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Sample records for solar dust corona

  1. The solar F-corona - Calculations of the optical and infrared brightness of circumsolar dust

    NASA Astrophysics Data System (ADS)

    Mann, I.

    1992-07-01

    The brightness of the solar F-corona along the ecliptic is calculated in the visual and near-IR spectral range, and the results are discussed with respect to future observations. It is shown that dust particles close to the sun have a strong influence on the corona brightness, which enables their investigation by remote sensing experiments. Comparison of model calculations with the observations indicates that the zodiacal dust cloud remains mainly undisturbed up to the beginning of a dust-free zone that amounts to about 5 solar radii. Calculations of visual brightness and polarization indicate a change of particle properties for a solar distance smaller than 20, which has to be proven by future experiments. The IR F-corona brightness has contributions from solar radiation scattered at dust particles up to wavelengths of 5 microns. The superposition with the thermal emission of particles produces a significant feature at the edge of the dust-free zone but the existence of an additional dust ring cannot be supported. The observational data at 10 microns are found to be in contradiction to the present study.

  2. The effect of the solar magnetic field on dust-particle orbits in the F corona

    NASA Astrophysics Data System (ADS)

    Rusk, Edwin T.

    1988-10-01

    In order to determine whether the solar magnetic field can align circumsolar dust into rings such as those described by Mizutani et al. (1984), the solar magnetic field is divided into its various multipole components and theoretical expressions are derived to determine the effect of each of these components on the orbital elements of circumsolar dust. Simulations are then carried out to determine the effect of a dynamic solar magnetic field on such particles using actual values of the solar magnetic field supplied by Hoeksema (1984). These results are compared to observations of the F corona.

  3. LASCO/SOHO Observations of Dust in the Outer Solar Corona

    NASA Astrophysics Data System (ADS)

    Kimura, H.; Mann, I.; Goldstein, B.; Korendyke, C.; Howard, R.

    1999-09-01

    The solar F-corona emission is comprised of solar radiation scattered by dust particles and thermal radiation emitted from near-solar dust particles. The visible brightness is mainly produced by scattering at medium scattering angles from particles near the Sun and by enhanced forward scattering from particles near the observer. The infrared brightness originates from the thermal emission from hot particles near the Sun. Studies of the F-corona are usually limited by the influence of atmospheric stray light and by difficulties of the separation of the K-corona, produced by sunlight scattered at electrons. The K-corona decreases steeply with increasing elongation and has a smaller contribution to the outer coronal brightness. This outer corona is observed from the SOHO satellite where the lack of atmospheric stray light and an optimized suppression of instrumental stray light in the LASCO coronagraph allow for the detection of the coronal brightness as far out as about 30 solar radii from the center of the Sun. These observations yield the opportunity to study the properties of interplanetary dust in the inner solar system. We will present preliminary results from the analysis of the data from the LASCO C3 coronagraph at distances from 10 to 30 solar radii from the center of the Sun in 3 wavelength intervals between 0.4 and 1.1 micron. We compare the data to brightness calculations in order to discuss the distribution of dust grains in the inner solar system. The Solar Heliospheric Observatory, SOHO, is a joint scientific space mission developed by ESA and NASA. The Large Angle Spectrometric Coronagraph (LASCO) was developed and is operated jointly by the Naval Research Laboratory (USA), the Max-Planck-Institut fur Aeronomie (Germany), the Laboratoire d'Astronomie Spatiale (France) and the University of Birmingham (UK).

  4. Influence of dust shape and material composition on the solar F-corona

    NASA Astrophysics Data System (ADS)

    Kimura, H.; Mann, I.; Mukai, T.

    1998-08-01

    We investigate the influences of dust shape and material composition on the brightness and reddening of the solar F-corona. Silicate and carbon are considered as the F-coronal dust material to represent low and high absorbing materials, respectively. The observational data of the visible and near-infrared F-coronal brightness are well reproduced by our model of porous grains. We find that a change in the amount of highly absorbing particles near the Sun can cause a variation in the radial slope of the near-infrared F-coronal brightness, as well as of the coronal reddening. Hence a temporal variation of coronal features may be connected to a variation of the dust cloud composition rather than to the variation of a solar dust ring, which may or may not exist around the Sun. Further analysis of the influence of the dust size distribution on the F-coronal reddening shows that a drastic change of the size distribution is unlikely.

  5. Solar Cycle Variations of the F Corona Brightness Resulting from the Interaction of Dust Grains with CMEs

    NASA Astrophysics Data System (ADS)

    Ragot, B.; Kahler, S.

    2002-12-01

    The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light intensity dominates that of the electron K corona above about 4 Rs. We consider the effects of interactions between the dust and the particles and fields of coronal mass ejections (CMEs). The dominant forces, with and without CMEs, acting on the dust close to the Sun are calculated for dust grain radii ranging from 0.01 to 100 microns. Dust grain orbits are then computed to compare the drift rates from assumed grain injections at 5 Rs to lower orbits for periods of minimum and maximum solar activity, where a simple CME model is adopted to distinguish the two periods. The CMEs result in significantly shorter drift times of the large (> 3 microns) dust grains, hence faster depletion rates and lower dust grain densities, at solar maxima. This would explain a relatively strong (> 30%) solar cycle variation of the near infrared brightness close to the dust plane of symmetry. While trapping the smallest of the grains, the CMEs also help scatter in latitude the grains of intermediate size (0.1 to 3 microns). The consequences for the optical brightness should be a time variation correlated to the solar cycle, not to exceed 10% at high latitude with a better isotropy reached at solar maxima. Limits on the dust size spectra are set from the basic features of the optical and infrared brightness distributions and variations.

  6. The F-corona and the circum-solar dust evidences and properties

    NASA Astrophysics Data System (ADS)

    Koutchmy, S.; Lamy, P. L.

    This review deals with the main properties of the F-corona. Analysis of its morphology and photometry allows to derive a new axisymmetric, non-spherical model. Polarization, color and infra-red properties are further considered. The authors suggest the existence of a variable "local" component superimposed on a quasi-stationary "far" component.

  7. Corona and solar wind

    NASA Technical Reports Server (NTRS)

    Withbroe, G. L.

    1986-01-01

    The Pinhole/Occulter Facility is a powerful tool for studying the physics of the extended corona and origins of the solar wind. Spectroscopic data acquired by the P/OF coronal instruments can greatly expand empirical information about temperatures, densities, flow velocities, magnetic fields, and chemical abundances in the corona out to r or approx. 10 solar radii. Such information is needed to provide tight empirical constraints on critical physical processes involved in the transport and dissipation of energy and momentum, the heating and acceleration of plasma, and the acceleration of energetic particles. Because of its high sensitivity, high spatial and temporal resolutions, and powerful capabilities for plasma diagnostics, P/OF can significantly increase our empirical knowledge about coronal streamers and transients and thereby advance the understanding of the physics of these phenomena. P/OF observations can be used to establish the role in solar wind generation, if any, of small-scale dynamical phenomena, such as spicules, macrospicules and coronal bullets, and the role of the fine-scale structures, such as polar plumes. Finally, simultaneous measurements by the P/OF coronal and hard X-ray instruments can provide critical empirical information concerning nonthermal energy releases and acceleration of energetic particles in the corona.

  8. The influence of circumsolar dust on the whitelight corona - Study of the visual F-corona brightness

    NASA Astrophysics Data System (ADS)

    Mann, Ingrid

    1993-04-01

    In order to discuss the benefit of whitelight observations for the understanding of dust close to the sun, the optical brightness of the Fraunhofer-corona in the visual spectral range within the ecliptic is studied in detail. The contribution of near-solar dust to the brightness is calculated and optical particle properties are derived. The brightness of the F-corona is found to result predominantly from near-solar dust and to point to a change of particle properties with solar distance r. We explain the color of the F-corona by diffraction effects, whereas the spectral variation of the albedo of dust particles has only a minor influence on the color. The polarization is shown to result from near-solar dust. A comparison of the derived polarization and albedo with optical properties known for surface structures in the Solar System shows no compatibility.

  9. Brightness of the solar F-corona

    NASA Astrophysics Data System (ADS)

    Kimura, Hiroshi; Mann, Ingrid

    1998-06-01

    We discuss our present knowledge about the brightness of the solar F-corona in the wavelength range from the visible to the middle infrared. From the general trend of the observational data, the F-corona is regarded as the continuous extension of the zodiacal light at smaller elongation of the line of sight. A contribution of thermal emission from dust is indicated by the increasing F-coronal brightness in comparison to the solar spectrum towards longer wavelength. As compared with the F-coronal brightness, the polarization and color in the visible regime are not well determined due to the high sensitivity of these quantities to the observational accuracy. Aside from observational problems, our present interpretation of the F-coronal brightness is also limited due to ambiguities in the inversion of the line of sight integral. Nevertheless, the measurements and model calculations of the brightness can be used to deduce some physical properties of dust grains. We show that the hump of the near-infrared brightness at 4 solar radii, which was sometimes observed in the corona, is related rather to the physical properties of dust grains along the line of sight than to the existence of a dust ring as previously discussed. We also show that the appearance or disappearance of the near-infrared peak in the coronal brightness cannot be described in any periodic cycle for each wavelength range.

  10. On the solar dust ring(s)

    NASA Astrophysics Data System (ADS)

    Mukai, T.

    Based on a mechanism to form the solar dust ring, it is proved that the observed peak in infrared F-corona cannot be explained by silicate type grains alone. Preliminary analysis on the recent infrared data of the F-corona by Maihara et al. (1984) has suggested that the ring particles have different physical properties compared with the dust grains, which produce the background F-corona.

  11. Interaction of dust grains with CMEs in the F corona

    NASA Astrophysics Data System (ADS)

    Ragot, B. R.; Kahler, S. W.

    2002-05-01

    The density of interplanetary dust increases Sunward to reach its maximum in the solar F corona. Although current models predict a broad range of plausible values for the total density of grains at a given distance from the Sun, the number of grains interacting with a CME around 4 solar radii is large enough to raise questions about the influence of the dust grains on the dynamics of CMEs. To answer these questions we estimate the various forces exerted on the dust grains in a CME. The enhanced magnetic field within CMEs results in the Lorentz force being the dominant force for practically all submicron particles, trapping the ones smaller than 0.1 micron and deflecting the others. For larger grains the solar gravitational force dominates, but the Lorentz force still exceeds the radiation pressure force up to almost 10 microns. In the absence of sputtering the ion drag force would become larger than the Lorentz force at about 20 microns, depending on the CME parameters. At 4 solar radii, however, a dominant contribution from the sputtered particles is expected in the ion drag force, due to the high temperature of the grains. The ion drag force from CMEs may therefore even exceed the radiation pressure force. It is in any case much larger than the Pointing-Robertson force. In conclusion it is clear that for all grain sizes, the presence of CMEs has critical effects on the dynamics of the dust grains in the F corona. It appears, however, that the dust grains have no influence on the dynamics of CMEs. The total energy lost by a CME through its interaction with the dust grains is, in the most optimistic estimate, less than one percent of the CME kinetic energy.

  12. Dynamics of interplanetary dust in the F corona

    NASA Astrophysics Data System (ADS)

    Rusk, Edwin T.

    The dynamical mechanisms in interplanetary space and in the F corona were studied using numerical simulations. An expression for the radiation pressure force due to a rotating spherical source of radiation was derived. Also, expressions relating the variation in inclination and the longitude of the ascending node to the solar magnetic field were derived. The latter are based on the spherical source surface model of the solar magnetic field. Simulation of particles released during perihelion passages of comet Encke show that cometary particles have lifetimes shorter than the lifetime calculated by Wyatt and Whipple in 1950. These simulations also resulted in higher eccentricities and a definite alignment of the particles' aphelia toward a direction 20 deg. east of the vernal equinox. An expression relating the size of a planet's zone of influence to perturbations on particles in solar orbits based on the closest approach between the planet and the particle show that the expression for the size of a planet's zone of influence is not singular, but varies with the particular orbital element which is being studied. Simulations of the interaction of the Lorentz force in the F corona, based on observed solar magnetic field values, result in a spreading of the inclinations of particles in circumsolar orbits. This result, along with a reevaluation of recent observations of the F corona, leads to the conclusion that the shape of the circumsolar dust cloud cannot be a ring, but must be a wide band or a spherical shell.

  13. F-corona-experiment: Requirements for remote sensing of interplanetary dust

    NASA Astrophysics Data System (ADS)

    Mann, Ingrid; Hartwig, Hermann

    1991-11-01

    The near solar dust that produces the brightness of the F corona represents the central region of the interplanetary dust cloud. The structure of the inner dust cloud and the properties of the near solar dust contribute to the understanding of the meteoritic complex and its relation to other constituents of the interplanetary medium. The flux rates of these micrometeorites have to be considered for the concept of near solar missions. To investigate this complex a synoptical observation in different spectral ranges is needed. The concept of the dedicated rocket-borne experiment is outlined.

  14. The solar F-corona at 2.12 pin: calculations of near-solar dust in comparison to 1991 eclipse observations

    NASA Astrophysics Data System (ADS)

    Mann, L.; MacQueen, R. M.

    1993-08-01

    A comparison of 1991 solar eclipse coronal observations over the range of 3Rsun-8Rsun at wavelength 2.12 μm, with model calculations of thermal emission and scattering from interplanetary dust particles (IDPs) is presented. The observed brightness in the ecliptic plane shows a monotonic decrease which can be approximated with a radial power law with exponent 2. No signature in the brightness, due to enhanced dust concentration or emission near the Sun can be detected. The modelling attempts result in an average deviation, relative to the observations, of less than 12%, under reasonable assumptions about the spatial distribution and optical and thermal properties of the IDPs. It is only possible to match the observational data with a model of scattering and thermal emission where particles can approach up to 3Rsun towards the Sun. The data suggest that it is necessary to alter the local variation of number density of dust particles within 10Rsun. The deduced temperature of the IDPs is about 10% below their blackbody temperature, and the best fit with observations involves a variation in the IDP albedo with distance from the Sun, suggesting physical changes to the near-solar IDP population.

  15. Solar wind acceleration in the solar corona

    NASA Technical Reports Server (NTRS)

    Giordano, S.; Antonucci, E.; Benna, C.; Kohl, J. L.; Noci, G.; Michels, J.; Fineschi, S.

    1997-01-01

    The intensity ratio of the O VI doublet in the extended area is analyzed. The O VI intensity data were obtained with the ultraviolet coronagraph spectrometer (UVCS) during the SOHO campaign 'whole sun month'. The long term observations above the north pole of the sun were used for the polar coronal data. Using these measurements, the solar wind outflow velocity in the extended corona was determined. The 100 km/s level is running along the streamer borders. The acceleration of the solar wind is found to be high in regions between streamers. In the central part of streamers, the outflow velocity of the coronal plasma remains below 100 km/s at least within 3.8 solar radii. The regions at the north and south poles, characterized by a more rapid acceleration of the solar wind, correspond to regions where the UVCS observes enhanced O VI line broadenings.

  16. The spin of cosmic dust: Rotational bursting of circumsolar dust in the F corona

    NASA Astrophysics Data System (ADS)

    Misconi, Nebil Y.

    1993-11-01

    This paper will list, investigate, and evaluate the various spin mechanisms for cosmic dust particles that have been suggested in the literature. This evaluation will concentrate on the possibility of particle fragmentation (rotational bursting) of cosmic dust. The importance of partical fragmentation is manifested by the fact that dust particle size distribution will be changed. More importantly, repeated fragmentation of interplanetary dust particles will give rise to some of the observed 'beta meteoroids.' Some of these particles are driven out of the solar system and into interstellar space by solar radiation pressure. If this mass loss mechanism is taking place in stellar systems, then it becomes a source for interstellar dust. This paper also addresses the possibility that massive rotational bursting by circumsolar dust particles is taking place in the F corona region. This rotational bursting of F coronal dust could be taking place because of the classical 'Paddack effect,' along with a similar spin mechanism suggested by the author, and caused by coronal mass ejections.

  17. Solar Corona on 08.01.2010

    NASA Video Gallery

    The solar corona on 2010/08/01, observed by SDO’s AIA. The false colors represent images taken with different filters that are sensitive to distinct coronal temperatures: blue- 1 million degrees...

  18. Solar Corona on 10.21.2010

    NASA Video Gallery

    The solar corona on 2010/10/21, observed by SDO’s AIA. The false colors represent images taken with different filters that are sensitive to distinct coronal temperatures: blue for one million de...

  19. Nanoflare heating model for collisionless solar corona

    NASA Astrophysics Data System (ADS)

    Visakh Kumar, U. L.; Varghese, Bilin Susan; Kurian, P. J.

    2017-02-01

    The problem of coronal heating remains one of the greatest unresolved problems in space science. Magnetic reconnection plays a significant role in heating the solar corona. When two oppositely directed magnetic fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of magnetic energy into thermal energy takes place. The present paper deals with a model for reconnection occurring in the solar corona under steady state in collisionless regime. The model predicts that reconnection time in the solar corona varies inversely with the cube of magnetic field and varies directly with the Lindquist number. Our analysis shows that reconnections are occurring within a time interval of 600 s in the solar corona, producing nanoflares in the energy range 10 21-10 23 erg /s which matches with Yohkoh X-ray observations.

  20. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    1998-01-01

    The coronal magnetic field defines the structure of the solar corona, the position of the heliospheric current sheet, the regions of fast and slow solar wind, and the most likely sites of coronal mass ejections. There are few measurements of the magnetic fields in the corona, but the line-of-sight component of the global magnetic fields in the photosphere have been routinely measured for many years (for example, at Stanford's Wilcox Solar Observatory, and at the National Solar Observatory at Kitt Peak). The SOI/MDI instrument is now providing high-resolution full-disk magnetograms several times a day. Understanding the large-scale structure of the solar corona and inner heliosphere requires accurately mapping the measured photospheric magnetic field into the corona and outward. Ideally, a model should not only extrapolate the magnetic field, but should self-consistently reconstruct both the plasma and magnetic fields in the corona and solar wind. Support from our NASA SR&T contract has allowed us to develop three-dimensional magnetohydrodynamic (MHD) computations of the solar corona that incorporate observed photospheric magnetic fields into the boundary conditions. These calculations not only describe the magnetic field in the corona and interplanetary spice, but also predict the plasma properties as well. Our computations thus far have been successful in reproducing many aspects of both coronal and interplanetary data, including the structure of the streamer belt, the location of coronal hole boundaries, and the position and shape of the heliospheric current sheet. The most widely used technique for extrapolating the photospheric magnetic field into the corona and heliosphere are potential field models, such as the potential field source-surface model (PFSS),and the potential field current-sheet (PFCS) model

  1. Alfven waves in the solar corona.

    PubMed

    Tomczyk, S; McIntosh, S W; Keil, S L; Judge, P G; Schad, T; Seeley, D H; Edmondson, J

    2007-08-31

    Alfvén waves, transverse incompressible magnetic oscillations, have been proposed as a possible mechanism to heat the Sun's corona to millions of degrees by transporting convective energy from the photosphere into the diffuse corona. We report the detection of Alfvén waves in intensity, line-of-sight velocity, and linear polarization images of the solar corona taken using the FeXIII 1074.7-nanometer coronal emission line with the Coronal Multi-Channel Polarimeter (CoMP) instrument at the National Solar Observatory, New Mexico. Ubiquitous upward propagating waves were seen, with phase speeds of 1 to 4 megameters per second and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. An estimate of the energy carried by the waves that we spatially resolved indicates that they are too weak to heat the solar corona; however, unresolved Alfvén waves may carry sufficient energy.

  2. Global MHD Models of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Rose, Franklin (Technical Monitor)

    2001-01-01

    Global magnetohydrodynamic (MHD) models of the solar corona are computationally intensive, numerically complex simulations that have produced important new results over the past few years. After a brief overview of how these models usually work, I will address three topics: (1) How these models are now routinely used to predict the morphology of the corona and analyze Earth and space-based remote observations of the Sun; (2) The direct application of these models to the analysis of physical processes in the corona and chromosphere and to the interpretation of in situ solar wind observations; and (3) The use of results from global models to validate the approximations used to make detailed studies of physical processes in the corona that are not otherwise possible using the global models themselves.

  3. Solar corona and prediction of the solar cycle 24 amplitude..

    NASA Astrophysics Data System (ADS)

    Pishkalo, M.

    2012-12-01

    Investigation of the solar cycle amplitude dependence on such quantitative parameters of shape and structure of the solar corona as indexes of photometrical and geometrical flattening and extension of polar coronal rays along the solar limb have been made. Observation of the solar corona during total solar eclipses in solar cycles 11-23 were used. The amplitude of solar cycle 24 was predicted on the basis of the parameters values at the cycle minimum. Solar cycle 24 is expected to be weaker than previous cycle 23. The Wolf number in the cycle maximum will amount to 83-113.

  4. Hot Plasma Flows in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Shibasaki, K.

    2012-12-01

    The Solar Corona is a non-equilibrium open system. Energy and mass are supplied from the lower atmosphere and flow upwards through the corona into the interplanetary space. Steady state could be possible but not equilibrium state. Temperature of the corona varies depending on solar activities. However, even under very quite state, coronal temperature is still kept around million degrees. Coronal heating mechanisms have to work under such condition. Temperature of plasma is an averaged kinetic energy of random motion of particles. Motion of charged particles in magnetic field generates Lorenz force and particles gyrate around magnetic field lines. Gyration of charged particles generates magnetic moment which is directed anti-parallel to the surrounding magnetic field. This is the origin of diamagnetism of plasma. Each particle can be considered as a small magnet directed opposite to the surrounding magnetic field. When these magnets are put in inhomogeneous magnetic field, they are pushed toward weak field region. In case of open magnetic field region in the solar corona, plasma particles are pushed upwards. If this force (diamagnetic or mirror force) exceeds the gravity force, plasma flows upwards. Magnetic moment of each charged particle in thermal plasma is proportional to temperature and inversely proportional to magnetic field strength. The condition for plasma to flow upwards in an open magnetic field is that the scale length of the change of magnetic field strength is shorter than the hydrostatic scale length, which is determined by temperature and the gravity acceleration. This can be a mechanism to regulate the coronal temperature around million degree. The solar corona is filled with magnetic field, which is rooted at the photosphere in the form of flux tubes. Flux tubes connect directly the corona and the sub-photospheric layer where temperature is higher than the photosphere. Hot plasma, trapped in the flux tubes when they are generated around the bottom

  5. The quiescent corona and slow solar wind

    NASA Technical Reports Server (NTRS)

    Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Gardner, L. D.; Korendyke, C. M.; Nicolosi, P.; Romoli, M.; Spadaro, D.; Maccari, L.; Raymond, J. C.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Giordano, S.; Michels, J.; Modigliani, A.; Naletto, G.

    1997-01-01

    The observations of the ultraviolet coronagraph spectrometer (UVCS), operating onboard the Solar and Heliospheric Observatory (SOHO) spacecraft, are discussed. The purpose of the UVCS is the study of the quiescent coronal streamer and the slow solar wind. The observations started in January 1996. Polarized radiance data in the visible continuum were obtained. Some characteristics of the coronal streamer from the UVCS recorded data are discussed. A model for the source of the slow solar wind in the inner corona is proposed.

  6. 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.

  7. Observations of the dust radial velocity field in the F-corona on March 29, 2006

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.; Demchenko, B. I.; Rspaev, F. K.; Chalabaev, A.

    2011-12-01

    The results of interferometer observations of the dust radial velocity field in the F-corona during the total solar eclipse of March 29, 2006, are presented. The observations were performed in the Mugalzhar settlement, Aqtobe region, Kazakhstan. The observation results indicated that the dust orbital motion is opposite to the planetary motion and is inclined at an angle of about 105° with respect to the ecliptic plane. It is assumed that the observed dust is genetically related to Kreutz comets falling on the Sun and registered with the SOHO spacecraft on March 28 and 31, 2006.

  8. Scattering models for the solar infrared F-corona brightness

    NASA Astrophysics Data System (ADS)

    Davidson, W. C.; MacQueen, R. M.; Mann, I.

    1995-02-01

    Model calculations are made of the infrared brightness in the solar F-corona motivated by recent infrared solar eclipse observations. Two different approaches are employed to describe the scattering properties of interplanetary dust : Mie scattering theory and diffraction theory, with and without an isotropic scattering term. In addition. two different particle size distributions are used in the calculations and the resultant line of sight brightness is compared with observational data of the solar F-corona between 3 and 8 solar radii ( R) in the ecliptic plane. It is found that the use of diffraction theory without an isotropic scattering contribution gives a very poor match with the observations, for both assumed particle size distributions. However, both the diffraction theory including isotropic scattering and the Mie scattering theory agree reasonably with the observed brightness, and especially its radial slope within the corona. for the model size distribution which is dominated by large particles. Only Mie theory may be employed in describing the second model size distribution because diffraction theory poorly describes the scattering due to the small particles which dominate this size distribution. It is concluded that the derivation of particle size distributions from the F-coronal brightness is still ambiguous and a further analysis needs either improved observations, or the application of further reasonable physical assumptions.

  9. 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.

  10. The F and K components of the solar corona.

    NASA Technical Reports Server (NTRS)

    Calbert, R.; Beard, D. B.

    1972-01-01

    Numerical calculations of the F component are conducted for a large range of parameters, particle size distribution, minimum particle size, minimum approach to the sun, albedo, and spatial distribution. Various parametrized functional forms for the electron spatial distribution are assumed, and the parametrical elongation dependence of the K component is calculated. New and old data are analyzed by fitting the theoretical parametrized elongation dependence to observations of the total intensity of the solar corona. The orbital behavior of the dust is estimated together with the temperature and thermal emission.

  11. STOCHASTIC COUPLING OF SOLAR PHOTOSPHERE AND CORONA

    SciTech Connect

    Uritsky, Vadim M.; Ofman, Leon; Davila, Joseph M.; Coyner, Aaron J.

    2013-05-20

    The observed solar activity is believed to be driven by the dissipation of nonpotential magnetic energy injected into the corona by dynamic processes in the photosphere. The enormous range of scales involved in the interaction makes it difficult to track down the photospheric origin of each coronal dissipation event, especially in the presence of complex magnetic topologies. In this paper, we propose an ensemble-based approach for testing the photosphere-corona coupling in a quiet solar region as represented by intermittent activity in Solar and Heliospheric Observatory Michelson Doppler Imager and Solar TErrestrial RElations Observatory Extreme Ultraviolet Imager image sets. For properly adjusted detection thresholds corresponding to the same degree of intermittency in the photosphere and corona, the dynamics of the two solar regions is described by the same occurrence probability distributions of energy release events but significantly different geometric properties. We derive a set of scaling relations reconciling the two groups of results and enabling statistical description of coronal dynamics based on photospheric observations. Our analysis suggests that multiscale intermittent dissipation in the corona at spatial scales >3 Mm is controlled by turbulent photospheric convection. Complex topology of the photospheric network makes this coupling essentially nonlocal and non-deterministic. Our results are in an agreement with the Parker's coupling scenario in which random photospheric shuffling generates marginally stable magnetic discontinuities at the coronal level, but they are also consistent with an impulsive wave heating involving multiscale Alfvenic wave packets and/or magnetohydrodynamic turbulent cascade. A back-reaction on the photosphere due to coronal magnetic reconfiguration can be a contributing factor.

  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

  13. Nanoflare Heating of Solar and Stellar Coronae

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.

    2010-01-01

    A combination of observational and theoretical evidence suggests that much, and perhaps most, of the Sun's corona is heated by small unresolved bursts of energy called nanoflares. It seems likely that stellar coronae are heated in a similar fashion. Kanoflares are here taken to mean any impulsive heating that occurs within a magnetic flux strand. Many mechanisms have this property, including waves, but we prefer Parker's picture of tangled magnetic fields. The tangling is caused by turbulent convection at the stellar surface, and magnetic energy is released when the stresses reach a critical level. We suggest that the mechanism of energy release is the "secondary instability" of electric current sheets that are present at the boundaries between misaligned strands. I will discuss the collective evidence for solar and stellar nanoflares and hopefully present new results from the Solar Dynamics Observatory that was just launched.

  14. Solar Corona Explorer: A mission for the physical diagnosis of the solar corona

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Mission objectives and spacecraft requirements for the Solar Corona Explorer (SCE), a proposed free flying, unmanned solar research craft to be tenatively launched in 1987, were defined. The SCE's purpose is to investigate structure, dynamics and evolution of the corona, globally and in the required physical detail, to study the close coupling between the inner corona and the heliosphere. Investigative objectives are: (1) to understand the corona as the source of varying interplanetary plasma and of varying solar X-ray and extreme ultraviolet fluxes; (2) to develop the capabilities to model the corona with sufficient precision to forecast the Earth's variable environment in space, on the scales from weeks to years; (3) to develop an understanding of the physical processes that determine the dynamics and physical state of the coronal plasma, particularly acceleration processes; and (4) to develop insight and test theory on the Sun applicable to stellar coronae and winds, and in particular, to understand why cool stars put such a large fraction of their energy into X-rays. Considered related factors are: (1) duration of the mission; (2) onboard measuring instrumentation; (3) ground support equipment and procedures; and (4) programs of interpretation and modeling.

  15. Radio seismology of the outer solar corona

    NASA Astrophysics Data System (ADS)

    Zaqarashvili, Teimuraz; Melnik, Valentin; Brazhenko, Anatoliy; Panchenko, Mykhaylo; Konovalenko, Alexander; Dorovskyy, Vladimir; Rucker, Helmut

    2014-05-01

    Observed oscillations of coronal loops in extreme ultraviolet (EUV) lines have been successfully used to estimate plasma parameters in the inner corona (< 0.2R0, where R0 is the solar radius). However, coronal seismology in EUV lines fails for higher altitudes because of rapid decrease in line intensity. We aim to use radio observations to estimate the plasma parameters of the outer solar corona (> 0.2R0). We used the large Ukrainian radio telescope URAN-2 to observe type IV radio bursts at the frequency range of 8-32 MHz during the time interval of 09:50-12:30 UT on April 14, 2011. The burst was connected to C2.3 flare, which occurred in AR 11190 during 09:38-09:49 UT. The dynamic spectrum of radio emission shows clear quasi-periodic variations in the emission intensity at almost all frequencies. Wavelet analysis at four different frequencies (29 MHz, 25 MHz, 22 MHz, and 14 MHz) shows the quasi-periodic variation of emission intensity with periods of ~ 34 min and ~ 23 min. The periodic variations can be explained by the first and second harmonics of vertical kink oscillation of transequatorial coronal loops, which were excited by the same flare. The apex of transequatorial loops may reach up to 1.2 R0 altitude. We derive and solve the dispersion relation of trapped magnetohydrodynamic (MHD) oscillations in a longitudinally inhomogeneous magnetic slab. The analysis shows that a thin (with width to length ratio of 0.1), dense (with the ratio of internal and external densities of ≥ 20) magnetic slab with weak longitudinal inhomogeneity may trap the observed oscillations. Seismologically estimated Alfvén speed inside the loop at the height of ~ 1 R0 is ~ 1000 km s-1. The magnetic field strength at this height is estimated as ~ 0.9 G. Extrapolation of magnetic field strength to the inner corona gives ~ 10 G at the height of 0.1 R0. Radio observations can be successfully used for the sounding of the outer solar corona, where EUV observations of coronal loops fail

  16. Radio seismology of the outer solar corona

    NASA Astrophysics Data System (ADS)

    Zaqarashvili, T. V.; Melnik, V. N.; Brazhenko, A. I.; Panchenko, M.; Konovalenko, A. A.; Franzuzenko, A. V.; Dorovskyy, V. V.; Rucker, H. O.

    2013-07-01

    Context. Observed oscillations of coronal loops in extreme ultraviolet (EUV) lines have been successfully used to estimate plasma parameters in the inner corona (<0.2 R0, where R0 is the solar radius). However, coronal seismology in EUV lines fails for higher altitudes because of rapid decrease in line intensity. Aims: We aim to use radio observations to estimate the plasma parameters of the outer solar corona (>0.2 R0). Methods: We used the large Ukrainian radio telescope URAN-2 to observe type IV radio bursts at the frequency range of 8-32 MHz during the time interval of 09:50-12:30 UT on April 14, 2011. The burst was connected to C2.3 flare, which occurred in AR 11190 during 09:38-09:49 UT. The dynamic spectrum of radio emission shows clear quasi-periodic variations in the emission intensity at almost all frequencies. Results: Wavelet analysis at four different frequencies (29 MHz, 25 MHz, 22 MHz, and 14 MHz) shows the quasi-periodic variation of emission intensity with periods of ~34 min and ~23 min. The periodic variations can be explained by the first and second harmonics of vertical kink oscillation of transequatorial coronal loops, which were excited by the same flare. The apex of transequatorial loops may reach up to 1.2 R0 altitude. We derive and solve the dispersion relation of trapped magnetohydrodynamic oscillations in a longitudinally inhomogeneous magnetic slab. The analysis shows that a thin (with width to length ratio of 0.1), dense (with the ratio of internal and external densities of ≥20) magnetic slab with weak longitudinal inhomogeneity of the Alfvén speed may trap the observed oscillations. Seismologically estimated Alfvén speed inside the loop at the height of ~1 R0 is ~1000 km s-1. The magnetic field strength at this height is estimated as ~0.9 G. Extrapolation of magnetic field strength to the inner corona gives ~10 G at the height of 0.1 R0. Conclusions: Radio observations can be successfully used for the sounding of the outer solar

  17. 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.

  18. Heating mechanisms of the solar corona

    NASA Astrophysics Data System (ADS)

    Sakurai, Takashi

    2017-02-01

    The solar corona is a tenuous outer atmosphere of the Sun. Its million-degree temperature was discovered spectroscopically in the 1940s, but its origin has been debated since then without complete convergence. Currently there are two classes of models; the wave theory and the microflare/nanoflare theory. Both models have merits and disadvantages, but the essential issues are nearly pinned down. Recent revival of the wave theory is one of the many contributions from Japanese solar observing satellite Hinode launched in 2006.

  19. Heating mechanisms of the solar corona.

    PubMed

    Sakurai, Takashi

    2017-01-01

    The solar corona is a tenuous outer atmosphere of the Sun. Its million-degree temperature was discovered spectroscopically in the 1940s, but its origin has been debated since then without complete convergence. Currently there are two classes of models; the wave theory and the microflare/nanoflare theory. Both models have merits and disadvantages, but the essential issues are nearly pinned down. Recent revival of the wave theory is one of the many contributions from Japanese solar observing satellite Hinode launched in 2006.

  20. Scintillation effects on radio wave propagation through solar corona

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Sue, M. K.; Bedrossian, A.; Sniffin, R. W.

    2002-01-01

    When RF waves pass through the solar corona and solar wind regions close to the Sun, strong scintillation effects appear at their amplitude, frequency and phase, especially in the regions very close to the Sun (less than 4 solar radius).

  1. Ultraviolet spectroscopy of the extended solar corona

    NASA Astrophysics Data System (ADS)

    Kohl, John L.; Noci, Giancarlo; Cranmer, Steven R.; Raymond, John C.

    2006-04-01

    The first observations of ultraviolet spectral line profiles and intensities from the extended solar corona (i.e., more than 1.5 solar radii from Sun-center) were obtained on 13 April 1979 when a rocket-borne ultraviolet coronagraph spectrometer of the Harvard-Smithsonian Center for Astrophysics made direct measurements of proton kinetic temperatures, and obtained upper limits on outflow velocities in a quiet coronal region and a polar coronal hole. Following those observations, ultraviolet coronagraphic spectroscopy has expanded to include observations of over 60 spectral lines in coronal holes, streamers, coronal jets, and solar flare/coronal mass ejection (CME) events. Spectroscopic diagnostic techniques have been developed to determine proton, electron and ion kinetic temperatures and velocity distributions, proton and ion bulk flow speeds and chemical abundances. The observations have been made during three sounding rocket flights, four Shuttle deployed and retrieved Spartan 201 flights, and the Solar and Heliospheric Observatory (SOHO) mission. Ultraviolet spectroscopy of the extended solar corona has led to fundamentally new views of the acceleration regions of the solar wind and CMEs. Observations with the Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO revealed surprisingly large temperatures, outflow speeds, and velocity distribution anisotropies in coronal holes, especially for minor ions. Those measurements have guided theorists to discard some candidate physical processes of solar wind acceleration and to increase and expand investigations of ion cyclotron resonance and related processes. Analyses of UVCS observations of CME plasma properties and the evolution of CMEs have provided the following: temperatures, inflow velocities and derived values of resistivity and reconnection rates in CME current sheets, compression ratios and extremely high ion temperatures behind CME shocks, and three dimensional flow velocities and magnetic field chirality in

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

    SciTech Connect

    Clayton, Geoffrey C.; Zhang Wanshu; Geballe, T. R. E-mail: wzhan21@lsu.edu

    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.

  3. Miniature loops in the solar corona

    NASA Astrophysics Data System (ADS)

    Barczynski, K.; Peter, H.; Savage, S. L.

    2017-03-01

    Context. Magnetic loops filled with hot plasma are the main building blocks of the solar corona. Usually they have lengths of the order of the barometric scale height in the corona that is 50 Mm. Aims: Previously it has been suggested that miniature versions of hot loops exist. These would have lengths of only 1 Mm barely protruding from the chromosphere and spanning across just one granule in the photosphere. Such short loops are well established at transition region temperatures (0.1 MK), and we investigate if such miniature loops also exist at coronal temperatures (>1 MK). Methods: We used extreme UV (EUV) imaging observations from the High-resolution Coronal Imager (Hi-C) at an unprecedented spatial resolution of 0.3'' to 0.4''. Together with EUV imaging and magnetogram data from the Solar Dynamics Observatory (SDO) and X-Ray Telescope (XRT) data from Hinode we investigated the spatial, temporal and thermal evolution of small loop-like structures in the solar corona above a plage region close to an active region and compared this to a moss area within the active region. Results: We find that the size, motion and temporal evolution of the loop-like features are consistent with photospheric motions, suggesting a close connection to the photospheric magnetic field. Aligned magnetograms show that one of their endpoints is rooted at a magnetic concentration. Their thermal structure, as revealed together with the X-ray observations, shows significant differences to moss-like features. Conclusions: Considering different scenarios, these features are most probably miniature versions of hot loops rooted at magnetic concentrations at opposite sides of a granule in small emerging magnetic loops (or flux tubes).

  4. Restitution of multiple overlaid components on extremely long series of solar corona images

    NASA Astrophysics Data System (ADS)

    Llebaria, A.; Loirat, J.; Lamy, P.

    2010-01-01

    This contribution describes the methods used to accurately disentangle the components observed on a very large series of images of the solar corona. This series consists of 12 years of continuous observations provided by the LASCO/C2 coronagraph aboard SOHO (the SOlar and Heliospheric Observatory). Continuously centred on the Sun, which is masked, the observed images display a blend of many components. The more conspicuous are the K-corona from the coronal plasma, the F-corona from the coronal dust and the instrumental straylight. All of them are optically thin but in the LASCO/C2 field of view only the K-corona is polarized. The set of observations is composed of two huge series of images: the "polarization series" (at least one observation every day) and the "white light series" (more than 50 images every day). The goal is to determine quantitatively the evolution of each image component during the 12 years. Assuming 1) a small and slow temporal evolution for the F-corona and straylight, 2) the 2D regularity of the F-corona and 3) the ability to deduce the influence of the SOHO-Sun distance, the F-corona function is determined from the polarized series and afterwards subtracted of the white light series to obtain the K-corona white light series.

  5. The J- and K-Band Brightness of the Solar F-Corona Observed During the Solar Eclipse on February 26, 1998

    NASA Astrophysics Data System (ADS)

    Ohgaito, R.; Mann, I.; Kuhn, J. R.; MacQueen, R. M.; Lin, H.; Edmunds, D.

    1999-09-01

    The solar eclipse on February 26 1998 was observed from an open flying aircraft at an altitude of almost 6 km above the Pacific about 800 km southwest from Panama City. The solar F-corona, produced by light scattering and thermal emission from dust around the Sun, was observed with a low atmospheric straylight level in the J and K-band over a field of view of 7 degrees. The data show no indication for the existence of pronounced brightness features in the solar F-corona, such as often discussed as evidence for the existence of dust rings. The shape of the corona is slightly elliptic but symmetric in the north-south direction. The data show a reddening of the coronal brightness compared to the solar spectrum. The color of the F-corona is influenced by the temperature of dust particles, by their spatial distribution, as well as by their size distribution that influences especially the forward scattering that is seen in the corona from dust particles close to the observer. We will discuss the color variation from the solar equator to the solar pole and with distances from the Sun and compare it to models of dust light scattering and thermal emission.

  6. On the evolution of dust in the solar vicinity

    NASA Astrophysics Data System (ADS)

    Mann, I.; Mukai, T.; Okamoto, H.

    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.

  7. On the evolution of dust in the solar vicinity

    NASA Astrophysics Data System (ADS)

    Mann, I.; Mukai, T.; Okamoto, H.

    1995-07-01

    The analysis of interplanetary dust shows that the majority of particles in out-of-ecliptic regions come from comets and also that near solar dust, in the ecliptic regions, results are 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 color 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 sillicate 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.

  8. Untwisting magnetic fields in the solar corona

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Ramit; Smolarkiewicz, Piotr; Chye Low, Boon

    2012-07-01

    The solar corona is the tenuous atmosphere of the Sun characterized by a temperature of the order of million degrees Kelvin, an ambient magnetic field of 10 to 15 Gauss and a very high magnetic Reynolds number because of which it qualifies as a near-ideal magnetofluid system. It is well known that for such a system, the magnetic flux across every fluid surface remains effectively constant to a good approximation. Under this so called ``frozen-in'' condition then, it is possible to partition this magnetofluid into contiguous magnetic subvolumes each entrapping its own subsystem of magnetic flux. Thin magnetic flux tubes are an elementary example of such magnetic subvolumes evolving in time with no exchange of fluid among them. The internal twists and interweaving of these flux tubes, collectively referred as the magnetic topology, remains conserved under the frozen-in condition. Because of the dynamical evolution of the magnetofluid, two such subvolumes can come into direct contact with each other by expelling a third interstitial subvolume. In this process, the magnetic field may become discontinuous across the surface of contact by forming a current sheet there. Because of the small spatial scales generated by steepening of magnetic field gradient, the otherwise negligible resistivity becomes dominant and allows for reconnection of field lines which converts magnetic energy into heat. This phenomenon of spontaneous current sheet formation and its subsequent resistive decay is believed to be a possible mechanism for heating the solar corona to its million degree Kelvin temperature. In this work the dynamics of spontaneous current sheet formation is explored through numerical simulations and the results are presented.

  9. A study of the background corona near solar minimum

    NASA Technical Reports Server (NTRS)

    Saito, K.; Poland, A. I.; Munro, R. H.

    1977-01-01

    Equatorial and polar K and F coronal components during the declining phase of the solar cycle are studied through use of the white light coronagraph data obtained by Skylab. At this phase of the solar cycle, streams and holes dominate the equatorial corona (approximately 50 and 30% of the time, respectively) between 2.5 and 5.5 solar radii; however, two episodes are noted when equatorial background density of the corona could be distinguished. The derived background density is less than 15% below values predicted by the models of Newkirk (1967) and Saito (1970). The brightness of the F-corona is also discussed.

  10. 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.

  11. Long-term variations in dust production in R Coronae Borealis

    NASA Technical Reports Server (NTRS)

    Clayton, Geoffrey C.; Whitney, Barbara A.; Mattei, Janet A.

    1993-01-01

    Several searches for periodicities in the historical visible light curves of RCB stars have found that the intervals between declines are random. This paper reexamines 70 declines of R Coronae Borealis since 1853 using one homogeneous data set, the AAVSO light curve. In this data set, pairs of consecutive declines also show a random distribution of intervals. However, if the sequence of declines is examined, there are semiperiodic variations between times of high- and low-decline activity on a time scale of a few years. Near-IR photometry of RCB stars indicates that there are large semiperiodic variations in the amount of dust being produced which have similar time scales. Possible interpretations of a semiperiodic variation in dust formation rates in RCB stars are presented. One is a magnetic activity cycle resulting in 'spots' on the star over which dust formation takes place. Such a magnetic activity cycle is similar to the solar cycle. Another is the changes in the period and amplitude of the pulsations over several years affecting the efficiency of dust production.

  12. Observational Associations Between the Solar Corona and Solar Interior

    NASA Astrophysics Data System (ADS)

    Woo, R.; Armstrong, J. W.; Habbal, S. R.; Habbal, S. R.

    2001-12-01

    Generated in the solar interior, magnetic fields make their way through the solar atmosphere, shaping solar wind flow and determining solar activity. Although essential for understanding and identifying the physical processes by which this occurs, there has been a lack of observational associations between the corona and interior of the Sun. A direct association was recently demonstrated when the latitudinal profile of the correlation of coronal density separated in latitude by 20 degrees was found to be similar to that of the alternating slow and fast zonal bands observed in the outer part of the solar convection zone (Woo et al., ApJ., 538, L171, 2000). The latter are also evident on the surface of the Sun where they are known as torsional oscillations. In this paper, we summarize further results from investigating and characterizing the morphology of coronal density and its relationship to surface and subsurface solar flow using measurements by the High Altitude Observatory Mauna Loa Mk III K-coronameter.

  13. The J- and K-Band Brightness of the Solar F Corona Observed during the Solar Eclipse on 1998 February 26

    NASA Astrophysics Data System (ADS)

    Ohgaito, R.; Mann, I.; Kuhn, J. R.; MacQueen, R. M.; Kimura, H.

    2002-10-01

    We analyze J- and K-band observations of the 1998 solar eclipse and derive the F-corona brightness in the K band between 3 and 7 Rsolar from the center of the Sun and in the J band out to 5 Rsolar. The falloff in the K-band brightness from 3 to 7 Rsolar is fitted with a radial power law with exponent -2.4+/-0.1 at the solar equator and with exponent -2.9+0.2-0.1 at the solar pole. This slope is gentler than that derived from observations in 1983 but is steeper than that derived from observations for the 1991 eclipse. The radial profiles agree well with models that explain the F corona with weakly absorbing dust particles. Comparison of the J- and K-band brightness at 3 Rsolar from the center of the Sun indicates a reddening of the F corona with respect to the solar spectrum. The reddening is, however, less pronounced compared to the F corona observed during the 1983 total solar eclipse. This fact may be attributed to a change in the composition of dust near the Sun. As with the radial profiles, the reddening in 1998 is better explained with models that assume weakly absorbing rather than strongly absorbing dust particles in the solar corona. Similar to recent eclipse observations, we do not detect an excess emission feature of near-solar dust in the F corona. We hence can reject the hypothesis that suggests a correlation between the detection of an emission feature and the solar activity cycle.

  14. Dynamics of interplanetary dust in the F corona

    SciTech Connect

    Rusk, E.T.

    1986-01-01

    Dynamical mechanisms in interplanetary space and in the F corona were studied by numerical simulations. An expression for the radiation pressure force due to a rotating spherical source of radiation was derived. Also, expressions relating the variation in inclination and the longitude of the ascending node to the solar magnetic field were derived. These expressions are based on the spherical source surface model of the solar magnetic field. Simulations of particles released during perihelion passages of comet Encke show that cometary particles have lifetimes shorter than the lifetime calculated by Wyatt and Whipple in 1950. These simulations also resulted in higher eccentricities and a definite alignment of the particles' aphelia toward a direction 20/sup 0/ east of the vernal equinox. An expression relating the size of a planet's zone of influence to perturbations on particles in solar orbits based on the closest approach between the planet and the particle show that the expression for the size of planet's zone of influence is not singular, but varies with the particular orbital element which is being studied.

  15. The circumsolar dust complex and solar magnetic field

    NASA Astrophysics Data System (ADS)

    Krivov, Alexander; Mann, Ingrid; Kimura, Hiroshi

    1998-06-01

    New model calculations for the dynamical evolution of dust particles at several solar radii around the Sun are presented. We choose a fractal aggregate consisting of either silicate or carbon as a representative of dielectric and absorbing fluffy particles. We take into account a large array of forces and effects acting on the dust particles—solar gravity, direct solar radiation pressure, Poynting-Robertson effect, sublimation, and the Lorentz force, with a special emphasis given to the latter. The Lorentz force was computed on the base of modeled grain's charges and a model of the actual solar magnetic field from 1976 to 1996. We have investigated the dynamics of individual grains, obtained radial and vertical density profiles of different-sized particles, and used the computed dust density distributions to calculate the expected F-corona brightness during the periods of weak and strong magnetic field. We have found that the solar magnetic field and its variations do not affect the dynamics and spatial distribution of carbon aggregates, which are thought to produce the peak features of the near-infrared F-corona brightness that were sometimes observed. On the other hand, the variations of the solar magnetic field may alter the latitudinal distribution of silicate aggregates. However, the effect is not strong enough to account for the observed temporal variations in the brightness. Thus we can rule out the correlation between the appearance or disappearance of a peak feature and the solar activity cycle.

  16. Broadband Spectroscopy of the Corona during the Total Solar Eclipse of March 29, 2006

    NASA Astrophysics Data System (ADS)

    Jaeggli, Sarah A.; Habbal, S. R.; Kuhn, J. R.; Nayfeh, M. H.

    2006-12-01

    We present coronal observations from the total solar eclipse of 29 March 2006 taken near Waw al Namus, Libya. During the 4 minutes and 6 seconds of totality, observations were made with a tracking collecting mirror and fiber-fed spectrograph. The spectrograph used is a high quantum efficiency commercial Ocean Optics QE65000 Spectrometer with a wavelength range of 350 to 1100 nm, and spectral resolution of about 0.75 nm. High quantum efficiency allowed for many short exposures of the inner (100 msec) and outer (10,000 msec) corona during the eclipse. Important spectral features, and the difference in color between the inner and outer corona are identified. Atmospheric contributions are discussed. Likely candidates for the nature of dust grains contributing to the F-corona measurements are also presented. These are compared with laboratory spectra of silicon nanoparticles.

  17. 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

    2011-01-07

    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.

  18. Results of observations of the dust distribution in the F-corona of the sun

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.; Demchenko, B. I.

    2016-03-01

    The results of modeling of the distribution of dust in the circumsolar zone are presented. The dust distribution was retrieved from observations of the line-of-sight velocities in the F-corona to the distances of 7-11 solar radii during the total eclipses of the Sun in different years: on July 31, 1981; August 11, 1991; March 29, 2006; and August 1, 2008. Comparison of the results has shown that the dust composition varies from year to year and the dust is dynamically nonuniform. In addition to the dust related to the zodiacal cloud and concentrating to the ecliptic plane, the dust of retrograde motion and the ejections and accretion in the polar regions are observed. From the results of observations of eclipses on July 31, 1981, August 11, 1991, and August 1, 2008, the east-west asymmetry in a sign of the line-of-sight velocities was detected: they are negative to the east of the Sun and positive to the west. Such distribution of the velocities is indicative of the nearecliptic orbital dust motion, whose direction coincides with that of the motion of the planets. In the course of the eclipse of March 29, 2006, almost no dynamical connection with the zodiacal cloud was found. At the same time, the direction, where the observed velocities are largest in value and opposite in sign on opposite sides of the Sun, was determined, which provides evidence of the orbital motion deviating from the ecliptic plane. The results of observations in 2006 reveal a clear genetic connection of the observed orbital motion of dust with the parent comets of the Kreutz family found near the Sun close to the eclipse date. The velocities observed near the symmetry line in the plane of the sky grow by absolute value with increasing the elongation, which may take place, if the line of sight croßses an empty zone that is free of dust. The modeling of the data of observations near the symmetry plane allowed the parameters of the dust distribution near the sublimation zone to be obtained. In

  19. Shape parameters of the solar corona from 1991 to 2016

    NASA Astrophysics Data System (ADS)

    Priyatikanto, Rhorom

    2016-12-01

    The global structure of the solar corona observed in the optical window is governed by the global magnetic field with different characteristics over a solar activity cycle. The Ludendorff flattening index has become a popular measure of global structure of the solar corona as observed during an eclipse. In this study, 15 digital images of the solar corona from 1991 to 2016 were analyzed in order to construct coronal flattening profiles as a function of radius. In most cases, the profile can be modeled with a 2nd order polynomial function so that the radius with maximum flattening index (Rmax) can be determined. Along with this value, Ludendorff index (a + b) was also calculated. Both Ludendorff index and Rmax show anti-correlation with monthly sunspot number, though the Rmax values are more scattered. The variation in Rmax can be regarded as the impact of the changing coronal brightness profile over the equator.

  20. Peculiarities of propagation of charged particles in solar corona

    NASA Technical Reports Server (NTRS)

    Morozova, E. I.; Pisarenko, N. F.; Mikryukova, N. A.; Klimenko, V. V.; Timofeev, V. E.; Shafer, Y. G.

