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Sample records for solar-minimum corona unraveled

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

    SciTech Connect

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

    2009-09-10

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

  2. A study of the background corona near solar minimum

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  4. 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.

  5. How unprecedented a solar minimum was it?

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Jian, L. K.; Luhmann, J. G.

    2013-05-01

    The end of the last solar cycle was at least 3 years late, and to date, the new solar cycle has seen mainly weaker activity since the onset of the rising phase toward the new solar maximum. The newspapers now even report when auroras are seen in Norway. This paper is an update of our review paper written during the deepest part of the last solar minimum [1]. We update the records of solar activity and its consequent effects on the interplanetary fields and solar wind density. The arrival of solar minimum allows us to use two techniques that predict sunspot maximum from readings obtained at solar minimum. It is clear that the Sun is still behaving strangely compared to the last few solar minima even though we are well beyond the minimum phase of the cycle 23-24 transition.

  6. How unprecedented a solar minimum was it?

    PubMed Central

    Russell, C.T.; Jian, L.K.; Luhmann, J.G.

    2012-01-01

    The end of the last solar cycle was at least 3 years late, and to date, the new solar cycle has seen mainly weaker activity since the onset of the rising phase toward the new solar maximum. The newspapers now even report when auroras are seen in Norway. This paper is an update of our review paper written during the deepest part of the last solar minimum [1]. We update the records of solar activity and its consequent effects on the interplanetary fields and solar wind density. The arrival of solar minimum allows us to use two techniques that predict sunspot maximum from readings obtained at solar minimum. It is clear that the Sun is still behaving strangely compared to the last few solar minima even though we are well beyond the minimum phase of the cycle 23–24 transition. PMID:25685425

  7. How unprecedented a solar minimum was it?

    PubMed

    Russell, C T; Jian, L K; Luhmann, J G

    2013-05-01

    The end of the last solar cycle was at least 3 years late, and to date, the new solar cycle has seen mainly weaker activity since the onset of the rising phase toward the new solar maximum. The newspapers now even report when auroras are seen in Norway. This paper is an update of our review paper written during the deepest part of the last solar minimum [1]. We update the records of solar activity and its consequent effects on the interplanetary fields and solar wind density. The arrival of solar minimum allows us to use two techniques that predict sunspot maximum from readings obtained at solar minimum. It is clear that the Sun is still behaving strangely compared to the last few solar minima even though we are well beyond the minimum phase of the cycle 23-24 transition. PMID:25685425

  8. A comparison of solar wind streams and coronal structure near solar minimum

    NASA Technical Reports Server (NTRS)

    Nolte, J. T.; Davis, J. M.; Gerassimenko, M.; Lazarus, A. J.; Sullivan, J. D.

    1977-01-01

    Solar wind data from the MIT detectors on the IMP 7 and 8 satellites and the SOLRAD 11B satellite for the solar-minimum period September-December, 1976, were compared with X-ray images of the solar corona taken by rocket-borne telescopes on September 16 and November 17, 1976. There was no compelling evidence that a coronal hole was the source of any high speed stream. Thus it is possible that either coronal holes were not the sources of all recurrent high-speed solar wind streams during the declining phase of the solar cycle, as might be inferred from the Skylab period, or there was a change in the appearance of some magnetic field regions near the time of solar minimum.

  9. Are Sunspots Different During This Solar Minimum?

    NASA Astrophysics Data System (ADS)

    Livingston, W.; Penn, M.

    2009-07-01

    For hundreds of years, humans have observed that the Sun has displayed activity where the number of sunspots increases and then decreases at approximately 11-year intervals. Sunspots are dark regions on the solar disk with magnetic field strengths greater than 1500 gauss (see Figure 1), and the 11-year sunspot cycle is actually a 22-year cycle in the solar magnetic field, with sunspots showing the same hemispheric magnetic polarity on alternate 11-year cycles. The last solar maximum occurred in 2001, and the magnetically active sunspots at that time produced powerful flares causing large geomagnetic disturbances and disrupting some space-based technology. But something is unusual about the current sunspot cycle. The current solar minimum has been unusually long, and with more than 670 days without sunspots through June 2009, the number of spotless days has not been equaled since 1933 (see http://users.telenet.be/j.janssens/Spotless//Spotless.html). The solar wind is reported to be in a uniquely low energy state since space measurements began nearly 40 years ago [Fisk and Zhao, 2009].

  10. An equatorial coronal hole at solar minimum

    NASA Technical Reports Server (NTRS)

    Bromage, B. J. I.; DelZanna, G.; DeForest, C.; Thompson, B.; Clegg, J. R.

    1997-01-01

    The large transequatorial coronal hole that was observed in the solar corona at the end of August 1996 is presented. It consists of a north polar coronal hole called the 'elephant's trunk or tusk'. The observations of this coronal hole were carried out with the coronal diagnostic spectrometer onboard the Solar and Heliospheric Observatory (SOHO). The magnetic field associated with the equatorial coronal hole is strongly connected to that of the active region at its base, resulting in the two features rotating at almost the same rate.

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

    SciTech Connect

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

    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 transterminator ion flow at Venus at solar minimum

    NASA Astrophysics Data System (ADS)

    Wood, A. G.; Pryse, S. E.; Grande, M.; Whittaker, I. C.; Coates, A. J.; Husband, K.; Baumjohann, W.; Zhang, T. L.; Mazelle, C.; Kallio, E.; Fränz, M.; McKenna-Lawlor, S.; Wurz, P.

    2012-12-01

    The transterminator ion flow in the Venusian ionosphere is observed at solar minimum for the first time. Such a flow, which transports ions from the day to the nightside, has been observed previously around solar maximum. At solar minimum this transport process is severely inhibited by the lower altitude of the ionopause. The observations presented were those made of the Venusian ionospheric plasma by the ASPERA-4 experiment onboard the Venus Express spacecraft, and which constitute the first extensive in-situ measurements of the plasma near solar minimum. Observations near the terminator of the energies of ions of ionospheric origin showed asymmetry between the noon and midnight sectors, which indicated an antisunward ion flow with a velocity of (2.5±1.5) km s-1. It is suggested that this ion flow contributes to maintaining the nightside ionosphere near the terminator region at solar minimum. The interpretation of the result was reinforced by observed asymmetries in the ion number counts. The observed dawn-dusk asymmetry was consistent with a nightward transport of ions while the noon-midnight observations indicated that the flow was highly variable but could contribute to the maintenance of the nightside ionosphere.

  13. 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.; Lamy, P.

    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.

  14. Recent studies of the behavior of the Sun's white-light corona over time

    NASA Astrophysics Data System (ADS)

    St. Cyr, O. C.; Young, D.; Pesnell, W. D.; Lecinski, A.; Eddy, J.

    2008-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  16. Atomic hydrogen on Mars - Measurements at solar minimum

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Mcdougal, D. S.; Anderson, D. E., Jr.; Barker, E. S.

    1978-01-01

    The Copernicus Orbiting Astronomical Observatory was used to obtain measurements of Mars Lyman-alpha (1215.671-angstrom) emission at the solar minimum, which has resulted in the first information on atomic hydrogen concentrations in the upper atmosphere of Mars at the solar minimum. The Copernicus measurements, coupled with the Viking in situ measurements of the temperature (170 plus or minus 30 K) of the upper atmosphere of Mars, indicate that the atomic hydrogen number density at the exobase of Mars (250 kilometers) is about 60 times greater than that deduced from Mariner 6 and 7 Lyman-alpha measurements obtained during a period of high solar activity. The Copernicus results are consistent with Hunten's hypothesis of the diffusion-limited escape of atomic hydrogen from Mars.

  17. Differential Emission Measure Analysis of a Polar Coronal Hole During the Recent Solar Minimum

    NASA Astrophysics Data System (ADS)

    Hahn, Michael; Landi, E.; Savin, D. W.

    2011-05-01

    We have performed a differential emission measure (DEM) analysis for a polar coronal hole observed during the solar minimum in 2007. The analysis was performed for the above-limb portions of five observations from the EUV Imaging Spectrometer on Hinode. The slit pointings also included quiet Sun corona near the boundary with the coronal hole. Our DEM analysis showed that none of the positions were completely isothermal. Instead the emitting material appeared to have a significant high-temperature tail and was consistent with being composed of two plasmas at different temperatures, as measured in K, of log T = 5.95 and log T = 6.15. The lower temperature peak was dominant in the coronal hole and the higher temperature peak dominant in the quiet Sun corona. We used our DEM curves to model isothermal analyses and found that relatively small deviations from isothermality can distort the results inferred using an isothermal analysis method. Isothermal temperature analyses actually measure a DEM-weighted average and can infer artificial temperature gradients if the high and low temperature parts of the DEM curve do not change uniformly with position. The isothermal analyses also do not detect different structures along the line-of-sight, which can affect the interpretation of density diagnostic line ratios.

  18. Transient flows of the solar wind associated with small-scale solar activity in solar minimum

    NASA Astrophysics Data System (ADS)

    Slemzin, Vladimir; Veselovsky, Igor; Kuzin, Sergey; Gburek, Szymon; Ulyanov, Artyom; Kirichenko, Alexey; Shugay, Yulia; Goryaev, Farid

    The data obtained by the modern high sensitive EUV-XUV telescopes and photometers such as CORONAS-Photon/TESIS and SPHINX, STEREO/EUVI, PROBA2/SWAP, SDO/AIA provide good possibilities for studying small-scale solar activity (SSA), which is supposed to play an important role in heating of the corona and producing transient flows of the solar wind. During the recent unusually weak solar minimum, a large number of SSA events, such as week solar flares, small CMEs and CME-like flows were observed and recorded in the databases of flares (STEREO, SWAP, SPHINX) and CMEs (LASCO, CACTUS). On the other hand, the solar wind data obtained in this period by ACE, Wind, STEREO contain signatures of transient ICME-like structures which have shorter duration (<10h), weaker magnetic field strength (<10 nT) and lower proton temperature than usual ICMEs. To verify the assumption that ICME-like transients may be associated with the SSA events we investigated the number of weak flares of C-class and lower detected by SPHINX in 2009 and STEREO/EUVI in 2010. The flares were classified on temperature and emission measure using the diagnostic means of SPHINX and Hinode/EIS and were confronted with the parameters of the solar wind (velocity, density, ion composition and temperature, magnetic field, pitch angle distribution of the suprathermal electrons). The outflows of plasma associated with the flares were identified by their coronal signatures - CMEs (only in few cases) and dimmings. It was found that the mean parameters of the solar wind projected to the source surface for the times of the studied flares were typical for the ICME-like transients. The results support the suggestion that weak flares can be indicators of sources of transient plasma flows contributing to the slow solar wind at solar minimum, although these flows may be too weak to be considered as separate CMEs and ICMEs. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project n° 284461, www.eheroes.eu).

  19. Observations of Lower Thermospheric Nitric Oxide During the Current Solar Minimum: Comparison with HALOE and the Previous Solar Minimum

    NASA Astrophysics Data System (ADS)

    Bailey, Scott; Thirukovelori, Padma; Hervig, Mark; Gordley, Larry; Deaver, Lance; Russell, J. M., III

    Nitric oxide (NO) is a key minor constituent in the lower thermosphere. Of particular im-portance is its role in the energy balance in that altitude region. NO is produced through the reaction of excited atomic nitrogen with molecular oxygen. Thus its production is very sensitive to those energy sources able to break the strong molecular nitrogen bond. These include solar soft X-rays and precipitating energetic particles. Nitric oxide emits efficiently in the infrared and is an important cooling mechanism in the lower thermosphere. The abundance of NO is thus both a direct response to recent energy deposition as well as a key mechanism by which the upper atmosphere releases that energy. The Solar Occultation for Ice Experiment (SOFIE) instrument was launched on-board the Aeronomy of Ice in the Mesosphere (AIM) satellite on April 25, 2007. SOFIE is a 16 channel differential absorption radiometer using the solar occultation technique to measure ice and environmental properties at a range of altitudes, and in particular the mesopause region. One of the constituents measured by SOFIE is NO in the mesosphere and lower thermosphere to about 130 km. The AIM orbit and the solar occultation technique confine observations to latitudes of 65 to 85 degrees in each hemisphere and varying with season. In this talk we overview the SOFIE observations of NO in the southern hemisphere lower thermosphere and provide a preliminary description of its behavior during the extended solar minimum. Because the measurements are similar to observations by the Halogen Occultation Experiment (HALOE) which observed NO during the previous solar minimum, the two data sets allow for a comparison of how NO, and by extension solar energy deposition, was different between the two solar minima. Preliminary results show the solar minimum observations from both experiments are similar to within the uncertainties of the measurements.

  20. 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, Gran; 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.

  1. UV solar irradiance low during recent solar minimum

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-10-01

    Solar irradiance, which varies with the 11-year solar cycle and on longer time scales, can affect temperatures and winds in the atmosphere, influencing Earth's climate. As the Sun currently wakes up from a period of low sunspot activity, researchers want to know how irradiance during the recent solar minimum compares to historical levels. In addition to understanding the total received power, it is important to know how various spectral bands behave, in particular, the ultraviolet, which causes heating and winds in the stratosphere. Lockwood analyzed solar ultraviolet spectral irradiance data from May 2003 to August 2005 from both the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) instrument on board the Upper Atmosphere Research Satellite (UARS) and the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) instrument on the Solar Radiation and Climate Experiment (SORCE) satellite. Using several different methods to intercalibrate the data, he developed a data composite that can be used to determine differences between the recent solar minimum and previous minima. The author found that solar irradiance during the recent sunspot minimum has been especially low. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2010JD014746, 2011)

  2. 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.; Kuzin, S.; Farnik, F.; Reale, F.; Phillips, K. J. H.

    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.

  3. Empirical constraints on O(5+) outflows and velocity distributions in a solar-minimum coronal streamer

    NASA Astrophysics Data System (ADS)

    Frazin, Richard Alan

    2002-08-01

    The three dimensional distribution of the electron density in the solar minimum corona from 2.4 to 6.0 R⊙ is determined via the robust, regularized, positive estimation (RRPE) tomography method applied to a time series of polarized white-light images taken by the Large Angle and Spectrometric Coronagraph Experiment (LASCO). The LASCO images are supported by inter- comparisons with the Ultraviolet Coronagraph Spectrometer White Light Channel (UVCS/WLC) and in-flight calibration of the UVCS/WLC. As part of an effort to understand how the solar wind is energized, the so-determined electron density is used to interpret O VI λ1032, 1037 Å spectra taken with UVCS. The spectra are interpreted in terms of empirical constraints on the O5+ ion velocity distributions and outflow speeds. Four conclusions result from this work: (1)our analysis shows O5+ velocity distribution anisotropy in the streamer legs and stalk and also shows that the microscopic velocity distribution (which excludes wave motions that equally affect all charged particles) is anisotropic, where the most probable speed perpendicular to the magnetic field direction exceeds that in the parallel direction; (2)there is preferential heating of the O5+ ions over the protons in the streamer stalk and legs; (3)there is no evidence for preferential O5+ heating in the core; (4)the outflow velocity of the O5+ ions is determined at heights above 4.6 R⊙ . All results have a confidence level of at least 70%.

  4. The unusual solar minimum in relation to the Sun's history

    NASA Astrophysics Data System (ADS)

    Usoskin, Ilya

    The recent solar minimum of 2008-2010 was quite unusual for the space era with the very quiet solar and heliospheric conditions. On the other hand, such low activity minima are typical in the centennial and millennial history of the Sun. Here, a review is presented of the long-term evolution of solar/heliospheric activity as reconstructed from direct observations and indirect proxy. A special emphasis is given to the occurrence of Grand minima and maxima on the long-term scale, and their relation to the heliospheric modulation of cosmic rays. It is shown that, after the recent Grand maximum of activity, the Sun is now in the normal mode of activity.

  5. 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.

  6. 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

  7. Radiation Environment on Mir Orbital Station During Solar Minimum

    NASA Technical Reports Server (NTRS)

    Badhwar, Gautam D.; McKay, Gordon A. (Technical Monitor)

    1999-01-01

    Space radiation poses a significant risk for the stay and rotation cycle of astronauts on the International Space Station (ISS). The ISS is in the same orbit as the Mir orbital station and as such, data acquired onboard the Mir station is of direct applicability to the ISS astronaut. During the seven NASA-Mir missions, data were acquired with a variety of both passive and active detectors, including measurements of astronaut doses. This paper describes these measurements and comparisons with measurements carried out by other groups. It is shown that trapped protons absorbed can be very well described by quadratic equation in In(p), where p is the atmospheric density. Similarly, the galactic cosmic ray absorbed dose is nearly exponentially related to the deceleration potential. The average radiation quality factor with the ICRP-60 definition is about 2.44. Using the measured quality factor, absorbed crew doses, and estimates of neutron dose equivalent, leads to crew stay times as short as 9 months during a deep solar minimum. The data are compared with in vivo dose estimates using chromosome aberrations (simple translocations and total exchange) on same astronauts.

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

    SciTech Connect

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

    1992-04-01

    The authors have used observations from both the Bennett ion mass spectrometer and the retarding potential analyzer on board the Atmosphere Explorer E satellite to study the longitudinally averaged O{sup +}, H{sup +}, and He{sup +} concentrations from 150 to 1,100 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{sup +} concentrations are about 2.5 {times} 10{sup 4} cm{sup {minus}3} during the day and 10{sup 4} cm{sup {minus}3} at night and vary little with season. The O{sup +}/H{sup +} transition altitude lies between 750 and 825 km during the day and between 550 and 600 km at night. He{sup +} is a minor species at all altitudes; its concentration is highly variable with a maximum value of about 10{sup 3} cm{sup {minus}3} during equinox daytime.

  9. 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.

  10. The solar L alpha flux near solar minimum

    NASA Astrophysics Data System (ADS)

    Vidal-Madjar, A.; Phissamay, B.

    1980-06-01

    Observations of the solar Lyman alpha flux obtained by the University of Paris experiment on board the reactivated OSO-5 spacecraft during solar minimum are presented. Measurements of total Lyman alpha flux and the flux at line center were obtained from August 1974 to August 1975, and were calibrated assuming instrument aging was due to solar illumination. In contrast to the relation observed earlier for periods of high solar activity, under low solar activity conditions the central Lyman alpha flux varies independently of the total flux. Empirical relations are derived for the variations of total Lyman alpha flux and central Lyman alpha flux with solar activity as measured by the 10.7 cm solar flux which are also found to differ from those obtained for periods of high solar activity. The observations confirm the factor of two variability of Lyman alpha emission between solar maximum and minimum and the existence of an early minimum in EUV lines, and reveal strong perturbations of the lower boundary of the transition region, possibly related to the large-scale evolution of coronal holes.

  11. 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.

  12. Coronal Rotation at Solar Minimum from UV Observations

    NASA Technical Reports Server (NTRS)

    Mancuso, S.

    2008-01-01

    UVCS/SOHO observations have been analyzed to reconstruct intensity time series of the O VI 1032 A and H 11216 A spectral lines at different coronal heliolatitudes from 1.5 to 3.0 solar radii from Sun center. Evidence was found for coronal differential rotation that differs significantly from that of the photospheric plasma. The study of the latitudinal variation shows that the UV corona decelerates toward the photospheric rates from the equator up to the poleward boundary 2 of the midlatitude streamers, reaching a peak of 28.16+/-0.20 days around +30 from the equator at 1.5 solar radii, 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.

  13. Lunar semidiurnal tide in the thermosphere under solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Forbes, Jeffrey M.; Zhang, Xiaoli; Bruinsma, Sean; Oberheide, Jens

    2013-04-01

    Renewed interest in lunar tidal influences on the ionosphere-thermosphere (IT) system has emerged in connection with recent studies of possible connections between stratospheric warmings and enhanced lunar tidal perturbations of the equatorial ionosphere. By virtue of its gravitational force, the Moon produces perturbations in the temperature, density, pressure, and winds throughout Earth's atmosphere. Lunar tidal winds in the dynamo region (~100-150 km) can furthermore generate electric fields that map into the F-region and redistribute ionospheric plasma. Direct penetration (propagation) of lunar tides to F-region heights can also transport ionospheric plasma. Decades-long satellite data sets now exist that can provide a global perspective on lunar tidal oscillations, but this resource has not yet been exploited for this purpose. In this paper, we examine the global structure of the main M2 (period = 12.42 h) lunar tide through examination of temperatures measured by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics SABER instrument at 110 km and densities at 360 and 480 km inferred from accelerometers on the CHAMP and Gravity Recovery and Climate Experiment satellites, respectively. Ten year mean SABER M2 temperature amplitudes are of order 5-10 K while the corresponding density perturbations during the 2007-2010 solar minimum period approach amplitudes of order 5% at 360 km and 10% at 480 km. The observed amplitudes are large enough to impose non-negligible day-to-day variability on the IT system. Global-Scale Wave Model simulations provide a theoretical and modeling context for interpreting these data, and moreover enable estimates of E- and F-region winds.

  14. STEREO ICMEs and their Solar Source Regions Near Solar Minimum

    NASA Astrophysics Data System (ADS)

    Toy, V.; Li, Y.; Luhmann, J. G.; Schroeder, P.; Vourlidas, A.; Jian, L. K.; Russell, C. T.; Galvin, A. B.; Simunac, K.; Acuna, M.; Sauvaud, J. A.; Skoug, R.; Petrie, G.

    2008-12-01

    Although the quiet activity period surrounding the current solar minimum has prevailed since the launch of STEREO in October 2006, there have been at least 9 clear in-situ detections of ICMEs (Interplanetary Coronal Mass Ejections) by one or more spacecraft during the time the imagers were also operating. These observations provide unusually complete data sets for evaluating helio-longitude extent of the ICMEs and for identifying the probable solar cause(s) of the events. In this poster we present information on these ICMEs from the IMPACT and PLASTIC and ACE in-situ investigations, together with solar images from STEREO and SOHO that seem to capture the causative activity at the Sun. We find that even though the Sun was very quiet in '07-'08, with few active regions visible in GONG and SOHO magnetograms, there were numerous CME candidates that erupted through the near-equatorial helmet streamers. Most events could be identified with EUV disk activity as well as a coronagraph CME, even if the associated active region was very small or weak. Old cycle active regions, new and decayed, continued to maintain a warp in the large-scale helmet streamer belt that was a frequent site of the eruptions. However, the warp in the streamer belt may simply indicate that the active region(s) present is(are) sufficiently strong to affect the large scale quiet coronal field structure. Overall we see no gross differences between the solar activity and ICME causes during this and the previous solar activity minimum, when the Streamer belt was less warped due to the existence of stronger solar polar fields.

  15. Meridional Surface Flows and the Recent Extended Solar Minimum

    NASA Astrophysics Data System (ADS)

    Martens, Petrus C.; Nandy, D.; Munoz-Jaramillo, A.

    2011-05-01

    Nandy, Munoz, & Martens, have published a kinematic dynamo model that successfully reproduces the main characteristics of the recent extended solar minimum (Nature 2011, 471, 80). The model depends on the solar meridional flow and its return flow along the tachocline determining the period and character of the cycle. In particular Nandy et al. found that a meridional flow that is fast in the first half of the cycle and then slows down around solar maximum, can lead to an extended minimum with the characteristics of the recent minimum: an extended period without sunspots and weak polar fields. It has been pointed out that the observed surface meridional flows over the last cycle do not fit the pattern assumed by Nandy et al. Hathaway & Rightmire (Science 2010, 327-1350) find that the meridional speed of small magnetic surface elements observed by SoHO/MDI decreased around solar maximum and has not yet recovered. Basu & Antia (ApJ 2010, 717, 488) find surface plasma meridional flow speeds that are lower at solar maximum 23 than at the surrounding minima, which is different from both Hathaway and Nandy. While there is no physical reason that solar surface flows -- both differential rotation and meridional flow -- would vary in lockstep with flows at greater depth, as the large radial gradients near the surface clearly indicate, and while Nandy et al. have demonstrated that the deeper flows dominate the net meridional mass flow, we find that there is in effect a very satisfying agreement between the observational results of Hathaway & Rightmire, Basu & Antia, and the model assumptions of Nandy, Munoz, & Martens. We present an analytical model that reconciles the first two, followed by a hydrodynamical model that demonstrates the consistency of these observational results with the model assumptions of Nandy et al.

  16. TEC fluctuations during recent Solar Minimum: technique and analysis.

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Krankowski, Andrzej; Zakharenkova, Irina; Shagimuratov, Irk; Sieradzki, Rafal

    2012-07-01

    The increasing number of permanent GNSS stations including regions near the North Geomagnetic Pole allows us to use the GPS-derived total electron content (TEC) observations to detect the ionospheric disturbances with high spatial and temporal resolution. The most intensive phase fluctuations are observed at the high latitude, equatorial and strong disturbed mid-latitude ionosphere. In the space weather service developed at GRL/UWM, the data from the Arctic stations belonging to IGS/EPN/POLENET networks were used in order to study TEC fluctuations and scintillations. The present research study is based on 30sec precise phase GPS measurements provided by permanent IGS network for period 2008-2011. Effects of the ionosphere irregularities were evaluated via rate of TEC variations. [1]. By use of these data the 2-hour maps of the TEC variability and daily map of the ionospheric fluctuations as a function of geomagnetic local time are created. Based on numerous TEC measurements (more than 200 permanent GNSS stations) it was obtained the statistical data about occurrence of TEC fluctuations at high and midlatitudes during the extended solar minimum period. The diurnal, seasonal, and storm-time variations of TEC fluctuation activity were estimated. The most intensive TEC fluctuations at considered period were observed during several weak and moderate geomagnetic disturbances at November 2008, July 2009 and May 2010. It was revealed that TEC fluctuations can be observed on quiet days at midlatitudes and midlatitudinal TEC fluctuations are regular phenomena which demonstrate day-to-day variability. The low frequency fluctuations can be caused directly due to electron density changes along transionospheric radio ray path or the TEC temporal changes. This type of TEC fluctuations was associated with wave-like processes in the ionosphere. It was carried out the statistical analysis of fluctuation intensity and TEC fluctuations maps. We propose that GNSS-derived monthly TEC medians and rate of TEC maps can be useful for IRI community in order to update the IRI model, in particular at high latitudes. Since the beginning of 2011, a near real-time service presenting the conditions in the ionosphere has being operational at GRL/UWM www site. This report presents the architecture, algorithms, performance and future developments of the space weather services at GRL/UWM. 1. Shagimuratov I.I., Krankowski A., Ephishov I., Zakharenkova I., Tepenitsyna N., 2009, Occurrence of GPS Phase Fluctuations in Northen and Southern Hemisphere, Proceedings of 20th International Symposium on Electromagnetic Compatibility. Zurich, Switzerland, 12-16 January 2009, pp. 305-308.

  17. 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

  18. Elemental GCR Observations during the 2009-2010 Solar Minimum Period

    NASA Technical Reports Server (NTRS)

    Lave, K. A.; Israel, M. H.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2013-01-01

    Using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer (ACE), we present new measurements of the galactic cosmic ray (GCR) elemental composition and energy spectra for the species B through Ni in the energy range approx. 50-550 MeV/nucleon during the record setting 2009-2010 solar minimum period. These data are compared with our observations from the 1997-1998 solar minimum period, when solar modulation in the heliosphere was somewhat higher. For these species, we find that the intensities during the 2009-2010 solar minimum were approx. 20% higher than those in the previous solar minimum, and in fact were the highest GCR intensities recorded during the space age. Relative abundances for these species during the two solar minimum periods differed by small but statistically significant amounts, which are attributed to the combination of spectral shape differences between primary and secondary GCRs in the interstellar medium and differences between the levels of solar modulation in the two solar minima. We also present the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe for both solar minimum periods, and demonstrate that these ratios are reasonably well fit by a simple "leaky-box" galactic transport model that is combined with a spherically symmetric solar modulation model.

  19. Characteristics of the Global Ionosphere During the Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Jee, G.; Lee, H.; Solomon, S. C.

    2013-12-01

    The last solar minimum period was anomalously low and lasted long compared with previous solar minima. The resulting solar irradiance received in the Earth's upper atmosphere was extremely low and therefore it can readily be expected that the upper atmosphere should be greatly affected by this low solar activity. It has been well reported that the thermospheric temperature was cooler and the density was lower during the last solar minimum than the previous solar minimum periods. The low solar irradiance should also affect the ionosphere, not only via the lower ion-electron production but also through the interactions with the thermosphere that was greatly influenced by the low solar irradiance. In this study, we utilized the measurements of total electron content (TEC) from the TOPEX and JASON-1 satellites for the precious solar minimum and the last solar minimum, respectively, in order to investigate the differences between the ionospheric TECs during the two minimum periods. For this investigation, we first made a comparison between TOPEX and JASON TECs to confirm that they produced identical TECs during the overlap period of the two satellite missions and can be considered as a single TEC observation. Next, the global ionospheric TEC maps are produced during the last two solar minimums for different seasons and the results of the comparison will be discussed, in particular, in relation to the thermospheric changes during the same periods.

  20. Could a future "Grand Solar Minimum" like the Maunder Minimum stop global warming?

    NASA Astrophysics Data System (ADS)

    Meehl, Gerald A.; Arblaster, Julie M.; Marsh, Daniel R.

    2013-05-01

    A future Maunder Minimum type grand solar minimum, with total solar irradiance reduced by 0.25% over a 50 year period from 2020 to 2070, is imposed in a future climate change scenario experiment (RCP4.5) using, for the first time, a global coupled climate model that includes ozone chemistry and resolved stratospheric dynamics (Whole Atmosphere Community Climate Model). This model has been shown to simulate two amplifying mechanisms that produce regional signals of decadal climate variability comparable to observations, and thus is considered a credible tool to simulate the Sun's effects on Earth's climate. After the initial decrease of solar radiation in 2020, globally averaged surface air temperature cools relative to the reference simulation by up to several tenths of a degree Centigrade. By the end of the grand solar minimum in 2070, the warming nearly catches up to the reference simulation. Thus, a future grand solar minimum could slow down but not stop global warming.

  1. Interplanetary shocks and sudden impulses in solar maximum (2000) and solar minimum (1995-1996)

    NASA Astrophysics Data System (ADS)

    Echer, E.; Gonzalez, W.; dal Lago, A.; Vieira, L.; Guarnieri, F.; Prestes, A.; Gonzalez, A.; Schuch, N.

    In this work a study is presented on the correlation between fast forward interplanetary shock parameters and sudden impulse (SI) amplitude in the H-component of the geomagnetic field, for periods of maximum (2000) and minimum (1995-1996) solar activity. Solar wind temperature, density and speed, and total magnetic field, as well static (thermal and magnetic) and dynamic pressures, were calculated in the upstream and downstream sides of the shock. The variation of the solar wind parameters and pressures was then correlated with SI amplitude. For the solar wind pressures, the difference between upstream and downstream square root values was taken, because in the balance pressure expression, the solar wind pressures are equal to the geomagnetic magnetic field pressure, that is proportional to the square magnetic field (and squared SI amplitude). The solar wind speed have showed good correlations with sudden impulse, with correlation coefficients higher than 0.70 both in solar maximum and solar minimum, whereas the solar wind density presented a poor correlation. The better correlated parameter with SI was the square root dynamic pressure variation, showing a higher correlation in solar maximum ( r = 0.82) than in solar minimum (r = 0.77). The correlations of SI with square root thermal and magnetic pressure was lower than with the dynamic pressure, but they also present a good correlation, with r > 0.70 both in solar maximum and minimum. Multiple correlation anaylsis of SI in terms of the three pressure terms resulted in that 78% and 85% of the variance in SI at solar maximum and minimum, respectively, are explained by the three pressure variations. Average sudden impulse amplitude was 25 nT in solar maximum and 20.9 nT in solar minimum, while square root dynamic pressure variation is 1.2 nPa1/2 at solar maximum and 0.9 nPa1/2 at solar minimum. Thus on average, fast forward interplanetary shocks are 33% stronger (in therms of squared root dynamic pressure variation) in solar maximum than in solar minimum, and the magnetospheric SI response had an amplitude 20% higher in solar maximum than in solar minimum.

  2. Solar Minimum

    NASA Astrophysics Data System (ADS)

    Lopresto, James C.; Mathews, John; Manross, Kevin

    1995-12-01

    Calcium K plage, H alpha plage and sunspot area have been monitored daily on the INTERNET since November of 1992. The plage and sunspot area have been measured by image processing. The purpose of the project is to investigate the degree of correlation between plage area and solar irradiance. The plage variation shows the expected variation produced by solar rotation and the longer secular changes produced by the solar cycle. The H alpha and sunspot plage area reached a minimum in about late 1994 or early 1995. This is in agreement with the K2 spectral index obtained daily from Sacramento Peak Observatory. The Calcium K plage area minimum seems delayed with respect to the others mentioned above. The minimum of the K line plage area is projected to come within the last few months of 1995.

  3. 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

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

    SciTech Connect

    Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J.; Stawarz, Joshua E.; Forman, Miriam A. E-mail: Charles.Smith@unh.edu E-mail: Joshua.Stawarz@Colorado.edu

    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.

  5. Ionospheric Response to Geomagnetic Activity during 2007-2009 Solar Minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Huijun Le, lake709.; Wan, Weixing

    The significant effect of weaker geomagnetic activity on ionospheric day-to-day variability during 2007-2009 solar minimum was highlighted by investigating the response of global electron content (GEC) to geomagnetic activity index Ap. A case distinctly manifests the modulation of recurrent weaker geomagnetic disturbance on GEC during the solar minimum. Statistical analyses indicate that the effect of weaker geomagnetic activity on GEC day-to-day variability is significant during 2007-2009, even under relatively quiet geomagnetic activity condition, while geomagnetic activity effect on GEC is not prominent during 2003-2005 solar cycle descending phase except under strong geomagnetic disturbance condition. Nevertheless, statistically the most important effect on GEC day-to-day variability during 2007-2009 comes from the factors other than geomagnetic activity and solar EUV irradiance.

  6. Ionospheric Response to Geomagnetic Activity during 2007-2009 Solar Minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing

    2014-05-01

    The significant effect of weaker geomagnetic activity on ionospheric day-to-day variability during 2007-2009 solar minimum was highlighted by investigating the response of global electron content (GEC) to geomagnetic activity index Ap. A case distinctly manifests the modulation of recurrent weaker geomagnetic disturbance on GEC during the solar minimum. Statistical analyses indicate that the effect of weaker geomagnetic activity on GEC day-to-day variability is significant during 2007-2009, even under relatively quiet geomagnetic activity condition, while geomagnetic activity effect on GEC is not prominent during 2003-2005 solar cycle descending phase except under strong geomagnetic disturbance condition. Nevertheless, statistically the most important effect on GEC day-to-day variability during 2007-2009 comes from the factors other than geomagnetic activity and solar EUV irradiance.

  7. 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.

  8. Galactic Cosmic-Ray Energy Spectra and Composition during the 2009-2010 Solar Minimum Period

    NASA Technical Reports Server (NTRS)

    Lave, K. A.; Wiedenbeck, Mark E.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Israel, M. H..; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; VonRosenvinge, T. T.

    2013-01-01

    We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 <= Z <= 28 in the energy range approx. 50-550 MeV / nucleon. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than approx. 7%, and the relative abundances changed by less than approx. 4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2sigma, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple "leaky-box" galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

  9. 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.

  10. Analysis of daytime ionospheric equatorial vertical drifts during the extreme solar minimum of 2008/2009

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The unique solar minimum period of 2008/2009 has led to interesting observations of the equatorial ionosphere and low-latitude ionosphere made by the C/NOFS satellite. It has been found, for instance, downward equatorial vertical drifts during afternoon hours and upward drifts around local midnight, which were associated with enhanced semi-diurnal tides (Stoneback et al., 2011). To better understand the behavior of equatorial drifts, we used ground-based measurements of daytime 150-km echo drifts made by the Jicamarca Unattended Long-term studies of the Ionosphere and Atmosphere (JULIA) radar. Our analysis did not show signatures of the enhanced semi-diurnal pattern in the 150-km drifts, as seen by C/NOFS during the 2008/2009 solar minimum. We attribute the differences in the C/NOFS drifts and 150-km echo drifts to the height variability of the drifts, the abnormal F-region contraction due to the extreme solar minimum conditions, and the coupling with low-latitude semi-diurnal tides. We investigated further the height variation of the vertical drifts by comparing the Scherliess and Fejer [1999] F-region drift model with the 150-km echo drifts. We found that the model overestimates the 150-km vertical drifts in the morning, and underestimates the 150-km drifts in the afternoon. The same height variation is observed in all seasons and solar flux conditions (2001 through 2011).

  11. Geomagnetic activity effect on the global ionosphere during the 2007-2009 deep solar minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing

    2014-05-01

    In this paper the significant effect of weaker geomagnetic activity during the 2007-2009 deep solar minimum on ionospheric variability on the shorter-term time scales of several days was highlighted via investigating the response of daily mean global electron content (GEC, the global area integral of total electron content derived from ground-based GPS measurements) to geomagnetic activity index Ap. Based on a case during the deep solar minimum, the effect of the recurrent weaker geomagnetic disturbances on the ionosphere was evident. Statistical analyses indicate that the effect of weaker geomagnetic activity on GEC variations on shorter-term time scales was significant during 2007-2009 even under relatively quiet geomagnetic activity condition; daily mean GEC was positively correlated with geomagnetic activity. However, GEC variations on shorter-term time scales were poorly correlated with geomagnetic activity during the solar cycle descending phase of 2003-2005 except under strong geomagnetic disturbance condition. Statistically, the effects of solar EUV irradiance, geomagnetic activity, and other factors (e.g., meteorological sources) on GEC variations on shorter-term time scales were basically equivalent during the 2007-2009 solar minimum.

  12. Unravelling Starlight

    NASA Astrophysics Data System (ADS)

    Becker, Barbara J.

    2011-02-01

    1. Introduction; 2. ' the astronomer must come to the chemist'; 3. The young observer; 4. 'A sudden impulse '; 5. The riddle of the nebulae; 6. Moving in the inner circle; 7. Stellar motion along the line of sight; 8. A new telescope; 9. Solar observatories; 10. An able assistant; 11. Photographing the solar corona; 12. A scientific lady; 13. Foes and allies; 14. The new astronomy; 15. 'One true mistress'; 16. Conclusion; Appendix; Index.

  13. 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....

  14. Statistical Analysis of Solar Wind Turbulence at Solar Maximum and Solar Minimum

    NASA Astrophysics Data System (ADS)

    Olson, D. K.; Coplan, M.; Ogilvie, K.; Holland, M.; Kulkarni, V.; Banerjee, A.

    2008-12-01

    We have applied statistical methods to a study of turbulence in the solar wind using data from the SWE experiment on NASA's WIND mission during solar minimum (1996 and 2006) and solar maximum (2001). We examined the probability distribution functions (PDFs) for solar wind velocity differences at lag times from 1 to 105 minutes. The statistical features of these PDFs reveal information regarding the cascade of momentum from large to small scale structures as well as intermittency within the solar wind. We have analyzed the velocity differences using three component velocity data, allowing us to determine turbulent anisotropies and examine the PDFs for velocity differences parallel and perpendicular to the local magnetic field. At small time differences, the PDFs of bulk velocity differences have the form of a double exponential function. For increasing time differences, there is a shift in the mean of the PDF to negative velocity difference with a noticeable asymmetry as seen previously by Burlaga et al. (J. Geophys. Res., 107, 1403, 2002). However, the shift and asymmetry are absent when examining velocities parallel to the magnetic field suggesting anisotropy in the turbulence is found in the component perpendicular to the magnetic field. The second statistical moment (variance) of the PDFs are found to have different behavior in time scales less and greater than about 103 minutes. These two regimes each follow a separate power law scaling with the time difference. The regimes appear to be related to the Kolmogorov 2/3 and 4/5 laws that define the power law scaling for inertial and Gaussian regimes. The third and fourth statistical moments (skew and kurtosis) also follow power laws. Comparison between solar minimum and solar maximum shows general similarity in the results. However, at solar maximum only a single regime exists for the kurtosis, while at solar minimum two regimes are present, similar to the regimes found for the variance.

  15. Observations of Lower Thermospheric Nitric Oxide During the Current Solar Minimum

    NASA Astrophysics Data System (ADS)

    Thirukoveluri, P. L.; Bailey, S. M.; Gordley, L. L.; Hervig, M. E.; Russell, J. M.; Randall, C. E.; Siskind, D. E.; Marshall, B. T.; Burton, J. C.; Deaver, L. E.; McHugh, M. J.; Paxton, G.; Thompson, R. E.

    2009-12-01

    Nitric oxide (NO) is a key minor constituent in the lower thermosphere. Of particular importance is its role in the energy balance in that altitude region. NO is produced through the reaction of excited atomic nitrogen with molecular oxygen. Thus its production is very sensitive to those energy sources able to break the strong molecular nitrogen bond. These include solar soft X-rays and precipitating energetic particles. Nitric oxide emits efficiently in the infrared and is an important cooling mechanism in the lower thermosphere. The abundance of NO is thus both a direct response to recent energy deposition as well as a key mechanism by which the upper atmosphere releases that energy. The current extended solar minimum is an interesting case study for NO and its role in the upper atmosphere. Reduction in energy deposition to the thermosphere leads to cooler temperatures. But the production of NO is also reduced and thus the cooling efficiency of the atmosphere is reduced as well. Thus NO may in some way control the minimum temperatures reached. For this reason, understanding the response of NO to this unique extended solar minimum is of significant importance. The Solar Occultation for Ice Experiment (SOFIE) instrument was launched on-board the Aeronomy of Ice in the Mesosphere (AIM) satellite on April 25, 2007. It is currently in its third year of operation. SOFIE is a 16 channel differential absorption radiometer using the solar occultation technique to measure ice and environmental properties at a range of altitudes, and in particular the mesopause region. One of the constituents measured by SOFIE is NO in the mesosphere and lower thermosphere to about 130 km. The AIM orbit and the solar occultation technique confine observations to latitudes of 65 to 85 degrees in each hemisphere and varying with season. In this talk we overview the SOFIE observations of NO in the southern hemisphere lower thermosphere and provide a preliminary description of its behavior during this curious extended solar minimum.

  16. GALACTIC COSMIC-RAY ENERGY SPECTRA AND COMPOSITION DURING THE 2009-2010 SOLAR MINIMUM PERIOD

    SciTech Connect

    Lave, K. A.; Binns, W. R.; Israel, M. H.; Wiedenbeck, M. E.; Christian, E. R.; De Nolfo, G. A.; Von Rosenvinge, T. T.; Cummings, A. C.; Davis, A. J.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.

    2013-06-20

    We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 {<=} Z {<=} 28 in the energy range {approx}50-550 MeV nucleon{sup -1}. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than {approx}7%, and the relative abundances changed by less than {approx}4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2{sigma}, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple ''leaky-box'' galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

  17. Comparison between IRI-2007 model predictions and ionospheric observations at European region during extended solar minimum

    NASA Astrophysics Data System (ADS)

    Zakharenkova, Irina; Krankowski, Andrzej; Bilitza, Dieter; Cherniak, Iurii; Shagimuratov, Irk; Krypiak-Gregorczyk, Anna

    The solar minimum began around March 2006 and many predictions of the start and size of Solar Cycle 24 were given since then. In 2007 the Solar Cycle 24 Prediction Panel anticipates the solar minimum marking the onset of Cycle 24 will occur in March 2008 (6 months). Then this date was shifted to the August 2008, after that -to the December 2008. At least solar minimum is extended to the end of 2009. This unusually deep and extended solar minimum makes corrections to the predicted values of solar cycle progression. With every update the predicted values of sunspot number is decreased. It leads to the significant discrepancies in IRI model results in depend on the predicted indices. To calculate the ionospheric parameters the IRI model uses indices file with ionospheric index IG12 and solar sunspot number (12-months running median) Rz12. This IRI file is regularly updated with the newest available indices and predictions. It was considered the IRI model results obtained with use of different predicted and observed IG and Rz indices during 2007-2009 years. For the given study it was done the comparison of the IRI-2007 predicted values of F2 layer critical frequency (foF2) with those observed at several mid-latitude ionospheric stations in European region. Values of foF2 have been scaled manually from ionograms to avoid the evident risks related with using of the autoscaled data that have ionosonde-related errors and uncertainties. It was the ionograms and foF2 values provided by European Digital Upper Atmosphere Server (DIAS). The DIAS bases on real-time and historical data provided by most operating ionospheric stations in Europe. This server collects information from stations located in Rome, Pruhonice, Juliusruh, Athens, Chilton, Ebre and El Arenosillo. For each station it was calculated monthly median of foF2 variation on the base of full month data analysis. We have considered observations taken in the months of January, April, July and October for 2007-2009 years. We present results of the analysis of diurnal variations for the different seasons of the observed and IRI-2007 predicted (using different IG and Rz indices) foF2 values. We acknowledge the IRI Working group for providing and evaluating of the IRI model FORTRAN code. We are grateful to European Digital Upper Atmosphere Server (DIAS) for providing the ionosondes' products.

