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Sample records for solar dust corona

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

    E-print Network

    Petrovay, Kristóf

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

  2. Extreme Ultraviolet Spectroscopy of the Solar Corona

    E-print Network

    Del Zanna, Giulio

    of Central Lancashire July 1999 #12;Abstract New Extreme Ultra-Violet (EUV) observations of the solar corona of accuracy and completeness of the CHIANTI atomic database, used throughout this thesis, has allowed

  3. 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.

  4. The Making of the Film, SOLAR CORONA

    E-print Network

    Beeler, Michael

    1973-02-01

    The film SOLAR CORONA was made from data taken from August 14, 1969 through May 7, 1970, by OSO-VI, one of the Orbiting Satellite Observatories. One of the experiments on board scanned across and up and down the image of ...

  5. Turbulent photospheric drivers of multiscale solar corona

    NASA Astrophysics Data System (ADS)

    Uritsky, Vadim M.; Ofman, Leon; Davila, Joseph M.

    2015-04-01

    We investigate the collective dynamics of transient photospheric and coronal events detected using high-resolution solar magnetograms and coronal emission images. We focus on statistical, ensemble-averaged properties of the interacting solar regions [Uritsky et al., 2011, 2013, 2014; Uritsky and Davila, 2012], as opposed to case-oriented methodologies recruited in some previous studies. The behavior of solar events is studied in the three-dimensional space-time enabling accurate representation of the event evolution. By applying advanced data analysis methods including feature tracking algorithms, multiscale correlation analysis and scaling analysis techniques, we identify leading physical scenarios of the photosphere - corona coupling in quiet and active solar regions, and strive to identify new statistical precursors of coronal eruptions. We also discuss the possibility of modeling multiscale photosphere - corona interactions using idealized three-dimensional MHD models. The obtained results shed a new light on the origin of multiscale dissipation in the solar corona by enabling quantitative validation of several popular statistical physical scenarios, such as e.g. intermittent turbulence, self-organized criticality, and topological complexity.

  6. 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.

  7. 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.

  8. 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.

  9. Nonlinear Plasma Physics of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Priest, Eric R.

    2011-01-01

    As a tribute to Dennis Papadopoulos, we present a review of some recent ideas in solar coronal plasma physics. In particular we discuss some models of coronal heating, notably the coronal tectonics model, as well as some ideas on the nature of reconnection in three dimensions. In addition, we summarise a model for the time-dependent response of the corona to the sudden dissipation of a current sheet.

  10. Solar corona at high resolution

    NASA Technical Reports Server (NTRS)

    Golub, L.; Rosner, R.; Zombeck, M. V. Z.; Vaiana, G. S.

    1982-01-01

    The earth's surface is shielded from solar X rays almost completely by the atmosphere. It is, therefore, necessary to place X-ray detectors on rockets or orbiting satellites. Solar rays were detected for the first time in the late 1940's, using V-2 rockets. In 1960, the first true X-ray images of the sun were obtained with the aid of a simple pinhole camera. The spatial resolution of the X-ray images could be considerably improved by making use of reflective optics, operating at grazing incidence. Aspects of X-ray mirror developments are discussed along with the results obtained in coronal studies utilizing the new devices for the observation of solar X-ray emission. It is pointed out that the major achievements of the Skylab missions were due primarily to the unique opportunity to obtain data over an extended period of time. Attention is given to normal incidence X-ray optics, achievements possible by making use of high spatial resolution optics, and details of improved mirror design.

  11. The solar corona through numerical eyes

    NASA Astrophysics Data System (ADS)

    Cohen, Ofer

    The Sun and the Space environment serve as a natural laboratory to study the physics of ionized gas (plasma) under extreme conditions, which are nearly impossible to achieve using artificial experiments. Understanding the behavior of this environment has become more and more important with our growing dependency on space-based technology and the growing number of space exploration missions. As a consequence, the new concept of Space Weather, which characterizes the conditions in space, requires the development of forecasting tools to provide prediction of these conditions. In this work, I present a numerical study of the solar corona and the space environment. Numerical simulations are important, due to the fact that they provide a more accurate solution than the approximated analytical solution. This work has three main parts: (1) I develop a global MagnetoHydroDynamic (MHD) model for the ambient conditions in the solar corona and the inner heliosphere and validate it with long-term satellite data. This model provides preconditioning for Coronal Mass Ejections (CMEs) and also can be used to study the large-scale evolution of the corona and the heliosphere. (2) I develop a flux-transport model for the solar surface to investigate the effect of magnetic reconnection on the transport of the Suns open magnetic flux. I show that this process can modify the surface meridional flow that is important in solar dynamo theory. (3) I simulate a Sun-to-Earth CME event in order to investigate the capabilities of the model to serve as an operational tool for space weather forecasting. This simulation demonstrates that it is possible and also addresses required improvements. This work is a step towards a better understanding of the space environment and the physics of the solar corona. I propose to further investigate the role of the open flux in the long-term, large-scale evolution of the solar and heliospheric magnetic field. I also propose to investigate the relations between the solar and stellar physics.

  12. 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.

  13. 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).

  14. High Energy Particles in the Solar Corona

    E-print Network

    A. Widom; Y. N. Srivastava; L. Larsen

    2008-04-16

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

  15. Turbulent heating of the corona and solar wind: the heliospheric

    E-print Network

    Turbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale that the gas is highly ionized, i.e. a magnetized collisionless plasma ( solar wind model A `solar wind' is accelerated from the corona - Hydrostatic solution (similar to Bondi accretion

  16. 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.

  17. Magnetic Relaxation in the Solar Corona Kenneth Miller1

    E-print Network

    Fornberg, Bengt

    Magnetic Relaxation in the Solar Corona Kenneth Miller1 , Bengt Fornberg2 , Natasha Flyer3 , & B. C- duced in the tenuous solar corona by the turbulent, resistive relaxation of a magnetic field under to a rigid, perfectly conducting base, and, (ii) that em- beds a force-free magnetic field in the form

  18. Dynamics and energetics of the solar corona

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.

    1992-01-01

    The primary objective of this research program is to improve our understanding of the dynamics and energetics of the solar corona both in the quiescent dynamic equilibrium state when coronal structure is dominated by the equatorial streamer belt and in the eruptive state when coronal plasma is ejected into the interplanetary medium. Numerical solutions of the time-dependent magnetohydrodynamic (MHD) equations and comparisons of the computed results with observations form the core of the approach to achieving this objective. Some of the specific topics that have been studied are: (1) quiescent coronal streamers in an atmosphere dominated by a dipole magnetic field at large radii, (2) the formation of coronal mass ejections (CMEs) in quiescent streamers due to the emergence of new magnetic flux and due to photospheric shear motion, (3) MHD shock formation near the leading edge of CMEs, (4) coronal magnetic arcade eruption as a result of applied photospheric shear motion, and (5) the three-dimensional structure of CMEs.

  19. Shock Acceleration in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Sandroos, Arto

    2010-03-01

    In this thesis acceleration of energetic particles at collisionless shock waves in space plasmas is studied using numerical simulations, with an emphasis on physical conditions applicable to the solar corona. The thesis consists of four research articles and an introductory part that summarises the main findings reached in the articles and discusses them with respect to theory of diffusive shock acceleration and observations. This thesis gives a brief review of observational properties of solar energetic particles and discusses a few open questions that are currently under active research. For example, in a few large gradual solar energetic particle events the heavy ion abundance ratios and average charge states show characteristics at high energies that are typically associated with flare-accelerated particles, i.e. impulsive events. The role of flare-accelerated particles in these and other gradual events has been discussed a lot in the scientific community, and it has been questioned if and how the observed features can be explained in terms of diffusive shock acceleration at shock waves driven by coronal mass ejections. The most extreme solar energetic particle events are the so-called ground level enhancements where particle receive so high energies that they can penetrate all the way through Earth's atmosphere and increase radiation levels at the surface. It is not known what conditions are required for acceleration into GeV/nuc energies, and the presence of both very fast coronal mass ejections and X-class solar flares makes it difficult to determine what is the role of these two accelerators in ground level enhancements. The theory of diffusive shock acceleration is reviewed and its predictions discussed with respect to the observed particle characteristics. We discuss how shock waves can be modeled and describe in detail the numerical model developed by the author. The main part of this thesis consists of the four scientific articles that are based on results of the numerical shock acceleration model developed by the author. The novel feature of this model is that it can handle complex magnetic geometries which are found, for example, near active regions in the solar corona. We show that, according to our simulations, diffusive shock acceleration can explain the observed variations in abundance ratios and average charge states, provided that suitable seed particles and magnetic geometry are available for the acceleration process in the solar corona. We also derive an injection threshold for diffusive shock acceleration that agrees with our simulation results very well, and which is valid under weakly turbulent conditions. Finally, we show that diffusive shock acceleration can produce GeV/nuc energies under suitable coronal conditions, which include the presence of energetic seed particles, a favourable magnetic geometry, and an enhanced level of ambient turbulence.

  20. Exploring dynamic events in the solar corona

    NASA Astrophysics Data System (ADS)

    Downs, Cooper James

    With the advent of modern computational technology it is now becoming the norm to employ detailed 3D computer models as empirical tools that directly account for the inhomogeneous nature of the Sun-Heliosphere environment. The key advantage of this approach lies in the ability to compare model results directly to observational data and to use a successful comparison (or lack thereof) to glean information on the underlying physical processes. Using extreme ultraviolet waves (EUV waves) as the overarching scientific driver, we apply this observation modeling approach to study the complex dynamics of the magnetic and thermodynamic structures that are observed in the low solar corona. Representing a highly non-trivial effort, this work includes three main scientific thrusts: an initial modeling effort and two EUV wave case-studies. First we document the development of the new Low Corona (LC) model, a 3D time-dependent thermodynamic magnetohydrodynamic (MHD) model implemented within the Space Weather Modeling Framework (SWMF). Observation synthesis methods are integrated within the LC model, which provides the ability to compare model results directly to EUV imaging observations taken by spacecraft. The new model is then used to explore the dynamic interplay between magnetic structures and thermodynamic energy balance in the corona that is caused by coronal heating mechanisms. With the model development complete, we investigate the nature of EUV waves in detail through two case-studies. Starting with the 2008 March 25 event, we conduct a series of numerical simulations that independently vary fundamental parameters thought to govern the physical mechanisms behind EUV waves. Through the subsequent analysis of the 3D data and comparison to observations we find evidence for both wave and non-wave mechanisms contributing to the EUV wave signal. We conclude with a comprehensive observation and modeling analysis of the 2010 June 13 EUV wave event, which was observed by the recently launched Solar Dynamics Observatory. We use a high resolution simulation of the transient to unambiguously characterize the globally propagating front of EUV wave as a fast-mode magnetosonic wave, and use the rich set of observations to place the many other facets of the EUV transient within a unified scenario involving wave and non-wave components.

  1. RADIO OBSERVATIONS OF THE SOLAR CORONA DURING AN ECLIPSE

    SciTech Connect

    Kathiravan, C.; Ramesh, R.; Barve, Indrajit V.; Rajalingam, M. E-mail: ramesh@iiap.res.in E-mail: rajalingam@iiap.res.in

    2011-04-01

    We carried out radio observations of the solar corona at 170 MHz during the eclipse of 2008 August 1, from the Gauribidanur observatory located about 100 km north of Bangalore in India. The results indicate the presence of a discrete radio source of very small angular dimension ({approx}15'') in the corona from where the observed radiation originated.

  2. Rotation characteristics of the Fe XIV (5303 A) solar corona

    NASA Astrophysics Data System (ADS)

    Sime, D. G.; Fisher, R. R.; Altrock, R. C.

    1989-01-01

    The rotational characteristics of the solar corona as revealed by the coronal Fe XIV line at 5303 A are examined. Measurements of the intensity at 5303 A observed at a radius of 1.15 solar radii between 1973 and 1985 are presented. It is found that, on average, the Fe XIV corona rotates more rigidly than do features in the photosphere or chromosphere. The observations support the theory that the Fe XIV coronal signal arises from the effects of local heating on the large-scale density structure of the corona.

  3. Bright point study. [of solar corona

    NASA Technical Reports Server (NTRS)

    Tang, F.; Harvey, K.; Bruner, M.; Kent, B.; Antonucci, E.

    1982-01-01

    Transition region and coronal observations of bright points by instruments aboard the Solar Maximum Mission and high resolution photospheric magnetograph observations on September 11, 1980 are presented. A total of 31 bipolar ephemeral regions were found in the photosphere from birth in 9.3 hours of combined magnetograph observations from three observatories. Two of the three ephemeral regions present in the field of view of the Ultraviolet Spectrometer-Polarimeter were observed in the C IV 1548 line. The unobserved ephemeral region was determined to be the shortest-lived (2.5 hr) and lowest in magnetic flux density (13G) of the three regions. The Flat Crystal Spectrometer observed only low level signals in the O VIII 18.969 A line, which were not statistically significant to be positively identified with any of the 16 ephemeral regions detected in the photosphere. In addition, the data indicate that at any given time there lacked a one-to-one correspondence between observable bright points and photospheric ephemeral regions, while more ephemeral regions were observed than their counterparts in the transition region and the corona.

  4. Modeling Jets in the Corona and Solar Wind

    E-print Network

    Torok, T; Titov, V S; Leake, J E; Mikic, Z; Linker, J A; Linton, M G

    2015-01-01

    Coronal jets are transient, collimated eruptions that occur in regions of predominantly open magnetic field in the solar corona. Our understanding of these events has greatly evolved in recent years but several open questions, such as the contribution of coronal jets to the solar wind, remain. Here we present an overview of the observations and numerical modeling of coronal jets, followed by a brief description of "next-generation" simulations that include an advanced description of the energy transfer in the corona ("thermodynamic MHD"), large spherical computational domains, and the solar wind. These new models will allow us to address some of the open questions.

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

    E-print Network

    California at Berkeley, University of

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

  6. 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 with this program corroborate our theoretical predictions. A comparison of these simulations with fully three-dimensional magnetohydrodynamic simulations is presented to assess the validity of the thin flux tube model. We also present an observational method based on total emission measure and mean temperature to determine where in the current sheet a tube was reconnected.

  7. Dust in the solar nebula

    NASA Technical Reports Server (NTRS)

    Grossman, L.

    1975-01-01

    The chemical and mineralogical features of the white, Ca-rich inclusions in Allende and other carbonaceous chondrites are strikingly similar to those predicted from thermodynamic models for the highest temperature condensates from the solar nebula. Many of the physical and chemical properties of the chondritic minerals may thus be quite like those of the dust in interstellar regions. The oxygen isotopic composition of meteoritic condensates suggests that they contain a component of interstellar dust that survived the birth of the solar system.

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

    SciTech Connect

    Pasachoff, J. M.; Rusin, V.; Saniga, M.; Minarovjech, M.; Druckmueller, M.; Aniol, P.

    2009-09-10

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

  9. 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.

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

    PubMed

    Soja, B; Heinkelmann, R; Schuh, H

    2014-01-01

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

  11. 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

  12. 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.

  13. 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 respect to the total emission along the line of sight, and the relationship of the coronal background emission to the resolved loop emission. It is apparent from this analysis that the unresolved corona is the dominant source of radiation in active regions. Additionally, the unresolved active region coronal emission can be characterized by hydrostatic scaling laws.

  14. Global seismology of the solar corona using "EIT waves"

    NASA Astrophysics Data System (ADS)

    Long, David

    2015-08-01

    “EIT waves” are globally-propagating disturbances in the solar corona that remain controversial more than fifteen years after their first observation by the Extreme ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). Originally identified as waves, opposing observations from a myriad of instruments and passbands have questioned this assumption and resulted in conflicting interpretations being proposed to explain this phenomenon. The launch in 2010 of the Solar Dynamics Observatory (SDO) has revolutionised our understanding of these features, providing high temporal and spatial resolution observations of “EIT waves” and their evolution through the solar corona. These observations have allowed the development of automated tracking algorithms and better data-driven simulations, which, combined with detailed case studies and statistical analysis of event databases are leading to a better understanding of “EIT waves”. Analysis of these features is therefore moving beyond a simple investigation of their physical nature towards using them to study the corona through which they propagate. Here, we review the theories proposed to explain “EIT waves”, placing them in the context of the observations available at the time and showing how these theories have been updated with improved observations and models. We then look towards the future, studying how “EIT waves” may be used to study the structure of the solar corona and infer the properties of their associated coronal mass ejections.

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

    E-print Network

    Steven R. Spangler; Catherine A. Whiting

    2008-09-26

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

  16. 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.

  17. Quantitative Evidence for Wave Heating of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Savin, Daniel Wolf; Hahn, Michael

    2015-08-01

    One of the major theories to explain the heating of the solar corona is that waves carry the required energy from lower layers of the solar atmosphere into the corona where the waves dissipate, thereby heating the plasma. Recent observational evidence has demonstrated that waves are ubiquitous in the corona, but a challenge for wave-driven heating models has been to determine if the waves are damped. In order to address this question, we analyzed observations from the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. In particular, we studied the non-thermal line width, which is proportional to the amplitude of transverse Alfvenic waves. Our results indicate that Alfvenic waves both carry and dissipate enough energy to heat coronal holes as well as quiet Sun regions. Thus, our results imply that such waves are responsible for the bulk of the heating of the corona outside of active regions. One of the questions raised by this work is the damping mechanism. The observed dissipation is faster than expected from viscosity or resistivity, but there are more complex theories that may explain the damping. We are developing laboratory plasma experiments that will test these theories.

  18. OBSERVATION OF ULTRAFINE CHANNELS OF SOLAR CORONA HEATING

    SciTech Connect

    Ji, Haisheng; Cao, Wenda; Goode, Philip R.

    2012-05-01

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

  19. 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.

  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. 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

  3. Interstellar Dust in the Solar System

    NASA Astrophysics Data System (ADS)

    Mann, Ingrid

    2010-09-01

    A fraction of the dust in the interstellar medium (ISM) enters the heliosphere and is measured in situ from spacecraft. This review surveys the in situ measurements and discusses a hence derived model of dust in the local interstellar cloud (LIC). The LIC dust model bears similarities to pristine cometary dust and is characteristic of the warm ISM clouds that fill a part of the ISM in the vicinity of the Sun. Recent and future dust in situ measurements provide a basis for closely studying physical processes in the ISM surrounding the Solar System. The LIC dust is the only dust component measurable in the Solar System that was not previously incorporated in larger Solar System objects. Issues for future LIC dust studies are measuring dust fluxes at the outer heliosphere, measuring the mass distribution with meteor observations and observations from spacecraft, and measuring the LIC dust composition in situ in space.

  4. On the Size of Structures in the Solar Corona

    E-print Network

    C. E. DeForest

    2007-02-22

    Fine-scale structure in the corona appears not to be well resolved by current imaging instruments. Assuming this to be true offers a simple geometric explanation for several current puzzles in coronal physics, including: the apparent uniform cross-section of bright threadlike structures in the corona; the low EUV contrast (long apparent scale height) between the top and bottom of active region loops; and the inconsistency between loop densities derived by spectral and photometric means. Treating coronal loops as a mixture of diffuse background and very dense, unresolved filamentary structures address these problems with a combination of high plasma density within the structures, which greatly increases the emissivity of the structures, and geometric effects that attenuate the apparent brightness of the feature at low altitudes. It also suggests a possible explanation for both the surprisingly high contrast of EUV coronal loops against the coronal background, and the uniform ``typical'' height of the bright portion of the corona (about 0.3 solar radii) in full-disk EUV images. Some ramifications of this picture are discussed, including an estimate (10-100 km) of the fundamental scale of strong heating events in the corona.

  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^{-?}dE. The power law index was derived to be ? = 2.4 ± 0.2, which is very close to the value reported by Krucker & Benz (1998): ? ? 2.3 - 2.4. The total energy input from registered events constitute about 10^4 erg \\cdot cm^{-2} \\cdot s^{-1}, which is well beyond net losses in quiet corona (3 \\cdot 10^5 erg \\cdot cm^{-2} \\cdot s^{-1}). However, the value of ? > 2 indicates that nanoflares with lower energies dominate over nanoflares with bigger energies and could contribute considerably to quiet corona heating.

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

    E-print Network

    Steven R. Spangler

    2007-09-11

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

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

    PubMed

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

    2011-07-28

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

  8. Synoptic, Global Mhd Model For The Solar Corona

    NASA Astrophysics Data System (ADS)

    Cohen, Ofer; Sokolov, I. V.; Roussev, I. I.; Gombosi, T. I.

    2007-05-01

    The common techniques for mimic the solar corona heating and the solar wind acceleration in global MHD models are as follow. 1) Additional terms in the momentum and energy equations derived from the WKB approximation for the Alfv’en wave turbulence; 2) some empirical heat source in the energy equation; 3) a non-uniform distribution of the polytropic index, ?, used in the energy equation. In our model, we choose the latter approach. However, in order to get a more realistic distribution of ?, we use the empirical Wang-Sheeley-Arge (WSA) model to constrain the MHD solution. The WSA model provides the distribution of the asymptotic solar wind speed from the potential field approximation; therefore it also provides the distribution of the kinetic energy. Assuming that far from the Sun the total energy is dominated by the energy of the bulk motion and assuming the conservation of the Bernoulli integral, we can trace the total energy along a magnetic field line to the solar surface. On the surface the gravity is known and the kinetic energy is negligible. Therefore, we can get the surface distribution of ? as a function of the final speed originating from this point. By interpolation ? to spherically uniform value on the source surface, we use this spatial distribution of ? in the energy equation to obtain a self-consistent, steady state MHD solution for the solar corona. We present the model result for different Carrington Rotations.

  9. High Resolution Analysis of the Eclipse Solar Corona

    NASA Astrophysics Data System (ADS)

    Koutchmy, S.

    1998-09-01

    A very large W-L coronal flux is made available during total eclipses. High speed analysis of very fine-scale structure of the magnetically dominated solar atmosphere is made possible, including the deeply seeded sources of the solar mass loss. Additional observations of both the disk and of the more outer corona should be simultaneusly collected from space, using the SOHO and the Yohkoh missions to complements the data. The most optimum eclipse studies should concentrate on the intermediate corona where acceleration processes are taking place. MHD waves, including magneto-acoustic propagating waves and standing loop-resonance waves are everywhere present with rather short periods. W-L fine imaging at high signal-to noise ratio is needed to avoid the overlapping problem and measure their magnitude. Ubiquituos plasmoid like objects are also produced in this region near the temperature maximum and they need a special attention. They are rather privileged site where both the radiation cooling and the magnetic dissipation mechanisms are occurring. Eclipses are good opportunities to look at the dynamics of coronal ejections. At larger scale, sharp edges of streamers and plumes can be used to deduce a 3-D view of the corona neutral sheets, provided pictures taken at several hours interval are made available along the path of the totality. Both the quasi-rigid rotation and the more subtle outward motions of coronal material are then evidenced, giving a good tool to study the origin of the slow wind.

  10. Joule Heating and Anomalous Resistivity in the Solar Corona

    E-print Network

    Steven R. Spangler

    2008-12-22

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

  11. 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.

  12. 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.

  13. Numerical Simulations of Helicity Condensation in the Solar Corona

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

  14. 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.

  15. 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.

  16. Prediction of Dn-Resonances in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Osherovich, V. A.; Fainberg, J.; Benson, R. F.; MacDowall, R.; Reinisch, B. W.

    2006-05-01

    A new plasma wave mode has been proposed with quantized frequencies fDn = 3/?(fpefce)½ n½ , n = 1,2,... where fpe is the electron plasma frequency and fce is the electron gyrofrequency. These frequencies have been associated with a spectrum of emissions known as the Dn resonance stimulated by ionospheric topside sounders [Osherovich, 1987]. The foundations and observational support for this new electromagnetic mode have been summarized in the recent review by Osherovich et al. [2005] for three plasmas: the Earth's ionosphere (topside radio sounding from Alouette 2, ISIS 1 and ISIS 2 satellites), the Earth's magnetosphere (radio sounding from the IMAGE spacecraft) and in Jupiter's Io plasma torus (radio sounding from the Ulysses space probe). For these plasmas, the electron densities, magnetic fields and electron temperatures are quite different but in each of these plasmas there exists extended regions where the range of fpe/fce is roughly the same, namely 1? fpe/fce ? 8. From available observations of the solar corona and coronal loops, we conclude that the two-million degree corona is the fourth example of a magnetized plasma containing extended regions with fpe/fce in the same range. Therefore we predict the presence of Dn resonances with their distinctive ? n frequency spectrum, in the solar corona. References: Osherovich, V.A.,"Physical nature of diffuse plasma resonances in the ionosphere", J. Geophys. Res, 92, 316-320, 1987. Osherovich, V.A., R.F. Benson and J. Fainberg, "Electromagnetic bounded states and challenges of plasma spectroscopy", IEEE Transactions of Plasma Science, 33(2), 2005.

  17. Dust in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Kramer, Emily; Bauer, James; Mainzer, Amy; Grav, Tommy; Nugent, Carolyn; Sonnett, Sarah; Stevenson, Rachel

    2015-08-01

    As some of the most pristine objects in the Solar System, comets present an excellent opportunity to understand the mechanics and chemistry of the planetary formation era. By studying a large number of comets in different dynamical classes, we can better understand their ensemble properties.NEOWISE is the planetary-funded mission that uses data from the Wide-field Infrared Survey Explorer (WISE) spacecraft to detect and characterize moving objects. The WISE mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22-microns) between January 2010 and February 2011, during which time over 160 comets were detected. Since the restart of the mission as NEOWISE in December 2013, over 60 additional comets have been observed in the shorter two wavelength channels. In both phases of the mission, a mix of both long-period comets and short-period comets were detected. Over half of the comets in the prime mission displayed a significant dust tail in the 12 and 22-micron (thermal emission) bands, showing a wide range of activity levels and dust morphology. In both the prime and restarted phases of the mission, extended dust structures were also detected for many of the comets in the 3.4 and 4.6-micron bands. For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method. We will present updated modeling results, comparing the different comet populations.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  19. 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.

  20. Multimodal Differential Emission Measure in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Nuevo, Federico A.; Vásquez, Alberto M.; Landi, Enrico; Frazin, Richard

    2015-10-01

    The Atmospheric Imaging Assembly (AIA) telescope on board the Solar Dynamics Observatory provides coronal extreme ultraviolet imaging over a broader temperature sensitivity range than the previous generations of instruments (Extreme Ultraviolet Imager; EUVI, EIT, and TRACE). Differential emission measure tomography (DEMT) of the solar corona based on AIA data is presented here for the first time. The main product of DEMT is the three-dimensional distribution of the local differential emission measure (LDEM). While in previous studies, based on EIT or EUVI data, there were three available EUV bands, the present study is based on the four cooler AIA bands (aimed at studying the quiet sun). The AIA filters allow exploration of new parametric LDEM models. Since DEMT is better suited for lower activity periods, we use data from Carrington Rotation 2099, when the Sun was in its most quiescent state during the AIA mission. Also, we validate the parametric LDEM models by using them to perform a bi-dimensional differential emission measure (DEM) analysis on sets of simultaneous AIA images, and comparing results with those obtained using other methods. Our study reveals a ubiquitous bimodal LDEM distribution in the quiet diffuse corona, characterized by two well-defined average centroid temperatures < {T}{0,1}> =(1.47+/- 0.05) {MK} and < {T}{0,2}> =(2.57+/- 0.05) {MK}. We argue that the nanoflare heating scenario is less likely to explain these results, and that alternative mechanisms, such as wave dissipation, appear better supported by our results.

  1. Radiative transfer of X-rays in the solar corona

    NASA Technical Reports Server (NTRS)

    Acton, L. W.

    1978-01-01

    The problem of resonance scattering of X-ray emission lines in the solar corona is investigated. For the resonance lines of some helium-like ions, significant optical depths are reached over distances small compared with the size of typical coronal features. A general integral equation for the transfer of resonance-line radiation under solar coronal conditions is derived. This expression is in a form useful for modeling the complex three-dimensional temperature and density structure of coronal active regions. The transfer equation is then cast in a form illustrating the terms which give rise to the attenuation or enhancement of the resonance-line intensity. The source function for helium-like oxygen (O VII) under coronal conditions is computed and discussed in terms of the relative importance of scattering.

  2. IAU, Joint Commission Meeting on Solar and Stellar Coronae, Buenos Aires, Argentina, July 30, 1991, Proceedings

    NASA Astrophysics Data System (ADS)

    Pallavicini, Roberto

    Papers are presented on coronal emission and stellar evolution, high-resolution observations of the solar corona, modeling solar coronal loops, heating and momentum deposition in hot stars, and heating of solar and stellar chromospheres and coronae by MHD waves, and magnetized and collimated meridional outflows. Other papers are on X-ray activity and magnetic fields of T Tauri stars, X-ray spectroscopy of solar and stellar coronae, radio observations of solar and stellar coronae, stellar coronae and their relation to convection zones and rotation rates, results from an extensive Einstein Observatory survey of B-type stars, and transient optical periodicities in coronal red dwarfs. Particular attention is given to radio observations of weak-lined T Tauri, spectra of MHD turbulence in the solar corona, the thermodynamic decay scaling laws in solar loop flares, the differential emission measure and the composition of the solar corona, the structural instability of nonlinear Alfven waves, and heating of solar coronal holes by reflected Alfven waves. (For individual items see A93-26152 to A93-26175)

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    The Mg XII spectroheliograph is a part of instrumentation complex TESIS (satellite CORONAS-PHOTON). This instrument builds monochromatic images of hot plasma of the solar corona (? = 8.42 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.

  4. 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.

  5. R Coronae Borealis Stars are Viable Factories of Pre-solar Grains

    E-print Network

    Karakas, Amanda I; Hampel, Melanie

    2015-01-01

    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 $\\approx$ 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 ($1.8 \\times 10^{-3}$ yr$^{-1}$) 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 graph...

  6. R Coronae Borealis Stars Are Viable Factories of Pre-solar Grains

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 × 10-3 yr-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.

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

    NASA Technical Reports Server (NTRS)

    Foukal, P.

    1978-01-01

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

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

    NASA Technical Reports Server (NTRS)

    1997-01-01

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

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

  9. Burgulence and Alfven waves heating mechanism of solar corona

    E-print Network

    T. M. Mishonov; Y. G. Maneva

    2007-01-16

    Heating of magnetized turbulent plasma is calculated in the framework of Burgers turbulence [A.M. Polyakov, Phys. Rev. E. 52, 6183 (1995)]. Explicit formula for the energy flux of Alfven waves along the magnetic field is presented. The Alfven waves are considered as intermediary between the turbulent energy and the heat. The derived results are related to a wave channel of heating of the solar corona. If we incorporate amplification of Alfven waves by shear flow the suggested model of heating can be applied to analysis of the missing viscosity of accretion discs and to reveal why the quasars are the most powerful sources of light in the universe. We suppose that the Langevin-Burgers approach to turbulence we have applied in the current work can be also helpful for other systems where we have intensive interaction between a stochastic turbulent system and waves and can be used in many multidisciplinary researches in hydrodynamics and MHD.

  10. 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.

  11. Interstellar Dust in the Solar System

    E-print Network

    Harald Krueger; Markus Landgraf; Nicolas Altobelli; Eberhard Gruen

    2007-06-21

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

  12. 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.

  13. Dust Accumulation on MER Solar Panels

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  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. 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.

  16. Interstellar dust measurements in the solar system

    NASA Astrophysics Data System (ADS)

    Krüger, H.; Altobelli, Nicolas; Landgraf, Markus; Grün, Eberhard

    2008-09-01

    In the early 1990s, after its Jupiter yby, the Ulysses spacecraft identified interstellar dust in the solar system. Since 1992 until the end of 2007 the in-situ dust detector on board Ulysses continuously monitored interstellar grains with masses up to 10-13 kg, penetrating deep into the solar system. While Ulysses measured the interstellar dust stream at high ecliptic latitudes between 3 and 5 AU, interstellar impactors were also measured with the dust detectors on board Cassini, Galileo and Helios, covering a heliocentric distance range between 0.3 and 3 AU in the ecliptic plane. The interstellar dust stream in the inner solar system is altered by the solar radiation pressure force, gravitational focussing and interaction of charged grains with the time varying interplanetary magnetic field. The grains act as tracers of the physical conditions in the local interstellar cloud (LIC). Our in-situ measurements imply the existence of a population of 'big' interstellar grains (up to 10-13 kg) and a gas-to-dust-mass ratio in the LIC which is a factor of > 2 larger than the one derived from astronomical observations, indicating a concentration of interstellar dust in the very local interstellar medium. Until 2004, the interstellar dust ow direction measured by Ulysses was close to the mean apex of the Sun's motion through the LIC, while in 2005, the data showed a 30 degree shift, the reason of which is presently unknown. We review the in-situ interstellar dust measurements obtained from a fleet of four spacecraft in the solar system and present the latest results from the Ulysses mission.

  17. 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.

  18. 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 (1-2) x 10(exp 10) cm, compatible with a few times the scale height of the cooler plasma component.

  19. Diagnostics of solar wind streams and their sources in the solar corona

    NASA Astrophysics Data System (ADS)

    Lotova, N. A.; Vladimirskii, K. V.; Obridko, V. N.

    2010-12-01

    The studies are based on the experimental mass sounding of the interplanetary plasma near the Sun at radial distances of R = 4-70 R S, performed at Pushchino RAO, Russian Academy of Sciences, and on the calculated magnetic fields in the solar corona based on the magnetic field strength and structure measured on the Sun's surface at J. Wilcox Solar Observatory, United States. The experimental data make it possible to localize the position of the boundary closest to the Sun of the transition transonic region of the solar wind in the near-solar space ( R ? 10-20 R S) and to perform an interrelated study of the solar wind structure and its sources, namely, the magnetic field components in the solar corona based on these data. An analysis of the evolution of the flow types in 2000-2007 makes it possible to formulate the physically justified criterion responsible for the time boundaries of different epochs in the solar activity cycle.

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

    SciTech Connect

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

    2011-09-20

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

  1. 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.

  2. 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.

  3. 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

    1992-09-01

    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. PMID:17738279

  4. 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.

  5. 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.

  6. ON THE DYNAMICS OF THE SOLAR CORONA: FIRST RESULTS OBTAINED WITH A NEW 3D MHD MODEL

    E-print Network

    Grauer, Rainer

    1 ON THE DYNAMICS OF THE SOLAR CORONA: FIRST RESULTS OBTAINED WITH A NEW 3D MHD MODEL J. Kleimann 1) is applied to the problem of the dynamics of the solar corona. First, we present the basic system of equations for a two- uid description of the solar wind plasma and point out possible numerical di

  7. 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.

  8. Magnetic and thermodynamic structure of the solar corona during sunspot minimum

    NASA Technical Reports Server (NTRS)

    Osherovich, V. A.; Tzur, I.; Gliner, E. B.

    1985-01-01

    A model of the solar corona during sunspot minimum was constructed. It was suggested that pole-equator asymmetry is caused by interaction of global azimuthal electric currents in the corona and potential magnetic fields originating below the corona. The problem was reduced to a nonlinear ordinary differential equation for a structural function. Taking the difference in electron density between the equatorial plane and the polar direction from observations, the basic equation was solved and the global electric current distribution around the Sun along with the magnetic and thermodynamic structures of the solar corona was derived. The asymmetry between the two hemispheres, which can be due to the magnetic quadrupole, is considered in detail. It is shown that an additional quadrupole term in the magnetic field representation affects the position of polar coronal hole boundaries differently in the two hemispheres. As a result, the outflow from the two polar regions is found to be different.

  9. 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.

  10. 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."

  11. 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."

  12. Evidence for wave heating in the solar corona.

    PubMed

    Hahn, Michael

    2013-07-01

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

  13. Dynamics of Solar System Dust

    NASA Technical Reports Server (NTRS)

    Dermott, Stanley F.

    2002-01-01

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

  14. On the Heating of the Solar Corona and the Acceleration of the Low-Speed Solar Wind by Acoustic Waves Generated in Corona

    E-print Network

    Takeru Ken Suzuki

    2002-08-06

    We investigate possibilities of solar coronal heating by acoustic waves generated not at the photosphere but in the corona, aiming at heating in the mid- to low-latitude corona where the low-speed wind is expected to come from. Acoustic waves of period tau ~ 100s are triggered by chromospheric reconnection, one model of small scale magnetic reconnection events recently proposed by Sturrock. These waves having a finite amplitude eventually form shocks to shape sawtooth waves (N-waves), and directly heat the surrounding corona by dissipation of their wave energy. Outward propagation of the N-waves is treated based on the weak shock theory, so that the heating rate can be evaluated consistently with physical properties of the background coronal plasma without setting a dissipation length in an ad hoc manner. We construct coronal structures from the upper chromosphere to the outside of 1AU for various inputs of the acoustic waves having a range of energy flux of F_{w,0} = (1-20) times 10^5 erg cm^{-2} s^{-1} and a period of tau = 60-300s. The heating by the N-wave dissipation effectively works in the inner corona and we find that the waves of F_{w,0} >= 2 times 10^5 erg cm^{-2} s^{-1} and tau >= 60s could maintain peak coronal temperature, T_{max} > 10^6 K. The model could also reproduce the density profile observed in the streamer region. However, due to its short dissipation length, the location of T_{max} is closer to the surface than the observation, and the resultant flow velocity of the solar wind is lower than the observed profile of the low-speed wind. The cooperations with other heating and acceleration sources with the larger dissipation length are inevitable to reproduce the real solar corona.

  15. Photometric studies of light scattering above the lunar terminator from Apollo solar corona photography

    NASA Technical Reports Server (NTRS)

    Mccoy, J. E.

    1976-01-01

    Excess brightness is found in 70-mm photographs of the solar corona above the lunar terminator during Apollo 15 and 17. Maximum brightness of this scattered light is determined from calibration of image density. The observed excess brightness displays circular symmetry above the lunar-horizon subsolar point, characteristic of forward diffraction scattering from micron or submicron size (solid) grains, and decays rapidly in intensity with altitude and distance from the lunar terminator. The observed brightness cannot be accounted for by a co-orbiting cloud of spacecraft contaminants, but requires a variable lunar dust 'atmosphere' over the terminator regions extending to altitudes in excess of 100 km. To maintain such large masses of lunar fines above the terminator requires either local mass-churning rates in excess of 2 by 10 to the -11th power g/sq cm sec or the assumption of some degree of high-altitude electrostatic suspension to increase the dwell time of individual grains at the altitudes observed. Such a model would reduce mass-churning rates while causing selective erosion/deposition and potential for escape of significant mass from the moon

  16. 3D Electron Density Distributions in the Solar Corona during Solar Minima: Assessment for More Realistic Solar Wind Modeling

    NASA Astrophysics Data System (ADS)

    de Patoul, Judith; Foullon, Claire; Riley, Pete

    2015-11-01

    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.