    1985-01-01

    The influence of boundaries of the large scale unipolar magnetic regions (UMR) on the Sun upon the charged particle propagation in the solar corona and interplanetary space is investigated. Increases of the charged particle fluxes from solar flares on November 4 and 20, 1978 detected by Venera-11 and Prognoz-1 and on December 7, 1982 by Venera-13 and "GMS-2" were analyzed.

  1. Patchy reconnection in the solar corona

    NASA Astrophysics Data System (ADS)

    Guidoni, Silvina Esther

    2011-05-01

    Magnetic reconnection in plasmas, a process characterized by a change in connectivity of field lines that are broken and connected to other ones with different topology, owes its usefulness to its ability to unify a wide range of phenomena within a single universal principle. There are newly observed phenomena in the solar corona that cannot be reconciled with two-dimensional or steady-state standard models of magnetic reconnection. Supra-arcade downflows (SADs) and supra-arcade downflowing loops (SADLs) descending from reconnection regions toward solar post-flare arcades seem to be two different observational signatures of retracting, isolated reconnected flux tubes with irreducible three-dimensional geometries. This dissertation describes work in refining and improving a novel model of patchy reconnection, where only a small bundle of field lines is reconnected across a current sheet (magnetic discontinuity) and forms a reconnected thin flux tube. Traditional models have not been able to explain why some of the observed SADs appear to be hot and relatively devoid of plasma. The present work shows that plasma depletion naturally occurs in flux tubes that are reconnected across nonuniform current sheets and slide trough regions of decreasing magnetic field magnitude. Moreover, through a detailed theoretical analysis of generalized thin flux tube equations, we show that the addition to the model of pressure-driven parallel dynamics, as well as temperature-dependent, anisotropic viscosity and thermal conductivity is essential for self-consistently producing gas-dynamic shocks inside reconnected tubes that heat and compress plasma to observed temperatures and densities. The shock thickness can be as long as the entire tube and heat can be conducted along tube's legs, possibly driving chromospheric evaporation. We developed a computer program that solves numerically the thin flux tube equations that govern the retraction of reconnected tubes. Simulations carried out

  2. Solar aureoles caused by dust, smoke, and haze.

    PubMed

    Mims, Forrest M

    2003-01-20

    The forward scattering of sunlight by atmospheric aerosols causes a bright glow to appear around the Sun. This phenomenon, the simplest manifestation of the solar corona, is called the solar aureole. Simple methods can be used to photograph the solar aureole with conventional and digital cameras. Aureole images permit both a visually qualitative and an analytically quantitative comparison of aureoles caused by dust, smoke, haze, pollen, and other aerosols. Many hundreds of aureole photographs have been made at Geronimo Creek Observatory in Texas, including a regular time series since September 1998. These images, and measurements extracted from them, provide an important supplement to studies of atmospheric aerosols.

  3. On the Use of Total Brightness Measurements for Tomography of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Frazin, R. A.; Kamalabadi, F.

    2005-08-01

    A time series of polarized white light coronagraph images may be used to make a tomographic estimate of the electron density (Ne) in three dimensions, as has been demonstrated by several authors. This technique has come to be known as solar rotational tomography (SRT). SRT relies on the fact that the polarized brightness (pB) is dominated by the electron-scattered K corona. In contrast, the total brightness contains a large contribution from the dust-scattered F-corona with some signal from the K corona. The K-corona contribution to the total brightness (B) is of interest because the Thomson scattering has different angular dependences for the polarized and unpolarized components. This difference in angular dependence in principle allows one to exploit total brightness measurements as a source of independent information for SRT. In this paper the problem of making optimal tomographic estimates of Ne using both total and polarized brightness data is considered under the assumption that the F-corona contribution can be determined with a known level of precision. Formulae for the reconstructions and the likely errors are given in terms of the singular value decomposition of the weighted measurement operators. It is shown that in order for the total brightness measurements to be useful for SRT, the process of removing the F-corona contribution must be almost perfect in the sense that it contributes uncertainty that is not much greater than the measurement noise in the polarized images. This result holds at heights below roughly 15 solar radii, where the F corona is almost completely unpolarized.

  4. 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

  5. HIGH SPATIAL RESOLUTION OBSERVATIONS OF LOOPS IN THE SOLAR CORONA

    SciTech Connect

    Brooks, David H.; Ugarte-Urra, Ignacio; Warren, Harry P.; Winebarger, Amy R.

    2013-08-01

    Understanding how the solar corona is structured is of fundamental importance to determine how the Sun's upper atmosphere is heated to high temperatures. Recent spectroscopic studies have suggested that an instrument with a spatial resolution of 200 km or better is necessary to resolve coronal loops. The High Resolution Coronal Imager (Hi-C) achieved this performance on a rocket flight in 2012 July. We use Hi-C data to measure the Gaussian widths of 91 loops observed in the solar corona and find a distribution that peaks at about 270 km. We also use Atmospheric Imaging Assembly data for a subset of these loops and find temperature distributions that are generally very narrow. These observations provide further evidence that loops in the solar corona are often structured at a scale of several hundred kilometers, well above the spatial scale of many proposed physical mechanisms.

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

    PubMed

    Soja, B; Heinkelmann, R; Schuh, H

    2014-06-20

    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.

  7. A theory of heating of quiet solar corona

    SciTech Connect

    Wu, C. S.; Yoon, P. H.; Wang, C. B.

    2015-03-15

    A theory is proposed to discuss the creation of hot solar corona. We pay special attention to the transition region and the low corona, and consider that the sun is quiet. The proposed scenario suggests that the protons are heated by intrinsic Alfvénic turbulence, while the ambient electrons are heated by the hot protons via collisions. The theory contains two prime components: the generation of the Alfvénic fluctuations by the heavy minor ions in the transition region and second, the explanation of the temperature profile in the low solar atmosphere. The proposed heating process operates continuously in time and globally in space.

  8. Solar Wind Speed Charged Dust

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Weimer, D.; Jian, L. K.; Luhmann, J. G.; Omidi, N.

    2009-04-01

    The correlation of the occurrence of magnetic disturbances, known as interplanetary field enhancements (IFEs), with the asteroid 2201 Oljato can only be explained as the interaction with charged dust in the asteroid's orbit, because the events occurred both before and after alignment with the asteroid. These single spacecraft observations did not determine how fast the dust was accelerated, or if they were affected at all by the solar wind. Shortly after STEREO A and B were launched, an IFE crossed the two spacecraft as well as ACE and Wind. This four-spacecraft configuration allowed us to determine that the disturbance was moving radially outward at 700 km/s, the solar wind speed. The conventional wisdom is that only the smallest dust particles can be affected by the solar wind, but examination of periods on STEREO when the spacecraft is being sprayed with multiple beta-meteoroid strikes shows no obvious correlation. Further, the IFEs are much less frequent than the "beta-meteoroid" impacts. Hence, it is possible that IFEs are associated with much larger dust particles, perhaps 1 micron-sized dust. If true, then those particles may be very dangerous albeit rare, possessing about 104 ergs.

  9. Time-dependent tomographic reconstruction of the solar corona

    NASA Astrophysics Data System (ADS)

    Vibert, D.; Peillon, C.; Lamy, P.; Frazin, R. A.; Wojak, J.

    2016-10-01

    Solar rotational tomography (SRT) applied to white-light coronal images observed at multiple aspect angles has been the preferred approach for determining the three-dimensional (3D) electron density structure of the solar corona. However, it is seriously hampered by the restrictive assumption that the corona is time-invariant which introduces significant errors in the reconstruction. We first explore several methods to mitigate the temporal variation of the corona by decoupling the "fast-varying" inner corona from the "slow-moving" outer corona using multiple masking (either by juxtaposition or recursive combination) and radial weighting. Weighting with a radial exponential profile provides some improvement over a classical reconstruction but only beyond ≈ 3R⊙. We next consider a full time-dependent tomographic reconstruction involving spatio-temporal regularization and further introduce a co-rotating regularization aimed at preventing concentration of reconstructed density in the plane of the sky. Crucial to testing our procedure and properly tuning the regularization parameters is the introduction of a time-dependent MHD model of the corona based on observed magnetograms to build a time-series of synthetic images of the corona. Our procedure, which successfully reproduces the time-varying model corona, is finally applied to a set of 53 LASCO-C2 pB images roughly evenly spaced in time from 15 to 29 March 2009. Our procedure paves the way to a time-dependent tomographic reconstruction of the coronal electron density to the whole set of LASCO-C2 images presently spanning 20 years.

  10. The solar extreme ultra-violet corona: Resolved loops and the unresolved active region corona

    NASA Astrophysics Data System (ADS)

    Cirtain, Jonathan Wesley

    In this work, physical characteristics of the solar corona as observed in the Extreme Ultra-Violet (EUV) regime are investigated. The focus will be the regions of intense EUV radiation generally found near the locations of sunspots. These regions are commonly called active regions. Multiple space- based observing platforms have been deployed in the last decade; it is possible to use several of these observatories in combination to develop a more complete picture of the solar corona. Joint Observing Program 146 was created to collect spectroscopic intensities using the Coronal Diagnostic Spectrometer on Solar and Heliospheric Observatory and EUV images using NASA's Transition Region and Coronal Explorer. The emission line intensities are analyzed to develop an understanding of the temperature and density of the active region coronal plasma. However, the performance of the CDS instrument in the spatial and temporal domains is limited and to compensate for these limitations, data collected by the TRACE instrument provide a high spatial and temporal resolution set of observations. One of the most exciting unsolved problems in solar astrophysics is to understand why the corona maintains a temperature roughly two orders of magnitude higher than the underlying material. A detailed investigation of the coronal emission has provided constraints on models of the heating mechanism, since the temperature, density and evolution of emission rates for multiple ionic species are indicative of the mechanism(s) working to heat the corona. The corona appears to consist of multiple unresolved structures as well as resolved active region structures, called coronal loops. The purpose of the present work is to determine the characteristics of the unresolved background corona. Using the characterizations of the coronal unresolved background, results for loops after background subtraction are also presented. This work demonstrates the magnitude of the unresolved coronal emission with

  11. Observation of Alfven Waves in the Solar Corona (Invited)

    NASA Astrophysics Data System (ADS)

    Tomczyk, S.

    2013-12-01

    I will review the extensive progress made in recent years on the observation of Alfven waves in the solar corona, with an emphasis on the measurements made with the Coronal Multi-channel Polarimeter. Application of the wave measurements to coronal seismology will be presented. Future prospects in the field will be discussed.

  12. Heating of the Solar Corona and its Loops

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.

    2009-01-01

    At several million degrees, the solar corona is more than two orders of magnitude hotter than the underlying solar surface. The reason for these extreme conditions has been a puzzle for decades and is considered one of the fundamental problems in astrophysics. Much of the coronal plasma is organized by the magnetic field into arch-like structures called loops. Recent observational and theoretical advances have led to great progress in understanding the nature of these loops. In particular, we now believe they are bundles of unresolved magnetic strands that are heated by storms of impulsive energy bursts called nanoflares. Turbulent convection at the solar surface shuffles the footpoints of the strands and causes them to become tangled. A nanoflare occurs when the magnetic stresses reach a critical threshold, probably by way of a mechanism called the secondary instability. I will describe our current state of knowledge concerning the corona, its loops, and how they are heated.

  13. Measuring the IR solar corona during the 2017 eclipse

    NASA Astrophysics Data System (ADS)

    Bryans, Paul; Hannigan, James; Philip, Judge; Larson, Brandon; Sewell, Scott; McIntire, Lauren

    2016-05-01

    On 21 August 2017 a total solar eclipse will pass across the continental United States, offering a unique opportunity to conduct scientific research of the solar atmosphere. With the light from the Sun eclipsed, the solar corona becomes visible in a way not possible when swamped by the light from the photosphere. The infrared (IR) spectrum of the corona, in particular, is predicted to contain some of the most magnetically sensitive spectral lines. However, no comprehensive survey of this spectral range has been carried out to date. Here, we describe a Fourier Transform Spectrometer, currently under construction at NCAR, to measure the IR spectrum from 2 to 12 microns. We will discuss the operation of the experiment, which will be deployed along the path of totality in Wyoming, and the scientific results we hope to obtain.

  14. The Role of Magnetic Helicity in Structuring the Solar Corona

    NASA Astrophysics Data System (ADS)

    Knizhnik, K. J.; Antiochos, S. K.; DeVore, C. R.

    2017-01-01

    Two of the most widely observed and striking features of the Sun's magnetic field are coronal loops, which are smooth and laminar, and prominences or filaments, which are strongly sheared. Loops are puzzling because they show little evidence of tangling or braiding, at least on the quiet Sun, despite the chaotic nature of the solar surface convection. Prominences are mysterious because the origin of their underlying magnetic structure—filament channels—is poorly understood at best. These two types of features would seem to be quite unrelated and wholly distinct. We argue that, on the contrary, they are inextricably linked and result from a single process: the injection of magnetic helicity into the corona by photospheric motions and the subsequent evolution of this helicity by coronal reconnection. In this paper, we present numerical simulations of the response of a Parker (1972) corona to photospheric driving motions that have varying degrees of helicity preference. We obtain four main conclusions: (1) in agreement with the helicity condensation model of Antiochos (2013), the inverse cascade of helicity by magnetic reconnection in the corona results in the formation of filament channels localized about polarity inversion lines; (2) this same process removes most complex fine structure from the rest of the corona, resulting in smooth and laminar coronal loops; (3) the amount of remnant tangling in coronal loops is inversely dependent on the net helicity injected by the driving motions; and (4) the structure of the solar corona depends only on the helicity preference of the driving motions and not on their detailed time dependence. We discuss the implications of our results for high-resolution observations of the corona.

  15. Development of a complex of activity in the solar corona

    NASA Technical Reports Server (NTRS)

    Howard, R.; Svestka, Z.

    1977-01-01

    Using Skylab observations of soft solar X-rays, the development of a complex of activity in the solar corona during its whole lifetime of seven solar rotations is studied. The basic components of the activity complex were determined to be permanently interconnected through sets of magnetic field lines, which suggests similar connections also below the photosphere. The visibility of individual loops in these connections, however, was greatly variable and typically shorter than one day. Each brightening of a coronal loop in X-rays seems to be related to a variation in the photospheric magnetic field near its footprint.

  16. Plasma Compression in Magnetic Reconnection Regions in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Provornikova, E.; Laming, J. M.; Lukin, V. S.

    2016-07-01

    It has been proposed that particles bouncing between magnetized flows converging in a reconnection region can be accelerated by the first-order Fermi mechanism. Analytical considerations of this mechanism have shown that the spectral index of accelerated particles is related to the total plasma compression within the reconnection region, similarly to the case of the diffusive shock acceleration mechanism. As a first step to investigate the efficiency of Fermi acceleration in reconnection regions in producing hard energy spectra of particles in the solar corona, we explore the degree of plasma compression that can be achieved at reconnection sites. In particular, we aim to determine the conditions for the strong compressions to form. Using a two-dimensional resistive MHD numerical model, we consider a set of magnetic field configurations where magnetic reconnection can occur, including a Harris current sheet, a force-free current sheet, and two merging flux ropes. Plasma parameters are taken to be characteristic of the solar corona. Numerical simulations show that strong plasma compressions (≥4) in the reconnection regions can form when the plasma heating due to reconnection is efficiently removed by fast thermal conduction or the radiative cooling process. The radiative cooling process that is negligible in the typical 1 MK corona can play an important role in the low corona/transition region. It is found that plasma compression is expected to be strongest in low-beta plasma β ˜ 0.01-0.07 at reconnection magnetic nulls.

  17. A study on solar dust ring formation based on fractal dust models.

    NASA Astrophysics Data System (ADS)

    Kimura, H.; Ishimoto, H.; Mukai, T.

    1997-10-01

    Using the fractal aggregate model for circumsolar dust grains, the nature of the circumsolar dust clouds is examined. As a fractal dimension of the aggregate decreases, the porosity of the aggregate increases. Consequently, its temperature becomes independent of its size, and approaches that of its constituent particles. This evidence suggests that the fractal aggregates with different sizes and made of the same chemical components sublimate at the same solar distance. This implies that the distance of the sublimation zone depends on the chemical composition alone. We have found that the aggregates consisting of silicate material, as well as carbon material, sublimate in the solar F-corona. On the other hand, a ratio of radiation pressure force to solar gravity on the fractal aggregate scarcely increases with decreasing size due to sublimation, in contrast with a strong dependence of its ratio on its size for a compact sphere. Our computer simulation for dynamical evolution of fractal aggregates suggests that they produce a narrow ring structure in the circumsolar dust cloud, compared with that expected for spherical dust grains. When the aggregates have more fluffy structure with a small fractal dimension, however, it is found that the circumsolar dust clouds would make no remarkable ring structure.

  18. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    2000-01-01

    This report covers technical progress during the third year of the NASA Space Physics Theory contract "The Structure and Dynamics of the Solar Corona," between NASA and Science Applications International Corporation, and covers the period June 16, 1998 to August 15, 1999. This is also the final report for this contract. 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 three-year duration of this contract we have published 49 articles in the scientific literature. These publications are listed in Section 3 of this report. In the Appendix we have attached reprints of selected articles. We summarize our progress during the third year of the contract. Full descriptions of our work can be found in the cited publications, a few of which are attached to this report.

  19. 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

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

    SciTech Connect

    McIntosh, Scott W.; De Pontieu, Bart

    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.

  2. Weak compressible magnetohydrodynamic turbulence in the solar corona.

    PubMed

    Chandran, Benjamin D G

    2005-12-31

    This Letter presents a calculation of the power spectra of weakly turbulent Alfvén waves and fast magnetosonic waves ("fast waves") in low- plasmas. It is shown that three-wave interactions transfer energy to high-frequency fast waves and, to a lesser extent, high-frequency Alfvén waves. High-frequency waves produced by MHD turbulence are a promising explanation for the anisotropic heating of minor ions in the solar corona.

  3. Magnetic tornadoes as energy channels into the solar corona.

    PubMed

    Wedemeyer-Böhm, Sven; Scullion, Eamon; Steiner, Oskar; van der Voort, Luc Rouppe; de la Cruz Rodriguez, Jaime; Fedun, Viktor; Erdélyi, Robert

    2012-06-27

    Heating the outer layers of the magnetically quiet solar atmosphere to more than one million kelvin and accelerating the solar wind requires an energy flux of approximately 100 to 300 watts per square metre, but how this energy is transferred and dissipated there is a puzzle and several alternative solutions have been proposed. Braiding and twisting of magnetic field structures, which is caused by the convective flows at the solar surface, was suggested as an efficient mechanism for atmospheric heating. Convectively driven vortex flows that harbour magnetic fields are observed to be abundant in the photosphere (the visible surface of the Sun). Recently, corresponding swirling motions have been discovered in the chromosphere, the atmospheric layer sandwiched between the photosphere and the corona. Here we report the imprints of these chromospheric swirls in the transition region and low corona, and identify them as observational signatures of rapidly rotating magnetic structures. These ubiquitous structures, which resemble super-tornadoes under solar conditions, reach from the convection zone into the upper solar atmosphere and provide an alternative mechanism for channelling energy from the lower into the upper solar atmosphere.

  4. Atomic Data for Solar Corona Studies

    SciTech Connect

    Feldman, Uri

    2011-05-11

    In recent years due to the increased sophistication of space instrumentation ever more detailed observations of a large variety of coronal structures became available. Nevertheless, thus far no credible model emerged that describes the means by which the solar upper atmosphere is created and maintained. Nevertheless, while interpreting such spectra, some unexpected properties of coronal plasmas were discovered. Although there are many cases where agreements between observations and calculations are found, there are cases were clear discrepancies do exist. I discuss some of the unexpected observational results that were recently discovered, and suggest some observations that if successfully executed could help explain the processes that form and maintain the solar upper atmosphere.

  5. 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 {Å} 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^{-α}dE. The power law index was derived to be α = 2.4 ± 0.2, which is very close to the value reported by Krucker & Benz (1998): α ≈ 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 α > 2 indicates that nanoflares with lower energies dominate over nanoflares with bigger energies and could contribute considerably to quiet corona heating.

  6. The Writhe of Helical Structures in the Solar Corona

    DTIC Science & Technology

    2010-04-23

    2010 The writhe of helical structures in the solar corona T. Török1,2, M. A. Berger2,3, and B. Kliem2,4,5 1 LESIA, Observatoire de Paris, CNRS, UPMC...2009; accepted ... ABSTRACT 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

  7. The Absolute Abundance of Iron in the Solar Corona.

    PubMed

    White; Thomas; Brosius; Kundu

    2000-05-10

    We present a measurement of the abundance of Fe relative to H in the solar corona using a technique that differs from previous spectroscopic and solar wind measurements. Our method combines EUV line data from the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory with thermal bremsstrahlung radio data from the VLA. The coronal Fe abundance is derived by equating the thermal bremsstrahlung radio emission calculated from the EUV Fe line data to that observed with the VLA, treating the Fe/H abundance as the sole unknown. We apply this technique to a compact cool active region and find Fe&solm0;H=1.56x10-4, or about 4 times its value in the solar photosphere. Uncertainties in the CDS radiometric calibration, the VLA intensity measurements, the atomic parameters, and the assumptions made in the spectral analysis yield net uncertainties of approximately 20%. This result implies that low first ionization potential elements such as Fe are enhanced in the solar corona relative to photospheric values.

  8. Corona-Solar Wind Coupling Review

    DTIC Science & Technology

    1987-06-01

    Spitzer which should be valid if the magne:ic field is radial and the plasma is collision dominated. Although both of these conditions are expected to hold...conduction has been studied by introducing a heat flux density given by the classical Spitzer value times the square of the cosine of the angle...Broussard, R. M., N. R. Shecley, Jr ., R. Tousey, and J. H. Underwood. A survey of coronal holes and their solar wind associations throughout sunspot cycle

  9. Joule heating and anomalous resistivity in the solar corona

    NASA Astrophysics Data System (ADS)

    Spangler, S. R.

    2009-06-01

    Recent radioastronomical observations of Faraday rotation in the solar corona can be interpreted as evidence for coronal currents, with values as large as 2.5×109 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 3×105. 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.

  10. Storing free magnetic energy in the solar corona

    NASA Astrophysics Data System (ADS)

    Vekstein, G.

    2016-08-01

    This article presents a mini-tutorial aimed at a wide readership not familiar with the field of solar plasma physics. The exposition is centred around the issue of excess/free magnetic energy stored in the solar corona. A general consideration is followed with a particular example of coronal magnetic arcade, where free magnetic energy builds up by photospheric convective flows. In the context of solar physics the major task is to explain how this free energy can be released quickly enough to match what is observed in coronal explosive events such as solar flares. Therefore, in the last section of the paper we discuss briefly a possible role of magnetic reconnection in these processes. This is done in quite simple qualitative physical terms, so that an interested reader can follow it up in more detail with help of the provided references.

  11. RGB color photometry of the solar corona from total solar eclipses

    NASA Astrophysics Data System (ADS)

    Shopov, Y. Y.; Varonov, A.; Stoykova, D. A.

    2016-02-01

    In the following article we present some of our results from observations of two total solar eclipses (TSE). By combining appropriate photographic equipment and post-processing techniques we show that numerous solar phenomena can be captured in details during TSE. We use color slide RGB photometry technique to visualize invisible regions of the solar corona and to highlight some of the solar phenomena that are very difficult for observation by Earth-based observatories. In fact it reveals more details of the far solar corona than any original image taken from ground-based observations. RGB photometry visualizes different components of the solar corona in one image, which is impossible using conventional observations. This makes it valuable tool for studies of the solar corona. Here we first observe peculiar near infrared emission regions around the upper part of the solar limb during the 1999 TSE. So far its origin is unknown and they need further studies including observations during other solar eclipses. Our observational experiment was designed for other purposes and their registration was completely unexpected.

  12. Comments on the 'minimum flux corona' concept. [solar model

    NASA Technical Reports Server (NTRS)

    Antiochos, S. K.; Underwood, J. H.

    1978-01-01

    Hearn's (1975) models of the energy balance and mass loss of stellar coronae, based on a 'minimum flux corona' concept, are critically examined. First, it is shown that the neglect of the relevant length scales for coronal temperature variation leads to an inconsistent computation of the total energy flux F. The stability arguments upon which the minimum flux concept is based are shown to be fallacious. Errors in the computation of the stellar wind contribution to the energy budget are identified. Finally we criticize Hearn's (1977) suggestion that the model, with a value of the thermal conductivity modified by the magnetic field, can explain the difference between solar coronal holes and quiet coronal regions.

  13. Dynamics and Thermodynamics of the Solar Corona as Inferred from Total Solar Eclipse Observations

    NASA Astrophysics Data System (ADS)

    Habbal, Shadia; Druckmuller, Miloslav; Morgan, Huw; Ding, Adalbert

    2015-04-01

    Imaging the solar corona during total solar eclipses in broadband white light and in a number of forbidden emission lines in the visible continues to yield unique insights into the dynamics and thermodynamics of the coronal plasma. An overview of recent multiwavelength eclipse observations, spanning almost a solar cycle, will be presented. Particular emphasis will be placed on the thermodynamics of dynamic events such prominence eruptions, plasmoids and CMEs, that are captured in the eclipse images either as they occurred, or from the trails they left behind in the corona.

  14. The EUV Emission in Comet-Solar Corona Interactions

    NASA Technical Reports Server (NTRS)

    Bryans, Paul; Pesnell, William Dean; Schrijver, Carolus J.; Brown, John C.; Battams, Karl; Saint-Hilaire, Pasal; Liu, Wei; Hudson, Hugh S.

    2011-01-01

    The Atmospheric Imaging Assembly (AlA) on the Solar Dynamics Observatory (SDO) viewed a comet as it passed through the solar corona on 2011 July 5. This was the first sighting of a comet by a EUV telescope. For 20 minutes, enhanced emission in several of the AlA wavelength bands marked the path of the comet. We explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Water ice in the comet rapidly sublimates as it approaches the Sun. This water vapor is then photodissociated, primarily by Ly-alpha, by the solar radiation field to create atomic Hand O. Other molecules present in the comet also evaporate and dissociate to give atomic Fe and other metals. Subsequent ionization of these atoms can be achieved by a number of means, including photoionization, electron impact, and charge exchange with coronal protons and other highly-charged species. Finally, particles from the cometary atmosphere are thermalized to the background temperature of the corona. Each step could cause emission in the AlA bandpasses. We will report here on their relative contribution to the emission seen in the AlA telescopes.

  15. Fractal aggregate analogues for near solar dust properties

    NASA Astrophysics Data System (ADS)

    Mann, I.; Okamoto, H.; Mukai, T.; Kimura, H.; Kitada, Y.

    1994-11-01

    The present study compares properties of near solar dust, deduced from inversion of F-corona brightness data, with calculations of fluffy aggregate particles. It is shown that silicate particles containing a slight amount of absorbing material have temperatures below the blackbody temperature if the impurity amounts to less than 0.1% in volume. This effect is especially significant for porous particles and points to the existence of such a component, possibly cometary dust, in the solar vicinity. In particular the silicate particles with a large impurity, which show a higher temperature than the blackbody at the same solar distance, the sublimation starts closer to the sun and the pure silicate, if it would exist, would survive even about 2 solar radii from the sun. This result which is based on calculations that apply model materials, may possibly explain the wide extended zone of sublimation derived from F-corona brightness data. Another finding of our calculations is an unexpected enhancement of temperature of the two-component aggregates. Namely the silicate aggregate with absorbing impurities attains higher temperature even than the pure carbon. This happens when the volume fraction of absorbing material exceeds 1% and the aggregate with a fractal dimension of 2.98 is located below about 100 solar radii from the sun; this critical solar distance depends on the volume fraction of absorbing material. A similar trend was also seen in the compact particle consisting of two components. This comes from the complex dependence of the energy loss from the particle on the temperature.

  16. MHD modeling of the solar corona: Progress and challenges

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    The Sun and its activity is the ultimate driver of space weather at Earth. This influence occurs not only via eruptive phenomena such as coronal mass ejections, but also through the structure of the corona itself, which forms the genesis of fast solar wind streams that trigger recurrent geomagnetic activity. Coronal structure also determines the connection of the ambient interplanetary magnetic field to CME-related shocks and impulsive solar flares, and thus controls where solar energetic particles propagate. In this talk we describe both the present state of the art and new directions in coronal modeling for both dynamic and slowly varying phenomena. We discuss the challenges to incorporating these capabilities into future space weather forecasting and specification models. Supported by NASA through the HTP, LWS, and SR&T programs, by NSF through the FESD and CISM programs, and by the AFOSR Space Science program.

  17. Solar Corona Simulation Model With Positivity-preserving Property

    NASA Astrophysics Data System (ADS)

    Feng, X. S.

    2015-12-01

    Positivity-preserving is one of crucial problems in solar corona simulation. In such numerical simulation of low plasma β region, keeping density and pressure is a first of all matter to obtain physical sound solution. In the present paper, we utilize the maximum-principle-preserving flux limiting technique to develop a class of second order positivity-preserving Godunov finite volume HLL methods for the solar wind plasma MHD equations. Based on the underlying first order building block of positivity preserving Lax-Friedrichs, our schemes, under the constrained transport (CT) and generalized Lagrange multiplier (GLM) framework, can achieve high order accuracy, a discrete divergence-free condition and positivity of the numerical solution simultaneously without extra CFL constraints. Numerical results in four Carrington rotation during the declining, rising, minimum and maximum solar activity phases are provided to demonstrate the performance of modeling small plasma beta with positivity-preserving property of the proposed method.

  18. Identification of moon craters and solar corona during total solar eclipse on 9th March 2016

    NASA Astrophysics Data System (ADS)

    Luthfiandari; Ekawanti, N.; Purwati, F. G.; Herdiwijaya, D.

    2016-11-01

    Total Solar Eclipse (TSE) is a rare natural event in which the positions of Sun, Moon, and Earth are perfectly aligned. In the past by using this phenomenon, many researches have been done to understand characteristic of the corona. In this paper we carried out the study of TSE which crossed over Indonesia from West to East on 9th March 2016. We observed TSE which occured in Palembang (2.9883° S 104.7513° E), Indonesia. The aim of this research is to understand the effect of moon craters on the appearance of solar corona and identification of solar active regions during TSE. This research was done using Canon SX170 IS camera with ND 5 sun-filter. Although the sky was cloudy during the totality of the phase, coronal video was still taken. Camera also took solar images of partial eclipse phase. Coronal images for every frame were then extracted from the video. Image processing of coronal images was done using RegiStax and PhotoScape freewares. To study solar corona, images from Virtual Moon Atlas, Hinode XRT, and SOHO-LASCO were compared with the result of oriented coronal image. Wider and many more moon craters were found having positive correlation with the brighter effect on solar corona as shown at westward coronal streamer. Those craters are represented by Bel'kovich crater, the biggest one. We also found that only the eastward coronal streamer was correlated with active region, sunspot number 12519, from behind solar limb.

  19. Exploring the prominence-corona connection and its expansion into the outer corona using total solar eclipse observations

    SciTech Connect

    Habbal, Shadia Rifai; Morgan, Huw; Druckmüller, Miloslav

    2014-10-01

    Prominences constitute the most complex magnetic structures in the solar corona. The ubiquitous presence of their seemingly confined dense and cool plasma in an otherwise million-degree environment remains a puzzle. Using a decade of white light total solar eclipse observations, we show how these images reveal an intricate relationship between prominences and coronal structures both in their immediate vicinity, known as coronal cavities, and in the extended corona out to several solar radii. Observations of suspended prominences and twisted helical structures spanning several solar radii are central to these findings. The different manifestations of the prominence-corona interface that emerge from this study underscore the fundamental role played by prominences in defining and controlling the complex expansion and dynamic behavior of the solar magnetic field in the neighborhood of magnetic polarity reversal regions. This study suggests that the unraveling of prominences and the outward expansion of the helical twisted field lines linked to them could be the solar origin of twisted magnetic flux ropes detected in interplanetary space, and of the mechanism by which the Sun sheds its magnetic helicity. This work also underscores the likely role of the prominence-corona interface as a source of the slow solar wind.

  20. Radio Observations of Weak Energy Releases in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Kathiravan, C.; Barve, Indrajit V.; Beeharry, G. K.; Rajasekara, G. N.

    2010-08-01

    We report observations of weak, circularly polarized, structureless type III bursts from the solar corona in the absence of Hα/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 ≈-30 MHz s-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 ≈1.5 R sun in the solar atmosphere. The estimated peak brightness temperature of the burst at 77 MHz is ~108 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 ≈2.5 ± 0.2 G. We also estimated the total energy of the non-thermal electrons responsible for the observed burst as ≈1.1 × 1024 erg. This is low compared to the energy of the weakest hard X-ray microflares reported in the literature, which is about ~1026 erg. The present result shows that non-thermal energy releases that correspond to the nanoflare category (energy ~1024 erg) are taking place in the solar corona, and the nature of such small-scale energy releases has not yet been explored.

  1. Neutral Hydrogen and Its Emission Lines in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Vial, Jean-Claude; Chane-Yook, Martine

    2016-12-01

    Since the Lyman-α rocket observations of Gabriel ( Solar Phys. 21, 392, 1971), it has been realized that the hydrogen (H) lines could be observed in the corona and that they offer an interesting diagnostic for the temperature, density, and radial velocity of the coronal plasma. Moreover, various space missions have been proposed to measure the coronal magnetic and velocity fields through polarimetry in H lines. A necessary condition for such measurements is to benefit from a sufficient signal-to-noise ratio. The aim of this article is to evaluate the emission in three representative lines of H for three different coronal structures. The computations have been performed with a full non-local thermodynamic-equilibrium (non-LTE) code and its simplified version without radiative transfer. Since all collisional and radiative quantities (including incident ionizing and exciting radiation) are taken into account, the ionization is treated exactly. Profiles are presented at two heights (1.05 and 1.9 solar radii, from Sun center) in the corona, and the integrated intensities are computed at heights up to five solar radii. We compare our results with previous computations and observations ( e.g. Lα from Ultraviolet Coronal Spectrometer) and find a rough (model-dependent) agreement. Since the Hα line is a possible candidate for ground-based polarimetry, we show that in order to detect its emission in various coronal structures, it is necessary to use a very narrow (less than 2 Å wide) bandpass filter.

  2. Numerical Simulations of Helicity Condensation in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Zhao, L.; DeVore, C. R.; Antiochos, S. K.; Zurbuchen, T. H.

    2015-01-01

    The helicity condensation model has been proposed by Antiochos (2013) to explain the observed smoothness of coronal loops and the observed buildup of magnetic shear at filament channels. The basic hypothesis of the model is that magnetic reconnection in the corona causes the magnetic stress injected by photospheric motions to collect only at those special locations where prominences form. In this work we present the first detailed quantitative MHD simulations of the reconnection evolution proposed by the helicity condensation model. We use the well-known ansatz of modeling the closed corona as an initially uniform field between two horizontal photospheric plates. The system is driven by applying photospheric rotational flows that inject magnetic helicity into the system. The flows are confined to a finite region on the photosphere so as to mimic the finite flux system of, for example, a bipolar active region. The calculations demonstrate that, contrary to common belief, coronal loops having opposite helicity do not reconnect, whereas loops having the same sense of helicity do reconnect. Furthermore, we find that for a given amount of helicity injected into the corona, the evolution of the magnetic shear is insensitive to whether the pattern of driving photospheric motions is fixed or quasi-random. In all cases, the shear propagates via reconnection to the boundary of the flow region while the total magnetic helicity is conserved, as predicted by the model. We discuss the implications of our results for solar observations and for future, more realistic simulations of the helicity condensation process.

  3. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1998-01-01

    This report covers technical progress during the first year of the NASA Space Physics Theory contract between NASA and Science Applications International Corporation. 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 26 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.

  4. Solar-Panel Dust Accumulation and Cleanings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Air-fall dust accumulates on the solar panels of NASA's Mars Exploration Rovers, reducing the amount of sunlight reaching the solar arrays. Pre-launch models predicted steady dust accumulation. However, the rovers have been blessed with occasional wind events that clear significant amounts of dust from the solar panels.

    This graph shows the effects of those panel-cleaning events on the amount of electricity generated by Spirit's solar panels. The horizontal scale is the number of Martian days (sols) after Spirit's Jan. 4, 2005, (Universal Time) landing on Mars. The vertical scale indicates output from the rover's solar panels as a fraction of the amount produced when the clean panels first opened. Note that the gradual declines are interrupted by occasional sharp increases, such as a dust-cleaning event on sol 420.

  5. NUMERICAL SIMULATIONS OF HELICITY CONDENSATION IN THE SOLAR CORONA

    SciTech Connect

    Zhao, L.; Zurbuchen, T. H.; DeVore, C. R.; Antiochos, S. K.

    2015-05-20

    The helicity condensation model has been proposed by Antiochos to explain the observed smoothness of coronal loops and the observed buildup of magnetic shear at filament channels. The basic hypothesis of the model is that magnetic reconnection in the corona causes the magnetic stress injected by photospheric motions to collect only at those special locations where prominences are observed to form. In this work we present the first detailed quantitative MHD simulations of the reconnection evolution proposed by the helicity condensation model. We use the well-known ansatz of modeling the closed corona as an initially uniform field between two horizontal photospheric plates. The system is driven by applying photospheric rotational flows that inject magnetic helicity into the corona. The flows are confined to a finite region on the photosphere so as to mimic the finite flux system of a bipolar active region, for example. The calculations demonstrate that, contrary to common belief, opposite helicity twists do not lead to significant reconnection in such a coronal system, whereas twists with the same sense of helicity do produce substantial reconnection. Furthermore, we find that for a given amount of helicity injected into the corona, the evolution of the magnetic shear is insensitive to whether the pattern of driving photospheric motions is fixed or quasi-random. In all cases, the shear propagates via reconnection to the boundary of the flow region while the total magnetic helicity is conserved, as predicted by the model. We discuss the implications of our results for solar observations and for future, more realistic simulations of the helicity condensation process.

  6. Remote-sensing Observations of the Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Sheeley, Neil R., Jr.

    2009-05-01

    On June 25, 1908, George Ellery Hale used the 60-foot Tower Telescope on Mount Wilson to make the first measurements of magnetic fields in sunspots. This began a series of studies that led to Hale's Law of sunspot polarities and established the Mount Wilson Observatory as a leading center of solar magnetic field research. The magnetic aura was still present in 1962 when I began solar research there as a Caltech graduate student. Mount Wilson astronomer Horace Babcock and his father had invented the solar magnetograph, discovered the polar fields of the Sun, and observed their reversal near the 1958 sunspot maximum. Caltech physicist Robert Leighton had added new instrumentation to the Mount Wilson spectroheliograph and obtained high-resolution maps of the magnetic field. Babcock had just published his classic paper on the topology of the field and its 22-year cycle. The paper contained a sketch, illustrating the coronal field-line reconnection, which he thought must occur in response to changes of the photospheric field. Some loops flew away in the yet-to-be-discovered solar wind and other loops collapsed back to the Sun. In this talk, I will present new observations from the SOHO and STEREO spacecraft, which show such coronal changes. Loops stretch out in the expanding corona and tear away from the Sun like drops from a leaky faucet. Simultaneous observations with different perspectives show that the detached loops are really helices in 3-D. Off-pointed heliospheric imagers allow us to track these ejections outward past planets (including Earth) and comets, and to observe their compression into a heliospheric spiral, as a consequence of longitudinal speed gradients on the rotating Sun. And XUV observations of the solar disk show brightness changes associated with reconnections high in the corona, like auroral displays in the magnetosphere.

  7. Heating of the solar corona by the resonant absorption of Alfven waves

    NASA Technical Reports Server (NTRS)

    Davila, Joseph M.

    1986-01-01

    An improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona. The primary conclusion to be drawn from these calculations is that to the level of the approximation adopted, the observations of the heating rate and nonthermal line broadening in the solar corona are consistent with heating by the resonance absorption mechanism.

  8. Solar wind Acceleration from the Upper Chromosphere to the Corona in Coronal Hole Regions

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1998-01-01

    The dynamic behavior of the plasma in the chromosphere/transition region /inner corona is vital for the acceleration of the solar wind. With new theoretical descriptions of the solar atmosphere and corona, and the increased observational possibilities provided by the SOHO spacecraft, it is possible to conduct an integrated study of the solar atmosphere and corona using observational and theoretical approaches. Over the past few years a series of observational techniques have been used to estimate the solar wind densities, temperatures and flow speed in the inner corona. These estimates suggest that the solar wind has higher outflow speeds in the inner corona and lower densities than previously assumed. A comparison with densities derived from atmospheric models support these lower densities.

  9. Interferometric observation of the F-corona radial velocities fields between 3 and 7 solar radii

    NASA Astrophysics Data System (ADS)

    Shcheglov, P. V.; Shestakova, L. I.; Aimanov, A. K.

    During the July 31, 1981 solar eclipse, F-corona interferograms near Mg I 5184 A were obtained using a Fabry-Perot etalon with an FWHM of 0.5 A (corresponding to 30 km/sec) and an image tube. Radial velocities V(r) of the interplanetary dust (ID) were measured in different directions. Both prograde and retrograde motions of ID in the ecliptic region is discovered. Most of velocity values do not exceed 50 km/sec. A negative velocity component appears after averaging all V(r) for all directions. Its average increases to -20 km/sec toward the sun. Some ejections are observed. The strongest (+130 km/sec) is located at the north ecliptic pole at a distance of 6 to 7 solar radii. From the lack of unshifted Fraunhofer lines in the scattered sky light, it is concluded that the sky brigntness continuous component is predominant and its source is K-corona scattered light in the earth's atmosphere.

  10. The global distribution of magnetic helicity in the solar corona

    NASA Astrophysics Data System (ADS)

    Yeates, A. R.; Hornig, G.

    2016-10-01

    By defining an appropriate field line helicity, we apply the powerful concept of magnetic helicity to the problem of global magnetic field evolution in the Sun's corona. As an ideal-magnetohydrodynamic invariant, the field line helicity is a meaningful measure of how magnetic helicity is distributed within the coronal volume. It may be interpreted, for each magnetic field line, as a magnetic flux linking with that field line. Using magneto-frictional simulations, we investigate how field line helicity evolves in the non-potential corona as a result of shearing by large-scale motions on the solar surface. On open magnetic field lines, the helicity injected by the Sun is largely output to the solar wind, provided that the coronal relaxation is sufficiently fast. But on closed magnetic field lines, helicity is able to build up. We find that the field line helicity is non-uniformly distributed, and is highly concentrated in twisted magnetic flux ropes. Eruption of these flux ropes is shown to lead to sudden bursts of helicity output, in contrast to the steady flux along the open magnetic field lines. Movies are available at http://www.aanda.org

  11. Observational tests for nonequilibrium ionization in the solar corona

    NASA Technical Reports Server (NTRS)

    Spadaro, D.; Leto, P.; Antiochos, S. K.

    1994-01-01

    Nonequilibrium ionization may be produced by a variety of processes in the solar corona, for example, by mass flows through the large temperature gradients of the transition region or by impulsive heating and cooling. Any deviation from equilibrium ionization would have a strong effect on the radiation from the corona and on the interpretation of solar observations; hence, it is important to determine observational signatures of nonequilibrium. The temperature-sensitive line ratios can be used as such signatures. We examine the line ratios: C IV I(1548.2 A)/I(312.4 A), O IV I(789.4 A)/I(554.4 A), O V I(629.7 A)/I(172.2 A), O VI I(1031.9 A)/I(173.0 A) and O VI I(1031.9 A)/I(150.1 A). These line ratios are calculated for four coronal loop models that have a steady flow and that are known to have significant departures from equilibrium ionization. Our results indicate that, in general, nonequilibrium causes a considerable reduction in the line ratios, more than an order of magnitude in the downflowing leg of the loop model with the largest mass flows. We find that the C IV line ratio is the most sensitive to nonequilibrium. We discuss the implications of our results for observations, specifically, the observations expected from the upcoming SOHO mission.

  12. 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.

  13. Radial evolution of density structure in the solar corona

    NASA Astrophysics Data System (ADS)

    Woo, Richard; Habbal, Shadia Rifai

    White-light measurements made by the SOHO coronagraphs (LASCO for Large Angle Spectrometric Coronagraph) and the HAO Mauna Loa Mk III K-coronameter are combined to follow the evolution of path-integrated density structure in the solar corona overlying both coronal hole and quiet Sun regions from 1.15 to 5.5 Ro. The global imaging provided by these two instruments confirms and strengthens earlier results discovered by spacecraft radio ranging measurements [Woo and Habbal, 1999], that the imprint of density structure at the Sun — as manifested in the background latitudinal density profile closest to the Sun at 1.15 Ro — is carried essentially radially into interplanetary space with the same density gradient. The only exceptions are coronal streamers that evolve into the heliospheric current sheet within a few solar radii of the Sun.

  14. 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.

  15. The solar corona through the sunspot cycle: preparing for the August 21, 2017, total solar eclipse

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Seaton, Daniel; Rusin, Vojtech

    2017-01-01

    We discuss the evolution of the solar corona as seen at eclipses through the solar-activity cycle. In particular, we discuss the variations of the overall shape of the corona through the relative proportions of coronal streamers at equatorial and other latitudes vs. polar plumes. We analyze the two coronal mass ejections that we observed from Gabon at the 2013 total solar eclipse and how they apparently arose from polar crown filaments, one at each pole. We describe the change in the Ludendorff flattening index from solar maximum in one hemisphere as of the 2013 eclipse through the 2015 totality's corona we observed from Svalbard and, with diminishing sunspot and other magnetic activity in each hemisphere, through the 2016 corona we observed from Ternate, Indonesia.We discuss our observational plans for the August 21, 2017, total solar eclipse from our main site in Salem, Oregon, and subsidiary sites in Madras, OR; Carbondale, IL; and elsewhere, our main site chosen largely by its favorable rating in cloudiness statistics. We discuss the overlapping role of simultaneous spacecraft observations, including those expected not only from NASA's SDO, ESA's SWAP on PROBA2, and NRL/NASA/ESA's LASCO on SOHO but also from the new SUVI (Solar Ultraviolet Imager) aboard NOAA's GOES-R satellite, scheduled as of this writing to have been launched by the time of this January 2017 meeting.Our research on the 2013 and 2015 total solar eclipses was supported by grants from the Committee for Research and Exploration of the National Geographic Society (NG-CRE). Our research on the 2017 total solar eclipse is supported by both NG-CRE and the Solar Terrestrial Program of the Atmospheric and Geospace Sciences Division of the National Science Foundation.

  16. 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

  17. Observations of the solar corona during the total solar eclipse of July 31, 1981

    NASA Astrophysics Data System (ADS)

    Khetsuriani, Ts. S.; Kulidzhanishvili, V. I.; Khutsishvili, E. V.; Kiladze, R. I.; Dzhavakhishvili, G. Sh.; Ambartsumian, A. A.; Dasaev, V. I.; Ivanishvili, A. A.; Dzhaparidze, D. R.

    Observations of the total solar eclipse of July 31, 1981 performed by the Abastumani Astrophysical Observatory expedition at Shortand (the Tselinograd region) and Tarma (the Bratsk region) are described. The instrumentation used, i.e., the coronagraph and a specially designed electrophotometer, are described. Preliminary results are examined with particular attention given to the structure and shape of the corona and coronal equidensities.

  18. The solar corona structures as inferred from July 11, 1991 total solar eclipse observation

    NASA Astrophysics Data System (ADS)

    Sykora, Julius; Badalyan, O. G.

    1992-11-01

    During the 11 Jul. 1991 total solar eclipse (La Paz, Mexico), very complete photographic records of the linearly polarized light of the solar corona in continuum and in spectral line FeXIV 530.3 nm were obtained. Degree of polarization is considerably different for both the mentioned spectral regions. This follows, of course, most of all from a difference of the physical substance of polarization both in continuum and in emission spectral lines. The distinct variety of the white light degree of polarization according to the type of coronal structures is discussed. For example, the high degree of polarization is characteristic for the coronal streamers which in case of this eclipse were localized at unusually high solar latitudes. Position of the streamers is certainly reflected in an exceptional position of the heliospheric current sheet and, except of that, seriously casts doubts on the general validity of the Ludendorff's definition of the solar corona flattening.

  19. Milli-Arcsecond Imaging of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Davila, Joseph; Kamalabadi, Farzad; Oktem, Figen S.

    2016-07-01

    Dissipation in the solar corona is believed to occur in extremely thin current sheets of order 1-100 km. Emission from these hot but thin current sheets is visible in coronal EUV emission lines, however, this spatial scale is unresolved in existing imaging instruments. Conventional optics cannot be easily manufactured with sufficient surface figure accuracy to obtain the required resolution. A photon sieve, a diffractive imaging element similar to a Fresnel zone plate, can be manufactured to provide a few milli-arcsec (mas) resolution, with much more relaxed tolerances than conventional imaging technology. Images from photon sieves will not only show the structure of the corona at a resolution never before obtained, they will also allow a study of the temperature structure in the dissipation region. Several photon sieves have been designed, fabricated, and tested by us at Goddard Space Flight Center. To fully exploit the potential of these devices two new technologies, (1) formation flying and (2) computational image deconvolution must be used. Recent progress on photon sieve development as well as these issues will be discussed. A simple design for a sounding rocket payload is presented that obtains 80 mas (0.080 arcsec) imaging with a 100 mm diameter photon sieve to image Fe XIV 334 and Fe XVI 335 which would provide a demonstration of this technology.

  20. Milli-Arcsecond (MAS) Imaging of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Davila, Joseph M.; Oktem, Figen S.; Kamalabadi, Farzad; O'Neill, John; Novo-Gradac, Anne-Marie; Daw, Adrian N.; Rabin, Douglas M.

    2016-05-01

    Dissipation in the solar corona is believed to occur in extremely thin current sheets of order 1-100 km. Emission from these hot but thin current sheets should be visible in coronal EUV emission lines. However, this spatial scale is far below the resolution of existing imaging instruments, so these dissipation sites have never been observed individually. Conventional optics cannot be manufactured with sufficient surface figure accuracy to obtain the required spatial resolution in the extreme-ultraviolet where these hot plasmas radiate. A photon sieve, a diffractive imaging element similar to a Fresnel zone plate, can be manufactured to provide a few milli-arcsec (MAS) resolution, with much more readily achievable tolerances than with conventional imaging technology. Prototype photon sieve elements have been fabricated and tested in the laboratory. A full-scale ultra-high resolution instrument will require formation flying and computational image deconvolution. Significant progress has been made in overcoming these challenges, and some recent results in these areas are discussed. A simple design for a sounding rocket concept demonstration payload is presented that obtains 80 MAS (0.080 arcsec) imaging with a 100 mm diameter photon sieve to image Fe XIV 334 and Fe XVI 335. These images will show the structure of the corona at a resolution never before obtained, and they will also allow a study of the temperature structure in the dissipation region.

  1. R CORONAE BOREALIS STARS ARE VIABLE FACTORIES OF PRE-SOLAR GRAINS

    SciTech Connect

    Karakas, Amanda I.; Ruiter, Ashley J.; Hampel, Melanie

    2015-08-20

    We present a new theoretical estimate for the birthrate of R Coronae Borealis (RCB) stars that is in agreement with recent observational data. We find the current Galactic birthrate of RCB stars to be ≈25% of the Galactic rate of Type Ia supernovae, assuming that RCB stars are formed through the merger of carbon–oxygen and helium-rich white dwarfs. Our new RCB birthrate (1.8 × 10{sup −3} yr{sup −1}) is a factor of 10 lower than previous theoretical estimates. This results in roughly 180–540 RCB stars in the Galaxy, depending on the RCB lifetime. From the theoretical and observational estimates, we calculate the total dust production from RCB stars and compare this rate to dust production from novae and born-again asymptotic giant branch (AGB) stars. We find that the amount of dust produced by RCB stars is comparable to the amounts produced by novae or born-again post-AGB stars, indicating that these merger objects are a viable source of carbonaceous pre-solar grains in the Galaxy. There are graphite grains with carbon and oxygen isotopic ratios consistent with the observed composition of RCB stars, adding weight to the suggestion that these rare objects are a source of stardust grains.

  2. The Astrophysics of the Solar Corona at the August 21, 2017, American Total Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay

    2017-01-01

    The first total solar eclipse to cross the United States from coast to coast in 99 years will occur on August 21, 2017, with a 70-mile-wide path of totality from Oregon to South Carolina, with cloudiness statistics more favorable in the northwest than in the southeast. I will discuss a series of observations of the solar corona made during recent solar eclipses and related spacecraft observations. I will further discuss plans for using the 2017 eclipse for furthering our studies of the heating of the solar corona to millions of kelvins, of the dynamics of coronal mass ejections and polar plumes, and of the response of the corona to the solar magnetic field. I will conclude by discussing public-education plans for the eclipse, during which the whole U.S., Mexico, Central America, and Canada will enjoy a partial eclipse. My work at solar eclipses has recently been supported by the NSF and the Committee for Research and Exploration of the National Geographic Society, and I thank them both for research grants for our scientific studies of the 2017 total eclipse, including AGS-1602461 from the NSF and 987816 from National Geographic.

