Sample records for solar-minimum corona unraveled

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

    SciTech Connect

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

    2009-09-10

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

  2. A study of the background corona near solar minimum

    Microsoft Academic Search

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

    1977-01-01

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

  3. The Equatorial Background Solar Corona during Solar Minimum

    Microsoft Academic Search

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

    2006-01-01

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

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

    Microsoft Academic Search

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

    2005-01-01

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

  5. THE SOLAR MINIMUM CORONA FROM DIFFERENTIAL EMISSION MEASURE TOMOGRAPHY

    SciTech Connect

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

    2010-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

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

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

    E-print Network

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

    2003-10-29

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

  8. Venus ionopause during solar minimum

    SciTech Connect

    Mahajan, K.K.; Mayr, H.G.

    1989-12-01

    During solar minimum, the Venus ionosphere is weak and the solar wind depresses the ionopause to a limiting altitude (Knudsen et al., 1987). With the knowledge gained from the ion composition measurements on Pioneer Venus during solar maximum and during conditions of high solar wind pressure, the authors argue that the typical topside electron density profile at Venus during solar minimum has two distinct regimes; one from about 140 km (the altitude of peak electron density) to 180 km and the other above 180 km. While the former is dominated by O{sub 2}{sup +} ions which are in photochemical equilibrium, the latter is dominated by O{sup +} ions which are strongly disturbed by the solar wind induced plasma transport. The disturbed ionosphere is formed in the photodynamical regime and has a scale height which is several times smaller than that expected under undisturbed conditions when the ionosphere is in diffusive equilibrium. The small scale height of the disturbed ionosphere is nearly equal to that of the ionizable constituent, atomic oxygen, and is only slightly larger than the chemical equilibrium scale height of the underlying chemical equilibrium region. While the photodynamical ionopause occurs rarely during solar maximum and only when the solar wind pressure is large, we believe that this kind of ionopause is observed much more frequently during solar minimum. The authors find evidence for this in the radio occultation data from Pioneer Venus, Mariner 10 and Venera 9 and 10.

  9. Coronal Rotation at Solar Minimum from UV Observations

    NASA Astrophysics Data System (ADS)

    Giordano, S.; Mancuso, S.

    2008-11-01

    The observations of the UVCS SOHO instrument from 1996 May to 1997 May have been analyzed to reconstruct intensity time series of the O VI 1032 Å and H I Ly? 1216 Å spectral lines at different coronal heliolatitudes from 1.5 to 3.0 Rsolar from Sun center. At solar minimum, some features persist for several rotations, thus allowing analysis of the UV emission as time series modulated at the period of the solar rotation. We find evidence of coronal differential rotation, which significantly differs from that of the photospheric plasma. The estimated equatorial synodic rotation period of the corona at 1.5 Rsolar is 27.48+/-0.10 days. The study of the latitudinal variation shows that the UV corona decelerates toward the photospheric rates from the equator up to the poleward boundary of the midlatitude streamers, reaching a peak of 28.16+/-0.20 days around +30° from the equator at 1.5 Rsolar, while a less evident peak is observed in the northern hemisphere. This result suggests a real north-south rotational asymmetry as a consequence of different activity and weak coupling between the magnetic fields of the two hemispheres. The study of the radial rotation profiles shows that the corona is rotating almost rigidly with height, but we find an abrupt increase by about half a day between 2.3 and 2.5 Rsolar. The larger gradients of the rotation rates are localized at the boundaries between open and closed field lines, suggesting that in these regions the differential rotation might be a source of magnetic stress and, consequently, of energy release.

  10. Viking solar corona experiment

    Microsoft Academic Search

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

    1977-01-01

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

  11. Mars ionopause during solar minimum: A lesson from Venus

    SciTech Connect

    Mahajan, K.K.; Mayr, H.G. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

    1990-06-01

    The ion densities measured by the Viking landers (Hanson et al., 1977) do not show an abrupt falloff with height, giving the false impression that Mars has no ionopause. On the basis of knowledge gained from the solar wind interaction at Venus during solar minimum, they demonstrate that the observed O{sub 2}{sup +} profile above about 160 km on Mars is a distributed photodynamical ionosphere and can produce an ionopause at around 325 km, similar to that observed on Venus during solar minimum. They conclude that the solar wind interacts directly with the Mars ionosphere, suggesting that the planet does not have an intrinsic magnetic field of any consequence.

  12. THE EVOLUTION OF PLASMA PARAMETERS ON A CORONAL SOURCE SURFACE AT 2.3 R{sub Sun} DURING SOLAR MINIMUM

    SciTech Connect

    Strachan, L.; Panasyuk, A. V.; Kohl, J. L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Lamy, P., E-mail: lstrachan@cfa.harvard.edu [Laboratoire d'Astrophysique de Marseille, UMR6110 CNRS/Universite de Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13 (France)

    2012-01-20

    We analyze data from the Solar and Heliospheric Observatory to produce global maps of coronal outflow velocities and densities in the regions where the solar wind is undergoing acceleration. The maps use UV and white light coronal data obtained from the Ultraviolet Coronagraph Spectrometer and the Large Angle Spectroscopic Coronagraph, respectively, and a Doppler dimming analysis to determine the mean outflow velocities. The outflow velocities are defined on a sphere at 2.3 R{sub Sun} from Sun-center and are organized by Carrington Rotations during the solar minimum period at the start of solar cycle 23. We use the outflow velocity and density maps to show that while the solar minimum corona is relatively stable during its early stages, the shrinkage of the north polar hole in the later stages leads to changes in both the global areal expansion of the coronal hole and the derived internal flux tube expansion factors of the solar wind. The polar hole areal expansion factor and the flux tube expansion factors (between the coronal base and 2.3 R{sub Sun }) start out as super-radial but then they become more nearly radial as the corona progresses away from solar minimum. The results also support the idea that the largest flux tube expansion factors are located near the coronal hole/streamer interface, at least during the deepest part of the solar minimum period.

  13. Analyzing the IAR with IRI During the Recent Solar Minimum

    NASA Technical Reports Server (NTRS)

    Ivanov, S.; Klenzing, J.; Simoes, F.

    2012-01-01

    The 2008-2009 solar minimum was deeper than any within the past century. As such, the performance of the empirical International Reference Ionosphere (IRI) model was impacted. This impact manifested as a disagreement between predicted and measured characteristic separation in frequency for a wave resonating within an Ionospheric Alfven Resonator (IAR). The predicted value of the characteristic was a factor of three lower than what was measured by the Communication/Navigation Outage Forecast System (C/NOFS). Analyzing the model performance and comparing output with measured ionospheric values showed that more than half of the inaccuracy could be explained by inaccuracies in the output of the model. The 2008-2009 solar minimum was outside of the bounds of the effectiveness of the empirical IRI model. Incorporating recent data measurements and new indices would increase the accuracy of IRI during this period.

  14. LANGMUIR WAVE ACTIVITY: COMPARING THE ULYSSES SOLAR MINIMUM AND SOLAR MAXIMUM ORBITS

    E-print Network

    California at Berkeley, University of

    ). The top three panels correspond to the southern segment of the solar minimum orbit; repeated passesLANGMUIR WAVE ACTIVITY: COMPARING THE ULYSSES SOLAR MINIMUM AND SOLAR MAXIMUM ORBITS R. J at the electron plasma frequency) during the solar minimum and solar maximum orbits of Ulysses. At high latitudes

  15. Morphological Study of Quiescent Streamers during Solar Minimum by Ultraviolet Emission Lines

    NASA Astrophysics Data System (ADS)

    Akinari, Nakagawa

    2007-10-01

    We perform, by utilizing spectroscopic measurements made with SOHO/UVCS, a morphological characterization of the quiescent streamer during solar minimum, by means of both a comprehensive survey of daily synoptic observations over 33 weeks from 1996 April to November and detailed analysis of several specialized observations targeting quiescent streamers. On more than half of the days in our synoptic survey, we detected the O VI bifurcation, a feature for which the O VI ?103.2 streamer image has a marked contrast with that of H I Ly?, with the former showing intensity reduction along the streamer axis. All quiescent streamers observed in our synoptic survey exhibited the O VI bifurcation, and all streamers that did not exhibit the bifurcation were associated with active regions. Thus, it can be inferred that the O VI bifurcation is likely a fundamental physical characteristic of quiescent streamers. This suggests that its occurrence represents a basic aspect of the equatorial corona during solar minimum and therefore it can be regarded as an intrinsic nature of the interplanetary neutral sheet on the border of its solar side. Within the quiescent streamer the region of larger H I Ly? widths is found to be organized in an inverted heart-shaped configuration. At the lateral side of the legs and, for larger heights (>2.1 Rsolar), even within the core, spectral profiles of the O VI ??103.2, 103.7 doublet have broad wings and thus cannot be fitted well with a single Gaussian, suggesting the presence of the broad component at those locations.

  16. Regional atmospheric circulation shifts induced by a grand solar minimum

    NASA Astrophysics Data System (ADS)

    Martin-Puertas, Celia; Matthes, Katja; Brauer, Achim; Muscheler, Raimund; Hansen, Felicitas; Petrick, Christof; Aldahan, Ala; Possnert, Göran; van Geel, Bas

    2012-06-01

    Large changes in solar ultraviolet radiation can indirectly affect climate by inducing atmospheric changes. Specifically, it has been suggested that centennial-scale climate variability during the Holocene epoch was controlled by the Sun. However, the amplitude of solar forcing is small when compared with the climatic effects and, without reliable data sets, it is unclear which feedback mechanisms could have amplified the forcing. Here we analyse annually laminated sediments of Lake Meerfelder Maar, Germany, to derive variations in wind strength and the rate of 10Be accumulation, a proxy for solar activity, from 3,300 to 2,000 years before present. We find a sharp increase in windiness and cosmogenic 10Be deposition 2,759 +/- 39 varve years before present and a reduction in both entities 199 +/- 9 annual layers later. We infer that the atmospheric circulation reacted abruptly and in phase with the solar minimum. A shift in atmospheric circulation in response to changes in solar activity is broadly consistent with atmospheric circulation patterns in long-term climate model simulations, and in reanalysis data that assimilate observations from recent solar minima into a climate model. We conclude that changes in atmospheric circulation amplified the solar signal and caused abrupt climate change about 2,800 years ago, coincident with a grand solar minimum.

  17. SphinX MEASUREMENTS OF THE 2009 SOLAR MINIMUM X-RAY EMISSION

    SciTech Connect

    Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Bakala, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B. [Space Research Centre, Polish Academy of Sciences, 51-622, Kopernika 11, Wroclaw (Poland); Kuzin, S. [P. N. Lebedev Physical Institute (FIAN), Russian Academy of Sciences, Leninsky Prospect 53, Moscow 119991 (Russian Federation); Farnik, F. [Astronomical Institute, Ondrejov Observatory (Czech Republic); Reale, F. [Dipartimento di Fisica, Universita di Palermo, Palermo, Italy, and INAF, Osservatorio Astronomico di Palermo, Palermo (Italy); Phillips, K. J. H., E-mail: js@cbk.pan.wroc.pl [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

    2012-06-01

    The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 Multiplication-Sign 10{sup 47} cm{sup -3} and 1.1 Multiplication-Sign 10{sup 48} cm{sup -3}. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals of exceptionally low activity identified in the SphinX data, the Sun's X-ray luminosity in an energy range roughly extrapolated to that of ROSAT (0.1-2.4 keV) was less than most nearby K and M dwarfs.

  18. Quiet-time Interplanetary ˜2-20keV Superhalo Electrons at Solar Minimum

    NASA Astrophysics Data System (ADS)

    Wang, L.; Lin, R. P.; Salem, C. S.; Pulupa, M.

    2011-12-01

    The average flux of the ~2-20 keV superhalo electrons in the solar wind during quiet-time periods, measured by the Suprathermal Electron instrument onboard the two STEREO spacecraft, slowly decreases with time from 2007 to 2009 and then increases in 2010, similar to the solar cycle variation around this solar minimum. We made a comprehensive study for a 2-year period from 2007 March through 2009 March, and found that the observed quiet-time ˜2-20 keV superhalo electrons have a nearly isotropic angular distribution and a power-law spectrum, f ˜ v-?, ranging from v-5 to v-8.7, with the average index of 6.69. The observed power-law spectrum varies significantly on spatial scales of >˜0.1 AU and/or temporal scale of >˜ days. There is no correlation (-0.1 < coefficient < 0.2) with the solar wind proton density, velocity and temperature, but the power-law index ? is weakly anti-correlated (coefficient -0.48) with the electron velocity distribution function at 14.8 keV. The origin of these quiet-time superhalo electrons remains unclear, but since they are present even in the absence of any solar activity, they may be due to resonant wave-particle interactions in the corona or the interplanetary space.

  19. The evolution of plasma parameters on a coronal source surface at 2.3 Rs during solar minimum

    E-print Network

    Strachan, Leonard; Kohl, John L; Lamy, Philippe

    2011-01-01

    We analyze data from the Solar and Heliospheric Observatory to produce global maps of coronal outflow velocities and densities in the regions where the solar wind is undergoing acceleration. The maps use UV and white light coronal data obtained from the Ultraviolet Coronagraph Spectrometer and the Large Angle Spectroscopic Coronagraph, respectively, and a Doppler dimming analysis to determine the mean outflow velocities. The outflow velocities are defined on a sphere at 2.3 Rs from Sun-center and are organized by Carrington Rotations during the solar minimum period at the start of solar cycle 23. We use the outflow velocity and density maps to show that while the solar minimum corona is relatively stable during its early stages, the shrinkage of the north polar hole in the later stages leads to changes in both the global areal expansion of the coronal hole and the derived internal flux tube expansion factors of the solar wind. The polar hole areal expansion factor and the flux tube expansion factors (between ...

  20. A NOTE ON THE TORSIONAL OSCILLATION AT SOLAR MINIMUM

    SciTech Connect

    Howe, R.; Hill, F.; Komm, R. [National Solar Observatory, P.O. Box 26732, Tucson, AZ 85726-6732 (United States); Christensen-Dalsgaard, J. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Schou, J. [HEPL Solar Physics, 452 Lomita Mall, Stanford University, Stanford, CA 94305-4085 (United States); Thompson, M. J. [School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom)], E-mail: rhowe@noao.edu

    2009-08-20

    We examine the evolution of the zonal flow pattern in the upper solar convection zone during the current extended solar minimum, and compare it with that during the previous minimum. The results suggest that a configuration matching that at the previous minimum was reached during 2008, but that the flow band corresponding to the new cycle has been moving more slowly toward the equator than was observed in the previous cycle, resulting in a gradual increase in the apparent length of the cycle during the 2007-2008 period. The current position of the lower-latitude fast-rotating belt corresponds to that seen around the onset of activity in the previous cycle.

  1. The New Solar Minimum: How Deep does the Problem Go?

    NASA Astrophysics Data System (ADS)

    Fletcher, S.; New, R.; Broomhall, A.-M.; Chaplin, W.; Elsworth, Y.

    2010-06-01

    Although there are now some tentative signs that the start of cycle 24 has begun there is still considerable interest in the somewhat unusual behavior of the current solar minimum and the apparent delay in the true start of the next cycle. While this behavior is easily tracked by observing the change in surface activity, a question can also be asked about what is happening beneath the surface where the magnetic activity ultimately originates. In order to try to answer this question we can look at the behavior of the frequencies of the Sun's natural seismic modes of oscillation—the p modes. These seismic frequencies also respond to changes in activity and are probes of conditions in the solar interior. The Birmingham Solar Oscillations Network (BiSON) has made measurements of low-degree (low-l) p mode frequencies over the last three solar cycles, and so is in a unique position to explore the current unusual and extended solar minimum. We compare the frequency shifts in the low-l p-modes obtained from the BiSON data with the change in surface activity as measured by different proxies and show there are significant differences especially during the declining phase of solar cycle 23 and into the current minimum. We also observe quasi-biennial periodic behavior in the p mode frequencies over the last two cycles that, unlike in the surface measurements, seems to be present at mid- and low-activity levels. Additionally we look at the frequency shifts of individual l modes.

  2. 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.

  3. Anomalously low solar extreme-ultraviolet irradiance and thermospheric density during solar minimum

    Microsoft Academic Search

    Stanley C. Solomon; Thomas N. Woods; Leonid V. Didkovsky; John T. Emmert; Liying Qian

    2010-01-01

    Solar activity during 2007–2009 was very low, and during this protracted solar minimum period, the terrestrial thermosphere was cooler and lower in density than expected. Measurements from instruments on the SOHO and TIMED spacecraft, and by suborbital rocket flights, indicate that solar extreme-ultraviolet irradiance levels were lower than they were during the previous solar minimum. Analysis of atmospheric drag on

  4. Ion-neutral Coupling During Deep Solar Minimum

    NASA Technical Reports Server (NTRS)

    Huang, Cheryl Y.; Roddy, Patrick A.; Sutton, Eric K.; Stoneback, Russell; Pfaff, Robert F.; Gentile, Louise C.; Delay, Susan H.

    2013-01-01

    The equatorial ionosphere under conditions of deep solar minimum exhibits structuring due to tidal forces. Data from instruments carried by the Communication Navigation Outage Forecasting System (CNOFS) which was launched in April 2008 have been analyzed for the first 2 years following launch. The Planar Langmuir Probe (PLP), Ion Velocity Meter (IVM) and Vector Electric Field Investigation (VEFI) all detect periodic structures during the 20082010 period which appear to be tides. However when the tidal features detected by these instruments are compared, there are distinctive and significant differences between the observations. Tides in neutral densities measured by the Gravity Recovery and Climate Experiment (GRACE) satellite were also observed during June 2008. In addition, Broad Plasma Decreases (BPDs) appear as a deep absolute minimum in the plasma and neutral density tidal pattern. These are co-located with regions of large downward-directed ion meridional velocities and minima in the zonal drifts, all on the nightside. The region in which BPDs occur coincides with a peak in occurrence rate of dawn depletions in plasma density observed on the Defense Meterological Satellite Program (DMSP) spacecraft, as well as a minimum in radiance detected by UV imagers on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) and IMAGE satellites

  5. Thermosphere Response to Geomagnetic Variability during Solar Minimum Conditions

    NASA Astrophysics Data System (ADS)

    Forbes, Jeffrey; Gasperini, Federico; Zhang, Xiaoli; Doornbos, Eelco; Bruinsma, Sean; Haeusler, Kathrin; Hagan, Maura

    2015-04-01

    The response of thermosphere mass density to variable geomagnetic activity at solar minimum is revealed as a function of height utilizing accelerometer data from GRACE near 480 km, CHAMP near 320 km, and GOCE near 260 km during the period October-December, 2009. The GOCE data at 260 km, and to some degree the CHAMP measurements at 320 km, reveal the interesting feature that the response maximum occurs at low latitudes, rather than at high latitudes where the geomagnetic energy input is presumed to be deposited. The latitude distribution of the response is opposite to what one might expect based on thermal expansion and/or increase in mean molecular weight due to vertical transport of N2 at high latitudes. We speculate that what is observed reflects the consequences of an equatorward meridional circulation with downward motion and compressional heating at low latitudes. A numerical simulation using the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Mesosphere Electrodynamics General Circulation Model (TIME-GCM) is used to assist with this diagnosis. At 480 km GRACE reveals maximum density responses at high southern (winter) latitudes, consistent with recent interpretations in terms of compositional versus temperature effects near the oxygen-helium transition altitude during low solar activity.

  6. Estimates of galactic cosmic ray shielding requirements during solar minimum

    NASA Technical Reports Server (NTRS)

    Townsend, Lawrence W.; Nealy, John E.; Wilson, John W.; Simonsen, Lisa C.

    1990-01-01

    Estimates of radiation risk from galactic cosmic rays are presented for manned interplanetary missions. The calculations use the Naval Research Laboratory cosmic ray spectrum model as input into the Langley Research Center galactic cosmic ray transport code. This transport code, which transports both heavy ions and nucleons, can be used with any number of layers of target material, consisting of up to five different arbitrary constituents per layer. Calculated galactic cosmic ray fluxes, dose and dose equivalents behind various thicknesses of aluminum, water and liquid hydrogen shielding are presented for the solar minimum period. Estimates of risk to the skin and the blood-forming organs (BFO) are made using 0-cm and 5-cm depth dose/dose equivalent values, respectively, for water. These results indicate that at least 3.5 g/sq cm (3.5 cm) of water, or 6.5 g/sq cm (2.4 cm) of aluminum, or 1.0 g/sq cm (14 cm) of liquid hydrogen shielding is required to reduce the annual exposure below the currently recommended BFO limit of 0.5 Sv. Because of large uncertainties in fragmentation parameters and the input cosmic ray spectrum, these exposure estimates may be uncertain by as much as a factor of 2 or more. The effects of these potential exposure uncertainties or shield thickness requirements are analyzed.

  7. Cosmic ray particles behavior during last solar minimum

    NASA Astrophysics Data System (ADS)

    Rockenbach, Marlos; Dal Lago, Alisson; Munakata, Kazuoki; Kato, Chihiro; Kuwabara, Takao; Bieber, John; Schuch, Nelson; Duldig, Marc; Humble, John; Jassar, Hala Al; Sharma, Madan; Sabbah, Ismail

    2013-04-01

    The work presents the Heliosphere characterization during the minimum solar activity. It is possible to identify phenomena caused by the Corrotating Interaction Regions - CIRs, during this solar activity phase. CIRs can be visualized in satellite data for each 27 days, approximately, and it is frequently accompanied by the Earth crossing through the Heliospheric Current Sheath - HCS. These crossing occur in a period of time lower than a day, and it is possible to study the behavior of cosmic rays particles in two different regions with opposite magnetic field polarities. The last solar minimum was special because their long duration and it was the first that the Global Muon Detector Network - GMDN operated in its full capacity. This cosmic ray detectors network is composed by muon scintillators installed in Nagoya - Japan, Hobart - Australia, São Martinho da Serra - Brazil and Kuwait City - Kuwait. Analyzing the GMDN data together with data from SOHO and/or ACE satellites it is possible to study the behavior of the cosmic ray particles and presents a Heliosphere characterization during the minimum solar activity, giving a better understanding of the cosmic ray particles modulation.

  8. Ion composition of the topside equatorial ionosphere during solar minimum

    NASA Technical Reports Server (NTRS)

    Gonzalez, S. A.; Fejer, B. G.; Heels, R. A.; Hanson, W. B.

    1992-01-01

    Observations from both the Bennett ion mass spectrometer and the retarding potential analyzer on board the Atmosphere Explorer E satellite were used to study the longitudinally averaged O(+), H(+), and He(+) concentrations from 150 to 1100 km in the equatorial ionosphere during the 1975-1976 solar minimum. The results suggest that the ion mass spectrometer measurements need to be increased by a factor of 2.15 to agree with the densities from the retarding potential analyzer and with ground-based measurements. The peak H(+) concentrations are about 2.5 x 10 exp 4/cu cm during the day and 10 exp 4/cu cm at night and vary little with season. The O(+)/H(+) transition altitude lies between 750 and 825 km during the day and between 550 and 600 km at night. He(+) is a minor species at all altitudes; its concentration is highly variable with a maximum value of about 10 exp 3/cu cm during equinox daytime.

  9. Quiet-time solar wind superhalo electrons at solar minimum

    NASA Astrophysics Data System (ADS)

    Wang, Linghua; Lin, Robert P.; Salem, Chadi; Pulupa, Marc; Larson, Davin E.; Yoon, Peter H.; Luhmann, Janet G.

    2013-06-01

    We survey the statistical properties of ~2-20 keV superhalo electrons in the solar wind measured by the STEREO/STE instrument during quiet-time periods from 2007 March through 2009 March at solar minimum. The observed quiet-time superhalo electrons have a nearly isotropic angular distribution and a power-law spectrum, f ?v-?, with ? ranging from 5 to 8.7, with nearly half between 6.5 and 7.5, and an average index of 6.69+/-0.90. The integrated density of quiet-time superhalo electrons at 2-20 keV ranges from 10-8 cm-3 to 10-6 cm-3, about 10-9-10-6 of the solar wind density, and it, as well as the power-law spectrum, shows no correlation with solar wind protons. The density of superhalo electrons decreases by approximately one order of magnitude between early 2007 and early 2009, probably reflecting the decay of solar cycle 23 and the approach to its unusually deep activity minimum, while the power-law spectral index ? has no solar-cycle variation. These quiet-time superhalo electrons are present even in the absence of any solar activity, e.g., active regions, flares or microflares, type III radio bursts, etc., suggesting that they may be accelerated by resonant wave-particle interactions in the interplanetary medium, or by nonthermal processes related to the acceleration of the solar wind such as nanoflares.

  10. 3D Coronal Density Reconstruction and Retrieving Coronal Magnetic Field Structures during Solar Minimum and Maximum

    NASA Astrophysics Data System (ADS)

    Kramar, M.; Airapetian, V.; Davila, J. M.

    2014-12-01

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. We employ STEREO/COR1 data obtained during minimum and maximum of solar activity (Carrington rotations, CR, 2066 and 2131) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 Rsun using the tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 A band obtained by tomography for the same CR periods. A global 3D thermodynamic MHD model of the solar corona was used to relate the reconstructed 3D density and emissivity to open/closed magnetic field structures. We show that the locations of density maximum can serve as an indicator of current sheet position, while the locations of the maximum of the density gradient can be a reliable indicator of closed-open magnetic field boundaries. We find that the magnetic field configuration during CR 2066 has a tendency to become radially open at heliocentric distances above 2.5 Rsun. We also find that the potential field model with a fixed source surface (PFSS) is not consistent with the positions of the boundaries between the regions with open and closed magnetic field structures. This indicates that the assumption of the potential nature of the coronal global magnetic field is not satisfied even during the deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  11. Quiet-Time Interplanetary Superhalo Electrons at Solar Minimum

    NASA Astrophysics Data System (ADS)

    Wang, Linghua; Lin, Robert; Salem, Chadi; Pulupa, Marc; Larson, Davin; Yoon, Peter; Luhmann, Janet

    2013-04-01

    We present a statistical survey of ~2-20 keV superhalo electrons in the solar wind measured by the SupraThermal Electron (STE) instrument onboard the two STEREO spacecraft, during quiet-time periods from March 2007 through March 2009 at solar minimum. The observed superhalo electrons have a nearly isotropic angular distribution and a power-law spectrum, f ? v-? , with ? ranging from 5 to 8.7, with nearly half between 6.5 and 7.5, and an average index of 6.69±0.90. The observed power-law spectrum varies significantly on a spatial scale of ?0.1 AU and temporal scale of ?days. The integrated density of quiet-time superhalo electrons at 2-20 keV ranges from ~10-8 cm-3 to 10-6 cm-3, about 10-9 -10-6 of the solar wind density and it, as well as the power-law spectrum shows no correlation with solar wind proton density, velocity or temperature. The density of superhalo electrons decreases by approximately one order of magnitude between early 2007 and early 2009, probably reflecting the decay of solar cycle 23 and the approach to its unusually deep activity minimum, while the power-law spectral index ? has no solar-cycle variation. These quiet-time superhalo electrons are present even in the absence of any solar activity, e.g., active regions, flares or microflares, type III radio bursts, etc., suggesting that they may be accelerated by resonant wave-particle interactions in the interplanetary medium, or by nonthermal processes related to the acceleration of the solar wind such as nanoflares.

  12. Cosmic rays during the unusual solar minimum of 2009

    NASA Astrophysics Data System (ADS)

    Gil, Agnieszka

    Examine the solar activity (SA) parameters during the quite long-lasting minimum epoch 23/24 shows that their values differ substantially in comparison with those measured in previous solar minimum epochs. The Sun was extremely quiet and there were nearly no sunspots (e.g. Smith, 2011). The averaged proton density was lower during this minimum (˜ 0.70) than in the three previous minimum epochs (Jian et al., 2011). The averaged strength of the interplanetary magnetic field during the last minimum was truly low (drop of ˜ 0.36) and the solar wind dynamic pressure decrease (˜ 0.22) was noticed (McComas et al., 2008). Solar polar magnetic fields were weaker (˜ 0.40) during this minimum in comparison with the last three minimum epochs of SA (Wang et al., 2009). Kirk et al. (2009) showed that EUV polar coronal holes area was less (˜ 0.15) than at the beginning of the Solar Cycle no. 23. The solar total irradiance at 1AU was lower more than 0.2Wm (-2) than in the last minimum in 1996 (Fröhlich, 2009). Values of the solar radio flux f10.7 were smaller than for the duration of the recent four minima (Jian et al., 2011). The tilt angle of the heliospheric current sheet declined much slower during the recent minimum in comparison with the previous two. The values of galactic cosmic rays (GCR) intensity measured by neutron monitors were the highest ever recorded (e.g. Moraal and Stoker, 2010). In 2007 neutron monitors achieved values measured during the last negative polarity minimum, 1987, and continued to grow throughout the beginning of 2010. In the same time, the level of anomalous cosmic ray intensities was comparable with the 1987 minimum (Leske et al., 2013). The average amplitude of the 27-days recurrence of the GCR intensity was as high as during the previous minimum epoch 1996 (positive polarity), much higher than during minimum one Hale cycle back (Gil et al., 2012). Modzelewska and Alania (2013) showed that 27-days periodicity of the GCR intensity stable during 2007-2008 evolved to longer period (up to 33-36 days) during 2009. Alania et al. (2014, submitted to JGR) have reported that the 2009 growth in the GCR intensity mostly was related with drop in the solar wind velocity, the strength of the interplanetary magnetic field, and the drift during the negative polarity epoch. Frohlich (2009) argued that the recent minimum was caused by a global temperature decline of 0.2 K in the effective temperature of the Sun. Dikpati (2013) suggested that the reason of the prolonged and deep minimum was somehow different operation of solar dynamo. On the other hand, revisions of the proxies showed that the Maunder Minimum was the latest, but not the only, of the grand minimum ages of solar activity that occurred in the past (e.g. Jones et al., 2010). It might be the case that the last 23/24 solar minimum was the precursor of the end of the Modern grand maximum (e.g. Usoskin, 2013). References: 1.Alania M.V, R. Modzelewska, A. Wawrzynczak, 2014, submitted to JGR 2.Dikpati M., SSRv 176, 279-287, 2013 3.Fröhlich C., A&A 501, L27-L30, 2009 4.Gil A., R. Modzelewska, M.V Alania, AdSpR 50, 712-715, 2012 5.Jian L.K., C.T. Russell, J.G. Luhmann, SoPh 274, 321-344, 2011 6.Jones Ch.A., M.J. Thompson, S.M. Tobias, SSRv 152, 591-616, 2010 7.Kirk M. S., W.D. Pesnell, C. A. Young, S.A. Hess Webber, SoPh 257, 99-112, 2009 8.Leske R. A., A.C. Cummings, R.A. Mewaldt, E.C. Stone, SSRv 176, 253-263, 2013 9.McComas D.J., R.W. Ebert, H.A. Elliott, et al., GeoRL 35, CiteID L18103, 2008 10.Modzelewska R, M.V. Alania, SoPh 286, 593-607, 2013 11.Moraal H., P.H. Stoker, JGR 115, CiteID A12109, 2010 12.Smith E.J, JASTP 73, 277-289, 2011 13.Usoskin I.G., LRSP 10, doi 10.12942/lrsp-2013-1, 2013 14.Wang Y.-M., E. Robbrecht, N.R. Sheeley, ApJ. 707, 1372-1386, 2009

  13. Impact of CIR Storms on Thermosphere Density Variability during the Solar Minimum of 2008

    E-print Network

    Lei, Jiuhou; Wang, Wenbin; McPherron, Robert L

    2010-01-01

    The solar minimum of 2008 was exceptionally quiet, with sunspot numbers at their lowest in 75 years. During this unique solar minimum epoch, however, solar wind high - speed streams emanating from near-equatorial coronal holes occurred frequently and were the primary contributor to the recurrent geomagnetic activity at Earth. These conditions enabled the isolation of forcing by geomagnetic activity on the preconditioned solar minimum state of the upper atmosphere caused by Corotating Interaction Regions (CIRs). Thermosphere density observations around 400 km from the CHAMP satellite are used to study the thermosphere density response to solar wind high - speed streams/CIRs. Superposed epoch results show that thermosphere density responds to high - speed streams globally, and the density at 400 km changes by 75% on average. The relative changes of neutral density are comparable at different latitudes, although its variability is largest at high latitudes. In addition, the response of thermosphere density to hi...

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

    Microsoft Academic Search

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

    1999-01-01

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

  15. Auroral Ionosphere During Solar Minimum in Very High Time Resolution , T. Turunen1

    E-print Network

    Ulich, Thomas

    Auroral Ionosphere During Solar Minimum in Very High Time Resolution Th.Ulich1 , T. Turunen1 , E taken a new vertical ionospheric sounder into use, which was built entirely in-house. The new instrument and it has revealed many rapid changes in the ionosphere, which cannot be observed with standard operation

  16. Global Characteristics of the Thermosphere and Ionosphere During the Current Solar Minimum

    Microsoft Academic Search

    S. Zhang; A. J. Coster; J. M. Holt; J. M. Forbes

    2009-01-01

    We discuss global scale variations of the thermospheric density and ionospheric electron content observed during the years of current solar minimum by CHAMP and other satellites. The variations to be presented include the annual variation and the day-to-day variability, and will be illustrated using a global or hemispheric mean parameter for either neutral density or electron content. In addition to

  17. Physics of the weird solar minimum: New observations of the Sun

    Microsoft Academic Search

    E. Zita; C. Smith; C. Ballou; B. Friedman; C. Showalter; R. Rex; N. Hurlburt

    2010-01-01

    While solar physicists expected more sunspots, flares, and coronal mass ejections by now, the Sun has defied most predictions by persisting in a relatively quiet state for an unusually long time. Can we tell whether this solar minimum is likely to ease in the next decade, or if it may become a Maunder-type minimum? What evidence is there for mechanisms

  18. If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals

    Microsoft Academic Search

    S. E. Gibson; J. U. Kozyra; G. de Toma; B. A. Emery; T. Onsager; B. J. Thompson

    2009-01-01

    Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth. The present solar minimum is exceptionally quiet, with sunspot

  19. Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum determined by CHAMP satellite

    E-print Network

    Forbes, Jeffrey

    Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum are used to determine the solar quiet (Sq) current system during the recent solar minimum. Observations. Richmond (2011), Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar

  20. THE TURBULENT CASCADE AND PROTON HEATING IN THE SOLAR WIND DURING SOLAR MINIMUM

    SciTech Connect

    Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CA (United States); Forman, Miriam A., E-mail: jtu46@wildcats.unh.edu, E-mail: Charles.Smith@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Joshua.Stawarz@Colorado.edu, E-mail: Miriam.Forman@sunysb.edu [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY (United States)

    2012-08-01

    The recently protracted solar minimum provided years of interplanetary data that were largely absent in any association with observed large-scale transient behavior on the Sun. With large-scale shear at 1 AU generally isolated to corotating interaction regions, it is reasonable to ask whether the solar wind is significantly turbulent at this time. We perform a series of third-moment analyses using data from the Advanced Composition Explorer. We show that the solar wind at 1 AU is just as turbulent as at any other time in the solar cycle. Specifically, the turbulent cascade of energy scales in the same manner proportional to the product of wind speed and temperature. Energy cascade rates during solar minimum average a factor of 2-4 higher than during solar maximum, but we contend that this is likely the result of having a different admixture of high-latitude sources.

  1. Little or no solar wind enters Venus' atmosphere at solar minimum.

    PubMed

    Zhang, T L; Delva, M; Baumjohann, W; Auster, H-U; Carr, C; Russell, C T; Barabash, S; Balikhin, M; Kudela, K; Berghofer, G; Biernat, H K; Lammer, H; Lichtenegger, H; Magnes, W; Nakamura, R; Schwingenschuh, K; Volwerk, M; Vörös, Z; Zambelli, W; Fornacon, K-H; Glassmeier, K-H; Richter, I; Balogh, A; Schwarzl, H; Pope, S A; Shi, J K; Wang, C; Motschmann, U; Lebreton, J-P

    2007-11-29

    Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum. PMID:18046399

  2. Wind Observations of Anomalous Cosmic Rays from Solar Minimum to Maximum

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; McDonald, F. B.

    2003-01-01

    We report the first observation near Earth of the time behavior of anomalous cosmic-ray N, O, and Ne ions through the period surrounding the maximum of the solar cycle. These observations were made by the Wind spacecraft during the 1995-2002 period spanning times from solar minimum through solar maximum. Comparison of anomalous and galactic cosmic rays provides a powerful tool for the study of the physics of solar modulation throughout the solar cycle.

  3. Ionospheric variability due to planetary waves and tides for solar minimum conditions

    Microsoft Academic Search

    H.-L. Liu; W. Wang; A. D. Richmond; R. G. Roble

    2010-01-01

    Large ionospheric variability is found at low to middle latitudes when a quasi-stationary planetary wave is specified in the winter stratosphere in the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere electrodynamics general circulation model for solar minimum conditions. The variability includes change of electric field\\/ion drift, F2 peak density and height, and the total electron content. The electric field\\/ion drift change

  4. Solar-minimum quiet time ion energization and outflow in dynamic boundary related coordinates

    Microsoft Academic Search

    W. K. Peterson; L. Andersson; B. C. Callahan; H. L. Collin; J. D. Scudder; A. W. Yau

    2008-01-01

    We report hemispheric average fluxes and energies of outflowing energetic (0.015 < E\\/q < 33 keV) H+, O+, and He+ ions in dynamic boundary-related coordinates, from observations obtained by the Polar\\/TIMAS instrument near 6000 km altitude in the southern hemisphere during quiet geomagnetic intervals at solar minimum. We discuss our observations in terms of known energization and transport processes. We

  5. Impact of CIR Storms on Thermosphere Density Variability during the Solar Minimum of 2008

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Thayer, Jeffrey P.; Wang, Wenbin; McPherron, Robert L.

    2011-12-01

    The solar minimum of 2008 was exceptionally quiet, with sunspot numbers at their lowest in 75 years. During this unique solar-minimum epoch, however, solar-wind high-speed streams emanating from near-equatorial coronal holes occurred frequently and were the primary contributor to the recurrent geomagnetic activity at Earth. These conditions enabled the isolation of forcing by geomagnetic activity on the preconditioned solar minimum state of the upper atmosphere caused by Corotating Interaction Regions (CIRs). Thermosphere density observations around 400 km from the CHAMP satellite are used to study the thermosphere density response to solar-wind high-speed streams/CIRs. Superposed epoch results show that the thermosphere density responds to high-speed streams globally, and the density at 400 km changes by 75% on average. The relative changes of neutral density are comparable at different latitudes, although its variability is largest at high latitudes. In addition, the response of thermosphere density to high-speed streams is larger at night than in daytime, indicating the preconditioning effect of the thermosphere response to storms. Finally, the thermosphere density variations at the periods of 9 and 13.5 days associated with CIRs are linked to the spatial distribution of low - middle latitude coronal holes on the basis of the EUVI observations from STEREO.

  6. The Viking solar corona experiment

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  7. Features of the middle- and low-latitude ionosphere during solar minimum as revealed from COSMIC radio occultation measurements

    Microsoft Academic Search

    Libo Liu; Huijun Le; Yiding Chen; Maosheng He; Weixing Wan; Xinan Yue

    2011-01-01

    Seasonal features of the COSMIC-observed ionosphere under deep solar minimumWave-like longitude pattern in peak density, peak height, and scale heightSolar EUV reduction can explain smaller NmF2 in 2008–2009

  8. Performance of the IRI-2007 and SAMI2 Models during Extreme Solar Minimum

    NASA Technical Reports Server (NTRS)

    Klenzing, J.; Bilitza, D.; Burrell, A. G.; Heelis, R. A.; Huba, J.; Simoes, F.

    2012-01-01

    During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth's ionosphere and thermosphere when compared to previous solar minima. Among these is the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Data from the CINDI instrument on board C/NOFS is used to evaluate the performance of the IRI-2007 and SAMI2 models during the deepest part of the minimum. Additionally, the inputs to SAMI2 are modified in order to estimate the contributions of a contracted thermosphere and reduced EUV on the resultant ionosphere.

  9. Longitudinal and seasonal variations of the equatorial ionospheric density and drift velocities during solar minimum

    NASA Astrophysics Data System (ADS)

    Mohapatra, S.; Earle, G. D.

    2010-12-01

    The C/NOFS satellite sensors measure the ion density, electric and magnetic fields, ion drift, ion and electron temperatures, neutral wind, total electron content and ionsopheric scintillation. The extended solar minimum prevailing during C/NOFS mission allow us to establish a baseline model of the seasonal variations of the topside equatorial ionosphere. The 13-degree inclination of the C/NOFS orbit causes the perigee to advances through all local times in about 66 days. This allows seasonal sampling of the ionsopheric density and drift velocity as a function of local time, magnetic latitude, altitude, and longitude. Measurements taken near the spacecraft's perigee at about 420 km altitude indicate an unusually cold low-density ionosphere with an O+ to H+ ratio of approximately 4 during nighttime conditions. Our analysis focuses on the behavior of the longitudinal structure of the equatorial ionospheric density and velocity at all the local times during the equinox months (August 21 to October 21st, February 21 to April 21st), northern summer months (April 21 to August 21st) and northern winter (October 21 to February 21) months for the year 2008 and 2009 near the perigee. The systematic study of the ion velocity and ion density with longitude will reveal new characteristics of the low latitude ionosphere during extreme solar minimum conditions.

  10. Longitudinal and Seasonal variation of ion density, temperature and composition during solar minimum

    NASA Astrophysics Data System (ADS)

    Mohapatra, S.

    2011-12-01

    Plasma temperature, composition and density observed below 500 km altitude during solar minimum by the ~13 degrees inclination C/NOFS satellite are studied. Based on the C/NOFS satellite observations from 2008 and 2009, the averaged longitudinal and seasonal distributions of the ion temperature (Ti), total ion density (Ni) and ion composition is studied in terms of local time, season, latitude, magnetic declination and solar flux intensity. The longitudinal variations of both Ti and Ni exhibit obvious seasonal dependence in different magnetic declinations in the morning and evening local hours. The electron temperature shows a steep rise in the early morning (well known as "morning overshoot"), a decrease after that and again an increase at ~18 hours (well known as "evening overshoot"). The extended solar minimum prevailing during the C/NOFS mission allows us to establish a baseline model of the quiescent seasonal variations of the topside equatorial ionosphere. The IRI measurements at ~500km altitude of the total ion density and temperature are compared with the C/NOFS measured parameters at the same altitude.

  11. 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.

  12. 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....

  13. Average photospheric poloidal and toroidal magnetic field components near solar minimum

    NASA Technical Reports Server (NTRS)

    Duvall, T. L., Jr.; Scherrer, P. H.; Svalgaard, L.; Wilcox, J. M.

    1979-01-01

    Average (over longitude and time) photospheric magnetic field components are derived from 3-min Stanford magnetograms made near the solar minimum of cycle 21. The average magnetograph signal is found to behave as the projection of a vector for measurements made across the disk. The poloidal field exhibits the familiar dipolar structure near the poles, with a measured signal in the line Fe I 5250 A of about 1 G. At low latitudes the poloidal field has the polarity of the poles, but is of reduced magnitude (about 0.1 G). A net photospheric toroidal field with a broad latitudinal extent is found. The polarity of the toroidal field is opposite in the northern and southern hemispheres and has the same sense as subsurface flux tubes giving rise to active regions of solar cycle 21. These observations are used to discuss large-scale electric currents crossing the photosphere and angular momentum loss to the solar wind.

  14. Three-Dimensional Reconstructions of the Solar Wind: During Solar Minimum Conditions

    NASA Astrophysics Data System (ADS)

    Bisi, Mario; Jackson, B. V.; Hick, P. P. L.; Clover, J. M.; Tokumaru, M.; Fujiki, K.; Fallows, R. A.; Breen, A. R.

    2009-05-01

    Interplanetary scintillation (IPS) observations provide information about a vast region of the inner heliosphere. We use Solar-Terrestrial Environment Laboratory (STELab) IPS velocity and g-level observations as well as IPS velocity observations from the European Incoherent SCATter (EISCAT) and EISCAT Svalbard Radar (ESR), with our three-dimensional (3D) reconstruction model to determine velocities and densities of the inner heliosphere. We present these observations using various forms of imaging from our time-dependent model that can measure changes with durations of less than a day and compare these with various spacecraft in situ measurements. We concentrate on the current solar-minimum period showing relatively-stable large-scale solar-wind structure during this time in relation to transients that are also sometimes present. Data primarily covers the 2007-2009 International Heliophysical Year (IHY) which includes the Whole Heliosphere Interval (CR2068).

  15. The Magnetic Field at the Inner Boundary of the Heliosphere Around Solar Minimum

    NASA Astrophysics Data System (ADS)

    Zhao, X. P.; Hoeksema, J. T.

    2010-10-01

    STEREO A and B observations of the radial magnetic field between 1 January 2007 and 31 October 2008 show significant evidence that in the heliosphere, the ambient radial magnetic field component with any dynamic effects removed is uniformly distributed. Based on this monopolar nature of the ambient heliospheric field we find that the surface beyond which the magnetic fields are in the monopolar configuration must be spherical, and this spherical surface can be defined as the inner boundary of the heliosphere that separates the monopole-dominated heliospheric magnetic field from the multipole-dominated coronal magnetic field. By using the radial variation of the coronal helmet streamers belts and the horizontal current - current sheet - source surface model we find that the spherical inner boundary of the heliosphere should be located around 14 solar radii near solar minimum phase.

  16. Low-latitude measurements of neutral thermospheric helium dominance near 400 km during extreme solar minimum

    NASA Astrophysics Data System (ADS)

    Haaser, R. A.; Earle, G. D.; Heelis, R. A.; Coley, W. R.; Klenzing, J. H.

    2010-11-01

    Since the middle of 2008 solar activity has been unusually low, resulting in unusual atmospheric conditions, including significant changes in the pressure and neutral constituents at altitudes near 400 km at low latitudes. These attributes have been measured by the Coupled Ion-Neutral Dynamics Investigation instruments aboard the Communication/Navigation Outage Forecast System (C/NOFS) satellite. The cross-track sensor aboard C/NOFS is designed to measure the neutral pressure in an atmosphere with pressures larger than 10-8 Torr, from which the atmospheric scale height can be estimated. In the contracted thermosphere during the current solar minimum (analyzed from June 2008 to August 2009), the instrument data indicate a dominance of neutral helium near the satellite perigee (400 km). This conclusion is found to be consistent with the measured mean drag on the satellite, thus validating the basic functionality of the cross-track sensor.