  17. Gyroscopic waves in the base of the solar corona: A model and possible observational manifestations

    NASA Technical Reports Server (NTRS)

    Pisanko, Y. V.; Tritakis, V. P.; Paliatsos, A. G.

    1997-01-01

    A linear model for gyroscopic waves in the base of the solar corona is proposed. The purpose was to point out possible observational manifestations of the phenomenon. According to the model, these waves move slowly around the sun along heliolatitude circles. The fact that the red line corona is fainter on the solar side facing the apex and north-south and east-west asymmetries of the red coronal emission line could be interpreted as a possible observational manifestation of the gyroscopic wave phenomenon in the coronal base.

  18. Nonlinear Damping of Alfvén Waves in the Solar Corona Below 1.5 Solar Radii

    NASA Astrophysics Data System (ADS)

    Zhao, J. S.; Voitenko, Y.; Guo, Y.; Su, J. T.; Wu, D. J.

    2015-10-01

    Nonthermal velocities measured in the solar corona imply a strong damping of upward-propagating low-frequency ? 0.01 {Hz} Alfvén waves at heliocentric distances from 1.02 to 1.4 solar radii. We propose a vector Alfvén wave decay as a feasible mechanism for the observed Alfvén wave damping. Contrary to the extensively studied scalar decay, the vector decay does not depend on the wave frequency and can be efficient for low-frequency coronal Alfvén waves. We show that the vector decay is much stronger than the scalar decay and can provide the observed damping of 0.01 Hz coronal Alfvén waves with perpendicular wavelengths of ? {10}4 {km} or less. Fully three-dimensional (3D) numerical simulations are needed to capture this decay, whose growth rate is proportional to the vector product of interacting wave vectors.

  19. 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.

  20. The corona near the time of the 1983 June 11 total solar eclipse

    NASA Technical Reports Server (NTRS)

    Sime, D. G.; Fisher, R. R.; Mccabe, M. K.; Mickey, D. L.

    1984-01-01

    Observations are presented of the corona during the June 11, 1983 total solar eclipse, together with preliminary results of a coordinated observing program conducted to investigate the relationship between the corona and the lower parts of the solar atmosphere. Synoptic observations of the white light corona and disk in H-alpha are compared with the eclipse image, together with the inferred longitudinal component of the photospheric magnetic field measured using the magnetically sensitive Fe line at 6303 A. Using these data, an interpretation of the global three-dimensional coronal structure is attempted; showing that the eclipse image contains bright features which are far from the plane of the sky, and that it is dominated by streamers over polar filament neutral lines.

  1. The structure of the white-light corona and the large-scale solar magnetic field

    NASA Technical Reports Server (NTRS)

    Sime, D. G.; Mccabe, M. K.

    1990-01-01

    The large-scale density structure of the white-light solar corona is compared to the organization of the solar magnetic field as identified by the appearance of neutral lines in the photosphere to examine whether any consistent relationship exists between the two. During the period covering Carrington rotations 1717 to 1736 brightness enhancements in the low corona tend to lie over the global neutral sheet identified in the photospheric magnetic field. The brightest of these enhancements are associated with neutral lines throguh active regions. These associations are not 1-1, but do hold both in stable and evolving conditions of the corona. A significant number of long-lived neutral lines is found, including filaments seen in H-alpha, for which there are not coronal enhancements.

  2. The structure of the white-light corona and the large-scale solar magnetic field

    NASA Astrophysics Data System (ADS)

    Sime, D. G.; McCabe, M. K.

    1990-04-01

    The large-scale density structure of the white-light solar corona is compared to the organization of the solar magnetic field as identified by the appearance of neutral lines in the photosphere to examine whether any consistent relationship exists between the two. During the period covering Carrington rotations 1717 to 1736 brightness enhancements in the low corona tend to lie over the global neutral sheet identified in the photospheric magnetic field. The brightest of these enhancements are associated with neutral lines through active regions. These associations are not 1-1, but do hold both in stable and evolving conditions of the corona. A significant number of long-lived neutral lines is found, including filaments seen in H-alpha, for which there are not coronal enhancements.

  3. 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.

  4. 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.

  5. 3D electron density distributions in the solar corona during solar minima: assessment for more realistic solar wind modeling

    E-print Network

    de Patoul, Judith; Riley, Pete

    2015-01-01

    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...

  6. ELECTRON DENSITY VARIATION IN OFF-LIMB SOLAR CORONA STRUCTURES I. Ugarte-Urra

    E-print Network

    1 ELECTRON DENSITY VARIATION IN OFF-LIMB SOLAR CORONA STRUCTURES I. Ugarte-Urra , J.G. Doyle a study of the electron density variation for off limb observations with the Coronal Diagnostic Spec- trometer (CDS) on board SoHO using the density sensi- tive coronal line ratio Si X (356

  7. MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. II. FIELD-PLASMA INTERACTION B. Fornberg,2

    E-print Network

    Fornberg, Bengt

    agent because it enhances the magnetic pressure to drive an outward expansion. A low-temperature plasma base. This is probably the magnetic role of quiescent prominences in coronal structures (TandbergMAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. II. FIELD-PLASMA INTERACTION N. Flyer,1 B. Fornberg

  8. A Low-Frequency Radio Spectropolarimeter for Observations of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Kishore, P.; Ramesh, R.; Kathiravan, C.; Rajalingam, M.

    2015-09-01

    A new spectropolarimeter for dedicated ground-based observations of radio emission from the solar corona at low frequencies ({< }100 MHz) has recently been commissioned at the Gauribidanur Radio Observatory near Bengaluru, India. We report the observational setup, the calibration scheme, and first results.

  9. IntrAst1 (Petrovay) The Sun THE CHROMOSPHERE AND THE SOLAR CORONA

    E-print Network

    Petrovay, Kristóf

    : magnetic field can levitate dense plasma due to freezing in. Observed as dark filaments on the solar disk; short lived (minutes­hours) Quiescent prominence: floating persistently (days­weeks) in one place Cause mass ejections (CMEs) : plasma clouds ejected from the corona. Cause: photospheric motions slowly

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

    E-print Network

    Fornberg, Bengt

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

  11. 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.

  12. Quasi-stereoscopic imaging of the solar X-ray corona

    NASA Technical Reports Server (NTRS)

    Batchelor, David

    1994-01-01

    The first published three-dimensional images of the solar X-ray corona obtained by means of solar rotational parallax, are presented in stereographic form. Image pairs approximately 12 hours apart during times of stable coronal conditions were selected from the digitized images obtained with the Skylab X-ray Spectrographic Telescope. The image resolution limit is approximately 10 arc sec. Many coronal structures not visible in the separate images are clearly observed when the image pairs are viewed stereoscopically. This method gives a preview of the potential resources for solar research and forecasting of solar-geomagnetic interactions that could be provided by stereoscopic observations of the Sun using a small group of spacecraft. The method is also applicable to other X-ray, ultraviolet, or other wavebands in which the corona has extended, transparent structure.

  13. 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.

  14. A Space Weather Mission Concept: Observatories of the Solar Corona and Active Regions (OSCAR)

    E-print Network

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

    2014-01-01

    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$^{\\circ}$ to provide optimum stereoscopic view of the solar corona. We ...

  15. 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.

  16. Nonlinear interaction between wave and convective disturbances in the solar corona

    NASA Astrophysics Data System (ADS)

    Veselovsky, I. S.; Mikhalyaev, B. B.; Bembitov, D. B.

    2015-12-01

    During more than two decades, many non-stationary events have been observed in the solar corona by different ground and space instruments, namely: oscillations and flows. These events play a crucial role in a solving two important problems of the solar physics: coronal heating and solar wind acceleration. Numerous observational data and theoretical works demonstrate the nonlinear interaction between waves and flows in the solar atmosphere. On other hand, nonlinear effects can also be used in coronal seismology, where a significant success leaded to many original works on linear disturbances in the coronal plasma. The nonlinear approach should make it possible to achieve more precise results.

  17. Search for the Alfven Waves in the Solar Corona on the Profiles of Coronal Spectral Lines

    NASA Astrophysics Data System (ADS)

    Mamedov, S. H.; Rustamov, A. A.; Dzhalilov, N. S.

    2007-06-01

    Many researchers of the mechanism of heating of the solar corona identify the nonthermal velocities found from half-width of observed coronal spectral lines with velocities of Alfven waves. On the basis of this assumption it was concluded that Alfven waves can heat the corona. For check up this assumption in this work we used the theoretical contours of coronal spectral lines are calculated by Maltby [15] for various values of the velocity amplitude of Alfven waves. It was found that if to identify observed velocities of nonthermal movements with movements on Alfven waves, it would be appear deep central depression in these lines . As in observed lines the central depression is absent and profiles of these lines are well approximated with Doppler profiles, we conclude that in the corona Alfven waves with large amplitude are missed.

  18. Electron heat flow in the solar corona: Implications of non-Maxwellian velocity distributions, the solar gravitational

    E-print Network

    Scudder, Jack

    Electron heat flow in the solar corona: Implications of non-Maxwellian velocity distributions January 2003; published 19 July 2003. [1] It has long been known that weak electron temperature gradients in fully ionized plamas (satisfying l jrTej/Te ] 10À4 , where le is the electron mean free path and Te

  19. 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."

  20. Multipoint Validation of a Global 3D MHD Model for the Solar Corona and Inner Heliosphere

    NASA Astrophysics Data System (ADS)

    Cohen, O.; Sokolov, I. V.; Roussev, I. I.; Gombosi, T. I.

    2007-12-01

    We present a long-term validation of a global, 3D MHD model for the solar corona and the solar wind. The model is driven by high resolution MDI magnetograms and is constrained by the empirical Wang-Sheeley-Arge (WSA) model. The model provides a three-dimensional steady-state structure of the heliosphere between the Sun and the Earth for a particular Carrington Rotation. We use the model to obtain the large-scale context for the information we collect from multipoint spacecraft observations and large-scale remote sensing imagine of the solar corona and the heliosphere. For the long-term validation of the model, we compare the result with ACE data and the available STEREO data.

  1. Presence Of A Reverse Shock In The Evolution Of A CME In The Lower Solar Corona

    NASA Astrophysics Data System (ADS)

    Das, I.; Opher, M.

    2008-12-01

    We study the birth and the evolution of a reverse shock in the evolution of a CME in the lower solar corona. We study the evolution of the CME with Space Weather Modeling Framework (SWMF). To initiate the CME, we inserted a Titov-Demoulin (TD) flux rope in an active region of the Sun with magnetic field based on the MDI data for the solar surface during Carrington rotation 1922. The CME advances on the top of a background solar wind created with the help of Wang-Sheeley-Arge (WSA) model. We'd explore the signature and characteristics of the reverse shock as the CME evolves through the lower corona. We also discuss it's implications on the acceleration of particles.

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

    NASA Technical Reports Server (NTRS)

    Withbroe, George L.

    1988-01-01

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

  3. 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.

  4. Theory of heating of hot magnetized plasma by Alfven waves. Application for solar corona

    E-print Network

    T. M. Mishonov; M. V. Stoev; Y. G. Maneva

    2007-02-13

    The heating of magnetized plasma by propagation of Alfven waves is calculated as a function of the magnetic field spectral density. The results can be applied to evaluate the heating power of the solar corona at known data from satellites' magnetometers. This heating rate can be incorporated in global models for heating of the solar corona and creation of the solar wind. The final formula for the heating power is illustrated with a model spectral density of the magnetic field obtained by analysis of the Voyager 1 mission results. The influence of high frequency dissipative modes is also taken into account and it is concluded that for evaluation of the total coronal heating it is necessary to know the spectral density of the fluctuating component of the magnetic field up to the frequency of electron-proton collisions.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  6. 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.

  7. 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.

  8. 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.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    E-print Network

    Uritsky, Vadim M

    2014-01-01

    Using data from 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 Alfv\\'{e}nic interactions.

  14. 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. PMID:26560611

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

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

    NASA Technical Reports Server (NTRS)

    Von Puttkamer, J.

    1973-01-01

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

  1. 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.

  2. The Source of Alfven Waves That Heat the Solar Corona

    NASA Technical Reports Server (NTRS)

    Ruzmaikin, A.; Berger, M. A.

    1998-01-01

    We suggest a source for high-frequency Alfven waves invoked in coronal heating and acceleration of the solar wind. The source is associated with small-scale magnetic loops in the chromospheric network.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  4. How Structures of the Solar Corona and Eruptions Interact to Create Extreme Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Evans, R. M.; Kozarev, K. A.; Zheng, Y.; Pulkkinen, A.; Taktakishvili, A.; Kuznetsova, M. M.; Opher, M.; Dayeh, M. A.; Schwadron, N. A.; van der Holst, B.

    2012-12-01

    As the Sun approaches maximum activity, the number of solar energetic particle (SEP) events is rapidly increasing. These strong events have the potential to damage technical systems, so it is essential to understand what causes them. Although relationships exist between the characteristics of SEP events and the associated flares and coronal mass ejections (CMEs), the strongest solar events may not lead to the most intense particle events. For example, the first Ground Level Enhancement event of Solar Cycle 24 was associated with only a moderately strong flare and CME. Presumably, there must be other factors that determine the acceleration of the highest energy particles. To address this question, we combine observations and innovative theoretical modeling of recent SEP events. We use a three-dimensional magnetohydrodynamics (MHD) model of the solar corona (within the Space Weather Modeling Framework) to simulate eruptions in the low to middle corona. The MHD output is coupled to a global kinetic simulation of particle acceleration and transport (within the Energetic Particle Radiation Environment Module). The output of the simulation is a synthetic spectral profile response to realistic solar corona conditions during the propagation of a CME. We study the evolution of the CME structures (shock and compression regions within the sheath) and the relation of these features to the preexisting coronal magnetic field geometry and solar wind distribution. Then we determine which factors affect the efficiency of particle acceleration and transport. For the first time, we can probe how particle acceleration varies in different regions of the CME as it interacts with the solar wind. R. M. E. is supported through an appointment to the NASA Postdoctoral Program at GSFC, administered by Oak Ridge Associated Universities through a contract with NASA.

  5. 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.

  6. 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.

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

    SciTech Connect

    Sterken, V. J.; Altobelli, N.; Schwehm, G.; Kempf, S.; Srama, R.; Strub, P.; Gruen, E.

    2011-11-29

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

  8. 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 ?pe and electron gyrofrequency ?e 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 ?pe/?e 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 ?pe/?e 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 ?pe/?e? 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 ?pe/?e 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 ?pe/?e, 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.

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  10. 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.

  11. The FIP and Inverse FIP Effects in Solar and Stellar Coronae

    NASA Astrophysics Data System (ADS)

    Laming, J. Martin

    2015-09-01

    We review our state of knowledge of coronal element abundance anomalies in the Sun and stars. We concentrate on the first ionization potential (FIP) effect observed in the solar corona and slow-speed wind, and in the coronae of solar-like dwarf stars, and the "inverse FIP" effect seen in the corona of stars of later spectral type; specifically M dwarfs. These effects relate to the enhancement or depletion, respectively, in coronal abundance with respect to photospheric values of elements with FIP below about 10 eV. They are interpreted in terms of the ponderomotive force due to the propagation and/or reflection of magnetohydrodynamic waves in the chromosphere. This acts on chromospheric ions, but not neutrals, and so can lead to ion-neutral fractionation. A detailed description of the model applied to closed magnetic loops, and to open field regions is given, accounting for the observed difference in solar FIP fractionation between the slow and fast wind. It is shown that such a model can also account for the observed depletion of helium in the solar wind. The helium depletion is sensitive to the chromospheric altitude where ion-neutral separation occurs, and the behavior of the helium abundance in the closed magnetic loop strongly suggests that the waves have a coronal origin. This, and other similar inferences may be expected to have a strong bearing on theories of solar coronal heating. Chromospheric waves originating from below as acoustic waves mode convert, mainly to fast-mode waves, can also give rise to ion-neutral separation. Depending on the geometry of the magnetic field, this can result in FIP or Inverse FIP effects. We argue that such configurations are more likely to occur in later-type stars (known to have stronger field in any case), and that this explains the occurrence of the Inverse FIP effect in M dwarfs. We conclude with a discussion of possible directions for future work.

  12. Interaction of Cometary Material With the Solar Corona: EUV Observations and MHD Simulations

    NASA Astrophysics Data System (ADS)

    Liu, W.; Jia, Y.; Downs, C.; Schrijver, C.; Saint-Hilaire, P.; Battams, K.; Tarbell, T. D.; Shine, R. A.

    2012-12-01

    Extreme ultraviolet (EUV) emission from two recent sun-grazing comets, C/2011 N3 and C/2011 W3 (Lovejoy), has been observed in the solar corona for the first time by the SDO/AIA and STEREO/EUVI instruments (Schrijver et al. 2011). These observations provided a unique opportunity to investigate the interaction of the cometary material with the solar corona and probe their physical conditions. We present here EUV observations and MHD simulations on this subject, focusing on the deceleration of the cometary tail material within the corona. We found that despite their different local coronal environments, the two comets exhibited quite similar characteristics. The initial EUV emitting tail had a projected velocity of 100-200 km/s, which was much lower than the orbital velocity of 500-600 km/s in the plane-of-sky. This indicates that significant deceleration had taken place while the tail material was heated to coronal temperatures on the order of 1 MK before it started to emit in EUV (Bryans & Pesnell 2012). After its initial appearance, the tail further experienced a projected deceleration of ~1 km/s^2 (or 4 g_Sun). In particular, in the Lovejoy case, the tail appeared as clusters of bright parallel striations roughly at right angles to the orbit direction, suggestive of magnetic field lines illuminated by the plasma frozen onto them. These striations came to a stop and then accelerated in an opposite direction (seen in projection), approaching a constant velocity of ~50 km/s. These observations suggest that a Lorentz force from the coronal magnetic field was operating on the newly ionized cometary plasma. To test this hypothesis and understand tail deceleration mechanisms, we adopted a multi-fluid MHD model (Jia et al. 2012) to simulate the interaction between charged particles and the magnetized coronal plasma. We used potential extrapolation (Schrijver & DeRosa 2003) and a more sophisticated global MHD model (Lionello et al. 2009) to infer the magnetic field and plasma conditions of the corona along the comet's orbit as inputs to the simulations. We will compare the observations and simulation results, and discuss the implications for using sun-grazing comets as probes to the solar corona in the context of NASA's future Solar Probe Plus mission.

  13. 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.

  14. The effects of restricted “EIT wave” propagation on the low solar corona

    NASA Astrophysics Data System (ADS)

    Long, David; Perez-Suarez, David

    2015-08-01

    We present observations of an “EIT wave” associated with an X-class flare from 2012-July-6, the propagation of which was severely restricted by the magnetic structure of the solar corona surrounding the erupting active region. The “EIT wave” was observed by both SDO and STEREO-A, allowing a three-dimensional examination of how the propagation of the disturbance was affected both by a neighbouring coronal hole and a trans-equatorial loop system. In addition, the eruption was observed at the limb by the ground-based CoMP instrument, allowing the Doppler motion associated with the eruption and resulting coronal loop oscillation to be investigated in detail. This combination of data-sets provides a unique insight into the three-dimensional evolution of the “EIT wave” and its effects on the surrounding corona.

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

    SciTech Connect

    Sittler, E.C. Jr.; Guhathakurta, M.

    1999-10-01

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

  16. 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.

  17. Propagating Disturbances in The Solar Corona and Spicular Connection

    E-print Network

    Samanta, Tanmoy; Banerjee, Dipankar

    2015-01-01

    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 observe these spicules in a south polar region of the Sun with a 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 this simultaneous observations we show that the spicules and the PDs may be originated by a common process. From space-time maps we find that the start of the trajectory of PDs is almost co-temporal with the time of the rise of the spicular envelope as seen by IRIS slit-jaw images at 2796 {\\deg}A and 1400 A{\\deg} . During the return of spicular material, brightenings are seen in AIA 171 {\\deg}A and 193 {\\deg}A images. The quasi-periodic nature of the spicular activity as revealed by the IRIS spectra...

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

    SciTech Connect

    Arshad, Kashif; Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad and University of Wah, Wah Cantt 47040 ; Ehsan, Zahida; Universita degli Studi del Molise, 86090 Pesche - IS; INFN Sezione di Napoli, 80126 Napoli; Department of Physics, COMSATS Institute of Information Technology , Defence Road, Off Raiwind Road, Lahore 86090 ; 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.

  19. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  1. 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.

  2. 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.

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

    PubMed

    Galinsky, V L; Shevchenko, V I

    2013-07-01

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

  4. 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=k?? with spectral index ? = -2.25 over frequencies ? = 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 description of FR fluctuations to deeper levels of the corona than previously reported. Further analysis should utilize models incorporating magnetohydrodynamic wave coherence scales estimated from independent lower corona observational data.

  5. 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.

  6. 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.

  7. Global Numerical Modeling of SEP Acceleration by a CME Shock in the Solar Corona and Subsequent Transport to 1 AU

    NASA Astrophysics Data System (ADS)

    Kozarev, K. A.; Evans, R. M.; Schwadron, N. A.; Dayeh, M. A.; Opher, M.; van der Holst, B.

    2012-12-01

    It has been suggested that solar energetic particles (SEP) may gain most of their energy at coronal mass ejection (CME)-driven shocks relatively close to the Sun. The observed and modeled Alfven speed profiles in the solar corona allow for fast shocks to develop within 10 solar radii. In addition, rapid changes occur in the ejected plasma structures and there is a great abundance of charged seed particles close to the Sun relative to the interplanetary populations. The combination of these conditions is favorable for the acceleration of large SEP fluxes, especially protons. However, the details of the acceleration process remain hidden due to the lack of in situ observations in the corona. As the next generation of solar exploratory missions (Solar Probe Plus and Solar Orbiter) gets ready to probe the plasma and particle conditions near the Sun directly, a better understanding of SEP acceleration processes in the corona is necessary. We have developed a comprehensive model for studying proton acceleration and global interplanetary transport. It consists of two parts: a three-dimensional magnetohydrodynamics (MHD) model of the solar corona and interplanetary space (part of the Space Weather Modeling Framework), which we use to simulate the corona, solar wind, and a CME; and a global energetic particle acceleration and transport kinetic model (the Energetic Particle Radiation Environment Module), which uses the results from the MHD simulation to model the time-dependent behavior of protons from the corona to 1 AU. We show that the shock and plasma structures may efficiently accelerate suprathermal protons to hundreds of MeV energies during their transit. We find that the resulting SEP spectra vary greatly depending on the location of their guiding field lines relative to the shock and CME.

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

    E-print Network

    Moore, Ronald L; Falconer, David A

    2015-01-01

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

  9. Signatures of the slow solar wind streams from active regions in the inner corona

    E-print Network

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

    2012-01-01

    Some of local sources of the slow solar wind can be associated with spectroscopically detected plasma outflows at edges of active regions accompanied with specific signatures in the inner corona. The EUV telescopes (e.g. SPIRIT/CORONAS-F, TESIS/CORONAS-Photon and SWAP/PROBA2) sometimes observed extended ray-like structures seen at the limb above active regions in 1MK iron emission lines and described as "coronal rays". To verify the relationship between coronal rays and plasma outflows, we analyze an isolated active region (AR) adjacent to small coronal hole (CH) observed by different EUV instruments in the end of July - beginning of August 2009. On August 1 EIS revealed in the AR two compact outflows with the Doppler velocities V =10-30 km/s accompanied with fan loops diverging from their regions. At the limb the ARCH interface region produced coronal rays observed by EUVI/STEREO-A on July 31 as well as by TESIS on August 7. The rays were co-aligned with open magnetic field lines expanded to the streamer sta...

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

    NASA Astrophysics Data System (ADS)

    Biggs, George; Asgari-Targhi, Mahboubeh

    2015-01-01

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

  11. "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.

  12. Low frequency radio observations of bi-directional electron beams in the solar corona

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    The radio signature of a shock travelling through the solar corona is known as a type II solar radio burst. In rare cases these bursts can exhibit a fine structure known as "herringbones", which are a direct indicator of particle acceleration occurring at the shock front. However, few studies have been performed on herringbones and the details of the underlying particle acceleration processes are unknown. Here, we use an image processing technique known as the Hough transform to statistically analyse the herringbone fine structure in a radio burst at ~20-90 MHz observed from the Rosse Solar-Terrestrial Observatory on 2011 September 22. We identify 188 individual bursts which are signatures of bi-directional electron beams continuously accelerated to speeds of 0.16-0.10+0.11 c. This occurs at a shock acceleration site initially at a constant altitude of ~0.6 R? in the corona, followed by a shift to ~0.5 R?. The anti-sunward beams travel a distance of 170-97+174 Mm (and possibly further) away from the acceleration site, while those travelling toward the Sun come to a stop sooner, reaching a smaller distance of 112-76+84 Mm. We show that the stopping distance for the sunward beams may depend on the total number density and the velocity of the beam. Our study concludes that a detailed statistical analysis of herringbone fine structure can provide information on the physical properties of the corona which lead to these relatively rare radio bursts.

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

    NASA Astrophysics Data System (ADS)

    Uritsky, Vadim; Davila, Joseph

    2014-05-01

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

  14. A Coherence-Based Approach for Tracking Waves in the Solar Corona

    E-print Network

    Scott W. McIntosh; Bart De Pontieu; Steven Tomczyk

    2008-08-21

    We consider the problem of automatically (and robustly) isolating and extracting information about waves and oscillations observed in EUV image sequences of the solar corona with a view to near real-time application to data from the Atmospheric Imaging Array (AIA) on the Solar Dynamics Observatory (SDO). We find that a simple coherence / travel-time based approach detects and provides a wealth of information on transverse and longitudinal wave phenomena in the test sequences provided by the Transition Region and Coronal Explorer (TRACE). The results of the search are "pruned" (based on diagnostic errors) to minimize false-detections such that the remainder provides robust measurements of waves in the solar corona, with the calculated propagation speed allowing automated distinction between various wave modes. In this paper we discuss the technique, present results on the TRACE test sequences, and describe how our method can be used to automatically process the enormous flow of data (~1Tb/day) that will be provided by SDO/AIA after launch in late 2008.

  15. 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

  16. 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.

  17. Numerical Modeling of the Solar Chromosphere and Corona: What Has Been Done? What Should Be Done?

    NASA Astrophysics Data System (ADS)

    Hansteen, V.; Carlsson, M.; Gudiksen, B.

    2015-10-01

    A number of increasingly sophisticated numerical simulations spanning the solar atmosphere from below the photosphere in the convection zone to far above in the corona have shed considerable insight into the role of the magnetic field in the structure and energetics of the Sun's outer layers. This development is strengthened by the wealth of observational data now coming on-line from both ground and space based observatories. In this talk we will concentrate on the successes and failures of the modeling effort thus far and discuss the inclusion of various effects not traditionally considered in the MHD description such as time dependent ionization, non-LTE radiative transfer, and generalized Ohm's law.

  18. 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.

  19. Modeling the corona and solar wind using ADAPT maps that include far-side observations

    NASA Astrophysics Data System (ADS)

    Arge, C. Nick; Henney, Carl J.; Hernandez, Irene Gonzalez; Toussaint, W. Alex; Koller, Josef; Godinez, Humberto C.

    2013-06-01

    As the primary input to nearly all coronal and solar wind models, global estimates of the solar photospheric magnetic field distribution are critical for reliable modeling of the corona and heliosphere. Over the last several years the Air Force Research Laboratory (AFRL), in collaboration with Los Alamos National Laboratory (LANL) and the National Solar Observatory (NSO), has developed a model that produces more realistic estimates of the instantaneous global photospheric magnetic field distribution than those provided by traditional photospheric field synoptic maps. The Air Force Data Assimilative Photospheric flux Transport (ADAPT) model is a photospheric flux transport model, originally developed at NSO, that makes use of data assimilation methodologies developed at LANL. The flux transport model evolves the observed solar magnetic flux using relatively well understood transport processes when measurements are not available and then updates the modeled flux with new observations using data assimilation methods that rigorously take into account model and observational uncertainties. ADAPT originally only made use of Earth-side magnetograms, but the code has now been modified to assimilate helioseismic far-side active region data such as those available from the Global Oscillation Network Group. As a preliminary test, a helioseismically detected active region that first emerged on the far-side of the Sun in early July 2010 is incorporated into maps produced by ADAPT and then used in the Wang-Sheeley-Arge (WSA) model to simulate the corona and solar wind. The WSA model results, with and without far-side data included in the ADAPT global maps, are compared here with coronal EUV and in situ solar wind observations available from STEREO. We find that the observed and modeled values are in better agreement when including the far-side detection.

  20. 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.

  1. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  3. 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.

  4. 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. PMID:19122714

  5. 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.

  6. 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.

  7. Polar and Equatorial Coronal Hole Winds at Solar Minima: From the Heliosphere to the Inner Corona

    NASA Astrophysics Data System (ADS)

    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.

  8. Interstellar Dust Measurements from Ulysses' Third Solar Orbit

    NASA Astrophysics Data System (ADS)

    Krueger, Harald; Altobelli, Nicolas; Landgraf, Markus; Gruen, Eberhard

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

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

    NASA Astrophysics Data System (ADS)

    Szalay, Jamey; Horanyi, M.

    2013-10-01

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

  10. 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 are not time-averaged, and they refer to particular days. The radio models are generally less dense, which is compatible with isothermal hydrostatic equilibrium in their range of heliocentric distances, and they show different behaviors with the solar cycle in the equatorial or polar radial directions. The electron kinetic temperature Te is substantially less than TH.

  11. A Simulation of a Coronal Mass Ejection Propagation and Shock Evolution in the Lower Solar Corona

    NASA Astrophysics Data System (ADS)

    Liu, Y. C.-M.; Opher, M.; Cohen, O.; Liewer, P. C.; Gombosi, T. I.

    2008-06-01

    We present a detailed simulation of the evolution of a moderately slow coronal mass ejection (CME; 800 km s-1 at 5 Rsolar, where Rsolar is solar radii) in the lower solar corona (2-5 Rsolar). The configuration of the Sun's magnetic field is based on the MDI data for the solar surface during Carrington rotation 1922. The pre-CME background solar wind is generated using the Wang-Sheeley-Arge (WSA) model. To initiate a CME, we inserted a modified Titov-Demoulin flux rope in an active region near the solar equator using the Space Weather Modeling Framework (SWMF). After the initiation stage (within 2.5 Rsolar), the CME evolves at a nearly constant and slow acceleration of the order of 100 m s-2, which corresponds to an intermediate-acceleration CME. Detailed analysis of the pressures shows that the thermal pressure accounts for most of the acceleration of the CME. The magnetic pressure contributes to the acceleration early in the evolution and becomes negligible when the CME moves beyond ~3 Rsolar. We also present the evolution of the shock geometry near the nose of the CME, which shows that the shock is quasi parallel most of the time.

  12. 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.

  13. 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.

  14. Time-dependent Turbulent Heating of Open Flux Tubes in the Chromosphere, Corona, and Solar Wind

    NASA Astrophysics Data System (ADS)

    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 1021.91 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.

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

    SciTech Connect

    Nuevo, Federico A.; Vasquez, Alberto M.; Huang Zhenguang; Frazin, Richard; Manchester, Ward B. IV; Jin Meng

    2013-08-10

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

  16. The filtering of interstellar dust in the solar system

    NASA Astrophysics Data System (ADS)

    Sterken, V. J.; Altobelli, N.; Kempf, S.; Krüger, H.; Srama, R.; Strub, P.; Grün, E.

    2013-04-01

    Context. Theoretical predictions demonstrate that small (<0.1 ?m) interstellar grains are mostly excluded from reaching the planetary system by electromagnetic interactions in the heliopause region and in the inner heliosphere. Bigger interstellar grains have been recorded in the planetary system by dust measurements on board Ulysses and other spacecraft. It was found that the interstellar dust flux is modulated by the interplanetary magnetic field. Aims: The objective of this study is to analyze the heliospheric filtering of the interstellar dust flow through the solar system and throughout the solar cycle. In the heliosphere the dynamics of interstellar dust is governed by the gravitational pull of the Sun, by the repulsion of solar radiation, and by the deflection caused by the interaction of the charged interstellar dust (ISD) grains with the interplanetary magnetic field. These interactions are described by the parameters of the radiation pressure constant ? and the charge-to-mass ratio Q/m, which depend on the particle's size, physical properties, and composition. A previous paper studied the flow characteristics of ISD moving through the solar system were studied. In this follow-up paper, we focus on how the ISD size distribution varies during its passage through the solar system. Methods: In a parametric study of 70 different ? and Q/m values, we calculated interstellar dust trajectories starting at the boundary of the heliosphere with starting times spread over a complete solar cycle of 22 years. Results: As a result we obtained the interstellar dust flux and dust speed for these times and positions and demonstrate the effects of the filtering on the dust size distributions. The size distribution of ISD observed at any time and at any position in the planetary system is strongly modified from when it entered the heliosphere. Peaks in relative flux of 10 times the original flux possibly depend on the grain size and place and time in the solar system. We did a detailed study of three cases of the flux and size distribution of interstellar grains reaching the planets Saturn, Jupiter, and the main-belt asteroid Ceres. These cases are used to get a first idea of what a dust detector or collector on a mission to these bodies might see of ISD. Appendices are available in electronic form at http://www.aanda.org

  17. 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.

  18. 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.

  19. 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.

  20. 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).

  1. Time-Dependent Turbulent Heating of Open Flux Tubes in the Chromosphere, Corona, and Solar Wind

    E-print Network

    Woolsey, Lauren N

    2015-01-01

    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 Alfven-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 (Cranmer et al., 2007) against fully time-dependent three-dimensional reduced-magnetohydrodynamics modeling of BRAID (van Ballegooijen et al., 2011). 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...

  2. Possible signature of Alfvén wave dissipation in the localized magnetic funnels of the equatorial solar corona

    NASA Astrophysics Data System (ADS)

    Dwivedi, Bhola N.; Srivastava, Abhishek Kumar; Mohan, Anita

    2014-12-01

    We analyse the Hinode/EIS 2?-spectroscopic scan data containing the spectral line formed at typical inner coronal temperature. The strong Fe XII 195.120 Å line shows the existence of funnel-like expanding flux-tubes which exhibit the signature of blue-/red-shifted plasma motions in the off-limb equatorial corona. These coronal funnels expand in the form of open magnetic field channels up to inner coronal heights. They are most likely the parts of large-scale and closed magnetic fields (loops) which exist at higher heights in the diffused equatorial corona. We also find the signature of decreasing line-widths with altitude in observed coronal funnels (e.g., funnel 1), which is the lower part of a curved loop system. This provides the most likely signature of Alfvén wave dissipation in lower part of this loop system. We also examine the blue-shifted and diffused coronal loop boundary and interfaced region (funnel 3) which shows increasing Fe XII 195.120 Å line-width along it. Therefore, it exhibits the most likely signature of Alfvén wave growth in this region which is slightly curved and rising higher in the corona. Density measurements in these funnels show that it falls off with height, but more rapidly in the second funnel. We conjecture the almost constant line-width trend as a most likely signature of Alfvén wave dissipation in this density-stratified second coronal funnel, which is also the lower part of a large-scale closed loop system. Both dissipative and growing Alfvén waves can change the non-thermal component and thus the full width at half-maximum of the Fe XII 195.120 Å line. We find the clues of Alfvén wave dissipation along the expanding field lines of the coronal funnel (lower parts of the loop system) imparting its energy to the outflowing plasma and thereby contributing to the formation of the nascent solar wind in the inner corona.

  3. A simulation of a CME propagation and shock evolution in the lower solar corona

    NASA Astrophysics Data System (ADS)

    Liu, Y. C.; Opher, M.; Cohen, O.; Gombosi, T. I.

    2007-12-01

    We present a simulation of the evolution of a CME (~800km/s at 5 solar radii) in the lower solar corona (until 5 solar radii) using Space Weather Modeling Framework (SWMF). The configuration of the sun's magnetic field is based on the MDI data on the solar surface during Carrington Rotation 1922. The pre-CME background solar wind is generated under this boundary condition and Wang-Sheeley-Arge (WSA) model. To initiate a CME, we inserted a Titov-Demoulin flux rope in an active region near the solar equator. The zone along nose of the CME is refined to resolve the CME-driven-shock. Our results show that a higher density region is followed by a dark cavity behind the shock and the higher density region is expanding while propagating away from the sun. These features are consistent with the CME observations which shows that a bright front followed by a dark area after the shock. After the initiation stage, in which the CME has a large acceleration followed by a deceleration, the CME demonstrates a nearly constant and slow acceleration of the order of 100m/s 2. At 5 solar radii, the CME has a speed of 800km/s. Although CME is accelerating, the Mach number of the shock is decreasing because the Alfven speed upstream of the shock is increasing. Detailed analysis of the pressures on the CME shows that the thermal pressure account for most of the acceleration of the CME and the magnetic pressure contribute to the acceleration at an early time but it becomes negligible when the CME moves further away from the sun. We also present the evolution of shock geometry near the nose of the CME and find that the shock is nearly perpendicular. Further investigation of the dependency in latitude of the shock and their effects on particle acceleration are required in a future work.

  4. CAN A NANOFLARE MODEL OF EXTREME-ULTRAVIOLET IRRADIANCES DESCRIBE THE HEATING OF THE SOLAR CORONA?

    SciTech Connect

    Tajfirouze, E.; Safari, H.