  3. Probing the Fundamental Physics of the Solar Corona with Lunar Solar Occultation Observations

    NASA Astrophysics Data System (ADS)

    Habbal, S. Rifai; Morgan, H.; Druckmüller, M.; Ding, A.; Cooper, J. F.; Daw, A.; Sittler, E. C.

    2013-07-01

    Imaging and spectroscopy of the solar corona, coupled with polarimetry, are the only tools available at present to capture signatures of physical processes responsible for coronal heating and solar wind acceleration within the first few solar radii above the solar limb. With the recent advent of improved detector technology and image processing techniques, broad-band white light and narrow-band multi-wavelength observations of coronal forbidden lines, made during total solar eclipses, have started to yield new views about the thermodynamic and magnetic properties of coronal structures. This paper outlines these unique capabilities, which until present, have been feasible primarily with observations during natural total solar eclipses. This work also draws attention to the exciting possibility of greatly increasing the frequency and duration of solar eclipse observations with Moon orbiting observatories utilizing lunar limb occultation of the solar disk for coronal measurements.

  4. The MiniMax24 corona at the November 14, 2012 total solar eclipse in Australia

    NASA Astrophysics Data System (ADS)

    Stoeva, Penka; Kuzin, Sergey; Benev, Boyan; Stoev, Alexey

    We discuss the results from observations of the white-light corona conducted half a year before the MiniMax24, during the November 14, 2012 total solar eclipse in Australia, in the region of Mount Molloy, 150km from Palm Cove, Cairns, Queensland. WL images show the continuum K-corona that result from scattering of photospheric light by electrons in the corona. Solar corona was observed with 300 mm objective and 2000 mm Macsutov-Cassegrain telescope. Photos were made with different exposures in order to obtain high-resolution composite image of the white light corona, which allows us to reveal its small- and large-scale structures. The eclipse observations were compared with near-simultaneous SOHO EUV and SOHO LASCO visible-light coronagraphic images. Analysis of the Ludendorf flattening index (0.024) and phase of the solar cycle (+0.87) shows that white light corona is solar maximum type - the shape is spherical with many streamers located at all azimuths around the occulted disk. Observations of the November 14, 2012 total solar eclipse give us the possibility to investigate solar corona structure during this unique minimal maximum of the solar activity cycle and compare it with previous eclipse observations during maximum.

  5. Creation of current filaments in the solar corona

    NASA Technical Reports Server (NTRS)

    Mikic, Z.; Schnack, D. D.; Van Hoven, G.

    1989-01-01

    It has been suggested that the solar corona is heated by the dissipation of electric currents. The low value of the resistivity requires the magnetic field to have structure at very small length scales if this mechanism is to work. In this paper it is demonstrated that the coronal magnetic field acquires small-scale structure through the braiding produced by smooth, randomly phased, photospheric flows. The current density develops a filamentary structure and grows exponentially in time. Nonlinear processes in the ideal magnetohydrodynamic equations produce a cascade effect, in which the structure introduced by the flow at large length scales is transferred to smaller scales. If this process continues down to the resistive dissipation length scale, it would provide an effective mechanism for coronal heating.

  6. 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.

  7. A New Diagnostic Technique for the Solar Corona

    NASA Technical Reports Server (NTRS)

    Nelson, R.; Davila, Joseph M.; St.Cyr, O. C.; Oegerle, William (Technical Monitor)

    2002-01-01

    Over the last 30-40 years spectroscopic observation of the EUV (extreme ultraviolet) line emission has proved invaluable as a diagnostic of the solar coronal plasma state. Line ratios have been used to determine electron density, electron temperature and ion flow velocity. In this paper, we present results obtained with a new measurement technique that uses spectroscopic observations of the white light corona to obtain the electron density, temperature, and flow velocity. A prototype instrument has been designed and built to obtain visible light spectra (3800-4300 A) with modest resolution. This instrument was used to obtain coronal observations during the June 2001 eclipse in Zambia. The data were corrected for sky and instrument transmission to derive the electron temperature and flow speed. Results from these measurements will be discussed.

  8. 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 (λ = 8.42 Å, 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.

  9. Results of interferometric observations of the F-corona radial velocity field between 3 and 7 solar radii

    NASA Astrophysics Data System (ADS)

    Shcheglov, P. V.; Shestakova, L. I.; Aimanov, A. K.

    1987-02-01

    During the July 31, 1981 eclipse, F-corona interferograms were obtained near the 5184-A Mg I line covering the 3-7 solar radius region. A Fabry-Perot etalon in the exit pupil and a contact fiber-optic intensifier were used, the instrumental FWHM being 0.5 A = about 30 km/s. Radial velocities of interplanetary dust were obtained measuring Doppler shift of absorption lines. A prograde Keplerian velocity component was found, giving after averaging Vr = (5.4 + or - 0.7)R/solar radius + (5 + or - 4) km/s, as well as a retrograde motion. At 6-7 solar radius near the north coronal hole, a local stream with Vr = +130 km/s was observed. Although at large distances from the sun the sky brightness exceeds that of the F-corona, absorption lines are absent, so the sky brightness continuous component is predominant, and the K-corona scattered light may be its main source.

  10. White-light corona and solar polar magnetic field strength over solar cycles

    NASA Astrophysics Data System (ADS)

    Rušin, V.; Saniga, M.; Komžík, R.

    2014-10-01

    We discuss the large-scale structure of the solar corona, in particular its helmet streamers, as observed during total solar eclipses around maxima of solar cycles and make its comparison with solar polar magnetic field strength as observed by the Wilcox Solar Observatory (WSO) since 1976. Even though the magnetic field strength at the solar poles around cycle minima decreased minimally twice in the last forty years, distributions of helmet streamers around the Sun in different cycles around cycle maxima remain nearly the same. This indicates that large-scale magnetic structures governing the shape and evolution of helmet streamers must be of a different nature than those related with solar polar fields.

  11. Signature of open magnetic field lines in the extended solar corona and of solar wind acceleration

    NASA Technical Reports Server (NTRS)

    Antonucci, E.; Giordano, S.; Benna, C.; Kohl, J. L.; Noci, G.; Michels, J.; Fineschi, S.

    1997-01-01

    The observations carried out with the ultraviolet coronagraph spectrometer onboard the Solar and Heliospheric Observatory (SOHO) are discussed. The purpose of the observations was to determine the line of sight and radial velocity fields in coronal regions with different magnetic topology. The results showed that the regions where the high speed solar wind flows along open field lines are characterized by O VI 1032 and HI Lyman alpha 1216 lines. The global coronal maps of the line of sight velocity were reconstructed. The corona height, where the solar wind reaches 100 km/s, was determined.

  12. No evidence of a circumsolar dust ring from infrared observations of the 1991 solar eclipse

    NASA Astrophysics Data System (ADS)

    Lamy, P.; Kuhn, J. R.; Lin, H.; Koutchmy, S.; Smartt, R. N.

    1992-09-01

    Large-format IR array detectors are employed to map the solar corona out to large angular distances from the sun during the 1991 eclipse, and the images are used to confirm the absence of a circumsolar dust ring. An HgCdTe-array detector is employed with broadband H, J, and K filters to study wavelengths of 1-2.5 microns. An inhomogeneous structure in the K-corona is noted in the images of the H- and K-band surface brightnesses, and elliptical flattening of the F-corona is cnfirmed. The 2D IR observations are argued to provide unambiguous evidence that no circumstellar dust ring existed during the time of observation. The dynamics of the interplanetary dust particles are theorized to be the product of influences other than or in addition to those described by gravitational-radiation drag calculations. The results suggest that previous detections of dust rings do not necessarily reflect the existence of 'local' coronal dust rings.

  13. Solar corona caused by juniper pollen in Texas.

    PubMed

    Mims, F M

    1998-03-20

    Coronas are colorful, concentric rings centered on a bright light such as the Sun, the Moon, or even a streetlamp. Coronas are most commonly caused by water droplets or ice particles of relatively uniform size. Observers in Finland have reported spectacular clear-sky coronas caused by pollen grains. A clear-sky corona in central Texas occurred during the peak of the juniper pollinating season. The aerosol optical thickness at each of three wavelengths was highest when the corona was most prominent. Photographic measurements of the corona infer a particle diameter of ~32.4 mum. Because juniper pollen grains have a diameter of from 22 to 30 mum, they are the aerosol most likely to have caused the corona.

  14. Diagnostics of the solar corona from comparison between Faraday rotation measurements and magnetohydrodynamic simulations

    SciTech Connect

    Le Chat, G.; Cohen, O.; Kasper, J. C.; Spangler, S. R.

    2014-07-10

    Polarized natural radio sources passing behind the Sun experience Faraday rotation as a consequence of the electron density and magnetic field strength in coronal plasma. Since Faraday rotation is proportional to the product of the density and the component of the magnetic field along the line of sight of the observer, a model is required to interpret the observations and infer coronal structures. Faraday rotation observations have been compared with relatively ad hoc models of the corona. Here for the first time we compare these observations with magnetohydrodynamic (MHD) models of the solar corona driven by measurements of the photospheric magnetic field. We use observations made with the NRAO Very Large Array of 34 polarized radio sources occulted by the solar corona between 5 and 14 solar radii. The measurements were made during 1997 May, and 2005 March and April. We compare the observed Faraday rotation values with values extracted from MHD steady-state simulations of the solar corona. We find that (1) using a synoptic map of the solar magnetic field just one Carrington rotation off produces poorer agreements, meaning that the outer corona changes in the course of one month, even in solar minimum; (2) global MHD models of the solar corona driven by photospheric magnetic field measurements are generally able to reproduce Faraday rotation observations; and (3) some sources show significant disagreement between the model and the observations, which appears to be a function of the proximity of the line of sight to the large-scale heliospheric current sheet.

  15. THE EXPANSION OF ACTIVE REGIONS INTO THE EXTENDED SOLAR CORONA

    SciTech Connect

    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 Degree-Sign , and expanding to heights of at least 12 R{sub Sun }. The expansion speeds are {approx}10 km s{sup -1} in the AIA/SDO field of view, below {approx}20 km s{sup -1} at 2.3 R{sub Sun }, and accelerate linearly to {approx}60 km s{sup -1} at 5 R{sub Sun }. They appear with a frequency of one every {approx}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.

  16. No evidence of a circumsolar dust ring from infrared observations of the 1991 solar eclipse.

    PubMed

    Lamy, P; Kuhn, J R; Lin, H; Koutchmy, S; Smartt, R N

    1992-09-04

    During the past 25 years there have been many attempts to detect a possible dust ring around the sun, with contradictory results. Before the 1991 eclipse, infrared eclipse experiments used single-element detectors to scan the corona along the ecliptic for excess surface brightness peaks. The availability of relatively large-format infrared array detectors now provides a considerable observational advantage: two-dimensional mapping of the brightness and polarization of the corona with high photometric precision. The 1991 eclipse path included the high-altitude Mauna Kea Observatory, a further advantage to measure the corona out to large angular distances from the sun. Results are reported from an experiment conducted on Mauna Kea with a HgCdTe-array detector sensitive to wavelengths between 1 and 2.5 micrometers, using broad-band J, H, and K filters. Although the sky conditions were not ideal, the H- and K-band surface brightnesses clearly show the inhomogeneous structure in the K-corona and the elliptical flattening of the F-corona, but no evidence of a circumsolar, local dust component out to 15 solar radii.

  17. Diagnostics of the Solar corona from Comparison Between Faraday Rotation Measurements and MHD Simulations

    NASA Astrophysics Data System (ADS)

    LE CHAT, G.; Kasper, J. C.; Cohen, O.; Spangler, S.

    2013-05-01

    Faraday rotation observations of natural radio sources allow remote diagnostics of the density and magnetic field of the solar corona. We use linear polarization observations made with the NRAO Very Large Array at frequencies of 1465 and 1665 MHz of 33 polarized radio sources occulted by the solar corona within 5 to 14 solar radii. The measurements were made during May 1997 (Mancuso and Spangler, 2000), March 2005 and april 2005 (Ingleby et al., 2005), corresponding to Carrington rotation number 1922, 1923, 2027 and 2028. We compare the observed Faraday rotation values with values extracted from MHD steady-state simulations of the solar corona using the BATS-R-US model. The simulations are driven by magnetogram data taken at the same time as the observed data. We present the agreement between the model and the Faraday rotation measurements, and we discuss the contraints imposed on models of the quiet corona and CMEs by these observations.

  18. Destruction of Sun-Grazing Comet C-2011 N3 (SOHO) Within the Low Solar Corona

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    Observations of comets in Sun-grazing orbits that survive solar insolation long enough to penetrate into the Suns 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 C2011 N3 (SOHO) within the low solar corona in five wavelength bands in the extreme ultraviolet (EUV). The comet penetrated to within 0.146 solarradius (100,000 kilometers) of the solar surface before its EUV signal disappeared.

  19. Solar Wind Disturbances and Their Sources in the EUV Solar Corona

    NASA Astrophysics Data System (ADS)

    Zhukov, A. N.; Veselovsky, I. S.; Clette, F.; Hochedez, J.-F.; Dmitriev, A. V.; Romashets, E. P.; Bothmer, V.; Cargill, P.

    2003-09-01

    We investigate possible links between the activity manifestations in the solar corona and conditions in the solar wind. For the reduction of this immense task we have selected 206 events in the solar wind in 1997 - 2000 corresponding to geomagnetic events with Ap > 20 (compiled into a database at http://alpha.sinp.msu.ru/apev). Up to now, 24 events during the epoch of low solar activity (January 1997 - January 1998) are investigated. The solar wind conditions monitored by ACE and WIND spacecraft were traced back to the solar corona observed by SOHO/EIT. The search for coronal signatures which are probably associated with the disturbed solar wind conditions was performed. The coronal sources of these 24 events are identified, namely: eruptions in active regions, filament eruptions and coronal holes. It is shown that halo and partial halo CMEs observed within the SOHO/LASCO sensitivity limits are not necessary indicators of Earth-directed eruptions, and coronal EUV dimmings can be used as a complementary indicator. We also found that a structure now conventionally called a ``sigmoid'' cannot be represented as a single S-shaped loop (flux tube), but exhibits an assembly of many smaller structures. It could be formed and destroyed via eruptions.

  20. Interacting Coronae of Two T Tauri Stars: First Observational Evidence for Solar-Like Helmet Streamers

    DTIC Science & Technology

    2008-01-01

    extended, associated with the radio emission. In the very well studied solar corona it is known that there exist small, closed coronal loops as well as...894 Vourlidas , A. 2006, Solar Activity and its Magnetic Origin, ed. V. Bothmer, & A. Hady (Cambridge University Press), 197 Welty, A. D. 1995, AJ...A&A 480, 489–494 (2008) DOI: 10.1051/0004-6361:20078637 c© ESO 2008 Astronomy & Astrophysics Interacting coronae of two T Tauri stars: first

  1. Laboratory identification of MHD eruption criteria in the solar corona

    NASA Astrophysics Data System (ADS)

    Myers, Clayton E.

    2015-11-01

    Ideal magnetohydrodynamic (MHD) instabilities such as the kink and torus instabilities are believed to play an important role in driving ``storage-and-release'' eruptions in the solar corona. These instabilities act on long-lived, arched magnetic flux ropes that are ``line-tied'' to the solar surface. In spite of numerous observational and computational studies, the conditions under which these instabilities produce an eruption remain a subject of intense debate. In this paper, we use a line-tied, arched flux rope experiment to study storage-and-release eruptions in the laboratory. An in situ array of miniature magnetic probes is used to assess the equilibrium and stability of the laboratory flux ropes. Two major results are reported here: First, a new stability regime is identified where torus-unstable flux ropes fail to erupt. In this ``failed torus'' regime, the flux rope is torus-unstable but kink-stable. Under these conditions, a dynamic ``toroidal field tension force'' surges in magnitude, causing the flux rope to contract. This tension force, which is missing from existing eruption models, is the J × B force between self-generated poloidal currents in the flux rope and the toroidal (guide) component of the vacuum field. Secondly, a clear torus instability threshold is observed in the kink-unstable regime. This latter result, which is consistent with existing theoretical and numerical results, verifies the key role of the torus instability in driving solar eruptions. In collaboration with M. Yamada, H. Ji, J. Yoo, W. Fox, J. Jara-Almonte, A. Savcheva, and E. E. DeLuca. This research is supported by DoE Contract No. DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

  2. The Corona of the Young Solar Analog EK Draconis

    NASA Technical Reports Server (NTRS)

    Gudel, M.; Schmitt, J. H. M. M.; Benz, A. O.; Elias, N. M., II

    1995-01-01

    First coronal microwave and new soft X-ray observations of the very active, near-Zero-Age Main-Sequence (ZAMS) dGOe star EK Dra = HD 129333 show that this analog of the young Sun is more luminous in both emissions than most single M-dwarf flare stars. Variations in the 8.4 GHz flux include modulation with the optically determined rotation period of 2.7 days. This result points to a non-uniform filling of the corona with energetic electrons due to an incomplete coverage of the surface with active regions and a source volume that is not concentric with the star. The radio luminosity varying between log L(sub R) = 13.6 and 14.6 (L(sub R) in erg/s/Hz) shows evidence for unpolarized gyrosynchrotron flares, while strongly polarized flares were absent during the observations. This star is the first young, truly solar-like main sequence G star discovered in microwaves. Having just arrived on the main sequence, it conclusively proves that young, solar-like G stars can maintain very high levels of radio emission after their T Tau phase. The X-ray observations were obtained from the ROSAT All-Sky Survey (RASS). The average X-ray luminosity amounts to log L(sub x) = 29.9 (L(sub x) in erg/s). A Raymond-Smith type plasma model fit yields two plasma components at temperatures of 1.9 and 10 MK, with volume emission measures of 1.2 and 2.5 x 10 (exp 52)/cu cm, respectively. The X-ray light curve is significantly variable, with the photon count rate from the cooler plasma being strongly modulated by the rotation period; the emission from the hotter plasma is only weakly variable. Modeling of the source distribution in the stellar corona yields electron densities of the order of 4 x 10(exp 10)/cu cm or higher for the cool plasma component. It indicates that a considerable portion of EK Dra's high X-ray luminosity is due to high-density plasma rather than large emission volume. Parameters for an X-ray flare indicate an electron density of 1.75 x 10(exp 11)/cu cm and a source height of

  3. Dust removal from solar cells

    NASA Technical Reports Server (NTRS)

    Ashpis, David E. (Inventor)

    2011-01-01

    A solar panel cleaning device includes a solar panel having a plurality of photovoltaic cells arranged in rows and embedded in the solar panel with space between the rows. A transparent dielectric overlay is affixed to the solar panel. A plurality of electrode pairs each of which includes an upper and a lower electrode are arranged on opposite sides of the transparent dielectric and are affixed thereto. The electrodes may be transparent electrodes which may be arranged without concern for blocking sunlight to the solar panel. The solar panel may be a dielectric and its dielectric properties may be continuously and spatially variable. Alternatively the dielectric used may have dielectric segments which produce different electrical field and which affects the wind "generated."

  4. Dust Removal from Solar Cells

    NASA Technical Reports Server (NTRS)

    Ashpis, David E. (Inventor)

    2015-01-01

    A solar panel cleaning device includes a solar panel having a plurality of photovoltaic cells arranged in rows and embedded in the solar panel with space between the rows. A transparent dielectric overlay is affixed to the solar panel. A plurality of electrode pairs each of which includes an upper and a lower electrode are arranged on opposite sides of the transparent dielectric and are affixed thereto. The electrodes may be transparent electrodes which may be arranged without concern for blocking sunlight to the solar panel. The solar panel may be a dielectric and its dielectric properties may be continuously and spatially variable. Alternatively the dielectric used may have dielectric segments which produce different electrical field and which affects the wind "generated."

  5. Inbound waves in the solar corona: A direct indicator of Alfvén surface location

    SciTech Connect

    DeForest, C. E.; Howard, T. A.; McComas, D. J.

    2014-06-01

    The tenuous supersonic solar wind that streams from the top of the corona passes through a natural boundary—the Alfvén surface—that marks the causal disconnection of individual packets of plasma and magnetic flux from the Sun itself. The Alfvén surface is the locus where the radial motion of the accelerating solar wind passes the radial Alfvén speed, and therefore any displacement of material cannot carry information back down into the corona. It is thus the natural outer boundary of the solar corona and the inner boundary of interplanetary space. Using a new and unique motion analysis to separate inbound and outbound motions in synoptic visible-light image sequences from the COR2 coronagraph on board the STEREO-A spacecraft, we have identified inbound wave motion in the outer corona beyond 6 solar radii for the first time and used it to determine that the Alfvén surface is at least 12 solar radii from the Sun over the polar coronal holes and 15 solar radii in the streamer belt, well beyond the distance planned for NASA's upcoming Solar Probe Plus mission. To our knowledge, this is the first measurement of inbound waves in the outer solar corona and the first direct measurement of lower bounds for the Alfvén surface.

  6. 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.

  7. The Soft X-Ray/Microwave Ratio of Solar and Stellar Flares and Coronae

    NASA Technical Reports Server (NTRS)

    Benz, A. O.; Guedel, M.

    1994-01-01

    We have carried out plasma diagnostics of solar flares using soft X-ray (SXR) and simultaneous microwave observations and have compared the ratio of X-ray to microwave luminosities of solar flares with various active late-type stars available in the published literature. Both the SXR low-level ('quiescent') emission from stellar coronae and the flaring emission from the Sun and stars are generally interpreted as thermal radiations of coronal plasmas. On the other hand, the microwave emission of stars and solar flares is generally attributed to an extremely hot or nonthermal population of electrons. Solar flare SXR are conventionally measured in a narrower and harder passband than the stellar sources. Observations of the GOES-2 satellite in two energy channels have been used to estimate the luminosity of solar flares as it would appear in the ROSAT satellite passband. The solar and stellar flare luminosities fit well at the lower end of the active stellar coronae. The flare SXR/microwave ratio is similar to the ratio for stellar coronae. The average ratio follows a power-law relation L(sub X) varies as L(sub R)(sup 0.73 +/- 0.03) over 10 orders of magnitude from solar microflares to RS CVn and FK Com-type coronae. Dwarf Me and Ke stars, and RS CVn stars are also compatible with a linear SXR/microwave relation, but the ratio is slightly different for each type of star. Considering the differences between solar flares, stellar flares and the various active stellar coronae, the similarity of the SXR/microwave ratios is surprising. It suggests that the energetic electrons in low-level stellar coronae observed in microwaves are related in a similar way to the coronal thermal plasma as flare electrons to the flare thermal plasma, and, consequently, that the heating mechanism of active stellar coronae is a flare-like process.

  8. DUST AROUND R CORONAE BOREALIS STARS. II. INFRARED EMISSION FEATURES IN AN H-POOR ENVIRONMENT

    SciTech Connect

    Garcia-Hernandez, D. A.; Lambert, D. L. E-mail: nkrao@iiap.res.in

    2013-08-20

    Residual Spitzer/Infrared Spectrograph 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 {approx}6-10 {mu}m dust emission complex is seen in the RCBs showing an extreme H-deficiency. A secondary and much weaker {approx}11.5-15 {mu}m broad emission feature is detected in a few RCBs with the strongest {approx}6-10 {mu}m dust complex. The Spitzer infrared spectra reveal for the first time the structure within the {approx}6-10 {mu}m dust complex, showing the presence of strong C-C stretching modes at {approx}6.3 and 8.1 {mu}m as well as of other dust features at {approx}5.9, 6.9, and 7.3 {mu}m, 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 and circumstellar properties, suggesting that the RCB dust features may not be dependent on the present physical conditions around RCB stars. The only exception seems to be the central wavelength of the 6.3 {mu}m feature, which is blueshifted in those RCBs showing also the UIRs, i.e., the RCBs with the smallest H deficiency.

  9. 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

    2011-07-27

    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.

  10. Sun-grazing comets as probes of the physics of the solar corona

    NASA Astrophysics Data System (ADS)

    Schrijver, C.

    2012-12-01

    In 2011, two Sun-grazing comets were observed at EUV wavelengths as they descended into the inner solar corona. The first, C/2011 N3 (SoHO), was observed by the Atmospheric Imaging Assembly of the Solar Dynamics Observatory up to the point at which it terminated its existence very near to its orbital perihelion. Its tail emission was visible to within 0.146 solar radii of the solar surface. The second comet in the inner corona, C/2011 W3, was observed by a fleet of observatories, including the STEREO spacecraft which saw it during its approach to, and subsequent voyage away from, its orbital perihelion behind the Sun as seen from Earth. C2011 W3 survied for only about 1.6 more days when the last of its material sublimated. The variable cometary tails, observed in a multiple EUV passbands, were seen to be deflected by the interaction with the solar magnetic field as the comets flew through the corona. In this talk, I will discuss lessons about the solar corona learned from the cometary emission and absorption features and from the interaction of the ionizing cometary material with the magnetized corona through which it traveled.

  11. Laboratory Identification of MHD Eruption Criteria in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Yamada, M.; Myers, C. E.; Ji, H.; Yoo, J.; Fox, W. R., II; Jara-Almonte, J.; Savcheva, A. S.; DeLuca, E. E.

    2015-12-01

    Ideal magnetohydrodynamic (MHD) instabilities such as the kink [1] and torus [2] instabilities are believed to play an important role in driving "storage-and-release" eruptions in the solar corona. These instabilities act on long-lived, arched magnetic flux ropes that are "line-tied" to the solar surface. In spite of numerous observational and computational studies, the conditions under which these instabilities produce an eruption remain a subject of intense debate. In this paper, we use a line-tied, arched flux rope experiment to study storage-and-release eruptions in the laboratory [3]. An in situ array of miniature magnetic probes is used to assess the equilibrium and stability of the laboratory flux ropes. Two major results are reported here: First, a new stability regime is identified where torus-unstable flux ropes fail to erupt. In this "failed torus" regime, the flux rope is torus-unstable but kink-stable. Under these conditions, a dynamic "toroidal field tension force" surges in magnitude and causes the flux rope to contract. This tension force, which is missing from existing eruption models, is the J×B force between self-generated poloidal currents in the flux rope and the toroidal (guide) component of the vacuum field. Secondly, a clear torus instability threshold is observed in the kink-unstable regime. This latter result, which is consistent with existing theoretical [4] and numerical [5] findings, verifies the key role of the torus instability in driving some solar eruptions. This research is supported by DoE Contract No. DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO). [1] Hood & Priest, Geophys. Astrophys. Fluid Dynamics 17, 297 (1981) [2] Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006) [3] Myers, Ph.D. Thesis, Princeton University (2015) [4] Olmedo & Zhang, Astrophys. J. 718, 433 (2010) [5] Török & Kliem, Astrophys. J. 630, L97 (2005)

  12. Circumstellar Dust Shells: Clues to the Evolution of R Coronae Borealis Stars

    NASA Astrophysics Data System (ADS)

    Montiel, Edward J.; Clayton, Geoffrey C.

    2016-06-01

    R Coronae Borealis (RCB) stars are an exotic group of extremely hydrogen- deficient, carbon-rich supergiants that are known for their spectacular declines in brightness (up to 8 mags) at irregular intervals. Two scenarios are currently competing to explain the origins of these stars. One suggests that RCB stars are the products after a binary white dwarf (WD) system merges. The other takes a single, evolved star and has it undergo a final, helium-shell flash (FF) and becoming a cool giant. Recently, observations of elemental abundances in RCB stars have strongly swung the argument in favor of the WD merger model. The FF scenario has maintained its relevancy by seemingly being the only model able to offer a suitable explanation for one RCB feature that merger model has historically struggled with explaining: the presence of cold, circumstellar dust envelopes which might be fossil planetary nebulae (PNe). In reality, the shells could actually be fossil PNe, material left over from the WD merger, or mass lost during the RCB phase, itself. I will present the results of my dissertation, which is to try and discern the nature and history of the far-IR dust shells around RCB stars to help understand the origin of these enigmatic stars. I will discuss our efforts to determine the mass, size, temperature, and morphology of these diffuse structures surrounding a sample of RCB stars using multi-wavelength observations ranging from the ultraviolet to the submillimeter. These observations have provided unprecedented wavelength coverage for both the central stars and their CSM. They have been examined by eye for morphology and have been used in the construction of maximum-light spectral energy distributions (SEDs). I will present the results of our Monte Carlo radiative transfer of the maximum-light SEDs. Finally, I will highlight our work investigating the HI abundance of the envelope of R Coronae Borealis, itself, using archival 21—cm observations from the Arecibo

  13. 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.

  14. Shock Formation Height in the Solar Corona Estimated from SDO and Radio Observations

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Nitta, N.

    2011-01-01

    Wave transients at EUV wavelengths and type II radio bursts are good indicators of shock formation in the solar corona. We use recent EUV wave observations from SDO and combine them with metric type II radio data to estimate the height in the corona where the shocks form. We compare the results with those obtained from other methods. We also estimate the shock formation heights independently using white-light observations of coronal mass ejections that ultimately drive the shocks.

  15. Laboratory Experiments to Simulate and Investigate the Physics Underlying the Dynamics of Merging Solar Corona Structures

    DTIC Science & Technology

    2016-06-05

    generation of whistler waves), particle energization (e.g., electron and ion heating , changes in ionization state, emission of energetic photons), complex...particle orbits in an electro-magnetic field (e.g., extension of adiabatic invariant concepts, stochastic heating , Hamiltonian concepts...TERMS solar physics, plasma physics, eruptions from the solar corona, MHD instabilities, waves, heating , diagnostic methods, magnetohydrodynamics

  16. 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.

  17. Study of the solar corona using radio and space observations

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.

    1984-01-01

    The physics of coronal transients, the characteristics of radiation and accelerated particles at the time of flares, and the density/temperature structure of the transition region and corona and the coronal magnetic field are investigated.

  18. 3D ELECTRON DENSITY DISTRIBUTIONS IN THE SOLAR CORONA DURING SOLAR MINIMA: ASSESSMENT FOR MORE REALISTIC SOLAR WIND MODELING

    SciTech Connect

    Patoul, Judith de; Foullon, Claire; Riley, Pete E-mail: c.foullon@exeter.ac.uk

    2015-11-20

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996–1997 and 2008–2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We deduce that tomography offers reliable density distributions in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how they are magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus.

  19. A New Solar System Dust Band

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

    The relative proportions of asteroidal and cometary material in the zodiacal cloud is an evolving debate. The determination of the asteroidal component is constrained through the study of the dust bands (the fine-structure component superimposed on the broad background cloud), since they have been confidently linked to specific, young, asteroid family disruptions in the main belt. These disruptions represent recent injections of dust into the cloud and thus hold the key to determining at least a minimum value of the asteroidal contribution. There are currently known to be three dust band pairs, one at approximately 10 degrees corresponding to the Veritas family and two central band pairs near the ecliptic, one of which corresponds to the Karin cluster of the Koronis family. However, through careful co-adding of almost all the pole-to-pole intensity scans in the mid infrared wavebands of the IRAS data set, a new solar system dust band has been found at approximately 17 degrees inclination. We think this is a confirmation of the M/N partial band pair suggested by Sykes (1988). The new dust band appears to be mostly, yet not completely formed, which we attribute to the young age of the likely sources. We will present dynamical modeling of the new band which allows us to determine the most likely source and amount of cross-sectional area of dust in the band. This is turn allows us to put constraints on the size of the precursor and amount of dust contributed by this source to the background cloud. Since the band is incomplete, the dynamics of the distribution of the node will allow us to put loose constraints on the time of formation of this band and compare with the ages of the potential sources. This work is funded by NASA GSRP.

  20. Simulated kinetic effects of the corona and solar cycle on high altitude ion transport at Mars

    NASA Astrophysics Data System (ADS)

    Curry, S. M.; Liemohn, M.; Fang, X.; Brain, D.; Ma, Y.

    2013-06-01

    We present results from the Mars Test Particle (MTP) simulation as part of a community‒wide model comparison in order to quantify the role of different neutral atmospheric conditions in planetary ion transport and escape. This study examines the effects of individual ion motion by simulating particle trajectories for three cases: solar minimum without the neutral corona, solar minimum with the inclusion of the neutral corona, and solar maximum with the inclusion of the neutral corona. The MTP simulates 1.5 billion test particles through background electric and magnetic fields computed by a global magnetohydrodynamic model. By implementing virtual detectors in the simulation, the MTP has generated velocity space distributions of pickup ions and quantifies the ion acceleration at different spatial locations. The study found that the inclusion of a hot neutral corona greatly affects the total O+ production and subsequent loss, roughly doubling the total escape for solar minimum conditions and directly contributing to high energy sources above 10 keV. The solar cycle influences the amount of O+ flux observed by the virtual detectors, increasing the O+ flux and total escape by an order of magnitude from solar minimum to maximum. Additionally, solar maximum case induces greater mass loading of the magnetic fields, which decreases the gyroradius of the ions and redirects a significant ion population downtail to subsequently escape.

  1. On the Possible Influence of the Solar Magnetic Field on the Circumsolar Dust Complex

    NASA Astrophysics Data System (ADS)

    Krivov, A. V.; Kimura, H.; Mann, I.

    We performed a dynamical modeling of the dust ring that presumably exists around the Sun near 4R_odot. The dust particles were assumed to be ballistic particle-cluster aggregates, and the following forces/effects acting on the grains were taken into account: solar gravity, direct solar radiation pressure, Poynting-Robertson force, sublimation, and the Lorentz force, with a special attention paid to the latter. We used the modeled grain charges, resulting from sticking and penetration of solar wind particles into dust grains, secondary electron emission, photo-electron emission, and thermionic emission. For solar magnetic field, we used the Potential Field - Source Surface model by Hoeksema and Scherrer (1986) and harmonic coefficients for 1976-1996 of Wilcox Solar Observatory. Our modeling suggests that the variations of solar magnetic field have a little effect on the spatial distribution of absorbing (amorphous carbon) grains that are believed to cause the observed peak feature in the F-corona brightness, and therefore does not support the idea about the correlation between the solar activity phase and observability of the peak feature. However, the magnetic variations may cause appreciable changes in the vertical (latitudinal) distribution of transparent silicate aggregates, responsible for the continuum in the elongation dependence of the brightness.

  2. Dust Accumulation and Cleaning of the MER Opportunity Solar Array

    NASA Astrophysics Data System (ADS)

    Herman, J.

    2015-12-01

    The solar array of the NASA Mars Exploration Rover (MER) Opportunity was expected to accumulate a sufficient quantity of dust after ninety Martian days (sols) such 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, Opportunity continues to operate on the Martian surface for over 4000 sols (over six Mars years). During this time period, the rover experienced six Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a method to scientifically 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 Meridiani Planum over the course of the entire mission to date.

  3. 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.

  4. 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.

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

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    2006-01-01

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

  6. Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F-Coronal Brightness

    NASA Technical Reports Server (NTRS)

    Ragot, B. R.; Kahler, S. W.

    2003-01-01

    The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Solar Radius. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of the CME/dust interactions we consider the dominant forces, with and without CMEs. acting on the dust in the 3-5 Solar Radius region. Dust grain orbits are then computed to compare the drift rates from 5 to 3 Solar Radius. for periods of minimum and maximum solar activity, where a simple CME model is adopted to distinguish between the two periods. The ion-drag force, even in the quiet solar wind, reduces the drift time by a significant factor from its value estimated with the Poynting-Robertson drag force alone. The ion-drag effects of CMEs result in even shorter drift times of the large (greater than or approx. 3 microns) dust grains. hence faster depletion rates and lower dust-pain densities, at solar maxima. If dominated by thermal emission, the near-infrared brightness will thus display solar cycle variations close to the dust plane of symmetry. While trapping the smallest of the grains, the CME magnetic fields also scatter the grains of intermediate size (0.1-3 microns) in latitude. If light scattering by small grains close to the Sun dominates the optical brightness. the scattering by the CME magnetic fields will result in a solar cycle variation of the optical brightness distribution not exceeding 100% at high latitudes, with a higher isotropy reached at solar maxima. A good degree of latitudinal isotropy is already reached at low solar activity since the magnetic fields of the quiet solar wind so close to the Sun are able to scatter the small (less than or approx. 3 microns) grains up to the polar regions in only a few days or less, producing strong perturbations of their trajectories in less than half their orbital

  7. Alfvenically driven slow shocks in the solar chromosphere and corona

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1992-01-01

    The nonlinear evolution of an Alfvenic impulse launched from the photosphere and its dynamical effects on the chromosphere, transition region (TR), and corona are investigated using a simple 1D model. It is found that the leading edge of the torsional pulse can steepen into a fast shock in the chromosphere if the pulse is of sufficiently large amplitude and short duration. A slow shock which develops behind the Alfvenic pulse can reflect downgoing Alfven waves back up to the corona. The upgoing reflected wave can induce a significant upward ejection of the TR. Nonlinear dynamics are found to lead to very impulsive behavior at later times. It is suggested that impulsive events occurring in the TR or corona need not be interpreted in terms of reconnection-driven microflares. It is also found that B(0) in the chromosphere can be amplified when the TR and chromosphere fall.

  8. Polarization of the corona during the maximum of the solar cycle

    NASA Astrophysics Data System (ADS)

    Badalian, O. G.; Livshits, M. A.; Sykora, J.

    The preliminary results of measuring the polarization of the white-light corona, carried out during the Feb. 16, 1980 solar eclipse, are presented. The degree of polarization was observed to be relatively high all round the sun, with the exception of a coronal hole near the south pole. Together with well-expressed streams, high degrees of polarization were observed in the narrow ray at P = 210 deg and also in the broad region P = 310 deg - 350 deg. A possible nonhomogenous model of the white-light corona for the period of the solar maximum is discussed.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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 (SAIC), 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 (magnetohydrodynamic) model.

  10. Modeling electron density, temperature distribution in the solar corona based on solar surface magnetic field observations

    NASA Astrophysics Data System (ADS)

    Lago, A.; Rodríguez, J. M.; Vieira, L.; Coelho Stekel, T. R.; Costa, J. E. R.; Pinto, T. S. N.

    2015-12-01

    Magnetic fields constitute a natural link between the Sun, the Earth and the Heliosphere in general. The solar dynamo action maintains and strengthens the magnetic field in the solar interior. The structure of the solar corona is mostly determined by the configuration and evolution of the magnetic field. While open magnetic field lines carry plasma into the heliosphere, closed field lines confine plasma. Additionally, key physical processes that impact the evolution of Earth's atmosphere on time-scale from days to millennia, such as the soft X-ray and EUV emission, are also determined by the solar magnetic field. However, observations of the solar spectral irradiance are restricted to the last few solar cycles and are subject to large uncertainties. Here we present a physics-based model to reconstruct in near-real time the evolution of the solar EUV emission based on the configuration of the magnetic field imprinted on the solar surface and assuming that the emission lines are optically thin. The structure of the coronal magnetic field is estimated employing a potential field source surface extrapolation based on the synoptic charts. The coronal plasma temperature and density are described by a hydrostatic model. The emission is estimated to employ the CHIANTI database. The performance of the model is compared to the emission observed by EVE instrument on board SDO spacecraft. The preliminary results and uncertainties are discussed in details. Furthermore, we examine the possibility of delivery the reconstruction of the solar spectral irradiance in near-real time using the infrastructure provided by the Brazilian Space weather program (EMBRACE/INPE). This work is partially supported by CNPq/Brazil under the grant agreement no. 140779/2015-9.

  11. Preliminary results of the solar corona spectroscopic observation of 9th March 2016 Total Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Sungging Mumpuni, Emanuel; Zamzam Nurzaman, Muhamad; Suryana, Nana

    2016-11-01

    Spectroscopy observation of solar corona has been carried out from 9th March 2016 Total Solar Eclipse expedition in Maba, East Halmahera. Due to limitation by the weather condition during the observation, the obtained data were not favorable. Because of the low signal to noise ratio, the wavelength calibration was not straightforward. To obtain the optimum results, steps for data reduction were performed as the following: selecting the finest data, extracting the 1D spectrum from 2D spectrum, and calibrating spectrum wavelength (including careful interpolation). In this preliminary result, we discuss the instrumentation, the data under investigation, the extraction process of spectrum, and the polynomial interpolation that has been used for extracting information from our data.

  12. White light corona during total solar eclipse on March 9, 2016

    NASA Astrophysics Data System (ADS)

    Imaduddin, Irfan; Akbar, Evan I.; Putri, Gerhana P.

    2016-11-01

    We observed the white-light corona during the total solar eclipse of 2016 March 9 from Corong Beach, East Borneo. The solar corona is nearly circular with exception on the southern part of the Sun. Coronal structures are clearly seen. Based on the data, we obtained the Ludendorff flattening index, Nikolsky geometric flattening index, and phases of solar activity (Φ and P) are 0.129, 1.32, -0.716, and 0.573 respectively. Relation between Ludendorff and Nikolsky index, sunspot number, and phases of solar activity were discussed. We also predicted the amplitude of solar cycle 25 to be 196 ± 52 (based on 13-month smoothed monthly data) and 130 ± 42 (based on monthly sunspot number data).

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

    NASA Astrophysics Data System (ADS)

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

    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 interior. En agosto de 1997 comenzó a operar el coronógrafo solar (MICA) en El Leoncito como parte del Observatorio Solar Alemán-Argentino. Desde su instalación obtiene imágenes de la corona solar (1.05 a 2.0 radios solares) en 2 líneas espectrales correspondientes a la emisión de Fe XIV y Fe X. El instrumento puede obtener imágenes cada minuto por lo que es ideal para estudiar procesos rápidos. Presentamos observaciones recientes que muestran la capacidad del coronógrafo así como la evolución de algunos eventos dinámicos observados por MICA.

  14. 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.

  15. Early Solar Nebula Grains - Interplanetary Dust Particles

    NASA Astrophysics Data System (ADS)

    Bradley, J. P.

    This chapter examines the compositions, mineralogy, sources, and geochemical significance of interplanetary dust particles (IDPs). Despite their micrometer-scale dimensions and nanogram masses, it is now possible, primarily as a result of advances in small particle handling techniques and analytical instrumentation, to examine IDPs at close to atomic-scale resolution. The most widely used instruments for IDP studies are presently the analytical electron microscope, synchrotron facilities, and the ion microprobe. These laboratory analytical techniques are providing fundamental insights about IDP origins, mechanisms of formation, and grain processing phenomena that were important in the early solar system and presolar environments. At the same time, laboratory data from IDPs are being compared with astronomical data from dust in comets, circumstellar disks, and the interstellar medium. The direct comparison of grains in the laboratory with grains in astronomical environments is known as "astromineralogy."

  16. 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.

  17. Energy-Dependent Ionization States of Shock-Accelerated Particles in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.; Ng, C. K.; Tylka, A. J.

    2000-01-01

    We examine the range of possible energy dependence of the ionization states of ions that are shock-accelerated from the ambient plasma of the solar corona. If acceleration begins in a region of moderate density, sufficiently low in the corona, ions above about 0.1 MeV/amu approach an equilibrium charge state that depends primarily upon their speed and only weakly on the plasma temperature. We suggest that the large variations of the charge states with energy for ions such as Si and Fe observed in the 1997 November 6 event are consistent with stripping in moderately dense coronal. plasma during shock acceleration. In the large solar-particle events studied previously, acceleration occurs sufficiently high in the corona that even Fe ions up to 600 MeV/amu are not stripped of electrons.

  18. 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.

  19. Analysis of IRAS solar system dust data

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.; Nicholson, P. D.

    1991-01-01

    Data in the Infrared Astronomical Satellite (IRAS) Zodiacal History File were analyzed to extract dust band locations and peak brightness measurements from approximately 1,000 individual IRAS scans. The study had three goals. One was to show that the prominent solar system dust bands are associated with Hirayama asteroid families and thus that collisions between asteroids account for a significant fraction of the particles in the zodiacal cloud. Recent work suggests that while the Hirayama families are a major source of the dust in the bands, there may also be contributions from two or three smaller, more recently recognized asteroid families. A second goal was to show that there is evidence in the IRAS dust data for the transport of particles from asteroid belt to the Earth by Poynting-Robertson light drag and thus account for the fact that asteroid particles are collected in the Earth's stratosphere. Results of the study will confirm the location of the dust bands within the inner asteroid belt, and show conclusively that the material seen by IRAS is now spread over a wide range of distances from the sun. The third goal was to construct a model of the background zodiacal cloud that satisfies the proper dynamical constraints. Figures are provided to show the scans processed to remove zodiacal background and Galactic signals, and the resulting polynomial fits to the 25 micron scan. The latter provided objective estimates of band widths, peak locations, and peak fluxes. Modelling and analysis of the resulting band data has been presented at several conferences and is the subject of a number of forthcoming papers.

  20. Radial velocity measurements in the F corona

    NASA Astrophysics Data System (ADS)

    Beavers, W. I.; Eitter, J. J.; Carr, P. H.; Cook, B. C.

    1980-05-01

    A photoelectric radial velocity spectrometer was employed at the February 26, 1979 total solar eclipse in an attempt to detect motion in the F corona. Multiple dip features were recorded in scans made at points 3.2 and 4.3 solar radii west of the sun. By employing simple dynamic models these observations may be interpreted as evidence of the following two separate components of dust in the inner regions of the solar system: dust moving in prograde orbits outside the region beginning at about four solar radii from the sun, and dust falling into the sun with velocities from about 50 to 250 km/s.

  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. New Limits on Small-Scale Turbulence in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Spangler, Steven

    2005-10-01

    Many observed characteristics of the solar corona are interpreted as heating by ion cyclotron waves. Intense electromagnetic plasma waves, with wavelengths of the order of the ion inertial length or smaller, can be detected via a phenomenon called Faraday screen depolarization (Spangler and Mancuso, ApJ 530,491,2000). The fine scale turbulent magnetic field randomizes the Faraday rotation within the beam of a radio telescope, causing a decrease in the degree of linear polarization. We present new observations specifically intended to measure this effect. Observations were made with the Very Large Array radiotelescope on August 16 and 18, 2003, of the extended radio source 3C228 when it was occulted by the corona. The line of sight to the source passed at a heliocentric distance of 6.2 R on August 16, and 4.7 R on August 18. No indication is seen of depolarization by the corona. On August 16, the most conservative limit is that the degree of polarization is >=0.75 of its intrinsic value. A more likely limit is that the degree of polarization with the corona interposed is >=0.85 that in the absence of the corona. Even stronger limits are obtained on August 18. We discuss the implications of these measurements for the amplitude and outer scale of Alfv'en-Ion Cyclotron turbulence in the corona.

  3. Erratum: SDO-AIA Observation of Kelvin-helmholtz Instability in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Ofman, Leon; Thompson, Barbara J.

    2012-01-01

    The first SDOAIA observation of the KelvinHelmholtz instability in the solar corona in the 2010 April 8 event was reported by Ofman Thompson (2010, 2011). Foullon et al. (2011), which was published prior to Ofman Thompson (2011), claimed the detection of the KelvinHelmholtz instability in a later event (2010 November 3), and should have been cited in Ofman Thompson (2011).

  4. Electron acceleration to high energies at quasi-parallel shock waves in the solar corona

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    In the solar corona shock waves are generated by flares and/or coronal mass ejections. They manifest themselves in solar type 2 radio bursts appearing as emission stripes with a slow drift from high to low frequencies in dynamic radio spectra. Their nonthermal radio emission indicates that electrons are accelerated to suprathermal and/or relativistic velocities at these shocks. As well known by extraterrestrial in-situ measurements supercritical, quasi-parallel, collisionless shocks are accompanied by so-called SLAMS (short large amplitude magnetic field structures). These SLAMS can act as strong magnetic mirrors, at which charged particles can be reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two SLAMS and reach suprathermal and relativistic velocities. This mechanism of accelerating electrons is discussed for circumstances in the solar corona and may be responsible for the so-called 'herringbones' observed in solar type 2 radio bursts.

  5. 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.

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

    SciTech Connect

    Guerreiro, N.; Hansteen, Viggo; De Pontieu, B.

    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.

  7. 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.

  8. Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F-Coronal Brightness

    NASA Astrophysics Data System (ADS)

    Ragot, B. R.; Kahler, S. W.

    2003-09-01

    The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Rsolar. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of the CME/dust interactions we consider the dominant forces, with and without CMEs, acting on the dust in the 3-5 Rsolar region. Dust grain orbits are then computed to compare the drift rates from 5 to 3 Rsolar for periods of minimum and maximum solar activity, where a simple CME model is adopted to distinguish between the two periods. The ion-drag force, even in the quiet solar wind, reduces the drift time by a significant factor from its value estimated with the Poynting-Robertson drag force alone. The ion-drag effects of CMEs result in even shorter drift times of the large (>~3 μm) dust grains, hence faster depletion rates and lower dust-grain densities, at solar maxima. If dominated by thermal emission, the near-infrared brightness will thus display solar cycle variations close to the dust plane of symmetry. While trapping the smallest of the grains, the CME magnetic fields also scatter the grains of intermediate size (0.1-3 μm) in latitude. If light scattering by small grains close to the Sun dominates the optical brightness, the scattering by the CME magnetic fields will result in a solar cycle variation of the optical brightness distribution not exceeding 10% at high latitudes, with a higher isotropy reached at solar maxima. A good degree of latitudinal isotropy is already reached at low solar activity since the magnetic fields of the quiet solar wind so close to the Sun are able to scatter the small (<~3 μm) grains up to the polar regions in only a few days or less, producing strong perturbations of their trajectories in less than half their orbital periods. Finally, we consider possible observable consequences of

  9. Dynamics and Thermodynamics of the Corona Observed During the Total Solar Eclipse of 20 March 2015

    NASA Astrophysics Data System (ADS)

    Habbal, S. R.; Ding, A.; Druckmuller, M.; Johnson, J.; Morgan, H.; Arndt, M. B.; Alzate, N.; Hutton, J.

    2015-12-01

    Total solar eclipse observations are snapshots of the instantaneous dynamic state of the corona, and each observation never fails to yield surprises. Occurring at the declining phase of solar cycle 24, the 20 March 2015 total solar eclipse was no exception. Images taken through narrow bandpass filters centered on the Fe XIV 530.3 nm and Fe XI 789.2 nm coronal emission lines, showed a corona dominated by strong Fe XIV emission, with a peak ionization temperature of 1.8 MK, and with weak Fe XI emission at 1.1 MK, present mostly over the two poles. Simultaneous imaging spectroscopy through a dual channel high-resolution spectrometer, centered on these two wavelengths, revealed Doppler red shifts exceeding 1000 km/s in the extended corona, covering a distance range of up to 1.5 solar radii above the solar surface. These redshifts together with the observed Doppler broadening could be assigned to specific coronal structures, which were observed simultaneously in high resolution white light images. By comparing these observations with contemporaneous observations from SDO, SWAP/Proba2 and LASCO/C2 and C3, the dynamics of the coronal plasma, as well as its thermodynamics, could be mapped in a region of space, untenable to present-day observatories. These latest eclipse observations underscore the unique scientific opportunities accessible with similar instrumentation during the all-american 21 August 2017 total solar eclipse.

  10. The global August 11, 1999 eclipse corona and solar cycle variations

    NASA Astrophysics Data System (ADS)

    Adjabshirizadeh, Ali; Koutchmy, Serge

    2002-03-01

    Qualitative results from the last solar total eclipse (August 11th, 1999) are presented in order to extract some quantitative parameters permitting to discuss the structure of the near-maximum corona and insert the results among what is known of the changing with the solar cycle of activity structure. The collaborative study of the solar corona has been performed in Iran, using a radial gradient filter in white light and other techniques. From the eclipse-processed pictures, a structural drawing was analysed to give the distribution of streamlines over the entire corona, in order to look at the deviations from the local radial direction of identified coronal streamers. From the deduced parameter and the known solar cycle variations of this instantaneous "average deviation" of coronal streamers, as deduced from eclipse observations of 4 preceding cycles, we correctly predicted the moment of the following maximum of activity. We further discuss the method, using the "average deviations" measured in 1996 - 2001 from the Lasco C2 coronagraph processed images (from NRL) of SoHO and found an excellent agreement with the parameters deduced from the last total eclipses of 1998, 1999 and 2001. We believe that "average deviations" are a good parameter to contribute in the understanding of the origin of solar cycle variations of the solar wind and of the magnetic field.

  11. STATISTICS OF DENSITY FLUCTUATIONS DURING THE TRANSITION FROM THE OUTER SOLAR CORONA TO THE INTERPLANETARY SPACE

    SciTech Connect

    Telloni, D.; Antonucci, E.; Bruno, R.; D'Amicis, R.; Carbone, V.

