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1

Latitudinal and Radial Variation of Solar Corona Rotation at Solar Minimum  

Microsoft Academic Search

The rotation of the solar corona at different heliolatitudes from 1.5 to 3.0 Rsolar from Sun center has been studied at solar minimum from the reconstructed intensity time series of the O VI 1032 Å and H I Lyalpha l216 Å spectral lines and visible light polarized brightness obtained by the observations of UVCS\\/SOHO instrument. The time period analyzed range

S. Giordano; S. Mancuso; M. Romoli

2007-01-01

2

Polar Coronal Jets at Solar Minimum  

NASA Astrophysics Data System (ADS)

We present an analysis of six polar coronal jets observed by the Ultraviolet Coronagraph Spectrometer (UVCS) at solar minimum (1996). Four of the events were also recorded by the Extreme-Ultraviolet Imaging Telescope (EIT) and/or the Large Angle Spectrometric Coronagraph (LASCO) C2 coronagraph. We compared the jets with others recorded in 1997. We modeled the observable properties of the jet from 1996 June 11, detected at 1.5 Rsolar. It represents a type of polar jet in which H I Ly? and O VI get brighter at the same time. The model reproduced the line properties with an electron density enhancement of a factor of 2 (with a resulting density of 4.8×106 cm-3), an outflow velocity enhancement of a factor of 3 (yielding a velocity of 200 km s-1), and an electron temperature decrease of a factor of 0.36 (with a resulting temperature of 5.3×105 K). We derived the jet's electron densities from the LASCO C2 white-light observations. They are a factor of 1.5 higher than in the interplume corona and comparable to those in plume regions within the C2 field of view. We developed a model for the origin of polar jets based on Wang's model for plumes. We envisioned that jets may be the result of short-lived bursts of base heating, while plumes may be the result of base-heating events that last longer than several hours. Models with the base heat flux near 3×105 ergs cm-2 s-1 come closest to matching the observations, though they are not entirely consistent.

Dobrzycka, D.; Cranmer, S. R.; Raymond, J. C.; Biesecker, D. A.; Gurman, J. B.

2002-01-01

3

Coronal electron temperature in the protracted solar minimum, the cycle 24 mini maximum, and over centuries  

NASA Astrophysics Data System (ADS)

Recent in situ observations of the solar wind show that charge states (e.g., the O7+/O6+and C6+/C5+abundance ratios) evolved through the extended, deep solar minimum between solar cycles 23 and 24 (i.e., from 2006 to 2009) reflecting cooler electron temperatures in the corona. We extend previous analyses to study the evolution of the coronal electron temperature through the protracted solar minimum and observe not only the reduction in coronal temperature in the cycles 23-24 solar minimum but also a small increase in coronal temperature associated with increasing activity during the "mini maximum" in cycle 24. We use a new model of the interplanetary magnetic flux since 1749 to estimate coronal electron temperatures over more than two centuries. The reduction in coronal electron temperature in the cycles 23-24 protracted solar minimum is similar to reductions observed at the beginning of the Dalton Minimum (˜1805-1840). If these trends continue to reflect the evolution of the Dalton Minimum, we will observe further reductions in coronal temperature in the cycles 24-25 solar minimum. Preliminary indications in 2013 do suggest a further post cycle 23 decline in solar activity. Thus, we extend our understanding of coronal electron temperature using the solar wind scaling law and compare recent reductions in coronal electron temperature in the protracted solar minimum to conditions that prevailed in the Dalton Minimum.

Schwadron, N. A.; Goelzer, M. L.; Smith, C. W.; Kasper, J. C.; Korreck, K.; Leamon, R. J.; Lepri, S. T.; Maruca, B. A.; McComas, D.; Steven, M. L.

2014-03-01

4

Modeling the Slow Solar Wind during the Solar Minimum  

NASA Astrophysics Data System (ADS)

During the solar minimum, STEREO observations show that the three-dimensional structure of the solar corona can be described well by a tilted bipolar magnetic configuration. The slow solar wind is modeled using a three-fluid model that includes heavy ions such as He II and O VI. The model is initialized with a dipole magnetic field and spherically symmetric density. The resulting steady state, non-potential, and non-uniform streamer configuration calculated with this model is compared to STEREO observations of the streamer density structure. SOHO/UVCS observations are used to compare the O VI emission to model results. We discuss the unique properties of the solar wind produced in this configuration.

Ofman, L.; Kramar, M.

2010-06-01

5

Solar Modulation along last solar minimum  

NASA Astrophysics Data System (ADS)

The effects of cosmic rays modulation on proton spectrum was studied using the HelMod - 2-D Monte Carlo code, that includes a general description of the diffusion tensor, and polar magnetic-field. The Numerical Approach used in this work is based on a set of Stochastic Differential Equations fully equivalent to the well know Parker Equation for the transport of Cosmic Rays. The model description was updated using Proton spectras measured by PAMELA during the last solar minimum.