    2012-01-10

    Nanoflares, the basic units of impulsive energy release, may produce much of the solar background emission. Extrapolation of the energy frequency distribution of observed microflares, which follows a power law to lower energies, can give an estimation of the importance of nanoflares for heating the solar corona. If the power-law index is greater than 2, then the nanoflare contribution is dominant. We model a time series of extreme-ultraviolet emission radiance as random flares with a power-law exponent of the flare event distribution. The model is based on three key parameters: the flare rate, the flare duration, and the power-law exponent of the flare intensity frequency distribution. We use this model to simulate emission line radiance detected in 171 A, observed by Solar Terrestrial Relation Observatory/Extreme-Ultraviolet Imager and Solar Dynamics Observatory/Atmospheric Imaging Assembly. The observed light curves are matched with simulated light curves using an Artificial Neural Network, and the parameter values are determined across the active region, quiet Sun, and coronal hole. The damping rate of nanoflares is compared with the radiative losses cooling time. The effect of background emission, data cadence, and network sensitivity on the key parameters of the model is studied. Most of the observed light curves have a power-law exponent, {alpha}, greater than the critical value 2. At these sites, nanoflare heating could be significant.

  5. 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.

  6. Exploring wave propagation in the outer solar corona using the Accelerating Expanding Box

    NASA Astrophysics Data System (ADS)

    Tenerani, A.; Velli, M. M.

    2013-05-01

    Magnetic field depressions are ubiquitous in the solar wind. In situ observations provide evidence of such drops in the magnetic field magnitude at different latitudes (from the ecliptic plane up to near-polar latitudes) and in a wide range of radial distances from the sun (0.3 - 17 AU). In addition, a detailed study shows the presence of such magnetic structures to be an intrinsic property of the solar wind and to have well defined and recognized features, e.g., the anti-correlation of magnetic pressure with thermal plasma pressure. In spite of the well-documented observations, a controversial issue is to understand how these magnetic field depressions are generated and where, and if they are stable or not. Two major paradigms are usually invoked to interpret these magnetic structures, namely, the mirror instability on the one hand, and solitary waves on the other hand. Besides these two possible interpretations, we propose here a self-consistent study of the evolution of magneto-hydrodynamic (MHD) waves by showing first results within the fluid model of the "accelerating expanding box". The aim is to highlight the role of the solar wind expansion in both the temporal and spatial evolution of MHD waves propagating out from the lower corona, and how the inhomogeneity, which sets in because of the radial expansion of the solar wind, act to modify the properties of the waves themselves.

  7. Faint H alpha emission in the solar corona: Morphological, situational and hydromagnetic analysis

    NASA Astrophysics Data System (ADS)

    Dermendjiev, V. N.; Mouradian, Z.; Duchlev, P.; Leroy, J.-L.

    1994-02-01

    A very faint H(alpha) emission in the solar corona registered on over-exposed photographs made by a coronagraph and an H(alpha) filter is studied. The over-exposed filtergrams have been processed by a Joyce Loebl automated microdensitometer and the two-dimensional scans have been analysed by the residual image method. A classification of the faint H(alpha) emission objects, revealed on the isodensity maps, is proposed and the latitudinal distribution, the morphology, and the location with respect to the other active phenomena are analyzed. Taking into account some possible plasma effects that could be caused by coronal magnetic field changes, a hydromagnetic interpretation of the faint H(alpha) emission is proposed.

  8. Stereoscopic investigation on plasma density fluctuations in the outer solar corona

    NASA Astrophysics Data System (ADS)

    Telloni, D.; Antonucci, E.; Dolei, S.; Romano, P.; Spadaro, D.; Ventura, R.

    2014-05-01

    This research note extends a previous work focused on the 2D reconstruction of the spatial distribution and temporal evolution of the plasma density fluctuations in the outer solar corona and based on STEREO COR1-A white-light observations. By using the corresponding total brightness images obtained in the same observational period with the coronagraph COR1-B onboard the "Behind" twin STEREO-B spacecraft, and adopting the same methodological approach as for COR1-A data, it was possible to confirm the results of the previous work and argue for the 3D configuration of the fluctuations of the coronal plasma. This provides further evidence in support of a scenario in which the fluctuating features, which are recurrent and spatially coherent, are localized along the magnetic field lines and points out the crucial role played by the 3D magnetic field topology in the confinement and evolution of the plasma density fluctuations.

  9. 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.

  10. The possible role of MHD waves in heating the solar corona

    NASA Technical Reports Server (NTRS)

    Porter, Lisa J.; Klimchuk, James A.; Sturrock, Peter A.

    1994-01-01

    The possible role of waves in the heating of the solar corona has been investigated. A general dispersion relation has been derived for waves propagating in a homogeneous plasma subject to dissipation by viscosity and thermal conduction. The dissipation mechanisms have been incorporated self-consistently into the equations, and no assumptions about the strength of the damping have been made. Solutions of the sixth-order dispersion relation provide information on how the damping of both slow and fast mode waves depends upon the plasma density, temperature, field strength, and angle of propagation relative to the background magnetic field. We provide a detailed comparison to the standard approach, which is to solve for the wave quantities in the absence of dissipation and then to use these quantities in expressions for the heating due to viscosity and thermal conduction.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Shen, Chengcai; Raymond, John C.; Miki?, 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. (Miki? & 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.

  13. DOUBLE POWER-LAW DISTRIBUTION OF MAGNETIC ENERGY IN THE SOLAR CORONA OVER AN ACTIVE REGION

    SciTech Connect

    Shen, Jinhua; Ji, Haisheng; Wiegelmann, Thomas; Inhester, Bernd

    2013-02-10

    In this paper, we study the magnetic energy (ME) structure contained in the solar corona over the active region NOAA 11158. The time period is chosen as from 0:00 to 06:00 UT on 2011 February 15, during which an X-class flare occurred. The nonlinear force-free field (NLFFF) and the potential field extrapolation are carried out to model the coronal magnetic field over this active region, using high-quality photospheric vector magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory as boundary conditions. We find that the volume distribution for the density of the ME (B {sup 2}/8{pi}) and the ohmic dissipation power (ODP, j {sup 2}/{sigma}), in which j is the electric current density (c/4{pi}{nabla} Multiplication-Sign B) and {sigma} is the conductivity in the corona, can be readily fitted by a broken-down double-power law. The turn-over density for the spectrum of the ME and ODP is found to be fixed at {approx}1.0 Multiplication-Sign 10{sup 4} erg cm{sup -3} and {approx}2.0 Multiplication-Sign 10{sup -15} W cm{sup -3} (assuming {sigma} = 10{sup 5} {Omega}{sup -1} m{sup -1}), respectively. Compared with their first power-law spectra (fitted below the corresponding turn-over value) which remain unchanged, the second power-law spectra (fitted above the corresponding turn-over value) for the NLFFF's ME and ODP show flare-associated changes. The potential field remains steady. These results indicate that a magnetic field with energy density larger than the turn-over energy density plays a dominant role in powering the flare.

  14. 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.

  15. Monitor PHOKA for solar XUV/EUV irradiation measurement onboard Coronas-Photon mission

    NASA Astrophysics Data System (ADS)

    Kotov, Yury; Kochemasov, Alexey; Yurov, Vitaly; Korde, Raj

    PHOKA is one of the scientific instruments onboard solar satellite Coronas-Photon. The instrument registries fluxes of solar disks radiation in two EUV bands (1-11nm and 27-37nm) and in Ly-?band (121.6nm). Minimum accumulating time of the fluxes is 0.1sec. The silicon Absolute XUV photodiodes AXUV-50(have been fabricated by IRD) are used in PHOKA. AXUV have one hundred percent internal carrier collection efficiency in EUV/XUV region. For blocking of light that is out of the measured EUV band the photodiodes have directly deposited metal filters: Ni-Pd for 1-11nm band and Cr/al for 27-37nm. The Cr/Al devices have at least 7 orders of magnitude visual light blocking. For the Ti/Pd filters the visual light blocking of six order magnitude is achieved. For measuring of visible light background signal the fused silica filters are used. Fused silica filters are placed in filter wheel. Different wheel positions correspond to different PHOKA operation regimes. In Ly-? channel (measuring solar irradiation at 121.6nm) the bare photodiode AXUV and two external filters Acron 122-XN-).5D are used. To ensure the flux measurements with good absolute accuracy the filtered photodiodes are calibrating at synchrotron radiation devices in VNIIOFI (Moscow) and PRB (Germany). The satellite will be launch in autumn season this year to 550km circular orbit with inclination 82.5 degrees. PHOKA instrument Data will be used for studying of development of solar flares and variation of solar irradiation over a long period. During entering and leaving the Earth shadow the instrument will measure solar irradiation passed throw the upper Earth atmosphere (for making occultation measurements to study of the Earth upper atmosphere layers). Detailed description of the instrument, used operation regimes, results of calibration and estimated values of signal/background will be presented and discussed in the report.

  16. 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.

  17. Discovery Of Cool Cloud-like Structures In The Corona With Hinode Solar Optical Telescope

    NASA Astrophysics Data System (ADS)

    Okamoto, Takenori; Tsuneta, S.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Nagata, S.; Shibata, K.; Tarbell, T.; Shine, R.; Berger, T.; Lites, B.; Myers, D.

    2007-05-01

    A solar observation satellite Hinode (Japanese for sun rise) was launched in September 2006.Hinode carried 3 advanced solar telescopes, visible light telescope, EUV imaging spectrometer, and X-ray telescope to simultaneously observe the photosphere, chromosphere, transition region, and corona. In the performance verification phase of the Hinode spacecraft with its telescopes, we observed an active region AR10921 near the west limb of the solar disk on November 9 2006. At this point, we planned to observe spicules on the limb with a broadband filter dedicated to Ca II H line (3968A). Ca II-H emission line (3968A) comes from plasma with temperature of approx. 10(4) K, which is much lower than the coronal temperature of 10(6-7) K. In addition to spectacular spicules, we find a large cloud-like structure located 10,000-20,000 km above the limb. The cloud has a very complex fine structure with dominant horizontal thread-like structure. Some features are moving horizontally and also have clear vertical oscillatory motions. The periods and amplitudes of these oscillations are 130-250 seconds and 200-850 km, respectively. The vertical oscillatory motion sometimes has a coherence length as long as 16,000 km. We conclude that from various observational features this vertical oscillation is a signature of Alfven waves propagating along the horizontal magnetic fields. We will discuss their origin and implications.

  18. 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.

  19. 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.

  20. 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.

  1. Are coronae of late type stars made of solar-like structures? The FX-HR diagram and the pressure-temperature correlation.

    E-print Network

    Are coronae of late type stars made of solar-like structures? The FX-HR diagram and the pressure) diagram as a fundamental tool for our study. We find that FX is strongly correlated to HR in stellar corona, i.e. the most quiet regions. We use the X-ray surface flux (FX) vs. spectral hardness ratio (HR

  2. 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).

  3. 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.

  4. Solar Corona/Wind Composition and Origins of the Solar Wind

    NASA Astrophysics Data System (ADS)

    Lepri, S. T.; Gilbert, J. A.; Landi, E.; Shearer, P.; von Steiger, R.; Zurbuchen, T.

    2014-12-01

    Measurements from ACE and Ulysses have revealed a multifaceted solar wind, with distinctly different kinetic and compositional properties dependent on the source region of the wind. One of the major outstanding issues in heliophysics concerns the origin and also predictability of quasi-stationary slow solar wind. While the fast solar wind is now proven to originate within large polar coronal holes, the source of the slow solar wind remains particularly elusive and has been the subject of long debate, leading to models that are stationary and also reconnection based - such as interchange or so-called S-web based models. Our talk will focus on observational constraints of solar wind sources and their evolution during the solar cycle. In particular, we will point out long-term variations of wind composition and dynamic properties, particularly focused on the abundance of elements with low First Ionization Potential (FIP), which have been routinely measured on both ACE and Ulysses spacecraft. We will use these in situ observations, and remote sensing data where available, to provide constraints for solar wind origin during the solar cycle, and on their correspondence to predictions for models of the solar wind.

  5. Are coronae of late type stars made of solar-like structures? The Fx-HR diagram and the pressure-temperature correlation

    E-print Network

    G. Peres; S. Orlando; F. Reale

    2004-05-14

    We show that stellar coronae can be composed of X-ray emitting structures like those in the solar corona, using a large set of ROSAT/PSPC observations of late-type-stars, and a large set of solar X-ray data collected with Yohkoh/SXT. We have considered data on the solar corona at various phases of the cycle and various kinds of X-ray coronal structures, from flares to the background corona. The surface flux (F_x) vs. spectral hardness ratio (HR) diagram is a fundamental tool for our study. We find that $F_X$ is strongly correlated to HR in stellar coronae, in the solar corona at all phases of the cycle, and in the individual solar coronal structures; all follow the same law. We therefore claim that coronae of late type stars are formed with X-ray structures very similar to the solar ones. In this scenario, the fraction of the stellar surface covered with active regions and with their bright cores increases with activity; the most active stars are brighter and hotter than if they were entirely covered with active regions so they can be explained only with the additional presence of several flares (or flare-like structures) at any time. Using the F_x vs. HR correlation (F_X ~ T^6) we derive new laws relating the temperature, pressure, volumetric heating and characteristic loop length of the coronal plasma, on all the late type stars Individual solar coronal structures and the whole solar corona, follow the same laws. We claim that the strong correlation between surface flux and temperature and the laws mentioned above are just the effect of more fundamental physical mechanisms driving the coronal structures of all the late-type stars from the emergence of new magnetic structures to their dissipation.

  6. 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.

  7. The solar cycle variation of topological structures in the global solar corona

    NASA Astrophysics Data System (ADS)

    Platten, S. J.; Parnell, C. E.; Haynes, A. L.; Priest, E. R.; Mackay, D. H.

    2014-05-01

    Context. The complicated distribution of magnetic flux across the solar photosphere results in a complex web of coronal magnetic field structures. To understand this complexity, the magnetic skeleton of the coronal field can be calculated. The skeleton highlights the (separatrix) surfaces that divide the field into topologically distinct regions, allowing open-field regions on the solar surface to be located. Furthermore, separatrix surfaces and their intersections with other separatrix surfaces (i.e., separators) are important likely energy release sites. Aims: The aim of this paper is to investigate, throughout the solar cycle, the nature of coronal magnetic-field topologies that arise under the potential-field source-surface approximation. In particular, we characterise the typical global fields at solar maximum and minimum. Methods: Global magnetic fields are extrapolated from observed Kitt Peak and SOLIS synoptic magnetograms, from Carrington rotations 1645 to 2144, using the potential-field source-surface model. This allows the variations in the coronal skeleton to be studied over three solar cycles. Results: The main building blocks which make up magnetic fields are identified and classified according to the nature of their separatrix surfaces. The magnetic skeleton reveals that, at solar maximum, the global coronal field involves a multitude of topological structures at all latitudes criss-crossing throughout the atmosphere. Many open-field regions exist originating anywhere on the photosphere. At solar minimum, the coronal topology is heavily influenced by the solar magnetic dipole. A strong dipole results in a simple large-scale structure involving just two large polar open-field regions, but, at short radial distances between ± 60° latitude, the small-scale topology is complex. If the solar magnetic dipole if weak, as in the recent minimum, then the low-latitude quiet-sun magnetic fields may be globally significant enough to create many disconnected open-field regions between ± 60° latitude, in addition to the two polar open-field regions.

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

    NASA Technical Reports Server (NTRS)

    Habbal, Shadia 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.

  9. Empirical model of the corona-solar wind with multiple current sheets

    NASA Astrophysics Data System (ADS)

    Sittler, Edward; Guhathakurta, Madhulika

    1999-06-01

    We have developed a 2D semi-empirical MHD model of the solar corona and solar wind. The model uses empirically derived electron density profiles from white light coronagraph data measured by SOHO and empirically derived model of the magnetic field which is fit to observed streamer topologies which also come from white light coronagraph data. The model requires an estimate of solar wind velocity as a function of latitude at 1 AU and radial component of the magnetic field at 1 AU for which we use Ulysses plasma and magnetic field data results. The model makes estimates as functions of radial distance and latitude of various fluid parameters such as flow velocity V, effective temperature Teff and effective heat flux qeff which are derived from conservation equations of mass, momentum and energy in the rotating frame of the Sun. The term effective indicates possible wave contributions. The model is a steady state calculation that assumes azimuthal symmetry. The magnetic field model shows that the large scale surface magnetic field is dominated by an octupole term. Initial attempts assumed the presence of a single current sheet which appears to be topologically incompatible with an internal field dominated by an octupole term. These earlier attempts had problems modeling the plasma and magnetic field near the Sun close to the equatorial plane. Therefore, for this study we have investigated the possible presence of multiple current sheets near the Sun for which initial results indicate that most of the problems with the magnetic field are corrected. For this paper we will present the results of this latest study.

  10. 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.

  11. Interchange Reconnection and Slow Solar Wind Formation at the boundaries of open field regions in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Rappazzo, A. F.; Matthaeus, W. H.; Ruffolo, D. J.; Servidio, S.; Velli, M.

    2014-12-01

    Interchange reconnection, i.e., magnetic reconnection at the interface between open and closed corona, is thought to contribute to the formation of the slowsolar wind, since it can inject the hotter and denserplasma from closed regions into the heliosphere,and account for the different slow wind composition (thatis similar to the plasma of closed regions) respectto the fast wind. The interchange process has mostly been investigatedfor magnetic field lines with opposite polarity and null points, either for the case of counterdirected loops (e.g., Fisk et al. 1999, Fisk and Schwadron 2001), or in correspondence of null points at the apex of streamers or pseudo-streamers (e.g., Wang et al. 1998,Edmondson et al. 2010, Del Zanna et al. 2011).Magnetic reconnection can certainly occur in these configurations,but they occupy a very small volume of the corona. On the other hand component magnetic reconnection at the boundarybetween coronal holes and streamers or pseudo-streamers hasreceived less attention, even though it can occur aroundthe entire extension of such boundaries. Magnetic reconnection is at the basis of Parker'snanoflare scenario for the heating of coronal loops.Modeling such regions in cartesian geometry with a strongguide field, it has been shown numerically that photosphericmotions induce a magnetic fieldcomponent orthogonal to the strong axial field characterizedby the presence of many current sheets, where the field lines are locally oppositely directed, and can reconnect (Einaudi et al. 1996; Dmitruk and Gomez 1997).The reconnection of the orthogonal component of the magneticfield leads to a change of connectivity of the field linesof the total magnetic field that connect one photospheric boundaryto the other. We have shown that a similar interchange mechanismcan operate in and around the boundaries between open and closedregions inducing a continual stochastic rearrangement of connectivityeverywhere along the open-closed boundary (Rappazzo et al. 2012). We examine a reduced MHD model of a simplified interfaceregion between open and closed corona. We extend previous results to quantify the flux of mass density,heat and momentum from the closed to the adjacent open regionthrough their shared boundary, and model the impact of this fluxon the acceleration of the slow component of the solar wind.

  12. Observations of Solar X-ray Spectra by the DIOGENESS and RESIK Spectrometers Onboard the CORONAS-F Satellite

    NASA Astrophysics Data System (ADS)

    Sylwester, J.; Sylwester, B.; Kordylewski, Z.; Phillips, K. J. H.; Kuznetsov, V. D.; Boldyrev, S. I.

    2005-11-01

    The first scientific results of the analysis of the X-ray spectra of flares and active regions in the solar corona obtained by Polish-led spectrometers RESIK and DIOGENESS onboard the CORONAS-F satellite are presented. The instruments were designed and made in the Solar Physics Division of the Space Research Center of the Polish Academy of Sciences (SRC PAS, Wroclaw, Poland). The Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (IZMIRAN, Russia) and the Astronomical Institute of the Czech Academy of Sciences also participated in designing the DIOGENESS spectrometer, while IZMIRAN (Russia), Mullard Space Science Laboratory (MSSL, Great Britain), Rutherford Appleton Laboratory (RAL, Great Britain), and Naval Research Laboratory (NRL, United States) contributed to the development of the RESIK spectrometer. In the paper, we give spectra obtained in a number of previously unstudied spectral ranges and a preliminary identification of new spectral lines. The results for the shifts of the X-ray spectral lines observed with the use of a so-called dopplerometer configuration are also presented. Methods for determining the abundances of the rare elements in the solar corona, including chlorine, potassium, and argon, are described.

  13. 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.

  14. Modeling the corona and solar wind using ADAPT maps with data assimilated helioseismic detected active regions (Invited)

    NASA Astrophysics Data System (ADS)

    Arge, C. N.; Henney, C. J.; Gonzalez-Hernandez, I. E.; Toussaint, W.; Koller, J.; Godinez, H. C.

    2013-12-01

    As the primary input to nearly all coronal and solar wind models, global estimates of the solar photospheric magnetic field distribution are critical for reliable modeling of the corona and heliosphere. Over the last several years the Air Force Research Laboratory (AFRL), in collaboration with Los Alamos National Laboratory (LANL) and the National Solar Observatory (NSO), has developed a model that produces more realistic estimates of the instantaneous global photospheric magnetic field distribution than those provided by traditional photospheric field synoptic maps. The Air Force Data Assimilative Photospheric flux Transport (ADAPT) model is a photospheric flux transport model, originally developed at NSO, that makes use of data assimilation methodologies developed at LANL. The flux transport model evolves the observed solar magnetic flux using relatively well understood transport processes when measurements are not available and then updates the modeled flux with new observations using data assimilation methods that rigorously take into account model and observational uncertainties. ADAPT originally only made use of Earth-side magnetograms, but the code has now been modified to assimilate helioseismic active region data such as those available from the Global Oscillation Network Group. In this presentation, we use the Wang-Sheeley-Arge (WSA) model driven by ADAPT maps with and without helioseismic detected active regions data assimilated into them to simulate the corona and solar wind. The WSA model results are then compared with coronal EUV and in situ solar wind observations available from STEREO & ACE.

  15. 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.

  16. 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.

  17. 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.

  18. From solar to stellar corona: the role of wind, rotation and magnetism

    E-print Network

    Réville, Victor; Strugarek, Antoine; Matt, Sean P; Bouvier, Jérôme; Folsom, Colin P; Petit, Pascal

    2015-01-01

    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 magnetic field. We recently demonstrated that the impact of coronal magnetic field topology on the rotational braking of a star can be parametrized 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 2.5Rsun. However this value likely varies from star to star...

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

    NASA Astrophysics Data System (ADS)

    Khalilpour, H.

    2015-06-01

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

  20. EUV Spectra of Solar Flares from the EUV Spectroheliograph SPIRIT aboard CORONAS-F satellite

    E-print Network

    Shestov, Sergey; Kuzin, Sergey

    2015-01-01

    We present detailed EUV spectra of 4 large solar flares: M5.6, X1.3, X3.4, and X17 classes in the spectral ranges 176-207 \\AA\\ and 280-330 \\AA. These spectra were obtained {by the slitless} spectroheliograph SPIRIT aboard the CORONAS-F satellite. To our knowledge these are the first detailed EUV spectra of large flares obtained with spectral resolution of $\\sim 0.1$ \\AA. 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 (CHIANTI database was used), with simultaneous {calculations of 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, 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 $T \\sim 10$ MK. The densities w...

  1. 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 include both amorphous and crystalline silicates. The organic matter in these samples also exhibits highly anomalous H, C, and N isotopic compositions that are consistent with formation in low temperature environments at the outermost regions of the solar nebula or presolar cold molecular cloud. The scientific frontiers for these samples include working toward a better understanding of the origins of the solar system amorphous and crystalline grains in IDPs and the very challenging task of determining the chemical composition of sub-micron organic grains. Laboratory studies of ancient and present-day dust in the Solar System thus reveal in exquisite detail the chemistry, mineralogy and isotopic properties of materials that derive from a range of astrophysical environments. These studies are an important complement to astronomical observations that help to place the laboratory observations into broader context.

  2. 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.

  3. Probing the inner heliosphere and corona with electric antennas: quasi-thermal noise spectroscopy on Solar Orbiter and Solar Probe Plus.

    NASA Astrophysics Data System (ADS)

    Zouganelis, Y.; Moncuquet, M.; Meyer-Vernet, N.; Issautier, K.; Zaslavsky, A.; Maksimovic, M.; LE CHAT, G.; Martinovic, M.

    2014-12-01

    Solar wind electrons are expected to play an important role for energy transport in the solar corona and wind. Solar wind electron velocity distributions exhibit three components: a thermal core, a suprathermal halo, and a magnetic field aligned strahl, which is usually moving away from the Sun. The origin of these non-thermal distributions is unknown. Are such distributions already present in the solar corona or are they only a consequence of the solar wind transport in the interplanetary medium? The answer to these questions is of paramount importance to understand the origin of the solar wind. It requires accurate in situ measurements of the electron properties. Traditional electron analysers generally suffer from spacecraft charging and photoelectron perturbations, but the alternative method of Quasi-Thermal Noise Spectroscopy (QTN), which has been successfully used in various space plasma environments, is immune to these limitations. This method is based on the electrostatic fluctuations induced by the thermal motion of the ambient plasma particles, which can be measured with a sensitive radio wave receiver connected to a wire dipole antenna. As this quasi-thermal noise is completely determined by the particle velocity distributions in the frame of the antenna, QTN is a high-accuracy robust method for determining electron moments together with some non-thermal features. After a short review of the QTN method, we describe its recent developments and how it will be implemented on the upcoming missions Solar Orbiter and Solar Probe Plus. New simulations of QTN measurements in the inner heliosphere are presented for typical expected corona, solar wind and ICMEs conditions down to 9.5 solar radii.

  4. Inferring the Structure of the Solar Corona and Inner Heliosphere During the Maunder Minimum Using Global Thermodynamic Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Riley, Pete; Lionello, Roberto; Linker, Jon A.; Cliver, Ed; Balogh, Andre; Beer, Jürg; Charbonneau, Paul; Crooker, Nancy; DeRosa, Marc; Lockwood, Mike; Owens, Matt; McCracken, Ken; Usoskin, Ilya; Koutchmy, S.

    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 10Be, 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.

  5. Correlation Length of Energy-Containing Structures in the Base of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Abramenko, V.; Zank, G. P.; Dosch, A. M.; Yurchyshyn, V.

    2013-12-01

    An essential parameter for models of coronal heating and fast solar wind acceleration that relay on the dissipation of MHD turbulence is the characteristic energy-containing length of the squared velocity and magnetic field fluctuations transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale defines directly the heating rate. Rather surprisingly, almost nothing is known observationally about this critical parameter. Currently, only a very rough estimate of characteristic length was obtained based on the fact that the network spacing is about 30000 km. We attempted estimation of this parameter from observations of photospheric random motions and magnetic fields measured in the photosphere inside coronal holes. We found that the characteristic length scale in the photosphere is about 600-2000 km, which is much smaller than that adopted in previous models. Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration. Fig. 1-- Plotted is the natural logarithm of the correlation function of the transverse velocity fluctuations u^2 versus the spatial lag r for the two CHs. The color code refers to the accumulation time intervals of 2 (blue), 5 (green), 10 (red), and 20 (black) minutes. The values of the Batchelor integral length ? the correlation length ? and the e-folding length L in km are shown. Fig. 2-- Plot of the natural logarithm of the correlation function of magnetic fluctuations b^2 versus the spatial lag r. The insert shows this plot with linear axes.

  6. 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

  7. Spectral solar irradiance before and during a Harmattan dust spell

    SciTech Connect

    Adeyefa, Z.D.; Holmgren, B.

    1996-09-01

    Measurements of the ground-level spectral distributions of the direct, diffuse and global solar irradiance between 300 and 1100 nm were made at Akure (7.15{degree}N, 5.5{degree}E), Nigeria, in December 1991 before and during a Harmattan dust spell employing a spectroradiometer (LICOR LI-1800) with 6 nm resolution. The direct spectral solar irradiance which was initially reduced before the dust storm was further attenuated by about 50% after the spell. Estimated values of the Angstrom turbidity coefficient {beta} indicated an increase of about 146% of this parameter while the Angstrom wavelength-exponent {alpha} decreased by about 65% within the 2-day study period. The spectral diffuse-to-direct and diffuse-to-global ratios suggest that the main cause of the significant reduction in solar irradiance at the surface was the scattering by the aerosol which led to an increase in the diffuse component. The global irradiance though reduced, was less sensitive to changing Harmattan conditions. It is recommended that solar energy devices that use radiation from Sun and sky be used under fluctuating Harmattan conditions. There are some deviations from the Angstrom formula under very turbid Harmattan conditions which could be explained by the relative increase of the particle sizes. 31 refs., 12 figs., 3 tabs.

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

    NASA Astrophysics Data System (ADS)

    Kocifaj, Miroslav; Kla?ka, Jozef

    2004-11-01

    Motion and possible capture of interstellar dust particles (ISDPs) in the Solar System are investigated. Gravitational force of the Sun, solar electromagnetic and corpuscular radiation and interplanetary magnetic field are considered. The effect of solar electromagnetic radiation plays an important role in the sense that nonspherical ISDPs can be captured (and survive) much more effectively than spherical particles. It turns out that particles of effective radii ? 0.4 ?m, moving initially near the solar equatorial plane and with impact parameter 400 RS ? b ? 500 RS (solar radii) exhibit a high probability of capture and survival in the Solar System. Only a very small number of spherical particles can be captured. Survived nonspherical ISDPs orbiting around the Sun are characterized by a quantity analogous to the Kepler's third law: /T2, where T is orbital period and is time average of cubed solar distance over the period T. The value of the quantity /T2 is 0.673 ± 0.002 [AU3 /year2 ].

  9. Decayless low-amplitude kink oscillations: a common phenomenon in the solar corona?

    NASA Astrophysics Data System (ADS)

    Anfinogentov, S. A.; Nakariakov, V. M.; Nisticò, G.

    2015-11-01

    Context. We investigate the decayless regime of coronal kink oscillations recently discovered in the Solar Dynamics Observatory (SDO)/AIA data. In contrast to decaying kink oscillations that are excited by impulsive dynamical processes, this type of transverse oscillations is not connected to any external impulsive impact, such as a flare or coronal mass ejection, and does not show any significant decay. Moreover the amplitude of these decayless oscillations is typically lower than that of decaying oscillations. Aims: The aim of this research is to estimate the prevalence of this phenomenon and its characteristic signatures. Methods: We analysed 21 active regions (NOAA 11637-11657) observed in January 2013 in the 171 Å channel of SDO/AIA. For each active region we inspected six hours of observations, constructing time-distance plots for the slits positioned across pronounced bright loops. The oscillatory patterns in time-distance plots were visually identified and the oscillation periods and amplitudes were measured. We also estimated the length of each oscillating loop. Results: Low-amplitude decayless kink oscillations are found to be present in the majority of the analysed active regions. The oscillation periods lie in the range from 1.5 to 10 min. In two active regions with insufficient observation conditions we did not identify any oscillation patterns. The oscillation periods are found to increase with the length of the oscillating loop. Conclusions: The considered type of coronal oscillations is a common phenomenon in the corona. The established dependence of the oscillation period on the loop length is consistent with their interpretation in terms of standing kink waves. Appendix A is available in electronic form at http://www.aanda.org

  10. Raytracing Software for the Simulation of the Solar K-Corona

    NASA Astrophysics Data System (ADS)

    Thernisien, A. F.; Patel, N. S.; Howard, R. A.; Marqué, C.; Vourlidas, A.

    2004-12-01

    In this talk we will present RAYTRACE, a raytracing software developed at the U.S. Naval Research Laboratory. The program is an implementation of the Thomson scattering equations applied to the solar corona (Billings 1966). Synthetic coronal images in total or polarized brightness can be calculated using models of various coronal structures. We have implemented many models for quiescent and dynamic coronal stuctures such as streamers, the heliospheric current sheet (HCS), jets and CMEs. The models are generally analytic representations of the volume electron density, but a generic data cube of electron density can also be used. The core of the program has been written in C++ pimarily for computation speed. An earlier version was written in IDL, but was quite slow. Due to the processing speed of common computers, a high resolution image (512 x 512) of the HCS streamer belt for instance can be generated in less than 1 minute (Pentium 4, 2.5 GHz, 512 Mb RAM, Linux OS). A graphical user interface has been developed in IDL and allows the user to easily enter the parameters required for each model, specifying the position and orientation of the observer and structure, the size and resolution of the images, and then to visualize the output and compare the results to actual coronal images obtained by SOHO/LASCO and in the future by the STEREO/SECCHI coronagraphs (COR1 and COR2). Some of the main features of the front-end interface include mesh plot positioning of structures in space, parameter tuning for the structures and movie making. Different studies have already been done using this software, such as the inversion of the electron density of the streamer belt or the modeling of CMEs for the STEREO mission (presented in another paper at this meeting).

  11. 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 totality, appeared in the shape of a hook in the cooler lines of Fe X and Fe XI, spanning 0.5 R(solar) in extent starting at a heliocentric distance of 1.3 R(solar), with a complex trail of hot and cool twisted structures connecting it to the solar surface. Simultaneous Fe X 17.4 nm observations from space by Proba2/SWAP provided an ideal opportunity for comparing emission from a coronal forbidden line, namely Fe X 637.4 nm, with a space-based EUV allowed line. Comparison of the Fe X 17.4 nm and 637.4 nm emission provided the first textbook example of the role of radiative excitation in extending the detectability of coronal emission to much larger heliocentric distances than its collisionally excited component. These eclipse observations demonstrate the unique capabilities of coronal forbidden lines for exploring the evolution of the coronal magnetic field in the heliocentric distance range of 1 - 3 R(solar), which is currently inaccessible to any space-borne or ground-based observatory.

  12. Short time variability of solar corona during recent solar cycle minimum

    NASA Astrophysics Data System (ADS)

    Siarkowski, Marek; Gryciuk, Magdalena; Gburek, Szymon; Sylwester, Janusz; Sylwester, Barbara; Kepa, Anna; Buczkowska, Agnieszka; Kowalinski, Miroslaw

    Sphinx is the X-ray spectrophotometer designed to measure X-ray emission from the Sun in the energy range between 0.8 keV and 15 keV. The instrument is placed onboard Russian KORONAS-PHOTON satellite launched on January 30, 2009. In this paper we present the observations of coronal emission obtained between March-April and August-September 2009, i.e. the times towards the end of the last, very prolonged and deep minimum of solar activity. Prompt analysis of SphinX spectra reveal the variability of the average coronal plasma charac-teristics like the temperature and emission measure. These data are used to compare SphinX and GOES measurements, for selected times. Examples of many sub/microflare events with maxima of the X-ray flux, observed much below the GOES sensitivity threshold level will be presented.

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

    E-print Network

    Enrico Landi; Steven R. Cranmer

    2008-09-30

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

  14. 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.

  15. 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.

  16. 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.

  17. A Low-Frequency (30 - 110 MHz) Antenna System for Observations of Polarized Radio Emission from the Solar Corona

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Kathiravan, C.; Sundararajan, M. S.; Barve, Indrajit V.; Sastry, C. V.

    2008-12-01

    An interferometer antenna system to observe polarized radio emission from the solar corona at different frequencies in the range 30 - 110 MHz has been commissioned recently by the Indian Institute of Astrophysics at the Gauribidanur Radio Observatory (latitude 13°36'12''N and longitude 77°27'07''E), about 100 km north of Bangalore ( http://www.iiap.res.in/centres_radio.htm ). This paper describes the antenna system, associated analog/digital receiver setup, calibration scheme, and preliminary results.

  18. Modern sources of dust in the solar system

    NASA Technical Reports Server (NTRS)

    Dermott, Stanley F.; Durda, D. D.; Gustafson, B. A. S.; Jayaraman, S.; Liou, J.-C.; Xu, Y.-L.

    1994-01-01

    The observed size-frequency distributions of the main-belt and family asteroids and the results of an analysis of the IRAS data on the zodiacal background and the solar system dustbands were used to estimate the extent of the contribution of asteroidal dust to the zodiacal cloud. It is concluded that the total asteroidal contribution to the zodiacal signal is probably 40% of the total flux. Thus, some 60% of the flux probably derives from a source other than main-belt asteroids.

  19. Spectroscopic Studies of Solar Corona VII. Formation of a Coronal Loop by Evaporation

    NASA Astrophysics Data System (ADS)

    Singh, Jagdev; Sakurai, Takashi; Ichimoto, Kiyoshi; Suzuki, Isao; Hagino, Masaoki

    2005-02-01

    We obtained time-sequence spectroscopic observations in (Fe x) 6374 Å and (Fe xiv) 5303 Å lines successively with the 25-cm coronagraph, and narrow-band and Doppler images in 5303 Å line by the 2-D 10-cm Doppler coronagraph “NOGIS” at the Norikura Solar Observatory, of a coronal region for about 7 h on 9 19 20, 2001. The raster scans were obtained with a quasi-periodicity of about 14 min and “NOGIS” obtained the images with an interval of about 1 min. The coronal region observed showed the formation of a coronal loop by a high-speed surge in the 6374 Å line rising from one of the footpoints of the loop. Off the limb spectroscopic observations in the 6374 Å line showed large velocities along the line of sight and vertical to the solar limb at the time of formation of the loop. The 5303 Å line observations showed negligible line-of-sight velocities and low vertical velocities when compared to those in the 6374 Å line. A hump in the intensity plots in 5303 Å with height appears to move up with respect to the solar limb with an average velocity of 4km s-1. The FWHM of the 6374 Å showed a much smaller value of about 0.7 Å near the foot point as compared to a value of 1.2 Å at larger heights at the beginning of observations. Later as the loop developed, the FWHM of 6374 Å line showed a gradual decrease along the loop up to 70? from the limb, reached a minimum value of about 0.5 Å and then increased with height during the formation of the loop; this trend lasted for about 2 h. About 3 h after the beginning of the formation of the loop, the FWHM of 6374 Å emission line showed normal values and normal rate of increase with height with some fluctuations. The FWHM of the 5303 Å line did not show such variations along the loop and showed normal decrease in FWHM with height found earlier (Singh et al., 2003a). These observations suggest that a relatively cooler plasma at a temperature of about 0.7 MK or less (corresponding to minimum value of FWHM of 0.5 Å) was ejected from the transition region with a large velocity of about 48km s-1, heated up in the corona by some process and formed a coronal loop with a height of about 200? above the limb that had lifetime greater than 4 h. It appears that the plasma moved from one of the footpoints and the loop was formed by evaporation of chromospheric plasma. No large-scale brightening and H? flare were observed in this region during the observational period of 7 h.

  20. 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.

  1. 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.

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

    E-print Network

    Pierre-Henri Chavanis

    1999-12-06

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

  3. 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 ? 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 ? falls off with height; and (3) the variations of the local fast magnetosonic speed and plasma ? 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.