  17. The turbulent cascade and proton heating in the solar wind during solar minimum

    SciTech Connect

    Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, Colorado (United States); Forman, Miriam A. [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, New York (United States)

    2013-06-13

    Solar wind measurements at 1 AU during the recent solar minimum and previous studies of solar maximum provide an opportunity to study the effects of the changing solar cycle on in situ heating. Our interest is to compare the levels of activity associated with turbulence and proton heating. Large-scale shears in the flow caused by transient activity are a source that drives turbulence that heats the solar wind, but as the solar cycle progresses the dynamics that drive the turbulence and heat the medium are likely to change. The application of third-moment theory to Advanced Composition Explorer (ACE) data gives the turbulent energy cascade rate which is not seen to vary with the solar cycle. Likewise, an empirical heating rate shows no significan changes in proton heating over the cycle.

  18. Anomalous behavior of the thermosphere during solar minimum observed by CHAMP and GRACE

    NASA Astrophysics Data System (ADS)

    Bruinsma, Sean L.; Forbes, Jeffrey M.

    2010-11-01

    High-resolution density observations inferred from accelerometer measurements on the Challenging Mini-Satellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites for the period 11-17 December 2008 during the solar minimum are analyzed and compared to reference model predictions. The density distribution as a function of altitude can be studied because the satellites were in the same 8.4/20.4 hour (0824/2024) local solar time plane, CHAMP at a mean altitude of 332 km and GRACE 144 km higher. The mean observed and model density profiles at 476 km reveal considerable differences, which, except for a 25% bias, is not the case at an altitude of 332 km. These differences result from the fact that during this solar minimum the transition from predominantly O to He occurs at a much lower altitude in connection with the winter helium bulge than is predicted by the model. When averaged over the 1 week period, striking wave-3 structures are revealed with respect to longitude that are remarkably consistent between CHAMP and GRACE. We interpret these as the manifestations of nonmigrating tides propagating upward from the lower atmosphere. Comparisons are made with similar data from August 2008, which reveal a wave-4 structure. However, whereas previous results and conventional wisdom would suggest that these features are produced by the eastward propagating diurnal tides with zonal wave numbers s = -2 (DE2) and s = -3 (DE3), respectively, the asymmetries and day-night phase differences that are present suggest the predominance of semidiurnal tides SE1 and SE2, respectively, along with the aforementioned diurnal tides as well as tides SW5 and SW6.

  19. Solar activity and climate change during the 1750 A.D. solar minimum

    NASA Astrophysics Data System (ADS)

    Bard, Edouard; Baroni, Mélanie; Aster Team

    2015-04-01

    The number of sunspots and other characteristics have been widely used to reconstruct the solar activity beyond the last three decades of accurate satellite measurements. It has also been possible to reconstruct the long-term solar behavior by measuring the abundance on Earth of cosmogenic nuclides such as carbon 14 and beryllium 10. These isotopes are formed by the interaction of galactic cosmic rays with atmospheric molecules. Accelerator mass spectrometry is used to measure the abundance of these isotopes in natural archives such as polar ice (for 10Be), tree rings and corals (for 14C). Over the last millennium, the solar activity has been dominated by alternating active and quiet periods, such as the Maunder Minimum, which occurred between 1645 and 1715 A.D. The climate forcing of this solar variability is the subject of intense research, both because the exact scaling in terms of irradiance is still a matter of debate and because other solar variations may have played a role in amplifying the climatic response. Indeed, the past few decades of accurate solar measurements do not include conditions equivalent to an extended solar minimum. A further difficulty of the analysis lies in the presence of other climate forcings during the last millennium, which are superimposed on the solar variations. Finally, the inherent precision of paleotemperature proxies are close to the signal amplitude retrieved from various paleoclimate archives covering the last millennium. Recent model-data comparisons for the last millennium have led to the conclusion that the solar forcing during this period was minor in comparison to volcanic eruptions and greenhouse gas concentrations (e.g. Schurer et al. 2013 J. Clim., 2014 Nat. Geo.). In order to separate the different forcings, it is useful to focus on a temperature change in phase with a well-documented solar minimum so as to maximize the response to this astronomical forcing. This is the approach followed by Wagner et al. (2005 Clim. Dyn.), who focused their data-model comparison on the Dalton Minimum, which occurred between 1790 and 1830 A.D. and which, fortuitously, included several major volcanic eruptions such as the Tambora eruption in 1815. Their conclusion was that the global imprint of the volcanic forcing was significantly larger than that of contemporaneous solar forcing and the increasing atmospheric CO2 concentrations. A different approach is to consider another recent solar minimum over a period characterized by a low volcanicity and minimal changes of greenhouse gases. Such a minimum does exist between the Maunder and the Dalton Minima and lasted for a mere two decades between 1745 and 1765 A.D. The sunspot number exhibits a clear 11-year cycle, but it only reaches a maximal value lower than 100, i.e. less than observed for the past seven 11-year cycles. Incidentally, the maximal values observed between 1745 and 1765 are similar to those observed during the maximum of the present solar cycle. The 1750 A.D. solar minimum can also be studied in other records such as counts of auroras at mid-latitudes and cosmogenic isotopes such as 14C and 10Be. In addition to reviewing published time series, we will report a new 10Be record from a well-dated ice core from Dome C in Antarctica. Sulfate concentration, a proxy for volcanic eruptions, has also been measured in the very same samples, allowing a precise comparison of both 10Be and sulfate profiles. The full record covers the last millennium and will be presented separately by Baroni, Bard and the ASTER Team. Zooming in on the century between 1700 and 1800 A.D. allows to identify an extended period of low volcanicity and to observe a clear 10Be increase corresponding to the solar minimum. We will present the new data over the 18th century as well as their first interpretation in the context of other useful records based on greenhouse gas concentrations, paleotemperature proxies and climate modeling available in the literature.

  20. 24/7 Solar minimum polar cap and auroral ion temperature observations

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

    2011-07-01

    During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 °N latitude, 212.5 °E longitude where the NSF's new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at mid-latitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 °N latitude, 16.0 °E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably with the quiet-background in temperature, both in magnitude and climatology.

  1. Comprehensive Ionospheric Polar and Auroral Observations for Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig

    Only the incoherent scatter radar (ISR) is able to simultaneously measure full profiles of elec-tron density, ion temperature, and electron temperatures through the E-and F-layers of the terrestrial ionosphere. Historically ISR's have been operated for periods much less than a month. Hence, their measurements do not constitute a continuous sequence from which quiet, disturbed, and storm periods can reliably be discerned. This is particularly true in the auroral and polar regions. During the International Polar Year (IPY) two ISRs achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the IRI with a fiduciary E-and F-region ionosphere descriptions for solar minimum conditions at auroral and polar cap locations. The ionospheric description being electron den-sity, ion temperature, electron temperature, and even molecular ion composition profiles from as low as 90 km extending several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.4° N, 147.5° W where the NSF's new Poker Flat Incoherent Scatter Radar (PFISR) is located. During solar minimum conditions this location is in the auroral region for most of the day and is at mid-latitudes, equatorward of the cusp, for about 4 to 8 hours per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78° N, 16° E where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap often with a noon sector passage through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be demarked between quiet and disturbed. During the IPY year, 1 March 2007 to 29 February 2008, a total of 50 solar wind corotating interaction regions (CIRs) impacted geospace. Each CIR has a one-to-three day geomagnetic disturbance that is observed in the ISR auroral and polar observations. Hence, this data set enables the quiet-background ionosphere to be established as a function of season and local time. This quiet-background ionosphere has the unique attribute that it has self-consistent altitude profiles of the density and the temper-ature. This we believe is a true fiduciary reference for the IRI in a high latitude region, that is otherwise particularly difficult to quantify.

  2. 24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

    NASA Technical Reports Server (NTRS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

    2011-01-01

    During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably with the quiet-background in temperature, both in magnitude and climatology.

  3. 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.

  4. Daytime ionospheric equatorial vertical drifts during the 2008-2009 extreme solar minimum

    NASA Astrophysics Data System (ADS)

    Rodrigues, F. S.; Smith, J. M.; Milla, M.; Stoneback, R. A.

    2015-02-01

    One of the most interesting observations made by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite mission was the detection of average equatorial ionospheric vertical drifts that largely differed from model predictions. C/NOFS measurements showed, in particular, downward drifts in the afternoon sector, and upward drifts around local midnight hours during the 2008 and 2009 extreme solar minimum. The unexpected behavior of the drifts has important implications for ionospheric modeling and suggests the necessity for a better understanding of the low-latitude electrodynamics. We used ground-based radar measurements to quantify the seasonal and solar flux variability of daytime equatorial drifts at lower altitudes (˜150 km) than those probed by C/NOFS (above ˜400 km). We found that average vertical drifts at 150 km altitude are in good agreement with model predictions of F region drifts and did not show the signatures of an enhanced semidiurnal pattern, as seen by C/NOFS. Comparison of the 150 km echo drifts with model predictions also shows that the increase (decrease) with height of the vertical drifts in the morning (afternoon) hours is a regular feature of the equatorial ionosphere. It occurred in all seasons and solar flux conditions between 2001 and 2011.

  5. Dayside ionospheric response to recurrent geomagnetic activity during the extreme solar minimum of 2008

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Lei, J.; Su, S.-Y.; Liu, C. H.; Lin, C. H.; Chen, W. S.

    2010-01-01

    Global observations of electron density profiles from the COSMIC satellites are used to investigate, for the first time, the altitudinal dependence of the ionospheric response to the recurrent geomagnetic activity at different latitudinal regions during the extreme solar minimum period of 2008. Our results show that the 9-day oscillations in NmF2 are out of phase with those in Kp at high latitudes, whereas they are in phase at low-middle latitudes. This is consistent with changes in neutral composition associated with the recurrent geomagnetic activity. Meanwhile, the 9-day perturbations in the hmF2 and the thickness parameter (HT) exhibit good correspondence with the perturbations in Kp from pole to pole, suggesting that the ionospheric response is global and undergoes periodic expansion/contraction. Further, the ionospheric response to the recurrent geomagnetic activity strongly depends on altitude. The density perturbations are generally in phase with Kp above the F2 peak, while they are out of phase around the F2 peak at high latitudes. These changes in electron density at different altitudes are explained by different physical processes, such as photoionization-chemistry, particle precipitation, and dynamic and diffusion transport.

  6. Chandra Observations of Comets 8P/Tuttle and 17P/Holmes during Solar Minimum

    E-print Network

    Christian, D J; Lisse, C M; Dennerl, K; Wolk, S J; Hsieh, H; Zurbuchen, T H; Zhao, L

    2010-01-01

    We present results for Chandra observations of comets, 17P/Holmes (17P) and 8P/Tuttle (8P). 17P was observed for 30 ksec right after its major outburst, on 31 Oct 2007 (10:07 UT) and comet 8P/Tuttle was observed in 2008 January for 47 ksec. During the two Chandra observations, 17P was producing at least 100 times more water than 8P but was 2.2 times further away from the Sun. Also, 17P is the first comet observed at high latitude (+19.1 degrees) during solar minimum, while 8P was observed at a lower solar latitude (3.4 degrees). The X-ray spectrum of 17P is unusually soft with little significant emission at energies above 500 eV. Depending on our choice of background, we derive a 300 to 1000 eV flux of 0.5 to 4.5 x 10^-13 ergs/cm2/sec, with over 90% of the emission in the 300 to 400 eV range. This corresponds to an X-ray luminosity between 0.4 to 3.3 x 10^15 ergs/sec. 17P's lack of X-rays in the 400 to 1000 eV range, in a simple picture, may be attributed to the polar solar wind, which is depleted in highly c...

  7. On the 27-day Variations of Cosmic Ray Intensity in Recent Solar Minimum 23/24

    E-print Network

    Modzelewska, R

    2015-01-01

    We have studied the 27-day variations and their harmonics of the galactic cosmic ray (GCR) intensity, solar wind velocity, and interplanetary magnetic field (IMF) components in the recent prolonged solar minimum 23 24. The time evolution of the quasi-periodicity in these parameters connected with the Suns rotation reveals that their synodic period is stable and is aprox 26-27 days. This means that the changes in the solar wind speed and IMF are related to the Suns near equatorial regions in considering the differential rotation of the Sun. However, the solar wind parameters observed near the Earths orbit provide only the conditions in the limited local vicinity of the equatorial region in the heliosphere (within in latitude). We also demonstrate that the observed period of the GCR intensity connected with the Suns rotation increased up to aprox 33-36 days in 2009. This means that the process driving the 27-day variations of the GCR intensity takes place not only in the limited local surroundings of the equato...

  8. Quiescent and Eruptive Prominences at Solar Minimum: A Statistical Study via an Automated Tracking System

    E-print Network

    Loboda, I P

    2015-01-01

    We employ an automated detection algorithm to perform a global study of solar prominence characteristics. We process four months of TESIS observations in the He II 304 A line taken close to the solar minimum of 2008-2009 and focus mainly on quiescent and quiescent-eruptive prominences. We detect a total of 389 individual features ranging from 25x25 to 150x500 Mm in size and obtain distributions of many their spatial characteristics, such as latitudinal position, height, size and shape. To study their dynamics, we classify prominences as either stable or eruptive and calculate their average centroid velocities, which are found to be rarely exceeding 3 km/s. Besides, we give rough estimates of mass and gravitational energy for every detected prominence and use these values to evaluate the total mass and gravitational energy of all simultaneously existing prominences (10e12-10e14 kg and 10e29-10e31 erg, respectively). Finally, we investigate the form of the gravitational energy spectrum of prominences and derive...

  9. Physics of the weird solar minimum: New observations of the Sun

    NASA Astrophysics Data System (ADS)

    Zita, E.; Smith, C.; Ballou, C.; Friedman, B.; Showalter, C.; Rex, R.; Hurlburt, N.

    2010-10-01

    While solar physicists expected more sunspots, flares, and coronal mass ejections by now, the Sun has defied most predictions by persisting in a relatively quiet state for an unusually long time. Can we tell whether this solar minimum is likely to ease in the next decade, or if it may become a Maunder-type minimum? What evidence is there for mechanisms that might explain the observed delayed and low-amplitude magnetic activity? What effects could decreased solar activity have on Earth's climate? Evergreen undergraduates study the Sun with colleagues who built the new Solar Dynamics Observatory (SDO). Students analyzed flow velocities with respect to magnetic field tilts; analyzed waves of UV light in active regions; developed a software suite to enable the public to engage with solar dynamics; and cataloged movies of solar events for public release. We use data from the high-resolution HINODE satellite and from the new full-disk SDO. Zita studied the solar dynamo, and found that resistivity gradients can drive magnetic advection. We summarize our work and the light it may shed on questions such as those above.

  10. Spread F occurrence over a southern anomaly crest location in Brazil during June solstice of solar minimum activity

    Microsoft Academic Search

    C. M. N. Candido; I. S. Batista; F. Becker-Guedes; M. A. Abdu; J. H. A. Sobral; H. Takahashi

    2011-01-01

    We present a study of Spread F occurrence over a location under the southern crest of the equatorial ionization anomaly (Cachoeira Paulista 22.7°S, 45.0°W, mag. Lat.: 16°S, dip angle: -32.3°, Brazil) during the last solar cycle, which presented an extended solar minimum activity. After analyzing hundreds of ionograms obtained with a digital ionosonde DGS 256, between 2001 and 2010, we

  11. Peculiar Features of Ionospheric F3-Layer during Prolonged Solar Minimum (2007-2009)

    NASA Astrophysics Data System (ADS)

    Nayak, C.; Yadav, V.; Kakad, B. A.; Sripathi, S.; Emperumal, K.; Pant, T. K.; Bhattacharyya, A.; Jin, S.

    2014-12-01

    Seasonal and local time occurrence of ionospheric F3-layer over Tirunelveli (geo. lon. 77.8° E, geo. lat. 8.7° N, dip 0.7°) during extremely low and prolonged solar activity period (2007-2009) has been presented in this paper. Almost three times increase in the occurence of the F3-layer has been observed 2009 (~ 48%) as compared to that during 2007(~ 16%). The increase of this order just within low solar activity period is unusual. In earlier studies similar increase in F3 occurrence has been reported when solar activity changes from high (F10.7=182) to low (F10.7=72). Another important feature of this study, is the presence of post-noon F3 layers that are observed predominantly during the summer solstice of 2009. Such occurrence of post-noon F3 layers was nearly absent during summer solstice of previous solar minimum (1996) over nearby dip equatorial station Trivandrum. Using the equatorial electrojet (EEJ) as a proxy for eastward electric field, we found that the EEJ strength and the maximum rate of change of EEJ are higher for F3-days as compared to that during non-F3 days. It was also observed that the peak occurrence of pre-noon F3-layer closely coincides with the time of maximum rate of change of EEJ. The present study reveals that the rate of change of eastward electric field (dE/dt) as well plays an important role in the formation of F3-layer.

  12. Corona Discharge in Clouds

    NASA Astrophysics Data System (ADS)

    Sin'kevich, A. A.; Dovgalyuk, Yu. A.

    2014-04-01

    We present a review of the results of theoretical studies and laboratory modeling of corona discharge initiation in clouds. The influence of corona discharges on the evolution of the cloud microstructure and electrification is analyzed. It is shown that corona discharges are initiated when large-size hydrometeors approach each other, whereas in some cases, corona discharges from crystals, ice pellets, and hailstones can appear. The corona discharges lead to significant air ionization, charging of cloud particles, and separation of charges in clouds and initiate streamers and lightnings. The influence of corona discharges on changes in the phase composition of clouds is analyzed.

  13. The Humanities, Unraveled

    ERIC Educational Resources Information Center

    Berube, Michael

    2013-01-01

    Graduate education in the humanities is in crisis. Every aspect, from the most specific details of the curriculum to the broadest questions about its purpose, is in crisis. It is a seamless garment of crisis: If one pulls on any one thread, the entire thing unravels. It is therefore exceptionally difficult to discuss any one aspect of graduate…

  14. Ionospheric VTEC and thermospheric infrared emission dynamics during corotating interaction region and high-speed stream intervals at solar minimum: 25 March to 26 April 2008

    Microsoft Academic Search

    O. P. Verkhoglyadova; B. T. Tsurutani; A. J. Mannucci; M. G. Mlynczak; L. A. Hunt; A. Komjathy; T. Runge

    2011-01-01

    Thermospheric infrared emission shows strong response to HSS drivingVTEC data show fast, continuous, and global response to external forcing by HSSsHeliospheric-magnetospheric-ionospheric-thermospheric coupling at solar minimum

  15. Space weather effects on the low latitude D-region ionosphere during solar minimum

    NASA Astrophysics Data System (ADS)

    Kumar, Abhikesh; Kumar, Sushil

    2014-12-01

    The effects of the solar flares and the geomagnetic storms (disturbance storm time ( Dst) < -50 nT) during December 2006 to 2008, a period during the unprecedented solar minimum of solar cycles 23 and 24, have been examined on sub-ionospheric very low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 kHz), VTX (18.2 kHz), and NLK (24.8 kHz) transmitters monitored at Suva (18.2° S, 178.4° E), Fiji. Apart from the higher class solar flares (C to X), a solar flare of class B8.5 also produced enhancements both on the amplitude and phase. The amplitude enhancements in NLK, NPM, and NWC signals as a function of peak solar flare X-ray flux in decibel (dB; relative to 1 ?W/m2) shows that the relationship curve is steeper and quite linear between the flare power levels of 0 to 15 dB; below 0 dB, the curve gets less steep and flattens towards -5 dB flare power level, while it also gets less steep above 15 dB and almost flattens above 20 dB. In general, the level of amplitude enhancement for NLK signal is higher than that for NPM and NWC signals for all solar flares. The enhancement in the amplitude and phase of VLF signals by solar flares is due to the increase in the D-region electron density by the solar flare-produced extra ionization. The modeling of VLF perturbations produced by B8.5 and C1.5 classes of solar flares on 29 January 2007 using LWPC (Long Wave Propagation Capability) V2.1 codes show that reflection height ( H') was reduced by 0.6 and 1.2 km and the exponential sharpness factor ( ?) was raised by 0.010 and 0.005 km-1, respectively. Out of seven storms with Dst < -50 nT, only the intense storm of 14 to 16 December 2006 with a minimum Dst of -145 nT has shown a clear reduction in the signal strength of NWC and NPM sub-ionospheric signals due to storm-induced reduction in the D-region electron density.

  16. Atmospheric effect of repeated high-energy electron precipitation at high latitude during solar minimum time

    NASA Astrophysics Data System (ADS)

    Turunen, Esa; Haggstrom, Ingemar; Enell, Carl-Fredrik

    2012-07-01

    Today it is a well established concept how high-energy auroral electrons and solar protons, when precipitating into the atmosphere, may cause significant variations of minor neutral gas concentrations. The excess ionization events initiate production of odd hydrogen and odd nitrogen, the latter even being long-lived in the absence of sunlight, so that the chemistry effects which finally may affect even the upper atmospheric ozone concentration, are transported even to lower altitudes and latitudes. Whereas the solar proton events, including experimental verification of the effects, are well studied in recent literature, very few experimental findings are published about the actual contribution of the high-energy electron precipitation events. After reviewing shortly the recent advance in understanding the effects of excess ionisation events on neutral atmospheric composition, we present an analysis of a unique data set of electron precipitation effects at high latitudes during solar minimum time: The one year long IPY data set of incoherent scatter radar measurements in Longyearbyen by the EISCAT Svalbard Radar (ESR). ESR was operated in a continuous mode from 1 March 2007 to 29 February 2008, and backscattered power measurements, with 3 km range resolution and 2.25 km range steps, start from the altitude of 45 km. Data is subject to sea and/or tropospheric clutter, which is variable with season/day up to 65 km. However, normally data is usable for altitudes higher than 70 km. This unique set of electron density data from a high-latitude station reveals repeated occurence of short lasting low-altitude ionisation enhancements and thus high-energy electron precipitation events, in spite of the generally geomagnetically quiet conditions. We perform analysis of the atmospheric effects of these ionisation events by using the detailed Sodankyla Ion Chemistry model of D region throughout the 1-year long IPY period, and point out possibilities to observe these variations in other sets of data, as well as the significance of improving continuous monitoring of D region ionisation by the existing and proposed new incohorent scatter facilities, such as the EISCAT 3D volumetric imaging incoherent scatter radar in Northern Scandinavia.

  17. The Solar Corona

    NSDL National Science Digital Library

    David Hathaway

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

  18. The Peculiar Solar Minimum 23/24 Revealed by the Microwave Butterfly Diagram

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Natchimuthuk; Yashiro, Seiji; Makela, Pertti; Shibasaki, Kiyoto; Hathaway, David

    2010-01-01

    The diminished polar magnetic field strength during the minimum between cycles 23 and 24 is also reflected in the thermal radio emission originating from the polar chromosphere. During solar minima, the polar corona has extended coronal holes containing intense unipolar flux. In microwave images, the coronal holes appear bright, with a brightness enhancement of 500 to 2000 K with respect to the quiet Sun. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is approx.10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radioheliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approx.250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes..

  19. Measurement of the Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight over Antarctica

    NASA Technical Reports Server (NTRS)

    Abe, K.; Fuke, H.; Haino, S.; Hams, T.; Hasegawa, M.; Horikoshi, A.; Kim, K. C.; Kusumoto, A.; Lee, M. H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Mitchell, J. W.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J. F.; Sakai, K.; Sasaki, M.; Seo, E. S.; Shinoda, R.; Streitmatter, R. E.; Suzuki, J.; Tanaka, K.; Thakur, N.

    2012-01-01

    The energy spectrum of cosmic-ray antiprotons (p-bar's) from 0.17 to 3.5 GeV has been measured using 7886 p-bar's detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary p-bar calculations. Cosmologically primary p-bar's have been investigated by comparing measured and calculated p-bar spectra. BESS-Polar II data.show no evidence of primary p-bar's from the evaporation of primordial black holes.

  20. Measurement of cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight in Antarctica

    E-print Network

    Abe, K; Haino, S; Hams, T; Hasegawa, M; Horikoshi, A; Kim, K C; Kusumoto, A; Lee, M H; Makida, Y; Matsuda, S; Matsukawa, Y; Mitchell, J W; Nishimura, J; Nozaki, M; Orito, R; Ormes, J F; Sakai, K; Sasaki, M; Seo, E S; Shinoda, R; Streitmatter, R E; Suzuki, J; Tanaka, K; Thakur, N; Yamagami, T; Yamamoto, A; Yoshida, T; Yoshimura, K

    2011-01-01

    The energy spectrum of cosmic-ray antiprotons has been measured in the range 0.17 to 3.5 GeV, based on 7886 antiprotons collected by the BESS-Polar II instrument during a long-duration flight over Antarctica in the solar minimum period of December 2007 through January 2008. The antiproton spectrum measured by BESS-Polar II shows good consistency with secondary antiproton calculations. Cosmologically primary antiprotons have been searched for by comparing the observed and calculated antiproton spectra. The BESS-Polar II result shows no evidence of primary antiprotons originating from the evaporation of PBH.

  1. CHANDRA OBSERVATIONS OF COMETS 8P/TUTTLE AND 17P/HOLMES DURING SOLAR MINIMUM

    SciTech Connect

    Christian, D. J. [Eureka Scientific, 2420 Delmer Ave, Suite 100, Oakland, CA, 94602 (United States); Bodewits, D. [NASA Goddard Space Flight Center, Solar System Exploration Division, Mailstop 690.3, Greenbelt, MD 20771 (United States); Lisse, C. M. [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States); Dennerl, K. [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1603, 85740 Garching (Germany); Wolk, S. J. [Chandra X-Ray Center, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hsieh, H. [Department of Physics and Astronomy, Queen's University Belfast, Astronomy Research Centre, Belfast (United Kingdom); Zurbuchen, T. H.; Zhao, L. [Department of Atmospheric Oceanic and Space Sciences, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143 (United States)], E-mail: damian.christ@gmail.com, E-mail: damian.christian@csun.edu, E-mail: Dennis.Bodewits@nasa.gov, E-mail: carey.lisse@jhuapl.edu, E-mail: kod@mpe.mpg.de, E-mail: swolk@cfa.harvard.edu, E-mail: h.hseih@qub.c.uk, E-mail: thomasz@umich.edu, E-mail: lzh@umich.edu

    2010-04-01

    We present results for Chandra X-ray Observatory observations of two comets made during the minimum of solar cycle 24. The two comets, 17P/Holmes (17P) and 8P/Tuttle (8P), were very different in their activity and geometry. 17P was observed, for 30 ks right after its major outburst, on 2007 October 31 (10:07 UT), and comet 8P/Tuttle was observed in 2008 January for 47 ks. During the two Chandra observations, 17P was producing at least 100 times more water than 8P but was 2.2 times further away from the Sun. Also, 17P was at a relatively high solar latitude (+19.{sup 0}1) while 8P was observed at a lower solar latitude (3.{sup 0}4). The X-ray spectrum of 17P is unusually soft with little significant emission at energies above 500 eV. Depending on our choice of background, we derive a 300-1000 eV flux of 0.5-4.5 x 10{sup -13} erg cm{sup -2} s{sup -1}, with over 90% of the emission in the 300-400 eV range. This corresponds to an X-ray luminosity between 0.4 and 3.3 x 10{sup 15} erg s{sup -1}. However, we cannot distinguish between this significant excess emission and possible instrumental effects, such as incomplete charge transfer across the CCD. 17P is the first comet observed at high latitude during solar minimum. Its lack of X-rays in the 400-1000 eV range, in a simple picture, may be attributed to the polar solar wind, which is depleted in highly charged ions. 8P/Tuttle was much brighter, with an average count rate of 0.20 counts s{sup -1} in the 300-1000 eV range. We derive an average X-ray flux in this range of 9.4 x 10{sup -13} erg cm{sup -2} s{sup -1} and an X-ray luminosity for the comet of 1.7 x 10{sup 14} erg s{sup -1}. The light curve showed a dramatic decrease in flux of over 60% between observations on January 1 and 4. When comparing outer regions of the coma to inner regions, its spectra showed a decrease in ratios of C VI/C V, O VIII/O VII, as predicted by recent solar wind charge exchange (SWCX) emission models. There are remarkable differences between the X-ray emission from these two comets, further demonstrating the qualities of cometary X-ray observations, and SWCX emission in general as a means of remote diagnostics of the interaction of astrophysical plasmas.

  2. Chandra Observations of Comets 8p/Tuttle and 17p/Holmes During Solar Minimum

    NASA Astrophysics Data System (ADS)

    Christian, D. J.; Bodewits, D.; Lisse, C. M.; Dennerl, K.; Wolk, S. J.; Hsieh, H.; Zurbuchen, T. H.; Zhao, L.

    2010-04-01

    We present results for Chandra X-ray Observatory observations of two comets made during the minimum of solar cycle 24. The two comets, 17P/Holmes (17P) and 8P/Tuttle (8P), were very different in their activity and geometry. 17P was observed, for 30 ks right after its major outburst, on 2007 October 31 (10:07 UT), and comet 8P/Tuttle was observed in 2008 January for 47 ks. During the two Chandra observations, 17P was producing at least 100 times more water than 8P but was 2.2 times further away from the Sun. Also, 17P was at a relatively high solar latitude (+19fdg1) while 8P was observed at a lower solar latitude (3fdg4). The X-ray spectrum of 17P is unusually soft with little significant emission at energies above 500 eV. Depending on our choice of background, we derive a 300-1000 eV flux of 0.5-4.5 × 10-13 erg cm-2 s-1, with over 90% of the emission in the 300-400 eV range. This corresponds to an X-ray luminosity between 0.4 and 3.3 × 1015 erg s-1. However, we cannot distinguish between this significant excess emission and possible instrumental effects, such as incomplete charge transfer across the CCD. 17P is the first comet observed at high latitude during solar minimum. Its lack of X-rays in the 400-1000 eV range, in a simple picture, may be attributed to the polar solar wind, which is depleted in highly charged ions. 8P/Tuttle was much brighter, with an average count rate of 0.20 counts s-1 in the 300-1000 eV range. We derive an average X-ray flux in this range of 9.4 × 10-13 erg cm-2 s-1 and an X-ray luminosity for the comet of 1.7 × 1014 erg s-1. The light curve showed a dramatic decrease in flux of over 60% between observations on January 1 and 4. When comparing outer regions of the coma to inner regions, its spectra showed a decrease in ratios of C VI/C V, O VIII/O VII, as predicted by recent solar wind charge exchange (SWCX) emission models. There are remarkable differences between the X-ray emission from these two comets, further demonstrating the qualities of cometary X-ray observations, and SWCX emission in general as a means of remote diagnostics of the interaction of astrophysical plasmas.

  3. The shape of the Venusian bow shock at solar minimum and maximum: Revisit based on VEX observations

    NASA Astrophysics Data System (ADS)

    Shan, Lican; Lu, Quanming; Mazelle, Christian; Huang, Can; Zhang, Tielong; Wu, Mingyu; Gao, Xinliang; Wang, Shui

    2015-05-01

    Several factors control the bow shock position at Venus, including short-term period responses (solar wind dynamic pressure) and long-term period variations (solar activity). Based on Venus Express (VEX) observations, we revisit the influence of solar activity on the Venusian bow shock location, by accurately determining not only the shock terminator distance but also the subsolar point with a three-parameter fit (TPF) method. At the same time, VEX covers a larger range of solar zenith angles (SZA) at the Venusian bow shock (from about 10 to 135 degrees) than the Pioneer Venus Orbiter (PVO) spacecraft. Fitting results display that the Venusian bow shock is farther away from Venus at solar maximum than at solar minimum. The subsolar stand-off distance increases from 1.364 planetary radii at solar minimum to 1.459RV at solar maximum, while the terminator shock distance changes from 2.087RV to 2.146RV. Inspection of the bow shock and the induced magnetosphere boundary (IMB) locations clearly shows a positive correlation for every orbit, while the average bow shock location is not responsive to changes in the solar wind dynamic pressure.

  4. Polar Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

    2010-01-01

    Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radioheliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approximately 250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

  5. Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum in Microwaves

    NASA Technical Reports Server (NTRS)

    Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

    2011-01-01

    Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radio-heliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approx.250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

  6. The Sun's X-ray Emission During the Recent Solar Minimum

    NASA Astrophysics Data System (ADS)

    Sylwester, Janusz; Kowalinski, Mirek; Gburek, Szymon; Siarkowski, Marek; Kuzin, Sergey; Farnik, Frantisek; Reale, Fabio; Phillips, Kenneth J. H.

    2010-02-01

    The Sun recently underwent a period of a remarkable lack of major activity such as large flares and sunspots, without equal since the advent of the space age a half century ago. A widely used measure of solar activity is the amount of solar soft X-ray emission, but until recently this has been below the threshold of the X-ray-monitoring Geostationary Operational Environmental Satellites (GOES). There is thus an urgent need for more sensitive instrumentation to record solar X-ray emission in this range. Anticipating this need, a highly sensitive spectrophotometer called Solar Photometer in X-rays (SphinX) was included in the solar telescope/spectrometer TESIS instrument package on the third spacecraft in Russia's Complex Orbital Observations Near-Earth of Activity of the Sun (CORONAS-PHOTON) program, launched 30 January 2009 into a near-polar orbit. SphinX measures X-rays in a band similar to the GOES longer-wavelength channel.

  7. Terrestrial exospheric hydrogen density distributions under solar minimum and solar maximum conditions observed by the TWINS stereo mission

    NASA Astrophysics Data System (ADS)

    Zoennchen, J. H.; Nass, U.; Fahr, H. J.

    2015-03-01

    Circumterrestrial Lyman-? column brightness observations above 3 Earth radii (Re) have been used to derive separate 3-D neutral hydrogen density models of the Earth's exosphere for solar minimum (2008, 2010) and near-solar-maximum (2012) conditions. The data used were measured by Lyman-? detectors (LAD1/2) onboard each of the TWINS satellites from very different orbital positions with respect to the exosphere. Exospheric H atoms resonantly scatter the near-line-center solar Lyman-? flux at 121.6 nm. Assuming optically thin conditions above 3Re along a line of sight (LOS), the scattered LOS-column intensity is proportional to the LOS H-column density. We found significant differences in the density distribution of the terrestrial exosphere under different solar conditions. Under solar maximum conditions we found higher H densities and a larger spatial extension compared to solar minimum. After a continuous, 2-month decrease in (27 day averaged) solar activity, significantly lower densities were found. Differences in shape and orientation of the exosphere under different solar conditions exist. Above 3 Re, independent of solar activity, increased H densities appear on the Earth's nightside shifted towards dawn. With increasing distance (as measured at 8Re) this feature is shifted westward/duskward by between -4 and -5° with respect to midnight. Thus, at larger geocentric distance the exosphere seems to be aligned with the aberrated Earth-solar-wind line, defined by the solar wind velocity and the orbital velocity of the Earth. The results presented in this paper are valid for geocentric distances between 3 and 8Re.

  8. 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.

  9. Unraveling STIM2 function.

    PubMed

    López, Esther; Salido, Ginés M; Rosado, Juan A; Berna-Erro, Alejandro

    2012-12-01

    The discovery of molecular players in capacitative calcium (Ca(2+)) entry, also referred to as store-operated Ca(2+) entry (SOCE), supposed a great advance in the knowledge of cellular mechanisms of Ca(2+) entry, which are essential for a broad range of cellular functions. The identification of STIM1 and STIM2 proteins as the sensors of Ca(2+) stored in the endoplasmic reticulum unraveled the mechanism by which depletion of intracellular Ca(2+) stores is communicated to store-operated Ca(2+) channels located in the plasma membrane, triggering the activation of SOCE and intracellular Ca(2+)-dependent signaling cascades. Initial studies suggested a dominant function of STIM1 in SOCE and SOCE-dependent cellular functions compared to STIM2, especially those that participate in immune responses. Consequently, most of the subsequent studies focused on STIM1. However, during the last years, STIM2 has been demonstrated to play a more relevant and complex function than initially reported, being even important to sustain normal life in mice. These studies have led to reconsider the role of STIM2 in SOCE and its relevance in cellular physiology. This review is intended to summarize and provide an overview of the current data available about this exciting isoform, STIM2, and its actual position together with STIM1 in the mechanism of SOCE. PMID:22477146

  10. Longitudinal and seasonal dependence of nighttime equatorial plasma density irregularities during solar minimum detected on the C/NOFS satellite

    NASA Astrophysics Data System (ADS)

    Dao, E.; Kelley, M. C.; Roddy, P.; Retterer, J.; Ballenthin, J. O.; de La Beaujardiere, O.; Su, Y.-J.

    2011-05-01

    During the night in the F region about the equator, plasma density depletions form, causing scintillation. In April 2008, the Communications/Navigation Outage Forecasting System (C/NOFS) satellite developed by the Air Force Research Laboratory was launched to predict ionospheric scintillation. Using its Planar Langmuir Probe (PLP), C/NOFS is capable of measuring in situ ion density within the F region over the equator. Plasma irregularities are found regularly during the night. We examine how these irregularities depend on longitude, latitude, and season. The most significant observations from this study are longitudinal structures in which these irregularities most frequently occur. Since similar structure has been found in diurnal tides, we conclude that lower atmospheric tides may play a strong role in determining the amplitude of equatorial irregularities, at least during low solar minimum conditions when the presented observations were made. We propose that this link is likely related to the generation of zonal electric fields by the E-region dynamo.

  11. Seasonal and longitudinal variations of the solar quiet current system during solar minimum determined by CHAMP satellite magnetic field observations

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.; Forbes, J. M.; Richmond, A. D.

    2010-12-01

    Vector magnetometer observations from the CHAllenging Mini-satellite Payload (CHAMP) satellite are used to determine the solar quiet (Sq) current system during the recent solar minimum. Observations from 2006-2008 are combined and after removal of a main field model and accounting for field aligned currents, the longitudinal and seasonal variation of the Sq currents are determined. Comparison with Sq currents derived from ground-based magnetometers in the European/African longitude sector reveals similar amplitudes and seasonal variations, indicating that CHAMP observations can reliably determine the Sq current system. The seasonal variation is consistent with prior observations with the largest currents occurring around the equinoxes. Significant longitudinal variations are also observed and they exhibit seasonal variability. During Northern Hemisphere summer the predominant structure is a wave-1 feature. During the remainder of the year, wave-3 and wave-4 longitudinal structures dominate. Variations in tidal winds due to nonmigrating tides may influence the dynamo generated electric fields and currents, leading to the observed Sq current system longitudinal variations. The present study represents the first time that satellite magnetic field observations have been used to determine the Sq current system. Furthermore, the use of satellite observations allows for the first determination of the complete longitudinal variations of the Sq current system.

  12. Polar cap ionosphere and thermosphere during the solar minimum period: EISCAT Svalbard radar observations and GCM simulations

    NASA Astrophysics Data System (ADS)

    Fujiwara, Hitoshi; Nozawa, Satonori; Maeda, Sawako; Ogawa, Yasunobu; Miyoshi, Yasunobu; Jin, Hidekatsu; Shinagawa, Hiroyuki; Terada, Kaori

    2012-06-01

    The IPY long-run data were obtained from the European Incoherent Scatter Svalbard radar (ESR) observations during March 2007 and February 2008. Since the solar and geomagnetic activities were quite low during the period, this data set is extremely helpful for describing the basic states (ground states) of the thermosphere and ionosphere in the polar cap region. The monthly-averaged ion temperatures for 12 months show similar local time (or UT) variations to each other. The ion temperatures also show significant seasonal variations. The amplitudes of the local time and seasonal variations observed are much larger than the ones predicted by the IRI-2007 model. In addition, we performed numerical simulations with a general circulation model (GCM), which covers all the atmospheric regions, to investigate variations of the neutrals in the polar thermosphere. The GCM simulations show significant variations of the neutral temperature in the polar region in comparison with the NRLMSISE-00 empirical model. These results indicate that both the ions and neutrals would show larger variations than those described by the empirical models, suggesting significant heat sources in the polar cap region even under solar minimum and geomagnetically quiet conditions.

  13. Differences in the winter-summer and diurnal anomalous variations of NmF2 over Millstone Hill and Argentine Islands at solar minimum and maximum

    Microsoft Academic Search

    Anatoli Pavlov; Nadezhda Pavlova; Anatoli Shevnin

    2008-01-01

    We present a comparison between the winter and summer geomagnetically quiet F2-layer peak electron density, NmF2, and peak altitude, hmF2, at solar minimum and maximum using the Millstone Hill radar data, the ionosonde data from Argentine Islands (which location is approximately conjugate to the Millstone Hill location), and a one-dimensional time-dependent theoretical model of the mid-latitude ionosphere and plasmasphere. The

  14. Study of maximum electron density N mF 2 at Karachi and Islamabad during solar minimum (1996) and solar maximum (2000) and its comparison with IRI

    Microsoft Academic Search

    M. Ayub; S. Iqbal; M. A. Ameen; B. W. Reinisch

    2009-01-01

    The monthly hourly medians of maximum electron density, NmF2, at two Pakistani ionospheric stations, Karachi and Islamabad, have been determined for solar minimum (1996) and solar maximum (2000) and compared with IRI predictions using the URSI coefficients. At night and pre-noon period the NmF2 values at both stations are almost equal during the 2years. However, at post-noon the values at

  15. Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum determined by CHAMP satellite magnetic field observations

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.; Forbes, J. M.; Richmond, A. D.

    2011-04-01

    Vector magnetometer observations from the Challenging Minisatellite Payload (CHAMP) satellite are used to determine the solar quiet (Sq) current system during the recent solar minimum. Observations from 2006 to 2008 are combined, and after removal of a main field model and accounting for field-aligned currents, the longitudinal and seasonal variation of the Sq currents are determined through the method of spherical harmonic analysis. Comparison with Sq currents derived from ground-based magnetometers in the African/European longitude sector reveals similar amplitudes and seasonal variations, indicating that the CHAMP observations can reliably determine the Sq current system. The seasonal variation is consistent with prior observations during solar minimum conditions and in the Northern Hemisphere exhibits a primarily annual variation with peak currents during local summer. The seasonal variation in the Southern Hemisphere is characterized by a semiannual variation with the maxima occurring around the equinoxes. Significant longitudinal variations are also observed, and they display a seasonal variability. During Northern Hemisphere summer, the predominant feature at local noon is a wave number 1 variation in longitude. During the remainder of the year, a wave 3 longitudinal structure is observed at this local time. The longitudinal variations are considered to be due to a combination of the orientation and strength of the geomagnetic field as well as the tidal winds in the lower thermosphere. Variations in tidal winds due to nonmigrating tides may influence the dynamo-generated electric fields and currents, resulting in the observed longitudinal variations of the Sq current function.

  16. Ionospheric total electron content, thermospheric emission and and stratospheric temperature dynamics during the SC23 deep solar minimum: 2008-2009

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Tsurutani, B.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Ao, C. O.; Runge, T.

    2011-12-01

    We will study external driving of the ionosphere-thermosphere and stratosphere systems during the deep solar minimum: the WHI 2008 interval as well as 2009. We report evidence of prompt penetrating interplanetary electric fields (PPEFs) into the ionosphere during CIR/HSS intervals for both 2008 and 2009. Daily averages of vertical daytime total electron content (VTEC) derived from GPS measurements from the JPL database are studied. VTEC data show the well-known semi-annual anomalies especially prominent in the low latitude ionosphere. Low- to middle-latitude VTEC variability is shown to coincide with PPEF events. Somewhat decreased variability is found around the solstices. CIR/HSS intervals are typically characterized by high energy deposition into the auroral regions through increased Joule heating and particle precipitation. Elevated nitric oxide densities and temperatures in the thermosphere lead to variations in corresponding infrared emission. We present measurements from SABER/TIMED of NO and CO2 emissions during 2008-2009 to illustrate efficient thermospheric response to moderate external driving and I-T dynamics throughout the time interval. We will discuss solar and geomagnetic activity influences on climate by analyzing lower stratospheric temperatures using GPS radio occultation measurements from CHAMP. Results for the deep solar minimum will be compared with the declining phase and solar maximum conditions.

  17. The Neutral Exosphere of the Earth Between Solar Minimum (2008-2010) and Solar Maximum (2012) Conditions Using Twins Lyman-Alpha Observations

    NASA Astrophysics Data System (ADS)

    Nass, U.; Zoennchen, J.; Fahr, H. J.

    2014-12-01

    The exospheric,neutral hydrogen (H) continuously appears as a source of Lyman-alpha resonance radiation at 121.5 nm. The process behind this is the resonant backscattering of solar Lyman-alpha radiation from exospheric hydrogen. Along a line of sight (LOS) above 3 Earth radii geocentric distance, the backscattered Lyman-alpha intensity is proportional to the H-column density (optically thin conditions). Based on a large number of LOSs the 3D exospheric H-density distribution is derived from exospheric Lyman-alpha observations. In the presented analysis we are using data from 2008-2010 (solar minimum) and 2012 (near solar maximum) from the Lyman-alpha detectors (LADs) on the Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission to model the 3D hydrogen density distribution under different solar conditions. We discuss the methods, the datasets, a recalibration procedure, and present structural differences of the 3D exospheric H-density distributions at solar minimum (2008-2010) and near solar maximum (2012) above 3 Earth radii.

  18. 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.

  19. AN XMM-NEWTON STUDY OF THE CORONAE OF 2 CORONAE BOREALIS

    E-print Network

    Audard, Marc

    AN XMM-NEWTON STUDY OF THE CORONAE OF 2 CORONAE BOREALIS Jin A. Suh and Marc Audard1 Columbia present results of XMM-Newton Guaranteed Time observations of the RS CVn binary 2 Coronae Borealis headinggs: stars: activity -- stars: coronae -- stars: flare -- stars: individual (2 Coronae Borealis

  20. Optical fiber sensing of corona discharges

    Microsoft Academic Search

    Gerry A. Woolsey; D. W. Lamb; M. C. Woerner

    1991-01-01

    Coronas are localized discharges which occur adjacent to high voltage points in gases at around atmospheric pressure. A corona may be in the form of a steady glow or it may be pulsing. Ions produced in the corona rapidly move away from the point, transfer momentum to the neutral gas molecules, and thus generate a corona wind with speeds of

  1. 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.

