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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

  4. Solar Cycle 23: Variation of the Solar Corona in the Ultraviolet from Solar Minimum to Solar Maximum

    NASA Astrophysics Data System (ADS)

    Miralles, M. P.; Panasyuk, A. V.; Strachan, L.; Gardner, L. D.; Suleiman, R.; Cranmer, S. R.; Kohl, J. L.

    2001-06-01

    UVCS/SOHO measurements of H I Ly-alpha and O VI (103.2 nm and 103.7 nm) intensities in the solar corona have been made from solar Cycle 23's minimum in 1996 to its current maximum. At solar minimum, the corona consisted of large coronal holes at the poles and quiescent streamers at the equator. During the approach to solar maximum, equatorial coronal holes and high latitude streamers became more conspicuous. Recently, coronal holes at higher latitudes have reappeared, allowing a comparison to be made of O VI intensities and line widths of coronal holes at different latitudes. We also characterize the variation of coronal hole properties with height, and location over the solar cycle. This work is supported by NASA under Grant NAG5-10093 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by PRODEX (Swiss contribution)

  5. Venus ionopause during solar minimum

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Pioneer Venus ion composition measurements are used to study the Venus ionosphere during solar minimum. It is suggested that the topside electron density profile at Venus during solar minimum has two distinct regimes. One beween 140 and 180 km is dominated by O2(+) ions which are in photochemical equilibrium. The other regime is above 180 km and is dominated by O(+) ions which are disturbed by the solar wind induced plasma transport. For Pioneer Venus, Mariner 10, and Venera 9 and 10 data, it is found that Venus exhibits a photodynamical type of ionopause during solar minimum.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. The periodicity of Grand Solar Minimum

    NASA Astrophysics Data System (ADS)

    Velasco Herrera, Victor Manuel

    2016-07-01

    The sunspot number is the most used index to quantify the solar activity. Nevertheless, the sunspot is a syn- thetic index and not a physical index. Therefore, we should be careful to use the sunspot number to quantify the low (high) solar activity. One of the major problems of using sunspot to quantify solar activity is that its minimum value is zero. This zero value hinders the reconstruction of the solar cycle during the Maunder minimum. All solar indexes can be used as analog signals, which can be easily converted into digital signals. In con- trast, the conversion of a digital signal into an analog signal is not in general a simple task. The sunspot number during the Maunder minimum can be studied as a digital signal of the solar activity In 1894, Maunder published a discovery that has maintained the Solar Physics in an impasse. In his fa- mous work on "A Prolonged Sunspot Minimum" Maunder wrote: "The sequence of maximum and minimum has, in fact, been unfailing during the present century [..] and yet there [..], the ordinary solar cycle was once interrupted, and one long period of almost unbroken quiescence prevailed". The search of new historical Grand solar minima has been one of the most important questions in Solar Physics. However, the possibility of estimating a new Grand solar minimum is even more valuable. Since solar activity is the result of electromagnetic processes; we propose to employ the power to quantify solar activity: this is a fundamental physics concept in electrodynamics. Total Solar Irradiance is the primary energy source of the Earth's climate system and therefore its variations can contribute to natural climate change. In this work, we propose to consider the fluctuations in the power of the Total Solar Irradiance as a physical measure of the energy released by the solar dynamo, which contributes to understanding the nature of "profound solar magnetic field in calm". Using a new reconstruction of the Total Solar Irradiance we found the

  11. 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.

  12. NEWLY DISCOVERED GLOBAL TEMPERATURE STRUCTURES IN THE QUIET SUN AT SOLAR MINIMUM

    SciTech Connect

    Huang Zhenguang; Frazin, Richard A.; Landi, Enrico; Manchester, Ward B.; Gombosi, Tamas I.; Vasquez, Alberto M.

    2012-08-20

    Magnetic loops are building blocks of the closed-field corona. While active region loops are readily seen in images taken at EUV and X-ray wavelengths, quiet-Sun (QS) loops are seldom identifiable and are therefore difficult to study on an individual basis. The first analysis of solar minimum (Carrington Rotation 2077) QS coronal loops utilizing a novel technique called the Michigan Loop Diagnostic Technique (MLDT) is presented. This technique combines Differential Emission Measure Tomography and a potential field source surface (PFSS) model, and consists of tracing PFSS field lines through the tomographic grid on which the local differential emission measure is determined. As a result, the electron temperature T{sub e} and density N{sub e} at each point along each individual field line can be obtained. Using data from STEREO/EUVI and SOHO/MDI, the MLDT identifies two types of QS loops in the corona: so-called up loops in which the temperature increases with height and so-called down loops in which the temperature decreases with height. Up loops are expected, however, down loops are a surprise, and furthermore, they are ubiquitous in the low-latitude corona. Up loops dominate the QS at higher latitudes. The MLDT allows independent determination of the empirical pressure and density scale heights, and the differences between the two remain to be explained. The down loops appear to be a newly discovered property of the solar minimum corona that may shed light on the physics of coronal heating. The results are shown to be robust to the calibration uncertainties of the EUVI instrument.

  13. A model of the trapped electron population for solar minimum

    NASA Technical Reports Server (NTRS)

    Teague, M. J.; Vette, J. I.

    1974-01-01

    A model is presented of the trapped electron environment of solar minimum conditions. Solar maximum models have been presented for the inner radiation zone (AE-5 1967), and for the outer radiation zone (AE-4 1967). The present solar minimum model consists of an inner zone model (AE-5 1975 Projected) with an epoch of 1975, and an outer zone model with an epoch of 1964. With only minor modifications this latter model is identical to the AE-4 1964 model presented previous. The model, however, has not previously been issued in computer form. AE-4 1964 is based upon satellite data, while the inner zone solar minimum model AE-5 1975 Projected consists entirely of extrapolations from AE-5 1967. While the two components of the solar minimum model have epochs 11 years part, it is assumed that any differences between the successive solar minima are smaller than the model error, and the complete model is associated with an epoch of 1975.

  14. 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.

  15. Mars ionopause during solar minimum - A lesson from Venus

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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, it is demonstrated that the observed O2 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. It is concluded that the solar wind interacts directly with the Mars ionosphere, suggesting that the planet does not have an intrinsic magnetic field of any consequence.

  16. STEREO's in-situ perspective on the solar minimum solar wind structure

    NASA Astrophysics Data System (ADS)

    Luhmann, J. G.; Larson, D.; Schroeder, P.; Lee, C. O.; Sauvaud, J.; Acuna, M. H.; Galvin, A. B.; Russell, C. T.; Jian, L.; Arge, C. N.; Odstrcil, D.; Riley, P.; Howard, R. A.; Aschwanden, M.; MacNeice, P.; Chulaki, A.

    2007-05-01

    STEREO multipoint measurements of the solar wind structure with the IMPACT and PLASTIC investigations, near Earth but off the Sun-Earth line, allow its sources and structure to be examined at solar minimum when such studies are particularly straightforward. With the aid of 3D models of the heliosphere available at the CCMC, we map the in-situ observations to their solar sources using a combination of the open field regions inferred from the SECCHI EUVI imagers and SOHO EIT, and the magnetogram-based models of the corona and solar wind. Our ultimate goal is the continuous tracking of solar wind source regions as the STEREO mission progresses, as well as the use of the mappings to deduce the distinctive properties of solar wind from different types of sources

  17. 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.

  18. 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.

  19. DIFFERENTIAL EMISSION MEASURE ANALYSIS OF A POLAR CORONAL HOLE DURING THE SOLAR MINIMUM IN 2007

    SciTech Connect

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

    2011-08-01

    We have performed a differential emission measure (DEM) analysis for a polar coronal hole observed during solar minimum in 2007. Five observations are analyzed spanning the coronal hole from the central meridian to the boundary with the quiet-Sun corona. The observed heights ranged from 1.05 to 1.20 R{sub sun}. The analysis shows that the plasma is not strictly isothermal anywhere, but rather has a high-temperature component that extends up to log T(K) = 6.2-6.3. The size and importance of this component depend on location, and its evolving magnitude with height marks the boundary between the coronal hole and the quiet corona, where it becomes dominant. The DEM of the coronal hole plasma below log T(K) = 6.0 decreases faster with height than that of the high-temperature component. We discuss the possible nature of the high-temperature component. Our results highlight the potential limitations of isothermal analyses. Such methods actually measure a DEM-weighted average temperature and as a result can infer artificial temperature gradients. Assuming the gas is isothermal along the line of sight can also yield incorrect electron densities. By revealing structures along the line of sight, a DEM analysis can also be used to more reliably interpret electron temperature and density measurements.

  20. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  2. Ground-Level Neutron Rates during the Recent Solar Minimum

    NASA Astrophysics Data System (ADS)

    Bieber, J. W.; Oh, S.; Evenson, P. A.; Clem, J. M.; Yi, Y.

    2010-12-01

    Neutron monitors have recorded by proxy the flux of Galactic cosmic rays since the 1950’s. This work evaluates cosmic ray fluxes during the recent extraordinary solar minimum in a longer-term context. Bartol neutron monitors are supported by the University of Delaware Department of Physics and Astronomy and Bartol Research Institute, by NSF grants ANT-0739620 and ANT-0838839, and by NASA EPSCoR.

  3. PROPERTIES OF A POLAR CORONAL HOLE DURING THE SOLAR MINIMUM IN 2007

    SciTech Connect

    Hahn, M.; Savin, D. W.; Bryans, P.; Landi, E.; Miralles, M. P.

    2010-12-10

    We report measurements of a polar coronal hole during the recent solar minimum using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Five observations are analyzed that span the polar coronal hole from the central meridian to the boundary with the quiet-Sun corona. We study the observations above the solar limb in the height range of 1.03-1.20 R{sub sun}. The electron temperature T{sub e} and emission measure (EM) are found using a geometric mean emission measure method. The EM derived from the elements Fe, Si, S, and Al are compared in order to measure relative coronal-to-photospheric abundance enhancement factors. We also studied the ion temperature T{sub i} and the non-thermal velocity v{sub nt} using the line profiles. All these measurements are compared to polar coronal hole observations from the previous (1996-1997) solar minimum and to model predictions for relative abundances. There are many similarities in the physical properties of the polar coronal holes between the two minima at these low heights. We find that the electron density, T{sub e}, and T{sub i} are comparable in both minima. T{sub e} shows a comparable gradient with height. Both minima show a decreasing T{sub i} with increasing charge-to-mass ratio q/M. A previously observed upturn of T{sub i} for ions above q/M>0.25 was not found here. We also compared relative coronal-to-photospheric elemental abundance enhancement factors for a number of elements. These ratios were {approx}1 for both the low first ionization potential (FIP) elements Si and Al and the marginally high FIP element S relative to the low FIP element Fe, as is expected based on earlier observations and models for a polar coronal hole. These results are consistent with no FIP effect in a polar coronal hole.

  4. Properties of a Polar Coronal Hole During the Solar Minimum in 2007

    NASA Astrophysics Data System (ADS)

    Hahn, M.; Bryans, P.; Landi, E.; Miralles, M. P.; Savin, D. W.

    2010-12-01

    We report measurements of a polar coronal hole during the recent solar minimum using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Five observations are analyzed that span the polar coronal hole from the central meridian to the boundary with the quiet-Sun corona. We study the observations above the solar limb in the height range of 1.03-1.20 R sun. The electron temperature T e and emission measure (EM) are found using a geometric mean emission measure method. The EM derived from the elements Fe, Si, S, and Al are compared in order to measure relative coronal-to-photospheric abundance enhancement factors. We also studied the ion temperature T i and the non-thermal velocity v nt using the line profiles. All these measurements are compared to polar coronal hole observations from the previous (1996-1997) solar minimum and to model predictions for relative abundances. There are many similarities in the physical properties of the polar coronal holes between the two minima at these low heights. We find that the electron density, T e, and T i are comparable in both minima. T e shows a comparable gradient with height. Both minima show a decreasing T i with increasing charge-to-mass ratio q/M. A previously observed upturn of T i for ions above q/M>0.25 was not found here. We also compared relative coronal-to-photospheric elemental abundance enhancement factors for a number of elements. These ratios were ~1 for both the low first ionization potential (FIP) elements Si and Al and the marginally high FIP element S relative to the low FIP element Fe, as is expected based on earlier observations and models for a polar coronal hole. These results are consistent with no FIP effect in a polar coronal hole.

  5. 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

  6. 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.

  7. 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.

  8. SphinX Measurements of the 2009 Solar Minimum X-Ray Emission

    NASA Astrophysics Data System (ADS)

    Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Kuzin, S.; Farnik, F.; Reale, F.; Phillips, K. J. H.; Bakała, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B.

    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 × 1047 cm-3 and 1.1 × 1048 cm-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.

  9. Activity associated with coronal mass ejections at solar minimum - SMM observations from 1984-1986

    NASA Technical Reports Server (NTRS)

    St. Cyr, O. C.; Webb, D. F.

    1991-01-01

    Seventy-three coronal mass ejections (CMEs) observed by the coronagraph aboard SMM between 1984 and 1986 were examined in order to determine the distribution of various forms of solar activity that were spatially and temporally associated with mass ejections during solar minimum phase. For each coronal mass ejection a speed was measured, and the departure time of the transient from the lower corona estimated. Other forms of solar activity that appeared within 45 deg longitude and 30 deg latitude of the mass ejection and within +/-90 min of its extrapolated departure time were explored. The statistical results of the analysis of these 73 CMEs are presented, and it is found that slightly less than half of them were infrequently associated with other forms of solar activity. It is suggested that the distribution of the various forms of activity related to CMEs does not change at different phases of the solar cycle. For those CMEs with associations, it is found that eruptive prominences and soft X-rays were the most likely forms of activity to accompany the appearance of mass ejections.

