mars Exploration Rover Spirit spied two dust devils in action. This pair of images is from the rover's rear hazard-avoidance camera. Views of the Gusev landing region from orbit show many dark streaks across the landscape -- tracks where dust devils have removed surface dust to show relatively darker soil below -- but this is the first time Spirit has photographed an active dust devil.

    Scientists are considering several causes of these small phenomena. Dust devils often occur when the Sun heats the surface of Mars. Warmed soil and rocks heat the layer of atmosphere closest to the surface, and the warm air rises in a whirling motion, stirring dust up from the surface like a miniature tornado. Another possibility is that a flow structure might develop over craters as wind speeds increase. As winds pick up, turbulence eddies and rotating columns of air form. As these columns grow in diameter they become taller and gain rotational speed. Eventually they become self-sustaining and the wind blows them down range.

    One sol before this image was taken, power output from Spirit's solar panels went up by about 50 percent when the amount of dust on the panels decreased. Was this a coincidence, or did a helpful dust devil pass over Spirit and lift off some of the dust?

    By comparing the separate images from the rover's different cameras, team members estimate that the dust devils moved about 500 meters (1,640 feet) in the 155 seconds between the navigation camera and hazard-avoidance camera frames; that equates to about 3 meters per second (7 miles per hour). The dust devils appear to be about 1,100 meters (almost three-quarters of a mile) from the rover.

  2. Improved Method for Calculating DC Corona Losses

    Microsoft Academic Search

    Mohammed Khalifa; Mazen Abdel-Salam

    1974-01-01

    Existing methods for calculating corona losses on monopolar and bipolar dc transmission lines have resorted to the assumption that the space charge of corona does not affect the direction of the electrostatic field. This assumption was aimed at making the calculations possible. In this report corena loss calculations are made in which this assumption and others are replaced by correlating

  3. System reliability analysis through corona testing

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

    1975-01-01

    A corona vacuum test facility for nondestructive testing of power system components was built in the Reliability and Quality Engineering Test Laboratories at the NASA Lewis Research Center. The facility was developed to simulate operating temperature and vacuum while monitoring corona discharges with residual gases. The facility is being used to test various high-voltage power system components.

  4. System reliability analysis through corona testing

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

    1975-01-01

    In the Reliability and Quality Engineering Test Laboratory at the NASA Lewis Research Center a nondestructive, corona-vacuum test facility for testing power system components was developed using commercially available hardware. The test facility was developed to simulate operating temperature and vacuum while monitoring corona discharges with residual gases. This facility is being used to test various high voltage power system components.

  5. Parga Chasma: Coronae and Rifting on Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, S. E.; Stofan, E. R.; Buck, W. R.; Martin, P.

    2005-01-01

    The majority of coronae (quasicircular volcano-tectonic features) are found along rifts or fracture belts, and the majority of rifts have coronae [e.g. 1,2]. However, the relationship between coronae and rifts remains unclear [3-6]. There is evidence that coronae can form before, after, or synchronously with rifts [3,4]. The extensional fractures in the rift zones have been proposed to be a result of broad scale upwelling and traction on the lower lithosphere [7]. However, not all rift systems have a significant positive geoid anomaly, as would be expected for an upwelling site [8]. This could be explained if the rifts lacking anomalies are no longer active. Coronae are generally accepted to be sites of local upwelling [e.g. 1], but the observed rifting is frequently not radial to the coronae and extends well beyond the coronae into the surrounding plains. Thus the question remains as to whether the rifts represent regional extension, perhaps driven by mantle tractions, or if the coronae themselves create local thinning and extension of the lithosphere. In the first case, a regional extension model should be consistent with the observed characteristics of the rifts. In the latter case, a model of lithospheric loading and fracturing would be more appropriate. A good analogy may be the propagation of oceanic intraplate volcanoes [9].

  6. Validation of a synoptic solar wind model

    Microsoft Academic Search

    O. Cohen; I. V. Sokolov; I. I. Roussev; T. I. Gombosi

    2008-01-01

    We present a validation of a three-dimensional magnetohydrodynamic model for the solar corona and the inner heliosphere. We compare the results of the model with long-term satellite data at 1 AU for a 1 year period during solar minimum and another year period of solar maximum. Overall, the model predicts rather well the magnitude of the magnetohydrodynamical variables for solar

  7. Electrodynamic Dust Shield Demonstrator

    NASA Technical Reports Server (NTRS)

    Stankie, Charles G.

    2013-01-01

    The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid running a multiphase low frequency AC signal. Electrostatically charged particles, such as those encountered on the moon, Mars, or an asteroid, are carried along by the traveling field due to the action of Coulomb and dielectrophoretic forces."2 The technical details have been described in a separate article. This document details the design and construction process of a small demonstration unit. Once finished, this device will go to the Office of the ChiefTechnologist at NASA headquarters, where it will be used to familiarize the public with the technology. 1 NASA KSC FO Intern, Prototype Development Laboratory, Kennedy Space Center, University of Central Florida Kennedy Space

  8. Processing method of images obtained during the TESIS/CORONAS-PHOTON experiment

    NASA Astrophysics Data System (ADS)

    Kuzin, S. V.; Shestov, S. V.; Bogachev, S. A.; Pertsov, A. A.; Ulyanov, A. S.; Reva, A. A.