  4. Two-fluid and magnetohydrodynamic modelling of magnetic reconnection in the MAST spherical tokamak and the solar corona

    NASA Astrophysics Data System (ADS)

    Browning, P. K.; Cardnell, S.; Evans, M.; Arese Lucini, F.; Lukin, V. S.; McClements, K. G.; Stanier, A.

    2016-01-01

    Twisted magnetic flux ropes are ubiquitous in laboratory and astrophysical plasmas, and the merging of such flux ropes through magnetic reconnection is an important mechanism for restructuring magnetic fields and releasing free magnetic energy. The merging-compression scenario is one possible start-up scheme for spherical tokamaks, which has been used on the Mega Amp Spherical Tokamak (MAST). Two current-carrying plasma rings or flux ropes approach each due to mutual attraction, forming a current sheet and subsequently merge through magnetic reconnection into a single plasma torus, with substantial plasma heating. Two-dimensional resistive and Hall-magnetohydrodynamic simulations of this process are reported, including a strong guide field. A model of the merging based on helicity-conserving relaxation to a minimum energy state is also presented, extending previous work to tight-aspect-ratio toroidal geometry. This model leads to a prediction of the final state of the merging, in good agreement with simulations and experiment, as well as the average temperature rise. A relaxation model of reconnection between two or more flux ropes in the solar corona is also described, allowing for different senses of twist, and the implications for heating of the solar corona are discussed.

  5. 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.

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

    SciTech Connect

    Clayton, Geoffrey C.; Gallagher, J. S.; Freeman, W. R.; Camp, K. A. E-mail: wfreem2@lsu.edu

    2011-08-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  8. 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).

  9. 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. .

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

    NASA Astrophysics Data System (ADS)

    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.

  11. IMPACT OF TEMPERATURE-DEPENDENT RESISTIVITY AND THERMAL CONDUCTION ON PLASMOID INSTABILITIES IN CURRENT SHEETS IN THE SOLAR CORONA

    SciTech Connect

    Ni Lei; Roussev, Ilia I.; Lin Jun; Ziegler, Udo E-mail: iroussev@ifa.hawaii.edu

    2012-10-10

    In this paper, we investigate, by means of two-dimensional magnetohydrodynamic simulations, the impact of temperature-dependent resistivity and thermal conduction on the development of plasmoid instabilities in reconnecting current sheets in the solar corona. We find that the plasma temperature in the current-sheet region increases with time and it becomes greater than that in the inflow region. As secondary magnetic islands appear, the highest temperature is not always found at the reconnection X-points, but also inside the secondary islands. One of the effects of anisotropic thermal conduction is to decrease the temperature of the reconnecting X-points and transfer the heat into the O-points, the plasmoids, where it gets trapped. In the cases with temperature-dependent magnetic diffusivity, {eta} {approx} T {sup -3/2}, the decrease in plasma temperature at the X-points leads to (1) an increase in the magnetic diffusivity until the characteristic time for magnetic diffusion becomes comparable to that of thermal conduction, (2) an increase in the reconnection rate, and (3) more efficient conversion of magnetic energy into thermal energy and kinetic energy of bulk motions. These results provide further explanation of the rapid release of magnetic energy into heat and kinetic energy seen during flares and coronal mass ejections. In this work, we demonstrate that the consideration of anisotropic thermal conduction and Spitzer-type, temperature-dependent magnetic diffusivity, as in the real solar corona, are crucially important for explaining the occurrence of fast reconnection during solar eruptions.

  12. 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 states measured by SWICS on the Advanced Composition Explorer, ACE, in the ecliptic plane at 1 AU, at the time of both eclipses. The remarkable correspondence between these two measurements establishes the first direct link between the distribution of charge states in the corona and in interplanetary space.

  13. ELECTRON DENSITY VARIATION IN OFFLIMB SOLAR CORONA STRUCTURES I. UgarteUrra , J.G. Doyle, and M.S. Madjarska

    E-print Network

    1 ELECTRON DENSITY VARIATION IN OFF­LIMB SOLAR CORONA STRUCTURES I. Ugarte­Urra #3; , J.G. Doyle a study of the electron density variation for off limb observations with the Coronal Diagnostic Spec­ trometer (CDS) on board SoHO using the density sensi­ tive coronal line ratio Si X (356

  14. 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.

  15. 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.

  16. 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.

  17. 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 flux (the amount of solar energy reaching the planet), solar spectrum, solar angle, rover tilt, and optical depth (the opacity of the atmosphere due to dust) were the most significant. Microsoft Excel and Visual Basic are used for data analysis. The results of this work will be used to improve the dust accumulation and atmosphere effects model that was first created after the Mars Pathfinder mission. This model will be utilized and applied when considering the design of solar panel array systems on future Mars projects. Based on this data, and depending upon the tenure and application of the mission, designers may also elect to employ special tools to abate dust accumulation, or decide that the expected level of accumulation is acceptable.

  18. 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.

  19. X-ray observations of characteristic structures and time variations from the solar corona - Preliminary results from Skylab.

    NASA Technical Reports Server (NTRS)

    Vaiana, G. S.; Davis, J. M.; Giacconi, R.; Krieger, A. S.; Silk, J. K.; Timothy, A. F.; Zombeck, M.

    1973-01-01

    Examples taken from the S-054 X-ray telescope observations made during the first Skylab mission show the hot coronal plasma tracing the configuration of the magnetic fields. The high spectral resolution and sensitivity of the instrument has enabled the following two facts to be more firmly established: (1) that the 'quiet homogeneous corona' is in fact highly structured and that the structures observed appear to be the results of dispersed active region magnetic fields; and (2) that numerous bright points are distributed randomly on the disk. Their presence at high latitudes may play a role in solar cycle models. In addition, the capability of Skylab for studying time evolution has enabled the restructuring of coronal features to be seen at times of high activity, indicating a restructuring of the coronal magnetic fields.

  20. Dielectronic recombination rates, ionization equilibrium, and radiative energy-loss rates for neon, magnesium, and sulfur ions in low-density plasmas. [in solar corona

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.; Davis, J.; Rogerson, J. E.; Blaha, M.

    1979-01-01

    Results of detailed and systematic calculations are presented for the total dielectronic recombination rate coefficients for the ions of Ne, Mg, and S in a low-density predominantly hydrogen plasma. The new recombination rates are used to calculate solar corona ionization-equilibrium distributions of the ions. The most important effect of dielectronic recombination for ions in corona equilibrium is found to be a shift in the maximum-abundance temperatures toward higher temperatures, which are in some cases reduced from those predicted on the basis of the simple Burgess formula.

  1. CHARGE STATE EVOLUTION IN THE SOLAR WIND. II. PLASMA CHARGE STATE COMPOSITION IN THE INNER CORONA AND ACCELERATING FAST SOLAR WIND

    SciTech Connect

    Landi, E.; Gruesbeck, J. R.; Lepri, S. T.; Zurbuchen, T. H.; Fisk, L. A.

    2012-12-10

    In the present work, we calculate the evolution of the charge state distribution within the fast solar wind. We use the temperature, density, and velocity profiles predicted by Cranmer et al. to calculate the ionization history of the most important heavy elements in the solar corona and solar wind: C, N, O, Ne, Mg, Si, S, and Fe. The evolution of each charge state is calculated from the source region in the lower chromosphere to the final freeze-in point. We show that the solar wind velocity causes the plasma to experience significant departures from equilibrium at very low heights, well inside the field of view (within 0.6 R{sub sun} from the solar limb) of nearly all the available remote-sensing instrumentation, significantly affecting observed spectral line intensities. We also study the evolution of charge state ratios with distance from the source region, and the temperature they indicate if ionization equilibrium is assumed. We find that virtually every charge state from every element freezes in at a different height, so that the definition of freeze-in height is ambiguous. We also find that calculated freeze-in temperatures indicated by charge state ratios from in situ measurements have little relation to the local coronal temperature of the wind source region, and stop evolving much earlier than their correspondent charge state ratio. We discuss the implication of our results on plasma diagnostics of coronal holes from spectroscopic measurements as well as on theoretical solar wind models relying on coronal temperatures.

  2. 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.

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

    E-print Network

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

    2015-01-01

    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 Pred...

  4. 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.

  5. 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.

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

    E-print Network

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

    2015-01-01

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

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

    E-print Network

    Javaraiah, J

    2013-01-01

    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 0.94Rsun, 0.95Rsun,...,1.0Rsun measured by 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) which 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 approximate 30 deg latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94Rsun and 0.98Rsun.The variation in the ...

  8. A solar escalator on Mars: Self-lifting of dust layers by radiative heating

    NASA Astrophysics Data System (ADS)

    Daerden, F.; Whiteway, J. A.; Neary, L.; Komguem, L.; Lemmon, M. T.; Heavens, N. G.; Cantor, B. A.; Hébrard, E.; Smith, M. D.

    2015-09-01

    Dust layers detected in the atmosphere of Mars by the light detection and ranging (LIDAR) instrument on the Phoenix Mars mission are explained using an atmospheric general circulation model. The layers were traced back to observed dust storm activity near the edge of the north polar ice cap where simulated surface winds exceeded the threshold for dust lifting by saltation. Heating of the atmospheric dust by solar radiation caused buoyant instability and mixing across the top of the planetary boundary layer (PBL). Differential advection by wind shear created detached dust layers above the PBL that ascended due to radiative heating and arrived at the Phoenix site at heights corresponding to the LIDAR observations. The self-lifting of the dust layers is similar to the "solar escalator" mechanism for aerosol layers in the Earth's stratosphere.

  9. 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.

  10. A theory for the radiation of magnetohydrodynamic surface waves and body waves into the solar corona

    NASA Technical Reports Server (NTRS)

    Davila, Joseph M.

    1988-01-01

    The Green's function for the slab coronal hole is obtained explicitly. The Fourier integral representation for the radiated field inside and outside the coronal hole waveguide is obtained. The radiated field outside the coronal hole is calculated using the method of steepest descents. It is shown that the radiated field can be written as the sum of two contributions: (1) a contribution from the integral along the steepest descent path and (2) a contribution from all the poles of the integrand between the path of the original integral and the steepest descent path. The free oscillations of the waveguide can be associated with the pole contributions in the steepest descent representation for the Green's function. These pole contributions are essentially generalized surface waves with a maximum amplitude near the interface which separates the plasma inside the coronal hole from the surrounding background corona. The path contribution to the integral is essentially the power radiated in body waves.

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

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1998-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1997-01-01

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

  13. 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 the maximum frequency becomes smaller, alpha particles and protons are more likely to be in thermal equilibrium. However, if the maximum frequency is below a critical value, ion cyclotron resonance occurs at a greater height and a hot corona cannot be produced.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Messenger, Scott R.; Nakamura-Messenger, Keiko

    2015-08-01

    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 (< 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. We will present an overview of the current state of understanding of the properties and origins of organic matter in primitive IDPs.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    SciTech Connect

    Didkovsky, L.; Judge, D.; Wieman, S.; Kosovichev, A. G.; Woods, T.

    2011-09-01

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

  18. Sixteen Years of Ulysses Interstellar Dust Measurements in the Solar System. II. Fluctuations in the Dust Flow from the Data

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  19. A tilted-dipole MHD model of the solar corona and solar wind A. V. Usmanov1

    E-print Network

    Usmanov, Arcadi V.

    a bimodal solar wind with a sharp transition from a relatively uniform fast and tenuous wind at high latitudes to a slower and denser wind near the solar equator [Phillips et al., 1995]. The magnetic field

  20. Dust in the Interplanetary Medium

    E-print Network

    Mann, Ingrid; Meyer-Vernet, Nicole; Zaslavsky, Arnaud; Lamy, Herve

    2010-01-01

    The mass density of dust particles that form from asteroids and comets in the interplanetary medium of the solar system is, near 1 AU, comparable to the mass density of the solar wind. It is mainly contained in particles of micrometer size and larger. Dust and larger objects are destroyed by collisions and sublimation and hence feed heavy ions into the solar wind and the solar corona. Small dust particles are present in large number and as a result of their large charge to mass ratio deflected by electromagnetic forces in the solar wind. For nano dust particles of sizes 1 - 10 nm, recent calculations show trapping near the Sun and outside from about 0.15 AU ejection with velocities close to solar wind velocity. The fluxes of ejected nano dust are detected near 1AU with the plasma wave instrument onboard the STEREO spacecraft. Though such electric signals have been observed during dust impacts before, the interpretation depends on several different parameters and data analysis is still in progress.

  1. Solar panel clearing events, dust devil tracks, and in-situ vortex detections on Mars

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Reiss, Dennis

    2015-03-01

    Spirit rover solar array data, which if publicly-archived would provide a useful window on Mars meteorology, shows dust-clearing events coinciding with the onset of dust devil season in three Mars years. The recurrence interval of 100-700 days is consistent with the extrapolation of Pathfinder and Phoenix vortex encounters indicated by pressure drops of ?6-40 Pa (similar to laboratory measurements of dust lifting threshold) and with observed areas and rates of generation of dust devil tracks on Mars.

  2. THERMODYNAMICS OF THE SOLAR CORONA AND EVOLUTION OF THE SOLAR MAGNETIC FIELD AS INFERRED FROM THE TOTAL SOLAR ECLIPSE OBSERVATIONS OF 2010 JULY 11

    SciTech Connect

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

    2011-06-20

    We report on the first multi-wavelength coronal observations, taken simultaneously in white light, 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, during the total solar eclipse of 2010 July 11 from the atoll of Tatakoto in French Polynesia. The data enabled temperature differentiations as low as 0.2 x 10{sup 6} K. The first-ever images of the corona in Fe IX and Ni XV showed that there was very little plasma below 5 x 10{sup 5} K and above 2.5 x 10{sup 6} K. The suite of multi-wavelength observations also showed that open field lines have an electron temperature near 1x 10{sup 6} K, while the hottest, 2x 10{sup 6} K, plasma resides in intricate loops forming the bulges of streamers, also known as cavities, as discovered in our previous eclipse observations. The eclipse images also revealed unusual coronal structures, in the form of ripples and streaks, produced by the passage of coronal mass ejections and eruptive prominences prior to totality, which could be identified with distinct temperatures for the first time. These trails were most prominent at 10{sup 6} K. Simultaneous Fe X 17.4 nm observations from Proba2/SWAP provided the first opportunity to compare Fe X emission at 637.4 nm with its extreme-ultraviolet (EUV) counterpart. This comparison demonstrated the unique diagnostic capabilities of the coronal forbidden lines for exploring the evolution of the coronal magnetic field and the thermodynamics of the coronal plasma, in comparison with their EUV counterparts in the distance range of 1-3 R{sub sun}. These diagnostics are currently missing from present space-borne and ground-based observatories.

  3. Radio antennas as in-situ dust detectors : from Voyager to Solar Probe Plus

    NASA Astrophysics Data System (ADS)

    Zaslavsky, A.

    2013-05-01

    Radio instruments onboard space probes can detect cosmic dust over a wide range of sizes via impact ionization. Such measurements have been performed on a number of spacecraft, using instruments that were basically not designed to do so. The first of such measurement was reported in 1983 when Voyager 1 and 2 crossed Saturn's ring plane. Since then, several dust radio detections have been carried out in various environements : planets, comets, free solar wind... More recently the STEREO mission, and its TDS electrostatic waveform analyzer, enabled us to make significant progress in our understanding of the mechanisms of radio signals generation by a dust impact. In particular, we could calibrate and use the technique in two size ranges : the sub-micron size range (0.2 micron) in which the orbital motion of the spacecraft permits identification of separate interstellar and interplanetary dust components ; and the nanometer (10 nm) size range, STEREO performing the only, up to now, measurements of interplanetary dust of such small sizes. I will show past and present radio measurements of dust and present the newly developped models for understanding the signal generation, and the calibration obtained. The developped technique has today a particular importance since, in the absence of dedicated dust experiments on future missions Solar Orbiter and Solar Probe Plus, it will be our only access to the in-situ study of the dust environment at distances from the Sun as close as 0.05 UA.

  4. 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.

  5. Stereoscopic observations of a solar flare hard X-ray source in the high corona

    NASA Technical Reports Server (NTRS)

    Kane, S. R.; Mctiernan, J.; Loran, J.; Fenimore, E. E.; Klebesadel, R. W.; Laros, J. G.

    1992-01-01

    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.

  6. Laboratory study of the equilibrium and eruption of line-tied magnetic flux ropes in the solar corona

    NASA Astrophysics Data System (ADS)

    Myers, Clayton Edward

    2015-03-01

    Ideal magnetohydrodynamic (MHD) instabilities such as the kink instability and the torus instability are leading candidates to explain the sudden onset of eruptive events in the solar corona. These instabilities act on line-tied magnetic flux ropes--long-lived arched structures anchored to the solar surface. In spite of substantial observational and numerical research, however, the role of these instabilities in the corona remains a subject of intense debate. For this thesis, we have constructed and operated a new line-tied flux rope experiment that permits for the first time the study of both the kink and torus instabilities in the laboratory. This experiment has the following key features: (1) the arched flux rope is line-tied to two conducting footpoints; (2) the system is magnetically dominated (low-beta) with significant stored energy; (3) the system is driven quasi-statically, producing a long-lived equilibrium; and (4) the flux rope is generated within a potential (vacuum) magnetic field arcade whose decay index---the predicted torus instability control parameter---can be externally controlled. The flux ropes are diagnosed using a two-dimensional in situ magnetic probe array whose cross-section covers a substantial portion of the plasma. The central result of this thesis is that toroidal field forces, which are traditionally neglected in the analysis of coronal flux ropes, are identified for the first time as an essential contributor to both the equilibrium and the stability of line-tied flux ropes. Most importantly, experimental measurements show that a tension force derived from a self-generated paramagnetic toroidal field exerts a restoring force on the line-tied plasma and suppresses eruptive behavior in a significant portion of the parameter space. This suppression extends to regimes that are both kink and torus unstable. We find that, in order to explain the measured tension force, low aspect ratio and line-tying effects must be considered. Finally, flux rope eruptions are observed in these experiments, but only in regimes with sufficiently low external toroidal field where the tension force is reduced. These results constitute a new condition for the prediction of line-tied magnetic flux rope eruptions: that of low external toroidal field.

  7. Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. I. Linear Force-Free Approximation

    E-print Network

    M. K. Georgoulis; Barry J. LaBonte

    2007-06-27

    We self-consistently derive the magnetic energy and relative magnetic helicity budgets of a three-dimensional linear force-free magnetic structure rooted in a lower boundary plane. For the potential magnetic energy we derive a general expression that gives results practically equivalent to those of the magnetic Virial theorem. All magnetic energy and helicity budgets are formulated in terms of surface integrals applied to the lower boundary, thus avoiding computationally intensive three-dimensional magnetic field extrapolations. We analytically and numerically connect our derivations with classical expressions for the magnetic energy and helicity, thus presenting a so-far lacking unified treatment of the energy/helicity budgets in the constant-alpha approximation. Applying our derivations to photospheric vector magnetograms of an eruptive and a noneruptive solar active regions, we find that the most profound quantitative difference between these regions lies in the estimated free magnetic energy and relative magnetic helicity budgets. If this result is verified with a large number of active regions, it will advance our understanding of solar eruptive phenomena. We also find that the constant-alpha approximation gives rise to large uncertainties in the calculation of the free magnetic energy and the relative magnetic helicity. Therefore, care must be exercised when this approximation is applied to photospheric magnetic field observations. Despite its shortcomings, the constant-alpha approximation is adopted here because this study will form the basis of a comprehensive nonlinear force-free description of the energetics and helicity in the active-region solar corona, which is our ultimate objective.

  8. The Plasma and Field Perturbation Around a Charged Dust Cloud in the Solar Wind

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    When asteroids and meteoroids collide at their typical speeds of 20km/s at 1AU, they can totally disrupt each other if their mass ratios are within a factor of 106. The resulting charged dust and gas can be picked up by the solar wind, resulting in a large magnetic structure containing over 106kg of mass, accelerated to almost the solar wind speed. This dust is invisible to our Earth-based detectors as are the impactors and targets but they can be detected by our interplanetary spacecraft and they do create ground-level magnetospheric disturbances when they impact the Earth. Moreover we can identify the parent bodies for these impacting bolides by determining which asteroids cross the ecliptic plane along the path of these disturbances carried by the solar wind. Hence, these structures can be used in a planetary defense strategy. Since they have a very practical application we need to understand their formation and evolution better. We apply our multi-fluid code to model this interaction, to show how the field is affected by charged dust. We assume a cloud of charged dust moving close to the solar wind speed, but a small velocity difference exists between the dust and ions. Gravity pulls horizontally opposite to the solar wind plasma, maintaining the concentration of dust cloud.

  9. 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.

  10. 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.

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

    E-print Network

    Hahn, Joseph M.

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

  12. 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.

  13. 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.

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

    SciTech Connect

    Pomoell, J.; Vainio, R.

    2012-02-01

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

  15. 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.

  16. 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.

  17. 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.

  18. 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 potential (FIP) values. The low FIP elements do not show enhancement in the stellar coronae as they do in the Sun, except perhaps for K in {sigma} Gem. While {sigma} Gem and HR 1099 differ in their emission measure distributions, they have very similar elemental abundances.

  19. Absolute velocity measurements in the solar transition region and corona from observations of ultraviolet emission line profiles

    NASA Astrophysics Data System (ADS)

    Hassler, Donald M.

    An experimental technique to measure absolute velocities of minor ions formed in the solar transition region and corona is presented. A sounding rocket experiment July 27, 1987 obtained high resolution extreme ultraviolet (EUV) spectra along a solar diameter with spatial resolution of 20 x 20 arcseconds. The center-to-limb behavior of four representative lines (Si II 1553, Fe II 1563, CIV 1548, Ne VIII 770) formed at different heights in the solar atmosphere is discussed. Assuming that horizontal motions cancel statistically so that the line-of-sight velocity approaches zero at the limb, we find a net radial downflow of approximately 7.5 +/- 1.0 km/s for C IV, 2.7 +/- 1.5 km/s for Fe II 1563, and upper limits of 0 +/- 1.2 km/s and 0 +/- 4 km/s for Si II and Ne VIII, respectively. The absolute wavelengths of each emission line were determined by direct comparison with wavelengths of known platinum lines generated by an inflight calibration lamp. We then test the assumption of line-of-sight velocity approaching zero at the limb by comparing our wavelengths with recently published laboratory rest wavelengths of the solar emission lines. We find agreement within the published uncertainties of the laboratory wavelengths. The result for Si II indicates that the next radial flow in the chromosphere is near zero, although small scale velocity structures may vary by as much as 4-6 km/sec. The center-to-limb behavior of Fe II 1563 suggests, contrary to previous thinking, that there might be a significant contribution of Fe II emission at higher temperatures characteristic of the lower transition region. Finally, the upper limit on the radial flow velocity for Ne VIII provides a constraint on the radial flow at coronal temperatures. Complicating the accurate measurement of Doppler velocities is the presence of small nonlinearities in the microchannel plates used in UV and EUV detectors which introduce small position offsets between the input and output of the detector. The results of these position offsets is a distortion in the spatial and spectral scale of the detector, causing slight shifts or deviations in the wavelength dispersion curve.

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

    SciTech Connect

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

    2008-06-09

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

  1. 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°.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  4. A model for absorption of solar radiation by mineral dust within liquid cloud drops

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Thompson, Jonathan E.

    2015-10-01

    Models of light scattering and absorption that consider the effect of insoluble inclusions present within liquid cloud droplets may assume the inclusion occupies random locations within the droplet. In certain cases, external forces can lead to certain orientations or alignments that are strongly preferred. Within this modeling study, we consider one such case in which an insoluble mineral dust inclusion (?=2.6 g/cm3) is placed within a liquid water drop (?=1.0 g/cm3). Such an instance mimics mineral dust aerosols being incorporated within cloud drops in Earth's atmosphere. Model results suggest super-micron mineral dust settles to the bottom of cloud droplets. However, Brownian motion largely randomizes the position of sub-micron mineral dust within the droplet. The inherent organization of the particles that result has important consequences for light absorption by mineral dust when present within a cloud drop. Modeled results suggest light absorption efficiency may be enhanced by as much as 4-6 fold for an isolated droplet experiencing direct solar illumination at solar zenith angles of <20°. For such an isolated droplet, the absorption efficiency enhancement falls rapidly with increasing solar zenith angle indicating a strong angle of incidence dependence. We also consider the more common case of droplets that contain dust inclusions deep within optically dense clouds. Absorption efficiency enhancements for these locales follow a dramatically different pattern compared to the optically isolated droplet due to the presence of diffuse rather than direct solar irradiation. In such cases, light absorption efficiency is decreased through including super-micron dust within water droplets. The study has important implications for modeling the absorption of sunlight by mineral dust aerosol within liquid water clouds. The angle of incidence dependence also reveals that experimental measurement of light absorption for cases in which particle alignment occurs may not always accurately reflect atmospheric absorption of sunlight. Therefore, care must be taken to extrapolate measurement data to climate models.

  5. Particle Acceleration in a Statistically Modeled Solar Active-Region Corona

    NASA Astrophysics Data System (ADS)

    Toutounzi, A.; Vlahos, L.; Isliker, H.; Dimitropoulou, M.; Anastasiadis, A.; Georgoulis, M.

    2013-09-01

    Elaborating a statistical approach to describe the spatiotemporally intermittent electric field structures formed inside a flaring solar active region, we investigate the efficiency of such structures in accelerating charged particles (electrons). The large-scale magnetic configuration in the solar atmosphere responds to the strong turbulent flows that convey perturbations across the active region by initiating avalanche-type processes. The resulting unstable structures correspond to small-scale dissipation regions hosting strong electric fields. Previous research on particle acceleration in strongly turbulent plasmas provides a general framework for addressing such a problem. This framework combines various electromagnetic field configurations obtained by magnetohydrodynamical (MHD) or cellular automata (CA) simulations, or by employing a statistical description of the field's strength and configuration with test particle simulations. Our objective is to complement previous work done on the subject. As in previous efforts, a set of three probability distribution functions describes our ad-hoc electromagnetic field configurations. In addition, we work on data-driven 3D magnetic field extrapolations. A collisional relativistic test-particle simulation traces each particle's guiding center within these configurations. We also find that an interplay between different electron populations (thermal/non-thermal, ambient/injected) in our simulations may also address, via a re-acceleration mechanism, the so called `number problem'. Using the simulated particle-energy distributions at different heights of the cylinder we test our results against observations, in the framework of the collisional thick target model (CTTM) of solar hard X-ray (HXR) emission. The above work is supported by the Hellenic National Space Weather Research Network (HNSWRN) via the THALIS Programme.

  6. 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.

  7. 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.

  8. 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, and Nicholas Weber (Dexter Southfield School) for collaboration on imaging at the Australian total eclipse.

  9. Characterization of small dust particles in the Solar System through polarization: Laboratory measurements

    NASA Astrophysics Data System (ADS)

    Muñoz, Olga

    2013-04-01

    Small dust particles are present in different scenarios in the Solar System like in the atmospheres of planets, satellites an comets, surfaces of different objects, in the space between them, and planetary rings. By analyzing the solar light scattered by those particles we can retrieve valuable information about their physical properties (shape, size, and composition) as well as their location within a certain atmosphere. The main purpose of this talk is to show how experimental data of intensity and polarization of the scattered light of different atmospheric dust analogues can be used to shed some light on the nature of dust particles in the Solar System. The experimental data presented in this talk are available in digital form in the Amsterdam-Granada Light scattering Database at www.iaa.es/scattering (Muñoz, Moreno, Guirado, Dabrowska, Volten, Hovenier; JQSRT 2012; 113(7): 565-574).

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

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Yokoyama, T.

    2015-06-01

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

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

    E-print Network

    Collier, Michael R

    2008-01-01

    We calculate the flux of neutral solar wind observed on the lunar surface at the terminator due to solar wind protons penetrating exospheric dust grains with (1) radii greater than 0.1 microns and (2) radii greater than 0.01 microns. For grains with radii larger than 0.1 microns, the ratio of the neutral solar wind flux produced by exospheric dust to the incident ionized solar wind flux is estimated to be about 10^-4-10^-3 for solar wind speeds in excess of 800 km/s, but much lower (less than 10^-5) at average to slow solar wind speeds. However, when the smaller grain sizes are considered, this ratio is estimated to be greater than 10^-5 at all speeds, and at speeds in excess of 700 km/s reaches about 10^-3. These neutral solar wind fluxes are easily measurable with current low energy neutral atom instrumentation. Observations of neutral solar wind from the surface of the Moon would provide independent information on the distribution of very small dust grains in the lunar exosphere that would complement and c...

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

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Stubbs, Timothy J.

    2007-01-01

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

  13. 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.

  14. 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.

  15. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  17. Fast magnetoacoustic wave trains of sausage symmetry in cylindrical waveguides of the solar corona

    E-print Network

    Shestov, S; Kuzin, S

    2015-01-01

    Fast magnetoacoustic waves guided along the magnetic field by plasma non-uniformities, in particular coronal loops, fibrils and plumes, are known to be highly dispersive, which leads to the formation of quasi-periodic wave trains excited by a broadband impulsive driver, e.g. a solar flare. We investigated effects of cylindrical geometry on the fast sausage wave train formation. We performed magnetohydrodynamic numerical simulations of fast magnetoacoustic perturbations of a sausage symmetry, propagating from a localised impulsive source along a field-aligned plasma cylinder with a smooth radial profile of the fast speed. The wave trains are found to have pronounced period modulation, with the longer instant period seen in the beginning of the wave train. The wave trains have also a pronounced amplitude modulation. Wavelet spectra of the wave trains have characteristic tadpole features, with the broadband large-amplitude heads preceding low-amplitude quasi-monochromatic tails. The mean period of the wave train...

  18. The evidence of magnetic energy accumulation in the solar corona before a flare

    NASA Astrophysics Data System (ADS)

    Podgorny, Igor; Meshalkina, Natalia; Podgorny, Alexander

    The magnetic field dynamics of active regions that produce large (X-class) flares are investigated. The active region magnetic flux is obtained by using the results of calculations of the normal magnetic component in the real active regions. It is shown that the main condition for appearance of an X-class flare is the big magnetic flux ( Phi > 10(22) Mx) of the active region. This condition is necessary but not a sufficient. The large flare appears above an active region, if the magnetic field distribution is very complex. The coronal magnetic field above such active region contains magnetic singular lines of X-type. In the vicinity of singular lines current sheets can be formed. There are no magnetic singular lines of X-type above a simple bipolar active region. The bipolar active regions do not produce solar flares. During a solar flare, when the accumulated energy is fast released, the conservation of the magnetic field distribution in the active region during the majority of flares takes place. The presented results support the flare theory based on the slow magnetic energy accumulation in the coronal current sheet before a flare and its explosive realize during this flare. The 3D MHD numerical simulations show that magnetic energy is accumulated in the magnetic field that created above an active region before the flare. The decay of the coronal current sheet does not produce some strong magnetic field disturbance on the photosphere. The calculations have been carried out for the real observed active regions. The results of the numerical simulation demonstrate most of flare phenomena including the relativistic proton (˜ 10 GeV) generation.

  19. The Coronal Global Evolutionary Model (CGEM): Using HMI Vector Magnetogram and Doppler Data to Model the Buildup of Free Magnetic Energy in the Solar Corona

    E-print Network

    Fisher, George H; Bercik, David J; Kazachenko, Maria D; Lynch, Benjamin J; Welsch, Brian T; Hoeksema, J Todd; Hayashi, Keiji; Liu, Yang; Norton, Aimee A; Dalda, Alberto Sainz; Sun, Xudong; DeRosa, Marc L; Cheung, Mark C M

    2015-01-01

    The most violent space weather events (eruptive solar flares and coronal mass ejections) are driven by the release of free magnetic energy stored in the solar corona. Energy can build up on timescales of hours to days, and then may be suddenly released in the form of a magnetic eruption, which then propagates through interplanetary space, possibly impacting the Earth's space environment. Can we use the observed evolution of the magnetic and velocity fields in the solar photosphere to model the evolution of the overlying solar coronal field, including the storage and release of magnetic energy in such eruptions? The objective of CGEM, the Coronal Global Evolutionary Model, funded by the NASA/NSF Space Weather Modeling program, is to develop and evaluate such a model for the evolution of the coronal magnetic field. The evolving coronal magnetic field can then be used as a starting point for magnetohydrodynamic (MHD) models of the corona, which can then be used to drive models of heliospheric evolution and predi...

  20. 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.

  1. A HR-like Diagram for Solar/Stellar Flares and Corona -- Emission Measure vs Temperature Diagram

    E-print Network

    Kazunari Shibata; Takaaki Yokoyama

    2002-06-03

    In our previous paper, we have presented a theory to explain the observed universal correlation between the emission measure ($EM=n^2 V$) and temperature (T) for solar/stellar flares on the basis of the magnetic reconnection model with heat conduction and chromospheric evaporation. Here n is the electron density and V is the volume. By extending our theory to general situations, we examined the EM-T diagram in detail, and found the following properties: 1) The universal correlation sequence (``main sequence flares'') with $EM \\propto T^{17/2}$ corresponds to the case of constant heating flux or equivalently the case of constant magnetic field strength in the reconnection model. 2) The EM-T diagram has a forbidden region, where gas pressure of flares exceeds magnetic pressure. 3) There is a coronal branch with $EM \\propto T^{15/2}$ for $T 10^7$ K. This branch is situated left side of the main sequence flares in the EM-T diagram. 4) There is another forbidden region determined by the length of flare loop; a lower limit of flare loop is $10^7$ cm. Small flares near this limit correspond to nanoflares observed by SOHO/EIT. 5) We can plot flare evolution track on the EM-T diagram. A flare evolves from the coronal branch to main sequence flares, then returns to the coronal branch eventually. These properties of the EM-T diagram are similar to those of the HR diagram for stars, and thus we propose that the EM-T diagram is quite useful to estimate the physical quantities (loop length, heating flux, magnetic field strength, total energy and so on) of flares and corona when there is no spatially resolved imaging observations.

  2. 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 waves (electrons) or ion-acoustic waves (protons).

  3. 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

  4. 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.

  5. VERTICAL KINK OSCILLATION OF A MAGNETIC FLUX ROPE STRUCTURE IN THE SOLAR CORONA

    SciTech Connect

    Kim, S.; Cho, K.-S.; Nakariakov, V. M.

    2014-12-20

    Vertical transverse oscillations of a coronal magnetic rope, observed simultaneously in the 171 Å and 304 Å bandpasses of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO), are detected. The oscillation period is about 700 s and the displacement amplitude is about 1 Mm. The oscillation amplitude remains constant during the observation. Simultaneous observation of the rope in the bandpasses corresponding to the coronal and chromospheric temperatures suggests that it has a multi-thermal structure. Oscillatory patterns in 171 Å and 304 Å are coherent, which indicates that the observed kink oscillation is collective, in which the rope moves as a single entity. We interpret the oscillation as a fundamental standing vertically polarized kink mode of the rope, while the interpretation in terms of a perpendicular fast wave could not be entirely ruled out. In addition, the arcade situated above the rope and seen in the 171 Å bandpass shows an oscillatory motion with the period of about 1000 s.

  6. 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.

  7. Observational Evidence of Sausage-pinch Instability in Solar Corona by SDO/AIA

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.; Erdélyi, R.; Tripathi, Durgesh; Fedun, V.; Joshi, N. C.; Kayshap, P.

    2013-03-01

    We present the first observational evidence of the evolution of sausage-pinch instability in active region 11295 during a prominence eruption using data recorded on 2011 September 12 by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We have identified a magnetic flux tube visible in AIA 304 Å that shows curvatures on its surface with variable cross-sections as well as enhanced brightness. These curvatures evolved and thereafter smoothed out within a timescale of a minute. The curved locations on the flux tube exhibit a radial outward enhancement of the surface of about 1-2 Mm (a factor of two larger than the original thickness of the flux tube) from the equilibrium position. AIA 193 Å snapshots also show the formation of bright knots and narrow regions in-between at the four locations as that of 304 Å along the flux tube where plasma emission is larger compared to the background. The formation of bright knots over an entire flux tube as well as the narrow regions in <60 s may be the morphological signature of the sausage instability. We also find the flows of confined plasma (propagation of brightness) in these bright knots along the field lines, which indicates the dynamicity of the flux tube that probably causes the dominance of the longitudinal field component over short temporal scales. The observed longitudinal motion of the plasma frozen in the magnetic field lines further vanishes the formed curvatures and plasma confinements as well as growth of instability to stabilize the flux tube.

  8. Fast Magnetoacoustic Wave Trains of Sausage Symmetry in Cylindrical Waveguides of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Shestov, S.; Nakariakov, V. M.; Kuzin, S.

    2015-12-01

    Fast magnetoacoustic waves guided along the magnetic field by plasma non-uniformities, in particular coronal loops, fibrils, and plumes, are known to be highly dispersive, which lead to the formation of quasi-periodic wave trains excited by a broadband impulsive driver, e.g., a solar flare. We investigated the effects of cylindrical geometry on the fast sausage wave train formation. We performed magnetohydrodynamic numerical simulations of fast magnetoacoustic perturbations of a sausage symmetry, propagating from a localized impulsive source along a field-aligned plasma cylinder with a smooth radial profile of the fast speed. The wave trains are found to have pronounced period modulation, with the longer instant period seen in the beginning of the wave train. The wave trains also have a pronounced amplitude modulation. Wavelet spectra of the wave trains have characteristic tadpole features, with the broadband large-amplitude heads preceding low-amplitude quasi-monochromatic tails. The mean period of the wave train is about the transverse fast magnetoacoustic transit time across the cylinder. The mean parallel wavelength is about the diameter of the wave-guiding plasma cylinder. Instant periods are longer than the sausage wave cutoff period. The wave train characteristics depend on the fast magnetoacoustic speed in both the internal and external media, the smoothness of the transverse profile of the equilibrium quantities, and also the spatial size of the initial perturbation. If the initial perturbation is localized at the axis of the cylinder, the wave trains contain higher radial harmonics that have shorter periods.