  18. A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

    NASA Technical Reports Server (NTRS)

    Thompson, Barbara J.; Gibson, Sarah E.; Schroeder, Peter C.; Webb, David F.; Arge, Charles N.; Bisi, Mario M.; de Toma, Giuliana; Emery, Barbara A.; Galvin, Antoinette B.; Haber, Deborah A.; Jackson, Bernard V.; Jensen, Elizabeth A.; Leamon, Robert J.; Lei, Jiuhou; Manoharan, Periasamy K.; Mays, M. Leila; McIntosh, Patrick S.; Petrie, Gordon J.D.; Plunkett, Simon P.; Qian, Liying

    2011-01-01

    We present an overview of the data and models collected for the Whole Heliosphere Interval, an international campaign to study the three-dimensional solar heliospheric planetary connected system near solar minimum. The data and models correspond to solar Carrington Rotation 2068 (20 March 16 April 2008) extending from below the solar photosphere, through interplanetary space, and down to Earth's mesosphere. Nearly 200 people participated in aspects of WHI studies, analyzing and interpreting data from nearly 100 instruments and models in order to elucidate the physics of fundamental heliophysical processes. The solar and inner heliospheric data showed structure consistent with the declining phase of the solar cycle. A closely spaced cluster of low-latitude active regions was responsible for an increased level of magnetic activity, while a highly warped current sheet dominated heliospheric structure. The geospace data revealed an unusually high level of activity, driven primarily by the periodic impingement of high-speed streams. The WHI studies traced the solar activity and structure into the heliosphere and geospace, and provided new insight into the nature of the interconnected heliophysical system near solar minimum.

  19. Measurement of cosmic-ray proton and helium spectra during the 1987 solar minimum

    NASA Technical Reports Server (NTRS)

    Seo, E. S.; Ormes, J. F.; Streitmatter, R. E.; Stochaj, S. J.; Jones, W. V.; Stephens, S. A.; Bowen, T.

    1991-01-01

    The differential cosmic-ray proton and helium spectra have been measured during the 1987 solar minimum using a balloon-borne superconducting magnetic spectrometer launched from Prince Albert, Canada. The changing geomagnetic cutoff along the balloon trajectory was observed in the low-energy proton data to be about 25 percent below the nominal calculated values. The absolute particle fluxes were approximately equal to the highest fluxes observed at the previous solar minimum in 1977. Above 10 GV the observed spectra are represented by a power law in rigidity with spectral indices of 2.74 + or - 0.02 for protons and 2.68 + or - 0.03 for helium. The measurements above 200 MeV per nucleon are consistent with rigidity power-law interstellar spectra modulated with the solar modulation parameter phi = 500 MV. The energy dependence of the proton-to-helium ratio is consistent with rigidity power-law injection spectra and rigidity-dependent propagation without reacceleration.

  20. A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

    NASA Astrophysics Data System (ADS)

    Thompson, Barbara J.; Gibson, Sarah E.; Schroeder, Peter C.; Webb, David F.; Arge, Charles N.; Bisi, Mario M.; de Toma, Giuliana; Emery, Barbara A.; Galvin, Antoinette B.; Haber, Deborah A.; Jackson, Bernard V.; Jensen, Elizabeth A.; Leamon, Robert J.; Lei, Jiuhou; Manoharan, Periasamy K.; Mays, M. Leila; McIntosh, Patrick S.; Petrie, Gordon J. D.; Plunkett, Simon P.; Qian, Liying; Riley, Peter; Suess, Steven T.; Tokumaru, Munetoshi; Welsch, Brian T.; Woods, Thomas N.

    2011-12-01

    We present an overview of the data and models collected for the Whole Heliosphere Interval, an international campaign to study the three-dimensional solar-heliospheric-planetary connected system near solar minimum. The data and models correspond to solar Carrington Rotation 2068 (20 March - 16 April 2008) extending from below the solar photosphere, through interplanetary space, and down to Earth’s mesosphere. Nearly 200 people participated in aspects of WHI studies, analyzing and interpreting data from nearly 100 instruments and models in order to elucidate the physics of fundamental heliophysical processes. The solar and inner heliospheric data showed structure consistent with the declining phase of the solar cycle. A closely spaced cluster of low-latitude active regions was responsible for an increased level of magnetic activity, while a highly warped current sheet dominated heliospheric structure. The geospace data revealed an unusually high level of activity, driven primarily by the periodic impingement of high-speed streams. The WHI studies traced the solar activity and structure into the heliosphere and geospace, and provided new insight into the nature of the interconnected heliophysical system near solar minimum.

  1. A Topside Equatorial Ionospheric Density and Composition Climatology During and After Extreme Solar Minimum

    NASA Technical Reports Server (NTRS)

    Klenzing, J. H.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R. F.; Rowland, D. E.

    2011-01-01

    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 are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Climatological altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the C/NOFS satellite to characterize the shape of the top side ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. [2009], here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

  2. Topside Equatorial Ionospheric Density and Composition During and After Extreme Solar Minimum

    NASA Technical Reports Server (NTRS)

    Klenzing, J.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R.; Rowland, D.

    2011-01-01

    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-thermosphere system when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the Communication/Navigation Outage Forecast System (C/NOFS) satellite to characterize the shape of the topside ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. (2009), here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

  3. Measurements of the radiation quality factor Q at aviation altitudes during solar minimum (2006-2008)

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M.; Hubiak, Melina

    2010-05-01

    In radiation protection, the Q-factor has been defined to describe the biological effectiveness of the energy deposition or absorbed dose to humans in the mixed radiation fields at aviation altitudes. This particular radiation field is generated by the interactions of primary cosmic particles with the atoms of the constituents of the Earth’s atmosphere. Thus the intensity, characterized by the ambient dose equivalent rate H∗(10), depends on the flight altitude and the energy spectra of the particles, mainly protons and alpha particles, impinging on the atmosphere. These charged cosmic projectiles are deflected both by the interplanetary and the Earth’s magnetic field such that the corresponding energy spectra are modulated by these fields. The solar minimum is a time period of particular interest since the interplanetary magnetic field is weakest within the 11-year solar cycle and the dose rates at aviation altitudes reach their maximum due to the reduced shielding of galactic cosmic radiation. For this reason, the German Aerospace Center (DLR) performed repeated dosimetric on-board measurements in cooperation with several German airlines during the past solar minimum from March 2006 to August 2008. The Q-factors measured with a TEPC range from 1.98 at the equator to 2.60 in the polar region.

  4. Automated identification and tracking of polar-cap plasma patches at solar minimum

    NASA Astrophysics Data System (ADS)

    Burston, R.; Hodges, K.; Astin, I.; Jayachandran, P. T.

    2014-03-01

    A method of automatically identifying and tracking polar-cap plasma patches, utilising data inversion and feature-tracking methods, is presented. A well-established and widely used 4-D ionospheric imaging algorithm, the Multi-Instrument Data Assimilation System (MIDAS), inverts slant total electron content (TEC) data from ground-based Global Navigation Satellite System (GNSS) receivers to produce images of the free electron distribution in the polar-cap ionosphere. These are integrated to form vertical TEC maps. A flexible feature-tracking algorithm, TRACK, previously used extensively in meteorological storm-tracking studies is used to identify and track maxima in the resulting 2-D data fields. Various criteria are used to discriminate between genuine patches and "false-positive" maxima such as the continuously moving day-side maximum, which results from the Earth's rotation rather than plasma motion. Results for a 12-month period at solar minimum, when extensive validation data are available, are presented. The method identifies 71 separate structures consistent with patch motion during this time. The limitations of solar minimum and the consequent small number of patches make climatological inferences difficult, but the feasibility of the method for patches larger than approximately 500 km in scale is demonstrated and a larger study incorporating other parts of the solar cycle is warranted. Possible further optimisation of discrimination criteria, particularly regarding the definition of a patch in terms of its plasma concentration enhancement over the surrounding background, may improve results.

  5. 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.

  6. The distribution of solar wind speeds during solar minimum: Calibration for numerical solar wind modeling constraints on the source of the slow solar wind

    NASA Astrophysics Data System (ADS)

    McGregor, S. L.; Hughes, W. J.; Arge, C. N.; Owens, M. J.; Odstrcil, D.

    2011-03-01

    It took the solar polar passage of Ulysses in the early 1990s to establish the global structure of the solar wind speed during solar minimum. However, it remains unclear if the solar wind is composed of two distinct populations of solar wind from different sources (e.g., closed loops which open up to produce the slow solar wind) or if the fast and slow solar wind rely on the superradial expansion of the magnetic field to account for the observed solar wind speed variation. We investigate the solar wind in the inner corona using the Wang-Sheeley-Arge (WSA) coronal model incorporating a new empirical magnetic topology-velocity relationship calibrated for use at 0.1 AU. In this study the empirical solar wind speed relationship was determined by using Helios perihelion observations, along with results from Riley et al. (2003) and Schwadron et al. (2005) as constraints. The new relationship was tested by using it to drive the ENLIL 3-D MHD solar wind model and obtain solar wind parameters at Earth (1.0 AU) and Ulysses (1.4 AU). The improvements in speed, its variability, and the occurrence of high-speed enhancements provide confidence that the new velocity relationship better determines the solar wind speed in the outer corona (0.1 AU). An analysis of this improved velocity field within the WSA model suggests the existence of two distinct mechanisms of the solar wind generation, one for fast and one for slow solar wind, implying that a combination of present theories may be necessary to explain solar wind observations.

  7. Unraveling expressionism

    NASA Astrophysics Data System (ADS)

    Truscott, Tadd; Darbois-Texier, Baptiste; Lovett, Benjamin; Brandenbourger, Martin; Maquet, Laurent; Pan, Zhao; Gilet, Tristan; Strivay, David; Dorbolo, Stéphane

    2015-11-01

    From the large facades of our buildings to the refinement of art canvas, paintings literally surround us and make our lives colorful. Artists are continually looking for novel methods to complement their expression and ideas, while instinctively manipulating the underlying physics. We attempt to unravel a phenomenon common to many modern canvas artists. In some paintings small droplets (0.1 - 5 mm) appear as a single color, however, on closer inspection are actually composed of multicolored spiral patterns (e.g., non-newtonian acrylic paint). High-speed imaging reveals that these assemblies occur when a droplet impinges on the edge of a small pool of paint. Upon impact, the droplet creates a crown with the falling droplet color on the inside of the crown and the pool colors on the outside. Ripping occurs in thin film feeding a rapid roll-up in the thicker ridge-line regions. These twisted formations are projected outward and break into small droplets that form the paint spirals. These beautiful formations, appreciated in their static form on canvas in museums around the world, are formed by equally beautiful physical phenomena.

  8. Pamela Measurements of Galactic and Solar Cosmic Rays in the 23rd Solar Minimum (Invited)

    NASA Astrophysics Data System (ADS)

    Casolino, M.; PAMELA Collaboration

    2010-12-01

    We will discuss the measurements of protons and helium of galactic, solar and trapped origin taken with PAMELA detector in the period 2006-2010. PAMELA was launched in 2006 and is currently orbiting the Earth in a 350*600 km, 70 degree inclination polar orbit in a pressurized container located on one side of the Russian Resurs-DK1 satellite. Data were acquired at solar minimum, but show the effect of solar modulation on p and he low energy spectra (about 100 MeV/n - 1 GeV/n). Galactic protons and helium particles are measured up to 1 TV. Trapped and secondary proton component will be compared with existing models; the spectra of solar particle events of 13 and 14 December 2006 will also be discussed.

  9. Solar energetic proton events and coronal mass ejections near solar minimum

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Cliver, E. W.; Cane, H. V.; Mcguire, R. E.; Reames, D. V.; Sheeley, N. R., Jr.; Howard, R. A.

    1987-01-01

    We have examined the association of coronal mass ejections (CME's) with solar energetic (9-23 MeV) proton (SEP) events during the 1983-1985 approach to solar minimum. Twenty-two of 25 SEP events were associated with CME's, a result comparable to that previously found for the period 1979-1982 around solar maximum. Peak SEP fluxes were correlated with CME speeds but not with CME angular sizes. In addition, many associated CME's lay well out of the ecliptic plane. In a reverse study using all west hemisphere CME's of speeds exceeding 800 km/s and covering the period 1979-1985, we found that 29 of 31 events originating on the solar disk or limb were associated with observed SEP's. However, in contrast to the previous study, we found no cases of SEP events associated with magnetically well connected flares of short duration that lacked CME's.

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

    SciTech Connect

    Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J.; Stawarz, Joshua E.; Forman, Miriam A.

    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.

  11. Solar modulation of GCR electrons over the 23rd solar minimum with PAMELA

    NASA Astrophysics Data System (ADS)

    Munini, R.; Di Felice, V.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Merge, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Potgieter, M. S.; Vos, E. E.

    2015-08-01

    The satellite-borne PAMELA experiment has been continuously collecting data since 15th June 2006, when it was launched from the Baikonur cosmodrome to detect the charged component of cosmic rays over a wide energy range and with unprecedented statistics. The apparatus design is particularly suited for particle and antiparticle identification. The PAMELA experiment has measured the electron spectrum at Earth in great detail, extending up to about 100 GeV and down to about 200 MeV. The galactic cosmic ray electron spectra for 2007 and 2009, i.e. measured during the A<0 solar minimum of solar cycle 23, are presented. These fluxes provide important information for the study of charge dependent solar modulation effects.

  12. QUIET-TIME INTERPLANETARY {approx}2-20 keV SUPERHALO ELECTRONS AT SOLAR MINIMUM

    SciTech Connect

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

    2012-07-01

    We present a statistical survey of {approx}2-20 keV superhalo electrons in the solar wind measured by the SupraThermal Electron instrument on board the two STEREO spacecraft during quiet-time periods from 2007 March through 2009 March at solar minimum. The observed superhalo electrons have a nearly isotropic angular distribution and a power-law spectrum, f{proportional_to}v{sup -{gamma}}, with {gamma} 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 {approx}>0.1 AU and a temporal scale of {approx}>several days. The integrated density of quiet-time superhalo electrons at 2-20 keV ranges from {approx}10{sup -8} cm{sup -3} to 10{sup -6} cm{sup -3}, about 10{sup -9}-10{sup -6} of the solar wind density, and, as well as the power-law spectrum, shows no correlation with solar wind proton density, velocity, or temperature. The density of superhalo electrons appears to show a solar-cycle variation at solar minimum, while the power-law spectral index {gamma} 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 processes such as resonant wave-particle interactions in the interplanetary medium, or possibly by nonthermal processes related to the acceleration of the solar wind such as nanoflares, or by acceleration at the CIR forward shocks.

  13. Solar minimum Lyman. alpha. sky background observations from Pioneer Venus orbiter ultraviolet spectrometer: Solar wind latitude variation

    SciTech Connect

    Ajello, J.M. )

    1990-09-01

    Measurements of interplanetary H I Lyman {alpha} over a large portion of the celestial sphere were made at the recent solar minimum by the Pioneer Venus orbiter ultraviolet spectrometer. These measurements were performed during a series of spacecraft maneuvers conducted to observe Halley's comet in early 1986. Analysis of these data using a model of the passage of interstellar wind hydrogen through the solar wind system shows that the rate of charge exchange with solar wind protons is 30% less over the solar poles than in the ecliptic. This result is in agreement with a similar experiment performed with Mariner 10 at the previous solar minimum.

  14. 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.

  15. 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.

  16. Comparative Study of foF2 Measurements with IRI-2007 Model Predictions During Extended Solar Minimum

    NASA Technical Reports Server (NTRS)

    Zakharenkova, I. E.; Krankowski, A.; Bilitza, D.; Cherniak, Iu.V.; Shagimuratov, I.I.; Sieradzki, R.

    2013-01-01

    The unusually deep and extended solar minimum of cycle 2324 made it very difficult to predict the solar indices 1 or 2 years into the future. Most of the predictions were proven wrong by the actual observed indices. IRI gets its solar, magnetic, and ionospheric indices from an indices file that is updated twice a year. In recent years, due to the unusual solar minimum, predictions had to be corrected downward with every new indices update. In this paper we analyse how much the uncertainties in the predictability of solar activity indices affect the IRI outcome and how the IRI values calculated with predicted and observed indices compared to the actual measurements.Monthly median values of F2 layer critical frequency (foF2) derived from the ionosonde measurements at the mid-latitude ionospheric station Juliusruh were compared with the International Reference Ionosphere (IRI-2007) model predictions. The analysis found that IRIprovides reliable results that compare well with actual measurements, when the definite (observed and adjusted) indices of solar activityare used, while IRI values based on earlier predictions of these indices noticeably overestimated the measurements during the solar minimum.One of the principal objectives of this paper is to direct attention of IRI users to update their solar activity indices files regularly.Use of an older index file can lead to serious IRI overestimations of F-region electron density during the recent extended solar minimum.

  17. Estimation of the Ionosphere and Plasmasphere Contribution to the GPS TEC under Solar Minimum Conditions

    NASA Astrophysics Data System (ADS)

    Zakharenkova, Irina; Cherniak, Iurii; Krankowski, Andrzej; Shagimuratov, Irk; Sieradzki, Rafal

    2012-07-01

    The plasmaspheric electron content (PEC) was estimated by comparison GPS observations and FORMOSAT-3/COSMIC radio occultation (RO) measurements at the extended solar minimum of cycle 23/24. GPS observations provide information about values of vertical total electron content (TEC) up to the metricconverterProductID20,200 km20,200 km. FORMOSAT-3/COSMIC now provides unprecedented global coverage of GPS RO measurements. Depending on the state of the constellation, COSMIC has been producing 1,500 -- 2,500 good soundings of the ionosphere and atmosphere per day, uniformly distributed around the globe. This number of RO is much higher than even before. In this study, COSMIC RO data for different seasons corresponded to equinoxes and solstices of 2007-2009 (March, June, September and December) were analyzed. All selected COSMIC RO electron density profiles were integrated up to the height of metricconverterProductID700 km700 km (altitude of COSMIC satellites), in that way the estimates of ionospheric electron content (IEC) were retrieved on a global scale. The final IGS combined global ionospheric maps (GIMs) were used to calculate the global maps of monthly medians of TEC values. As a result there were analyzed global distributions of GPS TEC and IEC estimates corresponded to the monthly median values for different seasons of 2007-2009. We consider the quantitative differences PEC = TEC -- IEC as a measure of the contribution of the PEC to GPS TEC. In order to analyze seasonal behaviour of PEC contribution to GPS TEC at the different regions we selected several specific points with coordinates, corresponded to the approximate positions of different, mid-latitude and low-latitude, ionospheric sounding stations. Such points were selected at Northern America, European and Asian regions, Southern America, Southern Africa and country-regionplaceAustralia. For each specific points GPS TEC, COSMIC IEC and PEC estimates were analyzed. Results of our comparative study revealed that for mid-latitude stations PEC estimates varied weakly with the time of a day and reached the value of several TECU (3-5 TECU) for the condition of solar minimum. Percentage contribution of PEC to GPS TEC indicates the clear dependence from the time and varies from a minimum of about 25-30% during day-time to the value of more than 60% at night-time. The presented results are compared with TEC, PEC and IEC estimates retrieved by Standard Plasmasphere-Ionosphere Model (SPIM, http://ftp.izmiran.ru/pub/izmiran/SPIM/).

  18. Disturbance zonal and vertical plasma drifts in the Peruvian sector during solar minimum phases

    NASA Astrophysics Data System (ADS)

    Santos, A. M.; Abdu, M. A.; Souza, J. R.; Sobral, J. H. A.; Batista, I. S.

    2016-03-01

    In the present work, we investigate the behavior of the equatorial F region zonal plasma drifts over the Peruvian region under magnetically disturbed conditions during two solar minimum epochs, one of them being the recent prolonged solar activity minimum. The study utilizes the vertical and zonal components of the plasma drifts measured by the Jicamarca (11.95°S; 76.87°W) incoherent scatter radar during two events that occurred on 10 April 1997 and 24 June 2008 and model calculation of the zonal drift in a realistic ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE. Two main points are focused: (1) the connection between electric fields and plasma drifts under prompt penetration electric field during a disturbed periods and (2) anomalous behavior of daytime zonal drift in the absence of any magnetic storm. A perfect anticorrelation between vertical and zonal drifts was observed during the night and in the initial and growth phases of the magnetic storm. For the first time, based on a realistic low-latitude ionosphere, we will show, on a detailed quantitative basis, that this anticorrelation is driven mainly by a vertical Hall electric field induced by the primary zonal electric field in the presence of an enhanced nighttime E region ionization. It is shown that an increase in the field line-integrated Hall-to-Pedersen conductivity ratio (∑H/∑P), which can arise from precipitation of energetic particles in the region of the South American Magnetic Anomaly, is capable of explaining the observed anticorrelation between the vertical and zonal plasma drifts. Evidence for the particle ionization is provided from the occurrence of anomalous sporadic E layers over the low-latitude station, Cachoeira Paulista (22.67°S; 44.9°W)—Brazil. It will also be shown that the zonal plasma drift reversal to eastward in the afternoon two hours earlier than its reference quiet time pattern is possibly caused by weakening of the zonal wind system during the prolonged solar minimum period.

  19. 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.

  20. Comparison of Transport Codes, HZETRN, HETC and FLUKA, Using 1977 GCR Solar Minimum Spectra

    NASA Technical Reports Server (NTRS)

    Heinbockel, John H.; Slaba, Tony C.; Tripathi, Ram K.; Blattnig, Steve R.; Norbury, John W.; Badavi, Francis F.; Townsend, Lawrence W.; Handler, Thomas; Gabriel, Tony A.; Pinsky, Lawrence S.; Reddell, Brandon; Aumann, Aric R.

    2009-01-01

    The HZETRN deterministic radiation transport code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events (SPE) on mission planning, astronaut shielding and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC-HEDS and FLUKA, and the deterministic transport code, HZETRN. Each code is used to transport ions from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm2 Aluminum slab followed by a 30 g/cm2 water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton fluxes, and the forward, backward and total neutron fluxes at various depths in the water slab. Comparisons of the secondary light ion 2H, 3H, 3He and 4He fluxes are also examined.

  1. Impact of a potential 21st century "grand solar minimum" on surface temperatures and stratospheric ozone

    NASA Astrophysics Data System (ADS)

    Anet, J. G.; Rozanov, E. V.; Muthers, S.; Peter, T.; BröNnimann, S.; Arfeuille, F.; Beer, J.; Shapiro, A. I.; Raible, C. C.; Steinhilber, F.; Schmutz, W. K.

    2013-08-01

    We investigate the effects of a recently proposed 21st century Dalton minimum like decline of solar activity on the evolution of Earth's climate and ozone layer. Three sets of two member ensemble simulations, radiatively forced by a midlevel emission scenario (Intergovernmental Panel on Climate Change RCP4.5), are performed with the atmosphere-ocean chemistry-climate model AOCCM SOCOL3-MPIOM, one with constant solar activity, the other two with reduced solar activity and different strength of the solar irradiance forcing. A future grand solar minimum will reduce the global mean surface warming of 2 K between 1986-2005 and 2081-2100 by 0.2 to 0.3 K. Furthermore, the decrease in solar UV radiation leads to a significant delay of stratospheric ozone recovery by 10 years and longer. Therefore, the effects of a solar activity minimum, should it occur, may interfere with international efforts for the protection of global climate and the ozone layer.

  2. The impact of a future solar minimum on climate change projections in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Chiodo, G.; García-Herrera, R.; Calvo, N.; Vaquero, J. M.; Añel, J. A.; Barriopedro, D.; Matthes, K.

    2016-03-01

    Solar variability represents a source of uncertainty in the future forcings used in climate model simulations. Current knowledge indicates that a descent of solar activity into an extended minimum state is a possible scenario. With aid of experiments from a state-of-the-art Earth system model,we investigate the impact of a future solar minimum on Northern Hemisphere climate change projections. This scenario is constructed from recent 11 year solar-cycle minima of the solar spectral irradiance, and is therefore more conservative than the ‘grand’ minima employed in some previous modeling studies. Despite the small reduction in total solar irradiance (0.36 W m-2), relatively large responses emerge in the winter Northern Hemisphere, with a reduction in regional-scale projected warming by up to 40%. To identify the origin of the enhanced regional signals, we assess the role of the different mechanisms by performing additional experiments forced only by irradiance changes at different wavelengths of the solar spectrum. We find that a reduction in visible irradiance drives changes in the stationary wave pattern of the North Pacific and sea-ice cover. A decrease in UV irradiance leads to smaller surface signals, although its regional effects are not negligible. These results point to a distinct but additive role of UV and visible irradiance in the Earth’s climate, and stress the need to account for solar forcing as a source of uncertainty in regional scale projections.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    Loboda, I. P.; Bogachev, S. A.

    2015-07-01

    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 304Å line taken close to the solar minimum of 2008-2009 and mainly focus on quiescent and quiescent-eruptive prominences. We detect a total of 389 individual features ranging from 25×25 to 150×500 Mm2 in size and obtain distributions of many of 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 rarely exceed 3 km/s. In addition, we give rough estimates of mass and gravitational energy for every detected prominence and use these values to estimate the total mass and gravitational energy of all simultaneously existing prominences (1012 - 1014 kg and 1029 - 1031 erg). Finally, we investigate the form of the gravitational energy spectrum of prominences and derive it to be a power-law of index -1.1 ± 0.2.

  5. 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.

  6. Ultrasonic corona sensor study

    NASA Technical Reports Server (NTRS)

    Harrold, R. T.

    1976-01-01

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

  7. Exploring the Role of Ionospheric Drivers During the Extreme Solar Minimum of 2008

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    During the recent solar minimum, solar activity reached the lowest levels observed during the space age, resulting in a contracted atmosphere. This extremely low solar activity provides an unprecedented opportunity to understand the variability of the Earth's ambient ionosphere. The average E x B drifts measured by the Vector Electric Field Instrument (VEFI) on the Communications/Navigation Outage Forecasting System (C/NOFS) satellite during this period are found to have several differences from the expected climatology based on previous solar minima, including downward drifts in the early afternoon and a weak to nonexistent pre-reversal enhancement. Using SAMI2 (Sami2 is Another Model of the Ionosphere) as a computational engine, we investigate the effects of these electrodynamical changes as well as the contraction of the thermosphere and reduced EUV ionization on the ionosphere. The sensitivity of the simulations to wind models is also discussed. These modeled ionospheres are compared to the C/NOFS average topside ion density and composition and Formosa Satellite-3/Constellation Observing System for Meteorology, Ionosphere, and Climate average NmF2 and hmF2. In all cases, incorporating the VEFI drift data significantly improves the model results when compared to both the C/NOFS density data and the F3/C GOX data. Changing the MSIS and EUVAC models produced changes in magnitude, but not morphology with respect to local time. The choice of wind model modulates the resulting topside density and composition, but only the use of the VEFI E x B drifts produces the observed post-sunset drop in the F peak.

  8. Peculiar features of ionospheric F3 layer during prolonged solar minimum (2007-2009)

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We present the seasonal and local time occurrence of ionospheric F3 layer over Tirunelveli (geographic longitude 77.8°E, geographic latitude 8.7°N, dip 0.7°) during extremely low and prolonged solar activity period (2007-2009). Canadian Advanced Digital Ionosonde observations from this station are used in the present study. We find that the occurrence of F3 layer is nearly 3 times higher during 2009 (˜ 48%) as compared to that during 2007 (˜16%). The increase of this order just within the 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). The other important feature is the presence of postnoon F3 layers which are observed dominantly during summer solstice of 2009. Such occurrence of postnoon F3 layers was nearly absent during summer solstice of the previous solar minimum (1996) over nearby dip equatorial station Trivandrum. We take equatorial electrojet (EEJ) as a proxy for eastward electric field. It is noticed that the EEJ strength and the maximum rate of change of EEJ are higher for F3 days as compared to those on non-F3 days. We find that the peak occurrence of prenoon F3 layer closely coincides with the time of maximum rate of change of EEJ. It is in general accordance with the theory proposed by Balan et al. (1998) that suggests the formation of F3 through vertically upward E × B drift in presence of equatorward neutral wind. 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.

  9. Possible impacts of a future grand solar minimum on climate: Stratospheric and global circulation changes

    NASA Astrophysics Data System (ADS)

    Maycock, A. C.; Ineson, S.; Gray, L. J.; Scaife, A. A.; Anstey, J. A.; Lockwood, M.; Butchart, N.; Hardiman, S. C.; Mitchell, D. M.; Osprey, S. M.

    2015-09-01

    It has been suggested that the Sun may evolve into a period of lower activity over the 21st century. This study examines the potential climate impacts of the onset of an extreme "Maunder Minimum-like" grand solar minimum using a comprehensive global climate model. Over the second half of the 21st century, the scenario assumes a decrease in total solar irradiance of 0.12% compared to a reference Representative Concentration Pathway 8.5 experiment. The decrease in solar irradiance cools the stratopause (˜1 hPa) in the annual and global mean by 1.2 K. The impact on global mean near-surface temperature is small (˜-0.1 K), but larger changes in regional climate occur during the stratospheric dynamically active seasons. In Northern Hemisphere wintertime, there is a weakening of the stratospheric westerly jet by up to ˜3-4 m s-1, with the largest changes occurring in January-February. This is accompanied by a deepening of the Aleutian Low at the surface and an increase in blocking over Northern Europe and the North Pacific. There is also an equatorward shift in the Southern Hemisphere midlatitude eddy-driven jet in austral spring. The occurrence of an amplified regional response during winter and spring suggests a contribution from a top-down pathway for solar-climate coupling; this is tested using an experiment in which ultraviolet (200-320 nm) radiation is decreased in isolation of other changes. The results show that a large decline in solar activity over the 21st century could have important impacts on the stratosphere and regional surface climate.

  10. The buildup to the deep solar minimum of cycle 23: Quasi-periodic changes of the solar photospheric fields

    NASA Astrophysics Data System (ADS)

    Kumar Bisoi, Susanta; Janardhan, P.; Chakrabarty, D.; Ananthakrishnan, S.

    We have witnessed a belated cycle 24, after a long and unusual solar minimum, characterized by almost complete absence of sunspots and very weak polar fields, at the end of cycle 23. Employing a special harmonic analysis along with a wavelet method, the periodicities in the solar photospheric fields are deduced using NSO/Kitt peak ground-based synoptic magnetograms spanning over solar cycles 21, 22 and 23. We find a clear north-south asymmetry in the Fourier power distribution in the quasi-periodic changes when the data are grouped into fields prior to and after 1996. In this presentation, I will discuss that this north-south asymmetry, when coupled with both the declined solar magnetic fields and the turbulence levels in the inner heliosphere that began around the mid-nineties (˜1995-1996), initiated the build-up to this deep solar minimum.

  11. Solar wind ion observations: Comparison from the depths of solar minimum to the rising of the cycle

    NASA Astrophysics Data System (ADS)

    Galvin, A. B.; Simunac, K. D. C.; Jian, L. K.; Farrugia, C. J.; Popecki, M. A.

    2013-06-01

    We report solar wind helium abundance (He/H) and average iron charge states through solar minimum and the rising solar cycle. Speed trends for interplanetary coronal mass ejections seen by STEREO [10] are also presented. ICME case studies contrast the Fe charge states observed in the approach to solar minimum into the rising cycle. During solar minimum, ICME charge states were often similar to the range reported for ambient values. Faster and ``hotter'' (based on ionization state) ICMEs are being observed as the cycle rises. Using 10-minute data, transient charge state signatures are compared to magnetic cloud boundaries. In one ``rising'' ICME event, there is a clear and well-contained correspondence between the elevation of iron ionization state and the magnetic cloud's boundaries, with the post-shock sheath region preceding the cloud remaining at ambient charge state levels. In another ``rising'' double cloud event, elevated charge states are observed within the magnetic clouds, but are not well contained to the clouds, being observed both within the post-shock sheath region and continuing for nearly a day after the passage of the second magnetic cloud.

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

    PubMed

    Mancuso, Salvatore; Giordano, Silvio

    2013-05-01

    Following previous investigations by Giordano and Mancuso [1] and Mancuso and Giordano [2,3] on the differential rotation of the solar corona as obtained through the analysis of the intensity time series of the O VI 1032 Å spectral line observed by the UVCS/SOHO telescope during solar cycle 23, we analysed the possible influence of projection effects of extended coronal structures on the observed differential rotation rate in the ultraviolet corona. Through a simple geometrical model, we found that, especially at higher latitudes, the differential rotation may be less rigid than observed, since features at higher latitudes could be actually linked to much lower coronal structures due to projection effects. At solar maximum, the latitudinal rigidity of the UV corona, with respect to the differential rotating photosphere, has thus to be considered as an upper limit of the possible rigidity. At solar minimum and near the equatorial region throughout the solar cycle, projection effects are negligible. PMID:25685430

  13. Implications of Prolonged Solar Minimum Conditions for the Space Debris Population

    NASA Astrophysics Data System (ADS)

    Lewis, Hugh G.; Horbury, Timothy

    2013-08-01

    Observations of the current solar cycle show the likely continuation of a long-term decline in solar activity that began during the 1980s. This decline could lead to conditions similar to the Maunder minimum within 40 years [1], which would have consequences for the space debris environment. Solar activity is a key driver of atmospheric mass density and, subsequently, drag on orbiting spacecraft and debris. Whilst several studies have investigated potential effects on the global climate, no assessment has been made of the impact of a Maunder-like minimum on the space debris population in Low Earth Orbit (LEO). Consequently, we present a new study of the future debris environment under Maunder minimum conditions and provide an assessment of the possible consequences to the LEO space debris population and space operations. The University of Southampton's Debris Analysis and Monitoring Architecture to the Geosynchronous Environment (DAMAGE) has been used to analyse the consequences of a Maunder minimum of approximately 50 years duration and to quantify the impact on the effectiveness of debris mitigation measures. Results from these studies suggest an increase in collision activity and a corresponding, rapid growth of the debris population during a Maunder minimum period, in spite of on-going mitigation efforts. In the best case, the DAMAGE results suggest that the population of debris > 10 cm could double in number by the end of Maunder minimum conditions. However, the rapid growth in the population is followed by a strong recovery period on exit from a Maunder minimum. The recovery is characterised by a decrease in the debris population, which can be to a level similar to that seen before the onset of the Maunder minimum, if mitigation efforts are sustained. As such, prolonged solar minimum conditions may have relatively benign implications for the long-term evolution of the debris environment. However, the risks to spacecraft from collisions with debris during a Maunder-like minimum would be considerably higher than present, and exacerbated by any deficiency in debris mitigation efforts, with corresponding impacts on space operations.

  14. 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 μW/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 ( β) 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.

  15. Preliminary Results Of the 2007 Flight of the Solar Bolometric Imager at Solar Minimum

    NASA Astrophysics Data System (ADS)

    Bernasconi, P. N.; Foukal, P. V.; Eaton, H. H.; Noble, M.

    2008-05-01

    On September 13 2007, the Solar Bolometric Imager (SBI) successfully observed the Sun for several hours while suspended from a balloon in the stratosphere above New Mexico. The SBI represents a totally new approach in finding the sources of the solar irradiance variation. The SBI detector is an array of 320x240 thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold-black. The telescope is a 30-cm Dall-Kirkham with uncoated primary and secondary Pyrex mirrors. The combination of telescope and bolometric array provide an image of the Sun with a constant spectral response between ~ 280 and 2600 nm, over a field of view of 960 x 720 arcsec with a pixel size of 3 arcsec. This is the second successful flight of SBI, following a successful one on September 2003 which produced the first measurements in broad band of the center-to-limb variation of bolometric facular contrast (a flight attempt from Antarctica in 2006 was aborted). This latest flight provided bolometric (integrated light) maps of the solar photosphere during a time of minimum of solar activity. The SBI imagery will enable us to evaluate the photometric contribution of weak magnetic structures (e.g. network) more accurately than has been achievable with spectrally selective imaging over restricted wavebands. It will also enable us to investigate the presence, if any, of other thermal structures unrelated to magnetic activity, such as e.g. giant cells and pole-to-equator temperature gradients. During the 16 hour flight the SBI gathered several thousand bolometric images that are now being processed to produce full-disk maps of spatial variation in total solar output at solar minimum. The SBI flight is also providing important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors. In this paper we will briefly describe the characteristics of the SBI, its in-flight performance, and we will present the first results of the analysis of the bolometric images.

  16. 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..

  17. STRUCTURE AND DYNAMICS OF THE 2009 JULY 22 ECLIPSE WHITE-LIGHT CORONA

    SciTech Connect

    Pasachoff, J. M.; Babcock, B. A.; Rusin, V.; Saniga, M.; Druckmuellerova, H. E-mail: bryce.a.babcock@williams.edu E-mail: msaniga@ta3.sk

    2011-11-20

    The white-light corona (WLC) during the total solar eclipse of 2009 July 22 was observed by several teams in the Moon's shadow stretching from India and China across the Pacific Ocean with its many isolated islands. We present a comparison of the WLC as observed by eclipse teams located in China (Shanghai region) and on the Enewetak Atoll in the Marshall Islands, with observations taken 112 minutes apart, combined with near-simultaneous space observations. The eclipse was observed at the beginning of solar cycle 24, during a deep solar minimum (officially estimated as 2008 December according to the smoothed sunspot number, but very extended). The solar corona shows several different types of features (coronal holes, polar rays, helmet streamers, faint loops, voids, etc.), though it was extremely sparse in streamers as shown from Large-Angle Spectroscopic Coronagraph data. No large-scale dynamical phenomena were seen when comparing the observations from the two sites, confirming that the corona was quiescent. We measure a Ludendorff flattening coefficient of 0.238, typical of solar minimum.

  18. Structure and Dynamics of the 2009 July 22 Eclipse White-light Corona

    NASA Astrophysics Data System (ADS)

    Pasachoff, J. M.; Ruin, V.; Saniga, M.; Druckmllerov, H.; Babcock, B. A.

    2011-11-01

    The white-light corona (WLC) during the total solar eclipse of 2009 July 22 was observed by several teams in the Moon's shadow stretching from India and China across the Pacific Ocean with its many isolated islands. We present a comparison of the WLC as observed by eclipse teams located in China (Shanghai region) and on the Enewetak Atoll in the Marshall Islands, with observations taken 112 minutes apart, combined with near-simultaneous space observations. The eclipse was observed at the beginning of solar cycle 24, during a deep solar minimum (officially estimated as 2008 December according to the smoothed sunspot number, but very extended). The solar corona shows several different types of features (coronal holes, polar rays, helmet streamers, faint loops, voids, etc.), though it was extremely sparse in streamers as shown from Large-Angle Spectroscopic Coronagraph data. No large-scale dynamical phenomena were seen when comparing the observations from the two sites, confirming that the corona was quiescent. We measure a Ludendorff flattening coefficient of 0.238, typical of solar minimum.

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

    SciTech Connect

    Christian, D. J.; Bodewits, D.; Lisse, C. M.; Dennerl, K.; Wolk, S. J.; Hsieh, H.; Zurbuchen, T. H.; Zhao, L. E-mail: damian.christian@csun.edu E-mail: carey.lisse@jhuapl.edu E-mail: swolk@cfa.harvard.edu E-mail: thomasz@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.

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

    SciTech Connect

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

    2014-07-10

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

  1. Modulation of Galactic Electrons in the Heliosphere during the Unusual Solar Minimum of 2006-2009: A Modeling Approach

    NASA Astrophysics Data System (ADS)

    Potgieter, M. S.; Vos, E. E.; Munini, R.; Boezio, M.; Di Felice, V.

    2015-09-01

    The last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. The highest levels of Galactic protons were recorded at Earth in late 2009 in contrast to expectations. A comprehensive model was used to study the proton modulation for the period from 2006 to 2009 in order to determine what basic processes were responsible for solar modulation during this period and why it differs from proton modulation during previous solar minimum modulation periods. This established model is now applied to studying the solar modulation of electron spectra as observed for 80 MeV-30 GeV by the PAMELA space detector from mid-2006 to the end of 2009. Over this period the heliospheric magnetic field had decreased significantly until the end of 2009 while the waviness of the heliospheric current sheet decreased moderately and the observed electron spectra increased by a factor of ˜1.5 at 1.0 GeV to ˜3.5 at 100 MeV. In order to reproduce the modulation evident from seven consecutive semesters, the diffusion coefficients had to increase moderately while maintaining the basic rigidity dependence. It is confirmed that the main diffusion coefficients are independent of rigidity below ˜0.5 GV, while the drift coefficient had to be reduced below this value. The 2006-2009 solar minimum epoch indeed was different than previously observed minima, at least since the beginning of the space exploration era. This period could be called “diffusion-dominated” as was also found for the modulation of protons.

  2. Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over antarctica.

    PubMed

    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; Yamagami, T; Yamamoto, A; Yoshida, T; Yoshimura, K

    2012-02-01

    The energy spectrum of cosmic-ray antiprotons (p's) from 0.17 to 3.5 GeV has been measured using 7886 p'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 calculations. Cosmologically primary p's have been investigated by comparing measured and calculated p spectra. BESS-Polar II data show no evidence of primary p's from the evaporation of primordial black holes. PMID:22400920

  3. 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.

  4. Measurement of Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight in 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.

    2011-01-01

    The energy spectrum of cosmic-ray antiprotons (p(raised bar)'s) 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 p(raised bar) spectrum measured by BESS-Polar II shows good consistency with secondary p(raised bar) calculations. Cosmologically primary p(raised bar)'s have been searched for by comparing the observed and calculated p(raised bar) spectra. The BESSPolar II result shows no evidence of primary p(raised bar)'s originating from the evaporation of PBH.

  5. Interplanetary scintillation signatures in the inner heliosphere of the deepest solar minimum in the past 100 years

    NASA Astrophysics Data System (ADS)

    Bisoi, Susanta Kumar; Janardhan, P.

    2013-07-01

    We have used interplanetary scintillation (IPS) observations at 327 MHz spanning years 1983-2009 to study microturbulence levels in the inner heliosphere. We find that the microturbulence levels show a steady and significant drop in the entire inner heliosphere starting from around 1995. The fact that the solar polar fields have also shown a similar declining trend provides a consistent result showing the buildup to the solar minimum between the solar cycles 23 and 24, the deepest in the past 100 years, actually began more than a decade earlier.

  6. 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.

  7. 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.

  8. DECLINE AND RECOVERY OF THE INTERPLANETARY MAGNETIC FIELD DURING THE PROTRACTED SOLAR MINIMUM

    SciTech Connect

    Smith, Charles W.; Schwadron, Nathan A.; DeForest, Craig E. E-mail: N.Schwadron@unh.edu

    2013-09-20

    The interplanetary magnetic field (IMF) is determined by the amount of solar magnetic flux that passes through the top of the solar corona into the heliosphere, and by the dynamical evolution of that flux. Recently, it has been argued that the total flux of the IMF evolves over the solar cycle due to a combination of flux that extends well outside of 1 AU and is associated with the solar wind, and additionally, transient flux associated with coronal mass ejections (CMEs). In addition to the CME eruption rate, there are three fundamental processes involving conversion of magnetic flux (from transient to wind-associated), disconnection, and interchange reconnection that control the levels of each form of magnetic flux in the interplanetary medium. This is distinct from some earlier models in which the wind-associated component remains steady across the solar cycle. We apply the model of Schwadron et al. that quantifies the sources, interchange, and losses of magnetic flux to 50 yr of interplanetary data as represented by the Omni2 data set using the sunspot number as a proxy for the CME eruption rate. We do justify the use of that proxy substitution. We find very good agreement between the predicted and observed interplanetary magnetic flux. In the absence of sufficient CME eruptions, the IMF falls on the timescale of ∼6 yr. A key result is that rising toroidal flux resulting from CME eruption predates the increase in wind-associated IMF.

  9. 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.

  10. Unraveling Parkinson's: Three Clues

    MedlinePlus

    ... Navigation Bar Home Current Issue Past Issues Unraveling Parkinson's: Three Clues Past Issues / Summer 2006 Table of ... or prevent disease progression. Studies have shown that Parkinson's patients have lost 60 to 80 percent of ...

  11. 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.

  12. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, Heather A.; Comfort, Richard H.; Craven, Paul D.; Chandler, Michael O.; Moore, Thomas E.