  10. A NOTE ON THE TORSIONAL OSCILLATION AT SOLAR MINIMUM

    SciTech Connect

    Howe, R.; Hill, F.; Komm, R.; Christensen-Dalsgaard, J.; Schou, J.; Thompson, M. J.

    2009-08-20

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

  11. Radiation-belt dynamics during solar minimum. Technical report

    SciTech Connect

    Gussenhoven, M.S.; Mullen, E.G.; Holeman, E.

    1989-12-01

    Two types of temporal variation in the radiation belts are studied using low altitude data taken onboard the DMSP F7 satellite: those associated with the solar cycle and those associated with large magnetic storm effects. Over a three-year period from 1984 to 1987 and encompassing solar minimum, the protons in the heart of the inner belt increased at a rate of approximately 6% per year. Over the same period, outer zone electron enhancements declined both in number and peak intensity. During the large magnetic storm of February 1986, following the period of peak ring current intensity, a second proton belt with energies up to 50 MeV was found at magnetic latitudes between 45 deg. and 55 deg. The belt lasted for more than 100 days. The slot region between the inner and outer electron belts collapsed by the merging of the two populations and did not reform for 40 days.

  12. 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.

  13. 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

  14. 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.

  15. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  17. Cosmic ray particles behavior during last solar minimum

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Martian ionosphere response to solar wind variability during solar minimum

    NASA Astrophysics Data System (ADS)

    Sanchez-Cano, Beatriz; Lester, Mark; Witasse, Olivier; Mays, M. Leila; Hall, Benjamin E. S.; Milan, Stephen E.; Cartacci, Marco; Blelly, Pierre-Louis; Andrews, David; Opgenoorth, Hermann; Odstrcil, Dusan

    2016-04-01

    Solar cycle variations in solar radiation create notable density changes in the Martian ionosphere. In addition to this long-term variability, there are numerous short-term and non-recurrent solar events that hit Mars which need to be considered, such as Interplanetary Coronal Mass Ejections (ICMEs), Co-Rotation Interaction Regions (CIRs), solar flares, or solar wind high speed streams. The response of the Martian plasma system to each of these events is often unusual, especially during the long period of extreme low solar activity in 2008 and 2009. This work shows the long-term solar cycle impact on the ionosphere of Mars using data from The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), and The Analyzer of Space Plasma and Energetic Atoms (ASPERA-3), and with empirical and numerical models on Mars Express. Particular attention is given to the different ionospheric responses observed during the last, extended solar minimum. Mars' ionospheric response followed a similar pattern to the response observed in the Earth's ionosphere, despite the large differences related to the inner-origin of the magnetic field of both planets. The ionospheric temperature was cooler, the topside scale height was smaller and almost constant with altitude, the secondary ionospheric layer practically disappeared and the whole atmospheric total electron content (TEC) suffered an extreme reduction of about 30-40%, not predicted before by models. Moreover, there is a larger probability for the induced magnetic field to be present in the ionosphere, than in other phases of the solar cycle. The short-term variability is also addressed with the study of an ICME followed by a fast stream that hit Mars in March 2008, where solar wind data are provided by ACE and STEREO-B and supported by simulations using the WSA-ENLIL Model. The solar wind conditions lead to the formation of a CIR centred on the interface of the fast and the slow solar wind streams. Mars' system reacted to

  3. 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

  4. Rocket measurements of the solar spectral irradiance during solar minimum, 1972-1977

    NASA Technical Reports Server (NTRS)

    Rottman, G. J.

    1981-01-01

    Five sounding rocket experiments conducted between December 1972 and March 1977, a period spanning solar minimum between cycles 20 and 21, provide full disc solar irradiance data in the spectral range 120-190 nm. The five measurements have been combined to give a solar minimum reference table. This spectrum is compared with other measurements obtained during the same time period. A table of intensities for the strong emission lines at wavelengths between 120 and 190 nm is presented.

  5. 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.

  6. Characteristics of the global ionospheric electron density during the extreme solar minimum condition

    NASA Astrophysics Data System (ADS)

    Jee, G.

    2010-12-01

    The last solar minimum period between the cycles 23 and 24 was anomalously low and lasted long compared with previous solar minimums. 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. There were several studies on this effect but many of them was on the thermosphere (Solomon et al., 2010; Emmert et al., 2010). According to these studies, the thermospheric temperature was cooler and the density was lower than the previous solar minimum periods. The low solar irradiance during the last solar minimum should also affect the ionosphere, not only via the lower ion-electron production due to the lower EUV radiation but also through the interactions with the thermosphere that was already influenced by the low solar irradiance. In this study, we utilized the measurements of total electron content (TEC) from the TOPEX and JASON satellites during the periods of 1992 to 2010, which includes the last two solar minimums, in order to investigate the differences between the ionospheric behaviors during the two minimum conditions. Initially the levels of the global ionization will be examined during these minimum periods and then further discussions will be continued on the details of the ionospheric behavior such as the seasonal and storm-time variations.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  8. 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.

  9. 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.

  10. 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.

  11. Ionospheric response to the High Speed Solar Streams during last solar minimum

    NASA Astrophysics Data System (ADS)

    Mosna, Zbysek; Koucka Knizova, Petra; Georgieva, Katya

    Ionosphere is a highly variable system. Response of ionospheric plasma to the High Speed Solar Streams (HSS) by means of critical frequencies fof2, heights of maximum electron concentration hmf2 and the occurrence of sporadic E-layer during last prolonged solar minimum is presented and we compare it to previous studies. State of the ionosphere depends on the daytime, season, phase of solar cycle etc. The extent of ionospheric response to the solar event (HSS, CME etc.) is a subject of mentioned conditions and strength of solar event itself but it also significantly depends on the actual geomagnetic and ionospheric situation and the memory of the system, e.g. length of the preceding quiet or disturbed period. Ionospheric storms have been relatively widely studied. However, last solar minimum gives us an exceptional possibility to study ionospheric processes under conditions of unusually long time of low solar activity.

  12. 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

  13. Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

    NASA Astrophysics Data System (ADS)

    Galvin, A. B.; Popecki, M. A.; Simunac, K. D. C.; Kistler, L. M.; Ellis, L.; Barry, J.; Berger, L.; Blush, L. M.; Bochsler, P.; Farrugia, C. J.; Jian, L. K.; Kilpua, E. K. J.; Klecker, B.; Lee, M.; Liu, Y. C.-M.; Luhmann, J. L.; Moebius, E.; Opitz, A.; Russell, C. T.; Thompson, B.; Wimmer-Schweingruber, R. F.; Wurz, P.

    2009-10-01

    STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h) sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007) which includes minor ion (He, Fe, O) kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

  14. a Study of Ionospheric Low Latitude Velocity and Density Irregularity Correlations during Solar Minimum

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    The C/NOFS satellite has measured ionospheric plasma density irregularities at low latitudes on scales larger than 10 km over a full set of seasons. The focus of this study is on data from the Ion Velocity Meter (IVM) from Jan-Dec 2009 for pre-midnight and post-midnight times when the data are most reliable. Correlations between the normalized changes in density and velocity (dni/n and dv-horz,vert) during spread-F events (plasma bubbles through the f-peak) and localized plasma enhancements associated with those events are analyzed and compared to investigate seasonal, spatial, and temporal properties during the 2009 solar minimum conditions. The correlations presented and their relationship to the unusually quiescent background conditions in this epoch challenge our understanding and add significantly to our knowledge of ionospheric irregularity events and distribution statistics at low latitudes during solar minimum.

  15. Energy spectrum of the recurrent cosmic rays variation during the solar minimum 23/24

    NASA Astrophysics Data System (ADS)

    Gil, Agnieszka; Alania, Michael

    2016-07-01

    We study temporal changes of the power-law energy/ rigidity spectrum of the first three harmonics of the recurrent variation of the galactic cosmic rays (GCR) intensity during the unusual solar minimum 23/24 and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation is soft in the minimum 23/24. Moreover, while the energy spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity practically behaves as during earlier four minima, the energy spectrum of the amplitudes of the second and the third harmonics demonstrate a valuable softening. We attribute this phenomenon to the decrease of an extension of heliosphere caused by the drop of the solar wind dynamic pressure during the solar minimum 23/24.

  16. 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.

  17. 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).

  18. 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.

  19. Impact of CIR storms on Thermosphere Density Variability during the Solar Minimum of 2008

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Thayer, Jeffrey; Forbes, Jeffrey M.; Wang, Wenbin; McPherron, Robert

    The solar minimum of 2008 was exceptionally quiet, with sunspot numbers at their lowest in at least 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 pri-mary contributor to the recurrent geomagnetic activity on the Earth. These conditions enable the isolation of forcing by geomagnetic activity on the preconditioned solar minimum state of the upper atmosphere caused by Corotating Interaction Regions (CIRs). Intense magnetic field regions or CIRs are due to the interaction of high-speed corotating streams with the upstream low speed solar wind, and high density current plasma sheet. Thermosphere density observa-tions around 400 km from the CHAMP satellite are used to study the thermosphere density response to the CIR storms. Superposed epoch results show that neutral density responds to CIR globally. The density at 400 km changed by 75%, on average, due to CIRs. The rela-tive changes of neutral density are comparable at different latitudes, although its variability is largest at high latitudes. In addition, the response of density to CIRs is larger at night than in daytime, indicating the pre-condition 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-mid latitudinal coronal holes on the basis of the EUVI observations from the STEREO satellites.

  20. 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.

  1. The TWINS exospheric neutral H-density distribution under solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Zoennchen, J. H.; Bailey, J. J.; Nass, U.; Gruntman, M.; Fahr, H. J.; Goldstein, J.

    2011-12-01

    Terrestrial exospheric atomic hydrogen (H) resonantly scatters solar Lyman-α (121.567 nm) radiation, observed as the glow of the H-geocorona. The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) satellites are equiped with two Lyman-α line-of-sight Detectors (LADs) each. Since during the past solar minimum conditions the relevant solar control parameters practically did not vary, we are using LAD data between June and September 2008 to create a time averaged hydrogen geocorona model representative for these solar minimum conditions. In this averaged model we assume that the H-geocorona is longitudinally symmetric with respect to the earth-sun line. We find a 3-dimensional H-density distribution in the range from 3 to 8 earth radii which with some caution can also be extrapolated to larger distances. For lower geocentric distances than 3 earth radii a best fitting r-dependent Chamberlain (1963)-like model is adapted. Main findings are larger than conventionally expected H-densities at heights above 5 RE and a pronounced day-to-night side H-density asymmetry. The H-geocorona presented here should serve as a reference H-atmosphere for the earth during solar minimum conditions.

  2. The Upper Atmosphere and Ionosphere at Solar Minimum: Cyclical and Secular Variation (Invited)

    NASA Astrophysics Data System (ADS)

    Solomon, S. C.; Qian, L.; Luan, X.

    2009-12-01

    Solar activity during 2007 and 2008 was extremely low, including ultraviolet irradiance, solar wind parameters, and the interplanetary magnetic field. During this protracted solar minimum period, the terrestrial upper atmosphere and ionosphere were expectedly cooler, lower in density, and consequently lower in altitude, than usual. The question remains as to whether the terrestrial response to this solar minimum is significantly different from previous solar minima, and if so, how different. This question is posed against the backdrop of secular change due to increased levels of carbon dioxide and other greenhouse gases, which increase tropospheric temperature but have the inverse effect of cooling the upper atmosphere. In order to understand the causes of these changes, and to quantify the interplay of the solar cycle with the evolution of upper atmosphere and ionosphere climate, we present a combination of data analysis and global numerical simulation. Thermospheric density data from atmospheric drag on satellites, ionospheric measurements by the COSMIC mission and from ground-based sources, and cooling rate data from the SABER instrument on the TIMED mission are compared to model simulations by the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). Solar ultraviolet irradiance observations, solar wind and geomagnetic data, and measurements of anthropogenic greenhouse gases, provide the external forcing of the model. Changes during the descent into solar minimum are compared to previous solar minima, and to model simulations, to evaluate how much of the current phenomenon is attributable to solar variation, and how much to anthropogenic sources.

  3. Initial Venus Express magnetic field observations of the magnetic barrier at solar minimum

    NASA Astrophysics Data System (ADS)

    Zhang, T. L.; Delva, M.; Baumjohann, W.; Volwerk, M.; Russell, C. T.; Barabash, S.; Balikhin, M.; Pope, S.; Glassmeier, K.-H.; Wang, C.; Kudela, K.

    2008-05-01

    Although there is no intrinsic magnetic field at Venus, the convected interplanetary magnetic field piles up to form a magnetic barrier in the dayside inner magnetosheath. In analogy to the Earth's magnetosphere, the magnetic barrier acts as an induced magnetosphere on the dayside and hence as the obstacle to the solar wind. It consists of regions near the planet and its wake for which the magnetic pressure dominates all other pressure contributions. The initial survey performed with the Venus Express magnetic field data indicates a well-defined boundary at the top of the magnetic barrier region. It is clearly identified by a sudden drop in magnetosheath wave activity, and an abrupt and pronounced field draping. It marks the outer boundary of the induced magnetosphere at Venus, and we adopt the name "magnetopause" to address it. The magnitude of the draped field in the inner magnetosheath gradually increases and the magnetopause appears to show no signature in the field strength. This is consistent with PVO observations at solar maximum. A preliminary survey of the 2006 magnetic field data confirms the early PVO radio occultation observations that the ionopause stands at ˜250 km altitude across the entire dayside at solar minimum. The altitude of the magnetopause is much lower than at solar maximum, due to the reduced altitude of the ionopause at large solar zenith angles and the magnetization of the ionosphere. The position of the magnetopause at solar minimum is coincident with the ionopause in the subsolar region. This indicates a sinking of the magnetic barrier into the ionosphere. Nevertheless, it appears that the thickness of the magnetic barrier remains the same at both solar minimum and maximum. We have found that the ionosphere is magnetized ˜95% of the time at solar minimum, compared with 15% at solar maximum. For the 5% when the ionosphere is un-magnetized at solar minimum, the ionopause occurs at a higher location typically only seen during solar

  4. Solar Cycle Variations of O VI and H I Lyman Alpha Intensities in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Miralles, M. P.; Panasyuk, A. V.; Strachan, L.; Gardner, L. D.; Suleiman, R. M.; Smith, P. L.; Kohl, J. L.