  2. Radiation Measured with Different Dosimeters for ISS-Expedition 18-19/ULF2 on Board International Space Station during Solar Minimum

    NASA Technical Reports Server (NTRS)

    Zhou, Dazhuang; Gaza, R.; Roed, Y.; Semones, E.; Lee, K.; Steenburgh, R.; Johnson, S.; Flanders, J.; Zapp, N.

    2010-01-01

    Radiation field of particles in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). GCR are modulated by solar activity, at the period of solar minimum activity, GCR intensity is at maximum and the main contributor for space radiation is GCR. At present for space radiation measurements conducted by JSC (Johnson Space Center) SRAG (Space Radiation Analysis Group), the preferred active dosimeter sensitive to all LET (Linear Energy Transfer) is the tissue equivalent proportional counter (TEPC); the preferred passive dosimeters are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET as well as CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET. For the method using passive dosimeters, radiation quantities for all LET can be obtained by combining radiation results measured with TLDs/OSLDs and CR-39 PNTDs. TEPC, TLDs/OSLDs and CR-39 detectors were used to measure the radiation field for the ISS (International Space Station) - Expedition 18-19/ULF2 space mission which was conducted from 15 November 2008 to 31 July 2009 - near the period of the recent solar minimum activity. LET spectra (differential and integral fluence, absorbed dose and dose equivalent) and radiation quantities were measured for positions TEPC, TESS (Temporary Sleeping Station, inside the polyethylene lined sleep station), SM-P 327 and 442 (Service Module - Panel 327 and 442). This paper presents radiation LET spectra measured with TEPC and CR-39 PNTDs and radiation dose measured with TLDs/OSLDs as well as the radiation quantities combined from results measured with passive dosimeters.

  3. Radiation Measured with Different Dosimeters for ISS-Expedition 18-19/ULF2 on Board International Space Station during Solar Minimum

    NASA Astrophysics Data System (ADS)

    Zhou, Dazhuang

    Radiation field of particles in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). GCR are modulated by solar activity, at the period of solar minimum activity, GCR intensity is at maximum and the main contributor for space radiation is GCR. At present for space radiation measurements conducted by JSC (Johnson Space Center) -SRAG (Space Radiation Analysis Group), the preferred active dosimeter sensitive to all LET (Linear Energy Transfer) is the tissue equivalent proportional counter (TEPC); the preferred passive dosimeters are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET as well as CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET. For the method using passive dosimeters, radiation quantities for all LET can be obtained by combining radiation results measured with TLDs/OSLDs and CR-39 PNTDs. TEPC, TLDs/OSLDs and CR-39 detectors were used to measure the radiation field for the ISS (International Space Station) -Expedition 18-19/ULF2 space mission which was conducted from 15 November 2008 to 31 July 2009 -near the period of the recent solar minimum activity. LET spectra (differential and integral fluence, absorbed dose and dose equivalent) and radiation quantities were measured for positions TEPC, TESS (Temporary Sleeping Station, inside the polyethylene lined sleep station), SM-P 327 and 442 (Service Module -Panel 327 and 442). This paper presents radiation LET spectra measured with TEPC and CR-39 PNTDs and radiation dose measured with TLDs/OSLDs as well as the radiation quantities combined from results measured with passive dosimeters.

  4. Topographic Corona Gravity Survey Results

    NASA Technical Reports Server (NTRS)

    Comstock, R. L.; Smrekar, S. E.; Anderson, F. S.

    2001-01-01

    We present estimates for elastic and crustal thickness obtained from a gravity survey of Venusian topographic coronae, and characterize advantages and disadvantages for generating spectral admittance. Additional information is contained in the original extended abstract.

  5. Structure and Dynamics of the 2010 July 11 Eclipse White-light Corona

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moon's shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83 minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loops and radial-oriented thin streamers, a coronal mass ejection, and a puzzling "curtain-like" object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASA's Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESA's PRoject for Onboard Autonomy, and the Naval Research Laboratory's Large Angle and Spectrometric Coronagraph on ESA's Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 R sun, for this rising phase of the solar-activity cycle.

  6. STRUCTURE AND DYNAMICS OF THE 2010 JULY 11 ECLIPSE WHITE-LIGHT CORONA

    SciTech Connect

    Pasachoff, J. M. [Williams College-Hopkins Observatory, Williamstown, MA 01267-2565 (United States); Rusin, V.; Saniga, M. [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia)

    2011-06-20

    The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moon's shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83 minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loops and radial-oriented thin streamers, a coronal mass ejection, and a puzzling 'curtain-like' object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASA's Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESA's PRoject for Onboard Autonomy, and the Naval Research Laboratory's Large Angle and Spectrometric Coronagraph on ESA's Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 Rs{sub un}, for this rising phase of the solar-activity cycle.

  7. Corona Discharge Influence on Moulds

    NASA Astrophysics Data System (ADS)

    Scholtz, Vladimir

    2004-09-01

    It is known that the electric discharge has bacteriocid effect. We are interesting on influence of corona discharge on moulds and searching for it's fungicide effect. In this work we study the mould penicillium digitatum by using an easy apparatus, where may be situated two measured samples. One in the burning corona discharge and one in the area with ozone generated by this corona only. We expose the spores of penicillium digitatum on a metal plate and on a cultivating medium on cca 0.01mA, 5kV corona discharge and on generated ozone only for time cca two days. It is the time needed for sprouting of spores and growing of they to a visible size. The pilot results show, that the ozone generated by the corona discharge has none or very low influence on the sprouting and growing of the spores. Direct corona discharge inhibit the sprouting only, but does not kill the spores. In next experiments we will try to find some minimum inhibit and killing concentration of ozone and try to expose the sprout inhibition.

  8. 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.

  9. Insights into corona formation through statistical analyses

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    Statistical analysis of an expanded database of coronae on Venus indicates that the populations of Type 1 (with fracture annuli) and 2 (without fracture annuli) corona diameters are statistically indistinguishable, and therefore we have no basis for assuming different formation mechanisms. Analysis of the topography and diameters of coronae shows that coronae that are depressions, rimmed depressions, and domes tend to be significantly smaller than those that are plateaus, rimmed plateaus, or domes with surrounding rims. This is consistent with the model of Smrekar and Stofan [1997] and inconsistent with predictions of the spreading drop model of Koch and Manga [1996]. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occurring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronae are found predominantly as isolated features in the plains. Coronae at hot spot rises tend to be significantly larger than coronae in other settings, consistent with a hotter upper mantle at hot spot rises and their active state.

  10. Topological Structure of the Magnetic Solar Corona

    NASA Astrophysics Data System (ADS)

    Maclean, R. C.

    2007-12-01

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

  11. Survey of the spectral properties of turbulence in the solar wind, the magnetospheres of Venus and Earth, at solar minimum and maximum

    NASA Astrophysics Data System (ADS)

    Echim, Marius M.

    2014-05-01

    In the framework of the European FP7 project STORM ("Solar system plasma Turbulence: Observations, inteRmittency and Multifractals") we analyze the properties of turbulence in various regions of the solar system, for the minimum and respectively maximum of the solar activity. The main scientific objective of STORM is to advance the understanding of the turbulent energy transfer, intermittency and multifractals in space plasmas. Specific analysis methods are applied on magnetic field and plasma data provided by Ulysses, Venus Express and Cluster, as well as other solar system missions (e.g. Giotto, Cassini). In this paper we provide an overview of the spectral properties of turbulence derived from Power Spectral Densities (PSD) computed in the solar wind (from Ulysses, Cluster, Venus Express) and at the interface of planetary magnetospheres with the solar wind (from Venus Express, Cluster). Ulysses provides data in the solar wind between 1992 and 2008, out of the ecliptic, at radial distances ranging between 1.3 and 5.4 AU. We selected only those Ulysses data that satisfy a consolidated set of selection criteria able to identify "pure" fast and slow wind. We analyzed Venus Express data close to the orbital apogee, in the solar wind, at 0.72 AU, and in the Venus magnetosheath. We investigated Cluster data in the solar wind (for time intervals not affected by planetary ions effects), the magnetosheath and few crossings of other key magnetospheric regions (cusp, plasma sheet). We organize our PSD results in three solar wind data bases (one for the solar maximum, 1999-2001, two for the solar minimum, 1997-1998 and respectively, 2007-2008), and two planetary databases (one for the solar maximum, 2000-2001, that includes PSD obtained in the terrestrial magnetosphere, and one for the solar minimum, 2007-2008, that includes PSD obtained in the terrestrial and Venus magnetospheres and magnetosheaths). In addition to investigating the properties of turbulence for the minimum and maximum of the solar cycle we also analyze the spectral similarities and differences between fast and slow wind turbulence. We emphasize the importance of our data survey and analysis in the context of understanding the solar wind turbulence, the exploitation of data bases and as a first step towards developing a (virtual) laboratory for studying solar system plasma turbulence. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.

  12. Hot oxygen corona of Mars

    SciTech Connect

    Ip, W.H.

    1988-10-01

    Electron dissociative recombination of O2(+) ions in the Venus ionosphere, which may be an important source of suprathermal atomic oxygen, is presently considered as a factor in the Mars exosphere; due to the weaker surface gravitational attraction of Mars, a hot oxygen corona thus formed would be denser than that of Venus at altitudes greater than 2000 km despite Mars' lower ionospheric content. If such an extended oxygen corona does exist on Mars, its collisional interaction with Phobos would lead to the formation of an oxygen gas torus whose average number density is of the order of only 1-2/cu cm along the Phobos orbit. 51 references.

  13. WINDS IN CORONAE BOREALIS STARS Geoffrey Clayton,

    E-print Network

    Bianchi, Luciana

    WINDS IN CORONAE BOREALIS STARS Geoffrey Clayton, 1 Geballe, Luciana Bianchi Received February accepted 2003 ABSTRACT present spectroscopic observations the i #10830 line Coronae Borealis (RCB) stars R Coronae Borealis (RCB) stars small group of hydrogen­deficient, carbon­rich supergiants

  14. Pulsed periodic corona discharges for biological decontamination

    Microsoft Academic Search

    I. V. Timoshkin; M. Maclean; S. J. MacGregor; J. G. Anderson; M. P. Wilson; T. Wang; M. J. Given

    2011-01-01

    The present paper explores the possibilities of using impulsive and steady-state corona discharges for biodecontamination operations. A high tension tubular corona electrode was stressed with positive or negative DC voltage with magnitude up to 26 kV, and a grounded mesh was used as an opposite electrode. Different operational regimes of this corona generator were investigated for the production of ozone

  15. Mutual Event Observations of Io's Sodium Corona

    Microsoft Academic Search

    M. H. Burger; N. M. Schneider; I. de Pater; M. E. Brown; A. H. Bouchez; L. M. Trafton; Y. Sheffer; E. S. Barker; A. Mallama

    2001-01-01

    We have measured the column density profile of Io's sodium corona using 10 mutual eclipses between the Galilean satellites. This approach circumvents the problem of spatially resolving Io's corona directly from Io's bright continuum in the presence of atmospheric seeing and telescopic scattering. The primary goal is to investigate the spatial and temporal variations of Io's corona. Spectra from the

  16. Nonlocal Unified Type-I and Type-II Model of the Low-Latitude E-region Irregularities at Solar Minimum and Solar Maximum

    NASA Astrophysics Data System (ADS)

    Hassan, E.; Horton, W.; Smolyakov, A.; Litt, S.; Hatch, D.

    2013-12-01

    The onset of the small-scale irregularities at the E-region are due to both Farley-Buneman and gradient-drift instabilities. Those instabilities were detected at Jicamarca Radar Observatory at 50-MHz and differentiated according their Doppler-Shifts and called Type-I and Type-II, respectively. We developed a nonlocal unified model to study the characteristics of these two instabilities in the linear a nonlinear regimes. The simulation results are based on data of the charged-carrier densities from IRI2012, neutral densities from NMSIS00, electric potential from TIEGCM-1.94, and magnetic field from IGRF-like model. In this model, which based on quasi-neutrality and isothermal approximations, we study the perturbations in the electron carrier density, the electric potential, and ion velocity to show how the instabilities are evolving due to the mode-interactions among these three fields. We compare the simulation results of this model under the conditions of solar minimum and solar maximum. W.H. is supported by NSF Grant 0964692 to the University of Texas at Austin. W.H. and A. S. are partially supported by Aix-Marseille/CNRS and the International Space Science Institute in Bern, Switzerland through the Grant on on "Vortices and zonal winds in planetary atmospheres/ionospheres."

  17. Solar corona electron density distribution

    Microsoft Academic Search

    P. B. Esposito; Peter Edenhofer; Ernst Lueneburg

    1980-01-01

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

  18. Ultraviolet Corona Discharge Detection Based on Photomultiplier

    NASA Astrophysics Data System (ADS)

    Yongli, Liao; Liming, Wang; Ke, Wang; Canlin, Wang; Zhicheng, Guan

    High voltage equipments, especially polymer insulators may be getting into aging conditions due to the existence of corona discharge on the surface after a long term of running, which would accelerate the deterioration of the surface insulation performance, and even make equipments step into calamity ultimately. So it is significant to detect corona discharge on surface to ensure insulators' stable running. This paper presents the development of a novel corona discharge detection system based on photomultiplier tube (PMT), which has good functions of distance detection for corona discharge in determined region from surface of high voltage equipment and corona characteristics data analysis. In the verification experiments, it was shown that UV corona light can be also taken as characteristic for detecting corona discharge, other than corona leakage current detection, and a linear relationship was shown between the light magnitude and the current magnitude. Furthermore, mean peak value and number of pulses whose peak value is above threshold are extracted from the basic data, which can be used to quantify the development of corona discharge. The results of investigation on polymer insulators suggested that detection of the region between metal end fitting and first shed should be emphasized. The measurements of corona discharge distribution along insulators can be used to learn about the degradation conditions. Detection of polymer insulators in lab and field inspection experience are both soundly verifying the usefulness of the corona detection system.

  19. Unraveling the Definitional Threads: Mentoring and Academe.

    ERIC Educational Resources Information Center

    Mertz, Norma T.

    This paper proposes a conceptual framework of mentoring for the academic context that will begin to unravel the confusing and conflicting definitions of mentoring that limit dialogue across disciplinary contexts. Two analytical concepts are suggested as a way to designate the common relationships of role model, advisor, and mentor in academe and…

  20. Effects of sporadic E-layer characteristics on spread-F generation in the nighttime ionosphere near a northern equatorial anomaly crest during solar minimum

    NASA Astrophysics Data System (ADS)

    Lee, C. C.; Chen, W. S.

    2015-06-01

    This study is to know how the characteristics of sporadic E-layer (Es-layer) affect the generation of spread-F in the nighttime ionosphere near the crest of equatorial ionization anomaly during solar minimum. The data of Es-layer parameters and spread-F are obtained from the Chungli ionograms of 1996. The Es-layer parameters include foEs (critical frequency of Es-layer), fbEs (blanketing frequency of Es-layer), and ?f (?foEs-fbEs). Results show that the nighttime variations of foEs and fbEs medians (?f medians) are different from (similar to) that of the occurrence probabilities of spread-F. Because the total number of Es-layer events is greater than that of spread-F events, the comparison between the medians of Es-layer parameters and the occurrence probabilities of spread-F might have a shortfall. Further, we categorize the Es-layer and spread-F events into each frequency interval of Es-layer parameters. For the occurrence probabilities of spread-F versus foEs, an increasing trend is found in post-midnight of all three seasons. The increasing trend also exists in pre-midnight of the J-months and in post-midnight of all seasons, for the occurrence probabilities of spread-F versus ?f. These demonstrate that the spread-F occurrence increases with increasing foEs and/or ?f. Moreover, the increasing trends indicate that polarization electric fields generated in Es-layer assist to produce spread-F, through the electrodynamical coupling of Es-layer and F-region. Regarding the occurrence probabilities of spread-F versus fbEs, the significant trend only appears in post-midnight of the E-months. This implies that fbEs might not be a major factor for the spread-F formation.

  1. Periodic solar wind forcing due to recurrent coronal holes during 1996-2009 and its impact on Earth's geomagnetic and ionospheric properties during the extreme solar minimum

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Liu, C. H.; Su, S.-Y.

    2010-12-01

    Periodicities in the area of coronal hole (CH) regions on the solar disk and solar wind (SW) high-speed streams (HSSs) have been studied, for the first time, during complete solar cycle 23 (SC 23) from 1996 to 2009 using solar EUV image data from the Solar and Heliospheric Observatory and STEREO satellites and ACE solar wind-magnetic data. Both the SW velocity and the area of CH regions consistently exhibit large values during the declining phase and the minimum of SC23 (2003-2009) due to equatorward extended holes and/or low-latitude isolated holes. Further, the SW velocity and CH area exhibit a greater tendency for subharmonic (13.5 and 9 day) periodicities during the declining phase and solar minimum. The response of Earths' geomagnetic and ionospheric properties to these periodicities associated with corotating interaction regions in SW HSSs is studied, with a focus on the extremely low-solar-activity period of 2008. Subharmonic oscillations in both day- and nightside ionospheric electron density are found to correlate well with oscillations in SW and Kp during 2008. The topside ionospheric response (above 350 km) appears to be dominated by changes in the plasma temperature and/or scale height and exhibits concurrent enhancements with the oscillations in geomagnetic activity during both day- and nighttime. However, the electron density response at altitudes between 200 and 350 km is dominated by changes in the neutral composition and exhibits significant latitudinal, local time, and seasonal variations. The results are discussed in light of equatorward wind perturbations during enhanced geomagnetic activity and summer-to-winter transequatorial neutral wind patterns.

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

    SciTech Connect

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

    2013-08-10

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

  3. Nebula around R Corona Borealis

    E-print Network

    Rao, N Kameswara

    2011-01-01

    The star R Corona Borealis (R CrB) shows forbidden lines of [O II], [N II], and [S II] during the deep minimum when the star is fainter by about 8 to 9 magnitudes from normal brightness, suggesting the presence of nebular material around it. We present low and high spectral resolution observations of these lines during the ongoing deep minimum of R CrB, which started in July 2007. These emission lines show double peaks with a separation of about 170 km/s. The line ratios of [S II] and [O II] suggest an electron density of about 100 cm$^{-3}$. We discuss the physical conditions and possible origins of this low density gas. These forbidden lines have also been seen in other R Coronae Borealis stars during their deep light minima and this is a general characteristic of these stars, which might have some relevance to their origins.

  4. Turbulence in the Solar Corona

    E-print Network

    Steven R. Cranmer

    2007-06-19

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

  5. The morphology of streamer coronas

    SciTech Connect

    Vitello, P.A.; Penetrante, B.M.; Bardsley, J.N. [Lawrence Livermore National Lab., CA (United States)

    1992-12-01

    Streamer coronas are of interest due to their application to pollution control devices. A streamer coronal discharge produces energetic electrons which, through dissociation and ionization processes, generate active radicals that in turn react with toxic molecules. The morphology of streamer coronas determines the energy distribution of the electrons produced. Streamers propagate due to a highly non-linear space charge driven ionization wave. Because of the complexity of the equations describing streamer dynamics, most of the numerical simulations have been restricted to one (longitudinal) spatial dimension. Some low resolution 2-D simulations have been previously performed, but so far have been restricted to plane-parallel electrode configurations. The authors have developed multi-dimensional streamer models that can be applied to arbitrarily shaped electrode structures. Their models have generated the first multi-dimensional fully resolved streamers which form self-consistent radial structure. They have applied these codes to study some of the issues related to finding the optimum working conditions for streamer corona reactors. Their results show that the radial components of the electron flow and the space charge field are very important in providing an accurate picture of the streamer morphology, especially near the highly stressed electrode.

  6. Tectonics of Neyterkob corona on Venus

    NASA Technical Reports Server (NTRS)

    Kauhanen, K.

    1993-01-01

    Neyterkob double corona (50 deg N 202 deg) presents an area of corona-related interfering tectonic patterns which are formed in different phases of evolution of the corona and modified by regional stresses. Analyzing the patterns can reveal something about the coronal formation. Tectonic features form distinct units on topographic depressions, slopes, and volcanic flows extending over one radius of the corona. A remarkable amount of compressional features were found near the rim and related to interaction between adjacent coronae. Radial extension was mainly observed on a peculiar NE-SW trending high crossing the corona. Concentric fractures were found to the east partly connected to the lithospheric flexure. Tectonic features indicate movements of volcanic activity and modification of the area by more regional stresses.

  7. Towards unraveling the photochemistry of TATB

    Microsoft Academic Search

    M. R. Manaa; R. D. Schmidt; G. E. Overturf; B. E. Watkins; L. E. Fried; J. R. Kolb

    2002-01-01

    A combined theoretical and experimental chemical analysis has been conducted to unravel the mechanism, underlying the color change of yellow 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) to green upon UV irradiation. There is a strong evidence to show, for the first time, that the process is photochemical in nature and due to the formation of the mono nitroso derivative. We have identified a chemical

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

    E-print Network

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

    2008-02-01

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

  9. Laser interferometry of SF6 coronas

    Microsoft Academic Search

    D W Lamb; G A Woolsey

    1995-01-01

    Radial profiles of gas density have been measured in positive and negative SF6 coronas at 101.3 kPa using optical interferometry. The results show that, in DC SF6 coronas, the electrical power input is confined to a small volume around the point electrode and energy transfer by the corona wind efficiently dissipates the heat generated there throughout the discharge chamber. Consequently,

  10. 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.

  11. Improved Method for Calculating DC Corona Losses

    Microsoft Academic Search

    Mohammed Khalifa; Mazen Abdel-Salam

    1974-01-01

    Existing methods for calculating corona losses on monopolar and bipolar dc transmission lines have resorted to the assumption that the space charge of corona does not affect the direction of the electrostatic field. This assumption was aimed at making the calculations possible. In this report corena loss calculations are made in which this assumption and others are replaced by correlating

  12. System reliability analysis through corona testing

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

    1975-01-01

    A corona vacuum test facility for nondestructive testing of power system components was built in the Reliability and Quality Engineering Test Laboratories at the NASA Lewis Research Center. The facility was developed to simulate operating temperature and vacuum while monitoring corona discharges with residual gases. The facility is being used to test various high-voltage power system components.

  13. System reliability analysis through corona testing

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

    1975-01-01

    In the Reliability and Quality Engineering Test Laboratory at the NASA Lewis Research Center a nondestructive, corona-vacuum test facility for testing power system components was developed using commercially available hardware. The test facility was developed to simulate operating temperature and vacuum while monitoring corona discharges with residual gases. This facility is being used to test various high voltage power system components.

  14. Dynamics of the quiescent solar corona

    Microsoft Academic Search

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

    1978-01-01

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

  15. Parga Chasma: Coronae and Rifting on Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, S. E.; Stofan, E. R.; Buck, W. R.; Martin, P.

    2005-01-01

    The majority of coronae (quasicircular volcano-tectonic features) are found along rifts or fracture belts, and the majority of rifts have coronae [e.g. 1,2]. However, the relationship between coronae and rifts remains unclear [3-6]. There is evidence that coronae can form before, after, or synchronously with rifts [3,4]. The extensional fractures in the rift zones have been proposed to be a result of broad scale upwelling and traction on the lower lithosphere [7]. However, not all rift systems have a significant positive geoid anomaly, as would be expected for an upwelling site [8]. This could be explained if the rifts lacking anomalies are no longer active. Coronae are generally accepted to be sites of local upwelling [e.g. 1], but the observed rifting is frequently not radial to the coronae and extends well beyond the coronae into the surrounding plains. Thus the question remains as to whether the rifts represent regional extension, perhaps driven by mantle tractions, or if the coronae themselves create local thinning and extension of the lithosphere. In the first case, a regional extension model should be consistent with the observed characteristics of the rifts. In the latter case, a model of lithospheric loading and fracturing would be more appropriate. A good analogy may be the propagation of oceanic intraplate volcanoes [9].

  16. Corona-related volcanism on Venus

    NASA Astrophysics Data System (ADS)

    Grindrod, Peter Martin

    This thesis reports the results of a study of volcanic processes at coronae on Venus. The Aglaonice F-Map region has been mapped, and its geological history interpreted, at the full-resolution of Magellan SAR data. Volcanism at coronae is shown to have occurred repeatedly over a protracted period of time, supporting a non-directional style of resurfacing in the F-Map region, and suggesting that corona-related flows may be an important resurfacing mechanism on Venus. It is likely that the magma storage system varies between each corona, with eruption dependent on local conditions such as location of magma body and local stress regime. Numerous flows which can be sourced to coronae, and were previously mapped as plains units, have also been identified. A global survey has revealed 29 volcano/corona 'hybrids', features which resemble both coronae and large volcanoes. Age, magma supply, stress state, thermal gradient and eruption duration are all important factors in determining gross hybrid morphology. It is likely that not all hybrids follow a similar evolutionary path. A detailed study of four selected hybrids is presented and suggests that processes typical of both large volcanoes and coronae have occurred throughout their history, and does not imply evolution from one type of feature into another. The presence of large central depressions and/or topographic rims at the hybrids support the theory that some large volcanoes undergo a sagging process similar to coronae. Study of the depth and extension at large radial graben at four centres of radial fractures is also reported. The inferred levels of hoop strain are too large to be explained by previous models of plume uplift, and a newly applied magma chamber inflation model concludes that dike formation is responsible for the strain at the large radial graben, and that intrusion is an important process at early-phase coronae.

  17. Cosmic radiation in the heliosphere at successive solar minima 4. Modulation of galactic cosmic rays during the three consecutive solar minimum periods of 1977/1978, 1987 and 1997

    NASA Astrophysics Data System (ADS)

    Reinecke, J. P. L.; McDonald, F. B.; Moraal, H.

    2000-06-01

    Extensive data sets have been measured for galactic and anomalous cosmic rays during the past three solar minimum modulation periods of 1977, 1987, and 1997 by various spacecraft at distances ranging from 1 to 66 AU from the Sun. In this paper we investigate the radial, latitudinal, and rigidity dependence of the diffusion mean free paths (?) deduced from galactic helium and hydrogen in the heliosphere and compare these values with those from earlier studies by Reinecke et al. [1993, 1996] and from theoretical calculations by Zank et al. [1997, 1998].

  18. Unraveling Flow Patterns through Nonlinear Manifold Learning

    PubMed Central

    Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

    2014-01-01

    From climatology to biofluidics, the characterization of complex flows relies on computationally expensive kinematic and kinetic measurements. In addition, such big data are difficult to handle in real time, thereby hampering advancements in the area of flow control and distributed sensing. Here, we propose a novel framework for unsupervised characterization of flow patterns through nonlinear manifold learning. Specifically, we apply the isometric feature mapping (Isomap) to experimental video data of the wake past a circular cylinder from steady to turbulent flows. Without direct velocity measurements, we show that manifold topology is intrinsically related to flow regime and that Isomap global coordinates can unravel salient flow features. PMID:24614890

  19. Unraveling the mystery of quantum-dot April 3, 2012

    E-print Network

    . At these tiny dimensions, the rules of quantum physics allow scientists to produce particles with finely tunable- 1 - Unraveling the mystery of quantum-dot blinking April 3, 2012 Unraveling the mystery of quantum-dot blinking Significant progress is being made in understanding the phenomenon of quantum

  20. Tectonic patterns and regional stresses near Venusian coronae

    NASA Astrophysics Data System (ADS)

    Cyr, K. E.; Melosh, H. J.

    1993-04-01

    A stress analysis of tectonic patterns near Venusian coronae is reported. Combined local corona stresses and uniform regional stresses are used to predict patterns of surface tectonic features. The patterns are compared to those of coronae on Magellan images to determine the regional stress and elastic lithospheric thickness about the coronae. Regional stresses of 0.1-0.6 kbar and elastic lithospheric thicknesses of 10 +/- 5 km are estimated for three specific coronae.

  1. Corona Associations and Their Implications for Venus

    USGS Publications Warehouse

    Chapman, M.G.; Zimbelman, J.R.

    1998-01-01

    Geologic mapping principles were applied to determine genetic relations between coronae and surrounding geomorphologic features within two study areas in order to better understand venusian coronae. The study areas contain coronae in a cluster versus a contrasting chain and are (1) directly west of Phoebe Regio (quadrangle V-40; centered at latitude 15??S, longitude 250??) and (2) west of Asteria and Beta Regiones (between latitude 23??N, longitude 239?? and latitude 43??N, longitude 275??). Results of this research indicate two groups of coronae on Venus: (1) those that are older and nearly coeval with regional plains, and occur globally; and (2) those that are younger and occur between Beta, Atla, and Themis Regiones or along extensional rifts elsewhere, sometimes showing systematic age progressions. Mapping relations and Earth analogs suggest that older plains coronae may be related to a near-global resurfacing event perhaps initiated by a mantle superplume or plumes. Younger coronae of this study that show age progression may be related to (1) a tectonic junction of connecting rifts resulting from local mantle upwelling and spread of a quasi-stationary hotspot plume, and (2) localized spread of post-plains volcanism. We postulate that on Venus most of the young, post-resurfacing coronal plumes may be concentrated within an area defined by the bounds of Beta, Atla, and Themis Regiones. ?? 1998 Academic Press.

  2. Positive corona inception voltages and corona currents for air at various pressures and humidities

    Microsoft Academic Search

    Xingming Bian; Liming Wang; J. M. K. Macalpine; Zhicheng Guan; Jianfeng Hui; Yong Chen

    2010-01-01

    The variation of positive dc corona characteristics with air pressure and humidity using a point\\/plane electrode system was studied in a perspex chamber allowing the pressure and humidity to be varied. A method of calculation was developed to determine the corona current for humid air over a range of pressures and humidities in which the effective ionization coefficient was calculated

  3. 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.

  4. RESEARCH ARTICLE Unraveling natural versus anthropogenic effects on genetic

    E-print Network

    Parkinson, Christopher L.

    RESEARCH ARTICLE Unraveling natural versus anthropogenic effects on genetic diversity within by erosion of genetic diversity. However, contemporary genetic diversity may be the legacy of natural processes acting prior to anthropogenic influences. Measurements of genetic diversity from contemporary

  5. Unraveling environmental histories from skeletal diaries --Advances in sclerochronology

    E-print Network

    Schöne, Bernd R.

    Preface Unraveling environmental histories from skeletal diaries -- Advances in sclerochronology and INCREMENTS Research Group, Earth System Science Research Center, Institute of Geosciences, University formed skeletal hard parts provide a means to place the proxy record in a precise temporal context

  6. A Statistical Analysis of Corona Topography: New Insights into Corona Formation and Evolution

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    Extensive mapping of the surface of Venus and continued analysis of Magellan data have allowed a more comprehensive survey of coronae to be conducted. Our updated corona database contains 514 features, an increase from the 326 coronae of the previous survey. We include a new set of 106 Type 2 or stealth coronae, which have a topographic rather than a fracture annulus. The large increase in the number of coronae over the 1992 survey results from several factors, including the use of the full Magellan data set and the addition of features identified as part of the systematic geologic mapping of Venus. Parameters of the population that we have analyzed to date include size and topography.

  7. Complementary analysis of the hard and soft protein corona: sample preparation critically effects corona composition

    NASA Astrophysics Data System (ADS)

    Winzen, S.; Schoettler, S.; Baier, G.; Rosenauer, C.; Mailaender, V.; Landfester, K.; Mohr, K.

    2015-02-01

    Here we demonstrate how a complementary analysis of nanocapsule-protein interactions with and without application media allows gaining insights into the so called hard and soft protein corona. We have investigated how both human plasma and individual proteins (human serum albumin (HSA), apolipoprotein A-I (ApoA-I)) adsorb and interact with hydroxyethyl starch (HES) nanocapsules possessing different functionalities. To analyse the hard protein corona we used sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and a protein quantitation assay. No significant differences were observed with regards to the hard protein corona. For analysis of the soft protein corona we characterized the nanocapsule-protein interaction with isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). DLS and ITC measurements revealed that a high amount of plasma proteins were adsorbed onto the capsules' surface. Although HSA was not detected in the hard protein corona, ITC measurements indicated the adsorption of an HSA amount similar to plasma with a low binding affinity and reaction heat. In contrast, only small amounts of ApoA-I protein adsorb to the capsules with high binding affinities. Through a comparison of these methods we have identified ApoA-I to be a component of the hard protein corona and HSA as a component of the soft corona. We demonstrate a pronounced difference in the protein corona observed depending on the type of characterization technique applied. As the biological identity of a particle is given by the protein corona it is crucial to use complementary characterization techniques to analyse different aspects of the protein corona.Here we demonstrate how a complementary analysis of nanocapsule-protein interactions with and without application media allows gaining insights into the so called hard and soft protein corona. We have investigated how both human plasma and individual proteins (human serum albumin (HSA), apolipoprotein A-I (ApoA-I)) adsorb and interact with hydroxyethyl starch (HES) nanocapsules possessing different functionalities. To analyse the hard protein corona we used sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and a protein quantitation assay. No significant differences were observed with regards to the hard protein corona. For analysis of the soft protein corona we characterized the nanocapsule-protein interaction with isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). DLS and ITC measurements revealed that a high amount of plasma proteins were adsorbed onto the capsules' surface. Although HSA was not detected in the hard protein corona, ITC measurements indicated the adsorption of an HSA amount similar to plasma with a low binding affinity and reaction heat. In contrast, only small amounts of ApoA-I protein adsorb to the capsules with high binding affinities. Through a comparison of these methods we have identified ApoA-I to be a component of the hard protein corona and HSA as a component of the soft corona. We demonstrate a pronounced difference in the protein corona observed depending on the type of characterization technique applied. As the biological identity of a particle is given by the protein corona it is crucial to use complementary characterization techniques to analyse different aspects of the protein corona. Electronic supplementary information (ESI) available: Pierce 660 nm protein assay, ITC data evaluation, DLS data evaluation, autocorrelation functions of protein - HES capsule mixtures. See DOI: 10.1039/c4nr05982d

  8. Complementary analysis of the hard and soft protein corona: sample preparation critically effects corona composition.

    PubMed

    Winzen, S; Schoettler, S; Baier, G; Rosenauer, C; Mailaender, V; Landfester, K; Mohr, K

    2015-02-21

    Here we demonstrate how a complementary analysis of nanocapsule-protein interactions with and without application media allows gaining insights into the so called hard and soft protein corona. We have investigated how both human plasma and individual proteins (human serum albumin (HSA), apolipoprotein A-I (ApoA-I)) adsorb and interact with hydroxyethyl starch (HES) nanocapsules possessing different functionalities. To analyse the hard protein corona we used sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and a protein quantitation assay. No significant differences were observed with regards to the hard protein corona. For analysis of the soft protein corona we characterized the nanocapsule-protein interaction with isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). DLS and ITC measurements revealed that a high amount of plasma proteins were adsorbed onto the capsules' surface. Although HSA was not detected in the hard protein corona, ITC measurements indicated the adsorption of an HSA amount similar to plasma with a low binding affinity and reaction heat. In contrast, only small amounts of ApoA-I protein adsorb to the capsules with high binding affinities. Through a comparison of these methods we have identified ApoA-I to be a component of the hard protein corona and HSA as a component of the soft corona. We demonstrate a pronounced difference in the protein corona observed depending on the type of characterization technique applied. As the biological identity of a particle is given by the protein corona it is crucial to use complementary characterization techniques to analyse different aspects of the protein corona. PMID:25599336

  9. News and Views: Kleopatra a pile of rubble, shedding moons; Did plasma flow falter to stretch solar minimum? Amateurs hit 20 million variable-star observations; Climate maths; Planetary priorities; New roles in BGA

    NASA Astrophysics Data System (ADS)

    2011-04-01

    Metallic asteroid 216 Kleopatra is shaped like a dog's bone and has two tiny moons - which came from the asteroid itself - according to a team of astronomers from France and the US, who also measured its surprisingly low density and concluded that it is a collection of rubble. The recent solar minimum was longer and lower than expected, with a low polar field and an unusually large number of days with no sunspots visible. Models of the magnetic field and plasma flow within the Sun suggest that fast, then slow meridional flow could account for this pattern. Variable stars are a significant scientific target for amateur astronomers. The American Association of Variable Star Observers runs the world's largest database of variable star observations, from volunteers, and reached 20 million observations in February.

  10. TRIANGLE-SHAPED DC CORONA DISCHARGE DEVICE FOR MOLECULAR DECOMPOSITION

    EPA Science Inventory

    The paper discusses the evaluation of electrostatic DC corona discharge devices for the application of molecular decomposition. A point-to-plane geometry corona device with a rectangular cross section demonstrated low decomposition efficiencies in earlier experimental work. The n...

  11. Seeing The Solar Corona in Three Dimensions

    E-print Network

    Vásquez, Alberto Marcos

    2015-01-01

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

  12. Development of the system disk - corona

    NASA Astrophysics Data System (ADS)

    Yankova, Krasimira

    Accretion is quantitatively and qualitatively more efficient in the presence of a magnetic field. MHD models of non-stationary accretion disc showed appeared more quickly and develop more diverse type instabilities. We investigate the interaction between stream and magnetic field. We are studying the structure of the accretion flow in the system disk - corona. Here we will present treatment theoretical magneto-hydrodynamic model on accretion disc. We obtained solution for the 2D- and the 3D-structure of disc. The results: 2D-evolution enable us to see the appear on the global structures like as spiral and corona. Behavior of the condition from distribution sound and magneto-sound velocities in 3D and velocity vector field in disk showed independent of tendency the disk to generating of corona. Discussion over results.

  13. Mechanical vibration of H. V. conductors induced by corona

    Microsoft Academic Search

    M. Farzaneh; Y. Teisseyre

    1988-01-01

    In this paper the corona induced force per hanging water drop from a H.V. conductor and the roles of the corona space charge and ionic wind in the mechanism of corona induced vibration were investigated. In order to determine the amplitude of the corona induced force F\\/sub t\\/, a water drop was simulated by a conical metal point. F\\/sub t\\/

  14. Double streamer phenomena in atmospheric pressure low frequency corona plasma

    SciTech Connect

    Kim, Dan Bee; Jung, H.; Gweon, B.; Choe, Wonho [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2010-07-15

    Time-resolved images of an atmospheric pressure corona discharge, generated at 50 kHz in a single pin electrode source, show unique positive and negative corona discharge features: a streamer for the positive period and a glow for the negative period. However, unlike in previous reports of dc pulse and low frequency corona discharges, multistreamers were observed at the initial time stage of the positive corona. A possible physical mechanism for the multistreamers is suggested.

  15. Electric wind in electrode systems with corona points

    Microsoft Academic Search

    B. A. Kozlov; V. I. Solovyov

    2007-01-01

    The characteristics of the electric wind attendant on the corona initiation are studied with the aim of reaching a maximal\\u000a velocity and flow rate. Systems with a single corona point and multi-in-line electrode are used. The dependences of the gas\\u000a flow rate on the current, voltage, voltage polarity, electrode spacing, corona point geometry, and corona-free electrode design\\u000a are determined.

  16. Transient corona effects on a wire over the ground

    NASA Technical Reports Server (NTRS)

    Chen, K. C.

    1980-01-01

    The nuclear EMP effect on VLF/trailing wire antennas is investigated in relation to new features of corona effects. Previous experimental results on transmission lines with corona under E 80 kV/cm recorded in the nanosecond time frame are analyzed. A nonlinear macroscopic model which describes a transmission line with corona is discussed. The model not only accounts for overall waveform, but also describes the sharp changes in the waveform associated with the corona onset.

  17. Device for generation of pulsed corona discharge

    DOEpatents

    Gutsol, Alexander F. (San Ramon, CA); Fridman, Alexander (Marlton, NJ); Blank, Kenneth (Philadelphia, PA); Korobtsev, Sergey (Moscow, RU); Shiryaevsky, Valery (Moscow, RU); Medvedev, Dmitry (Moscow, RU)

    2012-05-08

    The invention is a method and system for the generation of high voltage, pulsed, periodic corona discharges capable of being used in the presence of conductive liquid droplets. The method and system can be used, for example, in different devices for cleaning of gaseous or liquid media using pulsed corona discharge. Specially designed electrodes and an inductor increase the efficiency of the system, permit the plasma chemical oxidation of detrimental impurities, and increase the range of stable discharge operations in the presence of droplets of water or other conductive liquids in the discharge chamber.

  18. Electric Current Equilibrium in the Corona

    NASA Astrophysics Data System (ADS)

    Filippov, Boris

    2013-04-01

    A hyperbolic flux-tube configuration containing a null point below the flux rope is considered as a pre-eruptive state of coronal mass ejections that start simultaneously with flares. We demonstrate that this configuration is unstable and cannot exist for a long time in the solar corona. The inference follows from general equilibrium conditions and from analyzing simple models of the flux-rope equilibrium. A direct consequence of the stable flux-rope equilibrium in the corona are separatrices in the horizontal-field distribution in the chromosphere. They can be recognized as specific "herring-bone structures" in a chromospheric fibril pattern.

  19. Probing the Solar Corona with VLBI

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  20. 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

  1. Model of Ozone Production in the DC Corona Discharge

    Microsoft Academic Search

    Junhong Chen; Jane Davidson

    2002-01-01

    A comprehensive numerical model of ozone production in clean, dry air by DC corona discharges is presented. This model combines a first-principle corona plasma model with a chemistry and 2-D transport model to obtain the distributions of ozone and other gaseous products in the neighborhood of a corona discharge wire. Electron number density distribution is obtained by solving the continuity

  2. Unravelling the chemical characteristics of YSOs

    NASA Astrophysics Data System (ADS)

    van Dishoeck, Ewine F.

    1999-10-01

    The formation of stars is accompanied by orders of magnitude changes in the physical conditions, with densities in the envelopes and disks increasing from 104 cm-3 to > 1013 cm-3 and temperatures from ~ 10 K in the cold quiescent gas to 10,000 K in shocked regions. The abundances and excitation of the various molecules respond to these changes, and are therefore excellent probes of the physical evolution of YSOs. Moreover, a comprehensive inventory of the chemical composition of envelopes and disks at different evolutionary stages is essential to study the chemistry of matter as it is incorporated into new solar systems. Recent observations of the envelopes of YSOs using single-dish telescopes and millimeter interferometers clearly reveal the potential of submillimeter lines to probe these physical and chemical changes. However, the existing data generally lack the spatial resolution to separate the different physical components, such as the warm inner envelope or `hot core', the region of interaction of the outflow with the envelope and any possible circumstellar disk. ALMA will be essential to provide an `unblurred' view of the YSO environment and unravel the chemical evolution during star formation. In this talk, an overview will be given of recent single-dish and interferometer results of the chemistry in the envelopes and disks around low- and high-mass young stellar objects. Together with ISO data on solid-state material, these observations lead to a chemical scenario in which both gas-phase and gas-grain chemistry (in particular freeze-out and evaporation) play an important role. The evaporated molecules drive a rich chemistry in the warm gas, which can result in complex organic molecules. The potential of ALMA to test chemical theories and determine the composition of gas and dust as it enters forming planetary systems will be illustrated.

  3. Arecibo/Magellan Composite of Quetzalpetlatl Corona

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This composite image was created by inserting approximately 70 orbits of Magellan data into an image obtained at the Arecibo, Puerto Rico radiotelescope and shows a geologically complex region in the southern hemisphere of Venus. The region is centered on 65 degrees south, 359 degrees east and is about 1500 x 1500 km (900 x 900 miles) in extent. The large oval feature in the lower half of the image is Quetzalpetlatl Corona, approximately 700 km (420 miles) in diameter. Coronae are circular to oval regions defined by an annulus of ridges and are centers for tectonic and volcanic activity. Tectonic activity is largely observed in a relatively narrow rim region, which in this image is defined by a complex lineated terrain that surrounds much of the corona. Bright and dark volcanic flows are seen throughout the corona and surrounding terrain. Small shield volcanoes, 1-20 km (0.6-12 miles) in diameter, are seen near the southern limit of the Magellan data image. Narrow linear troughs (seen in the image as bright lines) trend to the north-northwest of Quetzalpetlatl.

  4. Corona discharge plasma reactor for decontamination

    Microsoft Academic Search

    J. G. Birmingham; P. M. Irving

    1998-01-01

    Summary form only given. The feasibility of using a gas phase corona plasma to sterilize objects from toxic battlefield, medical, and industrial environments was assessed. Plasma chemical processes can be highly effective in promoting oxidation, enhancing molecular dissociation, or producing free radicals to enhance chemical reaction. Until recently, plasma processes were applied in either the high temperature environment of arc

  5. Corona Considerations in Submarine Cable Communications Systems

    Microsoft Academic Search

    Earnest Franke

    1974-01-01

    Underwater repeatered telephone cable systems are series powered by high-voltage dc. Each repeater and equalizer contains a power separation filter (PSF) for extracting the dc current from the center conductor of the coaxial cable while allowing signal transmission. Corona discharges occurring across the high-voltage components are coupled through reactive components to the repeater's terminals. Each of the experimentally observed pulse

  6. Pulsed Corona in Air for Water PROEFSCHRIFT

    E-print Network

    Eindhoven, Technische Universiteit

    / waste water treatment / advanced oxidation processes / ozone / phenol / oxidation This research has been......................................................................22 2.2.1.4. Ozone for waste water treatmentPulsed Corona in Air for Water Treatment PROEFSCHRIFT ter verkrijging van de graad van doctor aan

  7. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    2001-01-01

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

  8. IONIZATION OF AIR BY CORONA DISCHARGE

    E-print Network

    Texas at Arlington, University of

    IONIZATION OF AIR BY CORONA DISCHARGE The members of the Committee approve the master's thesis DISCHARGE by PHILIP KOSHY PANICKER Presented to the Faculty of the Graduate School of The University of Texas at Arlington in Partial Fulfilment of the Requirements for the Degree of MASTER OF SCIENCE

  9. Black hole accretion disks with coronae

    NASA Technical Reports Server (NTRS)

    Svensson, Roland; Zdziarski, Andrzej A.