    2000-01-01

    We correlate solar wind and IMF properties with the properties of O(+) and H(+) in the polar cap in early 1996 during solar minimum conditions at altitudes between 5.5 and 8.9 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the POLAR satellite. Throughout the high altitude polar cap, we observe H(+) to be more abundant than O(+). H(+) is a significant fraction of both the ionosphere and the solar wind, and O(+) is not a significant species in the solar wind. O(+) is the major species in the ionosphere so the faction of O(+) present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. For these reasons, 0+ is of primary interest in this study. We observe O(+) to be most abundant at lower latitudes when the solar wind speed is low (and low Kp), and at higher solar wind speeds (and high Kp) O(+) is observed across most of the polar cap. We also find that O(+) density and parallel flux are well organized by solar wind dynamic pressure; they both increase with solar wind dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, but H(+) density and parallel flux have some negative correlation with IMF By, and some positive correlation with VswBIMF. In this solar minimum data set, H(+) is dominant so that contributions of this plasma to the plasma sheet would have a very low O(+) to H(+) ratio.

  13. 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.

  14. Corona of Magnetars

    NASA Astrophysics Data System (ADS)

    Beloborodov, Andrei M.; Thompson, Christopher

    2007-03-01

    We develop a theoretical model that explains the formation of hot coronae around strongly magnetized neutron stars-magnetars. The starquakes of a magnetar shear its external magnetic field, which becomes nonpotential and threaded by an electric current. Once twisted, the magnetosphere cannot untwist immediately because of its self-induction. The self-induction electric field lifts particles from the stellar surface, accelerates them, and initiates avalanches of pair creation in the magnetosphere. The created plasma corona maintains the electric current demanded by b.nabla XB and regulates the self-induction EMF by screening. This corona persists in dynamic equilibrium: it is continually lost to the stellar surface on the light crossing time ~10-4 s and replenished with new particles. In essence, the twisted magnetosphere acts as an accelerator that converts the toroidal field energy to particle kinetic energy. Using a direct numerical experiment, we show that the corona self-organizes quickly (on a millisecond timescale) into a quasi-steady state, with voltage 108-109 V along the magnetic lines. The voltage is maintained near the threshold for e+/- discharge. The heating rate of the corona is ~1036 ergs s-1, in agreement with the observed persistent, high-energy output of magnetars. We deduce that a static twist that is suddenly implanted into the magnetosphere will decay on a timescale of 1-10 yr. The particles accelerated in the corona impact the solid crust, knock out protons, and regulate the column density of the hydrostatic atmosphere of the star. The transition layer between the atmosphere and corona may be hot enough to create additional e+/- pairs. This layer can be the source of the observed 100 keV emission from magnetars. The corona emits curvature radiation and can supply the observed IR-optical luminosity.

  15. Unique latitudinal shape of ion upper transition height (HT) surface during deep solar minimum (2008-2009)

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Heelis, R.; Gowtam, V. Sai; Ajith, K. K.; Su, S.-Y.

    2015-02-01

    The ionospheric upper transition height (HT) is found to increase dramatically by ~100 km from 2008-2009 to 2010 only for a marginal increase in solar activity (F10.7) by 11.76 solar flux units. The latitudinal variation of HT surface during 2008-2009 period exhibits a local minimum at equatorial latitudes and increase at low latitudes. Further, the HT at equatorial latitudes exhibits slower rate of increase than at low latitudes. These interesting features are new and different from those reported in literature. A quick loss of O+ and increase in H+ ions are observed around ~550 to 650 km indicating that the charge exchange reaction is responsible for the slower rate of increase and lowered HT at equatorial latitudes. These new aspects of HT are more conspicuously observed during this deep solar minimum period where the resonant charge exchange reaction is taking place at altitudes as low as ~550 km.

  16. The impact of helium on thermosphere mass density response to geomagnetic activity during the recent solar minimum

    NASA Astrophysics Data System (ADS)

    Thayer, J. P.; Liu, X.; Lei, J.; Pilinski, M.; Burns, A. G.

    2012-07-01

    High-resolution mass density observations inferred from accelerometer measurements on the CHAMP and GRACE satellites are employed to investigate the thermosphere mass density response with latitude and altitude to geomagnetic activity during the recent solar minimum. Coplanar orbital periods in February 2007 and December 2008 revealed the altitude and latitude response in thermosphere mass density for their respective winter hemispheres was influenced by the relative amount of helium and oxygen present. The CHAMP-to-GRACE (C/G) mass density ratio depends on two terms; the first proportional to the ratio of the mean molecular weight to temperature and the second proportional to the vertical gradient of the logarithmic mean molecular weight. For the relative levels of helium and oxygen in February 2007, the winter hemisphere C/G mass density response to geomagnetic activity, although similar to the summer hemisphere, was caused predominantly by changes in the vertical gradient of the logarithmic mean molecular weight. In December 2008, the significant presence of helium caused the mean molecular weight changes to exceed temperature changes in the winter hemisphere leading to an increase in the C/G ratio with increasing geomagnetic activity, in opposition to the decrease observed in the summer hemisphere that was caused primarily by temperature changes. The observed behavior is indicative of composition effects influencing the mass density response and the dynamic action of the oxygen to helium transition region in both latitude and altitude will lead to complex behaviors in the mass density at GRACE altitudes throughout the extended solar minimum from 2007 to 2010.

  17. The response of the equatorial ionosphere to fast stream solar coronal holes during 2008 deep solar minimum over Indian region

    NASA Astrophysics Data System (ADS)

    Sripathi, S.; Singh, Ram; Banola, S.; Singh, Dupinder; Sathish, S.

    2016-01-01

    In this paper, we report ionospheric response to fast stream solar coronal holes during 2008 deep solar minimum year using ground-based multi-instruments over Indian region. To examine this, we analyzed foF2 (MHz) and hpF2(km) from Canadian Advanced Digital Ionosonde and total electron content (TEC) from GPS receiver over Tirunelveli (8.73°N, 77.70°E; dip 0.5°N) along with equatorial electrojet (EEJ) strength. Our analysis shows good correlation between solar wind and foF2/TEC, while hpF2 is poorly correlated. However, moderate correlation exists between solar wind and EEJ strength. When we performed periodogram analysis, we observed 9 and 13 day periods as dominant periods in foF2 and TEC. Interestingly, the occurrence pattern of plasma irregularities also resembles these periodic oscillations. Since it is believed that lower atmospheric waves are dominant forces for ionospheric variabilities during deep solar minimum, we examined the mesosphere/lower thermosphere region temperature using Thermosphere Ionosphere Mesosphere Energetics and Dynamics Sounding of the Atmosphere using Broadband Emission Radiometry and winds using medium frequency radar along with outgoing longwave radiation in the troposphere altitudes to rule out the sources for these periodic oscillations in the lower atmosphere. Using cross-wavelet and cross-coherence spectra of both solar wind and ionospheric/atmospheric parameters, we suggest that ionospheric periodicities are similar to that of solar wind. Based on these results, we suggest that while the periodic oscillations are associated with the disturbance dynamo winds/electric fields that are propagated to equatorial latitudes, the differences in their temporal/seasonal variations are attributed to the variations in the composition/recombination changes.

  18. The Solar Corona at the 2015 Total Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Carter, Allison L.

    2015-04-01

    We report on our successful observations of the solar corona at the 20 March 2015 total solar eclipse from our site at a latitude of about 78° on the Svalbard archipelago, and related observations by colleagues aloft. Our equipment included cameras for imaging at a variety of scales for use in making high-contrast composites, as reported our Astrophysical Journal article (2015) about our 2012 total solar eclipse observations and similar articles about the corona and changes in it at previous total eclipses. Our Svalbard equipment also included a spectrograph, with which we continued our monitoring of the ratio of the Fe XIV and Fe X coronal lines, which has recently been >1 with the solar maximum, a reversal from <1 at earlier eclipses closer to the last solar minimum. Our 2013 observations from Gabon showed two coronal mass ejections and an erupting prominence; the 2015 eclipse showed an erupting prominence and some unusual coronal structure in an overall coronal shape typical of solar maximum. We use our ground-based eclipse observations to fill the gap in imaging between the SDO and SWAP (17.4 nm) EUV observations on the solar disk and the inner location of the LASCO C2 occultation disk, with STEREO observations providing the possibility of three-dimensional interpretations. Our expedition was supported by a grant (9616-14) from the Committee for Research and Exploration of the National Geographic Society.

  19. 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

  20. 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…

  1. The New Solar Corona

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Poland, Arthur I.; Rabin, Douglas M.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We focus on new observational capabilities (Yohkoh, SoHO, TRACE) observations, modeling, approaches, and insights into physical processes of the solar corona. The most impressive new results and problems discussed in this article can be appreciated from the movies and available on the Annual Reviews web site.

  2. Current Sheets in the Corona and the Complexity of Slow Wind

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro

    2010-01-01

    The origin of the slow solar wind has long been one of the most important problems in solar/heliospheric physics. Two observational constraints make this problem especially challenging. First, the slow wind has the composition of the closed-field corona, unlike the fast wind that originates on open field lines. Second, the slow wind has substantial angular extent, of order 30 degrees, which is much larger than the widths observed for streamer stalks or the widths expected theoretically for a dynamic heliospheric current sheet. We propose that the slow wind originates from an intricate network of narrow (possibly singular) open-field corridors that emanate from the polar coronal hole regions. Using topological arguments, we show that these corridors must be ubiquitous in the solar corona. The total solar eclipse in August 2008, near the lowest point of cycle 23 affords an ideal opportunity to test this theory by using the ultra-high resolution Predictive Science's (PSI) eclipse model for the corona and wind. Analysis of the PSI eclipse model demonstrates that the extent and scales of the open-field corridors can account for both the angular width of the slow wind and its closed-field composition. We discuss the implications of our slow wind theory for the structure of the corona and heliosphere at solar minimum and describe further observational and theoretical tests.

  3. The structure of Io's corona

    NASA Technical Reports Server (NTRS)

    Schneider, N. M.; Hunten, D. M.; Wells, W. K.; Schultz, A. B.; Fink, U.

    1991-01-01

    A spatial profile of the distribution of sodium in Io's corona has been constructed using measurements obtained during satellite mutual eclipses. The data reveal a fairly symmetric corona whose density falls steeply from the surface out to 6 r(Io) and more slowly outside. An upper limit of 700 km is placed on the exobase altitude, but the observations do not constrain the surface density. Several theoretical models adequately match some traits of the corona, but none satisfies all the observations. No strong upstream/downstream asymmetry of the corona is observed, so it is unlikely that the corona is primarily generated by the impact of corotating ions into the trailing hemisphere.

  4. Galactic Cosmic Rays and Lunar Secondary Particles from Solar Minimum to Maximum: CRaTER Observations and Geant4 Modeling

    NASA Astrophysics Data System (ADS)

    Looper, M. D.; Mazur, J. E.; Blake, J. B.; Spence, H. E.; Schwadron, N.; Golightly, M. J.; Case, A. W.; Kasper, J. C.; Townsend, L. W.; Wilson, J. K.

    2014-12-01

    The Lunar Reconnaissance Orbiter mission was launched in 2009 during the recent deep and extended solar minimum, with the highest galactic cosmic ray (GCR) fluxes observed since the beginning of the space era. Its Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument was designed to measure the spectra of energy deposits in silicon detectors shielded behind pieces of tissue equivalent plastic, simulating the self-shielding provided by an astronaut's body around radiation-sensitive organs. The CRaTER data set now covers the evolution of the GCR environment near the moon during the first five years of development of the present solar cycle. We will present these observations, along with Geant4 modeling to illustrate the varying particle contributions to the energy-deposit spectra. CRaTER has also measured protons traveling up from the lunar surface after their creation during GCR interactions with surface material, and we will report observations and modeling of the energy and angular distributions of these "albedo" protons.

  5. Temporal Evolution of the Solar Wind Bulk Velocity at Solar Minimum by Correlating the STEREO A and B PLASTIC Measurements

    NASA Astrophysics Data System (ADS)

    Opitz, A.; Karrer, R.; Wurz, P.; Galvin, A. B.; Bochsler, P.; Blush, L. M.; Daoudi, H.; Ellis, L.; Farrugia, C. J.; Giammanco, C.; Kistler, L. M.; Klecker, B.; Kucharek, H.; Lee, M. A.; Möbius, E.; Popecki, M.; Sigrist, M.; Simunac, K.; Singer, K.; Thompson, B.; Wimmer-Schweingruber, R. F.

    2009-05-01

    The two STEREO spacecraft with nearly identical instrumentation were launched near solar activity minimum and they separate by about 45° per year, providing a unique tool to study the temporal evolution of the solar wind. We analyze the solar wind bulk velocity measured by the two PLASTIC plasma instruments onboard the two STEREO spacecraft. During the first half year of our measurements (March - August 2007) we find the typical alternating slow and fast solar wind stream pattern expected at solar minimum. To evaluate the temporal evolution of the solar wind bulk velocity we exclude the spatial variations and calculate the correlation between the solar wind bulk velocity measured by the two spacecraft. We account for the different spacecraft positions in radial distance and longitude by calculating the corresponding time lag. After adjusting for this time lag we compare the solar wind bulk velocity measurements at the two spacecraft and calculate the correlation between the two time-shifted datasets. We show how this correlation decreases as the time difference between two corresponding measurements increases. As a result, the characteristic temporal changes in the solar wind bulk velocity can be inferred. The obtained correlation is 0.95 for a time lag of 0.5 days and 0.85 for 2 days.

  6. Climatology of the O+ temperatures over Arecibo for the historical deep solar minimum using Incoherent Scatter Radar and airglow data.

    NASA Astrophysics Data System (ADS)

    Santos, P. T.; Brum, C. G. M.; Kerr, R.; Noto, J.

    2014-12-01

    At Arecibo Observatory (AO) a comprehensive description of the ionosphere and thermosphere environment is achieved by the synergy between the Incoherent Scatter Radar (ISR) and the optical instruments nested on site. An example of this synergy is present in his work where optical and radar techniques were reconciled in order to obtain the O+ temperature variability for 2008 and 2009. During this period, a historical deep solar minimum condition was registered with a remarkable absence of sunspots for a long period (translated into a decreasing in the EUV-UV irradiance). This particular feature implies in an important tool to investigate the variability of O+ temperature, once that any variation can be related to season (modulated by the neutral atmosphere) and/or another modulator different than solar energy input. The OII 7320 Å twilight airglow data used in this work were obtained during new moon periods using a high-spectral resolution Fabry-Perot Interferometer (FPI) with CCD array detection. The FPI was configured with 0.9 cm plate spacing, which produced a free spectral range of 0.298Å and a spectral resolution of 0.03Å, sufficient to sample line width temperatures as low as 500K. A very narrow 3Å Full Width at Half Maximum (FWHM) three-cavity interference filter was also used.

  7. Climatologies of nighttime thermospheric winds and temperatures from Fabry-Perot interferometer measurements: From solar minimum to solar maximum

    NASA Astrophysics Data System (ADS)

    Fisher, Daniel J.; Makela, Jonathan J.; Meriwether, John W.; Buriti, Ricardo A.; Benkhaldoun, Zouhair; Kaab, Mohamed; Lagheryeb, Amine

    2015-08-01

    We present a climatology of quiet time thermospheric winds and temperatures estimated from high-resolution Fabry-Perot interferometer measurements of the 630.0 nm airglow emission spectral line shape. Three locations are examined in this long-term study: northeastern Brazil (August 2009 to August 2014), a midlatitude site in North Carolina, USA (June 2011 to December 2014), and a midlatitude site in Morocco (November 2013 to December 2014). We discuss the day-to-day, seasonal, and solar cycle trends and variations of thermospheric meridional winds, zonal winds, neutral temperatures, and for the first time vertical winds. Observations made from solar minimum to solar maximum (with F10.7 values ranging from ˜70 to ˜159 solar flux units) confirm that neutral temperatures have a strong solar cycle dependence. However, this data set shows that the neutral winds are more closely tied to the seasonal variation, rather than the solar cycle. We also present comparisons between the two midlatitude sites and include neutral wind comparisons to the updated Horizontal Wind Model 14.

  8. Solar origins of solar wind properties during the cycle 23 solar minimum and rising phase of cycle 24.

    PubMed

    Luhmann, Janet G; Petrie, Gordon; Riley, Pete

    2013-05-01

    The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is 'typical' solar wind, even when the Sun is relatively inactive. PMID:25685422

  9. The New Solar Corona

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Poland, Arthur I.; Rabin, Douglas M.

    We focus on new observational capabilities (Yohkoh, SoHO, TRACE), observations, modeling approaches, and insights into physical processes of the solar corona. The most impressive new results and problems discussed in this article can be appreciated from the movies available on the Annual Reviews website and at http://www.lmsal.com/pub/araa/araa.html. "The Sun is new each day." Heraclites (ca 530-475 BC) "Everything flows." Heraclites (ca 530-475 BC)

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

    SciTech Connect

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

    2014-10-01

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

  11. Diurnal variation of winter F region ionosphere for solar minimum at both Zhongshan Station, Antarctica, and Svalbard Station, Arctic

    NASA Astrophysics Data System (ADS)

    Zhang, Bei-Chen; Yang, Sheng-Gao; Xu, Sheng; Liu, Rui-Yuan; Häggström, I.; Zhang, Qing-He; Hu, Ze-Jun; Huang, De-Hong; Hu, Hong-Qiao

    2015-11-01

    Diurnal variation features of wintertime F2 peak electron density (NmF2) representative for solar minimum at both Zhongshan station, Antarctica, and Svalbard station are compared and analyzed. Both stations are located around cusp latitude and are almost on the same geomagnetic meridian plane in both hemispheres. For quiet time period, typical NmF2 diurnal variation features at Svalbard station show double peaks with a decrease of NmF2 around magnetic local noon (~UT + 3 h); NmF2 diurnal variation at Zhongshan station shows one major peak around magnetic local noon (~UT + 1.75 h), followed by a sharp decrease of NmF2, and a subpeak around 1500 UT. Simulation results of the high-latitude ionospheres in both hemispheres agree well with observations at both stations. It is found that the major difference of NmF2 variation between both stations can be explained by the unique location of each station relative to the sunlit demarcation line during the day. For quiet time period, photoionization from lower latitude contributes to the major peak of NmF2 in the diurnal variation at Zhongshan station, while the interaction between horizontal convection and auroral precipitation is the main cause for NmF2 variation at Svalbard station. For active time period, both stations show the increase of NmF2 due to transportation of higher plasma density from lower latitudes on the dayside with the expansion of the polar cap and the additional ionization from soft-precipitating electrons.

  12. Latitudinal Variation of Solar Wind Speed and Mass Flux in the Acceleration Region of the Solar Wind during Solar Minimum Inferred from Spectral Broadening measurements

    NASA Technical Reports Server (NTRS)

    Woo, R.; Goldstein, R.

    1993-01-01

    In this paper, we use an aggregate of S-band 2.3 GHz (13 cm) spectral broadening observations conducted during solar minimum conditions by the Mariner 4, Pioneer 10, Mariner 10, Helios 1 & 2 and Viking spacecraft to infer the first measurements of the latitudinal variation of solar wind speed and mass flux in the acceleration region of the solar wind at 3-8 R(sub o).

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  14. Polarization of the solar corona.

    NASA Technical Reports Server (NTRS)

    Feibelman, W. A.

    1972-01-01

    A method of obtaining polarized photographs of the solar corona during total eclipse is described. The required equipment is a reflex viewing type camera with a lens of adequate focal length to give an image of the corona a few millimeters in diameter at the focal plane. A sheet of linear polarizing filter material is placed directly in front of the lens. The filter is mounted in such a way so as to permit a set of four exposures of equal length to be taken after totality begins. Since the light of the corona is highly polarized, the resultant set of photographs will show marked differences in the shape of the corona.

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

    EPA Science Inventory

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

  16. Coronae on stars

    NASA Technical Reports Server (NTRS)

    Haisch, B. M.

    1986-01-01

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

  17. 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.

  18. Alzheimer's Disease: Unraveling the Mystery

    MedlinePlus

    ... Referral Center Alzheimer's Disease Education and Referral Center Alzheimer's Disease Education and Referral Center Home About Alzheimer’s ... Plan National Alzheimer's Project Act (NAPA) About ADEAR Alzheimer's Disease: Unraveling the Mystery Preface Over the past ...

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

    SciTech Connect

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

    1986-10-01

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

  20. New insights into AGN coronae

    NASA Astrophysics Data System (ADS)

    Lohfink, Anne; Fabian, Andrew C.; Malzac, Julien; Belmont, Renaud; Buisson, Douglas

    2016-04-01

    Active galactic nuclei (AGN) are some of the most energetic sources of radiation in the Universe. The conversion of gravitational energy into radiation is thought to take place in an accretion disk/corona system just outside the black hole. In this system thermal, UV/optical photons from the accretion disk are upscattered in a corona of hot electrons situated above the accretion disk producing X-rays. The nature of this Comptonizing corona remains a key open question in AGN physics. The NuSTAR satellite provides the opportunity to study the Comptonization spectrum produced by the corona in great detail. In our talk we will show some key results from these new studies of the Comptonization spectrum. We explore how, together with our growing knowledge of coronal sizes, we are able to draw first conclusions about the physics taking place in the corona. We find evidence for coronae to be hot and radiatively compact, putting them close to the boundary of the region in the compactness-temperature diagram which is forbidden due to runaway pair production. This suggests that pair production and annihilation are essential ingredients in the coronae of AGN and that they control the coronal temperature and shape of the observed spectra.

  1. Magnetic Clouds at/near the 2007 - 2009 Solar Minimum: Frequency of Occurrence and Some Unusual Properties

    NASA Technical Reports Server (NTRS)

    Lepping. R. P.; Wu, C.-C.; Berdichevsky, D. B.; Szabo, A.

    2011-01-01

    Magnetic clouds (MCs) have been identified for the period 2007 2009 (at/near the recent solar minimum) from Wind data, then confirmed through MC parameter fitting using a force-free model. A dramatic increase in the frequency of occurrence of these events took place from the two early years of 2007 (with five MCs) and 2008 (one MC) compared to 2009 (12 MCs). This pattern approximately mirrors the occurrence-frequency profile that was observed over a three-year interval 12 years earlier, with eight events in 1995, four in 1996, and 17 in 1997, but decreased overall by a factor of 0.62 in number. However, the average estimated axial field strength taken over all of the 18 events of 2007 - 2009 (called the "recent period" here) was only 11.0 nT, whereas |BO| for the 29 events of 1995 - 1997 (called the "earlier period" ) was 16.5 nT. This 33% average drop in |BO| is more or less consistent with the decreased three-year average interplanetary magnetic field intensity between these two periods, which shows a 23% drop. In the earlier period, the MCs were clearly of mixed types but predominantly of the South-to-North type, whereas those in the recent period are almost exclusively the North-to-South type; this change is consistent with global solar field changes predicted by Bothmer and Rust (Geophys. Monogr. Ser. 99, 139, 1997). As we have argued in earlier work (Lepping and Wu, J. Geophys. Res. 112, A10103, 2007), this change should make it possible to carry out (accurate short-term) magnetic storm forecasting by predicting the latter part of an MC from the earlier part, using a good MC parameter-fitting model with real-time data from a spacecraft at L1, for example. The recent set s average duration is 15.2 hours, which is a 27% decrease compared to that of the earlier set, which had an average duration of 20.9 hours. In fact, all physical aspects of the recent MC set are shown to drop with respect to the earlier set; e.g., as well as the average internal magnetic field drop, the recent set had a somewhat low average speed of 379 km/s (5% drop), and the average diameter had a 24% drop. Hence, compared to the earlier set, the recent set consists of events that are smaller, slightly slower, and weaker in every respect (and fewer in number), but in a relative sense the two three-year sets have similar frequency-of-occurrence profiles. It is also interesting that the two sets have almost the same average axial inclinations, i.e., axial latitude approx. = 31deg (in GSE). These MC characteristics are compared to relevant solar features and their changes. A preliminary assessment of the statistics on possible shocks and pressure pulses upstream of these recent MCs yields the following: About 28% of the MCs, at most, had shocks, and 33% had shocks and/or pressure pulses. These are low values, since typically the percentage of cases with shocks is about 50%, and the percentage with shocks and/or pressure pulses is usually about 75%.

  2. Magnetic Clouds at/near the 2007 - 2009 Solar Minimum: Frequency of Occurrence and Some Unusual Properties

    NASA Astrophysics Data System (ADS)

    Lepping, R. P.; Wu, C.-C.; Berdichevsky, D. B.; Szabo, A.

    2011-12-01

    Magnetic clouds (MCs) have been identified for the period 2007 - 2009 (at/near the recent solar minimum) from Wind data, then confirmed through MC parameter fitting using a force-free model. A dramatic increase in the frequency of occurrence of these events took place from the two early years of 2007 (with five MCs) and 2008 (one MC) compared to 2009 (12 MCs). This pattern approximately mirrors the occurrence-frequency profile that was observed over a three-year interval 12 years earlier, with eight events in 1995, four in 1996, and 17 in 1997, but decreased overall by a factor of 0.62 in number. However, the average estimated axial field strength [<| B O|>] taken over all of the 18 events of 2007 - 2009 (called the “recent period” here) was only 11.0 nT, whereas <| B O|> for the 29 events of 1995 - 1997 (called the “earlier period”) was 16.5 nT. This 33% average drop in <| B O|> is more or less consistent with the decreased three-year average interplanetary magnetic field intensity between these two periods, which shows a 23% drop. In the earlier period, the MCs were clearly of mixed types but predominantly of the South-to-North type, whereas those in the recent period are almost exclusively the North-to-South type; this change is consistent with global solar field changes predicted by Bothmer and Rust ( Geophys. Monogr. Ser. 99, 139, 1997). As we have argued in earlier work (Lepping and Wu, J. Geophys. Res. 112, A10103, 2007), this change should make it possible to carry out (accurate short-term) magnetic storm forecasting by predicting the latter part of an MC from the earlier part, using a good MC parameter-fitting model with real-time data from a spacecraft at L1, for example. The recent set’s average duration is 15.2 hours, which is a 27% decrease compared to that of the earlier set, which had an average duration of 20.9 hours. In fact, all physical aspects of the recent MC set are shown to drop with respect to the earlier set; e.g., as well as the average internal magnetic field drop, the recent set had a somewhat low average speed of 379 km s-1 (5% drop), and the average diameter had a 24% drop. Hence, compared to the earlier set, the recent set consists of events that are smaller, slightly slower, and weaker in every respect (and fewer in number), but in a relative sense the two three-year sets have similar frequency-of-occurrence profiles. It is also interesting that the two sets have almost the same average axial inclinations, i.e., axial latitude ≈31° (in GSE). These MC characteristics are compared to relevant solar features and their changes. A preliminary assessment of the statistics on possible shocks and pressure pulses upstream of these recent MCs yields the following: About 28% of the MCs, at most, had shocks, and 33% had shocks and/or pressure pulses. These are low values, since typically the percentage of cases with shocks is about 50%, and the percentage with shocks and/or pressure pulses is usually about 75%.

  3. 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.

  4. Protein corona: Opportunities and challenges.

    PubMed

    Zanganeh, Saeid; Spitler, Ryan; Erfanzadeh, Mohsen; Alkilany, Alaaldin M; Mahmoudi, Morteza

    2016-06-01

    In contact with biological fluids diverse type of biomolecules (e.g., proteins) adsorb onto nanoparticles forming protein corona. Surface properties of the coated nanoparticles, in terms of type and amount of associated proteins, dictate their interactions with biological systems and thus biological fate, therapeutic efficiency and toxicity. In this perspective, we will focus on the recent advances and pitfalls in the protein corona field. PMID:26783938

  5. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High-Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    2001-01-01

    We correlate solar wind and interplanetary magnetic field (IMF) properties with the properties of O(+) and H(+) during early 1996 (solar minimum) at altitudes between 5.5 and 8.9 R(sub E) geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. Throughout the high-altitude polar cap we observe H(+) to be more abundant than O(+). O(+) is found to be more abundant at lower latitudes when the solar wind speed is low (and Kp is low), while at higher solar wind speeds (and high Kp), O(+) is observed across most of the polar cap. The O(+) density and parallel flux are well organized by solar wind dynamic pressure, both increasing with solar wind dynamic pressure. Both the O(+) density and parallel flux have positive correlations with both V(sub SW)B(sub IMF) and E(sub SW). No correlation is found between O(+) density and IMF Bz, although a nonlinear relationship with IMF By is observed, possibly due to a strong linear correlation with the dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, although H(+) density and parallel flux are negatively correlated with IMF By and positively correlated with both V(sub SW)B(sub IMF) and E(sub SW). In this solar minimum data set, H(+) is dominant, so that contributions of this plasma to the plasma sheet would have very low O(+) to H(+) ratios.

  6. Spectroscopic investigation of protein corona

    NASA Astrophysics Data System (ADS)

    Choudhary, Poonam

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

  7. 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.

  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 Munga. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occurring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronae are found predominantly as isolated features in the plains. Coronae at hot spot rises tend to be significantly lager than coronae in other settings, consistent with a hotter upper mantle at hot spot rises and their active state.

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

    SciTech Connect

    Pasachoff, J. M.; Rusin, V.; Saniga, M.

    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.

  10. A Determination of the North-South Heliospheric Magnetic Field Component from Inner Corona Closed-loop Propagation

    NASA Astrophysics Data System (ADS)

    Jackson, B. V.; Hick, P. P.; Buffington, A.; Yu, H.-S.; Bisi, M. M.; Tokumaru, M.; Zhao, X.

    2015-04-01

    A component of the magnetic field measured in situ near the Earth in the solar wind is present from north-south fields from the low solar corona. Using the Current-sheet Source Surface model, these fields can be extrapolated upward from near the solar surface to 1 AU. Global velocities inferred from a combination of interplanetary scintillation observations matched to in situ velocities and densities provide the extrapolation to 1 AU assuming mass and mass flux conservation. The north-south field component is compared with the same ACE in situ magnetic field component—the Normal (Radial Tangential Normal) Bn coordinate—for three years throughout the solar minimum of the current solar cycle. We find a significant positive correlation throughout this period between this method of determining the Bn field compared with in situ measurements. Given this result from a study during the latest solar minimum, this indicates that a small fraction of the low-coronal Bn component flux regularly escapes from closed field regions. The prospects for Space Weather, where the knowledge of a Bz field at Earth is important for its geomagnetic field effects, is also now enhanced. This is because the Bn field provides the major portion of the Geocentric Solar Magnetospheric Bz field coordinate that couples most closely to the Earth’s geomagnetic field.

  11. The H Corona of Mars

    NASA Astrophysics Data System (ADS)

    Chaffin, Michael Scott

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

  12. Solar tides in the equatorial upper thermosphere - A comparison between AE-E data and the TIGCM for solstice, solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Burrage, M. D.; Storz, M. F.; Abreu, V. J.; Fesen, C. G.; Roble, R. G.

    1991-01-01

    Equatorial thermospheric tidal temperatures and densities inferred from Atmosphere Explorer E (AE-E) mass spectrometer data are compared with theoretical predictions from a Thermosphere/Ionosphere GCM (TIGCM) for solar minimum, solstice conditions. The TIGCM reproduces the gross tidal features observed by satellite, including the midnight temperature anomaly, and the diurnal phases are in good agreement of the densities of atomic oxygen and molecular nitrogen. For the neutral temperature, the prediction phases are one to two hours earlier than observed, and the diurnal temperature and density amplitudes predicted by the model are considerably weaker than indicated by the AE-E measurements. The semidiurnal variations found in the observation agree well with the model for December solstice but not for June. The results indicate that upward-propagating tides from the lower atmosphere are responsible for at least half of the amplitude of the semidiurnal tide in the upper thermosphere.

  13. The cosmic-ray spectra of H-1, H-2, and He-4 as a test of the origin of the hydrogen superfluxes at solar minimum modulation

    NASA Technical Reports Server (NTRS)

    Beatty, J. J.; Garcia-Munoz, M.; Simpson, J. A.

    1985-01-01

    Low-energy 1-AU cosmic-ray spectra obtained using the IMP-8 satellite cosmic-ray telescope (Garcia-Munoz et al., 1975) at quiet times during the solar minimum of 1972-1977 are reported and combined with published data on that minimum and the previous one (1965), with a focus on the anomalous He-4 and heavy-nucleus spectra and proton and helium superfluxes observed in 1972-1977. The 56-MeV/nucleon H-2/H-1 and H-2/He-4 abundance ratios and the differential energy spectra are plotted versus time and solar modulation level over an entire cycle, and the proton and He superfluxes, which do not contribute to the anomalies, are attributed to the reduced levels of residual modulation present during 1972-1977.

  14. Kinetic description of the 3D electromagnetic structures formation in flows of expanding plasma coronas. Part 1: General

    NASA Astrophysics Data System (ADS)

    Gubchenko, V. M.

    2015-12-01

    In part I of the work, the physical effects responsible for the formation of low-speed flows in plasma coronas, coupled with formation of coronas magnetosphere-like structures, are described qualitatively. Coronal domain structures form if we neglect scales of spatial plasma dispersion: high-speed flows are accumulated in magnetic tubes of the open domains, while magnetic structures and low-speed flows are concentrated within boundaries of domains. The inductive electromagnetic process occurring in flows of the hot collisionless plasma is shown to underlie the formation of magnetosphere-like structures. Depending on the form of the velocity distribution function of particles (PDF), a hot flow differently reveals its electromagnetic properties, which are expressed by the induction of resistive and diamagnetic scales of spatial dispersion. These determine the magnetic structure scales and structure reconstruction. The inductive electromagnetic process located in lines of the plasma nontransparency and absorption, in which the structures of excited fields are spatially aperiodic and skinned to the magnetic field sources. The toroidal and dipole magnetic sources of different configurations are considered for describing the corona structures during the solar maximum and solar minimum.

  15. 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.

  16. 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.

  17. 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.

  18. Statistical study of the night-time F-layer dynamics at the magnetic equator in West Africa during the solar minimum period 1995-1997

    NASA Astrophysics Data System (ADS)

    Tanoh, K. S.; Adohi, B. J.-P.; Coulibaly, I. S.; Amory-Mazaudier, C.; Kobea, A. T.; Assamoi, P.

    2015-01-01

    In this paper, we report on the night-time equatorial F-layer height behaviour at Korhogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, in the West African sector during the solar minimum period 1995-1997. The data were collected from quarter-hourly ionograms of an Ionospheric Prediction Service (IPS) 42-type vertical sounder. The main focus of this work was to study the seasonal changes in the F-layer height and to clarify the equinox transition process recently evidenced at Korhogo during 1995, the year of declining solar flux activity. The F-layer height was found to vary strongly with time, with up to three main phases. The night-to-night variability of these morphological phases was then analysed. The early post-sunset slow rise, commonly associated with rapid chemical recombination processes in the bottom part of the F layer, remained featureless and was observed regardless of the date. By contrast, the following event, either presented like the post-sunset height peak associated with the evening E × B drift, or was delayed to the midnight sector, thus involving another mechanism. The statistical analysis of the occurrence of these events throughout the solar minimum period 1995-1997 revealed two main F-layer height patterns, each characteristic of a specific season. The one with the post-sunset height peak was associated with the northern winter period, whereas the other, with the midnight height peak, characterized the northern summer period. The transition process from one pattern to the other took place during the equinox periods and was found to last only a few weeks. We discuss these results in the light of earlier works.

  19. Towards Unraveling Multiscale Solar, Terrestrial, and Heliospheric Drivers of Global Change

    NASA Astrophysics Data System (ADS)

    Spence, H. E.; Schwadron, N. A.

    2011-12-01

    The Sun is emerging from a deep protracted solar minimum when Galactic Cosmic Rays (GCRs) achieved the highest levels observed in the space age, and the power, pressure, flux and magnetic flux of the solar wind were at their lowest levels. Even observations of the global heliosphere show remarkably rapid changes caused by dropping solar wind pressure. Does the recent anomalous deep solar minimum hint at larger changes in store and how anomalous was it both in terms of occurrence and severity? As these solar drivers, heliospheric conditions, and GCR fluxes change, we are forced to ask fundamental questions about their effects on our atmosphere, and even their implications for life on the planet. The Earth System is remarkably complex, driven both by internal variability and by these multiscale external drivers. The interplay between internal and external processes is further complicated in that elements of the same underlying variation may have multiple manifestations. Furthermore, these various manifestations affect the system in different ways and with magnitudes that are not typically well quantified. Consequently, unraveling the pathways of global change remain elusive, yet are also incredibly important to society. In this presentation, we outline early efforts of a group of broadly interdisciplinary scientists who are collectively exploring aspects of this grand challenge. We review potential agents of global change, including but not limited to: solar variability, ranging on time scales from billions of years down to fractions of a day; external variations of GCR imposed both by the heliosphere's passage through the local interstellar medium and by solar variability; and also internal processes such as geomagnetic field reversals. We review the evidence for such past changes by appealing to a variety of approaches and techniques, including: historic sunspot records; astronomical observations and models of Milky Way structures; chemical and isotopic tracers preserved in ice and ocean sediment cores; and even possible global change indicators in biodiversity records. Our goal is to identify such potential drivers as a first step towards establishing their relative importance.

  20. Interferometry of the e corona.

    PubMed

    Henderson, G

    1970-12-01

    Descriptions are given of Fabry-Perot spectrometer systems used in the total eclipses of 1965, 1966, and 1970 to observe the emission lines 5303 A, Fe XIV and 6374 A, Fe x at different points in the solar corona. Some results of coronal temperature measurements for the 12 November 1966 eclipse are presented. PMID:20094331

  1. The Day the Sun Stood Still: Using global Thermodynamic MHD Simulations to Infer the Structure of the Solar Corona and Inner Heliosphere during the Maunder Minimum

    NASA Astrophysics Data System (ADS)

    Riley, P.; Lionello, R.

    2012-12-01

    Observations of the Sun's corona during the space era have led to a picture of relatively constant, but modulating solar output and structure. Longer-term, more indirect measurements, such as from Beryllium-10, coupled by other albeit less reliable contemporaneous reports, however, suggest periods of significant departure from this standard, which, in turn, may have produced terrestrial weather effects. The Maunder Minimum, was one such epoch where: (1) Sunspots effectively disappeared for long intervals during a 70-year period; (2) Eclipse `observations' suggested the distinct lack of a visible K-corona but possible appearance of the F-corona; (3) Reports of aurora were notably reduced; and (4) Cosmic ray intensities at Earth were substantially higher. Using a global thermodynamic MHD model, we constructed a broad range of possible coronal configurations for the Maunder Minimum period and compared their predictions with these limited observational constraints. We conclude that the most likely state of the corona during the Maunder Minimum was not merely that of the 2008/2009 solar minimum, as has been suggested in several recent studies. Instead, we argue that the Sun's photospheric magnetic field was substantially reduced (by up to an order of magnitude) and this led to, and is consistent with the observations associated with this period. We discuss the implications of this work in terms of future long-term space weather forecasting.

  2. Coronae on Venus - Morphology, classification, and distribution

    SciTech Connect

    Pronin, A.A.; Stofan, E.R. JPL, Pasadena, CA )

    1990-10-01

    Venera 15/16 radar images of Venus show two circular features having no analog among the terrestrial planets: 21 coronae, which have a complex interior zone, and 11 corona-like features, which lack the ridge annuli of the coronae. Each of these two groups of features is subdivisible into three classes; coronae may be symmetrical, asymmetrical, and subdued, while corona-like structures are double, irregular, and heart-shaped. The various classes of both types of classes are interpreted as having a similar mode of origin, namely the uplift and volcanism generated by a thermal anomaly at depth, followed by gravitational relaxation. 37 refs.

  3. Coronae of Mnemosyne Regio - Morphology and origin

    SciTech Connect

    Stofan, E.R.; Head, J.W. )

    1990-01-01

    The Mnemosine Regio area of Venus contains seven of the circular-to-elliptical structures, characterized by an annulus of concentric ridges, that are known as coronae. Several corona-origin models are presently considered, and it is found that the processes associated with diapirism or hot-spots, and the gravitational relaxation of high topography, are most consistent with the topography and morphology of these coronae. The sequence of the formation and evolution of the coronae proceeds from regional volcanic and tectonic activity, through localized uplift and volcanism, to annulus and trough formation related to gravitational relaxation, and finally local volcanic flooding of the corona, annulus, and trough. 50 refs.

  4. MODELING THE LINE-OF-SIGHT INTEGRATED EMISSION IN THE CORONA: IMPLICATIONS FOR CORONAL HEATING

    SciTech Connect

    Viall, Nicholeen M.; Klimchuk, James A.

    2013-07-10

    One of the outstanding problems in all of space science is uncovering how the solar corona is heated to temperatures greater than 1 MK. Though studied for decades, one of the major difficulties in solving this problem has been unraveling the line-of-sight (LOS) effects in the observations. The corona is optically thin, so a single pixel measures counts from an indeterminate number (perhaps tens of thousands) of independently heated flux tubes, all along that pixel's LOS. In this paper we model the emission in individual pixels imaging the active region corona in the extreme ultraviolet. If LOS effects are not properly taken into account, erroneous conclusions regarding both coronal heating and coronal dynamics may be reached. We model the corona as an LOS integration of many thousands of completely independently heated flux tubes. We demonstrate that despite the superposition of randomly heated flux tubes, nanoflares leave distinct signatures in light curves observed with multi-wavelength and high time cadence data, such as those data taken with the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. These signatures are readily detected with the time-lag analysis technique of Viall and Klimchuk in 2012. Steady coronal heating leaves a different and equally distinct signature that is also revealed by the technique.

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

    PubMed

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

    2013-01-24

    It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1-3). The active corona needs additional heating to reach 2,000,000-4,000,000 K; this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic 'braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2 arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000 K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating. PMID:23344359

  6. 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.

  7. Chromospheres, transition regions, and coronas.

    PubMed

    Böhm-Vitense, E

    1984-02-24

    The increase in temperature outward from the surface of a stellar photosphere can be understood by looking at the local energy balance. The relatively high-density stellar photosphere is cooled effectively by radiative energy loss penetrating the optically thin corona. For the low-density chromosphere and corona, if the energy input cannot be balanced by radiative energy losses, the temperature will rise steeply, possibly up to 1 million degrees or more. Coronal heating and emission appear to be strongly influenced by magnetic fields, leading to large differences in x-ray emission for otherwise similar stars. Comparatively small variations are seen in the overall chromospheric emission of stars. Chromospheres are probably mainly heated by shock-wave energy dissipation, modified by magnetic fields. PMID:17737739

  8. 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."

  9. Early Results from the LRO Cosmic Ray Telescope for the Effects of Radiation (CRaTER) During this Historic Solar Minimum (Invited)

    NASA Astrophysics Data System (ADS)

    Spence, H. E.; Kasper, J. C.; Golightly, M. J.; Blake, J. B.; Mazur, J. E.; Townsend, L. W.; Case, A. W.; Looper, M. D.; Larsen, B. A.; Stubbs, T. J.; Zeitlin, C. J.; Semones, E.; Onsager, T. G.; Huang, C.; Jordan, A.

    2009-12-01

    We describe early results from a new instrument, the Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which is providing measurements of energetic particles while in orbit around the Moon onboard the Lunar Reconnaissance Orbiter (LRO) mission. CRaTER measures the effects of ionizing energy loss in matter due to penetrating solar energetic protons (SEP) and galactic cosmic rays (GCR), specifically in six silicon solid-state detectors and after interactions with tissue-equivalent plastic (TEP), a synthetic analog of human tissue. The CRaTER investigation quantifies the linear energy transfer (LET) spectrum in these materials through direct measurements with the lunar space radiation environment, particularly the interactions of ions with energies above 10 MeV. Combined with models of radiation transport through materials, CRaTER LET measurements constrain models of the biological effects of ionizing radiation in the lunar environment as well as provide valuable information on radiation effects on electronic systems in deep space. In addition to these human exploration goals, CRaTER measurement capabilities provide new insights on the spatial and temporal variability of the SEP and GCR populations and their interactions with the lunar surface. We present an overview of the CRaTER instrument, its exploration and science goals, and early results from flight observations obtained since LRO’s launch in June 2009 until present, an interesting interval during this historic solar minimum accompanied by record high GCR intensity.

  10. Study of cosmic-ray modulation during the recent deep solar minimum, mini maximum and intervening ascending phase of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Badruddin, B.; Aslam, O. P. M.