    2009-11-20

    This paper investigates the evolution of the plasma density fluctuations of the fast and slow solar wind from the solar corona into the interplanetary space. The study is performed by comparing the low-frequency spectra and the phase correlation of the proton density oscillations, measured in the inner heliosphere with the Helios 2 in situ instrumentation, with those due to the large-scale density perturbations observed with UVCS/SOHO in the outer corona. We find that the characteristics of density fluctuations of the fast solar wind are maintained in the transition from the outer corona to the inner heliosphere, thus suggesting a coronal imprint for the heliospheric large-scale 1/f {sup 2} noise spectrum. In contrast, a quick dynamical evolution is observed in the slow wind, which, starting from large-scale fluctuations with strong phase correlations in the outer corona, gives rise to a Kolmogorov-like spectrum and an accumulation of density structures at small scales at 0.3 AU. This can be explained in the framework of nearly incompressible turbulence.

  12. Interplanetary dust close to the Sun (F corona): Its observation in the visible and infrared by a rocket-borne coronagraph

    NASA Astrophysics Data System (ADS)

    Kneissel, B.; Mann, I.; Vandermeer, H.

    1989-06-01

    The observation of the Frauenhofer corona (F corona) is discussed. It provides the opportunity for studying the annihilation and creation of dust within circumstellar dust clouds. The specific patterns of scattering light and thermal radiation in the infrared, are studied. A spaceborne remote sensing experiment regarding the radiation properties of dust, in the visible for scattered sunlight, and in the infrared for the thermal emission of grains, is effectuated. It allows the analysis of this complex scenario. A rocketborne twin coronagraph is shown to be needed.

  13. New Constraints on Plasma Turbulence in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Spangler, S. R.; Spitler, L. G.

    2005-12-01

    One suggestion for coronal heating invokes the dissipation of high frequency, Alfvén-ion cyclotron waves which are generated in the photosphere and chromosphere and propagate into the corona. As we have previously noted (Spangler and Mancuso 2000, ApJ 530, 491) the properties of such waves can be constrained by radioastronomical observations. The observational effect is Faraday screen depolarization, in which stochastic Faraday rotation randomizes the polarization position angle on scales smaller than the telescope beam. We present observations made with the NRAO Very Large Array on August 16 and 18, 2003, when the radio galaxy 3C228 was viewed through the corona at heliocentric distances of 6.7 and 5.2 R⊙, respectively. The depolarization parameter D ≡ (m)/(m0) was measured, where m is the fractional linear polarization measured through the corona, and m0 is the intrinsic degree of polarization. Measurements were available for both hot spots of 3C228, and on both days of observation. The measurements are consistent with D=1 for both components on both days. These results are in agreement with, but superior to, previous reports of no coronal screen depolarization. Equations from Spangler and Mancuso (2000) are used to constrain the dimensionless amplitude and outer scale of the coronal turbulence. Turbulence with a dimensionless amplitude of 50 % or greater, and outer scale larger than 1000-2000 km, would have produced depolarization close to, or in excess of our limits. Turbulence with smaller dimensionless amplitude and outer scale would not have been detected with these measurements. This research was supported by grant ATM-0354782 from the National Science Foundation.

  14. Solar Wind Mass-Loading Due to Dust in the Vicinity of the Sun

    NASA Astrophysics Data System (ADS)

    Rasca, A.; Horanyi, M.

    2012-12-01

    Collisionless shocks due to mass-loading were first discussed to describe the solar wind flow around a cometary atmosphere, showing its choking effects on the flow. Recent observations have led to an increased interest in mass-loading occurring in the solar corona, due to sun-grazing comets and also due to collisional debris production by sunward migrating interplanetary dust particles. Using one-dimensional simulations with a hydrodynamic model we have shown the impact on the solar wind from abrupt mass-loading in the coronal region. Full three-dimensional MHD simulations using the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) accomplish more to mimic specific events applicable to modeling the mass-loaded coronal wind caused by the presence of a sun-grazing comet, for example.

  15. 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.

  16. 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.

  17. Windblown dust emission, transport and deposition in solar farms

    NASA Astrophysics Data System (ADS)

    Lan, Chuanjin; Li, Zhen; Ma, Yanbao

    2012-11-01

    Dust accumulation on solar collectors can significantly reduce the electrical output of solar farms. The presence of solar panel array can significantly accelerate or decelerate wind speed and distort the wind velocity profiles near the ground, which leads to considerable changes in dust emissions, transportation as well as deposition. To examine the effects of solar panels on dust emission, transportation and deposition, the incompressible viscous flow past flat solar panels with ground effect was numerically investigated based on finite volume method. A hybrid approach known as detached-eddy simulation (DES), combining the main features of both large-eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS), is utilized to the compute the turbulence flow. Results show how aerolian dust emissions, transport and deposition are affected by wind speeds, solar panel orientation angles and panel geometries.

  18. Composition of the Solar Wind

    NASA Technical Reports Server (NTRS)

    Suess, S. T.

    2007-01-01

    The solar wind reflects the composition of the Sun and physical processes in the corona. Analysis produces information on how the solar system was formed and on physical processes in the corona. The analysis can also produce information on the local interstellar medium, galactic evolution, comets in the solar wind, dust in the heliosphere, and matter escaping from planets.

  19. 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

  20. Spatiotemporal organization of energy release events in the quiet solar corona

    SciTech Connect

    Uritsky, Vadim M.; Davila, Joseph M.

    2014-11-01

    Using data from the STEREO and SOHO spacecraft, we show that temporal organization of energy release events in the quiet solar corona is close to random, in contrast to the clustered behavior of flaring times in solar active regions. The locations of the quiet-Sun events follow the meso- and supergranulation pattern of the underling photosphere. Together with earlier reports of the scale-free event size statistics, our findings suggest that quiet solar regions responsible for bulk coronal heating operate in a driven self-organized critical state, possibly involving long-range Alfvénic interactions.

  1. Spatiotemporal Organization of Energy Release Events in the Quiet Solar Corona

    NASA Technical Reports Server (NTRS)

    Uritsky, Vadim M.; Davila, Joseph M.

    2014-01-01

    Using data from the STEREO and SOHO spacecraft, we show that temporal organization of energy release events in the quiet solar corona is close to random, in contrast to the clustered behavior of flaring times in solar active regions. The locations of the quiet-Sun events follow the meso- and supergranulation pattern of the underling photosphere. Together with earlier reports of the scale-free event size statistics, our findings suggest that quiet solar regions responsible for bulk coronal heating operate in a driven self-organized critical state, possibly involving long-range Alfvenic interactions.

  2. Ultraviolet and extreme ultraviolet spectroscopy of the solar corona at the Naval Research Laboratory.

    PubMed

    Moses, J D; Ko, Y-K; Laming, J M; Provornikova, E A; Strachan, L; Beltran, S Tun

    2015-11-01

    We review the history of ultraviolet and extreme ultraviolet spectroscopy with a specific focus on such activities at the Naval Research Laboratory and on studies of the extended solar corona and solar-wind source regions. We describe the problem of forecasting solar energetic particle events and discuss an observational technique designed to solve this problem by detecting supra-thermal seed particles as extended wings on spectral lines. Such seed particles are believed to be a necessary prerequisite for particle acceleration by heliospheric shock waves driven by a coronal mass ejection.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    Observations, from the Apollo 16 Spacecraft, in lunar orbit, of the total radiance of the K + F corona, from 3 to 55 solar radii are presented and discussed. The logarithmic slope of the K + F coronal radiance, at distances greater than 20 solar radii, is found to be n equals 1.93, slightly less steep than previous determinations. The photometric axis of the radiance is found to be displaced 3 plus or minus 1 deg north of the ecliptic, at distances greater than 20 solar radii, and this displacement is interpreted as an annual variation due to non-coincidence of the ecliptic and the symmetry axis of the zodiacal cloud.

  4. 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)

    2004-01-01

    The PI (Cranmer) and Co-I (A. van Ballegooijen) made substantial progress toward the goal of producing a unified model of the basic physical processes responsible for solar wind acceleration. 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 1D model of plasma heating and acceleration. The accomplishments in Year 2 are divided into these two categories: 1a. Focused Study of Kinetic Magnetohydrodynamic (MHD) Turbulence. lb. Focused Study of Non - WKB Alfven Wave Rejection. and 2. The Unified Model Code. We have continued the development of the computational model of a time-study open flux tube in the extended corona. The proton-electron Monte Carlo model is being tested, and collisionless wave-particle interactions are being included. In order to better understand how to easily incorporate various kinds of wave-particle processes into the code, the PI performed a detailed study of the so-called "Ito Calculus", i.e., the mathematical theory of how to update the positions of particles in a probabilistic manner when their motions are governed by diffusion in velocity space.

  5. 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 R Sun in images from the Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph (LASCO)/C2 coronagraph. From AIA He ii 304 Å 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 R Sun at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most 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 R Sun. 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.

  6. MAGNETIC UNTWISTING IN SOLAR JETS THAT GO INTO THE OUTER CORONA IN POLAR CORONAL HOLES

    SciTech Connect

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

    2015-06-10

    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 R{sub Sun} in images from the Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph (LASCO)/C2 coronagraph. From AIA He ii 304 Å 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 R{sub Sun} at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most 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 R{sub Sun}. 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.

  7. DISCOVERY OF FINELY STRUCTURED DYNAMIC SOLAR CORONA OBSERVED IN THE Hi-C TELESCOPE

    SciTech Connect

    Winebarger, Amy R.; Cirtain, Jonathan; Savage, Sabrina; Alexander, Caroline; Golub, Leon; DeLuca, Edward; Schuler, Timothy

    2014-05-20

    In the Summer of 2012, the High-resolution Coronal Imager (Hi-C) flew on board 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% 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.

  8. 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.

  9. 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.

  10. Radial distribution of compressive waves in the solar corona revealed by Akatsuki radio occultation observations

    SciTech Connect

    Miyamoto, Mayu; Imamura, Takeshi; Ando, Hiroki; Toda, Tomoaki; Nakamura, Masato; Tokumaru, Munetoshi; Shiota, Daikou; Isobe, Hiroaki; Asai, Ayumi; Häusler, Bernd; Pätzold, Martin; Nabatov, Alexander

    2014-12-10

    Radial variations of the amplitude and the energy flux of compressive waves in the solar corona were explored for the first time using a spacecraft radio occultation technique. By applying wavelet analysis to the frequency time series taken at heliocentric distances of 1.5-20.5 R{sub S} (solar radii), quasi-periodic density disturbances were detected at almost all distances. The period ranges from 100 to 2000 s. The amplitude of the fractional density fluctuation increases with distance and reaches ∼30% around 5 R{sub S} , implying that nonlinearity of the wave field is potentially important. We further estimate the wave energy flux on the assumption that the observed periodical fluctuations are manifestations of acoustic waves. The energy flux increases with distance below ∼6 R{sub S} and seems to saturate above this height, suggesting that the acoustic waves do not propagate from the low corona but are generated in the extended corona, probably through nonlinear dissipation of Alfvén waves. The compressive waves should eventually dissipate through shock generation to heat the corona.

  11. Observations of mode coupling in the solar corona and bipolar noise storms

    NASA Technical Reports Server (NTRS)

    White, S. M.; Thejappa, G.; Kundu, M. R.

    1992-01-01

    High-spatial-resolution observations of the sun which reflect on the role of mode coupling in the solar corona, and a number of new observations are presented. It is shown that typically, polarization inversion is seen at 5 GHz in active region sources near the solar limb, but not at 1.5 GHz. Although this is apparently in contradiction to the simplest form of mode coupling theory, it remains consistent with current models for the active region emission. Microwave bursts show no strong evidence for polarization inversion. Bipolar noise storm continuum emission is discussed in some detail, utilizing recent VLA observations at 327 MHz. It is shown that bipolar sources are common at 327 MHz. Further, the trailing component of the bipole is frequently stronger than the leading component, in apparent conflict with the 'leading-spot' hypothesis. The observations indicate that, at 327 MHz, mode coupling is apparently strong at all mode-coupling layers in the solar corona. The 327 MHz observations require a much weaker magnetic field strength in the solar corona to explain this result than did earlier lower-frequency observations: maximum fields are 0.2 G. This is a much weaker field than is consistent with current coronal models.

  12. Alfvén waves in the structured solar corona

    NASA Astrophysics Data System (ADS)

    Cally, Paul S.

    2017-04-01

    A simple model of a periodic ensemble of closely packed flux tubes, sitting atop a vertically stratified layer, reveals that an incident fast wave from below preferentially converts almost immediately to Alfvén waves in the flux tubes, with kink waves restricted to at most a very few Fourier modes. This suggests that observations of coronal kink modes in such structured systems may greatly underestimate the net wave-energy flux being transported into and through the corona, much of which may reside in harder-to-observe Alfvén waves. The processes of mode conversion/resonant absorption and Alfvén phase mixing are implicated. It is suggested that the Sun's internal p-mode field - the 5-min oscillations - may contribute substantially to the process by supplying incident fast waves in the chromosphere that scatter and mode-convert in the tube ensemble.

  13. Solar wind from a corona with a large helium abundance

    NASA Technical Reports Server (NTRS)

    Leer, Egil; Holzer, Thomas E.; Shoub, Edward C.

    1992-01-01

    The possibility is investigated that the presence of alpha particles in the coronal base region can reduce the sensitivity of the proton mass flux to the base temperature. It is found that for an alpha particle to proton density ratio at the base as small as 10 percent, alpha particles can reduce the sensitivity of the proton mass flux density to variations in the base temperature. The effects of enhanced collisional coupling and of Alfven waves on the flux of protons and alpha particles are studied. As an aid to future observational determination of the alpha particle density in the corona, calculations of the intensities of the resonantly scattered lines He II 304A and H I 1216A for selected models are presented.

  14. 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.

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

    SciTech Connect

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

    2014-02-15

    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.

  16. Solar Corona During the Total Solar Eclipse of August 1, 2008 and Polar Magnetic Fields of the Sun

    NASA Astrophysics Data System (ADS)

    Pishkalo, N.

    2015-12-01

    The solar corona observed during the total solar eclipse of August 1, 2008 was compared with model configuration of open magnetic lines in the solarcorona started near the solar limb. Magnetic field in the solar corona was calculated in the classic (line-of-sight) approach of a potential field – source surfacemodel. The synoptic data of photosphere magnetic field from the Wilcox Solar Observatory was used as low boundary condition. Polar field corrections 0 to1200 microTesla and the saturation factor of 1.8 were used in calculations. The source surface was situated at the distance of 2.5 solar radii. Observedparameters of coronal rays from (Pishkalo and Baransky, Kinematics and Physics of Celestial Bodies, 2009, 25, 315–318) were compared with the modeledones. The best agreement of observed and modeled parameters was found when the calculation were made with polar field correction of about 600×cos8(θ)mcTesla. It was concluded that during the total solar eclipse of 2008 the strength of magnetic field at the solar poles was averaged to 650–700 microTesla atthe photosphere and to 13–14 microTesla at the source surface.

  17. Numerical simulations of microflare evolution in the solar transition region and corona

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.; Mariska, John T.; Shibata, Kazunari; Suematsu, Yoshinori

    1991-01-01

    Several observers report transient ultraviolet brightenings, often referred to as microflares, in the solar atmosphere. In this paper, the results are presented of a series of one-dimensional numerical simulations examining possible relationships between microflares and the generation of dynamical chromospheric and transition region features. Low-energy and medium-energy microflares eject long-lived cool, dense gas plugs into the corona, with the gas plug traversing the loop apex in the medium energy case. In the case of high-energy microflares, the gas plug is rapidly heated to the temperature of the surrounding corona, and the results resemble the dynamics occurring in standard solar flare thick-target electron beam models.

  18. 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.

  19. Ka-band and X-band observations of the solar corona aquired during the Cassini 2002 superior conjunction

    NASA Technical Reports Server (NTRS)

    Morabito, D. D.

    2002-01-01

    A superior solar conjunction occurs when the sun lies near the signal path of a source as observed from the Earth. Interplanetary spacecraft sent to the planets typically encounter one or more solar conjunctions during their mission lifetimes. During these periods, the signals sent to and from the spacecraft encounter degradation due to the intervening charged particles of the solar corona.

  20. Neon and Oxygen Absolute Abundances in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Landi, E.; Feldman, U.; Doschek, G. A.

    2007-04-01

    In the present work we use the UV spectrum of a solar flare observed with SOHO SUMER to measure the absolute abundance of Ne in the solar atmosphere. The measurement is carried out using the intensity ratio between the allowed 1s2s3S1-1s2p3P2 Ne IX line at 1248.28 Å and the free-free continuum radiation observed close to the Ne IX line. We find a value of the absolute Ne abundance ANe=8.11+/-0.12, in agreement with previous estimates but substantially higher than the very recent estimate by Asplund et al. based on the oxygen photospheric abundance and the Ne/O relative abundance. Considering our measured ANe value, we argue that the absolute oxygen abundance of Asplund et al. is too low by a factor 1.9. This result has important consequences for models of the solar interior based on helioseismology measurements, as well as on the FIP bias determination of the solar upper atmosphere, solar wind, and solar energetic particles.

  1. Focusing of 3C144 Source Radiation by the Solar Corona

    NASA Astrophysics Data System (ADS)

    Galanin, V. V.; Derevjagin, V. G.; Kravetz, R. O.

    The research of solar corona by the compact cosmic source radiation was made on URAN-4 radio telescope. In the period from June 6 to June 20 2012 the flow of Crab nebula was measured on the 20 MHz and 25 MHz frequencies. During the eclipse we observe the great increase of 3C144 flow, which is compare with the flow of 3C461 source. Data and results of measurement analysis is presented.

  2. Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar corona

    SciTech Connect

    Mirzoeva, I. K.

    2013-04-15

    The time profiles of the energy spectra of low-intensity flares and the structure of the thermal background of the soft X-ray component of solar corona emission over the period of January-February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of X-ray emission of the solar flares and the corona thermal background in the 2- to 15-keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball-Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained.

  3. Satellite project "CORONAS-PHOTON" for study of solar hard radiation

    NASA Astrophysics Data System (ADS)

    Kotov, Yu.; Cor-Phot Team

    "CORONAS-PHOTON" is the Russian mission for study of the solar hard electromagnetic radiation in the very wide energy range from Extreme UV up to high-energy gamma - radiation. GOAL OF PROJECT: The investigation of energy accumulation and its transformation into energy of accelerated particles processes during solar flares; the study of the acceleration mechanisms, propagation and interaction of fast particles in the solar atmosphere; the study of the solar activity correlation with physical-chemical processes in the Earth upper atmosphere. SCIENTIFIC PAYLOAD CAPABILITY Radiation / Energy region / Detector type: Full solar disk X- radiation / 2keV - 2000MeV / Prop. counter; NaI(Tl); Full solar disk X- and γ-radiation / NaI(Tl)/CsI(Na) phoswich; Full solar disk X- and γ-radiation and solar neutrons / 20 - 300MeV / YalO_3(Ce); CsI(Tl); Hard X-ray polarization in large flares / 20 - 150keV / p-terphenyl scatterer and CsI(Na) absorbers; Full solar disk EUV-radiation monitoring / 6 spectral windows in <10 - 130nm / Filtered photodiodes; Solar images in narrow spectral bands and monochromatic emission lines of hot plasma / Emission of HeII, SiXI, FeXXI, FeXXIII, MgXII ions / Multi-layer and Bregg spherical crystal quartz mirrors with CCDs; Additionally, the temporal and energy spectra of electrons (0.2-14MeV), protons (1-61MeV) and nuclei (Z<26, 2-50MeV/nuclon) at the satellite orbit will be registrated by several instruments. MAIN CHARACTERISTICS OF SPACECRAFT: Spacecraft weight: 1900 kg; Orbit type: Circular; Scientific payload weight: 540 kg; Height: 500 km; Orientation to the Sun [arc min]: better 5; Inclination: 82.5 degree; Instability of orientation [deg/s]: less 0.005; Solar - synchronous orbit is under study. Launching date of "CORONAS-PHOTON" spacecraft is 2006.

  4. 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.

  5. Filament Channels: Isolated Laboratories of Plasma Heating in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Panasenco, O.; Velli, M.

    2015-12-01

    Solar filament channels are complex systems comprising photospheric, chromospheric and coronal components. These components include magnetic neutral lines, supergranule cells, fibrils (spicules), filaments (prominences when observed on the limb), coronal cells, filament cavities and their overlying coronal arcades. Filaments are very highly structured and extend in height from the photosphere to the corona. Filament cores have chromospheric temperatures - 10,000 K (even at coronal heights ~ 100 Mm), surrounded by hotter plasma with temperature up to ~50,000 K. The whole filament is isolated from the rest of the solar corona by an envelope - the filament channel cavity - with temperatures of about 2,000,000 K. The filament channel cavity is even hotter than the solar corona outside the filament channel arcade. The compactness and big temperature variations make filament channels unique ready-to-go laboratories of coronal plasma heating and thermodynamics. In this work we discuss possible sources and mechanisms of heating in the filament channel environment. In particular, we address the mechanisms of magnetic canceling and current sheet dissipation.

  6. SUPRATHERMAL ELECTRONS IN THE SOLAR CORONA: CAN NONLOCAL TRANSPORT EXPLAIN HELIOSPHERIC CHARGE STATES?

    SciTech Connect

    Cranmer, Steven R.

    2014-08-20

    There have been several ideas proposed to explain how the Sun's corona is heated and how the solar wind is accelerated. Some models assume that open magnetic field lines are heated by Alfvén waves driven by photospheric motions and dissipated after undergoing a turbulent cascade. Other models posit that much of the solar wind's mass and energy is injected via magnetic reconnection from closed coronal loops. The latter idea is motivated by observations of reconnecting jets and also by similarities of ion composition between closed loops and the slow wind. Wave/turbulence models have also succeeded in reproducing observed trends in ion composition signatures versus wind speed. However, the absolute values of the charge-state ratios predicted by those models tended to be too low in comparison with observations. This Letter refines these predictions by taking better account of weak Coulomb collisions for coronal electrons, whose thermodynamic properties determine the ion charge states in the low corona. A perturbative description of nonlocal electron transport is applied to an existing set of wave/turbulence models. The resulting electron velocity distributions in the low corona exhibit mild suprathermal tails characterized by ''kappa'' exponents between 10 and 25. These suprathermal electrons are found to be sufficiently energetic to enhance the charge states of oxygen ions, while maintaining the same relative trend with wind speed that was found when the distribution was assumed to be Maxwellian. The updated wave/turbulence models are in excellent agreement with solar wind ion composition measurements.

  7. 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.

  8. Heating the Solar Corona: Observations for Model Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Nestlerode, C. M.; Poland, A. I.

    2005-12-01

    A prominent question in solar physics concerns the sources of coronal heating. This problem can be addressed through observations of closed magnetic loops which have high enough density to provide adequate temporal, spatial, and spectral resolution. Measurements of temperature, density, and velocity throughout the loop can be used for boundary conditions and compared with quantities for model calculations. In this paper, we present Solar Ultraviolet Measurements from Emitted Radiation (SUMER) data from the Solar and Heliospheric Observatory's (SOHO's) JOP 161 program. The SUMER instrument has high spatial and spectral resolution over several different spectral lines and therefore the data cover a large temperature range. The analyzed lines include Mg VIII, Mg IX, N III, N IV, Ne VIII, O IV, O V, S IV, S V, and S X with temperatures ranging from 60,000 K (S IV) to 0.9 MK (Mg IX). The velocity profiles are created using Gaussian fitting with wavelength calibration determined using average quiet Sun velocities from known Doppler velocity shifts. The velocity profiles show important changes in solar foot point plasma speed both spatially and temporally. This analysis builds on previous analysis of solar spectral lines observed with the SOHO Coronal Diagnostic Spectrometer (CDS); the advantage of the SUMER instrument is better resolution, both spectrally and spatially. This work was funded by NASA, Living with a Star Program.

  9. "Kicking Up Some Dust": An Experimental Investigation Relating Lunar Dust Erosive Wear to Solar Power Loss

    NASA Technical Reports Server (NTRS)

    Mpagazehe, Jeremiah N.; Street, Kenneth W., Jr.; Delgado, Irebert R.; Higgs, C. Fred, III

    2013-01-01

    The exhaust from retrograde rockets fired by spacecraft landing on the Moon can accelerate lunar dust particles to high velocities. Information obtained from NASA's Apollo 12 mission confirmed that these high-speed dust particles can erode nearby structures. This erosive wear damage can affect the performance of optical components such as solar concentrators. Solar concentrators are objects which collect sunlight over large areas and focus the light into smaller areas for purposes such as heating and energy production. In this work, laboratory-scale solar concentrators were constructed and subjected to erosive wear by the JSC-1AF lunar dust simulant. The concentrators were focused on a photovoltaic cell and the degradation in electrical power due to the erosive wear was measured. It was observed that even moderate exposure to erosive wear from lunar dust simulant resulted in a 40 percent reduction in power production from the solar concentrators.

  10. Energy release in the solar corona from spatially resolved magnetic braids.

    PubMed

    Cirtain, J W; Golub, L; Winebarger, A R; De Pontieu, B; Kobayashi, K; Moore, R L; Walsh, R W; Korreck, K E; Weber, M; McCauley, P; Title, A; Kuzin, S; DeForest, C E

    2013-01-24

    It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1-3). The active corona needs additional heating to reach 2,000,000-4,000,000 K; this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic 'braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2 arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000 K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating.

  11. Properties of the white-light corona polarization during maximum of the solar cycle.

    NASA Astrophysics Data System (ADS)

    Sýkora, J.

    1991-01-01

    The results of measuring the polarization of the white-light corona, carried out during the February 16, 1980 solar eclipse, are presented. The degree of polarization was observed to be relatively high all round the sun, with the exception of a coronal hole near the south pole. Together with the well-expressed streamers, the high degrees of polarization were observed in the narrow ray at P = 210° and also in the broad region P = 310° - 350°. The general increase of coronal density characteristic for solar cycle maximum and accidental concentration of the coronal structures to the plane of sky could be responsible for such peculiarities.

  12. Conditions for electron-cyclotron maser emission in the solar corona

    NASA Astrophysics Data System (ADS)

    Morosan, D. E.; Zucca, P.; Bloomfield, D. S.; Gallagher, P. T.

    2016-05-01

    Context. The Sun is an active source of radio emission ranging from long duration radio bursts associated with solar flares and coronal mass ejections to more complex, short duration radio bursts such as solar S bursts, radio spikes and fibre bursts. While plasma emission is thought to be the dominant emission mechanism for most radio bursts, the electron-cyclotron maser (ECM) mechanism may be responsible for more complex, short-duration bursts as well as fine structures associated with long-duration bursts. Aims: We investigate the conditions for ECM in the solar corona by considering the ratio of the electron plasma frequency ωp to the electron-cyclotron frequency Ωe. The ECM is theoretically possible when ωp/ Ωe< 1. Methods: Two-dimensional electron density, magnetic field, plasma frequency, and electron cyclotron frequency maps of the off-limb corona were created using observations from SDO/AIA and SOHO/LASCO, together with potential field extrapolations of the magnetic field. These maps were then used to calculate ωp/Ωe and Alfvén velocity maps of the off-limb corona. Results: We found that the condition for ECM emission (ωp/ Ωe< 1) is possible at heights <1.07 R⊙ in an active region near the limb; that is, where magnetic field strengths are >40 G and electron densities are >3 × 108 cm-3. In addition, we found comparatively high Alfvén velocities (>0.02c or >6000 km s-1) at heights <1.07 R⊙ within the active region. Conclusions: This demonstrates that the condition for ECM emission is satisfied within areas of the corona containing large magnetic fields, such as the core of a large active region. Therefore, ECM could be a possible emission mechanism for high-frequency radio and microwave bursts.

  13. A new approach to the maser emission in the solar corona

    NASA Astrophysics Data System (ADS)

    Régnier, S.

    2015-09-01

    Aims: The electron plasma frequency ωpe and electron gyrofrequency Ωe are two parameters that allow us to describe the properties of a plasma and to constrain the physical phenomena at play, for instance, whether a maser instability develops. In this paper, we aim to show that the maser instability can exist in the solar corona. Methods: We perform an in-depth analysis of the ωpe/Ωe ratio for simple theoretical and complex solar magnetic field configurations. Using the combination of force-free models for the magnetic field and hydrostatic models for the plasma properties, we determine the ratio of the plasma frequency to the gyrofrequency for electrons. For the sake of comparison, we compute the ratio for bipolar magnetic fields containing a twisted flux bundle, and for four different observed active regions. We also study how ωpe/Ωe is affected by the potential and non-linear force-free field models. Results: We demonstrate that the ratio of the plasma frequency to the gyrofrequency for electrons can be estimated by this novel method combining magnetic field extrapolation techniques and hydrodynamic models. Even if statistically not significant, values of ωpe/Ωe≤ 1 are present in all examples, and are located in the low corona near to photosphere below one pressure scale-height and/or in the vicinity of twisted flux bundles. The values of ωpe/Ωe are lower for non-linear force-free fields than potential fields, thus increasing the possibility of maser instability in the corona. Conclusions: From this new approach for estimating ωpe/Ωe, we conclude that the electron maser instability can exist in the solar corona above active regions. The importance of the maser instability in coronal active regions depends on the complexity and topology of the magnetic field configurations.

  14. Spectroscopic diagnostics of extended corona and solar wind with UVCS/Spartan

    NASA Technical Reports Server (NTRS)

    Strachan, L.; Gardner, L. D.; Kohl, J. L.

    1995-01-01

    The primary goal of the Ultraviolet Coronal Spectrometer on Spartan 201 (UVCS/Spartan) is to make spectroscopic diagnostic measurements that can be used to derive plasma parameters in the extended solar corona where it is believed that significant heating of the corona and acceleration of the solar wind take place. Direct and indirect measurements of particle velocity distribution, thermal and non-thermal temperatures, and bulk outflow velocities are crucial to aid in the identification of physical processes that may be responsible for coronal heating and solar wind acceleration. UVCS/Spartan has made two flights in April 1993 and September 1994, the latter coinciding with the South Polar Passage of the Ulysses spacecraft. Observations were made of the large-scale structures and sub-structures of coronal holes and streamers at heliocentric heights between 1.5 solar radii and 3.5 solar radii. Measurements were made of H I Lyman-alpha intensities and profiles, and line intensities of minor ions like O(5+) and Fe(11+). We will present results from the flights and discuss how these measurements are used to constrain values for the proton thermal and non-thermal kinetic temperatures, proton bulk outflow velocities, and minor ion temperatures and bulk outflow velocities. Plans for the upcoming flight in July 1995 will also be discussed.

  15. MAXIMIZING MAGNETIC ENERGY STORAGE IN THE SOLAR CORONA

    SciTech Connect

    Wolfson, Richard; Drake, Christina; Kennedy, Max

    2012-05-01

    The energy that drives solar eruptive events such as coronal mass ejections (CMEs) almost certainly originates in coronal magnetic fields. Such energy may build up gradually on timescales of days or longer before its sudden release in an eruptive event, and the presence of free magnetic energy capable of rapid release requires nonpotential magnetic fields and associated electric currents. For magnetic energy to power a CME, that energy must be sufficient to open the magnetic field to interplanetary space, to lift the ejecta against solar gravity, and to accelerate the material to speeds of typically several hundred km s{sup -1}. Although CMEs are large-scale structures, many originate from relatively compact active regions on the solar surface-suggesting that magnetic energy storage may be enhanced when it takes place in smaller magnetic structures. This paper builds on our earlier work exploring energy storage in large-scale dipolar and related bipolar magnetic fields. Here we consider two additional cases: quadrupolar fields and concentrated magnetic bipoles intended to simulate active regions. Our models yield stored energies whose excess over that of the corresponding open field state can be greater than 100% of the associated potential field energy; this contrasts with maximum excess energies of only about 20% for dipolar and symmetric bipolar configurations. As in our previous work, energy storage is enhanced when we surround a nonpotential field with a strong overlying potential field that acts to 'hold down' the nonpotential flux as its magnetic energy increases.

  16. Reconciling Spectroscopic Electron Temperature Measurements in the Solar Corona with In Situ Charge State Observations.

    PubMed

    Esser; Edgar

    2000-03-20

    It has been a puzzle for quite some time that spectroscopic measurements in the inner corona indicate electron temperatures far too low to produce the ion fractions observed in situ in the solar wind. In the present Letter, we show that in order to reconcile the two sets of measurements, a number of conditions have to exist in the inner corona: (1) The electron distribution function has to be Maxwellian or close to Maxwellian at the coronal base, (2) the non-Maxwellian character of the distribution has to develop rapidly as a function of height and has to reach close to interplanetary properties inside of a few solar radii, and (3) ions of different elements have to flow with significantly different speeds to separate their "freezing-in" distances sufficiently so that they can encounter different distribution functions. We choose two examples to demonstrate that these conditions are general requirements if both coronal electron temperatures and in situ ion fractions are correct. However, these two examples also show that the details of the required distribution functions are very sensitive to the exact electron temperature, density, and ion flow speed profiles in the region of the corona where the ions predominantly form.

  17. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  19. A Simple Dynamical Model for Filament Formation in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Litvinenko, Y.

    2005-12-01

    Filament formation in the solar corona is considered in the case of a slowly evolving force-free magnetic field. The strong-field approximation is used, which takes into account the magnetohydrodynamic equations of motion, induction, and compressibility. Methods for solving the relevant equations are presented and applied to filament modeling. A three-dimensional calculation is presented, which uses linear force-free magnetic fields. The boundary conditions are chosen to resemble the qualitative linkage model for the formation of filaments, suggested by Martens and Zwaan (2001). Consistent with this model, dense formations, reminiscent of filament pillars, are shown to appear in the corona above the region of converging and canceling magnetic bipoles. The results demonstrate the principal role of magnetic field in the dynamical processes of dense plasma accumulation and support in filaments. The model can be useful for clarifying the role of flux emergence in coronal mass ejection initiation.

  20. Flares on A-type Stars: Evidence for Heating of Solar Corona by Nanoflares?

    NASA Astrophysics Data System (ADS)

    Švanda, Michal; Karlický, Marian

    2016-11-01

    We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted toward a high-energy tail for A-type stars compared to stars of cooler spectral types. We extrapolated the fitted power laws toward flares with smaller energies (nanoflares) and made estimates for total energy flux to stellar atmospheres by flares. We found that, for A-type stars, the total energy flux density was at least four-times smaller than for G stars. We speculate that this deficit in energy supply may explain the lack of hot coronae on A-type stars. Our results indicate the importance of nanoflares for heating and formation of the solar corona.

  1. Shock–Cloud Interaction in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Takahashi, Takuya

    2017-02-01

    Flare-associated coronal shock waves sometimes interact with solar prominences, leading to large-amplitude prominence oscillations (LAPOs). Such prominence activation gives us a unique opportunity to track the time evolution of shock–cloud interaction in cosmic plasmas. Although the dynamics of interstellar shock–cloud interaction has been extensively studied, coronal shock–solar prominence interaction is rarely studied in the context of shock–cloud interaction. Associated with the X5.4 class solar flare that occurred on 2012 March 7, a globally propagated coronal shock wave interacted with a polar prominence, leading to LAPO. In this paper, we studied bulk acceleration and excitation of the internal flow of the shocked prominence using three-dimensional magnetohydrodynamic (MHD) simulations. We studied eight MHD simulation runs, each with different mass density structure of the prominence, and one hydrodynamic simulation run, and we compared the result. In order to compare the observed motion of activated prominence with the corresponding simulation, we also studied prominence activation by injection of a triangular-shaped coronal shock. We found that the prominence is first accelerated mainly by magnetic tension force as well as direct transmission of the shock, and later decelerated mainly by magnetic tension force. The internal flow, on the other hand, is excited during the shock front sweeps through the prominence and damps almost exponentially. We construct a phenomenological model of bulk momentum transfer from the shock to the prominence, which agreed quantitatively with all the simulation results. Based on the phenomenological prominence activation model, we diagnosed physical parameters of the coronal shock wave. The estimated energy of the coronal shock is several percent of the total energy released during the X5.4 flare.

  2. Radio Spectroscopic Imaging of Electron Beams in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Bastian, Timothy S.; Chen, B.

    2012-05-01

    The recently upgraded Jansky Very Large Array was used to observe the radio emission from a C class solar flare. Observations were performed from 1-2 GHz with a spectral resolution of 1 MHz and time resolution of 100 ms. A number of fast-drift, type-III-like radio bursts was observed, the result of nonthermal electron beams propagating from the flare site, guided by the coronal magnetic field. Using these dynamic, imaging, spectroscopic observations, the electron beam trajectories are deduced.Implications are briefly discussed.

  3. Formation and Evolution of Large-Scale Magnetic Funnels in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Panasenco, Olga; Velli, Marco

    2016-05-01

    The existence of open coronal magnetic fields with peculiar geometry - large-scale magnetic funnels - can be attributed to three factors: (i) the presence of two or more corona holes of the same polarity (or pseudostreamers - PSs), (ii) specific configurations of closed magnetic field in the low corona up to 1.3 Rs (filament channels) and (iii) the presence of strong active regions in the vicinity of the pseudostreamer. The important property of magnetic funnels is their strongly non-monotonic expansion factor below 2 Rs. The case study presented here is a pseudostreamer near the equator, formed between two isolated coronal holes of the same polarity, and harboring a pair of twin filaments in its base. Following the evolution of these coronal holes we find that the PS topology changes when two coronal holes merged together. Using a potential field source-surface (PFSS) extrapolation to compute the coronal field from photospheric maps (SDO/HMI), we show that the funnel-like geometry of the open magnetic field changes to a regular one with monotonic expansion factor after the merging of coronal holes. The presence of coronal magnetic funnels becomes directly visible when sufficient plasma accumulates inside them: when the plasma density grows to become observable coronal cloud prominences appear in the corona. The plasma suspension at heights of 0.3 Rs coincides with the largest gradients in the field which naturally leads to a diamagnetic hypothesis for the force counteracting gravity. We study the evolution of the funnel-like open fields during several solar rotations and find a direct relation between funnels and the presence of coronal clouds at great heights in the solar corona.

  4. PROPAGATING DISTURBANCES IN THE SOLAR CORONA AND SPICULAR CONNECTION

    SciTech Connect

    Samanta, Tanmoy; Pant, Vaibhav; Banerjee, Dipankar

    2015-12-10

    Spicules are small, hairy-like structures seen at the solar limb, mainly at chromospheric and transition region lines. They generally live for 3–10 minutes. We study these spicules in a south polar region of the Sun with coordinated observations using the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory. Propagating disturbances (PDs) are observed everywhere in the polar off-limb regions of the Sun at coronal heights. From these simultaneous observations, we show that the spicules and the PDs may have originated through a common process. From spacetime maps, we find that the start of the trajectory of PDs is almost cotemporal with the time of the rise of the spicular envelope as seen by IRIS slit-jaw images at 2796 and 1400 Å. During the return of spicular material, brightenings are seen in AIA 171 and 193 Å images. The quasi-periodic nature of the spicular activity, as revealed by the IRIS spectral image sequences, and its relation to coronal PDs, as recorded by the coronal AIA channels, suggest that they share a common origin. We propose that reconnection-like processes generate the spicules and waves simultaneously. The waves escape while the cool spicular material falls back.

  5. Propagating Disturbances in the Solar Corona and Spicular Connection

    NASA Astrophysics Data System (ADS)

    Samanta, Tanmoy; Pant, Vaibhav; Banerjee, Dipankar

    2015-12-01

    Spicules are small, hairy-like structures seen at the solar limb, mainly at chromospheric and transition region lines. They generally live for 3-10 minutes. We study these spicules in a south polar region of the Sun with coordinated observations using the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory. Propagating disturbances (PDs) are observed everywhere in the polar off-limb regions of the Sun at coronal heights. From these simultaneous observations, we show that the spicules and the PDs may have originated through a common process. From spacetime maps, we find that the start of the trajectory of PDs is almost cotemporal with the time of the rise of the spicular envelope as seen by IRIS slit-jaw images at 2796 and 1400 Å. During the return of spicular material, brightenings are seen in AIA 171 and 193 Å images. The quasi-periodic nature of the spicular activity, as revealed by the IRIS spectral image sequences, and its relation to coronal PDs, as recorded by the coronal AIA channels, suggest that they share a common origin. We propose that reconnection-like processes generate the spicules and waves simultaneously. The waves escape while the cool spicular material falls back.

  6. Hα Doppler shifts in a tornado in the solar corona

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Mein, P.; Mein, N.; Levens, P. J.; Labrosse, N.; Ofman, L.

    2017-01-01

    Context. High resolution movies in 193 Å from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO) show apparent rotation in the leg of a prominence observed during a coordinated campaign. Such structures are commonly referred to as tornadoes. Time-distance intensity diagrams of the AIA data show the existence of oscillations suggesting that the structure is rotating. Aims: The aim of this paper is to understand if the cool plasma at chromospheric temperatures inside the tornado is rotating around its central axis. Methods: The tornado was also observed in Hα with a cadence of 30 s by the MSDP spectrograph, operating at the Solar Tower in Meudon. The MSDP provides sequences of simultaneous spectra in a 2D field of view from which a cube of Doppler velocity maps is retrieved. Results: The Hα Doppler maps show a pattern with alternatively blueshifted and redshifted areas of 5 to 10'' wide. Over time the blueshifted areas become redshifted and vice versa, with a quasi-periodicity of 40 to 60 min. Weaker amplitude oscillations with periods of 4 to 6 min are superimposed onto these large period oscillations. Conclusions: The Doppler pattern observed in Hα cannot be interpreted as rotation of the cool plasma inside the tornado. The Hα velocity observations give strong constraints on the possible interpretations of the AIA tornado.

  7. A Space Weather mission concept: Observatories of the Solar Corona and Active Regions (OSCAR)

    NASA Astrophysics Data System (ADS)

    Strugarek, Antoine; Janitzek, Nils; Lee, Arrow; Löschl, Philipp; Seifert, Bernhard; Hoilijoki, Sanni; Kraaikamp, Emil; Isha Mrigakshi, Alankrita; Philippe, Thomas; Spina, Sheila; Bröse, Malte; Massahi, Sonny; O'Halloran, Liam; Pereira Blanco, Victor; Stausland, Christoffer; Escoubet, Philippe; Kargl, Günter

    2015-02-01

    Coronal Mass Ejections (CMEs) and Corotating Interaction Regions (CIRs) are major sources of magnetic storms on Earth and are therefore considered to be the most dangerous space weather events. The Observatories of Solar Corona and Active Regions (OSCAR) mission is designed to identify the 3D structure of coronal loops and to study the trigger mechanisms of CMEs in solar Active Regions (ARs) as well as their evolution and propagation processes in the inner heliosphere. It also aims to provide monitoring and forecasting of geo-effective CMEs and CIRs. OSCAR would contribute to significant advancements in the field of solar physics, improvements of the current CME prediction models, and provide data for reliable space weather forecasting. These objectives are achieved by utilising two spacecraft with identical instrumentation, located at a heliocentric orbital distance of 1 AU from the Sun. The spacecraft will be separated by an angle of 68° to provide optimum stereoscopic view of the solar corona. We study the feasibility of such a mission and propose a preliminary design for OSCAR.

  8. PROPAGATION OF ALFVENIC WAVES FROM CORONA TO CHROMOSPHERE AND CONSEQUENCES FOR SOLAR FLARES

    SciTech Connect

    Russell, A. J. B.; Fletcher, L.

    2013-03-10

    How do magnetohydrodynamic waves travel from the fully ionized corona, into and through the underlying partially ionized chromosphere, and what are the consequences for solar flares? To address these questions, we have developed a two-fluid model (of plasma and neutrals) and used it to perform one-dimensional simulations of Alfven waves in a solar atmosphere with realistic density and temperature structure. Studies of a range of solar features (faculae, plage, penumbra, and umbra) show that energy transmission from corona to chromosphere can exceed 20% of incident energy for wave periods of 1 s or less. Damping of waves in the chromosphere depends strongly on wave frequency: waves with periods 10 s or longer pass through the chromosphere with relatively little damping, however, for periods of 1 s or less, a substantial fraction (37%-100%) of wave energy entering the chromosphere is damped by ion-neutral friction in the mid- and upper chromosphere, with electron resistivity playing some role in the lower chromosphere and in umbras. We therefore conclude that Alfvenic waves with periods of a few seconds or less are capable of heating the chromosphere during solar flares, and speculate that they could also contribute to electron acceleration or exciting sunquakes.

  9. New View of Gas and Dust in the Solar Nebula

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2010-08-01

    The recognizable components in meteorites differ in their relative abundances of the three oxygen isotopes (16O, 17O, and 18O). In particular, the amount of 16O varies from being like that of the Earth to substantially enriched compared to the other two isotopes. The current explanation for this interesting range in isotopic composition is that dust and gas in the solar nebula (the cloud of gas and dust surrounding the primitive Sun) began with the same 16O-rich composition, but the solids evolved towards the terrestrial value. A new analysis of the problem by Alexander Krot (University of Hawaii) and colleagues at the University of Hawaii, the University of Chicago, Clemson University, and Lawrence Livermore National Laboratory leads to the bold assertion that primordial dust and gas differed in isotopic composition. The gas was rich in 16O as previously thought (possibly slightly richer in 16O than the measurements of the solar wind returned by the Genesis Mission), but that the dust had a composition close to the 16O-depleted terrestrial average. In this new view, the dust had a different history than did the gas before being incorporated into the Solar System. Solids with compositions near the terrestrial line may have formed in regions of the solar nebula where dust had concentrated compared to the mean solar dust/gas ratio (1 : ~100). The idea has great implications for understanding the oxygen-isotope composition of the inner Solar System and the origin of materials in the molecular cloud from which the Solar System formed.

  10. A Comparison between Physics-based and Polytropic MHD Models for Stellar Coronae and Stellar Winds of Solar Analogs

    NASA Astrophysics Data System (ADS)

    Cohen, O.

    2017-02-01

    The development of the Zeeman–Doppler Imaging (ZDI) technique has provided synoptic observations of surface magnetic fields of low-mass stars. This led the stellar astrophysics community to adopt modeling techniques that have been used in solar physics using solar magnetograms. However, many of these techniques have been neglected by the solar community due to their failure to reproduce solar observations. Nevertheless, some of these techniques are still used to simulate the coronae and winds of solar analogs. Here we present a comparative study between two MHD models for the solar corona and solar wind. The first type of model is a polytropic wind model, and the second is the physics-based AWSOM model. We show that while the AWSOM model consistently reproduces many solar observations, the polytropic model fails to reproduce many of them, and in the cases where it does, its solutions are unphysical. Our recommendation is that polytropic models, which are used to estimate mass-loss rates and other parameters of solar analogs, must first be calibrated with solar observations. Alternatively, these models can be calibrated with models that capture more detailed physics of the solar corona (such as the AWSOM model) and that can reproduce solar observations in a consistent manner. Without such a calibration, the results of the polytropic models cannot be validated, but they can be wrongly used by others.

  11. Coronagraph observations and analyses of the ultraviolet solar corona

    NASA Technical Reports Server (NTRS)

    Kohl, John L.

    1989-01-01

    The major activities on the Spartan Ultraviolet Coronal Spectrometer project include both scientific and experimental/technical efforts. In the scientific area, a detailed analysis of the previously reported Doppler dimming of HI Ly-alpha from the July 1982 rocket flight has determined an outflow velocity at 2 solar radii from sun center to be between 153 and 251 km/s at 67 percent confidence. The technical activities include, several improvements made to the instrument that will result in enhanced scientific performance or in regaining a capability that had deteriorated during the delay time in the launch date. These include testing and characterizing the detector for OVI radiation, characterizing a serrated occulter at UV and visible wavelengths, fabricating and testing telescope mirrors with improved edges, testing and evaluating a new array detector system, modifying the slit mask mechanism and installing a mask in the instrument to block the Ly-alpha resonance line when the electron scattered component is being observed.

  12. 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.

  13. Faraday Rotation Fluctuations of MESSENGER radio signals through the Corona during the 2009 Solar Minimum.

    NASA Astrophysics Data System (ADS)

    Wexler, David; Vierinen, Juha; Coster, Anthea; Jensen, Elizabeth A.

    2015-04-01

    Faraday rotation (FR) techniques have been used to probe variations of coronal plasma velocity, density and magnetic field. The plane of polarization for an electromagnetic wave rotates in proportion to the integrated product of parallel magnetic field components and electron density along the radio signal line-of-sight as directed towards the receiving antenna. Fluctuations in FR through the corona thus represent the evolution of these line-integrated plasma parameters, providing a unique measurement of regional corona physics. The MESSENGER spacecraft radio 8 GHz radio beacon, transmitting through the corona at offsets 1.6 to 1.9 solar radii and near-equatorial heliolatitude, was recorded on the Green Bank radio telescope during the solar minimum of 2009. Here we reanalyze at higher temporal resolution the data previously published (Jensen et al 2013, Solar Physics 285:83-95). Combinations of coherent and incoherent integration were used to estimate Stokes parameters, from which the FR phase differences were obtained for serial one-second frames. Results were concatenated and corrected for phase wrap-around to produce a continuous FR phase curve. The general FR phase curve was broad and sweeping, with greatest spectral power observed in periods of hours. Also, finer wave-like fluctuations were noted with periods on the order of 100's of seconds. With the lowest-frequency components removed by detrending techniques, spectral analysis revealed a power spectrum of form P=kνα with spectral index α = -2.25 over frequencies ν = 2-20 milliHertz (mHz), and a flat noise spectrum at higher frequencies. Imposed upon the general power spectrum were trends of enhanced spectral power around 3.5 and 6 mHz, corresponding to approximately 5- and 3-minute period waves. Temporal evolution plots demonstrated that the increased power in these spectral bands appeared intermittently and irregularly. Our results reinforce the findings of prior coronal FR studies, and now extend the

  14. Dust inventory through the Solar System: From Earth to Pluto

    NASA Astrophysics Data System (ADS)

    Piquette, M. R.; Horanyi, M.; Stern, A.; Bagenal, F.; Szalay, J.; Poppe, A. R.; Weaver, H. A., Jr.; Young, L. A.; Olkin, C.; Ennico Smith, K.

    2015-12-01

    The Student Dust Counter (SDC) is an impact dust detector onboard the New Horizons spacecraft, observing the dust density distribution since April 2006 across the Solar System. SDC measures 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 compared to model predictions following the orbital evolution of dust grains originating from the Edgeworth-Kuiper Belt and migrating inward due to Poynting-Robertson drag. SDC's results, as well as data taken by the Pioneer 10 dust detector, are compared to model predictions to estimate the mass production rate and the ejecta size distribution power law exponent. On July 14, 2015, the New Horizons spacecraft passed through the Pluto system and is now continuing to take measurements in the solar system's third zone, the Kuiper Belt. The measurements SDC has taken throughout the solar system, including in the Pluto-Charon system, will be discussed in this presentation, as well as predictions for the dust distribution it will measure as it explores the Kuiper Belt.

  15. Nonequilibrium ionization effects in asymmetrically heated loops. [in solar corona

    NASA Technical Reports Server (NTRS)

    Spadaro, D.; Antiochos, Spiro K.; Mariska, J. T.

    1991-01-01

    The effects of nonequilibrium ionization on magnetic loop models with a steady siphon flow that is driven by a nonuniform heating rate are investigated. The model developed by Mariska (1988) to explain the observed redshifts of transition region emission lines is examined, and the number densities of the ions of carbon and oxygen along the loop are computed, with and without the approximation of ionization equilibrium. Considerable deviations from equilibrium were found. In order to determine the consequences of these nonequilibrium effects on the characteristics of the EUV emission from the loop plasma, the profiles and wavelength positions of all the important emission lines due to carbon and oxygen were calculated. The calculations are in broad agreement with Mariska's conclusions, although they show a significant diminution of the Doppler shifts, as well as modifications to the line widths. It is concluded that the inclusion of nonequilibrium effects make it more difficult to reproduce the observed characteristics of the solar transition region by means of the asymmetric-heating models.

  16. Spectro-Imaging Polarimetry of the Local Corona During Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Qu, Z. Q.; Dun, G. T.; Chang, L.; Murray, G.; Cheng, X. M.; Zhang, X. Y.; Deng, L. H.

    2017-02-01

    Results are presented from spectro-imaging polarimetry of radiation from the local solar corona during the 2013 total solar eclipse in Gabon. This polarimetric observation was performed from 516.3 nm to 532.6 nm using a prototype Fiber Arrayed Solar Optical Telescope (FASOT). A polarimetric noise level on the order of 10^{-3} results from a reduced polarimetric optical switching demodulation (RPOSD) procedure for data reduction. It is revealed that the modality of fractional linear polarization profiles of the green coronal line shows a diversity, which may indicate complex mechanisms. The polarization degree can approach 3.2 % above the continuum polarization level on a scale of 1500 km, and the nonuniform spatial distribution in amplitude and polarization direction is found even within a small field of view of 7500 km. All of this implies that the coronal polarization is highly structured and complex even on a small scale.