    1994-01-01

    Observations suggest the existence of both hot and cold dark matter in the centers of active galactic nuclei. Recent spectral models require a major fraction of power to be dissipated in the hot matter. We study the case when the hot matter forms a corona around a standard cold alpha-disk. In particular, we investigate the case when a major fraction, f, of the power released when the cold matter accretes is transported to and dissipated in the corona. This has major effects on the cold disk, making it colder, more geometrically thin, denser, and having larger optical depths. One important consequence is the disappearance of the effectively optically thin zone as well as of the radiation pressure dominated zone for values of f sufficiently closed to unity. The disappearance of the radiation pressure dominated zone will result in a cold disk with only a gas pressure dominated zone that is stable against thermal and viscous instabilities. We also show that the pressure ( and the radiation) from the corona will only affect the surface layers of the cold disk. Our results disagree with those of other recent work on accretion disks with coronae. We find those works to be based on unphysical assumptions.

  10. The peculiar Rosetta stone - beta Coronae Borealis

    Microsoft Academic Search

    S. J. Adelman; B. A. Boytim; S. N. Shore; D. H. Pyper

    1981-01-01

    Spectrophotometric and spectral observations of the spectroscopic binary beta Coronae Borealis, one of the brightest cooler Ap stars, are discussed in relation to the oblique rotator model. Spectrophotometry carried out between 1972 and 1977 indicates the presence of a weak 4200 A and a moderate 5200 A feature, with no convincing evidence for cyclic variations. The spectrophotometric variability is phase

  11. Dependence of ozone formation by corona discharge in humid air on corona electrode type and power supply mode

    SciTech Connect

    Ponizovskii, A.Z. [Gorizont Development Bureau, Moscow (Russian Federation); Shvedchikov, A.P. [Semenov Institute of Chemical Physics, Moscow (Russian Federation)

    1995-07-01

    The ozone yield in a corona discharge at humid air flow rates ranging from 1.5 to 11 1/min was studied using different types of corona electrodes and power-supply modes (continuous and pulsed coronas). The discharge was generated between coaxial electrodes in a cylindrical stainless-steel chamber, 70 mm in diameter with a volume of 1.5 1. The ozone yield was affected considerably by the type of corona electrode. The discharge current decreased with rising ozone concentration in the flow when operated in both continuous and pulsed modes of corona discharge.

  12. Cosmic radiation in the heliosphere at successive solar minima 5. Modulation of anomalous cosmic ray helium during the three consecutive solar minimum periods of 1977/1978, 1987, and 1997

    NASA Astrophysics Data System (ADS)

    Reinecke, J. P. L.; McDonald, F. B.; Moraal, H.

    2000-12-01

    A renewed attempt is made to model anomalous cosmic ray He+ spectra observed during the solar minimum periods of 1977/1978, 1987, and 1997, from 1 to 66 AU in the heliosphere. This model improves on the one in our paper 3 in this series [Reinecke et al., 1996], because it now contains the new 1997 observations, and because a physically justified input spectrum for anomalous species on the solar wind termination shock is used. This input spectrum is based on the work of Steenberg [1998] and Steenberg and Moraal [1999]. For simplicity, only anomalous He+ is considered. This is partially justified because the properties of other anomalous species, such as O+, are quite similar. This paper extends the work of paper 4 in the series [Reinecke et al., 2000], in which similar fits to galactic He++ were done. It is shown that it remains impossible to find a single set of modulation parameters that fit the 1977, 1987, and 1997 anomalous and galactic spectra simultaneously. In addition, the new 1997 observations introduce further constraints that make it impossible to even find a single set of parameters for 1977 and 1997 with the current model, although these two periods are in the same so-called drift cycle.

  13. Unraveling "Braid": Puzzle Games and Storytelling in the Imperative Mood

    ERIC Educational Resources Information Center

    Arnott, Luke

    2012-01-01

    "Unraveling Braid" analyzes how unconventional, non-linear narrative fiction can help explain the ways in which video games signify. Specifically, this essay looks at the links between the semiotic features of Jonathan Blow's 2008 puzzle-platform video game Braid and similar elements in Georges Perec's 1978 novel "Life A User's Manual," as well as…

  14. Unraveling quantum mechanical effects in water using isotopic fractionation

    E-print Network

    Berne, Bruce J.

    Unraveling quantum mechanical effects in water using isotopic fractionation Thomas E. Marklanda that equilibrium fractionation ratios, an entirely quantum mechan- ical property, also provide a sensitive probe- predict the magnitude of isotope fractionation. Models that account for anharmonicity in this coordinate

  15. Green corona and solar sector structure

    NASA Technical Reports Server (NTRS)

    Antonucci, E.; Svalgaard, L.

    1974-01-01

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

  16. Corona and Motor Voltage Interim Report

    SciTech Connect

    Hsu, J.S.

    2005-05-06

    It has been suggested that to meet the FreedomCAR objectives for cost, size, weight, efficiency, and reliability higher buss voltages be utilized in HEV and FC automotive applications. The reasoning is that since electric power is equal to the product of voltage and current for a given power a higher voltage and lower current would result in smaller cable and inverter switching components. Consequently, the system can be lighter and smaller. On the other hand, higher voltages are known to require better and thicker electrical insulation that reduce the available slot area for motor windings. One cause of slow insulation breakdown is corona that gradually erodes the insulation and shortens the life expectancy of the motor. This study reports on the results of a study on corona initiating voltages for mush-wound and bobbin-wound stators. A unique testing method is illustrated.

  17. Helium corona-assisted air discharge

    SciTech Connect

    Jiang Nan; Gao Lei; Ji Ailing; Cao Zexian [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-15

    Operation of atmospheric discharge of electronegative gases including air at low voltages yet without consuming any inert gas will enormously promote the application of non-thermal plasmas. By taking advantage of the low onset voltage for helium corona, air discharge was successfully launched at much reduced voltages with a needle-plate system partly contained in a helium-filled glass bulb--for a needle-plate distance of 12 mm, 1.0 kV suffices. Ultraviolet emission from helium corona facilitates the discharging of air, and the discharge current manifests distinct features such as relatively broad Trichel pulses in both half periods. This design allows safe and economic implementation of atmospheric discharge of electronegative gases, which will find a broad palette of applications in surface modification, plasma medicine and gas treatment, etc.

  18. MASC: Magnetic Activity of the Solar Corona

    NASA Astrophysics Data System (ADS)

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

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

  19. Ultramassive Black Holes: Fundamental Plane and Coronae

    NASA Astrophysics Data System (ADS)

    Gultekin, Kayhan

    2014-09-01

    We will measure the X-ray flux and radio continuum of 7 ultramassive BHs (M>3e9) to test competing models of the fundamental plane (FP) of BH accretion. The FP relates the X-ray, radio, and mass of an accreting BH, and demonstrates there is a connection between BH inflow and outflow. The FP is derived mostly from BHs with masses under 2e9. It is not clear if the FP holds for the largest BHs. The 2 ways to create the FP, with only SMBHs OR jointly with SMBHs and stellar BHs, differ by 100 for the largest BHs. Only with Chandra we can separate corona and AGN to determine it. Coronae around huge BHs are critical in limiting feeding so that we can understand the gas supply around and accretion onto the largest BHs.

  20. The Magnitude of Corona Point Discharge Current

    Microsoft Academic Search

    Seville Chapman

    1977-01-01

    The magnitude of corona point discharge current is calculated by an approximate quantitative theory. Using plausible values for one adjustable constant, the current i agrees exactly with experiment. For an isolated point of potential Vp in a wind of speed w, i=1.3150w(VpV0p) [Eq. (I)], or for a paint of height h in an ambient field E0, i=3.90kE0(VpV0p) [Eq. (II)], where

  1. Experimental investigation on altitude correction factor of positive dc corona inception voltages of transmission lines based on the mobile corona cage

    Microsoft Academic Search

    Xingming Bian; Liming Wang; Zhicheng Guan; Jing Cao; Yingjian Yang; Xiong Wu

    2010-01-01

    In order to obtain the altitude correction factor of corona inception voltage of HVDC transmission lines within the range 23 to 4000 meters, a mobile corona test cage was used to research the influence of altitude changes on positive DC corona characteristics of several kinds of conductors. Photons released as a result of corona discharge on the conductors were detected

  2. Stereo Science Results at Solar Minimum

    NASA Technical Reports Server (NTRS)

    Christian, Eric R.; Kaiser, Michael L.; Kucera Therese A.; St. Cyr, O. C.; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H.

    2009-01-01

    The magnetic fields that drive solar activity are complex and inherently three-dimensional structures. Twisted flux ropes, magnetic reconnection and the initiation of solar storms, as well as space weather propagation through the heliosphere, are just a few of the topics that cannot properly be observed or modeled in only two dimensions. Examination of this three-dimensional complex has been hampered by the fact that solar remote sensing observations have occurred only from the Earth-Sun line, and in situ observations, while available from a greater variety of locations, have been sparse throughout the heliosphere.

  3. Deep solar minimum and global Climate Changes

    NASA Astrophysics Data System (ADS)

    Abdel Hady, Ahmed

    2012-07-01

    This paper examines the deep minimum of solar cycle 23 and its likely impact on climate change. In addition, a source region of the solar winds at solar activity minimum, especially in the solar cycle 23, the deepest during the last 100 years, has been studied. Solar activities have had notable effect on palaeoclimatic changes. Contemporary solar activities are so weak and hence expected to cause global cooling. Prevalent global warming, caused by building-up of green-house gases in the troposphere, seems to exceed this solar effect. This paper discusses this issue.

  4. Deep solar minimum and global climate changes

    NASA Astrophysics Data System (ADS)

    Hady, Ahmed A.

    2013-05-01

    This paper examines the deep minimum of solar cycle 23 and its potential impact on climate change. In addition, a source region of the solar winds at solar activity minimum, especially in the solar cycle 23, the deepest during the last 500 years, has been studied. Solar activities have had notable effect on palaeoclimatic changes. Contemporary solar activity are so weak and hence expected to cause global cooling. Prevalent global warming, caused by building-up of green-house gases in the troposphere, seems to exceed this solar effect. This paper discusses this issue.

  5. Deep solar minimum and global climate changes.

    PubMed

    Hady, Ahmed A

    2013-05-01

    This paper examines the deep minimum of solar cycle 23 and its potential impact on climate change. In addition, a source region of the solar winds at solar activity minimum, especially in the solar cycle 23, the deepest during the last 500 years, has been studied. Solar activities have had notable effect on palaeoclimatic changes. Contemporary solar activity are so weak and hence expected to cause global cooling. Prevalent global warming, caused by building-up of green-house gases in the troposphere, seems to exceed this solar effect. This paper discusses this issue. PMID:25685420

  6. Igneous and tectonic evolution of Venusian and terrestrial coronae

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.; Komatsu, G.

    1992-01-01

    A great variety of tectonic and volcanic features have been documented on Venus. It is widely appreciated that there are close spatial associations among certain types of tectonic structures and some classes of volcanic flows and constructs. Coronae are endowed with a particularly rich variety of volcanism. It is thought that coupled tectonic and volcanic aspects of coronae are cogenetic manifestations of mantle plumes. An outstanding feature of most venusian coronae is their circular or elliptical shape defined by peripheral zones of fracturing and/or folding. Some coronae are composite, consisting of two or more small coronae within a larger enclosing corona, suggesting complex histories of structured diapirism analogous in some ways to salt dome tectonics. Coronae range widely in size, from smaller than 100 km to over 1000 km in diameter. Volcanic features associated with venusian coronae include lunar-like sinuous rilles, thin lava flows, cinder cone-like constructs, shield volcanos, and pancake domes. Several types of volcanic features are often situated within or near a single corona, in many instances including land-forms indicating effusions of both low- and high-viscosity lavas. In some cases stratigraphic evidence brackets emplacement of pancake domes during the period of tectonic development of the corona, thus supporting a close link between the igneous and tectonic histories of coronae. These associations suggest emplacement of huge diapirs and massive magmatic intrusions, thus producing the tectonic deformations defining these structures. Igneous differentiation of the intrusion could yield a range of lava compositions. Head and Wilson suggested a mechanism that would cause development of neutral buoyancy zones in the shallow subsurface of Venus, thereby tending to promote development of massive igneous intrusions.

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

    Microsoft Academic Search

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

    2003-01-01

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

  8. Fluorine in R Coronae Borealis Stars

    E-print Network

    Pandey, Gajendra; Rao, N Kameswara

    2007-01-01

    Neutral fluorine (F I) lines are identified in the optical spectra of several R Coronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine is enriched in some RCBs by factors of 800 to 8000 relative to its likely initial abundance. The overabundances of fluorine are evidence for the synthesis of fluorine. These results are discussed in the light of the scenario that RCBs are formed by accretion of an He white dwarf by a C-O white dwarf. Sakurai's object (V4334 Sgr), a final He-shell flash product, shows no detectable F I lines.

  9. Fragmentation and Collapse in Coronae-Australis

    NASA Astrophysics Data System (ADS)

    Llewellyn, R.; Payne, P.; Sakellis, S.; Taylor, K. N. R.

    1981-07-01

    Observations of H I in the vicinity of the dust lane of Corona Austrinae reveal a region of almost complete conversion of H I to H2. The results suggest that about 103Msun of material may be in a state of collapse. The projected centre of this region coincides with a small dense cloud which may be the physical centre of the collapsing fragment, while the limits of the collapsing zone appear to be defined by an almost complete dust ring of diameter 1.3 pc.

  10. Pulsed corona discharge at atmospheric and supercritical conditions

    Microsoft Academic Search

    Evgeniya Hristova Lock

    2006-01-01

    Pulsed corona discharge is one of the non-equilibrium plasma techniques, by which electrical power is mainly utilized to generate high-energy electrons. These react further with the background gas to produce radicals, which can be further employed in chemically selective reactions. Study of the initiation of pulsed corona discharge in carbon dioxide and air was conducted. Furthermore due to its high

  11. Chaotic characteristics of corona discharges in atmospheric air

    SciTech Connect

    Tan Xiangyu; Zhang Qiaogen; Wang Xiuhuan; Sun Fu; Zha Wei; Jia Zhijie [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, 28 West Xianning Road, Xi'an 710049 (China)

    2008-11-15

    A point-plane electrode system in atmospheric air is established to investigate the mechanism of the corona discharge. By using this system, the current pulses of the corona discharges under the 50 Hz ac voltage are measured using partial discharge (PD) measurement instrument and constitute the point-plane voltage-current (V-I) characteristic equation together with the voltage. Then, this paper constructs the nonlinear circuit model and differential equations of the system in an attempt to give the underlying dynamic mechanism based on the nonlinear V-I characteristics of the point-plane corona discharges. The results show that the chaotic phenomenon is found in the corona circuit by the experimental study and nonlinear dynamic analysis. The basic dynamic characteristics, including the Lyapunov exponent, the existence of the strange attractors, and the equilibrium points, are also found and analyzed in the development process of the corona circuit. Moreover, the time series of the corona current pulses obtained in the experiment is used to demonstrate the chaotic characteristics of the corona current based on the nonlinear dynamic circuit theory and the experimental basis. It is pointed out that the corona phenomenon is not a purely stochastic phenomenon but a short term deterministic chaotic activity.

  12. A linear array of point coronodes for negative corona discharge

    Microsoft Academic Search

    A. W. F. Lo; M. Omodani; Y. Hoshino

    1993-01-01

    Negative corona discharge from a novel linear metal point array structure has been investigated. The inherent advantage of using such a structure is that its rigidity eliminates vibration and sagging problems experienced by conventional wire corona emitters. More importantly, it is found that longitudinal current emission more uniform than that from wire emitters can be obtained by sufficiently reducing the

  13. Hydrophobicity recovery of polydimethylsiloxane after exposure to corona discharges

    Microsoft Academic Search

    H. Hillborg; U. W. Gedde

    1998-01-01

    A high-temperature-vulcanized polydimethylsiloxane (PDMS) elastomer has been subjected to corona discharges for different periods of time in dry air. The loss and recovery of hydrophobicity of the surface have been characterized by contact angle measurements. Immediately after exposure to corona discharges, samples showed a low surface hydrophobicity and, on storage in dry air, a continuous increase in hydrophobicity finally approaching

  14. Study of magnetically enhanced corona pre-charger

    Microsoft Academic Search

    Dexuan Xu; Lianxi Sheng; Haijun Wang; Yinghao Sun; Xiaoyu Zhang; Junfeng Mi

    2007-01-01

    In this paper, experimental investigations of the discharge characteristics of magnetically enhanced corona discharges, for the purpose of capturing fine aerosol particles, are presented. The discharge mechanism during such a process is analyzed as well. The effects of magnetic enhancement under different magnet flux densities, and in positive- or negative-corona discharges, were experimentally compared. The magnetically enhanced effects in different

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

    Microsoft Academic Search

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

    1975-01-01

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

  16. ORIGINAL PAPER The Corona lava tube, Lanzarote: geology, habitat diversity

    E-print Network

    Iliffe, Thomas M.

    ORIGINAL PAPER The Corona lava tube, Lanzarote: geology, habitat diversity and biogeography Horst # Senckenberg, Gesellschaft für Naturforschung and Springer 2009 Abstract The Corona lava tube on the Canarian with a total length of almost 8 km. Here, we present the results of a diving exploration of the lava tube

  17. CORONAS-F satellite: Tasks for study of particle acceleration

    Microsoft Academic Search

    S. N. Kuznetsov; K. Kudela; S. P. Ryumin; Y. V. Gotselyuk

    2002-01-01

    A low altitude satellite with polar orbit, namely CORONAS-F has been launched on July 31, 2001. We briefly list the possibilities of a complex instrument SKL, and on the basis of similar measurements by CORONAS-I we illustrate the possible tasks for magnetospheric studies. Such orbit allows to sample with relatively high time resolution the projection series of various magnetospheric regions

  18. Modulated corona nanosecond discharge in air under ambient pressure

    NASA Astrophysics Data System (ADS)

    Lepekhin, N. M.; Priseko, Yu. S.; Filippov, V. G.; Bulatov, M. U.; Sukharevskii, D. I.; Syssoev, V. S.

    2015-04-01

    A unique type of corona discharge-modulated corona nanosecond discharge-has been obtained, the parameters of which have been determined in a geometric system of electrodes with a sharply heterogeneous electric field in air under ambient pressure and natural humidity.

  19. An experimental measurement of corona discharge using laser Doppler velocimetry

    Microsoft Academic Search

    C. A. Belhadj; M. H. Shwehdi; A. S. Farag; F. M. Zedan; U. K. A. Klein

    1998-01-01

    A point to plane testing discharge system was constructed allowing the flow of air to pass, circulate and return to its initial status, when corona is initiated by the alternating applied voltage on the stressed electrode. The corona wind velocity was measured by means of a laser Doppler velocimetry system implemented and calibrated in the laboratory. The velocity measurement was

  20. Rapid formation of plasma protein corona critically affects nanoparticle pathophysiology

    NASA Astrophysics Data System (ADS)

    Tenzer, Stefan; Docter, Dominic; Kuharev, Jörg; Musyanovych, Anna; Fetz, Verena; Hecht, Rouven; Schlenk, Florian; Fischer, Dagmar; Kiouptsi, Klytaimnistra; Reinhardt, Christoph; Landfester, Katharina; Schild, Hansjörg; Maskos, Michael; Knauer, Shirley K.; Stauber, Roland H.

    2013-10-01

    In biological fluids, proteins bind to the surface of nanoparticles to form a coating known as the protein corona, which can critically affect the interaction of the nanoparticles with living systems. As physiological systems are highly dynamic, it is important to obtain a time-resolved knowledge of protein-corona formation, development and biological relevancy. Here we show that label-free snapshot proteomics can be used to obtain quantitative time-resolved profiles of human plasma coronas formed on silica and polystyrene nanoparticles of various size and surface functionalization. Complex time- and nanoparticle-specific coronas, which comprise almost 300 different proteins, were found to form rapidly (<0.5 minutes) and, over time, to change significantly in terms of the amount of bound protein, but not in composition. Rapid corona formation is found to affect haemolysis, thrombocyte activation, nanoparticle uptake and endothelial cell death at an early exposure time.

  1. Model for R Coronae Borealis stars

    SciTech Connect

    Whitney, B.A.; Soker, N.; Clayton, G.C. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA) Colorado, University, Boulder (USA))

    1991-07-01

    An evolutionary model is proposed in which R Coronae Borealis stars are in a second common-envelope phase, with a low-mass companion orbiting well inside the envelope. The high mass-loss rate in the first common-envelope phase turns the massive star into a hydrogen-deficient star. In the second common-envelope phase, as a result of shear induced by the inner envelope rotation and possibly by excited gravity-wave-induced turbulence, carbon and oxygen are being dredged up from the core into the envelope. This evolutionary scenario smoothly connects R CrB stars to the double-mass-loss-episodes evolutionary scenario of hydrogen-deficient binaries suggested by Plavec (1973). This model may have consequences for the nature of mass loss in R Coronae Borealis stars: the orbiting companion breaks spherical symmetry allowing for nonradial pulsations and asymmetric mass loss. The optical polarization and IR observations may point to axisymmetric mass loss with the same axis of symmetry for the different mass-loss episodes. 38 refs.

  2. The corona of HD 223460 (HR 9024)

    NASA Astrophysics Data System (ADS)

    Gondoin, P.

    2003-10-01

    HD 223460 (HR 9024), a chromospherically active late-type giant with a high X-ray luminosity, was observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. Analysis results suggest a scenario where the corona of HD 223460 is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The surface area coverage of these active regions may approach up to 30%. A hypothesis is that the interaction of these structures themselves induces a flaring activity on a small scale not visible in the EPIC light curves that is responsible for heating HD 223460 plasma to coronal temperatures of T >=107 K. The intense X-ray activity of HD 223460 is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that its rotation will spin down in the future with the effect of decreasing its helicity-related, dynamo-driven activity and suppressing large-scale magnetic structures in its corona.

  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. Coronae as a result of giant magma intrusions in the lithosphere of Venus: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Galland, Olivier; Polteau, Stephane; Werner, Stephanie C.

    2013-04-01

    Coronae on the surface of Venus are unique volcano-tectonic structures in the solar systems. Their circular morphology is associated with various topographic signatures, from bell-shape domes, flat-topped plateaus, to uplifted rings surrounding a subsided centre similar to caldera. Their extensive size and associated lava flows erupting from their periphery, indicate that they result from deep processes in the Venus mantle. Understanding their origin is thus essential for unraveling the dynamics of Venus through time. There are several scenarios explaining the formation of coronae, the most popular being the interaction between an upwelling mantle plume and the lithosphere, creating dynamic topography. In this contribution, we propose that coronae can result from the emplacement of giant magma intrusions below the Venus' lithosphere, on the basis of laboratory experiments. The experimental apparatus consists of a square box filled with compacted fine-grained silica flour (model crust), in which a low viscosity vegetable oil (model magma) is injected at constant flow rate. The initial conditions are such that magma initially flows horizontally, forming a sill-like body, to simulate magmatic underplating. During the experiments, oil injection triggers deformation of the model surface, which is monitored periodically using a moiré projection device, producing time series topographic maps of the model surface. Our results show that the surface evolution of the models follows three stages: (1) initial bell-shaped doming occurs above the injection inlet, producing radial open fractures at the model surfaces; (2) the bell-shape dome evolves to a flat-topped plateau, at the rim of which the oil erupts; (3) after the injection stops, the centre of the plateau subsides, and a positive topographic ring surrounding a depression, like a caldera, remains. The collapse of the plateau also generates concentric extensional fractures at the rims of the caldera. After the dynamic experiment, the oil solidifies and we extracted the intrusion, which exhibits a sill-shape, feeding outward circular inclined sheets at its external edges (i.e. a saucer-shaped sill). From a series of experiments in which the depth of injection h was varied, we show that the diameter of the intrusion and its associated topographic structure correlates linearly with h. The three evolutionary stages simulated in the experiments reproduce remarkably well (1) the three main corona morphologies observed on Venus, and (2) their established succession through time. In addition, the relationships between the structures and the oil flow in our experiments are also similar to those observed on Venus. Therefore, our experimental results suggest that corona structures are the result of giant magma intrusions in the lithosphere of Venus. In addition, our experiments suggest that the diameters of coronae are related to the depth of emplacement of the underlying intrusions, which might be controlled by the rheological architecture of the Venus' lithosphere. Therefore, the analysis of the dimensions and morphologies of coronae are likely to provide crucial information of the structure of the lithosphere of Venus.

  5. Charging of moving surfaces by corona discharges sustained in air

    SciTech Connect

    Wang, Jun-Chieh, E-mail: junchwan@umich.edu; Kushner, Mark J., E-mail: mjkush@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109-2122 (United States); Zhang, Daihua, E-mail: dhzhang@tju.edu.cn [Tianjin University, Tianjin (China); Leoni, Napoleon, E-mail: napoleon.j.leoni@hp.com; Birecki, Henryk, E-mail: henryk.birecki@hp.com; Gila, Omer, E-mail: omer-gila@hp.com [Hewlett-Packard Research Labs, Palo Alto, California 94304 (United States)

    2014-07-28

    Atmospheric pressure corona discharges are used in electrophotographic (EP) printing technologies for charging imaging surfaces such as photoconductors. A typical corona discharge consists of a wire (or wire array) biased with a few hundred volts of dc plus a few kV of ac voltage. An electric discharge is produced around the corona wire from which electrons drift towards and charge the underlying dielectric surface. The surface charging reduces the voltage drop across the gap between the corona wire and the dielectric surface, which then terminates the discharge, as in a dielectric barrier discharge. In printing applications, this underlying surface is continuously moving throughout the charging process. For example, previously charged surfaces, which had reduced the local electric field and terminated the local discharge, are translated out of the field of view and are replaced with uncharged surface. The uncharged surface produces a rebound in the electric field in the vicinity of the corona wire which in turn results in re-ignition of the discharge. The discharge, so reignited, is then asymmetric. We found that in the idealized corona charging system we investigated, a negatively dc biased corona blade with a dielectric covered ground electrode, the discharge is initially sustained by electron impact ionization from the bulk plasma and then dominated by ionization from sheath accelerated secondary electrons. Depending on the speed of the underlying surface, the periodic re-ignition of the discharge can produce an oscillatory charging pattern on the moving surface.

  6. Corona Formation on Venus Via Extension and Lithospheric Instability

    NASA Astrophysics Data System (ADS)

    Piskorz, D.; Elkins-Tanton, L. T.; Smrekar, S. E.

    2014-12-01

    Given the absence of plate tectonics on Venus, the origin of major rift systems like Parga Chasma is unclear. As Venus and Earth have similar radii and radiogenic abundances, we assume they have a similar internal structure and composition. Venus does not appear to have plate tectonics, and its surface displays a range of volcanic and tectonic features, including those that are both similar and dissimilar to those on Earth. In order to understand how Venus loses its heat, we study coronae at Parga Chasma. There are over 500 quasi-circular volcano-tectonic features called coronae on Venus, 131 of which are associated with Parga Chasma. Are these coronae important in the formation of the rift, or vice versa? How do they contribute to planetary heat loss? Coronae are believed to form via small-scale mantle upwellings, lithospheric instability, or a combination thereof. However, the genetic link between the coronae and rifts has remained unclear. By drawing an analogy to the East African Rift, we propose a mechanism for the formation of off-rift coronae due to the rifting process. We model the interaction of a rising mantle plume associated with a rift with a preexisting layer of dense material at the lithosphere-mantle boundary and show that a rift and its associated off-rift coronae may be genetically linked. We calculate the resulting surface topographies, melt volumes, and Bouguer gravity anomalies and find a correlation to observations.

  7. Charging of moving surfaces by corona discharges sustained in air

    NASA Astrophysics Data System (ADS)

    Wang, Jun-Chieh; Zhang, Daihua; Leoni, Napoleon; Birecki, Henryk; Gila, Omer; Kushner, Mark J.

    2014-07-01

    Atmospheric pressure corona discharges are used in electrophotographic (EP) printing technologies for charging imaging surfaces such as photoconductors. A typical corona discharge consists of a wire (or wire array) biased with a few hundred volts of dc plus a few kV of ac voltage. An electric discharge is produced around the corona wire from which electrons drift towards and charge the underlying dielectric surface. The surface charging reduces the voltage drop across the gap between the corona wire and the dielectric surface, which then terminates the discharge, as in a dielectric barrier discharge. In printing applications, this underlying surface is continuously moving throughout the charging process. For example, previously charged surfaces, which had reduced the local electric field and terminated the local discharge, are translated out of the field of view and are replaced with uncharged surface. The uncharged surface produces a rebound in the electric field in the vicinity of the corona wire which in turn results in re-ignition of the discharge. The discharge, so reignited, is then asymmetric. We found that in the idealized corona charging system we investigated, a negatively dc biased corona blade with a dielectric covered ground electrode, the discharge is initially sustained by electron impact ionization from the bulk plasma and then dominated by ionization from sheath accelerated secondary electrons. Depending on the speed of the underlying surface, the periodic re-ignition of the discharge can produce an oscillatory charging pattern on the moving surface.

  8. Discharge and NO x removal characteristics of nonthermal plasma reactor with a heated corona wire

    Microsoft Academic Search

    Jae-Duk Moon; Geun-Taek Lee; Sang-Taek Geum

    2000-01-01

    The NOx removal characteristics of a wire-to-cylinder type nonthermal plasma reactor with a heated corona wire were investigated experimentally. A heated corona wire can produce energetic electrons and activate the oxidation of generated ozone. It was found that the corona starting voltage decreased with an increase in either the corona wire temperature or the initially fed NO concentration. At higher

  9. Corona Discharge to Water Surface and Its Transition to a Spark

    Microsoft Academic Search

    Igor V. Bozhko; Igor P. Kondratenko; Yuriy V. Serdyuk

    2011-01-01

    Impulse corona discharge in atmospheric air to the surface of a water layer with different electric conductivities is studied. The discharge was initiated from a corona electrode con- sisting of a metallic disk with evenly distributed corona needles. The dependences of the magnitudes of the measured impulse currents on the polarity of the corona electrode as well as the parameters

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

    Microsoft Academic Search

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

    2001-01-01

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

  11. The effects of atmospheric parameters on a corona probe used in measuring thunderstorm electric fields

    Microsoft Academic Search

    G. J. Byrne; A. A. Few; M. F. Stewart

    1986-01-01

    The effects of atmospheric parameters (pressure, temperature, relative humidity, and wind) on the induced corona current through a corona probe are evaluated through a laboratory investigation. The corona probe has a high series resistance, which tends to linearize the relationship between the induced corona current and the electric field. From a best fit of the data, the slope of the

  12. Slow magnetoacoustic waves in the solar corona

    NASA Astrophysics Data System (ADS)

    Nakariakov, Valery

    2012-07-01

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

  13. Energy Storage in an Asymmetric Bipolar Corona

    NASA Astrophysics Data System (ADS)

    Wolfson, Richard; Kennedy, M.

    2010-05-01

    We consider magnetic energy storage in a force-free model corona with bipolar boundary conditions at the coronal base. Unlike the usual dipole, our boundary conditions are asymmetric, with the bipolar structure centered in one hemisphere. We explore the role of latitudinal position and extent of the bipolar structure on the amount of energy that can be stored by longitudinal shearing of the magnetic footpoints. As found earlier for dipolar and quadrupolar boundary conditions, our solutions develop detached flux ropes, whose energy can exceed that of the corresponding open field. We compare this energy with that of previously-examined configurations, and with the energy needed to drive coronal mass ejections. This work is funded by NSF grant AGS0940503 to Middlebury College.

  14. Magnetohydrodynamic modeling of the solar corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1990-01-01

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

  15. Shock accelerated electron beams in the corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    2003-04-01

    In the solar corona shock waves can be observed as type II radio bursts in dynamic spectra of the solar radio radiation. Some of these type II bursts show sub-structures, so-called "herringbones", which are regarded as signatures of electron beams produced by the associated shock waves. A sample of solar type II radio bursts with "herringbone" - structures has been investigated with respect to their properties in dynamic radio spectra. It is well-known, that the electrons accelerated by a quasi-perpendicular shock establish a shifted loss-cone velocity distribution. The resulting properties of such a distribution for the shock accelerated electrons is compared with the features of "herringbones" in dynamic radio spectra. This study shows that the "herringbones" are mainly produced by nearly perpendicular shocks. The rapid pitch angle diffusion in the velocity space leads to a limited life time of the electron beams associated with the "herringbones".

  16. Electron Acceleration in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Mann, G.

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

  17. High Energy Particles in the Solar Corona

    E-print Network

    Widom, A; Larsen, L

    2008-01-01

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

  18. Coronae of stars with supersolar elemental abundances

    NASA Astrophysics Data System (ADS)

    Peretz, Uria; Behar, Ehud; Drake, Stephen A.

    2015-05-01

    Coronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the first ionization potential (FIP). This study focuses on the coronal composition of stars with supersolar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, ? Hor, HR 7291, ? Boo, and ? Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances we measured were obtained using the line-resolved spectra of the Reflection Grating Spectrometer (RGS) in conjunction with the higher throughput EPIC-pn camera spectra onboard the XMM-Newton observatory. A collisionally ionized plasma model with two or three temperature components is found to represent the spectra well. All elements are found to be consistently depleted in the coronae compared to their respective photospheres. For 11 LMi and ? Boo no FIP effect is present, while ? Hor, HR 7291, and ? Cen A and B show a clear FIP trend. These conclusions hold whether the comparison is made with solar abundances or the individual stellar abundances. Unlike the solar corona, where low-FIP elements are enriched, in these stars the FIP effect is consistently due to a depletion of high-FIP elements with respect to actual photospheric abundances. A comparison with solar (instead of stellar) abundances yields the same fractionation trend as on the Sun. In both cases, a similar FIP bias is inferred, but different fractionation mechanisms need to be invoked.

  19. 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.

  20. Ergodicity-breaking and the unraveling dynamics of a polymer in linear and nonlinear extensional flows

    E-print Network

    Shaqfeh, Eric

    Ergodicity-breaking and the unraveling dynamics of a polymer in linear and nonlinear extensional Synopsis We present both theory and simulations describing the unraveling dynamics of polymer chains in linear and nonlinear extensional flows. The nonlinearities associated with the hydrodynamic drag force

  1. Who Benefits from Economic Freedom? Unraveling the Effect of Economic Freedom on Subjective Well-Being

    E-print Network

    Kirches, Christian

    Who Benefits from Economic Freedom? Unraveling the Effect of Economic Freedom on Subjective Well.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html #12;University of Heidelberg Discussion Paper Series No. 531 Department of Economics Benefit or burden? Unraveling the effect of economic freedom on subjective well-being Kai Gehring July 2012 #12;1 Benefit

  2. Viscoelastic Relaxation of Topographic Highs on Venus to Produce Coronae

    NASA Technical Reports Server (NTRS)

    Janes, Daniel M.; Squyres, Steven W.

    1995-01-01

    Coronae on Venus are believed to result from the gravitationally driven relaxation of topography that was originally raised by mantle diapirs. We examine this relaxation using a viscoelastic finite element code, and show that an initially plateau shaped load will evolve to the characteristic corona topography of central raised bowl, annular rim, and surrounding moat. Stresses induced by the relaxation are consistent with the development of concentric extensional fracturing common on the outer margins of corona moats. However, relaxation is not expected to produce the concentric faulting often observed on the annular rim. The relaxation timescale is shorter than the diapir cooling timescale, so loss of thermal support controls the rate at which topography is reduced. The final corona shape is supported by buoyancy and flexural stresses and will persist through geologic time. Development of lower, flatter central bowls and narrower and more pronounced annular rims and moats enhanced by thicker crusts, higher thermal gradients, and crustal thinning over the diapir.

  3. A Data-Driven Evolution Model for the Global Corona

    NASA Astrophysics Data System (ADS)

    Feng, X. S.; Jiang, C.; Xiang, C. Q.; Wu, S.

    2011-12-01

    In this work we have developed a new time-dependent global corona model for the study of dynamic evolution of the global corona that can respond continuously to the changing of the photospheric magnetogram. A surface flux transport (SFT) model is employed to produce the time-varying and self-consistent magnetogram with synoptic map as input. The global corona model is established with our newly-developed numerical code AMR-CESE-MHD on an overset grid of Yin-Yang overlapping structure. The SFT model and the three-dimensional global corona model is coupled through the boundary condition of projected-characteristic method. Numerical study of the coronal evolution from Carrington rotation 1913 to 1915 presents results comparable with multi-observed coronal images.

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

    PubMed

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

    2011-01-01

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

  5. Evidence for compact structuring in the corona of active stars

    E-print Network

    F. Favata

    2000-11-27

    The ``current wisdom'' regarding the structuring of the X-ray emitting corona in active stars (i.e. a corona dominated by extended coronal structures) is briefly reviewed, followed by a review of a new approach to flare analysis and the analysis of a significant number of newly observed and previously published large flares, all leading to a much more compactly structured corona. Recent observations showing the polar location of the flaring plasma are then discussed, showing how the current evidence points toward a (flaring) corona composed of rather low-lying polar structures, also in agreement with some recent radio VLBI observational results and with starspot Doppler images. The resulting picture is significantly different from the solar case.

  6. Semi-analytical modelling of positive corona discharge in air

    NASA Astrophysics Data System (ADS)

    Pontiga, Francisco; Yanallah, Khelifa; Chen, Junhong

    2013-09-01

    Semianalytical approximate solutions of the spatial distribution of electric field and electron and ion densities have been obtained by solving Poisson's equations and the continuity equations for the charged species along the Laplacian field lines. The need to iterate for the correct value of space charge on the corona electrode has been eliminated by using the corona current distribution over the grounded plane derived by Deutsch, which predicts a cos m ? law similar to Warburg's law. Based on the results of the approximated model, a parametric study of the influence of gas pressure, the corona wire radius, and the inter-electrode wire-plate separation has been carried out. Also, the approximate solutions of the electron number density has been combined with a simplified plasma chemistry model in order to compute the ozone density generated by the corona discharge in the presence of a gas flow. Semianalytical approximate solutions of the spatial distribution of electric field and electron and ion densities have been obtained by solving Poisson's equations and the continuity equations for the charged species along the Laplacian field lines. The need to iterate for the correct value of space charge on the corona electrode has been eliminated by using the corona current distribution over the grounded plane derived by Deutsch, which predicts a cos m ? law similar to Warburg's law. Based on the results of the approximated model, a parametric study of the influence of gas pressure, the corona wire radius, and the inter-electrode wire-plate separation has been carried out. Also, the approximate solutions of the electron number density has been combined with a simplified plasma chemistry model in order to compute the ozone density generated by the corona discharge in the presence of a gas flow. This work was supported by the Consejeria de Innovacion, Ciencia y Empresa (Junta de Andalucia) and by the Ministerio de Ciencia e Innovacion, Spain, within the European Regional Development Fund contracts FQM-4983 and FIS2011-25161.

  7. Electric charging of flowing fuels by a corona discharge 

    E-print Network

    Santos, Ricardo Joaquin

    1977-01-01

    ~ ~ ~ ~ ~ ~ ~ ~ ~ . . ~ . ~ ~ ~ 12 Illustration of the ions velocity components inside the electric fields ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 14 Experimental results of electric current vs. applied voltage as measured at the corona point, ~ . . ~ . ~ . . . ~ . 18 Radial heat transfer... to a N. J E High Voltage (D C ) power supply, this power supply has been set to produce a negative potential at the ring The corona point has been grounded and because the negative polarity of the outer electrode this needle becomes the positive...

  8. Radicals generated from 2-chloro-5-fluorotoluene by corona discharge

    NASA Astrophysics Data System (ADS)

    Yi, Eun Hye; Yoon, Young Wook; Lee, Sang Kuk

    2014-06-01

    The generation of molecular radicals in corona discharge was investigated spectroscopically by varying the experimental conditions applied to a substituted toluene precursor. Vibronic emission spectra were observed from the corona discharge of 2-chloro-5-fluorotoluene seeded in a large amount of carrier gas helium. From an analysis of emission spectra observed, it was confirmed that bond dissociation energy plays a key role in radical formation. The possible pathway for the formation of benzyl-type radicals is proposed to explain the observation.

  9. The Extended Solar Cycle Tracked High into the Corona

    E-print Network

    Tappin, S J

    2012-01-01

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

  10. Elastic Thickness Estimates for Coronae Associated with Chasmata on Venus

    NASA Technical Reports Server (NTRS)

    Hoogenboom, T.; Martin, P.; Housean, G. A.

    2005-01-01

    Coronae are large-scale circular tectonic features surrounded by annular ridges. They are generally considered unique to Venus and may offer insights into the differences in lithospheric structure or mantle convective pattern between Venus and Earth. 68% of all coronae are associated with chasmata or fracture belts. The remaining 32% are located at volcanic rises or in the plains. Chasmata are linear to arcuate troughs, with trough parallel fractures and faults which extend for 1000 s of kilometers. Estimates of the elastic thickness of the lithosphere (T(sub e)) have been calculated in a number of gravity/topography studies of Venus and for coronae specifically. None of these studies, however, have explored the dependence of T(sub e) on the tectonic history of the region, as implied from the interpretation of relative timing relationships between coronae and surrounding features. We examine the relationship between the local T(sub e) and the relative ages of coronae and chasmata with the aim of further constraining the origin and evolution of coronae and chasmata systems.

  11. Hot Gaseous Coronae around Spiral Galaxies: Probing the Illustris Simulation

    NASA Astrophysics Data System (ADS)

    Bogdán, Ákos; Vogelsberger, Mark; Kraft, Ralph P.; Hernquist, Lars; Gilfanov, Marat; Torrey, Paul; Churazov, Eugene; Genel, Shy; Forman, William R.; Murray, Stephen S.; Vikhlinin, Alexey; Jones, Christine; Böhringer, Hans

    2015-05-01

    The presence of hot gaseous coronae around present-day massive spiral galaxies is a fundamental prediction of galaxy formation models. However, our observational knowledge remains scarce, since to date only four gaseous coronae have been detected around spirals with massive stellar bodies (? 2× {{10}11} {{M}? }). To explore the hot coronae around lower mass spiral galaxies, we utilized Chandra X-ray observations of a sample of eight normal spiral galaxies with stellar masses of (0.7-2.0)× {{10}11} {{M}? }. Although statistically significant diffuse X-ray emission is not detected beyond the optical radii (?20 kpc) of the galaxies, we derive 3? limits on the characteristics of the coronae. These limits, complemented with previous detections of NGC 1961 and NGC 6753, are used to probe the Illustris Simulation. The observed 3? upper limits on the X-ray luminosities and gas masses exceed or are at the upper end of the model predictions. For NGC 1961 and NGC 6753 the observed gas temperatures, metal abundances, and electron density profiles broadly agree with those predicted by Illustris. These results hint that the physics modules of Illustris are broadly consistent with the observed properties of hot coronae around spiral galaxies. However, one shortcoming of Illustris is that massive black holes, mostly residing in giant ellipticals, give rise to powerful radio-mode active galactic nucleus feedback, which results in under-luminous coronae for ellipticals.

  12. What are the R Coronae Borealis Stars?

    E-print Network

    Clayton, Geoffrey C

    2012-01-01

    The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich, supergiants, best known for their spectacular declines in brightness at irregular intervals. Efforts to discover more RCB stars have more than doubled the number known in the last few years and they appear to be members of an old, bulge population. Two evolutionary scenarios have been suggested for producing an RCB star, a double degenerate merger of two white dwarfs, or a final helium shell flash in a planetary nebula central star. The evidence pointing toward one or the other is somewhat contradictory, but the discovery that RCB stars have large amounts of 18O has tilted the scales towards the merger scenario. If the RCB stars are the product of white dwarf mergers, this would be a very exciting result since RCB stars would then be low-mass analogs of type Ia supernovae. The predicted number of RCB stars in the Galaxy is consistent with the predicted number of He/CO WD mergers. But, so far, only about 65 of the predicted 5000 RCB s...

  13. Galactic Corona or Local Group Intergalactic Medium?

    E-print Network

    Rik J. Williams; Smita Mathur; Fabrizio Nicastro

    2005-11-21

    Cosmological hydrodynamic simulations predict that the low redshift universe comprises a web of warm-hot intergalactic gas and galaxies, with groups of galaxies and clusters forming at dense knots in these filaments. Our own Galaxy being no exception is also expected to be surrounded by the warm-hot intergalactic medium, filling the Local Group. Some theoretical models also predict the existence of a hot Galactic corona. With X-ray and FUV observations of extragalactic sources, we can probe the warm-hot gas through absorption lines of highly ionized elements. Indeed, Chandra, XMM and FUSE observations have detected z=0 absorption lines toward many sightlines. The debate that has emerged is over the interpretation of these observations: are the z=0 absorption systems from the halo of our Galaxy or from the extended Local Group environment? This has important implications for our understanding of the mass of the Local Group, the physical conditions in the intergalactic medium, the structure of the Galaxy and galaxy formation in general. We will present the current status of the debate and discuss our ongoing observing program aimed at understanding the z=0 absorption systems, with an emphasis on the high quality Chandra spectra of the Mrk 421 and Mrk 279 sightlines.

  14. Mechanical vibration of H. V. conductors induced by corona

    SciTech Connect

    Farzaneh, M.; Teisseyre, Y. (Universite du Quebec a Chicoutimi, Chicoutimi, Quebec G7H 2B1 (CA))

    1988-07-01

    In this paper the corona induced force per hanging water drop from a H.V. conductor and the roles of the corona space charge and ionic wind in the mechanism of corona induced vibration were investigated. In order to determine the amplitude of the corona induced force F/sub t/, a water drop was simulated by a conical metal point. F/sub t/ was determined using two experimental set-ups: in the first, conical points were fixed along the underside of a smooth conductor, subjected to a dc high voltage; the corona induced force was then determined from the vertical displacement of the conductor. The second set-up is a pin-wheel consisting of a rotating arm at the ends of which two conical points were fixed on opposing sides. The forces exerted on the conical points were determined from the acceleration of the arm when subjected to a H.V.. The velocity of the ionic wind in the vicinity of a H.V. water drop was measured by a laser anemometer system and the order of the amplitude of the reactive force due to the ionic wind was estimated. On the other hand, it was observed that even in the absence of the ionic wind, a H.V. sphere suspended above a grounded plane vibrates when an intermittent space charge was injected in the intervening space. It was concluded that the reactive force due to the ionic wind was small compared to the electrostatic force between the corona space charge and the water drop. Thus, the intermittent presence of the corona space charge, produced by the drops hanging from the H.V. conductor, would appear to be the main cause of the vibration.