  9. OBSERVATIONAL EVIDENCE OF SAUSAGE-PINCH INSTABILITY IN SOLAR CORONA BY SDO/AIA

    SciTech Connect

    Srivastava, A. K.; Joshi, N. C.; Kayshap, P.; Erdelyi, R.; Fedun, V.; Tripathi, Durgesh

    2013-03-10

    We present the first observational evidence of the evolution of sausage-pinch instability in active region 11295 during a prominence eruption using data recorded on 2011 September 12 by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We have identified a magnetic flux tube visible in AIA 304 A that shows curvatures on its surface with variable cross-sections as well as enhanced brightness. These curvatures evolved and thereafter smoothed out within a timescale of a minute. The curved locations on the flux tube exhibit a radial outward enhancement of the surface of about 1-2 Mm (a factor of two larger than the original thickness of the flux tube) from the equilibrium position. AIA 193 A snapshots also show the formation of bright knots and narrow regions in-between at the four locations as that of 304 A along the flux tube where plasma emission is larger compared to the background. The formation of bright knots over an entire flux tube as well as the narrow regions in <60 s may be the morphological signature of the sausage instability. We also find the flows of confined plasma (propagation of brightness) in these bright knots along the field lines, which indicates the dynamicity of the flux tube that probably causes the dominance of the longitudinal field component over short temporal scales. The observed longitudinal motion of the plasma frozen in the magnetic field lines further vanishes the formed curvatures and plasma confinements as well as growth of instability to stabilize the flux tube.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  11. Fluxes of MeV particles at Earth's orbit and their relationship with the global structure of the solar corona: Observations from SOHO

    NASA Technical Reports Server (NTRS)

    Posner, A.; Bothmer, V.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Delaboudiniere, J.-P.; Thompson, B. J.; Brueckner, G. E.; Howard, R. A.; Michels, D. J.

    1997-01-01

    The SOHO satellite, launched on 2 December 1995, combines a unique set of instruments which allow comparative studies of the interior of the sun, the outer corona and solar to be carried out. In its halo orbit around the L1 Lagrangian point of the sun-earth system, SOHO's comprehensive suprathermal and energetic particle analyzer (COSTEP) measures in situ energetic particles in the energy range of 44 keV/particle to greater than 53 MeV/n. The MeV proton, electron and helium nuclei measurements from the COSTEP electron proton helium instrument (EPHIN) were used to investigate the relationships of intensity increases of these particle species with the large-scale structures of the solar corona and heliosphere, including temporal variations. Coronal observatons are provided by the large angle spectroscopic coronagraph (LASCO) and the extreme ultraviolet imaging telescope (EIT). It was found that during times of minimum solar activity, intensity increases of the particles have two well defined sources: corotating interaction regions (CIRs) in the heliosphere related to coronal holes at the sun and coronal mass ejections.

  12. 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/Churyumov-Gerasimenko, further studies of interplanetary dust should provide a better insight on possible delivery of carbonaceous particles on telluric planets through dust impacts at an epoch of heavy bombardment, and thus to the early solar system evolution. Support from CNES is warmly acknowledged.

  13. Solar fine scale structures in the corona, transition region, and lower atmosphere

    NASA Astrophysics Data System (ADS)

    Moses, Dan; Cook, J. W.; Bartoe, J.-D. F.; Brueckner, G. E.; Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Recely, F.; Martin, S. F.; Zirin, H.

    1994-08-01

    The American Science and Engineering Soft X-ray Imaging Payload and the Naval Research Laboratory High Resolution Telescope and Spectrograph (HRTS) were launched from White Sands on 1987 December 11 in coordinated sounding rocket flights. The goal was to investigate the correspondence of fine-scale structures from different temperature regimes in the solar atmosphere, and particularly the relationship between X-ray bright points (XBPs) and transition region explosive events. We present results of the analysis of co-aligned X-ray images, maps of sites of transition region explosive events observed in C IV 105, HRTS 1600 A spectroheliograms of the Tmin region, and ground-based magnetogram and He I 10830 A images. We examined the relationship of He I 10830 A dark features and evolving magnetic features which correspond to XBPs. We note a frequent double ribbon pattern of the He I dark feature counterparts to XBPs. We discuss an analysis of the relationship of XBPs to evolving magnetic features by Webb et al., which shows that converging magnetic features of opposite polarity are the most significant magnetic field counterparts to XBPs. The magnetic bipolar features associated with XBPs appear as prominent network elements in chromospheric and transition region images. The features in C IV observations corresponding to XBP sites are in general bright, larger scale (approximately 10 arcsec) regions of complex velocity fields of order 40 km/s, which is typical of brighter C IV network elements. These C IV features do not reach the approximately 100 km/s velocities seen in the C IV explosive events. Also, there are many similar C IV bright network features without a corresponding XBP in the X-ray image. The transition region explosive events do not correspond directly to XBPs. The explosive events appear to be concentrated in the quiet Sun at the edges of strong network, or within weaker field strength network regions. We find a greater number of C IV events than expected from the results of a previous Spacelab 2 HRTS disk survey. We attribute this at least partly to better spatial resolution with the newer HRTS data. The full-disk X-ray image shows a pattern of dark lanes in quiet Sun areas. The number density of C IV events is twice as large inside as outside a dark lane (4.6 x 10-3 vs. 2.3 x 10-3 explosive events per arcsec 2). The dark lane corresponds to an old decaying magnetic neutral line. We suggest that this provides an increased opportunity for small-scale convergence and reconnection of opposite polarity magnetic field features, in analogy with the results of Webb et al. for XBPs but at a reduced scale of reconnection.

  14. Solar fine scale structures in the corona, transition region, and lower atmosphere

    NASA Technical Reports Server (NTRS)

    Moses, Dan; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Realy, F.; Martin, S. F.

    1994-01-01

    The American Science and Engineering Soft X-ray Imaging Payload and the Naval Research Laboratory High Resolution Telescope and Spectrograph (HRTS) were launched from White Sands on 1987 December 11 in coordinated sounding rocket flights. The goal was to investigate the correspondence of fine-scale structures from different temperature regimes in the solar atmosphere, and particularly the relationship between X-ray bright points (XBPs) and transition region explosive events. We present results of the analysis of co-aligned X-ray images, maps of sites of transition region explosive events observed in C IV 10(exp 5), HRTS 1600 A spectroheliograms of the T(sub min) region, and ground-based magnetogram and He I 10830 A images. We examined the relationship of He I 10830 A dark features and evolving magnetic features which correspond to XBPs. We note a frequent double ribbon pattern of the He I dark feature counterparts to XBPs. We discuss an analysis of the relationship of XBPs to evolving magnetic features by Webb et al., which shows that converging magnetic features of opposite polarity are the most significant magnetic field counterparts to XBPs. The magnetic bipolar features associated with XBPs appear as prominent network elements in chromospheric and transition region images. The features in C IV observations corresponding to XBP sites are in general bright, larger scale (approximately 10 arcsec) regions of complex velocity fields of order 40 km/s, which is typical of brighter C IV network elements. These C IV features do not reach the approximately 100 km/s velocities seen in the C IV explosive events. Also, there are many similar C IV bright network features without a corresponding XBP in the X-ray image. The transition region explosive events do not correspond directly to XBPs. The explosive events appear to be concentrated in the quiet Sun at the edges of strong network, or within weaker field strength network regions. We find a greater number of C IV events than expected from the results of a previous Spacelab 2 HRTS disk survey. We attribute this at least partly to better spatial resolution with the newer HRTS data. The full-disk X-ray image shows a pattern of dark lanes in quiet Sun areas. The number density of C IV events is twice as large inside as outside a dark lane (4.6 x 10(exp -3) vs. 2.3 x 10(exp -3) explosive events per arcsec (exp 2)). The dark lane corresponds to an old decaying magnetic neutral line. We suggest that this provides an increased opportunity for small-scale convergence and reconnection of opposite polarity magnetic field features, in analogy with the results of Webb et al. for XBPs but at a reduced scale of reconnection.

  15. ELECTROMAGNETIC ESCAPE OF DUST FROM THE SOLAR SYSTEM

    E-print Network

    Hamilton, Douglas P.

    configuration of the solar magnetic field, perhaps accounting for particles detected by the Ulysses spacecraft escape from the solar system. The recent findings of the Ulysses spacecraft provide motivation for our study. After a swing by Jupiter, Ulysses was deflected onto a highly­inclined path which reached

  16. Single Stage Evaporation of Solar Condensate Dust to Make CAIs

    NASA Astrophysics Data System (ADS)

    Ebel, D. S.; Grossman, L.

    2001-03-01

    Cooling rates and peak T are found, to predict observed chemical and isotopic compositions, and melilite zoning, of Type A and B CAIs, by cooling, evaporating, and crystallizing solar condensate precursors instantly heated in 1 microbar pure H_2.

  17. Absorption and scattering properties of the Martian dust in the solar wavelengths

    NASA Technical Reports Server (NTRS)

    Ockert-Bell, M. E.; Pollack, J. B.; McKay, C. P.; Forget, F.

    1997-01-01

    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.

  18. Detection of plasma fluctuations in white-light images of the outer solar corona: investigation of the spatial and temporal evolution

    E-print Network

    Telloni, D; Romano, P; Spadaro, D; Antonucci, E

    2013-01-01

    This work focus on the first results on the identification and characterization of periodic plasma density fluctuations in the outer corona, observed in STEREO-A COR1 white-light image time series. A 2D reconstruction of the spatial distribution and temporal evolution of the coronal fluctuation power has been performed over the whole plane of the sky, from 1.4 to 4.0 solar radii. The adopted diagnostic tool is based on wavelet transforms. This technique, with respect to the standard Fourier analysis, has the advantage of localizing non-persistent fluctuating features and exploring the variations of the relating wavelet power in both space and time. The map of the variance of the coronal brightness clearly outlines intermittent, spatially coherent fluctuating features, localized along, or adjacent to, the strongest magnetic field lines. In most cases they do not correspond to the coronal structures visible in the brightness maps. The results obtained provide a scenario in which the solar corona shows quasi-per...

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Feldman, Uri

    1993-07-01

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

  2. 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.

  3. CHINA'S DUST AFFECTS SOLAR RESOURCE IN THE U.S.: A CASE STUDY Christian A. Gueymard Nels S. Laulainen

    E-print Network

    Oregon, University of

    radiation, sunphotometry, turbidity. 1. INTRODUCTION Geographical, as well as short-term and long-term solarCHINA'S DUST AFFECTS SOLAR RESOURCE IN THE U.S.: A CASE STUDY Christian A. Gueymard Nels S of how long- range aerosol transport may temporarily affect the U.S. solar resource. Broadband

  4. Corona Borealis

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3 approx. less than epsilon approx. less than 30 deg from the Sun. This surface brightness map is then used to infer the spatial distribution of interplanetary dust over heliocentric distances of about 10 solar radii to the orbit of Venus. The averaged ecliptic surface brightness of the zodiacal light falls off as Z(epsilon) is a member of epsilon(sup -2.45 +/- 0.05), which suggests that the dust cross-sectional density nominally falls off as sigma(r) is a member of r(sup - 1.45 +/- 0.05). The interplanetary dust also has an albedo of alpha approx. = 0.1 that is uncertain by a factor of approx. 2. Asymmetries of approx. 10% are seen in directions east-west and north-south of the Sun, and these may be due the giant planets' secular gravitational perturbations. We apply a simple model that attributes the zodiacal light as due to three dust populations having distinct inclination distributions, namely, dust from asteroids and Jupiter-family comets (JFCs) having characteristic inclinations of i approx. 7 deg, dust from Halley-type comets having i approx. 33 deg, and an isotropic cloud of dust from Oort Cloud comets. The best-fitting scenario indicates that asteroids + JFCs are the source of about 45% of the optical dust cross section seen in the ecliptic at 1 AU but that at least 89% of the dust cross section enclosed by a 1-AU-radius sphere is of a cometary origin. Each population's radial density variations can also deviate somewhat from the nominal sigma(r) is a member of r(sup -1.45). When these results are extrapolated out to the asteroid belt, we find an upper limit on the mass of the light-reflecting asteroidal dust that is equivalent to a 12-km asteroid, and a similar extrapolation of the isotropic dust cloud out to Oort Cloud distances yields a mass equivalent to a 30-km comet, although the latter mass is uncertain by orders of magnitude.

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

    NASA Astrophysics Data System (ADS)

    Shirley, James H.

    2015-05-01

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

  7. Hydrocarbons on Saturns Satellites: Relationship to Interstellar Dust and the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Cruikshank, D. P.

    2012-01-01

    To understand the origin and evolution of our Solar System, and the basic components that led to life on Earth, we study interstellar and planetary spectroscopic signatures. The possible relationship of organic material detected in carbonaceous meteorites, interplanetary dust particles (IDPs), comets and the interstellar medium have been the source of speculation over the years as the composition and processes that governed the early solar nebula have been explored to understand the extent to which primitive material survived or became processed. The Cassini VIMS has provided new data relevant to this problem. Three of Saturn's satellites, Phoebe, Iapetus, and Hyperion, are found to have aromatic and aliphatic hydrocarbons on their surfaces. The aromatic hydrocarbon signature (C-H stretching mode at 3.28 micrometers) is proportionally significantly stronger (relative to the aliphatic bands) than that seen in other Solar System bodies (e.g., comets) and materials (Stardust samples, IDPs, meteorites) and the distinctive sub-features of the 3.4 micrometer aliphatic band (CH2 and CH3 groups) are reminiscent of those widely detected throughout the diffuse ISM. Phoebe may be a captured object that originated in the region beyond the present orbit of Neptune, where the solar nebula contained a large fraction of original interstellar ice and dust that was less processed than material closer to the Sun. Debris from Phoebe now resident on Iapetus and Hyperion, as well as o Phoebe itself, thus presents a unique blend of hydrocarbons, amenable to comparisons with interstellar hydrocarbons and other Solar System materials. The dust ring surrounding Saturn, in which Phoebe is embedded, probably originated from a collision with Phoebe. Dust ring particles are the likely source of the organic-bearing materials, and perhaps the recently identified small particles of Fe detected on Saturn's satellites. Lab measurements of the absolute band strengths of representative aliphatic and aromatic molecules, together with measurements from the VIMS data, allow us to calculate the number of C atoms to find the relative abundances of C atoms in the two kinds of organic molecules. The strength of the prominent aromatic C-H stretch band relative to the aliphatic band complex in Phoebe and Iapetus indicates that the relative abundance of aromatic to aliphatic carbon is very large (greater than 200). In contract, the aromatic band is nearly imperceptible in spectra of interplanetary dust particles (IDP), returned samples from comet 91P/Wild 2, insoluable carbonaceous material in most meteorites, and the diffuse interstellar dust (DISM) (although aromatics are known in all these materials-here we consider only the spectroscopic signature)

  8. Sixteen Years of Ulysses Interstellar Dust Measurements in the Solar System. I. Mass Distribution and Gas-to-dust Mass Ratio

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    In the early 1990s, contemporary interstellar dust penetrating deep into the heliosphere was identified with the in situ dust detector on board the Ulysses spacecraft. Between 1992 and the end of 2007 Ulysses monitored the interstellar dust stream. The interstellar grains act as tracers of the physical conditions in the local interstellar medium (ISM) surrounding our solar system. Earlier analyses of the Ulysses interstellar dust data measured between 1992 and 1998 implied the existence of a population of “big” interstellar grains (up to 10?13 kg). The derived gas-to-dust-mass ratio was smaller than the one derived from astronomical observations, implying a concentration of interstellar dust in the very local ISM. In this paper we analyze the entire data set from 16 yr of Ulysses interstellar dust measurements in interplanetary space. This paper concentrates on the overall mass distribution of interstellar dust. An accompanying paper investigates time-variable phenomena in the Ulysses interstellar dust data, and in a third paper we present the results from dynamical modeling of the interstellar dust flow applied to Ulysses. We use the latest values for the interstellar hydrogen and helium densities, the interstellar helium flow speed of {v}{ISM? }=23.2 {km} {{{s}}}-1, and the ratio of radiation pressure to gravity, ?, calculated for astronomical silicates. We find a gas-to-dust mass ratio in the local interstellar cloud of {R}{{g}/{{d}}}={193}-57+85, and a dust density of (2.1 ± 0.6) × 10?24 kg m?3. For a higher inflow speed of 26 {km} {{{s}}}-1, the gas-to-dust mass ratio is 20% higher, and, accordingly, the dust density is lower by the same amount. The gas-to-dust mass ratio derived from our new analysis is compatible with the value most recently determined from astronomical observations. We confirm earlier results that the very local ISM contains “big” (i.e., ?1 ?m sized) interstellar grains. We find a dust density in the local ISM that is a factor of three lower than values implied by earlier analyses.

  9. Comprehensive Analyses of Data Collected from TEREK (Solar EUV Telescope) RES-C (Solar X-Ray Spectrometer) and SORS (Solar Radio Spectrometer) on board CORONAS-1 Using Magnetohydrodynamic Models

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1997-01-01

    By using the observed magnetic field data obtained from the Wilcox Solar Observatory at Stanford University as the inputs to a two-dimensional plane-of-sky magnetohydrodynamic model, via numerical relaxation method, we have deduced the plasma and magnetic field parameters for the observed coronal hole by CORONAS-1. The method for this self-consistent MHD analysis will be discussed in detail. Numerical results for the magnetic field configuration, velocity distribution, density and temperature distributions will be presented. We have converted the computed density to polarization brightness in order to directly compare the MHD outputs with observations. Also included is a summary of achievements made during the grant period. This section is summarized into three categories: 1) Visit of Co-Investigators; 2) Presentations; and 3) Papers published, accepted and submitted for publication in journals.

  10. Variability of Solar Five-Minute Oscillations in the Corona as Observed by the Extreme Ultraviolet Spectrophotometer (ESP) on the Solar Dynamics Observatory Extreme Ultraviolet Variability Experiment (SDO/EVE)

    E-print Network

    Didkovsky, Leonid; Judge, Darrell; Wieman, Seth; Woods, Tom

    2012-01-01

    Solar five-minute oscillations have been detected in the power spectra of two six-day time intervals from soft X-ray measurements of the Sun observed as a star using the Extreme Ultraviolet Spectrophotometer (ESP) onboard the Solar Dynamics Observatory (SDO) Extreme Ultraviolet Variability Experiment (EVE). The frequencies of the largest amplitude peaks were found matching within 3.7 microHz the known low-degree (l = 0--3) modes of global acoustic oscillations, and can be explained by a leakage of the global modes into the corona. Due to strong variability of the solar atmosphere between the photosphere and the corona the frequencies and amplitudes of the coronal oscillations are likely to vary with time. We investigate the variations in the power spectra for individual days and their association with changes of solar activity, e.g. with the mean level of the EUV irradiance, and its short-term variations due to evolving active regions. Our analysis of samples of one-day oscillation power spectra for a 49-day ...

  11. Intensity oscillations observed with Hinode near the south pole of the Sun: leakage of low frequency magneto-acoustic waves into the solar corona

    E-print Network

    A. K. Srivastava; D. Kuridze; T. V. Zaqarashvili; B. N. Dwivedi

    2008-03-07

    Aims. To study intensity oscillations in the solar chromosphere/corona above a quiet-Sun magnetic network. Methods. We analyse the time series of He II 256.32, Fe XI 188.23 and Fe XII 195.12 spectral lines observed by EUV Imaging Spectrometer (EIS) on board Hinode near the south pole. Then we use a standard wavelet tool to produce power spectra of intensity oscillations above the magnetic network. Results. We get ~7 min intensity oscillations in all spectral lines and ~13 min intensity oscillations only in He II with the probability of ~96-98 %, which probably reflects the process of magneto-acoustic wave propagation above the network. Conclusions. We suggest that field-free cavity areas under bipolar magnetic canopies in the vicinity of magnetic network may serve as resonators for the magneto-acoustic waves. The cavities with photospheric sound speed and granular dimensions may produce the waves with the observed periods. The waves may propagate upwards in the transition region/corona and cause observed intensity oscillations.

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

    NASA Technical Reports Server (NTRS)

    Habbal, Shadia Rifai

    2005-01-01

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

  13. Dust Populations in the Outer Solar System: 10 years of monitoring by CASSINI-CDA

    NASA Astrophysics Data System (ADS)

    Altobelli, N.; Kempf, S.; Postberg, F.; Horanyi, M.; Srama, R.

    2015-10-01

    The analysis of different CDA subsystems data, acquired since SOI, reveals that the Saturnian system is permanently crossed by dust grains originating from the Interplanetary medium, as well as from the neighboring interstellar medium surrounding the Solar System. We observe two main types of particles: on the one hand, those with low injection velocity with respect to Saturn, and whose flux is significantly enhanced by gravitation focusing. On the other hand, particles with fast injection velocities, essentially unperturbed by gravitation focusing. The fast grains are found to be interstellar dust (ISD) from the Local Interstellar Cloud (LIC), as well as particles on retrograde orbits around the Sun, most likely dust released by Halley-type comets. The dynamics of the slow grains is found to be compatible with collisional debris from the Kuiper-Belt, migrating inward the Solar System under influence of the Poynting-Robertson drag. Alternatively, we show that the origin of the slow grains entering the Saturnian System can be the recently discovered cometary activity of Centaurs.

  14. Organic grain coatings in primitive interplanetary dust particles: Implications for grain sticking in the Solar Nebula

    NASA Astrophysics Data System (ADS)

    Flynn, George J.; Wirick, Sue; Keller, Lindsay P.

    2013-10-01

    The chondritic porous interplanetary dust particles (CP IDPs), fragments of asteroids and comets collected by NASA high-altitude research aircraft from the Earth's stratosphere, are recognized as the least altered samples of the original dust of the Solar Nebula available for laboratory examination. We performed high-resolution, ~25 nm/pixel, x-ray imaging and spectroscopy on ultramicrotome sections of CP IDPs, which are aggregates of >104 grains, and identified and characterized ~100 nm thick coatings of organic matter on the surfaces of the individual grains. We estimated the minimum tensile strength of this organic glue to be ~150 to 325 N/m2, comparable to the strength of the weakest cometary meteors, based on the observation that the individual grains of ~5 ?m diameter aggregate CP IDPs are not ejected from the particle by electrostatic repulsion due to charging of these IDPs to 10 to 15 volts at 1 A.U. in space. Since organic coatings can increase the sticking coefficient over that of bare mineral grains, these organic grain coatings are likely to have been a significant aid in grain sticking in the Solar Nebula, allowing the first dust particles to aggregate over a much wider range of collision speeds than for bare mineral grains.

  15. Time-dependent MHD modeling of the global solar corona for year 2007: Driven by daily-updated magnetic field synoptic data

    NASA Astrophysics Data System (ADS)

    Yang, L. P.; Feng, X. S.; Xiang, C. Q.; Liu, Yang; Zhao, Xuepu; Wu, S. T.

    2012-08-01

    In this paper, we develop a time-dependent MHD model driven by the daily-updated synoptic magnetograms (MHD-DUSM) to study the dynamic evolution of the global corona with the help of the 3D Solar-Interplanetary (SIP) adaptive mesh refinement (AMR) space-time conservation element and solution element (CESE) MHD model (SIP-AMR-CESE MHD Model). To accommodate the observations, the tangential component of the electric field at the lower boundary is specified to allow the flux evolution to match the observed changes of magnetic field. Meanwhile, the time-dependent solar surface boundary conditions derived from the method of characteristics and the mass flux limit are incorporated to couple the observation and the 3D MHD model. The simulated evolution of the global coronal structure during 2007 is compared with solar observations and solar wind measurements from both Ulysses and spacecrafts near the Earth. The MHD-DUSM model is also validated by comparisons with the standard potential field source surface (PFSS) model, the newly improved Wang-Sheeley-Arge (WSA) empirical formula, and the MHD simulation with a monthly synoptic magnetogram (MHD-MSM). Comparisons show that the MHD-DUSM results have good overall agreement with coronal and interplanetary structures, including the sizes and distributions of coronal holes, the positions and shapes of the streamer belts, and the transitions of the solar wind speeds and magnetic field polarities. The MHD-DUSM results also display many features different from those of the PFSS, the WSA, and the MHD-MSM models.

  16. Microphysics of Waves and Instabilities in the Solar Wind and their Macro Manifestations in the Corona and Interplanetary Space

    NASA Technical Reports Server (NTRS)

    Gurman, Joseph (Technical Monitor); Habbal, Shadia Rifai

    2004-01-01

    Investigations of the physical processes responsible for coronal heating and the acceleration of the solar wind were pursued with the use of our recently developed 2D MHD solar wind code and our 1D multifluid code. In particular, we explored (1) the role of proton temperature anisotropy in the expansion of the solar wind, (2) the role of plasma parameters at the coronal base in the formation of high speed solar wind streams at mid-latitudes, and (3) the heating of coronal loops.

  17. ON A TRANSITION FROM SOLAR-LIKE CORONAE TO ROTATION-DOMINATED JOVIAN-LIKE MAGNETOSPHERES IN ULTRACOOL MAIN-SEQUENCE STARS

    SciTech Connect

    Schrijver, Carolus J.

    2009-07-10

    For main-sequence stars beyond spectral type M5, the characteristics of magnetic activity common to warmer solar-like stars change into the brown-dwarf domain: the surface magnetic field becomes more dipolar and the evolution of the field patterns slows, the photospheric plasma is increasingly neutral and decoupled from the magnetic field, chromospheric and coronal emissions weaken markedly, and the efficiency of rotational braking rapidly decreases. Yet, radio emission persists, and has been argued to be dominated by electron-cyclotron maser emission instead of the gyrosynchrotron emission from warmer stars. These properties may signal a transition in the stellar extended atmosphere. Stars warmer than about M5 have a solar-like corona and wind-sustained heliosphere in which the atmospheric activity is powered by convective motions that move the magnetic field. Stars cooler than early-L, in contrast, may have a Jovian-like rotation-dominated magnetosphere powered by the star's rotation in a scaled-up analog of the magnetospheres of Jupiter and Saturn. A dimensional scaling relationship for rotation-dominated magnetospheres by Fan et al. is consistent with this hypothesis.

  18. Acceleration of ions and nano dust at a comet in the solar wind

    NASA Astrophysics Data System (ADS)

    Gunell, H.; Mann, I.; Simon Wedlund, C.; Kallio, E.; Alho, M.; Nilsson, H.; De Keyser, J.; Dhooghe, F.; Maggiolo, R.

    2015-12-01

    A quasi-neutral hybrid simulation of the interaction of the solar wind with the atmosphere of a comet is used together with a test particle simulation of cometary ions and dust to compute trajectories and velocity distribution functions of charged particles, starting outside the diamagnetic cavity at 150 km cometocentric distance. The simulations are run with parameters suited to make predictions for comet 67P/Churyumov-Gerasimenko when it is at a heliocentric distance of 1.45 AU. It is found that the shape of the ion trajectories depends on the location of the source, and that a velocity distribution that is observed at a given point in space is influenced by the spatial structure of the source. Charged dust grains with radii in the 1-10 nm range are accelerated from the nucleus to a distance of 2.9 ×104 km in between 15 min and 2 h approximately. Dust particles smaller than 10 nm in radius are accelerated to speeds over 10 km/s.

  19. Alteration of Organic Compounds in Small Bodies and Cosmic Dusts by Cosmic Rays and Solar Radiation

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kensei; Kaneko, Takeo; Mita, Hajime; Obayashi, Yumiko; Takahashi, Jun-ichi; Sarker, Palash K.; Kawamoto, Yukinori; Okabe, Takuto; Eto, Midori; Kanda, Kazuhiro

    2012-07-01

    A wide variety of complex organic compounds have been detected in extraterrestrial bodies like carbonaceous chondrites and comets, and their roles in the generation of terrestrial life are discussed. It was suggested that organics in small bodies were originally formed in ice mantles of interstellar dusts in dense cloud. Irradiation of frozen mixture of possible interstellar molecules including CO (or CH _{3}OH), NH _{3} and H _{2}O with high-energy particles gave complex amino acid precursors with high molecular weights [1]. Such complex organic molecules were taken in planetesimals or comets in the early solar system. In prior to the generation of the terrestrial life, extraterrestrial organics were delivered to the primitive Earth by such small bodies as meteorites, comets and space dusts. These organics would have been altered by cosmic rays and solar radiation (UV, X-rays) before the delivery to the Earth. We examined possible alteration of amino acids, their precursors and nucleic acid bases in interplanetary space by irradiation with high energy photons and heavy ions. A mixture of CO, NH _{3} and H _{2}O was irradiated with high-energy protons from a van de Graaff accelerator (TIT, Japan). The resulting products (hereafter referred to as CAW) are complex precursors of amino acids. CAW, amino acids (dl-Isovaline, glycine), hydantoins (amino acid precursors) and nucleic acid bases were irradiated with continuous emission (soft X-rays to IR; hereafter referred to as soft X-rays irradiation) from BL-6 of NewSUBARU synchrotron radiation facility (Univ. Hyogo). They were also irradiated with heavy ions (eg., 290 MeV/u C ^{6+}) from HIMAC accelerator (NIRS, Japan). After soft X-rays irradiation, water insoluble materials were formed. After irradiation with soft X-rays or heavy ions, amino acid precursors (CAW and hydantoins) gave higher ratio of amino acids were recovered after hydrolysis than free amino acids. Nucleic acid bases showed higher stability than free amino acids. Complex amino acid precursors with high molecular weights could be formed in simulated dense cloud environments. They would have been altered in the early solar system by irradiation with soft X-rays from the young Sun, which caused increase of hydrophobicity of the organics of interstellar origin. They were taken up by parent bodies of meteorites or comets, and could have been delivered to the Earth by meteorites, comets and cosmic dusts. Cosmic dusts were so small that they were directly exposed to the solar radiation, which might be critical for the survivability of organics in them. In order to evaluate the roles of space dusts as carriers of bioorganic compounds to the primitive Earth, we are planning the Tanpopo Mission, where collection of cosmic dusts by using ultra low-density aerogel, and exposure of amino acids and their precursors for years are planned by utilizing the Japan Experimental Module / Exposed Facility of the ISS [2]. The mission is now scheduled to start in 2013. We thank Dr. Katsunori Kawasaki of Tokyo Institute of Technology, and Dr. Satoshi Yoshida of National Institute of Radiological Sciences for their help in particles irradiation. We also thank to the members of JAXA Tanpopo Working Group (PI: Prof. Akihiko Yamagishi) for their helpful discussion. [1] K. Kobayashi, et al., in ``Astrobiology: from Simple Molecules to Primitive Life,'' ed. by V. Basiuk, American Scientific Publishers, Valencia, CA, (2010), pp. 175-186. [2] K. Kobayashi, et al., Trans. Jpn. Soc. Aero. Space Sci., in press (2012).

  20. Optimization of the Nano-Dust Analyzer (NDA) for operation under solar UV illumination

    NASA Astrophysics Data System (ADS)

    O`Brien, L.; Grün, E.; Sternovsky, Z.

    2015-12-01

    The performance of the Nano-Dust Analyzer (NDA) instrument is analyzed for close pointing to the Sun, finding the optimal field-of-view (FOV), arrangement of internal baffles and measurement requirements. The laboratory version of the NDA instrument was recently developed (O'Brien et al., 2014) for the detection and elemental composition analysis of nano-dust particles. These particles are generated near the Sun by the collisional breakup of interplanetary dust particles (IDP), and delivered to Earth's orbit through interaction with the magnetic field of the expanding solar wind plasma. NDA is operating on the basis of impact ionization of the particle and collecting the generated ions in a time-of-flight fashion. The challenge in the measurement is that nano-dust particles arrive from a direction close to that of the Sun and thus the instrument is exposed to intense ultraviolet (UV) radiation. The performed optical ray-tracing analysis shows that it is possible to suppress the number of UV photons scattering into NDA's ion detector to levels that allow both high signal-to-noise ratio measurements, and long-term instrument operation. Analysis results show that by avoiding direct illumination of the target, the photon flux reaching the detector is reduced by a factor of about 103. Furthermore, by avoiding the target and also implementing a low-reflective coating, as well as an optimized instrument geometry consisting of an internal baffle system and a conical detector housing, the photon flux can be reduced by a factor of 106, bringing it well below the operation requirement. The instrument's FOV is optimized for the detection of nano-dust particles, while excluding the Sun. With the Sun in the FOV, the instrument can operate with reduced sensitivity and for a limited duration. The NDA instrument is suitable for future space missions to provide the unambiguous detection of nano-dust particles, to understand the conditions in the inner heliosphere and its temporal variability, and to constrain the chemical differentiation and processing of IDPs.

  1. Penetration of solar radiation into pure and Mars-dust contaminated snow

    NASA Astrophysics Data System (ADS)

    Kaufmann, E.; Hagermann, A.

    2015-05-01

    Rock and soil surface layers absorb and reflect incoming solar radiation immediately at the surface. Ices on the other hand, whilst opaque in the infrared, are partially transparent in the visible spectral range. These properties are responsible for the "solid-state greenhouse effect" (SSGE), which may play an important role in the energy balance of icy surfaces in the Solar System. To model the SSGE, we need to know not only thermal properties but also optical properties such as the albedo and the absorption scale length of the ice. We have investigated the absorption scale length, also known as e-folding scale, of snow/dust mixtures within the scope of a project directed at investigating the behaviour of the martian polar caps. After measuring the e-folding scale of recrystallized snow we can now also relate the dust content of contaminated snow to the penetration depth of sunlight into the mixture. Equally important, however, is our observation that light penetration through the mixture is dramatically affected by small-scale inhomogeneities.

  2. Electric fields and field-aligned currents in polar regions of the solar corona: 3-D MHD consideration

    NASA Technical Reports Server (NTRS)

    Pisanko, Yu. V.

    1995-01-01

    The calculation of the solar rotation electro-dynamical effects in the near-the-Sun solar wind seems more convenient from the non-inertial corotating reference frame. This implies some modification of the 3-D MHD equations generally on the base of the General Theory of Relativity. The paper deals with the search of stationary (in corotating non-inertial reference frame) solutions of the modified 3-D MHD equations for the in near-the-Sun high latitude sub-alfvenic solar wind. The solution is obtained requiring electric fields and field-aligned electric currents in the high latitude near-the-Sun solar wind. Various scenario are explored self-consistently via a number of numerical experiments. The analogy with the high latitude Earth's magnetosphere is used for the interpretation of the results. Possible observational manifestations are discussed.

  3. Remote sensing of dust in the Solar system and beyond using wavelength dependence of polarization

    NASA Astrophysics Data System (ADS)

    Kolokolova, L.

    2011-12-01

    For a long time, the main polarimetric tool to study dust in the Solar system has been the dependence of polarization on phase (scattering) angle. Surprisingly, a variety of cosmic dusts (interplanetary and cometary dust, dust on the surfaces of asteroids and in debris disks) possesses a very similar phase dependence of polarization with a negative bowl-shaped part at small phase angles and a positive bell-shaped region with maximum polarization around 95-105 deg. Numerous laboratory and theoretical simulations showed that a polarimetric phase curve of this shape is typical for fluffy materials, e.g., porous, aggregated particles. By contrast, the wavelength dependence of polarization is different for different types of dust. In the visual, polarization decreases with wavelength (negative gradient) for asteroids and interplanetary dust, but usually increases with wavelength (positive gradient) for cometary dust. In debris disks both signs of the spectral gradient of polarization have been found. Moreover, it was found that a cometary positive spectral gradient can change to a negative one as observations move to longer (near-infrared) wavelengths (Kelley et al. AJ, 127, 2398, 2004) and some comets(Kiselev et al. JQSRT, 109, 1384, 2008) have negative gradient even in the visible. The diversity of the spectral dependence of polarization therefore gives us hope that it can be used for characterization of the aggregates that represent different types of cosmic dust. To accomplish this, the physics behind the spectral dependence of polarization need to be revealed. Our recent study shows that the spectral dependence of polarization depends on the strength of electromagnetic interaction between the monomers in aggregates. The strength of the interaction mainly depends on how many monomers the electromagnetic wave covers on the light path equal to one wavelength. Since the electromagnetic interaction depolarizes the light, the more particles a single wavelength covers the smaller is the polarization of the scattered light. Thus, at a given monomer size the polarization decreases as wavelength increases resulting in the negative spectral gradient of polarization. However, this tendency occurs only for rather compact aggregates. For porous particles, an increase of wavelength may not increase the number of the covered monomers. In this case, polarization increases with wavelength as a result of decreasing monomer's size parameter. We performed computer modeling of light scattering by aggregates of different porosity using MSTM (multisphere T-matrix) code by D. Mackowski (see http://eng.auburn.edu/users/dmckwski/scatcodes/). The results show that for each porosity a critical wavelength exists at which the spectral gradient of polarization changes from positive to negative. The electromagnetic interaction is also stronger for more transparent materials which in turn affects the value of the critical wavelength. Thus, measurements of polarization over a broad range of wavelength can be a powerful tool to study the porosity and composition of dust in a variety of cosmic environments, especially when detailed phase dependence of polarization cannot be established (e.g. for TNO and other distant objects).

  4. Solar wind sputtering of dust on the surface of 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Wurz, Peter; Rubin, Martin; Altwegg, Kathrin; Balsiger, Hans; Berthelier, Jean-Jacques; Bieler, André; Calmonte, Ursina; De Keyser, Johan; Fiethe, Björn; Fuselier, Stephen A.; Galli, André; Gasc, Sébastien; Gombosi, Tamas I.; Jäckel, Annette; Le Roy, Léna; Mall, Urs A.; Rème, Henri; Tenishev, Valeriy; Tzou, Chia-Yu

    2015-11-01

    Aims: Far away from the Sun, at around 3 AU, the activity of comet 67P/Churyumov-Gerasimenko is low and changes with local time (solar insolation), with location (chemical heterogeneity of the surface), and with season. When the activity is very low because the total cross section of the comet against the Sun is small, the solar wind has access to the surface of the comet and causes ion-induced sputtering of surface material, which we wish to observe. Methods: We used the Double Focussing Mass Spectrometer (DFMS) of the ROSINA experiment on ESA's Rosetta mission to search for mass spectrometric evidence of sputtered refractory species. In high-resolution mode, DFMS can separate some of the mass peaks of refractory elements from the many volatile species present in the coma. Results: At present, the locations of solar wind surface access are in the southern hemisphere of the comet (the local winter). Of particular interest is sputtering of dust grains on the surface. We observe global averages over the winter hemisphere of the refractory elements Na, K, Si, and Ca, presumably sputtered from grains residing on the surface. Compared to carbonaceous chondrites, the comet has the same Na abundance, is depleted in Ca, and has an excess of K. In addition, for Si the signal strength is strong enough to compile a coarse compositional map of the southern hemisphere. Most, perhaps all, of the observed variation can be explained by the solar wind being affected by the atmosphere of the comet.