  17. Thermodynamic MHD Simulations of Jets in the Solar Corona and Inner Heliosphere

    NASA Astrophysics Data System (ADS)

    Lionello, R.; Torok, T.; Titov, V. S.; Linker, J.; Mikic, Z.; Leake, J. E.; Linton, M.

    2015-12-01

    Coronal jets are transient, collimated plasma ejections that occur predominantly in coronal holes and are observed in EUV, soft X-ray, and occasionally in white-light coronagraphs. While these intriguing phenomena have been studied and modeled for more than two decades, the details of their formation mechanism(s) are not yet fully understood, and their potential role for the generation of the fast solar wind remains largely elusive. Here we present 3D MHD simulations of coronal jets which are performed in a large computational domain (up to 20 solar radii) and incorporate the effects of thermal conduction, radiative cooling, empirical coronal heating, and the solar wind. These features allow us to model the plasma properties and energy transfer of coronal jets in a more realistic manner than done so far, and to study the amount of energy and mass transported by these phenomena into the higher corona and inner heliosphere. In order to produce a jet, we consider a simple, purely radial background magnetic field and slowly introduce a magnetic flux rope into the coronal configuration by coupling our model to dynamic flux emergence simulations at the lower boundary of the computational domain. We find two types of jets in our simulations: a very impulsive event reminiscent of so-called blowout jets and a slowly developing, more extended event that produces a long-lasting signature in the corona. We present synthetic satellite images for both types of events and discuss their respective formation mechanisms. Our analysis is supported by a detailed investigation of the magnetic topology for the blowout-type case and of the transport of energy and plasma into the higher corona and inner heliosphere for the long-lasting event.

  18. Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Titov, V. S.

    2007-01-01

    The study of magnetic connectivity in the solar corona reveals a need to generalize the field line mapping technique to arbitrary geometry of the boundaries and systems of coordinates. Indeed, the global description of the connectivity in the corona requires the use of the photospheric and solar wind boundaries. Both are closed surfaces and therefore do not admit a global regular system of coordinates. At least two overlapping regular systems of coordinates for each of the boundaries are necessary in this case to avoid spherical-pole-like singularities in the coordinates of the footpoints. This implies that the basic characteristic of magnetic connectivity-the squashing degree or factor Q of elemental flux tubes, according to Titov and coworkers-must be rewritten in covariant form. Such a covariant expression of Q is derived in this work. The derived expression is very flexible and highly efficient for describing the global magnetic connectivity in the solar corona. In addition, a general expression for a new characteristic Q1, which defines a squashing of the flux tubes in the directions perpendicular to the field lines, is determined. This new quantity makes it possible to filter out the quasi-separatrix layers whose large values of Q are caused by a projection effect at the field lines nearly touching the photosphere. Thus, the value Q1 provides a much more precise description of the volumetric properties of the magnetic field structure. The difference between Q and Q1 is illustrated by comparing their distributions for two configurations, one of which is the Titov-Demoulin model of a twisted magnetic field.

  19. On the Predominance of the Radial Component of the Magnetic Field in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Habbal, Shadia Rifai; Woo, Richard; Arnaud, Jean

    2001-09-01

    Polarimetric measurements of the corona out to 2 Rsolar in the Fe XIII 10747 Å line, the strongest of the iron forbidden lines, are placed for the first time in the context of spatially resolved images of coronal density structures. These measurements, which are the only tool currently available to yield the direction of the magnetic field, date to 1980, the only year when they were available with polarized brightness images of the corona. Through this comparison, the observed predominance of the radial component of the coronal magnetic field, discovered over three decades ago from eclipse observations and established systematically by Arnaud, is shown to point to the coexistence of two magnetic field components in the corona: a nonradial field associated with the large-scale structures known as streamers and a more pervasive radial magnetic field. This finding suggests that these two components are the coronal counterparts of the strong- and weak-field components recently observed in the quiet-Sun photospheric field and supported by recent theoretical investigations of the solar dynamo.

  20. SIMULATIONS OF PROMINENCE FORMATION IN THE MAGNETIZED SOLAR CORONA BY CHROMOSPHERIC HEATING

    SciTech Connect

    Xia, C.; Chen, P. F.; Keppens, R.

    2012-04-01

    Starting from a realistically sheared magnetic arcade connecting the chromospheric, transition region to coronal plasma, we simulate the in situ formation and sustained growth of a quiescent prominence in the solar corona. Contrary to previous works, our model captures all phases of the prominence formation, including the loss of thermal equilibrium, its successive growth in height and width to macroscopic dimensions, and the gradual bending of the arched loops into dipped loops, as a result of the mass accumulation. Our 2.5 dimensional, fully thermodynamically and magnetohydrodynamically consistent model mimics the magnetic topology of normal-polarity prominences above a photospheric neutral line, and results in a curtain-like prominence above the neutral line through which the ultimately dipped magnetic field lines protrude at a finite angle. The formation results from concentrated heating in the chromosphere, followed by plasma evaporation and later rapid condensation in the corona due to thermal instability, as verified by linear instability criteria. Concentrated heating in the lower atmosphere evaporates plasma from below to accumulate at the top of coronal loops and supply mass to the later prominence constantly. This is the first evaporation-condensation model study where we can demonstrate how the formed prominence stays in a force balanced state, which can be compared to the Kippenhahn-Schlueter type magnetohydrostatic model, all in a finite low-beta corona.

  1. SWAP OBSERVATIONS OF THE LONG-TERM, LARGE-SCALE EVOLUTION OF THE EXTREME-ULTRAVIOLET SOLAR CORONA

    SciTech Connect

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

    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.

  2. Hot carbon corona in Mars' upper thermosphere and exosphere: 2. Solar cycle and seasonal variability

    NASA Astrophysics Data System (ADS)

    Lee, Yuni; Combi, Michael R.; Tenishev, Valeriy; Bougher, Stephen W.

    2014-12-01

    This work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self-consistently the exosphere and the upper thermosphere, a 3-D kinetic particle simulator, the Adaptive Mesh Particle Simulator, and the 3-D Mars Thermosphere General Circulation Model are one-way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s-1 (AL) to 55.1 × 1023 s-1 (PL).

  3. Heating of the solar chromosphere and corona. I - Generalized inhomogeneous wave equation for magnetoacoustic motions

    NASA Technical Reports Server (NTRS)

    Anand, S. P. S.

    1976-01-01

    The generalized inhomogeneous wave equation that governs magnetoacoustic, vortical, and thermal motions in compressible fluids and that is applicable to the problem of heating of the solar chromosphere and corona is obtained. The effects of kinematic and bulk viscosity, heat conduction, Joule dissipation, and magnetic diffusivity are included. Under the usual assumptions, the generalized wave equation reduces to the well-known equations of Lighthill, Kulsrud, Phillips, and others. The major problems encountered in applying Lighthill's (1952) mechanism to sound generation in turbulent media are reviewed for both the subsonic and supersonic cases.

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

    SciTech Connect

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

    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.

  5. Heating of the solar corona by dissipative Alfvén solitons.

    PubMed

    Stasiewicz, K

    2006-05-05

    Solar photospheric convection drives myriads of dissipative Alfvén solitons (hereinafter called alfvenons) capable of accelerating electrons and ions to energies of hundreds of keV and producing the x-ray corona. Alfvenons are exact solutions of two-fluid equations for a collisionless plasma and represent natural accelerators for conversion of the electromagnetic energy flux driven by convective flows into kinetic energy of charged particles in space and astrophysical plasmas. Their properties have been experimentally verified in the magnetosphere, where they accelerate auroral electrons to tens of keV.

  6. Radio Tracking of a White-Light Coronal Mass Ejection from Solar Corona to Interplanetary Medium.

    PubMed

    Reiner; Kaiser; Plunkett; Prestage; Manning

    2000-01-20

    For a solar flare/coronal mass ejection (CME) event on 1999 May 3, type II radio emissions were observed from the metric through the hectometric wavelength regimes. By comparing the dynamics of the CME with that implied by the frequency range and frequency drift rates of the type II radio emissions, it is concluded that the decametric-hectometric type II radio emissions were associated with the CME. The dynamics implied by the metric type II radio burst suggest a distinct coronal shock, associated with the flare, which only produced radio emissions in the low corona.

  7. Coexistence of self-organized criticality and intermittent turbulence in the solar corona.

    PubMed

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

    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.

  8. Electrodynamic Dust Shield for Solar Panels on Mars

    NASA Technical Reports Server (NTRS)

    Calle, C. I.; Buhler, C. R.; Mantovani, J. G.; Clements S.; Chen, A.; Mazumder, M. K.; Biris, A. S.; Nowicki, A. W.

    2004-01-01

    The Materials Adherence Experiment on the Mars Pathfinder mission measured an obscuration of the solar arrays due to dust deposition at a rate of about 0.2 8% per day. It was estimated that settling dust may cause degradation in performance of a solar panel of between 22% and 89% over the course of two years [1, 2]. These results were obtained without the presence of a global dust storm. Several types of adherence forces keep dust particles attached to surfaces. The most widely discussed adherence force is the electrostatic force. Laboratory experiments [3] as well as indirect evidence from the Wheel Abrasion Experiment on Pathfinder [4] indicate that it is very likely that the particles suspended in the Martian atmosphere are electrostatically charged.

  9. 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

  10. STEREO OBSERVATIONS OF FAST MAGNETOSONIC WAVES IN THE EXTENDED SOLAR CORONA ASSOCIATED WITH EIT/EUV WAVES

    SciTech Connect

    Kwon, Ryun-Young; Ofman, Leon; Kramar, Maxim; Olmedo, Oscar; Davila, Joseph M.; Thompson, Barbara J.; Cho, Kyung-Suk

    2013-03-20

    We report white-light observations of a fast magnetosonic wave associated with a coronal mass ejection observed by STEREO/SECCHI/COR1 inner coronagraphs on 2011 August 4. The wave front is observed in the form of density compression passing through various coronal regions such as quiet/active corona, coronal holes, and streamers. Together with measured electron densities determined with STEREO COR1 and Extreme UltraViolet Imager (EUVI) data, we use our kinematic measurements of the wave front to calculate coronal magnetic fields and find that the measured speeds are consistent with characteristic fast magnetosonic speeds in the corona. In addition, the wave front turns out to be the upper coronal counterpart of the EIT wave observed by STEREO EUVI traveling against the solar coronal disk; moreover, stationary fronts of the EIT wave are found to be located at the footpoints of deflected streamers and boundaries of coronal holes, after the wave front in the upper solar corona passes through open magnetic field lines in the streamers. Our findings suggest that the observed EIT wave should be in fact a fast magnetosonic shock/wave traveling in the inhomogeneous solar corona, as part of the fast magnetosonic wave propagating in the extended solar corona.

  11. 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.

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

    SciTech Connect

    Weidenschilling, S.J.

    1980-10-01

    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.

  13. Solar Spectral Radiative Forcing Due to Dust Aerosol During the Puerto Rico Dust Experiment

    NASA Technical Reports Server (NTRS)

    Pilewskie, P.; Bergstrom, R.; Rabbette, M.; Livingston, J.; Russell, P.; Gore, Warren J. (Technical Monitor)

    2000-01-01

    During the Puerto Rico Dust Experiment (PRIDE) upwelling and downwelling solar spectral irradiance was measured on board the SPAWAR Navajo and downwelling solar spectral flux was measured at a surface site using the NASA Ames Solar Spectral Flux Radiometer. These data will be used to determine the net solar radiative forcing of dust aerosol and to quantify the solar spectral radiative energy budget in the presence of elevated aerosol loading. We will assess the variability in spectral irradiance using formal principal component analysis procedures and relate the radiative variability to aerosol microphysical properties. Finally, we will characterize the sea surface reflectance to improve aerosol optical depth retrievals from the AVHRR satellite and to validate SeaWiFS ocean color products.

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

    SciTech Connect

    Habbal, Shadia Rifai; Morgan, Huw; Druckmueller, Miloslav; Ding, Adalbert

    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.

  15. High Performance Computing Application: Solar Dynamo Model Project II, Corona and Heliosphere Component Initialization, Integration and Validation

    DTIC Science & Technology

    2015-06-24

    space environment, and ultimately our ability to anticipate solar disturbances and to guard accordingly. The Sun brings life-giving energy but has...function of the photosphere magnetic field magnitude that represents solar energy input to the corona, the other the simple negative exponential of...Sokolov et al. (2013) also suggested that this energy source is sufficient to explain the increase in solar wind speed between regions of closed and

  16. Polar and equatorial coronal hole winds at solar minima: From the heliosphere to the inner corona

    SciTech Connect

    Zhao, L.; Landi, E.

    2014-02-01

    Fast solar wind can be accelerated from at least two different sources: polar coronal holes and equatorial coronal holes. Little is known about the relationship between the wind coming from these two different latitudes and whether these two subcategories of fast wind evolve in the same way during the solar cycle. Nineteen years of Ulysses observations, from 1990 to 2009, combined with ACE observations from 1998 to the present provide us with in situ measurements of solar wind properties that span two entire solar cycles. These missions provide an ideal data set to study the properties and evolution of the fast solar wind originating from equatorial and polar holes. In this work, we focus on these two types of fast solar wind during the minima between solar cycles 22 and 23 and 23 and 24. We use data from SWICS, SWOOPS, and VHM/FGM on board Ulysses and SWICS, SWEPAM, and MAG on board ACE to analyze the proton kinetic, thermal, and dynamic characteristics, heavy ion composition, and magnetic field properties of these two fast winds. The comparison shows that: (1) their kinetic, thermal, compositional, and magnetic properties are significantly different at any time during the two minima and (2) they respond differently to the changes in solar activity from cycle 23 to 24. These results indicate that equatorial and polar fast solar wind are two separate subcategories of fast wind. We discuss the implications of these results and relate them to remote-sensing measurements of the properties of polar and equatorial coronal holes carried out in the inner corona during these two solar minima.

  17. 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.

  18. Tracing Dust Grains from Supernovae to The Solar Nebulae

    NASA Astrophysics Data System (ADS)

    Luebbers, Ian; Goodson, Matthew; Heitsch, Fabian

    2016-01-01

    Short-lived radioisotopes (SLRs) were present in the early solar system, providing evidence that the solar system was impacted by a supernova prior to or during its formation. However, hydrodynamical models of the injection of SLRs fail to achieve sufficient mixing, presenting a challenge to this hypothesis. We propose the injection of SLRs via dust grains in an attempt to overcome the mixing barrier. To test this hypothesis we simulate injection into a presolar gas cloud under various assumptions. Our results suggest that SLR transport in dust grains is a viable mechanism for generating observed SLR abundances.

  19. T he Faint Drifting Decameter Radio Bursts From The Solar Corona

    NASA Astrophysics Data System (ADS)

    Briand, C.; Zaslavsky, A.; Lecacheux, A.; Zarka, P.; Maksimovic, M.; Mangeney, A.

    2007-01-01

    The radio observations of solar corona at decameter wavelengths reveal the presence of numerous faint, frequency drifting structures. We analyse observations performed on July 13th , 2002 with the DSP wideband spectrometer instrument implemented at the UTR-2 radiote- lescope. The main characteristics of these structures are statistically studied. Three populations of bursts are iden- tifies. The largest one presents negative frequency drifts of about -0.89 MHz.s-1 and a lifetime extending up to 11 sec (median value 2.72 sec). A second one shows positive frequency drifts of about +0.95 MHz.s-1 and a life- time extending up to 3 sec. The last population consists in structures with very small frequency drifts of about -0.1 MHz.s-1 and a shorter lifetime (about 1 sec). Assuming that those emissions are the signature of elec- tron beams propagating through the solar corona, we deduce that they have a velocity of about 3-5 times the electron thermal velocity. A new mechanism is proposed to explain the formation of plasma waves with such low beam velocity: spatially localized, temporal fluctuations of the electron distribution function width (heating).

  20. Physical properties of the quiet solar chromosphere-corona transition region

    NASA Astrophysics Data System (ADS)

    Dunin-Barkovskaya, O. V.; Somov, B. V.

    2016-12-01

    The physical properties of the quiet solar chromosphere-corona transition region are studied. Here the structure of the solar atmosphere is governed by the interaction of magnetic fields above the photosphere. Magnetic fields are concentrated into thin tubes inside which the field strength is great. We have studied how the plasma temperature, density, and velocity distributions change along a magnetic tube with one end in the chromosphere and the other one in the corona, depend on the plasma velocity at the chromospheric boundary of the transition region. Two limiting cases are considered: horizontally and vertically oriented magnetic tubes. For various plasma densities we have determined the ranges of plasma velocities at the chromospheric boundary of the transition region for which no shock waves arise in the transition region. The downward plasma flows at the base of the transition region are shown to be most favorable for the excitation of shock waves in it. For all the considered variants of the transition region we show that the thermal energy transfer along magnetic tubes can be well described in the approximation of classical collisional electron heat conduction up to very high velocities at its base. The calculated extreme ultraviolet (EUV) emission agrees well with the present-day space observations of the Sun.

  1. A Simple Dynamical Model for Filament Formation in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Litvinenko, Yuri E.; Wheatland, M. S.

    2005-09-01

    Filament formation in the solar atmosphere is considered. In the limit of sub-Alfvénic but supersonic motion, plasma flow in the solar corona is driven via the induction equation by a slow evolution of force-free magnetic fields. Methods for solving the relevant magnetohydrodynamic equations are presented and applied to filament modeling in two and three dimensions. An illustrative two-dimensional example is given, which is based on a potential magnetic field with a dip. The example describes the formation of a normal filament between two bipolar regions on the Sun. Next a detailed three-dimensional calculation is presented, which uses linear force-free magnetic fields. The boundary conditions are chosen to resemble the qualitative ``head-to-tail'' linkage model for the formation of filaments, suggested by Martens & Zwaan. Consistent with this model, dense formations, reminiscent of filament pillars, are shown to appear in the corona above the region of converging and canceling magnetic bipoles. The numerical results are consistent with the principal role of magnetic field in the dynamical processes of dense plasma accumulation and support in filaments, advocated by Martens & Zwaan.

  2. The potential of hydrogen lines for the spectropolarimetry of the solar corona

    NASA Astrophysics Data System (ADS)

    Vial, Jean-Claude; Chane-Yook, Martine

    2016-07-01

    Neutral Hydrogen lines have been detected in the hot and ionized solar corona as early as 1970 (Gabriel et al. 1971) and since then with the Spartan and UVCS/SoHO space experiments. Moreover, because of the sensitivity of the Lyman lines to the Hanle effect (Bommier and Sahal-Brechot 1982, Trujillo Bueno et al. 2005), polarization measurements in these lines could lead to the diagnostic of weak magnetic fields in the corona (Derouich et al. 2010), a challenge which has led to various space mission proposals such as LYOT/SMESE or MASC. Our investigation concerns the computation of the emission in 10 selected lines of Hydrogen (Lyman, Balmer, and Paschen) taking into account the proper computation of the NonLTE H ionization and atomic levels populations. We present the results for three different coronal models (streamer, quiet Sun and coronal hole) in terms of profiles and absolute intensities at altitudes varying from 1.05 to 1.9 solar radius. These spectrophotometric results could help for the determination of the space and ground-based polarimetric instrumentation best suited for the measurement of the coronal magnetic field.

  3. Observing the solar corona with a tunable Fabry-Perot filter.

    PubMed

    Noble, Matthew W; Rust, David M; Bernasconi, Pietro N; Pasachoff, Jay M; Babcock, Bryce A; Bruck, Megan A

    2008-11-01

    A solid Fabry-Perot etalon with a 0.16 A passband was used during the 180 s solar eclipse of 2006 for rapid scans of an emission line of the solar corona. The etalon was a Y-cut lithium niobate wafer coated with reflective and conductive (ITO) layers. Voltage applied perpendicular to the etalon face produced a passband shift of 0.0011 A V(-1). During the eclipse, 18 filtergrams were obtained at six 0.22 A steps across the profile of the forbidden [Fe X] spectral emission line at 6374.4 A, which results from the 10(6) K coronal plasma. The 9.3 x 9.3 arcmin field of view showed the structure of the corona above a newly emerged sunspot region. We discuss tests performed on the etalon before and after the eclipse. We also discuss the coronal observations, which show some features with 10 km s(-1) velocities in the line of sight.

  4. Finest Filamentary Structures of the Corona in the Slow and Fast Solar Wind

    NASA Astrophysics Data System (ADS)

    Woo, Richard; Habbal, Shadia Rifai

    1997-01-01

    Recent progress in our understanding of electron density fluctuations observed by radio occultation measurements has demonstrated that a break in the vicinity of 1 Hz in the temporal frequency spectrum of the density fluctuations provides a measure of the size of the finest filamentary structures in the solar corona. Breaks in frequency have been inferred from the density spectra deduced by Coles et al. from 1979-1980 Voyager phase scintillation and spectral broadening measurements. These results show that the finest filamentary structures are found in the extensions or stalks of coronal streamers--the likely sources of the slow solar wind--and are over a factor of 3 smaller than those in the fast wind emanating from coronal holes. The inferred sizes of the finest filamentary structures are approximately 6 km in the slow wind at 8 Rsolar and 22 km in the fast wind at 9.1 Rsolar.

  5. Synthetic Hydrogen Spectra of Oscillating Prominence Slabs Immersed in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Zapiór, M.; Oliver, R.; Ballester, J. L.; Heinzel, P.

    2016-08-01

    We study the behavior of Hα and Hβ spectral lines and their spectral indicators in an oscillating solar prominence slab surrounded by the solar corona, using an MHD model combined with a 1D radiative transfer code taken in the line of sight perpendicular to the slab. We calculate the time variation of the Doppler shift, half-width, and maximum intensity of the Hα and Hβ spectral lines for different modes of oscillation. We find a non-sinusoidal time dependence of some spectral parameters with time. Because Hα and Hβ spectral indicators have different behavior for different modes, caused by differing optical depths of formation and different plasma parameter variations in time and along the slab, they may be used for prominence seismology, especially to derive the internal velocity field in prominences.

  6. Sparse Bayesian Inference and the Temperature Structure of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Warren, Harry P.; Byers, Jeff M.; Crump, Nicholas A.

    2017-02-01

    Measuring the temperature structure of the solar atmosphere is critical to understanding how it is heated to high temperatures. Unfortunately, the temperature of the upper atmosphere cannot be observed directly, but must be inferred from spectrally resolved observations of individual emission lines that span a wide range of temperatures. Such observations are “inverted” to determine the distribution of plasma temperatures along the line of sight. This inversion is ill posed and, in the absence of regularization, tends to produce wildly oscillatory solutions. We introduce the application of sparse Bayesian inference to the problem of inferring the temperature structure of the solar corona. Within a Bayesian framework a preference for solutions that utilize a minimum number of basis functions can be encoded into the prior and many ad hoc assumptions can be avoided. We demonstrate the efficacy of the Bayesian approach by considering a test library of 40 assumed temperature distributions.

  7. The 3-D solar radioastronomy and the structure of the corona and the solar wind. [solar probes of solar activity

    NASA Technical Reports Server (NTRS)

    Steinberg, J. L.; Caroubalos, C.

    1976-01-01

    The mechanism causing solar radio bursts (1 and 111) is examined. It is proposed that a nonthermal energy source is responsible for the bursts; nonthermal energy is converted into electromagnetic energy. The advantages are examined for an out-of-the-ecliptic solar probe mission, which is proposed as a means of stereoscopically viewing solar radio bursts, solar magnetic fields, coronal structure, and the solar wind.

  8. THE ORIGIN OF NON-MAXWELLIAN SOLAR WIND ELECTRON VELOCITY DISTRIBUTION FUNCTION: CONNECTION TO NANOFLARES IN THE SOLAR CORONA

    SciTech Connect

    Che, H.; Goldstein, M. L.

    2014-11-10

    The formation of the observed core-halo feature in the solar wind electron velocity distribution function is a long-time puzzle. In this Letter, based on the current knowledge of nanoflares, we show that the nanoflare-accelerated electron beams are likely to trigger a strong electron two-stream instability that generates kinetic Alfvén wave and whistler wave turbulence, as we demonstrated in a previous paper. We further show that the core-halo feature produced during the origin of kinetic turbulence is likely to originate in the inner corona and can be preserved as the solar wind escapes to space along open field lines. We formulate a set of equations to describe the heating processes observed in the simulation and show that the core-halo temperature ratio of the solar wind is insensitive to the initial conditions in the corona and is related to the core-halo density ratio of the solar wind and to the quasi-saturation property of the two-stream instability at the time when the exponential decay ends. This relation can be extended to the more general core-halo-strahl feature in the solar wind. The temperature ratio between the core and hot components is nearly independent of the heliospheric distance to the Sun. We show that the core-halo relative drift previously reported is a relic of the fully saturated two-stream instability. Our theoretical results are consistent with the observations while new tests for this model are provided.

  9. The Time-Dependent Chemistry of Cometary Debris in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Pesnell, W. D.; Bryans, P.

    2015-01-01

    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.

  10. Reconstructing the open-field magnetic geometry of solar corona using coronagraph images

    NASA Astrophysics Data System (ADS)

    Uritsky, Vadim M.; Davila, Joseph M.; Jones, Shaela; Burkepile, Joan

    2015-04-01

    The upcoming Solar Probe Plus and Solar Orbiter missions will provide an new insight into the inner heliosphere magnetically connected with the topologically complex and eruptive solar corona. Physical interpretation of these observations will be dependent on the accurate reconstruction of the large-scale coronal magnetic field. We argue that such reconstruction can be performed using photospheric extrapolation codes constrained by white-light coronagraph images. The field extrapolation component of this project is featured in a related presentation by S. Jones et al. Here, we focus on our image-processing algorithms conducting an automated segmentation of coronal loop structures. In contrast to the previously proposed segmentation codes designed for detecting small-scale closed loops in the vicinity of active regions, our technique focuses on the large-scale geometry of the open-field coronal features observed at significant radial distances from the solar surface. Coronagraph images are transformed into a polar coordinate system and undergo radial detrending and initial noise reduction followed by an adaptive angular differentiation. An adjustable threshold is applied to identify candidate coronagraph features associated with the large-scale coronal field. A blob detection algorithm is used to identify valid features against a noisy background. The extracted coronal features are used to derive empirical directional constraints for magnetic field extrapolation procedures based on photospheric magnetograms. Two versions of the method optimized for processing ground-based (Mauna Loa Solar Observatory) and satellite-based (STEREO Cor1 and Cor2) coronagraph images are being developed.

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

    SciTech Connect

    Pesnell, W. D.; Bryans, P.

    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.

  12. Observation and analysis of the F-corona brightness

    NASA Astrophysics Data System (ADS)

    Mann, I.; MacQueen, R. M.

    In the context of dust measurements on a solar probe, we present an analysis of a 1991 eclipse observation by Hodapp et al. /1/ with respect to the solar F-corona brightness (published in MacQueen and Greeley, /2/). Although the data are limited by observing conditions, we can still gain some information which may be compared with our present knowledge about the interplanetary dust cloud based on the analysis of zodiacal light data, which describe the dust in regions outward from the sun. Past visible light measurements showed that the F-corona has roughly the same brightness in the ecliptic and over the poles, but that the radial gradient of the latter is steeper. In the 1991 infrared observations, the ecliptic radial gradient is flatter than has been observed in the visible, whereas the polar radial gradient is rather similar to past, visible spectral region observations. This appears to point to the existence of different components in the dust cloud as also discussed to explain the zodiacal light /3/. Also in the present data there is no clear signature for the beginning of the dust free zone around the sun, one conclusion being that dust (of some type) possibly approaches the sun to within 4 solar radii. As far as the size distribution of dust in the solar vicinity is concerned we discuss a study by Davidson et al. /4/, which shows that the present F-corona data can be fitted with distinctly different size distributions.

  13. Electron density and temperature in the solar corona from multifrequency radio imaging

    NASA Astrophysics Data System (ADS)

    Mercier, C.; Chambe, G.

    2015-11-01

    Context. The 2D images obtained through rotational aperture synthesis with the Nançay Radioheliograph are suitable for quantitative exploitation. First results are presented. Aims: We study the variations of the quiet corona in brightness and size during an 8-year period and derive electron density and temperature in the corona. Methods: Images at 6 frequencies between 150 and 450 MHz for 183 quiet days between 2004 and 2011 were used. Measurements of the brightness temperature Tb beyond the limb allowed coronal density models to be derived in both EW and NS radial directions, with a weak dependence on the electron temperature. The total ranges in the heliocentric distance r are 1.15-1.60 R⊙ (EW) and 1.0-1.4 R⊙ (NS). The agreement between results from different frequencies, in the ranges of r where there is overlapping shows the robustness of the method. The electron temperature, in turn, can be derived from the comparison of the observed mean spectra on the disk with those predicted through transfer calculations from the density models derived from limb observations. Results: The widths of the brightness profiles that were averaged yearly have minima at cycle minimum (2008-2009). These minima are more pronounced for EW profiles than for NS ones. The derived yearly-averaged density models along equatorial and polar diameters are consistent with isothermal and hydrostatic models. They are characterized by their density value n0 extrapolated down to the base of the corona and their scale-height temperature TH. Changes in n0 and TH with solar cycle are given for equatorial and polar regions. The kinetic temperature Te of electrons in the corona (~0.62 MK) is found to be significantly less than TH (~1.5 MK). This implies an ion temperature Ti ~ 2.2 MK. Conclusions: The yearly-averaged variations of these models are less than the dispersion between models derived from other techniques, such as white light and EUV observations, partly because these two techniques

  14. International Solar Cycle Studies [ISCS] Working Group 2: solar magnetic field variability - from the lower atmosphere through the inner corona

    NASA Astrophysics Data System (ADS)

    Harrison, Richard A.; Michels, Donald

    This report is a summary of activities and plans relating to the International Solar Cycle Studies (ISCS) Working Group 2, which is concerned with solar magnetic field variability, from the lower atmosphere through the inner corona. Whilst the Working Group carries a rather general title, the activities are focusing on several well defined topics - in particular the onset of coronal mass ejection events. Recognising the large number of scientific meetings worldwide, the working style of this group is aimed at improving communication, information exchange and collaboration making use of existing meetings and with a minimum of red tape. The core of the activity is through the use of the World Wide Web and e-mail. In this way, this Working Group does not introduce extra effort, but provides a better focus for on-going projects.

  15. 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.

  16. TIME-DEPENDENT TURBULENT HEATING OF OPEN FLUX TUBES IN THE CHROMOSPHERE, CORONA, AND SOLAR WIND

    SciTech Connect

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

    2015-10-01

    We investigate several key questions of plasma heating in open-field regions of the corona that connect to the solar wind. We present results for a model of Alfvén-wave-driven turbulence for three typical open magnetic field structures: a polar coronal hole, an open flux tube neighboring an equatorial streamer, and an open flux tube near a strong-field active region. We compare time-steady, one-dimensional turbulent heating models against fully time-dependent three-dimensional reduced-magnetohydrodynamic modeling of BRAID. We find that the time-steady results agree well with time-averaged results from BRAID. The time dependence allows us to investigate the variability of the magnetic fluctuations and of the heating in the corona. The high-frequency tail of the power spectrum of fluctuations forms a power law whose exponent varies with height, and we discuss the possible physical explanation for this behavior. The variability in the heating rate is bursty and nanoflare-like in nature, and we analyze the amount of energy lost via dissipative heating in transient events throughout the simulation. The average energy in these events is 10{sup 21.91} erg, within the “picoflare” range, and many events reach classical “nanoflare” energies. We also estimated the multithermal distribution of temperatures that would result from the heating-rate variability, and found good agreement with observed widths of coronal differential emission measure distributions. The results of the modeling presented in this paper provide compelling evidence that turbulent heating in the solar atmosphere by Alfvén waves accelerates the solar wind in open flux tubes.

  17. Alfvén wave propagation in the high solar corona

    NASA Astrophysics Data System (ADS)

    Grappin, R.; Léorat, J.; Buttighoffer, A.

    2000-10-01

    We consider monochromatic Alfvén perturbations propagating upward in the high corona, in the distance range between 2 and 9 solar radii. The corona is made of a closed loop region and of an open flow region, with or without structured streams generated by stationary temperature inhomogeneities in the corona. The wave period is 36 min., the plasma beta varies between 0.25 at the poles and 1.2 at the equator. We integrate the time-dependent, three-dimensional axisymmetric polytropic MHD equations. Filters are used to damp energy at the grid scale. The mean flow and waves are dealt with self-consistently, by using transparent boundary conditions, which prevent spurious reflections at the inner coronal boundary. We find that the mother Alfvén wave remains everywhere Alfvénic: the normalized cross-helicity is sigma_c =~ 1-10-3 except within a thin layer around the heliospheric current sheet. The radial evolution depends on the latitude. In a large domain around the heliospheric current sheet, the wave is very strongly damped, whatever its amplitude, by the phase mixing, i.e., the shear of the wave front due to transverse gradients of the Alfvén speed and bulk velocity. As a consequence, the Alfvén wave nowhere reaches the heliospheric current sheet. At higher latitudes, and outside structured streams, the amplitude varies in agreement with the WKB prediction, albeit with some dissipation due to nonlinear steepening (depending on the wave amplitude); as a rule, the propagation angle varies, i.e., the propagation is alternatively oblique and quasi-parallel. On the other hand, streams show specific properties: the amplitude does not follow the WKB law, but the propagation angle remains constantly oblique. As a consequence, the streams show a strong minimum in the amplitude of the compressive fluctuations.

  18. 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 (Technical Monitor)

    2001-01-01

    This report covers technical progress during the first quarter of the second year of NASA Sun-Earth Connections Theory Program (SECTP). 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.

  19. The Structure and Dynamics of the Solar Corona and Inner Heliosphere-First Quarter First Year Progress Report

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    This report details progress during the first quarter of the first year of our Sun-Earth Connections Theory Program (SECTP) contract. Science Applications International Corporation (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.

  20. Three-Dimensional Reconstruction of the Electron Density in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Burnett, L. W.; Nychka, D. W.; Gibson, S. E.; Dalmasse, K.

    2015-12-01

    The need to understand the Sun's magnetic field motivates much of present-day solar physics research. Our ultimate goal is to quantitatively validate models of the global coronal magnetic field by comparing forward models of synthetic data to real observations. As a necessary first step, we seek to build a three-dimensional (3D) model of the electron density in the solar corona, based on white-light coronagraph data. Given that these observations are two-dimensional snapshots, we employ a new application of statistical tomography to piece together the full 3D picture. In an initial step, we demonstrate that our method is capable of reconstructing geometrically-simple density formations. We next turn to more realistic coronal density structures as represented by the global magnetohydrodynamic models made available by Predictive Science Inc., and integrated to create synthetic data using the FORWARD SolarSoft codes. Finally, we consider the application of our method to Mauna Loa Solar Observatory K-Coronagraph observations, and discuss the strengths and limitations of our method.

  1. Finding of low-contrast formations in the solar corona using a low contrast method

    NASA Astrophysics Data System (ADS)

    Kuznetsova, S. M.; Krissinel, B. B.; Obukhov, A. G.; Prosovetsky, D. V.; Smolkov, G. Ya.

    2009-12-01

    Coronal holes, bright coronal points, filaments, and prominences are among the initial factors responsible for variability of the space weather conditions. Radioheliographic data on low-contrast formations contain valuable information necessary for studying conditions of origination, peculiarities of evolution, and prediction of solar-terrestrial relations. It is important to identify these formations on the solar disk when physical properties of coronal holes are revealed. The algorithm based on the Wiener-Tikhonov filter modification with controlled parameters and a high-frequency contrast filter was developed in order to isolate low-contrast formations in the solar corona brightness distributions obtained at a wavelength of 5.2 cm from the Siberian solar radio telescope observations. In this case low-contrast sources are isolated in two main stages: (1) HF noise smoothing based on an evolutionary filter with controlled parameters and (2) contrasting of sources using an HF filter. The evolutionary filter regularization parameters and the dimensions of an HF contrast filter mask are selected depending on the signal-to-noise ratio and dimensions of the studied region based on the results of preliminary data processing. The corresponding software has been developed in order to identify low-contrast objects on the Sun’s radio images using this method. The algorithm is used to isolate filaments and coronal holes and the results of this usage are presented in this work.

  2. 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.

  3. Evidence for mass outflow in the low solar corona over a large sunspot

    NASA Technical Reports Server (NTRS)

    Neupert, Werner M.; Brosius, Jeffrey W.; Thomas, Roger J.; Thompson, William T.

    1992-01-01

    Spatially resolved EUV coronal emission-line profiles have been obtained in a solar active region, including a large sunspot, using an EUV imaging spectrograph. Relative Doppler velocities were measured in the lines of Mg IX, Fe XV, and Fe XVI with a sensitivity of 2-3 km/s at 350 A. The only significant Doppler shift occurred over the umbra of the large sunspot, in the emission line of Mg IX (at Te of about 1.1 x 10 exp 6 K). The maximum shift corresponded to a peak velocity toward the observer of 14 +/- 3 km/s relative to the mean of measurements in this emission line made elsewhere over the active region. The magnetic field in the low corona was aligned to within 10 deg of the line of sight at the location of maximum Doppler shift. Depending on the closure of the field, such a mass flow could either contribute to the solar wind or reappear as a downflow of material in distant regions on the solar surface. The site of the source, near a major photospheric field boundary, was consistent with origins of low-speed solar wind typically inferred from interplanetary plasma observations.

  4. THE ENERGETICS OF A GLOBAL SHOCK WAVE IN THE LOW SOLAR CORONA

    SciTech Connect

    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 × 10{sup 31} erg to produce the ''EIT wave'', which is approximately 10% the kinetic energy of the associated CME (shown to be ≈2.5 × 10{sup 32} 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. Brightness contribution of zodiacal dust along the line of sight in and out of the ecliptic plane and in the F-corona

    NASA Astrophysics Data System (ADS)

    Misconi, Nebil Y.; Rusk, Edwin T.

    1987-12-01

    Model calculations are used to determine the location of interplanetary dust particles that contribute most of the brightness of the zodiacal light as seen from earth, in and out of the ecliptic plane and in the F-corona. It is found that, as one observes in increasing ecliptic latitude (beta), the distance to the earth decreases for dust contributing equal fractions to the line-of-sight brightness. This and other results will help in the analysis of: (1) structures in the observed brightness of the zodiacal light, (2) bands such as those observed by IRAS, (3) temporal variations in the brightness of the zodiacal light, (4) observations of the photometric axis, and (5) past and future observations of the F-corona.

  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. Origin of the ten degree Solar System dust bands

    NASA Astrophysics Data System (ADS)

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

    1997-12-01

    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 mechanism of dust band production could involve either a continual comminution of material associated with the major Hirayama asteroid families, the equilibrium model (Dermott et al. (1984) Nature312, 505-509) or random disruptions in the asteroid belt of small, single asteroids (Sykes and Greenberg (1986) Icarus65, 51-69). The IRAS observations of the zodiacal cloud from which the dust band profiles are isolated have excellent resolution, and the manner in which these profiles change around the sky should allow the origin of the bands, their radial extent, the size-frequency distribution of the material and the optical properties of the dust itself to be determined. The equilibrium model of the dust bands suggests Eos as the parent of the 10° band pair. Results from detailed numerical modeling of the 10° band pair are presented. It is demonstrated that a model composed of dust particles having mean semimajor axis, proper eccentricity and proper inclination equal to those of the Eos family member asteroids, but with a dispersion in proper inclination of 2.5°, produces a convincing match with observations. Indeed, it is impossible to reproduce the observed profiles of the 10° band pair without imposing such a dispersion on the dust band material. Since the dust band profiles are matched very well with Eos, Themis and Koronis type material alone, the result is taken as strong evidence in favor of the equilibrium model. The effects of planetary perturbations are included by imposing the appropriate forced elements on the dust particle orbits (these forced elements vary with

  8. The charging processes of dust particles and the effects of Lorentz scattering in the circum-solar dust band

    NASA Astrophysics Data System (ADS)

    Kumar, A. S.; Isobe, Syuzo

    1992-03-01

    An analysis is presented of the charging processes for the dust particles in the circumsolar dust band at 4 solar radii, as well as the effects of the interactions between these charged particles and the magnetized ambient solar wind plasma on the evolution of their orbits. It is concluded that due to the higher values of the potential on the dust particle and the ambient solar wind magnetic field, the Lorentz force affects a much wider size range of particles in the near-solar regions. Since the magnitude of the Lorentz force is much higher and its characteristic time to affect the particle's orbit is much lower than those for the Poynting-Robertson drag force, the Lorentz force is a major perturbing force for dust particles in the circumsolar dust band at 4 solar radii.

  9. Spectrally-resolved Soft X-ray Observations and the Temperature Structure of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Caspi, Amir; Warren, Harry; McTiernan, James; Woods, Thomas N.

    2015-04-01

    Solar X-ray observations provide important diagnostics of plasma heating and particle acceleration, during solar flares and quiescent periods. How the corona is heated to its ~1-3 MK nominal temperature remains one of the fundamental unanswered questions of solar physics; heating of plasma to tens of MK during solar flares -- particularly to the hottest observed temperatures of up to ~50 MK -- is also still poorly understood. Soft X-ray emission (~0.1-10 keV; or ~0.1-10 nm) is particularly sensitive to hot coronal plasma and serves as a probe of the thermal processes driving coronal plasma heating. Spectrally- and temporally-resolved measurements are crucial for understanding these energetic processes, but there have historically been very few such observations. We present new solar soft X-ray spectra from the Amptek X123-SDD, measuring quiescent solar X-ray emission from ~0.5 to ~30 keV with ~0.15 keV FWHM resolution from two SDO/EVE calibration sounding rocket underflights in 2012 and 2013. Combined with observations from RHESSI, GOES/XRS, SDO/EVE, and SDO/AIA, the temperature distribution derived from these data suggest significant hot (5-10 MK) emission from active regions, and the 2013 spectra suggest a low-FIP enhancement of only ~1.6 relative to the photosphere, 40% of the usually-observed value from quiescent coronal plasma. We explore the implications of these findings on coronal heating. We discuss future missions for spectrally-resolved soft X-ray observations using the X123-SDD, including the upcoming MinXSS 3U CubeSat using the X123-SDD and scheduled for deployment in mid-2015, and the CubIXSS 6U CubeSat mission concept.

  10. Solar Array Panels With Dust-Removal Capability

    NASA Technical Reports Server (NTRS)

    Dawson, Stephen; Mardesich, Nick; Spence, Brian; White, Steve

    2004-01-01

    It has been proposed to incorporate piezoelectric vibrational actuators into the structural supports of solar photovoltaic panels, for the purpose of occasionally inducing vibrations in the panels in order to loosen accumulated dust. Provided that the panels were tilted, the loosened dust would slide off under its own weight. Originally aimed at preventing obscuration of photovoltaic cells by dust accumulating in the Martian environment, the proposal may also offer an option for the design of solar photovoltaic panels for unattended operation at remote locations on Earth. The figure depicts a typical lightweight solar photovoltaic panel comprising a backside grid of structural spars that support a thin face sheet that, in turn, supports an array of photovoltaic cells on the front side. The backside structure includes node points where several spars intersect. According to the proposal, piezoelectric buzzers would be attached to the node points. The process of designing the panel would be an iterative one that would include computational simulation of the vibrations by use of finite- element analysis to guide the selection of the vibrational frequency of the actuators and the cross sections of the spars to maximize the agitation of dust.

  11. Evidence for Small-Scale Filamentation and Dynamics in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Warren, H.

    2004-05-01

    Observations with the Transition Region and Coronal Explorer (TRACE) have revealed that the solar corona is both highly dynamic and highly filamented. In this talk I will discuss how dynamics and filamentation play an important role in explaining some of the observational properties of the Sun's atmosphere. TRACE observations have shown, for example, that many relatively cool ( ˜1 MK), long-lived active region loops have density and temperature profiles that are difficult to reconcile with static models. By modeling these loops as a sequence of impulsively heated filaments, in contrast, it is possible to account for the high densities, flat temperature profiles, and the temporal evolution of these structures. A similar approach to modeling the evolution of flare emission yields much better agreement with observation than treating the flare as a single loop.

  12. Balloon observations of the F-corona at the 1983 total solar eclipse

    NASA Astrophysics Data System (ADS)

    Isobe, S.; Tanabe, H.; Hirayama, T.; Koma, Y.; Soegijo, J.

    A balloon observation of the F-corona in visual and infrared regions was carried out by Japanese and Indonesian teams at the total solar eclipse on June 11, 1983, in Java, Indonesia. For the visual observation, a SIT television camera, with 4 interference filters (5300 Å, 6000 Å, 7200 Å and 8000 Å) and a 45°-step rotating polarizer, was used. The camera measured brightness distributions in a sky area of 5°×5° centered at the eclipsed sun at each polarizer position for each filter. In this paper, a part of results, which are the brightness and polarization distributions in a half area of the 6000 Å picture, is shown.

  13. X-ray spectrometer spectrograph telescope system. [for solar corona study

    NASA Technical Reports Server (NTRS)

    Bruner, E. C., Jr.; Acton, L. W.; Brown, W. A.; Salat, S. W.; Franks, A.; Schmidtke, G.; Schweizer, W.; Speer, R. J.

    1979-01-01

    A new sounding rocket payload that has been developed for X-ray spectroscopic studies of the solar corona is described. The instrument incorporates a grazing incidence Rowland mounted grating spectrograph and an extreme off-axis paraboloic sector feed system to isolate regions of the sun of order 1 x 10 arc seconds in size. The focal surface of the spectrograph is shared by photographic and photoelectric detection systems, with the latter serving as a part of the rocket pointing system control loop. Fabrication and alignment of the optical system is based on high precision machining and mechanical metrology techniques. The spectrograph has a resolution of 16 milliangstroms and modifications planned for future flights will improve the resolution to 5 milliangstroms, permitting line widths to be measured.

  14. Tracking Type III Radio Burst Sources in the Solar Corona by Heliographic Means

    NASA Astrophysics Data System (ADS)

    Koval, A. A.; Stanislavsky, A. A.; Konovalenko, A. A.; Volvach, Ya. S.

    We present the preliminary results of heliographic measurements of solar type III radio bursts in the low-frequency range (16.5-33 MHz) using the UTR-2 radio heliograph. The radio astronomy tools permit us to obtain two-dimensional spatial structures of burst sources in dependence of frequency and time. Each heliogram consists of 40 pixels (beams) as a result of the serial sweep in UV-plane wherein signals of each beam are recorded in a dynamic spectrum with both high temporal (˜ 2.482 ms) and top spectral (˜ 4 kHz) resolutions. The rate of output heliograph is one image per 3 seconds. Over a session in April, 2013 many type III radio and IIIb-III bursts were observed. On the heliograms the source motion direction in the upper corona is clearly detectable. The heliogram features are discussed.

  15. The relative abundance of neon and magnesium in the solar corona

    NASA Technical Reports Server (NTRS)

    Rugge, H. R.; Walker, A. B. C., Jr.

    1976-01-01

    A technique is proposed for specifically determining the relative solar coronal abundance of neon and magnesium. The relative abundance is calculated directly from the relative intensity of the resonance lines of Ne X (12.134A) and Mg XI (9.169A) without the need for the development of a detailed model of the thermal structure of the corona. Moderate resolution Bragg crystal spectrometer results from the OVI-10 satellite were used to determine a coronal neon to magnesium relative abundance of 1.47 + or - 0.38. The application of this technique to a recent higher resolution rocket observation gave an abundance ratio of approximately 0.93 + or - 0.15.

  16. Line-Of Velocities Observed in the Inner Solar Corona during the Total Solar Eclipses of 1980 and 1983

    NASA Astrophysics Data System (ADS)

    Raju, K. P.; Desai, J. N.; Chandrasekhar, T.; Ashok, N. M.

    1993-08-01

    Line-of-sight velocities in the inner solar corona are calculated from the coronal green-line profiles obtained from Fabry-Perot interferometric observations of the solar corona during the total solar eclipses of 1980 and 1983. The main features of the line-of-sight velocities seen in the Fabry-Perot fringes are reported here. Line profiles obtained from the 1980 observations show strong signatures of multiple components. The line profiles, in general, are found to contain one main component and a few subsidiary components. A large excess of components on the blue side of the main component is found. Line profiles belonging to the coronal active regions often show line splitting. The derived velocities associated with the 1980 coronal line profiles in general show an outward increase with respect to the innermost regions. This increase is found to be dependent on the coronal position angle and hence related to the activity of the underlying coronal region. The dispersion in velocities is found to be smaller in the closed magnetic field regions than that in the open regions, indicative of a more ordered flow in the former regions. The majority of the line profiles obtained from the 1983 observations show single components. The derived velocities associated with the fringes are small in comparison to 1980 values. The trend of increasing velocity with increasing coronal height is seen only in one case out of three. The line-of-sight velocities in the line profiles are interpreted as due to the discrete moving plasma components in the line of sight, which arise as a result of the motion of plasma inside the coronal loops. It is suggested that coronal loop motions were stronger in 1980 than in 1983.

  17. Non-equilibrium Ionization Modeling of Simulated Pseudostreamers in a Solar Corona Model

    NASA Astrophysics Data System (ADS)

    Shen, Chengcai; Raymond, John C.; Mikić, Zoran; Linker, Jon; Reeves, Katharine K.; Murphy, Nicholas A.

    2015-04-01

    Time-dependent ionization is important for diagnostics of coronal streamers, where the thermodynamic time scale could be shorter than the ionization or recombination time scales, and ions are therefor in non-equilibrium ionization states. In this work, we perform post-processing time-dependent ionization calculations for a three dimensional solar corona and inner heliosphere model from Predictive Sciences Inc. (Mikić & Linker 1999) to analyze the influence of non-equilibrium ionization on emission from coronal streamers. Using the plasma temperature, density, velocity and magnetic field distributions provided by the 3D MHD simulation covering the Whole Sun Month (Carrington rotation CR1913, 1996 August 22 to September 18), we calculate non-equilibrium ionization states in the region around a pseudostreamer. We then obtain the synthetic emissivities with the non-equilibrium ion populations. Under the assumption that the corona is optically thin, we also obtain intensity profiles of several emission lines. We compare our calculations with intensities of Lyman-alpha lines and OVI lines from SOHO/Ultraviolet Coronagraph Spectrometer (UVCS) observations at 14 different heights. The results show that intensity profiles of both Lyman-alpha and OVI lines match well UVCS observations at low heights. At large heights, OVI intensites are higher for non-equilibrium ionization than equilibrium ionization inside this pseudostreamer. The assumption of ionization equilibrium would lead to a underestimate of the OVI intensity by about ten percent at a height of 2 solar radii, and the difference between these two ionization cases increases with height. The intensity ratio of OVI 1032 line to OVI 1037 lines is also obtained for non-equilibrium ionization modeling.

  18. Evidence for Nanoflare Heating of the Solar Corona from the EUNIS Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Brosius, J. W.; Daw, A. N.; Rabin, D. M.

    2015-12-01

    We present spatially resolved EUV spectroscopic measurements ofpervasive, faint Fe XIX 592.2 A line emission in AR 11726,observed during the 2013 April 23 flight of the Extreme UltravioletNormal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectralresolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 A (formedat temperature T around 8.9 MK) and Fe XII at 592.6 A (T around 1.6MK). The Fe XIX line emission, observed over an area in excess of4920 square arcsec (2.58x10^9 square km, more than 60% of the activeregion), provides strong evidence for the nanoflare heating model ofthe solar corona. No GOES events occurred in the region less than 2hours before the rocket flight, but a microflare was observed northand east of the region with RHESSI and EUNIS during the flight. Theabsence of significant upward velocities anywhere in the region,particularly the microflare, indicates that the pervasive Fe XIXemission is not propelled outward from the microflare site, but ismost likely attributed to localized heating (due to reconnection,wave dissipation, or some other mechanism) consistent with thenanoflare heating model of the solar corona. We measure average FeXIX/Fe XII intensity ratios of 0.070 outside the AR core, 0.22 inarea of bright coronal emission (the area in which the Fe XIIintensity exceeds half its maximum observed value), and 0.55 in theregion's hot core. Using the CHIANTI atomic physics database andassuming ionization equilibrium, we estimate corresponding Fe XIX/FeXII emission measure ratios of about 0.076, 0.23 and 0.59. Theemission measure ratios must be viewed with caution in light oflingering uncertainties in the Fe XII contribution functions.EUNIS-13 was supported by the NASA Heliophysics Division through itsLow Cost Access to Space program.

  19. Three-Dimensional MHD Modeling of The Solar Corona and Solar Wind: Comparison with The Wang-Sheeley Model

    NASA Technical Reports Server (NTRS)

    Usmanov, A. V.; Goldstein, M. L.