  15. High-resolution spectroscopy of the R Coronae Borealis Star V Coronae Australis

    E-print Network

    N. Kameswara Rao; David L. Lambert

    2007-10-26

    Optical high-resolution spectra of the R Coronae Borealis star V CrA at light maximum and during minimum light arediscussed. Abundance analysis confirms previous results showing that V CrA has the composition of the small subclass of R Coronae Borealis (RCB) stars know as `minority' RCBs, i.e., the Si/Fe and S/Fe ratios are 100 times their solar values. A notable novel result for RCBs is the detection of the 1-0 Swan system $^{12}$C$^{13}$C bandhead indicating that $^{13}$C is abundant: spectrum synthesis shows that $^{12}$C/$^{13}$C is about 3 to 4. Absorption line profiles are variable at maximum light with some lines showing evidence of splitting by about 10 km s$^{-1}$. A spectrum obtained as the star was recovering from a deep minimum shows the presence of cool C$_2$ molecules with a rotational temperature of about 1200K, a temperature suggestive of gas in which carbon is condensing into soot. The presence of rapidly outflowing gas is shown by blue-shifted absorption components of the Na {\\sc i} D and K {\\sc i} 7698 \\AA resonance lines.

  16. Systems biology unravels interferon responses to respiratory virus infections

    PubMed Central

    Kroeker, Andrea L; Coombs, Kevin M

    2014-01-01

    Interferon production is an important defence against viral replication and its activation is an attractive therapeutic target. However, it has long been known that viruses perpetually evolve a multitude of strategies to evade these host immune responses. In recent years there has been an explosion of information on virus-induced alterations of the host immune response that have resulted from data-rich omics technologies. Unravelling how these systems interact and determining the overall outcome of the host response to viral infection will play an important role in future treatment and vaccine development. In this review we focus primarily on the interferon pathway and its regulation as well as mechanisms by which respiratory RNA viruses interfere with its signalling capacity. PMID:24600511

  17. Interchange Reconnection in a Turbulent Corona

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    Magnetic reconnection at the interface between coronal holes and loops, the so-called interchange reconnection, can release the hotter, denser plasma from magnetically confined regions into the heliosphere, contributing to the formation of the highly variable slow solar wind. The interchange process is often thought to develop at the apex of streamers or pseudo-streamers, near Y- and X-type neutral points, but slow streams with loop composition have been recently observed along fanlike open field lines adjacent to closed regions, far from the apex. However, coronal heating models, with magnetic field lines shuffled by convective motions, show that reconnection can occur continuously in unipolar magnetic field regions with no neutral points: photospheric motions induce a magnetohydrodynamic turbulent cascade in the coronal field that creates the necessary small scales, where a sheared magnetic field component orthogonal to the strong axial field is created locally and can reconnect. We propose that a similar mechanism operates near and around boundaries between open and closed regions inducing a continual stochastic rearrangement of connectivity. We examine a reduced magnetohydrodynamic model of a simplified interface region between open and closed corona threaded by a strong unipolar magnetic field. This boundary is not stationary, becomes fractal, and field lines change connectivity continuously, becoming alternatively open and closed. This model suggests that slow wind may originate everywhere along loop-coronal-hole boundary regions and can account naturally and simply for outflows at and adjacent to such boundaries and for the observed diffusion of slow wind around the heliospheric current sheet.

  18. INTERCHANGE RECONNECTION IN A TURBULENT CORONA

    SciTech Connect

    Rappazzo, A. F.; Matthaeus, W. H. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Servidio, S. [Dipartimento di Fisica, Universita della Calabria, I-87036 Cosenza (Italy); Velli, M., E-mail: rappazzo@udel.edu [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-10-10

    Magnetic reconnection at the interface between coronal holes and loops, the so-called interchange reconnection, can release the hotter, denser plasma from magnetically confined regions into the heliosphere, contributing to the formation of the highly variable slow solar wind. The interchange process is often thought to develop at the apex of streamers or pseudo-streamers, near Y- and X-type neutral points, but slow streams with loop composition have been recently observed along fanlike open field lines adjacent to closed regions, far from the apex. However, coronal heating models, with magnetic field lines shuffled by convective motions, show that reconnection can occur continuously in unipolar magnetic field regions with no neutral points: photospheric motions induce a magnetohydrodynamic turbulent cascade in the coronal field that creates the necessary small scales, where a sheared magnetic field component orthogonal to the strong axial field is created locally and can reconnect. We propose that a similar mechanism operates near and around boundaries between open and closed regions inducing a continual stochastic rearrangement of connectivity. We examine a reduced magnetohydrodynamic model of a simplified interface region between open and closed corona threaded by a strong unipolar magnetic field. This boundary is not stationary, becomes fractal, and field lines change connectivity continuously, becoming alternatively open and closed. This model suggests that slow wind may originate everywhere along loop-coronal-hole boundary regions and can account naturally and simply for outflows at and adjacent to such boundaries and for the observed diffusion of slow wind around the heliospheric current sheet.

  19. New Images of the Solar Corona

    NASA Astrophysics Data System (ADS)

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

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

  20. 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

  1. Comparison of direct current and 50?Hz alternating current microscopic corona characteristics on conductors

    SciTech Connect

    Zhang, Shuai, E-mail: zhangshuai94@gmail.com; Zhang, Bo, E-mail: shizbcn@mail.tsinghua.edu.cn; He, Jinliang, E-mail: hejl@tsinghua.edu.cn [State Key Lab of Power Systems, and Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)

    2014-06-15

    Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and AC coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.

  2. Comparison of direct current and 50 Hz alternating current microscopic corona characteristics on conductors

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Zhang, Bo; He, Jinliang

    2014-06-01

    Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and AC coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.

  3. 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

  4. 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

  5. On the nature of the prominence - corona transition region

    NASA Astrophysics Data System (ADS)

    Parenti, Susanna; Vial, Jean-Claude

    2014-01-01

    Due to the complexity of their environment, prominences properties are still a matter of controversy. Prominences cool and dense plasma is suspended in the hot corona by a magnetic structure poorly known. Their thermal insulation from the corona results in a thin geometrical interface called prominence-corona-transition-region (PCTR). Here we will review the main properties of such a region as derived primarily from observations. We will introduce the thermal structure properties, describe the fine structure together with the Doppler-shift and width properties of lines of the emitting plasma. We will introduce the proposed interpretations of such observations and the limits of our knowledge imposed by the present instrumentation. We will conclude with a perspective for the future observations of the PCTR.

  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. 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.

  8. Measurements of Ion Current from a Corona-needle Charger Using a Faraday Cup Electrometer

    Microsoft Academic Search

    Panich Intra; Nakorn Tippayawong

    Corona-needle charger is widely used to impose a known net charge distribution on the aerosol particles for the electrical mobility particle sizer. However, the corona discharge and charging processes in the corona-needle charger at different operating conditions is not well understood. In the present paper, measurement of ion current from a corona-needle charger using a Faraday cup electrometer was performed

  9. An XMM-Newton Study of the Coronae of $?^2$ Coronae Borealis

    E-print Network

    J. A. Suh; M. Audard; M. Guedel; F. B. S. Paerels

    2005-06-10

    (Abridged) We present results of XMM-Newton observations of the RS CVn binary $\\sigma^2$ Coronae Borealis. The RGS and EPIC MOS2 spectra were simultaneously fitted with collisional ionization equilibrium plasma models to determine coronal abundances of various elements. Contrary to the solar first ionization potential (FIP) effect in which elements with a low FIP are overabundant in the corona compared to the solar photosphere, and contrary to the ``inverse'' FIP effect observed in several active RS CVn binaries, coronal abundance ratios in $\\sigma^2$ CrB show a complex pattern as supported by similar findings in the Chandra HETGS analysis of $\\sigma^2$ CrB with a different methodology (Osten et al. 2003). Low-FIP elements ($<10$ eV) have their abundance ratios relative to Fe consistent with the solar photospheric ratios, whereas high-FIP elements have their abundance ratios increase with increasing FIP. We find that the coronal Fe abundance is consistent with the stellar photospheric value, indicating that there is no metal depletion in $\\sigma^2$ CrB. However, we obtain a higher Fe absolute abundance than in Osten et al. (2003). Except for Ar and S, our absolute abundances are about 1.5 times larger than those reported by Osten et al. (2003). However, a comparison of their model with our XMM-Newton data (and vice versa) shows that both models work adequately in general. We find, therefore, no preference for one methodology over the other to derive coronal abundances. Despite the systematic discrepancy in absolute abundances, our abundance ratios are very close to those obtained by Osten et al. (2003). Finally, we confirm the measurement of a low density in \\ion{O}{7} ($< 4 \\times 10^{10}$ cm$^{-3}$), but could not confirm the higher densities measured in spectral lines formed at higher temperatures.

  10. Fabrication of Corona-Free Nanoparticles with Tunable Hydrophobicity

    PubMed Central

    2014-01-01

    A protein corona is formed at the surface of nanoparticles in the presence of biological fluids, masking the surface properties of the particle and complicating the relationship between chemical functionality and biological effects. We present here a series of zwitterionic NPs of variable hydrophobicity that do not adsorb proteins at moderate levels of serum protein and do not form hard coronas at physiological serum concentrations. These particles provide platforms to evaluate nanobiological behavior such as cell uptake and hemolysis dictated directly by chemical motifs at the nanoparticle surface. PMID:24971670

  11. Connecting the Quiet-Sun Convection Zone and Corona

    NASA Astrophysics Data System (ADS)

    Abbett, W. P.

    We present the first results of a new numerical model designed to simultaneously evolve the upper convection zone and low-corona within a single computational domain. We characterize (1) the properties of a quiet-Sun model atmosphere that forms as a result of the action of a convective dynamo; (2) the efficacy of parameterized cooling as a means of approximating the physics of optically-thick radiative transfer in the model chromosphere; (3) the magnetic and thermodynamic properties of the quiet-Sun atmosphere, and the magnetic connectivity between the turbulent sub-surface layers and corona; and (4) the properties of horizontally-directed magnetic fields in the low atmosphere.

  12. Effect of humidity on negative corona Trichel pulses

    NASA Astrophysics Data System (ADS)

    Deng, Fucheng; Ye, Lingyun; Song, Kaichen; Huang, Tiantian

    2014-08-01

    The effects of environmental parameters, e.g., humidity, on the corona discharges in practical applications are important. A two-dimensional (2D) hydrodynamic drift-diffusion model has been used to investigate the effects of humidity on the negative corona Trichel pulses (TPs). The simulations are performed with a conventional needle-to-plate configuration in humid air. It is found that the magnitude of TPs grows gradually with increasing humidity and the frequency of TPs increases with humidity. The movements and formations of charged particles are faster in higher humidity. The numerical results are consistent with the experimental observation.

  13. On Stellar Coronae and Solar Active Regions

    NASA Astrophysics Data System (ADS)

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

    2000-12-01

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

  14. Ionic wind generation by a wire-cylinder-plate corona discharge in air at atmospheric pressure

    E-print Network

    Paris-Sud XI, Université de

    -cylinder-plate electrode configuration is presented to generate ionic wind with a dc corona discharge in air at atmosphericIonic wind generation by a wire-cylinder-plate corona discharge in air at atmospheric pressure control.6 We examine here several configurations using a corona discharge. The principle of the ionic wind

  15. Impulse corona inception in dielectric covered rod-plane air gaps

    Microsoft Academic Search

    P. N. Mavroidis; P. N. Mikropoulosand; C. A. Stassinopoulos

    2009-01-01

    Positive corona inception in dielectric covered rod-plane air gaps stressed by lightning and switching impulse voltages is investigated. Corona inception probability distributions were obtained and the salient characteristics of the corona discharge, namely inception time and voltage, were measured as influenced by the gap length, waveshape of the applied impulse voltage and by the cover material, namely PTFE and epoxy

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

    E-print Network

    Mackay, Duncan

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

  17. Time dependence of NOx removal rate by a corona radical shower system

    Microsoft Academic Search

    Toshikazu Ohkubo; Seiji Kanazawa; Yukiharu Nomoto; Jen-Shih Chang; Takayoshi Adachi

    1996-01-01

    In this paper, the effects of flue gas flow rate and seed gas on the dynamics of corona discharge current-voltage characteristics and NO x removal characteristics are experimentally investigated for a corona radical shower system. The corona discharge current-voltage characteristics have two operating modes which have a significant influence on NOx removal characteristics, where the threshold value of the treatment

  18. Effect of relative humidity on electron distribution and ozone production by DC coronas in air

    Microsoft Academic Search

    Junhong Chen; Pengxiang Wang

    2005-01-01

    The effect of relative humidity on the electron distribution and the ozone production in the direct current (dc) corona discharge from a thin wire is evaluated with a numerical model. The model is based on the prior models of ozone production by dc coronas in dry air, with modifications to incorporate the effect of water vapor on the corona plasma

  19. New test method for evaluation of corona-caused aging in fiber-optic cables

    Microsoft Academic Search

    George G. Karady; M. Torgerson; D. Torgerson; J. Wild; M. Tuominen

    1999-01-01

    Fiber-optic communication cables installed on high voltage transmission line structures are subject to high electric fields, which may cause corona discharge near the grounded cable support. This corona discharge, in the long term, deteriorates the cable jacket, which may result in puncture and failure. This paper proposes a new test method to evaluate the corona resistance of fiber-optic cable jackets.

  20. Ozone Production in the Negative DC Corona: The Dependence of Discharge Polarity

    Microsoft Academic Search

    Junhong Chen; Jane H. Davidson

    2003-01-01

    The rate of production and the spatial distribution of ozone in the negative DC corona discharge are predicted with a numerical model. The results are compared to prior experimental data and to results previously presented by the authors for the positive corona discharge. In agreement with experimental data, ozone production rate in the negative corona is an order of magnitude

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

    Microsoft Academic Search

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

    1999-01-01

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

  2. Spontaneous unraveling of hagfish slime thread skeins is mediated by a seawater-soluble protein adhesive.

    PubMed

    Bernards, Mark A; Oke, Isdin; Heyland, Andreas; Fudge, Douglas S

    2014-04-15

    Hagfishes are known for their ability to rapidly produce vast quantities of slime when provoked. The slime is formed via the interaction between seawater and two components released by the slime glands: mucin vesicles from gland mucous cells, which swell and rupture in seawater to form a network of mucus strands, and intermediate filament-rich threads, which are produced within gland thread cells as tightly coiled bundles called skeins. A previous study showed that the unraveling of skeins from Atlantic hagfish (Myxine glutinosa) requires both the presence of mucins and hydrodynamic mixing. In contrast, skeins from Pacific hagfish (Eptatretus stoutii) unravel in the absence of both mucins and mixing. We tested the hypothesis that spontaneous unraveling of E. stoutii skeins is triggered by the dissolution of a seawater-soluble protein adhesive and the release of stored strain energy within the coiled thread. Here we show that, as predicted by this hypothesis, unraveling can be initiated by a protease under conditions in which unraveling does not normally occur. We also demonstrate, using high resolution scanning electron microscopy, that the treatment of skeins with solutions that cause unraveling also leads to the disappearance of surface and inter-thread features that remain when skeins are washed with stabilizing solutions. Our study provides a mechanism for the deployment of thread skeins in Pacific hagfish slime, and raises the possibility of producing novel biomimetic protein adhesives that are salt, temperature and kosmotrope sensitive. PMID:24744422

  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. Unravelling the mechanism of dual-specificity GAPs

    PubMed Central

    Sot, Begoña; Kötting, Carsten; Deaconescu, Delia; Suveyzdis, Yan; Gerwert, Klaus; Wittinghofer, Alfred

    2010-01-01

    The molecular mechanism by which dual-specificity RasGAPs of the Gap1 subfamily activate the GTP hydrolysis of both Rap and Ras is an unresolved phenomenon. RasGAPs and RapGAPs use different strategies to stimulate the GTPase reaction of their cognate G-proteins. RasGAPs contribute an arginine finger to orient through the Gln61 of Ras the nucleophilic water molecule. RapGAP contributes an asparagine (Asn thumb) into the active site to substitute for the missing Gln61. Here, by using steady-state kinetic assays and time-resolved Fourier-transform infrared spectroscopy (FTIR) experiments with wild type and mutant proteins, we unravel the remarkable mechanism for the specificity switch. The plasticity of GAP1IP4BP and RASAL is mediated by the extra GTPase-activating protein (GAP) domains, which promote a different orientation of Ras and Rap's switch-II and catalytic residues in the active site. Thereby, Gln63 in Rap adopts the catalytic role normally taken by Gln61 of Ras. This re-orientation requires specific interactions between switch-II of Rap and helix-?6 of GAPs. This supports the notion that the specificities of fl proteins versus GAP domains are potentially different. PMID:20186121

  5. Asynchronous Corona Training Protocols in Wireless Sensor and Actor Networks

    E-print Network

    Pinotti, Maria Cristina

    capabilities, can send long-range directional broadcasts to the sensors at distance at most , can receiveAsynchronous Corona Training Protocols in Wireless Sensor and Actor Networks F. Barsi A.A. Bertossi protocols are proposed for wireless networks consisting of sensors and a single actor, where the sensors

  6. Time-dependent heating of the solar corona

    Microsoft Academic Search

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

    1995-01-01

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

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

    Microsoft Academic Search

    C.-Y. Tu; E. Marsch

    2001-01-01

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

  8. The energy and pressure balance in the corona

    Microsoft Academic Search

    R. W. P. McWhirter; R. Wilson

    1976-01-01

    The paper presents a brief review of studies related to the energy balance in the solar atmosphere above the chromosphere. Processes discussed include heating of the outer corona by the dissipation of mechanical waves generated in the lower atmosphere, convective outflow of the atmosphere giving rise to the solar wind, thermal conductivity, and radiated power loss. Energy-balance models dealing primarily

  9. Calculation of corona onset voltage for duct-type precipitators

    Microsoft Academic Search

    Mazen Abdel-Salam; Dennis Wiitanen

    1993-01-01

    A pure theoretical method for calculating the onset voltage of corona in duct-type electrostatic precipitators that is independent of the arrangement of discharge wires relative to the collecting plates is described. This method is based on a criterion for self-recurring single electron avalanches in a known electric field distribution in the ionization zone surrounding the discharge wire. The results computed

  10. Factors that influence the corona charging of fibrous dielectric materials

    Microsoft Academic Search

    Belaid Tabti; Lucian Dascalescu; Marius Plopeanu; Mohamed Mekideche

    2009-01-01

    Corona discharge has a wide range of industry applications, such as charging the photosensitive layer and the toner particles in photocopying machines, modifying the wet-ability of plastic films, and conditioning the electrets for air filters. In all these situations, it is important to evaluate the surface charge density and compare it to the dielectric rigidity of atmospheric air. Experiments were

  11. 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.

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

    Microsoft Academic Search

    A. Usmanov; M. Goldstein

    2004-01-01

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

  13. Chemical composition of R Coronae Borealis and XX Camelopardalis

    SciTech Connect

    Cottrell, P.L.; Lambert, D.

    1982-10-15

    Three R Coronae Borealis stars (R CrB, XX Cam, and RY Sgr) have been examined using extensive, high resolution, high signal-to-noise Reticon data. From He- and C-rich models and an appropriate model atmosphere code, the following atmospheric parameters were derived

  14. Corona ageing tests of RTV and RTV nanocomposite materials

    Microsoft Academic Search

    Lan Lei; Wen Xishan; Cai Dengke

    2004-01-01

    Silicone rubber insulating materials are superior to conventional porcelain materials, whose special water repellency and transfer of water repellency is favorable in power industry. However, two points are concerned in its application, and these are long-term reliability and lack of methods to assess their long-term performance. Corona and arc are important factors that induce degradation of RTV insulating materials during

  15. SIMBA observations of the R Corona Australis molecular cloud

    Microsoft Academic Search

    K. Kampgen; B. Reipurth; M. Albrecht; E. Kreysa; R. Lemke; M. Nielbock; L. A. Reichertz; A. Sievers; R. Zylka

    2003-01-01

    We have mapped the R Corona Australis molecular cloud at 1.2 mm with SIMBA on SEST and detected 25 distinct dust emission peaks. While 7 of them coincide with positions of previously known young stars, 18 are seemingly not associated with any known stellar object. We discuss the nature of individual sources and conclude that there are at least four

  16. Numerical modeling of ozone production in direct current corona discharge

    Microsoft Academic Search

    K. Yanallah; S. Hadj Ziane; A. Belasri; Y. Meslem

    2006-01-01

    Ozone has many industrial uses, including treatment of municipal water, wastewater, cooling towers, industrial process water, effluent water treatment, food processing, through to water fit for consumption and marine life. In this paper, we study the ozone production by negative electric corona discharge, witch involves passing the feed of gas, air rich, through an electrical discharge. This is done by

  17. Gas-magnetic field interactions in the solar corona

    Microsoft Academic Search

    G. W. Pneuman; Roger A. Kopp

    1971-01-01

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

  18. Novel dielectric reduces corona breakdown in ac capacitors

    NASA Technical Reports Server (NTRS)

    Loehner, J. L.

    1972-01-01

    Dielectric system was developed which consists of two layers of 25-gage paper separated by one layer of 50-gage polypropylene to reduce corona breakdown in ac capacitors. System can be used in any alternating current application where constant voltage does not exceed 400 V rms. With a little research it could probably be increased to 700 to 800 V rms.

  19. Corona-induced electrohydrodynamic instabilities in low conducting liquids

    Microsoft Academic Search

    F. Vega; A. T. Pérez

    2003-01-01

    The rose-window electrohydrodynamic (EHD) instability has been observed when a perpendicular field with an additional unipolar ion injection is applied onto a low conducting liquid surface. This instability has a characteristic pattern with cells five to 10 times greater than those observed in volume instabilities caused by unipolar injection. We have used corona discharge from a metallic point to perform

  20. Corona point measurements in a thundercloud at Langmuir laboratory

    Microsoft Academic Search

    M. E. Weber; M. F. Stewart; A. A. Few

    1983-01-01

    A meteorological radiosonde, modified by the attachment of vertically oriented, pointed, metal rods, and associated insrumentation, was released beneath a thundercloud at Langmuir Laboratory, New Mexico. In addition to information on temperature and winds, the instrument provided an estimate of the vertical component of the cloud electric field by measurement of corona current induced in the rods. Charge volumes inferred

  1. Ion Heating in the Solar Corona and Solar Wind

    Microsoft Academic Search

    Steven Cranmer

    2009-01-01

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

  2. Negative ion\\/molecule reactions in a negative corona discharge

    Microsoft Academic Search

    V. Kotasek

    1981-01-01

    An atmospheric pressure negative corona discharge (point to plane) coupled to a quadrupole mass spectrometer was used to study negative ion\\/molecular chemistry. It was shown that neutral intermediates, mainly 03, N02 and N0, are produced by high energy electron dissociation of air constituents in a very narrow volume close to the point electrode. The neutrals are transported by air flow

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

    Microsoft Academic Search

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

    1990-01-01

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

  4. 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.

  5. A Positive Corona-Based Ion Wind Generator

    Microsoft Academic Search

    Erdinc Karakas; Asma Begum; Mounir Laroussi

    2008-01-01

    Using an electrical discharge to control airflow has recently been an active area of research. This is mostly because of the interest in the manipulation of free airflow for aerodynamic applications. Corona discharges are well suited for these applications. In this paper, we present photographs illustrating the ion wind effect in a clear visual manner. The device used is a

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  7. The Optical Diagnosis of Underwater Positive Sparks and Corona Discharges

    NASA Astrophysics Data System (ADS)

    Chen, Dan; Zeng, Xinwu; Wang, Yibo

    2014-12-01

    In this paper, two types of underwater discharges, spark discharge and corona discharge, are investigated by optical diagnosis using a high speed framing camera (HSFC) with the framing time within nanoseconds under the same experimental conditions. In order to capture the photographs of streamer propagation, the influence of the randomicity of the pre-breakdown duration is taken into consideration. By increasing the conductivity of water, the randomicity reduces effectively. Experimental results show that, for a spark discharge, the process can be separated into three stages: the generation and propagation of a streamer, the generation and expansion of the discharge channel, and the development and annihilation of the plasma. The streamers do not directly move to the opposite electrode, but form a bush-like figure. With the increase of the number of branches, the velocity of streamer propagation slows down. The trajectory of the initial channel between electrodes is not straight. However, with the channel expanding, its shape transforms into a straight column. For a corona discharge, there are two stages: the generation and propagation of a streamer, and the stagnation and annihilation of the streamer. The initial streamer in a corona discharge is generated later than in a spark discharge. The forms of streamers for both kinds of discharge are similar; however, streamers generated by a corona discharge propagate with a slower velocity and the number of branches is less compared with a spark discharge. When the energy injection stops, the luminescence of plasma inside the discharge channel (spark discharge) or streamers (corona discharge) becomes weaker and weaker, and finally disappears.

  8. Fast Time Analysis of Intermittent Point-to-Plane Corona in Air. III. The Negative Point Trichel Pulse Corona

    Microsoft Academic Search

    M. R. AMINt

    1954-01-01

    Fast oscilloscopic time analysis of the negative point Trichel pulse corona in room air at various pressures and gap geometries reveals the following data. The very short rise and quenching time of the pulse at atmospheric pressure observed by English is confirmed. Under these conditions the secondary action is a photoelectric liberation from the cathode and discharge extinguishes by dissociative

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

    NASA Astrophysics Data System (ADS)

    Schmit, D. J.

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

  10. Physical conditions in the corona for a bipolar magnetic region

    NASA Technical Reports Server (NTRS)

    Vorpahl, J. A.

    1978-01-01

    The S-056 X-ray data from Skylab are used to determine quantitative values for the coronal conditions characterizing a new bipolar magnetic region (BMR). In particular, the analysis includes: (1) the time variation of the total soft X-ray flux from the BMR as a function of time; (2) the temporal and spatial variation of the temperature and emission measure; (3) the variation with time of thermal energy density; (4) the (calculated) magnetic-field configuration and magnetic flux density in the corona; and (5) the temporal variation of the magnetic-field energy in the corona. Detailed comparisons are made between the configuration of X-ray features and the magnetic-field topology.

  11. The Effect of a Corona Discharge on a Lightning Attachment

    SciTech Connect

    Aleksandrov, N.L. [Moscow Institute of Physics and Technology, Institutskii pr. 9, Dolgoprudnyi, Moscow oblast, 141700 (Russian Federation); Bazelyan, E.M. [Krzhizhanovskii Rower Engineering Institute, Leninskii pr. 19, Moscow, 117927 (Russian Federation); Raizer, Yu.P. [Institute for Problems of Mechanics, Russian Academy of Sciences, pr. Vernadskogo 101, Moscow, 117526 (Russian Federation)

    2005-01-15

    The interaction between the lightning leader and the space charge accumulated near the top of a ground object in the atmospheric electric field is considered using analytical and numerical models developed earlier to describe spark discharges in long laboratory gaps. The specific features of a nonstationary corona discharge that develops in the electric field of a thundercloud and a downward lightning leader are analyzed. Conditions for the development of an upward lightning discharge from a ground object and for the propagation of an upward-connecting leader from the object toward a downward lightning leader (the process determining the point of strike to the ground) are investigated. Possible mechanisms for the interaction of the corona space charge with an upward leader and prospects of using it to control downward lightning discharges are analyzed.

  12. Corona method and apparatus for altering carbon containing compounds

    DOEpatents

    Sharma, Amit K. (Richland, WA); Camaioni, Donald M. (Richland, WA); Josephson, Gary B. (Richland, WA)

    1999-01-01

    The present invention is a method and apparatus for altering a carbon containing compound in an aqueous mixture. According to a first aspect of the present invention, it has been discovered that for an aqueous mixture having a carbon containing compound with an ozone reaction rate less than the ozone reaction rate of pentachlorophenol, use of corona discharge in a low or non-oxidizing atmosphere increases the rate of destruction of the carbon containing compound compared to corona discharge an oxidizing atmosphere. For an aqueous mixture containing pentachlorphenol, there was essentially no difference in destruction between atmospheres. According to a second aspect of the present invention, it has been further discovered that an aqueous mixture having a carbon containing compound in the presence of a catalyst and oxygen resulted in an increased destruction rate of the carbon containing compound compared to no catalyst.

  13. Corona Method And Apparatus For Altering Carbon Containing Compounds

    DOEpatents

    Sharma, Amit K. (Plainsboro, NJ); Camaioni, Donald M. (Richland, WA); Josephson; Gary B. (Richland, WA)

    2004-05-04

    The present invention is a method and apparatus for altering a carbon-containing compound in an aqueous mixture. According to a first aspect of the present invention, it has been discovered that for an aqueous mixture having a carbon containing compound with an ozone reaction rate less than the ozone reaction rate of pentachlorophenol, use of corona discharge in a low or non-oxidizing atmosphere increases the rate of destruction of the carbon containing compound compared to corona discharge an oxidizing atmosphere. For an aqueous mixture containing pentachlorphenol, there was essentially no difference in destruction between atmospheres. According to a second aspect of the present invention, it has been further discovered that an aqueous mixture having a carbon-containing compound in the presence of a catalyst and oxygen resulted in an increased destruction rate of the carbon containing compound compared to no catalyst.

  14. Kinetics of Electrons in the Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Vocks, C.; Mann, G.

    2003-09-01

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

  15. Investigation of the corona current in a vacuum bulb

    NASA Astrophysics Data System (ADS)

    Chyhin, Vasyl

    2014-05-01

    The dependence of the negative corona current on the gas pressure was studied experimentally and theoretically in view of designing a gas-pressure sensor to be applied in the production of light bulbs. The gas pressure was varied in the range 1×10-2 Torr - 7.4×102 Torr. The dependence of the current on the gas pressure is characterized by a strong heterogeneity. This allowed the implementation of a prototype of a high-speed sensor for a wide range of gas pressures. A mathematical model was developed of the negative corona current behavior by taking into account the ionization of the gas molecules, the attachment and detachment of electrons, the charge drift and the surface ion-electron emission. The results of the numerical simulations describe satisfactorily the experimental dependences.

  16. The degradation of organic dyes by corona discharge

    SciTech Connect

    Goheen, S.C.; McCulloch, M.; Durham, D.E.; Heath, W.O.

    1992-02-01

    Several dyes in water were individually exposed to corona discharge. Light absorbance decreased for all organic dyes with time. Absorbance losses with methylene blue, malachite green, and new coccine were studied. The loss of color was followed using an in situ colorimeter and the effects of varying the current, voltage, gas phase, stirring rates, salinity, and electrode spacing were investigated. The highest reaction rates were observed using the highest current, highest voltage (up to 10kV), highest stirring rate, lowest salinity, smallest electrode spacing, and an environment containing enhanced levels of oxygen. Current was higher in the presence of nitrogen than in the presence of oxygen (for the same voltage), but the reaction of methylene blue did not proceed unless oxygen was present. These results help identify conditions using corona discharge in which dyes, and potentially other organics, can be destroyed. 22 refs., 5 figs.

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

    NASA Astrophysics Data System (ADS)

    Vourlidas, A.

    2012-01-01

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

  18. Acoustic field effects on a negative corona discharge

    NASA Astrophysics Data System (ADS)

    Bálek, R.; ?ervenka, M.; Pekárek, S.

    2014-06-01

    For a negative corona discharge under atmospheric pressure in different regimes, we investigated the effects of an acoustic field both on its electrical parameters and on the change in its visual appearance. We found that the application of an acoustic field on the true corona discharge, for particular currents, decreases the discharge voltage. The application of an acoustic field on the discharge in the filamentary streamer regime substantially extends the range of currents for which the discharge voltage remains more or less constant, i.e. it allows a substantial increase in the power delivered to the discharge. The application of an acoustic field on the discharge causes the discharge to spread within the discharge chamber and consequently, a highly reactive non-equilibrium plasma is created throughout the inter-electrode space. Finally, our experimental apparatus radiates almost no acoustic energy from the discharge chamber.

  19. Confirmed assignments of isomeric dimethylbenzyl radicals generated by corona discharge.

    PubMed

    Yoon, Young Wook; Lee, Sang Kuk

    2011-12-01

    The controversial vibronic assignments of isomeric dimethylbenzyl radicals were clearly resolved by using different precursors. By employing corresponding dimethylbenzyl chlorides as precursors, we identified the origins of the vibronic bands of the dimethylbenzyl radicals generated by corona discharge of 1,2,4-trimethylbenzene. From the analysis of the spectra observed from the dimethylbenzyl chlorides in a corona excited supersonic expansion, we revised previous assignments of the 3,4-, 2,4-, and 2,5-dimethylbenzyl radicals. Spectroscopic data of electronic transition and vibrational mode frequencies in the ground electronic state of each isomer were accurately determined by comparing them with those obtained by an ab initio calculation and with the known vibrational data of 1,2,4-trimethylbenzene. PMID:22149790

  20. Confirmed assignments of isomeric dimethylbenzyl radicals generated by corona discharge

    NASA Astrophysics Data System (ADS)

    Wook Yoon, Young; Kuk Lee, Sang

    2011-12-01

    The controversial vibronic assignments of isomeric dimethylbenzyl radicals were clearly resolved by using different precursors. By employing corresponding dimethylbenzyl chlorides as precursors, we identified the origins of the vibronic bands of the dimethylbenzyl radicals generated by corona discharge of 1,2,4-trimethylbenzene. From the analysis of the spectra observed from the dimethylbenzyl chlorides in a corona excited supersonic expansion, we revised previous assignments of the 3,4-, 2,4-, and 2,5-dimethylbenzyl radicals. Spectroscopic data of electronic transition and vibrational mode frequencies in the ground electronic state of each isomer were accurately determined by comparing them with those obtained by an ab initio calculation and with the known vibrational data of 1,2,4-trimethylbenzene.

  1. A system for repetitive pulsed corona plasmas, with ecological applications

    Microsoft Academic Search

    N. Georgeseut; A. Vulpe; R. Minea

    2003-01-01

    A depollution system for gases, using the repetitive pulsed corona plasmas, is described. The main sub-systems are: High-voltage repetitive pulser; treatment chamber; gas flow circuit; gas analyzer. The high-voltage repetitive pulser discharges a capacitor in the primary of a pulse transformer. The high-voltage switch is a thyratron. Many construction manners were tested for the pulse transformer. High-voltage pulses with 25-100

  2. Initiation of pulsed corona discharge under supercritical conditions

    Microsoft Academic Search

    Evgeniya H. Lock; Alexei V. Saveliev; Lawrence A. Kennedy

    2005-01-01

    Supercritical carbon dioxide is a medium with unique properties and variety of applications in modern green chemistry. The generation of pulsed corona discharge in supercritical CO2 is studied experimentally for point-to-plane and wire-to-plane geometries. The low breakdown voltages recorded near the critical point are attributed to peculiarities of electron kinetics in a medium characterized by high spatial inhomogeneity and enhanced

  3. Corona discharge ion mobility spectrometry of aliphatic and aromatic hydrocarbons

    Microsoft Academic Search

    Helko Borsdorf; Hubert Schelhorn; Johannes Flachowsky; Hans-Rüdiger Döring; Joachim Stach

    2000-01-01

    Positive ion mobility spectra of n-alkanes (n-C5 to n-C19), branched chain alkanes (C5 to C9) and aromatic compounds (benzene and alkylated benzenes) were acquired with an ion mobility spectrometer equipped with a corona discharge ionization source. Reduced mobilities and mass-to-mobility correlation curves were determined for these compounds. Depending on their concentration, the n-alkanes form one or two product ion peaks.

  4. Formation and Investigation of Corona Charged Films from Polylactic Acid

    Microsoft Academic Search

    E. A. Gencheva; T. A. Yovcheva; M. G. Marudova; A. P. Viraneva; I. P. Bodurov; G. A. Mekishev; S. H. Sainov

    2010-01-01

    The aim of the present work is the development of technology for formation of corona charged electret films from polylactic acid and investigation of their structural, optical and electret properties. Polylactide films with different degree of crystalinity were prepared by casting of poly-L-lactide and poly-DL lactide blended solutions. Then glass transition, crystallization and melting temperatures, as well as the crystalinity

  5. Magnetic fields and the structure of the solar corona

    Microsoft Academic Search

    Martin D. Altschuler; Gordon Newkirk

    1969-01-01

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

  6. 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.

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

    SciTech Connect

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

    2012-12-20

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

  8. Peptide fragmentation by corona discharge induced electrochemical ionization

    Microsoft Academic Search

    John R. Lloyd; Sonja Hessb

    2010-01-01

    Fundamental studies have greatly improved our understanding of electrospray, including the underlying electrochemical reactions.\\u000a Generally regarded as disadvantageous, we have recently shown that corona discharge (CD) can be used as an effective method\\u000a to create a radical cation species [M]+., thus optimizing the electrochemical reactions that occur on the surface of the stainless steel (SS) electrospray capillary\\u000a tip. This technique

  9. A naturally driven reconnection mechanism for the solar corona

    NASA Astrophysics Data System (ADS)

    Lapenta, G.; Knoll, D.

    2002-12-01

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

  10. Weak compressible magnetohydrodynamic turbulence in the solar corona

    E-print Network

    Benjamin D. G. Chandran

    2005-11-21

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

  11. OBSERVATION OF ULTRAFINE CHANNELS OF SOLAR CORONA HEATING

    SciTech Connect

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

    2012-05-01

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

  12. Neutrally buoyant diapirs: A model for Venus coronae

    Microsoft Academic Search

    Dorothy M. Koch; Michael Manga

    1996-01-01

    Coronae are typically circular features, 100-600 km in diameter, characterized by a deformed annular ring that is often topographically high. The central region may be raised or depressed relative to the ambient elevation. Previous studies have proposed an evolutionary progression beginning with dome-shaped features which have radiating extensional rifts, followed by plateau-shaped features which have both concentric deformation and radial

  13. Estimation of winding insulation resistance to the corona discharges

    NASA Astrophysics Data System (ADS)

    Leonov, A.; Red'ko, V.; Soldatenko, E.

    2014-10-01

    This article presents test results of enameled winding wires, characterizing an insulation electrical and mechanical strength. Standard and original test methods were used. Note that existing standard test methods do not estimate enamel insulation resistance to the electrical loads under winding operation of variable-speed drive. We show that estimation of wire corona resistance can be done by high frequency electrical impulse testing. Wire insulation plays the main role of reliability of insulation system.

  14. Collisional damping of surface waves in the solar corona

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  15. 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.

  16. On the effect of corona treatment on polypropylene for capacitors

    Microsoft Academic Search

    J. Sarlaboux; C. Mayoux

    1979-01-01

    In order to improve the adhesion of the electrodes which are most often vacuum-evaporated, the surface of the polypropylene film has been subjected to a high-pressure corona discharge at a frequency of the order of 10 kHz or higher. This type of surface treatment is very easily used and does not produce any transformation of the material for short expositions.

  17. Unraveling the chemical space of terrestrial and meteoritic organic matter

    NASA Astrophysics Data System (ADS)

    Schmitt-Kopplin, Philippe; Harir, Mourad; Hertkorn, Norbert; Kanawati, Basem; Ruf, Alexander; Quirico, Eric; Bonal, Lydie; Beck, Pierre; Gabelica, Zelimir

    2015-04-01

    In terrestrial environments natural organic matter (NOM) occurs in soils, freshwater and marine environments, in the atmosphere and represents an exceedingly complex mixture of organic compounds that collectively exhibits a nearly continuous range of properties (size-reactivity continuum). In these materials, the "classical" biogeosignatures of the (biogenic and geogenic) precursor molecules, like lipids, lignins, proteins and natural products have been attenuated, often beyond recognition, during a succession of biotic and abiotic (e.g. photo- and redox chemistry) reactions. Because of this loss of biochemical signature, these materials can be designated non-repetitive complex systems. The access to extra-terrestrial organic matter is given i.e. in the analysis of meteoritic materials. Numerous descriptions of organic molecules present in organic chondrites have improved our understanding of the early interstellar chemistry that operated at or just before the birth of our solar system. However, many molecular analyses are so far targeted toward selected classes of compounds with a particular emphasis on biologically active components in the context of prebiotic chemistry. Here we demonstrate that a non-targeted ultrahigh-resolution molecular analysis of the solvent-accessible organic fraction of meteorite extracted under mild conditions allows one to extend its indigenous chemical diversity to tens of thousands of different molecular compositions and likely millions of diverse structures. The description of the molecular complexity provides hints on heteroatoms chronological assembly, shock and thermal events and revealed recently new classes of thousands of novel organic, organometallic compounds uniquely found in extra-terrestrial materials and never described in terrestrial systems. This high polymolecularity suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biological and biogeochemical-driven chemical space. (ultra)High resolution analytical approaches will be presented in their application to unravel the chemical nature and organic signatures in bio-geosystems and especially in selected chondritic (organic and ordinary) and achondritic meteorites. We will focus on thermal effects in CM types of materials and describe the effect of shock events on the changes in chemodiversity and the formation of unique novel organic compounds using high magnetic field ultrahigh resolution mass spectrometry (12 Tesla ion cyclotron resonance Fourier transform mass spectrometry - ICR-FT/MS) and nuclear magnetic resonance spectroscopy (Cryo 800MHz NMR).

  18. Plasma Outflows in the Corona as Observed With Hinode XRT

    NASA Astrophysics Data System (ADS)

    Sakao, T.; Kano, R.; Narukage, N.; Deluca, E. E.; Grigis, P.

    2008-12-01

    We present imaging observations of plasma outflows in the solar corona made with X-Ray Telescope (XRT) aboard Hinode satellite. The XRT employs a back-illuminated CCD as the focal-plane imaging device which enables us, together with an optimized set of analysis filters, to investigate, for the first time, dynamic behavior of relatively cool (1-2 MK, say) plasmas in the corona. The XRT revealed a clear pattern of continuous outflow of plasmas from the edge of an active region NOAA AR 10942 right adjacent to a coronal hole. Plasmas of temperature ~1 MK flowed out with a sub-sonic velocity of typically ~140 km/s along magnetic field lines that are most likely open towards the interplanetary space. These outflowing plasmas may constitute a fraction of the (slow) solar wind. In addition to this discovery, the XRT has so far identified rich patterns of continuous outflows including those from coronal hole boundaries and along fan-like field lines rooted inside coronal holes. XRT observations of such plasma outflows in the corona are presented and their possible implications to the solar wind discussed.

  19. 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.

  20. Formation and Investigation of Corona Charged Films from Polylactic Acid

    NASA Astrophysics Data System (ADS)

    Gencheva, E. A.; Yovcheva, T. A.; Marudova, M. G.; Viraneva, A. P.; Bodurov, I. P.; Mekishev, G. A.; Sainov, S. H.

    2010-01-01

    The aim of the present work is the development of technology for formation of corona charged electret films from polylactic acid and investigation of their structural, optical and electret properties. Polylactide films with different degree of crystalinity were prepared by casting of poly-L-lactide and poly-DL lactide blended solutions. Then glass transition, crystallization and melting temperatures, as well as the crystalinity degree were determined by a differential scanning calorimetry. The charging of the samples in a corona discharge was carried out by means of a conventional corona triode system. Sample surface potential was measured by the method of the vibrating electrode with compensation. The time dependences of the sample surface potential under room conditions were studied for 50 days. The effect of lower pressure on the surface potential of charged samples was investigated. It was established that the reduced pressure leaded to the surface potential decay of the PLA electrets. The same effect was earlier observed for other polymer films. The optical characteristics—surface refractive index and optical dispersion, were determined by the method of the disappearing diffraction pattern using a laser refractometer.

  1. Soot oxidation in a corona plasma-catalytic reactor

    NASA Astrophysics Data System (ADS)

    Ranji-Burachaloo, H.; Masoomi-Godarzi, S.; Khodadadi, A. A.; Vesali-Naseh, M.; Mortazavi, Y.

    2014-08-01

    Oxidation of soot by corona plasma was investigated at conditions of exhaust gases from diesel engines, both in the absence and presence of CoOx as a catalyst. The CoOx catalyst nanoparticles were synthesized by a precipitation method. The BET surface area of the catalyst was 50 m2/g, corresponding to 23 nm particles. An aluminum grid was sequentially dip-coated for several times by suspensions of the soot in toluene and/or fine catalyst powder in DI water. The grid was used as the plate of a pin-to-plate corona reactor. Air at 180 °C was passed through the corona reactor to oxidize the soot, oxidation products of which were analyzed by both gas chromatograph and FTIR with a gas cell. Soot oxidation rate linearly increased with an increase of input energy. When the soot was deposited on a layer of the CoOx catalyst, the soot oxidation rate increased up to 2 times. The only product of the plasma (catalytic) oxidation of soot was CO2 determined by FTIR. O produced in the plasma discharge oxidized the soot and the active surface oxygen enhanced its rate.

  2. Microstructural Changes of Anterior Corona Radiata in Bipolar Depression

    PubMed Central

    Karababa, I. Fatih; Bayaz?t, Huseyin; K?l?çaslan, Nihat; Celik, Mustafa; Cece, Hasan; Karakas, Ekrem

    2015-01-01

    Objective In bipolar disorder, dysregulation of mood may result from white matter abnormalities that change fiber tract length and fiber density. There are few studies evaluating the white matter microstructural changes in bipolar I patients (BD) with depressive episodes. The present study aimed to evaluate anterior corona radiata in BD patients with depressive episode using Diffusion Tensor Imaging (DTI). Methods Twenty-one patients with bipolar depression and 19 healthy controls were investigated and groups were matched for age and gender. Diffusion-weighted echoplanar brain images (DW-EPI) were obtained using a 1.5 T MRI scanner. Regions of interest (ROIs) were manually placed on directional maps based on principal anisotropy. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of white matter were measured in the anterior corona radiata (ACR) bilaterally by diffusion tensor imaging. Results There was not a significant difference between groups of age and gender (p>0.05). Significantly lower FA was observed in bilateral ACR in bipolar patients with depression compared with healthy individuals. And there is significantly higher ADC values in the left frontal corona radiate in bipolar patients. Conclusion White matter abnormalities can be detected in patients with BD using DTI. The neuropathology of these abnormalities is unclear, but neuronal and axonal loss, myelin abnormalities and reduced white matter fiber density are likely to be relevant.