  5. A new method of presentation the large-scale magnetic field structure on the Sun and solar corona

    NASA Technical Reports Server (NTRS)

    Ponyavin, D. I.

    1995-01-01

    The large-scale photospheric magnetic field, measured at Stanford, has been analyzed in terms of surface harmonics. Changes of the photospheric field which occur within whole solar rotation period can be resolved by this analysis. For this reason we used daily magnetograms of the line-of-sight magnetic field component observed from Earth over solar disc. We have estimated the period during which day-to-day full disc magnetograms must be collected. An original algorithm was applied to resolve time variations of spherical harmonics that reflect time evolution of large-scale magnetic field within solar rotation period. This method of magnetic field presentation can be useful enough in lack of direct magnetograph observations due to sometimes bad weather conditions. We have used the calculated surface harmonics to reconstruct the large-scale magnetic field structure on the source surface near the sun - the origin of heliospheric current sheet and solar wind streams. The obtained results have been compared with spacecraft in situ observations and geomagnetic activity. We tried to show that proposed technique can trace shon-time variations of heliospheric current sheet and short-lived solar wind streams. We have compared also our results with those obtained traditionally from potential field approximation and extrapolation using synoptic charts as initial boundary conditions.

  6. Laboratory Evidence That Line-Tied Toroidal Magnetic Fields Can Suppress Loss-of-Equilibrium Flux Rope Eruptions in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W. R., II; Jara-Almonte, J.

    2014-12-01

    Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (potential) and internal (plasma-generated) magnetic fields. We find that forces due to the line-tied toroidal magnetic field, which are not included in the basic torus instability theory, can play a major role in preventing eruptions. The dependence of these toroidal magnetic forces on various potential field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

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

    PubMed

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    PubMed Central

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

    2014-01-01

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

  10. Sixteen Years of Ulysses Interstellar Dust Measurements in the Solar System. III. Simulations and Data Unveil New Insights into Local Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Sterken, Veerle J.; Strub, Peter; Krüger, Harald; von Steiger, Rudolf; Frisch, Priscilla

    2015-10-01

    Interstellar dust (ISD) in the solar system was detected in situ for the first time in 1993 by the Ulysses dust detector. The study of ISD is important for understanding its role in star and solar system formation. The goal of this paper is to understand the variability in the ISD observations from the Ulysses mission by using a Monte Carlo simulation of ISD trajectories, with the final aim to constrain the ISD particle properties from simulations and the data. The paper is part of a series of three: Strub et al. describe the variations of the ISD flow from the Ulysses data set, and Krüger et al. focus on its ISD mass distribution. We describe and interpret the simulations of the ISD flow at Ulysses orbit for a wide range of particle properties and discuss four open issues in ISD research: the existence of very big ISD particles, the lack of smaller ISD particles, the shift in dust flow direction in 2005, and particle properties. We conclude that the shift in the dust flow direction in 2005 can best be explained by Lorentz force in the inner heliosphere, but that an extra filtering mechanism is needed to fit the fluxes. A time-dependent filtering in the outer regions of the heliosphere is proposed for this. Also, the high charge-to-mass ratio values found for the heavier particles after 2003 indicate that these particles are lower in density than previously assumed. This method gives new insights into the ISD properties and paves the way toward getting a complete view on the ISD from the local interstellar cloud. We conclude that in combination with the data and simulations, also impact ionization experiments are necessary using low-density dust, in order to constrain the density of the particles.

  11. THE DIGITAL SYSTEM ARTEMIS FOR REAL-TIME PROCESSING OF RADIO TRANSIENT EMISSIONS IN THE SOLAR CORONA

    E-print Network

    Athens, University of

    THE DIGITAL SYSTEM ARTEMIS FOR REAL-TIME PROCESSING OF RADIO TRANSIENT EMISSIONS IN THE SOLAR system named 'ARTEMIS' that was developed and constructed by the Space Research Department (DESPA time signals from multichannel receivers. This system is controlled by a multiprocessor computer based

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  13. Solar Wind Five

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (editor)

    1983-01-01

    Topics of discussion were: solar corona, MHD waves and turbulence, acceleration of the solar wind, stellar coronae and winds, long term variations, energetic particles, plasma distribution functions and waves, spatial dependences, and minor ions.

  14. Ultrasonic corona sensor study

    NASA Technical Reports Server (NTRS)

    Harrold, R. T.

    1976-01-01

    The overall objective of this program is to determine the feasibility of using ultrasonic (above 20 kHz) corona detection techniques to detect low order (non-arcing) coronas in varying degrees of vacuum within large high vacuum test chambers, and to design, fabricate, and deliver a prototype ultrasonic corona sensor.

  15. DETECTION OF PLASMA FLUCTUATIONS IN WHITE-LIGHT IMAGES OF THE OUTER SOLAR CORONA: INVESTIGATION OF THE SPATIAL AND TEMPORAL EVOLUTION

    SciTech Connect

    Telloni, D.; Antonucci, E.; Ventura, R.; Romano, P.; Spadaro, D.

    2013-04-20

    This work focuses on the first results from the identification and characterization of periodic plasma density fluctuations in the outer corona, observed in STEREO-A COR1 white-light image time series. A two-dimensional reconstruction of the spatial distribution and temporal evolution of the coronal fluctuation power has been performed over the whole plane of the sky, from 1.4 to 4.0 R{sub Sun }. The adopted diagnostic tool is based on wavelet transforms. This technique, with respect to the standard Fourier analysis, has the advantage of localizing non-persistent fluctuating features and exploring variations of the relating wavelet power in both space and time. The map of the variance of the coronal brightness clearly outlines intermittent spatially coherent fluctuating features, localized along, or adjacent to, the strongest magnetic field lines. In most cases, they do not correspond to the visible coronal structures in the brightness maps. The results obtained provide a scenario in which the solar corona shows quasi-periodic, non-stationary density variations characterized by a wide range of temporal and spatial scales and strongly confined by the magnetic field topology. In addition, structures fluctuating with larger power are larger in size and evolve more slowly. The characteristic periodicities of the fluctuations are comparable to their lifetimes. This suggests that plasma fluctuations lasting only one or two wave periods and initially characterized by a single dominant periodicity either rapidly decay into a turbulent mixed flow via nonlinear interactions with other plasma modes, or they are damped by thermal conduction. The periodic non-stationary coronal fluctuations outlined by the closed field lines at low and mid latitudes might be associated with the existence of slow standing magneto-acoustic waves excited by the convective supergranular motion. The fluctuating ray-like structures observed along open field lines appear to be linked either to the intermittent nature of the processes underlying the generation of magnetic reconnection in the polar regions or to the oscillatory transverse displacements of the coronal ray itself.

  16. QUASI-PERIODIC PROPAGATING SIGNALS IN THE SOLAR CORONA: THE SIGNATURE OF MAGNETOACOUSTIC WAVES OR HIGH-VELOCITY UPFLOWS?

    SciTech Connect

    De Pontieu, Bart; McIntosh, Scott W. E-mail: mscott@ucar.ed

    2010-10-20

    Since the discovery of quasi-periodic propagating oscillations with periods of order 3-10 minutes in coronal loops with TRACE and SOHO/EIT (and later with STEREO/EUVI and Hinode/EIS), they have been almost universally interpreted as evidence for propagating slow-mode magnetoacoustic waves in the low plasma {beta} coronal environment. Here we show that this interpretation is not unique, and that for coronal loops associated with plage regions (as opposed to sunspots), the presence of magnetoacoustic waves may not be the only cause for the observed quasi-periodicities. We focus instead on the ubiquitous, faint upflows at 50-150 km s{sup -1} that were recently discovered as blueward asymmetries of spectral line profiles in footpoint regions of coronal loops, and as faint disturbances propagating along coronal loops in EUV/X-ray imaging time series. These faint upflows are most likely driven from below and have been associated with chromospheric jets that are (partially) rapidly heated to coronal temperatures at low heights. These two scenarios (waves versus flows) are difficult to differentiate using only imaging data, but careful analysis of spectral line profiles indicates that faint upflows are likely responsible for some of the observed quasi-periodic oscillatory signals in the corona. We show that recent EIS measurements of intensity and velocity oscillations of coronal lines (which had previously been interpreted as direct evidence for propagating waves) are actually accompanied by significant oscillations in the line width that are driven by a quasi-periodically varying component of emission in the blue wing of the line. This faint additional component of blue-shifted emission quasi-periodically modulates the peak intensity and line centroid of a single Gaussian fit to the spectral profile with the same small amplitudes (respectively a few percent of background intensity and a few km s{sup -1}) that were previously used to infer the presence of slow-mode magnetoacoustic waves. Our results indicate that it is possible that a significant fraction of the quasi-periodicities observed with coronal imagers and spectrographs that have previously been interpreted as propagating magnetoacoustic waves are instead caused by these upflows. The different physical cause for coronal oscillations would significantly impact the prospects of successful coronal seismology using propagating disturbances in coronal loops.

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  18. How Common Are Hot Magnetic Flux Ropes in the Low Solar Corona? A Statistical Study of EUV Observations

    NASA Astrophysics Data System (ADS)

    Nindos, A.; Patsourakos, S.; Vourlidas, A.; Tagikas, C.

    2015-08-01

    We use data at 131, 171, and 304 Å from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to search for hot flux ropes in 141 M-class and X-class solar flares that occurred at solar longitudes equal to or larger than 50°. Half of the flares were associated with coronal mass ejections. The goal of our survey is to assess the frequency of hot flux ropes in large flares irrespective of their formation time relative to the onset of eruptions. The flux ropes were identified in 131 Å images using morphological criteria and their high temperatures were confirmed by their absence in the cooler 171 and 304 Å passbands. We found hot flux ropes in 45 of our events (32% of the flares); 11 of them were associated with confined flares while the remaining 34 were associated with eruptive flares. Therefore almost half (49%) of the eruptive events involved a hot flux rope configuration. The use of supplementary Hinode X-Ray Telescope data indicates that these percentages should be considered as lower limits of the actual rates of occurrence of hot flux ropes in large flares.

  19. Global Numerical Modeling of Energetic Proton Acceleration in a Coronal Mass Ejection Traveling through the Solar Corona

    NASA Astrophysics Data System (ADS)

    Kozarev, Kamen A.; Evans, Rebekah M.; Schwadron, Nathan A.; Dayeh, Maher A.; Opher, Merav; Korreck, Kelly E.; van der Holst, Bart

    2013-11-01

    The acceleration of protons and electrons to high (sometimes GeV/nucleon) energies by solar phenomena is a key component of space weather. These solar energetic particle (SEP) events can damage spacecraft and communications, as well as present radiation hazards to humans. In-depth particle acceleration simulations have been performed for idealized magnetic fields for diffusive acceleration and particle propagation, and at the same time the quality of MHD simulations of coronal mass ejections (CMEs) has improved significantly. However, to date these two pieces of the same puzzle have remained largely decoupled. Such structures may contain not just a shock but also sizable sheath and pileup compression regions behind it, and may vary considerably with longitude and latitude based on the underlying coronal conditions. In this work, we have coupled results from a detailed global three-dimensional MHD time-dependent CME simulation to a global proton acceleration and transport model, in order to study time-dependent effects of SEP acceleration between 1.8 and 8 solar radii in the 2005 May 13 CME. We find that the source population is accelerated to at least 100 MeV, with distributions enhanced up to six orders of magnitude. Acceleration efficiency varies strongly along field lines probing different regions of the dynamically evolving CME, whose dynamics is influenced by the large-scale coronal magnetic field structure. We observe strong acceleration in sheath regions immediately behind the shock.

  20. Global numerical modeling of energetic proton acceleration in a coronal mass ejection traveling through the solar corona

    SciTech Connect

    Kozarev, Kamen A.; Opher, Merav; Evans, Rebekah M.; Dayeh, Maher A.; Korreck, Kelly E.; Van der Holst, Bart

    2013-11-20

    The acceleration of protons and electrons to high (sometimes GeV/nucleon) energies by solar phenomena is a key component of space weather. These solar energetic particle (SEP) events can damage spacecraft and communications, as well as present radiation hazards to humans. In-depth particle acceleration simulations have been performed for idealized magnetic fields for diffusive acceleration and particle propagation, and at the same time the quality of MHD simulations of coronal mass ejections (CMEs) has improved significantly. However, to date these two pieces of the same puzzle have remained largely decoupled. Such structures may contain not just a shock but also sizable sheath and pileup compression regions behind it, and may vary considerably with longitude and latitude based on the underlying coronal conditions. In this work, we have coupled results from a detailed global three-dimensional MHD time-dependent CME simulation to a global proton acceleration and transport model, in order to study time-dependent effects of SEP acceleration between 1.8 and 8 solar radii in the 2005 May 13 CME. We find that the source population is accelerated to at least 100 MeV, with distributions enhanced up to six orders of magnitude. Acceleration efficiency varies strongly along field lines probing different regions of the dynamically evolving CME, whose dynamics is influenced by the large-scale coronal magnetic field structure. We observe strong acceleration in sheath regions immediately behind the shock.

  1. Revealing the structure and dust content of debris disks on solar systems scales with GPI

    NASA Astrophysics Data System (ADS)

    Duchene, Gaspard; Fitzgerald, Michael P.; Kalas, Paul; Graham, James R.; Arriaga, Pauline; Bruzzone, Sebastian; Chen, Christine; Dawson, Rebekah Ilene; Dong, Ruobing; Draper, Zachary; Esposito, Thomas; Follette, Katherine; Hung, Li-Wei; Lawler, Samantha; Metchev, Stanimir; Millar-Blanchaer, Max; Murray-Clay, Ruth; Perrin, Marshall D.; Rameau, Julien; Wang, Jason; Wolff, Schuyler; Macintosh, Bruce; GPIES team

    2016-01-01

    High contrast scattered light images offer the best prospect to assess the detailed geometry and structure of dusty debris disks. In turn, such images can yield profound insight on the architecture of the underlying planetary system as dust grains respond to the gravitational pull of planetary bodies. A new generation of extreme adaptive optics systems now enables an unprecedented exploration of circumstellar disks on solar system scales. Here we review the new science derived from over a dozen debris disks imaged with the Gemini Planet Imager (GPI) as part of the GPI Exoplanet Survey (GPIES). In addition to its exquisite imaging capability, GPI's polarimetric mode provides invaluable insight on the dust content of each disk, in most cases for the very first time. These early results typically reveal narrow belts of material with evacuated regions roughly 50-100 AU in radius, subtle asymmetries in structure and high degree of linear polarization. We will provide an overview of the disk observations made during the GPIES campaign to date and will discuss in more detail some of the most remarkable systems.This work is supported by grants NSF AST-0909188, -1411868, -1413718; NASA NNX-15AD95G, -14AJ80G, -11AD21G; and the NExSS research network.

  2. OSO-8 observations of the impulsive phase of solar flares in the transition-zone and corona

    NASA Technical Reports Server (NTRS)

    Lites, B. W.; Bruner, E. C., Jr.; Wolfson, C. J.

    1981-01-01

    Several solar flares were observed from their onset in C IV 1548.2 A and 1-8 A X-rays using instruments on OSO-8. It is found that impulsive brightening in C IV is often accompanied by redshifts, interpreted as downflows, of the order of 80 km/s. The maximum soft X-ray intensity usually arrives several minutes after the maximum C IV intensity. The most energetic C IV event observed shows a small blueshift just before reaching maximum intensity; estimates of the mass flux associated with this upflow through the transition zone are consistent with the increase of mass in the coronal loops as observed in soft X-rays. Finally, it is suggested that the frequent occurrence of violent dynamical processes at the onset of the flare is associated with the initial energy release mechanism.

  3. Status of Knowledge after Ulysses and SOHO: Session 2: Investigate the Links between the Solar Surface, Corona, and Inner Heliosphere.

    NASA Technical Reports Server (NTRS)

    Suess, Steven

    2006-01-01

    As spacecraft observations of the heliosphere have moved from exploration into studies of physical processes, we are learning about the linkages that exist between different parts of the system. The past fifteen years have led to new ideas for how the heliospheric magnetic field connects back to the Sun and to how that connection plays a role in the origin of the solar wind. A growing understanding these connections, in turn, has led to the ability to use composition, ionization state, the microscopic state of the in situ plasma, and energetic particles as tools to further analyze the linkages and the underlying physical processes. Many missions have contributed to these investigations of the heliosphere as an integrated system. Two of the most important are Ulysses and SOHO, because of the types of measurements they make, their specific orbits, and how they have worked to complement each other. I will review and summarize the status of knowledge about these linkages, with emphasis on results from the Ulysses and SOHO missions. Some of the topics will be the global heliosphere at sunspot maximum and minimum, the physics and morphology of coronal holes, the origin(s) of slow wind, SOHO-Ulysses quadrature observations, mysteries in the propagation of energetic particles, and the physics of eruptive events and their associated current sheets. These specific topics are selected because they point towards the investigations that will be carried out with Solar Orbiter (SO) and the opportunity will be used to illustrate how SO will uniquely contribute to our knowledge of the underlying physical processes.

  4. A search for high frequency waves in the visible-light corona during the 2001 total solar eclipse

    NASA Astrophysics Data System (ADS)

    Rudawy, Pawel; Phillips, Kenneth

    Some 8000 images obtained with the SECIS fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 2001 March 21 have been analyzed to search for short-period oscillations in intensity that could be a signature of solar coronal heating mecha-nisms. The images were taken in white-light and Fe xiv green-line (5303 A) channels over 205 s (frame rate 39 images per second), nearly the entire length of totality at this location. The pixel size is 4 arcseconds square. The data are of considerably better quality than the data obtained during the 1999 August 11 total eclipse, observed by us and already reported, in that the images are much better exposed and improvements in the drive system of the heliostat used gave a far better image stability. Of the 29800 locations in each image,. some 12740 had usable signal levels. Classical Fourier and wavelet techniques have been used to analyze the emission at these locations, only some of which were in recognizable coronal structures, searching for periodic uctuations in the range 0.06-10 Hz. While a number of possible periodicities were apparent in the wavelet analysis, none of the peaks in the Fourier spectra was found to be sig-nicant above the 4 level and so definitely attributable to the solar processes. This implies that the pervasive Alfven wave-like phenomena previously reported using polarimetric observations with the CoMP instrument do not give rise to signicant oscillatory intensity uctuations.

  5. CORONAS-F observation of HXR and gamma-ray emissions from the solar flare X10 on 29 October 2003 as a probe of accelerated proton spectrum

    NASA Astrophysics Data System (ADS)

    Kurt, V. G.; Yushkov, B. Yu.; Kudela, K.; Galkin, V. I.; Kashapova, L. K.

    2015-04-01

    HXR and gamma-ray emissions in the 0.04—150 MeV energy range associated with the solar flare on 29 October 2003 (X10/3B) were observed at 20:38—20:58 UT by the SONG instrument aboard the CORONAS-F mission. We restored consecutive flare gamma-emission spectra from SONG and RHESSI data and found a good agreement of these spectra in the 0.1—10 MeV energy range. Two phases were identified which showed major changes in the spectral shape of flare emission: 20:38:00-20:44:20 UT and 20:44:20-20:58:00 UT. During the second phase an efficiency of proton acceleration increased considerably relatively to the efficiency of acceleration of high energy electrons. The pion-decay component of the flare gamma-emission was elicited statistically significant only during the second phase since 20:47:40 UT. A power law spectrum index of accelerated protons was estimated from the ratio between intensities of the pion-decay and gamma-line components. The hardest spectrum (power law index S=3.7) was at 20:48—20:51 UT when the intensity of the pion-decay emission was maximal. Our subdivision of the flare into two phases is consistent with sharp changes in the structure of the flare found by Ji et al. (2008) and Liu et al. (2009). This flare was accompanied by GLE 66. The time profile of the pion-decay gamma-emission was compared with the GLE onset time. It was shown that both protons interacting at the Sun and the particles responsible for the GLE onset could belong to the same population of accelerated particles.

  6. Assemblage of Presolar Materials and Early Solar System Condensates in Chondritic Porous Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Nakamura-Messenger, K.; Messenger, S.; Keller, L. P.; Kloeck, W.

    2015-01-01

    Anhydrous chondritic porous inter-planetary dust particles (CP IDPs) contain an assortment of highly primitive solar system components, molecular cloud matter, and presolar grains. These IDPs have largely escaped parent body processing that has affected meteorites, advocating cometary origins. Though the stardust abundance in CP IDPs is generally greater than in primitive meteorites, it can vary widely among individual CP IDPs. The average abundance of silicate stardust among isotopically primitive IDPs is approx. 375 ppm while some have extreme abundances up to approx. 1.5%. H and N isotopic anomalies are common in CP IDPs and the carrier of these anomalies has been traced to organic matter that has experienced chemical reactions in cold molecular clouds or the outer protosolar disk. Significant variations in these anomalies may reflect different degrees of nebular processing. Refractory inclusions are commonly observed in carbonaceous chondrites. These inclusions are among the first solar system condensates and display 16O-rich isotopic compositions. Refractory grains have also been observed in the comet 81P/Wild-2 samples re-turned from the Stardust Mission and in CP IDPs, but they occur with much less frequency. Here we conduct coordinated mineralogical and isotopic analyses of CP IDPs that were characterized for their bulk chemistry by to study the distribution of primitive components and the degree of nebular alteration incurred.

  7. The Solar Chromosphere/Corona Interface. I; FUV-EUV Observations and Modeling of Unresolved Coronal Funnels

    NASA Technical Reports Server (NTRS)

    Martinez-Galarce, D. S.; Walker, A. B. C.; Barbee, T. W., II; Hoover, R. B.

    2003-01-01

    A coronal funnel model, developed by Rabin (199l), was tested against a calibrated spectroheliogram recorded in 171 - 175 Angstrom bandpass. This image was recorded on board a sounding rocket experiment flown on 1994 November 3, called the Multi-Spectral Solar Telescope Array, II (MSSTA II), MSSTA, a joint project of Stanford University, the NASA Marshall Space Flight Center and the Lawrence Livermore National Laboratory, is an observing platform composed of a set of normal-incidence, multilayer-coated optics designed to obtain narrow bandpass, high resolution images (1 - 3 arc sec) at selected FUV, EUV and soft X-ray wavelengths (44 Angstroms - 1550 Angstroms). Using full-disk images centered at 1550 Angstroms (C IV) and 173 Angstroms (FE IX/X), the funnel model, which is based on coronal back-heating, was tested against the data incorporating observed constraints on global coverage and measured flux. Found, was a class of funnel models that could account for the quiescent, globally diffuse and unresolved emission seen in the 171 - 175 Angstrom bandpass, where the funnels are assumed to be rooted in the C IV supergranular network. These models, when incorporated with the Chianti spectral code, suggest that this emission is mostly of upper transition region origin and primarily composed of FE IX plasma. The funnels are found to have constrictions, Gamma approx. 6 - 20, which is in good agreement with the observations. Further, the fitted models simultaneously satisfy global areal constraints seen in both images; namely, that a global network of funnels must cover approx. 70 - 95 % of the total solar surface area seen in the 171 - 175 Angstrom image, and = 45 % of the disk area seen in the 1550 Angstrom bandpass. These findings support the configuration of the EUV magnetic network as suggested by Reeves et af. (1974) and put forth in more detail by Gabriel (1976). Furthermore, the models are in good agreement with differential emission measure estimates made of the transition region by Raymond & Doyle (1981) for temperatures, 250,000 K = T = 650,000 K, based on full-disk observations made on board by SkyLab.

  8. The Old Feeble Transition Regions and Coronae of Solar-like Dwarf Stars in the Arcturus Moving Group

    NASA Astrophysics Data System (ADS)

    Brown, Alexander; Hodges-Kluck, E. J.; Ayres, T. R.; Harper, G. M.

    2012-05-01

    Old dwarf stars have generally spun down significantly thus dampening one of the main contributors (rotation) to solar-like alpha-omega magnetic dynamo activity. Studying how stellar activity on stars older than the Sun changes in terms of the chromospheric/transition-region/coronal temperature structure and how much energy is radiated as a function of temperature provides important constraints on how solar-like dynamos work. Stars with different metallicities provide information on how the radiative cooling channels control the temperature structure. We have measured fluxes and profiles of FUV emission lines using the HST COS spectrograph and the broad-band X-ray fluxes using Chandra ACIS-S for a sample of old inactive dwarfs. Our sample comprises five members of the 7-8 Gyr Arcturus Moving Group --- HD90508/LHS2266 (F9 V/M4 V, [Fe/H] = -0.4), HD65583 (G8 V, Fe/H]=-0.7), and HD145417 (K0 V, [Fe/H]=-1.4) --- plus three well-studied comparison stars -- HD103095 (G8 V, [Fe/H]=-1.4), Tau Ceti (G8 V, [Fe/H]=-0.4), and the Quiet Sun (G2 V, [Fe/H]=0.0). In this poster we provide estimates of atmospheric radiative losses as a function of temperature and metallicity. The atmospheres of these low-metallicity stars are more heavily weighted towards cooler temperatures than those of more active stars or even the Sun. Chromospheric emission lines, e.g. C I lines, are far stronger relative transition region lines, e.g C IV. Similarly the X-ray data provide detections for all the targets but with primarily very soft (0.3-0.5 keV) photons and imply "coronal" temperatures of less than 1 MK. While the temperature distributions are cooler, the overall integrated X-ray and FUV luminosities are similar to those of the "Quiet Sun" -- implying that similar amounts of non-radiative energy input are being dissipated. This work is supported by NASA GALEX grant NNX06AB46G, HST grants GO-11555 and GO-11829, and Chandra grants GO6-7018X, GO7-8020X, and GO9-0021X to the University of Colorado.

  9. The TESIS experiment on the CORONAS-PHOTON spacecraft

    NASA Astrophysics Data System (ADS)

    Kuzin, S. V.; Zhitnik, I. A.; Shestov, S. V.; Bogachev, S. A.; Bugaenko, O. I.; Ignat'ev, A. P.; Pertsov, A. A.; Ulyanov, A. S.; Reva, A. A.; Slemzin, V. A.; Sukhodrev, N. K.; Ivanov, Yu. S.; Goncharov, L. A.; Mitrofanov, A. V.; Popov, S. G.; Shergina, T. A.; Solov'ev, V. A.; Oparin, S. N.; Zykov, A. M.

    2011-04-01

    On February 26, 2009, the first data was obtained in the TESIS experiment on the research of the solar corona using imaging spectroscopy. The TESIS is a part of the scientific equipment of the CORONAS-PHO-TON spacecraft and is designed for imaging the solar corona in soft X-ray and extreme ultraviolet regions of the spectrum with high spatial, spectral, and temporal resolutions at altitudes from the transition region to three solar radii. The article describes the main characteristics of the instrumentation, management features, and operation modes.

  10. DENSITY FLUCTUATIONS AND THE ACCELERATION OF ELECTRONS BY BEAM-GENERATED LANGMUIR WAVES IN THE SOLAR CORONA

    SciTech Connect

    Ratcliffe, H.; Bian, N. H.; Kontar, E. P.

    2012-12-20

    Non-thermal electron populations are observed throughout the heliosphere. The relaxation of an electron beam is known to produce Langmuir waves which, in turn, may substantially modify the electron distribution function. As the Langmuir waves are refracted by background density gradients and as the solar and heliospheric plasma density is naturally perturbed with various levels of inhomogeneity, the interaction of Langmuir waves with non-thermal electrons in inhomogeneous plasmas is an important topic. We investigate the role played by ambient density fluctuations on the beam-plasma relaxation, focusing on the effect of acceleration of beam electrons. The scattering of Langmuir waves off turbulent density fluctuations is modeled as a wavenumber diffusion process which is implemented in numerical simulations of the one-dimensional quasilinear kinetic equations describing the beam relaxation. The results show that a substantial number of beam electrons are accelerated when the diffusive timescale in wavenumber space {tau}{sub D} is of the order of the quasilinear timescale {tau}{sub ql}, while when {tau}{sub D} << {tau}{sub ql}, the beam relaxation is suppressed. Plasma inhomogeneities are therefore an important means of energy redistribution for waves and hence electrons, and so must be taken into account when interpreting, for example, hard X-ray or Type III emission from flare-accelerated electrons.

  11. 16 Years of Ulysses Interstellar Dust Measurements in the Solar System: I. Mass Distribution and Gas-to-Dust Mass Ratio

    E-print Network

    Krüger, Harald; Gruen, Eberhard; Sterken, Veerle J

    2015-01-01

    In the early 1990s, contemporary interstellar dust (ISD) penetrating deep into the heliosphere was identified with the in-situ dust detector on board the Ulysses spacecraft. Between 1992 and the end of 2007 Ulysses monitored the ISD stream. The interstellar grains act as tracers of the physical conditions in the local interstellar medium surrounding our solar system. Earlier analyses of the Ulysses ISD data measured between 1992 and 1998 implied the existence of 'big' ISD grains [up to 10^-13kg]. The derived gas-to-dust-mass ratio was smaller than the one derived from astronomical observations, implying a concentration of ISD in the very local interstellar medium. We analyse the entire data set from 16 yr of Ulysses ISD measurements in interplanetary space. This paper concentrates on the overall mass distribution of ISD. An accompanying paper investigates time-variable phenomena in the Ulysses ISD data, and in a third paper we present the results from dynamical modelling of the ISD flow applied to Ulysses. We...

  12. A close-up of the sun. [solar probe mission planning conference

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (editor); Davies, R. W. (editor)

    1978-01-01

    NASA's long-range plan for the study of solar-terrestrial relations includes a Solar Probe Mission in which a spacecraft is put into an eccentric orbit with perihelion near 4 solar radii (0.02 AU). The scientific experiments which might be done with such a mission are discussed. Topics include the distribution of mass within the Sun, solar angular momentum, the fine structure of the solar surface and corona, the acceleration of the solar wind and energetic particles, and the evolution of interplanetary dust. The mission could also contribute to high-accuracy tests of general relativity and the search for cosmic gravitational radiation.

  13. Interplanetary dust in the transmission electron microscope - Diverse materials from the early solar system

    NASA Technical Reports Server (NTRS)

    Fraundorf, P.

    1981-01-01

    An analytical electron microscope study of dispersed interplanetary dust aggregates collected in the earth's stratosphere shows that, in spite of their similarities, the aggregates exhibit significant differences in composition, internal morphology, and mineralogy. Of 11 chondritic particles examined, two consist mostly of a noncrystalline chondritic material with an atomic S/Fe ratio equal to or greater than 2 in places, one consists of submicron metal and reduced silicate 'microchondrules' and sulfide grains embedded in a carbonaceous matrix, and another consists of submicron magnetic-decorated unequilibrated silicate and sulfide grains with thick low-Z coatings. Although the particles are unmetamorphosed by criteria commonly applied for chondritic meteorites, the presence of reduced chemistries and the ubiquity of mafic, instead of hydrated, silicates confirm that they are not simply C1 or C2 chondrite matrix material. The observations indicate that portions of some particles have not been significantly altered by thermal or radiation processes since their assembly, and that the particles probably contain fine debris from diverse processes in the early solar system.

  14. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites.

    PubMed

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H; Ramasse, Quentin M; Hoppe, Peter; Nittler, Larry R

    2014-10-28

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight (15)N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C-O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C-O bonding environments and nanoglobular organics with dominant aromatic and C-N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  15. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites

    PubMed Central

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H.; Ramasse, Quentin M.; Hoppe, Peter; Nittler, Larry R.

    2014-01-01

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight 15N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C–O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C–O bonding environments and nanoglobular organics with dominant aromatic and C–N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  16. Interaction of comets with the solar wind: the effective radius of a dust coma of Halley-type comets and the origin of metallic ions.

    NASA Astrophysics Data System (ADS)

    Ibadov, S.

    1996-10-01

    A theoretical study is carried out of the interaction between the dust coma of Halley 1986 III type comets with the proton flux of the solar wind and with energetic hydrogen atoms genetically related to these protons. Analytical formulae are obtained for the effective radius re(pd) of the dust coma for protons of the solar wind, allowing for the power-law size and mass distributions of dust particles, which have been inferred from in situ measurements performed on board the spacecraft Vega and Giotto.

  17. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, Dániel; Lauretta, Dante S.

    2010-01-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  18. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, D.´niel; Lauretta, Dante S.

    2014-02-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  19. DIRECT IMAGING OF QUASI-PERIODIC FAST PROPAGATING WAVES OF {approx}2000 km s{sup -1} IN THE LOW SOLAR CORONA BY THE SOLAR DYNAMICS OBSERVATORY ATMOSPHERIC IMAGING ASSEMBLY

    SciTech Connect

    Liu Wei; Title, Alan M.; Schrijver, Carolus J.; Aschwanden, Markus J.; De Pontieu, Bart; Tarbell, Theodore D.; Zhao Junwei; Ofman, Leon

    2011-07-20

    Quasi-periodic propagating fast mode magnetosonic waves in the solar corona were difficult to observe in the past due to relatively low instrument cadences. We report here evidence of such waves directly imaged in EUV by the new Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory. In the 2010 August 1 C3.2 flare/coronal mass ejection event, we find arc-shaped wave trains of 1%-5% intensity variations (lifetime {approx}200 s) that emanate near the flare kernel and propagate outward up to {approx}400 Mm along a funnel of coronal loops. Sinusoidal fits to a typical wave train indicate a phase velocity of 2200 {+-} 130 km s{sup -1}. Similar waves propagating in opposite directions are observed in closed loops between two flare ribbons. In the k-{omega} diagram of the Fourier wave power, we find a bright ridge that represents the dispersion relation and can be well fitted with a straight line passing through the origin. This k-{omega} ridge shows a broad frequency distribution with power peaks at 5.5, 14.5, and 25.1 mHz. The strongest signal at 5.5 mHz (period 181 s) temporally coincides with quasi-periodic pulsations of the flare, suggesting a common origin. The instantaneous wave energy flux of (0.1-2.6) x 10{sup 7} erg cm{sup -2} s{sup -1} estimated at the coronal base is comparable to the steady-state heating requirement of active region loops.

  20. ON THE REMOTE DETECTION OF SUPRATHERMAL IONS IN THE SOLAR CORONA AND THEIR ROLE AS SEEDS FOR SOLAR ENERGETIC PARTICLE PRODUCTION

    SciTech Connect

    Laming, J. Martin; Moses, J. Daniel; Ko, Yuan-Kuen; Ng, Chee K.; Rakowski, Cara E.; Tylka, Allan J.

    2013-06-10

    Forecasting large solar energetic particle (SEP) events associated with shocks driven by fast coronal mass ejections (CMEs) poses a major difficulty in the field of space weather. Besides issues associated with CME initiation, the SEP intensities are difficult to predict, spanning three orders of magnitude at any given CME speed. Many lines of indirect evidence point to the pre-existence of suprathermal seed particles for injection into the acceleration process as a key ingredient limiting the SEP intensity of a given event. This paper outlines the observational and theoretical basis for the inference that a suprathermal particle population is present prior to large SEP events, explores various scenarios for generating seed particles and their observational signatures, and explains how such suprathermals could be detected through measuring the wings of the H I Ly{alpha} line.

  1. The role of presolar dust in the formation of the solar system

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.

    1988-01-01

    The characteristics of presolar dust are discussed and evidence is provided to support the possibility that presolar dust was the primary building material for the meteorites and terrestrial planets. The material in the sun's parent molecular cloud is divided into eight reservoirs. The results show that presolar dust and objects made from processed dust make up the vast majority of the material in primitive chondrites. The present theory is able to account for the chemical and oxygen isotopic variations between meteorite classes, the formation of chondrules, the accretion of chondrites, and parent body metamorphism.

  2. Heating of the corona by magnetic singularities

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.

    1990-01-01

    Theoretical models of current-sheet formation and magnetic heating in the solar corona are examined analytically. The role of photospheric connectivity in determining the topology of the coronal magnetic field and its equilibrium properties is explored; nonequilibrium models of current-sheet formation (assuming an initially well connected field) are described; and particular attention is given to models with discontinuous connectivity, where magnetic singularities arise from smooth footpoint motions. It is shown that current sheets arise from connectivities in which the photospheric flux structure is complex, with three or more polarity regions and a magnetic null point within the corona.

  3. Disease specific protein corona

    NASA Astrophysics Data System (ADS)

    Rahman, M.; Mahmoudi, M.

    2015-03-01

    It is now well accepted that upon their entrance into the biological environments, the surface of nanomaterials would be covered by various biomacromolecules (e.g., proteins and lipids). The absorption of these biomolecules, so called `protein corona', onto the surface of (nano)biomaterials confers them a new `biological identity'. Although the formation of protein coronas on the surface of nanoparticles has been widely investigated, there are few reports on the effect of various diseases on the biological identity of nanoparticles. As the type of diseases may tremendously changes the composition of the protein source (e.g., human plasma/serum), one can expect that amount and composition of associated proteins in the corona composition may be varied, in disease type manner. Here, we show that corona coated silica and polystyrene nanoparticles (after interaction with in the plasma of the healthy individuals) could induce unfolding of fibrinogen, which promotes release of the inflammatory cytokines. However, no considerable releases of inflammatory cytokines were observed for corona coated graphene sheets. In contrast, the obtained corona coated silica and polystyrene nanoparticles from the hypofibrinogenemia patients could not induce inflammatory cytokine release where graphene sheets do. Therefore, one can expect that disease-specific protein coronas can provide a novel approach for applying nanomedicine to personalized medicine, improving diagnosis and treatment of different diseases tailored to the specific conditions and circumstances.

  4. Interstellar Dust: Contributed Papers

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M. (editor); Allamandola, Louis J. (editor)

    1989-01-01

    A coherent picture of the dust composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: dust in diffuse interstellar medium; overidentified infrared emission features; dust in dense clouds; dust in galaxies; optical properties of dust grains; interstellar dust models; interstellar dust and the solar system; dust formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.

  5. Micron-Sized Dust Particles Detected in the Outer Solar System by the Voyager 1 and 2 Plasma Wave Instruments

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Ansher, J. A.; Kurth, W. S.; Granroth, L. J.