    After a prolonged and deep solar minimum at the end of cycle 23, current solar cycle 24 is one of the very low active cycles, weakest cycle in more than 50 years. These two periods of deep minima and mini maxima are separated by a period of increasing solar activity as measured by sunspot numbers. We study the cosmic ray relationship with the solar activity, heliospheric plasma and field parameters including the heliospheric current sheet (HCS), during these three periods (phases) of different level and nature of solar activity; (a) a deep minimum, (b) an increasing period and (c) a ‘mini’ maximum. We utilize the neutron monitor data from stations located around the globe to study the rigidity dependence of modulation during the two extremes, i.e., minima and maxima. We also study the time lag between the GCR intensity and various solar/interplanetary parameters separately during the three activity phases. Using the cosmic ray data of neutron monitors with different cutoff rigidities, we study the rigidity dependence of time lag during individual phases. The role/effectiveness of various parameters, including the HCS tilt, in modulating the GCR intensity during the three different phases has also been studied by correlation analysis. The relative importance of various physical processes during different phases and the implication of these results for modulation models are also discussed.

  11. Quiet-time properties of low-energy (less than 10 MeV per nucleon) interplanetary ions during solar maximum and solar minimum

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Reames, D. V.; Wenzel, K.-P.; Rodriguez-Pacheco, J.

    1990-01-01

    The abundances and spectra of 1-10 MeV per nucleon protons, He-3, He-4, C, O, and Fe have been exmained during solar quiet periods from 1978 to 1987 in an effort to investigate the recent suggestion by Wenzel et al. (1990) that the ions may be of solar origin. It is found that the intensities of the ions, other than O, fall by an order of magnitude between solar maximum and solar minimum, and that the greater than 1 MeV per nucleon ions exhibit weak streaming away from the sun. More significantly, the quiet-time ions during solar maximum have He-3-rich and Fe-rich abundances which are established characteristics of small impulsive solar flares. Thus, it is suggested that small unresolved impulsive flares make a substantial contribution to the 'quiet-time' fluxes. He-4 from these flares may also contribute strongly to the ion spectra that were reported for the 35-1600 keV energy range by Wenzel et al.

  12. Climatological study of the daytime occurrence of the 3-meter EEJ plasma irregularities over Jicamarca close to the solar minimum (2007 and 2008)

    NASA Astrophysics Data System (ADS)

    Guizelli, L. M.; Denardini, C. M.; Moro, J.; Resende, L. C. A.

    2013-01-01

    We have developed algorithms for conducting a seasonal statistical study of the occurrence of plasma irregularities in the Peruvian sector as a function of height and local time, covering two years of data (2007 and 2008) close to the solar minimum. This study was performed based on radar measurements carried out at the Jicamarca Radio Observatory (JRO), which is located in Lima-Peru (11.57°S, 76.52°W, dip: 2°N), under the magnetic equator. The statistical analysis runs over daily Range Time Intensity (RTI) maps obtained with the radar operating in the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) mode. Our results revealed relevant features of the diurnal variation of the plasma irregularities embedded in the equatorial electrojet, such as: a more often occurring presence of the 3-m irregularities during equinox, and a descent of the scattering profile in the morning hours, followed by its ascent in the afternoon.

  13. Response of the Midlatitude F2 Layer to Some Strong Geomagnetic Storms during Solar Minimum as Observed at Four Sites of the Globe

    NASA Astrophysics Data System (ADS)

    Kim, Vitaly P.; Hegai, Valery V.

    2015-12-01

    In this study, we documented the midlatitude F2-layer response to five strong geomagnetic storms with minimum Dst < -150 nT that occurred in solar minimum years using hourly values of the F2-layer critical frequency (foF2) from four ionosondes located in different hemispheres. The results were very limited, but they illustrated some peculiarities in the behavior of the F2-layer storm. During equinox, the characteristic ionospheric disturbance patterns over the Japanese station Wakkanai in the Northern Hemisphere and the Australian station Mundaring in the Southern Hemisphere were consistent with the well-known scenario by Prölss (1993); however, during a December solstice magnetic storm, both stations did not observe any noticeable positive ionospheric disturbances. Over the "near-pole" European ionosonde, clear positive ionospheric storms were not observed during the events, but the "far-from-pole" Southern Hemisphere station Port Stanley showed prominent enhancements in F2-layer peak electron density in all magnetic storms except one. No event produced noticeable nighttime enhancements in foF2 over all four ionosondes.

  14. Solar tides in the equatorial upper thermosphere: A comparison between AE-E data and the TIGCM for solstice, solar minimum conditions

    SciTech Connect

    Burrage, M.D.; Storz, M.F.; Abreu, V.J. ); Fesen, C.G. ); Roble, R.G. )

    1991-01-01

    Equatorial thermospheric tidal temperatures and densities inferred from Atmosphere Explorer E (AE-E) mass spectrometer data are compared with theoretical predictions from the National Center for Atmospheric Research Thermosphere/Ionisphere General Circulation Model (TIGCM) for solar minimum, solstice conditions. The thermospheric diurnal and semidiurnal tides are excited in situ by solar heating and by ion-neutral momentum coupling. Semidiurnal tides are also generated by upward propagating waves excited by heating in the lower atmosphere. The model calculations include all of these sources. The TIGCM reproduces the gross tidal features observed by the satellite, including the midnight temperature anomaly, and the diurnal phases are in good agreement for the densities of atomic oxygen and molecular nitrogen. However, for the neutral temperature, the predicted phases are 1-2 hours earlier than observed. In addition, the diurnal temperature and density amplitudes predicted by the model are considerably weaker than indicated by the AE-E measurements. The semidiurnal variations found in the observations agree well with the model for December solstice but not for June. The present results indicate that upward propagating tides from the lower atmosphere are responsible for at least half of the amplitude of the semidiurnal tide in the upper thermosphere.

  15. Prediction of galactic cosmic ray proton intensities from simultaneous proton and electron measurements during an A smaller than zero solar minimum

    NASA Astrophysics Data System (ADS)

    Heber, Bernd; Gieseler, Jan; Herbst, Klaudia; Kopp, Andreas; Müller-Mellin, Reinhold; Fichtner, Horst; Scherer, Klaus; Steinhilber, Friedhelm; Potgieter, Marius; Ferreira, Stefan

    Galactic cosmic rays (GCRs) are high energy charged particles, mainly protons and doubly ionized helium, originating in the galaxy and striking the Earth from all directions. There are three lines of defends which protect humans on Earth against this radiation. While the inner two shields, the atmosphere and magnetosphere, protect us against cosmic rays from several hundreds of MeV/nuc to about 15 GeV/nuc depending on geomagnetic latitude, the outer shield, the heliosphere, is reducing the intensities of particles with energies up to a few tens of GeV. This reduction depends on the solar activity and can vary by a few ten percent at 5 GeV to several orders of magnitude at a few tenth of MeV. Nevertheless, on a long journey to Mars galactic cosmic rays will pose a risk to astronauts of receiving a harmful dose of radiation. An often used tool to describe this modulation is the force-field solution. This approximation can not take into account the differences between positive and negative solar magnetic epochs or the difference in the modulation of electrons and protons. The current solar minimum is the lowest observed since the space area. The intensity of GCR electrons measured by the Kiel Electron Telescope aboard Ulysses exceed that of protons by more than 30

  16. Corona discharge of Titan's troposphere

    NASA Astrophysics Data System (ADS)

    Navarro-González, Rafael; Ramírez, Sandra I.

    1997-05-01

    The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charge particles leads to corona discharges which are characterized by low current densities. These electric discharges could induce a number of chemical reactions in the troposphere and hence it is of interest to explore such effects. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene + propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butene, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and an uncharacterized film deposit. We present their trends of formation as a function of discharge time in an ample interval and have derived their initial yields of formation. These results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is to low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, its production by corona processes and subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface.

  17. Re-visiting the atmospheric corona.

    PubMed

    Laven, Philip

    2015-02-01

    The atmospheric corona is a well-known diffraction phenomenon, typically seen as colored rings surrounding the Sun or Moon. In many respects, Fraunhofer diffraction provides a good explanation of the corona. As the angular sizes of the corona's rings are inversely proportional to the radius, r, of the spherical particles causing the corona, it should be easy to estimate the particle size from observations and photographs. Noting that some of the techniques commonly used for particle sizing based on diffraction theory can give misleading results for coronas caused by the scattering of sunlight, this paper uses Mie theory simulations to demonstrate that the inner 3 red rings of the corona have angular radii of θ≈16/r, 31/r, and 47/r, when θ is measured in degrees and r is measured in μm. PMID:25967838

  18. 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.

  19. Gravity over coronae and chasmata on Venus

    NASA Technical Reports Server (NTRS)

    Schubert, Gerald; Moore, William B.; Sandwell, David T.

    1994-01-01

    The global spherical harmonic model of Venus' gravity field MGNP60FSAAP, with horizontal resolution of about 600 km, shows that most coronae have little or no signature in the gravity field. Nevertheless, some coronae and some segments of chasmata are associated with distinct positive gravity anomalies. No corona has been found to have a negative gravity anomaly. The spatial coincidence of the gravity highs over four closely spaced 300- to 400-km-diameter coronae in Eastern Eistla Regio with the structures themselves is remarkable and argues for a near-surface or lithospheric origin of the gravity signals over such relatively small features. Apparent depths of compensation (ADCs) of the prominent gravity anomalies at Artemis, Latona, and Heng-o Coronae are about 150 to 200 km. The geoid/topography ratios (GTRs) at Artemis, Latona, and Heng-o Coronae lie in the range 32 to 35 m/km. The large ADCs and GTRs of Artemis, Latona, and Heng-o Coronae are consistent with topographically related gravity and a thick Venus lithosphere or shallowly compensated topography and deep positive mass anomalies due to subduction of underthrusting at these coronae. At arcuate segments of Hecate and Parga Chasmata ADCs are about 125 to 150 km, while those at Fauta Corona, four coronae in Eastern Eistla Regio, and an arcuate segment of Wester Parga Chasmata are about 75 km. The GTRs at Fauta Corona, the four coronae in eastern Eistla Regio, and the accurate segments of Hecate, Parga, and Western Parga Chasmata are about 12 to 21 m/km. By analogy with gravity anomalies of similar horizontal scale (600 km-several thousand kilometers) on the concave sides of terrestrial subduction zone arcs, which are due in large part to subducted lithosphere, it is inferred that the gravity anomalies on Venus are consistent with retrograde subduction at Artemis Chasma, along the northern and southern margins of Latona Coronam, and elsewhere along Parga and Hecate Chasmata.

  20. System for increasing corona inception voltage of insulating oils

    DOEpatents

    Rohwein, Gerald J.

    1998-01-01

    The Corona Inception Voltage of insulating oils is increased by repetitive cycles of prestressing the oil with a voltage greater than the corona inception voltage, and either simultaneously or serially removing byproducts of corona by evacuation and heating the oil.

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

    SciTech Connect

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

    2013-08-10

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

  2. NmF2 enhancement during ionospheric F2 region nighttime: A statistical analysis based on COSMIC observations during the 2007-2009 solar minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing; Zhang, Hui

    2015-11-01

    In this paper the global features of NmF2 enhancement occurring during ionospheric F2 region nighttime (the period when the sunlight is occulted by the Earth in the altitudinal range of ionospheric F2 region) and lasting for more than 2 h were investigated based on Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements during the 2007-2009 solar minimum. This nighttime enhancement of NmF2 mainly appears at the latitudes with dips larger than 45° in the winter hemisphere in solstice seasons. The magnitude of NmF2 enhancement reaches latitudinal maxima (minima) at the geomagnetic latitudes of about 40°-50° (60°-70°), with larger magnitudes in the northern winter hemisphere than in the southern winter hemisphere. The longitudinal variation of nighttime enhancement is also evident; especially the magnitude of NmF2 enhancement shows a significant longitudinal modulation in the southern winter hemisphere. The controlling factors of the spatial variations of NmF2 nighttime enhancement were analyzed. The longitudinal variation of NmF2 nighttime enhancement is suggested to be related to the longitudinal differences in background NmF2, thermospheric density, and interhemispheric plasma transport, and the latitudinal variation of NmF2 nighttime enhancement is possibly related to the latitudinal variations of geomagnetic inclination and the plasma storage in the topside ionosphere and the plasmasphere. The configuration of the geomagnetic field plays an important role in the longitudinal and latitudinal variations of NmF2 nighttime enhancement.

  3. Comparison of the extended solar minimum of 2006-2009 with the Spoerer, Maunder, and Dalton Grand Minima in solar activity in the past

    NASA Astrophysics Data System (ADS)

    McCracken, K. G.; Beer, J.

    2014-04-01

    We use cosmic radiation records (neutron monitor and the cosmogenic radionuclides, 10Be and 14C) as a proxy to compare the solar activity during the extended solar minimum 2006-2009, with that during the Grand Solar Minima and Maxima that occurred between 1391 and 2010. The inferred cosmic ray intensities during the Spoerer, Maunder, and Dalton Grand Minima were significantly greater than those during 2006-2009. The onset phases of the three Grand Minima extended over between two and five Schwabe (sunspot) cycles, the cosmic ray intensity at the Schwabe minima increasing from a value approximating that of 2006-2009, to substantially higher values later in the Grand Minimum. The minimum estimated strengths of the heliospheric magnetic field near Earth during the Grand Minima were 2.4 nT (Spoerer), <2.0 nT (Maunder), and 2.6 nT (Dalton), compared to 3.9 nT in 2009. We conclude that the periods of highest solar activity during the Maunder Minimum approximated those near the sunspot minima between 1954 and 1996. The average ratio of the maximum to minimum estimated HMF in the six Schwabe cycles in the Maunder Minimum is 1.54 (range 1.30-1.85) compared to 1.52 (1.31-1.63) for the modern epoch suggesting similar operation of the solar dynamo in both intervals. The onset phase of the Maunder Minimum extending over five Schwabe cycles, and the large increase in cosmic ray flux (and decrease in estimated heliospheric magnetic field), leads us to speculate that the magnetohydrodynamic amplification in the solar dynamo exhibits a relaxation time well in excess of the 11 year period of the Schwabe cycle.

  4. 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.

  5. The corona associated with solar filaments

    NASA Technical Reports Server (NTRS)

    Chapman, R. D.

    1981-01-01

    Spectroheliograms in high temperature ions such as Fe XV show the existence of both filaments that are brighter than the ambient corona and filaments that are darker than the ambient corona. The relationship of the filaments to photospheric magnetograms is described, and a possible physical mechanism to explain the differences is discussed.

  6. 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.

  7. 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].

  8. Corona structures on Venus - Models of origin

    NASA Technical Reports Server (NTRS)

    Stofan, Ellen R.; Bindschadler, Duane L.; Parmentier, E. M.; Head, James W.

    1991-01-01

    The present study assesses the mantle diapir models of corona origin using the basic characteristics of coronas: relatively raised topography, annuli of compressional ridges, volcanism, and peripheral trough. Both rising and and sinking diapirs are modeled quantitatively. Rising mantle diapirs are caused by heating at depth, while sinking mantle diapirs may result from cooling or a phase change causing increased density and negative buoyancy at the base of the lithosphere. The hotspot model is most consistent with the major characteristics of coronas, with gravitational relaxation occurring as a modificational process. The sinking mantle diapir produces dominant central compression that is not observed at coronas. Higher-resolution image and altimetry data from Magellan can be used to distinguish more fully between the two models. Coronas in various states of formation and degradation can be identified in the Venera 15/16 data, suggesting that the process may be continuing today.

  9. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.; Wagner, William (Technical Monitor)

    2001-01-01

    The solar corona, the hot, tenuous outer atmosphere of the Sun, exhibits many fascinating phenomena on a wide range of scales. One of the ways that the Sun can affect us here at Earth is through the large-scale structure of the corona and the dynamical phenomena associated with it, as it is the corona that extends outward as the solar wind and encounters the Earth's magnetosphere. The goal of our research sponsored by NASA's Supporting Research and Technology Program in Solar Physics is to develop increasingly realistic models of the large-scale solar corona, so that we can understand the underlying properties of the coronal magnetic field that lead to the observed structure and evolution of the corona. We describe the work performed under this contract.

  10. Inverted Temperature Loops in The Quiet Corona: Properties and Physical Origin

    NASA Astrophysics Data System (ADS)

    Huang, Z.; van der Holst, B.; Frazin, R. A.; Nuevo, F.; Vásquez, A. M.; Manchester, W.; Sokolov, I.; Gombosi, T. I.

    2013-12-01

    Huang et al. 2012 revealed the existence of inverted temperature ("down") loops, in which temperature decreases with height, as well as the usual ("up") loops, in which the temperature increases with height, in the quiet solar Corona. It was shown that the "down" loops are mostly located at low latitudes and "up" loops most often appear in high latitudes. A recent study by Nuevo et al. 2013 confirmed this discovery and further showed that the "down" loop population is greatest at solar minimum; and strongly decreases with solar activity. Moreover, the "down" loops were found to be associated with values of the plasma beta greater than about unity, while the "up" loops were associated with much smaller values of beta. Here, we review the properties of "up" and "down" loops, and employ a state-of-the-art global MHD model to understand the physics of these loops as well as to investigate their thermodynamic stability. The 3D MHD model uses a phenomenological wave dissipation model based on wave reflection (proportional to the Alfvén speed gradients) and turbulent dissipation.

  11. 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.

  12. Magnetohydrostatic modelling of stellar coronae

    NASA Astrophysics Data System (ADS)

    MacTaggart, D.; Gregory, S. G.; Neukirch, T.; Donati, J.-F.

    2016-02-01

    We introduce to the stellar physics community a method of modelling stellar coronae that can be considered to be an extension of the potential field. In this approach, the magnetic field is coupled to the background atmosphere. The model is magnetohydrostatic and is a balance between the Lorentz force, the pressure gradient and gravity. Analytical solutions are possible and we consider a particular class of equilibria in this paper. The model contains two free parameters and the effects of these on both the geometry and topology of the coronal magnetic field are investigated. A demonstration of the approach is given using a magnetogram derived from Zeeman-Doppler imaging of the 0.75 M⊙ M-dwarf star GJ 182.

  13. Remote Sensing of Low and Mid-Latitude Ionospheric Disturbances During Solar Minimum Using CITRIS and CERTO Measurements of TEC and Radio Scintillation

    NASA Astrophysics Data System (ADS)

    Siefring, C. L.; Bernhardt, P. A.

    2010-12-01

    Unique data on ionospheric plasma disturbances from the Naval Research Laboratory CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35 inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) three-frequency beacons transmitting at 150/400/1067 MHz and 2) the French global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons transmitting at 401.25 and 2036.25 MHz. CITRIS was operated in a complementary fashion with the C/NOFS satellite during most of its first year of operations; C/NOFS carries CERTO beacon along with in-situ diagnostics. CITRIS and ground receivers can simultaneously measure TEC and scintillations on different paths using CERTO on C/NOFS. When C/NOFS is not in view, CITRIS makes measurements from DORIS beacons and other LEO satellites. Because of the orbits CITRIS will always make measurements at the same longitude within 48 min of C/NOFS. The ability to look at multiple paths is unique and useful for studying the spatial extent and time duration of disturbances. The combination of TEC and scintillation measurements provides information on a range of scale-sizes from >1 km to about 100 m. The joint data set on plasma structures at low-latitudes is a focus of our presentation, with the addition of comparisons to CITRIS data taken at mid-latitude. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. The data covers large portions of the Earth (including the Pacific, African and South American sectors) during an unusually quite portion of the most recent solar minimum.

  14. Dynamics of the transition corona

    SciTech Connect

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

    2014-06-01

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

  15. The spatial distribution of coronae on Venus

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.; Schubert, G.; Bindschadler, D. L.; Janes, D. M.; Moersch, J. E.; Moore, W.; Olson, P.; Ratcliff, J. T.; Stofan, E. R.; Turcotte, D. L.

    1992-01-01

    Coronae on Venus are large, generally circular surface features that have distinctive tectonic, volcanic, and topographic expressions. They range in diameter from less than 200 km to at least 1000 km. Data from the Magellan spacecraft have now allowed complete global mapping of the spatial distribution of coronae on the planet. Unlike impact craters, which show a random (i.e., Poisson) spatial distribution, the distribution of coronae appears to be nonrandom. We investigate the distribution here in detail, and explore its implications in terms of mantle convection and surface modification processes.

  16. Tectonic patterns and regional stresses near Venusian coronae

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  17. Olivines and olivine coronas in mesosiderites

    NASA Technical Reports Server (NTRS)

    Nehru, C. E.; Zucker, S. M.; Harlow, G. E.; Prinz, M.

    1980-01-01

    The paper presents a study of olivines and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. Olivine composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; olivine occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified olivine orthopyroxenites. Fine-grained coronas surround olivine, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.

  18. Olivines and olivine coronas in mesosiderites

    NASA Astrophysics Data System (ADS)

    Nehru, C. E.; Zucker, S.; Harlow, G. E.; Prinz, M.

    1980-08-01

    The paper presents a study of olivines and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. Olivine composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; olivine occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified olivine orthopyroxenites. Fine-grained coronas surround olivine, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.

  19. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    1998-01-01

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

  20. Dynamics of the Transition Corona

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  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. Interplanetary Fast Shocks and Associated Drivers Observed through the Twenty-Third Solar Minimum by WIND Over its First 2.5 Years

    NASA Technical Reports Server (NTRS)

    Mariani, F.; Berdichevsky, D.; Szabo, A.; Lepping, R. P.; Vinas, A. F.

    1999-01-01

    A list of the interplanetary (IP) shocks observed by WIND from its launch (in November 1994) to May 1997 is presented. Forty two shocks were identified. The magnetohydrodynamic nature of the shocks is investigated, and the associated shock parameters and their uncertainties are accurately computed using a practical scheme which combines two techniques. These techniques are a combination of the "pre-averaged" magnetic-coplanarity, velocity-coplanarity, and the Abraham-Schrauner-mixed methods, on the one hand, and the Vinas and Scudder [1986] technique for solving the non-linear least-squares Rankine-Hugoniot shock equations, on the other. Within acceptable limits these two techniques generally gave the same results, with some exceptions. The reasons for the exceptions are discussed. It is found that the mean strength and rate of occurrence of the shocks appears to correlated with the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and start of solar cycle 23, which began around June 1996. Eighteen shocks appeared to be associated with corotating interaction regions (CIRs). The distribution of their shock normals showed a mean direction peaking in the ecliptic plane and with a longitude (phi(sub n)) in that plane between perpendicular to the Parker spiral and radial from the Sun. When grouped according to the sense of the direction of propagation of the shocks the mean azimuthal (longitude) angle in GSE coordinates was approximately 194 deg for the fast-forward and approximately 20 deg for the fast-reverse shocks. Another 16 shocks were determined to be driven by solar transients, including magnetic clouds. These shocks had a broader distribution of normal directions than those of the CIR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origin had normal orientation well off the ecliptic plane. No shock propagated with longitude phi(sub n) >= 220 +/- 10 deg, this would suggest strong hindrance to the propagation of shocks contra a rather tightly winding Parker spiral. Examination of the obliquity angle theta(sub Bn) (that between the shock normal and the upstream interplanetary magnetic field) for the full set of shocks revealed that about 58% was quasi-perpendicular, and some were very nearly perpendicular. About 32% of the shocks were oblique, and the rest (only 10%) were quasi-parallel, with one on Dec. 9, 1996 that showed field pulsations. Small uncertainty in the estimated angle theta(sub Bn) was obtained for about 10 shocks with magnetosonic Mach numbers between 1 and 2, hopefully significantly contributing to studies researching particle acceleration mechanisms at IP shocks, and to investigations where accurate values of theta(sub Bn) are crucial.

  3. Many Flares Make a Corona

    NASA Astrophysics Data System (ADS)

    Saar, Steven H.; Kashyap, V.; Drake, J.; Reeves, K.; Connors, A.

    2011-05-01

    It is well known that solar flare energies have a self-similar distribution. The number of flares, N, of any given energy, E, follows a power-law distribution, dN/dE E^(-alpha), over many orders of magnitude, with alpha 1.8. A similar distribution holds for stellar coronae, but in this case, typically alpha > 2. The value alpha=2 is important because it represents a threshold beyond which it is possible to ascribe all of the coronal luminosity to increasingly weaker, but more numerous, flares. Current methods to evaluate the flare distribution index alpha for stars are limited by two factors: they either depend on explicit detections of flares, or if the flare distribution itself is being modeled, then they are highly computation intensive and are thus slow. We have developed analytical methodology that substitutes for Monte Carlo simulations over a majority of the latter calculations. This causes improvements in computational speed of over 100x. We describe these methods below, and apply it to some simulated and observed data. This work was supported by CXC NASA contract NAS8-39073 and Chandra grant AR0-11001X.

  4. Heating of the stellar corona

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1986-01-01

    The present state of development of the theory of coronal heating is summarized. Coronal heating is the general cause of stellar X-ray emission, and it is also the cause of stellar mass loss in most stars. Hence a quantitive theory of coronal heating is an essential part of X-ray astronomy, and the development of a correct theory of coronal heating should be a primary concern of X-ray astronomers. The magnetohydrodynamical effects involved in coronal heating are not without interest in their own right, representing phenomena largely unknown in the terrestrial laboratory. Until these effects can be evaluated and assembled into a comprehensive theory of coronal heating for at least one star, the interpretation of the X-ray emissions of all stars is a phenomenological study at best, based on arbitrary organization and display of X-ray luminosity against bolometric luminosity, rotation rate, etc. The sun provides the one opportunity to pursue the exotic physical effects that combine to heat a stellar corona.

  5. Io's Corona: Asymmetries and AO Observations

    NASA Astrophysics Data System (ADS)

    Schneider, N. M.; Burger, M. H.; Sutton, S. E.; Dubson, M. A.

    2003-05-01

    Io's corona is the critical link between Io's atmosphere and the plasma torus. This region, from the exobase to the Hill sphere at about 6 RIo, has now been studied in enough detail to search for temporal variations, spatial asymmetries, and differences between atomic species. Our mutual eclipse observations reveal a relatively stable sodium corona with a significant asymmetry: Io's sub-Jupiter side is 50% brighter than the anti-Jupiter side (Burger et al., ApJ 563, 2001). We also find that Io's sodium corona falls off more steeply than the oxygen corona (measured by HST, Wolven et al., JGR 106, 2001). This effect exceeds that expected from their different ionization potentials, and is better explained by electron cooling near Io. Despite the promise of coronal studies, observations to date have required either the UV capability of HST or satellite mutual eclipses occurring every six years. We have undertaken an adaptive optics study of sodium in Io's corona to allow more routine diagnostic observations. Standard groundbased imaging suffers from the inevitable blurring of Io's 1.2"-wide disk with the 6" corona, fainter by up to 4 orders of magnitude. AO has the potential of imaging the corona by limiting the blurring of Io's disk. We will report on observations using the Air Force's 3.67m AEOS telescope at Haleakala, Maui, and our efforts to measure coronal emissions through rigorous differencing of on-band and off-band images. This work has been supported by NASA's Planetary Astronomy program and NSF's Advanced Technology and Instrumentation program.

  6. 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

  7. 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.

  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. Coronas and iridescence in mountain wave clouds.

    PubMed

    Shaw, Joseph A; Neiman, Paul J

    2003-01-20

    We use Fraunhofer diffraction theory and meterological data to determine the nature of cloud-particle distributions and the mean particle sizes required for interpreting photographs of coronas and iridescence in mountain wave clouds. Traditional descriptions of coronas and iridescence usually explain these optical phenomena as diffraction by droplets of liquid water. Our analysis shows that the photographed displays have mean particle sizes from 7.6 to 24.3 microm, with over half the cases requiring diffraction by small (approximatley 20 microm) quasispherical ice particles rather than liquid water droplets. Previous documentation of coronas produced by ice particles are limited to observations in cirrus clouds that appear to be composed of small ice crystals, whereas our observations suggest that coronas and iridescence quite often can be created by tiny quasispherical ice particles that might be unique to mountain wave clouds. Furthermore, we see that the dominant colors in mountain wave-cloud coronas are red and blue, rather than the traditionally described red and green. PMID:12570269

  10. Stellar coronas, X-rays, and Einstein

    SciTech Connect

    Stern, R.A.

    1984-07-01

    Observations of the sun at ultraviolet and X-ray wavelengths reveal a structure connected with the configuration of the solar magnetic field. The Einstein Observatory (HEAO 2), the first satellite to use an imaging X-ray telescope, searched for faint coronas on the basis of visual brightness and their proximity to the sun. Observed temperatures of transition regions between the chromosphere and the corona exceed 1,000,000 K. A possible correlation between X-ray luminosity and rotation rate has been observed and Einstein observations also indicated that stellar coronas showed changes in X-ray brightness during the most stable period of a star's life. Solar flares and transients, which generate substantial amounts of X-rays, radio waves and charged particles, are believed to be other properties of stellar coronas which change with age. Future missions such as NASA's Extreme Ultraviolet Explorer, the Advanced X-ray Astrophysics Facility and Space Telescope will enable astronomers to greatly increase their sampling of stellar coronas available for study. Observations also suggest the early development of a strong stellar dynamo due to X-ray activity in pre-main-sequence objects. It is hoped that the study of activity cycles in other stars will yield a greater understanding of the dynamo theory.

  11. Dynamics of the coronas of open star clusters

    NASA Astrophysics Data System (ADS)

    Danilov, V. M.; Putkov, S. I.; Seleznev, A. F.

    2014-12-01

    A method for distinguishing coronas in models of open star clusters is proposed. The method uses trajectories of stars that do not leave the coronas over time intervals t comparable to the mean lifetime τ of the clusters. Corona models are constructed for six numerical cluster models, and the direction and character of the dynamical evolution of the coronas are determined. Retrograde stellar motions are dominant in the coronas. In spite of some signs of dynamical instability of the coronas (small densities compared to the critical density and accelerated expansion of the coronas), the formation of close-toequilibrium density and phase-density distributions at distances from one to three cluster tidal radii from the cluster center can be seen. Approximations are constructed for the corona and cluster phase density using distributions that depend on three parameters (the parameters of the stellar motion in the Lindblad rotating coordinate system). This temporary equilibrium of the corona is due to balance in the number of starsmoving from the central areas of the cluster to the corona, and from the corona to the corona periphery or beyond. Evidence that corona stars can be gravitationally bound at distances out to four tidal radii from the cluster center is found: the presence of nearly periodic retrograde mean motions of a large number of corona stars in the Galactic plane; 91-99% of corona stars satisfy the gravitational binding criterion of Ross, Mennim and Heggie over time intervals that are close to the mean cluster lifetime. The escape rate from the corona is estimated for t ≥ τ, and found to be from 0.03 to 0.23 of the number of corona stars per violent relaxation time.

  12. Direct observation of laser guided corona discharges.

    PubMed

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-01-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere. PMID:26679271

  13. Seeing the solar corona in three dimensions

    NASA Astrophysics Data System (ADS)

    Vásquez, Alberto M.

    2016-03-01

    The large availability and rich spectral coverage of today's observational data of the solar corona, and the high spatial and temporal resolution provided by 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 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 on its future development and applications.

  14. Corona losses in HVdc bipolar lines

    SciTech Connect

    Corbellini, U.; Pelacchi, P.

    1996-07-01

    The problem related to the prediction of corona losses in HVdc bipolar lines has been solved, in the past, by means of semi-empirical monomial formulae. However, the proposed formulae that are simpler to use do not always give adequate calculation precision, while the formulae that provide the closest results require implicit functions of different complexity, which are difficult to apply; moreover, it is not possible to understand clearly what influence the variations of the different line parameters have on the losses themselves. The new monomial semi-empirical relationship, proposed to predict the corona losses in HVdc bipolar lines, is very simple to use; it highlights the dependence of power losses due to the corona effect by the different line parameters. The formula has been developed by elaborating a considerable amount of available experimental data.

  15. Direct observation of laser guided corona discharges

    PubMed Central

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-01-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere. PMID:26679271

  16. Abundances of Elements in Stellar Coronae

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy

    1998-01-01

    Interest in stellar coronal abundances was piqued several years ago by the launch of satellites that were able to study the compositions of coronae on stars other than the sun. Motivated by the possibility that other stellar coronae might share the First Ionization Potential (FIP) Effect solar abundance anomaly, we have in recent years been attempting to determine coronal element abundances in other stars. I will review these results, together with similar results reported in the literature, from a critical perspective of understanding the true uncertainties involved in the measurements. The importance of element abundances for coronal physics will be highlighted, and it will be shown that the differences in the chemical compositions of active stars allow us to draw new conclusions regarding the nature of stellar coronae and coronal heating.

  17. Direct observation of laser guided corona discharges

    NASA Astrophysics Data System (ADS)

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-12-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere.

  18. Stellar Coronae: The First Twenty - Five Years

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy

    2000-01-01

    Hot X-ray emitting coronae were detected on stars other than the Sun about twenty-five years ago. Within only a few years of the first detections, the Einstein Observatory had mapped out coronal activity across the HR diagram. These observations provided the foundations for a coarse theoretical understanding of the physical mechanisms responsible for hot coronae on stars that has changed relatively little in the intervening years: plasma trapped in magnetic structures generated by dynamo processes somewhere beneath the photosphere is heated by as yet unidentified mechanisms that appear to transfer kinetic energy from underlying convective regions of the stellar envelope into the outer atmosphere. This review will describe the observational advances that have lead to some further theoretical understanding of stellar coronae, including the first results from high resolution X-ray spectroscopy obtained by Chandra and XMM-Newton, and will highlight the observational directions needed to make further progress.

  19. 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...

  20. Device for generation of pulsed corona discharge

    DOEpatents

    Gutsol, Alexander F.; Fridman, Alexander; Blank, Kenneth; Korobtsev, Sergey; Shiryaevsky, Valery; Medvedev, Dmitry

    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.

  1. 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.

  2. 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.

  3. System for increasing corona inception voltage of insulating oils

    DOEpatents

    Rohwein, G.J.

    1998-05-19

    The Corona Inception Voltage of insulating oils is increased by repetitive cycles of prestressing the oil with a voltage greater than the corona inception voltage, and either simultaneously or serially removing byproducts of corona by evacuation and heating the oil. 5 figs.

  4. Ejection of the Corona at State Transitions: a Common Behavior in Microquasars?

    NASA Astrophysics Data System (ADS)

    Prat, L.; Rodriguez, J.

    2009-05-01

    The onset of most microquasar outbursts is characterized by a state transition between a Low/Hard State (LHS) and a High/Soft State (HSS). Besides drastic spectral and timing changes, this transition often shows a discrete ejection event detectable in the radio range. However, the exact nature of the ejected material and the mechanisms that give birth to these phenomena are yet to be unraveled. Recent simultaneous radio and X-ray observations on several sources point to a coronal nature of the ejected material. In the cases of GRS 1915+105, XTE J1550-564, and the 2002 outburst of GX 339-4, the flux of the Compton component decreases sharply just before an ejection is detected in the radio range. Finally, in the case of H1743-322, drastic physical changes occurred in the corona just before the state transition, compatible with the disappearance of part of this medium. Thus, the behavior of at least 4 microquasars points in the direction of an ejection of the corona at the state transition, feature that is yet to be confirmed (or infirmed) in the case of other available sources.

  5. 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.

  6. PEGylated nanoparticles: protein corona and secondary structure

    NASA Astrophysics Data System (ADS)

    Runa, Sabiha; Hill, Alexandra; Cochran, Victoria L.; Payne, Christine K.

    2014-09-01

    Nanoparticles have important biological and biomedical applications ranging from drug and gene delivery to biosensing. In the presence of extracellular proteins, a "corona" of proteins adsorbs on the surface of the nanoparticles, altering their interaction with cells, including immune cells. Nanoparticles are often functionalized with polyethylene glycol (PEG) to reduce this non-specific adsorption of proteins. To understand the change in protein corona that occurs following PEGylation, we first quantified the adsorption of blood serum proteins on bare and PEGylated gold nanoparticles using gel electrophoresis. We find a threefold decrease in the amount of protein adsorbed on PEGylated gold nanoparticles compared to the bare gold nanoparticles, showing that PEG reduces, but does not prevent, corona formation. To determine if the secondary structure of corona proteins was altered upon adsorption onto the bare and PEGylated gold nanoparticles, we use CD spectroscopy to characterize the secondary structure of bovine serum albumin following incubation with the nanoparticles. Our results show no significant change in protein secondary structure following incubation with bare or PEGylated nanoparticles. Further examination of the secondary structure of bovine serum albumin, ?2-macroglobulin, and transferrin in the presence of free PEG showed similar results. These findings provide important insights for the use of PEGylated gold nanoparticles under physiological conditions.

  7. Recycling of the Solar Corona's Magnetic Field

    NASA Astrophysics Data System (ADS)

    Close, R. M.; Parnell, C. E.; Longcope, D. W.; Priest, E. R.

    2004-09-01

    Magnetic fields play a dominant role in the atmospheres of the Sun and other Sun-like stars. Outside sunspot regions, the photosphere of the so-called quiet Sun contains myriads of small-scale magnetic concentrations, with strengths ranging from the detection limit of ~1016 Mx up to ~3×1020 Mx. The tireless motion of these magnetic flux concentrations, along with the continual appearance and disappearance of opposite-polarity pairs of fluxes, releases a substantial amount of energy that may be associated with a whole host of physical processes in the solar corona, not least the enigma of coronal heating. We find here that the timescale for magnetic flux to be remapped in the quiet-Sun corona is, surprisingly, only 1.4 hr (around 1/10 of the photospheric flux recycling time), implying that the quiet-Sun corona is far more dynamic than previously thought. Besides leading to a fuller understanding of the origins of magnetically driven phenomena in our Sun's corona, such a process may also be crucial for the understanding of stellar atmospheres in general.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

    1981-01-01

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

  11. Solar cycle variations in F-region Te in the vicinity of the midlatitude trough based on AE-C measurements at solar minimum and DE-2 measurements at solar maximum

    NASA Technical Reports Server (NTRS)

    Brace, Larry H.

    1990-01-01

    Magnetospheric energy deposited in the plasmasphere produces large enhancements in the electron temperature in the nightside ionosphere at the foot of the geomagnetic L shell that traverses the plasmapause. This temperature peak, which is associated with the midlatitude trough in electron density, often has a great enough amplitude to produce 630 nm emission known as a Sar-arc. The Atmosphere Explorer-C measurements made at solar minimum and the Dynamics Explorer-2 measurements made at solar maximum are used to illustrate how this signature of F-region electron heating changes with solar activity. Global empirical models of the electron temperature and density have not been able to resolve these features thus far because of their large movements with geomagnetic activity and because of the large bin sizes used in the models. It is not yet clear how this major feature of the F-region temperature structure could be included easily in the IRI model.

  12. 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.

  13. Radio seismology of the outer solar corona

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Observed oscillations of coronal loops in extreme ultraviolet (EUV) lines have been successfully used to estimate plasma parameters in the inner corona (< 0.2R0, where R0 is the solar radius). However, coronal seismology in EUV lines fails for higher altitudes because of rapid decrease in line intensity. We aim to use radio observations to estimate the plasma parameters of the outer solar corona (> 0.2R0). We used the large Ukrainian radio telescope URAN-2 to observe type IV radio bursts at the frequency range of 8-32 MHz during the time interval of 09:50-12:30 UT on April 14, 2011. The burst was connected to C2.3 flare, which occurred in AR 11190 during 09:38-09:49 UT. The dynamic spectrum of radio emission shows clear quasi-periodic variations in the emission intensity at almost all frequencies. Wavelet analysis at four different frequencies (29 MHz, 25 MHz, 22 MHz, and 14 MHz) shows the quasi-periodic variation of emission intensity with periods of ~ 34 min and ~ 23 min. The periodic variations can be explained by the first and second harmonics of vertical kink oscillation of transequatorial coronal loops, which were excited by the same flare. The apex of transequatorial loops may reach up to 1.2 R0 altitude. We derive and solve the dispersion relation of trapped magnetohydrodynamic (MHD) oscillations in a longitudinally inhomogeneous magnetic slab. The analysis shows that a thin (with width to length ratio of 0.1), dense (with the ratio of internal and external densities of ≥ 20) magnetic slab with weak longitudinal inhomogeneity may trap the observed oscillations. Seismologically estimated Alfvén speed inside the loop at the height of ~ 1 R0 is ~ 1000 km s-1. The magnetic field strength at this height is estimated as ~ 0.9 G. Extrapolation of magnetic field strength to the inner corona gives ~ 10 G at the height of 0.1 R0. Radio observations can be successfully used for the sounding of the outer solar corona, where EUV observations of coronal loops fail. Therefore, radio seismology of the outer solar corona is complementary to EUV seismology of the inner corona. The research leading to these results has received funding from the Austrian 'Fonds zur Förderung der wissenschaftlichen Forschung' under project P24740-N27.

  14. Radio seismology of the outer solar corona

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  15. 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.

  16. Helium corona-assisted air discharge

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Gao, Lei; Ji, Ailing; Cao, Zexian

    2011-10-01

    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.

  17. Protein coronas of Graphene and Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Podila, Ramakrishna; Ke, Pu; Brown, Jared; Rao, Apparao; Clemson Physics Team; East Carolina University Team

    2013-03-01

    We explored the effects of protein coating on the optical and vibrational properties of single-walled carbon nanotubes (SWCNTs) and bi- and few layer graphene nanosheets using micro-Raman spectroscopy, UV-visible absorption and electron microscopy. We found that bovine serum albumin (BSA) forms a hard corona on the surfaces of both graphene and SWCNTs. Our results suggest that the BSA hard corona acted as a weak acceptor to facilitate charge transfer from the carbon nanostructures. Notably, we observed that charge transfer occurred only in the case of SWNTs possibly due to their sharp and discrete electronic density of states. On the contrary, we find that graphene did not show a similar charge transfer due to its continuous energy dispersion. Furthermore, the nanostructures induced significant changes in the secondary structure of the BSA by relaxing their external ?-helices. These results are expected to guide controlled nanostructure-biomolecule interactions and prove beneficial in developing benign nanomaterials.

  18. Protein-targeted corona phase molecular recognition.

    PubMed

    Bisker, Gili; Dong, Juyao; Park, Hoyoung D; Iverson, Nicole M; Ahn, Jiyoung; Nelson, Justin T; Landry, Markita P; Kruss, Sebastian; Strano, Michael S

    2016-01-01

    Corona phase molecular recognition (CoPhMoRe) uses a heteropolymer adsorbed onto and templated by a nanoparticle surface to recognize a specific target analyte. This method has not yet been extended to macromolecular analytes, including proteins. Herein we develop a variant of a CoPhMoRe screening procedure of single-walled carbon nanotubes (SWCNT) and use it against a panel of human blood proteins, revealing a specific corona phase that recognizes fibrinogen with high selectivity. In response to fibrinogen binding, SWCNT fluorescence decreases by >80% at saturation. Sequential binding of the three fibrinogen nodules is suggested by selective fluorescence quenching by isolated sub-domains and validated by the quenching kinetics. The fibrinogen recognition also occurs in serum environment, at the clinically relevant fibrinogen concentrations in the human blood. These results open new avenues for synthetic, non-biological antibody analogues that recognize biological macromolecules, and hold great promise for medical and clinical applications. PMID:26742890

  19. 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.

  20. Protein-targeted corona phase molecular recognition

    NASA Astrophysics Data System (ADS)

    Bisker, Gili; Dong, Juyao; Park, Hoyoung D.; Iverson, Nicole M.; Ahn, Jiyoung; Nelson, Justin T.; Landry, Markita P.; Kruss, Sebastian; Strano, Michael S.

    2016-01-01

    Corona phase molecular recognition (CoPhMoRe) uses a heteropolymer adsorbed onto and templated by a nanoparticle surface to recognize a specific target analyte. This method has not yet been extended to macromolecular analytes, including proteins. Herein we develop a variant of a CoPhMoRe screening procedure of single-walled carbon nanotubes (SWCNT) and use it against a panel of human blood proteins, revealing a specific corona phase that recognizes fibrinogen with high selectivity. In response to fibrinogen binding, SWCNT fluorescence decreases by >80% at saturation. Sequential binding of the three fibrinogen nodules is suggested by selective fluorescence quenching by isolated sub-domains and validated by the quenching kinetics. The fibrinogen recognition also occurs in serum environment, at the clinically relevant fibrinogen concentrations in the human blood. These results open new avenues for synthetic, non-biological antibody analogues that recognize biological macromolecules, and hold great promise for medical and clinical applications.

  1. Protein-targeted corona phase molecular recognition

    PubMed Central

    Bisker, Gili; Dong, Juyao; Park, Hoyoung D.; Iverson, Nicole M.; Ahn, Jiyoung; Nelson, Justin T.; Landry, Markita P.; Kruss, Sebastian; Strano, Michael S.