    2011-04-01

    In January 2009, the CORONAS-PHOTON spacecraft was successfully launched. It includes a set of telescopes and spectroheliometers—TESIS—designed to image the solar corona in soft X-ray and EUV spectral ranges. Due to features of the reading system, to obtain physical information from these images, it is necessary to preprocess them, i.e., to remove the background, correct the white field, level, and clean. The paper discusses the algorithms and software developed and used for the preprocessing of images.

  9. Theoretical models for the solar wind

    Microsoft Academic Search

    E. Marsch

    1994-01-01

    Theoretical models for the solar wind are reviewed from the point of view that a hot corona cannot be simply assumed as a given inner boundary but rather as part of the overall problem and needs to be explained in the first place. Models including the transition region and the heating of the corona and the coronal radiative and conductive

  10. Corona-related volcanism on Venus

    NASA Astrophysics Data System (ADS)

    Grindrod, Peter Martin

    This thesis reports the results of a study of volcanic processes at coronae on Venus. The Aglaonice F-Map region has been mapped, and its geological history interpreted, at the full-resolution of Magellan SAR data. Volcanism at coronae is shown to have occurred repeatedly over a protracted period of time, supporting a non-directional style of resurfacing in the F-Map region, and suggesting that corona-related flows may be an important resurfacing mechanism on Venus. It is likely that the magma storage system varies between each corona, with eruption dependent on local conditions such as location of magma body and local stress regime. Numerous flows which can be sourced to coronae, and were previously mapped as plains units, have also been identified. A global survey has revealed 29 volcano/corona 'hybrids', features which resemble both coronae and large volcanoes. Age, magma supply, stress state, thermal gradient and eruption duration are all important factors in determining gross hybrid morphology. It is likely that not all hybrids follow a similar evolutionary path. A detailed study of four selected hybrids is presented and suggests that processes typical of both large volcanoes and coronae have occurred throughout their history, and does not imply evolution from one type of feature into another. The presence of large central depressions and/or topographic rims at the hybrids support the theory that some large volcanoes undergo a sagging process similar to coronae. Study of the depth and extension at large radial graben at four centres of radial fractures is also reported. The inferred levels of hoop strain are too large to be explained by previous models of plume uplift, and a newly applied magma chamber inflation model concludes that dike formation is responsible for the strain at the large radial graben, and that intrusion is an important process at early-phase coronae.

  11. Dust Devils in Gusev Crater, Sol 463

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a several dust devils -- whirlwinds that loft dust into the air -- moving across a plain below the hillside vantage point of NASA's Mars Exploration Rover Spirit. Several of the dust devils are visible at once in some of the frames in this sequence. The local solar time was about 2 p.m., when the ground temperature was high enough to cause turbulence that kicks up dust devils as the wind blows across the plain. The number of seconds elapsed since the first frame is indicated at lower left of the images, typically 20 seconds between frames. Spirit's navigation camera took these images on the rover's 463rd martian day, or sol (April 22, 2005.) Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection can trigger dust devils.

  12. The retrieval of optical properties from terrestrial dust devil vortices

    NASA Astrophysics Data System (ADS)

    Mason, Jonathon P.; Patel, Manish R.; Lewis, Stephen R.

    2014-03-01

    The retrieval of the optical properties of desert aerosols in suspension within terrestrial dust devils is presented with possible future application for martian dust devils. The transmission of light through dust devil vortices was measured in situ to obtain the wavelength-dependent attenuation by the aerosols. A Monte Carlo model was applied to each dust devil with the retrieved optical properties corresponding to the set of parameters which lead to the best model representation of the observed transmission spectra. The retrieved optical properties agree well with single scattering theory and are consistent with previous studies of dust aerosols. The enhanced absorption observed for dust devils with a higher tangential wind speed, and in comparison to atmospheric aerosol studies, suggests that larger dust particles are lofted and suspended around dust devil vortices. This analysis has shown that the imaginary refractive indices (and thus the optical properties of the suspended dust) are generally overestimated when these larger dust grains entrained by dust devils are neglected. This will lead to an overestimation of the amount of solar radiation absorbed by the small particles that remain in suspension after the dust devil terminates. It is also demonstrated that a 10% uncertainty in the particle size distribution of the dust entrained in the dust devils can result in a 50% increase in the predicted amount of incident solar radiation absorbed by the dust particles once the dust devil has terminated. The method used here provides the capability to retrieve the optical properties of the dust entrained in martian dust devils by taking advantage of transits over surface spacecraft which are capable of making optical measurements at ultraviolet and visible wavelengths. Our results suggest that we would observed higher absorption at all wavelengths for dust particles entrained in dust devil vortices compared to the ubiquitous dust haze.

  13. Sahara Dust

    Atmospheric Science Data Center

    2013-04-15

    ... a large amount of Saharan dust aloft and transported the material westward over the Atlantic Ocean. These observations from the ... NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed ...