  3. Slingshot prominences above stellar X-ray coronae

    E-print Network

    M. Jardine; A. A. van Ballegooijen

    2005-06-10

    We present a new model for the coronal structure of rapidly rotating solar-type stars. The presence of prominences trapped in co-rotation 2 to 5 stellar radii above the stellar surface has been taken as evidence that the coronae of these stars must be very extended. The observed surface magnetic fields, however, cannot contain X-ray emitting gas out to these distances. We present an alternative model: that these prominences are trapped in long thin loops embedded not in the X-ray corona, but in the wind. Above coronal helmet streamers, oppositely-directed wind-bearing field lines reconnect to form closed loops which then fill up with gas that was originally part of the wind. We demonstrate that static equilibria exist for these loops at a range of pressures and temperatures. The maximum loop height falls as the rotation rate increases, but rises as the loop temperature decreases. For a solar-mass star with rotation period 0.5 days, whose X-ray corona extends 1stellar radius above the surface, loops at temperatures of 10, 000 K can extend out to 5 stellar radii.

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

    SciTech Connect

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

    2013-05-20

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

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

    Microsoft Academic Search

    Ed Sittler; Madhullika Guhathakurta; Ruth Skoug

    2001-01-01

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

  6. Aerosol Charge Neutralization by a Mixing-Type Bipolar Charger using Corona Discharge at High Pressure

    Microsoft Academic Search

    S. Kimoto; K. Mizota; M. Kanamaru; H. Okuda; D. Okuda; M. Adachi

    2009-01-01

    An aerosol neutralizer called the Mixing-type Bipolar Charger using Corona-Discharge at High Pressure (MBCCHP) was developed. In the MBCCHP, a corona discharge (High-Pressure Corona Ionizer; HPC Ionizer) induced by high frequency voltage (>100 Hz) at high pressure (>0.2 MPa) is used to generate bipolar ions at high concentration (1–3 × 10 ions\\/cm) that are then mixed with aerosol particles flowing

  7. Effects of corona discharge and UV treatment on the properties of jute-fibre epoxy composites

    Microsoft Academic Search

    Jochen Gassan; Voytek S Gutowski

    2000-01-01

    In this paper, tossa jute fibres were corona discharge and ultraviolet (UV) treated to improve the mechanical properties of natural-fibre\\/epoxy composites. Corona-treated fibres exhibited significantly higher polar components of the free surface energy with increasing treatment energy output. Owing to the difficulties in effective treatment of three-dimensional objects with corona discharge, the increase of polarity of treated yarns is relatively

  8. DC negative corona discharge in atmospheric pressure helium: transition from the corona to the ‘normal’ glow regime

    NASA Astrophysics Data System (ADS)

    Hasan, Nusair; Antao, Dion S.; Farouk, Bakhtier

    2014-06-01

    Direct current (dc) negative corona discharges in atmospheric pressure helium are simulated via detailed numerical modeling. Simulations are conducted to characterize the discharges in atmospheric helium for a pin plate electrode configuration. A self-consistent two-dimensional hybrid model is developed to simulate the discharges and the model predictions are validated with experimental measurements. The discharge model considered consists of momentum and energy conservation equations for a multi-component (electrons, ions, excited species and neutrals) gas mixture, conservation equations for each component of the mixture and state relations. A drift-diffusion approximation for the electron and the ion fluxes is used. A model for the external circuit driving the discharge is also considered and solved along with the discharge model. Many of the key features of a negative corona discharge, namely non-linear current-voltage characteristics, spatially flat cathode current density and glow-like discharge in the high current regime are displayed in the predictions. A transition to the ‘normal’ glow discharge from the corona discharge regime is also observed. The transition is identified from the calculated current-voltage characteristic curve and is characterized by the radial growth of the negative glow and the engulfment of the cathode wire.

  9. Unveiling the nature of coronae in active galactic nuclei through submillimeter observations

    NASA Astrophysics Data System (ADS)

    Inoue, Yoshiyuki; Doi, Akihiro

    2014-12-01

    The heating mechanism of a corona above an accretion disk in active galactic nuclei (AGNs) is still unknown. One possible mechanism is magnetic reconnection heating requiring energy equipartition between magnetic energy and gas energy in the disk. Here, we investigate the expected observed properties in the radio band from such a magnetized corona. A magnetized corona can generate synchrotron radiation since a huge amount of electrons exists. Although most of the radiation would be absorbed by synchrotron self-absorption, high-frequency end of synchrotron emission can escape from a corona and appear at the submillimeter range. If only thermal electrons exist in a corona, the expected flux from nearby Seyferts is below the Atacama Large Millimeter/submillimeter Array (ALMA) sensitivity. However, if non-thermal electrons coexist in a corona, ALMA can measure the non-thermal tail of the synchrotron radiation from a corona. Such a non-thermal population is naturally expected to exist if the corona is heated by magnetic reconnections. Future ALMA observations will directly probe the coronal magnetic field strength and the existence of non-thermal electrons in coronae of AGNs.

  10. Unraveling tobacco BY-2 protein complexes with BN PAGE/LCMS/MS and clustering methods

    E-print Network

    Antwerpen, Universiteit

    . Through a combination of blue native gel electrophoresis and LC­MS/MS, we were able to isolate protein. Furthermore, it searches for associations between proteins that co-occur frequently throughout the BN gelUnraveling tobacco BY-2 protein complexes with BN PAGE/LC­MS/MS and clustering methods Noor

  11. Israel must pursue peace urgently as Egypt unravels, former U.S. Rep. Wexler says

    E-print Network

    Belogay, Eugene A.

    Israel must pursue peace urgently as Egypt unravels, former U.S. Rep. Wexler says By Ana M. Valdes turned upside down." For decades, Egypt has been Israel's closest ally in the Middle East, particularly peace in their nation, should heed Egypt's crisis. "Israel ought to seek to resolve its issues

  12. Unraveling the chemical dynamics of bimolecular reactions of ground state boron atoms, B(2

    E-print Network

    Kaiser, Ralf I.

    Unraveling the chemical dynamics of bimolecular reactions of ground state boron atoms, B(2 PjArticle on the web 8th March 2004 The reaction dynamics of atomic boron, B(2 P), with acetylene, C2H2(X 1 Sg þ molecular beams technique. Only the atomic boron versus hydrogen atom exchange pathway was observed. Forward

  13. Unraveling the early steps of prokaryotic replication Erin L Cunningham and James M Berger

    E-print Network

    Berger, James M.

    Unraveling the early steps of prokaryotic replication Erin L Cunningham and James M Berger In prokaryotes, many of the physical mechanisms governing the process of initiating DNA replication are now studies have shown that prokaryotic initiator structures are both modular and conserved, and have begun

  14. Unravelling the influence of water depth and wave energy on the facies diversity of shelf carbonates

    E-print Network

    Purkis, Sam

    Unravelling the influence of water depth and wave energy on the facies diversity of shelf their production is tied to light and wave energy, carbonate sediments are most effectively produced in shallow processes of storm and wave reworking influence the seabed through submarine erosion and sediment

  15. Unraveling of a Tethered Polymer Chain in Uniform Solvent Flow Aruna Mohan and Patrick S. Doyle*

    E-print Network

    Doyle, Patrick S.

    chains of varying lengths has emerged, based on the electro- phoresis of the DNA chains through an array of a magnetic field. Size-based separation has also been achieved via dilute solution capillary electrophoresis in the review of Viovy.11 The transient unraveling of the polymer chain following a polymer-obstacle collision

  16. Unraveling the mysteries of the non-thermal universe using -ray observations of Active Galactic Nuclei

    E-print Network

    California at Santa Cruz, University of

    Unraveling the mysteries of the non-thermal universe using -ray observations of Active Galactic / min; Crab-like source at 0o Energy resolution: ~15% Low systematic errors: Flux ~20%, Photon index hole at the center (~106 to 109 x solar mass) At least 5% of all galaxies are active galaxies Active

  17. Phosphoproteomics as a tool to unravel plant regulatory Sergio de la Fuente van Bentema

    E-print Network

    Hirt, Heribert

    REVIEW Phosphoproteomics as a tool to unravel plant regulatory mechanisms Sergio de la Fuente van on recent developments in the field of phosphoproteomics that are based on phosphopeptide isolation from at any time (Hubbard and Cohen 1993), indicating that the phosphoproteome of each multicel- lular

  18. Unravelling the Cretaceous-Paleogene (KT) Turnover, Evidence from Flora, Fauna and

    E-print Network

    Vajda, Vivi

    Unravelling the Cretaceous-Paleogene (KT) Turnover, Evidence from Flora, Fauna and Geology Adriana, leading to a reduction of solar transmission to 10-20% of normal for that period. Southern Hemisphere terrestrial Cretaceous-Paleogene boundary sediments in New Zealand reveal that a diverse Late Cretaceous

  19. Unraveling male and female histories from human genetic data Jon F Wilkins

    E-print Network

    Wilkins, Jon F.

    Unraveling male and female histories from human genetic data Jon F Wilkins The increasing of human genetic diversity, and what that structure can teach us about human demographic history. Global, multi-locus analyses have suggested that human genetic diversity may fall into clusters that correspond

  20. Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions Unraveling Relaxor Phase Transitions by

    E-print Network

    Osnabrück, Universität

    Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions Unraveling Relaxor 2009 WILLIAMSBURG WORKSHOP ON FUNDAMENTAL PHYSICS OF FERROELECTRICS #12;Introduction Strontium Barium ferroelectrics Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions SBN ­ SrxBa1-xNb2O6

  1. Symptoms of Eating Disorders Among Female Distance Runners: Can the Inconsistencies Be Unraveled?

    Microsoft Academic Search

    Donald H. Ryujin; Cynthia Breaux; Amanda D. Marks

    2000-01-01

    Research on eating disorders among female distance runners has produced a modest, but inconsistent body of findings. To unravel the confusion, we hypothesized a model whereby studies finding greater symptomatology have involved obligatory runners or elite national\\/international competitors. Studies not finding greater symptomatology have involved a more typical group of athletes. To test our hypothesis, we used the Eating Disorders

  2. Assessing the ability of first-order reversal curve (FORC) diagrams to unravel complex magnetic signals

    Microsoft Academic Search

    Adrian R. Muxworthy; James G. King

    2005-01-01

    (1) First-order reversal curve (FORC) diagrams for mixtures of different magnetic phases and bimodal distributions have been measured to examine the efficiency of the FORC method at unraveling complex magnetic signals. The FORC distributions for various magnetic minerals, including magnetite, maghemite, hematite, and goethite, and their linear additivity are assessed. Mixtures containing only hard magnetic minerals like hematite or goethite,

  3. Assessing the ability of first-order reversal curve (FORC) diagrams to unravel complex magnetic signals

    Microsoft Academic Search

    Adrian R. Muxworthy; James G. King; David Heslop

    2005-01-01

    First-order reversal curve (FORC) diagrams for mixtures of different magnetic phases and bimodal distributions have been measured to examine the efficiency of the FORC method at unraveling complex magnetic signals. The FORC distributions for various magnetic minerals, including magnetite, maghemite, hematite, and goethite, and their linear additivity are assessed. Mixtures containing only hard magnetic minerals like hematite or goethite, which

  4. Eukaryotic complex I: functional diversity and experimental systems to unravel the assembly process

    E-print Network

    Meier, Iris

    -like enzymes in the hydrogenosome, a mitochondria-derived organelle is also discussed here. Complex I assembly mitochondrial genes in this organism. Keywords Mitochondria Á Human disease Á Complex I Á Assembly factors ÁREVIEW Eukaryotic complex I: functional diversity and experimental systems to unravel the assembly

  5. Unravelling the Sources of Adolescent Substance Use: A Test of Rival Theories

    ERIC Educational Resources Information Center

    Jonson, Cheryl Lero; McArthur, Rachel; Cullen, Francis T.; Wilcox, Pamela

    2012-01-01

    Among any cohort of American youths, some will use drugs and alcohol whereas others will not. Further, some youngsters will not only use these illegal substances but also abuse them, at times wreaking havoc with their lives and ruining their futures. The purpose of this study is to attempt to unravel this heterogeneity of substance abuse; that is,…

  6. UNRAVELING STUDENTS' BELIEF SYSTEMS RELATING TO MATHEMATICS LEARNING AND PROBLEM SOLVING

    E-print Network

    Spagnolo, Filippo

    96 UNRAVELING STUDENTS' BELIEF SYSTEMS RELATING TO MATHEMATICS LEARNING AND PROBLEM SOLVING Erik De of Leuven, Belgium RESEARCH ON STUDENTS' BELIEFS AND MATHEMATICS LEARNING: AN INTRODUCTION Inspired that influence mathematical learning and, on the other hand, to understand the processes through which

  7. PHYSICAL REVIEW B 85, 165440 (2012) Unraveling the acoustic electron-phonon interaction in graphene

    E-print Network

    Thygesen, Kristian

    2012-01-01

    PHYSICAL REVIEW B 85, 165440 (2012) Unraveling the acoustic electron-phonon interaction in graphene-phonon couplings in graphene for the transverse and longitudinal acoustic phonons. Analytic forms of the coupling-2 . We find that the intrinsic effective acoustic deformation potential of graphene is eff = 6.8 e

  8. Desorption corona beam ionization source for mass spectrometry.

    PubMed

    Wang, Hua; Sun, Wenjian; Zhang, Junsheng; Yang, Xiaohui; Lin, Tao; Ding, Li

    2010-04-01

    A novel Desorption Corona Beam Ionization (DCBI) source for direct analysis of samples from surface in mass spectrometry is reported. The DCBI source can work under ambient conditions without time-consuming sample pretreatments. The source shares some common features with another ionization source - Direct Analysis in Real Time (DART), developed earlier. For example, helium was used as the discharge gas (although only corona discharge is involved in the present source), and heating of the discharge gas is required for sample desorption. However, the difference between the two sources is substantial. In the present source, a visible thin corona beam extending out around 1 cm can be formed by using a hollow needle/ring electrode structure. This feature would greatly facilitate localizing sampling areas and performing imaging/profiling experiments. The DCBI source is also capable of performing progressive temperature scans between room temperature and 450 degrees C in order to sequentially desorb samples from the surface and, therefore, to achieve a rough separation of the individual components in a complex mixture, resulting in less congestion in the mass spectrum acquired. Mass spectra for a broad range of compounds (pesticides, veterinary additives, OTC drugs, explosive materials) have been acquired using the DCBI source. For most of the compounds tested, the heater temperature required for efficient desorption is at least 150 degrees C. The molecular weight of the sample that can be desorbed/ionized is normally below 600 dalton even at the highest heater temperature, which is mainly limited by the volatility of the sample. PMID:20349536

  9. Particle acceleration in helical magnetic fields in the corona

    NASA Astrophysics Data System (ADS)

    Gordovskyy, Mykola; Browning, Philippa; Bareford, Michael; Pinto, Rui; Kontar, Eduard; Bian, Nicolas

    2014-05-01

    Twisted magnetic fields should be ubiquitous in the solar corona. Emerging twisted ropes as well as complex photospheric motions provide continuous influx of the magnetic helicity. Twisted coronal fields, in turn, contain excess magnetic energy, which can be released, causing solar flares and other explosive phenomena. It has been shown recently, that reconnection in helical magnetic structures results in particle acceleration distributed within large volume, including the lower corona and chromosphere. Hence, the magnetic reconnection and particle acceleration scenario involving magnetic helicity can be a viable alternative to the standard flare model, where particles are accelerated in a small volume located in the upper corona. We discuss our recent results on the energy release and particle acceleration during magnetic reconnection in twisted coronal loops. Evolution of various helical structures is described in terms of resistive MHD, including heat conduction and radiation. We consider the effects of field topology and photospheric motions on the energy accumulation and release. In particular, we focus on scenarios with continuous helicity injection, leading to recurrent explosive events. Using the obtained MHD models, ion and electron acceleration is investigated, taking into account Coulomb collisions. We derive time-dependent energy spectra and spatial distribution for these species, and calculate resulting non-thermal radiation intensities. Based on the developed numerical models, we investigate observational implications of particle acceleration in helical magnetic structures. Thus, we compare temporal variations of thermal and non-thermal emission in different configurations. Furthermore, we consider spatial distributions of the thermal EUV and X-ray emission and non-thermal X-ray emission and compare them with observational data.

  10. Hot Carbon Corona in Mars’ Upper Thermosphere and Exosphere

    NASA Astrophysics Data System (ADS)

    Lee, Yuni; Combi, M.; Tenishev, V.; Bougher, S.

    2013-10-01

    The production of energetic particles results in the formation of the hot corona, where the most of the escape of neutral atoms occur, in the Martian upper atmosphere. In order to investigate the dynamics of these energetic neutral atoms, we have carried out a study that provides a self-consistent global description of the hot corona in the upper thermosphere and exosphere by employing a self-consistent global kinetic model coupled with a thermosphere/ionosphere model. In this work, we evaluate the carbon atom inventory by studying the production and distribution of energetic carbon atoms. The most important source reactions for hot atomic carbon are expected to be photodissociation of CO and dissociative recombination of CO+, which are highly sensitive to solar activity and occur mostly deep in the dayside of the thermosphere. The latest available branching ratios is adopted, and appropriate choices of the rate coefficient and the photodissociation frequencies are made. In this study, we simulate the variations of the hot carbon corona over the solar cycle and seasons. The spatial distributions and profiles of density and temperature, atmospheric loss rates are discussed for the cases considered. The total global escape of hot carbon from all dominant photochemical processes is computed and compared with those from other previous models. To describe self-consistently the upper thermosphere and exosphere, a combination of our 3D Direct Simulation Monte Carlo (DSMC) model [Valeille, A., Combi, M., Bougher, S., Tenishev, V., Nagy, A., 2009. J. Geophys. Res. 114, E11006. doi:10.1029/2009JE003389] and the 3D Mars Thermosphere General Circulation Model (MTGCM) [Bougher, S. W., Bell, J. M., Murphy, J. R., Lopez-Valverde, M. A., Withers, P. G., 2006. Geophys. Res. Lett. 32, doi: 10.1029/2005GL024059. L02203] is used. Finally, our computed global total escape rate of hot carbon ranges ~ (5.2 - 57.1) × 1023 s-1 for the aphelion solar low to perihelion solar high case.

  11. 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

  12. Constant cross section of loops in the solar corona

    NASA Astrophysics Data System (ADS)

    Peter, H.; Bingert, S.

    2012-12-01

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

  13. Fluorine in R Coronae Borealis and Extreme Helium Stars

    E-print Network

    Pandey, Gajendra; Rao, N Kameswara

    2007-01-01

    Neutral fluorine lines are identified in the optical spectra of several R Coronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine is enriched in some RCBs by factors of 800 to 8000 relative to its likely initial abundance. The overabundances of fluorine are evidence for the synthesis of fluorine. These results are discussed in the light of the scenario that RCBs are formed by accretion of an He white dwarf by a C-O white dwarf. Sakurai's object (V4334 Sgr), a final He-shell flash product, shows no detectable neutral fluorine lines.

  14. Rigid and differential rotation of the solar corona

    NASA Technical Reports Server (NTRS)

    Antonucci, E.; Svalgaard, L.

    1974-01-01

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

  15. Study of a dual frequency atmospheric pressure corona plasma

    SciTech Connect

    Kim, Dan Bee; Moon, S. Y.; Jung, H.; Gweon, B.; Choe, Wonho [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2010-05-15

    Radio frequency mixing of 2 and 13.56 MHz was investigated by performing experimental measurements on the atmospheric pressure corona plasma. As a result of the dual frequency, length, current density, and electron excitation temperature of the plasma were increased, while the gas temperature was maintained at roughly the same level when compared to the respective single frequency plasmas. Moreover, observation of time-resolved images revealed that the dual frequency plasma has a discharge mode of 2 MHz positive streamer, 2 MHz negative glow, and 13.56 MHz continuous glow.

  16. On red shifs in the transition region and corona

    E-print Network

    Hansteen, Viggo H; de Pontieu, Bart; Carlsson, Mats

    2010-01-01

    We present evidence that transition region red-shifts are naturally produced in episodically heated models where the average volumetric heating scale height lies between that of the chromospheric pressure scale height of 200 km and the coronal scale height of 50 Mm. In order to do so we present results from 3d MHD models spanning the upper convection zone up to the corona, 15 Mm above the photosphere. Transition region and coronal heating in these models is due both the stressing of the magnetic field by photospheric and convection `zone dynamics, but also in some models by the injection of emerging magnetic flux.

  17. Plasma Chemistry and Plasma Processing, Vol. 22, No. 4, December 2002 ( 2002) Ozone Production in the Positive DC Corona

    E-print Network

    Chen, Junhong

    Plasma Chemistry and Plasma Processing, Vol. 22, No. 4, December 2002 ( 2002) Ozone Production the distribution of ozone, but does not affect the rate of production. KEY WORDS: Corona discharge; corona plasma

  18. Mapping the Magnetic Structure of the Corona During the ULYSSES Fast-Latitude Scan

    Microsoft Academic Search

    J. A. Linker; Z. Mikic

    1997-01-01

    The coronal magnetic field defines the large-scale structure of the solar corona, the position of the heliospheric current sheet, and the regions of fast and slow solar wind. To understand the structure of the solar corona and inner heliophere, we must relate observations of the large-scale magnetic field at the photosphere to coronal and interplanetary observations. Global magnetohydrodynamic (MHD) models

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

    Microsoft Academic Search

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

    1999-01-01

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

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

    Microsoft Academic Search

    Kuang Wu Lee; Jörg Büchner; Nina Elkina

    2007-01-01

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

  1. Modeling of DC corona discharge along an electrically conductive flat plate with gas flow

    Microsoft Academic Search

    G. M. Colver; S. El-Khabiry

    1997-01-01

    The development of a corona discharge was evaluated numerically over a region of a semi-infinite flat plate having small (Ohmic) surface conductivity with a flowing gas. The model simulates a positive corona discharge (ionic wind) generated by two parallel wires mounted flush with the surface of the plate and directed with the free-stream gas flow. The deposition and removal of

  2. Modeling of DC corona discharge along an electrically conductive flat plate with gas flow

    Microsoft Academic Search

    Gerald M. Colver; Samir El-Khabiry

    1999-01-01

    The development of a corona discharge was evaluated numerically over a finite region of a semi-infinite flat plate having small (ohmic) surface conductivity with flowing gas. The model simulates a positive ion corona discharge (ionic wind) in the direction of gas flow generated by two parallel wires mounted flush with the surface of the plate. The deposition and removal of

  3. High-quality surface passivation by corona-charged oxides for semiconductor surface characterization

    SciTech Connect

    Schoefthaler, M.; Brendel, R.; Langguth, G.; Werner, J.H. [Max-Planck-Inst. fuer Festkoerperforschung, Stuttgart (Germany)

    1994-12-31

    A new surface passivation method using corona-charged oxides is discussed and applied to effective lifetime measurements by microwave-detected photoconductivity decay. Three lifetime measurements are required for evaluating surface recombination velocities and semiconductor bulk lifetimes in monocrystalline silicon wafers. Surface recombination velocities lower than 1 cm/s are achieved with corona passivation.

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

    Microsoft Academic Search

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

    2001-01-01

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

  5. Large area pulsed corona discharge in water for disinfection and pollution control

    Microsoft Academic Search

    Werner Hartmann; Michael Roemheld; Klaus-Dieter Rohde; Franz-Josef Spiess

    2009-01-01

    To investigate the efficiency of submerged pulse corona (SPC) discharges in water we built a laboratory scale, parallel-plate reactor that is part of a closed loop water circulation system. A pulsed voltage is applied across the electrodes. One of the electrodes is coated with a porous ceramic layer to create local field enhancements to initiate corona discharges. For energization of

  6. Study on Busbar Corona Characteristic Test of ±800 kV Yunguang HVDC Converter Substation

    Microsoft Academic Search

    WAN Baoquan; ZHANG Xiaowu; ZHANG Guangzhou; WU Xiong; RAO Hong; NI Xiaolin; LUO Bin; WANG Qi

    2006-01-01

    The problem about corona characteristics of busbar in ±800 kV HVDC converter substation has influences on the optimal design and economic operation of tubular busbar in converter substation. The paper makes the tests in laboratory for corona starting voltage, radio interference, audio noise and ground total electric field strength of the tubular busbars with the diameter of 250 and 300

  7. Coronas and iridescence in mountain wave clouds Joseph A. Shaw and Paul J. Neiman

    E-print Network

    Shaw, Joseph A.

    Coronas and iridescence in mountain wave clouds Joseph A. Shaw and Paul J. Neiman We use Fraunhofer particle sizes required for interpreting photographs of coronas and iridescence in mountain wave clouds particles that might be unique to mountain wave clouds. Further- more, we see that the dominant colors

  8. Helium corona-assisted air discharge Nan Jiang, Lei Gao, Ailing Ji, and Zexian Caoa)

    E-print Network

    Zexian, Cao

    Helium corona-assisted air discharge Nan Jiang, Lei Gao, Ailing Ji, and Zexian Caoa) Institute of non-thermal plasmas. By taking advantage of the low onset voltage for helium corona, air discharge was successfully launched at much reduced voltages with a needle-plate system partly contained in a helium

  9. Pulsed corona generation using a diode-based pulsed power generator

    NASA Astrophysics Data System (ADS)

    Pemen, A. J. M.; Grekhov, I. V.; van Heesch, E. J. M.; Yan, K.; Nair, S. A.; Korotkov, S. V.

    2003-10-01

    Pulsed plasma techniques serve a wide range of unconventional processes, such as gas and water processing, hydrogen production, and nanotechnology. Extending research on promising applications, such as pulsed corona processing, depends to a great extent on the availability of reliable, efficient and repetitive high-voltage pulsed power technology. Heavy-duty opening switches are the most critical components in high-voltage pulsed power systems with inductive energy storage. At the Ioffe Institute, an unconventional switching mechanism has been found, based on the fast recovery process in a diode. This article discusses the application of such a "drift-step-recovery-diode" for pulsed corona plasma generation. The principle of the diode-based nanosecond high-voltage generator will be discussed. The generator will be coupled to a corona reactor via a transmission-line transformer. The advantages of this concept, such as easy voltage transformation, load matching, switch protection and easy coupling with a dc bias voltage, will be discussed. The developed circuit is tested at both a resistive load and various corona reactors. Methods to optimize the energy transfer to a corona reactor have been evaluated. The impedance matching between the pulse generator and corona reactor can be significantly improved by using a dc bias voltage. At good matching, the corona energy increases and less energy reflects back to the generator. Matching can also be slightly improved by increasing the temperature in the corona reactor. More effective is to reduce the reactor pressure.

  10. APPLICATION OF CORONA DESTRUCTION AS A METHOD TO CONTROL VOLATILEORGANIC COMPOUNDS

    EPA Science Inventory

    The paper discusses EPA tests of two types of corona reactors. nemakes use of a bed of ferroelectric pellets across which analternating current electric field is impressed. he otherdevelops corona between two electrodes that have been energized bya fast rise time (nanosecond rang...

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

    Microsoft Academic Search

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

    1996-01-01

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

  12. The Effects of Geometry on the Corona-to-Streamer Discharge Transition

    E-print Network

    Humbird, Kelli D

    2013-01-31

    and the principle of least action. For a sufficiently small anode, the corona discharge is also shown to be energetically more favorable at all radii of curvature, supporting the general claim that corona discharges are most readily produced on thin wires....

  13. Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae in the BAT region

    E-print Network

    Jellinek, Mark

    Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae on a timescale of thermal diffusion. Applied to Venus, our results support a hypothesis that the contemporaneous convection; Venus; coronae; highlands; mantle thermals and mantle plumes Earth and Planetary Science Letters

  14. Computation of Corona Space Charge, Electric Field, and VI Characteristic Using Equipotential Charge Shells

    Microsoft Academic Search

    Mark N. Horenstein

    1984-01-01

    A charge simulation technique incorporating discretized equipotential charge shells in the volume is used to approximate the electric field and space charge around a single conductor in corona and to compute the voltage-current relationship for the discharge. No iteration is required in the solution method. Results are compared to corona in coaxial geometry, for which analytical treatment is also possible,

  15. Corona discharge and electrostatic precipitation in carbon dioxide under reduced pressure simulating Mars atmosphere

    Microsoft Academic Search

    Hai Long PANG; P. Atten; J.-L. Reboud

    2005-01-01

    The possibility of using electrostatic precipitation to clean the gas above solar panels on the surface of planet Mars is investigated. Results are presented on corona discharge in carbon dioxide gas under reduced pressure ranging from 5 to 10 mbar with different electrode configurations. The corona discharge inception voltage and the threshold of bipolar discharge have been measured for the

  16. A magmatic loading model for coronae on Venus Andrew J. Dombard,1

    E-print Network

    Johnson, Catherine Louise

    exceed the thermal energy in the melt that comprises the corona. Band-pass-filtered maps of the topography and gravity fields in the Beta-Atla-Themis region are consistent with upwellings now impinging and Head, 1993; Stofan et al., 1997, 2005]. Type 1 coronae are concentrated in a region defined by the Beta

  17. Corona processes and lightning attachment: The effect of wind during thunderstorms

    Microsoft Academic Search

    E. M. Bazelyan; Yu. P. Raizer; N. L. Aleksandrov; F. D'Alessandro

    2009-01-01

    A simple model of a glow corona occurring near the tip of a grounded electrode in a thundercloud electric field that can be enhanced by an approaching downward leader has been studied analytically and numerically with regard to the effect of wind. We obtained an approximate expression for corona current taking into account the (i) removal of space charge from

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

    E-print Network

    Guedel, Manuel

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

  19. Effect of relative humidity on electron distribution and ozone production by DC coronas in air

    Microsoft Academic Search

    Junhong Chen; Pengxiang Wang

    2004-01-01

    Summary form only given. A numerical model of electron distribution and ozone production in clean and humid air by DC corona discharges from a thin wire is presented. The model is based on the prior models of ozone production by DC coronas in dry air, with modifications to incorporate the effect of water vapor on the electrical characteristics and the

  20. NASA's Great Observatories May Unravel 400-Year Old Supernova Mystery

    NASA Astrophysics Data System (ADS)

    2004-10-01

    Four hundred years ago, sky watchers, including the famous astronomer Johannes Kepler, best known as the discoverer of the laws of planetary motion, were startled by the sudden appearance of a "new star" in the western sky, rivaling the brilliance of the nearby planets. Kepler's Supernova Remnant Multiple Images of Kepler's Supernova Remnant Modern astronomers, using NASA's three orbiting Great Observatories, are unraveling the mysteries of the expanding remains of Kepler's supernova, the last such object seen to explode in our Milky Way galaxy. When a new star appeared Oct. 9, 1604, observers could use only their eyes to study it. The telescope would not be invented for another four years. A team of modern astronomers has the combined abilities of NASA's Great Observatories, the Spitzer Space Telescope (SST), Hubble Space Telescope (HST), and Chandra X-ray Observatory, to analyze the remains in infrared radiation, visible light, and X-rays. Ravi Sankrit and William Blair of the Johns Hopkins University in Baltimore lead the team. The combined image unveils a bubble-shaped shroud of gas and dust, 14 light-years wide and expanding at 4 million mph. Observations from each telescope highlight distinct features of the supernova, a fast-moving shell of iron-rich material, surrounded by an expanding shock wave sweeping up interstellar gas and dust. Interview with Dr. Ravi Sankrit Interview with Dr. Ravi Sankrit "Multi-wavelength studies are absolutely essential for putting together a complete picture of how supernova remnants evolve," Sankrit said. Sankrit is an associate research scientist, Center for Astrophysical Sciences at Hopkins and lead for HST astronomer observations. "For instance, the infrared data are dominated by heated interstellar dust, while optical and X-ray observations sample different temperatures of gas," Blair added. Blair is a research professor, Physics and Astronomy Department at Hopkins and lead astronomer for SST observations. "A range of observations is needed to help us understand the complex relationship that exists among the various components," Blair said. The explosion of a star is a catastrophic event. The blast rips the star apart and unleashes a roughly spherical shock wave that expands outward at more than 22 million mph like an interstellar tsunami. The shock wave spreads out into surrounding space, sweeping up any tenuous interstellar gas and dust into an expanding shell. The stellar ejecta from the explosion initially trail behind the shock wave. It eventually catches up with the inner edge of the shell and is heated to X-ray temperatures. Kepler's Supernova Remnant Hubble Optical Image of Kepler's Supernova Remnant Visible-light images from Hubble's Advanced Camera for Surveys reveal where the supernova shock wave is slamming into the densest regions of surrounding gas. The bright glowing knots are dense clumps that form behind the shock wave. Sankrit and Blair compared their HST observations with those taken with ground-based telescopes to obtain a more accurate distance to the supernova remnant of about 13,000 light-years. Kepler's Supernova Remnant Spitzer Infrared Image of Kepler's Supernova Remnant The astronomers used the SST to probe for material that radiates in infrared light, which shows heated microscopic dust particles that have been swept up by the supernova shock wave. SST is sensitive enough to detect both the densest regions seen by HST and the entire expanding shock wave, a spherical cloud of material. Instruments on SST also reveal information about the chemical composition and physical environment of the expanding clouds of gas and dust ejected into space. This dust is similar to dust which was part of the cloud of dust and gas that formed the sun and planets in our solar system. Interview with Dr. William Blair Interview with Dr. William Blair The Chandra X-ray data show regions of very hot gas. The hottest gas, higher-energy X-rays, is located primarily in the regions directly behind the shock front. These regions also show up

  1. Personalized disease-specific protein corona influences the therapeutic impact of graphene oxide

    NASA Astrophysics Data System (ADS)

    Hajipour, Mohammad Javad; Raheb, Jamshid; Akhavan, Omid; Arjmand, Sareh; Mashinchian, Omid; Rahman, Masoud; Abdolahad, Mohammad; Serpooshan, Vahid; Laurent, Sophie; Mahmoudi, Morteza

    2015-05-01

    The hard corona, the protein shell that is strongly attached to the surface of nano-objects in biological fluids, is recognized as the first layer that interacts with biological objects (e.g., cells and tissues). The decoration of the hard corona (i.e., the type, amount, and conformation of the attached proteins) can define the biological fate of the nanomaterial. Recent developments have revealed that corona decoration strongly depends on the type of disease in human patients from which the plasma is obtained as a protein source for corona formation (referred to as the `personalized protein corona'). In this study, we demonstrate that graphene oxide (GO) sheets can trigger different biological responses in the presence of coronas obtained from various types of diseases. GO sheets were incubated with plasma from human subjects with different diseases/conditions, including hypofibrinogenemia, blood cancer, thalassemia major, thalassemia minor, rheumatism, fauvism, hypercholesterolemia, diabetes, and pregnancy. Identical sheets coated with varying protein corona decorations exhibited significantly different cellular toxicity, apoptosis, and uptake, reactive oxygen species production, lipid peroxidation and nitrogen oxide levels. The results of this report will help researchers design efficient and safe, patient-specific nano biomaterials in a disease type-specific manner for clinical and biological applications.The hard corona, the protein shell that is strongly attached to the surface of nano-objects in biological fluids, is recognized as the first layer that interacts with biological objects (e.g., cells and tissues). The decoration of the hard corona (i.e., the type, amount, and conformation of the attached proteins) can define the biological fate of the nanomaterial. Recent developments have revealed that corona decoration strongly depends on the type of disease in human patients from which the plasma is obtained as a protein source for corona formation (referred to as the `personalized protein corona'). In this study, we demonstrate that graphene oxide (GO) sheets can trigger different biological responses in the presence of coronas obtained from various types of diseases. GO sheets were incubated with plasma from human subjects with different diseases/conditions, including hypofibrinogenemia, blood cancer, thalassemia major, thalassemia minor, rheumatism, fauvism, hypercholesterolemia, diabetes, and pregnancy. Identical sheets coated with varying protein corona decorations exhibited significantly different cellular toxicity, apoptosis, and uptake, reactive oxygen species production, lipid peroxidation and nitrogen oxide levels. The results of this report will help researchers design efficient and safe, patient-specific nano biomaterials in a disease type-specific manner for clinical and biological applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00520e

  2. Numerical modelling of ozone production in a wire-cylinder corona discharge and comparison with a wire-plate corona discharge

    Microsoft Academic Search

    Pengxiang Wang; Junhong Chen

    2009-01-01

    The effect of electrode configuration on ozone production in the direct-current corona discharge of dry and humid air is studied by a numerical model that combines the electron distribution in the corona plasma, plasma chemistry and transport phenomena. Two electrode configurations are considered: wire-cylinder discharge with air flowing along the wire axis and wire-plate discharge with air flowing transverse to

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

    NASA Technical Reports Server (NTRS)

    Foukal, P. V.

    1980-01-01

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

  4. Analysis of current-voltage characteristics in the wires-to-planes geometry during corona discharge

    NASA Astrophysics Data System (ADS)

    Ait Said, Hakim; Nouri, Hamou; Zebboudj, Youcef

    2014-09-01

    The behaviour of DC corona discharge in air that is free of particulate matter with the wires-to-plane geometry was analysed in this work. The formulae I = KV (V - V0) and I = A (V - V0)m commonly used for the current-voltage characteristics were used to determine the various corona parameters for the two polarities of the corona discharge. Using curve fitting, it has been shown that the geometric factors K and A and the exponent m are strongly affected by the number n of the discharging wires. However, the corona inception voltage determined from the measurements is weakly influenced when n is small, and it remained constant for n > 5 discharging wires. As for the breakdown voltage of the discharge, it is practically independent of the number n. Furthermore, it was verified that the two formulae above can be used for both negative and positive corona in multiple wires-to-plane geometries.

  5. Development of a positive corona from a long grounded wire in a growing thunderstorm field

    NASA Astrophysics Data System (ADS)

    Mokrov, M. S.; Raizer, Yu P.; Bazelyan, E. M.

    2013-11-01

    The properties of a non-stationary corona initiated from a long grounded wire suspended horizontally above the ground and coronating in a slowly varying thundercloud electric field are studied. A two-dimensional (2D) model of the corona is developed. On the basis of this model, characteristics of the corona produced by a lightning protection wire are calculated under thunderstorm conditions. The corona characteristics are also found by using approximate analytical and quasi-one-dimensional numerical models. The results of these models agree reasonably well with those obtained from the 2D simulation. This allows one to estimate the corona parameters without recourse to the cumbersome simulation. This work was performed with a view to study the efficiency of lightning protection wires later on.

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

    Microsoft Academic Search

    Keiji Hayashi

    2005-01-01

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

  7. Corona Generation and Deposition of Metal Nanoparticles on Conductive Surfaces and Their Effects on the Substrate Surface Texture and Chemistry

    Microsoft Academic Search

    A. S. BIRIS; S. DE; M. K. MAZUMDER; R. A. SIMS; D. A. BUZATU; R. MEHTA

    2004-01-01

    A corona discharge ion bombardment technique was used successfully to generate gold particles of submicron diameters. In a negative corona discharge, the glow region contains electrons, negative ions, and positive ions. Positive ions collided with the negative corona tip electrode, causing it to sputter and emit fine particles of the electrode material. These nanoparticles were deposited on grounded metal substrates

  8. Plasma Chemistry and Plasma Processing, Vol. 23, No. 1, March 2003 ( 2003) Model of the Negative DC Corona Plasma

    E-print Network

    Chen, Junhong

    Plasma Chemistry and Plasma Processing, Vol. 23, No. 1, March 2003 ( 2003) Model of the Negative DC Corona Plasma: Comparison to the Positive DC Corona Plasma Junhong Chen1 and Jane H. Davidson1,2 Receiûed March 26, 2002, reûised June 14, 2002 A numerical model of the negatiûe DC corona plasma along a thin

  9. RXTE Observation of Cygnus X-1: III. Implications for Compton Corona and ADAF Models. Report 3; Implications for Compton Corona and ADAF Models

    NASA Technical Reports Server (NTRS)

    Nowak, Michael A.; Wilms, Joern; Vaughan, Brian A.; Dove, James B.; Begelman, Mitchell C.

    1999-01-01

    We have recently shown that a 'sphere + disk' geometry Compton corona model provides a good description of Rossi X-ray Timing Explorer (RXTE) observations of the hard/low state of Cygnus X-1. Separately, we have analyzed the temporal data provided by RXTE. In this paper we consider the implications of this timing analysis for our best-fit 'sphere + disk' Comptonization models. We focus our attention on the observed Fourier frequency-dependent time delays between hard and soft photons. We consider whether the observed time delays are: created in the disk but are merely reprocessed by the corona; created by differences between the hard and soft photon diffusion times in coronae with extremely large radii; or are due to 'propagation' of disturbances through the corona. We find that the time delays are most likely created directly within the corona; however, it is currently uncertain which specific model is the most likely explanation. Models that posit a large coronal radius [or equivalently, a large Advection Dominated Accretion Flow (ADAF) region] do not fully address all the details of the observed spectrum. The Compton corona models that do address the full spectrum do not contain dynamical information. We show, however, that simple phenomenological propagation models for the observed time delays for these latter models imply extremely slow characteristic propagation speeds within the coronal region.

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

    NASA Astrophysics Data System (ADS)

    Morgan, Huw; Jeska, Lauren; Leonard, Drew

    2013-06-01

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

  11. The corona of V390 Aurigae (HD 33798)

    NASA Astrophysics Data System (ADS)

    Gondoin, P.

    2003-06-01

    V390 Aurigae (HD 33798) is a rapidly rotating, lithium rich, late-type giant whose distinctive characteristics include a high X-ray luminosity observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. X-ray emission from plasma at high temperature (T> 107 K) indicates intense flaring activity on this star. Analysis results suggest a scenario where the corona of V390 Aurigae is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The interaction of these structures could explain the permanent flaring activity on large scales that is responsible for heating plasma to high temperatures. The intense activity on V390 Aurigae is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that the rotation of the star will spin-down in the future, thus decreasing the efficiency of its alpha -Omega dynamo with the suppressing of large scale magnetic structures in its corona.

  12. Driving disk winds and heating hot coronae by MRI turbulence

    SciTech Connect

    Io, Yuki; Suzuki, Takeru K., E-mail: stakeru@nagoya-u.jp [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)

    2014-01-01

    We investigate the formation of hot coronae and vertical outflows in accretion disks by magnetorotational turbulence. We perform local three-dimensional magnetohydrodynamical (MHD) simulations with the vertical stratification by explicitly solving an energy equation with various effective ratios of specific heats, ?. Initially imposed weak vertical magnetic fields are effectively amplified by magnetorotational instability and winding caused by the differential rotation. In the isothermal case (? = 1), the disk winds are driven mainly by the Poynting flux associated with the MHD turbulence and show quasi-periodic intermittency. In contrast, in the non-isothermal cases with ? ? 1.1, the regions above 1-2 scale heights from the midplane are effectively heated to form coronae with temperature ?50 times the initial value, which are connected to the cooler midplane region through the pressure-balanced transition regions. As a result, the disk winds are driven mainly by the gas pressure, exhibiting more time-steady nature, although the nondimensional time-averaged mass loss rates are similar to that of the isothermal case. Sound-like waves are confined in the cool midplane region in these cases, and the amplitude of the density fluctuations is larger than that of the isothermal case.

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

  14. Optics to rectify CORONA panoramic photographs for map making

    NASA Astrophysics Data System (ADS)

    Hilbert, Robert S.

    2006-08-01

    In the 1960's, accurate maps of the United States were available to all, from the U.S. Government, but maps of the Soviet Union were not, and in fact were classified. Maps of the Soviet Union were needed by the U.S. Government, including for U.S. targeting of Soviet ICBM sites, and for negotiating the SALT ICBM disarmament treaty. Although mapping cameras were historically frame cameras with low distortion, the CORONA panoramic film coverage was used to identify any ICBM sites. If distortion-free photographs could be produced from this inherently distorted panoramic material, accurate maps could be produced that would be valuable. Use of the stereo photographs from CORONA, for developing accurate topographical maps, was the mission of Itek's Gamma Rectifier. Bob Shannon's department at Itek was responsible for designing the optics for the Gamma Rectifier. He assigned the design to the author. The optical requirements of this system are described along with the optical design solution, which allowed the inherent panoramic distortion of the original photographs to be "rectified" to a very high level of accuracy, in enlarged photographs. These rectifiers were used three shifts a day, for over a decade, and produced the most accurate maps of the earth's surface, that existed at that time. The results facilitated the success of the Strategic Arms Limitation Talks (SALT) Treaty signed by the US and the Soviet Union in 1972, which were verified by "national means of verification" (i.e. space reconnaissance).

  15. Nitrogen fixation by corona discharge on the early precambrian Earth.

    PubMed

    Nna-Mvondo, Delphine; Navarro-González, Rafael; Raulin, François; Coll, Patrice

    2005-10-01

    We report the first experimental study of nitrogen fixation by corona discharge on the anoxic primitive Earth. The energy yields of nitric oxide (NO) and nitrous oxide (N(2)O) were experimentally determined over a wide range of CO(2)-N(2) mixtures simulating the evolution of the Earth's atmosphere during the Hadean and Archean eras (from 4.5 ba to 2.5 ba). NO, the principal form of fixed nitrogen in lightning and coronal discharge in early Earth, is produced ten times less efficiently in the latter type of electrical discharge with an estimated maximum annual production rate of the order of 10(10) g yr(-1). For N(2)O the maximum production rate was estimated to be approximately 10(9) g yr(-1). These low rates of syntheses indicate that corona discharges as point discharges on the clouds and ground did not play a significant role in the overall pool of reactive nitrogen needed for the emergence and sustainability of life. PMID:16231204

  16. 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.