    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 model specified at the coronal base and our simulation region extends out to 10 AU. We assumed that a flux of Alfven waves with amplitude of 35 km per second emanates from the Sun and provides additional heating and acceleration for the coronal outflow in the open field regions. The waves are treated in the WKB approximation. The incorporation of wave acceleration allows us to reproduce the fast wind measurements obtained by Ulysses, while preserving reasonable agreement with plasma densities typically found at the coronal base. We find that our simulation results agree well with Wang and Sheeley's empirical model.

  20. White light solar corona: an atlas of 1985 K- coronameter synoptic charts, December 1984-December 1985. Technical note

    SciTech Connect

    Sime, D.G.; Garcia, C.; Yasukawa, E.; Lundin, E.; Rock, K.

    1986-10-01

    The synoptic observing program of the Mauna Loa Solar Observatory (MLSO) has as its goal the specification of the time-dependent structure of the solar corona. The growth of the low intensity polar regions and ordering of the brighter corona into a band near the equator seen in the second, third, and fourth years of observations (1981-1983) continued through 1984. In 1985, the corona remains in the same general form, with the brightest regions concentrated in a band around the equator, similar to the situation noted near the last solar minimum. The apparent excursions of the darkest regions (polar holes) towards the equator seen at the start of the year become less pronounced with time. However, the area embraced by the highest brightness contours tends to increase throughout the year, perhaps indicating that the corona has gone through its minimum configuration. The material presented here is in a format providing a convenient access to investigators intending to make correlation studies or an intercomparison of standard synoptic data sets.

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

    SciTech Connect

    Chowdhury, Partha; Jain, Rajmal; Awasthi, Arun K. E-mail: parthares@gmail.com E-mail: awasthi@prl.res.in

    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.

  2. The Rate of Flux Pile-up Magnetic Reconnection in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Litvinenko, Y. E.

    2000-05-01

    The rate of two-dimensional flux pile-up magnetic reconnection is known to be severely limited by gas pressure in a low-beta plasma of the solar corona. For a two-dimensional stagnation point flow with nonzero vorticity, for example, the rate cannot exceed the Sweet-Parker scaling. The limitation should be less restrictive, however, for three-dimensional flux pile-up. This paper examines the maximum rate of three-dimensional pile-up reconnection in the approximation of reduced magnetohydrodynamics (RMHD), which is valid in the solar coronal loops. Gas pressure effects are ignored in RMHD, but a similar limitation on the rate of magnetic merging exists. Both the magnetic energy dissipation rate and the reconnection electric field are shown to increase by several orders of magnitude in RMHD as compared with strictly two-dimensional pile-up. This is enough to explain small solar flares and slow coronal transients with energy release rates of order 1025 - 1026 erg s-1, as well as heating of quiet coronal loops. Notably, the reconnection electric field is several orders of magnitude greater than the Dreicer field, hence it can efficiently accelerate charged particles in flares. This work was supported by NSF grant ATM-9813933.

  3. Thermal structure of current sheets and supra-arcade downflows in the solar corona

    SciTech Connect

    Hanneman, Will J.; Reeves, Katharine K. E-mail: kreeves@cfa.harvard.edu

    2014-05-10

    After the peak intensity of many large solar flares, magnetic and thermodynamic processes give rise to a phenomenon known as supra-arcade downflows (SADs). SADs are sunward flowing density depletions, often observed in post-flare plasma sheets. Some models have suggested that the plasma in the dark lanes is heated to temperatures of 20-80 MK, which is much hotter than temperatures of the surrounding plasma. In this work, we use data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory and the X-Ray Telescope on the Hinode satellite to determine the thermal structure of SADs in the solar corona. We examine four flares that took place on 2011 October 22, 2012 January 14, 2012 January 16, and 2012 January 27. Differential emission measures are calculated for each flare and we compare the temperatures in the SADs to those of the surrounding plasma. We find that the SADs are hotter than the background, but cooler than the surrounding plasma in most cases, with only 1 out of the 11 SADs examined here having a slightly higher temperature than its surroundings.

  4. Hot carbon corona in Mars' upper thermosphere and exosphere: 1. Mechanisms and structure of the hot corona for low solar activity at equinox

    NASA Astrophysics Data System (ADS)

    Lee, Yuni; Combi, Michael R.; Tenishev, Valeriy; Bougher, Stephen W.

    2014-05-01

    Two important source reactions for hot atomic carbon on Mars are photodissociation of CO and dissociative recombination of CO+; both reactions are highly sensitive to solar activity and occur mostly deep in the dayside thermosphere. The production of energetic particles results in the formation of hot coronae that are made up of neutral atoms including hot carbon. Some of these atoms are on ballistic trajectories and return to the thermosphere, and others escape. Understanding the physics in this region requires modeling that captures the complicated dynamics of hot atoms in 3-D. This study evaluates the carbon atom inventory by investigating the production and distribution of energetic carbon atoms using the full 3-D atmospheric input. The methodology and details of the hot atomic carbon model calculation are given, and the calculated total global escape of hot carbon from the assumed dominant photochemical processes at a fixed condition, equinox (Ls = 180°), and low solar activity (F10.7 = 70 at Earth) are presented. To investigate the dynamics of these energetic neutral atoms, we have coupled a self-consistent 3-D global kinetic model, the Adaptive Mesh Particle Simulator, with a 3-D thermosphere/ionosphere model, the Mars Thermosphere General Circulation Model to provide a self-consistent global description of the hot carbon corona in the upper thermosphere and exosphere. The spatial distributions of density and temperature and atmospheric loss are simulated for the case considered.

  5. 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

    NASA Technical Reports Server (NTRS)

    Reginald, Nelson L.; Fisher, Richard R. (Technical Monitor)

    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 theoretical K-coronal spectra. The anti-nodes are separated by temperature-insensitive nodes. Remarkably, Cram showed that the wavelengths of the nodes and anti-nodes are almost independent of altitude above the solar limb. Because of these features, Cram suggested that the intensity ratios at two anti-nodes could be used as a diagnostic of the electron temperature in the K-corona. Based on this temperature diagnostic technique prescribed by Cram a slit-based spectroscopic study was performed by Ichimoto et al. on the solar corona in conjunction with the total solar eclipse of 3 Nov 1994 in Putre, Chile to determine the temperature profile of the solar corona. 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 measurement 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 Aug 1999 in Elazig, Turkey. In this instrument one end of each of twenty fiber optic tips were positioned in the focal plane of the telescope in such a way that we could observe conditions simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends of the fibers were vertically aligned and placed at the primary focus of

  6. 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 Astrophysics Data System (ADS)

    Reginald, Nelson Leslie

    2001-06-01

    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 in the theoretical K-coronal spectra. The anti-nodes are separated by temperature-insensitive nodes. Remarkably, Cram showed that the wavelengths of the nodes and anti- nodes are almost independent of altitude above the solar limb. Because of these features, Cram suggested that the intensity ratios at two anti-nodes could be used as a diagnostic of the electron temperature in the K-corona. Based on this temperature diagnostic technique prescribed by Cram a slit-based spectroscopic study was performed by Ichimoto et.al (1996) on the solar corona in conjunction with the total solar eclipse of 3 November 1994 in Putre, Chile to determine the temperature profile of the solar corona. 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 measurement 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. In this instrument one end of each of twenty fiber optic tips were positioned in the focal plane of the telescope in such a way that we could observe conditions simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends of the fibers were vertically aligned and placed at

  7. 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).

  8. 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.

  9. Dust in the Solar System - Properties and Origins

    NASA Technical Reports Server (NTRS)

    Messenger, Scott; Keller, Lindsay; Nakamura-Messenger, Keiko

    2013-01-01

    Interplanetary dust pervades the inner Solar System, giving rise to a prominent glow above the horizon at sunrise and sunset known as the zodiacal light. This dust derives from the disintegration of comets as they approach the Sun and from collisions among main-belt asteroids. The Earth accretes roughly 4x10(exp 6) kg/year of 1 - 1,000 micron dust particles as they spiral into the Sun under the influence of Poynting-Robertson drag and solar wind drag. Samples of these grains have been collected from deep sea sediments, Antarctic ice and by high-altitude aircraft and balloon flights. Interplanetary dust particles (IDPs) collected in the stratosphere have been classified by their IR spectra into olivine, pyroxene, and hydrated silicate-dominated classes. Most IDPs have bulk major and minor element abundances that are similar to carbonaceous chondrite meteorites. Hydrated silicate-rich IDPs are thought to derive from asteroids based on their mineralogy and low atmospheric entry velocities estimated from peak temperatures reached during atmospheric entry. Anhydrous IDPs are typically aggregates of 0.1 - approx. 1 micron Mg-rich olivine and pyroxene, amorphous silicates (GEMS), Fe, Nisulfides and rare spinel and oxides bound together by carbonaceous material. These IDPs are often argued to derive from comets based on compositional similarities and high atmospheric entry velocities that imply high eccentricity orbits. Infrared spectra obtained from anhydrous IDPs closely match remote IR spectra obtained from comets. The most primitive (anhydrous) IDPs appear to have escaped the parent-body thermal and aqueous alteration that has affected meteorites. These samples thus consist entirely of grains that formed in the ancient solar nebula and pre-solar interstellar and circumstellar environments. Isotopic studies of IDPs have identified silicate stardust grains that formed in the outflows of red giant and asymptotic giant branch stars and supernovae]. These stardust grains

  10. Dust Hazard Management in the Outer Solar System

    NASA Technical Reports Server (NTRS)

    Seal, David A.

    2012-01-01

    Most robotic missions to the outer solar system must grapple with the hazards posed by the dusty rings of the gas giants. Early assessments of these hazards led simply to ring avoidance due to insufficient data and high uncertainties on the dust population present in such rings. Recent approaches, principal among them the Cassini dust hazard management strategy, provide useful results from detailed modeling of spacecraft vulnerabilities and dust hazard regions, which along with the range of mission trajectories are used to to assess the risks posed by each passage through a zone of potential hazard. This paper shows the general approach used to implement the analysis for Cassini, with recommendations for future outer planet missions.

  11. Electrostatic lofting variability of lunar dust under solar wind and solar uv irradiance

    NASA Astrophysics Data System (ADS)

    Cihan Örger, Necmi; Rodrigo Cordova Alarcon, Jose; Cho, Mengu; Toyoda, Kazuhiro

    2016-07-01

    It has been considered that lunar horizon glow is produced by forward scattering of the sunlight above the terminator region by the electrically charged dust grains. Previous lunar missions showed that lunar horizon glow is highly varying phenomenon; therefore, it is required to understand how this physical mechanism fundamentally occurs in order to be able to observe it. Therefore, terminator region and the dayside of the moon are the focus areas of this study in order to explain forward scattering of the sunlight towards night side region in the future steps of this work. In this paper, the results of lunar dust height calculations are presented as a function of solar zenith angle and solar wind properties. First, equilibrium surface potential, Debye length and surface electric field have been calculated to be used in the dust model to predict the lofting of lunar dust under various solar wind conditions. Dependence of the dust lofting on different parameters such as electron temperature or plasma density can be explained from the initial results. In addition, these results showed that zero potential occurs between subsolar point and terminator region as it is expected, where the maximum height of dust particles are minimum, and its position changes according to the solar wind properties and photoemission electron temperature. Relative to this work, a CubeSat mission is currently being developed in Kyushu Institute of Technology to observe lunar horizon glow.

  12. Magnetic Flux Emergence into the Solar Corona. I. Its Role for the Reversal of Global Coronal Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Low, B. C.

    2001-11-01

    Some physical insights into how the corona reverses its global magnetic field are described in this paper based on a set of elementary hydromagnetic calculations. We assume that a fresh magnetic field of opposite polarity has emerged into a corona containing a preexisting magnetic field. The inevitable magnetic reconnection that takes place between the two magnetic flux systems may result in an expulsion of magnetic flux to infinity. Our calculations suggest the following physical story of the coronal reversal process: When the emerged flux exceeds the preexisting flux by a critical amount, the corona will reverse its polarity. Before this critical ratio is attained, the field with the emerged flux may have enough energy to let only one or two bipolar parts of the multipolar field open up. This opening-up process, taking place as a coronal mass ejection (CME), may take some of the preexisting flux out of the corona and thus increase the emerged-to-preexisting flux ratio and bring the corona closer to the critical value for its global magnetic reversal. Our calculations also indicate that it is possible that the position where the field opens up may be different from that where the new flux emerges. This may help explain the difference in the latitude distribution of active regions and CMEs during a solar cycle as observed by Hundhausen.

  13. The Effect of Hydrostatic Weighting on the Vertical Temperature Structure of the Solar Corona.

    PubMed

    Aschwanden; Nitta

    2000-05-20

    We investigate the effect of hydrostatic scale heights lambda(T) in coronal loops on the determination of the vertical temperature structure T&parl0;h&parr0; of the solar corona. Every method that determines an average temperature at a particular line of sight from optically thin emission (e.g., in EUV or soft X-ray wavelengths) of a mutlitemperature plasma is subject to the emission measure-weighted contributions dEM&parl0;T&parr0;&solm0;dT from different temperatures. Because most of the coronal structures (along open or closed field lines) are close to hydrostatic equilibrium, the hydrostatic temperature scale height introduces a height-dependent weighting function that causes a systematic bias in the determination of the temperature structure T&parl0;h&parr0; as function of altitude h. The net effect is that the averaged temperature seems to increase with altitude, dT&parl0;h&parr0;&solm0;dh>0, even if every coronal loop (of a multitemperature ensemble) is isothermal in itself. We simulate this effect with differential emission measure distributions observed by SERTS for an instrument with a broadband temperature filter such as Yohkoh/Soft X-Ray Telescope and find that the apparent temperature increase due to hydrostatic weighting is of order DeltaT approximately T0h&solm0;r middle dot in circle. We suggest that this effect largely explains the systematic temperature increase in the upper corona reported in recent studies (e.g., by Sturrock et al., Wheatland et al., or Priest et al.), rather than being an intrinsic signature of a coronal heating mechanism.

  14. 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.).

  15. Electron Acceleration by Cascading Reconnection in the Solar Corona. II. Resistive Electric Field Effects

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Büchner, J.; Bárta, M.; Gan, W.; Liu, S.

    2016-08-01

    We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics. Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.

  16. Hard X-ray Detectability of Small Impulsive Heating Events in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Glesener, L.; Klimchuk, J. A.; Bradshaw, S. J.; Marsh, A.; Krucker, S.; Christe, S.

    2015-12-01

    Impulsive heating events ("nanoflares") are a candidate to supply the solar corona with its ~2 MK temperature. These transient events can be studied using extreme ultraviolet and soft X-ray observations, among others. However, the impulsive events may occur in tenuous loops on small enough timescales that the heating is essentially not observed due to ionization timescales, and only the cooling phase is observed. Bremsstrahlung hard X-rays could serve as a more direct and prompt indicator of transient heating events. A hard X-ray spacecraft based on the direct-focusing technology pioneered by the Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket could search for these direct signatures. In this work, we use the hydrodynamical EBTEL code to simulate differential emission measures produced by individual heating events and by ensembles of such events. We then directly predict hard X-ray spectra and consider their observability by a future spaceborne FOXSI, and also by the RHESSI and NuSTAR spacecraft.

  17. Early Evaluation of the Corona at the 2016 March 9 Total Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Seaton, Daniel B.; Sterling, Alphonse C.

    2016-05-01

    We observed the corona on 2016 March 9 with a variety of assets on the ground and in space. The umbra of the total eclipse swept across Indonesia and into the Pacific, with totality at our Indonesian observation sites lasting 2 min 45 s at Ternate in the Spice Islands (Malukus) and 2 min 10 at Belitung. We compare our ground-based results with the coronal configurations observed with PROBA2/SWAP and Hinode XRT. One of our scientific goals is to follow the coronal configuration over the solar-activity cycle, with the sunspot number now half its maximum of either its 2012 or 2014 peak. We are evaluating temporal changes by comparing eclipse observations made at several ground-based sites along the path, with the longest span being 75 min from Belitung to the Woleia atoll in mid-Pacific, 1:25 UTC to 2:40 UTC; we are evaluating whether the airborne observations made at 3:35 UTC on March 8 (across the International Dateline) are of suitable quality to provide further comparison at high spatial resolution. We also compare our images with the near-simultaneous coronal observations made with SOHO/LASCO, SDO/AIA, STEREO-A/SECCHI, and the Mauna Loa Solar Observatory's K-cor coronagraph. ACS received support for image analysis from the Hinode project.

  18. Electric Current Filamentation Induced by 3D Plasma Flows in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Nickeler, Dieter H.; Wiegelmann, Thomas; Karlický, Marian; Kraus, Michaela

    2017-03-01

    Many magnetic structures in the solar atmosphere evolve rather slowly, so they can be assumed as (quasi-)static or (quasi-)stationary and represented via magnetohydrostatic (MHS) or stationary magnetohydrodynamic (MHD) equilibria, respectively. While exact 3D solutions would be desired, they are extremely difficult to find in stationary MHD. We construct solutions with magnetic and flow vector fields that have three components depending on all three coordinates. We show that the noncanonical transformation method produces quasi-3D solutions of stationary MHD by mapping 2D or 2.5D MHS equilibria to corresponding stationary MHD states, that is, states that display the same field-line structure as the original MHS equilibria. These stationary MHD states exist on magnetic flux surfaces of the original 2D MHS states. Although the flux surfaces and therefore also the equilibria have a 2D character, these stationary MHD states depend on all three coordinates and display highly complex currents. The existence of geometrically complex 3D currents within symmetric field-line structures provides the basis for efficient dissipation of the magnetic energy in the solar corona by ohmic heating. We also discuss the possibility of maintaining an important subset of nonlinear MHS states, namely force-free fields, by stationary flows. We find that force-free fields with nonlinear flows only arise under severe restrictions of the field-line geometry and of the magnetic flux density distribution.

  19. NEON AND OXYGEN ABUNDANCES AND ABUNDANCE RATIO IN THE SOLAR CORONA

    SciTech Connect

    Landi, E.; Testa, P.

    2015-02-20

    In this work we determine the Ne/O abundance ratio from Solar and Heliospheric Observatory (SOHO)/Solar Ultraviolet Measurement of Emitted Radiation (SUMER) off-disk observations of quiescent streamers over the 1996-2008 period. We find that the Ne/O ratio is approximately constant over solar cycle 23 from 1996 to 2005, at a value of 0.099 ± 0.017; this value is lower than the transition region determinations from the quiet Sun used to infer the neon photospheric abundance from the oxygen photospheric abundance. Also, the Ne/O ratio we determined from SUMER is in excellent agreement with in situ determinations from ACE/SWICS. In 2005-2008, the Ne/O abundance ratio increased with time and reached 0.25 ± 0.05, following the same trend found in the slowest wind analyzed by ACE/SWICS. Further, we measure the absolute abundance in the corona for both oxygen and neon from the data set of 1996 November 22, obtaining A {sub o} = 8.99 ± 0.04 and A {sub Ne} = 7.92 ± 0.03, and we find that both elements are affected by the first ionization potential (FIP) effect, with oxygen being enhanced by a factor of 1.4-2.1 over its photospheric abundance, and neon being changed by a factor of 0.75-1.20. We conclude that the Ne/O ratio is not constant in the solar atmosphere, both in time and at different heights, and that it cannot be reliably used to infer the neon abundance in the photosphere. Also, we argue that the FIP effect was less effective during the minimum of solar cycle 24, and that the Ne/O = 0.25 ± 0.05 value measured at that time is closer to the true photospheric value, leading to a neon photospheric abundance larger than assumed by ≈40%. We discuss the implications of these results for the solar abundance problem, for the FIP effect, and for the identification of the source regions of the solar wind.

  20. 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.

  1. 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.

  2. 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 R.; Gurman, Joseph (Technical Monitor)

    2003-01-01

    Investigations of the physical processes responsible for the acceleration of the solar wind were pursued with the development of two new solar wind codes: a hybrid code and a 2-D MHD code. Hybrid simulations were performed to investigate the interaction between ions and parallel propagating low frequency ion cyclotron waves in a homogeneous plasma. In a low-beta plasma such as the solar wind plasma in the inner corona, the proton thermal speed is much smaller than the Alfven speed. Vlasov linear theory predicts that protons are not in resonance with low frequency ion cyclotron waves. However, non-linear effect makes it possible that these waves can strongly heat and accelerate protons. This study has important implications for study of the corona and the solar wind. Low frequency ion cyclotron waves or Alfven waves are commonly observed in the solar wind. Until now, it is believed that these waves are not able to heat the solar wind plasma unless some cascading processes transfer the energy of these waves to high frequency part. However, this study shows that these waves may directly heat and accelerate protons non-linearly. This process may play an important role in the coronal heating and the solar wind acceleration, at least in some parameter space.

  3. Interpretation of F-corona radial velocity observations

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.

    1987-03-01

    The observations made during the July 31, 1981 solar eclipse of the F-corona radial velocities between 3 and 7 solar radii are interpreted, assuming direct circular Keplerian motion of dust grains. Diffraction and isotropic scattering are considered. If the grains are assumed to be of silica, a best fit to observations is found for grain radii of about 0.4 micron, a border of dust-free zone from 6 to 14 solar radii, or a high concentration of grains at the same interval of heliocentric distances.

  4. Radio interferometer observations of solar wind turbulence from the orbit of Helios to the solar corona

    NASA Technical Reports Server (NTRS)

    Spangler, Steven R.; Sakurai, Takayuki

    1995-01-01

    We report observations of Very Long Baseline Interferometer (VLBI) phase scintillations due to turbulence in the solar wind. The observations were made at 5.00 and 8.42 GHz with the Very Long Baseline Array (VLBA) on three dates in 1991 July and August. We observed the sources 0851 + 202 and 0735 + 178 at solar elongations ranging from 2.66 deg to 13.29 deg; the closest approach of the line of sight to the Sun ranged from 10 to 49.8 solar radii. We have also included previously unpublished 5 GHz VLBI phase scintillation measurements from 1989. These measurements probe solar wind density fluctuations on spatial scales from about 200 km to 2000 km. Our measurements are in quite good agreement with the Coles & Harmon model for the radio phase structure function, which was largely determined from observations on both shorter and larger spatial scales. Departures from the Coles & Harmon functions are attributable to day-to-day variations in the solar wind conditions. Phase scintillations at the greatest solar elongations are in very good agreement with extrapolated estimates from direct measurements made with the Helios spacecraft at slightly larger heliocentric distances. Thus there is a consistency between the in-situ spacecraft and radio sensing measurements of density turbulence. All of the VLBI data are consistent with a Kolmogorov spectrum for the density fluctuations, although at the closest elongations there may be excess power at small spatial scales. An advantage of interferometric techniques over other radio propagation measurements is that they provide a measure of the anisotropy of the irregularities. Our observations at closest approach (10 solar radii) show weak evidence for anisotropic, field-aligned density irregularities with an axial ratio of order 2. This degree of anisotropy would appear to be less than that measured at similar solar elongations but on smaller spatial scales by Armstrong and colleagues. Finally, a combination of the radio

  5. Imaging observation of quasi-periodic disturbances' amplitudes increasing with height in the polar region of the solar corona

    SciTech Connect

    Su, J. T.; Priya, T. G.; Liu, Y.; Shen, Y. D.

    2014-08-01

    At present, there have been few extreme ultraviolet (EUV) imaging observations of spatial variations of the density perturbations due to the slow magnetoacoustic waves (SMWs) propagating along the solar coronal magnetic fields. In this paper, we present such observations taken from the polar region of the corona with the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and investigate the amplitude of quasi-periodic propagating disturbances that increase with height in the lower corona (0-9 Mm over the solar limb). We statistically determined the following parameters associated with the disturbances: pressure scale height, period, and wavelength in AIA 171 Å, 193 Å, and 211 Å channels. The scale height and wavelength are dependent of temperature, while the period is independent of temperature. The acoustic velocities inferred from the scale height highly correlate with the ratios of wavelength to period, i.e., phase speeds. They provide evidence that the propagating disturbances in the lower corona are likely SMWs and the spatial variations in EUV intensity in the polar region likely reflects the density compressional effect by the propagating SMWs.

  6. The total number of spicules on the solar surface and their role in heating and mass balanace in the solar corona

    NASA Astrophysics Data System (ADS)

    Mamedov, S. G.; Kuli-Zade, D. M.; Alieva, Z. F.; Musaev, M. M.; Mustafa, F. R.

    2016-09-01

    A critical review of determinations of the number of spicules is presented, and the role of both classical and Type 2 spicules in heating and mass balance in the corona is considered. The total number of Type 2 spicules is determined, together with the upward fluxes of energy and mass to which they give rise. The total number of Type 2 spicules on the solar surface is found to be ~105, close to values obtained in other studies. The associated particle flux toward the corona is 2.5 × 1014 cm-2 s-1, an order of magnitude lower than the corresponding flux for classical spicules. The associated energy flux is 104 erg cm-2 s-1, an order of magnaitude lower than estimates obtained in other studies. The results indicate that Type 2 spicules can supply the mass lost from the corona, but are not able to fully explain coronal energy losses.

  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

  8. Anomalous Surge of the White-Light Corona at the Onset of the Declining Phase of Solar Cycle 24

    NASA Astrophysics Data System (ADS)

    Lamy, P.; Boclet, B.; Wojak, J.; Vibert, D.

    2017-04-01

    In late 2014, when the current Solar Cycle 24 entered its declining phase, the white-light corona as observed by the LASCO-C2 coronagraph underwent an unexpected surge that increased its global radiance by 60%, reaching a peak value comparable to the peak values of the more active Solar Cycle 23. A comparison of the temporal variation of the white-light corona with the variations of several indices and proxies of solar activity indicate that it best matches the variation of the total magnetic field. The daily variations point to a localized enhancement or bulge in the electron density that persisted for several months. Carrington maps of the radiance and of the HMI photospheric field allow connecting this bulge to the emergence of the large sunspot complex AR 12192 in October 2014, the largest since AR 6368 observed in November 1990. The resulting unusually high increase of the magnetic field and the distortion of the neutral sheet in a characteristic inverse S-shape caused the coronal plasma to be trapped along a similar pattern. A 3D reconstruction of the electron density based on time-dependent solar rotational tomography supplemented by 2D inversion of the coronal radiance confirms the morphology of the bulge and reveals that its level was well above the standard models of a corona of the maximum type, by typically a factor of 3. A rather satisfactory agreement is found with the results of the thermodynamic MHD model produced by Predictive Sciences, although discrepancies are noted. The specific configuration of the magnetic field that led to the coronal surge resulted from the interplay of various factors prevailing at the onset of the declining phase of the solar cycles, which was particularly efficient in the case of Solar Cycle 24.

  9. 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.

  10. Comparative study of the loss cone-driven instabilities in the low solar corona

    NASA Technical Reports Server (NTRS)

    Sharma, R. R.; Vlahos, L.

    1984-01-01

    A comparative study of the loss cone-driven instabilities in the low solar corona is undertaken. The instabilities considered are the electron cyclotron maser, the whistler, and the electrostatic upper hybrid. It is shown that the first-harmonic extraordinary mode of the electron cyclotron maser instability is the fastest growing mode for strong magnetized plasma (the ratio of plasma frequency to cyclotron frequency being less than 0.35). For values of the ratio between 0.35 and 1.0, the first-harmonic ordinary mode of the electron cyclotron maser instability dominates the emission. For ratio values greater than 1.0, no direct electromagnetic radiation is expected since other instabilities, which do not escape directly, saturate the electron cyclotron maser (the whistler or the electrostatic upper hybrid waves). It is also shown that the second-harmonic electron cyclotron maser emission never grows to an appreciable level. Thus, it is suggested that the electron cyclotron maser instability can be the explanation for the escape of the first harmonic from a flaring loop.

  11. 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.

    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.

  12. Diffusion effects on the helium abundance of the solar transition region and corona

    NASA Technical Reports Server (NTRS)

    Hansteen, Viggo H.; Holzer, Thomas E.; Leer, Egil

    1993-01-01

    The diffusion of helium in the solar transition region is studied by solving the mass and momentum conservation equations for a hydrogen-helium plasma given a representative temperature profile. Steady state solutions show that two distinct atmospheres may result. In cases where the thermal force on alpha-particles is balanced by the partial pressure gradient force, helium is the dominant coronal species. On the other hand, if it is the frictional force between protons and alpha-particles which balances the thermal force on alpha-particles then hydrogen is the major coronal component. In order to explore which of these solutions are attainable within reasonable time scales, the time-dependent equations are solved, starting from an initial state with a uniform helium abundance of 10 percent. The atmosphere as a whole is close to hydrostatic equilibrium, but due the thermal forces the individual elements are not. This force inbalance leads to a differential flow between species. It is found that this differential flow leads to a significant enhancement of the coronal helium abundance. Even for the relatively shallow temperature gradient used the helium abundance in the lower corona increases to 30 percent over a 24 hr period.

  13. Solar Micro-Type III Burst Storms and Long Dipolar Magnetic Field in the Outer Corona

    NASA Astrophysics Data System (ADS)

    Morioka, A.; Miyoshi, Y.; Iwai, K.; Kasaba, Y.; Masuda, S.; Misawa, H.; Obara, T.

    2015-08-01

    Solar micro-type III radio bursts are elements of the so-called type III storms and are characterized by short-lived, continuous, and weak emissions. Their frequency of occurrence with respect to radiation power is quite different from that of ordinary type III bursts, suggesting that the generation process is not flare-related, but due to some recurrent acceleration processes around the active region. We examine the relationship of micro-type III radio bursts with coronal streamers. We also explore the propagation channel of bursts in the outer corona, the acceleration process, and the escape route of electron beams. It is observationally confirmed that micro-type III bursts occur near the edge of coronal streamers. The magnetic field line of the escaping electron beams is tracked on the basis of the frequency drift rate of micro-type III bursts and the electron density distribution model. The results demonstrate that electron beams are trapped along closed dipolar field lines in the outer coronal region, which arise from the interface region between the active region and the coronal hole. A 22 year statistical study reveals that the apex altitude of the magnetic loop ranges from 15 to 50 RS. The distribution of the apex altitude has a sharp upper limit around 50 RS suggesting that an unknown but universal condition regulates the upper boundary of the streamer dipolar field.

  14. SOLAR MICRO-TYPE III BURST STORMS AND LONG DIPOLAR MAGNETIC FIELD IN THE OUTER CORONA

    SciTech Connect

    Morioka, A.; Misawa, H.; Obara, T.; Miyoshi, Y.; Masuda, S.; Iwai, K.; Kasaba, Y.

    2015-08-01

    Solar micro-type III radio bursts are elements of the so-called type III storms and are characterized by short-lived, continuous, and weak emissions. Their frequency of occurrence with respect to radiation power is quite different from that of ordinary type III bursts, suggesting that the generation process is not flare-related, but due to some recurrent acceleration processes around the active region. We examine the relationship of micro-type III radio bursts with coronal streamers. We also explore the propagation channel of bursts in the outer corona, the acceleration process, and the escape route of electron beams. It is observationally confirmed that micro-type III bursts occur near the edge of coronal streamers. The magnetic field line of the escaping electron beams is tracked on the basis of the frequency drift rate of micro-type III bursts and the electron density distribution model. The results demonstrate that electron beams are trapped along closed dipolar field lines in the outer coronal region, which arise from the interface region between the active region and the coronal hole. A 22 year statistical study reveals that the apex altitude of the magnetic loop ranges from 15 to 50 R{sub S}. The distribution of the apex altitude has a sharp upper limit around 50 R{sub S} suggesting that an unknown but universal condition regulates the upper boundary of the streamer dipolar field.

  15. Generation of radiation in solar corona and interplanetary space by energetic electrons

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Yoon, Peter H.; Zhou, G. C.

    1994-01-01

    Emissions of electromagnetic waves with frequencies close to the plasma frequency and/or its second harmonic have been frequently observed in the solar corona and interplanetary space. In the past, a number of theories have been put forward to esplain the generation mechanism of the observed radiation. In this paper, a new model is proposed. The essential point of the present theory is that the Langmuir waves amplified as a result of the usual beam instability can lead to two important effects: first, electrostatic waves with frequencies close to twice the plasma frequency can be excited; and second, a significant modification of the dispersion relation can occur, so that these electrostatic waves can naturally change into electomagnetic waves as they propagate in a plasma in which the plasma density decreases spatially. The latter effect is attributed to a mode couplng process. In addition to the second harmonic emission, emission at the fundamental is also briefly discussed. In this case, as in many other theories, the presence of a very low frequency electostatic wave such as the ion-acoustic wave is assumed. The emission process discussed in the present theory stresses the importance of mode coupling and conversion rather than kinetic processes such as a nonlinear wave-wave or wave-particle scattering.

  16. Linear tearing modes of a forced current-sheet equilibrium. [in solar corona

    NASA Technical Reports Server (NTRS)

    Liewer, Paulett C.; Payne, David G.

    1990-01-01

    Linear tearing modes are studied in a nearly singular forced current-sheet equilibrium, such as could result from global magnetic forces in the solar corona. Growth rates for the tearing modes, determined by solving the linearized reduced MHD (Strauss) equations numerically, were found to scale as (gamma)tau(d) = about S exp 4/5 k(y) exp 4/5, where S is the Lundquist number, k(y) is the wavenumber, and tau(d) is the classical resistive diffusion time. This scaling is in agreement with predictions from analytical theory. Because of the faster S scaling of these modes compared to the tearing modes of a diffuse current-sheet equilibrium, the modes have much higher growth rates (by a factor of about 10,000) for coronal values of S (about 10 to the 12th). For coronal parameters, the growth times of these new modes are estimated to be on the order of several hours to days, as compared to growth times of months to years for the tearing modes in a diffuse current-shear equilibrium. The growth times are comparable to reconnection times scales required in models of coronal heating by magnetic field dissipation.

  17. Influence of solar wind ions on photoemission charging of dust

    NASA Astrophysics Data System (ADS)

    Nouzak, Libor; Richterova, Ivana; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek

    2016-04-01

    The lunar surface covered by a layer of dust grains is exposed to solar wind particles and photons coming from the Sun on the sunlit side. Solar wind ions cause sputtering of dust grains or can be implanted into grains. We suppose that as a consequence of ion implantation, an additional energy is transferred to grains, more valence band electrons are excited, and the photoelectron yield is increased. An increase of the photoelectron current causes the enhanced density of electrons that form a sheet above the illuminated lunar surface. Thus, an influence of solar wind ions on the Debye length and photoelectron sheet formation is expected. We present laboratory estimations of work functions and photoelectron yields of a single micron-sized silica grain before and after ion implantation. The silica grain used as a lunar simulant is caught in the electrodynamic trap. Grain's specific charge is evaluated by an analysis of the grain motion within the trap, while its work function is determined from observations of a time evolution of the charge-to-mass ratio when the grain is irradiated by photons of different emission lines. By comparison of the photoelectron current (from grain) with photon flux (from UV source), we establish the photoelectron yield of the trapped object. The influence of ion implantation is thoroughly analyzed and discussed.

  18. INFERRING THE STRUCTURE OF THE SOLAR CORONA AND INNER HELIOSPHERE DURING THE MAUNDER MINIMUM USING GLOBAL THERMODYNAMIC MAGNETOHYDRODYNAMIC SIMULATIONS

    SciTech Connect

    Riley, Pete; Lionello, Roberto; Linker, Jon A. E-mail: lionel@predsci.com; and others

    2015-04-01

    Observations of the Sun’s corona during the space era have led to a picture of relatively constant, but cyclically varying solar output and structure. Longer-term, more indirect measurements, such as from {sup 10}Be, coupled by other albeit less reliable contemporaneous reports, however, suggest periods of significant departure from this standard. The Maunder Minimum was one such epoch where: (1) sunspots effectively disappeared for long intervals during a 70 yr period; (2) eclipse observations suggested the distinct lack of a visible K-corona but possible appearance of the F-corona; (3) reports of aurora were notably reduced; and (4) cosmic ray intensities at Earth were inferred to be substantially higher. Using a global thermodynamic MHD model, we have constructed a range of possible coronal configurations for the Maunder Minimum period and compared their predictions with these limited observational constraints. We conclude that the most likely state of the corona during—at least—the later portion of the Maunder Minimum was not merely that of the 2008/2009 solar minimum, as has been suggested recently, but rather a state devoid of any large-scale structure, driven by a photospheric field composed of only ephemeral regions, and likely substantially reduced in strength. Moreover, we suggest that the Sun evolved from a 2008/2009-like configuration at the start of the Maunder Minimum toward an ephemeral-only configuration by the end of it, supporting a prediction that we may be on the cusp of a new grand solar minimum.

  19. Explaining Inverted-temperature Loops in the Quiet Solar Corona with Magnetohydrodynamic Wave-mode Conversion

    NASA Astrophysics Data System (ADS)

    Schiff, Avery J.; Cranmer, Steven R.

    2016-11-01

    Coronal loops trace out bipolar, arch-like magnetic fields above the Sun’s surface. Recent measurements that combine rotational tomography, extreme-ultraviolet imaging, and potential-field extrapolation have shown the existence of large loops with inverted-temperature profiles, i.e., loops for which the apex temperature is a local minimum, not a maximum. These “down loops” appear to exist primarily in equatorial quiet regions near solar minimum. We simulate both these and the more prevalent large-scale “up loops” by modeling coronal heating as a time-steady superposition of (1) dissipation of incompressible Alfvén wave turbulence and (2) dissipation of compressive waves formed by mode conversion from the initial population of Alfvén waves. We found that when a large percentage (>99%) of the Alfvén waves undergo this conversion, heating is greatly concentrated at the footpoints and stable “down loops” are created. In some cases we found loops with three maxima that are also gravitationally stable. Models that agree with the tomographic temperature data exhibit higher gas pressures for “down loops” than for “up loops,” which is consistent with observations. These models also show a narrow range of Alfvén wave amplitudes: 3 to 6 km s-1 at the coronal base. This is low in comparison to typical observed amplitudes of 20-30 km s-1 in bright X-ray loops. However, the large-scale loops we model are believed to compose a weaker diffuse background that fills much of the volume of the corona. By constraining the physics of loops that underlie quiescent streamers, we hope to better understand the formation of the slow solar wind.

  20. Using the EUV to Weigh a Sun-Grazing Comet as it Disappears in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Pesnell, William Dean; Schrijiver, Carolus J.; Brown, John C.; Battams, Karl; Saint-Hilaire, Pascal; Hudson Hugh S.; Lui, Wei

    2012-01-01

    On July 6,2011, the Atmospheric Imaging Assembly (AlA) on the Solar Dynamics Observatory (SDO) observed a comet in most of its EUY passbands. The comet disappeared while moving through the solar corona. The comet penetrated to 0.146 solar radii ($\\simapprox.100,000 km) above the photosphere before its EUY faded. Before then, the comet's coma and a tail were observed in absorption and emission, respectively. The material in the variable tail quickly fell behind the nucleus. An estimate of the comet's mass based on this effect, one derived from insolation, and one using the tail's EUY brightness, all yield $\\sim 50$ giga-grams some 10 minutes prior to the end of its visibility. These unique first observations herald a new era in the study of Sun-grazing comets close to their perihelia and of the conditions in the solar corona and solar wind. We will discuss the observations and interpretation of the comet by SDO as well as the coronagraph observations from SOHO and STEREO. A search of the SOHO comet archive for other comets that could be observed in the SDO; AlA EUY channels will be described

  1. 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.

  2. Thermodynamics of the Solar Corona and Evolution of the Solar Magnetic Field as Inferred from the Total Solar Eclipse Observations of 11 July 2010

    NASA Technical Reports Server (NTRS)

    Habbal, Shadia Rifai; Druckmueller, Miloslav; Morgan, Huw; Ding, Adalbert; Johnson, Judd; Druckmuellerova, Hana; Daw, Adrian; Arndt, Martina B.; Dietzel, Martin; Saken, Jon

    2011-01-01

    We report on multi-wavelength observations of the corona taken simultaneously in broadband white light, and in seven spectral lines, H-alpha 656.3 nm, Fe IX 435.9 nm, Fe X 637.4 nm, Fe XI 789.2 nm, Fe XIII 1074.7 nm, Fe XIV 530.3 nm and Ni XV 670.2 nm. The observations were made during the total solar eclipse of 11 July 2010 from the atoll of Tatakoto in French Polynesia. Simultaneous imaging with narrow bandpass filters in each of these spectral lines and in their corresponding underlying continua maximized the observing time during less than ideal observing conditions and yielded outstanding quality data. The application of two complementary image processing techniques revealed the finest details of coronal structures at 1" resolution in white light, and 6.5" in each of the spectral lines. This comprehensive wavelength coverage confirmed earlier eclipse findings that the solar corona has a clear two-temperature structure: The open field lines, expanding outwards from the solar surface, are characterized by electron temperatures near 1 X 10(exp 6) K, while the hottest plasma around 2X 10(exp 6) K resides in loop-like structures forming the bulges of streamers. The first images of the corona in the forbidden lines of Fe IX and Ni XV, showed that there was very little coronal plasma at temperatures below 5 X 10(exp 5) K and above 2.5X 10(exp 6) K. The data also enabled temperature differentiations as low as 0:2 X 10(exp 6) K in different density structures. These observations showed how the passage of CMEs through the corona, prior to totality, produced large scale ripples and very sharp streaks, which could be identified with distinct temperatures for the first time. The ripples were most prominent in emission from spectral lines associated with temperatures around 10(exp 6) K. The most prominent streak was associated with a conical-shaped void in the emission from the coolest line of Fe IX and from the hottest line of Ni XV. A prominence, which erupted prior to

  3. Catalysis by Dust Grains in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Kress, Monika E.; Tielens, Alexander G. G. M.

    1996-01-01

    In order to determine whether grain-catalyzed reactions played an important role in the chemistry of the solar nebula, we have applied our time-dependent model of methane formation via Fischer-Tropsch catalysis to pressures from 10(exp -5) to 1 bar and temperatures from 450 to 650 K. Under these physical conditions, the reaction 3H2 + CO yields CH4 + H2O is readily catalyzed by an iron or nickel surface, whereas the same reaction is kinetically inhibited in the gas phase. Our model results indicate that under certain nebular conditions, conversion of CO to methane could be extremely efficient in the presence of iron-nickel dust grains over timescales very short compared to the lifetime of the solar nebula.

  4. 22-year cycle of differential rotation of the solar corona and the rule by Gnevyshev-Ohl

    NASA Astrophysics Data System (ADS)

    Badalyan, O. G.; Obridko, V. N.

    2017-01-01

    The time variation of the parameters of differential rotation of the solar corona is considered based on data on the coronal green-line brightness. Separate analysis is performed for even and odd cycles. It is shown that the equatorial rotation rate of the corona increases in the epochs of minimum between the even and odd cycles and reaches its minimum values between the odd and even cycles. Besides, it is found that the differential rotation gradient in absolute value increases in the even cycles. Both these factors may act to increase the amplitude of the odd cycle compared to the preceding even one. Perhaps this is what explains the effect of Gnevyshev-Ohl.

  5. Field-Lines-Threaded Model for: (1) the Low Solar Corona; (2) Electrons in the Transition Region; and (3) Solar Energetic Particle Acceleration and Transport

    NASA Astrophysics Data System (ADS)

    Sokolov, I.; van der Holst, B.; Jin, M.; Gombosi, T. I.; Taktakishvili, A.; Khazanov, G. V.

    2013-12-01

    In numerical simulations of the solar corona, both for the ambient state and especially for dynamical processes the most computational resources are spent for maintaining the numerical solution in the Low Solar Corona and in the transition region, where the temperature gradients are very sharp and the magnetic field has a complicated topology. The degraded computational efficiency is caused by the need in a highest resolution as well as the use of the fully three-dimensional implicit solver for electron heat conduction. On the other hand, the physical nature of the processes involved is rather simple (which still does not facilitate the numerical methods) as long as the heat fluxes as well as slow plasma motional velocities are aligned with the magnetic field. The Alfven wave turbulence, which is often believed to be the main driver of the solar wind and the main source of the coronal heating, is characterized by the Poynting flux of the waves, which is also aligned with the magnetic field. Therefore, the plasma state in any point of the three-dimensional grid in the Low Solar Corona can be found by solving a set of one-dimensional equations for the magnetic field line ('thread'), which passes through this point and connects it to the chromosphere and to the global Solar Corona. In the present paper we describe an innovative computational technology based upon the use of the magnetic-field-line-threads to find the local solution. We present the development of the AWSoM code of the University of Michigan with the field-lines-threaded Low Solar Corona. In the transition region, where the essentially kinetic description of the electron energy fluxes is required, we solve the Fokker-Plank equation on the system of threads, to achieve the physically consistent description of chromosphere evaporation. The third application for the field-lines-treaded model is the Solar Energetic Particle (SEP) acceleration and transport. Being the natural extension of the Field

  6. Intermittent Energy Dissipation in Magnetohydrodynamic Turbulence: Applications to the Solar Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Zhdankin, Vladimir

    2015-11-01

    Energy dissipation is highly intermittent in large-scale turbulent plasmas, being localized in space and in time. This intermittency is manifest by the presence of coherent structures such as current (and vorticity) sheets, which account for a large fraction of the overall energy dissipation and may serve as sites for magnetic reconnection and particle acceleration. The statistical analysis of these dissipative structures is a robust and informative methodology for probing the underlying dynamics, both in numerical simulations and in observations. In this talk, the statistical properties of current sheets in numerical simulations of driven magnetohydrodynamic (MHD) turbulence are described, including recent results obtained from applying new methods for characterizing their morphology. Instantaneously, the overall energy dissipation is found to be evenly spread among current sheets spanning a continuum of energy dissipation rates and inertial-range sizes, while their thicknesses are localized deep inside the dissipation range. The temporal dynamics are then investigated by tracking the current sheets in time and considering the statistics of the resulting four-dimensional spatiotemporal structures, which correspond to dissipative events or flares in astrophysical systems. These dissipative events are found to exhibit robust power-law distributions and scaling relations, and are often highly complex, long-lived, and weakly asymmetric in time. Based on the distribution for their dissipated energies, the strongest dissipative events are found to dominate the overall energy dissipation in the system. These results are compared to the observed statistics of solar flares, and some possible implications for the solar wind are also described.

  7. Quasi-Equilibrium Density Distributions of Small Dust Aggregations in the Solar Nebula

    NASA Astrophysics Data System (ADS)

    Sekiya, Minoru

    1998-06-01

    The rotational velocity of a fluid element around the midplane of the solar nebula increased as dust settled toward the midplane. The Kelvin and Helmholtz instability due to velocity difference of a dust-rich region and a dust-poor region should have occurred and the dust layer became turbulent when the Richardson number decreased below the critical value. Then, dust aggregations stirred up due to turbulent diffusion and were prevented to settle further. In this paper, the sizes of dust aggregations are assumed to be equal to or smaller than the typical radius of chondrules (∼0.3 mm). In this case, even very weak turbulence stirs up dust aggregations. Therefore a dust density distribution is considered to be self regulated so that the Richardson number is nearly equal to the critical value. The quasi-equilibrium dust density distribution is derived analytically by assuming that the Richardson number is equal to the critical value. The derived dust density at the midplane is much smaller than the critical density of the gravitational stability, if the solar composition of dust to gas ratio is assumed. On the other hand, the dust aggregations concentrate around the midplane and the dust layer becomes gravitationally unstable, if more than 97% (at 1 AU from the Sun) of the gaseous components have been dissipated from the nebula, leaving dusty components. Two alternative scenarios of planetesimal formation are proposed: planetesimals were formed by (1) mutual sticking of dust aggregations by nongravitational forces or by (2) gravitational instabilities in the nebula where the dust to gas ratio is much larger than the ratio with solar elemental abundance. Case (2) might be realized due to dissipation of the nebular gas and/or addition of dust by the bipolar outflow. In case (1), chondrule sizes do not indicate the maximum size of dust aggregations in the solar nebula.

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

    SciTech Connect

    Wozniakiewicz, P. J.; Bradley, J. P.; Ishii, H. A.; Brownlee, D. E.; Kearsley, A. T.; Burchell, M. J.; Price, M. C.

    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.

  9. On the effects of magnetic field line topology on the energy propagation in the solar corona

    NASA Astrophysics Data System (ADS)

    Candelaresi, Simon

    2016-05-01

    Using the MHD approximation, we study the propagation of energy from photospheric footpoint motions into the corona. Our model consists of a magnetic carpet with closed and open magnetic field lines. Magnetic null points are present close at the surface. The applied photospheric driver twists the field into a topologically non-trivial configuration which leads to reconnection and a change in field line topology. Prior to this event, the energy propagation into the corona is largely inhibited due to closed field lines. After such events the energy is free to propagate into the corona.

  10. 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.

  11. Mate and Dart: An Instrument Package for Characterizing Solar Energy and Atmospheric Dust on Mars

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Jenkins, Phillip; Scheiman, David; Baraona, Cosmo

    2000-01-01

    The MATE (Mars Array Technology Experiment) and DART (Dust Accumulation and Removal Test) instruments were developed to fly as part of the Mars ISPP Precursor (MIP) experiment on the (now postponed) Mars-2001 Surveyor Lander. MATE characterizes the solar energy reaching the surface of Mars, and measures the performance and degradation of solar cells under Martian conditions. DART characterizes the dust environment of Mars, measures the effect of settled dust on solar arrays, and investigates methods to mitigate power loss due to dust accumulation.

  12. Solar wind implication on dust ion acoustic rogue waves

    NASA Astrophysics Data System (ADS)

    Abdelghany, A. M.; Abd El-Razek, H. N.; Moslem, W. M.; El-Labany, S. K.

    2016-06-01

    The relevance of the solar wind with the magnetosphere of Jupiter that contains positively charged dust grains is investigated. The perturbation/excitation caused by streaming ions and electron beams from the solar wind could form different nonlinear structures such as rogue waves, depending on the dominant role of the plasma parameters. Using the reductive perturbation method, the basic set of fluid equations is reduced to modified Korteweg-de Vries (KdV) and further modified (KdV) equation. Assuming that the frequency of the carrier wave is much smaller than the ion plasma frequency, these equations are transformed into nonlinear Schrödinger equations with appropriate coefficients. Rational solution of the nonlinear Schrödinger equation shows that rogue wave envelopes are supported by the present plasma model. It is found that the existence region of rogue waves depends on the dust-acoustic speed and the streaming temperatures for both the ions and electrons. The dependence of the maximum rogue wave envelope amplitude on the system parameters has been investigated.

  13. Wide-field investigation of the velocity field of the circumsolar dust during the total solar eclipse on July 22, 2009

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.; Rspaev, F. K.; Chalabaev, A.; Bram, D.; Dubovitskiy, A. I.; Bonev, T.; Golev, V.; Le Coarer, E.

    We describe preliminary results of the wide-field (up to 30 div 40 R_⊙ heliocentric distance) spectro-imaging of the dust grains in the solar F-corona carried out during the total solar eclipse (TSE) of July 22, 2009 at Yuexi, China. The aim of the observations was to measure the radial velocities of the circumsolar dust grains. The field of radial velocities of dust was obtained by Doppler shifts of the Ca II K λ383.4 nm absorption line. The instrument used was a spectro-imaging camera with a Fabry-Perot (FP) etalon. Thin clouds during the eclipse modulated the intensity of the dust scattered light but the experiment was successful giving the valuable data on the dust radial velocity of the Ca II K line in absorption (no emission in this line was seen in the FP data). The resulting mean radial velocity in the selected strips of the interferogram images is ≈ -100 km/s. The definite conclusions on the radial velocity field will be drawn only when the on-going thorough data reduction and final analysis of the data will be completed.

  14. From Solar to Stellar Corona: The Role of Wind, Rotation, and Magnetism

    NASA Astrophysics Data System (ADS)

    Réville, Victor; Brun, Allan Sacha; Strugarek, Antoine; Matt, Sean P.; Bouvier, Jérôme; Folsom, Colin P.; Petit, Pascal

    2015-12-01

    Observations of surface magnetic fields are now within reach for many stellar types thanks to the development of Zeeman-Doppler Imaging. These observations are extremely useful for constraining rotational evolution models of stars, as well as for characterizing the generation of the magnetic field. We recently demonstrated that the impact of coronal magnetic field topology on the rotational braking of a star can be parameterized with a scalar parameter: the open magnetic flux. However, without running costly numerical simulations of the stellar wind, reconstructing the coronal structure of the large-scale magnetic field is not trivial. An alternative—broadly used in solar physics—is to extrapolate the surface magnetic field assuming a potential field in the corona, to describe the opening of the field lines by the magnetized wind. This technique relies on the definition of a so-called source surface radius, which is often fixed to the canonical value of 2.5{R}⊙ . However this value likely varies from star to star. To resolve this issue, we use our extended set of 2.5D wind simulations published in 2015 to provide a criterion for the opening of field lines as well as a simple tool to assess the source surface radius and the open magnetic flux. This allows us to derive the magnetic torque applied to the star by the wind from any spectropolarimetric observation. We conclude by discussing some estimations of spin-down timescales made using our technique and compare them to observational requirements.