Bobik, P.; Boschini, M. J.; Delia Torre, S.; Gervasi, M.; Grandi, D.; Kudela, K.; La Vacca, G.; Mallamaci, M.; Pensotti, S.; Rancoita, P. G.; Rozza, D.; Tacconi, M.

2014-06-01

6

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

SciTech Connect

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.

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

2012-08-20

7

A model of the trapped electron population for solar minimum  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

8

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

9

STEREO ICMEs and their Solar Source Regions Near Solar Minimum  

Microsoft Academic Search

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

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

2008-01-01

10

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

E-print Network

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

California at Berkeley, University of

11

The asymmetrical features in electron density during extreme solar minimum  

NASA Astrophysics Data System (ADS)

The variations of plasma density in topside ionosphere during 23rd/24th solar cycle minimum attract more attentions in recently years. In this analysis, we use the data of electron density (Ne) from DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite at the altitude of 660-710 km to investigate the solstitial and equinoctial asymmetry under geomagnetic coordinate system at LT (local time) 1030 and 2230 during 2005-2010, especially in solar minimum years of 2008-2009. The results reveal that ?Ne (December-June) is always positive over Southern Hemisphere and negative over northern part whatever at LT 1030 or 2230, only at 0-10°N the winter anomaly occurs with ?Ne (December-June) > 0, and its amplitude becomes smaller with the declining of solar flux from 2005 to 2009. The ?Ne between September and March is completely negative during 2005-2008, but in 2009, it turns to be positive at latitudes of 20°S-40°N at LT 1030 and 10°S-20°N at LT 2230. Furthermore, the solstitial and equinoctial asymmetry index (AI) are calculated and studied respectively, which all depends on local time, latitude and longitude. The notable differences occur at higher latitudes in solar minimum year of 2009 with those in 2005-2008. The equinoctial AI at LT 2230 is quite consistent with the variational trend of solar flux with the lowest absolute AI occurring in 2009, the extreme solar minimum, but the solstitial AI exhibits abnormal enhancement during 2008 and 2009 with bigger AI than those in 2005-2007. Compared with the neutral compositions at 500 km altitude, it illustrates that [O/N2] and [O] play some roles in daytime and nighttime asymmetry of Ne at topside ionosphere.

Zhang, Xuemin; Shen, Xuhui; Liu, Jing; Yao, Lu; Yuan, Guiping; Huang, Jianping

2014-12-01

12

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

NASA Astrophysics Data System (ADS)

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

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

13

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

E-print Network

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

Enrico Landi; Steven R. Cranmer

2008-09-30

14

SphinX Measurements of the 2009 Solar Minimum X-Ray Emission  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

15

Multi-fluid Model of a Streamer at Solar Minimum and Comparison with Observations  

NASA Astrophysics Data System (ADS)

We present the results of a time-dependent 2.5-dimensional three-fluid magnetohydrodynamic model of the coronal streamer belt, which is compared with the slow solar wind plasma parameters obtained in the extended corona by the UV spectroscopic data from the Ultraviolet Coronagraph Spectrometer (UVCS) on board SOHO during the past minimum of solar activity (Carrington Rotation 1913). Our previous three-fluid streamer model has been improved by considering the solar magnetic field configuration relevant for solar minimum conditions, and preferential heating for O5 + ions. The model was run until a fully self-consistent streamer solution was obtained in the quasi-steady state. The plasma parameters from the multi-fluid model were used to compute the expected UV observables from H I Ly? 1216 Å and O VI 1032 Å spectral lines, and the results were compared in detail with the UVCS measurements. A good agreement between the model and the data was found. The results of the study provide insight into the acceleration and heating of the multi-ion slow solar wind.

Ofman, Leon; Abbo, Lucia; Giordano, Silvio

2011-06-01

16

Ion-neutral Coupling During Deep Solar Minimum  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

17

Estimates of galactic cosmic ray shielding requirements during solar minimum  

NASA Astrophysics Data System (ADS)

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.

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

1990-02-01

18

Ion-neutral coupling during deep solar minimum  

NASA Astrophysics Data System (ADS)

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 (C/NOFS) 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 2008-2010 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.

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

2013-10-01

19

TEC fluctuations during recent Solar Minimum: technique and analysis.  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

20

Cosmic rays during the unusual solar minimum of 2009  

NASA Astrophysics Data System (ADS)

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

Gil, Agnieszka

21

Elemental GCR Observations during the 2009-2010 Solar Minimum Period  

NASA Technical Reports Server (NTRS)

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.