    2016-01-01

    Corona phase molecular recognition (CoPhMoRe) uses a heteropolymer adsorbed onto and templated by a nanoparticle surface to recognize a specific target analyte. This method has not yet been extended to macromolecular analytes, including proteins. Herein we develop a variant of a CoPhMoRe screening procedure of single-walled carbon nanotubes (SWCNT) and use it against a panel of human blood proteins, revealing a specific corona phase that recognizes fibrinogen with high selectivity. In response to fibrinogen binding, SWCNT fluorescence decreases by >80% at saturation. Sequential binding of the three fibrinogen nodules is suggested by selective fluorescence quenching by isolated sub-domains and validated by the quenching kinetics. The fibrinogen recognition also occurs in serum environment, at the clinically relevant fibrinogen concentrations in the human blood. These results open new avenues for synthetic, non-biological antibody analogues that recognize biological macromolecules, and hold great promise for medical and clinical applications. PMID:26742890

  2. STOCHASTIC COUPLING OF SOLAR PHOTOSPHERE AND CORONA

    SciTech Connect

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

    2013-05-20

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

  3. Nonlinear Plasma Physics of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Priest, Eric R.

    2011-01-01

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

  4. Ionization fronts in negative corona discharges.

    PubMed

    Arrays, Manuel; Fontelos, Marco A; Trueba, Jos L

    2005-03-01

    We use a hydrodynamic minimal streamer model to study negative corona discharge. By reformulating the model in terms of a quantity called a shielding factor, we deduce laws for the evolution in time of both the radius and intensity of the ionization fronts. We also compute the evolution of the front thickness under the conditions for which it diffuses due to the geometry of the problem and show its self-similar character. PMID:15903643

  5. Coronae on Venus observations and models of origin

    NASA Technical Reports Server (NTRS)

    Stofan, E. R.

    1989-01-01

    The Venera 15/16 spacecraft revealed a number of features of unknown origin including coronae, elongate to circular structures with a complex interior surrounded by an annulus of concentric ridges. Eighteen coronae were identified in Venera 15/16 data of Venus; an additional thirteen possible coronae are found in Pioneer Venus and Arecibo data. Coronae, with maximum widths of 160 to over 650 km, are found primarily in two clusters in the Northern Hemisphere located to the east and west of Ishtar Terra. Another possible cluster is located in Themis Regio in the Southern Hemisphere. The majority of coronae are at least partially raised less than 1.5 km above the surrounding region, and over half are partially surrounded by a peripheral trough. A sequence of events for coronae has been determined through mapping. Prior to corona formation, regional compression or extension creates bands of lineaments along which coronae tend to later form. During the early stages of corona formation, relatively raised topography is produced by uplift and volcanic construction. The evolution of coronae and their general characteristics have been compared to two models of corona origin: hotspots and sinking mantle diapirs. In the hotspot or rising mantle diapir model, heating and melting at depth create uplift at the surface. Uplift is accompanied by central extension, facilitating volcanism. Gravitational relaxation of the uplifted region follows producing the compressional features within the annulus and the peripheral trough. Both models can predict the major characteristics and evolutionary sequence of coronae. The sinking diapir model does predict an early-time low and central compression as well as broadening and shallowing of the peripheral trough with time, all of which are not observed at current data resolution. In addition, the sinking mantle diapir mode predicts more simultaneous formation of the high topography, annulus and trough unlike the hotspot or rising mantle diapir mode. High resolution Magellan data will be used to distinguish between the two models of corona origin.

  6. Energy Storage in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Wolfson, R.

    2000-12-01

    Coronal mass ejections (CMEs) involve the expulsion of some 1016 g of solar material into interplanetary space, at hundreds of kilometers per second. In one common scenario, the energy that powers a CME is stored gradually in the solar corona until a triggering event, instability, or loss of equilibrium initiates the mass ejection. Energy is required to open the coronal magnetic field, to accelerate the ejected material, and to lift the ejecta against solar gravity. In this work, we develop a model corona that includes both field-aligned (force-free) and cross-field electric currents supporting a mass distribution like that of the coronal helmet streamers in which many CMEs originate. We show how magnetic shear, when coupled with an appropriate mass distribution, can result in the buildup of energy sufficient to power a CME. We explore a range of shear profiles, and show that the ability of the corona to store sufficient energy for a CME may depend on the details of the shear applied to its magnetic footpoints. This work was supported by NASA grant NAG5-9733 to Middlebury College.

  7. Stellar coronae from Einstein - Observations and theory

    NASA Technical Reports Server (NTRS)

    Rosner, R.; Vaiana, G. S.

    1980-01-01

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

  8. Differential rotation in the solar corona

    NASA Technical Reports Server (NTRS)

    Weber, Mark; Acton, Loren W.; Alexander, David

    1994-01-01

    The soft X-ray telescope (SXT) instrument on board the Yohkoh satellite was designed to observe the solar corona for over three years. It was shown in previous works that different tracers of solar rotation, each sensitive to a different part of the solar atmosphere, yield varying results for the latitude dependence of the rotation rate; the differential rotation measured using photospheric structures is markedly different from that obtained using coronal tracers. The long term observations of the solar corona by the SXT make it ideal for the investigation of coronal differential rotation. The soft X-ray emission of the solar corona is used to trace out the rotation rate at different latitudes. This is done by dividing the solar disk into a number of latitude strips and carrying out a power-spectrum analysis of the total soft X-ray intensity in each strip over a twelve week period of the Yohkoh observations. The results are compared with the differential rotation rates obtained from other coronal tracers.

  9. 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

  10. Reconnection Processes in the Chromosphere and Corona

    NASA Astrophysics Data System (ADS)

    Shibata, Kazunari

    2012-07-01

    Magnetic reconnection is a fundamental key physical process in magnetized plasmas. Recent space solar observations revealed that magnetic reconnection is ubiquitous in the solar chromospheres and corona. Especially recent Hinode observations has found various types of tiny chromospheric jets, such as chromospheric anemone jets (Shibata et al. 2007), penumbral microjets (Katsukawa et al. 2007), light bridge jets from sunspot umbra (Shimizu et al. 2009), etc. It was also found that the corona is full of tiny X-ray jets (Cirtain et al. 2007). Often they are seen as helical spinning jets (Shimojo et al. 2007, Patsourakos et al. 2008, Pariat et al. 2009, Filippov et al. 2009, Kamio et al. 2010) with Alfvenic waves (Nishizuka et al. 2008, Liu et al. 2009) and there are increasing evidence of magnetic reconnection in these tiny jets. We can now say that as spatial resolution of observations become better and better, smaller and smaller flares and jets have been discovered, which implies that the magnetized solar atmosphere consist of fractal structure and dynamics, i.e., fractal reconnection. Bursty radio and hard X-ray emissions from flares also suggest the fractal reconnection and associated particle acceleration. Since magnetohydrodynamics (MHD) does not contain any characteristic length and time scale, it is natural that MHD structure, dynamics, and reconnection, tend to become fractal in ideal MHD plasmas with large magnetic Reynolds number such as in the solar atmosphere. We would discuss recent observations and theories related to fractal reconnection in the chromospheres and corona, and discuss possible implication to chromospheric and coronal heating.

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

    NASA Astrophysics Data System (ADS)

    Cirtain, Jonathan Wesley

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

  12. Characterization of a Cylindrical Corona Discharge Reactor

    NASA Astrophysics Data System (ADS)

    Chung, K.-S.; Jung, Y. H.; Choi, Y. S.; Jung, S. W.; Kim, G. H.; Ko, K. C.; Han, Y. W.; Lee, C. W.; Chang, K. R.

    1999-11-01

    Temporal variation of current was measured in a pulsed corona discharge reactor for dissociation of NOx and SOx from the flue gas. Industrial scale reactor with height of 3 m and diameter of 0.5 m was made for dissociation of 500 liters of flue gas per hour with temperature of 80 - 120 degrees of Celcius. Reactor is made as a three-stage cyclinder-cylinder type with a rugged inner cylindrical electrode. Electric probes have been used to measure the current density variation with potential. Effects of gas temperature, flow rate, power input, and additives on the dissociation efficiency will be addressed.

  13. Large-scale volcanism associated with coronae on Venus

    NASA Technical Reports Server (NTRS)

    Roberts, K. Magee; Head, James W.

    1993-01-01

    The formation and evolution of coronae on Venus are thought to be the result of mantle upwellings against the crust and lithosphere and subsequent gravitational relaxation. A variety of other features on Venus have been linked to processes associated with mantle upwelling, including shield volcanoes on large regional rises such as Beta, Atla and Western Eistla Regiones and extensive flow fields such as Mylitta and Kaiwan Fluctus near the Lada Terra/Lavinia Planitia boundary. Of these features, coronae appear to possess the smallest amounts of associated volcanism, although volcanism associated with coronae has only been qualitatively examined. An initial survey of coronae based on recent Magellan data indicated that only 9 percent of all coronae are associated with substantial amounts of volcanism, including interior calderas or edifices greater than 50 km in diameter and extensive, exterior radial flow fields. Sixty-eight percent of all coronae were found to have lesser amounts of volcanism, including interior flooding and associated volcanic domes and small shields; the remaining coronae were considered deficient in associated volcanism. It is possible that coronae are related to mantle plumes or diapirs that are lower in volume or in partial melt than those associated with the large shields or flow fields. Regional tectonics or variations in local crustal and thermal structure may also be significant in determining the amount of volcanism produced from an upwelling. It is also possible that flow fields associated with some coronae are sheet-like in nature and may not be readily identified. If coronae are associated with volcanic flow fields, then they may be a significant contributor to plains formation on Venus, as they number over 300 and are widely distributed across the planet. As a continuation of our analysis of large-scale volcanism on Venus, we have reexamined the known population of coronae and assessed quantitatively the scale of volcanism associated with them. In particular, we have examined the percentage of coronae associated with volcanic flow fields (i.e., a collection of digitate or sheet-like lava flows extending from the corona interior or annulus); the range in scale of these flow fields; the variations in diameter, structure and stratigraphy of coronae with flow fields; and the global distribution of coronae associated with flow fields.

  14. 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.

  15. Relationship of coronae, regional plains and rift zones on Venus

    NASA Astrophysics Data System (ADS)

    Krassilnikov, A. S.; Kostama, V.-P.; Aittola, M.; Guseva, E. N.; Cherkashina, O. S.

    2012-08-01

    Coronae and rifts are the most prominent volcano-tectonic features on the surface of Venus. Coronae are large radial-concentric structures with diameters of 100 to over 1000 km. They have varied topographical shapes, radial and concentric fracturing and compressional tectonic structures are common for their annuli. Massive volcanism is also connected with some of the structures. Coronae are interpreted to be the result of updoming and fracturing on the surface due to interaction of mantle diapirs with the lithosphere and its subsequent gravitational relaxation. According to Stofan et al. (2001), two types of coronae are observed: type 1 - coronae that have annuli of concentric ridges and/or fractures (407 structures), and type 2 that have similar characteristics to type 1 but lack a complete annulus of ridges and fractures (107 structures). We analyzed 20% of this coronae population (we chose each fifth structure from the Stofan et al. (2001) catalog; 82 coronae of type 1 and 22 coronae of type 2, in total 104 coronae) for the (1) spatial distribution of rift structures and time relationship of rift zones activity with time of regional volcanic plains emplacement, and (2) tectonics, volcanism, age relative to regional plains and relationship with rifts. Two different age groups of rifts on Venus were mapped at the scale 1:50 000 000: old rifts that predate and young rifts that postdate regional plains. Most of young rifts inherit strikes of old rifts and old rifts are reworked by them. This may be evidence of rift-produced uplift zones that were probably mostly stable during both types of rifts formation. Evolution of distribution of rift systems with time (decreasing of distribution and localization of rift zones) imply thickening of the lithosphere with time. Coronae-producing mantle diapirism and uplift of mantle material in rift zones are not well correlated at least in time in most cases, because majority of coronae (77%) of both types has no genetic association with rifts. Majority of coronae (72%) were mostly active before regional plains formation, and only 3% appear to have begun to form after the plains emplacement, which may be also due to thickening of the lithosphere. According to the relationship with regional plains type 2 coronae are in general older than type 1 coronae. Three types of corona-related volcanic activity were observed: shield volcanoes and their clusters, as well as extensive lobate lava flows and smooth volcanic plains. Shield volcanoes during coronae evolution were mostly active before regional plains emplacement. Most active phase of volcanism of corona may not coincide with the time of the major tectonic activity of corona, as majority of coronae (77%) were most active before regional plains formation, but almost half of all coronae have traces of post regional plains volcanism. Detailed mapping and stratigraphic analysis of seven regions with 34 examples of coronae showed a similarity in the sequence of regional geologic units.

  16. Silver nanoparticle protein corona and toxicity: a mini-review.

    PubMed

    Durán, Nelson; Silveira, Camila P; Durán, Marcela; Martinez, Diego Stéfani T

    2015-01-01

    Silver nanoparticles are one of the most important materials in the nanotechnology industry. Additionally, the protein corona is emerging as a key entity at the nanobiointerface; thus, a comprehensive understanding of the interactions between proteins and silver nanoparticles is imperative. Therefore, literature reporting studies involving both single molecule protein coronas (i.e., bovine and human serum albumin, tubulin, ubiquitin and hyaluronic-binding protein) and complex protein coronas (i.e., fetal bovine serum and yeast extract proteins) were selected to demonstrate the effects of protein coronas on silver nanoparticle cytotoxicity and antimicrobial activity. There is evidence that distinct and differential protein components may yield a "protein corona signature" that is related to the size and/or surface curvature of the silver nanoparticles. Therefore, the formation of silver nanoparticle protein coronas together with the biological response to these coronas (i.e., oxidative stress, inflammation and cytotoxicity) as well as other cellular biophysicochemical mechanisms (i.e., endocytosis, biotransformation and biodistribution) will be important for nanomedicine and nanotoxicology. Researchers may benefit from the information contained herein to improve biotechnological applications of silver nanoparticles and to address related safety concerns. In summary, the main aim of this mini-review is to highlight the relationship between the formation of silver nanoparticle protein coronas and toxicity. PMID:26337542

  17. RADIO OBSERVATIONS OF THE SOLAR CORONA DURING AN ECLIPSE

    SciTech Connect

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

    2011-04-01

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

  18. Ozone synthesis initiated by a nanosecond corona in air

    SciTech Connect

    Amirov, R.Kh.; Asinovskii, E.I.; Samoilov, I.S.

    1992-07-01

    The dynamics of power absorption in a pulsed corona was investigated experimentally as a function of the polarity, amplitude, and voltage rise time. The experiment was compared with calculations using a capacitive model of the corona. The efficiency of ozone synthesis was measured as a function of the polarity and diameter of the discharging electrode.

  19. Protein corona - from molecular adsorption to physiological complexity.

    PubMed

    Treuel, Lennart; Docter, Dominic; Maskos, Michael; Stauber, Roland H

    2015-01-01

    In biological environments, nanoparticles are enshrouded by a layer of biomolecules, predominantly proteins, mediating its subsequent interactions with cells. Detecting this protein corona, understanding its formation with regards to nanoparticle (NP) and protein properties, and elucidating its biological implications were central aims of bio-related nano-research throughout the past years. Here, we discuss the mechanistic parameters that are involved in the protein corona formation and the consequences of this corona formation for both, the particle, and the protein. We review consequences of corona formation for colloidal stability and discuss the role of functional groups and NP surface functionalities in shaping NP-protein interactions. We also elaborate the recent advances demonstrating the strong involvement of Coulomb-type interactions between NPs and charged patches on the protein surface. Moreover, we discuss novel aspects related to the complexity of the protein corona forming under physiological conditions in full serum. Specifically, we address the relation between particle size and corona composition and the latest findings that help to shed light on temporal evolution of the full serum corona for the first time. Finally, we discuss the most recent advances regarding the molecular-scale mechanistic role of the protein corona in cellular uptake of NPs. PMID:25977856

  20. Origin of Corona-Dominated Topographic Rises on Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, S.; Stofan, E.

    1999-01-01

    Both large-scale mantel upwellings, comparable to terrestrial hotspots on Earth, and smaller scale mantel upwellings, known as coronae, occur on Venus. Corona-dominated rises have many of the characteristics of large scale mantle upwellings, or hotspots, such as broad topographic rises greater than 1000km in diameter and large positive gravity anomalies.

  1. The nanoparticle biomolecule corona: lessons learned - challenge accepted?

    PubMed

    Docter, D; Westmeier, D; Markiewicz, M; Stolte, S; Knauer, S K; Stauber, R H

    2015-10-01

    Besides the wide use of engineered nanomaterials (NMs) in technical products, their applications are not only increasing in biotechnology and biomedicine, but also in the environmental field. While the physico-chemical properties and behaviour of NMs can be characterized accurately under idealized conditions, this is no longer the case in complex physiological or natural environments. Herein, proteins and other biomolecules rapidly bind to NMs, forming a protein/biomolecule corona that critically affects the NMs' (patho)biological and technical identities. As the corona impacts the in vitro and/or in vivo NM applications in humans and ecosystems, a mechanistic understanding of its relevance and of the biophysical forces regulating corona formation is mandatory. Based on recent insights, we here critically review and present an updated concept of corona formation and evolution. We comment on how corona signatures may be linked to effects at the nano-bio interface in physiological and environmental systems. In order to comprehensively analyse corona profiles and to mechanistically understand the coronas' biological/ecological impact, we present a tiered multidisciplinary approach. To stimulate progress in this field, we introduce the potential impact of the corona for NM-microbiome-(human)host interactions and the novel concept of 'nanologicals', i.e., the nanomaterial-specific targeting of molecular machines. We conclude by discussing the relevant challenges that still need to be resolved in this field. PMID:26065524

  2. Chaotic characteristics of corona discharges in atmospheric air

    NASA Astrophysics Data System (ADS)

    Tan, Xiangyu; Zhang, Qiaogen; Wang, Xiuhuan; Sun, Fu; Zha, Wei; Jia, Zhijie

    2008-11-01

    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.

  3. Rings Around the Sun and Moon: Coronae and Diffraction

    ERIC Educational Resources Information Center

    Cowley, Les; Laven, Philip; Vollmer, Michael

    2005-01-01

    Atmospheric optical effects can teach much about physics and especially optics. Coronae--coloured rings around the sun or moon--are large-scale consequences of diffraction, which is often thought of as only a small effect confined to the laboratory. We describe coronae, how they are formed and experiments that can be conducted on ones in the sky.…

  4. Protein corona – from molecular adsorption to physiological complexity

    PubMed Central

    Docter, Dominic; Maskos, Michael

    2015-01-01

    Summary In biological environments, nanoparticles are enshrouded by a layer of biomolecules, predominantly proteins, mediating its subsequent interactions with cells. Detecting this protein corona, understanding its formation with regards to nanoparticle (NP) and protein properties, and elucidating its biological implications were central aims of bio-related nano-research throughout the past years. Here, we discuss the mechanistic parameters that are involved in the protein corona formation and the consequences of this corona formation for both, the particle, and the protein. We review consequences of corona formation for colloidal stability and discuss the role of functional groups and NP surface functionalities in shaping NP–protein interactions. We also elaborate the recent advances demonstrating the strong involvement of Coulomb-type interactions between NPs and charged patches on the protein surface. Moreover, we discuss novel aspects related to the complexity of the protein corona forming under physiological conditions in full serum. Specifically, we address the relation between particle size and corona composition and the latest findings that help to shed light on temporal evolution of the full serum corona for the first time. Finally, we discuss the most recent advances regarding the molecular-scale mechanistic role of the protein corona in cellular uptake of NPs. PMID:25977856

  5. Radiative Heating of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Moran, Thomas G.

    2011-10-01

    We investigate the effect of solar visible and infrared radiation on electrons in the Sun's atmosphere using a Monte Carlo simulation of the wave-particle interaction and conclude that sunlight provides at least 40% and possibly all of the power required to heat the corona, with the exception of dense magnetic flux loops. The simulation uses a radiation waveform comprising 100 frequency components spanning the solar blackbody spectrum. Coronal electrons are heated in a stochastic manner by low coherence solar electromagnetic radiation. The wave "coherence time" and "coherence volume" for each component is determined from optical theory. The low coherence of solar radiation allows moving electrons to gain energy from the chaotic wave field which imparts multiple random velocity "kicks" to these particles causing their velocity distribution to broaden or heat. Monte Carlo simulations of broadband solar radiative heating on ensembles of 1000 electrons show heating at per particle levels of 4.0 × 10-21 to 4.0 × 10-20 W, as compared with non-loop radiative loss rates of ≈1 × 10-20 W per electron. Since radiative losses comprise nearly all of the power losses in the corona, sunlight alone can explain the elevated temperatures in this region. The volume electron heating rate is proportional to density, and protons are assumed to be heated either by plasma waves or through collisions with electrons.

  6. Comparison Between the White-Light and Green Emission Coronae

    NASA Astrophysics Data System (ADS)

    Minarovjech, M.

    2000-04-01

    We have carried out a region-distribution study of both the white-light corona and green emission corona (Fe XIV 530.3 nm). The goal has been to find a relation between both the white-light and green emission coronae. Using the non-eclipse observations of the white-light coronal images obtained at Mauna Loa Mark-III with the K-coronameter a comparison is made with the green emission corona intensity as observed at Lomnický štít coronal station. It was found that there is a strong relation between regions of maximum intensity of the white-light coronal structures and the green emission corona intensity.

  7. Flexural ridges, trenches, and outer rises around coronae on Venus

    NASA Technical Reports Server (NTRS)

    Sandwell, David T.; Schubert, Gerald

    1992-01-01

    Flexural signatures outboard of Venusian coronal rims are examined with the purpose of inferring the thickness of the planet's elastic lithosphere. Topographic profiles of several prominent coronae which display clear trench and outer rise signatures are presented. Via a thin elastic plate flexure model to characterize the shape of the trench and outer rise, Venusian flexures are found to be similar in both amplitude and wavelength to lithospheric flexures seaward of subduction zones on earth. It is shown that circumferential fractures are concentrated in areas where the topography is curved downward, in good agreement with the high tensile stress predicted by the flexure models. Two scenarios for the development of the ridge-trench-outer rise flexural topography and circumferential fractures of coronae are presented. The first scenario involves reheating and thermal subsidence of the lithosphere interior to the corona, while the second involves expansion of the corona interior and roll back of the subducting lithosphere exterior to the corona.

  8. Coronae formation on Venus via extension and lithospheric instability

    NASA Astrophysics Data System (ADS)

    Piskorz, Danielle; Elkins-Tanton, Linda T.; Smrekar, Suzanne E.

    2014-12-01

    Over 500 quasi-circular volcano-tectonic features called coronae occur on Venus. They are believed to form via small-scale mantle upwellings, lithospheric instability, or a combination thereof. Coronae and rifts commonly occur together, including many coronae that lie outside of the fracture zone. However, the genetic link between the two has remained unclear. This paper proposes 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 hypothetical preexisting layer of dense material in the lithosphere. We show that a rift and its associated off-rift coronae could be genetically linked by the process of development of secondary ringlike dripping instabilities initiating at the plume margins. We calculate the resulting surface topographies, melt volumes, and Bouguer gravity anomalies and compare them to observations.

  9. Isothermal, Compton-heated coronae above accretion disks

    NASA Technical Reports Server (NTRS)

    Ostriker, Eve C.; Mckee, Christopher F.; Klein, Richard I.

    1991-01-01

    The structure of Compton-heated coronae above accretion disks is studied here by using analytic and numerical approaches are used here to determine the direct and scattered radiation reaching the base of the corona for a range of central source luminosities. It is found that the outer region of the corona is unaffected by multiple scattering in the interior, provided that the luminosity of the central source is sufficient below the Eddington limit. How attenuation and scattering by the corona affects the strength of chromospheric emission lines is determined, as is the condition for which the irradiation due to the central source exceeds the locally generated flux from the disk. Finally, it is shown that the stability analysis for irradiated accretion disks of Tuchman et al. is not substantially altered by the corona.

  10. Development of ac corona discharge modes at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed

    2011-02-01

    Corona discharges in gases exist under several distinctive forms. In this paper, a survey study has been made of ac corona discharge modes generated in some different gases fed in a wire-duct reactor with a constant rate of flowing at atmospheric pressure. The properties of different corona modes are analyzed under some condition transitions from Trichel pulses to a steady glow. In the course of the presented experimental work, numerous apparent contradictions with earlier observations necessitated further study and are given to provide more information on the physical mechanisms of the ac corona discharges. Furthermore, we have gained insight into some new technologies and applications of the environmentally friendly corona and plasma discharges.

  11. Unraveling the Miswired Connectome: A Developmental Perspective

    PubMed Central

    Di Martino, Adriana; Fair, Damien A.; Kelly, Clare; Satterthwaite, Theodore D.; Castellanos, F. Xavier; Thomason, Moriah E.; Craddock, R. Cameron; Luna, Beatriz; Leventhal, Bennett L.; Zuo, Xi-Nian; Milham, Michael P.

    2014-01-01

    Summary The vast majority of mental illnesses can be conceptualized as developmental disorders of neural interactions within the connectome, or developmental miswiring. The recent maturation of pediatric in vivo brain imaging is bringing within reach the identification of clinically meaningful brain-based biomarkers of developmental disorders. Even more auspicious, is the ability to study the evolving connectome throughout life, beginning in utero, which promises to move the field from topological phenomenology to etiological nosology. Here, we scope advances in pediatric imaging of the brain connectome as the field faces the challenge of unraveling developmental miswiring. We highlight promises while also providing a pragmatic review of the many obstacles ahead that must be overcome to significantly impact public health. PMID:25233316

  12. Unraveling the miswired connectome: a developmental perspective.

    PubMed

    Di Martino, Adriana; Fair, Damien A; Kelly, Clare; Satterthwaite, Theodore D; Castellanos, F Xavier; Thomason, Moriah E; Craddock, R Cameron; Luna, Beatriz; Leventhal, Bennett L; Zuo, Xi-Nian; Milham, Michael P

    2014-09-17

    The vast majority of mental illnesses can be conceptualized as developmental disorders of neural interactions within the connectome, or developmental miswiring. The recent maturation of pediatric in vivo brain imaging is bringing the identification of clinically meaningful brain-based biomarkers of developmental disorders within reach. Even more auspicious is the ability to study the evolving connectome throughout life, beginning in utero, which promises to move the field from topological phenomenology to etiological nosology. Here, we scope advances in pediatric imaging of the brain connectome as the field faces the challenge of unraveling developmental miswiring. We highlight promises while also providing a pragmatic review of the many obstacles ahead that must be overcome to significantly impact public health. PMID:25233316

  13. Observational Study of the Tridimensional Trajectory of Small White-Light Transients in the Inner Solar Corona

    NASA Astrophysics Data System (ADS)

    Lopez-Portela, C.; Blanco-Cano, X.; Stenborg, G.; Vourlidas, A.

    2013-05-01

    The physical mechanisms responsible for the low corona origin and subsequent interplanetary development of the small scale white-light transients, known as blobs, is relevant to the formation and acceleration mechanisms of the slow solar wind (Sheeley et al., 1997). Since they are considered to be reliable tracers of the slow solar wind, a statistical kinematical characterization of these faint features should provide to the understanding of its origins and acceleration. The vantage observing points provided by the SECCHI and LASCO imagers aboard the STEREO and SOHO missions, respectively, allows us to get a good estimation of their trajectory in the 3D space and hence perform a detailed analysis of their unprojected kinematical parameters. To address this issue, we have surveyed the SOHO/LASCO C2 and C3, and the STEREO/SECCHI COR 1 and COR 2 databases for the year 2007 through 2010 (i.e., a period comprising the declining phase of the extended past solar minimum and the ascending phase of cycle 24) and selected about 100 blob-like features. The selection of events was facilitated by the scarce presence of coronal mass ejection events during this period, and it was limited to ±30° from the Sun's equator. The restricted latitudinal range is inspired by the work of Wang et al. (1998), who proposed that blobs are liberated from the cusp of helmet steamers. Two methods have been considered for the determination of the 3D kinematical parameters: (1) the tie-pointing and triangulation technique (Thompson W.T., 2008) and (2) the Height-Time analysis as developed by Mierla et al. (2008). In this work, we report on the set of transients studied by both techniques, discuss the limitations encountered on the determination of the 3D trajectories, and explore their significance on understanding the physical mechanisms behind the generation/propagation of the slow solar wind.

  14. Warm and optically thick dissipative coronae above accretion disks

    NASA Astrophysics Data System (ADS)

    Różańska, A.; Malzac, J.; Belmont, R.; Czerny, B.; Petrucci, P.-O.

    2015-08-01

    Context. In past years, several observations of AGN and X-ray binaries suggested the existence of a warm (T ~ 0.5 - 1 keV) and optically thick (τcor ~ 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. Aims: We investigate the properties of such warm, optically thick coronae and put constraints on their existence. Methods: 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 that it is cooled by Compton scattering, with the underlying dissipative disk providing photons to the corona. Results: Our analytic calculations show that a dissipative thick corona (τcor in the range 10-12) on top of a standard accretion disk can reach temperatures of the order of 0.5-1 keV in its upper layers provided that the disk is passive. However, in the absence of strong magnetic fields, the requirement of a Compton cooled corona in hydrostatic equilibrium in the vertical direction sets an upper limit on the Thomson optical depth τcor ≲ 5. We show that this value cannot be exceeded independently of the accretion disk parameters. However, magnetic pressure can extend this result to larger optical depths. Namely, a dissipative corona might have an optical depth up to ~20 when the magnetic pressure is 100 times higher than the gas pressure. Conclusions: The observation of warm coronae with Thomson depth larger than ≃5 puts tight constraints on the physics of the accretion disk/corona systems and requires either strong magnetic fields or vertical outflows to stabilize the system.

  15. 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".

  16. Deep solar minimum and global climate changes

    PubMed Central

    Hady, Ahmed A.

    2013-01-01

    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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. The photosphere-corona Interface: enrichement of the corona in low FIP elements and helium shells

    NASA Astrophysics Data System (ADS)

    Bazin, C.; Koutchmy, S.; Lamy, P.; Veselovski, I.

    2014-12-01

    Slitless consecutive spectra were obtained during the contacts of the last total solar eclipses (2008, 2009, 2010, 2012, et 2013). They allowed to show that the overabundance of low First Ionisation Potential (FIP) elements (Fe II, Ti II, Ba II) in the corona comes from the low layers of the solar atmosphere, just near and above the temperature minimum region of the high photosphere. All spectra are recorded with a fast CCD/CMOS camera, with an equivalent radial resolution of 60 milliarcseconds, or 45 km in the solar atmosphere, above a solar edge not affected by the parasitic light like it is outside of total eclipse conditions. Many emission lines of low FIP elements appear in regions situated between 200 to 600 km above the solar limb defined by the true continuum measured between the lines. This continuum appears at these altitudes where the beta of the plasma is near 1. The He I 4713 and He II 4686 (Paschen alpha line) shells appear at the height of 800 km above the solar edge and higher. The light curve I = f(h) of each ion is located at a particuliar altitude in the solar atmosphere. The scale height corresponds to a density variation, which allows to evaluate the temperature thanks to the hydrostatic equilibrium assumption. Moreover, with ionised Titanium lines taken as markers, we show a similarity between the photosphere-corona interface and the prominence-corona interface. We discuss the role of the magnetic field and the ambipolar diffusion for supplying the corona in mass, without taking into account the role of spicules. The photo-ionisation of the helium lines by the EUV coronal lines is illustrated thanks to an extract of SDO/AIA coronal stacked image simultaneously obtained.

  2. The X-ray corona of Procyon

    NASA Technical Reports Server (NTRS)

    Schmitt, J. H. M. M.; Harnden, F. R., Jr.; Rosner, R.; Peres, G.; Serio, S.

    1985-01-01

    X-ray emission from the nearby system Procyon A/B (F5 IV + DF) was detected, using the IPC (Imaging Proportional Counter) on board the Einstein Observatory. Analysis of the X-ray pulse height spectrum suggests that the observed X-ray emission originates in Procyon A rather than in the white dwarf companion Procyon B, since the derived X-ray temperature, log T = 6.2, agrees well with temperatures found for quiescent solar X-ray emission. Modeling Procyon's corona with loops characterized by some apex temperature Tmax and emission length scale L, it is found that Tmax is well constrained, but L, and consequently the filling factor of the X-ray emitting gas, are essentially unconstrained even when EUV emission from the transition region is included in the analysis.

  3. Doping of polyaniline by corona discharge

    SciTech Connect

    Job, A.E.; Giacometti, J.A.; Mattoso, L.H.C.

    1998-07-01

    It is well known that conductive polyaniline (PANI) films are usually doped by immersing dedoped PANI films in HCl solution. This paper shows that a corona discharge can be successfully employed to dope thin films of polyaniline coated on poly (ethylene terephthalate) films. Similarly to the conventional doping with aqueous HCl the process is accompanied by a color change from blue to green and the conductivity can be tuned in the range from 10{sup {minus}10} up to 0.3 Scm{sup {minus}1}. Such new doping method presents several advantages over the conventional one namely, dry process, use of no chemicals, rapidity and no dopant migration. Measurements also showed that the conductivity persists for a long time as observed for films prepared in chemical solution doping. It is believed that this novel technique could be employed in a continuous doping process aiming to produce films with large area for anti electrostatic packing applications.

  4. Corona-discharge-initiated mine explosions

    SciTech Connect

    Sacks, H.K.; Novak, T.

    2005-10-01

    Strong circumstantial evidence suggests that lightning has initiated methane explosions in abandoned and sealed areas of underground coal mines. The Mine Safety and Health Administration (MSHA) investigated several of these occurrences within recent years. The investigated explosions occurred at significant depths, ranging from 700 to 1200 ft. Data from the National Lightning Detection Network indicated a strong correlation between the times and locations of the explosions with those of specific lightning strikes. This paper proposes that corona discharge from a steel borehole casing is the most likely mechanism responsible for these ignitions. A recently investigated mine explosion and fire at a depth greater than 1000 ft was selected for this study. Computer simulations were performed, using data collected at the mine site. CDEGS software from Safe Engineering Services & Technologies, Ltd. and MaxwellSV from Ansoft Corporation were used for the simulations.

  5. Dynamics and energetics of the solar corona

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.

    1992-01-01

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

  6. 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, ι Hor, HR 7291, τ Boo, and α 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 τ Boo no FIP effect is present, while ι Hor, HR 7291, and α 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.

  7. Flue gas cleaning by pulse corona streamer

    NASA Astrophysics Data System (ADS)

    Keping, Yan; Vanveldhuizen, E. M.

    1993-03-01

    Currents of up to 600 A are obtained on a corona wire of 1 m length by applying DC and pulse voltage. The energy input is upto 6 J/pulse. The current duration is between 100 and 600 ns, and depends strongly on the DC voltage, the stray inductance and resistance of the circuit. Breakdown can be avoided by choosing the appropriate values for the components in the pulse circuit. Average electron energies resolved in space and in time are obtained by means of optical spectroscopy for corona discharge streamers in a wire cylinder reactor in air and in flue gas. The electron energy for primary streamers in air is found to be in the order of 10 eV and increases slightly with the pulse voltage and is almost constant during the streamer propagation. The electron energy for the secondary streamer is about a factor two lower near the anode where its optical emission is strong. In the gap and near the cathode, its emission is much less and the electron energy is another three times lower. The secondary streamer is limited in length, because it must satisfy the stability field requirement. The larger attachment coefficient of flue gas in the low field region explains that in flue gas the secondary streamer is shorter than in air. The ratio of the electrical energy input into primary and secondary streamers is controlled by the length of the electrical pulse. Measurements of NO removal from flue gas indicate that a pulse duration equal to the time required by the primary streamer to cross the gap gives the highest cleaning efficiency.

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

    SciTech Connect

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

    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.

  9. 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.

  10. NASA's SDO Sees Unraveling Solar Prominence - Duration: 20 seconds.

    NASA Video Gallery

    An elongated solar prominence rose up above the sun’s surface and slowly unraveled on Feb. 3, 2016, as seen in this video by NASA’s Solar Dynamics Observatory, or SDO. The sun appears to move in th...

  11. What the cell surface does not see: The gene vector under the protein corona.

    PubMed

    Motta, Simona; Rondelli, Valeria; Cantu, Laura; Del Favero, Elena; Aureli, Massimo; Pozzi, Daniela; Caracciolo, Giulio; Brocca, Paola

    2016-05-01

    The fate of lipid-based nanovectors, used in genetic targeting inside cells, depends on their behavior in biological media. In fact, during both in vitro and in vivo transfection, nanovectors come in contact with proteins that compete for their surface and build the protein corona, their true biological identity while engaging the cell membrane. Nonetheless, after cell internalization, the efficacy of transfection may depend also on structural modifications that occurred under the protein cover, following interaction with biological fluids. Here, based on previous in vivo experiments, two widely used lipid mixtures, namely DOTAP/DOPC and DC-Chol/DOPE, were identified as paradigms to investigate the impact of the inner structure of nanovectors on the transfection efficiency, all being proficiently internalized. The evolution of the inner structure of cationic lipoplexes and nanoparticles based on such lipid mixtures, following interaction with human plasma, could be unraveled. Particles were investigated in high dilution, approaching the biosimilar conditions. Data have demonstrated that the modulation of their inner structure depends on their lipid composition and the plasma concentration, still preserving the genetic payload. Interestingly, protein contact induces a variety of inner structures with different perviousness, including reshaping into cubic phases of different porosity, sometimes observed upon interaction between carrier-lipids and cell-lipids. Cubic reshaping is of biological relevance, as lipid cubic phases have been recently associated to both fusogenicity and to the readiness in releasing the payload to the final target via endosomal escape. PMID:26852100

  12. 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.

  13. Statistical characteristic in time-domain of direct current corona-generated audible noise from conductor in corona cage

    NASA Astrophysics Data System (ADS)

    Li, Xuebao; Cui, Xiang; Lu, Tiebing; Ma, Wenzuo; Bian, Xingming; Wang, Donglai; Hiziroglu, Huseyin

    2016-03-01

    The corona-generated audible noise (AN) has become one of decisive factors in the design of high voltage direct current (HVDC) transmission lines. The AN from transmission lines can be attributed to sound pressure pulses which are generated by the multiple corona sources formed on the conductor, i.e., transmission lines. In this paper, a detailed time-domain characteristics of the sound pressure pulses, which are generated by the DC corona discharges formed over the surfaces of a stranded conductors, are investigated systematically in a laboratory settings using a corona cage structure. The amplitude of sound pressure pulse and its time intervals are extracted by observing a direct correlation between corona current pulses and corona-generated sound pressure pulses. Based on the statistical characteristics, a stochastic model is presented for simulating the sound pressure pulses due to DC corona discharges occurring on conductors. The proposed stochastic model is validated by comparing the calculated and measured A-weighted sound pressure level (SPL). The proposed model is then used to analyze the influence of the pulse amplitudes and pulse rate on the SPL. Furthermore, a mathematical relationship is found between the SPL and conductor diameter, electric field, and radial distance.

  14. Unraveling the complex metabolic nature of astrocytes

    PubMed Central

    Bouzier-Sore, Anne-Karine; Pellerin, Luc

    2013-01-01

    Since the initial description of astrocytes by neuroanatomists of the nineteenth century, a critical metabolic role for these cells has been suggested in the central nervous system. Nonetheless, it took several technological and conceptual advances over many years before we could start to understand how they fulfill such a role. One of the important and early recognized metabolic function of astrocytes concerns the reuptake and recycling of the neurotransmitter glutamate. But the description of this initial property will be followed by several others including an implication in the supply of energetic substrates to neurons. Indeed, despite the fact that like most eukaryotic non-proliferative cells, astrocytes rely on oxidative metabolism for energy production, they exhibit a prominent aerobic glycolysis capacity. Moreover, this unusual metabolic feature was found to be modulated by glutamatergic activity constituting the initial step of the neurometabolic coupling mechanism. Several approaches, including biochemical measurements in cultured cells, genetic screening, dynamic cell imaging, nuclear magnetic resonance spectroscopy and mathematical modeling, have provided further insights into the intrinsic characteristics giving rise to these key features of astrocytes. This review will provide an account of the different results obtained over several decades that contributed to unravel the complex metabolic nature of astrocytes that make this cell type unique. PMID:24130515

  15. Solar Corona on 10.21.2010 - Duration: 9 seconds.

    NASA Video Gallery

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

  16. 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.

  17. On the transition from stable positive glow corona to streamers

    NASA Astrophysics Data System (ADS)

    Liu, Lipeng; Becerra, Marley

    2016-06-01

    A 2D numerical simulation of the transition from stable positive glow corona to streamers in coaxial cylindrical configuration is presented. The hydrodynamic model with several convection-dominated continuity equations together with Poisson equation are solved with consideration of the ionization layer. The transition from a stable positive glow corona produced under a DC voltage to streamers is investigated under a sudden change of the applied voltage. The critical rate of rise of voltage required for the transition from positive glow to streamer corona is evaluated with a voltage ramp. By introducing either physical or numerical instabilities into the model, streamers with filamentary structures are observed, which produce a sudden increase of the discharge current by more than two orders of magnitude. It is also found that the surface electric field of the corona-generating conductor deviates from the onset electric field, casting doubts about the validity of Kaptzov’s approximation to evaluate the transition from stable glow to streamers.

  18. Scintillation effects on radio wave propagation through solar corona

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.

    1984-01-01

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

  20. Experimental Tools to Study Molecular Recognition within the Nanoparticle Corona

    PubMed Central

    Landry, Markita P.; Kruss, Sebastian; Nelson, Justin T.; Bisker, Gili; Iverson, Nicole M.; Reuel, Nigel F.; Strano, Michael S.

    2014-01-01

    Advancements in optical nanosensor development have enabled the design of sensors using syntheticmolecular recognition elements through a recently developed method called Corona Phase MolecularRecognition (CoPhMoRe). The synthetic sensors resulting from these design principles are highly selective for specific analytes, and demonstrate remarkable stability for use under a variety of conditions. An essential element of nanosensor development hinges on the ability to understand the interface between nanoparticles and the associated corona phase surrounding the nanosensor, an environment outside of the range of traditional characterization tools, such as NMR. This review discusses the need for new strategies and instrumentation to study the nanoparticle corona, operating in both in vitro and in vivo environments. Approaches to instrumentation must have the capacity to concurrently monitor nanosensor operation and the molecular changes in the corona phase. A detailed overview of new tools for the understanding of CoPhMoRe mechanisms is provided for future applications. PMID:25184487

  1. Expectation of ozone generation in alternating current corona discharges

    NASA Astrophysics Data System (ADS)

    Yehia, Ashraf; Mizuno, Akira

    2012-03-01

    An analytical study was made in this paper to calculate the ozone generation inside an ac corona discharge reactor. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature and stressed by an ac voltage. Concentration of the ozone generated inside the reactor was measured as a function of the ac corona current under different discharge conditions. An empirical equation was derived from the experimental results for calculating the ozone concentration generated inside the reactor. The results, that have been calculated by using the derived equation, have agreed with the experimental results over the whole range of the investigated parameters. Therefore, the derived equation represents a suitable criterion for expecting the ozone concentration that will generate by ac coronas in dry air fed coaxial wire-cylinder reactors under any discharge conditions in range of the investigated parameters.

  2. Solar Corona on 08.01.2010 - Duration: 38 seconds.

    NASA Video Gallery

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

  3. Decomposition characteristics of toluene by a corona radical shower system.

    PubMed

    Wu, Zu-liang; Gao, Xiang; Luo, Zhong-yang; Ni, Ming-jiang; Cen, Ke-fa

    2004-01-01

    Non-thermal plasma technologies offer an innovative approach to decomposing various volatile organic compounds(VOCs). The decomposition of toluene from simulated flue gas was investigated using a pipe electrode with nozzles for the generation of free radicals. Corona characteristics and decomposition of toluene were investigated experimentally. In addition, the decomposition mechanism of toluene was explored in view of reaction rate. The experimental results showed that the humidity of additional gas has an important effect on corona characteristics and modes and stable streamer corona can be generated through optimizing flow rate and humidity of additional gas. Applied voltage, concentration of toluene, humidity of toluene and resident time are some important factors affecting decomposition efficiency. Under optimizing conditions, the decomposition efficiency of toluene can reach 80%. These results can give a conclusion that the corona radical shower technology is feasible and effective on the removal of toluene in the flue gas. PMID:15495952

  4. 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.

  5. Solar corona/prominence seen through the White Light Coronograph

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The solar corona and a solar prominence as seen through the White Light Coronograph, Skylab Experiment S052, on January 17, 1974. This view was reproduced from a television transmission made by a TV camera aboard the Skylab space station in Earth orbit. The bright spot is a burn in the vidicon. The solar corona is the halo around the Sun which is normally visible only at the time of solar eclipse by the Moon. The Skylab coronography uses an externally-mounted disk system which occults the brilliant solar surface while allowing the fainter radiation of the corona to enter an annulus and be photographed. A mirror system allows either TV viewing of the corona or photographic recording of the image.