  15. Dust Detection Using Radio and Plasma Wave Instruments in the Solar System

    NASA Astrophysics Data System (ADS)

    Ye, S.; Gurnett, D. A.; Kurth, W. S.; Averkamp, T. F.; Kempf, S.; Hsu, S.; Srama, R.; Grün, E.; Morooka, M. W.; Sakai, S.; Wahlund, J. E.

    2014-12-01

    Nanometer to micrometer sized dust particles pervade our solar system. The origins of these dust particles include asteroid collisions, cometary activity, and geothermal activity of the planetary moons, for example, the water dust cloud ejected from Saturn's moon Enceladus. Radio and plasma wave instruments have been used to detect such dust particles via voltage pulses induced by impacts on the spacecraft body and antennas. The first detection of such dust impacts occurred when Voyager 1 passed through Saturn's ring plane. Since then, dust impacts have been detected by radio and plasma wave instruments on many spacecraft, including ISEE-3, Cassini, and STEREO. In this presentation, we review the detection of dust particles in the solar system using radio and plasma wave instruments aboard various spacecraft since the Voyager era. We also show characteristics of the dust particles derived from recent observations by Cassini RPWS in Saturn's magnetosphere. The dust size distribution and density are consistent with those measured by the conventional dust detectors. A new method of measuring the electron density inside the Enceladus plume based on plasma oscillations observed after dust impacts will also be discussed. The dust measurement by radio and plasma wave instruments complements that by conventional dust detectors and provide important information about the spatial distribution of dust particles due to less pointing constraints and the larger detection area.

  16. The excitation mechanism of Fe XIV 5303 A forbidden line in the inner regions of solar corona

    NASA Astrophysics Data System (ADS)

    Raju, K. P.; Desai, J. N.; Chandrasekhar, T.; Ashok, N. M.

    1991-12-01

    The line intensity of the green coronal line and the continuum intensity are derived from the filter and white light photographs of the solar corona obtained during the 1980 total solar eclipse. Ratio of the line to continuum intensity is plotted against the radial distance r(= R/R0, R0 is the solar radius), in various position angles. A simple model assuming an electron density dependence of the line and continuum intensities suggests a dominant collisional mechanism for the excitation of the line in the innermost regions (about 1.4 R0). The measured line to continuum ratio tends to a constant value at different radial distances in different position angles. The constancy of the measured line to continuum ratio indicates significant radiative excitation beyond 1.4 R0, in some of the position angles.

  17. COUPLING THE SOLAR DYNAMO AND THE CORONA: WIND PROPERTIES, MASS, AND MOMENTUM LOSSES DURING AN ACTIVITY CYCLE

    SciTech Connect

    Pinto, Rui F.; Brun, Allan Sacha; Grappin, Roland

    2011-08-20

    We study the connections between the Sun's convection zone and the evolution of the solar wind and corona. We let the magnetic fields generated by a 2.5-dimensional (2.5D) axisymmetric kinematic dynamo code (STELEM) evolve in a 2.5D axisymmetric coronal isothermal magnetohydrodynamic code (DIP). The computations cover an 11 year activity cycle. The solar wind's asymptotic velocity varies in latitude and in time in good agreement with the available observations. The magnetic polarity reversal happens at different paces at different coronal heights. Overall the Sun's mass-loss rate, momentum flux, and magnetic braking torque vary considerably throughout the cycle. This cyclic modulation is determined by the latitudinal distribution of the sources of open flux and solar wind and the geometry of the Alfven surface. Wind sources and braking torque application zones also vary accordingly.

  18. 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

    2013-07-05

    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.

  19. A CRITICAL ASSESSMENT OF NONLINEAR FORCE-FREE FIELD MODELING OF THE SOLAR CORONA FOR ACTIVE REGION 10953

    SciTech Connect

    DeRosa, Marc L.; Schrijver, Carolus J.; Aschwanden, Markus J.; Cheung, Mark C. M.; Lites, Bruce W.; Amari, Tahar; Canou, Aurelien; McTiernan, James M.; Regnier, Stephane; Thalmann, Julia K.; Wiegelmann, Thomas; Inhester, Bernd; Tadesse, Tilaye; Valori, Gherardo; Wheatland, Michael S.; Conlon, Paul A.; Fuhrmann, Marcel

    2009-05-10

    Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics, and evolution of the coronae of solar active regions. In a series of NLFFF modeling studies, we have found that NLFFF models are successful in application to analytic test cases, and relatively successful when applied to numerically constructed Sun-like test cases, but they are less successful in application to real solar data. Different NLFFF models have been found to have markedly different field line configurations and to provide widely varying estimates of the magnetic free energy in the coronal volume, when applied to solar data. NLFFF models require consistent, force-free vector magnetic boundary data. However, vector magnetogram observations sampling the photosphere, which is dynamic and contains significant Lorentz and buoyancy forces, do not satisfy this requirement, thus creating several major problems for force-free coronal modeling efforts. In this paper, we discuss NLFFF modeling of NOAA Active Region 10953 using Hinode/SOT-SP, Hinode/XRT, STEREO/SECCHI-EUVI, and SOHO/MDI observations, and in the process illustrate three such issues we judge to be critical to the success of NLFFF modeling: (1) vector magnetic field data covering larger areas are needed so that more electric currents associated with the full active regions of interest are measured, (2) the modeling algorithms need a way to accommodate the various uncertainties in the boundary data, and (3) a more realistic physical model is needed to approximate the photosphere-to-corona interface in order to better transform the forced photospheric magnetograms into adequate approximations of nearly force-free fields at the base of the corona. We make recommendations for future modeling efforts to overcome these as yet unsolved problems.

  20. The relation between the properties of pressure variations in the lower corona and solar energetic particle events

    NASA Astrophysics Data System (ADS)

    Rouillard, A. P.; Vourlidas, A.; Tylka, A. J.; Cohen, C. M.; Mewaldt, R. A.; Mason, G. M.; Thernisien, A. F.

    2012-12-01

    We combine ultraviolet and white-light images obtained by the Solar Dynamics Observatory (SDO) and the Solar-Terrestrial Relations Observatory (STEREO) to track, in the lower corona, the spatial and temporal evolution of pressure waves associated with the onset of Coronal Mass Ejections (CMEs). We use in-situ measurements of the onset of solar energetic particle events (SEPs) to determine their release time near the Sun. We concentrate on the proton-rich events detected by the near-Earth spacecraft and the STEREOs during 2011 and 2012. We use a simple model of the distribution of interplanerary magnetic field lines to determine the foopoint locations of field lines connecting the lower corona to the points of in-situ measurements. We (1) determine the height and spatial extent of the pressure waves at the SEP release times, (2) compare the longitudinal extent of SEP events with the extent of the pressure waves, (3) compare the kinematic properties of pressure waves launched over widely separated longitudes. We discuss the successes and challenges faced when interpreting these observations in terms of the acceleration of particles at coronal shocks.

  1. 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.

  2. On the Coexistence of a Radial Magnetic Field with the Large Scale Field in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Habbal, S. R.; Woo, R.; Arnaud, J.

    2001-05-01

    Polarimetric measurements of the corona out to 2 Rs in the Fe XIII 10747 A line, the strongest of the iron forbidden lines, are placed for the first time in the context of spatially resolved images of coronal density structures. These measurements, which are the only tool currently available to yield the direction of the magnetic field, date to 1980, the only year when they were available with polarized brightness images of the corona. Through this comparison, the observed predominance of the radial component of the coronal magnetic field, discovered over three decades ago from eclipse observations, and established systematically by Arnaud (1982), is shown to point to the existence of two components of the coronal magnetic field: a non-radial component associated with the large scale structures known as streamers, and the second, more dominant one, a pervasive radial magnetic field. The coexistence of these two components provides new information for the distribution of open and closed magnetic flux in the solar corona.

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

    SciTech Connect

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

    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.

  4. Physical conditions in the low corona and chromosphere of solar active regions according to spectral radar measurements

    NASA Astrophysics Data System (ADS)

    Kaltman, T. I.; Bogod, V. M.; Stupishin, A. G.; Yasnov, L. V.

    2013-12-01

    The physical conditions in the low corona and chromosphere of solar active regions are studied. A diagnostics technique based on multiwave observations in the centimeter range, photospheric magnetic field extrapolation, and radioemission calculations has been applied. The calculated spatial and spectral structure of the radioemission has been compared with RATAN-600 spectral-polarization observations with a high spatial resolution. The effect of the plasma physical parameters on the emission structure character in a complex magnetic field topology in active regions is analyzed. Modeling of the spectral singularities at a quasi-periodic propagation of the radioemission is presented.

  5. Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Carley, Eoin P.; Vilmer, Nicole; Gallagher, Peter T.

    2016-12-01

    Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption are still subject to much investigation. Observing the exact sites of particle acceleration can help confirm how the flare and eruption are initiated and how they evolve. Here we use the Atmospheric Imaging Assembly to analyze a flare and erupting flux rope on 2014 April 18, while observations from the Nançay Radio Astronomy Facility allow us to diagnose the sites of electron acceleration during the eruption. Our analysis shows evidence of a pre-formed flux rope that slowly rises and becomes destabilized at the time of a C-class flare, plasma jet, and the escape of ≳75 keV electrons from the rope center into the corona. As the eruption proceeds, continued acceleration of electrons with energies of ˜5 keV occurs above the flux rope for a period over 5 minutes. At the flare peak, one site of electron acceleration is located close to the flare site, while another is driven by the erupting flux rope into the corona at speeds of up to 400 km s-1. Energetic electrons then fill the erupting volume, eventually allowing the flux rope legs to be clearly imaged from radio sources at 150-445 MHz. Following the analysis of Joshi et al. (2015), we conclude that the sites of energetic electrons are consistent with flux rope eruption via a tether cutting or flux cancellation scenario inside a magnetic fan-spine structure. In total, our radio observations allow us to better understand the evolution of a flux rope eruption and its associated electron acceleration sites, from eruption initiation to propagation into the corona.

  6. A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun's Subsurface, Surface, Corona, and Sunspot Groups

    NASA Astrophysics Data System (ADS)

    Javaraiah, J.

    2013-10-01

    Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985 - 2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the solar equatorial-rotation rates determined from the following data: i) the plasma rotation rates at 0.94R⊙,0.95R⊙,…,1.0R⊙ measured by the Global Oscillation Network Group (GONG) during the period 1995 - 2010, ii) the data on the soft-X-ray corona determined from Yohkoh/SXT full-disk images for the years 1992 - 2001, iii) the data on small bright coronal structures (SBCS) that were traced in Solar and Heliospheric Observatory (SOHO)/EIT images during the period 1998 - 2006, and iv) the Mount Wilson Doppler-velocity measurements during the period 1986 - 2007. A large portion (up to ≈ 30∘ latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94R⊙ and 0.98R⊙. The variation in the yearly mean equatorial-rotation rate of the sunspot groups seems to be lagging behind that of the equatorial-rotation rate determined from the GONG measurements by one to two years. The amplitude of the GONG measurements is very small. The solar-cycle variation in the equatorial-rotation rate of the solar corona closely matches that determined from the sunspot-group data. The variation in the equatorial-rotation rate determined from the Mount Wilson Doppler-velocity data closely resembles the corresponding variation in the equatorial-rotation rate determined from the sunspot-group data that included the values of the abnormal angular motions (> |3∘| day-1) of the sunspot groups. Implications of these results are pointed out.

  7. Dust Accumulation and Solar Panel Array Performance on the Mars Exploration Rover (MER) Project

    NASA Technical Reports Server (NTRS)

    Turgay, Eren H.

    2004-01-01

    One of the most fundamental design considerations for any space vehicle is its power supply system. Many options exist, including batteries, fuel cells, nuclear reactors, radioisotopic thermal generators (RTGs), and solar panel arrays. Solar arrays have many advantages over other types of power generation. They are lightweight and relatively inexpensive, allowing more mass and funding to be allocated for other important devices, such as scientific instruments. For Mars applications, solar power is an excellent option, especially for long missions. One might think that dust storms would be a problem; however, while dust blocks some solar energy, it also scatters it, making it diffuse rather than beamed. Solar cells are still able to capture this diffuse energy and convert it into substantial electrical power. For these reasons, solar power was chosen to be used on the 1997 Mars Pathfinder mission. The success of this mission set a precedent, as NASA engineers have selected solar power as the energy system of choice for all future Mars missions, including the Mars Exploration Rover (MER) Project. Solar sells have their drawbacks, however. They are difficult to manufacture and are relatively fragile. In addition, solar cells are highly sensitive to different parts of the solar spectrum, and finding the correct balance is crucial to the success of space missions. Another drawback is that the power generated is not a constant with respect to time, but rather changes with the relative angle to the sun. On Mars, dust accumulation also becomes a factor. Over time, dust settles out of the atmosphere and onto solar panels. This dust blocks and shifts the frequency of the incoming light, degrading solar cell performance. My goal is to analyze solar panel telemetry data from the two MERs (Spirit and Opportunity) in an effort to accurately model the effect of dust accumulation on solar panels. This is no easy process due to the large number of factors involved. Changing solar

  8. THE DYNAMICS OF DUST GRAINS IN THE OUTER SOLAR SYSTEM

    SciTech Connect

    Belyaev, Mikhail A.; Rafikov, Roman R. E-mail: rrr@astro.princeton.ed

    2010-11-10

    We study the dynamics of large dust grains {approx}>1 {mu}m with orbits outside of the heliosphere (beyond 250 AU). Motion of the solar system through the interstellar medium (ISM) at a velocity of 26 km s{sup -1} subjects these particles to gas and Coulomb drag (grains are expected to be photoelectrically charged) as well as the Lorentz force and the electric force caused by the induction electric field. We show that to zeroth order the combined effect of these forces can be well described in the framework of the classical Stark problem: particle motion in a Keplerian potential subject to an additional constant force. Based on this analogy, we elucidate the circumstances in which the motion becomes unbound, and show that under local ISM conditions dust grains smaller than {approx}100 {mu}m originating in the Oort Cloud (e.g., in collisions of comets) beyond 10{sup 4} AU are ejected from the solar system under the action of the electric force. Orbital motion of larger, bound grains is described analytically using the orbit-averaged Hamiltonian approach and consists of orbital plane precession at a fixed semimajor axis, accompanied by the periodic variations of the inclination and eccentricity (the latter may approach unity in some cases). A more detailed analysis of the combined effect of gas and Coulomb drag shows it is possible to reduce particle semimajor axes, but that the degree of orbital decay is limited (a factor of several at best) by passages through atomic and molecular clouds, which easily eject small particles.

  9. 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).

  10. Electrostatic Charging of Lunar Dust by UV Photoelectric Emissions and Solar Wind Electrons

    NASA Technical Reports Server (NTRS)

    Abbas, Mian M.; Tankosic, Dragana; Spann, James f.; LeClair, Andre C.; Dube, Michael J.

    2008-01-01

    The ubiquitous presence of dust in the lunar environment with its high adhesive characteristics has been recognized to be a major safety issue that must be addressed in view of its hazardous effects on robotic and human exploration of the Moon. The reported observations of a horizon glow and streamers at the lunar terminator during the Apollo missions are attributed to the sunlight scattered by the levitated lunar dust. The lunar surface and the dust grains are predominantly charged positively by the incident UV solar radiation on the dayside and negatively by the solar wind electrons on the night-side. The charged dust grains are levitated and transported over long distances by the established electric fields. A quantitative understanding of the lunar dust phenomena requires development of global dust distribution models, based on an accurate knowledge of lunar dust charging properties. Currently available data of lunar dust charging is based on bulk materials, although it is well recognized that measurements on individual dust grains are expected to be substantially different from the bulk measurements. In this paper we present laboratory measurements of charging properties of Apollo 11 & 17 dust grains by UV photoelectric emissions and by electron impact. These measurements indicate substantial differences of both qualitative and quantitative nature between dust charging properties of individual micron/submicron sized dust grains and of bulk materials. In addition, there are no viable theoretical models available as yet for calculation of dust charging properties of individual dust grains for both photoelectric emissions and electron impact. It is thus of paramount importance to conduct comprehensive measurements for charging properties of individual dust grains in order to develop realistic models of dust processes in the lunar atmosphere, and address the hazardous issues of dust on lunar robotic and human missions.

  11. MHD simulation of the evolution of the solar corona around August 1st 2010 using the HMI solar magnetic field data

    NASA Astrophysics Data System (ADS)

    Hayashi, K.; Hmi Team

    2010-12-01

    We will report results of the MHD simulation of the solar corona and solar wind using the HMI magnetic field data, especially focusing on a simulated eruption of a coronal streamer that reasonably corresponds to a large-scale coronal eruption event observed on August 1, 2010. The pre-event coronal situation is prepared through the time-relaxation MHD simulation using the synoptic map data of the solar surface magnetic field for a period of the Carrington Rotation 2098. Then, the global magnetic field evolutions from CR 2098 to 2099 are introduced in the simulation by means of a boundary model we recently developed, which enable to trace the sub-Alfvenic MHD responses of the corona numerically. The simulated coronal features include the formation of the two twisted coronal magnetic field structures along the magnetically inversion lines at the lowermost corona (coinciding the two observed filaments at west-north part of the solar disk) and the large-scale outward motions and decay of the closed-field streamer above the two twisted-field regions. Our MHD simulation model did not include the triggering event directly, and our simulations were done in somewhat low resolution in space. However, the reasonable success in reproducing coronal features relating a specific event in a well-known manner (using the synoptic map format data and the MHD simulation model) shows that the new dataset from HMI will be useful for the models, such as the MHD and the potential field models, as the previous dataset by SOHO/MDI.

  12. GLOBAL CORONAL SEISMOLOGY IN THE EXTENDED SOLAR CORONA THROUGH FAST MAGNETOSONIC WAVES OBSERVED BY STEREO SECCHI COR1

    SciTech Connect

    Kwon, Ryun-Young; Kramar, Maxim; Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.; Chae, Jongchul; Zhang, Jie

    2013-10-10

    We present global coronal seismology for the first time, which allows us to determine inhomogeneous magnetic field strength in the extended corona. From the measurements of the propagation speed of a fast magnetosonic wave associated with a coronal mass ejection (CME) and the coronal background density distribution derived from the polarized radiances observed by the STEREO SECCHI COR1, we determined the magnetic field strengths along the trajectories of the wave at different heliocentric distances. We found that the results have an uncertainty less than 40%, and are consistent with values determined with a potential field model and reported in previous works. The characteristics of the coronal medium we found are that (1) the density, magnetic field strength, and plasma β are lower in the coronal hole region than in streamers; (2) the magnetic field strength decreases slowly with height but the electron density decreases rapidly so that the local fast magnetosonic speed increases while plasma β falls off with height; and (3) the variations of the local fast magnetosonic speed and plasma β are dominated by variations in the electron density rather than the magnetic field strength. These results imply that Moreton and EIT waves are downward-reflected fast magnetosonic waves from the upper solar corona, rather than freely propagating fast magnetosonic waves in a certain atmospheric layer. In addition, the azimuthal components of CMEs and the driven waves may play an important role in various manifestations of shocks, such as type II radio bursts and solar energetic particle events.

  13. The white light solar corona--an atlas of k-coronameter synoptic charts August 1980 - September 1981. Technical note

    SciTech Connect

    Fisher, R.; Garcia, C.; Rock, K.; Seagraves, P.; Yasukawa, E.

    1982-01-01

    A synoptic observing program was undertaken at the Mauna Loa Solar Observatory, a site operated by the High Altitude Observatory to study the solar corona using the Mark III K-Coronameter. Daily pB images were used to extract three pB ( ) azimuthal scans located at heights of 1.3, 1.7, and 2.1 Rq. Four final data products are given in this atlas: (1) interpolated pB contour plots for h = 1.3 and 1.7 Rq for each Carrington rotation; (2) shaded pB charts for each Carrington rotation; (3) standard zonal pB average values for each day; and (4) autocorrelation estimates of pB variation for equatorial and high latitude structure and an autocorrelation coefficient for an amplitude-independent, first moment of the pB distribution.

  14. An improved model for interplanetary dust fluxes in the outer Solar System

    NASA Astrophysics Data System (ADS)

    Poppe, Andrew R.

    2016-01-01

    We present an improved model for interplanetary dust grain fluxes in the outer Solar System constrained by in situ dust density observations. A dynamical dust grain tracing code is used to establish relative dust grain densities and three-dimensional velocity distributions in the outer Solar System for four main sources of dust grains: Jupiter-family comets, Halley-type comets, Oort-Cloud comets, and Edgeworth-Kuiper Belt objects. Model densities are constrained by in situ dust measurements by the New Horizons Student Dust Counter, the Pioneer 10 meteoroid detector, and the Galileo Dust Detection System (DDS). The model predicts that Jupiter-family comet grains dominate the interplanetary dust grain mass flux inside approximately 10 AU, Oort-Cloud cometary grains may dominate between 10 and 25 AU, and Edgeworth-Kuiper Belt grains are dominant outside 25 AU. The model also predicts that while the total interplanetary mass flux at Jupiter roughly matches that inferred by the analysis of the Galileo DDS measurements, mass fluxes to Saturn, Uranus, and Neptune are at least one order-of-magnitude lower than that predicted by extrapolations of dust grain flux models from 1 AU. Finally, we compare the model predictions of interplanetary dust oxygen influx to the giant planet atmospheres with various observational and photochemical constraints and generally find good agreement, with the exception of Jupiter, which suggests the possibility of additional chemical pathways for exogenous oxygen in Jupiter's atmosphere.

  15. The Multi-Instrument, Comprehensive Differential Emission Measure (DEM) of the Solar Corona During Flares and Quiescent Periods

    NASA Astrophysics Data System (ADS)

    Caspi, Amir; McTiernan, James; Warren, Harry; Woods, Thomas N.

    2014-06-01

    Thermal plasma in the solar corona, while often modeled as isothermal for ease of analysis, is in fact decidedly multi-thermal, ranging from ~1-2 MK in the quiescent corona to ~30-50 MK in intensely flaring loops. It has proven difficult to obtain a well-constrained differential emission measure (DEM) from a single instrument, as the wavelength ranges of individual instruments, even those with broadband coverage, provide sensitivity to only a limited range of plasma temperatures. Recently, we developed a new technique using combined extreme ultraviolet (EUV) and soft and hard X-ray (SXR, HXR) data from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), respectively, to obtain a self-consistent DEM that is strongly constrained across the full range of coronal plasma temperatures (<2 to >50 MK). An accurate, precise determination of the plasma temperature distribution enables not only studies of plasma heating and thermal plasma evolution, but can also provide strong constraints on the non-thermal accelerated electron population, including the low-energy cutoff which is typically determined only as a loose upper limit.We present EVE+RHESSI DEM results from selected intense (X-class) flares from solar cycle 24, including determining the non-thermal low-energy cutoff and examining how this evolves with the temperature distribution. We also apply this technique to combine EUV data from EVE with SXR data from the GOES X-ray Sensor (XRS) and the X123, a new SXR spectrometer flown on two recent SDO/EVE calibration sounding rockets, to examine the DEM during quiescent (non-flaring) times with varying activity levels; the X-ray data provide crucial constraints on the high-temperate extent of the DEM and any potential non-thermal emission. We compare these results with those from a parallel technique to derive DEMs from imaging data from the Atmospheric Imaging Assembly (AIA

  16. Photometric analysis of the corona during the 20 March 2015 total solar eclipse: density structures, hydrostatic temperatures and magnetic field inference.

    NASA Astrophysics Data System (ADS)

    Bazin, C.; Vilinga, J.; Wittich, R.; Koutchmy, S.; Mouette, J.; Nitschelm, C.

    2015-12-01

    We present some new accurate CCD photometry analysis of the white light solar corona at the time of the last 20 March 2015 total eclipse (airborne observations on a Falcon 7X and at ground-based- Svalbard). We measured coronal brightness profiles taken along radial directions from 1.001 to 3 solar radii in the northern, southern and equatorial regions, after removing the F-corona and the sky background. These studies allow to evaluate the density gradients, structures and temperature heterogeneity, by considering the Thomson scattering in white light of the K- corona and also emissions of the EUV Fe XII 193A (1 to 2 MK) and Fe XI 171/174 (lower temperature) simultaneously observed by SDO/AIA and SWAP/Proba2 space missions. Some dispersion between the regions is noticed. The limitation of the hydrostatic equilibrium assumption in the solar atmosphere is discussed as well as the contribution of the magnetic field pressure gradients as illustrated by a comparison with the model stationary magnetic corona from Predictive Sc. Inc. These results are compared with the results of the quieter 2010 total solar eclipse corona analyzed with the same method. This photometric analysis of the inner and intermediate white light corona will contribute to the preparation of the Aspiics/Proba 3 flying formation future coronagraphic mission of ESA for new investigation at time of artificial eclipses produced in Space. Note that Aspiics will also observe in the He I D3 line at 5876 A, and will record intensities of the Fe XIV line 5303A simultaneously with the analysis of the orange white- light continuum, including precise polarimetry analysis. .

  17. Minor constituents in the solar wind originating from plasma-dust interactions

    NASA Technical Reports Server (NTRS)

    Ripken, H. W.

    1983-01-01

    Atoms, molecules, and atomic and molecular ions generated by solar wind interactions with dust grains of the zodiacal cloud are discussed. The main processes leading to the generation of these particles are described and relevant methods of observation are examined.

  18. White Light Solar Corona: An Atlas of 1988 K-Coronameter Synoptic Charts, December 1987-January 1989. Technical note

    SciTech Connect

    Sime, D.G.; Garcia, C.; Yasukawa, E.; Lundin, E.

    1990-03-01

    The synoptic observing project of the High Altitude Observatory's Coronal Dynamics Program began on 30 July 1980. The data obtained for it are gathered by the Mark-III K-coronameter located at the Mauna Loa Solar Observatory, Hawaii, and are published yearly in volumes of The White Light Solar Corona: An Atlas of K-Coronameter Synoptic Charts (Table 1). The data, in the form of synoptic charts, are extended at both the beginning and the end of each year to provide some overlap with the preceding and succeeding volumes. This is also necessary to provide a complete set of the data organized into Carrington rotations covering a specific time period, since the rotations do not coincide with the yearly calendar. Further observations are made at the limb, and west limb passage occurs 14 days after east limb passage. Thus, an entire rotation's data requires more than 28 days to collect. Together with the synoptic maps and polar synoptic maps, two additional sections designed to aid the user are included in the volume. As in previous Atlases, the Activity Report Summary for the year is given and the Mauna Loa Solar Observatory Calendar for 1988 (Table III) is also included. This is a list of days on which no coronal observations were achieved. These synoptic data should be regarded as a preliminary presentation in which corrections have not fully been made for the day-to-day variations and scattering of polarized light by the earth's atmosphere. Data from the east and west limbs are presented separately in the synoptic charts, as transient and evolutionary changes in the white light corona can substantially modify the distribution of coronal material over the 14 days between sequential limb passages.

  19. Whie light solar corona: An atlas of 1988 K-coronameter synoptic charts, December 1987 to January 1989

    SciTech Connect

    Sime, D.G.; Garcia, C.; Yasukawa, E.; Lundin, E.

    1990-03-01

    The synoptic observing project of the High Altitude Observatory's Coronal Dynamics Program began on 30 July 1980. The data obtained for it are gathered by the Mark-III K-coronameter located at the Mauna Loa Solar Observatory, Hawaii, and are published yearly in volumes of The White Light Solar Corona: An Atlas of K-Coronameter Synoptic Charts (Table 1). The data, in the form of synoptic charts, are extended at both the beginning and the end of each year to provide some overlap with the preceding and succeeding volumes. This is also necessary to provide a complete set of the data organized into Carrington rotations covering a specific time period since the rotations do not coincide with the yearly calendar. Further observations are made at the limb, and west limb passage occurs 14 days after east limb passage. Thus, an entire rotation's data requires more than 28 days to collect. Together with the synoptic maps and polar synoptic maps, two additional sections designed to aid the user are included in the volume. As in previous Atlases, the Activity Report Summary for the year is given and the Mauna Loa Solar Observatory Calendar for 1988 (Table III) is also included. This is a list of days on which no coronal observations were achieved. These synoptic data should be regarded as a preliminary presentation in which corrections have not fully been made for the day-to-day variations and scattering of polarized light by the earth's atmosphere. Data from the east and west limbs are presented separately in the synoptic charts, as transient and evolutionary changes in the white light corona can substantially modify the distribution of coronal material over the 14 days between sequential limb passages.

  20. Height of Shock Formation in the Solar Corona Inferred from Observations of Type II Radio Bursts and Coronal Mass Ejections

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Xie, H.; Makela, P.; Yashiro, S.; Akiyama, S.; Uddin, W.; Srivastava, A. K.; Joshi, N. C.; Chandra, R.; Manoharan, P. K.

    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 frequency of the type II bursts was very low, in the range 25-40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.

  1. 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.; Druckmueller, M.; Daw, A.; Johnson, J.; Ding, A.; Arndt, M.; Esser, R.; Rusin, V.

    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

  2. Exploring Small Spatial Scales in the Transition Region and Solar Corona with the Very High Angular Resolution Imaging Spectrometer (VERIS)

    NASA Astrophysics Data System (ADS)

    Chua, D. H.; Korendyke, C. M.; Vourlidas, A.; Brown, C. M.; Tun-Beltran, S.; Klimchuk, J. A.; Landi, E.; Seely, J.; Davila, J. M.; Hagood, R.; Roberts, D.; Shepler, E.; Feldman, R.; Moser, J.; Shea, J.

    2012-12-01

    Theoretical and experimental investigations of the transition region and coronal loops point to the importance of processes occurring on small spatial scales in governing the strong dynamics and impulsive energy release in these regions. As a consequence, high spatial, temporal, and temperature resolution over a broad temperature range, and accuracy in velocity and density determinations are all critical observational parameters. Current instruments lack one or more of these properties. These observational deficiencies have created a wide array of opposing descriptions of coronal loop heating and questions such as whether or not the plasma within coronal loops is multi-thermal or isothermal. High spectral and spatial resolution spectroscopic data are absolutely required to resolve these controversies and to advance our understanding of the dynamics within the solar atmosphere. We will achieve this with the Very High Angular Resolution Imaging Spectrometer (VERIS) sounding rocket payload. VERIS consists of an off-axis paraboloid telescope feeding a very high angular resolution, extreme ultraviolet (EUV) imaging spectrometer that will provide the first ever, simultaneous sub-arcsecond (0.16 arcsecond/pixel) spectra in bright lines needed to study plasma structures in the transition region, quiet corona, and active region core. It will do so with a spectral resolution of >5000 to allow Doppler velocity determinations to better than 3 km/s. VERIS uses a novel two-element, normal incidence optical design with highly reflective, broad wavelength coverage EUV coatings to access a spectral range with broad temperature coverage (0.03-15 MK) and density-sensitive line ratios. Combined with Hinode Solar Optical Telescope (SOT) and ground based observatories, VERIS will deliver simultaneous observations of the entire solar atmosphere from the photosphere to the multi-million degree corona at sub-arcsecond resolution for the first time ever, allowing us to understand the

  3. The Temperature and Density Structure of the Solar Corona. I. Observations of the Quiet Sun with the EUV Imaging Spectrometer on Hinode

    NASA Astrophysics Data System (ADS)

    Warren, Harry P.; Brooks, David H.

    2009-07-01

    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.

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

    SciTech Connect

    Martisek, K.; Druckmuellerova, H.

    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.

  5. 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.

  6. SIXTEEN YEARS OF ULYSSES INTERSTELLAR DUST MEASUREMENTS IN THE SOLAR SYSTEM. II. FLUCTUATIONS IN THE DUST FLOW FROM THE DATA

    SciTech Connect

    Strub, Peter; Krüger, Harald; Sterken, Veerle J.

    2015-10-20

    The Ulysses spacecraft provided the first opportunity to identify and study interstellar dust (ISD) in situ in the solar system between 1992 and 2007. Here we present the first comprehensive analysis of the ISD component in the entire Ulysses dust data set. We analyzed several parameters of the ISD flow in a time-resolved fashion: flux, flow direction, mass index, and flow width. The general picture is in agreement with a time-dependent focusing/defocusing of the charged dust particles due to long-term variations of the solar magnetic field throughout a solar magnetic cycle of 22 years. In addition, we confirm a shift in dust direction of 50° ± 7° in 2005, along with a steep, size-dependent increase in flux by a factor of 4 within 8 months. To date, this is difficult to interpret and has to be examined in more detail by new dynamical simulations. This work is part of a series of three papers. This paper concentrates on the time-dependent flux and direction of the ISD. In a companion paper we analyze the overall mass distribution of the ISD measured by Ulysses, and a third paper discusses the results of modeling the flow of the ISD as seen by Ulysses.

  7. 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.

  8. Spectroscopy of Stellar Coronae

    NASA Astrophysics Data System (ADS)

    Laming, J. Martin

    I review the important spectroscopic results that have come from observations of stellar coronae, mainly by EUVE and ASCA, but also from HST. The plasma parameters that can be determined from such spectra include the electron density and temperature distributions, and relative element abundances. With high resolution spectra dynamical information can be obtained. Such parameters can then be used to put constraints on models of the heating and structure of stellar coronae. Throughout, I try to emphasise the similarities and differences between stellar coronal spectroscopy and that of the solar corona.

  9. The impact of UVCS/SOHO observations on models of ion-cyclotron resonance heating of the solar corona

    NASA Technical Reports Server (NTRS)

    Cranmer, S. R.; Field, G. B.; Noci, G.; Kohl, J. L.

    1997-01-01

    The compatibility between theoretical models and observations of the temperatures and anisotropic distributions of hydrogen and minor ions in the solar corona is examined. The ultraviolet coronagraph spectrometer (UVCS) instrument onboard SOHO measured hydrogen kinetic temperatures along lines of sight in coronal holes in excess of 3 x 10(exp 6) K and O(+5) ion kinetic temperatures of at least 2 x 10(exp 8) K. Various features of plasma heating by the dissipation of high-frequency ion-cyclotron resonance Alfven waves, which may be the most natural physical mechanism to produce certain plasma conditions, are examined. Preliminary quantitative models of the ion motion in polar coronal holes are presented, and it is shown that such models can be used to predict the spectrum of waves required to reproduce the observations. Indeed, the more ionic species that are observed spectroscopically, the greater the extent in frequency space the wave spectrum can be inferred.

  10. 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

  11. Time delays in the nonthermal radiation of solar flares according to observations of the CORONAS-F satellite

    NASA Astrophysics Data System (ADS)

    Tsap, Yu. T.; Stepanov, A. V.; Kashapova, L. K.; Myagkova, I. N.; Bogomolov, A. V.; Kopylova, Yu. G.; Goldvarg, T. B.

    2016-07-01

    In 2001-2003, the X-ray and microwave observations of ten solar flares of M- and X-classes were carried out by the CORONAS-F orbital station, the RSTN Sun service, and Nobeyama radio polarimeters. Based on these observations, a correlation analysis of time profiles of nonthermal radiation was performed. On average, hard X-ray radiation outstrips the microwave radiation in 9 events, i.e., time delays are positive. The appearance of negative delays is associated with effective scattering of accelerated electrons in pitch angles, where the length of the free path of a particle is less than the half-length of a flare loop. The additional indications are obtained in favor of the need to account for the effect of magnetic mirrors on the dynamics of energetic particles in the coronal arches.

  12. Numerical model for the acceleration of a dust cloud by the solar wind

    NASA Astrophysics Data System (ADS)

    Jia, Y.-D.; Russell, C. T.; Lai, H. R.; Wei, H. Y.

    2015-10-01

    In this study we investigate the behavior of two massive fluids: protons in the solar wind and charged dust. For simplification we temporarily ignore the charging process of dust particles. The mass of charged dust can be 103 amu to grams, but we only model the lighter ones because the behavior of grains more massive than 105 are similar. A multi-fluid MHD code is used to simulate the large scale structure formed around a dust cloud released into the solar wind, and its evolution. Dust clouds as we are simulating can be made by meteoroid-meteoroid collisions with size from 1 to 100 m in diameter. These are dangerous if they hit the Earth's atmosphere. Detecting them in space can help detect where such objects are in near Earth space.

  13. The long-term stability of the visible F corona at heights of 3-6 R_⊙

    NASA Astrophysics Data System (ADS)

    Morgan, H.; Habbal, S. R.

    2007-08-01

    Context: CMEs can effect the distribution of dust grains in the corona. The brightness of the visible F corona is expected therefore to change as the frequency of CMEs varies with solar cycle. Aims: We search for a variation in the F corona by comparing LASCO C2 observations from solar minimum and maximum. Methods: An established inversion method is used to calculate the visible F corona brightness from LASCO C2 solar minimum observations made during 1996/10. Good agreement is found with the F corona brightness calculated from Skylab observations during 1973/05-1974/02 for heights of 3-6 R_⊙. The unpolarized brightness, which is dominated by the unpolarized F corona brightness at these heights, is obtained by subtracting many pairs of polarized brightness images from total brightness images and averaging over a solar rotation. We calculate the unpolarized brightness for both solar activity minimum and maximum. Results: The unpolarized brightness, and therefore the F corona, remain virtually unchanged between solar minimum and maximum at heights above 2.6 R_⊙, despite the large change in the shape and activity of the corona. Using a simple density model, it is shown that the small variation in unpolarized brightness seen below 2.6 R_⊙ can arise from differences in the distribution of electron density, and therefore cannot be attributed to a variation in the F corona. Conclusions: Despite the large rise in frequency of CMEs from solar minimum to maximum, the F coronal brightness, at heights of 3-6 R_⊙ in the visible, remains very stable.

  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. Electrically-Charged Dust in the Solar System: Direct and Indirect Evidence

    NASA Astrophysics Data System (ADS)

    Horanyi, Mihaly

    2010-05-01

    Dust particles exposed the solar UV radiation and plasmas in the solar system will collect electrostatic charges. Depending on their charge-to-mass ratio, their dynamics could be perturbed or possibly dominated by electromagnetic forces. This talk will first briefly review the dominant charging processes and the resulting dynamics of dust particles where the gravitational and electromagnetic forces are of similar magnitude. In addition to the unusual dynamics of single grains, we will also explore possible dusty plasma collective effects. We will briefly tour the solar system and show unusual observations that could be best explained by exploring the physics of dust charging, and dusty plasmas. Examples will include the surfaces of airless bodies, the high-speed stream particles ejected from the magnetosphere of Jupiter, Saturn's rings, and the flow of interstellar dust through the heliosphere.

  16. White light solar corona: an atlas of 1986 K-coronameter synoptic charts, December 1985-January 1987. Technical note

    SciTech Connect

    Sime, D.G.; Garcia, C.; Yasukawa, E.; Lundin, E.; Rock, K.

    1987-03-01

    The synoptic observing project of the High Altitude Observatory's Coronal Dynamics Program began on 5 August 1980. The data obtained for it are gathered by the Mark-III K-coronameter located at the Mauna Loa Solar Observatory, Hawaii, and are published yearly in volumes of The White Solar Corona: An Atlas Of K-Coronameter Synoptic Charts. The data are extended at both the beginning and the end of each volume to provide some overlap with the preceding and succeeding volumes. This is necessary to provide a complete set of the data organized into Carrington rotations covering a specific time period, since the rotations do not coincide with the yearly calendar. Further, observations are made at the limb, and west limb passage occurs 14 days after east limb passage. Thus, an entire rotation's data require more than 28 days to collect. As well as the synoptic maps, there are two additional sections designed to aid the user are included in this volume. As in previous Atlases, the Activity Report Summary for the year and Polar Synoptic Charts are included. Further, in this volume, the authors also include the Manuna Loa Solar Observatory Calendar for 1986. This is a list of days on which no coronal observations were achieved.

  17. White Light Solar Corona: An ATLAS of 1987 K-coronameter Synoptic Charts, December 1986-January 1988. Technical note

    SciTech Connect

    Sime, D.G.; Garcia, C.; Yasukawa, E.; Lundin, E.; Hoffman, F.

    1988-03-01

    The synoptic observing project of the High Altitude Observatory's Coronal Dynamics Program began on 5 August 1980. The data obtained for it are gathered by the Mark III K-coronameter located at the Mauna Loa Solar Observatory, Hawaii, and are published yearly in volumes of The White Light Solar Corona: An Atlas of K-Coronameter Synoptic Charts. The data, in the form of synoptic charts, are extended at both the beginning and the end of each year to provide some overlap with the preceding and succeeding volumes. This is also necessary to provide a complete set of the data organized into Carrington rotations covering a specific time period, since the rotations do not coincide with the yearly calendar. Further, observations are made at the limb, and west limb passage occurs 14 days after east limb passage. Thus, an entire rotation's data requires more than 28 days to collect. As well as the synoptic maps, two additional sections designed to aid the user are included in the volume. As in previous Atlases, the Activity Report Summary for the year and Polar Synoptic Charts are included. Also included the Mauna Loa Solar Observatory Calendar for 1987.

  18. Soft X-ray Images of the Solar Corona with a Normal-Incidence Cassegrain Multilayer Telescope.

    PubMed

    Walker, A B; Lindblom, J F; Barbee, T W; Hoover, R B

    1988-09-30

    High-resolution images of the sun in the soft x-ray to extreme ultraviolet(EUV) regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 angstroms. The bandpass centered at 173 angstroms is dominated by emission from the ions Fe IX Fe X. This emission is from coronal plasma in the temperature range 0.8 x 10(6) to 1.4 x 10(6)K. The images have angular resolution of about 1.0 to 1.5 arc seconds, and show no degradation because of x-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to overlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.

  19. Self-similar signature of the active solar corona within the inertial range of solar-wind turbulence.

    PubMed

    Kiyani, K; Chapman, S C; Hnat, B; Nicol, R M

    2007-05-25

    We quantify the scaling of magnetic energy density in the inertial range of solar-wind turbulence seen in situ at 1 AU with respect to solar activity. At solar maximum, when the coronal magnetic field is dynamic and topologically complex, we find self-similar scaling in the solar wind, whereas at solar minimum, when the coronal fields are more ordered, we find multifractality. This quantifies the solar-wind signature that is of direct coronal origin and distinguishes it from that of local MHD turbulence, with quantitative implications for coronal heating of the solar wind.

  20. FINE STRAND-LIKE STRUCTURE IN THE SOLAR CORONA FROM MAGNETOHYDRODYNAMIC TRANSVERSE OSCILLATIONS

    SciTech Connect

    Antolin, P.; Yokoyama, T.; Van Doorsselaere, T.

    2014-06-01

    Current analytical and numerical modeling suggest the existence of ubiquitous thin current sheets in the corona that could explain the observed heating requirements. On the other hand, new high resolution observations of the corona indicate that its magnetic field may tend to organize itself in fine strand-like structures of few hundred kilometers widths. The link between small structure in models and the observed widths of strand-like structure several orders of magnitude larger is still not clear. A popular theoretical scenario is the nanoflare model, in which each strand is the product of an ensemble of heating events. Here, we suggest an alternative mechanism for strand generation. Through forward modeling of three-dimensional MHD simulations we show that small amplitude transverse MHD waves can lead in a few periods time to strand-like structure in loops in EUV intensity images. Our model is based on previous numerical work showing that transverse MHD oscillations can lead to Kelvin-Helmholtz instabilities that deform the cross-sectional area of loops. While previous work has focused on large amplitude oscillations, here we show that the instability can occur even for low wave amplitudes for long and thin loops, matching those presently observed in the corona. We show that the vortices generated from the instability are velocity sheared regions with enhanced emissivity hosting current sheets. Strands result as a complex combination of the vortices and the line-of-sight angle, last for timescales of a period, and can be observed for spatial resolutions of a tenth of loop radius.

  1. 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.

  2. Solar heating of the Uranian mesopause by dust of ring origin

    SciTech Connect

    Rizk, B.; Hunten, D.M. )

    1990-12-01

    Submicron dust absorption of visible-wavelength solar energy, in conjunction with inhibition of IR radiation, is assumed in the present estimate of the magnitude of an equatorial heat source due to such dust in the upper atmosphere of Uranus. The dust is noted to be capable of generating enough mesopause-level heat to account for heat sources observed only near the equator. Such dust is nevertheless excluded as a heat source for the 500-800 K thermospheric temperatures recorded by the Voyager UV spectrometer. The influx needed for a significant heat source corresponds to decomposition into submicron dust of about 100, 10-km diameter moons with 1.5 g/cu cm density; this is a plausible average dust flux for the rings of Uranus. 32 refs.

  3. On the correlation between interplanetary nano dust particles and solar wind properties from STEREO/SWAVES

    NASA Astrophysics Data System (ADS)

    Issautier, K.; LE CHAT, G.; Meyer-Vernet, N.; Belheouane, S.; Zaslavsky, A.; Zouganelis, I.; Mann, I.; Maksimovic, M.

    2012-12-01

    Dust particles provide an important fraction of the matter composing the interplanetary medium, their mass density at 1 AU being comparable to the one of the solar wind. Among them, dusts of nanometer size-scale can be detected using radio and plasma waves instruments because they move at roughly the solar wind speed. The high velocity impact of a dust particle generates a small crater on the spacecraft: the dust particle and the crater material are vaporized. This produces a plasma cloud whose associated electrical charge induces an electric pulse measured with radio and plasma instruments. Since their first detection in the interplanetary medium (Meyer-Vernet et al. 2009), nanodusts have been routinely measured using STEREO/WAVES instrument (Zaslavsky et al. 2012) We present the nanodust properties during the 2007-2012 period on STEREO. Since the maximum size of the plasma cloud is larger for smaller local solar wind density, we expect to observe an anticorrelation between the detected voltage amplitude and the ambient solar wind density, as suggested recently by Le Chat et al. (2012). Moreover, the variations in solar wind speed and magnetic field are expected to affect the nano dust dynamics. Using STEREO/WAVES/Low Frequency Receiver (LFR) data, we study correlations of in situ solar wind properties and detection of nanodust impacts as well as some possible effects of Coronal Mass Ejections (CME) on nanodusts acceleration.

  4. Electron acceleration at localized wave structures in the solar corona (German Title: Elektronenbeschleunigung an lokalen Wellenstrukturen in der Sonnenkorona)

    NASA Astrophysics Data System (ADS)

    Miteva, Rositsa Stoycheva

    2007-07-01

    Our dynamic Sun manifests its activity by different phenomena: from the 11-year cyclic sunspot pattern to the unpredictable and violent explosions in the case of solar flares. During flares, a huge amount of the stored magnetic energy is suddenly released and a substantial part of this energy is carried by the energetic electrons, considered to be the source of the nonthermal radio and X-ray radiation. One of the most important and still open question in solar physics is how the electrons are accelerated up to high energies within (the observed in the radio emission) short time scales. Because the acceleration site is extremely small in spatial extent as well (compared to the solar radius), the electron acceleration is regarded as a local process. The search for localized wave structures in the solar corona that are able to accelerate electrons together with the theoretical and numerical description of the conditions and requirements for this process, is the aim of the dissertation. Two models of electron acceleration in the solar corona are proposed in the dissertation: I. Electron acceleration due to the solar jet interaction with the background coronal plasma (the jet--plasma interaction) A jet is formed when the newly reconnected and highly curved magnetic field lines are relaxed by shooting plasma away from the reconnection site. Such jets, as observed in soft X-rays with the Yohkoh satellite, are spatially and temporally associated with beams of nonthermal electrons (in terms of the so-called type III metric radio bursts) propagating through the corona. A model that attempts to give an explanation for such observational facts is developed here. Initially, the interaction of such jets with the background plasma leads to an (ion-acoustic) instability associated with growing of electrostatic fluctuations in time for certain range of the jet initial velocity. During this process, any test electron that happen to feel this electrostatic wave field is drawn to co

  5. HEATING OF THE SOLAR CHROMOSPHERE AND CORONA BY ALFVEN WAVE TURBULENCE

    SciTech Connect

    Van Ballegooijen, A. A.; Cranmer, S. R.; DeLuca, E. E.; Asgari-Targhi, M.

    2011-07-20

    A three-dimensional magnetohydrodynamic (MHD) model for the propagation and dissipation of Alfven waves in a coronal loop is developed. The model includes the lower atmospheres at the two ends of the loop. The waves originate on small spatial scales (less than 100 km) inside the kilogauss flux elements in the photosphere. The model describes the nonlinear interactions between Alfven waves using the reduced MHD approximation. The increase of Alfven speed with height in the chromosphere and transition region (TR) causes strong wave reflection, which leads to counter-propagating waves and turbulence in the photospheric and chromospheric parts of the flux tube. Part of the wave energy is transmitted through the TR and produces turbulence in the corona. We find that the hot coronal loops typically found in active regions can be explained in terms of Alfven wave turbulence, provided that the small-scale footpoint motions have velocities of 1-2 km s{sup -1} and timescales of 60-200 s. The heating rate per unit volume in the chromosphere is two to three orders of magnitude larger than that in the corona. We construct a series of models with different values of the model parameters, and find that the coronal heating rate increases with coronal field strength and decreases with loop length. We conclude that coronal loops and the underlying chromosphere may both be heated by Alfvenic turbulence.

  6. Heating of solar and stellar chromospheres and coronae by MHD waves

    NASA Technical Reports Server (NTRS)

    Musielak, Z. E.

    1992-01-01

    The two general classes of models that deal with the required heating of stellar chromospheres and coronae assume that outer stellar atmospheres are heated by hydrodynamic or by magnetohydrodynamic (MHD) waves and that these waves are generated by turbulent motions in the stellar convection zones. This paper considers the types of MHD waves and the source of these waves in stars like sun, the efficiency of the generation of MHD waves, and the manner of propagation and energy dissipation of MHD waves. It is shown that the basic criteria for the validity of any theory of MHD wave heating must account for the mean level of heating observed in stellar chromospheres and coronae, and for the range of radiative losses observed for a given spectral type. It is also required that the MHD wave heating theory accounts for the existence of inhomogeneities in stellar atmospheres. The results obtained indicate that magnetic tube waves might supply enough energy for the chromospheric and coronal heating and might also account for the observed range of variations of stellar radiative losses for a given spectral type.

  7. Design of a solar-blind ultraviolet zoom lens in corona detection

    NASA Astrophysics Data System (ADS)

    Kang, Sirui; Fan, Wenwen; Chen, Yu

    2016-11-01

    Based on the requirements of corona detection on searching targets with large field of view and detecting objects with small field of view, a refractive zoom optical system using mechanical compensation technology, which operates at 0.24μm~0.28μm wavelength ,is designed with aspherical surfaces. S8844-0909 ultraviolet CCD is selected as a sensor with pixel size 24μm×24μm. The zooming region is 35mm~70mm with F number of 3.5 and the corresponding field of view of 7°~14°.The zoom lens consists of seven lenses with two aspherical surfaces, so it has the advantages of compact size and simple structure. The results show that in full zooming range, the MTF values over all fields of view are above 0.8 at cut-off frequency 21lp/mm. The distortion is less than 5%.The zoom lens system has good image quality and stable image plane, which meets the overall design requirements of the optical system. Keywords: Corona detection, Zoom lens, Aspheric surface

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

    PubMed

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

    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.

  9. 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; Gurman, Joseph (Technical Monitor)

    2002-01-01

    A breakthrough resulted from the investigation of plasma heating by ion-cyclotron waves in rapidly expanding flow tubes, often referred to as coronal funnels and expected to originate in the low transition region where the temperature gradient in the solar atmosphere rises very sharply. The investigation was made using a three-fluid plasma consisting of protons, electrons and alpha particles. It was found that these waves heat the solar wind plasma by directly heating the heavier species, namely the alphas. Although only alpha particles dissipate the waves, the strong Coulomb coupling between alpha particles and protons, and between protons and electrons, makes it possible for protons and electrons to be heated also to more than one million degrees, i.e. to coronal temperatures. Interestingly, the extreme heating of the alpha particles, however, is such that they end up being hotter and faster, and are no longer in thermal equilibrium with the protons and electrons. once the rapid expansion of the flow tube is complete, the particles return to thermal equilibrium. The observational signatures of these results are such that if spectral lines formed below a million degrees are observed at different heights in the corona, the inferred outflow velocities may vary by a factor of 5 to 6. In addition, if minor ions are indeed much faster than protons and electrons at temperatures below a million degrees, then one cannot reliably determine the bulk outflow velocity of the solar wind in that region from inferences of minor ion outflow velocities. A detailed parameter study on the resonant interaction between ion cyclotron waves and alpha particles and other minor ions is also under way. It is found that the highest frequency of the waves, or the location of the heating determines whether a thermal equilibrium can be established between minor ions and protons. As the maximum frequency is increased, alpha particles and protons become farther away from thermal equilibrium. As

  10. 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.

  11. Spectroscopic Evidence of Alfvén Wave Damping in the Off-limb Solar Corona

    NASA Astrophysics Data System (ADS)

    Gupta, G. R.