  17. Pulsed corona and dielectric-barrier discharge processing of trichloroethylene

    SciTech Connect

    Hsiao, M.C.; Merritt, B.T.; Penetrante, B.M.; Vogtlin, G.E.; Wallman, P.H. [Lawrence Livermore National Lab., CA (United States)

    1995-12-31

    This paper presents experimental results on the plasma assisted decomposition of dilute concentrations (100--200 ppm) of trichloroethylene (TCE) in atmospheric-pressure dry air streams by pulsed corona and dielectric-barrier discharge processing. The experiments were performed at gas temperatures up to 300 A1C. One of the objectives in these experiments is to study the effect of gas temperature on the removal chemistry and product formation. The data on the gas temperature dependence provide a good basis for elucidating the chemical kinetics of TCE decomposition in the plasma. Under identical gas conditions the type of electrical discharge reactor does not affect the electrical energy requirements for decomposing the same amount of TCE; the reactor type also does not affect the product formation. For input energy densities up to 300 Joules per liter, the authors observe that carbon monoxide (CO) and carbon dioxide (CO2) are only minor products in the decomposition of TCE. The main organic products are phosgene and dichloroacetyl chloride (DCAC), as inferred from the Fourier Transform Infrared (FTIR) spectra. Processing at higher gas temperatures (around 300 A1C) increases the electrical energy required to remove the same amount of TCE; however, the CO and CO2 yields increase substantially and higher amounts of hydrochloric acid (HCl) are formed. These trends suggest increased competition from decomposition of DCAC and/or phosgene at high temperatures. In all cases, pulsed corona or dielectric-barrier discharge processing produces CO preferentially over CO2.

  18. An experimental investigation of ionization of supersonic air by a corona discharge

    NASA Astrophysics Data System (ADS)

    Satyanand, Udyavar S.

    A technique is developed to ionize supersonic air flow in a shock tube by a weak corona discharge. The driven section of the tube is open to the atmosphere. The shock propagates in the driven section at about 1 km/s by means of an area contraction near the downstream end of the driven section. Air is ionized by a unipolar corona discharge device comprising of a sharp-edged wedge as a high-field electrode inserted in a 41.25 mm (2") ID tube that forms a low-field electrode. The device requires less than 0.5 W. A ring probe, downstream of the corona discharge device, collects charges (ions and electrons) from the air; its output voltage is thus a measure of the degree of ionization. The degree of ionization is varied by varying the corona discharge voltage and the flow speed. Corona generation was initially demonstrated with bench tests. These indicated an increased degree of ionization with an air flow created by a fan, relative to that in static air. Tests in a shock tube, with subsonic and supersonic air flow, and with a negative corona, provided results with the same ionization behavior. The operating range of discharge voltages is relatively small for a positive corona; hence, shock tube tests were confined to a negative corona. Shock tube test results indicate that, on a 10 millisecond time scale, corona generated ionization was convected downstream to the probe location in a supersonic flow. An anomalous shock tube result is a probe signal, without a corona discharge, that is similar, but weaker, to the signal with a discharge. Although the tests were done with shock speeds up to about 1 km/s and with atmospheric air ahead of shock wave, the technique of ionization and plasma measurement can be extended to higher speeds and lower pressures. It is also suggested that a supersonic wind tunnel with a Langmuir probe be used for this type of work.

  19. Unraveling the sequence of serpentinization reactions: petrography, mineral chemistry, and petrophysics of serpentinites from MAR 15N

    E-print Network

    Demouchy, Sylvie

    Unraveling the sequence of serpentinization reactions: petrography, mineral chemistry the sequence of serpentinization reactions: petrography, mineral chemistry, and petrophysics of serpentinites], experimental [Allen and Seyfried, 2003], and theoretical studies [Wetzel and Shock, 2000; Sleep et al., 2004

  20. Spatial and temporal relations between coronae and extensional belts, northern Lada Terra, Venus

    NASA Astrophysics Data System (ADS)

    Baer, G.; Schubert, G.; Bindschadler, D. L.; Stofan, E. R.

    1994-04-01

    Preliminary studies of the distribution of coronae and volcanic rises on Venus show that many of these features tend to cluster along zones of rifting and extension. The plains north of Lada Terra are crossed by two such extensional belts. Each belt is composed of grabens, ridges, faults, volcanic flows, coronae and coronalike features. The longer and more prominent belt is the NW trending Alpha-Lada extensional belt, which is over 6000 km long and 50-200 km wide, and includes the coronae Eve, Tamfana, Carpo, Selu, Derceto, Otygen, and an unnamed corona south of Otygen. The second belt is the NNE trending Derceto-Quetzalpetlatl extensional belt, which is about 2000 km long and in places over 300 km wide, and includes the coronae Sarpanitum, Eithinoha, and Quetzalpetlatl. The two belts intersect at the 1600 x 600 km wide Derceto volcanic plateau. It is apparent that deformation along the two belts overlapped in time, though deformation along the Alpha-Lada extensional belt probably continued after the deformation along the Derceto-Quetzalpetlatl extensional belt terminated. In certain areas, volcanism originated in grabens within the extensional belts, whereas in other areas, such as in Eve, Selu, Derceto, and Quetzalpetlatl, volcanism originated in the coronae and flowed into the lower parts of the extensional belts. Regional extension has affected the evolution of all the coronae at some stage of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha and after the initiation of Carpo, Tamfana, Otygen, and Sarpanitum. It is thus unlikely that coronae formation along the belts is solely a consequence of the regional extension, and it is also unlikely that regional extension has been caused solely by the coronae. No corona along the belts was formed subsequent to the cessation of the regional extension. We therefore suggest that the regional extension and the coronae are interrelated. Some of the coronae may have determined the location of the surface expression of the regional extension, whereas the locations of other coronae may have been influenced by the concentration of regional extensional stresses.

  1. Unraveling the commercial market for medicinal plants and plant parts on the witwatersrand, South Africa

    Microsoft Academic Search

    Vivienne L. Williams; Kevin Balkwill; Edward T. F. Witkowski

    2000-01-01

    To unravel the market for commercial medicinal plants on the Witwatersrand in South Africa, a semiquantitative approach was\\u000a taken. A stratified random sample of 50 herb-traders was surveyed, and an inventory of all plants and parts sold was compiled.\\u000a Research participants were questioned on the scarcity and popularity of the plants traded, as well as suppliers and origins.\\u000a The rarefaction

  2. ISS and Space Shuttle Radiation Measurements at Solar Minimum

    NASA Technical Reports Server (NTRS)

    Gaza, Ramona; Welton, Andrew; Dunegan, Audrey; Lee, Kerry

    2011-01-01

    A summary of 2008-2011 ISS and Space Shuttle radiation dosimetry results for inside vehicle radiation monitoring in low-Earth orbit will be presented. Results include new data from ISS Expedition 22-25/20A radiation area monitors (RAM) and Shuttle Missions STS127-STS133 passive radiation dosimeters (PRD). ISS 20A radiation measurement locations included three Node 2 crew quarters locations at NOD2S5_CQ, NOD2P5_CQ and CQ-3 (Deck), as well as ESA Columbus, and JAXA Kibo locations. ISS 20A and STS127-STS133 missions were flown at 51.6 inclination with an altitude range of 330-350 km. The passive radiation results will be presented in terms of measured daily dose obtained using luminescence detectors (i.e., Al2O3:C, LiF:Mg,Ti and CaF2:Tm). In addition, preliminary results from the DOSIS 2 Project, in collaboration with the German Space Agency (DLR) will be presented. SRAG s participation to the DOSIS 2 exposure on ISS (11/16/2009-05/26/2010) involved passive radiation measurements at 10 different shielding locations inside the ESA Columbus Module.

  3. Measurements and IRI model predictions during the recent solar minimum

    NASA Astrophysics Data System (ADS)

    Bilitza, Dieter; Brown, Steven A.; Wang, Mathew Y.; Souza, Jonas R.; Roddy, Patrick A.

    2012-09-01

    Cycle 23 was exceptional in that it lasted almost two years longer than its predecessors and in that it ended in an extended minimum period that proved all predictions wrong. Comparisons of the International Reference Ionosphere (IRI) with CHAMP and GRACE in-situ measurements of electron density during the minimum have revealed significant discrepancies at 400-500 km altitude (Lühr and Xiong, 2010). Our study investigates the causes for these discrepancies with the help of ionosonde and Planar Langmuir Probe (PLP) data from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. Our C/NOFS comparisons confirm the earlier CHAMP and GRACE results. But the ionosonde measurements of the F-peak plasma frequency (foF2) show generally good agreement throughout the whole solar cycle. At mid-latitude stations yearly averages of the data-model difference are within 10% and at low latitudes stations within 20%. The 60-70% differences found at 400-500 km altitude are not seen at the F peak. We will discuss how these seemingly contradicting results from the ionosonde and insitu data-model comparisons can be explained and which parameters need to be corrected in the IRI model.

  4. Differences Between the Current Solar Minimum and Earlier Minima

    NASA Astrophysics Data System (ADS)

    Basu, S.; Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; Fletcher, S.; New, R.

    2010-06-01

    The Birmingham Solar-Oscillations Network (BiSON) has collected helioseismic data over three solar cycles. We use these data to determine how the internal properties of the Sun during this minimum differ from the previous two minima. The Cycle 24 data show oscillatory differences with respect to the other two sets, indicating relatively localized changes in the solar interior. Analysis of MDI data from Cycle 23 and Cycle 24 also show significant signs of differences.

  5. Time-Series Analysis of Supergranule Characterstics at Solar Minimum

    NASA Technical Reports Server (NTRS)

    Williams, Peter E.; Pesnell, W. Dean

    2013-01-01

    Sixty days of Doppler images from the Solar and Heliospheric Observatory (SOHO) / Michelson Doppler Imager (MDI) investigation during the 1996 and 2008 solar minima have been analyzed to show that certain supergranule characteristics (size, size range, and horizontal velocity) exhibit fluctuations of three to five days. Cross-correlating parameters showed a good, positive correlation between supergranulation size and size range, and a moderate, negative correlation between size range and velocity. The size and velocity do exhibit a moderate, negative correlation, but with a small time lag (less than 12 hours). Supergranule sizes during five days of co-temporal data from MDI and the Solar Dynamics Observatory (SDO) / Helioseismic Magnetic Imager (HMI) exhibit similar fluctuations with a high level of correlation between them. This verifies the solar origin of the fluctuations, which cannot be caused by instrumental artifacts according to these observations. Similar fluctuations are also observed in data simulations that model the evolution of the MDI Doppler pattern over a 60-day period. Correlations between the supergranule size and size range time-series derived from the simulated data are similar to those seen in MDI data. A simple toy-model using cumulative, uncorrelated exponential growth and decay patterns at random emergence times produces a time-series similar to the data simulations. The qualitative similarities between the simulated and the observed time-series suggest that the fluctuations arise from stochastic processes occurring within the solar convection zone. This behavior, propagating to surface manifestations of supergranulation, may assist our understanding of magnetic-field-line advection, evolution, and interaction.

  6. Regional climate impacts of a possible future grand solar minimum.

    PubMed

    Ineson, Sarah; Maycock, Amanda C; Gray, Lesley J; Scaife, Adam A; Dunstone, Nick J; Harder, Jerald W; Knight, Jeff R; Lockwood, Mike; Manners, James C; Wood, Richard A

    2015-01-01

    Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations. PMID:26102364

  7. Radiation environment on the Mir orbital station during solar minimum.

    PubMed

    Badhwar, G D; Atwell, W; Cash, B; Petrov, V M; Akatov YuA; Tchernykh, I V; Shurshakov, V A; Arkhangelsky, V A

    1998-01-01

    The Mir station has been in a 51.65 degrees inclination orbit since March 1986. In March 1995, the first US astronaut flew on the Mir-18 mission and returned on the Space Shuttle in July 1995. Since then three additional US astronauts have stayed on orbit for up to 6 months. Since the return of the first US astronaut, both the Spektr and Priroda modules have docked with Mir station, altering the mass shielding distribution. Radiation measurements, including the direct comparison of US and Russian absorbed dose rates in the Base Block of the Mir station, were made during the Mir-18 and -19 missions. There is a significant variation of dose rates across the core module; the six locations sampled showed a variation of a factor of nearly two. A tissue equivalent proportional counter (TEPC) measured a total absorbed dose rate of 300 microGy/day, roughly equally divided between the rate due to trapped protons from the South Atlantic Anomaly (SAA) and galactic cosmic radiation (GCR). This dose rate is about a factor of two lower than the rate measured by the thinly shielded (0.5 g cm-2 of Al) operational ion chamber (R-16), and about 3/2 of the rate of the more heavily shielded (3.5 g cm-2 of Al) ion chamber. This is due to the differences in the mass shielding properties at the location of these detectors. A comparison of integral linear energy transfer (LET) spectra measured by TEPC and plastic nuclear track detectors (PNTDs) deployed side by side are in remarkable agreement in the LET region of 15-1000 keV/micrometer, where the PNTDs are fully efficient. The average quality factor, using the ICRP-26 definition, was 2.6, which is higher than normally used. There is excellent agreement between the measured GCR dose rate and model calculations, but this is not true for trapped protons. The measured Mir-18 crew skin dose equivalent rate was 1133 microSv/day. Using the skin dose rate and anatomical models, we have estimated the blood-forming organ (BFO) dose rate and the maximum stay time in orbit for International Space Station crew members. PMID:11542778

  8. 1997 and 2006 Solar Minimum Comparisons of Geocoronal Hydrogen Data

    Microsoft Academic Search

    S. M. Nossal; E. J. Mierkiewicz; F. L. Roesler; L. M. Haffner; R. J. Reynolds

    2007-01-01

    Ground-based Fabry-Perot observations of the hydrogen Balmer-alpha emission have been used since the late 1970s to investigate hydrogen in the geocorona, spanning the upper thermosphere and exosphere. Atomic hydrogen in this region is a byproduct of hydrogen-containing species below such as methane and water vapor. Models have predicted 50-75 % increases in upper atmospheric hydrogen as a consequence of a

  9. Chandra HETGS Observes Tortured Coronae in the Rapid Braking Zone

    NASA Astrophysics Data System (ADS)

    Ayres, T. R.; Osten, R. A.; Brown, A.; Gagne, M.; Linsky, J. L.

    2002-05-01

    We have obtained Chandra High Energy Transmission Grating Spectrometer observations of five moderate mass (2--3 Msun) giants straddling the portion of the Hertzsprung gap where early-G III stars---evolving rapidly toward the red giant branch---suffer strong rotational braking and dramatic changes in their X-ray emitting coronae. G0 III giants prior to the braking epoch are fast rotators (? rot ~ 50-100 km s-1) and display very hot (T> 107 K) coronae, but nevertheless have curiously depressed X-ray luminosities. The post-braking giants are slow rotators (? rot< 10 km s-1) with cooler coronae (T ~ 106.8 K), but nevertheless manage a healthy level of X-ray emission. We believe the differences reflect the violent replacement of a ``fossil'' magnetosphere---inherited from the late-B or early-A MS progenitor---by a solar-like regenerative magnetic dynamo. The latter becomes dominant when the initially shallow surface convection in yellow giants at the blue edge of the Hertzsprung gap gives way to deep convective layers as the stars evolve to the red edge. Three of the targets were observed in Cycle 2: 31 Com (G0 III) on 2001-03-12 [132.0 ks]; HR 9024 (G1 III) on 2001-08-11 [96.9 ks]; and ? Vel (G5 III) on 2001-09-24 [19.9 ks], 2001-10-29 [58.1 ks], and 2001-12-18 [57.7 ks]. (The first ? Vel observation was scheduled for 80 ks, but was cut short by a solar flare. The second pointing was intended to complete the exposure, but was affected by ``threshold crossing plane'' latchup in the ACIS CCDs, and was repeated two months later, accounting for the third pointing.) The remaining two stars are: Cycle 3 target 24 UMa (G4 III; ~50 ks pointings on 2002-03-26 and 2002-03-29); and GTO target ? Ceti (K0 III) observed on 2001-06-29 [87.5 ks]. We describe the HETGS spectra and our efforts to infer plasma conditions (temperature/density models), chemical fractionation, gas dynamics (through emission line Doppler shifts), and coronal variability. [-3mm] This work was supported by Chandra grant GO1-2018X to the University of Colorado.

  10. Jump-like unravelings for non-Markovian open quantum systems

    E-print Network

    Jay Gambetta; T. Askerud; H. M. Wiseman

    2007-04-06

    Non-Markovian evolution of an open quantum system can be `unraveled' into pure state trajectories generated by a non-Markovian stochastic (diffusive) Schr\\"odinger equation, as introduced by Di\\'osi, Gisin, and Strunz. Recently we have shown that such equations can be derived using the modal (hidden variable) interpretation of quantum mechanics. In this paper we generalize this theory to treat jump-like unravelings. To illustrate the jump-like behavior we consider a simple system: A classically driven (at Rabi frequency $\\Omega$) two-level atom coupled linearly to a three mode optical bath, with a central frequency equal to the frequency of the atom, $\\omega_0$, and the two side bands have frequencies $\\omega_0\\pm\\Omega$. In the large $\\Omega$ limit we observed that the jump-like behavior is similar to that observed in this system with a Markovian (broad band) bath. This is expected as in the Markovian limit the fluorescence spectrum for a strongly driven two level atom takes the form of a Mollow triplet. However the length of time for which the Markovian-like behaviour persists depends upon {\\em which} jump-like unraveling is used.

  11. Quality and matching performance analysis of three-dimensional unraveled fingerprints

    NASA Astrophysics Data System (ADS)

    Wang, Yongchang; Hao, Qi; Fatehpuria, Abhishika; Hassebrook, Laurence G.; Lau, Daniel L.

    2010-07-01

    The use of fingerprints as a biometric is both the oldest mode of computer-aided personal identification and the most-relied-on technology in use today. However, current acquisition methods have some challenging and peculiar difficulties. For higher performance fingerprint data acquisition and verification, a novel noncontact 3-D fingerprint scanner is investigated, where both the detailed 3-D and albedo information of the finger is obtained. The obtained high-resolution 3-D prints are further converted into 3-D unraveled prints, to be compatible with traditional 2-D automatic fingerprint identification systems. As a result, many limitations imposed on conventional fingerprint capture and processing can be reduced by the unobtrusiveness of this approach and the extra depth information acquired. To compare the quality and matching performances of 3-D unraveled with traditional 2-D plain fingerprints, we collect both 3-D prints and their 2-D plain counterparts. The print quality and matching performances are evaluated and analyzed by using National Institute of Standard Technology fingerprint software. Experimental results show that the 3-D unraveled print outperforms the 2-D print in both quality and matching performances.

  12. 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)

  13. 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

  14. Back corona enhanced organic film deposition inside an Atmospheric Pressure Weakly Ionized Plasma reactor

    NASA Astrophysics Data System (ADS)

    Islam, Rokibul; Xie, Shuzheng; Englund, Karl; Pedrow, Patrick

    2014-10-01

    A grounded screen with short needle-like protrusions has been designed to generate back corona in an Atmospheric Pressure Weakly Ionized Plasma (APWIP) reactor. The grounded screen with protrusions is placed downstream at a variable gap length from an array of needles that is energized with 60 Hz high voltage. The excitation voltage is in the range 0--10 kV RMS and the feed gas mixture consists of argon and acetylene. A Lecroy 9350AL 500 MHz digital oscilloscope is used to monitor the reactor voltage and current using a resistive voltage divider and a current viewing resistor, respectively. The current signal contains many positive and negative current pulses associated with corona discharge. Analysis of the current signal shows asymmetry between positive and negative corona discharge currents. Photographs show substantial back corona generated near the tips of the protrusions situated at the grounded screen. The back corona activates via bond scission acetylene radicals that are transported downstream to form a plasma-polymerized film on a substrate positioned downstream from the grounded screen. The oscillograms will be used to generate corona mode maps that show the nature of the corona discharge as a function of gap spacing, applied voltage and many other reactor parameters.

  15. Geology of coronae and domal structures on Venus and models of their origin

    SciTech Connect

    Stofan, E.R.

    1989-01-01

    Coronae (160 to 670 km across) and domal structures (greater than 1000 km across) are complex topographic highs on Venus that were affected by volcanic and topographic processes. The geology of coronae and a major domal structure, Beta Regio, are documented using Pioneer Venus, Arecibo, and Venera 15/16 data. The evolution and possible models of origin of these features are also investigated. Beta Regio is a 2000 x 2300 km topographic high located in the equatorial region of Venus that rises over 5 km above the surrounding region. Within Beta Regio lie two large volcanic shields, Theia and Rhea Mons. Coronae are circular to elongate structures on Venus, characterized by an annulus of concentric compressional ridges and relatively raised topography surrounded by a peripheral trough. Volcanic domes, flows and edifices, as well as tectonic lineaments characterize the interiors of coronae. Thirty one coronae were detected on Venus. Two analytical models were developed that are consistent with the general characteristics and evolution of coronae: hotspot or rising mantle diapir model and sinking mantle diapir model. Coronae appear to be part of a continuum of thermally produced features on Venus, along with volcanic complexes and domal structures such as Beta Regio.

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

    NASA Astrophysics Data System (ADS)

    Rusin, V.; Rybansky, M.

    1999-03-01

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

  17. Corona discharge ion mobility spectrometry at reduced pressures

    SciTech Connect

    Tabrizchi, Mahmoud; Rouholahnejad, Fereshteh [College of Chemistry, Isfahan University of Technology, Isfahan, 84154 (Iran, Islamic Republic of)

    2004-11-01

    Ion mobility spectrometers (IMSs) normally operate at ambient pressure. In this work an IMS cell has been designed and constructed to allow the pressure to be reduced inside the IMS cell. In this cell, corona discharge was employed as the ionization source. Reducing pressure affected both the discharge and the performance of the IMS. The discharge current was observed to increase with reducing pressure while the ignition potential decreased. The ion current received at the collector plate was also increased about 50 times when the pressure was reduced from ambient pressure to 15 Torr. The higher ion current can lead to an extended dynamic range. IMS spectra were recorded at various pressures and the results show that the drift times shift perfectly linear with pressure. This suggests that unlike temperature, pressure correction for ion mobility spectra is as simple as multiplying the drift times by a factor of 760/P.

  18. Large Scale Circumgalactic Coronae around Massive Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Li, Jiangtao

    2013-10-01

    Extended coronae around massive spiral galaxies is a key prediction of galaxy formation theory. There are very few such galaxies in the local Universe and even fewer deep X-ray observations of them. We propose to observe 5 luminous, fast rotating, isolated, SF quiescent, and massive spiral galaxies with a total effective exposure of 337ks with XMM-Newton. When combined with archival X-ray observations of 4 other galaxies, the proposal will enable us to compile a mini-sample optimized to constrain the mechanisms responsible for establishing the hot CGM. We will compare radial distributions of coronal properties to the state-of-the-art hydrodynamical simulations, measure the total baryon content, and establish scaling relations of the coronal and other galaxy properties.

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

    E-print Network

    Clayton, Geoffrey C; Zhang, Wanshu

    2013-01-01

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

  20. Mid-Infrared Variations of R Coronae Borealis Stars

    E-print Network

    Rao, N Kameswara

    2014-01-01

    Mid-infrared photometry of R Coronae Borealis stars obtained from various satellites from IRAS to WISE has been utilized in studying the variations of the circumstellar dust's contributions to the spectral energy distribution of these stars. The variation of the fractional coverage (R) of dust clouds and their blackbody temperatures (T$_d$) have been used in trying to understand the dust cloud evolution over the three decades spanned by the satellite observations. In particular, it is shown that a prediction R $ \\propto T_d^4$ developed in this paper is satisfied, especially by those stars for which a single collection of cloud dominates the IR fluxes. Correlations of R with photospheric abundance and luminosity of the stars are explored.

  1. A Dynamical Analysis of the Corona Borealis Supercluster

    E-print Network

    Batiste, Merida

    2013-01-01

    Using data from the Sloan Digital Sky Survey we assess the current dynamical state of the Corona Borealis Supercluster (CSC), a highly dense and compact supercluster at z = 0.07. The Fundamental Plane relation is used to determine redshift independent distances to six clusters in the densest region of the supercluster, with mean accuracy in the relative distance estimates of 4 per cent. Peculiar velocities determined from these distance estimates indicate that the clusters have broken from the Hubble Flow, suggesting that the CSC likely contains two regions that have reached turnaround and are currently undergoing gravitational collapse. These results provide the strongest observational evidence to date that the CSC is a bound system similar to the much more extensive Shapley Supercluster, which is the most extensive confirmed bound supercluster yet identified in the Universe. When compared with simulations of the CSC our results require substantially more mass than is contained within the clusters, possibly ...

  2. Coronagraphic observations and analyses of the ultraviolet solar corona

    NASA Technical Reports Server (NTRS)

    Kohl, John L.

    1994-01-01

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

  3. 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.

  4. Modeling X-ray emission from stellar coronae

    E-print Network

    S. G. Gregory; M. Jardine; C. Argiroffi; J. -F. Donati

    2008-09-24

    By extrapolating from observationally derived surface magnetograms of low-mass stars we construct models of their coronal magnetic fields and compare the 3D field geometry with axial multipoles. AB Dor, which has a radiative core, has a very complex field, whereas V374 Peg, which is completely convective, has a simple dipolar field. We calculate global X-ray emission measures assuming that the plasma trapped along the coronal loops is in hydrostatic equilibrium and compare the differences between assuming isothermal coronae, or by considering a loop temperature profiles. Our preliminary results suggest that the non-isothermal model works well for the complex field of AB Dor, but not for the simple field of V374 Peg.

  5. Modeling X-ray emission from stellar coronae

    E-print Network

    Gregory, S G; Argiroffi, C; Donati, J -F

    2008-01-01

    By extrapolating from observationally derived surface magnetograms of low-mass stars we construct models of their coronal magnetic fields and compare the 3D field geometry with axial multipoles. AB Dor, which has a radiative core, has a very complex field, whereas V374 Peg, which is completely convective, has a simple dipolar field. We calculate global X-ray emission measures assuming that the plasma trapped along the coronal loops is in hydrostatic equilibrium and compare the differences between assuming isothermal coronae, or by considering a loop temperature profiles. Our preliminary results suggest that the non-isothermal model works well for the complex field of AB Dor, but not for the simple field of V374 Peg.

  6. Is the galactic corona produced by galactic flares?

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Stern, R.

    1979-01-01

    The effect of the differential rotation of the disk of the Galaxy on magnetic field which penetrates the disk is considered. The magnetic field will be progressively distorted from a potential (current-free) form and will at some stage become unstable. It is expected that an MHD instability, a resistive instability, or a combination of the two, will result in the release of the excess magnetic energy and that part of the released energy will be converted into heat. By estimating the energy release and the rate at which this process will occur and by assuming that this energy input is balanced by radiation, estimates were obtained of the parameters of the resulting plasma. It appears that this process alone can heat a galactic corona to temperatures of order 10 to the 6th power K.

  7. Mapping protein binding sites on the biomolecular corona of nanoparticles

    NASA Astrophysics Data System (ADS)

    Kelly, Philip M.; Åberg, Christoffer; Polo, Ester; O'Connell, Ann; Cookman, Jennifer; Fallon, Jonathan; Krpeti?, Željka; Dawson, Kenneth A.

    2015-05-01

    Nanoparticles in a biological milieu are known to form a sufficiently long-lived and well-organized ‘corona’ of biomolecules to confer a biological identity to the particle. Because this nanoparticle–biomolecule complex interacts with cells and biological barriers, potentially engaging with different biological pathways, it is important to clarify the presentation of functional biomolecular motifs at its interface. Here, we demonstrate that by using antibody-labelled gold nanoparticles, differential centrifugal sedimentation and various imaging techniques it is possible to identify the spatial location of proteins, their functional motifs and their binding sites. We show that for transferrin-coated polystyrene nanoparticles only a minority of adsorbed proteins exhibit functional motifs and the spatial organization appears random, which is consistent, overall, with a stochastic and irreversible adsorption process. Our methods are applicable to a wide array of nanoparticles and can offer a microscopic molecular description of the biological identity of nanoparticles.

  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. Corona discharge ionization of paracetamol molecule: Peak assignment

    NASA Astrophysics Data System (ADS)

    Bahrami, H.; Farrokhpour, H.

    2015-01-01

    Ionization of paracetamol was investigated using ion mobility spectrometry equipped with a corona discharge ionization source. The measurements were performed in the positive ion mode and three peaks were observed in the ion mobility spectrum. Experimental evidence and theoretical calculations were used to correlate the peaks to related ionic species of paracetamol. Two peaks were attributed to protonated isomers of paracetamol and the other peak was attributed to paracetamol fragment ions formed by dissociation of the N-C bond after protonation of the nitrogen atom. It was observed that three sites of paracetamol compete for protonation and their relative intensities, depending on the sample concentration. The ratio of ion products could be predicted from the internal proton affinity of the protonation sites at each concentration.

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

    SciTech Connect

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

    2013-08-01

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

  11. Stellar coronae - What can be predicted with minimum flux models?

    NASA Technical Reports Server (NTRS)

    Hammer, R.; Endler, F.; Ulmschneider, P.

    1983-01-01

    In order to determine the possible errors of various minimum flux corona (MFC) predictions, MFC models are compared with a grid of detailed coronal models covering a range of two orders of magnitude in coronal heating and damping length values. The MFC concept is totally unreliable in the prediction of mass loss and the relative importance of various kinds of energy losses, and MFC predictions for the mass loss rate and energy losses due to stellar wind can be wrong by many orders of magnitude. It is suggested that for future applications, the unreliable MFC formulas should be replaced by a grid of related models accounting for the coronal dependence on damping length, such as the models underlying the present study.

  12. Partial oxidation of methane by pulsed corona discharges

    NASA Astrophysics Data System (ADS)

    Hoeben, W. F. L. M.; Boekhoven, W.; Beckers, F. J. C. M.; van Heesch, E. J. M.; Pemen, A. J. M.

    2014-09-01

    Pulsed corona-induced partial oxidation of methane in humid oxygen or carbon dioxide atmospheres has been investigated for future fuel synthesis applications. The obtained product spectrum is wide, i.e. saturated, unsaturated and oxygen-functional hydrocarbons. The generally observed methane conversion levels are 6-20% at a conversion efficiency of about 100-250 nmol J-1. The main products are ethane, ethylene and acetylene. Higher saturated hydrocarbons up to C6 have been detected. The observed oxygen-functional hydrocarbons are methanol, ethanol and lower concentrations of aldehydes, ketones, dimethylether and methylformate. Methanol seems to be exclusively produced with CH4/O2 mixtures at a maximum production efficiency of 0.35 nmol J-1. CH4/CO2 mixtures appear to yield higher hydrocarbons. Carboxylic acids appear to be mainly present in the aqueous reactor phase, possibly together with higher molecular weight species.

  13. 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.

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

    SciTech Connect

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

    2010-08-10

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

  15. Properties of the two-temperature corona model for active galactic nuclei and galactic black holes

    E-print Network

    Agnieszka Janiuk; Bozena Czerny

    1999-12-22

    We study in detail the properties of the accreting corona model for active galactic nuclei and galactic black holes. In this model the fraction of the energy liberated in the corona at a given radius is calculated from the global parameters of the model (mass of the central object, accretion rate and viscosity parameter) and it appears to be a strong function of the radius. The model predicts the relative decrease of the coronal hard X-ray emission with an increase of the accretion rate. The presented description of disc/corona interaction forms a basis for further studies of disc disruption mechanism.

  16. The antifungal activity of corona treated polyamide and polyester fabrics loaded with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Saponjic, Z.; Ilic, V.; Vodnik, V.; Mihailovic, D.; Jovancic, P.; Nedeljkovic, J.; Radetic, M.

    2008-07-01

    This study is aimed to highlight the possibility of using the corona treatment for fiber surface activation that can facilitate the loading of silver nanoparticles from colloids onto the polyester and polyamide fabrics and thus enhance their antifungal activity against Candida albicans. Additionally, the laundering durability of achieved effects was studied. Corona activated polyamide and polyester fabrics loaded with silver nanoparticles showed better antifungal properties compared to untreated fabrics. The positive effect of corona treatment became even more prominent after 5 washing cycles, especially for polyester fabrics.

  17. Radio and television interference caused by corona discharges from high-voltage transmission lines

    SciTech Connect

    Sarmadi, M. [Bucknell Univ., Lewisburg, PA (United States). Dept. of Electrical Engineering

    1996-11-01

    Increase in power utility loads in industrialized countries, as well as developing countries, demands a higher level of transmission line voltage. Radio interference (RI) problems have been determined to be a limiting factor in selecting the size of transmission line conductors. Transmission line noise is primarily caused by corona discharges in the immediate vicinity of the conductor. It has been observed that discharges occur during both half-cycles of the applied voltage, but positive corona is usually predominant at AM radio frequencies range with practical high-voltage and extra high-voltage transmission lines. The corona radio noise effect is highly dependent upon the presence of particles on the surface of the conductor and the increase of the electrical gradient beyond the breakdown value of the air. Therefore, corona radio noise varies significantly with the weather and atmospheric conditions and generally increases by 10 to 30 dB in foul weather.

  18. Radio and television interference caused by corona discharges from high-voltage transmission lines

    SciTech Connect

    Sarmadi, M. [Bucknell Univ., Lewisburg, PA (United States)

    1995-10-01

    Increase in power utility loads in industrialized countries, as well as developing countries, demands a higher level of transmission line voltage. Radio interference (RI) problems have been determined to be a limiting factor in selecting the size of transmission line conductors. Transmission line noise is primarily caused by corona discharges in the immediate vicinity of the conductor. It has been observed that discharges occur during both half-cycles of the applied voltage, but positive corona is usually predominant at AM radio frequencies range with practical high-voltage and extra high-voltage transmission lines. The corona radio noise effect is highly dependent upon the presence of particles on the surface of the conductor and the increase of the electrical gradient beyond the breakdown value of the air. Therefore, corona radio noise varies significantly with the weather and atmospheric conditions and generally increases by 10 to 30 dB in foul weather.

  19. Effect of the protein corona on nanoparticles for modulating cytotoxicity and immunotoxicity

    PubMed Central

    Lee, Yeon Kyung; Choi, Eun-Ju; Webster, Thomas J; Kim, Sang-Hyun; Khang, Dongwoo

    2015-01-01

    Although the cytotoxicity of nanoparticles (NPs) is greatly influenced by their interactions with blood proteins, toxic effects resulting from blood interactions are often ignored in the development and use of nanostructured biomaterials for in vivo applications. Protein coronas created during the initial reaction with NPs can determine the subsequent immunological cascade, and protein coronas formed on NPs can either stimulate or mitigate the immune response. Along these lines, the understanding of NP-protein corona formation in terms of physiochemical surface properties of the NPs and NP interactions with the immune system components in blood is an essential step for evaluating NP toxicity for in vivo therapeutics. This article reviews the most recent developments in NP-based protein coronas through the modification of NP surface properties and discusses the associated immune responses. PMID:25565807

  20. Corona contraction and polyelectrolyte complexation of polybasic micelles in buffered aqueous solution

    NASA Astrophysics Data System (ADS)

    Laaser, Jennifer; Jiang, Yaming; Reineke, Theresa; Lodge, Timothy

    2015-03-01

    We investigate the pH- and ionic strength-induced contraction of polycationic micelles with a polystyrene core and poly(dimethylaminoethyl methacrylate) corona in buffered aqueous solutions, and report on complexation of these micelles with poly(styrene sulfonate) under varying ionic strength conditions. We find that in monoprotic buffers, the micelle corona behaves as a salted osmotic brush, as has been observed for other block polyelectrolyte micelle systems in unbuffered solutions. In polyprotic buffers, however, we find that concentration of the charged buffer species in the micelle corona shifts the buffer dissociation equilibrium farther toward multivalent species than in the bulk, resulting in an anomalously high degree of corona contraction. In our complexation experiments, we observe multimodal size distributions that evolve on timescales of days to weeks at physiologically relevant ionic strengths, which may have implications for the design of gene- and drug-delivery vehicles using these types of interpolyelectrolyte complexes.

  1. Alignment of cellulose chains of regenerated cellulose by corona poling and its piezoelectricity

    NASA Astrophysics Data System (ADS)

    Yun, Sungryul; Kim, Jung Hwan; Li, Yuanxie; Kim, Jaehwan

    2008-04-01

    Cellulose based electroactive paper has been developed as smart material. In this paper, corona poled cellulose films were prepared to improve their piezoelectricity and the influence of grid voltage to the corona poling was investigated. Cellulose was regenerated by dissolving cellulose natural fibers using a solvent, and removing it. During the regeneration process, alignment of cellulose was attempted by applying corona electrical poling. These characteristics were investigated by field emission scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. As increasing the grid voltage of the corona poling, the generation of cellulose nanofibers in the cellulose layered structures was observed, which influenced the increased crystallinity resulting in improved piezoelectric charge constant of cellulose films.

  2. IUE and the search for a lukewarm corona. [of cooler stars

    NASA Technical Reports Server (NTRS)

    Pasachoff, J. M.; Linsky, J. L.; Haisch, B. M.; Boggess, A.

    1979-01-01

    The use of the International Ultraviolet Explorer (IUE) to search for stars having neither a hot corona nor a cool outer atmosphere, but a lukewarm corona is outlined. An interactive computer system permits extensive analysis of the data immediately after transmission to earth, allowing the results of one exposure to influence the taking of subsequent exposures. The observation program is illustrated for the star HR 1099, noting that observations were taken while previous spectra were being analyzed. Observations of many stars of spectral types G and K lead to the construction of a border region on the Hertzsprung-Russell diagram between stars with hot coronas and those with cool outer atmospheres. Stars lying near this border region were then observed, however none with lukewarm coronas were found. The interactive control facility in the satellite control room is considered an important factor in the efficient implementation of the search procedure.

  3. Carbohydrate-Based Nanocarriers Exhibiting Specific Cell Targeting with Minimum Influence from the Protein Corona.

    PubMed

    Kang, Biao; Okwieka, Patricia; Schöttler, Susanne; Winzen, Svenja; Langhanki, Jens; Mohr, Kristin; Opatz, Till; Mailänder, Volker; Landfester, Katharina; Wurm, Frederik R

    2015-06-15

    Whenever nanoparticles encounter biological fluids like blood, proteins adsorb on their surface and form a so-called protein corona. Although its importance is widely accepted, information on the influence of surface functionalization of nanocarriers on the protein corona is still sparse, especially concerning how the functionalization of PEGylated nanocarriers with targeting agents will affect protein corona formation and how the protein corona may in turn influence the targeting effect. Herein, hydroxyethyl starch nanocarriers (HES-NCs) were prepared, PEGylated, and modified on the outer PEG layer with mannose to target dendritic cells (DCs). Their interaction with human plasma was then studied. Low overall protein adsorption with a distinct protein pattern and high specific affinity for DC binding were observed, thus indicating an efficient combination of "stealth" and targeting behavior. PMID:25940402

  4. The Effects of Geometry on the Corona-to-Streamer Discharge Transition 

    E-print Network

    Humbird, Kelli D

    2013-01-31

    the corona and the streamer discharge. The parameters that characterize the transition region are purely geometric for a given potential difference applied between two electrodes. For the case of a point-to-plane electrode geometry, the transition between...

  5. A GENERAL RELATIVISTIC MODEL OF ACCRETION DISKS WITH CORONAE SURROUNDING KERR BLACK HOLES

    SciTech Connect

    You Bei; Cao Xinwu [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Yuan Yefei, E-mail: youbei@shao.ac.cn, E-mail: cxw@shao.ac.cn, E-mail: yfyuan@ustc.edu.cn [Department of Astronomy, University of Sciences and Technology of China, Hefei, Anhui 230026 (China)

    2012-12-20

    We calculate the structure of a standard accretion disk with a corona surrounding a massive Kerr black hole in the general relativistic frame, in which the corona is assumed to be heated by the reconnection of the strongly buoyant magnetic fields generated in the cold accretion disk. The emergent spectra of accretion disk-corona systems are calculated by using the relativistic ray-tracing method. We propose a new method to calculate the emergent Comptonized spectra from the coronae. The spectra of disk-corona systems with a modified {alpha}-magnetic stress show that both the hard X-ray spectral index and the hard X-ray bolometric correction factor L{sub bol}/L{sub X,2-10keV} increase with the dimensionless mass accretion rate, which is qualitatively consistent with the observations of active galactic nuclei. The fraction of the power dissipated in the corona decreases with increasing black hole spin parameter a, which leads to lower electron temperatures of the coronae for rapidly spinning black holes. The X-ray emission from the coronae surrounding rapidly spinning black holes becomes weak and soft. The ratio of the X-ray luminosity to the optical/UV luminosity increases with the viewing angle, while the spectral shape in the X-ray band is insensitive to the viewing angle. We find that the spectral index in the infrared waveband depends on the mass accretion rate and the black hole spin a, which deviates from the f{sub {nu}}{proportional_to}{nu}{sup 1/3} relation expected by the standard thin disk model.

  6. Degradation Processes in Corona-Charged Electret Filter-Media with Exposure to Ethyl Benzene

    Microsoft Academic Search

    Warren J. Jasper; Anushree Mohan; Juan Hinestroza; Roger Barker

    2007-01-01

    The degradation of filtration performance for corona- charged electret filter media exposed to ethyl benzene was assessed. Nonwoven corona-charged polypropy- lene fiber mats were exposed to ethyl-benzene using a custom made apparatus. Evaluated scenarios included ethyl-benzene vapor and liquid exposures. The filtra- tion performance was evaluated using DOP as a test aerosol to measure filtration performance. It was ob- served

  7. Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure

    NASA Technical Reports Server (NTRS)

    Tiwari, S. K.; Alexander, C. E.; Winebarger, A.; Moore, R. L.

    2014-01-01

    The solar corona is much hotter (>=10(exp 6) K) than its surface (approx 6000 K), puzzling astrophysicists for several decades. Active region (AR) corona is again hotter than the quiet Sun (QS) corona by a factor of 4-10. The most widely accepted mechanism that could heat the active region corona is the energy release by current dissipation via reconnection of braided magnetic field structure, first proposed by E. N. Parker three decades ago. The first observational evidence for this mechanism has only recently been presented by Cirtain et al. by using High-resolution Coronal Imager (Hi-C) observations of an AR corona at a spatial resolution of 0.2 arcsec, which is required to resolve the coronal loops, and was not available before the rocket flight of Hi-C in July 2012. The Hi-C project is led by NASA/MSFC. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. We are currently investigating the changes taking place in photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. For this purpose, we are also using SDO/AIA data of +/- 2 hours around the 5 minutes Hi-C flight. In the present talk, I will first summarize some of the results of the Hi-C observations and then present some results from our recent analysis on what photospheric processes feed the magnetic energy that dissipates into heat in coronal loops.

  8. DC corona discharge from floating particle in low pressure SF6

    Microsoft Academic Search

    Yulistya Negara; Kohei Yaji; Junya Suehiro; Noriyuki Hayashi; Masanori Hara

    2006-01-01

    The final objective of this research project is clarification of the particle-triggered corona mechanism in SF6 gas-insulated electrical equipment as well as development of high precision diagnostic method of foreign metallic particle in GIS insulated by SF6 gas using the electrical signal due to corona discharge. The following research steps are conducting to achieve our goal: 1) clarification of particle-triggered

  9. Injecting charges on large-area electret thin film by corona multi-pin discharge method

    Microsoft Academic Search

    Yu-Hao Su; Cheng-En Chung; Wen-Ching Ko; Chih-Hsiang Yang; Wen-Jong Wu; Chih-Kung Lee

    2010-01-01

    Corona discharge plays an important role in industrial and commercial applications, especially for large-area corona discharge need. It is a common method for the electrets industry. Nevertheless, achieving uniform charge distribution of the large area electret films is difficult. In order to achieve uniform surface charges distribution in large plane, the multi-pin-grid-plate electrode system which was powered from two continuously-adjustable

  10. Vibration of High Voltage Conductors Induced by Corona from Water Drops or Hanging Metal Points

    Microsoft Academic Search

    Masoud Farzaneh; Luan Phan

    1984-01-01

    Corona-induced vibration was studied in experimental set-ups consisting of a single smooth conductor placed on the axis of a cylindrical mesh cage. Under artificial rain the beam type of vibration, i.e. whe, re the conductor is simply supported at two ends by the insulators, was used. Amplitude of the vibration of the conductor and corona current were Tmeasured under rain

  11. Non-Linear Corona Models in an Electromagnetic Transients Program (EMTP)

    Microsoft Academic Search

    K. C. Lee

    1983-01-01

    Corona attenuation and distortion of overvoltage waves is an important factor in determining the overvoltage level inside the electrical system due to atmospheric lightning discharges. Simulation of overvoltage wave propagation in electrical network by digital computers is often used in the electric power industry.1,2 This paper describes the implementation of a simple and accurate numerical model representing the non-linear corona

  12. Chemical Vapor Deposition in the Corona Discharge of Electrostatic Air Cleaners

    Microsoft Academic Search

    Jane H. Davidson; Peter J. McKinney

    1998-01-01

    The purpose of this experimental study was to determine if corona-enhanced chemical vapor deposition of silicone found in personal care products can cause silicon-oxide to grow on the discharge wires of electrostatic air cleaners. To test the hypothesis, a wire-cylinder precipitator was operated with a positive corona discharge for 180 hours with an air\\/octamethylcyclotetrasiloxane mixture. The 30.5 cm-long precipitator has

  13. Radial current-density distributions and sample charge uniformity in a corona triode

    Microsoft Academic Search

    J. A. Giacometti

    1987-01-01

    Reports on the radial distribution of the current density produced by a corona triode using the metallic point placed in the axis of insulating tubing. The experimental results are fitted with a model, accounting for the space charge in the grid-to-plate gap, and the corona wind. For a small grid bias, the simulation yields a current-density distribution similar to that

  14. Induction of waves on a horizontal water film by an impinging corona wind

    Microsoft Academic Search

    Walter Grassi; Daniele Testi

    2009-01-01

    The electric wind produced by corona discharge of a high-voltage electrode in air is employed for destabilizing a horizontal water film. In wire-to-plane geometry, the phenomenon is characterised by current versus voltage curves and visual observations of the onset of free-surface oscillations. The effect of the following parameters is examined for both positive and negative coronas: distance between the wire

  15. Self-Consistent Thermal Accretion Disk Corona Models for Compact Objects. I: Properties of the Corona and the Spectrum of Escaping Radiation

    NASA Technical Reports Server (NTRS)

    Dove, James B.; Wilms, Jorn; Begelman, Mitchell C.