  6. Shock Acceleration in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Sandroos, Arto

    2010-03-01

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

  7. Miniature Dual-Corona Ionizer for Bipolar Charging of Aerosol

    PubMed Central

    Qi, Chaolong; Kulkarni, Pramod

    2015-01-01

    A corona-based bipolar charger has been developed for use in compact, field-portable mobility size spectrometers. The charger employs an aerosol flow cavity exposed to two corona ionizers producing ions of opposite polarity. Each corona ionizer houses two electrodes in parallel needle-mesh configuration and is operated at the same magnitude of corona current. Experimental measurement of detailed charge distribution of near-monodisperse particles of different diameter in the submicrometer size range showed that the charger is capable of producing well-defined, consistent bipolar charge distributions for flow rates up to 1.5 L/min and aerosol concentration up to 107 per cm3. For particles with preexisting charge of +1, 0, and −1, the measured charge distributions agreed well with the theoretical distributions within the range of experimental and theoretical uncertainties. The transmission efficiency of the charger was measured to be 80% for 10 nm particles (at 0.3 L/min and 5 μA corona current) and increased with increasing diameter beyond this size. Measurement of uncharged fractions at various combinations of positive and negative corona currents showed the charger performance to be insensitive to fluctuations in corona current. Ion concentrations under positive and negative unipolar operation were estimated to be 8.2 × 107 and 3.37 × 108 cm−3 for positive and negative ions; the n·t product value under positive corona operation was independently estimated to be 8.5 × 105 s/cm3. The ion concentration estimates indicate the charger to be capable of “neutralizing” typical atmospheric and industrial aerosols in most measurement applications. The miniature size, simple and robust operation makes the charger suitable for portable mobility spectrometers. PMID:26512158

  8. Venus - Aine Corona (F-MIDR 59S164)

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This Magellan radar image shows a region approximately 300 kilometers (180 miles) across, centered on 59 degrees south latitude, 164 degrees east longitude and located in a vast plain to the south of Aphrodite Terra. The data for this image was obtained in January 1991. The large circular structure near the center of the image is a corona, approximately 200 kilometers (120 miles) in diameter and provisionally named Aine Corona. Just north of Aine Corona is one of the flat-topped volcanic constructs known as 'pancake' domes for their shape and flap-jack appearance. This pancake dome is about 35 kilometers (21 miles) in diameter and is thought to have formed by the eruption of an extremely viscous lava. Another pancake dome is located inside the western parts of the annulus of the corona fractures. Complex fracture patterns like the one in the upper right of the image are often observed in association with coronae and various volcanic features. They are thought to form because magma beneath the surface follows pre-existing fracture patterns. When eruptions or other movements of the magma occur, the magma drains from the fractures and the overlying surface rock collapses. Other volcanic features associated with Aine Corona include a set of small domes, each less than 10 kilometers (6 miles) across, located along the southern portion of the annulus of fractures, and a smooth, flat region in the center of the corona, probably a relatively young lava flow. The range of volcanic features associated with coronae suggests that volcanism plays a significant role in their formation.

  9. Electric-Field Instrument With Ac-Biased Corona Point

    NASA Technical Reports Server (NTRS)

    Markson, R.; Anderson, B.; Govaert, J.

    1993-01-01

    Measurements indicative of incipient lightning yield additional information. New instrument gives reliable readings. High-voltage ac bias applied to needle point through high-resistance capacitance network provides corona discharge at all times, enabling more-slowly-varying component of electrostatic potential of needle to come to equilibrium with surrounding air. High resistance of high-voltage coupling makes instrument insensitive to wind. Improved corona-point instrument expected to yield additional information assisting in safety-oriented forecasting of lighting.

  10. Millimeter wave radiation sources visible in solar corona

    NASA Astrophysics Data System (ADS)

    Urpo, S.; Pohjolainen, S.; Krüger, A.

    1994-10-01

    Coronal millimeter wave sources (CMMS) have been observed at radio frequencies 22 90 GHz (at wavelengths 3 13 mm). The observed CMMS have been classified into three different categories according to their time scale and relation to other wave-length events. The CMMS indicate enhancement of electron density in the corona, as well as magnetic loop structures. The CMMS are evidence of dynamical processes taking place at the lower levels of the corona, propagating into the higher levels.

  11. 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.

  12. 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.

  13. 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.

  14. Treatment of rheumatoid arthritis: Unraveling the conundrum.

    PubMed

    Zampeli, Evangelia; Vlachoyiannopoulos, Panayiotis G; Tzioufas, Athanasios G

    2015-12-01

    Rheumatoid arthritis (RA) is a heterogeneous disease with a complex and yet not fully understood pathophysiology, where numerous different cell-types contribute to a destructive process of the joints. This complexity results into a considerable interpatient variability in clinical course and severity, which may additionally involve genetics and/or environmental factors. After three decades of focused efforts scientists have now achieved to apply in clinical practice, for patients with RA, the "treat to target" approach with initiation of aggressive therapy soon after diagnosis and escalation of the therapy in pursuit of clinical remission. In addition to the conventional synthetic disease modifying anti-rheumatic drugs, biologics have greatly improved the management of RA, demonstrating efficacy and safety in alleviating symptoms, inhibiting bone erosion, and preventing loss of function. Nonetheless, despite the plethora of therapeutic options and their combinations, unmet therapeutic needs in RA remain, as current therapies sometimes fail or produce only partial responses and/or develop unwanted side-effects. Unfortunately the mechanisms of 'nonresponse' remain unknown and most probable lie in the unrevealed heterogeneity of the RA pathophysiology. In this review, through the effort of unraveling the complex pathophysiological pathways, we will depict drugs used throughout the years for the treatment of RA, the current and future biological therapies and their molecular or cellular targets and finally will suggest therapeutic algorithms for RA management. With multiple biologic options, there is still a need for strong predictive biomarkers to determine which drug is most likely to be effective, safe, and durable in a given individual. The fact that available biologics are not effective in all patients attests to the heterogeneity of RA, yet over the long term, as research and treatment become more aggressive, efficacy, toxicity, and costs must be balanced within the therapeutic equation to enhance the quality of life in patients with RA. PMID:26515757

  15. Unravelling the enigma of Perthes disease

    PubMed Central

    2013-01-01

    Perthes disease is an idiopathic avascular necrosis of a juvenile hip. Although 2010 marked a century since it was first described, the aetiology remains unknown. It is suggested that adverse socioeconomic circumstances may be a key precipitant. This work describes recent studies that explore the disease epidemiology. Descriptive studies include a case register from Merseyside, hospital discharge data from Scotland, analysis of the world’s largest community disease register (General Practice Research Database [GPRD]) and a systematic review of incidence. Analytical studies include a nested case-controlled study in the GPRD and a hospital case-controlled study. The studies demonstrated a striking north–south divide in the UK incidence of Perthes disease, similar to that seen in many adult diseases. There was a sustained fall in disease frequency in all studies, with a narrowing of the north–south divide. There was a strong association with area deprivation, independent of living in an urban environment. Internationally, equatorial regions were unaffected by disease and northern Europe had the highest incidence, which was primarily a function of race although latitude was an independent predictor. Individual characteristics associated with the disease were congenital anomalies of the genitourinary tract and a structural abnormality of arterial calibre. Despite a falling incidence, Perthes disease remains an important cause of child morbidity and exemplifies socioeconomic inequalities. A deprivation-related exposure, acting early in development, appears critical. The aetiological factor in Perthes disease remains elusive but it is likely that unravelling this enigma may unlock additional secrets pertaining to the developmental origins of this and other diseases. PMID:23838491

  16. Common Periodicities of Gle's and Solar Corona

    NASA Astrophysics Data System (ADS)

    Perez-Peraza, Jorge Alberto; Velasco Herrera, Victor Manuel; Miroshnichenko, Leonty I.; Vashenyuk, Eduard V.

    Using different techniques of Wavelet Analysis, particularly, cross-wavelet coherence and the Global Wavelet Spectrum, we analyze data of intensity of 70 GLE's of the solar cycles 17 -23 vs data of the solar corona. We have found common periodicities of short period (2.8, 5.2 and 27 days), medium period (0.5, 1.2, 1.8, 3.2) as well as a the 4.6 and 11 yrs. periodicities. The two later are continuous over all the time interval, with a high synchronization and linear phase. In contrast, the short and medium periodicities are rather concentrated around the maximums of solar cycles, with some few cases in the minimums of solar activity, and present in general a complex phase. Results are discussed in terms of the works of others authors related to periodicities of the solar dynamo, solar atmosphere, interplanetary space and cosmic rays. We also evaluated the power anomalies of solar activity by means of sunspots, and have found that anomalies are positives when the GLE 's are of high intensity (higher than 100

  17. Titan's corona: The contribution of exothermic chemistry

    NASA Astrophysics Data System (ADS)

    De La Haye, V.; Waite, J. H.; Cravens, T. E.; Nagy, A. F.; Johnson, R. E.; Lebonnois, S.; Robertson, I. P.

    2007-11-01

    The contribution of exothermic ion and neutral chemistry to Titan's corona is studied. The production rates for fast neutrals N 2, CH 4, H, H 2, 3CH 2, CH 3, C 2H 4, C 2H 5, C 2H 6, N( 4S), NH, and HCN are determined using a coupled ion and neutral model of Titan's upper atmosphere. After production, the formation of the suprathermal particles is modeled using a two-stream simulation, as they travel simultaneously through a thermal mixture of N 2, CH 4, and H 2. The resulting suprathermal fluxes, hot density profiles, and energy distributions are compared to the N 2 and CH 4 INMS exospheric data presented in [De La Haye, V., Waite Jr., J.H., Johnson, R.E., Yelle, R.V., Cravens, T.E., Luhmann, J.G., Kasprzak, W.T., Gell, D.A., Magee, B., Leblanc, F., Michael, M., Jurac, S., Robertson, I.P., 2007. J. Geophys. Res., doi:10.1029/2006JA012222, in press], and are found insufficient for producing the suprathermal populations measured. Global losses of nitrogen atoms and carbon atoms in all forms due to exothermic chemistry are estimated to be 8.3×10 Ns and 7.2×10 Cs.

  18. Measuring electron temperature in the extended corona

    NASA Technical Reports Server (NTRS)

    Hassler, Donald M.; Gardner, L. D.; Kohl, John L.

    1992-01-01

    A technique for measuring electron temperature in the extended corona from the line profile of the electron scattered component of coronal H I Ly alpha produced by Thomson scattering of chromospheric Ly alpha emission is discussed. Because of the high thermal velocity of electrons at coronal temperatures (approximately 6800 km/s at T(sub e) = 1,500,000 K) the effect of nonthermal velocities and solar wind flows on the electron velocity distribution are negligible. However, the low electron mass which is responsible for the high thermal velocity also results in a very wide profile (approximately equal to 50 A). This wide profile, together with an intensity that is three orders of magnitude weaker than the resonantly scattered component of Ly alpha makes the direct measurement of T(sub e) a challenging observational problem. An evaluation of this technique based on simulated measurements is presented and the subsequent instrumental requirements necessary to make a meaningful determination of the electron temperature are discussed. Estimates of uncertainties in the measured electron temperature are related to critical instrument parameters such as grating stray light suppression.

  19. Measuring the Electron Temperature in the Corona

    NASA Technical Reports Server (NTRS)

    Davila, Joseph; SaintCyr, Orville C.; Reginald, Nelson

    2008-01-01

    We report on an experiment to demonstrate the feasibility of a new method to obtain the electron temperature and flow speed in the solar corona by observing the visible Kcoronal spectrum during the total solar eclipse on 29 March 2006 in Libya. Results show that this new method is indeed feasible, giving electron temperatures and speeds of 1.10 $\\pm$ 0.05 MK, 103.0 $\\pm$ 92.0 $kmsA{-l}$; 0.98 $\\pm$ 0.12 MK, 0.0 + 10.0 $kmsA{-1)s; 0.70 $\\pm$ 0.08 MK, 0.0 + 10.0 $kmsA{-l)$ at l.l{\\it R)$ {\\odot}$ in the solar north, east and west, respectively, and 0.93 $\\pm$ 0.12 MK, 0.0 + 10.0 $kmsA{-l}$ at 1.2{\\it R}$ {\\odot}$ in the solar east. This new technique could be easily used from a space-based platform in a coronagraph to produce two dimensional maps of the electron temperature and bulk flow speed at the base of the solar wind useful for the study of heliospheric structure and space weather.

  20. The theory of positive glow corona

    NASA Astrophysics Data System (ADS)

    Morrow, R.

    1997-11-01

    A theory for the current and light pulses of positive glow corona from a point in air is presented; this phenomenon was first observed as an apparently continuous glow by Michael Faraday. Results are obtained, in concentric sphere geometry, for air at atmospheric pressure, by solving the continuity equations for electrons, positive ions, negative ions and metastable oxygen molecules, coupled with Poisson's equation. A series of `saw-toothed' current pulses of period about 0022-3727/30/22/008/img1 is predicted with a DC current level. Accompanying the current peaks are discrete pulses of light 30 ns wide. Successive `shells' of positive ions, from successive current pulses, carry 96% of the mean current. The mean current - voltage relationship has the classic square-law form. The seed electrons required for successive pulses are detached from negative ions by metastable oxygen molecules. Photo-ionization is crucial for the discharge at the anode and for the formation of negative ions throughout the gap. The pulse frequency varies with applied voltage and is found to be approximately proportional to the positive-ion mobility. The surface electric field at the central electrode remains close to Peek's onset field. The origin of onset streamers is explained and sub-microsecond voltage pulses are found to produce streamers. The results for concentric-cylinder electrodes are described briefly.

  1. Heating of the Solar Corona: Review

    NASA Astrophysics Data System (ADS)

    Erdélyi, R.

    2005-06-01

    The heating of solar and stellar chromospheres and coronae are one of the key fundamental and yet unresolved questions of modern space and plasma physics. In spite of the multi-fold efforts spanning over half a century including the many superb technological advances and theoretical developments (both analytical and computational) the unveiling of the subtles of coronal heating still remained an exciting job for the 21st century! In the present paper I review the various popular heating mechanisms put forward in the existing extensive literature. The heating processes are, somewhat arbitrarily, classified as hydrodynamic (HD), magnetohydrodynamic (MHD) or kinetic based on the model medium. These mechanisms are further divided based on the time scales of the ultimate dissipation involved (i.e. AC and DC heating, turbulent heating). In particular, attention is paid to discuss shock dissipation, Landau damping, mode coupling, resonant absorption, phase mixing, and, reconnection. Finally, I briefly review the various observational consequences of the many proposed heating mechanisms and confront them with high-resolution ground-based and satellite data currently available.

  2. Direct observation of a single nanoparticle-ubiquitin corona formation

    NASA Astrophysics Data System (ADS)

    Ding, Feng; Radic, Slaven; Chen, Ran; Chen, Pengyu; Geitner, Nicholas K.; Brown, Jared M.; Ke, Pu Chun

    2013-09-01

    The advancement of nanomedicine and the increasing applications of nanoparticles in consumer products have led to administered biological exposure and unintentional environmental accumulation of nanoparticles, causing concerns over the biocompatibility and sustainability of nanotechnology. Upon entering physiological environments, nanoparticles readily assume the form of a nanoparticle-protein corona that dictates their biological identity. Consequently, understanding the structure and dynamics of a nanoparticle-protein corona is essential for predicting the fate, transport, and toxicity of nanomaterials in living systems and for enabling the vast applications of nanomedicine. Here we combined multiscale molecular dynamics simulations and complementary experiments to characterize the silver nanoparticle-ubiquitin corona formation. Notably, ubiquitins competed with citrates for the nanoparticle surface, governed by specific electrostatic interactions. Under a high protein/nanoparticle stoichiometry, ubiquitins formed a multi-layer corona on the particle surface. The binding exhibited an unusual stretched-exponential behavior, suggesting a rich binding kinetics. Furthermore, the binding destabilized the α-helices while increasing the β-sheet content of the proteins. This study revealed the atomic and molecular details of the structural and dynamic characteristics of nanoparticle-protein corona formation.The advancement of nanomedicine and the increasing applications of nanoparticles in consumer products have led to administered biological exposure and unintentional environmental accumulation of nanoparticles, causing concerns over the biocompatibility and sustainability of nanotechnology. Upon entering physiological environments, nanoparticles readily assume the form of a nanoparticle-protein corona that dictates their biological identity. Consequently, understanding the structure and dynamics of a nanoparticle-protein corona is essential for predicting the fate, transport, and toxicity of nanomaterials in living systems and for enabling the vast applications of nanomedicine. Here we combined multiscale molecular dynamics simulations and complementary experiments to characterize the silver nanoparticle-ubiquitin corona formation. Notably, ubiquitins competed with citrates for the nanoparticle surface, governed by specific electrostatic interactions. Under a high protein/nanoparticle stoichiometry, ubiquitins formed a multi-layer corona on the particle surface. The binding exhibited an unusual stretched-exponential behavior, suggesting a rich binding kinetics. Furthermore, the binding destabilized the α-helices while increasing the β-sheet content of the proteins. This study revealed the atomic and molecular details of the structural and dynamic characteristics of nanoparticle-protein corona formation. Electronic supplementary information (ESI) available: Experimental and computational methods as well as supporting figures. See DOI: 10.1039/c3nr02147e

  3. Towards a Comprehensive Model of Coronae Formation on Venus

    NASA Astrophysics Data System (ADS)

    Smrekar, S. E.; Stofan, E. R.

    1996-03-01

    Coronae are roughly circular volcano-tectonic features that are interpreted as a manifestation of small-scale upwelling and are unique to Venus. The topographic expression of coronae is highly variable, ranging from domes to plateaus, with or without moats or single or multiple outer rises. Two outstanding questions in the study of coronae are how the full range of topographic profiles are produced and the relationship between topography and the annulus of fractures that characterize coronae. Domes, plateaus, and outer rises can be formed by thermal relaxation of a topographic high due to a rising and cooling of a hot upwelling, but interior depressions, isolated rims, and inner highs with rims, troughs and outer rises, can not. Relaxation can produce fracture annuli, but observed annuli frequently do not occur on the outer rise, as predicted by relaxation models. A new model of upwelling is presented that can produce nearly the full range of observed topographic morphologies and commonly observed off-set between tectonic fracture annuli and the outer topographic rise. The cold lithosphere at the edge of the plume head is sucked downward until the thermal anomaly dissipates, explaining the limited subduction qualities of some coronae. This model differs from past approaches to corona formation in the use of temperature-dependent rheology and the prediction of pressure-release melting. Other aspects that may be key to the development of certain coronae topographic features are the presence of a low-density depleted mantle layer beneath the high viscosity thermal lithosphere and the cooling of the thermal lithosphere during upwelling. This approach could provide constraints on thermal history.

  4. 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.

  5. Discovering New R Coronae Borealis Stars

    NASA Astrophysics Data System (ADS)

    Clayton, Geoffrey C.; Tisserand, Patrick; Welch, Douglas L.; LeBleu, Amy

    2016-01-01

    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 dwarfs, or a final helium shell flash in a PN central star. The evidence pointing toward a white-dwarf merger or a final-flash origin for RCB stars is contradictory. The distribution on the sky and radial velocities of the RCB stars tend toward those of the bulge population but a much larger sample of stars is needed to determine the true population. We need to discover RCB stars much more efficiently. In order to do this, we have used a series of IR color-color cuts, using the recent release of the WISE All-Sky Catalog, to produce a sample of 2200 candidates that may yield over 200 new RCB star identifications. Most of these candidates do not have lightcurves, the traditional technique of identifying RCB stars from their characteristic large and irregular light variations. We have obtained optical spectra of several hundred candidates and have confirmed over 40 new RCB stars in the Galaxy. We are attempting to develop a quantitative spectral classification system for the RCB stars so that they can be identified without an accompanying light curve. The cooler RCB stars look like carbon stars with strong C2 bands, but they can be differentiated from carbon stars by their extreme hydrogen deficiency and very low 13C/12C ratio. Also, the red CN bands are much weaker in RCB stars than in carbon stars. The number of RCB stars in the Galaxy may be consistent with the predicted number of He/CO white-dwarf mergers. Solving the mystery of how the RCB stars evolve would be a watershed event in the study of stellar evolution that will lead to a better understanding of other important types of stellar merger events such as Type Ia SNe.

  6. INTERCHANGE RECONNECTION IN A TURBULENT CORONA

    SciTech Connect

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

    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.

  7. Spatial mapping and quantification of soft and hard protein coronas at silver nanocubes.

    PubMed

    Micl?u?, Teodora; Bochenkov, Vladimir E; Ogaki, Ryosuke; Howard, Kenneth A; Sutherland, Duncan S

    2014-01-01

    Protein coronas around silver nanocubes were quantified in serum-containing media using localized surface plasmon resonances. Both soft and hard coronas showed exposure-time and concentration-dependent changes in protein surface density with time-dependent hardening. We observed spatially dependent kinetics of the corona-formation at cube edges/corners versus facets at short incubation times, where the polymer stabilization agent delayed corona hardening. The soft corona contained more protein than the hard corona at all time-points (8-fold difference with 10% serum conditions). PMID:24617413

  8. Dissertation talk: The EUV Unresolved Corona and Coronal Loops

    NASA Astrophysics Data System (ADS)

    Cirtain, J.

    2005-05-01

    In this work, physical characteristics of the solar corona in the Extreme Ultra-Violet (EUV) regime of the electromagnetic spectrum are investigated. Regions of heightened coronal activity are generally found near the locations of sunspots. These regions are commonly called Active Regions and are the focus of the project. Multiple space based observing platforms have been deployed in the last decade and it is possible to use several of these observatories in combination to develop a more complete picture of the solar corona. Joint Observing Program 146 was created to collect spectroscopic intensities using the Coronal Diagnostic Spectrometer (CDS) on Solar and Heliospheric Observatory (SoHO) and EUV images using NASA's Transition Region and Coronal Explorer (TRACE). The emission line intensities are used to develop an understanding of the temperature and density of the active region coronal plasma. However, the performance of the CDS instrument in the spatial and temporal domains is limited and to compensate for these limitations data collected by the TRACE instrument provide a high spatial and temporal resolution set of observations. The combination of the information contained in the data from these two instruments is used to determine the temperature, density and dynamics of the solar coronal active regions. One of the most exciting unsolved problems in solar astrophysics is to understand why the corona maintains a temperature roughly two orders of magnitude higher than the underlying material. An detailed investigation of the coronal emission has provided constraints on models of the heating mechanism, since the temperature, density and evolution of emission rates for multiple ionic species are indicative of the mechanism(s) working to heat the corona. The observed corona appears to consist of multiple unresolved structures as well as resolved active region structures, called coronal loops. The purpose of the present work is to determine the characteristics of the unresolved background corona. This has two important applicatons. Any model of the corona must account for the emission comprising the unresolved background, and the study of coronal loops can be improved by subtracting the emission along the line-of-sight due to the background contribution to the total intensity. Using the characterizations of the coronal unresolved background, results for loops after background subtraction are also presented. This work demostrates the magnitude of the unresolved coronal emission with respect to the total emission along the line of sight, and how this compares to that of the resolved loops. It is apparent from this analyis that the unresolved corona is the dominant source of radiation in the active region corona.

  9. Properties of optically thick coronae around accreting black holes

    NASA Astrophysics Data System (ADS)

    Belmont, R.; Różańska, A.; Malzac, J.; Czerny, B.; Petrucci, P.-O.

    2015-12-01

    Accreting black holes are complex sources exhibiting several spectral components (disc, jet, hot corona etc). The exact nature and the interplay between these components is still uncertain, and constraining the accretion flow in the vicinity of the compact object has become a key problem to understand the general physics of accretion and ejection. In the past years, the X-ray spectra of several X-ray binaries and AGN have suggested the existence of a new type of coronae in the inner part of their accretion disk. These coronae are warm (about 1 keV) and have Thomson optical depths of about τ ≈ 10, much larger than the standard comptonizing medium inferred in black hole systems. However, simple radiative models based on the diffusion approximation are unable to sustain a large temperature over such high optical depths, therefore questioning existence of these thick coronae. Here we investigate the radiative and hydrostatic properties of slabs, thick coronae covering a standard accretion disc. A precise modelling of the radiation transfer shows that the observed temperature inversion can be reproduced, provided that most of the accretion power is dissipated in this upper layer and that the medium is strongly magnetised.

  10. CORONA DISCHARGE IGNITION FOR ADVANCED STATIONARY NATURAL GAS ENGINES

    SciTech Connect

    Dr. Paul D. Ronney

    2003-09-12

    An ignition source was constructed that is capable of producing a pulsed corona discharge for the purpose of igniting mixtures in a test chamber. This corona generator is adaptable for use as the ignition source for one cylinder on a test engine. The first tests were performed in a cylindrical shaped chamber to study the characteristics of the corona and analyze various electrode geometries. Next a test chamber was constructed that closely represented the dimensions of the combustion chamber of the test engine at USC. Combustion tests were performed in this chamber and various electrode diameters and geometries were tested. The data acquisition and control system hardware for the USC engine lab was updated with new equipment. New software was also developed to perform the engine control and data acquisition functions. Work is underway to design a corona electrode that will fit in the new test engine and be capable igniting the mixture in one cylinder at first and eventually in all four cylinders. A test engine was purchased for the project that has two spark plug ports per cylinder. With this configuration it will be possible to switch between corona ignition and conventional spark plug ignition without making any mechanical modifications.

  11. Protein corona formation for nanomaterials and proteins of a similar size: hard or soft corona?

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Rose, Jérôme; Plantevin, Sophie; Auffan, Mélanie; Bottero, Jean-Yves; Vidaud, Claude

    2013-01-01

    Nanoparticles (NPs) entering a biological fluid undergo surface modification due to dynamic, physicochemical interactions with biological components, especially proteins. In this work we used complementary bio-physico-chemical approaches to characterize the effects of interactions between CeO2 NPs, immunoglobulins (IgGs) and bovine serum albumin (BSA) of a similar size on protein structural evolution as well as formation of (hetero-) aggregates. Using circular dichroism we showed that IgGs and BSA underwent significant structural changes after interaction with NPs. The NPs and protein-NPs were observed after size exclusion chromatography, highlighting the fact that few aggregates were stable enough to pass this mild separation step. X-ray absorption spectroscopy suggested that the surface chemistry of NPs was not affected by these proteins, also implying weak interactions. Competitive experiments revealed that, while the serum was more concentrated for BSA, IgG-NP aggregates were more stable. Altogether, our results indicate that, under our experimental conditions, the formation of a ``protein corona'' is an unstable and reversible mechanism. This indicates that, when NPs and proteins are similar in size, the adsorption concept (i.e. protein corona concept) cannot be applied to model the NP-protein interaction, and a heteroaggregation model is more appropriate.Nanoparticles (NPs) entering a biological fluid undergo surface modification due to dynamic, physicochemical interactions with biological components, especially proteins. In this work we used complementary bio-physico-chemical approaches to characterize the effects of interactions between CeO2 NPs, immunoglobulins (IgGs) and bovine serum albumin (BSA) of a similar size on protein structural evolution as well as formation of (hetero-) aggregates. Using circular dichroism we showed that IgGs and BSA underwent significant structural changes after interaction with NPs. The NPs and protein-NPs were observed after size exclusion chromatography, highlighting the fact that few aggregates were stable enough to pass this mild separation step. X-ray absorption spectroscopy suggested that the surface chemistry of NPs was not affected by these proteins, also implying weak interactions. Competitive experiments revealed that, while the serum was more concentrated for BSA, IgG-NP aggregates were more stable. Altogether, our results indicate that, under our experimental conditions, the formation of a ``protein corona'' is an unstable and reversible mechanism. This indicates that, when NPs and proteins are similar in size, the adsorption concept (i.e. protein corona concept) cannot be applied to model the NP-protein interaction, and a heteroaggregation model is more appropriate. Electronic supplementary information (ESI) available: Details of control of sterile CeO2 NP suspension preparation by DLS; the fluorescence measurement data from fractional analysis of chromatographic elution; EXAFS spectra analysis of the structure of CeO2 in contact with BSA and IgG; the zeta potential measurement of NPs in different experimental media. See DOI: 10.1039/c2nr33611a

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  14. A polarization-color effect in the K-corona.

    NASA Technical Reports Server (NTRS)

    Billings, D. E.; Oh, Y.

    1971-01-01

    An observation of the corona during the 7 March, 1970 eclipse through a Wollaston prism-red and blue filter combination was carried out for the purpose of confirming the prediction that the component of the K-corona with electric vector radial to the Sun is redder than the tangential component. An analysis of a portion of the resulting data seems to confirm this prediction, and also indicates that the method is useful for determining the three-dimensional configuration of the very inner corona. A three-dimensional configuration is suggested for a portion of the NE quadrant of the Sun, including the large NE streamer and an adjacent low-lying loop.

  15. Triggering Excimer Lasers by Photoionization from Corona Discharges

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Duffey, Thomas; Brown, Daniel; Kushner, Mark

    2009-10-01

    High repetition rate ArF (192 nm) excimer lasers are used for photolithography sources in microelectronics fabrication. In highly attaching gas mixtures, preionization is critical to obtaining stable, reproducible glow discharges. Photoionization from a separate corona discharge is one technique for preionization which triggers the subsequent electron avalanche between the main electrodes. Photoionization triggering of an ArF excimer laser sustained in multi-atmosphere Ne/Ar/F2/Xe gas mixtures has been investigated using a 2-dimensional plasma hydrodynamics model including radiation transport. Continuity equations for charged and neutral species, and Poisson's equation are solved coincident with the electron temperature with transport coefficients obtained from solutions of Boltzmann's equation. Photoionizing radiation is produced by a surface discharge which propagates along a corona-bar located adjacent to the discharge electrodes. The consequences of pulse power waveform, corona bar location, capacitance and gas mixture on uniformity, symmetry and gain of the avalanche discharge will be discussed.

  16. 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

  17. Induced Scattering Limits on Fast Radio Bursts from Stellar Coronae

    NASA Astrophysics Data System (ADS)

    Lyubarsky, Yuri; Ostrovska, Sofiya

    2016-02-01

    The origin of fast radio bursts remains a puzzle. Suggestions have been made that they are produced within the Earth’s atmosphere, in stellar coronae, in other galaxies, or at cosmological distances. If they are extraterrestrial, the implied brightness temperature is very high, and therefore the induced scattering places constraints on possible models. In this paper, constraints are obtained on flares from coronae of nearby stars. It is shown that the radio pulses with the observed power could not be generated if the plasma density within and in the nearest vicinity of the source is as high as is necessary to provide the observed dispersion measure. However, one cannot exclude the possibility that the pulses are generated within a bubble with a very low density and pass through the dense plasma only in the outer corona.

  18. Simulation of low temperature atmospheric pressure corona discharge in helium

    NASA Astrophysics Data System (ADS)

    Bekasov, V.; Chirtsov, Alex; Demidova, Maria; Kudryavtsev, Anatoly

    2015-11-01

    The main objective of this work was to construct a numerical model of corona discharge in helium at atmospheric pressure. Calculations were based on the two-dimensional hybrid model. Two different plasma-chemical models were considered. Models were built for RF corona and negative DC corona discharges. The system of equations was solved by the finite element method in the COMSOL Multiphysics. Main parameters of the discharge (the density of charged and excited particles and the electron temperature) and their dependence on the input parameters of the model (geometry, electrode voltage and power) were calculated. The calculations showed that the shape of the electron distribution near the electrode depends on the discharge power. The neutral gas heating data obtained will allow for the prediction of the temperature of the gases in atmospheric pressure helium plasma sources. This work was supported by Russian Science Foundation (project 14-19-00311).

  19. 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

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

    SciTech Connect

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

    2013-08-01

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

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

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1992-01-01

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

  2. Patchy reconnection in the solar corona

    NASA Astrophysics Data System (ADS)

    Guidoni, Silvina Esther

    2011-05-01

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

  3. 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…

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

    SciTech Connect

    Zhang, Shuai Zhang, Bo He, Jinliang

    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.

  5. Corona graphs as a model of small-world networks

    NASA Astrophysics Data System (ADS)

    Lv, Qian; Yi, Yuhao; Zhang, Zhongzhi

    2015-11-01

    We introduce recursive corona graphs as a model of small-world networks. We investigate analytically the critical characteristics of the model, including order and size, degree distribution, average path length, clustering coefficient, and the number of spanning trees, as well as Kirchhoff index. Furthermore, we study the spectra for the adjacency matrix and the Laplacian matrix for the model. We obtain explicit results for all the quantities of the recursive corona graphs, which are similar to those observed in real-life networks.

  6. A theory of heating of quiet solar corona

    SciTech Connect

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

    2015-03-15

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

  7. Nonuniform magnetohydrodynamic nature of the solar corona. I. Basic solutions

    SciTech Connect

    Priest, E.R.

    1988-06-01

    The highly structured nature of the corona is explained in terms of standing MHD disturbances of several types which are spread over extended regions rather than being concentrated in narrow regions like shock waves. The results suggest that plumes of enhanced plasma pressure and flow may be associated with fast-mode compressions having streamlines and magnetic field lines than converge relative to a uniform background corona. The deflection and compression of a coronal ray and the legs of a mass ejection may also be the result of a fast-mode compression. Holes or voids of reduced plasma and flow may be created by slow-mode compressions. 22 references.

  8. 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

  9. Joint Soviet--French investigations of the solar corona. 2. Photometry of solar corona of June 30, 1973

    SciTech Connect

    Vsekhsvyatskii, S.; Dzyubenko, N.; Ivanchuk, V.; Popov, O.; Rubo, G.; Koutchmy, S.; Koutchmy, O.; Stellmacher, G.

    1981-03-01

    The results are presented on a study of eclipse negative obtained on June 30, 1973, in Africa in the program of the Soviet--French experiment ''Dynamics of the White Corona'' by expeditions of Kiev University (Atar, Mauritania) and the Paris Astropysical Institute (Moussoro, Chad). The distributions of the total brightness of the corona out to rapprox. =4.5 R/sub sun/ and of its K and F components for the E and N directions are found with high accuracy on the basis of a new method of photometry and colorimetry using the images of stars down to 8.5/sup m/ as photometric standards. Neither reddening nor flattening of the dusty F component were detected at r<2.5 R/sub sun/. The integral brightness of the corona in the standard zone (1.03--6.0 R/sub sun/) is 0.64 x 10/sup -6/ E/sub sun/.

  10. Polymer micelles with hydrophobic core and ionic amphiphilic corona. 2. Starlike distribution of charged and nonpolar blocks in corona.

    PubMed

    Lysenko, Evgeny A; Kulebyakina, Alevtina I; Chelushkin, Pavel S; Rumyantsev, Artem M; Kramarenko, Elena Yu; Zezin, Alexander B

    2012-08-28

    Mixed polymer micelles with hydrophobic polystyrene (PS) core and ionic amphiphilic poly(4-vinylpyridine)/poly(N-ethyl-4-vinylpyridinium bromide) corona (P4VP/PEVP) spontaneously self-assembled from mixtures of PS-b-PEVP and PS-b-P4VP macromolecules in dimethylformamide/methanol/water selective solvent. The fraction of PEVP units in corona was β = [PEVP]/([PEVP] + [P4VP]) = 0.05-1.0. Micelles were transferred into pure water via dialysis technique and pH was adjusted to 9, where P4VP blocks are insoluble. Structural characteristics of micelles as a function of corona composition β were investigated. Methods of dynamic and static light scattering, electrophoretic mobility measurements, sedimentation velocity, transmission electron microscopy, and UV spectrophotometry were applied. Spherical morphology with core (PS)-shell (P4VP)-corona (PEVP) organization was postulated. Micelles demonstrated a remarkable inflection in structural characteristics near β ~ 0.5-0.7. Above this region, aggregation number (m), core and corona radii of mixed micelles coincided with those of individual PS-b-PEVP micelles. When β decreased below 0.5, dramatic growth of aggregation number was observed, accompanied by growth in micelle size and stretching PEVP chains. At β below 0.2, dispersions of mixed micelles were unstable and easily precipitated upon addition of NaCl. Scaling relationships between micelle characteristics and β were obtained via minimization the micelle free energy, taking into account electrostatic, osmotic, volume, and surface contributions. Theoretical estimations predicted dramatic influence of β on aggregation number, m ~ β(-3). This result is in general agreement with experimental data and confirms the correctness of the core-shell-corona model. The inflection in micelle characteristics entails drastic changes in micelle dispersion stability in the presence of oppositely charged polymeric (sodium polymethacrylate) or amphiphilic (sodium dodecyl sulfate) complexing agents. PMID:22846072

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  12. Large scale structure of the sun's radio corona

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.

    1986-01-01

    Results of studies of large scale structures of the corona at long radio wavelengths are presented, using data obtained with the multifrequency radioheliograph of the Clark Lake Radio Observatory. It is shown that features corresponding to coronal streamers and coronal holes are readily apparent in the Clark Lake maps.

  13. Observational Signatures of Magnetic Reconnection in the Extended Corona

    NASA Astrophysics Data System (ADS)

    Savage, Sabrina; West, Matthew; Seaton, Daniel B.; Kobelski, Adam

    2016-05-01

    Observational signatures of reconnection have been studied extensively in the lower corona for decades, successfully providing insight into energy release mechanisms in the region above post-flare arcade loops and below 1.5 solar radii. During large eruptive events, however, energy release continues to occur well beyond the presence of reconnection signatures at these low heights. Supra-arcade downflows (SADs) and downflowing loops (SADLs) are particularly useful measures of continual reconnection in the corona as they may indicate the presence and path of retracting post-reconnection loops. SADs and SADLs have been faintly observed up to 18 hours beyond the passage of corona mass ejections through the SOHO/LASCO field of view, but a recent event from 2014 October 14 associated with giant arches provides very clear observations of these downflows for days after the initial eruption. We report on this unique event and compare these findings with observational signatures of magnetic reconnection in the extended corona for more typical eruptions.

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

    NASA Astrophysics Data System (ADS)

    Tomczyk, S.

    2013-12-01

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

  15. 37. VIEW OF SIX GAP ROTARY RECTIFIER FOR MAINTAINING CORONA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    37. VIEW OF SIX GAP ROTARY RECTIFIER FOR MAINTAINING CORONA DISCHARGE IN THE COTTRELL ELECTROSTATIC GENERATORS. THE SYSTEM WAS CAPABLE OF PROVIDING 88,000 VOLTS TO THE ELECTRODES WITHIN THE PRECIPITATOR CHAMBER THE UNIT WAS LOCATED TO THE REAR OF BOILER 904 IN AN ENCLOSED ROOM. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

  16. Simulating halos and coronas in their atmospheric environment.

    PubMed

    David Gedzelman, Stanley

    2008-12-01

    Models are developed that simulate the light and color of the sky and of circular halos and coronas as a function of atmospheric pressure, cloud height, width, and optical depth, solar zenith angle, aerosol concentration and size, and ozone content. Halos, coronas, and skylight are treated as singly scattered sunbeams that are depleted in their passage through the atmosphere and cloud. Multiple scattering is included only for background cloud light. Halos produced by hexagonal crystal prisms and coronas produced by monodisperse droplets are visible for cloud optical depths in the range 0.0003 coronas can be bright only at smaller cloud optical depths and tend to be faint at their bottoms when produced in high cloud layers but can be bright at the horizon when produced by narrow cloud cells near ground level. PMID:19037337

  17. 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.

  18. NUMERICAL SIMULATION OF THREE-DIMENSIONAL TUFT CORONA AND ELECTROHYDRODYNAMICS

    EPA Science Inventory

    The numerical simulation of three-dimensional tuft corona and electrohydrodynamics (EHD) is discussed. The importance of high-voltage and low-current operation in the wire-duct precipitator has focused attention on collecting high-resistivity dust. The local current density of in...

  19. 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 θ 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.

  20. Electric winds driven by time oscillating corona discharges

    NASA Astrophysics Data System (ADS)

    Drews, Aaron M.; Cademartiri, Ludovico; Whitesides, George M.; Bishop, Kyle J. M.

    2013-10-01

    We investigate the formation of steady gas flows—so-called electric winds—created by point-plane corona discharges driven by time oscillating (ac) electric fields. By varying the magnitude and frequency of the applied field, we identify two distinct scaling regimes: (i) a low frequency (dc) regime and (ii) a high frequency (ac) regime. These experimental observations are reproduced and explained by a theoretical model describing the transport and recombination of ions surrounding the discharge and their contribution to the measured wind velocity. The two regimes differ in the spatial distribution of ions and in the process by which ions are consumed. Interestingly, we find that ac corona discharges generate strong electric forces localized near the tip of the point electrode, while dc corona discharges generate weaker forces distributed throughout the interelectrode region. Consequently, the velocity of the electric winds (>1 m/s) generated by ac discharges is largely independent of the position of the counter electrode. The unified theoretical description of dc and ac electric winds presented here reconciles previous observations of winds driven by dc corona and ac dielectric barrier discharges; insights from the model should also prove useful in the design of other plasma actuators.

  1. Ultralong optical-pulse corona preionized XeCl laser

    SciTech Connect

    Taylor, R.S.; Leopold, K.E.

    1989-01-01

    A simple corona preionization scheme together with magnetic spiker and pulse forming line technology has resulted in the production of 100-mJ, 1-..mu..s duration as well as 500-mJ, 0.5-..mu..s duration XeCl laser pulses.

  2. Energy distribution of nanoflares in the quiet solar corona

    NASA Astrophysics Data System (ADS)

    Ulyanov, Artyom

    2012-07-01

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

  3. Anisotropic radiation from accretion disc coronae in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Xu, Ya-Di

    2015-05-01

    In the unification scheme for active galactic nuclei, type 1 Seyfert galaxies and type 2 Seyfert galaxies are thought to be intrinsically the same but viewed at different angles. However, the Fe Kα emission line luminosity of type 1 Seyfert galaxies was found on average to be about twice that of type 2 Seyfert galaxies for a given X-ray continuum luminosity in previous work. We construct an accretion disc-corona model in which a fraction of the energy dissipated in the disc is extracted to heat the corona above the disc. The radiation transfer equation with Compton scattering processes is an integro-differential equation, which is solved numerically for the corona with a parallel plane geometry. We find that the specific intensity of X-ray radiation from the corona changes little with the viewing angle θ when θ is small (nearly face-on), and it is sensitive to θ if the viewing angle is large (θ ≳ 40°). The radiation from the cold disc, mostly in infrared, optical and UV bands, is almost proportional to cos θ when θ ≲ 40°, while it decreases more rapidly than cos θ when θ ≳ 40° because of strong absorption in the corona in this case. For Seyfert galaxies, the Fe Kα line may probably be emitted from the disc irradiated by the X-ray continuum emission. The observed equivalent width difference between type 1 Seyfert galaxies and type 2 Seyfert galaxies can be reproduced by our model calculations, provided the type 1 Seyfert galaxies are observed nearly face-on and the average inclination angle of type 2 Seyfert galaxies is ˜65°.

  4. Production mechanisms for faint but possibly detectable coronae about asteroids

    NASA Astrophysics Data System (ADS)

    Morgan, Thomas H.; Killen, Rosemary M.

    1998-08-01

    Asteroidal surfaces are exposed to the same processes which create observable exospheres about such refractory, volatile-free surfaces as those of the Moon and Mercury. Are there modest coronae about asteroids? We have chosen to examine this problem for two species, sodium and water vapor. Sodium was chosen because NaD emission is easily observed from the Earths surface and emissions are observed in the exospheres of both the Moon and Mercury. In addition, the spatial distribution of emission in the sodium D lines about an asteroid would be a direct measure of the velocity distribution of the sodium source, which cannot be measured directly in the case of Mercury or the Moon. This provides a new technique for assessing the possible water content of asteroids. There is now very good evidence that water is present in hydrates and other aqueous alteration products. A detection of an hydroxyl corona about one of these asteroids would be proof of the presence of these aqueous bi-products ; the amount of the water production would a direct measure of the water content of the asteroidal regolith. Water-rich asteroids are of course a potential resource and hold important clues to the evolution of the planets. We have calculated the production of sodium and water (hydroxyl) coronae about asteroids due to just two production mechanisms : sputtering and impact vaporization. We find that for realistic assumptions an asteroid with perihelion near 2 AU would have a small (about 3R) OH corona, while the likely sodium coronae would be about half as bright. These emissions will be extremely difficult to detect from the ground, but they may be detectable from space.