    2000-05-01

    UVCS/SOHO measurements of O VI (103.2 and 103.7 nm) and H I Lyman alpha intensities in the solar corona have been made from 1996 to the present spanning the rising phase of cycle 23. During solar minimum the corona consisted of large coronal holes at the poles and quiescent streamers at the equator. During the ascending phase of the cycle, the corona presented high latitude streamers and finally polar streamers as the Sun approached solar maximum. Recent observations of the solar corona show the presence of coronal holes at the equator and streamers at the poles. Our observations provide descriptions of these structures over the rising phase of the solar cycle. We compare the properties of quiescent equatorial streamers which occurred at solar minimum to high latitude and polar streamers observed toward solar maximum. We also compare solar minimum polar coronal holes to equatorial coronal holes present at solar maximum. We discuss how these results are related to the plasma properties. This work is supported by NASA under Grant NAG5-7822 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by PRODEX (Swiss contribution).

  5. 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

  6. Energetic H/He intensity ratio under solar maximum and solar minimum conditions: Ulysses observations

    NASA Astrophysics Data System (ADS)

    Lario, D.; Roelof, E. C.; Decker, R. B.; Ho, G. C.; Maclennan, C. G.; Gosling, J. T.

    2003-08-01

    We study the solar cycle variability of the heliospheric energetic proton-to-helium abundance ratios. We use 0.5-1.0 MeV nucleon -1 proton and helium intensities observed by the Ulysses spacecraft at both high and low heliographic latitudes. Ulysses observations show that during solar maximum the 0.5-1.0 MeV nucleon -1H/He intensity ratios are, on average, higher than during solar minimum. Under solar minimum conditions the interaction between slow and fast solar wind streams is strong, producing long-lasting and stable corotating interaction regions (CIRs) which are efficient accelerators of pickup He +. During solar maximum, transient events of solar origin (characterized by high H/He ratios) are able to globally fill the heliosphere. In addition, the absence of large and stable coronal holes results in a lack of recurrent strong corotating solar wind interactions, and consequently a less efficient acceleration of pickup He +. Even when solar wind stream interaction regions (SIRS) are observed, the H/He intensity ratio during solar maximum rarely decreases to the low (˜6) values typically observed during solar minimum CIR events. The latest data collected by Ulysses during its solar maximum descent from northern polar latitudes (mid-2002) show nearly-recurrent CIR events, which occasionally decrease the H/He ratios to these low (˜6) values. The still frequent occurrence of SEP events, however, produces increases of the H/He intensity ratios to high (˜30) values. Although SEP events still dominate the particle population in the inner heliosphere, the low H/He ratios observed in these specific CIR events suggest an efficient acceleration of pickup He + rather than the acceleration of remnant SEP material.

  7. Special Sensor Ultraviolet Limb Imager (SSULI) Observations of the Equatorial Nightside Ionosphere at Solar Minimum

    NASA Astrophysics Data System (ADS)

    Chua, D. H.; Coker, C.; Dymond, K.; McDonald, S. E.; Nicholas, A. C.; Budzien, S. A.; Dandenault, P. B.; Serengulian, P.; Walker, P. W.; Bust, G. S.

    2011-12-01

    We investigate the variability of the equatorial, nightside ionosphere during solar minimum conditions using observations by the Special Sensor Ultraviolet Limb Imager (SSULI) on the Defense Meteorological Satellite Program (DMSP) F18 satellite. SSULI limb profiles of the OI 135.6 nm radiative recombination emission are inverted using a 2-D tomographic code to infer nightside electron density profiles in the equatorial, post-sunset ionosphere near 2000 local time (LT) every 100 minutes. Through its first two years of operation in 2010 and 2011, SSULI/F18 has provided a new perspective on the daily variability of the equatorial ionosphere and the seasonal climatology of this region as we transition out of solar minimum into the rise of the next solar cycle. We find that variations in the low-latitude, nightside electron density have no clear correlation with changes in solar flux, suggesting that the ionosphere is driven more by transport than by daytime production (photoionization). During this period, the most prominent departures to the daily and seasonal variations in the low-latitude ionosphere are associated with quasi-periodic geomagnetic disturbances driven mainly by solar co-rotating interaction regions (CIRs). For most of these ionospheric disturbances we observe significant increases in electron density at all altitudes but find little evidence of uplift in the F-layer, suggesting that penetration electric fields are not playing a strong role in shaping the equatorial, post-sunset ionosphere at these times. The SSULI electron density reconstructions are compared to output from the IDA4D assimilative model of the ionosphere to provide further insight into the short term and seasonal variability of the equatorial, nightside ionosphere during these solar minimum conditions.

  8. 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.

  9. 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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  11. The impact of energetic electron precipitation on mesospheric hydroxyl during a year of solar minimum

    NASA Astrophysics Data System (ADS)

    Zawedde, Annet Eva; Nesse Tyssøy, Hilde; Hibbins, Robert; Espy, Patrick J.; Ødegaard, Linn-Kristine Glesnes; Sandanger, Marit Irene; Stadsnes, Johan

    2016-06-01

    In 2008 a sequence of geomagnetic storms occurred triggered by high-speed solar wind streams from coronal holes. Improved estimates of precipitating fluxes of energetic electrons are derived from measurements on board the NOAA/POES 18 satellite using a new analysis technique. These fluxes are used to quantify the direct impact of energetic electron precipitation (EEP) during solar minimum on middle atmospheric hydroxyl (OH) measured from the Aura satellite. During winter, localized longitudinal density enhancements in the OH are observed over northern Russia and North America at corrected geomagnetic latitudes poleward of 55°. Although the northern Russia OH enhancement is closely associated with increased EEP at these longitudes, the strength and location of the North America enhancement appear to be unrelated to EEP. This OH density enhancement is likely due to vertical motion induced by atmospheric wave dynamics that transports air rich in atomic oxygen and atomic hydrogen downward into the middle atmosphere, where it plays a role in the formation of OH. In the Southern Hemisphere, localized enhancements of the OH density over West Antarctica can be explained by a combination of enhanced EEP due to the local minimum in Earth's magnetic field strength and atmospheric dynamics. Our findings suggest that even during solar minimum, there is substantial EEP-driven OH production. However, to quantify this effect, a detailed knowledge of where and when the precipitation occurs is required in the context of the background atmospheric dynamics.

  12. The anomalous helium component in the heliosphere - The 1965 versus the 1972-1977 solar minimum

    NASA Technical Reports Server (NTRS)

    Garcia-Munoz, M.; Pyle, K. R.; Simpson, J. A.

    1983-01-01

    The anomalous He-4 component, hereafter He(A), was first observed in the galactic cosmic-ray helium spectrum at energies below about 60 MeV per nucleon in 1972 at the beginning of the extended period of minimum solar modulation, 1972-1977, after which period it again disappeared as solar modulation increased in the new solar activity cycle. This component was not apparent during the 1965 solar minimum. It is found that the helium spectrum measured during a short interval of enhanced modulation in 1974-1975 shows the same level as the He spectrum measured during 1965. This fact demonstrates that the absence of He(A) in 1965 can be explained as the consequence of a greater level of solar modulation at low energies in 1965 than in most of the 1972-1977 solar minimum. It is concluded that He(A) may be present at all times in the outer heliosphere and be observable at successive solar minima if the residual solar modulation is sufficiently low, as in most of the 1972-1977 minimum.

  13. 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.

  14. UVCS/SOHO Observations of Coronal Holes from Solar Minimum to Solar Maximum

    NASA Astrophysics Data System (ADS)

    Miralles, M. P.; Cranmer, S. R.; Esser, R.; Kohl, J. L.

    2001-12-01

    Coronal holes are open field, low-density source regions of the solar wind. At solar minimum, large coronal holes are present at the poles and are the dominant source of the solar wind flow for this part of the solar cycle. At solar maximum, coronal holes of varying sizes and shapes appear at all latitudes and last for several rotations. During this stage of the cycle, the dominant component is mainly slow wind, but fast wind streams are generated by large coronal holes. UVCS/SOHO has been used to measure the plasma properties in several types of coronal holes from 1996 to 2001. Spectroscopic diagnostics of O5+ velocity distributions and outflow velocities are derived from measurements of intensities and line widths for O~VI 103.2 and 103.7 nm as a function of height. We compare the plasma properties of coronal holes from solar minimum to solar maximum and discuss the evolution of coronal holes during the solar cycle. We also study the compatibility between the growing database of coronal hole plasma properties and theoretical models of extended coronal heating via ion cyclotron resonance. This work is supported by NASA under Grant NAG5-10093 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by PRODEX (Swiss contribution).

  15. 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.

  16. 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.

  17. 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.

  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. 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.

  20. 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....

  1. A Study of the Coronal Non-thermal Velocity in Polar Regions During the Rise from Solar Minimum to Solar Maximum in Cycle 24

    NASA Astrophysics Data System (ADS)

    Harra, L.; Baker, D.; Edwards, S. J.; Hara, H.; Howe, R.; van Driel-Gesztelyi, L.

    2015-11-01

    We explore the changes in coronal non-thermal velocity ( V nt) measurements at the poles from solar minimum to solar maximum using Hinode EUV Imaging Spectrometer data. We find that although the intensity in the corona at the poles does tend to increase with the cycle, there are no significant changes in the V nt values. The locations of enhanced V nt values measured do not always have a counterpart in intensity, and they are sometimes located in weak emission regions. Unipolar magnetic streams, created through diffusion of the following polarity of the decaying active regions, slowly progress towards the poles. These streams are expected to be related to magnetic nulls as locations that indicate an increased likelihood for magnetic reconnection to occur. Through global potential field source-surface modelling, we determine how the number of nulls varied during the cycle and find that those that lie at < 1.1 solar radii vary significantly. We search for a correlation between the variation of the magnetic nulls and the V nt values, as it may be expected that with an increasing number of nulls, the V nt values in the corona increase as well. There is no correlation with the V nt values, however. This indicates that the magnetic structures that create the enhanced V nt behaviour are small-scale features and hence not easily measurable at the poles. Because they do not change during the solar cycle, they are likely to be created by a local dynamo. The variation of the upper range of V nt is reduced, which highlights that strongly dynamic behaviour is reduced as the solar maximum approaches. This is likely to be due to the reduced area of the polar coronal hole, which allows fewer opportunities for reconnection to occur between open and closed magnetic fields.

  2. 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.

  3. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    1997-01-01

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

  4. MERIDIONAL CIRCULATION DURING THE EXTENDED SOLAR MINIMUM: ANOTHER COMPONENT OF THE TORSIONAL OSCILLATION?

    SciTech Connect

    Gonzalez Hernandez, I.; Howe, R.; Komm, R.; Hill, F.

    2010-04-10

    We show here a component of the meridional circulation developing at medium-high latitudes (40 deg. - 50 deg.) before the new solar cycle starts. Like the torsional oscillation of the zonal flows, this extra circulation seems to precede the onset of magnetic activity at the solar surface and moves slowly toward lower latitudes. However, the behavior of this component differs from that of the torsional oscillation regarding location and convergence toward the equator at the end of the cycle. The observation of this component before the magnetic regions appear at the solar surface has only been possible due to the prolonged solar minimum. The results could settle the discussion as to whether the extra component of the meridional circulation around the activity belts, which has been known for some time, is or is not an effect of material motions around the active regions.

  5. 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.

  6. Variability of the nitric oxide nightglow at Venus during solar minimum

    NASA Astrophysics Data System (ADS)

    Royer, E. M.; Montmessin, F.; Marcq, E.

    2016-05-01

    We present results from a NO airglow inversion method based on Venus Express data acquired from 2006 to 2010, during the last solar minimum period. We retrieve an altitude of 114 ± 10 km for the emission peak of the NO layer, with an associated scale height of 20 ± 10 km and an average limb brightness of 59.3 kR with a standard deviation of 63 kR. The inversion method allows for the quantification of the horizontal homogeneity of the NO layer. Images of the SPICAV field of view show a great variability of airglow morphologies, with NO layers that can be horizontally homogenous and continuous over distances exceeding 100 km, as well as sporadic patches of NO on a smaller horizontal scale. Frequent secondary emissions seen at lower tangent altitudes are the signatures of the complex dynamics of the upper Venusian atmosphere.

  7. 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.

  8. Global distribution of helium in the upper atmosphere during solar minimum

    NASA Technical Reports Server (NTRS)

    Cageao, R. P.; Kerr, R. B.