  14. California Dust

    Atmospheric Science Data Center

    2014-05-15

    ... when forced through narrow canyons and mountain passes. Due to Southern California's uneven terrain, the strength of the winds varies ... MISR category:  gallery date:  Feb 9, 2002 Images:  California Dust ...

  15. Particle acceleration in helical magnetic fields in the corona

    NASA Astrophysics Data System (ADS)

    Gordovskyy, Mykola; Browning, Philippa; Bareford, Michael; Pinto, Rui; Kontar, Eduard; Bian, Nicolas

    2014-05-01

    Twisted magnetic fields should be ubiquitous in the solar corona. Emerging twisted ropes as well as complex photospheric motions provide continuous influx of the magnetic helicity. Twisted coronal fields, in turn, contain excess magnetic energy, which can be released, causing solar flares and other explosive phenomena. It has been shown recently, that reconnection in helical magnetic structures results in particle acceleration distributed within large volume, including the lower corona and chromosphere. Hence, the magnetic reconnection and particle acceleration scenario involving magnetic helicity can be a viable alternative to the standard flare model, where particles are accelerated in a small volume located in the upper corona. We discuss our recent results on the energy release and particle acceleration during magnetic reconnection in twisted coronal loops. Evolution of various helical structures is described in terms of resistive MHD, including heat conduction and radiation. We consider the effects of field topology and photospheric motions on the energy accumulation and release. In particular, we focus on scenarios with continuous helicity injection, leading to recurrent explosive events. Using the obtained MHD models, ion and electron acceleration is investigated, taking into account Coulomb collisions. We derive time-dependent energy spectra and spatial distribution for these species, and calculate resulting non-thermal radiation intensities. Based on the developed numerical models, we investigate observational implications of particle acceleration in helical magnetic structures. Thus, we compare temporal variations of thermal and non-thermal emission in different configurations. Furthermore, we consider spatial distributions of the thermal EUV and X-ray emission and non-thermal X-ray emission and compare them with observational data.

  16. Dust Catchers

    NSDL National Science Digital Library

    Nancy P. Moreno

    2007-01-01

    In this activity related to indoor air pollution, learners build take-home dust catchers with wax paper and petroleum jelly. After a set monitoring period, learners conduct representative particle counts using a comparison grid. Learners will also graph the results. This activity can be enhanced by sharing the "Health Hazards of Lunar Dust" Podcast with learners (see related resource link). This resource includes background information, variation ideas and a handout for learners in both English and Spanish.

  17. Dust Measurements On-board the New Horizons Mission

    Microsoft Academic Search

    A. Poppe; D. James; M. Horanyi

    2007-01-01

    The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft was successfully commissioned on March 3, 2006 (DOY 2006\\/061). VSDC is a dust impact detector designed to map the dust distribution along the trajectory of the New Horizons spacecraft as it traverses our solar system. VSDC is the first student built instrument on a deep space mission and

  18. How Pre-Eruption Configurations Lead to Bz in the Corona

    NASA Astrophysics Data System (ADS)

    Schrijver, K.

    2014-12-01

    One of the key properties that determines the strength of geomagnetic disturbances is the pattern of the magnetic field contained in coronal mass ejections (CME), often summarized in the term 'Bz' that characterizes the field orientation in the leading segment of the CME. That Bz has its origin in the field that leaves the solar corona at the initial phases of the eruption, and is thus set by the properties of the erupting active region field and the field into which the eruption initially propagates. Mapping the 3D configuration of these fields remains a challenge, but as observational and modeling capabilities advance, we can expect to improve our knowledge of the field leaving the Sun. I will review the current status of our capabilities to model the 3D field above solar active regions, summarize our growing skills at using observations of solar surface and corona to drive these models, and discuss opportunities for the near future.

  19. Study of the dynamics of the corona using July 11, 2010 eclipse data recorded from Easter Island

    NASA Astrophysics Data System (ADS)

    Samanta, Tanmoy

    Spectroscopic observations of the solar corona were performed during the total solar eclipse of 11 July 2010 in the green line at 5303 Ĺ [Fe XIV] and the red line at 6374 Ĺ [Fe X] from Easter Island, Chile. The data is analyzed to study the periodic variations in the intensity, line width and doppler velocity using wavelet analysis at all pixels within our field of view. We have found that there are few locations where significant oscillations are present. These oscillations can be interpreted in terms of the presence of magnetoacoustic waves or Alfvén waves in the corona.

  20. Dust Measurements Between Earth and Saturn by the Venetia Burney Student Dust Counter of the New Horizons Mission

    Microsoft Academic Search

    D. James; A. Poppe; M. Horanyi

    2008-01-01

    The Venetia Burney Student Dust Counter (VSDC) on the New Horizons mission is a dust impact detector designed to map the interplanetary dust distribution along the trajectory of the spacecraft as it traverses our solar system. VSDC is the first student-built instrument on a deep space mission and is currently operated by a small group of undergraduate and graduate students