  5. Regulation of Macrophage Recognition through the Interplay of Nanoparticle Surface Functionality and Protein Corona.

    PubMed

    Saha, Krishnendu; Rahimi, Mehran; Yazdani, Mahdieh; Kim, Sung Tae; Moyano, Daniel F; Hou, Singyuk; Das, Ridhha; Mout, Rubul; Rezaee, Farhad; Mahmoudi, Morteza; Rotello, Vincent M

    2016-04-26

    Using a family of cationic gold nanoparticles (NPs) with similar size and charge, we demonstrate that proper surface engineering can control the nature and identity of protein corona in physiological serum conditions. The protein coronas were highly dependent on the hydrophobicity and arrangement of chemical motifs on NP surface. The NPs were uptaken in macrophages in a corona-dependent manner, predominantly through recognition of specific complement proteins in the NP corona. Taken together, this study shows that surface functionality can be used to tune the protein corona formed on NP surface, dictating the interaction of NPs with macrophages. PMID:27040442

  6. Interaction between the solar corona plasma and the dust grains of the interplanetary medium

    NASA Astrophysics Data System (ADS)

    Lamy, H.; Lemaire, J.

    2005-12-01

    When interplanetary grains approach the Sun, they undergo different processes like sublimation or vaporisation. The vaporized atoms constitute a source of heavy ions constantly modifying the composition of the solar wind and of the solar corona. We have adapted current models of heating and ablation of meteoroids entering Earth's atmosphere to the case of the solar corona. In particular, it is well known that the abundances ratios of iron and silicium compared to oxygen are larger in the solar corona and solar wind than in the solar photosphere. We study the possibility that this enrichment in the corona may be due to a continuous deposition of refractory material coming from the ablation of these interplanetary grains from distances of a few solar radii to the basis of the corona. We also calculate the amount of kinetic energy converted into heat and locally deposited in the deepest layers of the solar corona following the braking of the grains by the solar corona plasma.

  7. 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 χ2 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.).

  8. The biomolecular corona of nanoparticles in circulating biological media

    NASA Astrophysics Data System (ADS)

    Pozzi, D.; Caracciolo, G.; Digiacomo, L.; Colapicchioni, V.; Palchetti, S.; Capriotti, A. L.; Cavaliere, C.; Zenezini Chiozzi, R.; Puglisi, A.; Laganà, A.

    2015-08-01

    When nanoparticles come into contact with biological media, they are covered by a biomolecular `corona', which confers a new identity to the particles. In all the studies reported so far nanoparticles are incubated with isolated plasma or serum that are used as a model for protein adsorption. Anyway, bodily fluids are dynamic in nature so the question arises on whether the incubation protocol, i.e. dynamic vs. static incubation, could affect the composition and structure of the biomolecular corona. Here we let multicomponent liposomes interact with fetal bovine serum (FBS) both statically and dynamically, i.e. in contact with circulating FBS (~40 cm s-1). The structure and composition of the liposome-protein corona, as determined by dynamic light scattering, electrophoretic light scattering and liquid chromatography tandem mass spectrometry, were found to be dependent on the incubation protocol. Specifically, following dynamic exposure to FBS, multicomponent liposomes were less enriched in complement proteins and appreciably more enriched in apolipoproteins and acute phase proteins (e.g. alpha-1-antitrypsin and inter-alpha-trypsin inhibitor heavy chain H3) that are involved in relevant interactions between nanoparticles and living systems. Supported by our results, we speculate that efficient predictive modeling of nanoparticle behavior in vivo will require accurate knowledge of nanoparticle-specific protein fingerprints in circulating biological media.When nanoparticles come into contact with biological media, they are covered by a biomolecular `corona', which confers a new identity to the particles. In all the studies reported so far nanoparticles are incubated with isolated plasma or serum that are used as a model for protein adsorption. Anyway, bodily fluids are dynamic in nature so the question arises on whether the incubation protocol, i.e. dynamic vs. static incubation, could affect the composition and structure of the biomolecular corona. Here we let multicomponent liposomes interact with fetal bovine serum (FBS) both statically and dynamically, i.e. in contact with circulating FBS (~40 cm s-1). The structure and composition of the liposome-protein corona, as determined by dynamic light scattering, electrophoretic light scattering and liquid chromatography tandem mass spectrometry, were found to be dependent on the incubation protocol. Specifically, following dynamic exposure to FBS, multicomponent liposomes were less enriched in complement proteins and appreciably more enriched in apolipoproteins and acute phase proteins (e.g. alpha-1-antitrypsin and inter-alpha-trypsin inhibitor heavy chain H3) that are involved in relevant interactions between nanoparticles and living systems. Supported by our results, we speculate that efficient predictive modeling of nanoparticle behavior in vivo will require accurate knowledge of nanoparticle-specific protein fingerprints in circulating biological media. Electronic supplementary information (ESI) available: Table S1: estimation of the corona thickness, sk, of elementary units (liposome-protein corona) clustered in k-fold equilibrium aggregates (t > 15 min). Tables S2 and S3: the full list of the most abundant corona proteins identified on the surface of multicomponent liposomes following dynamic and static incubation with fetal bovine serum. Table S4: the list of the unique proteins bound to MC liposomes following 90 min incubation with FBS under dynamic and static incubation. See DOI: 10.1039/c5nr03701h

  9. Jumplike unravelings for non-Markovian open quantum systems

    SciTech Connect

    Gambetta, Jay; Askerud, T.; Wiseman, H.M.

    2004-05-01

    Non-Markovian evolution of an open quantum system can be 'unraveled' into pure state trajectories generated by a non-Markovian stochastic (diffusive) Schroedinger equation, as introduced by Diosi, 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 jumplike unravelings. To illustrate the jumplike 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}{sub 0}, and the two side bands have frequencies {omega}{sub 0}{+-}{omega}. In the large {omega} limit we observed that the jumplike 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 behavior persists depends upon which jumplike unraveling is used.

  10. 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.

  11. Detailed characteristics of intermittent current pulses due to positive corona

    SciTech Connect

    Liu, Yang Cui, Xiang; Lu, Tiebing; Wang, Zhenguo; Li, Xuebao; Xiang, Yu; Wang, Xiaobo

    2014-08-15

    In order to get detailed characteristics of intermittent current pulses due to positive corona such as the repetition rate of burst-pulse trains, the peak value ratio of the primary pulse to the secondary pulse, the number of pulses per burst, and the interval of the secondary pulses, a systematic study was carried out in a coaxial conductor-cylinder electrode system with the conductor electrode being set with a discharge point. Empirical formulae for the number of pulses per burst and the interval of the secondary pulses are first presented. A theoretical model based on the motion of the space-charge clouds is proposed. Analysis with the model gives explanations to the experimental results and reveals some new insights into the physical mechanism of positive intermittent corona.

  12. Corona Method And Apparatus For Altering Carbon Containing Compounds

    DOEpatents

    Sharma, Amit K.; Camaioni, Donald M.; Josephson; Gary B.

    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.

  13. Corona method and apparatus for altering carbon containing compounds

    DOEpatents

    Sharma, Amit K.; Camaioni, Donald M.; Josephson, Gary B.

    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.

  14. Air trichloroethylene oxidation in a corona plasma-catalytic reactor

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    The oxidative decomposition of trichloroethylene (TCE; 300 ppm) by non-thermal corona plasma was investigated in dry air at atmospheric pressure and room temperature, both in the absence and presence of catalysts including MnOx, CoOx. The catalysts were synthesized by a co-precipitation method. The morphology and structure of the catalysts were characterized by BET surface area measurement and Fourier Transform Infrared (FTIR) methods. Decomposition of TCE and distribution of products were evaluated by a gas chromatograph (GC) and an FTIR. In the absence of the catalyst, TCE removal is increased with increases in the applied voltage and current intensity. Higher TCE removal and CO2 selectivity is observed in presence of the corona and catalysts, as compared to those with the plasma alone. The results show that MnOx and CoOx catalysts can dissociate the in-plasma produced ozone to oxygen radicals, which enhances the TCE decomposition.

  15. The Structure and Dynamics of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Mikic, Zoran

    2000-03-01

    This report covers technical progress during the third year of the NASA Space Physics Theory contract "The Structure and Dynamics of the Solar Corona," between NASA and Science Applications International Corporation, and covers the period June 16, 1998 to August 15, 1999. This is also the final report for this contract. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the three-year duration of this contract we have published 49 articles in the scientific literature. These publications are listed in Section 3 of this report. In the Appendix we have attached reprints of selected articles. We summarize our progress during the third year of the contract. Full descriptions of our work can be found in the cited publications, a few of which are attached to this report.

  16. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    2000-01-01

    This report covers technical progress during the third year of the NASA Space Physics Theory contract "The Structure and Dynamics of the Solar Corona," between NASA and Science Applications International Corporation, and covers the period June 16, 1998 to August 15, 1999. This is also the final report for this contract. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the three-year duration of this contract we have published 49 articles in the scientific literature. These publications are listed in Section 3 of this report. In the Appendix we have attached reprints of selected articles. We summarize our progress during the third year of the contract. Full descriptions of our work can be found in the cited publications, a few of which are attached to this report.

  17. MAVEN IUVS observation of the hot oxygen corona at Mars

    NASA Astrophysics Data System (ADS)

    Deighan, J.; Chaffin, M. S.; Chaufray, J.-Y.; Stewart, A. I. F.; Schneider, N. M.; Jain, S. K.; Stiepen, A.; Crismani, M.; McClintock, W. E.; Clarke, J. T.; Holsclaw, G. M.; Montmessin, F.; Eparvier, F. G.; Thiemann, E. M. B.; Chamberlin, P. C.; Jakosky, B. M.

    2015-11-01

    Observation of the hot oxygen corona at Mars has been an elusive measurement in planetary science. Characterizing this component of the planet's exosphere provides insight into the processes driving loss of oxygen at the current time, which informs understanding of the planet's climatic evolution. The Mars Atmosphere and Volatile EvolutioN (MAVEN) Imaging Ultraviolet Spectrograph (IUVS) instrument is now regularly collecting altitude profiles of the hot oxygen corona as part of its investigation of atmospheric escape from Mars. Observations obtained thus far have been examined and found to display the expected gross structure and variability with EUV forcing anticipated by theory. The quality and quantity of the data set provides valuable constraints for the coronal modeling community.

  18. X-ray observations to detect hot coronae around galaxies

    NASA Technical Reports Server (NTRS)

    Bregman, J. N.; Glassgold, A. E.

    1982-01-01

    X-ray observations were made of two nearby edge-on spiral galaxies with the Imaging Proportional Counter (IPC) on the Einstein Observatory in an effort to detect hot (1,000,000 K), gaseous galactic coronae. No diffuse emission from galactic coronae was detected. Upper limits to diffuse emission (0.3-2.9 keV) are 10 to the 39th ergs/sec (NGC 3628) and 2 x 10 to the 38th ergs/sec (NGC 4244). The measurements indicate that less than 1/1000 of the energy supplied by supernovae in these galaxies appears as soft X-rays. The energy from supernovae may be radiated away by cool gas (less than 600,000 K) whose emission is undetectable by the Einstein Observatory, or the energy may be carried away by a hot wind (10,000,000 K) which radiates inefficiently. Serendipitous X-ray sources from the two IPC fields are listed.

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

    SciTech Connect

    Aleksandrov, N.L.; Bazelyan, E.M.; Raizer, Yu.P.

    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.

  20. 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.

  1. 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.

  2. THE CONNECTION OF TYPE II SPICULES TO THE CORONA

    SciTech Connect

    Judge, Philip G.; McIntosh, Scott W.; De Pontieu, Bart; Olluri, Kosovare

    2012-02-20

    We examine the hypothesis that plasma associated with 'Type II' spicules is heated to coronal temperatures, and that the upward moving hot plasma constitutes a significant mass supply to the solar corona. One-dimensional hydrodynamical models including time-dependent ionization are brought to bear on the problem. These calculations indicate that heating of field-aligned spicule flows should produce significant differential Doppler shifts between emission lines formed in the chromosphere, transition region, and corona. At present, observational evidence for the computed 60-90 km s{sup -1} differential shifts is weak, but the data are limited by difficulties in comparing the proper motion of Type II spicules with spectral and kinematic properties of an associated transition region and coronal emission lines. Future observations with the upcoming infrared interferometer spectrometer instrument should clarify if Doppler shifts are consistent with the dynamics modeled here.

  3. Measuring the IR solar corona during the 2017 eclipse

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  4. Nanoflares and the solar X-ray corona

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1988-01-01

    Observations of the sun with high time and spatial resolution in UV and X-rays show that the emission from small isolated magnetic bipoles is intermittent and impulsive, while the steadier emission from larger bipoles appears as the sum of many individual impulses. We refer to the basic unit of impulsive energy release as a nanoflare. The observations suggest, then, that the active X-ray corona of the sun is to be understood as a swarm of nanoflares. This interpretation suggests that the X-ray corona is created by the dissipation at the many tangential discontinuities arising spontaneously in the bipolar fields of the active regions of the sun as a consequence of random continuous motion of the footpoints of the field in the photospheric convection. The quantitative characteristics of the process are inferred from the observed coronal heat input.

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

    NASA Astrophysics Data System (ADS)

    Vourlidas, A.

    2012-01-01

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

  6. Compton heated winds and coronae above accretion disks. I Dynamics

    NASA Technical Reports Server (NTRS)

    Begelman, M. C.; Mckee, C. F.; Shields, G. A.

    1983-01-01

    X rays emitted in the inner part of an accretion disk system can heat the surface of the disk farther out, producing a corona and possibly driving off a strong wind. The dynamics of Compton-heated coronae and winds are analyzed using an approximate two-dimensional technique to estimate the mass loss rate as a function of distance from the source of X rays. The findings have important dynamical implications for accretion disks in quasars, active galactic nuclei, X ray binaries, and cataclysmic variables. These include: mass loss from the disk possibly comparable with or exceeding the net accretion rate onto the central compact object, which may lead to unstable accretion; sufficient angular momentum loss in some cases to truncate the disk in a semidetached binary at a smaller radius than that predicted by tidal truncation theories; and combined static plus ram pressure in the wind adequate to confine line-emitting clouds in quasars and Seyfert galaxies.

  7. A novel simulation method for positive corona current pulses

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Cui, Xiang; Lu, Tie-Bing; Li, Xue-Bao; Wang, Zhen-Guo; Xiang, Yu; Wang, Xiao-Bo

    2015-06-01

    A novel two-dimensional (2D) simulation method of positive corona current pulses is proposed. A control-volume-based finite element method (CV-FEM) is used to solve continuity equations, and the Galerkin finite element method (FEM) is used to solve Poissons equation. In the proposed method, photoionization is considered by adopting an exact Helmholtz photoionization model. Furthermore, fully implicit discretization and variable time step are used to ensure the time-efficiency of the present method. Finally, the method is applied to a positive rod-plane corona problem. The numerical results are in agreement with the experimental results, and the validity of the proposed method is verified. Project supported by the National Basic Research Program of China (Grant No. 2011CB209402), the National Natural Science Foundation of China (Grant No. 51177041), and the Fundamental Research Funds for the Central Universities, China (Grant No. 12QX01).

  8. Core/corona modeling of diode-imploded annular loads

    NASA Astrophysics Data System (ADS)

    Terry, R. E.; Guillory, J. U.

    1980-11-01

    The effects of a tenuous exterior plasma corona with anomalous resistivity on the compression and heating of a hollow, collisional aluminum z-pinch plasma are predicted by a one-dimensional code. As the interior ("core") plasma is imploded by its axial current, the energy exchange between core and corona determines the current partition. Under the conditions of rapid core heating and compression, the increase in coronal current provides a trade-off between radial acceleration and compression, which reduces the implosion forces and softens the pitch. Combined with a heuristic account of energy and momentum transport in the strongly coupled core plasma and an approximate radiative loss calculation including Al line, recombination and Bremsstrahlung emission, the current model can provide a reasonably accurate description of imploding annular plasma loads that remain azimuthally symmetric. The implications for optimization of generator load coupling are examined.

  9. Imaging the Transition from Corona to Solar Wind

    NASA Astrophysics Data System (ADS)

    DeForest, Craig; Howard, Tim A.; Howard, Russell A.; Tenerani, Anna

    2016-05-01

    The region around the Alfvén surface -- the last frontier of the solar system -- is largely unexplored, mostly because of the difficulty of detecting the surface itself. Many important transitions happen between the mid-to-outer corona and the innermost heliosphere, including: the transition to superAlfvénic flow; the transition from structured, highly anisotropic structure to nearly isotropic turbulent structures; and the formation of identifiable, separable fast and slow wind streams. We will report new results from two recent imaging campaigns -- one with STEREO and one with SOHO/LASCO (coincidentally performed on the 20th anniversary of the first SOHO campaign) -- to explore and image the transition to turbulent flow and the outer boundary of the corona.

  10. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    This report details progress during the third year of our Space Physics Theory Contract. This is the Final Report for this contract. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona. and the inner heliosphere, using the MHD model. During the three-year duration of this contract we have published 49 articles in the scientific literature.

  11. Properties and Distribution of Current Sheets in Accretion Disk Coronae

    NASA Astrophysics Data System (ADS)

    Salvesen, Greg; Begelman, M. C.; Simon, J. B.; Beckwith, K.

    2013-04-01

    Theoretical models involving the interplay of a geometrically thin, optically thick accretion disk embedded in an extended coronal atmosphere may describe black hole X-ray binaries across all spectral states. Buoyant magnetic field generated in the accretion disk is continuously supplied to the corona by a dynamo process driven by the magnetorotational instability. This rising field leads to the formation of a magnetic pressure-dominated, low-density, geometrically thick corona where substantial accretion energy is dissipated, likely by collisionless magnetic reconnection, perhaps even generating outflows. Despite the potential importance of magnetic reconnection in shaping the energetics and kinematics of the corona, studies of multiple reconnection sites in a large volume are currently prohibited by the computational expense required to properly treat the microphysical nature of reconnection. Under the assumption that coronal structure is determined by ideal magnetohydrodynamics, we analyze local simulations of accretion disks (i.e., shearing boxes) performed with the ATHENA code, where the spatial domains are extended to capture 'mesoscale' structures that are dynamically important in accretion disk evolution. We employ a location routine to identify zones of enhanced current density, which trace likely sites of magnetic reconnection. We describe the positions, orientations, sizes, shapes, strengths, and kinematics of these regions and correlate them with the spatial distribution of numerical dissipation. Statistical distributions of these various properties of current density zones are presented to determine the heights within the corona that contribute most to the dissipation rate, the flow properties associated with reconnection sites, and representative parameters for future large volume reconnection simulations.

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

    SciTech Connect

    McIntosh, Scott W.; De Pontieu, Bart

    2012-12-20

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

  13. 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.

  14. DIRECT MEASUREMENTS OF MAGNETIC TWIST IN THE SOLAR CORONA

    SciTech Connect

    Malanushenko, A.; Longcope, D. W.; Yusuf, M. H.

    2011-08-01

    In the present work, we study the evolution of magnetic helicity in the solar corona. We compare the rate of change of a quantity related to the magnetic helicity in the corona to the flux of magnetic helicity through the photosphere and find that the two rates are similar. This gives observational evidence that helicity flux across the photosphere is indeed what drives helicity changes in the solar corona during emergence. For the purposes of estimating coronal helicity, we neither assume a strictly linear force-free field nor attempt to construct a nonlinear force-free field. For each coronal loop evident in extreme ultraviolet, we find a best-matching line of a linear force-free field and allow the twist parameter {alpha} to be different for each line. This method was introduced and its applicability discussed in Malanushenko et al. The object of this study is emerging and rapidly rotating AR 9004 over about 80 hr. As a proxy for coronal helicity, we use the quantity ({alpha}{sub i} L{sub i} /2) averaged over many reconstructed lines of magnetic field. We argue that it is approximately proportional to the 'flux-normalized' helicity H/{Phi}{sup 2}, where H is the helicity and {Phi} is the total enclosed magnetic flux of the active region. The time rate of change of such a quantity in the corona is found to be about 0.021 rad hr{sup -1}, which is comparable with the estimates for the same region obtained using other methods, which estimated the flux of normalized helicity to be about 0.016 rad hr{sup -1}.

  15. Method and apparatus for processing exhaust gas with corona discharge

    DOEpatents

    Barlow, S.E.; Orlando, T.M.; Tonkyn, R.G.

    1999-06-22

    The present invention is placing a catalyst coating upon surfaces surrounding a volume containing corona discharge. In addition, the electrodes are coated with a robust dielectric material. Further, the electrodes are arranged so that at least a surface portion of each electrode extends into a flow path of the exhaust gas to be treated and there is only exhaust gas in the volume between each pair of electrodes. 12 figs.

  16. Method and apparatus for processing exhaust gas with corona discharge

    DOEpatents

    Barlow, Stephan E.; Orlando, Thomas M.; Tonkyn, Russell G.

    1999-01-01

    The present invention is placing a catalyst coating upon surfaces surrounding a volume containing corona discharge. In addition, the electrodes are coated with a robust dielectric material. Further, the electrodes are arranged so that at least a surface portion of each electrode extends into a flow path of the exhaust gas to be treated and there is only exhaust gas in the volume between each pair of electrodes.

  17. OBSERVATION OF ULTRAFINE CHANNELS OF SOLAR CORONA HEATING

    SciTech Connect

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

    2012-05-01

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

  18. Electrical Auxiliary Power Unit (EAPU) Corona Design Guideline. Revised

    NASA Technical Reports Server (NTRS)

    Hall, David K.; Kirkici, Hulya; Schweickart, Dan L.; Dunbar, William; Hillard, Barry

    2000-01-01

    This document is the result of a collaborative effort between NASA's Johnson Space Center, Marshall Space Flight Center, Glenn Research Center, and the United States Air Force Research Laboratory at Wright Patterson AFB in support of the Space Shuttle Orbiter Upgrades Program, specifically the Electric Auxiliary Power Unit Program. This document is intended as a guideline for design applications for corona and partial discharge avoidance and is not a requirements specification instrument.

  19. Monitoring of the Enzymatic Degradation of Protein Corona and Evaluating the Accompanying Cytotoxicity of Nanoparticles.

    PubMed

    Ma, Zhifang; Bai, Jing; Jiang, Xiue

    2015-08-19

    Established nanobio interactions face the challenge that the formation of nanoparticle-protein corona complexes shields the inherent properties of the nanoparticles and alters the manner of the interactions between nanoparticles and biological systems. Therefore, many studies have focused on protein corona-mediated nanoparticle binding, internalization, and intracellular transportation. However, there are a few studies to pay attention to if the corona encounters degradation after internalization and how the degradation of the protein corona affects cytotoxicity. To fill this gap, we prepared three types of off/on complexes based on gold nanoparticles (Au NPs) and dye-labeled serum proteins and studied the extracellular and intracellular proteolytic processes of protein coronas as well as their accompanying effects on cytotoxicity through multiple evaluation mechanisms, including cell viability, adenosine triphosphate (ATP) content, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS). The proteolytic process was confirmed by recovery of the fluorescence of the dye-labeled protein molecules that was initially quenched by Au NPs. Our results indicate that the degradation rate of protein corona is dependent on the type of the protein based on systematical evaluation of the extracellular and intracellular degradation processes of the protein coronas formed by human serum albumin (HSA), γ-globulin (HGG), and serum fibrinogen (HSF). Degradation is the fastest for HSA corona and the slowest for HSF corona. Notably, we also find that the Au NP-HSA corona complex induces lower cell viability, slower ATP production, lower MMP, and higher ROS levels. The cytotoxicity of the nanoparticle-protein corona complex may be associated with the protein corona degradation process. All of these results will enrich the database of cytotoxicity induced by nanomaterial-protein corona complexes. PMID:26200209

  20. Manifestations of electric currents observed in the K-corona

    NASA Astrophysics Data System (ADS)

    Kim, I. S.; Popov, V. V.

    2015-12-01

    The 2D distribution of tangential velocities of the coronal plasma electron component (K-corona) was obtained and interpreted. Coronal continuum linear polarization films in the green spectral range obtained during the total solar eclipse of March 29, 2006, are used. The developed method of high-precision linear polarimetry made it possible to obtain the first 2D distribution in the K-corona linear polarimetry history for the polarization angle sign at distances smaller than 1.5 Rsun. For clarity, we accepted that clockwise deviations of the polarization direction from tangential to the solar limb have positive polarity, whereas counterclockwise deviations have negative polarity. The distribution differs from the anticipated pattern for scattering by resting electrons and reveals a correlation with the coronal structure and the presence of diffuse and structural components and largeand small-scale regions of opposite polarities. The interpretation in the scope of scattering by moving electrons indicates that free electron tangential velocities (tangential electric currents) are strongly fragmented in the inner corona.

  1. 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.

  2. Kilometre-Scale Structures in the Sun's Corona

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1996-01-01

    Knowledge of the structure of the Sun's corona is important for our understanding of how this high-temperature plasma is heated, and of the processes involved in the acceleration of the solar wind. The structure can be investigated directly by imaging at optical and shorter wavelengths, or indirectly through the effects of changing electron density on the propagation of radio waves (scattering and scintillation). Radio measurements have established many of the characteristics of the density fluctuations in the corona and solar wind, but the fundamental nature of these structures is not yet fully understood. Two specific features that have proved difficult to explain are an abrupt increase in anisotropy of the irregularities close to the Sun, and a break in the power-law spectrum describing the density fluctuations. Here I argue that these features are the manifestation of a transition from small ray-like or filamentary structures in the corona that rotate with the Sun to turbulent density irregularities convecting with the solar wind. I estimate the size of the smallest filamentary structure within coronal holes to be about I km at the Sun, approximately three orders of magnitude smaller than the smallest filamentary structures observed in images of different wavelengths.

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

    SciTech Connect

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

    2013-05-20

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

  4. 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.

  5. Pellet ignition using shock-accelerated ions in the corona

    NASA Astrophysics Data System (ADS)

    Bingham, R.; Cairns, R. A.; Boella, E.; Vranic, M.; Silva, L. O.; Trines, R.; Norreys, P.

    2015-11-01

    Recently we have suggested that fast ignition with ions might be possible using a scheme in which, towards the end of the compression phase in inertial fusion, a sequence of intense short pulses is used, first to heat the corona to a high temperature then to launch a shock wave to accelerate ions into the compressed core. This is in contrast to other ion fast ignition schemes in which a separate target is envisaged for the generation of the ions. Initial estimates of the range of energetic ions moving into the core suggest that ions in the 1-10 Mev range will deposit their energy when the density reaches 1025 -1026 cm-3. We will report on detailed studies to identify the range of corona temperatures and shock Mach numbers needed to produce ions of the energy necessary to produce core heating. With the aid of computer simulations of the heating of the corona and production of shock waves in the resulting high electron temperature plasma we will study the requirements for laser systems to make this scheme viable.

  6. 3- and 5- Minute Oscillatory Behavior in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Calabro, Brandon; McAteer, James; Pevtsov, Alexander

    2011-10-01

    We study the spatially- and temporally-localized oscillatory behavior of the solar corona using a 6-hour sequence of narrowband 171A (extreme ultraviolet) image from the SWAP instrument onboard Proba2. We use a Morlet wavelet transform to extract oscillation parameters from the temporal evolution of emission in each pixel and study the variation in space and time of oscillatory power in the 3- and 5-minute band. We extract and compare these parameters between active Sun, quiet Sun and coronal hole regions. In each region of the corona studied the 5-minute periodicity is more prevalent than the 3-minute periodicity by a factor of 2--3. All areas of the corona exhibit a similar temporal behavior in the 5-minute band, suggesting a global driving mechanism. However, the dominance of the 5-minute periodicity is stronger in active regions than in other areas of the Sun. The 3-minute periodicity in active regions tends to be localized in the sunspot umbra, whereas the 5-minute is more prevalent in the penumbra.

  7. Intentional formation of a protein corona on nanoparticles: Serum concentration affects protein corona mass, surface charge, and nanoparticle-cell interaction.

    PubMed

    Gräfe, Christine; Weidner, Andreas; Lühe, Moritz V D; Bergemann, Christian; Schacher, Felix H; Clement, Joachim H; Dutz, Silvio

    2016-06-01

    The protein corona, which immediately is formed after contact of nanoparticles and biological systems, plays a crucial role for the biological fate of nanoparticles. In the here presented study we describe a strategy to control the amount of corona proteins which bind on particle surface and the impact of such a protein corona on particle-cell interactions. For corona formation, polyethyleneimine (PEI) coated magnetic nanoparticles (MNP) were incubated in a medium consisting of fetal calf serum (FCS) and cell culture medium. To modulate the amount of proteins bind to particles, the composition of the incubation medium was varied with regard to the FCS content. The protein corona mass was estimated and the size distribution of the participating proteins was determined by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Additionally, the zeta potential of incubated particles was measured. Human blood-brain barrier-representing cell line HBMEC was used for in vitro incubation experiments. To investigate the consequences of the FCS dependent protein corona formation on the interaction of MNP and cells flow cytometry and laser scanning microscopy were used. Zeta potential as well as SDS-PAGE clearly reveal an increase in the amount of corona proteins on MNP with increasing amount of FCS in incubation medium. For MNP incubated with lower FCS concentrations especially medium-sized proteins of molecular weights between 30kDa and 100kDa could be found within the protein corona, whereas for MNP incubated within higher FCS concentrations the fraction of corona proteins of 30kDa and less increased. The presence of the protein corona reduces the interaction of PEI-coated MNP with HBMEC cells within a 30min-incubation. PMID:26556312

  8. On the sizes of stellar X-ray coronae

    NASA Astrophysics Data System (ADS)

    Ness, J.-U.; Güdel, M.; Schmitt, J. H. M. M.; Audard, M.; Telleschi, A.

    2004-11-01

    Spatial information from stellar X-ray coronae cannot be assessed directly, but scaling laws from the solar corona make it possible to estimate sizes of stellar coronae from the physical parameters temperature and density. While coronal plasma temperatures have long been available, we concentrate on the newly available density measurements from line fluxes of X-ray lines measured for a large sample of stellar coronae with the Chandra and XMM-Newton gratings. We compiled a set of 64 grating spectra of 42 stellar coronae. Line counts of strong H-like and He-like ions and Fe XXI lines were measured with the CORA single-purpose line fitting tool by \\cite{newi02}. Densities are estimated from He-like f/i flux ratios of O VII and Ne IX representing the cooler (1-6 MK) plasma components. The densities scatter between log ne ≈ 9.5-11 from the O VII triplet and between log ne ≈ 10.5-12 from the Ne IX triplet, but we caution that the latter triplet may be biased by contamination from Fe XIX and Fe XXI lines. We find that low-activity stars (as parameterized by the characteristic temperature derived from H- and He-like line flux ratios) tend to show densities derived from O VII of no more than a few times 1010 cm-3, whereas no definitive trend is found for the more active stars. Investigating the densities of the hotter plasma with various Fe XXI line ratios, we found that none of the spectra consistently indicates the presence of very high densities. We argue that our measurements are compatible with the low-density limit for the respective ratios (≈ 5× 1012 cm-3). These upper limits are in line with constant pressure in the emitting active regions. We focus on the commonly used \\cite{rtv} scaling law to derive loop lengths from temperatures and densities assuming loop-like structures as identical building blocks. We derive the emitting volumes from direct measurements of ion-specific emission measures and densities. Available volumes are calculated from the loop-lengths and stellar radii, and are compared with the emitting volumes to infer filling factors. For all stages of activity we find similar filling factors up to 0.1. Appendix A is only available in electronic form at http://www.edpsciences.org

  9. Time dependence of NO{sub x} removal rate by a corona radical shower system

    SciTech Connect

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

    1996-09-01

    In this paper, the effects of the flue gas flow rate and seed gas on the dynamics of corona discharge current-voltage characteristics and NO{sub 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 NO{sub x} removal characteristics, where the threshold value of the treatment gas to seed gas flow rate ratio is about 8. The hysteresis of corona current-voltage characteristics is observed in this system. For longer operational time, corona current and NO{sub x} removal rate significantly changes with time. When the operation of the apparatus starts at relatively low applied voltage, the corona current under constant applied voltage increases with time to reach a maximum value, then decreasing with time to reach a steady state. At this condition, high NO{sub x} removal efficiency can be achieved.

  10. Current-voltage characteristics of dc corona discharges in air between coaxial cylinders

    SciTech Connect

    Zheng, Yuesheng; Zhang, Bo He, Jinliang

    2015-02-15

    This paper presents the experimental measurement and numerical analysis of the current-voltage characteristics of dc corona discharges in air between coaxial cylinders. The current-voltage characteristics for both positive and negative corona discharges were measured within a specially designed corona cage. Then the measured results were fitted by different empirical formulae and analyzed by the fluid model. The current-voltage characteristics between coaxial cylinders can be expressed as I = C(U − U{sub 0}){sup m}, where m is within the range 1.5–2.0, which is similar to the point-plane electrode system. The ionization region has no significant effect on the current-voltage characteristic under a low corona current, while it will affect the distribution for the negative corona under a high corona current. The surface onset fields and ion mobilities were emphatically discussed.

  11. The Survival and Destruction of Galactic X-ray Coronae in Groups and Clusters

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, Rukmani; Milton Ricker, Paul

    2015-08-01

    The discovery of long-lived, ubiquitous, hot galactic coronae in groups and clusters by Chandra poses a challenge to our understanding of galactic ISM survival in harsh environments. These coronae are unique probes of ICM and ISM microphysics, since their survival depends on a delicate balance between external ICM physical processes that can alternatively destroy or replenish these coronae and internal galactic physics that can replenish them. In this talk, I present MHD simulations of the evolution of hot coronae of cosmological populations of galaxies in group and cluster environments. I summarize the effects of external ICM phenomena, like tidal and ram pressure stripping, shielding by magnetic fields, and thermal conduction on the survival of these coronae. I also present synthetic X-ray observations which I use to motivate a stacking analysis on combined optical and X-ray surveys to quantify the effect of the local environment on galactic coronae.

  12. Availability of corona cage for predicting audible noise generated from HVDC transmission line

    SciTech Connect

    Nakano, Y.; Sunaga, Y.

    1989-04-01

    This paper describes a prospect that a corona cage is available for predicting audible noise (AN) generated from HVDC transmission line. This is based on the assumption that generation quantities of AN and corona current are determined by Fmax (the true maximum conductor surface gradient in the presence of space charge) regardless of the surrounding electrode arrangement. This assumption has been verified by tests using corona cages and a test line.

  13. Determination of enamel insulation corona resistance by high- frequency modulated pulses

    NASA Astrophysics Data System (ADS)

    Leonov, A. P.; Red'ko, V. V.; Red'ko, L. A.; Y Soldatenko, E.

    2015-04-01

    In the article test equipment is described for corona resistance testing of enameled winding wire samples. The primary element of equipment is generator producing test voltage with necessary waveform and magnitude according to the required PWM. Test conditions are accurately simulated by operational loads on a winding insulation (simultaneous impact of temperature and corona discharges). Obtained results of average time to breakdown show that the enamel insulation modified by silicon nanoparticles has a maximum corona resistance.

  14. Unraveling RNA-mediated networks: new insights from new technologies.

    PubMed

    Rossbach, Oliver; Bindereif, Albrecht

    2014-01-01

    Eukaryotic gene expression is regulated in a combinatorial manner and on several interconnected layers, ranging from epigenetic mechanisms, transcription, RNA processing to protein stages. mRNA processing plays a major role in tissue- and development-dependent regulation, in particular alternative pre-mRNA splicing, which greatly enhances the capacity and composition of the proteome. Within the last decade, novel methods have been developed to systematically study the complex networks between regulatory alternative splicing factors and their RNA targets. This minireview focuses on cross-linking and immunoprecipitation methods, which - in combination with deep RNA sequencing - have made an important contribution in unraveling these networks. PMID:23959691

  15. Gathering Computational Genomics and Proteomics to Unravel Adaptive Evolution

    PubMed Central

    Antunes, Agostinho; Ramos, Maria João

    2007-01-01

    A recent editorial in PLoS Biology by MacCallum and Hill (2006) pointed out the inappropriateness of studies evaluating signatures of positive selection based solely in single-site analyses. Therefore the rising number of articles claiming positive selection that have been recently published urges the question of how to improve the bioinformatics standards for reliably unravel positive selection? Deeper integrative efforts using state-of-the-art methodologies at the gene-level and protein-level are improving positive selection studies. Here we provide some computational guidelines to thoroughly document molecular adaptation. PMID:19461985

  16. Impact of protein pre-coating on the protein corona composition and nanoparticle cellular uptake.

    PubMed

    Mirshafiee, Vahid; Kim, Raehyun; Park, Soyun; Mahmoudi, Morteza; Kraft, Mary L

    2016-01-01

    Nanoparticles (NPs) are functionalized with targeting ligands to enable selectively delivering drugs to desired locations in the body. When these functionalized NPs enter the blood stream, plasma proteins bind to their surfaces, forming a protein corona that affects NP uptake and targeting efficiency. To address this problem, new strategies for directing the formation of a protein corona that has targeting capabilities are emerging. Here, we have investigated the feasibility of directing corona composition to promote targeted NP uptake by specific types of cells. We used the well-characterized process of opsonin-induced phagocytosis by macrophages as a simplified model of corona-mediated NP uptake by a desired cell type. We demonstrate that pre-coating silica NPs with gamma-globulins (γ-globulins) produced a protein corona that was enriched with opsonins, such as immunoglobulins. Although immunoglobulins are ligands that bind to receptors on macrophages and elicit phagocytois, the opsonin-rich protein corona did not increase NP uptake by macrophage RAW 264.7 cells. Immunolabeling experiments indicated that the binding of opsonins to their target cell surface receptors was impeded by other proteins in the corona. Thus, corona-mediated NP targeting strategies must optimize both the recruitment of the desired plasma proteins as well as their accessibility and orientation in the corona layer. PMID:26513421

  17. Orbital fleet dispatched to unravel magnetic storms' roots

    NASA Astrophysics Data System (ADS)

    Klotz, Irene

    2007-03-01

    Five satellites at the heart of a unique mission that should greatly improve scientists' understanding of geomagnetic storms in Earth's magnetosphere, which can be highly disruptive to a variety of technologies and a health risk to astronauts, were shifting into orbits as far as halfway to the Moon following the successful Feb. 17 launch of a Delta 2 rocket from Cape Canaveral Air Force Station in Florida. The quintet is designed to detect changes in Earth's space environment including charged particle accelerations and flows, and enhanced plasma waves, all of which occur when the Sun's corona is blasted toward Earth in both the steady stream of the solar wind and during solar storms.

  18. Symmetries of general non-Markovian Gaussian diffusive unravelings

    NASA Astrophysics Data System (ADS)

    Budini, Adrián A.

    2015-11-01

    By using a condition of average trace preservation we rederive a general class of non-Markovian Gaussian diffusive unravelings [L. Diósi and L. Ferialdi, Phys. Rev. Lett. 113, 200403 (2014), 10.1103/PhysRevLett.113.200403], here valid for arbitrary non-Hermitian system operators and noise correlations. The conditions under which the generalized stochastic Schrödinger equation has the same symmetry properties (invariance under unitary changes of operator base) as a microscopic system-bath Hamiltonian dynamics are determined. While the standard quantum diffusion model (standard noise correlations) always shares the same invariance symmetry, the generalized stochastic dynamics can be mapped with an arbitrary bosonic environment only if some specific correlation constraints are fulfilled. These features are analyzed for different non-Markovian unravelings equivalent on average. Results based on quantum measurement theory that leads to specific cases of the generalized dynamics [J. Gambetta and H. M. Wiseman, Phys. Rev. A 66, 012108 (2002), 10.1103/PhysRevA.66.012108] are studied from the perspective of the present analysis.

  19. 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.

  20. 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

  1. 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

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

    NASA Technical Reports Server (NTRS)

    Calbert, R.; Beard, D. B.

    1972-01-01

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

  3. Remote Sensing Measurements of the Corona with the Solar Probe

    NASA Technical Reports Server (NTRS)

    Habbal, Shadia Rifai; Woo, Richard

    1996-01-01

    Remote sensing measurements of the solar corona are indespensible for the exploration of the source and acceleration regions of the solar wind which are inaccessible to in situ plasma, paritcles and field experiments.Furthermore, imaging the solar disk and coronal from the unique vantage point of the trajectory and the proximity of the Solar Probe spacecraft, will provide the first ever opportunity to explore the small scale structures within coronal holes and streamers from viewing angles and with spatial resolutions never attained before.

  4. On the Inner Circumstellar Envelopes of R Coronae Borealis Stars

    NASA Astrophysics Data System (ADS)

    Leão, I. C.; Bright, S. N.; Chesneau, O.

    2015-12-01

    We present different analyses of Very Large Telescope Interferometer (VLTI) data to interpret the inner circumstellar envelope (CSE) morphology of R Coronae Borealis (RCB) stars. Three objects were considered: RY Sgr, V CrA, and V854 Cen. Chi-squared maps of different geometrical models allow to identify a reasonable description of these CSEs, which can be further studied in radiative transfer codes. Overall, the inner CSE morphology of these RCB stars are consistent with a central star surrounded by a dusty shell with at least a bright clump (or a dust cluster).

  5. High Resolution Imaging of the Sun with CORONAS-1

    NASA Technical Reports Server (NTRS)

    Karovska, Margarita

    1998-01-01

    We applied several image restoration and enhancement techniques, to CORONAS-I images. We carried out the characterization of the Point Spread Function (PSF) using the unique capability of the Blind Iterative Deconvolution (BID) technique, which recovers the real PSF at a given location and time of observation, when limited a priori information is available on its characteristics. We also applied image enhancement technique to extract the small scale structure imbeded in bright large scale structures on the disk and on the limb. The results demonstrate the capability of the image post-processing to substantially increase the yield from the space observations by improving the resolution and reducing noise in the images.

  6. Toxic Gas Removal by Dielectric Discharge with Corona Effect

    SciTech Connect

    Moreno, H.; Pacheco, M.; Mercado, A.; Cruz, A.; Pacheco, J.; Yousfi, M.; Eichwald, O.; Benhenni, M.

    2006-12-04

    In this work, a theoretical and experimental study on SO2 and NOx removal by non-thermal plasma technology, more specifically a dielectric barrier (DBD) discharge combined with the Corona effect, is presented. Results obtained from a theoretical study describe the chemical kinetic model of SO2 and NOx removal processes; the effect of OH radicals in removal of both gases is noteworthy. Experimental results of de-SO2 process are reported. Also, optical emission spectroscopy study was applied on some atomic helium lines to obtain temperature of electrons in the non-thermal plasma.

  7. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1998-01-01

    This report covers technical progress during the first year of the NASA Space Physics Theory contract between NASA and Science Applications International Corporation. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the period covered by this report we have published 26 articles in the scientific literature. These publications are listed in Section 4 of this report. In the Appendix we have attached reprints of selected articles.

  8. Corona patterns around inclusions in freely suspended smectic films.

    PubMed

    Harth, K; Stannarius, R

    2009-03-01

    We discuss the structure and physical origin of corona patterns observed around solid or liquid spherical inclusions in freely suspended smectic films. Such patterns are observed when droplets or solid beads of micrometer size are sprayed onto the films. They are found in the smectic C phase and in the smectic A phase above such a smectic C phase, but disappear, for example, at the transition into a lower-temperature smectic B phase. We show that these structures are equivalent to splay domains found in the meniscus of freely suspended films, originating from surface-induced spontaneous splay. PMID:19169722

  9. Study of a dual frequency atmospheric pressure corona plasma

    SciTech Connect

    Kim, Dan Bee; Moon, S. Y.; Jung, H.; Gweon, B.; Choe, Wonho

    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.

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

    NASA Technical Reports Server (NTRS)

    Davila, Joseph M.

    1986-01-01

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

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

    SciTech Connect

    Schoefthaler, M.; Brendel, R.; Langguth, G.; Werner, J.H.

    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.

  12. Subduction on the margins of coronae on Venus: Evidence from radiothermal emissivity measurements

    NASA Technical Reports Server (NTRS)

    Robinson, C. A.

    1993-01-01

    Retrograde subduction has been suggested to occur at three coronae on Venus: Latona, Artemis, and Eithinoha. Using the mineralogical arguments of Klose to explain surface emissivity, a study of radio thermal emissivity of Venus coronae showed that emissivity changes associated with Latona, Artemis, and Ceres imply the same crustal movements predicted by the subduction model of Sandwell and Schubert.

  13. CORONA DESTRUCTION: AN INNOVATIVE CONTROL TECHNOLOGY FOR VOCS AND AIR TOXICS

    EPA Science Inventory

    This paper discusses the work and results to date leading to the demonstration of the corona destruction process at pilot scale. The research effort in corona destruction of volatile organic compounds (VOCs) and air toxics has shown significant promise for providing a valuable co...