    1984-01-01

    The annual variations in the concentration of helium in the atmosphere have been measured by open mass spectrometry from onboard the Atmosphere Explorer C (AE-C) satellite. The observations were performed during the solar minimum in 1976 when geomagnetic activity was relatively low. It is shown that the monthly variation in helium number density has a smooth distribution over all latitudes throughout the year. The enhancement of helium over the winter pole (the helium bulge) is found to change slowly as the seasons progress. The progression of winter helium enhancement is given in a series of latitudinal profiles of helium number density for each month of the year. On the basis of the gradual variations in helium concentrations, it is suggested that the global thermospheric wind systems may also change gradually throughout the year.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  11. Anomalous and galactic cosmic ray intensities at 1 AU during the present solar minimum

    NASA Astrophysics Data System (ADS)

    Leske, Richard; Cummings, A. C.; Cohen, Christina; Mewaldt, R. A.; Stone, E. C.; Wiedenbeck, Mark; von Rosenvinge, Tycho

    Anomalous cosmic ray (ACR) intensities at 1 AU at solar minimum typically track galactic cosmic ray (GCR) intensities as measured by neutron monitors. Throughout the current A<0 cycle, however, the ACR intensities have consistently been a factor of 3-4 lower than expected from scaling neutron monitor rates; a similar discrepancy seems to have been present during the last A<0 period in the mid-1980's. Also, although the present solar minimum has been deep and long-lasting in terms of sunspot numbers and major solar particle events, ACR intensities remain almost a factor of 2 below their maximum values during each of the last two A>0 solar minima and have just barely reached the last A<0 levels. This is probably associated with the fact that ACRs drift inward along the heliospheric current sheet (HCS) during A<0 cycles, and the tilt of the current sheet has been relatively high, dropping below 15° for only 3 solar rotations starting in August 2009. However, while ACR intensities are typical or low, GCR intensities are at the highest levels recorded during the last 50 years, indicating these particles are not being as heavily modulated during their transport from the outer heliosphere. Using neutron monitor data along with ACR and GCR measurements from the ACE spacecraft, we find that both ACR and GCR intensities are actually much higher now for a given HCS tilt angle than they were during the last A<0 cycle. We present updated measurements of the ACR and GCR intensity variations at 1 AU through-out the solar cycle and discuss possible explanations for the different behavior between the present A<0 epoch and the previous one.

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

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.

    1990-01-01

    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 system shows that the rate of charge exchange with solar wind protons is 30 percent 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.

  15. Unraveling Parkinson's: Three Clues

    MedlinePlus

    ... Bar Home Current Issue Past Issues Unraveling Parkinson's: Three Clues Past Issues / Summer 2006 Table of Contents ... Dream Robber: Living with Parkinson's disease / Unraveling Parkinson's: Three Clues / Parkinson's Disease: The Newest Advances Summer 2006 ...

  16. 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

  17. 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.

  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

  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

  20. HERSCHEL Sounding Rocket Mission Observations of the Helium Corona

    NASA Astrophysics Data System (ADS)

    Newmark, Jeffrey; Moses, J.; Antonucci, E.; Fineschi, S.; Abbo, L.; Telloni, D.; Auchere, F.; Barbey, N.; Romoli, M.

    2010-05-01

    The HERSCHEL (Helium Resonant Scattering in the Corona and Heliosphere) investigation successfully obtained unprecedented images of the helium and hydrogen components of the solar corona out to 3 solar radii during a suborbital flight on 14 September 2009. Preliminary analysis of these observations indicates the spatial distribution of the helium abundance and outflow velocity provides powerful diagnostics for the source and dynamics of the slow solar wind during the time of solar minimum activity. An analysis of co-temporal STEREO EUVI data to derive the temperature of low coronal structures associated with the regions of enhanced helium abundance observed by HERSCHEL provides evidence the relative first ionization potential (FIP) of helium and hydrogen may play an important role in the observed abundance distribution. NRL was supported by the Office of Naval Research and NASA under NDPRS6598G.

  1. 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.

  2. 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.

  3. The Mapping of high-latitude TEC fluctuations during the last extended solar minimum

    NASA Astrophysics Data System (ADS)

    Sieradzki, R.; Cherniak, I.

    2012-04-01

    During the last few years the number of the GPS permanent stations have been increasing systematically. Currently it is possible to use phase GPS observations for detecting of the ionospheric disturbances with high spatial and temporal resolution. In this study 30 second GPS measurements were used to investigate the occureance of the TEC fluctuations at high and mid latitudes during the extended solar minimum period (2008-2011). Based on observations from more than 100 permanent stations the 2-hour maps of the TEC variability and daily map of the ionospheric fluctuations as a function geomagnetic local time were created. In order to determine the variability of the ionosphere ROT (Rate of TEC) and ROTI (Rate of TEC index) were used. 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. The statistical characteristics of fluctuation intensity and TEC fluctuations maps as well as data processing technique are presented.

  4. 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.

  5. Observations and models of the slow solar wind in coronal streamers during solar minimum

    NASA Astrophysics Data System (ADS)

    Ofman, L.

    2013-05-01

    A quiescent dipolar streamer belt often dominated the coronal streamer structures during past solar minima. Past UV observations with SOHO/UVCS show that the intensity of heavy ion emission lines (such as O VI and Mg X) is dimmer at the cores than at the streamer edges. Three-fluid 2.5D models indicated that the observed emission variability is the signature of slow solar wind outflow regions, where Coulomb coupling between the electron, protons, and heavy ions leads to enhanced emission of heavy ions at the edges of streamers. Recently, Ofman et al (2011, 2012) have modeled in detail the three-fluid interactions and the emission in a quiescent streamer due to Ly α, O 5+, and Mg 9+ ions at solar minimum, and used the model results to synthesize the corresponding line emissions. They found that the model results are in good agreement with observations, provided that the heavy ions experience preferential heating compared to protons. Similar results were found to hold for He++ ions in quiescent streamers. Recently, the 2.5D three-fluid model was extended to full 3D, allowing modeling the ion abundance variations in tilted dipole streamer belt, and eventually in solar maximum streamers. I will discuss the implication of heavy ion emission structure in streamers and the corresponding three-fluid models on the understanding of the slow solar wind sources.

  6. 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.

  7. Proton modulation and global gradients during the solar minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Vos, Etienne; Potgieter, Marius

    2016-07-01

    The PAMELA detector is capable of providing accurate measurements of the modulated proton energy spectrum at Earth. Between mid-2006 and mid-2009, the PAMELA and Ulysses missions overlapped, leading to the availability of simultaneous measurements of protons at Earth and along Ulysses' orbit which spans across a range of latitudes. These simultaneous measurements enable a detailed study of the global gradients of cosmic rays (CRs), especially when combined with a comprehensive 3D modulation model that include all of the important modulation mechanisms. In this study, a selection of PAMELA proton energy spectra at Earth were reproduced at different times during the solar minimum period of Cycle 23/24 using such a modulation model. Intensities along the orbit of Ulysses were also calculated for corresponding times. By comparing model solutions with measurements and consequently calculating the global gradients, the physics behind solar modulation can be tested and verified, in particular drifts which cause charge-sign dependent modulation. Moreover, with the crossing of the heliopause (HP) by Voyager 1 in 2012, measurements from beyond the HP allow us to constrain the very local interstellar spectrum for energies below ~100MeV, while PAMELA and AMS-02 measurements can be used to normalize the LIS for energies above ~30GeV, where modulation becomes negligible. This eliminates many uncertainties in modulation studies that existed before.

  8. Characteristics of winter-time meridional thermospheric winds over Tromsø during solar minimum

    NASA Astrophysics Data System (ADS)

    Cai, Hongtao; Zhan, Weijia; Huang, Dingjuan; Li, Fei; Zhou, Kangjun; Shen, Ge; Willian McCrea, Ian; Ma, Shuying

    2015-04-01

    The background of the winter-time thermospheric wind over Tromsø (69 °N, 19 °E) were focused on in this paper. The meridional component of the neutral wind in F-region were derived from the field-aligned ion velocity detected by the European incoherent scattering (EISCAT) radar. In order to eliminate possible influences from solar activity variances and geomagnetic disturbance, only measurements accomplished under geomagnetically quiet conditions (with maximum Kp ≤ 3) around the winter solstice during solar minimum (2008-2009) were chosen in present work. Two major characteristics of the radar derived winds are revealed. The first feature is the vertical variations of the meridional winds. Magnitudes of the equatorward winds observed show a hint of increasing with altitudes during nighttime. The second one is the persistent equatorward winds at altitudes higher than 280 km height during daytime, especially around local noon, whilst the prevailing poleward winds appear at lower altitudes. Thus, significant shears of horizontal winds are expected in the vertical direction. Detail comparisons with models and discussions of the possible driving forces for the day-time equatorward winds will be presented in the report.

  9. 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.

  10. CME-related particle acceleration regions during a simple eruptive event near solar minimum

    NASA Astrophysics Data System (ADS)

    Salas Matamoros, Carolina; Klein, Karl-Ludwig; Rouillard, Alexis

    2016-04-01

    An intriguing feature of many solar energetic particle (SEP) events is the detection of particles over a very extended range of longitudes in the Heliosphere. This may be due to peculiarities of the magnetic field in the corona, to a broad accelerator, to cross-field transport of the particles, or to a combination of these processes. The eruptive flare of the 26th of April 2008 offered an opportunity to study relevant processes under particularly favorable conditions, since it occurred in a very quiet solar and interplanetary environment. This allowed us to investigate the physical link between a single well-identified Coronal Mass Ejection (CME), electron acceleration as traced by radio emission, and the production of SEPs. We conduct a detailed analysis combining radio observations (Nançay Radioheliograph and Decameter Array, Wind/WAVES spectrograph) with remote-sensing observations of the corona in extreme ultraviolet (EUV) and white light as well as in-situ measurements of energetic particles near 1AU (SoHO and STEREO spacecraft). By combining images taken from multiple vantage points we were able to derive the time-dependent evolution of the 3-D pressure front developing around the erupting CME. Magnetic reconnection in the post-CME current sheet accelerated electrons that remained confined in closed magnetic fields in the corona, while the acceleration of escaping particles can be attributed to the pressure front generated ahead of the expanding CME. The CME accelerated electrons remotely from the parent active region, due to the interaction of its laterally expanding flank, traced by an EUV wave, with the ambient corona. SEPs detected at one STEREO spacecraft and SoHO were accelerated later, when the frontal shock of the CME intercepted the spacecraft-connected interplanetary magnetic field line. The injection regions into the Heliosphere inferred from the radio and SEP observations are separated in longitude by about 140°. The observations for this event

  11. Corona Discharge in Clouds

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  12. Empirical densities, kinetic temperatures, and outflow velocities in the equatorial streamer belt at solar minimum

    NASA Astrophysics Data System (ADS)

    Strachan, L.; Suleiman, R.; Panasyuk, A. V.; Biesecker, D. A.; Kohl, J. L.

    2002-05-01

    We use combined Ultraviolet Coronagraph Spectrometer (UVCS) and Large Angle Spectroscopic Coronagraph (LASCO) data to determine the O(5+) outflow velocities as a function of height along the axis of an equatorial streamer at solar minimum and as a function of latitude (at 2.3 solar radii from sun center). The results show that outflow increases rather abruptly in the region between 3.6 and 4.1 solar radii near the streamer cusp, and gradually increases to 90 km/s at about 5 solar radii in the streamer stalk beyond the cusp. The latitudinal variation at 2.3 solar radii shows that there is no outflow (within the measurement uncertainties) in the center of the streamer called the core, and that a steep increase in outflow occurs just beyond the streamer legs, where the O VI 1032 intensity relative to H I 1216 (Ly alpha) is higer than in the core. Velocity variations in both height and latitude show that the transitions from no measurable outflow to positive outflow are relatively sharp and thus can be used to infer the location of the transition from closed to open field lines in streamer magnetic field topologies. Such information, including the densities and kinetic temperatures derived from the observations, provides hard constraints for realistic theoretical models of streamers and the source regions of the slow solar wind. This work is supported by NASA Grant NAG5-11420 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency, and by the ESA PRODEX program (Swiss contribution). do not accept author defined LaTeX macros.

  13. Gyro-resonant scattering of radiation belt electrons during the solar minimum by fast magnetosonic waves

    NASA Astrophysics Data System (ADS)

    Shprits, Yuri Y.; Runov, Andrei; Ni, Binbin

    2013-02-01

    In the current study, we perform statistical analysis of the magnetosonic (MS) waves (also often referred to as extremely low frequency (ELF) equatorial noise) in the range between the ion cyclotron frequency and the lower hybrid resonance frequency within 10° of the magnetic equator. Observations were made between 2 and 9 RE using THEMIS Filter Bank (FBK) data. ELF waves with spectral power exceeding 10-6 nT2/Hz are registered in ~3% of all samples in the inner magnetosphere. The survey has shown that, during the solar minimum, the average amplitude of equatorial ELF waves is less than 0.025 nT. Interpreting ELF events as MS waves, we have evaluated the corresponding wave-induced resonant scattering coefficients of radiation belt energetic electrons. We also study the effect of heavy ions on the scattering rates. The analysis reveals that the scattering by magnetosonic waves for various plasma compositions during geomagnetically quiet times is by up to two orders of magnitude slower than was previously reported and cannot significantly contribute to the long-term dynamics of the radiation belts. Computed electron scattering rates by magnetosonic waves extends to higher αeq when the fraction of H+ in the plasma decreases, while the range of pitch angles for which resonance occurs remains relatively insensitive to the plasma composition. While inclusion of multi-ion species into the wave dispersion relation produces noticeable changes in bounce-averaged scattering rates, the average rates are still significantly below typical scattering rates of chorus or hiss waves.

  14. 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.

  15. Galactic cosmic ray radiation hazard in the unusual extended solar minimum between solar cycles 23 and 24

    NASA Astrophysics Data System (ADS)

    Schwadron, N. A.; Boyd, A. J.; Kozarev, K.; Golightly, M.; Spence, H.; Townsend, L. W.; Owens, M.

    2010-05-01

    Galactic cosmic rays (GCRs) are extremely difficult to shield against and pose one of the most severe long-term hazards for human exploration of space. The recent solar minimum between solar cycles 23 and 24 shows a prolonged period of reduced solar activity and low interplanetary magnetic field strengths. As a result, the modulation of GCRs is very weak, and the fluxes of GCRs are near their highest levels in the last 25 years in the fall of 2009. Here we explore the dose rates of GCRs in the current prolonged solar minimum and make predictions for the Lunar Reconnaissance Orbiter (LRO) Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which is now measuring GCRs in the lunar environment. Our results confirm the weak modulation of GCRs leading to the largest dose rates seen in the last 25 years over a prolonged period of little solar activity.