    1997-01-01

    We present the properties of accretion disk corona (ADC) models in which the radiation field, the temperature, and the total opacity of the corona are determined self-consistently. We use a nonlinear Monte Carlo code to perform the calculations. As an example, we discuss models in which the corona is situated above and below a cold accretion disk with a plane-parallel (slab) geometry, similar to the model of Haardt & Maraschi. By Comptonizing the soft radiation emitted by the accretion disk, the corona is responsible for producing the high-energy component of the escaping radiation. Our models include the reprocessing of radiation in the accretion disk. Here the photons either are Compton-reflected or photoabsorbed, giving rise to fluorescent line emission and thermal emission. The self- consistent coronal temperature is determined by balancing heating (due to viscous energy dissipation) with Compton cooling, determined using the fully relativistic, angle-dependent cross sections. The total opacity is found by balancing pair productions with annihilations. We find that, for a disk temperature kT(sub BB) approx. less than 200 eV, these coronae are unable to have a self-consistent temperature higher than approx. 140 keV if the total optical depth is approx. less than 0.2, regardless of the compactness parameter of the corona and the seed opacity. This limitation corresponds to the angle-averaged spectrum of escaping radiation having a photon index approx. greater than 1.8 within the 5-30 keV band. Finally, all models that have reprocessing features also predict a large thermal excess at lower energies. These constraints make explaining the X-ray spectra of persistent black hole candidates with ADC models very problematic.

  16. The existence of warm and optically thick dissipative coronae above accretion disks

    E-print Network

    Rozanska, A; Belmont, R; Czerny, B; Petrucci, P -O

    2015-01-01

    In the past years, several observations of AGN and X-ray binaries have suggested the existence of a warm T around 0.5-1 keV and optically thick, \\tau ~ 10-20, corona covering the inner parts of the accretion disk. These properties are directly derived from spectral fitting in UV to soft-X-rays using Comptonization models. However, whether such a medium can be both in radiative and hydrostatic equilibrium with an accretion disk is still uncertain. We investigate the properties of such warm, optically thick coronae and put constraints on their existence. We solve the radiative transfer equation for grey atmosphere analytically in a pure scattering medium, including local dissipation as an additional heating term in the warm corona. The temperature profile of the warm corona is calculated assuming it is cooled by Compton scattering, with the underlying dissipative disk providing photons to the corona. Our analytic calculations show that a dissipative thick, (\\tau_{cor} ~ 10-12) corona on the top of a standard ac...

  17. 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

  18. Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-Heated Corona

    E-print Network

    N. Kawanaka; S. Mineshige; K. Iwasawa

    2005-08-24

    We investigate the iron K$\\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk photoelectrically absorb X-ray photons and radiate K$\\alpha$ line photons. Therefore, the activity of corona is responsible to the iron line emission from the underlying disk. In previous studies, oversimplified X-ray photon sources are often assumed above the disk in order to compute the iron line profile or power-law line emissivity profiles are assumed with an index being a free parameter. We adopt the more realistic corona model constructed by Liu et al. in which the corona is heated by magnetic energy released through the reconnection of magnetic flux loops and which has no free parameter. Then the accretion energy is dominantly dissipated in the corona, in which X-ray photons are efficiently produced and irradiate the underlying disk. We find the local emmisivity of iron line on the disk is approximated as $F_{{\\rm K}\\alpha}(r)\\propto r^{-5}$. The iron line profiles derived from this model give excellent fits to the observational data of MCG-6-30-15 with the profiles derived theoretically for $i\\sim 30^{\\circ}$ for energy band 4-7keV. Possible origins of line variability are briefly discussed.

  19. Experimental Study of Magnetic Field Effect on dc Corona Discharge in Low Vacuum

    NASA Astrophysics Data System (ADS)

    Elabbas, K.

    2014-09-01

    In the present paper, an attempt was made to investigate the effect of applying a transverse magnetic field on the dc corona discharge behavior in low vacuum. In general, two experiments were carried out in this work: the first is the ionization-region magnetic field experiment, and the second was the drift region magnetic field experiment. In these experiments, permanent magnets were used to produce magnetic field. The degree of vacuum used in this test was 0.4×105 Pa. It is found that the effect of the magnetic field increases as the degree of vacuum increases. It is also seen from this study that the corona current values are higher with magnetic fields than without magnetic fields. The experimental results indicate that the enhancement of the magnetic field near the wire discharge electrode has a significant influence on the increment of the discharge current. The effect of the magnetic field on the discharge current is the most significant with the negative corona discharges rather than with positive corona discharge. In contrast to, the curves were demonstrated that the application of magnetic fields in drift region magnetic field does not significantly change the corona discharge current. Discharge characteristics of magnetically enhanced corona discharges, extracted from this study, can be applied to various industrial applications, such as, in an electrostatic enhancement filter for the purpose of capturing fine particles, and as effective method for production of high ozone concentrations in a generator as compared to the ultraviolet (UV) radiation method.

  20. Atmospheric negative corona discharge using Taylor cone as a liquid cathode

    NASA Astrophysics Data System (ADS)

    Shirai, Naoki; Sekine, Ryuto; Uchida, Satoshi; Tochikubo, Fumiyoshi

    2014-02-01

    We examined the characteristics of atmospheric negative corona discharge using a liquid needle cathode. As a liquid needle cathode, a Taylor cone with conical shape was adopted. A micronozzle was filled with liquid, and a plate electrode was placed above the nozzle. By applying a dc voltage between electrodes, a Taylor cone is formed. To change the liquid property, we added sodium dodecyl sulfate to reduce the surface tension, sodium sulfate to increase the conductivity, and polyvinyl alcohol to increase the viscosity, in distilled water. Liquids with a high surface tension such as pure water could not form a Taylor cone. When we reduced the surface tension, a Taylor cone was formed and a stable corona discharge was observed at the tip of the cone. When we increased viscosity, a liquid filament protruding from the solution surface was formed and corona discharge was observed along the filament at a position 0.7-1.0 mm above the tip of the cone. Increasing the conductivity resulted in the higher light intensity of the corona and the lower corona onset voltage. Using a Taylor cone, different types of corona discharge were observed by changing the property of the liquid.

  1. Corona discharges and their effect on lightning attachment revisited: Upward leader initiation and downward leader interception

    NASA Astrophysics Data System (ADS)

    Becerra, Marley

    2014-11-01

    Previous studies have suggested the possibility of using glow corona discharges to control the frequency of lightning flashes to grounded objects. In order to revisit the theoretical basis of this proposal, the self-consistent leader inception and propagation model - SLIM - is used together with a two-dimensional glow corona drift model. The analysis is performed to quantify the effect of glow corona generated at the tip of ground-based objects on the initiation and propagation of upward positive connecting leaders under the influence of downward lightning leaders. It is found that the presence of glow corona does not influence the performance of Franklin lightning rods shorter than 15 m, while it slightly reduces the lateral distance of rods up to 60 m tall by a maximum of 10%. Furthermore, the results indicate that it is not possible to suppress the initiation of upward connecting leaders by means of glow corona. It is found instead that unconventional lightning protection systems based on the generation of glow corona attract downward lightning flashes in a similar way as a standard lightning rod with the same height.

  2. Primary and secondary tip coronae from splashing water drops in electric fields

    NASA Astrophysics Data System (ADS)

    Kinsey, P. B.

    2012-06-01

    An enquiry has been carried out into millimetre size water drops falling through vertical electric fields, at terminal and near terminal velocities, and impacting a water surface. A laboratory method was devised to electronically observe the splashing event, together with the onset, duration and magnitude of all ensuing coronae. The production of a secondary jet tip and the discovery of a previously unknown corona were originally recorded by Kinsey (1986) and are here described in detail. Emanating from the secondary jet tip, the corona is synonymous with the release and electrification of an airborne water drop and its nC range of charge transfer (being field/momentum dependant) offer low level luminosity to the dark adapted eye (mentioned by ur Rahman and Saunders, 1988). For terminal and near terminal velocity drops, the resulting water jets follow under-damped sinusoidal oscillation and, in fields above a critical value (Ec), their primary tips often support more than one corona, thus yielding charge to the aerosol and space charge below oceanic thunderstorms. Secondary tip, or jet drop, corona data show the phenomenon to occur in fields of 100 V cm- 1 and maybe even lower. The role of such drops, in oceanic thunderstorm electrification, being subject to drop size, ambient field, updraft and wind shear speeds. Oscilloscopic and photographic evidence is presented in support of the discovered corona and oscillographs, photographs and data are taken from P. B. Kinsey Ph.D. thesis (1986).

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

    NASA Astrophysics Data System (ADS)

    Schrijver, Carolus J.; Title, Alan M.

    2003-11-01

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

  4. Physics and Chemistry of Strongly Irradiated Protostars in Corona Australis

    NASA Astrophysics Data System (ADS)

    Lindberg, J. E.; Jørgensen, J. K.; Bisschop, S.; Sakai, N.; Watanabe, Y.; Yamamoto, S.; Digit Team, Alma Cycle 0 Protostars Team

    2013-10-01

    We have conducted interferometric spectral-line observations with the SMA and APEX of the R CrA region, a star-forming region with a handful of low-mass young stellar objects. We have also conducted single-dish observations of the same spectral lines in 17 young stellar objects in the CrA star-forming region, conducted APEX and ASTE unbiased line surveys of IRS7B, a Class 0/I source in the region, and performed far-infrared continuum mapping with the Herschel Space Observatory. We find unexpectedly high H2CO excitation temperatures in the R CrA region, but also in other protostars in the CrA (Corona Australis) star-forming region. Our models show that the Herbig Be star R CrA is the dominant heat source in this region. Thus, also intermediate-mass stars have large effects on the physical properties in such regions. ALMA observations of H2CO can be used to trace such heating also in more distant regions.

  5. Mining R Coronae Borealis stars from Catalina surveys

    NASA Astrophysics Data System (ADS)

    Lee, C.-H.

    2015-03-01

    Aims: R Coronae Borealis stars (RCBs) are rare carbon stars that lack of hydrogen in their photospheresand are most likely products of white dwarf mergers. A census of RCBs can shed light on the progenitors of SNe Ia in the context of a double degenerate scenario. Methods: Traditionally, RCBs are identified by their unpredictable photometric variation with dimmings up to 9 mag, and thus discoveries of RCBs are heavily biased to the limited regions monitored by long-term microlensing experiments. However, recent studies of galactic RCBs have shown that they exhibit distinct mid-infrared colors originating from their cool circumstellar shells, and the all-sky WISE survey facilitates the identification of RCB candidates. Therefore, combining the WISE colors with large area time-domain surveys will enable us to discover more RCBs. Results: This study presents the results of 26 RCB candidates from the Catalina surveys, where five of them are spectroscopically confirmed RCBs and seven of them are previously known carbon stars. This demonstrates the efficacy of this kind of an approach and the potential to discover uncharted RCBs in ongoing and future synoptic surveys.

  6. What is the Shell Around R Coronae Borealis?

    E-print Network

    Montiel, Edward J; Marcello, Dominic C; Lockman, Felix J

    2015-01-01

    The hydrogen-deficient, carbon-rich R Coronae Borealis (RCB) stars are known for being prolific producers of dust which causes their large iconic declines in brightness. Several RCB stars, including R CrB, itself, have large extended dust shells seen in the far-infrared. The origin of these shells is uncertain but they may give us clues to the evolution of the RCB stars. The shells could form in three possible ways. 1) they are fossil Planetary Nebula (PN) shells, which would exist if RCB stars are the result of a final, helium-shell flash, 2) they are material left over from a white-dwarf merger event which formed the RCB stars, or 3) they are material lost from the star during the RCB phase. Arecibo 21-cm observations establish an upper limit on the column density of H I in the R CrB shell implying a maximum shell mass of $\\lesssim$0.3 M$_{\\odot}$. A low-mass fossil PN shell is still a possible source of the shell although it may not contain enough dust. The mass of gas lost during a white-dwarf merger even...

  7. How Many R Coronae Borealis Stars Are There Really? (Abstract)

    NASA Astrophysics Data System (ADS)

    Clayton, G. C.

    2014-12-01

    (Abstract only) The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich supergiants. Two evolutionary scenarios have been suggested, a double degenerate merger of two white dwrfs (WDs), or a final helium shell flash in a planetary nebula central star. Only about 100 of the predicted 3,000 RCB stars in the Galaxy have been discovered. But the pace of discovery of new RCB stars in the Milky Way has been accelerating. We recently discovered over twenty new RCB stars by examining ASAS-e light curves. Using the recent release of the WISE All-Sky Catalog, a series of IR color-color cuts have produced a sample of candidates that may yield over 200 new RCB stars. We are trying to obtain spectra of these stars to confirm their identifications. The evidence pointing toward a WD merger or a final-flash origin for RCB stars is contradictory. Increasing the sample of known RCB stars, so that we can better study their spatial distribution in the Galaxy, can give us clues to their origins. Their number and distribution may be consistent with WD mergers. If so, this would be an exciting result since RCB stars may be low-mass analogs of Type Ia supernovae.

  8. V532 Oph is a New R Coronae Borealis Star

    E-print Network

    Clayton, Geoffrey C; Wils, P; Welch, D L

    2009-01-01

    V532 Oph has been found to be a member of the rare, hydrogen-deficient R Coronae Borealis (RCB) stars from new photometric and spectroscopic data reported in this paper. The lightcurve of V532 Oph shows the sudden, deep, irregularly spaced declines characteristic of RCB stars. Its optical spectrum is typical of a warm (T(eff)~7000 K) RCB star, showing weak or absent hydrogen lines, the C2 Swan bands, and no evidence for 13C. In addition, the star shows small pulsations typical of an RCB star and an infrared excess due to circum- stellar dust. It also appears to be significantly reddened by foreground dust. The distance to V532 Oph is estimated to be 5.5-8.7 kpc. These new data show that this star was misclassified as an eclipsing binary in the General Catalog of Variable Stars. The new data presented here for V532 Oph reveal the power of high-quality, high-cadence all-sky photometric surveys, such as ASAS-3, to identify new RCB candidates on the basis of lightcurve data alone, now that they have been collecti...

  9. NSV 11154 Is a New R Coronae Borealis Star

    E-print Network

    Kijbunchoo, Nutsinee; Vieux, Timothy C; Dickerman, N; Hillwig, T C; Welch, D L; Pagnotta, Ashley; Tang, Sumin; Grindlay, J E; Henden, A

    2011-01-01

    NSV 11154 has been confirmed as a new member of the rare hydrogen deficient R Coronae Borealis (RCB) stars based on new photometric and spectroscopic data. Using new photometry, as well as archival plates from the Harvard archive, we have constructed the historical lightcurve of NSV 11154 from 1896 to the present. The lightcurve shows the sudden, deep, irregularly spaced declines characteristic of RCB stars. The visible spectrum is typical of a cool (Teff < 5000 K) RCB star showing no hydrogen lines, strong C2 Swan bands, and no evidence of 13C. In addition, the star shows small pulsations typical of an RCB star, and an infrared excess due to circumstellar dust with a temperature of ~800 K. The distance to NSV 11154 is estimated to be ~14.5 kpc. RCB stars are very rare in the Galaxy so each additional star is important to population studies leading to a better understanding the origins of these mysterious stars. Among the known sample of RCB stars, NSV 11154 is unusual in that it lies well above the Galact...

  10. Oxygen isotopic ratios in cool R Coronae Borealis stars

    E-print Network

    Garcia-Hernandez, D Anibal; Rao, N Kameswara; Hinkle, Ken H; Eriksson, Kjell

    2010-01-01

    We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise 16O/18O ratios for five cool RCB stars. The 16O/18O ratios are derived by spectrum synthesis from high-resolution (R=50,000) K-band spectra. Lower limits to the 16O/17O and 14N/15}N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less 18O than HdC stars - the derived 16O/18O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be a HdC-like star with 16O/18O=0.3. Our result of a higher 16O/18O ratio for the RCB stars must be accounted for by a theory of the formation and evolution of HdC and RCB stars. We speculate that a late dredge-up of products of He-burning, principally 12C and 16O, may convert a 18O-rich HdC star into a 18O-poor RCB star as the H-deficient star begins its final evolution from a cool supergiant to the top of the white dwarf cooling track.

  11. Food waste management using an electrostatic separator with corona discharge

    NASA Astrophysics Data System (ADS)

    Lai, Koonchun; Lim, Sooking; Teh, Pehchiong

    2015-05-01

    In Malaysia, municipal solid waste contains a high portion of organic matters, typically contributed by food waste. It is estimated that about 45% of the municipal waste are food waste, followed by the non-food waste such as plastics, metals, glass and others. Food waste, while being properly sorted and contamination free from non-food waste, can be reused (e.g. fertiliser) instead of being landfilled. Therefore, recycling of food waste is crucial not only from the view point of waste management, but also with respect to the reduction of resource losses and greenhouse gases emission. A new waste separation process involved food particles, non-food particles and electrostatic discharge was investigated in this study. The empirical results reveal that the corona electrostatic separation is an environmental-friendly way in recovering foods from municipal waste. The efficiency of the separator, under same operating conditions, varies with the particle size of the food and non-food particles. The highest efficiency of 82% is recorded for the particle sizes between 1.5 and 3.0 mm.

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

    NASA Astrophysics Data System (ADS)

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

    1999-04-01

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

  13. Current Sheet Formation, Equilibria and Heating in the Closed Corona

    NASA Astrophysics Data System (ADS)

    Rappazzo, A. F.

    2014-12-01

    Parker model for coronal heating is investigated within theframework of reduced magnetohydrodynamics (RMHD) in cartesian geometry. A popular hypothesis is that in response to slow photospheric motionsthe magnetic field evolves quasi-statically through a seriesof unstable equilibria. Instabilities, e.g., kink modes or else,allow the release of energy while the field relaxes to a new equilibrium.On the other hand it has long been suggested that the dynamics relevant to the basic heating of coronal loops may not entaila quasi-static evolution (Parker 1972, 1994), and recently it has beenshown that the relaxation of an initial configuration out of equilibriumdevelops current sheets without accessing intermediate equilibria (Rappazzo & Parker 2013).The properties of the equilibria are therefore key in understanding thedynamics of coronal heating both in the case of low-frequency photospheric motions (DC) and for propagating waves (AC).Equilibria and nonlinear dynamics are studied numerically and theoretically,explaining why dynamics are inhibited below a critical twist, while for highervalues of the fluctuations nonlinear dynamics lead to the formation of current sheets (and magnetic reconnection in the non ideal case), whose thickness istracked with the analiticity strip method and shown to decrease at least exponentiallydown to dissipative lenght-scales on fast ideal Alfvenic timescales. The impact onthe heating of solar and stellar coronae will be discussed.

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

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    2005-10-01

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

  15. Shock accelerated electron beams in the solar corona

    NASA Astrophysics Data System (ADS)

    Mann, G.; Klassen, A.

    2002-12-01

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

  16. Reconnection driven by natural flows in the solar corona

    NASA Astrophysics Data System (ADS)

    Knoll, D.; Lapenta, G.

    2003-12-01

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

  17. Effect of catalysts on dc corona discharge poisoning

    NASA Astrophysics Data System (ADS)

    Pekárek, S.

    2011-02-01

    The processes of ozone generation in non-thermal plasma produced by an electrical discharge in air at atmospheric pressure are burdened by the presence of nitrogen oxides, which on the one hand contribute to ozone generation and on the other hand are responsible for unpleasant discharge poisoning. The term discharge poisoning refers to the situation when the discharge ozone formation completely breaks down. Discharge poisoning can be affected by placing a catalyst in the discharge chamber. For the dc hollow needle to mesh corona discharge enhanced by the flow of air through the needle electrode we studied the effect of titanium dioxide TiO2, ZSM-5 zeolite or Cu++ZSM-5 zeolite on discharge poisoning by monitoring the ozone, nitrogen monoxide and nitrogen dioxide discharge production. We found that placing globules of any of these catalysts on the mesh decreases the energy density of the onset of discharge poisoning, and this energy density is smallest for a discharge with globules of a TiO2 on the mesh.

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

    SciTech Connect

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

    1990-06-01

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

  19. Magnetic jam in the corona of the Sun

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  20. Numerical modelling of ozone production in a wire-cylinder corona discharge and comparison with a wire-plate corona discharge

    NASA Astrophysics Data System (ADS)

    Wang, Pengxiang; Chen, Junhong

    2009-02-01

    The effect of electrode configuration on ozone production in the direct-current corona discharge of dry and humid air is studied by a numerical model that combines the electron distribution in the corona plasma, plasma chemistry and transport phenomena. Two electrode configurations are considered: wire-cylinder discharge with air flowing along the wire axis and wire-plate discharge with air flowing transverse to the wire. The ozone distributions in both types of discharges are compared. For both electrode configurations, the ozone production rate is higher in the negative corona than in the positive corona and it decreases with an increase in relative humidity. More importantly, the detailed ozone distribution in the neighbourhood of the discharge wire, together with the ozone kinetics, reveals the possible difference in the ozone production from the two discharges. With the same operating conditions and sufficiently short flow residence time, the ozone production rate is nearly the same for both electrode configurations. When the flow residence time is longer than the characteristic time for homogeneous ozone destruction, the net ozone production is higher in the wire-cylinder discharge than in the wire-plate discharge due to relatively less ozone destruction.

  1. Generation of Runaway Electrons and X-rays in Repetitive Nanosecond Pulse Corona Discharge in Atmospheric Pressure Air

    NASA Astrophysics Data System (ADS)

    Shao, Tao; Tarasenko, Victor F.; Zhang, Cheng; Kostyrya, Igor D.; Jiang, Hui; Xu, Rong; Rybka, Dmitri V.; Yan, Ping

    2011-06-01

    A pulsed corona discharge in an inhomogeneous electric field was studied in atmospheric air. A runaway electron beam from the corona discharge was detected with a collector at nanosecond-pulse duration. It is shown that with a nanosecond-pulse voltage of 300 kV, the full width at half maximum of the beam current during the pulsed corona discharge is about 100 ps. It is demonstrated that with a pulse voltage of 90 kV, a full width at half maximum of 40 ns, and pulse repetition frequencies of up to 1 kHz, the corona discharge is an X-ray source.

  2. The fate of a designed protein corona on nanoparticles in vitro and in vivo

    PubMed Central

    Bargheer, Denise; Nielsen, Julius; Gébel, Gabriella; Heine, Markus; Salmen, Sunhild C; Stauber, Roland; Weller, Horst; Heeren, Joerg

    2015-01-01

    Summary A variety of monodisperse superparamagnetic iron oxide particles (SPIOs) was designed in which the surface was modified by PEGylation with mono- or bifunctional poly(ethylene oxide)amines (PEG). Using 125I-labeled test proteins (transferrin, albumin), the binding and exchange of corona proteins was studied first in vitro. Incubation with 125I-transferrin showed that with increasing grade of PEGylation the binding was substantially diminished without a difference between simply adsorbed and covalently bound protein. However, after incubation with excess albumin and subsequently whole plasma, transferrin from the preformed transferrin corona was more and more lost from SPIOs in the case of adsorbed proteins. If non-labeled transferrin was used as preformed corona and excess 125I-labeled albumin was added to the reaction mixtures with different SPIOs, a substantial amount of label was bound to the particles with initially adsorbed transferrin but little or even zero with covalently bound transferrin. These in vitro experiments show a clear difference in the stability of a preformed hard corona with adsorbed or covalently bound protein. This difference seems, however, to be of minor importance in vivo when polymer-coated 59Fe-SPIOs with adsorbed or covalently bound 125I-labeled mouse transferrin were injected intravenously in mice. With both protein coronae the 59Fe/125I-labelled particles were cleared from the blood stream within 30 min and appeared in the liver and spleen to a large extent (>90%). In addition, after 2 h already half of the 125I-labeled transferrin from both nanodevices was recycled back into the plasma and into tissue. This study confirms that adsorbed transferrin from a preformed protein corona is efficiently taken up by cells. It is also highlighted that a radiolabelling technique described in this study may be of value to investigate the role of protein corona formation in vivo for the respective nanoparticle uptake. PMID:25671150

  3. Preparation of Core-Shell Hybrid Materials by Producing a Protein Corona Around Magnetic Nanoparticles.

    PubMed

    Weidner, A; Gräfe, C; von der Lühe, M; Remmer, H; Clement, J H; Eberbeck, D; Ludwig, F; Müller, R; Schacher, F H; Dutz, S

    2015-12-01

    Nanoparticles experience increasing interest for a variety of medical and pharmaceutical applications. When exposing nanomaterials, e.g., magnetic iron oxide nanoparticles (MNP), to human blood, a protein corona consisting of various components is formed immediately. The composition of the corona as well as its amount bound to the particle surface is dependent on different factors, e.g., particle size and surface charge. The actual composition of the formed protein corona might be of major importance for cellular uptake of magnetic nanoparticles. The aim of the present study was to analyze the formation of the protein corona during in vitro serum incubation in dependency of incubation time and temperature. For this, MNP with different shells were incubated in fetal calf serum (FCS, serving as protein source) within a water bath for a defined time and at a defined temperature. Before and after incubation the particles were characterized by a variety of methods. It was found that immediately (seconds) after contact of MNP and FCS, a protein corona is formed on the surface of MNP. This formation led to an increase of particle size and a slight agglomeration of the particles, which was relatively constant during the first minutes of incubation. A longer incubation (from hours to days) resulted in a stronger agglomeration of the FCS incubated MNP. Quantitative analysis (gel electrophoresis) of serum-incubated particles revealed a relatively constant amount of bound proteins during the first minutes of serum incubation. After a longer incubation (>20 min), a considerably higher amount of surface proteins was determined for incubation temperatures below 40 °C. For incubation temperatures above 50 °C, the influence of time was less significant which might be attributed to denaturation of proteins during incubation. Overall, analysis of the molecular weight distribution of proteins found in the corona revealed a clear influence of incubation time and temperature on corona composition. PMID:26153125

  4. Unraveling Protein-Protein Interactions in Clathrin Assemblies via Atomic Force Spectroscopy

    PubMed Central

    Jin, Albert J.; Lafer, Eileen M.; Peng, Jennifer Q.; Smith, Paul D.; Nossal, Ralph

    2013-01-01

    Atomic force microscopy (AFM), single molecule force spectroscopy (SMFS), and single particle force spectroscopy (SPFS) are used to characterize intermolecular interactions and domain structures of clathrin triskelia and clathrin-coated vesicles (CCVs). The latter are involved in receptor-mediated endocytosis (RME) and other trafficking pathways. Here, we subject individual triskelia, bovine-brain CCVs, and reconstituted clathrin-AP180 coats to AFM-SMFS and AFM-SPFS pulling experiments and apply novel analytics to extract force-extension relations from very large data sets. The spectroscopic fingerprints of these samples differ markedly, providing important new information about the mechanism of CCV uncoating. For individual triskelia, SMFS reveals a series of events associated with heavy chain alpha-helix hairpin unfolding, as well as cooperative unraveling of several hairpin domains. SPFS of clathrin assemblies exposes weaker clathrin-clathrin interactions that are indicative of inter-leg association essential for RME and intracellular trafficking. Clathrin-AP180 coats are energetically easier to unravel than the coats of CCVs, with a non-trivial dependence on force-loading rate. PMID:23270814

  5. Percutaneous removal of unraveled HELEX® septal occluder 4 months post deployment.

    PubMed

    Suntharos, Patcharapong; Komarlu, Rukmini; Prieto, Lourdes R

    2015-07-01

    The GORE® HELEX® Septal Occluder (HSO: W.L. Gore & Associates; Flagstaff, AZ) is preferentially used at our institution for percutaneous closure of the patent foramen ovale (PFO). Adequate deployment of the device requires capture of three sequential eyelets by the locking loop. At times, the right atrial eyelet is not caught, particularly when a long tunnel PFO causes too much separation between the discs. Although rarely, unlocked devices have been left in the atrial septum with no untoward events provided they appear stable in the catheterization laboratory and the shunt has been eliminated. We report a patient in whom an unlocked, but otherwise well positioned, HSO subsequently unraveled with the right atrial disc migrating through the tricuspid valve while the left atrial disc remained well apposed to the left side of the atrial septum. The PFO was closed prior to liver transplantation to prevent an embolic event during the transplant. The patient required placement of several internal jugular central lines prior to transplant, and this instrumentation in the right atrium may have caused unraveling of the device. The HSO was removed percutaneously 15 weeks after implantation despite a well-seated and likely partially endothelialized left atrial disc. © 2015 Wiley Periodicals, Inc. PMID:25639512

  6. Unraveling Traveling

    NSDL National Science Digital Library

    Charalambos Kyriacou (University of Leicester; )

    2009-09-25

    Access to the article is free, however registration and sign-in are required. There are few more awesome sights in the animal world than the seasonal mass migrations of the monarch butterfly, Danaus plexippus, from the northern United States and southern Canada to its overwintering grounds in central Mexico. As with other insect orientations, the monarch uses the position of the Sun to calculate where it should be going. However, as the Sun moves across the sky during the day, the monarch must continuously adjust its calculations, which it does by using its 24-hour circadian clock. So where is this time-compensated clock located? Merlin et al. reveal that it's in the antennae.

  7. Multiscale simulation of DC corona discharge and ozone generation from nanostructures

    NASA Astrophysics Data System (ADS)

    Wang, Pengxiang

    Atmospheric direct current (dc) corona discharge from micro-sized objects has been widely used as an ion source in many devices, such as photocopiers, laser printers, and electronic air cleaners. Shrinking the size of the discharge electrode to the nanometer range (e.g., through the use of carbon nanotubes or CNTs) is expected to lead to a significant reduction in power consumption and detrimental ozone production in these devices. The objectives of this study are to unveil the fundamental physics of the nanoscale corona discharge and to evaluate its performance and ozone production through numerical models. The extremely small size of CNTs presents considerable complexity and challenges in modeling CNT corona discharges. A hybrid multiscale model, which combines a kinetic particle-in-cell plus Monte Carlo collision (PIC-MCC) model and a continuum model, is developed to simulate the corona discharge from nanostructures. The multiscale model is developed in several steps. First, a pure PIC-MCC model is developed and PIC-MCC simulations of corona plasma from micro-sized electrode with same boundary conditions as prior model are performed to validate the PIC-MCC scheme. The agreement between the PIC-MCC model and the prior continuum model indicates the validity of the PIC-MCC scheme. The validated PIC-MCC scheme is then coupled with a continuum model to simulate the corona discharge from a micro-sized electrode. Unlike the prior continuum model which only predicts the corona plasma region, the hybrid model successfully predicts the self-consistent discharge process in the entire corona discharge gap that includes both corona plasma region and unipolar ion region. The voltage-current density curves obtained by the hybrid model agree well with analytical prediction and experimental results. The hybrid modeling approach, which combines the accuracy of a kinetic model and the efficiency of a continuum model, is thus validated for modeling dc corona discharges. For simulation of corona discharges from nanostructures, a one-dimensional (1-D) multiscale model is used due to the prohibitive computational expense associated with two-dimensional (2-D) modeling. Near the nanoscale discharge electrode surface, a kinetic model based on PIC-MCC is used due to a relatively large Knudsen number in this region. Far away from the nanoscale discharge electrode, a continuum model is used since the Knudsen number is very small there. The multiscale modeling results are compared with experimental data. The quantitative agreement in positive discharges and qualitative agreement in negative discharges validate the modeling approach. The mechanism of sustaining the discharge process from nanostructures is revealed and is found to be different from that of discharge from micro- or macro-sized electrodes. Finally, the corona plasma model is combined with a plasma chemistry model and a transport model to predict the ozone production from the nanoscale corona. The dependence of ozone production on the applied potential and air velocity is studied. The electric field distribution in a 2-D multiscale domain (from nanoscale to microscale) is predicted by solving the Poisson's equation using a finite difference scheme. The discretized linear equations are solved using a multigrid method under the framework of PETSc on a paralleled supercomputer. Although the Poisson solver is able to resolve the multiscale field, the prohibitively long computation time limits the use of a 2-D solver in the current PIC-MCC scheme.

  8. OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS

    SciTech Connect

    Garcia-Hernandez, D. A. [Instituto de Astrofisica de Canarias (IAC), C/Via Lactea s/n, 38200 La Laguna, Tenerife (Spain); Lambert, David L. [W. J. McDonald Observatory, University of Texas at Austin. 1 University Station, C1400. Austin, TX 78712-0259 (United States); Rao, N. Kameswara [Indian Institute of Astrophysics, Bangalore 560 034 (India); Hinkle, Ken H. [National Optical Astronomy Observatory (NOAO), Tucson, AZ 85726 (United States); Eriksson, Kjell, E-mail: agarcia@iac.e, E-mail: dll@astro.as.utexas.ed, E-mail: nkrao@iiap.res.i, E-mail: hinkle@noao.ed, E-mail: Kjell.Eriksson@astro.uu.s [Department of Physics and Astronomy, Uppsala University, Box 515, 75120 Uppsala (Sweden)

    2010-05-01

    We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise {sup 16}O/{sup 18}O ratios for five cool RCB stars. The {sup 16}O/{sup 18}O ratios are derived by spectrum synthesis from high-resolution (R {approx} 50, 000) K-band spectra. Lower limits to the {sup 16}O/{sup 17}O and {sup 14}N/{sup 15}N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less {sup 18}O than HdC stars-the derived {sup 16}O/{sup 18}O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with {sup 16}O/{sup 18}O = 0.3. Our result of a higher {sup 16}O/{sup 18}O ratio for the RCB stars must be accounted for by a theory of the formation and evolution of HdC and RCB stars. We speculate that a late dredge-up of products of He burning, principally {sup 12}C and {sup 16}O, may convert an {sup 18}O-rich HdC star into an {sup 18}O-poor RCB star as the H-deficient star begins its final evolution from a cool supergiant to the top of the white dwarf cooling track.

  9. The Writhe of Helical Structures in the Solar Corona

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  10. R Coronae Borealis Stars formed from Double White Dwarf Mergers

    NASA Astrophysics Data System (ADS)

    Staff, Jan E.; Herwig, F.; Menon, A.; Even, W.; Tohline, J.; Clayton, G.; Motl, P.; Fryer, C.; Geballe, T.

    2011-01-01

    R Coronae Borealis (RCB) stars are hydrogen-deficient variable stars that suddenly fade by several magnitudes at irregular intervals whereafter they gradually return to their original brightness over a period of some months. The origin of RCBs remain a mystery. It is often thought that they are the result of the merger of a He and a CO white dwarf, while the fading is thought to be due to the formation of dust blocking light from the star. We are working on revealing the secrets behind the origin of RCBs. Here we present the results of 3 dimensional hydrodynamic simulations of the merger of a double white dwarf system where total mass is 0.9 M? and initial mass ratio is q=0.7. We use a zero-temperature plus ideal gas equation of state that allows for heating through shocks. These simulations allow us to follow the evolution of the system for 10-20 initial orbital periods (1000-2000 seconds), from the onset of mass-transfer to a point after merger when the combined object has settled into a nearly axisymmetric, rotationally flattened configuration. The final merged object from the hydrodynamics simulation is then used as input for a stellar evolution code where the object's evolution can be followed over a much longer (thermal and/or nuclear) timescale. A preliminary post-merger stellar evolution simulation shows how an initial configuration of a 0.7 CO WD surrounded by 0.3 M? of dynamically accreted He evolves on a time scale of 105 years to the location of the RCB stars in the H-R diagram at an effective temperature Teff<7000 K and log L 4. We acknowledge support from NASA Astrophysics Theory Program grant number NNX10AC72G.

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

    NASA Astrophysics Data System (ADS)

    Warmuth, A.; Mann, G.

    2005-06-01

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

  12. CHARACTERIZING TRANSITION TEMPERATURE GAS IN THE GALACTIC CORONA

    SciTech Connect

    Wakker, Bart P.; Savage, Blair D. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Fox, Andrew J. [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile); Benjamin, Robert A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218 (United States); Shapiro, Paul R., E-mail: wakker@astro.wisc.edu, E-mail: savage@astro.wisc.edu, E-mail: afox@stsci.edu, E-mail: benjamir@uww.edu, E-mail: shapiro@astro.as.utexas.edu [University of Texas at Austin, Department of Astronomy, Austin, TX 78712 (United States)

    2012-04-20

    We present a study of the properties of the transition temperature (T {approx} 10{sup 5} K) gas in the Milky Way corona, based on the measurements of O VI, N V, C IV, Si IV, and Fe III absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km s{sup -1}. On average the integrated column densities are log N(O VI) = 14.3, log N(N V) = 13.5, log N(C IV) = 14.2, log N(Si IV) = 13.6, and log N(Fe III) = 14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor {approx}2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling, and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that NIE radiative cooling is important in generating the transition temperature gas.

  13. Corona streamer onset as an optimization criterion for design of high voltage hardware on transmission lines

    SciTech Connect

    Pedrow, P.D.; Olsen, R.G. [Washington State Univ., Pullman, WA (United States). School of Electrical Engineering and Computer Science

    1996-12-31

    To design hardware for compact high voltage lines it is necessary to predict conditions for which corona streamers are initiated. Existing techniques for optimizing hardware shape and calculating streamer onset are based on corona measurements in a coaxial geometry that uses concentric cylinders for electrodes. Peek`s law shows that the formation of corona streamers is related not only to electric field but also to surface curvature. It is not clear that Peek`s law (developed in a coaxial geometry for which radius of curvature in the axial direction is infinite) is appropriate for designing hardware surfaces which are defined at any point by two finite radii of curvature. In this work the authors seek a corona onset criterion for these more general surfaces which reduces to Peeks law in the limit that one of the radii of curvature is infinite. An existing electrostatic code is being modified to allow for iterative optimization of electrode shapes based on results of previous field calculations. Experimental corona performance testing of electrode shapes will take place in an air-filled chamber with ac voltage as high as 100 kV rms. Experiments will be used to evaluate various electrode shapes designed by the trial optimization criterion.

  14. Tracing Electron Beams in the Sun's Corona with Radio Dynamic Imaging Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Bastian, T. S.; White, S. M.; Gary, D. E.; Perley, R.; Rupen, M.; Carlson, B.

    2013-01-01

    We report observations of type III radio bursts at decimeter wavelengths (type IIIdm bursts)—signatures of suprathermal electron beams propagating in the low corona—using the new technique of radio dynamic imaging spectroscopy provided by the recently upgraded Karl G. Jansky Very Large Array. For the first time, type IIIdm bursts were imaged with high time and frequency resolution over a broad frequency band, allowing electron beam trajectories in the corona to be deduced. Together with simultaneous hard X-ray and extreme ultraviolet observations, we show that these beams emanate from an energy release site located in the low corona at a height below ~15 Mm, and propagate along a bundle of discrete magnetic loops upward into the corona. Our observations enable direct measurements of the plasma density along the magnetic loops, and allow us to constrain the diameter of these loops to be less than 100 km. These overdense and ultra-thin loops reveal the fundamentally fibrous structure of the Sun's corona. The impulsive nature of the electron beams, their accessibility to different magnetic field lines, and the detailed structure of the magnetic release site revealed by the radio observations indicate that the localized energy release is highly fragmentary in time and space, supporting a bursty reconnection model that involves secondary magnetic structures for magnetic energy release and particle acceleration.

  15. Outflow structure of the quiet sun corona probed by spacecraft radio scintillations in strong scattering

    SciTech Connect

    Imamura, Takeshi; Ando, Hiroki; Toda, Tomoaki; Nakamura, Masato [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Tokumaru, Munetoshi; Shiota, Daikou [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 484-8601 (Japan); Isobe, Hiroaki; Asai, Ayumi [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471, Japan. (Japan); Miyamoto, Mayu [Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Häusler, Bernd [Institut für Raumfahrttechnik, Universität der Bundeswehr München, D-85577 Neubiberg (Germany); Pätzold, Martin [Rheinisches Institut für Umweltforschung, Department Planetenforschung, Universität zu Köln, Aachener Strasse 209, D-50931 Köln (Germany); Nabatov, Alexander [The Institute of Radio Astronomy, National Academy of Science of Ukraine, Chervonoprapornaya, Strasse 4, Kharkov 61002 (Ukraine); Yaji, Kentaro [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Yamada, Manabu, E-mail: imamura.takeshi@jaxa.jp [Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba 275-0016 (Japan)

    2014-06-20

    Radio scintillation observations have been unable to probe flow speeds in the low corona where the scattering of radio waves is exceedingly strong. Here we estimate outflow speeds continuously from the vicinity of the Sun to the outer corona (heliocentric distances of 1.5-20.5 solar radii) by applying the strong scattering theory to radio scintillations for the first time, using the Akatsuki spacecraft as the radio source. Small, nonzero outflow speeds were observed over a wide latitudinal range in the quiet-Sun low corona, suggesting that the supply of plasma from closed loops to the solar wind occurs over an extended area. The existence of power-law density fluctuations down to the scale of 100 m was suggested, which is indicative of well-developed turbulence which can play a key role in heating the corona. At higher altitudes, a rapid acceleration typical of radial open fields is observed, and the temperatures derived from the speed profile show a distinct maximum in the outer corona. This study opened up a possibility of observing detailed flow structures near the Sun from a vast amount of existing interplanetary scintillation data.

  16. Relativistic effects on radiative ejection of coronae in variable X-ray sources

    NASA Astrophysics Data System (ADS)

    Mishra, B.; Klu?niak, W.

    2014-06-01

    Context. Optically thin coronae around neutron stars suffering an X-ray burst can be ejected as a result of rapid increase in stellar luminosity. In general relativity, radiation pressure from the central luminous star counteracts gravitational attraction more strongly than in Newtonian physics. However, motion near the neutron star is very effectively impeded by the radiation field. Aims: To explore the mechanisms leading to ejection of accretion disk coronae Methods: We perform a general relativistic calculation of the motion of a test particle in a spherically symmetric radiation field. Results: At every radial distance from the star larger than that of the innermost stable circular orbit (ISCO), and any initial luminosity of the star, there exists a luminosity change which leads to coronal ejection. The luminosity required to eject from the system the inner parts of the optically thin neutron-star corona is very high in the presence of radiation drag and always close to the Eddington luminosity. Outer parts of the corona, at a distance of 20 RG or more, will be ejected by a sub-Eddington outburst. Mildly fluctuating luminosity will lead to dissipation in the plasma and may explain the observed X-ray temperatures of coronae in low mass X-ray binaries. At large radial distances from the star (3 × 103 RG or more) the results do not depend on whether or not Poynting-Robertson drag is included in the calculation.

  17. A semi-analytical study of positive corona discharge in wire-plane electrode configuration

    NASA Astrophysics Data System (ADS)

    Yanallah, K.; Pontiga, F.; Chen, J. H.

    2013-08-01

    Wire-to-plane positive corona discharge in air has been studied using an analytical model of two species (electrons and positive ions). The spatial distributions of electric field and charged species are obtained by integrating Gauss's law and the continuity equations of species along the Laplacian field lines. The experimental values of corona current intensity and applied voltage, together with Warburg's law, have been used to formulate the boundary condition for the electron density on the corona wire. To test the accuracy of the model, the approximate electric field distribution has been compared with the exact numerical solution obtained from a finite element analysis. A parametrical study of wire-to-plane corona discharge has then been undertaken using the approximate semi-analytical solutions. Thus, the spatial distributions of electric field and charged particles have been computed for different values of the gas pressure, wire radius and electrode separation. Also, the two dimensional distribution of ozone density has been obtained using a simplified plasma chemistry model. The approximate semi-analytical solutions can be evaluated in a negligible computational time, yet provide precise estimates of corona discharge variables.

  18. Modeling Time-variation Of Disk And Corona Flow In LMC X-3

    NASA Astrophysics Data System (ADS)

    Cambier, Hal J.; Smith, D.

    2011-09-01

    The X-ray binary system LMC X-3 is a simple test-bed for accretion physics: its orbital period implies that mass-transfer always takes place via Roche-lobe overflow, and a thermal x-ray component is almost always observed, with a luminosity that varies with temperature according to the expected relation for a disk blackbody. The power-law hard x-ray tail is seen only during periods of declining blackbody luminosity, and not when the luminosity is increasing; this effect is seen in 600 days of data from the Rossi-X-ray Timing Explorer (Smith, Dawson & Swank 2007, ApJ 669, 1138). Using the power-law component as a proportional measure of the Comptonizing corona's optical depth, and assuming that total mass input is constant but split between disk and corona in some time-varying manner, we can independently predict a blackbody time-series to compare with observations. Applying a (quasistatic) model of disk-corona mass exchange (based on Liu et al. 2007, ApJ 671, 695L) to a non-equilibrium disk (evolved numerically), we can qualitatively explain the data, but for simpler models where disk and corona flows remain independent inside of some injection radius, we can not. Since we still take time-dependence of the initial disk-to-corona accretion ratio as an input, for completeness we also discuss what mechanism(s) might set this ratio.

  19. Technical tip: high-resolution isolation of nanoparticle-protein corona complexes from physiological fluids.

    PubMed

    Di Silvio, Desirè; Rigby, Neil; Bajka, Balazs; Mayes, Andrew; Mackie, Alan; Baldelli Bombelli, Francesca

    2015-07-28

    Nanoparticles (NPs) in contact with biological fluids are generally coated with environmental proteins, forming a stronger layer of proteins around the NP surface called the hard corona. Protein corona complexes provide the biological identity of the NPs and their isolation and characterization are essential to understand their in vitro and in vivo behaviour. Here we present a one-step methodology to recover NPs from complex biological media in a stable non-aggregated form without affecting the structure or composition of the corona. This method allows NPs to be separated from complex fluids containing biological particulates and in a form suitable for use in further experiments. The study has been performed systematically comparing the new proposed methodology to standard approaches for a wide panel of NPs. NPs were first incubated in the biological fluid and successively recovered by sucrose gradient ultracentrifugation in order to separate the NPs and their protein corona from the loosely bound proteins. The isolated NP-protein complexes were characterized by size and protein composition through Dynamic Light Scattering, Nanoparticle Tracking Analysis, SDS-PAGE and LC-MS. The protocol described is versatile and can be applied to diverse nanomaterials and complex fluids. It is shown to have higher resolution in separating the multiple protein corona complexes from a biological environment with a much lower impact on their in situ structure compared to conventional centrifugal approaches. PMID:26108682

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

    NASA Astrophysics Data System (ADS)

    Ptitsyna, Olga; Somov, Boris

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