  14. 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...

  15. Stealth effect of biomolecular corona on nanoparticle uptake by immune cells.

    PubMed

    Caracciolo, Giulio; Palchetti, Sara; Colapicchioni, Valentina; Digiacomo, Luca; Pozzi, Daniela; Capriotti, Anna Laura; La Barbera, Giorgia; Laganà, Aldo

    2015-10-01

    When injected in a biological milieu, a nanomaterial rapidly adsorbs biomolecules forming a biomolecular corona. The biomolecular corona changes the interfacial composition of a nanomaterial giving it a biological identity that determines the physiological response. Characterization of the biomolecular structure and composition has received increasing attention mostly due to its detrimental impact on the nanomaterial's metabolism in vivo. It is generally accepted that an opsonin-enriched biomolecular corona promotes immune system recognition and rapid clearance from circulation. Here we applied dynamic light scattering and nanoliquid chromatography tandem mass spectrometry to thoroughly characterize the biomolecular corona formed around lipid and silica nanoparticles (NPs). Incubation with human plasma resulted in the formation of NP-biomolecular coronas enriched with immunoglobulins, complement factors, and coagulation proteins that bind to surface receptors on immune cells and elicit phagocytosis. Conversely, we found that protein-coated NPs were protected from uptake by macrophage RAW 264.7 cells. This implies that the biomolecular corona formation provides a stealth effect on macrophage recognition. Our results suggest that correct prediction of the NP's fate in vivo will require more than just the knowledge of the biomolecular corona composition. Validation of efficient methods for mapping protein binding sites on the biomolecular corona of NPs is an urgent task for future research. PMID:26378619

  16. PLASMA DYNAMICS AT THE PROMINENCE-CORONA INTERFACE

    SciTech Connect

    Miloch, W. J.; Esser, R.; Habbal, S. R.

    2012-06-20

    The interface between the cool and dense plasma typical of a prominence and its tenuous and hot surrounding coronal plasma is poorly understood. We study the plasma dynamics at this interface using a three-dimensional particle-in-cell code, which enables us to carry out simulations on spatial and temporal scales of the order of the Debye length and plasma period, respectively. The results show that anomalous Bohm diffusion across magnetic field lines occurs at the interface, leading to mixing of the two plasmas. It is also shown that collisions with neutral hydrogen within the prominence plasma are of little importance for the plasma dynamics in the prominence-corona transition region. In particular, the temperature of the prominence plasma crossing the interface into the corona can become anisotropic due to preferential heating by instabilities originating from unstable velocity distributions. Our results pertain to spatial scales significantly smaller than scales commonly used in magnetohydrodynamic simulations, and they shed light on processes that are very likely to be present at the interface.

  17. Ultraviolet radiation from the pulsed corona discharge in water

    NASA Astrophysics Data System (ADS)

    Lukes, Petr; Clupek, Martin; Babicky, Vaclav; Sunka, Pavel

    2008-05-01

    Quantitative analysis of ultraviolet radiation from the pulsed corona discharge in water with needle-plate electrode geometry (~1-3 J pulse-1) was performed using the potassium ferrioxalate actinometry. Photon flux J190-280 and radiant energy Q190-280 of the UV light emitted from the discharge at spectral region 190-280 nm was determined in dependence on the applied voltage (17-29 kV, positive polarity) and the solution conductivity (100-500 µS cm-1). The intensity of the UV radiation strongly increased with increasing water conductivity and applied voltage. Depending on the applied voltage the determined photon flux varied by more than two orders of magnitude within the range of solution conductivities 100-500 µS cm-1. It was found that photon flux from the discharge may be directly related to the discharge pulse mean power Pp as J190-280 = 44.33 P_p^{2.11} (quanta pulse-1). A significant role of UV radiation in the production of hydrogen peroxide and bacterial inactivation by the corona discharge in water has been identified. As the solution conductivity increased the yield of H2O2 produced by the discharge decreased due to increasing photolysis of H2O2 accounting for up to 14% of the total decomposition rate of H2O2. As regards bactericidal effects, it was estimated that the UV radiation contributes about 30% to the overall inactivation of Escherichia coli.

  18. Observational tests for nonequilibrium ionization in the solar corona

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    SciTech Connect

    Io, Yuki; Suzuki, Takeru K.

    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, γ. Initially imposed weak vertical magnetic fields are effectively amplified by magnetorotational instability and winding caused by the differential rotation. In the isothermal case (γ = 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 γ ≥ 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.

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

    PubMed

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

    2012-06-28

    Heating the outer layers of the magnetically quiet solar atmosphere to more than one million kelvin and accelerating the solar wind requires an energy flux of approximately 100 to 300 watts per square metre, but how this energy is transferred and dissipated there is a puzzle and several alternative solutions have been proposed. Braiding and twisting of magnetic field structures, which is caused by the convective flows at the solar surface, was suggested as an efficient mechanism for atmospheric heating. Convectively driven vortex flows that harbour magnetic fields are observed to be abundant in the photosphere (the visible surface of the Sun). Recently, corresponding swirling motions have been discovered in the chromosphere, the atmospheric layer sandwiched between the photosphere and the corona. Here we report the imprints of these chromospheric swirls in the transition region and low corona, and identify them as observational signatures of rapidly rotating magnetic structures. These ubiquitous structures, which resemble super-tornadoes under solar conditions, reach from the convection zone into the upper solar atmosphere and provide an alternative mechanism for channelling energy from the lower into the upper solar atmosphere. PMID:22739314

  1. A Corona Discharge Initiated Electrochemical Electrospray Ionization Technique

    PubMed Central

    Lloyd, John R.; Hess, Sonja

    2009-01-01

    We report here the development of a corona discharge (CD) initiated electrochemical (EC) electrospray ionization (ESI) technique using a standard electrospray ion source. This is a new ionization technique distinct from ESI, electrochemistry inherent to ESI, APCI, and techniques using hydroxyl radicals produced under atmospheric pressure conditions. By maximizing the observable CD at the tip of a stainless steel ESI capillary, efficient electrochemical oxidation of electrochemically active compounds is observed. For electrochemical oxidation to be observed, the ionization potential of the analyte must be lower than Fe. Ferrocene labeled compounds were chosen as the electrochemically active moiety. The electrochemical cell in the ESI source was robust and generated ions with selectivity according to the ionization potential of the analytes and up to zeptomolar sensitivity. Our results indicate that CD initiated electrochemical ionization has the potential to become a powerful technique to increase the dynamic range, sensitivity and selectivity of ESI experiments. Synopsis Using a standard ESI source a corona discharge initiated electrochemical ionization technique was established resulting from the electrochemistry occurring at the CD electrode surface. PMID:19747843

  2. Tracing Helioseismic Waves from the Photosphere to the Corona

    NASA Astrophysics Data System (ADS)

    Zhao, Junwei; Felipe, Tobias; Chen, Ruizhu; Khomenko, Elena

    2016-05-01

    Can p-mode waves in sunspots propagate to the chromosphere and the corona? And what are their counterparts in different atmospheric heights? In order to study the connection between the photospheric p-mode waves and the waves observed above the photosphere, we use a helioseismic analysis technique, namely time-distance helioseismology, and analyze multi-height observations from different instruments. We find clear evidences that some p-mode waves in the photosphere, running penumbral waves in the chromosphere, and the periodic disturbances in the coronal fan structures are actually same magnetoacoustic waves that exhibit differently at the different atmospheric heights. The 6-mHz waves, with inclined wavefronts, propagate slantingly upward along magnetic field lines. The 3-mHz waves, forming backward-'C'-shape wavefronts, propagate mostly horizontally. Through numerical simulations, we demonstrate that these p-mode waves that can travel upward to the corona, possibly originate from sources located a few megameters beneath sunspots' surface.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  4. 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.

  5. Confirmed Assignments of Isomeric Dimethylbenzyl Radicals Generated by Corona Discharge

    NASA Astrophysics Data System (ADS)

    Yoon, Young Wook; Lee, Sang Kuk

    2012-06-01

    Polymethylbenzyl radicals, multi-methyl-substituted benzyl radicals, have been believed to be an ideal model for understanding the torsional effect of methyl group and substitution effect on electronic transition. These radicals are mainly generated from polymethylbenzenes by electric discharge for spectroscopic observation. However, the existence of several methyl groups on the benzene ring may produce several isomeric polymethylbenzyl radicals by removing one of the C-H bonds of each methyl group at different substitution position, which makes the assignment of spectrum ambiguous. In this work, the controversial vibronic assignments of isomeric dimethylbenzyl radicals were clearly resolved by using different precursors. By using corresponding dimethylbenzyl chlorides as precursors, we identified the origins of the vibronic bands of the dimethylbenzyl radicals generated by corona discharge of precursors 1,2,3- and 1,2,4-trimethylbenzenes. From the analysis of the spectra observed from the dimethylbenzyl chlorides in a corona excited supersonic expansion using a pinhole-type glass nozzle, we revised previous assignments of the 2,6- and 2,3-dimethylbenzyl radicals as well as the 3,4-, 2,4-, and 2,5-dimethylbenzyl radicals. In addition, 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 precursors.

  6. Multimodal Differential Emission Measure in the Solar Corona

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  7. The EUV Emission in Comet-Solar Corona Interactions

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  8. Local time variations of the Venusian hydrogen corona

    NASA Astrophysics Data System (ADS)

    Chaufray, J.-Y.; Bertaux, J.-L.; Quémerais, E.; Sulis, S.; Leblanc, F.

    2014-04-01

    Atomic hydrogen in the upper atmosphere of Venus is produced by chemical reactions involving hydrogen bearing molecules such as H2O. Due to its low mass, atomic hydrogen can reach high altitudes and become the dominant species in the Venusian exosphere. The density of atomic hydrogen retrieved by Pioneer Venus Orbiter from H+ measurement of the ion mass spectrometer indicated large diurnal variation of the hydrogen content with a peak of density near 4:00 local time (1). The large dayside/nightside ratio ~ 1000 was attributed to the wind system induced from temperature contrast. First dayside observations of the atomic hydrogen Lymanalpha resonant line performed by the UV spectrometer SPICAV (2) aboard Venus Express suggested a lower ratio ~ 30 between morning side and evening side (3). In this presentation, we will present several recent observations of the Venusian hydrogen corona obtained by SPICAV at different local times at nightside to investigate more accurately the diurnal variations of the Venusian hydrogen corona.

  9. Utilizing the protein corona around silica nanoparticles for dual drug loading and release

    NASA Astrophysics Data System (ADS)

    Shahabi, Shakiba; Treccani, Laura; Dringen, Ralf; Rezwan, Kurosch

    2015-10-01

    A protein corona forms spontaneously around silica nanoparticles (SNPs) in serum-containing media. To test whether this protein corona can be utilized for the loading and release of anticancer drugs we incorporated the hydrophilic doxorubicin, the hydrophobic meloxicam as well as their combination in the corona around SNPs. The application of corona-covered SNPs to osteosarcoma cells revealed that drug-free particles did not affect the cell viability. In contrast, SNPs carrying a protein corona with doxorubicin or meloxicam lowered the cell proliferation in a concentration-dependent manner. In addition, these particles had an even greater antiproliferative potential than the respective concentrations of free drugs. The best antiproliferative effects were observed for SNPs containing both doxorubicin and meloxicam in their corona. Co-localization studies revealed the presence of doxorubicin fluorescence in the nucleus and lysosomes of cells exposed to doxorubicin-containing coated SNPs, suggesting that endocytotic uptake of the SNPs facilitates the cellular accumulation of the drug. Our data demonstrate that the protein corona, which spontaneously forms around nanoparticles, can be efficiently exploited for loading the particles with multiple drugs for therapeutic purposes. As drugs are efficiently released from such particles they may have a great potential for nanomedical applications.A protein corona forms spontaneously around silica nanoparticles (SNPs) in serum-containing media. To test whether this protein corona can be utilized for the loading and release of anticancer drugs we incorporated the hydrophilic doxorubicin, the hydrophobic meloxicam as well as their combination in the corona around SNPs. The application of corona-covered SNPs to osteosarcoma cells revealed that drug-free particles did not affect the cell viability. In contrast, SNPs carrying a protein corona with doxorubicin or meloxicam lowered the cell proliferation in a concentration-dependent manner. In addition, these particles had an even greater antiproliferative potential than the respective concentrations of free drugs. The best antiproliferative effects were observed for SNPs containing both doxorubicin and meloxicam in their corona. Co-localization studies revealed the presence of doxorubicin fluorescence in the nucleus and lysosomes of cells exposed to doxorubicin-containing coated SNPs, suggesting that endocytotic uptake of the SNPs facilitates the cellular accumulation of the drug. Our data demonstrate that the protein corona, which spontaneously forms around nanoparticles, can be efficiently exploited for loading the particles with multiple drugs for therapeutic purposes. As drugs are efficiently released from such particles they may have a great potential for nanomedical applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04726a

  10. 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

  11. Understanding the nanoparticle-protein corona complexes using computational and experimental methods.

    PubMed

    Kharazian, B; Hadipour, N L; Ejtehadi, M R

    2016-06-01

    Nanoparticles (NP) have capability to adsorb proteins from biological fluids and form protein layer, which is called protein corona. As the cell sees corona coated NPs, the protein corona can dictate biological response to NPs. The composition of protein corona is varied by physicochemical properties of NPs including size, shape, surface chemistry. Processing of protein adsorption is dynamic phenomena; to that end, a protein may desorb or leave a surface vacancy that is rapidly filled by another protein and cause changes in the corona composition mainly by the Vroman effect. In this review, we discuss the interaction between NP and proteins and the available techniques for identification of NP-bound proteins. Also we review current developed computational methods for understanding the NP-protein complex interactions. PMID:26873405

  12. Measurement of positive direct current corona pulse in coaxial wire-cylinder gap

    SciTech Connect

    Yin, Han Zhang, Bo He, Jinliang Wang, Wenzhuo

    2014-03-15

    In this paper, a system is designed and developed to measure the positive corona current in coaxial wire-cylinder gaps. The characteristic parameters of corona current pulses, such as the amplitude, rise time, half-wave time, and repetition frequency, are statistically analyzed and a new set of empirical formulas are derived by numerical fitting. The influence of space charges on corona currents is tested by using three corona cages with different radii. A numerical method is used to solve a simplified ion-flow model to explain the influence of space charges. Based on the statistical results, a stochastic model is developed to simulate the corona pulse trains. And this model is verified by comparing the simulated frequency-domain responses with the measured ones.

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

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1998-01-01

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

  14. 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.

  15. 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

  16. Microbiome to Brain: Unravelling the Multidirectional Axes of Communication.

    PubMed

    El Aidy, Sahar; Stilling, Roman; Dinan, Timothy G; Cryan, John F

    2016-01-01

    The gut microbiome plays a crucial role in host physiology. Disruption of its community structure and function can have wide-ranging effects making it critical to understand exactly how the interactive dialogue between the host and its microbiota is regulated to maintain homeostasis. An array of multidirectional signalling molecules is clearly involved in the host-microbiome communication. This interactive signalling not only impacts the gastrointestinal tract, where the majority of microbiota resides, but also extends to affect other host systems including the brain and liver as well as the microbiome itself. Understanding the mechanistic principles of this inter-kingdom signalling is fundamental to unravelling how our supraorganism function to maintain wellbeing, subsequently opening up new avenues for microbiome manipulation to favour desirable mental health outcome. PMID:26589226

  17. 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 (υ 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 (υ 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 μ 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 μ 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 β 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.

  18. Spatial and temporal relations between coronae and extensional belts, northern Lada Terra, Venus

    NASA Technical Reports Server (NTRS)

    Baer, Gidon; Schubert, Gerald; Bindschadler, Duane L.; Stofan, Ellen R.

    1994-01-01

    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.

  19. Creation of current filaments in the solar corona

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  20. 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.

  1. Chromospheres and coronae of late-type stars

    NASA Technical Reports Server (NTRS)

    Dupree, A. K.; Black, J. H.; Davis, R.; Hartmann, L.; Raymond, J. C.

    1979-01-01

    IUE short wavelength (1150-2000 A) spectra of late-type dwarfs, giant, and supergiant stars show a variety of emission features varying in excitation from about 10,000 K to about 3 x 10 to the 5th K. High excitation species are found most strongly in main sequence stars. Dwarf stars with active chromospheres (e.g., Xi Boo) and flare stars (EQ Peg) show enhancement of surface flux as compared to the quiet sun; binary systems of W UMa and RS CVn types show even larger surface fluxes. The enhancement increases with temperature of formation much like a solar active region. The presence of high excitation species in the giant and supergiant stars suggests that parameters other than effective temperature and luminosity are important in establishing a transition region and corona.

  2. 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.

  3. Multiphysics simulation of corona discharge induced ionic wind

    NASA Astrophysics Data System (ADS)

    Cagnoni, Davide; Agostini, Francesco; Christen, Thomas; Parolini, Nicola; Stevanović, Ivica; de Falco, Carlo

    2013-12-01

    Ionic wind devices or electrostatic fluid accelerators are becoming of increasing interest as tools for thermal management, in particular for semiconductor devices. In this work, we present a numerical model for predicting the performance of such devices; its main benefit is the ability to accurately predict the amount of charge injected from the corona electrode. Our multiphysics numerical model consists of a highly nonlinear, strongly coupled set of partial differential equations including the Navier-Stokes equations for fluid flow, Poisson's equation for electrostatic potential, charge continuity, and heat transfer equations. To solve this system we employ a staggered solution algorithm that generalizes Gummel's algorithm for charge transport in semiconductors. Predictions of our simulations are verified and validated by comparison with experimental measurements of integral physical quantities, which are shown to closely match.

  4. Theory of transition-layer emission measures and coronae

    NASA Technical Reports Server (NTRS)

    Bohm-Vitense, Erika

    1987-01-01

    The basic equations describing the energy equilibria, the conductive heat flux, and the temperature stratifications for stellar transition layers and coronae with 'open' field lines are summarized. The temperature dependence of the emission measures for lines originating in different temperature regions of the transition zone is determined. It is found that the stellar transition regions consist of two basically different parts: the lower part where mechnical energy input is balanced by the radiative losses, and the upper part where the mechanical energy input is balanced by the divergence of the conductive flux and radiative losses. In the lower part, the temperature stratification is determined by an equilibrium between mechanical flux input and radiative energy losses. The coronal temperatures increase with increasing mechanical flux and damping length in the upper transition zone.

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

    SciTech Connect

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

    2013-08-01

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

  6. Pulsed corona discharge for oxidation of gaseous elemental mercury

    NASA Astrophysics Data System (ADS)

    Ko, Kyung Bo; Byun, Youngchul; Cho, Moohyun; Namkung, Won; Hamilton, Ian P.; Shin, Dong Nam; Koh, Dong Jun; Kim, Kyoung Tae

    2008-06-01

    Positive pulsed corona discharge has been applied for the oxidation of gaseous elemental mercury (Hg0) from a simulated flue gas. The oxidation of Hg0 to HgO and HgCl2 can significantly enhance the mercury removal from flue gas. At a gas condition of O2 (10%), H2O (3%), and N2 (balance), Hg0 oxidation efficiency of 84% was achieved at an input energy density of 45J /l. The presence of NO, however, hinders Hg0 oxidation due to the preferential reaction of NO with O and O3. On the contrary, SO2 shows little effect on Hg0 oxidation due to its preferential reaction with OH. It has been also observed that the HCl in gas stream can be dissociated to Cl and Cl2 and can induce additional Hg0 oxidation to HgCl2.

  7. Multiphysics simulation of corona discharge induced ionic wind

    SciTech Connect

    Cagnoni, Davide; MOX - Dipartimento di Matematica “F. Brioschi,” Politecnico di Milano, 20133 Milano ; Agostini, Francesco; Christen, Thomas; Parolini, Nicola; Stevanović, Ivica; Laboratory of Electromagnetics and Acoustics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne ; Falco, Carlo de; CEN - Centro Europeo di Nanomedicina, 20133 Milano

    2013-12-21

    Ionic wind devices or electrostatic fluid accelerators are becoming of increasing interest as tools for thermal management, in particular for semiconductor devices. In this work, we present a numerical model for predicting the performance of such devices; its main benefit is the ability to accurately predict the amount of charge injected from the corona electrode. Our multiphysics numerical model consists of a highly nonlinear, strongly coupled set of partial differential equations including the Navier-Stokes equations for fluid flow, Poisson's equation for electrostatic potential, charge continuity, and heat transfer equations. To solve this system we employ a staggered solution algorithm that generalizes Gummel's algorithm for charge transport in semiconductors. Predictions of our simulations are verified and validated by comparison with experimental measurements of integral physical quantities, which are shown to closely match.

  8. Structures in the Algol Corona: Searching for Flare Eclipses

    NASA Astrophysics Data System (ADS)

    Favata, Fabio

    Our recent successful observation of a total eclipse of a large flare on Algol (with BeppoSAX) has demonstrated the diagnostic power of flare eclipses, allowing for the first time to derive the size of the coronal structure responsible for a stellar flare (and thus by inference the size of coronal structures in general) on purely geometrical grounds. The loop is compact, much smaller than deduced by the analysis of the flare decay, and located on the pole of the active star. We propose to observe Algol for two binary orbits searching for similar flare eclipses. Further detections of flare eclipses (for which RXTE, with its large effective area is ideally suited) will allow to directly constrain the characteristic sized of structures in the Algol corona.

  9. 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.

  10. Models of hot galactic coronae around early-type galaxies

    NASA Technical Reports Server (NTRS)

    Forman, W.; Jones, C.; Tucker, W.

    1994-01-01

    We have computed simple non-steady state models of X-ray-emitting, hot galactic coronae which are observed around early-type galaxies. Our models, appropriate for elliptical galaxies, include the effect of the formation of new stars which occurs as the gas radiatively cools and the effect of supernova explosions which serve to heat the cooling gas component from which the stars are forming. We develop scaling relations for the galaxy parameters including the optical galaxy as well as a dark matter halo which we use to generate galaxy models spanning a range of absolute magnitudes from -19.5 to -22.5. We compare our models to a sample of approximately 150 galaxies with measured X-ray luminosities. We show that our simple model does exhibit the observed correlation between X-ray and optical luminosity. However, the model cannot explain the broad range in X-ray luminosity at a given optical luminosity.

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

    NASA Technical Reports Server (NTRS)

    Acton, L. W.

    1978-01-01

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

  12. ES Aquilae Is an R Coronae Borealis Star

    NASA Astrophysics Data System (ADS)

    Clayton, Geoffrey C.; Hammond, D.; Lawless, J.; Kilkenny, D.; Evans, T. Lloyd; Mattei, J.; Landolt, A. U.

    2002-08-01

    ES Aql, initially classified as a semiregular variable, is now believed to be a member of the R Coronae Borealis (RCB) class of stars, a small group of carbon-rich supergiants that undergo dramatic declines in brightness at irregular intervals. We present photometry of ES Aql going back as far as 1893 using plates from the Harvard College Observatory as well as more recent photoelectric and visual observations. ES Aql displays the typical behavior of an RCB star, consisting of sharp declines at irregular intervals. The spectrum of ES Aql is also typical of a cool (Teff~5000 K) RCB star, showing strong absorption bands of C2 and CN, along with weak hydrogen and no detectable 13C. ES Aql is also an IRAS source indicating the presence of dust. Based on these data, we conclude that ES Aql is indeed an RCB star.

  13. Sunspot Oscillations From The Chromosphere To The Corona

    NASA Astrophysics Data System (ADS)

    Brynildsen, N.; Maltby, P.; Fredvik, T.; Kjeldseth-Moe, O.

    The behavior of the 3 minute sunspot oscillations is studied as a function of temper- ature through the transition region using observations with CDS/SOHO and TRACE. The oscillations occur above the umbra, with amplitudes increasing to a maximum near 200 000 K, then decreasing towards higher temperatures. Deviations from pure linear oscillations are present in several cases. Power spectra of the oscillations are remarkably similar in the chromosphere and through the transition region in contra- diction to the predictions of the sunspot filter theory. The 3 minute oscillations pene- trate to the low temperature end of the corona, where they are channeled into smaller areas coinciding with the endpoints of sunspot coronal loops. This differs from the transition zone where the oscillating region covers the umbra.

  14. Observational evidence for a hot gaseous Galactic corona

    NASA Technical Reports Server (NTRS)

    Savage, B. D.; De Boer, K. S.

    1979-01-01

    Galactic absorption features observed in high-dispersion far-UV spectra of two Large Magellanic Cloud (LMC) stars obtained with the IUE satellite are discussed. The stars observed were HD 38268 (OB + WN5) and HD 38282 (WN6), which lie at a distance of about 55 kpc and in the galactic direction corresponding to a latitude of about -32 deg and a longitude of about 280 deg. The line of sight to these stars passes through the disk and halo of the Milky Way and the halo and disk of the LMC. Evidence is presented for the existence of a hot (somewhat below 1 million K), low-density (about 0.001 H atom per cu cm) Galactic corona.

  15. Evidence for hot gaseous coronae around the Magellanic Clouds

    NASA Technical Reports Server (NTRS)

    De Boer, K. S.; Savage, B. D.

    1980-01-01

    High-dispersion IUE far-UV spectra were obtained for five stars in the LMC and two stars in the SMC. At Magellanic Cloud velocities, all the spectra exhibit very strong interstellar lines of Al III, Si IV, and C IV, in addition to the usual lower ionization stage lines associated with H I region absorption. In two stars interstellar N V is also detected at the 50 mA level. From a consideration of the strength, width, and radial velocity of these high ionization stage lines, it is argued that regions of hot halo gas have probably been detected in front of the Magellanic Clouds. The regions detected exhibit absorption characteristics very similar to that of the Milky Way corona described previously by Savage and de Boer (1979). A cloud detected in the line of sight to HD 5980 in the SMC at a radial velocity of 300 km/s is of unknown origin.

  16. NPOI Observations of the Exoplanet Host Kappa Coronae Borealis

    NASA Astrophysics Data System (ADS)

    Baines, Ellyn K.; Armstrong, J. T.; van Belle, G.

    2014-01-01

    Kappa Coronae Borealis is a "retired A star", otherwise known as a former A-type dwarf that is now a K-type subgiant. It is a particularly fascinating target because of its unusual configuration of companions and dust rings. It hosts at least one exoplanet and perhaps two, and features a single wide dust ring or two narrow ones. We observed the star interferometrically in order to characterize the main star and the environment in which the planet(s) and dust ring(s) reside. We determined a variety of fundamental parameters for kappa CrB: the limb-darkened angular diameter, physical size, effective temperature, luminosity, mass, age, and the extent of the habitable zone range. We combined our mass with the orbital parameters from four sources from the literature to calculate the planet's mass as well.

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

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.

    1979-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. The observed properties of coronal transients concentrating on the white-light and radio manifestations. The possible mechanisims involved in the radio bursts are discussed. The estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the Sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the fields, provides a possible driving force for the coronal and interplanetary shock waves.

  18. Mid-infrared variations of R Coronae Borealis stars

    NASA Astrophysics Data System (ADS)

    Rao, N. Kameswara; Lambert, David L.

    2015-03-01

    Mid-infrared (IR) photometry of R Coronae Borealis stars obtained from various satellites from Infrared Astronomical Satellite (IRAS) to Wide-field Infrared Survey Explorer (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 (Td) 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 ? T_d^4 developed in the paper is satisfied, especially by those stars for which a single collection of clouds dominates the IR fluxes.

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

  20. 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.

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

    SciTech Connect

    Morgan, Huw; Jeska, Lauren; Leonard, Drew

    2013-06-01

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

  2. Buoyant subduction on Venus: Implications for subduction around coronae

    NASA Technical Reports Server (NTRS)

    Burt, J. D.; Head, J. W.

    1993-01-01

    Potentially low lithospheric densities, caused by high Venus surface and perhaps mantle temperatures, could inhibit the development of negative buoyancy-driven subduction and a global system of plate tectonics/crustal recycling on that planet. No evidence for a global plate tectonic system was found so far, however, specific features strongly resembling terrestrial subduction zones in planform and topographic cross-section were described, including trenches around large coronae and chasmata in eastern Aphrodite Terra. The cause for the absence, or an altered expression, of plate tectonics on Venus remains to be found. Slab buoyancy may play a role in this difference, with higher lithospheric temperatures and a tendency toward positive buoyancy acting to oppose the descent of slabs and favoring under thrusting instead. The effect of slab buoyancy on subduction was explored and the conditions which would lead to under thrusting versus those allowing the formation of trenches and self-perpetuating subduction were defined. Applying a finite element code to assess the effects of buoyant forces on slabs subducting into a viscous mantle, it was found that mantle flow induced by horizontal motion of the convergent lithosphere greatly influences subduction angle, while buoyancy forces produce a lesser effect. Induced mantle flow tends to decrease subduction angle to near an under thrusting position when the subducting lithosphere converges on a stationary overriding lithosphere. When the overriding lithosphere is in motion, as in the case of an expanding corona, subduction angles are expected to increase. An initial stage involved estimating the changes in slab buoyancy due to slab healing and pressurization over the course of subduction. Modeling a slab, descending at a fixed angle and heated by conduction, radioactivity, and the heat released in phase changes, slab material density changes due to changing temperature, phase, and pressure were derived.

  3. 2MASS wide-field extinction maps. V. Corona Australis

    NASA Astrophysics Data System (ADS)

    Alves, João; Lombardi, Marco; Lada, Charles J.

    2014-05-01

    We present a near-infrared extinction map of a large region (~870 deg2) covering the isolated Corona Australis complex of molecular clouds. We reach a 1-σ error of 0.02 mag in the K-band extinction with a resolution of 3 arcmin over the entire map. We find that the Corona Australis cloud is about three times as large as revealed by previous CO and dust emission surveys. The cloud consists of a 45 pc long complex of filamentary structure from the well known star forming Western-end (the head, N ≥ 1023 cm-2) to the diffuse Eastern-end (the tail, N ≤ 1021 cm-2). Remarkably, about two thirds of the complex both in size and mass lie beneath AV ~ 1 mag. We find that the probability density function (PDF) of the cloud cannot be described by a single log-normal function. Similar to prior studies, we found a significant excess at high column densities, but a log-normal + power-law tail fit does not work well at low column densities. We show that at low column densities near the peak of the observed PDF, both the amplitude and shape of the PDF are dominated by noise in the extinction measurements making it impractical to derive the intrinsic cloud PDF below AK < 0.15 mag. Above AK ~ 0.15 mag, essentially the molecular component of the cloud, the PDF appears to be best described by a power-law with index -3, but could also described as the tail of a broad and relatively low amplitude, log-normal PDF that peaks at very low column densities. FITS files of the extinction maps are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/A18

  4. Equilibria, Dynamics, and Current Sheet Formation in Magnetically Confined Coronae

    NASA Astrophysics Data System (ADS)

    Rappazzo, A. F.

    2015-12-01

    The dynamics of magnetic fields in closed regions of solar and stellar coronae are investigated with a reduced magnetohydrodynamic (MHD) model in the framework of the Parker scenario for coronal heating. A novel analysis of reduced MHD equilibria shows that their magnetic fields have an asymmetric structure in the axial direction with variation length scale zℓ ˜ ℓB0/b, where B0 is the intensity of the strong axial guide field, b that of the orthogonal magnetic field component, and ℓ the scale of {\\boldsymbol{b}}. Equilibria are then quasi-invariant along the axial direction for variation scales larger than approximatively the loop length zℓ ≳ Lz, and increasingly more asymmetric for smaller variation scales zℓ ≲ Lz. The critical length zℓ ˜ Lz corresponds to the magnetic field intensity threshold b ˜ ℓB0/Lz. Magnetic fields stressed by photospheric motions cannot develop strong axial asymmetries. Therefore, fields with intensities below such a threshold evolve quasi-statically, readjusting to a nearby equilibrium, without developing nonlinear dynamics or dissipating energy. But stronger fields cannot access their corresponding asymmetric equilibria hence, they are out of equilibrium and develop nonlinear dynamics. The subsequent formation of current sheets and energy dissipation is necessary for the magnetic field to relax to equilibrium, since dynamically accessible equilibria have variation scales larger than the loop length zℓ ≳ Lz, with intensities smaller than the threshold b ≲ ℓB0/Lz. The dynamical implications for magnetic fields of interest to solar and stellar coronae are investigated numerically and the impact on coronal physics discussed.

  5. On the Origin of Magnetic Helicity in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Tian, Lirong; Alexander, David

    2008-01-01

    Twenty-three active regions associated with pronounced sigmoidal structure in Yohkoh soft X-ray observations are selected to investigate the origin of magnetic helicity in the solar corona. We calculate the radial magnetic flux of each polarity, the rate of magnetic helicity injection, and total flux of the helicity injection (Δ HLCT) over 4-5 days using MDI 96 minute line-of-sight magnetograms and a local correlation tracking technique. We also estimate the contribution from differential rotation to the overall helicity budget (Δ Hrot). It is found that of the seven active regions for which the flux emergence exceeds 1.0 × 1022 Mx, six exhibited a helicity flux injection exceeding 1.0 × 1043 Mx2 (i.e., Δ H = Δ HLCT - Δ Hrot). Moreover, the rate of helicity injection and the total helicity flux are larger (smaller) during periods of more (less) increase of magnetic flux. Of the remaining 16 active regions, with flux emergence less than 1022 Mx, only 4 had significant injection of helicity, exceeding 1043 Mx2. Typical contributions from differential rotation over the same period were 2-3 times smaller than that of the strong magnetic field emergence. These statistical results signify that the strong emergence of magnetic field is the most important origin of the coronal helicity, while horizontal motions and differential rotation are insufficient to explain the measured helicity injection flux. Furthermore, the study of the helicity injection in nineteen newly emerging active regions confirms the result on the important role played by strong magnetic flux emergence in controlling the injection of magnetic helicity into the solar corona.

  6. Current Sheet Formation and Reconnection Dynamics in the Solar Corona

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    Current sheet formation is a necessary consequence of the evolution of the multi-polar magnetic field topologies that are ubiquitous throughout the solar corona. We present a very high-resolution study of 3D MHD current sheet formation and the resulting reconnection dynamics in an environment appropriate for the corona. The initial field consists of a translationally invariant, potential field with a null-point topology (i.e., 4-flux systems) and a low-beta plasma. A finite-extent, 3D Syrovatskii-type current sheet forms as a result of stressing of this system by a uniform, incompressible flow applied at the line-tied photospheric boundary. The system is assumed to be ideal, except for the presence of numerical resistivity. The fully 3-D evolution is calculated with very high resolution (9x and 10x refinement across the full extent of the current sheet) using the Adaptively Refined MHD Solver (ARMS). The initial evolution of this computationally-intensive simulation results in a current sheet with a nearly 30-to-1 aspect ratio, a significant fraction of the system characteristic length, that unexpectedly appears to be stable. In addition, up to this point in the evolution any magnetic reconnection that we observe is of the slow Sweet-Parker type. We expect, however, that as we continue stressing the field, the current sheet will become unstable and develop explosive dynamics. We discuss the implications of our results on coronal structure and activity, such as heating and eruptions. This work has been supported, in part, by the NASA HTP and SR&T programs.

  7. Distribution of electric currents in sunspots from photosphere to corona

    SciTech Connect

    Gosain, Sanjay; Démoulin, Pascal; López Fuentes, Marcelo

    2014-09-20

    We present a study of two regular sunspots that exhibit nearly uniform twist from the photosphere to the corona. We derive the twist parameter in the corona and in the chromosphere by minimizing the difference between the extrapolated linear force-free field model field lines and the observed intensity structures in the extreme-ultraviolet images of the Sun. The chromospheric structures appear more twisted than the coronal structures by a factor of two. Further, we derive the vertical component of electric current density, j{sub z} , using vector magnetograms from the Hinode Solar Optical Telescope (SOT). The spatial distribution of j{sub z} has a zebra pattern of strong positive and negative values owing to the penumbral fibril structure resolved by Hinode/SOT. This zebra pattern is due to the derivative of the horizontal magnetic field across the thin fibrils; therefore, it is strong and masks weaker currents that might be present, for example, as a result of the twist of the sunspot. We decompose j{sub z} into the contribution due to the derivatives along and across the direction of the horizontal field, which follows the fibril orientation closely. The map of the tangential component has more distributed currents that are coherent with the chromospheric and coronal twisted structures. Moreover, it allows us to map and identify the direct and return currents in the sunspots. Finally, this decomposition of j{sub z} is general and can be applied to any vector magnetogram in order to better identify the weaker large-scale currents that are associated with coronal twisted/sheared structures.

  8. ZnO Nanowire-Based Corona Discharge Devices Operated Under Hundreds of Volts.

    PubMed

    Yang, Wenming; Zhu, Rong; Zong, Xianli

    2016-12-01

    Minimizing the voltage of corona discharges, especially when using nanomaterials, has been of great interest in the past decade or so. In this paper, we report a new corona discharge device by using ZnO nanowires operated in atmospheric air to realize continuous corona discharge excited by hundreds of volts. ZnO nanowires were synthesized on microelectrodes using electric-field-assisted wet chemical method, and a thin tungsten film was deposited on the microchip to enhance discharging performance. The testing results showed that the corona inception voltages were minimized greatly by using nanowires compared to conventional dischargers as a result of the local field enhancement of nanowires. The corona could be continuously generated and self-sustaining. It was proved that the law of corona inception voltage obeyed the conventional Peek's breakdown criterion. An optimal thickness of tungsten film coated over ZnO nanowires was figured out to obtain the lowest corona inception voltage. The ion concentration of the nanowire-based discharger attained 10(17)/m(3) orders of magnitude, which is practicable for most discharging applications. PMID:26880727

  9. Predicting Cell Association of Surface-Modified Nanoparticles Using Protein Corona Structure - Activity Relationships (PCSAR).

    PubMed

    Kamath, Padmaja; Fernandez, Alberto; Giralt, Francesc; Rallo, Robert

    2015-01-01

    Nanoparticles are likely to interact in real-case application scenarios with mixtures of proteins and biomolecules that will absorb onto their surface forming the so-called protein corona. Information related to the composition of the protein corona and net cell association was collected from literature for a library of surface-modified gold and silver nanoparticles. For each protein in the corona, sequence information was extracted and used to calculate physicochemical properties and statistical descriptors. Data cleaning and preprocessing techniques including statistical analysis and feature selection methods were applied to remove highly correlated, redundant and non-significant features. A weighting technique was applied to construct specific signatures that represent the corona composition for each nanoparticle. Using this basic set of protein descriptors, a new Protein Corona Structure-Activity Relationship (PCSAR) that relates net cell association with the physicochemical descriptors of the proteins that form the corona was developed and validated. The features that resulted from the feature selection were in line with already published literature, and the computational model constructed on these features had a good accuracy (R(2)LOO=0.76 and R(2)LMO(25%)=0.72) and stability, with the advantage that the fingerprints based on physicochemical descriptors were independent of the specific proteins that form the corona. PMID:25961528

  10. 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.

  11. Effect of ion pair formation on the structure of polymer micelles with ionic amphiphilic coronae

    NASA Astrophysics Data System (ADS)

    Rumyantsev, A. M.; Kramarenko, E. Yu.

    2013-05-01

    We report a theoretical study of micelles from diblock copolymers with an insoluble core-forming block and an amphiphilic ionic corona-forming block. We calculate the micelle structural parameters depending on the composition of the coronal block (ratio between the non-polar and ion-containing groups) as well as solvent quality and polarity for the coronal block. We focus on the effect of ion pair formation in a low polar corona medium and predict the existence of novel micelles with ionomer-type coronae. In these micelles most part of counterions is bound with ions in polymer chains. Two consecutive jump-like first-order phase transitions between different-type micelles can take place in the solution upon change of hydrophobic/polyelectrolyte balance within the micelle corona: large micelles with polyelectrolyte collapsed coronae → large micelles with ionomer-type coronae → small micelles with polyelectrolyte swollen coronae. These transitions are accompanied by non-monotonous change in the micelle aggregation number. New insight into the role of counterions is important for design of stimuli responsive systems.

  12. Ex situ evaluation of the composition of protein corona of intravenously injected superparamagnetic nanoparticles in rats.

    PubMed

    Sakulkhu, Usawadee; Maurizi, Lionel; Mahmoudi, Morteza; Motazacker, Mahdi; Vries, Marcel; Gramoun, Azza; Ollivier Beuzelin, Marie-Gabrielle; Valle, Jean-Paul; Rezaee, Farhad; Hofmann, Heinrich

    2014-10-01

    It is now well recognized that the surfaces of nanoparticles (NPs) are coated with biomolecules (e.g., proteins) in a biological medium. Although extensive reports have been published on the protein corona at the surface of NPs in vitro, there are very few on the in vivo protein corona. The main reason for having very poor information regarding the protein corona in vivo is that separation of NPs from the in vivo environment has not been possible by using available techniques. Knowledge of the in vivo protein corona could lead to better understanding and prediction of the fate of NPs in vivo. Here, by using the unique magnetic properties of superparamagnetic iron oxide NPs (SPIONs), NPs were extracted from rat sera after in vivo interaction with the rat's physiological system. More specifically, the in vivo protein coronas of polyvinyl-alcohol-coated SPIONs with various surface charges are defined. The compositions of the corona at the surface of various SPIONs and their effects on the biodistribution of SPIONs were examined and compared with the corona composition of particles incubated for the same time in rat serum. PMID:25154771

  13. ZnO Nanowire-Based Corona Discharge Devices Operated Under Hundreds of Volts

    NASA Astrophysics Data System (ADS)

    Yang, Wenming; Zhu, Rong; Zong, Xianli

    2016-02-01

    Minimizing the voltage of corona discharges, especially when using nanomaterials, has been of great interest in the past decade or so. In this paper, we report a new corona discharge device by using ZnO nanowires operated in atmospheric air to realize continuous corona discharge excited by hundreds of volts. ZnO nanowires were synthesized on microelectrodes using electric-field-assisted wet chemical method, and a thin tungsten film was deposited on the microchip to enhance discharging performance. The testing results showed that the corona inception voltages were minimized greatly by using nanowires compared to conventional dischargers as a result of the local field enhancement of nanowires. The corona could be continuously generated and self-sustaining. It was proved that the law of corona inception voltage obeyed the conventional Peek's breakdown criterion. An optimal thickness of tungsten film coated over ZnO nanowires was figured out to obtain the lowest corona inception voltage. The ion concentration of the nanowire-based discharger attained 1017/m3 orders of magnitude, which is practicable for most discharging applications.

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

    NASA Astrophysics Data System (ADS)

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

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

  15. 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.

  16. Oxidation of nitric oxide in a two-stage chemical scrubber using dc corona discharge.

    PubMed

    Yang, C L; Chen, L

    2000-12-30

    The dc corona was studied as an alternative for NO oxidation in a two-stage chemical scrubber. The dc corona plasma reactor completely oxidized 150ppm of NO to NO2 in an air stream. The NO2 was further oxidized at a higher voltage. For some cases, the NO2 in the effluents of the plasma reactor was absorbed quantitatively by a caustic sodium sulfite aqueous solution in a 2l bubble column gas absorber. The outlet concentrations of both NO and NO2 from the plasma-scrubber combination system (corona-induced chemical scrubber) were below the detection limit of the chemiluminescent NOx analyzer. PMID:11080574

  17. Three-dimensional time domain model of lightning including corona effects

    NASA Technical Reports Server (NTRS)

    Podgorski, Andrew S.

    1991-01-01

    A new 3-D lightning model that incorporates the effect of corona is described for the first time. The new model is based on a Thin Wire Time Domain Lightning (TWTDL) Code developed previously. The TWTDL Code was verified during the 1985 and 1986 lightning seasons by the measurements conducted at the 553 m CN Tower in Toronto, Ontario. The inclusion of corona in the TWTDL code allowed study of the corona effects on the lightning current parameters and the associated electric field parameters.

  18. 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.

  19. The State of the Corona During the Weak Solar Cycle 24: the View from LASCO Images

    NASA Astrophysics Data System (ADS)

    Barlyaeva, T.; Lamy, P.; Llebaria, A.; Boclet, B.

    2016-04-01

    The LASCO-C2 coronagraph onboard SOHO continues its white-light imaging of the corona from 1.5 to 6.0 solar radii, thus allowing investigating the consequences of the weak Solar Cycle 24 on the corona and comparing it to the previous cycle (23). Temporal variations of the global radiance of the corona are presented. We pay particular attention to the mid-term variations which are distinctly different between the two cycles and highlight the similarities and differences. Finally, we rely on our ARTEMIS II catalog of coronal mass ejections (CMEs) to compare their global rates during these two cycles.

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

    NASA Astrophysics Data System (ADS)

    Candelaresi, Simon

    2016-05-01

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