  16. Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

    NASA Astrophysics Data System (ADS)

    Gil, Agnieszka; Alania, Michael V.

    2016-08-01

    The Sun during the recent epoch of solar activity operated in a different way than during the last 60 years, being less active. We study temporal changes of the energy spectrum of the first three harmonics of the 27-day variation of the galactic cosmic rays (GCR) intensity during the unusual, recent solar minimum, between Solar Cycles 23 and 24 (SC 23/24) and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation of the GCR intensity is hard in the maximum epochs and is soft in the minimum epochs during Solar Cycles 20 - 24, but with peculiarities during the Solar Minimum 23/24. In particular, while the energy/rigidity spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity behaves practically the same as for previous epochs, the energy/rigidity spectrum of the amplitudes of the second and the third harmonics demonstrates a pronounced softening. We attribute this phenomenon to the decrease of the extension of the heliosphere caused by the decrease of the solar-wind dynamic pressure during the unusual Solar Minimum 23/24.

  17. Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

    NASA Astrophysics Data System (ADS)

    Gil, Agnieszka; Alania, Michael V.

    2016-07-01

    The Sun during the recent epoch of solar activity operated in a different way than during the last 60 years, being less active. We study temporal changes of the energy spectrum of the first three harmonics of the 27-day variation of the galactic cosmic rays (GCR) intensity during the unusual, recent solar minimum, between Solar Cycles 23 and 24 (SC 23/24) and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation of the GCR intensity is hard in the maximum epochs and is soft in the minimum epochs during Solar Cycles 20 - 24, but with peculiarities during the Solar Minimum 23/24. In particular, while the energy/rigidity spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity behaves practically the same as for previous epochs, the energy/rigidity spectrum of the amplitudes of the second and the third harmonics demonstrates a pronounced softening. We attribute this phenomenon to the decrease of the extension of the heliosphere caused by the decrease of the solar-wind dynamic pressure during the unusual Solar Minimum 23/24.

  18. Possible impacts of a descent into a Grand Solar Minimum on extratropical regional surface climate

    NASA Astrophysics Data System (ADS)

    Maycock, A. C.; Ineson, S.; Gray, L. J.; Scaife, A. A.; Lockwood, M. M.

    2012-12-01

    The Sun's output varies on a number of characteristic timescales, the most well-known of which is the approximately 11-year solar cycle. It has been shown that the Sun also exhibits cycles with a period of ~200 years, so-called Grand Solar Cycles. Reconstructions indicate that levels of solar activity have been relatively high for the past ~70 years, and it has been suggested that the Sun might be expected to evolve towards a state of lower output; however, the timescale and extent of such a 'Grand Solar Minimum' event is highly uncertain. This study presents sensitivity experiments with a state-of-the-art climate model to investigate the impact of reaching very low levels of solar output, similar to those thought to have occurred during the Maunder Minimum, by the middle of the 21st century. We investigate the effect of uncertainties in spectral solar irradiance by using both the semi-empirical model of Lean et al., which gives a relatively modest change in the ultraviolet (UV) spectral region and is commonly used to represent solar variability in climate models, as well as the recent measurements from the SORCE satellite, which suggest a much larger change in the UV across the solar cycle for the period 2004-07. Under the assumption of there being a large change in the UV derived from a linear extrapolation of the SORCE data, it is shown that a period of very low solar activity would be associated with a more negative North Atlantic Oscillation index. This signature in the large-scale circulation is associated with changes in regional surface climate, including cooler temperatures across the UK and western Europe. In the experiment which assumes a smaller change in UV irradiance, the extratropical circulation responses in the stratosphere and troposphere are found to be of a consistent sign but smaller in magnitude. This highlights the importance of one possible mechanism for solar-climate interactions, namely the impact of tropical upper stratospheric heating on

  19. 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

  20. 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.

  1. 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..

  2. 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

  3. Performance of IRI-2012 model during a deep solar minimum and a maximum year over global equatorial regions

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay

    2016-06-01

    Present paper inspects the prediction capability of the latest version of the International Reference Ionosphere (IRI-2012) model in predicting the total electron content (TEC) over seven different equatorial regions across the globe during a very low solar activity phase 2009 and a high solar activity phase 2012. This has been carried out by comparing the ground-based Global Positioning System (GPS)-derived VTEC with those from the IRI-2012 model. The observed GPS-TEC shows the presence of winter anomaly which is prominent during the solar maximum year 2012 and disappeared during solar minimum year 2009. The monthly and seasonal mean of the IRI-2012 model TEC with IRI-NeQ topside has been compared with the GPS-TEC, and our results showed that the monthly and seasonal mean value of the IRI-2012 model overestimates the observed GPS-TEC at all the equatorial stations. The discrepancy (or over estimation) in the IRI-2012 model is found larger during solar maximum year 2012 than that during solar minimum year 2009. This is a contradiction to the results recently presented by Tariku (2015) over equatorial regions of Uganda. The discrepancy is found maximum during the December solstice and a minimum during the March equinox. The magnitude of discrepancy in the IRI-2012 model showed longitudinal dependent which maximized in western longitude sector during both the years 2009 and 2012. The significant discrepancy in the IRI-2012 model observed during the solar minimum year 2009 could be attributed to larger difference between F10.7 flux and EUV flux (26-34 nm) during low solar activity period 2007-2009 than that during high solar activity period 2010-2012. This suggests that to represent the solar activity impact in the IRI model, implementation of new solar activity indices is further required for its better performance.

  4. Global Gradients for Cosmic-Ray Protons in the Heliosphere During the Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Vos, E. E.; Potgieter, M. S.

    2016-08-01

    Global gradients for cosmic-ray (CR) protons in the heliosphere are computed with a comprehensive modulation model for the recent prolonged solar minimum of Cycle 23/24. Fortunately, the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) and Ulysses/KET (Kiel Electron Telescope) instruments simultaneously observed proton intensities for the period between July 2006 and June 2009. This provides a good opportunity to compare the basic features of the model with these observations, including observations from Voyager-1 in the outer heliosphere, beyond 50 AU. Radial and latitudinal gradients are calculated from measurements, with the latter possible because Ulysses changed its position significantly in the heliocentric meridional plane during this period. The modulation model is set up for the conditions that prevailed during this unusual solar-minimum period to gain insight into the role that particle drifts played in establishing the observed gradients for this period. Four year-end PAMELA proton spectra were reproduced with the model, from 2006 to 2009, followed by corresponding radial profiles that were computed along the Voyager-1 trajectory, and compared to available observations. It is found that the computed intensity levels are in agreement with solar-minimum observations from Voyager-1 at multiple energies. The model also reproduces the steep intensity increase observed when Voyager-1 crossed the heliopause region. Good agreement is found between computed and observed latitudinal gradients, so that we conclude that the model gives a most reasonable representation of modulation conditions from the Earth to the heliopause for the period from 2006 to 2009. As a characteristic feature of CR drifts, the most negative latitudinal gradient is computed for 2009, with a value of -0.15 % degree^{-1} around 600 MV. The maximum radial gradient in the inner heliosphere (as covered by Ulysses) also occurs in this range, with the highest value

  5. Potential impacts of a future Grand Solar Minimum on decadal regional climate change and interannual hemispherical climate variability

    NASA Astrophysics Data System (ADS)

    Spiegl, Tobias; Langematz, Ulrike

    2016-04-01

    The political, technical and socio-economic developments of the next decades will determine the magnitude of 21st century climate change, since they are inextricably linked to future anthropogenic greenhouse gas emissions. To assess the range of uncertainty that is related to these developments, it is common to assume different emission scenarios for 21st climate projections. While the uncertainties associated with the anthropogenic greenhouse gas forcing have been studied intensely, the contribution of natural climate drivers (particularly solar variability) to recent and future climate change are subject of intense debate. The past 1,000 years featured at least 5 excursions (lasting 60-100 years) of exceptionally low solar activity, induced by a weak magnetic field of the Sun, so called Grand Solar Minima. While the global temperature response to such a decrease in solar activity is assumed to be rather small, nonlinear mechanisms in the climate system might amplify the regional temperature signal. This hypothesis is supported by the last Grand Solar Minimum (the Maunder Minimum, 1645-1715) which coincides with the Little Ice Age, an epoch which is characterized by severe cold and hardship over Europe, North America and Asia. The long-lasting minimum of Solar Cycle 23 as well as the overall weak maximum of Cycle 24 reveal the possibility for a return to Grand Solar Minimum conditions within the next decades. The quantification of the implications of such a projected decrease in solar forcing is of ultimate importance, given the on-going public discussion of the role of carbon dioxide emissions for global warming, and the possible role a cooling due to decreasing solar activity could be ascribed to. Since there is still no clear consensus about the actual strength of the Maunder Minimum, we used 3 acknowledged solar reconstruction datasets that show significant differences in both, total solar irradiance (TSI) and spectral irradiance (SSI) to simulate a future

  6. 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

  7. Validation of IRI-2012 TEC model over Ethiopia during solar minimum (2009) and solar maximum (2013) phases

    NASA Astrophysics Data System (ADS)

    Asmare, Yekoye; Kassa, Tsegaye; Nigussie, Melessew

    2014-06-01

    This paper investigates the capacity of the latest version of the International Reference Ionosphere (IRI-2012) model in predicting the vertical Total Electron Content (vTEC) over Ethiopian regions during solar minimum (2009) and solar maximum (2013) phases. This has been carried out by comparing the IRI-2012 modeled and experimental vTEC inferred from eight ground based dual frequency GPS (Global Positioning System) receivers installed recently at different regions of the country. In this work, the diurnal, monthly and seasonal variation in the measured vTEC have been analyzed and compared with the IRI-2012 modeled vTEC. During the solar minimum phase, the lowest and highest diurnal peak of the experimental vTEC are observed in July and October, respectively. In general, the diurnal variability of vTEC has shown minimum values around 0300 UT (0600 LT) and maximum values between around 1000 and 1300 UT (1300 and 1600 LT) during both solar activity phases. Moreover, the maximum and minimum monthly and seasonal mean hourly vTEC values are observed in October and July and in the March equinox and June solstice, respectively. It is also shown that the IRI-2012-model better predicts the diurnal vTEC in the time interval of about 0000-0300 UT (0300-0600 LT) during the solar minimum phase. However, the model generally overestimates the diurnal vTEC except in the time interval of about 0900-1500 UT (1200-1800 LT) during the solar maximum phase. The overall result of this work shows that the diurnal vTEC prediction performance of the model is generally better during the solar minimum phase than during solar maximum phase. Regarding the monthly and seasonal prediction capacity of the model, there is a good agreement between the modeled and measured monthly and seasonal mean hourly vTEC values in January and December solstice, respectively. Another result of the work depicts that unlike the GPS-TEC the IRI-2012 TEC does not respond to the effect resulted from geomagnetic

  8. A theoretical study of the high-latitude winter F region at solar minimum for low magnetic activity

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Raitt, W. J.; Schunk, R. W.

    1981-01-01

    A simple plasma convection model is combined with an ionospheric-atmospheric composition model in order to study the high-latitude winter F region at the solar minimum for low magnetic activity. The high latitude ionospheric features, such as the main trough, the ionization hole, the tongue of ionization, the aurorally produced ionization peaks, and the universal time effects are a natural consequence of the competition between the various chemical and transport processes known to be operating in the high-latitude ionosphere. In the polar hole, the F region peak electron density is below 300 km, and the dominant process at 300 km for NO(+) ions is diffusion.

  9. 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.

  10. Performance of the IRI-2007 Model for Topside Ion Density and Composition Profiles During the 23/24 Solar Minimum

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    The recent solar minimum between cycles 23 and 24 was unusually extended and deep, resulting in an ionosphere that is significantly different from that expected based on previous solar minima. The ion density and composition estimates from the Communication/Navigation Outage Forecast System (C/NOFS) satellite are used to evaluate the performance of the IRI-2007 model between 400 and 850 kIn altitude in equatorial regions. The current model is shown to typically overestimate the expected topside density of 0+ and underestimate the density of H+ during 2008 and 2009. The overestimation of ion density by IRI-2007 is found to vary with local time and longitude.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Global Gradients for Cosmic-Ray Protons in the Heliosphere During the Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Vos, E. E.; Potgieter, M. S.

    2016-08-01

    Global gradients for cosmic-ray (CR) protons in the heliosphere are computed with a comprehensive modulation model for the recent prolonged solar minimum of Cycle 23/24. Fortunately, the PAMELA ( Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) and Ulysses/KET ( Kiel Electron Telescope) instruments simultaneously observed proton intensities for the period between July 2006 and June 2009. This provides a good opportunity to compare the basic features of the model with these observations, including observations from Voyager-1 in the outer heliosphere, beyond 50~AU. Radial and latitudinal gradients are calculated from measurements, with the latter possible because Ulysses changed its position significantly in the heliocentric meridional plane during this period. The modulation model is set up for the conditions that prevailed during this unusual solar-minimum period to gain insight into the role that particle drifts played in establishing the observed gradients for this period. Four year-end PAMELA proton spectra were reproduced with the model, from 2006 to 2009, followed by corresponding radial profiles that were computed along the Voyager-1 trajectory, and compared to available observations.

  19. 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.

  20. 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.