    2017-02-01

    We investigate the off-limb active-region and quiet-Sun corona using spectroscopic data. The active region is clearly visible in several spectral lines formed in the temperature range of 1.1–2.8 MK. We derive the electron number density using the line ratio method, and the nonthermal velocity in the off-limb region up to the distance of 140 Mm. We compare density scale heights derived from several spectral line pairs with expected scale heights per the hydrostatic equilibrium model. Using several isolated and unblended spectral line profiles, we estimate nonthermal velocities in the active region and quiet Sun. Nonthermal velocities obtained from warm lines in the active region first show an increase and then later either a decrease or remain almost constant with height in the far off-limb region, whereas nonthermal velocities obtained from hot lines show consistent decrease. However, in the quiet-Sun region, nonthermal velocities obtained from various spectral lines show either a gradual decrease or remain almost constant with height. Using these obtained parameters, we further calculate Alfvén wave energy flux in both active and quiet-Sun regions. We find a significant decrease in wave energy fluxes with height, and hence provide evidence of Alfvén wave damping. Furthermore, we derive damping lengths of Alfvén waves in the both regions and find them to be in the range of 25–170 Mm. Different damping lengths obtained at different temperatures may be explained as either possible temperature-dependent damping or by measurements obtained in different coronal structures formed at different temperatures along the line of sight. Temperature-dependent damping may suggest some role of thermal conduction in the damping of Alfvén waves in the lower corona.

  12. Validation of Earth atmosphere models using solar EUV observations from the CORONAS and PROBA2 satellites in occultation mode

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Aims: Knowledge of properties of the Earth's upper atmosphere is important for predicting the lifetime of low-orbit spacecraft as well as for planning operation of space instruments whose data may be distorted by atmospheric effects. The accuracy of the models commonly used for simulating the structure of the atmosphere is limited by the scarcity of the observations they are based on, so improvement of these models requires validation under different atmospheric conditions. Measurements of the absorption of the solar extreme ultraviolet (EUV) radiation in the upper atmosphere below 500 km by instruments operating on low-Earth orbits (LEO) satellites provide efficient means for such validation as well as for continuous monitoring of the upper atmosphere and for studying its response to the solar and geomagnetic activity. Method: This paper presents results of measurements of the solar EUV radiation in the 17 nm wavelength band made with the SPIRIT and TESIS telescopes on board the CORONAS satellites and the SWAP telescope on board the PROBA2 satellite in the occulted parts of the satellite orbits. The transmittance profiles of the atmosphere at altitudes between 150 and 500 km were derived from different phases of solar activity during solar cycles 23 and 24 in the quiet state of the magnetosphere and during the development of a geomagnetic storm. We developed a mathematical procedure based on the Tikhonov regularization method for solution of ill-posed problems in order to retrieve extinction coefficients from the transmittance profiles. The transmittance profiles derived from the data and the retrieved extinction coefficients are compared with simulations carried out with the NRLMSISE-00 atmosphere model maintained by Naval Research Laboratory (USA) and the DTM-2013 model developed at CNES in the framework of the FP7 project ATMOP. Results: Under quiet and slightly disturbed magnetospheric conditions during high and low solar activity the extinction coefficients

  13. Dust Models Paint Alien's View of Solar System

    NASA Video Gallery

    Dust in the Kuiper Belt, the cold-storage zone that includes Pluto, creates a faint infrared disk potentially visible to alien astronomers looking for planets around the sun. Neptune's gravitationa...

  14. Solar Wind Slowdown Due to Dust Pickup during Interplanetary Field Enhancements

    NASA Astrophysics Data System (ADS)

    Lai, Hairong; Russell, Christopher; Wei, Hanying

    2013-04-01

    The interplanetary field enhancements (IFEs) are characterized by their cusp-shaped enhancement in the magnetic field magnitude. They are observed throughout the inner solar system from 0.72AU by Pioneer Venus Orbiter to 5AU by Ulysses. The annual IFE rate is ten at 0.72AU and around eight at 1AU, i.e., decreases as the heliocentric distance increases. Multiple-spacecraft observations show that IFEs are moving radially away from the Sun at nearly the ambient solar wind speed. During the IFE events, case studies show that while there are correlated diamagnetic compensations in pressure there are no significant correlated changes in the solar wind speed. An IFE formation mechanism that explains most of the IFE features is that IFEs result from interactions between solar wind and clouds of picked up nanoscale charged dust, which is released in interplanetary collisions between objects of 10 to 1000m in diameter. The enhanced magnetic field behaves as a magnetic barrier that can transfer momentum to the charged dust from the solar wind. Momentum lifts the dust outward in the solar gravitational well. A prediction of this hypothesis is that solar wind will be slowed down even when the IFEs have reached exactly the solar wind speed. To test this hypothesis, we perform a superposed analysis on the radial velocity of IFEs observed at 1AU. In contrast to the case studies, the statistical results have a significant change in speed. The velocity on the solar wind side of the IFEs is smaller than the ambient velocity. This slowdown increases for larger IFEs with larger estimated mass. In addition, the amount of momentum due to the solar wind slowdown is quantitatively consistent with the momentum expected to be needed to lift the dust out of the Sun's gravitational potential well, which is in strong support of our IFE formation mechanism.

  15. Chemical enrichment of the pre-solar cloud by supernova dust grains

    NASA Astrophysics Data System (ADS)

    Goodson, Matthew D.; Luebbers, Ian; Heitsch, Fabian; Frazer, Christopher C.

    2016-11-01

    The presence of short-lived radioisotopes (SLRs) in Solar system meteorites has been interpreted as evidence that the Solar system was exposed to a supernova shortly before or during its formation. Yet results from hydrodynamical models of SLR injection into the proto-solar cloud or disc suggest that gas-phase mixing may not be efficient enough to reproduce the observed abundances. As an alternative, we explore the injection of SLRs via dust grains as a way to overcome the mixing barrier. We numerically model the interaction of a supernova remnant containing SLR-rich dust grains with a nearby molecular cloud. The dust grains are subject to drag forces and both thermal and non-thermal sputtering. We confirm that the expanding gas shell stalls upon impact with the dense cloud and that gas-phase SLR injection occurs slowly due to hydrodynamical instabilities at the cloud surface. In contrast, dust grains of sufficient size ( ≳ 1 μm) decouple from the gas and penetrate into the cloud within 0.1 Myr. Once inside the cloud, the dust grains are destroyed by sputtering, releasing SLRs and rapidly enriching the dense (potentially star-forming) regions. Our results suggest that SLR transport on dust grains is a viable mechanism to explain SLR enrichment.

  16. Charge States of Solar Cosmic Rays and Constraints on Acceleration Times and Transport within the Corona

    NASA Astrophysics Data System (ADS)

    Ruffolo, David

    1997-04-01

    We examine effects on the charge states of solar cosmic ray ions due to shock heating or stripping at suprathermal ion velocities. Recent measurements of the mean charges of various elements after the gradual solar flares of 1992 Oct 30 and 1992 Nov 2 allow one to place limits on the product of the electron density times the acceleration or coronal residence time experienced by the escaping ions. In particular, any residence in coronal loops must be for <0.03 s, which rules out models of coronal transport (e.g., the bird cage model) in which escaping ions travel to distant solar longitudes within coronal loops. The results do not contradict models of distributed shock acceleration of energetic ions from coronal plasma at various solar longitudes, followed by prompt injection into the interplanetary medium.

  17. A Next-Generation Model of the Corona and Solar Wind

    DTIC Science & Technology

    2011-03-31

    instruments. The user can select from 6 different magnetographs for the input boundary data: Mount Wilson Observa- tory (MWO); the National Solar...incorporation of the WSA model for quick look solutions, and the use of multiple solar observatories for magnetic map input. 15. SUBJECT TERMS...different observatories and different map filtering. Third, this new version of WSA allows the development of higher resolution potential field

  18. On the Remote Detection of Suprathermal Ions in the Solar Corona and their Role as Seeds for Solar Energetic Particle Production (Invited)

    NASA Astrophysics Data System (ADS)

    Laming, J. M.; Moses, J.; Ko, Y.; Ng, C. K.; Rakowski, C. E.; Tylka, A. J.

    2013-12-01

    We calculate the growth rate for field aligned Alfven waves generated by streaming preshock ions. The ions are assumed to be in a "kappa" distribution, and we calculate growth rates as a function of shock obliquity and kappa, for shocks of different Alfven Mach number. As the shock Alfven Mach number increases, the constraints on kappa and the shock obliquity lessen. Less significant departures from a Maxwellian distribution in the upstream medium are required for wave growth, which may also extend out to quasi-perpendicular shocks of higher obliquity. Taking a positive wave growth in such conditions ahead of a shock as a necessary condition for particle acceleration, we use the derived values of kappa to predict the detectability of a seed particle distribution upstream of shocks of various parameters through spectroscopic observations of the Lyman alpha line profile. Within 3-4 solar radii, suprathermal protons can charge exchange with neutral H in the solar corona giving rise to a kappa distribution of neutral H, that scatters disk Lyman alpha radiation into a line profile with extended wings. We define the essential characteristics of a spectrometer designed to detect such a seed particle population, as a means of forecasting the likely solar energetic particle effectiveness of any following coronal mass ejection. Work supported by basic research funds of the Office of Naval Research and by NASA ADAP grant NNH10A009I.

  19. On the Remote Detection of Suprathermal Ions in the Solar Corona and their Role as Seeds for Solar Energetic Particle Production

    NASA Astrophysics Data System (ADS)

    Laming, J. Martin; Moses, Daniel; Ko, Yuan-Kuen; Ng, Chee; Tylka, Allan; Rakowski, Cara

    We calculate the growth rate for field aligned Alfven waves generated by streaming preshock ions. The ions are assumed to be in a "kappa" distribution, and we calculate growth rates as a function of shock obliquity and kappa, for shocks of different Alfven Mach number. As the shock Alfven Mach number increases, the constraints on kappa and the shock obliquity lessen. Less significant departures from a Maxwellian distribution in the upstream medium are required for wave growth, which may also extend out to quasi-perpendicular shocks of higher obliquity. Taking a positive wave growth in such conditions ahead of a shock as a necessary condition for particle acceleration, we use the derived values of kappa to predict the detectability of a seed particle distribution upstream of shocks of various parameters through spectroscopic observations of the Lyman alpha line profile. Within 3-4 solar radii, suprathermal protons can charge exchange with neutral H in the solar corona giving rise to a kappa distribution of neutral H, that scatters disk Lyman alpha radiation into a line profile with extended wings. We define the essential characteristics of a spectrometer designed to detect such a seed particle population, as a means of forecasting the likely solar energetic particle effectiveness of any following coronal mass ejection. Work supported by basic research funds of the Office of Naval Research and by NASA ADAP grant NNH10A009I.

  20. Structure, Dynamics, and Spectra of the Solar Corona at the 2013 and 2015 Total Eclipses and Plans for 2017's American Totality

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Dantowitz, Ronald; Voulgaris, Aristeidis

    2016-01-01

    We observed the total solar eclipses of 3 November 2013 from Gabon and of 20 March 2015 from Svalbard in clear skies with cameras to image the solar corona at high resolution and with spectrographs for coronal emission lines. We report on the composite images showing coronal structure and (in comparison with other sites' images) dynamics, as well as the relation of our inner- and middle-corona composite images with surface EUV images from SDO and SWAP and with the outer-corona images from the coronagraphs on SOHO/LASCO. Our spectra show not only the common forbidden lines of Fe XIV (green line) and Fe X (red line) but also rarer species such as Ca XV. Finally, we describe our planned suite of observations for the 21 August 2017 solar eclipse, whose path of totality will cross the United States from Pacific to Atlantic, with more-favorable cloudiness statistics for western sites.Our Gabon and Svalbard expeditions were supported by grants from the Committee for Research and Exploration of the National Geographic Society.

  1. The Observation of Total Solar Eclipse on March 29,2006 in Kazakhstan

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.; Rspaev, F. K.; Minasyants, G. S.; Dubovitskiy, A. I.; Chalabaev, A.

    The observations of total solar eclipse on March 29, 2006 were carried out by forces of united expedition of Fesenkov Astrophysical institute in Kazakhstan (settlement Mugalghar, Actobe region). The main problem was the interferometric observations of the outer solar corona at distances from 3 to 10 solar radii. The field of radial velocities of dust was obtained by Doppler shifts of absorption lines.

  2. Stereoscopic observations of a solar flare hard X-ray source in the high corona

    SciTech Connect

    Kane, S.R.; Mctiernan, J.; Loran, J.; Fenimore, E.E.; Klebesadel, R.W.; Laros, J.G. Los Alamos National Laboratory, NM )

    1992-05-01

    The vertical structure of the impulsive and gradual hard X-ray sources in high coronae and the characteristics of the impulsive soft X-ray emission are investigated on the basis of PVE, ICE, and GOES observations of the energetic flare on February 16, 1984. The average photon spectra observed by these instruments during the impulsive and gradual hard X-ray bursts are summarized. A comparison of these unocculted and partially occulted spectra shows that the sources of the impulsive hard X-ray (greater than about 25 keV) and impulsive soft X-ray (2-5 keV) emissions in this flare extended to coronal altitudes greater than about 200,000 km above the photosphere. At about 100 keV, the ratio of the coronal source brightness to the total source brightness was 0.001 during the impulsive phase and less than about 0.01 during the gradual hard X-ray burst. The sources of the gradual hard X-ray burst and gradual soft X-ray burst were almost completely occulted, indicating that these sources were located at heights less than 200,000 km above the photosphere. 47 refs.

  3. EUV analysis of an active region. [of solar corona in limb region

    NASA Technical Reports Server (NTRS)

    Raghavan, N.; Withbroe, G. L.

    1975-01-01

    A sequence of extreme-ultraviolet (EUV) spectroheliograms of McMath region No. 10283 were obtained by OSO-6. The lines O VI (1032 A) Mg X (625 A), Si XII (499 A), and Fe XVI (335 A) were used to determine coronal temperatures and densities above the active region. A comparison of theoretical and observed line ratios yielded coronal temperatures of 2.2 to 2.3 million K above the active region and 2.0 to 2.1 million K in the surrounding area. The temperatures derived from ratios involving the O VI intensities are systematically higher than the others. This is attributed to an error in the theoretical O VI intensities. The intensities observed above the limb are compared with intensities predicted by a simple model based on cylindrical geometry. The overall agreement shows that the assumption of an isothermal corona in hydrostatic equilibrium above the active region is a resonable working hypothesis and that the adopted geometrical model for the electron density distribution is adequate.

  4. Observational Evidence for the Associated Formation of Blobs and Raining Inflows in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Sanchez-Diaz, E.; Rouillard, A. P.; Davies, J. A.; Lavraud, B.; Sheeley, N. R.; Pinto, R. F.; Kilpua, E.; Plotnikov, I.; Genot, V.

    2017-01-01

    The origin of the slow solar wind is still a topic of much debate. The continual emergence of small transient structures from helmet streamers is thought to constitute one of the main sources of the slow wind. Determining the height at which these transients are released is an important factor in determining the conditions under which the slow solar wind forms. To this end, we have carried out a multipoint analysis of small transient structures released from a north–south tilted helmet streamer into the slow solar wind over a broad range of position angles during Carrington Rotation 2137. Combining the remote-sensing observations taken by the Solar-TErrestrial RElations Observatory (STEREO) mission with coronagraphic observations from the SOlar and Heliospheric Observatory (SOHO) spacecraft, we show that the release of such small transient structures (often called blobs), which subsequently move away from the Sun, is associated with the concomitant formation of transient structures collapsing back toward the Sun; the latter have been referred to by previous authors as “raining inflows.” This is the first direct association between outflowing blobs and raining inflows, which locates the formation of blobs above the helmet streamers and gives strong support that the blobs are released by magnetic reconnection.

  5. LADEE UVS Observations of Solar Occultation by Exospheric Dust Above the Lunar Limb

    NASA Technical Reports Server (NTRS)

    Wooden, D. H.; Cook, A. M.; 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 greater than 500) for 20-30 ms integration times. The 1-degree solar viewer field of view subtends a diameter of approximately 8 km at a distance of 400-450 km.

  6. 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

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

    SciTech Connect

    Goossens, M.; Soler, R.; Arregui, I.

    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.

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

    SciTech Connect

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

    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 Å and 280-330 Å. 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 Å. 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.

  9. 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.

  10. 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.

  11. Understanding coronal mass ejections and associated shocks in the solar corona by merging multiwavelength observations

    SciTech Connect

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

    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.

  12. STELLAR CORONAE, SOLAR FLARES: A DETAILED COMPARISON OF {sigma} GEM, HR 1099, AND THE SUN IN HIGH-RESOLUTION X-RAYS

    SciTech Connect

    Huenemoerder, David P.; Phillips, Kenneth J. H.; Sylwester, Janusz; Sylwester, Barbara E-mail: kennethjhphillips@yahoo.com E-mail: bs@cbk.pan.wroc.pl

    2013-05-10

    The Chandra High Energy Transmission Grating Spectrometer (HETG) spectra of the coronally active binary stars {sigma} Gem and HR 1099 are among the highest fluence observations for such systems taken at high spectral resolution in X-rays with this instrument. This allows us to compare their properties in detail to solar flare spectra obtained with the Russian CORONAS-F spacecraft's RESIK instrument at similar resolution in an overlapping bandpass. Here we emphasize the detailed comparisons of the 3.3-6.1 A region (including emission from highly ionized S, Si, Ar, and K) from solar flare spectra to the corresponding {sigma} Gem and HR 1099 spectra. We also model the larger wavelength range of the HETG, from 1.7 to 25 A - having emission lines from Fe, Ca, Ar, Si, Al, Mg, Ne, O, and N-to determine coronal temperatures and abundances. {sigma} Gem is a single-lined coronally active long-period binary which has a very hot corona. HR 1099 is a similar, but shorter period, double-lined system. With very deep HETG exposures we can even study emission from some of the weaker species, such as K, Na, and Al, which are important since they have the lowest first ionization potentials, a parameter well known to be correlated with elemental fractionation in the solar corona. The solar flare temperatures reach Almost-Equal-To 20 MK, comparable to the {sigma} Gem and HR 1099 coronae. During the Chandra exposures, {sigma} Gem was slowly decaying from a flare and its spectrum is well characterized by a collisional ionization equilibrium plasma with a broad temperature distribution ranging from 2 to 60 MK, peaking near 25 MK, but with substantial emission from 50 MK plasma. We have detected K XVIII and Na XI emission which allow us to set limits on their abundances. HR 1099 was also quite variable in X-rays, also in a flare state, but had no detectable K XVIII. These measurements provide new comparisons of solar and stellar coronal abundances, especially at the lowest first ionization

  13. 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 Ω ∝ (ωL)1/3(ωc/ω) somewhat less than 1, contrary to previous ideas. Only o mode is produced for Ω and somewhat greater than 1.5. Here ωc is the (angular) electron cyclotron frequency, ω 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 Ω increases. (4) As Ω 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 Ω 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 Ω 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

  14. LASCO Observations of the F-Corona

    NASA Astrophysics Data System (ADS)

    Andrews, M. D.

    2002-05-01

    The LASCO coronagraphs on SOHO have been taking a regular series of images since May 1996. Minimum images have been calculated approximately every two weeks. While the images are dominated by stray light near the occulting disks, it does appear that these minimum images are the F-corona. The brightness varies by approximately 10% with an annual cycle due to the change in Earth--Sun distance. There is no change of the brightness that correlates with solar cycle. The combined C2 data between 4.5--6.4 Rsun and the C3 data between 6--28 Rsun are well fit by a single power-law. This power-law is a function of the angular distance from the plane of symmetry of the dust. In the plane of symmetry, B ~ R-2.1 while perpendicular to the symmetry plane the brightness scales as R-2.4. The observed brightnesses have been corrected to a common distance of 1AU using these power-laws. After the distance correction, the brightness varies by 1-2% with brightness peaks every six months. The brightness peaks occur at the time that SOHO is in the symmetry plane of the F-corona. These data are fully consistent with the properties of the F-corona derived from Helios data (C.~Leinert et~al., Astron. Astrophys. 82, 328, 1980.)

  15. Solar Activity and Motions in the Solar Chromosphere and Corona at the 2012 and 2013 Total and Annular Eclipses in the U.S., Australia, and Africa

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Babcock, B. A.; Davis, A. B.; Demianski, M.; Lucas, R.; Lu, M.; Dantowitz, R.; Rusin, V.; Saniga, M.; Seaton, D. B.; Gaintatzis, P.; Voulgaris, A.; Seiradakis, J. H.; Gary, D. E.; Shaik, S. B.

    2014-01-01

    Our studies of the solar chromosphere and corona at the 2012 and 2013 eclipses shortly after cycle maximum 24 (2011/2012) of solar activity (see: http://www.swpc.noaa.gov/SolarCycle/) involved radio observations of the 2012 annular eclipse with the Jansky Very Large Array, optical observations of the 2012 total eclipse from Australia, optical observations of the 2013 annular eclipse from Tennant Creek, Australia, and the 3 November 2013 total solar eclipse from Gabon. Our observations are coordinated with those from solar spacecraft: Solar Dynamics Observatory AIA and HMI, Hinode XRT and SOT, SOHO LASCO and EIT, PROBA2 SWAP, and STEREO SECCHI. Our 2012 totality observations include a CME whose motion was observed with a 37-minute interval. We include first results from the expedition to Gabon for the 3 November 2013 eclipse, a summary of eclipse results from along the path of totality across Africa, and a summary of the concomitant spacecraft observations. The Williams College 2012 expeditions were supported in part by NSF grant AGS-1047726 from Solar Terrestrial Research/NSF AGS, and by the Rob Spring Fund and Science Center funds at Williams. The JVLA is supported by the NSF. The Williams College 2013 total-eclipse expedition was supported in part by grant 9327-13 from the Committee for Research and Exploration of the National Geographic Society. ML was also supported in part by a Grant-In-Aid of Research from the National Academy of Sciences, administered by Sigma Xi, The Scientific Research Society (Grant ID: G20120315159311). VR and MS acknowledge support for 2012 from projects VEGA 2/0003/13 and NGS-3139-12 of the National Geographic Society. We are grateful to K. Shiota (Japan) for kindly providing us with some of his 2012 eclipse coronal images. We thank Alec Engell (Montana State U) for assistance on site, and Terry Cuttle (Queensland Amateur Astronomers) for help with site arrangements. We thank Aram Friedman (Ansible Technologies), Michael Kentrianakis

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

    SciTech Connect

    Sandford, S.A.

    1986-12-01

    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 in, such dust particles accumulate solar flare tracks. The accumulated track density for a given dust grain is a function of the duration of its space exposure and its distance from the sun. Using a computer model, it was determined that the expected track density distributions from grains produced by comets are very different from those produced by asteroids. Individual asteroids produce populations of particles that arrive at 1 AU with scaled track density distributions containing spikes, while comets supply particles with a flatter and wider distribution of track densities. 36 references.

  17. Polarimetric Studies of Solar Light Scattered by Interplanetary Dust Particles and the Eye-Sat Project

    NASA Astrophysics Data System (ADS)

    Levasseur-Regourd, A. C.; Lasue, J.

    2014-12-01

    Studying intensity and linear polarization of the solar light scattered by interplanetary dust is of interest for various reasons. This so-called zodiacal light constitutes a faint polarized glow that constitutes a changing foreground for observations of faint extended astronomical sources. Besides, analysis of its polarization provides information on properties of the dust particles, such as spatial density, morphology and complex refractive index. Previous observations, mostly from the Earth and with a resolution in the 10° range, have been used to infer that the local polarization at 90° phase angle increases with increasing solar distance. Numerical simulations suggest that, in the inner solar system, interplanetary dust particles consist of a mixture of absorbing and less absorbing materials, and that radial changes originate in a decrease of organic materials with decreasing solar distance under alteration or evaporation processes. To improve the quality of data on zodiacal light polarimetry, Eye-Sat nanosat is being developed in the context of the JANUS CNES cubesats program for students. The project is now in phase C-D, for a piggy-back launch in 2016. Eye-Sat triple cubesat is anticipated to demonstrate the feasibility of a series of new on-board technologies. Moreover, during its one-year mission, zodiacal light intensity and polarization are to be measured, for the first time with a spatial resolution of about 1° over a wide portion of the sky and in four different wavelengths (visible to near-IR), leading to a better assessment of interplanetary dust properties. Finally, a significant fraction of the interplanetary dust is estimated to come from comets, the most pristine objects to be found in the inner solar system. While similarities have indeed been noticed between polarimetric properties of interplanetary and cometary dust particles, the latter being currently extensively documented by the Rosetta mission to comet 67P

  18. Implantation in interplanetary dust of rare-gas ions from solar flares.

    PubMed

    Tilles, D

    1966-08-26

    Measurements of excess Ar(36) + Ar(38) ( released mainly at 1200 degrees C) in magnetic concentrates of Pacific sediments and in a dense concentrate of Greenland dust agree within an order of magnitude with expected concentrations implanted by solar-flare ion streams of energy less than 10 Mev per atomic-mass unit. The agreement implies that more than 10 percent of each concentrate may be extraterrestrial, depending on size distribution and flare spectra. Rare-gas measurements on fine-grained dust can provide data on: solar-flare "paleo-ion" fluxes, energy spectra, and isotopic abundances; identification, mineralogy, and chemistry of interplanetary dust; influx rates to Earth and sedimentation rates of oceanic cores; and lunar-surface residence and mixing times.

  19. Studies of acceleration processes in the corona using ion measurements on the solar probe mission

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1978-01-01

    The energy spectra and composition of particles escaping from the Sun provide essential information on mechanisms responsible for their acceleration, and may also be used to characterize the regions where they are accelerated and confined and through which they propagate. The suprathermal energy range, which extends from solar wind energies (approximately 1 KeV) to about 1 MeV/nucleon, is of special interest to studies of nonthermal acceleration processes because a large fraction of particles is likely to be accelerated into this energy range. Data obtained from near earth observations of particles in the suprathermal energy range are reviewed. The necessary capabilities of an a ion composition experiment in the solar probe mission and the required ion measurements are discussed. A possible configuration of an instrument consisting of an electrostatic deflection system, modest post acceleration, and a time of flight versus energy system is described as well as its possible location on the spacecraft.

  20. North-south asymmetric solar cycle evolution: Signatures in the photosphere and consequences in the corona

    SciTech Connect

    Virtanen, I. I.; Mursula, K.

    2014-02-01

    The heliospheric current sheet is the continuum of the coronal magnetic equator that divides the heliospheric magnetic field into two sectors (polarities). Several recent studies have shown that the heliospheric current sheet is southward shifted during approximately 3 years in the solar declining phase (the so-called bashful ballerina phenomenon). In this article we study the hemispherical asymmetry in the photospheric and coronal magnetic fields using Wilcox Solar Observatory measurements of the photospheric magnetic field since 1976 as well as the potential field source surface model. Multipole analysis of the photospheric magnetic field shows that during the late declining phase of solar cycles since the 1970s, the 'bashful ballerina phenomenon' is a consequence of the g{sub 2}{sup 0} quadrupole term, signed oppositely to the dipole moment. Surges of new flux transport magnetic field from low latitudes to the poles, thus leading to a systematically varying contribution to the g{sub 2}{sup 0}-term from different latitudes. In the case of a north-south asymmetric flux production, this is seen as a quadrupole contribution traveling toward higher latitudes. When the quadrupole term is largest, the main contribution comes from the polar latitudes. At least during the four recent solar cycles, the g{sub 2}{sup 0}-term arises because the magnitude of the southern polar field is larger than the magnitude found in the north in the declining phase of the cycle. In the heliosphere this hemispheric asymmetry of the coronal fields is seen as a southward shift of the heliospheric current sheet by about 2°.

  1. North-South Asymmetric Solar Cycle Evolution: Signatures in the Photosphere and Consequences in the Corona

    NASA Astrophysics Data System (ADS)

    Virtanen, I. I.; Mursula, K.

    2014-02-01

    The heliospheric current sheet is the continuum of the coronal magnetic equator that divides the heliospheric magnetic field into two sectors (polarities). Several recent studies have shown that the heliospheric current sheet is southward shifted during approximately 3 years in the solar declining phase (the so-called bashful ballerina phenomenon). In this article we study the hemispherical asymmetry in the photospheric and coronal magnetic fields using Wilcox Solar Observatory measurements of the photospheric magnetic field since 1976 as well as the potential field source surface model. Multipole analysis of the photospheric magnetic field shows that during the late declining phase of solar cycles since the 1970s, the "bashful ballerina phenomenon" is a consequence of the g^{0}_{2} quadrupole term, signed oppositely to the dipole moment. Surges of new flux transport magnetic field from low latitudes to the poles, thus leading to a systematically varying contribution to the g^{0}_{2}-term from different latitudes. In the case of a north-south asymmetric flux production, this is seen as a quadrupole contribution traveling toward higher latitudes. When the quadrupole term is largest, the main contribution comes from the polar latitudes. At least during the four recent solar cycles, the g^{0}_{2}-term arises because the magnitude of the southern polar field is larger than the magnitude found in the north in the declining phase of the cycle. In the heliosphere this hemispheric asymmetry of the coronal fields is seen as a southward shift of the heliospheric current sheet by about 2°.

  2. Modeling the Corona and Solar Wind using ADAPT Maps that Include Far-Side Observations

    DTIC Science & Technology

    2013-11-01

    document for any purpose other than Government procurement does not in any way obligate the U.S. Government. The fact that the Government formulated...Government’s approval or disapproval of its ideas or findings. Approved for public release; distribution is unlimited. REPORT DOCUMENTATION PAGE...Los Alamos National Laboratory ( LANL ) and the National Solar Observatory (NSO), has developed a model that produces more realistic estimates of the

  3. Relative elemental abundance and heating constraints determined for the solar corona from SERTS measurements

    NASA Technical Reports Server (NTRS)

    Falconer, David A.

    1994-01-01

    Intensities of EUV spectral lines were measured as a function of radius off the solar limb by two flights of Goddard's Solar EUV Rocket Telescope and Spectrograph (SERTS) for three quiet sun regions. The density scale height, line-ratio densities, line-ratio temperatures, and emission measures were determined. The line-ratio temperature determined from the ionization balances of Arnaud and Rothenflug (1985) were more self-consistent than the line-ratio temperatures obtained from the values of Arnaud and Raymond (1992). Limits on the filling factor were determined from the emission measure and the line-ratio densities for all three regions. The relative abundances of silicon, aluminum, and chromium to iron were determined. Results did agree with standard coronal relative elemental abundances for one observation, but did not agree for another. Aluminum was overabundant while silicon was underabundant. Heating was required above 1.15 solar radii for all three regions studied. For two regions, local nonconductive heating is needed for any filling factor, and in all three regions for filling factor of 0.1.

  4. Solar Wind Speed Structure in the Inner Corona at 3-12 Ro

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1995-01-01

    Estimates of solar wind speed obtained by Armstrong et al. [1986] based on 1983 VLA multiple-station intensity scintillation measurements inside 12 R(sub o) have been correlated with the electron density structure observed in white-light coronagraph measurements. The observed large- scale and apparently systematic speed variations are found to depend primarily on changes in heliographic latitude and longitude, which leads to the first results on large-scale speed structure in the acceleration region of the solar wind. Over an equatorial hole, solar wind speed is relatively steady, with peak-to-peak variations of 50 km/s and an average of 230 km/s. In contrast, the near-Sun flow speed across the streamer belt shows regular large-scale variations in the range of 100-300 km/s. Based on four groups of data, the gradient is 36 km/s per degree in heliocentric coordinates (corresponding to a rise of 260 km/s over a spatial distance on the Sun of two arcmin) with a standard deviation of 2.4 km/s per degree. The lowest speeds most likely coincide with the stalks of coronal streamers observed in white-light measurements. The detection of significant wind shear over the streamer belt is consistent with in situ and scintillation measurements showing that the density spectrum has a power-law form characteristic of fully developed turbulence over a much broader range of scales than in neighboring regions.

  5. Coupling of the Photosphere to the Solar Corona: A laboratory and observational study of Alfvén wave interaction with a neutral gas

    SciTech Connect

    watts, Christopher

    2010-01-31

    The grant funded a three year project to investigate the role of Alfvén waves as a possible mechanism heating plasmas, with relevance to solar coronal heating. Evidence suggests that there is strong coupling between the solar photosphere, corona and solar wind through Alfvén wave interaction with the neutral gas particles. A laboratory experimental and solar observational plan was designed to investigate in detail this interaction. Although many of the original research goals were met, difficulties in detecting the Alfvén wave signature meant that much of the research was stymied. This report summaries the work during the grant period, the challenges encountered and overcome, and the future research directions.

  6. Comparing the solar magnetic field in the corona and in the inner heliosphere during solar cycles 21-23

    NASA Astrophysics Data System (ADS)

    Virtanen, I. I.; Mursula, K.

    2009-04-01

    We compare the open solar magnetic field estimated by the PFSS model based on the WSO photospheric field observations, with the inner heliospheric magnetic field. We trace the observed radial HMF into the coronal PFSS boundary at 2.5 solar radii using the observed solar wind velocity, and determine the PFSS model field at the line-of-sight footpoint. Comparing the two field values, we calculate the power n of the apparent decrease of the radial field. According to expectations based on Maxwell's equations, also reproduced by Parker's HMF model, the radial HMF field should decrease with n=2. However, comparison gives considerably lower values of n, indicating the effect of HCS in the PFSS model and the possible superexpansion. The n values vary with solar cycle, being roughly 1.3-1.4 at minima and about 1.7 at maxima. Interestingly, the n values for the two HMF sectors show systematic differences in the late declining to minimum phase, with smaller n values for the HMF sector dominant in the northern hemisphere. This is in agreement with the smaller field value in the northern hemisphere and the southward shifted HCS, summarized by the concept of the bashful ballerina. We also find that the values of n during the recent years, in the late declining phase of solar cycle 23, are significantly larger than during the same phase of the previous cycles. This agrees with the exceptionally large tilt of the solar dipole at the end of cycle 23. We also find that the bashful ballerina appears even during SC 23 but the related hemispheric differences are smaller than during the previous cycles.

  7. Dust Cloud near the Sun

    NASA Astrophysics Data System (ADS)

    Mann, Ingrid; Krivov, Alexander; Kimura, Hiroshi

    2000-08-01

    General structure and composition of the near-solar dust cloud are investigated. Based on estimates for sources and transport of dust to the near-solar region, we derive a representative set of trajectories of dust grains by numerical integrations and obtain the spatial distribution of different dust populations within 10 solar radii ( R⊙) from the Sun. For the radial structure, we find the dust number density to be enhanced by a factor of 1 to 4 in a typical heliocentric distance zone with a width of 0.2 R⊙ in the sublimation region—the formation of a dust ring—depending on the materials and porosities considered. The excess density in the ring increases with increasing initial size for porous grains and decreases for compact ones. Non-zero eccentricities of the dust orbits decrease the enhancement. Moderate enhancements that we predict are consistent with eclipse observations, most of which have not shown any peak features in the F-corona brightness at several solar radii. We describe typical features of β-meteoroids formed by the sublimation of particles near the Sun and estimate the total mass loss due to this mechanism to range between 1 and 10 kg s -1. For the vertical structure of the dust cloud we show that grains larger than ˜10 μm in size keep in a disk with a typical thickness of tens degrees; grains with radii of several μm fill in a broader disk-like volume which is tilted off the ecliptic plane by a variable angle depending on the solar activity cycle; submicrometer-sized grains form a nearly spherical halo around the Sun with a radius of more than 10 R⊙. From our present knowledge we cannot exclude the existence of an additional spheroidal component of larger grains near the Sun, which depends on how effective long-period comets are as sources of dust. Estimates of absolute number densities and local fluxes of dust show that simple extrapolation of the interplanetary dust cloud into the solar vicinity does not describe the dust cloud

  8. Dust Astronomy: New venues in interplanetary and interstellar dust research

    NASA Astrophysics Data System (ADS)

    Grün, E.; Hahn, J.; Hamilton, D.; Harris, W.; Horanyi, Mihaly; Huestis, D. L.; Krivov, Alexander; Levasseur-Regourd, A. C.; Liou, J. C.; Lisse, C.; Kuchner, M.; Meisel, D.; Reach, W. T.; Snow, T. P.; Stansberry, J.; Sykes, M.; Yano, H.; Zolensky, M.

    2001-11-01

    Dust particles, like photons, are born at remote sites in space and time. From knowledge of the dust particles' birthplace, and the particles' bulk properties, we can learn about the remote environment out of which the particles were formed and how those particles have evolved physically and dynamically. Remote sensing and in-situ methods, combined with sample analysis and theory, allow us to make a global assessment of dust origin and production in our solar system and its context within the local interstellar environment. Born in the expanding atmospheres of high-luminosity stars or in supernova remnants, interstellar grains provide the seeds that grow in cool interstellar clouds by accretion of atoms and molecules and by agglomeration. Ultimately, interstellar grains can be incorporated in newly forming stars, or they can become part of planetary systems. Reborn from comets, asteroids, Kuiper belt objects and satellites, inter- and circumplanetary dust particles populate our own planetary system. Key issues addressed by space measurements are: - Determination of the total inventory of dust (size, composition, shape, spatial distribution, and temporal variations) in the Solar System. - Characterization and analysis of interstellar dust inside and outside the heliosphere. - Exploration of the dusty environments in the F-corona, near comets, in the asteroid belt and in the Kuiper belt. - Determination of sources, dynamics, and sinks of dust in planetary environs (from Mercury to Pluto). These issues will be supported by ground-based observations, theoretical modeling studies and laboratory measurements.

  9. Using the ionospheric response to the solar eclipse on 20 March 2015 to detect spatial structure in the solar corona.

    PubMed

    Scott, C J; Bradford, J; Bell, S A; Wilkinson, J; Barnard, L; Smith, D; Tudor, S

    2016-09-28

    The total solar eclipse that occurred over the Arctic region on 20 March 2015 was seen as a partial eclipse over much of Europe. Observations of this eclipse were used to investigate the high time resolution (1 min) decay and recovery of the Earth's ionospheric E-region above the ionospheric monitoring station in Chilton, UK. At the altitude of this region (100 km), the maximum phase of the eclipse was 88.88% obscuration of the photosphere occurring at 9:29:41.5 UT. In comparison, the ionospheric response revealed a maximum obscuration of 66% (leaving a fraction, Φ, of uneclipsed radiation of 34±4%) occurring at 9:29 UT. The eclipse was re-created using data from the Solar Dynamics Observatory to estimate the fraction of radiation incident on the Earth's atmosphere throughout the eclipse from nine different emission wavelengths in the extreme ultraviolet (EUV) and X-ray spectrum. These emissions, having varying spatial distributions, were each obscured differently during the eclipse. Those wavelengths associated with coronal emissions (94, 211 and 335 Å) most closely reproduced the time varying fraction of unobscured radiation observed in the ionosphere. These results could enable historic ionospheric eclipse measurements to be interpreted in terms of the distribution of EUV and X-ray emissions on the solar disc.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.

  10. 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.

  11. The effect of the hot oxygen corona on the interaction of the solar wind with Venus

    NASA Technical Reports Server (NTRS)

    Belotserkovskii, O. M.; Mitnitskii, V. IA.; Breus, T. K.; Krymskii, A. M.; Nagy, A. F.

    1987-01-01

    A numerical gasdynamic model, which includes the effects of mass loading of the shocked solar wind, was used to calculate the density and magnetic field variations in the magnetosheath of Venus. These calculations were carried out for conditions corresponding to a specific orbit of the Pioneer Venus Orbiter (PVO orbit 582). A comparison of the model predictions and the measured shock position, density and magnetic field values showed a reasonable agreement, indicating that a gasdynamic model that includes the effects of mass loading can be used to predict these parameters.

  12. On the predominance of the radial component of the magnetic field in the solar corona

    NASA Technical Reports Server (NTRS)

    Habbal, S. R.; Woo, R.; Arnaud, J.

    2002-01-01

    In this paper, the polarized intensity measurements of the Fe XIII 10747 A line described by Arnaud are placed, for the first time, in the context of the corresponding pB images from the HAO Mauna Loa MkIII K-Coronameter, which first became available in 1980. It is shown how the predominance of the radial direction of the coronal magnetic field at solar maximum is consistent with radially expanding magnetic field lines coexisting with the large-scale structures associated with streamers.

  13. On Determination of 3D Morphology and Plasma Properties of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Gary, G. Allen; Davis, John M.; Moore, Ronald; Six, N. Frank (Technical Monitor)

    2002-01-01

    An earlier analysis preformed and published will be revisited and applied to SECCHI's observations. Using coronal models and imaging-rendering techniques we will investigate several important facts regarding the solar stereographic mission. A synthesized image will be presented formed from integrating the emission from the volume elements along the line-of-sight path through a three-dimensional volume. We used analysis of pairs of these synthesized images with various angular perspectives to investigate the effect of angular separation on mission objectives. The resulting images and analysis provide guidelines for developing a stereographic mission analysis program.

  14. NUMERICAL STUDY ON IN SITU PROMINENCE FORMATION BY RADIATIVE CONDENSATION IN THE SOLAR CORONA

    SciTech Connect

    Kaneko, T.; Yokoyama, T.

    2015-06-10

    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.

  15. Solar wind plasma profiles during interplanetary field enhancements (IFEs): Consistent with charged-dust pickup

    NASA Astrophysics Data System (ADS)

    Lai, H. R.; Wei, H. Y.; Russell, C. T.

    2013-06-01

    The solar wind contains many magnetic structures, and most of them have identifiable correlated changes in the flowing plasma. However, the very characteristic rise and fall of the magnetic field in an interplanetary field enhancement has no clear solar wind counterpart. It appears to be a pure magnetic ``barrier'' that transfers solar wind momentum to charged dust produced in collisions of interplanetary bodies in the size range of tens to hundreds of meters. This transfer lifts the fine scale dust out of the Sun's gravitational well. We demonstrate the lack of field-plasma correlation with several examples from spacecraft records as well as show an ensemble average velocity profile during IFEs which is consistent with our IFE formation hypothesis.

  16. Absorption and scattering properties of the Martian dust in the solar wavelengths.

    PubMed

    Ockert-Bell, M E; Bell JF 3rd; Pollack, J B; McKay, C P; Forget, F

    1997-04-25

    A new wavelength-dependent model of the single-scattering properties of the Martian dust is presented. The model encompasses the solar wavelengths (0.3 to 4.3 micrometers at 0.02 micrometer resolution) and does not assume a particular mineralogical composition of the particles. We use the particle size distribution, shape, and single-scattering properties at Viking Lander wavelengths presented by Pollack et al. [1995]. We expand the wavelength range of the aerosol model by assuming that the atmospheric dust complex index of refraction is the same as that of dust particles in the bright surface geologic units. The new wavelength-dependent model is compared to observations taken by the Viking Orbiter Infrared Thermal Mapper solar channel instrument during two dust storms. The model accurately matches afternoon observations and some morning observations. Some of the early morning observations are much brighter than the model results. The increased reflectance can be ascribed to the formation of a water ice shell around the dust particles, thus creating the water ice clouds which Colburn et al. [1989], among others, have predicted.

  17. Rocket studies of solar corona and transition region. [X-Ray spectrometer/spectrograph telescope

    NASA Technical Reports Server (NTRS)

    Acton, L. W.; Bruner, E. C., Jr.; Brown, W. A.; Nobles, R. A.

    1979-01-01

    The XSST (X-Ray Spectrometer/Spectrograph Telescope) rocket payload launched by a Nike Boosted Black Brant was designed to provide high spectral resolution coronal soft X-ray line information on a spectrographic plate, as well as time resolved photo-electric records of pre-selected lines and spectral regions. This spectral data is obtained from a 1 x 10 arc second solar region defined by the paraboloidal telescope of the XSST. The transition region camera provided full disc images in selected spectral intervals originating in lower temperature zones than the emitting regions accessible to the XSST. A H-alpha camera system allowed referencing the measurements to the chromospheric temperatures and altitudes. Payload flight and recovery information is provided along with X-ray photoelectric and UV flight data, transition camera results and a summary of the anomalies encountered. Instrument mechanical stability and spectrometer pointing direction are also examined.

  18. The effects of nonequilibrium ionization on the radiative losses of the solar corona

    NASA Technical Reports Server (NTRS)

    Spadaro, D.; Zappala, R. A.; Antiochos, S. K.; Lanzafame, G.; Noci, G.

    1990-01-01

    The emissivity of the ions of carbon and oxygen has been recalculated for a set of solar coronal loop models with a steady state siphon flow. The ion densities were calculated from the plasma velocities, temperatures, and densities of the models, and large departures from equilibrium were found. For purposes of comparison, the emissivity was calculated with and without the approximation of ionization equilibrium. Considerable differences in the radiative loss function Lambda(T) curve between equilibrium and nonequilibrium conditions were found. The nonequilibrium Lambda(T) function was then used to solve again the steady state flow equations of the loop models. The differences in the structure of these models with respect to the models calculated adopting the Lambda(T) curve in equilibrium are discussed.

  19. The thermal structure of solar coronal loops and implications for physical models of coronae

    NASA Technical Reports Server (NTRS)

    Raymond, J. C.; Foukal, P.

    1982-01-01

    EUV spectra of three active region loops observed above the solar limb with the SO55 spectrometer on Skylab are analyzed. It is noted that the lengths, peak temperatures, and pressures of the loops are typical of the X-ray coronal loops to which static models have been applied. It is found that the physical parameters of the coronal loop plasma derived from EUV spectra and raster pictures are not well represented by the static models. Although the loops also contain a significant quantity of cool plasma, no physical reason is found to differentiate them from other active region loops of similar length, pressure, and temperature. Several line ratios in the loop spectrum suggest departures from ionization equilibrium caused by rapid cooling. The source of this cooling material is discussed with reference to several models of loop dynamics.

  20. Soft X-ray images of the solar corona using normal incidence optics

    NASA Technical Reports Server (NTRS)

    Bruner, M. E.; Haisch, B. M.; Brown, W. A.; Acton, L. W.; Underwood, J. H.

    1988-01-01

    A solar coronal loop system has been photographed in soft X-rays using a normal incidence telescope based on multilayer mirror technology. The telescope consisted of a spherical objective mirror of 4 cm aperture and 1 m focal length, a film cassette, and a focal plane shutter. A metallized thin plastic film filter was used to exclude visible light. The objective mirror was covered with a multilayer coating consisting of alternating layers of tungsten and carbon whose combined thicknesses satisfied the Bragg diffraction condition for 44 A radiation. The image was recorded during a rocket flight on October 25, 1985 and was dominated by emission lines arising from the Si XII spectrum. The rocket also carried a high resolution soft X-ray spectrograph that confirmed the presence of Si XII line radiation in the source. This image represents the first successful use of multilayer technology for astrophysical observations.

  1. Particle acceleration in 3D single current sheets formed in the solar corona and heliosphere: PIC approach

    NASA Astrophysics Data System (ADS)

    Zharkova, V. V.; Siversky, T.

    2015-09-01

    Acceleration of protons and electrons in a reconnecting current sheet (RCS) is investigated with the test particle and particle-in-cell (PIC) approaches in a 3D magnetic topology. PIC simulations confirm a spatial separation of electrons and protons with respect to the midplane depending on the guiding field. Simulation reveals that the separation occurs in magnetic topologies with strong guiding fields and lasts as long as the particles are kept dragged into a current sheet. This separation produces a polarisation electric field induced by the plasma feedback to a presence of accelerated particles, which shape can change from symmetric towards the midplane (for weak guiding field) to fully asymmetric (for strong guiding field). Particles are found accelerated at a midplane of any current sheets present in the heliosphere to the energies up to hundred keV for electrons and hundred MeV for protons. The maximum energy gained by particles during their motion inside the current sheet is defined by its magnetic field topology (the ratio of magnetic field components), the side and location from the X-nullpoint, where the particles enter a current sheet. In strong magnetic fields of the solar corona with weaker guiding fields, electrons are found circulating about the midplane to large distances where proton are getting accelerated, creating about the current sheet midplane clouds of high energy electrons, which can be the source of hard X-ray emission in the coronal sources of flares. These electrons are ejected into the same footpoint as protons after the latter reach the energy sufficicent to break from a current sheet. In a weaker magnetic field of the heliosphere the bounced electrons with lower energies cannot reach the midplane turning instead at some distance D before the current sheet midplane by 180 degrees from their initial motion. Also the beams of accelerated transit and bounced particles are found to generate turbulent electric fields in a form of Langmuir

  2. 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.

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

    SciTech Connect

    Patsourakos, S.; Klimchuk, J. A.; Young, P. R. E-mail: james.a.klimchuk@nasa.gov

    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 Å 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.

  4. Probability of solar panel clearing events at the Insight landing sites (Mars) from a dust devil track survey

    NASA Astrophysics Data System (ADS)

    Reiss, D.; Lorenz, R. D.

    2015-10-01

    The InSight robotic lander is scheduled to land on Mars in September 2016. InSight was designed to perform the first comprehensive surface-based geophysical investigation of Mars [1]. Passage of vortices may have a number of influences on the geophysical measurements to be made by InSight. Seismic data could be influenced by dust devils and vortices via several mechanisms such as loading of the elastic ground by a surface pressure field which causes a local tilt [e.g. 2]. In addition, the power supply of the InSight instruments is provided by solar arrays. Solar-powered missions on Mars like the Sojourner rover in 1997 were affected by a decline in electrical power output by 0.2-0.3 %per day caused by steadily dust deposition on its horizontal solar panel [3]. The solar-powered Mars Exploration Rovers (MERs) Spirit and Opportunity experienced similar dust deposition rates [4] which led to steady power decrease over time endangering longer rover operation times. The much longer operation times of the rovers were made possible by unanticipated 'dust clearing events' of the solar arrays by wind gust or dust devils [5]. Recent studies imply that dust devils are primarily responsible for those recurrent 'dust clearing events' [6]. In this study we investigate the potential frequency of intense dust devil occurrences at the InSight landing site regions, which are able to remove dust from its solar panels. We analyzed newly formed dust devil tracks within a given time span using multi-temporal HiRISE image data covering the same surface area. Based on these measurements we will give encounter rate predictions of intense (high tangential speed and high pressure drop) dust devils with the InSight lander.

  5. Protostellar collapse, dust grains and solar system formation

    NASA Technical Reports Server (NTRS)

    Cassen, Patrick; Boss, Alan P.

    1988-01-01

    Attempts to understand the origin of the solar system come from two perspectives. The first is that of the insider looking out; the system components beyond the earth are examined in detail, their properties categorized, and explanations are sought that make sense of the patterns and relations among them. The primitive meteorites are prime objects of study from this perspective. The other perspective is that of the outsider looking in, considering other stars that are now in their formative stages and trying to understand the physical processes that govern all such events, under the assumption that the solar system is not unique. A compelling theory of the origin of the solar system must, of course, merge the fruits of both perspectives.

  6. CORONAS-F detection of gamma-ray emission from the solar flare on 29 October 2003

    NASA Astrophysics Data System (ADS)

    Kurt, Victoria; Kashapova, Larisa; Yushkov, Boris; Kudela, Karel; Galkin, Vladimir

    Appreciable HXR/gamma-ray emissions in the 0.015-150 MeV energy range associated with the solar flare on 29 October 2003 (X10/3B) were observed at 20:41-20:58 with the SPR-N and SONG instruments onboard the CORONAS-F mission. Two time intervals were identified which showed major changes in the intensity of these emissions. To specify the details of the spectral changes with time, we fitted the SONG energy loss spectra with a three-component model of incident gamma-ray spectrum: (1) a power law in energy, assumed to be due to electron bremsstrahlung; (2) a broad continuum produced by nuclear de-excitation gamma-lines; and (3) a broad gamma-line generated from pion decay. We study the relationship between non-imaging observations, particularly between time of pion-decay emission onset and motions in this solar flare, using HXR foot points (FP) separation and flare shear temporal behavior presented by (Ji et al., 2008). In this work it was shown that significant FP converging and unshearing motion occurred during the first flare interval. During this interval the primary bremsstrahlung extended to tens of MeV and de-excitation gamma-lines dominated. During the second interval after 20:45 the FPs began to move apart. We found out that starting from 20:46, the gamma-emission spectrum revealed a feature attributed to pion-decay. It means that the effective acceleration of protons to energies above 300 MeV (pion-production threshold) occurred coincidently with a change of the flare magnetic structure. The maximum intensity of the pion-decay gamma emission was observed at 20:49 and proved to be 2.0•10-4 photons cm-2 s-1 MeV-1 at 100 MeV. This flare was accompanied by GLE-66. Using the data of the world neutron monitor network, we found its onset as 20:59 which corresponds to a reasonable propagation time of protons with ~ 0.5-2 GeV energy on the assumption that proton acceleration began at 20:46.

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

    SciTech Connect

    Raymond, J. C.; McCauley, P. I.; Cranmer, S. R.; Downs, C.

    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.