    1997-01-01

    During the Voyager 1 and 2 flybys of the outer planets it has been demonstrated that the plasma wave instrument can detect small dust particles striking the spacecraft. In this paper, we examine the Voyager plasma wave data for dust impacts in the interplanetary medium at heliocentric radial distances ranging from 6 to 60 astronomical units (AU). The results show that a small but persistent level of dust impacts exists out to at least 30 to 50 AU. The average number density of these particles is about 2 x 10(exp -8)/cu m, and the average mass of the impacting particles is believed to be a few times 10(exp -11) g, which corresponds to particle diameters in the micron range. Possible sources of these particles are planets, moons, asteroids, comets, and the interstellar medium. Of these, comets appear to be the most likely source. The number densities are only weakly dependent on ecliptic latitude, which indicates that the particles probably do not originate from planets, moons, or asteroids. Comparisons with interstellar dust fluxes measured in the inner regions of the solar system by the Ulysses spacecraft indicate that the particles are not of interstellar origin.

  6. Micron-Sized Dust Particles Detected in the Outer Solar System by the Voyager 1 and 2 Plasma Wave Instruments

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Ansher, J. A.; Kurth, W. S.; Granroth, L. J.

    1997-01-01

    During the Voyager 1 and 2 flybys of the outer planets it has been demonstrated that the plasma wave instrument can detect small dust particles striking the spacecraft. In this paper, we examine the Voyager plasma wave data for dust impacts in the interplanetary medium at heliocentric radial distances ranging from 6 to 60 astronomical units (AU). The results show that a small but persistent level of dust impacts exists out to at least 30 to 50 AU. The average number density of these particles is about 2 x 10(exp -8)/cu m, and the average mass of the impacting particles is believed to be a few times 10(exp -11) g, which corresponds to particle diameters in the micron range. Possible sources of these particles are planets, moons, asteroids, comets, and the interstellar medium. Of these, comets appear to be the most likely source. ne number densities are only weakly dependent on ecliptic latitude, which indicates that the particles probably do not originate from planets, moons, or asteroids. Comparisons with interstellar dust fluxes measured in the inner regions of the solar system by the Ulysses spacecraft indicate that the particles are not of interstellar origin.

  7. Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field

    NASA Astrophysics Data System (ADS)

    Lehtinen, K.; Mattila, K.

    2013-01-01

    Context. The optical surface brightness of dark nebulae is mainly due to scattering of integrated starlight by classical dust grains. It contains information on the impinging interstellar radiation field, cloud structure, and grain scattering properties. We have obtained spectra of the scattered light from 3500 to 9000 Å in two globules, the Thumbprint Nebula and DC 303.8-14.2. Aims. We use observations of the scattered light to study the impinging integrated starlight spectrum as well as the scattered H? and other line emissions from all over the sky. We search also for the presence of other than scattered light in the two globules. Methods. We obtained long-slit spectra encompassing the whole globule plus adjacent sky in a one-slit setting, thus enabling efficient elimination of airglow and other foreground sky components. We calculated synthetic integrated starlight spectra for the solar neighbourhood using HIPPARCOS-based stellar distributions and the spectral library of Pickles. Results. Spectra are presented separately for the bright rims and dark cores of the globules. The continuum spectral energy distributions and absorption line spectra can be well modelled with the synthetic integrated starlight spectra. Emission lines of H? +[N II], H?, and [S II] are detected and are interpreted in terms of scattered light plus an in situ warm ionized medium component behind the globules. We detected an excess of emission over the wavelength range 5200-8000 Å in DC 303.8-14.2 but the nature of this emission remains open. Based on observations collected at the European Southern Observatory, Chile, under programme ESO No. 073.C-0239(A). Appendix A is available in electronic form at http://www.aanda.org.

  8. Identification and Characterization of Early Solar system Organic Matter Preserved in Chondritic Porous Interplanetary Dust Particles

    NASA Astrophysics Data System (ADS)

    Flynn, George; Wirick, Sue; Keller, Lindsay

    2015-04-01

    The chondritic porous interplanetary dust particles (CP IDPs), collected by NASA from the Earth's stratosphere, have experienced minimal aqueous or thermal alteration since their formation. These CP IDPs are the best preserved samples of the minerals and organic matter that was present in the primitive Solar Nebula that are currently available for laboratory analysis [1]. The ~10 ?m CP IDPs are aggregates of tens-of-thousands of mostly sub-micron grains of diverse compositions and mineralogies. Many of the individual mineral grains are coated by a 50 to 200 nm thick rims of carbonaceous material, and other carbonaceous material occurs as larger, discrete subunits within the particles [2]. We characterize this carbonaceous material using two high-resolution, synchrotron-based instruments: a Scanning Transmission X-ray Microscope (STXM) to locate and map the carbon and to identify its major functional groups by X-ray Absorption Near-Edge Structure (XANES) spectroscopy, and a micro-Fourier Transform Infrared (?-FTIR) spectrometer to further characterize the functional groups by mid-infrared spectroscopy. Carbon-XANES spectroscopy identifies the rims coating the individual grains in CP IDPs as organic matter, dominated by the C=C, likely C-rings, and the C=O functional groups [3]. This structure, with the organic rims being the contact surfaces between the grains, implies a 3-step formation sequence: grain condensation, organic rim emplacement, and, finally, aggregation of the grains to form the dust particles. This suggests these organic rims formed very early in the evolution of the Solar Nebula, after grain condensation but before grain aggregation [3]. These organic rims coat grains of diverse compositions, including silicates, sulfides, and carbonates, which is inconsistent with formation by Fischer-Tropsch-like, mineral-specific catalysis, one of the mechanisms suggested for the formation of primitive organic matter. Our observations are consistent with an alternate model where carbon-bearing ices condense on the surfaces of grains, the ices are irradiated by ionizing radiation, and subsequent heating removes the ices leaving more refractory organic matter on the grain surfaces, as described by Bernstein et al. [4]. In one case we obtained C-, N-, and O-XANES spectra on the rim material. The O-XANES confirmed the presence of C=O. We found high N:C and O:C ratios that plot on the extension of the N:C vs. O:C correlation line, found in analysis of meteoritic organic matter [5], towards even more primitive organic matter than found in any meteorite. The organic rims are too thin for ?-FTIR spectroscopy, which is diffraction limited to about the wavelength/2, or ~2 ?m for the aliphatic C-H stretching features. However, mid-infrared spectra obtained on CP IDPs show the presence of aliphatic C-H, C=O, C-C, and O-H, as well as crystalline and amorphous silicates [6]. Aromatic C-H is rarely detected in CP IDPs. Neither the organic rims nor the bulk organic matter in CP IDPs show the graphite exciton feature, whose strength in meteorite organic matter correlates with increasing parent body thermal metamorphism [7], indicating the organic matter in CP IDPs experienced minimal metamorphism after it formed. The spectra show variation in the aliphatic -C-H2- to -C-H3 and C=O to aliphatic C-H ratios from spot to spot on the same particle. C-XANES of ultramicrotome sections of CP IDPs also show significant variability, particularly in the C=O to C=C ratio. Variability in the C-XANES and the mid-infrared spectra indicates the organic matter in primitive CP IDPs consists of several compositionally distinct components. Our C-XANES and ?-FTIR results indicate the organic matter in CP IDPs is extremely primitive and that much of the pre-biotic organic matter of our Solar System formed early in the evolution of the Solar Nebula, by a process that preceded parent body aqueous processing. References: [1] Ishii, H. A. et al. (2008) Science, 319, 447-450. [2] Thomas, K. L. et al. (1996) ASP Conference Series, 104, 295-298. [3] Flynn, G. J

  9. Dust Interactions on Small Solar System Bodies and Technology Considerations for Exploration

    NASA Technical Reports Server (NTRS)

    Kobrick, Ryan,; Hoffman, Jeffrey; Pavone, Marco; Street, Kenneth; Rickman, Douglas

    2014-01-01

    Small-bodies such as asteroids and Mars' moons Phobos and Deimos have relatively unknown regolith environments. It is hypothesized that dust preserved in the regolith on the surfaces will have similar mechanical properties to lunar dust because of similar formation processes from micrometeorite bombardment, low relative gravity for slow settling times, and virtually no weathering because there is no atmosphere. This combination of processes infers that small-body dust particles will be highly angular and retain abrasive properties. The focus of this paper uses the mission architecture and engineering design for an asteroid hopper known as Hedgehog, a spherical spacecraft with several symmetric spikes used to aid with tumbling mobility in a low gravity environment. Dust abrasion considerations are highlighted throughout the paper relating to the lead authors' previous work, but act as an example of one of many important dust or regolith physical properties that need to be considered for future exploration. Measurable regolith properties are summarized in order to identify technologies that may be useful for exploration in terms of scientific return and spacecraft design. Previous instruments are summarized in this paper that could be used on the Hedgehog. Opportunities for hardware payloads are highlighted that include low mass solutions or dualpurpose instruments that can measure regolith or dust properties. Finally, dust mitigation suggestions are made for vehicles of this mobility profile.

  10. Dust in brown dwarfs and extra-solar planets. III. Testing synthetic spectra on observations

    NASA Astrophysics Data System (ADS)

    Witte, S.; Helling, Ch.; Barman, T.; Heidrich, N.; Hauschildt, P. H.

    2011-05-01

    Context. This work is concerned with dust formation in ultra-cool atmospheres, encompassing the latest type stars, brown dwarfs, and hot giant exoplanets. Dust represents one of the most important and yet least understood sources of opacity in these types of objects. Aims: We compare our model spectra with SpeX data in order to draw conclusions about the dust cloud structure and related quantities in ultra-cool atmospheres. Methods: We use the self-consistent Drift-Phoenix atmosphere code, which features a kinetic dust formation mechanism and accounts for the dust cloud influence on the spectra. Results: We present fits of our latest model spectra to observations that cover a wide range of our model grid. The results are remarkably good, yielding significant improvement over the older Cond-/Dusty-Phoenix models, especially in the L-dwarf regime. The new models are able to properly reproduce observed spectra, including complicated features such as the molecular band strengths. This raises confidence in the reliability of our dust-modeling approach. Conclusions: We demonstrate that our code produces excellent results concerning the fitting with observations. This suggests that our dust cloud and atmosphere structures are reasonably accurate. Like all other current cloud models, ours is not able to produce satisfying results for spectral types later than L6 without manually tuning down the amount of dust. Our results show the formation of convective cells within the cloud, which are able to destroy the lower cloud parts. The dust opacity is reduced significantly without the need to tune the dust cloud thickness. There are indications that the cycle of dust accumulation and cloud destruction by convection is time-dependent on rather long timescales. Considering a statistical distribution of locally variable dust clouds over a dwarf's surface can result in a large number of spectral configurations for the same model atmosphere parameters, hence introducing an additional and more or less random degree of freedom to those atmospheres. Without resorting to the model atmosphere parameters, this alone can account for the unusually red and blue objects that have been discovered.

  11. Dust Production from Sub-Solar to Super-Solar Metallicity in Thermally Pulsing Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Nanni, A.; Bressan, A.; Marigo, P.; Girardi, L.; Javadi, A.; van Loon, J. Th.

    2015-08-01

    We discuss the dust chemistry and growth in the circumstellar envelopes (CSEs) of Thermally Pulsing Asymptotic Giant Branch (TP-AGB) star models, computed with the COLIBRI code, at varying initial mass and metallicity (Z = 0.001, 0.008, 0.02, 0.04, 0.06). A relevant result of our analysis deals with silicate production in M stars. We show that, in order to reproduce the observed trend between terminal velocities and mass-loss rates in Galactic M giants, one has to significantly reduce the efficiency of chemisputtering by H2 molecules, usually considered the most effective dust destruction mechanism. This conclusion is in agreement with the most recent laboratory results, which show that silicates may condense already at Tcond˜1400 K, rather than only at Tcond˜1000 K, as obtained by models that include chemisputtering. From analysis of the total dust ejecta, we find that the dust-to-gas ratios of the total ejecta from intermediate-mass stars are much less dependent on metallicity than usually assumed. In a broader context, our results are suitable for studying the dust enrichment of the interstellar medium provided by TP-AGB stars in both nearby and high-redshift galaxies.

  12. On the Intrinsic Difficulty of Producing Stellar Coronae With Acoustic Waves

    E-print Network

    Ulmschneider, Peter

    , however, severe empirical limits could be placed on the role that these waves play in heating the solar to heat the open corona, even though such waves are certainly abundant in the photosphere, Finally budget of a corona that is heated exclusively by acoustic waves of the given period. Solar coronal hole

  13. Dust Models Paint Alien's View of Solar System - Duration: 2 minutes, 47 seconds.

    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. Signatures of Recent Asteroid Disruptions in the Formation and Evolution of Solar System Dust Bands

    NASA Astrophysics Data System (ADS)

    Espy Kehoe, A. J.; Kehoe, T. J. J.; Colwell, J. E.; Dermott, S. F.

    2015-09-01

    We have performed detailed dynamical modeling of the structure of a faint dust band observed in coadded InfraRed Astronomical Satellite data at an ecliptic latitude of 17° that convincingly demonstrates that it is the result of a relatively recent (significantly less than 1 Ma) disruption of an asteroid and is still in the process of forming. We show here that young dust bands retain information on the size distribution and cross-sectional area of dust released in the original asteroid disruption, before it is lost to orbital and collisional decay. We find that the Emilkowalski cluster is the source of this partial band and that the dust released in the disruption would correspond to a regolith layer ˜3 m deep on the ˜10 km diameter source body's surface. The dust in this band is described by a cumulative size-distribution inverse power-law index with a lower bound of 2.1 (implying domination of cross-sectional area by small particles) for dust particles with diameters ranging from a few ?m up to a few cm. The coadded observations show that the thermal emission of the dust band structure is dominated by large (mm-cm size) particles. We find that dust particle ejection velocities need to be a few times the escape velocity of the Emilkowalski cluster source body to provide a good fit to the inclination dispersion of the observations. We discuss the implications that such a significant release of material during a disruption has for the temporal evolution of the structure, composition, and magnitude of the zodiacal cloud.

  15. Signatures of recent asteroid disruptions in the formation and evolution of solar system dust bands

    E-print Network

    Kehoe, A J Espy; Colwell, J E; Dermott, S F

    2015-01-01

    We have performed detailed dynamical modeling of the structure of a faint dust band observed in coadded IRAS data at an ecliptic latitude of 17$^{\\circ}$ that convincingly demonstrates that it is the result of a relatively recent (significantly less than 1 Ma) disruption of an asteroid and is still in the process of forming. We show here that young dust bands retain information on the size distribution and cross-sectional area of dust released in the original asteroid disruption, before it is lost to orbital and collisional decay. We find that the Emilkowalski cluster is the source of this partial band and that the dust released in the disruption would correspond to a regolith layer $\\sim$3 m deep on the $\\sim$10 km diameter source body's surface. The dust in this band is described by a cumulative size-distribution inverse power-law index with a lower bound of 2.1 (implying domination of cross-sectional area by small particles) for dust particles with diameters ranging from a few $\\mu$m up to a few cm. The co...

  16. Numerical and Analytical Model of an Electrodynamic Dust Shield for Solar Panels on Mars

    NASA Technical Reports Server (NTRS)

    Calle, C. I.; Linell, B.; Chen, A.; Meyer, J.; Clements, S.; Mazumder, M. K.

    2006-01-01

    Masuda and collaborators at the University of Tokyo developed a method to confine and transport particles called the electric curtain in which a series of parallel electrodes connected to an AC source generates a traveling wave that acts as a contactless conveyor. The curtain electrodes can be excited by a single-phase or a multi-phase AC voltage. A multi-phase curtain produces a non-uniform traveling wave that provides controlled transport of those particles [1-6]. Multi-phase electric curtains from two to six phases have been developed and studied by several research groups [7-9]. We have developed an Electrodynamic Dust Shield prototype using threephase AC voltage electrodes to remove dust from surfaces. The purpose of the modeling work presented here is to research and to better understand the physics governing the electrodynamic shield, as well as to advance and to support the experimental dust shield research.

  17. Early inner solar system impactors: physical properties of comet nuclei and dust particles revisited.

    PubMed

    Levasseur-Regourd, A C; Lasue, J; Desvoivres, E

    2006-12-01

    During the epoch of early bombardment, terrestrial planets have been heavily impacted by cometary nuclei and cometary dust particles progressively injected in the interplanetary medium. Stardust and Deep Impact missions confirm that the nuclei are porous, loosely consolidated objects, with densities below 1,000 kg m(-3), and that they often release small fragments of ices and dust. Recent numerical simulations of the light scattering properties of cometary dust particles indicate that they are highly porous, most likely fractal, and rich in absorbing organics compounds (with a mixture ratio of e.g. 33 to 60% in mass for comet Hale-Bopp). Taking into account the fact that porous structures survive more easily than compact ones during atmospheric entry, such results reinforce the scenario of the early terrestrial planets enrichment--in organics needed for life to originate--by comets. PMID:17120128

  18. Reconnection-driven Double Layers in the Stratified Plasma of the Solar Transition Region: Supply of Hot Plasma into the Corona

    NASA Astrophysics Data System (ADS)

    Singh, Nagendra

    2015-09-01

    A novel mechanism for the supply of hot plasma into the corona from the chromosphere is suggested here; the mechanism involves collisionless magnetic reconnection (CMR) in the transition region (TR) followed by double layer (DL) formation in the enhanced expansion of the chromospheric cold plasma mixed with CMR-heated hot electrons. It is well known that (i) the CMR produces energetic electrons and (ii) DLs naturally form in expanding dense plasmas containing a minor population of hot electrons. We apply these plasma physics facts to the dynamics of stratified plasma in the TR. In the TR where densities fall below ˜1016 m-3, all collisional mean-free paths, electron-ion, ion-neutral, and electron-neutral, become long enough to render plasma collisionless at kinetic scale lengths, making CMR and DL formation possible. The DLs accelerate the chromospheric cold ions to energies comparable to the energy of the hot electrons. When the upflowing energized ions neutralized by the escaping hot electrons thermalize, the resulting hot tenuous plasma supplies an energy flux ˜3 × 105 erg cm-2 s-1 = 3 × 102 J m-2 s-1 into the corona. The CMR-DL mechanism introduces sudden transitions in the TR as microstructures in both density and energy. The global transition in the TR could be a fractal structure containing such microscopic features. If not impossible, it is difficult to measure such microstructures, but it seems that the coronal heating begins in the nearly collisionless TR by CMR and DL formation.

  19. Recent Studies of the Behavior of the Sun's White-Light Corona Over Time

    NASA Technical Reports Server (NTRS)

    SaintCyr, O. C.; Young, D. E.; Pesnell, W. D.; Lecinski, A.; Eddy, J.

    2008-01-01

    Predictions of upcoming solar cycles are often related to the nature and dynamics of the Sun's polar magnetic field and its influence on the corona. For the past 30 years we have a more-or-less continuous record of the Sun's white-light corona from groundbased and spacebased coronagraphs. Over that interval, the large scale features of the corona have varied in what we now consider a 'predictable' fashion--complex, showing multiple streamers at all latitudes during solar activity maximum; and a simple dipolar shape aligned with the rotational pole during solar minimum. Over the past three decades the white-light corona appears to be a better indicator of 'true' solar minimum than sunspot number since sunspots disappear for months (even years) at solar minimum. Since almost all predictions of the timing of the next solar maximum depend on the timing of solar minimum, the white-light corona is a potentially important observational discriminator for future predictors. In this contribution we describe recent work quantifying the large-scale appearance of the Sun's corona to correlate it with the sunspot record, especially around solar minimum. These three decades can be expanded with the HAO archive of eclipse photographs which, although sparse compared to the coronagraphic coverage, extends back to 1869. A more extensive understanding of this proxy would give researchers confidence in using the white-light corona as an indicator of solar minimum conditions.

  20. A thermodynamic and mechanical model for the earliest Solar System: Formation via 3-d collapse of dust in the pre-Solar nebula

    NASA Astrophysics Data System (ADS)

    Criss, R. E.; Hofmeister, A.

    2012-12-01

    The fundamental and shared rotational characteristics of the Solar System (nearly circular, co-planar orbits and mostly upright axial spins of the planets) record conditions of origin, yet are not explained by prevailing 2-dimensional disk models. Current planetary spin and orbital rotational energies (R.E.) each nearly equal and linearly depend on gravitational self-potential of formation (Ug), revealing mechanical energy conservation. We derive ?Ug ˜= ?R.E. and stability criteria from thermodynamic principles, and parlay these relationships into a detailed model of simultaneous accretion of the protoSun and planets from the dust-bearing pre-solar nebula (PSN). Gravitational heating is insignificant because Ug is negative, the 2nd law of thermodynamics must be fulfilled, and ideal gas conditions pertain until the objects were nearly fully formed. Combined conservation of angular momentum and mechanical energy during 3-dimensional collapse of spheroidal dust shells in a contracting nebula provides ?R.E. ˜= R.E. for the central body, whereas for formation of orbiting bodies, ?R.E.depends on the contraction of orbits during collapse. Orbital data for the inner planets follow 0.04xR.E.f ˜= -Ug which confirms conservation of angular momentum. Measured spins of the youngest stars confirm that R.E.˜= -Ug. Heat production occurs after nearly final sizes are reached via mechanisms such as shear during differential rotation and radioactivity. We focus on the dilute stage, showing that the PSN was compositionally graded due to light molecules diffusing preferentially, providing the observed planetary chemistry, and set limits on PSN mass, density, and temperature. From measured planetary masses and orbital characteristics, accounting for dissipation of spin, we deduce mechanisms and the sequence of converting a 3-d dusty cloud to the present 2-d Solar System, and infer the evolution of dust and gas densities. Duration of events is obtained from the time-dependent virial theorem. As the PSN slowly contracted, collapse of pre-solar dust in spheroidal shells simultaneously formed rocky protoplanets embedded in a dusty debris disk, creating their nearly circular co-planar orbits and upright axial spins with the same sense as orbital rotation, which were then enhanced via subsequent local contraction of nearby nebulae. Because rocky kernels at great distance out-competed the pull of the co-accreting star, gas giants formed in the outer reaches within ~3 Ma as PSN contraction hastened. This pattern repeated to form satellite systems. The PSN imploded, once constricted to within Jupiter's orbit. Afterwards, disk debris slowly spiraled toward the protoSun, cratering and heating intercepted surfaces. Our conservative 3-d model, which allows for different behaviors of gas and dust, explains key Solar System characteristics (spin, orbits, gas giants and their compositions) and second-order features (dwarf planets, comet mineralogy, satellite system sizes).

  1. Persistent Doppler Shift Oscillations Observed with HINODE-EIS in the Solar Corona: Spectroscopic Signatures of Alfvenic Waves and Recurring Upflows

    NASA Technical Reports Server (NTRS)

    Tian, Hui; McIntosh, Scott W.; Wang, Tongjiang; Offman, Leon; De Pontieu, Bart; Innes, Davina E.; Peter, Hardi

    2012-01-01

    Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfv´en waves rather than flows. In a few cases, there seems to be a p/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfv´enic oscillations. In this scenario, the intensity oscillations associated with Alfv´enic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.

  2. PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS

    SciTech Connect

    Tian Hui; McIntosh, Scott W.; Wang, Tongjiang; Ofman, Leon; De Pontieu, Bart; Innes, Davina E.; Peter, Hardi

    2012-11-10

    Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfven waves rather than flows. In a few cases, there seems to be a {pi}/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfvenic oscillations. In this scenario, the intensity oscillations associated with Alfvenic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.

  3. Chemical Signatures of Interstellar Dusts Preserved in Primitive Chondrites and Inner Planets of the Solar System

    NASA Technical Reports Server (NTRS)

    Yin, Qing-Zhu

    2002-01-01

    We show that the inheritance of interstellar materials by the solar system is not only documented by the presence of presolar grains, various isotopic anomalies, but also expressed in the chemical element distribution in the inner solar system. Additional information is contained in the original extended abstract.

  4. Evolution of chromospheres and coronae in solar mass stars: A far-ultraviolet and soft x-ray comparison of Arcturus (K2III) and Alpha Centauri A (G2 V)

    SciTech Connect

    Ayres, T.R.; Simon, T.; Linsky, J.L.

    1982-12-15

    We compare IUE far-ultraviolet and Einstein soft X-ray observations of the red giant Arcturus (..cap alpha.. Booetis, K2III) and the nearby yellow dwarf ..cap alpha.. Centauri A (G2 V), which are archetypes of solar mass stars in very different stages of evolution. We find no evidence for coronal (Troughly-equal10/sup 6/ K) soft X-ray emission from the red giant at surface flux levels of only 0.0006 (3sigma) that detected previously for ..cap alpha.. Cen A, and no evidence for C iv lambdalambda1548, 1551 (Troughly-equal10/sup 5/ K) or C ii lambdalambda1335, 1336 (Troughly-equal2 x 10/sup 4/ K) resonance line emission at surface flux levels of only 0.02 (3sigma) those of the yellow dwarf. Instead of a solar-like hot corona and warm (Troughly-equal10/sup 5/ K) transition region, the resonance line upper limits and previous detections of the C ii intersystem UV multiplet 0.01 near 2325 A provide evidence that the outer atmosphere of Arcturus is geometrically extended (..delta..happrox.R/sub asterisk/), tenuous (n/sub e/roughly-equal3 x 10/sup 8/ cm/sup -3/), and cool (T< or approx. =10/sup 4/ K).

  5. Dynamics of the transition corona

    SciTech Connect

    Masson, Sophie; McCauley, Patrick; Golub, Leon; Reeves, Katharine K.; DeLuca, Edward E.

    2014-06-01

    Magnetic reconnection between the open and closed magnetic fields in the corona is believed to play a crucial role in the corona/heliosphere coupling. At large scale, the exchange of open/closed connectivity is expected to occur in pseudo-streamer (PS) structures. However, there is neither clear observational evidence of how such coupling occurs in PSs, nor evidence for how the magnetic reconnection evolves. Using a newly developed technique, we enhance the off-limb magnetic fine structures observed with the Atmospheric Imaging Assembly and identify a PS-like feature located close to the northern coronal hole. We first identify that the magnetic topology associated with the observation is a PS, null-point (NP) related topology bounded by the open field. By comparing the magnetic field configuration with the EUV emission regions, we determined that most of the magnetic flux associated with plasma emission are small loops below the PS basic NP and open field bounding the PS topology. In order to interpret the evolution of the PS, we referred to a three-dimensional MHD interchange reconnection modeling the exchange of connectivity between small closed loops and the open field. The observed PS fine structures follow the dynamics of the magnetic field before and after reconnecting at the NP obtained by the interchange model. Moreover, the pattern of the EUV plasma emission is the same as the shape of the expected plasma emission location derived from the simulation. These morphological and dynamical similarities between the PS observations and the results from the simulation strongly suggest that the evolution of the PS, and in particular the opening/closing of the field, occurs via interchange/slipping reconnection at the basic NP of the PS. Besides identifying the mechanism at work in the large-scale coupling between the open and closed fields, our results highlight that interchange reconnection in PSs is a gradual physical process that differs from the impulsive reconnection of the solar-jet model.

  6. Far-infrared observations of young clusters embedded in the R Coronae Australis and Rho Ophiuchi dark clouds

    NASA Technical Reports Server (NTRS)

    Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

    1985-01-01

    Multicolor far-infrared maps in two nearby dark clouds, R Coronae Australis and Rho Ophiuchi, have been made in order to investigate the individual contribution of low-mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low-mass stars has been detected in CrA and four in Rho Oph; their far-infrared luminosities range from 2 solar luminosities to 40 solar luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50 percent of the star's energy was radiated longward of 20 microns. Meaningful limits to the far-infrared luminosities of an additional 11 association members in CrA and two in Rho Oph were also obtained. The dust optical depth surrounding the star R CrA appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of these results for the cloud energetics and star formation efficiency in these two clouds are discussed.

  7. Optical and adhesive properties of dust deposits on solar mirrors and their effects on specular reflectivity and electrodynamic cleaning for mitigating energy-yield loss

    NASA Astrophysics Data System (ADS)

    Mazumder, Malay; Yellowhair, Julius; Stark, Jeremy; Heiling, Calvin; Hudelson, John; Hao, Fang; Gibson, Hannah; Horenstein, Mark

    2014-10-01

    Large-scale solar plants are mostly installed in semi-arid and desert areas. In those areas, dust layer buildup on solar collectors becomes a major cause for energy yield loss. Development of transparent electrodynamic screens (EDS) and their applications for self-cleaning operation of solar mirrors are presented with a primary focus on the removal dust particles smaller than 30 µm in diameter while maintaining specular reflection efficiency < 90%. An EDS consists of thin rectangular array of parallel transparent conducting electrodes deposited on a transparent dielectric surface. The electrodes are insulated from each other and are embedded within a thin transparent dielectric film. The electrodes are activated using three-phase high-voltage pulses at low current (< 1 mA/m2 ). The three-phase electric field charges the deposited particles, lifts them form the substrate by electrostatic forces and propels the dust layer off of the collector's surface by a traveling wave. The cleaning process takes less than 2 minutes; needs energy less than 1 Wh/m2 without requiring any water or manual labor. The reflection efficiency can be restored > 95% of the original clean-mirror efficiency. We briefly present (1) loss of specular reflection efficiency as a function of particle size distribution of deposited dust, and (2) the effects of the electrode design and materials used for minimizing initial loss of specular reflectivity in producing EDS-integrated solar mirrors. Optimization of EDS by using a figure of merit defined by the ratio of dust removal efficiency to the initial loss of specular reflection efficiency is discussed.

  8. The Newly Active R Coronae Borealis Star, V2552 Ophiuchi

    NASA Astrophysics Data System (ADS)

    Hesselbach, E.; Clayton, Geoffrey C.; Smith, Paul S.

    2003-11-01

    In 2001, V2552 Oph (CD -22°12017, Had V98) quickly faded by several magnitudes in a manner typical of the R Coronae Borealis (RCB) stars. Photometry of V2552 Oph obtained over 70 years previous to 2001 shows no indication of variability. Optical spectra of this star subsequently confirmed that V2552 Oph is a member of the hydrogen-deficient, carbon-rich RCB class of variables. It resembles the warm (Teff~7000 K) RCB stars such as R Coronae Borealis itself. Other RCB stars, such as XX Cam and Y Mus, have experienced similar periods of inactivity, going decades without significant dust formation. Further observations of V2552 Oph will be of great interest since there is an opportunity to monitor an RCB star that may be moving from prolonged inactivity into an active phase of dust production.

  9. The Structure and Dynamics of the Corona - Heliosphere Connection

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2010-01-01

    Determining the source at the Sun of the slow solar wind is one of the major unsolved problems in solar and heliospheric physics. First, we review the existing theories for the slow wind and argue that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory in which the slow wind originates from the continuous opening and closing of narrow open field corridors, the S-Web model, is described. Support for the S-Web model is derived from MHD solutions for the quasisteady corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona - heliosphere connection, in general.

  10. The Structure and Dynamics of the Corona - Heliosphere Connection

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2011-01-01

    Determining the source at the Sun of the slow solar wind is one of the major unsolved problems in solar and heliospheric physics. First, we review the existing theories for the slow wind and argue that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory in which the slow wind originates from the continuous opening and closing of narrow open field corridors, the S-Web model, is described. Support for the S-Web model is derived from MHD solutions for the quasisteady corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona - heliosphere connection, in general.

  11. Simultaneous measurements of wire electrode surface contamination and corona discharge characteristics in an air-cleaning electrostatic precipitator

    SciTech Connect

    Kanazawa, Seiji; Ohkubo, Toshikazu; Nomoto, Yukiharu; Adachi, Takayoshi; Chang, J.S.

    1997-01-01

    Contamination of the corona wire in a wire-to-plate type air-cleaning electrostatic precipitator is studied experimentally. In order to enhance the contamination of wire, air containing dusts is directly supplied to a part of the wire electrode. Spores of Lycopodium and cigarette smoke particles are used as test dusts. Simultaneous measurements of wire electrode optical images and corona discharge modes are carried out during contamination processes. Results show that corona discharge modes and optical emission from the wire electrode change with time due to the surface contamination. In the case of cigarette smoke, after a time elapsed, streamer coronas appear due to the buildup of smoke particles on the wire surface. After the first streamer generation, the corona current fluctuates with time because the formation and diminution of the projections occur alternately at the different parts on the wire electrode surface.

  12. PULSE ENERGIZATION IN THE TUFT CORONA REGIME OF NEGATIVE CORONA

    EPA Science Inventory

    The paper discusses pulse energization in the tuft corona regime of negative corona. Fabric filtration, with integral particle charging and collection in a combined electric and flow field, is sensitive to maldistribution of current among bags energized by one power source, espec...

  13. The Role of Magnetic Reconnection in Self-Organization of the Corona: Theory and Observations

    NASA Astrophysics Data System (ADS)

    Cassak, P. A.; Mullan, D. J.; Shay, M. A.

    2008-12-01

    Based on observations that solar flares obey power law statistics, it was suggested that the solar corona is in a state of self-organized criticality [1]. However, the physical mechanism underlying the dynamics is not well understood. A recent model [2] describing the catastrophic onset of fast (Hall) magnetic reconnection in weakly collisional plasmas may potentially contribute to this discussion. We suggest that the condition at which the catastrophic onset of reconnection occurs sets the critical state of the corona and the physics of reconnection organizes the corona into this critical state [3]. (See also [4].) The model makes a quantitative prediction for the conditions of the corona at the onset of eruptions, which is known to be consistent with observations of the solar corona. We present new observational evidence from stellar flares (107 events in 37 sun-like stars) that stellar coronae are near the same critical state at flare onset. This provides observational evidence in support of the model and suggests that magnetic reconnection plays an active role in constraining the conditions in solar and stellar coronae. Implications for self-organization in coronal heating and solar eruptions will be discussed. [1] E. T. Lu and R. J. Hamilton, Ap. J., 380, L89, 1991; [2] P. A. Cassak et al., Phys. Rev. Lett., 95, 235002, 2005; P. A. Cassak et al., Ap. J. Lett., 644, L145, 2006; [3] P. A. Cassak et al., Ap. J. Lett., 676, L69, 2008; [4] D. A. Uzdensky, Ap. J., 671, 2139, 2007.

  14. Electric interactions between dust and hot plasmas in the solar system.

    PubMed

    Lafon, J P; Millet, J M

    1995-01-01

    Interaction of the charged particles of a plasma with a solid body is an old problem which has been investigated under various conditions, in particular by the authors in several papers. However, the electric potential of the grains may be more sensitive than expected to the physical state of grain matter and the physical parameters of plasmas in the solar system. Using a new model accounting for porosity, a characteristic feature of grains observed in the solar system, we have investigated the secondary electron emission under electron impact for porous materials. The conclusion is that porosity has a significant influence on the rate of electron ejection. It follows that the floating potential of porous grains can be different from that of grains made of bulk material, with consequences for grain dynamics in the environment of planets or comets. PMID:11543532

  15. Coronae on stars

    NASA Technical Reports Server (NTRS)

    Haisch, B. M.

    1986-01-01

    Three lines of evidence are noted to point to a flare heating source for stellar coronae: a strong correlation between time-averaged flare energy release and coronal X-ray luminosity, the high temperature flare-like component of the spectral signature of coronal X-ray emission, and the observed short time scale variability that indicates continuous flare activity. It is presently suggested that flares may represent only the extreme high energy tail of a continuous distribution of coronal energy release events.

  16. The Origin of Organic Matter in the Solar System: Evidence from Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Keller, L. P.; Jacobsen, C.; Wirick, S.

    2001-01-01

    The origin of the organic matter in interplanetary materials has not been established. A variety of mechanisms have been proposed, with two extreme cases being a Fisher-Tropsch type process operating in the gas phase of the solar nebula or a Miller-Urey type process, which requires interaction with an aqueous fluid, presumably occurring on an asteroid. In the Fisher-Tropsch case, we might expect similar organic matter in hydrated and anhydrous interplanetary materials. However, aqueous alteration is required in the case of the Miller-Urey process, and we would expect to see organic matter preferentially in interplanetary materials that exhibit evidence of aqueous activity, such as the presence of hydrated silicates. The types and abundance of organic matter in meteorites have been used as an indicator of the origin of organic matter in the Solar System. Indigenous complex organic matter, including amino acids, has been found in hydrated carbonaceous chondrite meteorites, such as Murchison. Much lower amounts of complex organic matter, possibly only terrestrial contamination, have been found in anhydrous carbonaceous chondrite meteorites, such as Allende, that contain most of their carbon in elemental form. These results seem to favor production of the bulk of the organic matter in the Solar System by aqueous processing on parent bodies such as asteroids, a Miller-Urey process. However, the hydrated carbonaceous chondrite meteorites have approximately solar abundances of the moderately volatile elements, while all anhydrous carbonaceous chondrite meteorites have significantly lower contents of these moderately volatile elements. Two mechanisms, incomplete condensation or evaporation, both of which involve processing at approx. 1200 C, have been suggested to explain the lower content of the moderately volatile elements in all anhydrous meteorites. Additional information is contained in the original extended abstract.

  17. Stellar coronae from Einstein - Observations and theory

    NASA Technical Reports Server (NTRS)

    Rosner, R.; Vaiana, G. S.

    1980-01-01

    Einstein Observatory observations of stellar X-ray emission are presented and their implications for the formation of stellar coronae and the problem of stellar angular momentum loss are discussed. Solar coronal X-ray observations and observations of stellar coronae made prior to Einstein are reviewed, and it is noted that they already suggest that the standard theory of acoustic coronal heating is inadequate. The principal results of the Einstein/CfA stellar survey are summarized, with attention given to variations of the level of X-ray flux detected along the main sequence, the decline of X-ray flux with increasing age of giants and supergiants, and indications of a large range of X-ray emission levels within a given type, which are clearly incompatible with models for acoustic flux generation. A new theory to explain stellar coronae and hence X-ray emission from them is then proposed in which stellar magnetic fields play the key role in determining the level of coronal emission, and the modulation of the surface magnetic flux level and the level of stressing of surface magnetic fields essentially determine the variation of mean coronal activity in the H-R diagram.

  18. Venus: Craters, Coronae, and Chasmata Donna M. Jurdy

    E-print Network

    Jurdy, Donna M.

    Venus: Craters, Coronae, and Chasmata Donna M. Jurdy Northwestern University #12;Early View of Venus #12;#12;Venus, as seen by Veneras 9 and 10 #12;Venus as seen by Venera 13 (1-Mar-1982) #12;Pioneer Venus Topography #12;Inner Solar System Hypsographic Comparisons #12;Magellan Deployment #12;Magellan

  19. Corona And Ultraviolet Equipment For Testing Materials

    NASA Technical Reports Server (NTRS)

    Laue, Eric G.