  1. Simulating coronas in color.

    PubMed

    Gedzelman, Stanley D; Lock, James A

    2003-01-20

    Coronas are simulated in color by use of the Mie scattering theory of light by small droplets through clouds of finite optical thickness embedded in a Rayleigh scattering atmosphere. The primary factors that affect color, visibility, and number of rings of coronas are droplet size, width of the size distribution, and cloud optical thickness. The color sequence of coronas and iridescence varies when the droplet radius is smaller than approximately 6-microm. As radius increases to approximately 3.5 microm, new color bands appear at the center of the corona and fade as they move outward. As the radius continues to increase to approximately 6 microm, successively more inner rings become fixed in the manner described by classical diffraction theory, while outer rings continue their outward migration. Wave clouds or rippled cloud segments produce the brightest and most vivid multiple ringed coronas and iridescence because their integrated dropsize distributions along sunbeams are much narrower than in convective or stratiform clouds. The visibility of coronas and the appearance of the background sky vary with cloud optical depth tau. First the corona becomes visible as a white aureole in a blue sky when tau approximately 0.001. Color purity then rapidly increases to an almost flat maximum in the range 0.05 < or = tau < or = 0.5 and then decreases, so coronas are almost completely washed out by a bright gray background when tau > or = 4. PMID:12570272

  2. Equatorial plasma depletions observed by the DMSP F13 satellite near dawn during geomagnetic disturbances in a solar minimum

    NASA Astrophysics Data System (ADS)

    Kim, V. P.; Min, K. W.; Hegai, V. V.

    2015-01-01

    We report on in situ measurements of equatorial plasma depletions in the dawn sector from the DMSP F13 satellite during magnetic disturbances which occurred within the solar minimum period of 1995-1996. Examples are given when DMSP F13 observed prominent pre-sunrise depletions associated with weak magnetic disturbances, while the most severe magnetic storms of the period showed only small amplitude depletions of plasma density. Our results indicate that the depletions were observed within about two third of the magnetically perturbed days with the negative maximum excursions of SYM-H less than -40 nT at any season and at various longitudes. Commonly, the depletions appear following the negative SYM-H peaks in the recovery phase of the magnetic disturbances. We discuss the roles of corotating evening depletions and near-dawn effects of the prompt penetration overshielding and the disturbance dynamo eastward electric fields as sources for the reported depletions.

  3. Detection of large scale geomagnetic pulsations by MAGDAS-egypt stations during the solar minimum of the solar cycle 24

    NASA Astrophysics Data System (ADS)

    Fathy, Ibrahim

    2016-07-01

    This paper presents a statistical study of different types of large-scale geomagnetic pulsation (Pc3, Pc4, Pc5 and Pi2) detected simultaneously by two MAGDAS stations located at Fayum (Geo. Coordinates 29.18 N and 30.50 E) and Aswan (Geo. Coordinates 23.59 N and 32.51 E) in Egypt. The second order butter-worth band-pass filter has been used to filter and analyze the horizontal H-component of the geomagnetic field in one-second data. The data was collected during the solar minimum of the current solar cycle 24. We list the most energetic pulsations detected by the two stations instantaneously, in addition; the average amplitude of the pulsation signals was calculated.

  4. 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.

  5. Effects of the magnetic activity on F region zonal and vertical plasma drifts over Jicamarca during solar minimum

    NASA Astrophysics Data System (ADS)

    Santos, Angela; Sobral, J. H. A.; Batista, Inez S.; Abdu, Mangalathayil; Souza, Jonas

    2016-07-01

    In this work, we investigate the equatorial F region zonal plasma drifts over Jicamarca, Peru, under magnetically disturbed conditions during two solar minimum epochs, one of them being the recent prolonged solar activity minimum. The study utilizes 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 SUPIM-INPE. Two main points are focused: (1) the connection between prompt penetration electric fields and zonal and vertical plasma drifts 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. Based on a detailed quantitative analysis we will show that this anticorrelation is driven mainly by a vertical Hall electric field induced by the primary zonal penetration electric field in the presence of enhanced nighttime E region conductivity. An increase in the field line integrated Hall-to-Pedersen conductivity ratio, arising from energetic particle precipitation in the South American Magnetic Anomaly (SAMA) region is found to be capable of explaining the observed anti correlation between the vertical and zonal plasma drifts. Evidence for the particle ionization is provided from the occurrence of anomalous sporadic E layers over the SAMA region. It will also be shown that the zonal plasma drift reversal to eastward in the afternoon can occur earlier due to the weakening of the zonal wind system during the prolonged solar minimum period.

  6. 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…

  7. 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.

  8. 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.

  9. 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.

  10. Equatorial longitude and local time variations of topside magnetic field-aligned ion drifts at solar minimum

    NASA Astrophysics Data System (ADS)

    Burrell, A. G.; Heelis, R. A.; Stoneback, R. A.

    2012-04-01

    In the topside ionosphere, the high mobility of the plasma along the magnetic field allows field-aligned ion drifts to occur readily as a result of field-aligned gravitational forces, collisional forces, or pressure gradients. Therefore, variations in the field-aligned ion drifts can be used to explore the influence of thermospheric, electrodynamic, and chemical processes on the ionosphere. Longitude and local time variations in the field-aligned ion drifts near the magnetic equator are presented using observations from the Coupled Ion Neutral Dynamics Investigation on board the Communications/Navigation Outage Forecast System satellite. These observations were obtained during the period of extremely low solar activity present in 2008 and 2009, allowing the seasonal, local time, and longitudinal variations to reveal the relative importance of the processes responsible for topside field-aligned plasma drifts during solar minimum. This investigation found that the low-altitude winds and tides, the net ionization or loss, and the meridional E×B drift were all influential in creating longitudinal and local time variations in the field-aligned drift, though the strength of the influence seen by each driver was found to vary with season, local time, and longitude.

  11. 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.

  12. How well reflects IRI the electron density during the recent solar minimum? Comparison with CHAMP and GRACE (Invited)

    NASA Astrophysics Data System (ADS)

    Luhr, H.; Xiong, C.

    2010-12-01

    There have been indications that empirical models show difficulties to reflect the environmental conditions properly during this recent deep solar minimum. We have tested the reliability of electron density predictions from the latest IRI-07 version by comparison with CHAMP and GRACE observations. The whole data series from 2000 to 2010 was utilized. Orbital averages of electron density readings at the two altitudes 480km (GRACE) and 450-300km (CHAMP) are compared with collocated predictions from IRI. When considering monthly averages the model values track the observations reasonably well during solar maximum years. From 2005 onward the model progressively overestimates the electron density at both altitudes. By the end of 2009 the model is too high by a factor of 2. For investigating the global structure of the discrepancy we have plotted the latitudinal/local time distribution of the modelled and observed electron density. It becomes clear that the difference can be traced back to a significant overestimate of the equatorial ionization anomaly (EIA) by the model. As an explanation we suggest that the controlling parameters F10.7 and Ap are no longer sufficient for describing the processes during this deep minimum.

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

    PubMed Central

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

    2012-01-01

    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

  14. 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

  15. 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.

  16. Variability of Total Electron Content at Low Latitude Region During Solar Minimum 2008: Impact of High Speed Streams, HSSs

    NASA Astrophysics Data System (ADS)

    Nicoli Candido, C. M.; Batista, I. S.; Becker-Guedes, F.; Klausner, V.

    2015-12-01

    The solar minimum period of solar cycle 23 was unusually long and quiet in comparison to other solar minima in last century. Several reports have analyzed its features and its impact under diverse points-of-view. In this work, we analyze the low latitude ionosphere behavior in Brazil and its response during this peculiar period. The ionospheric variation is analyzed through typical parameters such as vertical total electron content (VTEC), the peak height of F2 layer and its critical frequency, hmF2 and foF2, in 2008, around the southern crest of the Equatorial Ionization Anomaly (EIA), in Cachoeira Paulista (22.5o S, 45.0 o W, mag. lat: 16 o S, dip angle: -32.3o) and at an equatorial station, São Luís (2.33o S, 44.2o W, dip angle: -6.7o). VTEC values present a semiannual variation pattern and two well-defined peaks in March and October. Daily maximum values are observed around 15:00 LT. It was observed periodicities observed of 9, 13.5 and 27 days in VTEC and hmF2, mainly at the first and the second half of 2008. These periods match with the observed periods in solar and geomagnetic indexes such as Vsw, Kp and AE and are associated with occurrence of high speed streams (HSS) coming from solar coronal holes. A complex response of the low latitude ionosphere is observed, with prominent increases and decreases of VTEC at daytime during the interval of occurrence of HSSs. It is suggested that a combination of several factors such as prompt penetration of electric field, disturbed dynamo electric field, meridional winds, thermal expansion of thermosphere and composition changes of neutral atmosphere are responsible for the high day-to-day variability of the ionosphere

  17. 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.

  18. 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).

  19. The structure of Io's corona

    NASA Astrophysics Data System (ADS)

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

    1991-02-01

    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.

  20. Corotating interaction regions and the 27 day variation of galactic cosmic rays intensity at 1 AU during the cycle 23/24 solar minimum

    NASA Astrophysics Data System (ADS)

    Guo, X.; Florinski, V.

    2014-04-01

    We investigate the formation and evolution of corotating interaction regions (CIRs) in the solar wind and their effects on galactic cosmic rays (GCR) during the recent solar cycle 23/24 solar minimum. The output from a three-dimensional MHD model serves as background for kinetic time-dependent simulations of GCR transport based on the Parker equation. The results show that the CIR forward/reverse shock pairs or compression/rarefaction regions play important roles in the transport of GCR particles and directly control the observed 27 day periodic intensity variations. We find that stream interfaces (SIs) in CIRs and the heliospheric current sheet (HCS) are both closely associated with the GCR depression onset, in agreement with the observations at 1 AU. The HCS is more important when its tilt angle becomes small during the declining phase of the solar minimum, while the passages of SIs control the onset of GCR depressions for larger HCS tilt angles. The mechanism of GCR intensity variation near 1 AU can be explained through an interplay between the effects of particle drift and diffusion. The simulated plasma background and GCR intensity are compared with the observations from spacecraft and a neutron monitor on the ground, to find good qualitative agreement. Evidently, CIRs had a substantial modulational effect on GCR during the recent solar minimum.

  1. 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.

  2. 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.

  3. 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)

  4. 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

  5. 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...

  6. Influence of meteorological and wave processes on the lower ionosphere during solar minimum conditions according to the data on midlatitude VLF-LF propagation

    NASA Astrophysics Data System (ADS)

    Egoshin, A. A.; Ermak, V. M.; Zetzer, Yu. I.; Kozlov, S. I.; Kudryavtsev, V. P.; Lyakhov, A. N.; Poklad, Yu. V.; Yakimenko, E. N.

    2012-03-01

    The statistical characteristics of the intensity of VLF-LF radio signals transmitted from the midlatitude radio stations and recorded by the receiver at the Mikhnevo geophysical observatory (54.94°N, 37.73°E; Institute of Geosphere Dynamics, Russian Academy of Sciences) in 2007-2010 are analyzed. The experiments revealed strong variations in the intensity of radio signals during the deep solar minimum conditions, when the medium does not experience impacts from above associated with solar and geomagnetic activity. We relate the observed variations to the disturbances from below, which are caused by the meteorological and wave processes occurring in the lower atmosphere.

  7. Solar corona top heating

    NASA Astrophysics Data System (ADS)

    Molotkov, I. A.; Ryabova, N. A.

    2016-05-01

    The solar magnetic field fragmentation into thin magnetic tubes above the photosphere makes it possible to transform and factorize MHD equations analytically and to obtain explicit expressions for Alfvén and magnetosonic fields. A physical model that enables an explanation of the effect of strong heating of the solar chromosphere and corona has been proposed. This model makes it possible to estimate analytically a powerful Alfvén disturbance entering the chromosphere due to convective motions of the photosphere and a thermal release due to a three-wave interaction within the chromosphere.

  8. 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.

  9. A plasma protein corona enhances the biocompatibility of Au@Fe3O4 Janus particles.

    PubMed

    Landgraf, Lisa; Christner, Carolin; Storck, Wiebke; Schick, Isabel; Krumbein, Ines; Dähring, Heidi; Haedicke, Katja; Heinz-Herrmann, Karl; Teichgräber, Ulf; Reichenbach, Jürgen R; Tremel, Wolfgang; Tenzer, Stefan; Hilger, Ingrid

    2015-11-01

    Au@Fe3O4 Janus particles (JPs) are heteroparticles with discrete domains defined by different materials. Their tunable composition and morphology confer multimodal and versatile capabilities for use as contrast agents and drug carriers in future medicine. Au@Fe3O4 JPs have colloidal properties and surface characteristics leading to interactions with proteins in biological fluids. The resulting protein adsorption layer ("protein corona") critically affects their interaction with living matter. Although Au@Fe3O4 JPs displayed good biocompatibility in a standardized in vitro situation, an in-depth characterization of the protein corona is of prime importance to unravel underlying mechanisms affecting their pathophysiology and biodistribution in vitro and in vivo. Here, we comparatively analyzed the human plasma corona of Au-thiol@Fe3O4-SiO2-PEG JPs (NH2-functionalized and non-functionalized) and spherical magnetite (Fe3O4-SiO2-PEG) particles and investigated its effects on colloidal stability, biocompatibility and cellular uptake. Label-free quantitative proteomic analyses revealed that complex coronas including almost 180 different proteins were formed within only one minute. Remarkably, in contrast to spherical magnetite particles with surface NH2 groups, the Janus structure prevented aggregation and the adhesion of opsonins. This resulted in an enhanced biocompatibility of corona sheathed JPs compared to spherical magnetite particles and corona-free JPs. PMID:26276693

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

    NASA Astrophysics Data System (ADS)

    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 to 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.

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  14. Comparison of IRI-2012 with JASON-1 TEC and incoherent scatter radar observations during the 2008-2009 solar minimum period

    NASA Astrophysics Data System (ADS)

    Ji, Eun-Young; Jee, Geonhwa; Lee, Changsup

    2016-08-01

    The 2008-2009 solar minimum period was unprecedentedly deep and extended. We compare the IRI-2012 with global TEC data from JASON-1 satellite and with electron density profiles observed from incoherent scatter radars (ISRs) at middle and high latitudes for this solar minimum period. Global daily mean TECs are calculated from JASON-1 TECs to compare with the corresponding IRI TECs during the 2008-2009 period. It is found that IRI underestimates the global daily mean TEC by about 20-50%. The comparison of global TEC maps further reveals that IRI overall underestimates TEC for the whole globe except for the low-latitude region around the equatorial anomaly, regardless of season. The underestimation is particularly strong in the nighttime winter hemisphere where the ionosphere seems to almost disappear in IRI. In the daytime equatorial region, however, the overestimation of IRI is mainly due to the misrepresentation of the equatorial anomaly in IRI. Further comparison with ISR electron density profiles confirms the significant underestimation of IRI at night in the winter hemisphere.

  15. 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.

  16. 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.

  17. Properties of accretion disk coronae

    NASA Technical Reports Server (NTRS)

    Wilms, J.; Dove, J.; Staubert, R.; Begelman, M. C.

    1997-01-01

    The properties of accretion disk corona in a parameter regime suitable for Galactic black hole candidates are considered and the results of an analysis of these properties using a self-consistent Monte Carlo code are presented. Examples of the coronal temperature structure, the shape and angular dependency of the spectrum and the maximum temperature allowed for each optical depth of the corona are presented. It is shown that the observed spectrum of the Galactic black hole candidate Cygnus X-1 cannot be explained by accreting disk corona models with a slab geometry, where the accretion disk is sandwiched by the comptonizing medium.

  18. 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.

  19. Biophysical chemistry: Unravelling capsid transformations

    NASA Astrophysics Data System (ADS)

    Uchida, Masaki; Douglas, Trevor

    2013-06-01

    The interactions between a virus capsid and its cargo are essential for viral infection as well as in the design of synthetic virus-like particles. Now a combination of analytical techniques has unravelled key steps in the transformation of a model virus and the release of its RNA cargo.

  20. 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

  1. 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

  2. Changes in radial gradients of low-energy cosmic rays between solar minimum and maximum: - Observations from 1 to 31 AU

    NASA Technical Reports Server (NTRS)

    Mckibben, R. B.; Pyle, K. R.; Simpson, J. A.

    1985-01-01

    Observations of the fluxes and radial gradients of protons and helium (with energies of 10-70 Mev per n) between the period of minimum solar modulation ending in 1977 and the period of maximum modulation in 1981-1983 show that, over the radial range 1-31 AU, radial gradients decreased for both species from their solar minimum values (5-10 percent per AU for galactic protons and helium) to values of 2-4 percent per AU or less. For these low-energy cosmic rays it is found that the variation in modulation with the phase of the solar cycle is much stronger at radii of 20-30 AU than at 1 AU, and that at solar maximum, more than 99 percent of the total modulation takes place beyond 31 AU.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Rainbows, Coronas and Glories

    NASA Astrophysics Data System (ADS)

    Laven, Philip

    Rainbows, coronas and glories are examples of atmospheric optical phenomena caused by the scattering of sunlight from spherical drops of water. It is surprising that the apparently simple process of scattering of light by spherical drops of water can result in this wide range of colourful effects. However, the scattering mechanisms are very complicated. Eminent scientists (such as Descartes, Newton, Young, Airy and many others) offered various explanations for the formation of rainbows—thus making major contributions to our understanding of the nature of light. The basic features of rainbows can be explained by geometrical optics but, in the early 1800s, supernumerary arcs on rainbows provided crucial supporting evidence for the wave theory of light. In 1908, Mie provided a rigorous (but very complicated) solution to the problem of scattering of light by spherical particles. More than 100 years later, Mie's solution can now be used to produce excellent full-colour simulations. Examples of such simulations show how the appearance of these phenomena vary with the size of the water drops, as well as describing the scattering mechanisms that are responsible for their formation.

  8. Signatures of Two Distinct Initiation Mechanisms while CMEs Evolve in the Lower Corona

    NASA Astrophysics Data System (ADS)

    Alves, M. V.; de Souza Costa, C. L.; Opher, M.; Liu, Y. C.; Manchester, W. B.; Gombosi, T. I.

    2009-04-01

    We present a comparison of a three-dimensional (3D) simulation of coronal mass ejections (CMEs) formed with two different initiation mechanisms: Gibson & Low (1998) (as GL98 from now on) and Titov & Démoulin (1999) (as TD99 from now on). Mainly we aim to compare how the CME magnetic configuration changes during their propagation in the lower corona, until 6RS. The simulations are performed using the Space Weather Modeling Framework (SWMF) during the solar minimum (CR1922). We found that both CME-driven shocks are quasi-parallel at the nose and that GL98 presents a higher shock acceleration (~150 m/ s2versus ~100 m/ s2) and a higher Mach number, suggesting it would accelerate particles more efficiently. Both initiation mechanisms also presented a post-shock compression for R>3RS, being slightly larger in TD99. They presented also a similar sheath width that increases while propagating away from the Sun (larger in GL98 case). We also found that in GL98 case the CME is driven by a combination of magnetic and thermal pressure, while in TD99 case the thermal pressure dominates its evolution. GL98 presents a sheath mass 20% larger than TD99, a possible explanation for the presence of higher force values for GL98. This paper intends to serve as a prototype for future comparisons of CME evolution, in the lower corona.

  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. 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.

  12. 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.

  13. 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.

  14. Corona processing of insulating oil

    SciTech Connect

    Rohwein, G.J.

    1996-07-01

    It is well known that sustained corona discharge in insulating oil lowers its dielectric strength and simultaneously reduces its corona resistance. Therefore, for operating stresses in the corona regime, activity typically increases with time and, if allowed to continue, eventually leads to breakdown of the oil and failure of the component or system. It is, therefore, common practice to periodically replace oil in devices such as large power transformers and switch gear before breakdown occurs. Sealed components such as capacitors are typically replaced. Recent experiments have demonstrated that the dielectric properties of corona weakened oil can not only be restored, but actually improved by a simple regeneration process. These experiments were carried out on high voltage pulse transformer windings which were operated at high rep rates until partial discharges formed. Reprocessing the oil after each operating cycle resulted in successively longer operational periods before partial discharges appeared. In a separate experiment, a process was developed to precondition transformer oil to raise its corona inception voltage before using it to insulate a high voltage component, thus giving it a longer initial service life for a given operating stress or permitting higher stress operation for limited operating times.

  15. Topological Structure of the Magnetic Solar Corona

    NASA Astrophysics Data System (ADS)

    Maclean, R. C.

    2007-12-01

    magnetic field. I perform a comprehensive study of quadrupolar topologies in this new geometry, producing several detailed bifurcation diagrams. These results are compared to the equivalent study for a flat photosphere. A new topological state is found on the sphere which has no flat photosphere analogue; it is named the dual intersecting state because of its twin separators joining a pair of magnetic null points. The new spherical techniques are then applied to develop a simple six-source topological model of global magnetic field reversal during the solar cycle. The evolution of the large-scale global magnetic field is modelled through one complete eleven-year cycle, beginning at solar minimum. Several distinct topological stages are exhibited: active region flux connecting across the equator to produce transequatorial loops; the dominance of first the leading and then the following polarities of the active regions; the magnetic isolation of the poles; the reversal of the polar field; the new polar field connecting back to the active regions; the polar flux regaining its dominance; and the disappearance of the transequatorial loops.

  16. The 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.

  17. 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

  18. Some crucial corona and prominence observations

    NASA Technical Reports Server (NTRS)

    Tandberg-Hanssen, E. A.

    1986-01-01

    A number of theories and hypotheses are currently being developed to explain the often complex behavior of corona and prominence plasmas. In order to test the theories and hypotheses certain crucial observations are necessary. Some of these observations are examined and a few conclusions are drawn. Corona mass balance, corona and prominence classifications, prominence formation and stability, and coronal mass ejection are dicussed.

  19. 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

  20. LABORATORY ANALYSES OF CORONA DISCHARGES

    EPA Science Inventory

    The paper discusses an experimental research program to characterize corona generation from different electrode geometries in a range of conditions comparable to those found in electrostatic precipitators (ESPs). A wire-parallel plate device and a wire-cylinder device were used t...

  1. Unusual time histories of galactic and anomalous cosmic rays at 1 AU over the deep solar minimum of cycle 23/24

    NASA Astrophysics Data System (ADS)

    McDonald, Frank B.; Webber, William R.; Reames, Donald V.

    2010-09-01

    The unusually quiet Sun of the cycle 23/24 solar minimum (that ended in December, 2009) has resulted in lower values of the interplanetary magnetic field and a slower approach of the tilt angle of the heliospheric current sheet toward the solar equator than has been observed for recent solar minima. As a result of these changes, the time-histories of galactic and anomalous cosmic rays over this period are very different from those of recent minima at the same phase of the heliomagnetic cycle. Since ˜2005.6 there has been an on-going increase in cosmic-ray intensity (except for one brief transient decrease) that lasted for 4.4 years. The relative rigidity dependences of these increases compared to previous cycles are complex and should provide insight into the role of various solar and interplanetary phenomena in the modulation process. The largest increase occurs in the nominal “cross-over energy” region (where the modulation is essentially the same for each minimum of the two past 22 year heliomagnetic cycles) which extends from ˜200 MeV/n to >500 MeV/n.

  2. 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.

  3. 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.

  4. 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

  5. Medium-scale equatorial plasma irregularities observed by Coupled Ion-Neutral Dynamics Investigation sensors aboard the Communication Navigation Outage Forecast System in a prolonged solar minimum

    NASA Astrophysics Data System (ADS)

    Heelis, R. A.; Stoneback, R.; Earle, G. D.; Haaser, R. A.; Abdu, M. A.

    2010-10-01

    The distribution of medium-scale irregularities in the total ion density at the equator is investigated. In the scale size range between 10 and 400 km, it is found that, as expected, these irregularities preferentially appear near 2100 local time (LT) in longitude regions that are selected by season according to an alignment between the magnetic meridian and the sunset terminator. However, these irregularities have a maximum occurrence frequency in the postmidnight sector and do not conform to the expected behavior seen for irregularities that appear after sunset. We suggest that the postmidnight peak in the occurrence frequency for these irregularities arose from the weak vertical drifts that prevail in the afternoon and evening during a prolonged solar minimum. It is also suggested that the observed longitude and seasonal dependence in the peak occurrence frequency is influenced by seeding from tropospheric sources, and therefore responds to the seasonal variations in the colocation of the magnetic equator and the Intertropical Convergence Zone. The irregularities appear throughout the nighttime period when the background density is declining rapidly. Thus, despite the postmidnight maximum in occurrence frequency, the maximum absolute perturbation density, most likely to be responsible for radio scintillation, occurs in the premidnight sector.

  6. 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."

  7. 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.

  8. 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.

  9. 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.

  10. Theoretical predictions for ion composition in the high-latitude winter F-region for solar minimum and low magnetic activity

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Raitt, W. J.; Schunk, R. W.

    1981-01-01

    A simple plasma convection model is combined with an ionospheric-atmospheric density model in order to study the ion composition in the high-latitude winter F-region at solar minimum for low geomagnetic activity. The numerical study produces time-dependent, three-dimensional ion density distributions for the ions NO(+), O2(+), N2(+), O(+), N(+), and He(+). The high-latitude ionosphere above 54 deg N magnetic latitude is covered at altitudes between 160 and 800 km for one complete day. Among the conclusions are the following: the ion composition varies significantly with latitude, local time, altitude, and universal time; the variations in the ion composition with latitude and local time are in good agreement with the Atmosphere Explorer measurements both quantitatively and qualitatively; and at times and at certain locations the molecular ion density can be comparable to the O(+) density at 300 km, and at 200 km the O(+) density can be comparable to the molecular ion density.

  11. 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.

  12. 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

  13. 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.

  14. Variability of the ionospheric plasma density, NmF2, and of Total Electron Content, TEC, over equatorial and low latitude region in Brazil during solar minimum activity

    NASA Astrophysics Data System (ADS)

    Candido, Claudia; Batista, Inez S.; Negreti, Patricia M. S.; Klausner, Virginia

    The recent solar minimum period was unusually deep and prolonged, which opened a window to observe the ionospheric behavior under unprecedented low solar activity conditions. This work is part of a multi-instrumental effort to investigate the equatorial and low latitude ionosphere over Brazilian sector during low solar activity. We present a study of the ionospheric plasma densities variations through ionosondes measurements and dual frequency GPS receivers (L1= 1275.4 MHz, L2 = 1227.6 MHz) for two equatorial stations, Sao Luis (3° S, 45º W) e Fortaleza (4° S, 39.5° W), and for a station close to the south crest of the equatorial ionization anomaly region, Cachoeira Paulista (23º S, 45º W). From ionosondes we extract the plasma critical frequency foF2 which is related to F2 region peak electron density, NmF2, by the relationship: NmF2 = 1.24 x 104 (foF2)2, and the F2 layer peak height, hmF2. From GPS receivers we used the quantity VTEC (Vertical total electron content). We analyzed the seasonal and local time variations of NmF2 and VTEC, as well as the differences between two solar minima, 2008-2009 and 1996. We observe that the ionospheric plasma densities were lower in 2008-2009 than in 1996 for both regions. In addition, we observe that the lowest plasma densities persisted longer during 2008/2009 than in 1996, especially for nighttime periods. Finally, we applied the wavelet technique to investigate the impact of some distinct time scales drivers on the ionosphere, such as the wave activity from below that seems have been better observed and appreciated during this unusual solar quiescence.