    1993-01-01

    Two assemblies of laboratory equipment developed for use in testing abilities of polymers, paints, and other materials to withstand ultraviolet radiation and charged particles. One is vacuum ultraviolet source built around commercial deuterium lamp. Other exposes specimen in partial vacuum to both ultraviolet radiation and brush corona discharge. Either or both assemblies used separately or together to simulate approximately combination of solar radiation and charged particles encountered by materials aboard spacecraft in orbit around Earth. Also used to provide rigorous environmental tests of materials exposed to artificial ultraviolet radiation and charged particles in industrial and scientific settings or to natural ultraviolet radiation and charged particles aboard aircraft at high altitudes.

  20. Doppler distortion of solar Fraunhofer lines in zodiacal light by reflection from interplanetary dust

    NASA Astrophysics Data System (ADS)

    Hirschi, Dean Carlyle

    The effects that distributions of orbital eccentricity, radial outflowings of particles, and radiative pressure have on both the shift and distortion of the scattered Fraunhofer line are studied. The location of the various features depends on the exact parameters used to obtain the distorted line profile. Radiation pressure and orbital eccentricity add more complexity as both could broaden the scattered line profile and shift it to red in the evening sky. At a 180 degree elongation angle, a distortion of orbital eccentricity widens the line, whereas particles in circular orbit, even with radiation pressure, do not. The line profile shows the minimum width when all orbits are circular. When all the particles are in nearly parabolic orbits, the line profile can be broadened to the maximum width. An outward moving component of the dust is found to give a non-zero shift opposite the Sun. Since radiation pressure does not affect the light scattered from circular orbits in the area opposite the Sun, and since an outflowing of particles would be most evident in the spectra taken opposite the Sun, this area of the sky would be the most suited in separating out the effects of orbital eccentricity, radiation pressure, and radial outflow.

  1. Plasma properties and magnetic field structure of the solar corona, based on coordinated Max 1991 observations from SERTS, the VLA, and magnetographs

    NASA Technical Reports Server (NTRS)

    Brosius, Jeffrey W.

    1995-01-01

    The purposes of this investigation are to use existing, calibrated, coaligned sets of coordinated multiwaveband observations of the Sun to determine the coronal magnetic field strength and structure, and interpret the collective observations in terms of a self-consistent model of the coronal plasma and magnetic field. This information is vital to understanding processes such as coronal heating, solar wind acceleration, pre-flare energy storage, and active region evolution. Understanding these processes is the central theme of Max '91, the NASA-supported series of solar observing campaigns under which the observations acquired for this work were obtained. The observations came from NASA/GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and magnetographs. The technique of calculating the coronal magnetic field is to establish the contributions to the microwave emission from the two main emission mechanisms: thermal bremsstrahlung and thermal gyroemission. This is done by using the EUV emission to determine values of the coronal plasma quantities needed to calculate the thermal bremsstrahlung contribution to the microwave emission. Once the microwave emission mechanism(s) are determined, the coronal magnetic field can be calculated. A comparison of the coronal magnetic field derived from the coordinated multiwaveband observations with extrapolations from photospheric magnetograms will provide insight into the nature of the coronal magnetic field.

  2. Accretion disk coronae

    NASA Technical Reports Server (NTRS)

    White, N. E.; Holt, S. S.

    1981-01-01

    Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains an ADC. The possible origin of an ADC is discussed and a simple hydrostatic evaporated ADC model is developed which, when applied to 4U1822-37, 4U2129+47 and Cyg X-3, can explain their temporal and spectral properties. The quasi-sinusoidal modulation of all three sources can be reconciled with the partial occultation of the ADC by a bulge at the edge of the accretion disk which is caused by the inflowing material. The height of this bulge is an order of magnitude larger than the hydrostatic disk height and is the result of turbulence in the outer region of the disk. The spectral properties of all three sources can be understood in terms of Compton scattering of the original source spectrum by the ADC. Spectral variations with epoch in Cyg X-3 are probably caused by changes in the optical depth of the corona. A consequence of our model is that any accreting neutron star X-ray source in a semi-detached binary system which is close to its Eddington limit most likely contains an optically thick ADC.

  3. R Coronae Australis: A Cosmic Watercolour

    NASA Astrophysics Data System (ADS)

    2010-06-01

    This magnificent view of the region around the star R Coronae Australis was created from images taken with the Wide Field Imager (WFI) at ESO's La Silla Observatory in Chile. R Coronae Australis lies at the heart of a nearby star-forming region and is surrounded by a delicate bluish reflection nebula embedded in a huge dust cloud. The image reveals surprising new details in this dramatic area of sky. The star R Coronae Australis lies in one of the nearest and most spectacular star-forming regions. This portrait was taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. The image is a combination of twelve separate pictures taken through red, green and blue filters. This image shows a section of sky that spans roughly the width of the full Moon. This is equivalent to about four light-years at the distance of the nebula, which is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The complex is named after the star R Coronae Australis, which lies at the centre of the image. It is one of several stars in this region that belong to the class of very young stars that vary in brightness and are still surrounded by the clouds of gas and dust from which they formed. The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength. These complex processes, determined by the physics of the interstellar medium and the properties of the stars, are responsible for the magnificent colours of nebulae. The light blue nebulosity seen in this picture is mostly due to the reflection of starlight off small dust particles. The young stars in the R Coronae Australis complex are similar in mass to the Sun and do not emit enough ultraviolet light to ionise a substantial fraction of the surrounding hydrogen. This means that the cloud does not glow with the characteristic red colour seen in many star-forming regions. The huge dust cloud in which the reflection nebula is embedded is here shown in impressively fine detail. The subtle colours and varied textures of the dust clouds make this image resemble an impressionist painting. A prominent dark lane crosses the image from the centre to the bottom left. Here the visible light emitted by the stars that are forming inside the cloud is completely absorbed by the dust. These objects could only be detected by observing at longer wavelengths, by using a camera that can detect infrared radiation. R Coronae Australis itself is not visible to the unaided eye, but the tiny, tiara-shaped constellation in which it lies is easily spotted from dark sites due to its proximity on the sky to the larger constellation of Sagittarius and the rich star clouds towards the centre of our own galaxy, the Milky Way. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

  4. The Catalytic Potential of Cosmic Dust: Implications for Prebiotic Chemistry in the Solar Nebula and Other Protoplanetary Systems

    NASA Astrophysics Data System (ADS)

    Hill, Hugh G. M.; Nuth, Joseph A.

    2003-06-01

    The synthesis of important prebiotic molecules is fundamentally reliant on basic starting ingredients: water, organic species [e.g., methane (CH4)], and reduced nitrogen compounds [e.g., ammonia (NH3), methyl cyanide (CH3CN) etc.]. However, modern studies conclude that the primordial Earth's atmosphere was too rich in CO, CO2, and water to permit efficient synthesis of such reduced molecules as envisioned by the classic Miller-Urey experiment. Other proposed sources of terrestrial nitrogen reduction, like those within submarine vent systems, also seem to be inadequate sources of chemically reduced C-H-O-N compounds. Here, we demonstrate that nebular dust analogs have impressive catalytic properties for synthesizing prebiotic molecules. Using a catalyst analogous to nebular iron silicate condensate, at temperatures ranging from 500K to 900K, we catalyzed both the Fischer-Tropsch conversion of CO and H2 to methane and water, and the corresponding Haber-Bosch synthesis of ammonia from N2 and H2. Remarkably, when CO, N2, and H2 were allowed to react simultaneously, these syntheses also yielded nitrogen-containing organics such as methyl amine (CH3NH2), acetonitrile (CH3CN), and N-methyl methylene imine (H3CNCH2). A fundamental consequence of this work for astrobiology is the potential for a natural chemical pathway to produce complex chemical building blocks of life throughout our own Solar System and beyond.

  5. Cosmic Dust: The Ulysses perspective

    E-print Network

    Eberhard Grün; Harald Krüger; Markus Landgraf

    2000-12-11

    The Ulysses spacecraft, launched in October 1990, orbits the Sun on a polar trajectory. The spacecraft is equipped with a highly sensitive impact- ionization dust detector which can in situ measure cosmic dust grains in the mass range 10^-9 to 10^-19 kg. With the Ulysses dust detector dust streams originating from Jupiter's volcanically active moon Io have been discovered as well as interstellar dust particles sweeping through the solar system. The distribution of interplanetary dust grains has been measured at high ecliptic latitudes with Ulysses for the first time. The Ulysses measurements of interplanetary dust, dust grains interacting electromagnetically with the magnetosphere of Jupiter and measurements of interstellar dust in the solar system are reviewed.

  6. Dynamics of the Transition Corona

    NASA Technical Reports Server (NTRS)

    Masson, Sophie; McCauley, Patrick; Golub, Leon; Reeves, Katharine K.; DeLuca, Edward E.

    2014-01-01

    Magnetic reconnection between the open and closed magnetic fields in the corona is believed to play a crucial role in the corona/heliosphere coupling. At large scale, the exchange of open/closed connectivity is expected to occur in pseudo-streamer (PS) structures. However, there is neither clear observational evidence of how such coupling occurs in PSs, nor evidence for how the magnetic reconnection evolves. Using a newly developed technique, we enhance the off-limb magnetic fine structures observed with the Atmospheric Imaging Assembly and identify a PS-like feature located close to the northern coronal hole. We first identify that the magnetic topology associated with the observation is a PS, null-point (NP) related topology bounded by the open field. By comparing the magnetic field configuration with the extreme ultraviolet (EUV) emission regions, we determined that most of the magnetic flux associated with plasma emission are small loops below the PS basic NP and open field bounding the PS topology. In order to interpret the evolution of the PS, we referred to a three-dimensional MHD interchange reconnection modeling the exchange of connectivity between small closed loops and the open field. The observed PS fine structures follow the dynamics of the magnetic field before and after reconnecting at the NP obtained by the interchange model. Moreover, the pattern of the EUV plasma emission is the same as the shape of the expected plasma emission location derived from the simulation. These morphological and dynamical similarities between the PS observations and the results from the simulation strongly suggest that the evolution of the PS, and in particular the opening/closing of the field, occurs via interchange/slipping reconnection at the basic NP of the PS. Besides identifying the mechanism at work in the large-scale coupling between the open and closed fields, our results highlight that interchange reconnection in PSs is a gradual physical process that differs from the impulsive reconnection of the solar-jet model.

  7. High-cadence observations of CME initiation and plasma dynamics in the corona with TESIS on board CORONAS-Photon

    NASA Astrophysics Data System (ADS)

    Bogachev, Sergey; Kuzin, Sergey; Zhitnik, I. A.; Bugaenko, O. I.; Goncharov, A. L.; Ignatyev, A. P.; Krutov, V. V.; Lomkova, V. M.; Mitrofanov, A. V.; Nasonkina, T. P.; Oparin, S. N.; Petzov, A. A.; Shestov, S. V.; Slemzin, V. A.; Soloviev, V. A.; Suhodrev, N. K.; Shergina, T. A.

    The TESIS is an ensemble of space instruments designed in Lebedev Institute of Russian Academy of Sciences for spectroscopic and imaging investigation of the Sun in EUV and soft X-ray spectral range with high spatial, temporal and spectral resolution. From 2009 January, when TESIS was launched onboard the Coronas-Photon satellite, it provided about 200 000 new images and spectra of the Sun, obtained during one of the deepest solar minimum in last century. Because of the wide field of view (4 solar radii) and high sensitivity, TESIS provided high-quality data on the origin and dynamics of eruptive prominences and CMEs in the low and intermediate solar corona. TESIS is also the first EUV instrument which provided high-cadence observations of coronal bright points and solar spicules with temporal resolution of a few seconds. We present first results of TESIS observations and discuss them from a scientific point of view.

  8. Accepted Manuscript Dust in the planetary system: Dust interactions in space plasmas of the

    E-print Network

    Aulanier, Guillaume

    Accepted Manuscript Dust in the planetary system: Dust interactions in space plasmas of the solar November 2013 Please cite this article as: I. Mann, N. Meyer-Vernet, A. Czechowski, Dust in the planetary system: Dust interactions in space plasmas of the solar system, Physics Reports (2013), http

  9. The Differential Emission Measure Distribution in the Multiloop Corona

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.

    2002-11-01

    This is a rebuttal of a recent Letter on the inadequacy of temperature measurements in the solar corona through narrowband filter and line ratios by Martens et al. We simulate the differential emission measure (DEM) distribution of a multiloop corona and find that the temperature profile of individual loops can be retrieved with narrowband filter ratios. The apparently flat DEM distributions constructed from Coronal Diagnostics Spectrometer line fluxes by Schmelz et al. are an artifact of a smoothing function (in temperature), while the unsmoothed DEM distribution reveals multiple peaks of near-isothermal loops.

  10. Dust Mitigation Vehicle

    NASA Technical Reports Server (NTRS)

    Cardiff, Eric H.

    2011-01-01

    A document describes the development and demonstration of an apparatus, called a dust mitigation vehicle, for reducing the amount of free dust on the surface of the Moon. The dust mitigation vehicle would be used to pave surfaces on the Moon to prevent the dust from levitating or adhering to surfaces. The basic principle of operation of these apparatuses is to use a lens or a dish mirror to concentrate solar thermal radiation onto a small spot to heat lunar regolith. In the case of the prototype dust mitigation vehicle, a Fresnel lens was used to heat a surface layer of regolith sufficiently to sinter or melt dust grains into a solid mass. The prototype vehicle has demonstrated paving rates up to 1.8 square meters per day. The proposed flight design of the dust mitigation vehicle is also described.

  11. Combining Linear Polarization Measurements of both Forbidden/Permitted Coronal Emission Lines for measuring the Vector Magnetic Field in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Dima, G. I.; Kuhn, J. R.; Mickey, D.

    2014-12-01

    Measuring the coronal vector magnetic field is still a major challenge in solar physics. This is due to the intrinsic weakness of the field (~4 G at a height of 0.1 Rsun above an active region) and the large thermal broadening of coronal emission lines. Current methods deduce either the direction of the magnetic field or the magnetic flux density. We propose using concurrent linear polarization measurements in the near IR of forbidden and permitted lines to calculate the coronal vector magnetic field. The effect of the magnetic field on the polarization properties of emitted light is encapsulated in the Hanle effect. In the unsaturated Hanle regime both the direction and strength of the magnetic field affect the linear polarization, while for saturated Hanle the polarization is insensitive to the strength of the field. Coronal forbidden lines are always in the saturated Hanle regime so the linear polarization holds no information on the strength of the field. By pairing measurements of both forbidden and permitted lines we would be able to obtain both the direction and strength of the field. The near-IR region of the spectrum offers the opportunity to study this problem from the ground. The FeXIII 1.075 um and SiX 1.431 um forbidden lines are strongly polarizable and are sufficiently bright over a large field of view (out to 1.5 Rsun). Measurements of both these lines can be paired up with the recently observed coronal HeI 1.083 um permitted line. The first data set used to test this technique was taken during the March 29, 2006 total solar eclipse and consisted of near-IR spectra covering the spectral region 0.9-1.8 um, with a field of view of 3 x 3 Rsun. The data revealed unexpectedly strong SiX emission compared to FeXIII. Using the HAO FORWARD suite of codes we produced simulated emission maps from a global HMD model for the day of the eclipse. Comparing the intensity variation of the measurements and the model we predict that SiX emission is more extended for this day that the model would suggest, further supporting the possible usefulness of SiX polarimetry. The development of this method and associated tools will be critical in interpreting the high spectral, spatial and temporal IR measurements that will be possible when the Daniel K. Inouye Solar Telescope (DKIST) is completed in a few years time.

  12. Ultraviolet corona detection sensor study

    NASA Technical Reports Server (NTRS)

    Schmitt, R. J.; MATHERN

    1976-01-01

    The feasibility of detecting electrical corona discharge phenomena in a space simulation chamber via emission of ultraviolet light was evaluated. A corona simulator, with a hemispherically capped point to plane electrode geometry, was used to generate corona glows over a wide range of pressure, voltage, current, electrode gap length and electrode point radius. Several ultraviolet detectors, including a copper cathode gas discharge tube and a UV enhanced silicon photodiode detector, were evaluated in the course of the spectral intensity measurements. The performance of both silicon target vidicons and silicon intensified target vidicons was evaluated analytically using the data generated by the spectroradiometer scans and the performance data supplied by the manufacturers.

  13. The Solar Chromosphere/Corona Interface. I. Far-Ultraviolet to Extreme-Ultraviolet Observations and Modeling of Unresolved Coronal Funnels

    NASA Technical Reports Server (NTRS)

    Martinez-Galarce, Dennis S.; Walker, Arthur C., III; Barbee, Troy W., II; Hoover, Richard B.

    2003-01-01

    A coronal funnel model, developed by D. Rabin, was tested against a calibrated spectroheliogram recorded in the 170-1 75 A bandpass. This image was recorded on board a sounding-rocket experiment flown on 1994 November 3, called the Multi-Spectral Solar Telescope Array II (MSSTA II). MSSTA, a joint project of Stanford University, the NASA Marshall Space Flight Center, and the Lawrence Livermore National Laboratory' is an observing platform composed of a set of normal-incidence, multilayer-coated optics designed to obtain narrow-bandpass, high-resolution images (1 sec.- 3 sec.) at selected far-ultraviolet (FUV), extreme-ultraviolet (EUV), and soft X-ray wavelengths (44-1550 A). Using full disk images centered at 1550 A (C IV) and 173 A (Fe IX/X), the funnel model, which is based on coronal back-heating, was tested against the data incorporating observed constraints on global coverage and measured flux. Found was a class of funnel models that could account for the quiescent, globally diffuse and unresolved emission seen in the 171-175 A bandpass, where the funnels are assumed to be rooted in the C IV supergranular network. These models, when incorporated with the CHIANTI spectral code, suggest that this emission is mostly of upper transition region origin and primarily composed of Fe IX plasma. The funnels are found to have constrictions, Gamma approx. 6-20, which is in good agreement with the observations. Further, the fitted models simultaneously satisfy global areal constraints seen in both images; namely,that a global network of funnels must cover approx. 700 - 95% of the total solar surface area seen in the 171-175 A image, and a 5% of the disk area seen in the 1550 A bandpass. These findings support the configuration of the EUV magnetic network as suggested by Reeves et al. and put forth in more detail by Gabriel. Furthermore, the models are in good agreement with differential emission measure estimates made of the transition region by J. C. Raymond & J. G. Doyle for temperatures 250,000 K less than or = T less than or = 650,000 K, based on full-disk observations made on board Skylab.

  14. Ground-based observation of emission lines from the corona of a red-dwarf star.

    PubMed

    Schmitt, J H; Wichmann, R

    2001-08-01

    All 'solar-like' stars are surrounded by coronae, which contain magnetically confined plasma at temperatures above 106 K. (Until now, only the Sun's corona could be observed in the optical-as a shimmering envelope during a total solar eclipse.) As the underlying stellar 'surfaces'-the photospheres-are much cooler, some non-radiative process must be responsible for heating the coronae. The heating mechanism is generally thought to be magnetic in origin, but is not yet understood even for the case of the Sun. Ultraviolet emission lines first led to the discovery of the enormous temperature of the Sun's corona, but thermal emission from the coronae of other stars has hitherto been detectable only from space, at X-ray wavelengths. Here we report the detection of emission from highly ionized iron (Fe XIII at 3,388.1 A) in the corona of the red-dwarf star CN Leonis, using a ground-based telescope. The X-ray flux inferred from our data is consistent with previously measured X-ray fluxes, and the non-thermal line width of 18.4 km s-1 indicates great similarities between solar and stellar coronal heating mechanisms. The accessibility and spectral resolution (45,000) of the ground-based instrument are much better than those of X-ray satellites, so a new window to the study of stellar coronae has been opened. PMID:11484044

  15. Lower solar chromosphere-corona transition region. III - Implications of the observed quiet-sun emission measure including wave pressure effects

    NASA Technical Reports Server (NTRS)

    Woods, D. Tod; Holzer, Thomas E.; Macgregor, Keith B.

    1990-01-01

    The observed form of the emission measure (EM) is used as a function of temperature to infer the wave energy flux density and pressure throughout the lower transition region (TR). This procedure eliminates the need for specifying how the wave energy flux density is damped and addresses the question of whether there is any form of the mechanical heating associated with the degradation of an upward traveling wave energy flux density which is consistent with the observed EM and other observational constraints for the quiet sun. It is found that the observed form of the EM curve is incompatible with waves traveling vertically at the sound speed, regardless of any filling factor arguments. The same conclusion also applies to waves traveling at the Alfven speed, unless it is assumed that the emission in lower TR lines originates solely from small, spatially unresolved regions of large magnetic field strength (100 G), which cover a small fraction (filling factors of 1 percent) of the solar surface.

  16. Microparticle impact calibration of the Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) onboard the solar power sail demonstrator IKAROS

    NASA Astrophysics Data System (ADS)

    Hirai, Takayuki; Cole, Michael J.; Fujii, Masayuki; Hasegawa, Sunao; Iwai, Takeo; Kobayashi, Masanori; Srama, Ralf; Yano, Hajime

    2014-10-01

    The Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) is an array of polyvinylidene fluoride (PVDF) based dust detectors aboard the solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). The total sensor area of ALADDIN (0.54 m2) is the world's largest among the past PVDF-based dust detectors. IKAROS was launched in May 2010 and then ALADDIN measured cosmic dust impacts for 16 months while orbiting around between 0.7 and 1.1 AU. The main scientific objective of ALADDIN is to reveal number density of ?10-?m-sized dust in the zodiacal cloud with much higher time-space resolution than that achieved by any past in-situ measurements. The distribution of ?10-?m-sized dust can be also observed mainly with the light scattering by optical instruments. This paper gives the scientific objectives, the instrumental description, and the results of microparticle impact calibration of ALADDIN conducted in ground laboratories. For the calibration tests we used Van de Graaf accelerators (VdG), two-stage light gas guns (LGG), and a nano-second pulsed Nd:YAG laser (nsPL). Through these experiments, we obtained depolarization charge signal caused by hypervelocity impacts or laser irradiation using the flight spare of 20-?m-thick PVDF sensor and the electronics box of ALADDIN. In the VdG experiment we accelerated iron, carbon, and silver microparticles at 1-30 km/s, while in the LGG experiment we performed to shoot 100's-?m-sized particles of soda-lime glass and stainless steel at 3-7 km/s as single projectile. For interpolation to ?10-?m size, we irradiated infrared laser at the energy of 15-20 mJ directly onto the PVDF sensor. From the signal analysis, we developed a calibration law for estimation of masses of impacted dust particles. The dynamic range of ALADDIN corresponds from 9×10-14 kg to 2×10-10 kg (4-56 ?m in diameter at density of 2.0 g/cm3) at the expected impact velocity of 10 km/s at 1 AU on the IKAROS inbound orbit. It was found that ALADDIN has ability to measure spatial densities of interplanetary dust particles larger than 10 ?m in size by setting the sensor threshold to an output voltage of 1 V.

  17. The Martian Hot Oxygen Corona at Ancient times

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Combi, M. R.; Tenishev, V.; Bougher, S. W.; Dong, C.; Pawlowski, D. J.

    2014-12-01

    The evaluation of the global atomic oxygen loss rate and its changes over geologic time is necessary for a better understanding of the evolution of the Martian atmosphere. The recent surface geomorphological evidence suggests that water has played a key role in forming the present atmospheric environment. Throughout the planet's history, the inventory of water has been affected in part by changing solar radiation and solar wind conditions. In this study, we investigate the evolution of the oxygen atom inventory by simulating the hot oxygen corona for solar conditions appropriate to about 2.5 Gyr ago (about 3 times the current solar EUV flux). Dissociative recombination of O2+ion is assumed to remain as the dominant source of hot atomic oxygen at ancient times. To describe ancient Mars, we present the 3D self-consistent simulations of the Martian hot oxygen corona by one-way coupling our Adaptive Mesh Particle Simulator (AMPS) with the ancient thermosphere and ionosphere as simulated by the 3D Mars Global Ionosphere Thermosphere Model (M-GITM), a newly developed atmospheric model. The structure and composition of the Martian upper atmosphere and the hot oxygen corona during early solar conditions are compared with those at the current epoch to study the evolution of the macroscopic parameters and their effects on the hot oxygen corona. The coupled framework provides the density and escape probabilities of hot oxygen and estimates the global atmospheric loss rates for the conditions considered. These results are also being used as input into calculations of the global solar wind interaction with Mars' atmosphere, ionosphere and exosphere.

  18. Influence of projection effects on the observed differential rotation rate in the UV corona

    E-print Network

    Mancuso, Salvatore

    2012-01-01

    Following previous investigations by Giordano and Mancuso [1] and Mancuso and Giordano [2, 3] on the differential rotation of the solar corona as obtained through the analysis of the intensity time series of the O VI 1032 Ang. spectral line observed by the UVCS/SOHO telescope during solar cycle 23, we analysed the possible influence of projection effects of extended coronal structures on the observed differential rotation rate in the ultraviolet corona. Through a simple geometrical model, we found that, especially at higher latitudes, the differential rotation may be less rigid than observed, since features at higher latitudes could be actually linked to much lower coronal structures due to projection effects. At solar maximum, the latitudinal rigidity of the UV corona, with respect to the differential rotating photosphere, has thus to be considered as an upper limit of the possible rigidity. At solar minimum and near the equatorial region throughout the solar cycle, projection effects are negligible.

  19. What Is the Shell Around R Coronae Borealis?

    NASA Astrophysics Data System (ADS)

    Montiel, Edward J.; Clayton, Geoffrey C.; Marcello, Dominic C.; Lockman, Felix J.

    2015-07-01

    The hydrogen-deficient, carbon-rich R Coronae Borealis (RCB) stars are known for being prolific producers of dust which causes their large iconic declines in brightness. Several RCB stars, including R Coronae Borealis (R CrB), itself, have large extended dust shells seen in the far-infrared. The origin of these shells is uncertain but they may give us clues to the evolution of the RCB stars. The shells could form in three possible ways. (1) They are fossil Planetary Nebula (PN) shells, which would exist if RCB stars are the result of a final, helium-shell flash, (2) they are material left over from a white-dwarf (WD) merger event which formed the RCB stars, or (3) they are material lost from the star during the RCB phase. Arecibo 21 cm observations establish an upper limit on the column density of H I in the R CrB shell implying a maximum shell mass of ?0.3 M?. A low-mass fossil PN shell is still a possible source of the shell although it may not contain enough dust. The mass of gas lost during a WD merger event will not condense enough dust to produce the observed shell, assuming a reasonable gas-to-dust ratio. The third scenario where the shell around R CrB has been produced during the star’s RCB phase seems most likely to produce the observed mass of dust and the observed size of the shell. But this means that R CrB has been in its RCB phase for ?104 years.

  20. Nano-Dust Analyzer

    NASA Astrophysics Data System (ADS)

    Gruen, E.; Horanyi, M.; Moebius, E.; Sternovsky, Z.; Auer, S.; Srama, R.; Juhasz, A.

    2010-12-01

    Recently, the STEREO WAVES instruments recorded a large number of intense electric field signals, which were interpreted as impacts from nanometer sized particles striking the spacecraft with velocities of about the solar wind speed [1]. This high flux and strong spatial and/or temporal variations of nanometer sized dust grains at low latitude appears to be uncorrelated with the solar wind properties. Early dust instruments onboard Pioneer 8 and 9 and Helios spacecraft detected a flow of submicron sized dust particles coming from the direction of the Sun. These particles originate in the inner solar system from mutual collisions among meteoroids and move on hyperbolic orbits that leave the Solar System under the prevailing radiation pressure force [2]. The observed fluxes of inner-source pickup ions also point to the existence of a much enhanced dust population in the nanometer size range [3]. A new highly sensitive instrument is being developed within NASA's Heliophysics Program to confirm the existence of the so-called nano-dust particles, characterize their impact parameters, and measure their chemical composition. The instrument is based on the Cassini Dust Analyzer (CDA) that has analyzed the composition of nanometer sized dust particles emanating from the Jovian and Saturnian systems but could not be pointed towards the Sun. By applying technologies implemented in solar wind instruments and coronagraphs a highly sensitive dust analyzer will be developed and tested in the laboratory. The measurements will enable us to identify the source of the dust by comparing their elemental composition with that of larger micrometeoroid particles of cometary and asteroid origin and will reveal interaction of nano-dust with the interplanetary medium by investigating the relation of the dust flux with solar wind and IMF properties. [1] Meyer-Vernet, N. et al., Solar Physics, 256, 463, 2009 [2] Zook, H.A. and Berg, O.E.: A source for hyperbolic cosmic dust particles. Planetary and Space Science, 23 (1975) 183-203. [3] Schwadron, N. A., et al., J. Geophys. Res., 105, 7465, 2000.

  1. Spectroscopic investigation of protein corona

    NASA Astrophysics Data System (ADS)

    Choudhary, Poonam

    Nanotechnology has revolutionalized the landscape of modern science and technology, including materials, electronics, therapeutics, bioimaging, sensing, and the environment. Research in the past decade has examined the fate of nanomaterials in vitro and in vivo, as well as the interactions between nanoparticles and biological and ecosystems using primarily toxicological and ecotoxicological approaches. However, due to the versatility in the physical and physicochemical properties of nanoparticles, and due to the vast complexity of their hosting systems, the solubility, transformation, and biocompatibility of nanomaterials are still poorly understood. Nanotechnology has been undergoing tremendous development in recent decades, driven by realized perceived applications of nanomaterials in electronics, therapeutics, imaging, sensing, environmental remediation, and consumer products. Nanoparticles on entering the blood stream undergo an identity change, they become coated with proteins. There are different kind of proteins present in blood. Proteins compete for getting coated over the surface of nanoparticle and this whole entity of proteins coated over nanoparticle surface is called Protein Corona. Proteins tightly bound to the surface of nanoparticle form hard corona and the ones loosely bound on the outer surface form soft corona. This dissertation is aimed at spectroscopic investigation of Protein Corona. Chapter I of this dissertation offers a comprehensive review of the literature based on nanomaterials with the focus on carbon based nanomaterilas and introduction to Protein Corona. Chapter II is based different methods used for Graphene Synthesis,different types of defects and doping. In Chapter III influence of defects on Graphene Protein Corona was investigated. Chapter IV is based on the study of Apoptosis induced cell death by Gold and silver nanoparticles. In vitro study of effect of Protein Corona on toxicity of cells was done.

  2. Effects of levitated dust on astronomical observations from the lunar surface

    NASA Technical Reports Server (NTRS)

    Murphy, D. L.; Vondrak, R. R.

    1993-01-01

    It is believed that a substantial population of levitated dust is present in the terminator region of the moon. Stray light scattered by this dust layer may contaminate astronomical observations made from the lunar surface using infrared, visible, and ultraviolet light. The evidence for dust levitation stems from: Surveyor vidicon images of horizon glow; anomalous brightness in photographs of the solar corona taken by Apollo astronauts while the spacecraft was just inside the moon's shadow; and observations by Apollo astronauts of streamers just prior to lunar orbital sunrise or just after lunar orbital sunset. It has been proposed that the differential charging of the lunar surface in the terminator region due to photoemission and the consequent strong local electric fields comprise the mechanism responsible for this levitation. Although quantitative data on the levitated lunar dust distribution are meager, it is possible to estimate column densities and sizes. In this paper we summarize the estimates of particulate sizes and number densities of previous authors, and construct a nominal terminator dust distribution, as a function of particulate radius and altitude above the lunar surface. Using the model we estimate the brightness of scattered sunshine for three wavelength bands. For the results in the visible wavelengths, we compare the estimated brightness with the known brightness of selected astronomical objects and discuss the implications for lunar-based astronomy.

  3. Interstellar Medium: dust Interstellar dust

    E-print Network

    Estalella, Robert

    Interstellar Medium: dust Interstellar dust Dust grains (silicate/carbon cores, ice mantles) Sizes of ~0.1 m Effects in the visible domain: extinction, reddening, polarization Dust opacity , = 1-2 Thermal emission: mm, submm, FIR (optically thin) #12;Interstellar dust Dust grains (silicate

  4. Insights into Corona Formation Through Statistical Analyses

    NASA Technical Reports Server (NTRS)

    Glaze, L. S.; Stofan, E. R.; Smrekar, S. E.; Baloga, S. M.

    2002-01-01

    Statistical analysis of an expanded database of coronae on Venus indicates that the populations of Type 1 (with fracture annuli) and 2 (without fracture annuli) corona diameters are statistically indistinguishable, and therefore we have no basis for assuming different formation mechanisms. Analysis of the topography and diameters of coronae shows that coronae that are depressions, rimmed depressions, and domes tend to be significantly smaller than those that are plateaus, rimmed plateaus, or domes with surrounding rims. This is consistent with the model of Smrekar and Stofan and inconsistent with predictions of the spreading drop model of Koch and Munga. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occurring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronae are found predominantly as isolated features in the plains. Coronae at hot spot rises tend to be significantly lager than coronae in other settings, consistent with a hotter upper mantle at hot spot rises and their active state.

  5. Insights into Corona Formation through Statistical Analyses

    NASA Technical Reports Server (NTRS)

    Glaze, L. S.; Stofan, E. R.; Smrekar, S. E.; Baloga, S. M.

    2002-01-01

    Statistical analysis of an expanded database of coronae on Venus indicates that the populations of Type 1 (with fracture annuli) and 2 (without fracture annuli) corona diameters are statistically indistinguishable, and therefore we have no basis for assuming different formation mechanisms. Analysis of the topography and diameters of coronae shows that coronae that are depressions, rimmed depressions, and domes tend to be significantly smaller than those that are plateaus, rimmed plateaus, or domes with surrounding rims. This is consistent with the model of Smrekar and Stofan and inconsistent with predictions of the spreading drop model of Koch and Manga. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occuring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronas are found predominantly as isolated features in the plains. Coronae at hotspot rises tend to be significantly larger than coronae in other settings, consistent with a hotter upper mantle at hotspot rises and their active state.

  6. The Structure and Dynamics of the Corona—Heliosphere Connection

    NASA Astrophysics Data System (ADS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Miki?, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2012-11-01

    Determining how the heliospheric magnetic field and plasma connect to the Sun's corona and photosphere is, perhaps, the central problem in solar and heliospheric physics. For much of the heliosphere, this connection appears to be well understood. It is now generally accepted that so-called coronal holes, which appear dark in X-rays and are predominantly unipolar at the photosphere, are the sources of quasi-steady wind that is generally fast, >500 km/s, but can sometimes be slow. However, the connection to the Sun of the slow, non-steady wind is far from understood and remains a major mystery. We review the existing theories for the sources of the non-steady wind and demonstrate that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory is described in which this wind originates from the continuous opening and closing of narrow open field corridors in the corona, which give rise to a web of separatrices (the S-Web) in the heliosphere. Note that in this theory the corona—heliosphere connection is intrinsically dynamic, at least for this type of wind. Support for the S-Web model is derived from MHD solutions for the corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona—heliosphere connection, in general.

  7. Solar Cycle Variations in Ice Acidity at the End of the Last Ice Age: Possible Marker of a Climatically Significant Interstellar Dust Incursion

    E-print Network

    Paul LaViolette

    2005-02-04

    Hammer et al. [1997] report the presence of regularly spaced acidity peaks (H+, F-, Cl-) in the Byrd Station, Antarctica ice core. The event has a duration of about one century and falls at the beginning of the deglacial warming. Volcanism appears to be an unlikely cause since the total acid deposition of this event was about 18 fold greater than the largest known volcanic eruption, and since volcanic eruptions are not known to recur with such regularity. We show that the recurrence period of these peaks averages to 11.5 +/- 2.4 years, which approximates the solar cycle period, and suggest that this feature may have an extraterrestrial origin. We propose that this material may mark a period of enhanced interstellar dust and gas influx modulated by the solar cycle. The presence of this material could have made the Sun more active and have been responsible for initiating the warming that ended the last ice age.

  8. Laplacian State Transfer in Coronas

    E-print Network

    Ethan Ackelsberg; Zachary Brehm; Ada Chan; Joshua Mundinger; Christino Tamon

    2015-08-22

    We prove that the corona product of two graphs has no Laplacian perfect state transfer whenever the first graph has at least two vertices. This complements a result of Coutinho and Liu who showed that no tree of size greater than two has Laplacian perfect state transfer. In contrast, we prove that the corona product of two graphs exhibits Laplacian pretty good state transfer, under some mild conditions. This provides the first known examples of families of graphs with Laplacian pretty good state transfer. Our result extends of the work of Fan and Godsil on double stars to the Laplacian setting. Moreover, we also show that the corona product of any cocktail party graph with a single vertex graph has Laplacian pretty good state transfer, even though odd cocktail party graphs have no perfect state transfer.

  9. The H Corona of Mars

    NASA Astrophysics Data System (ADS)

    Chaffin, Michael Scott

    The atmosphere of every planet is surrounded by a tenuous cloud of hydrogen gas, referred to as a hydrogen corona. At Mars, a substantial fraction of the H present in the corona is moving fast enough to escape the planet's gravity, permanently removing H from the Martian atmosphere. Because this H is ultimately derived from lower atmospheric water, loss of H from Mars is capable of drying and oxidizing the planet over geologic time. Understanding the processes that supply the H corona and control its escape is therefore essential for a complete understanding of the climate history of Mars and for assessing its habitability. In this thesis, I present the most complete analysis of the H corona ever attempted, surveying eight years of data gathered by the ultraviolet spectrograph SPICAM on Mars Express. Using a coupled radiative transfer and physical density model, I interpret brightness measurements of the corona in terms of escape rates of H from the planet, uncovering an order-of-magnitude variability in the H escape rate never before detected. These variations are interpreted using a completely new photochemical model of the atmosphere, demonstrating that newly discovered high altitude water vapor layers are sufficient to produce the observed variation. Finally, I present first results of the SPICAM successor instrument IUVS, an imaging ultraviolet spectrograph carried by NASA's MAVEN spacecraft. IUVS measurements are producing the most complete dataset ever gathered for the Martian H corona, enabling supply and loss processes to be assessed in more complete detail than ever before. This dataset will allow present-day loss rates to be extrapolated into the past, determining the absolute amount of water Mars has lost to space over the