  15. Solar and Interplanetary Signatures of a Maunder-like Grand Solar Minimum around the Corner - Implications to Near-Earth Space

    NASA Astrophysics Data System (ADS)

    Janardhan, P.; Bisoi, S. K.; Ananthakrishnan, S.; Sridharan, R.; Jose, L.

    2015-12-01

    Our study of a steady decline of solar high-latitude (?45?) photospheric magnetic fields for the past 20 years combined with the fact that cycle 24 is already past its peak, implies that high-latitude fields are likely to decline until ˜2020, the expected minimum of cycle 24.Also, interplanetary scintillation (IPS) observations, at 327 MHz, of solar wind micro-turbulence levels during 1983-2013, have shown a steady decline, in sync with the declining solar high-latitude fields. An estimateof both the heliospheric magnetic field (HMF) strength in 2020 and the floor value of the HMF, using the correlation between the polar field and the HMF at solar minimum, was found to be 4.0 (±0.6) nT and 3.2 (±0.4) nT, respectively. Using the estimated value of the HMF in 2020, the peak sunspot number for solar Cycle 25 was estimated to be 69 (±12). These results and the fact that solar magnetic fields continue to decline at present, begs the question as to whether we are headed towards a long period of very low sunspot activity similar to the well known Maunder minimum between 1645-1715. An assessment of possible impact of such a likely grand minimum on terrestrial ionospheric current systems, based on the one-to-one correlation of sunspot number and night time F-region maximum electron density, reveals that the period post 2020 will be useful for undertaking systematic ground based low-frequency radio astronomy observations, as the night time ionospheric cutoff-frequency could be well below 10 MHz.

  16. The R Coronae Borealis Stars

    NASA Astrophysics Data System (ADS)

    Clayton, Geoffrey C.

    1996-03-01

    This year marks the bicentennial of the discovery of the variability of R Coronae Borealis. The R Coronae Borealis (RCB) stars are distinguished from other hydrogen-deficient objects by their spectacular dust formation episodes. They may decline by up to 8 magnitudes in a few weeks revealing a rich emission-line spectrum. Their atmospheres have unusual abundances with very little hydrogen and an overabundance of carbon and nitrogen. The RCB stars are thought to be the product of a final helium shell flash or the coalescence of a binary white-dwarf system. Dust may form in non-equilibrium conditions created behind shocks caused by pulsations in the atmospheres of these stars. The RCB stars are interesting and important, first because they represent a rare, or short-lived stage of stellar evolution, and second because these stars regularly produce large amounts of dust so they are laboratories for the study of dust formation and evolution. (SECTION: Invited Review Paper)

  17. 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

  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. Corona Discharge Influences Ozone Concentrations Near Rats

    SciTech Connect

    Goheen, Steven C.; Gaither, Kari A.; Anantatmula, Shantha M.; Mong, Gary M.; Sasser, Lyle B.; Lessor, Delbert L.

    2004-02-26

    Ozone is produced by corona discharge in air. Its production is enhanced near grounded water. Whether grounded animals behave like grounded water, producing more ozone was investigated. Rats were exposed to corona discharge in a plastic cage. The concentration of ozone in the gas phase was monitored. The ozone concentration exceeded ambient levels only in the presence of corona discharge and either rats or water. When water or rats were exposed to corona discharge, ozone levels were more than 10 times higher than controls. Ozone levels increased rapidly with applied voltage. There was also a correlation between the distance of the corona needle to the rats and the amount of ozone produced. As the distance increased, ozone production decreased. These results are discussed in relation to the potential exposure of mammals to ozone in the vicinity of corona discharge and electric fields.

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

    SciTech Connect

    Nuevo, Federico A.; Vasquez, Alberto M.; 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.

  1. Signatures of two distinct driving mechanisms in the evolution of coronal mass ejections in the lower corona

    NASA Astrophysics Data System (ADS)

    Loesch, C.; Opher, M.; Alves, M. V.; Evans, R. M.; Manchester, W. B.

    2011-04-01

    We present a comparison between two simulations of coronal mass ejections (CMEs), in the lower corona, driven by different flux rope mechanisms presented in the literature. Both mechanisms represent different magnetic field configurations regarding the amount of twist of the magnetic field lines and different initial energies. They are used as a “proof of concept” to explore how different initialization mechanisms can be distinguished from each other in the lower corona. The simulations are performed using the Space Weather Modeling Framework (SWMF) during solar minimum conditions with a steady state solar wind obtained through an empirical approach to mimic the physical processes driving the solar wind. Although the two CMEs possess different initial energies (differing by an order of magnitude) and magnetic configurations, the main observables such as acceleration, shock speed, Mach number, and $\\theta$Bn (the angle between the shock normal and the upstream magnetic field) present very similar behavior between 2 and 6 R$\\odot$. We believe that through the analysis of other quantities, such as sheath width and postshock compression (pileup and shock indentation compressions), the effect of different magnetic configurations and initializations can be distinguished. We discuss that coronal models that employ a reduced value of polytropic index (γ) may significantly change the energetics of the CME and that the background solar wind plays an important role in the CMEs' shock and sheath evolution.

  2. Pulsed Corona Discharge Generated By Marx Generator

    NASA Astrophysics Data System (ADS)

    Sretenovic, G. B.; Obradovic, B. M.; Kovacevic, V. V.; Kuraica, M. M.; Puric J.

    2010-07-01

    The pulsed plasma has a significant role in new environmental protection technologies. As a part of a pulsed corona system for pollution control applications, Marx type repetitive pulse generator was constructed and tested in arrangement with wire-plate corona reactor. We performed electrical measurements, and obtained voltage and current signals, and also power and energy delivered per pulse. Ozone formation by streamer plasma in air was chosen to monitor chemical activity of the pulsed corona discharge.

  3. Corona solar blind ultraviolet image detecting method

    NASA Astrophysics Data System (ADS)

    Yin, Li-min; Tang, Wen-qing; Zhang, Yu

    2009-07-01

    Corona is one of important reasons of electrical energy loss in the electric power. According to incomplete statistics, corona loss electrical energy has achieved two thousands and fifty millions kW.h in our nation every year. Sometimes corona also can have some disturbance to radio and communication. Therefore to discover and examine corona promptly has the extremely vital significance for conserving energy and realizing high quality communication. Ultraviolet image detecting technology is a preferred corona detection method in electric power. It may realize all-weather reliable survey to corona. The solar blind ultraviolet signal discharged by corona is quite weak. Moreover the ultraviolet image quality has been affected seriously by the detection system noise. A corona solar blind ultraviolet image processing method is proposed in this paper. Ultraviolet image has so small target, low contrast image, district characteristic and real-time demand that it is processed by multi-scale ultraviolet morphology filter technology based on mathematics morphology in this paper. Results show that the method can stretch image contrast, enhance target and weaken noise. The algorithm is easy to deal in parallel and it can be realized easily by hardware. It will be accurately demarcated when the condition of device need to be absolutely measured. The paper proposes a kind of mathematics morphology algorithm. Solar blind ultraviolet image will be further processed according to temperature and humidity in order to remove the infection of corona discharge demarcation and solve correct demarcation question when equipment condition need to be absolutely measured.

  4. NASA's SDO Sees Unraveling Solar Prominence

    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...

  5. 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.

  6. Evolución de la Estructura Térmica Global de la Corona alrededor del Último Mínimo de Actividad Solar

    NASA Astrophysics Data System (ADS)

    Nuevo, F. A.; Vásquez, A. M.; Huang, Z.; Frazin, R. A.

    We study the solar corona temperature structure during several Carrington rotations (CR) around the last minimum of solar activity (CR 2077). The combination of Differential Emission Measure Tomography (DEMT) with magnetic models allows determination of the electron density and electron temperature along individual magnetic field lines. Two types of quiet Sun (QS) coronal loops were identified: "up" loops in which the temperature increases with height, and "down" loops in which the temperature decreases with height. We find that the population of up loops dominates the intermediate latitudes, while down loops are always located in the low-latitude region. We also find that the population of down loops was maximum at solar minimum. FULL TEXT IN SPANISH

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  8. 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].

  9. 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.

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

    NASA Technical Reports Server (NTRS)

    Wang, Tongjiang; Davila, Joseph M.

    2014-01-01

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

  11. 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.

  12. 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

  13. The protein corona of circulating PEGylated liposomes.

    PubMed

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

    2016-02-01

    Following systemic administration, liposomes are covered by a 'corona' of proteins, and preserving the surface functionality is challenging. Coating the liposome surface with polyethylene glycol (PEG) is the most widely used anti-opsonization strategy, but it cannot fully preclude protein adsorption. To date, protein binding has been studied following in vitro incubation to predict the fate of liposomes in vivo, while dynamic incubation mimicking in vivo conditions remains largely unexplored. The main aim of this investigation was to determine whether shear stress, produced by physiologically relevant dynamic flow, could influence the liposome-protein corona. The corona of circulating PEGylated liposome was thoroughly compared with that formed by incubation in vitro. Systematic comparison in terms of size, surface charge and quantitative composition was made by dynamic light scattering, microelectrophoresis and nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS). Size of coronas formed under static vs. dynamic incubation did not appreciably differ from each other. On the other side, the corona of circulating liposomes was more negatively charged than its static counterpart. Of note, the variety of protein species in the corona formed in a dynamic flow was significantly wider. Collectively, these results demonstrated that the corona of circulating PEGylated liposomes can be considerably different from that formed in a static fluid. This seems to be a key factor to predict the biological activity of a liposomal formulation in a physiological environment. PMID:26607013

  14. 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.

  15. Corona discharge influences ozone concentrations near rats.

    PubMed

    Goheen, Steven C; Gaither, Kari; Anantatmula, Shantha M; Mong, Gary M; Sasser, Lyle B; Lessor, Delbert

    2004-02-01

    Ozone can be produced by corona discharge either in dry air or when one electrode is submerged in water. Since ozone is toxic, we examined whether ozone production by corona near laboratory animals could reach levels of concern. Male rats were exposed to a corona discharge and the concentration of ozone produced was measured. The resulting concentration of ozone ranged from ambient levels to 250 ppb when animals were located 1 cm from a 10 kV source. Similar ozone concentrations were observed when a grounded water source was present. Possible explanations for, as well as concerns regarding, ozone production under these conditions are discussed. PMID:14735560

  16. The helium shells of HeI and HeII at solar minimum: New results from eclipse flash spectra of 2008- 2010

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Flash spectra taken at high frame rate during the total solar eclipse of August 1st 2008 in Siberia and during the July 11th 2010 in French Polynesia are compared in the context of the quiet Sun near the minimum of activity. They both reveal the weak Paschen α 468.6 nm ionized helium line, seen as a helium shell in layers up to the 8 Mm heights. The preliminary evaluated effective height of the He I 4713 shell is 1.8 Mm and it is approximately 2.0 Mm for the He II 4686 emissions outside polar regions. These lines can be measured only in eclipse conditions, when the parasitic scattered light is negligible for very low solar fluxes corresponding to the coronal levels. Many faint lines are also seen in emission such as Ba +, Ti +, Fe +, but with a much lower radial extension. They were observed to be superposed to F-lines when defining the solar limb using the continuum background. A cartoon is proposed to describe the structuration of these low layers and to illustrate the contribution of the magnetic field. These observations are important new insights for understanding (i) the magnetic field inference in the very low layers of the solar transition region and (ii) the ionisation mechanisms producing the big jump of the temperature towards the corona, including the source of heating.

  17. Electrode structure for uniform corona discharge

    NASA Technical Reports Server (NTRS)

    Gange, R. A.; Steinmetz, C. C.

    1976-01-01

    Single corona-discharge needle is used to apply uniform charge to thermoplastic medium in holograph-storage system. Needle is connected to flat transparent electrode that is parallel to thermoplastic.

  18. Solar Corona on 08.01.2010

    NASA Video Gallery

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

  19. Solar Corona on 10.21.2010

    NASA Video Gallery

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

  20. 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.

  1. 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

  2. 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.

  3. 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

  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. 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.

  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

  7. 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.

  8. 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

  9. Determination of the North-South Heliospheric Magnetic-Field Component from Inner-Corona Closed-Loop Propagation

    NASA Astrophysics Data System (ADS)

    Jackson, B. V.; Yu, H. S.; Hick, P. P.; Buffington, A.; Bisi, M. M.; Tokumaru, M.; Kim, J.; Hong, S.; Lee, B.; Yi, J.; Yun, J.

    2015-12-01

    We find that a portion of the north-south interplanetary magnetic field measured in situ near Earth is present from a direct outward mapping of closed fields from the low solar corona. Using the Current-Sheet Source Surface (CSSS) model (Zhao & Hoeksema, 1995 JGR 100, 19), these lower coronal fields are extrapolated upward from near the solar surface. Global velocities inferred from a combination of observations of interplanetary scintillation (IPS) matched to in-situ velocities and densities measured by spacecraft instrumentation provide an accurate outward timing to 1 AU from a model assuming conservation of mass and mass flux. The north-south field component at 1 AU is compared with the appropriate ACE magnetometer in-situ Normal (RTN) or Bn field coordinate (Jackson et al., 2015, ApJL, 803:L1). From a significant positive correlation between this method of determining the Bn field compared with in-situ measurements over a three-year period during the last solar minimum, we find that a small fraction of the low-coronal Bn component flux (~1%) regularly escapes from closed-field regions. Since the Bn field provides the major portion of the Geocentric Solar Magnetospheric (GSM) Bz field component that couples most closely to the Earth's geomagnetic field, the prospects for its determination using this technique for space weather use are being actively developed by our many colleague groups.

  10. 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.