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

22

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

23

Global ionospheric total electron contents (TECs) during the last two solar minimum periods  

NASA Astrophysics Data System (ADS)

last solar minimum period was anomalously extended and low in EUV irradiance compared with previous solar minima. It can readily be expected that the thermosphere and the ionosphere must be correspondingly affected by this low solar activity. While there have been unanimous reports on the thermospheric changes, being cooler and lower in its density as expected, the ionospheric responses to low solar activity in previous studies were not consistent with each other, probably due to the limited ionospheric observations used for them. In this study, we utilized the measurements of total electron content (TEC) from TOPEX and JASON-1 satellites during the periods of 1992 to 2010, which includes both the last two solar minimum periods, in order to investigate how the ionosphere responded to the extremely low solar activity during the last solar minimum compared with previous solar minimum. Although the global daily mean TECs show negligible differences between the two solar minimum periods, the global TEC maps reveal that there are significant systematic differences ranging from about -30% to +50% depending on local time, latitude, and season. The systematic variations of the ionospheric responses seem to mainly result from the relative effects of reduced solar EUV production and reduced recombination rate due to thermospheric changes during the last solar minimum period.

Jee, Geonhwa; Lee, Han-Byul; Solomon, Stanley C.

2014-03-01

24

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

NASA Astrophysics Data System (ADS)

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.

Jee, G.

2010-12-01

25

Field-aligned currents during the extreme solar minimum between the solar cycles 23 and 24  

NASA Astrophysics Data System (ADS)

solar minimum between solar cycles 23 and 24 was unusually long and deep. The upward region-1 (R1) field-aligned current (FAC) response to this extreme solar minimum was investigated using Defense Meteorological Satellite Program observations. The solar cycle responses on the dayside are different than those on the nightside. The field-aligned current density (J//) on the dayside, at 12-17 magnetic local time (MLT), peaks in the declining phase of the solar cycle, in 2003, when the solar wind speed also peaks, whereas J// on the nightside, at 18-23 MLT, appears insensitive to the solar cycle. In 1995-2010, J// at 15-17 MLT reaches the lowest value during the extreme solar minimum in 2009, when the solar wind speed also reaches the lowest value. At 12-17 MLT, R1 is located mostly on open field lines or at the boundary layer, where the current is driven mostly by the velocity shear at the magnetopause boundary. However, on the nightside, R1 is located mostly on the closed field lines where J// is not driven directly and immediately by the solar wind. The nightside current width (?) exhibits a solar cycle effect such that ? is smaller at the solar minimum and smallest in 2009. However, the dayside ? exhibits little solar cycle effect. As a result, the FAC intensity (latitudinally integrated J//) exhibits a solar cycle variation at all local times and the FAC intensity is lower during the extreme solar minimum than that of the previous solar minimum.

Wing, Simon; Ohtani, Shinichi; Johnson, Jay; Wilson, Gordon R.; Higuchi, Tomoyuki

2014-04-01

26

Initial Venus Express magnetic field observations of the Venus bow shock location at solar minimum  

Microsoft Academic Search

In this study, magnetic field measurements obtained by the Venus Express spacecraft are used to determine the bow shock position at solar minimum. The best fit of bow shock location from solar zenith angle 20–120° gives a terminator bow shock location of 2.14 RV (1 RV=6052km) which is 1600km closer to Venus than the 2.40 RV determined during solar maximum

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

2008-01-01

27

Corona Borealis  

NASA Astrophysics Data System (ADS)

(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....

Murdin, P.

2000-11-01

28

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

SciTech Connect

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.

Lave, K. A.; Binns, W. R.; Israel, M. H. [Department of Physics and the McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130 (United States); Wiedenbeck, M. E. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Christian, E. R.; De Nolfo, G. A.; Von Rosenvinge, T. T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cummings, A. C.; Davis, A. J.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C. [California Institute of Technology, Pasadena, CA 91125 (United States)

2013-06-20

29

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

30

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

31

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

NASA Technical Reports Server (NTRS)

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.

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

32

The unusual solar minimum of 2006-2009 as observed by PAMELA  

NASA Astrophysics Data System (ADS)

PAMELA is a satellite-borne experiment, designed to study charged particles in the cosmic radiation, with a particular focus on antiparticles for searching antimatter and signals of dark matter annihilation. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows charged particle and antiparticle identification over a wide energy range and with an unprecedented precision. The quasi-polar orbit of the instrument, with an inclination of 70 degrees, makes it possible to measure low energy particles starting from about 100 MeV/n. We will present data collected in the first 4 years of operation during the A<0 solar minimum of solar cycle 23. In particular we will show the variation of the low energy proton spectrum as a function of time and solar activity. We will also compare the proton spectra measured by PAMELA during this peculiar solar minimum with those measured by previous experiment.

Mori, Nicola; De Simone, Nicola

2012-07-01

33

Solar corona electron density distribution  

NASA Technical Reports Server (NTRS)

The paper discusses the three and one-half months of single-frequency time delay data which were acquired from the Helios 2 spacecraft around the time of its solar occultation. The excess time delay due to integrated effect of free electrons along the signal's ray path could be separated and modeled following the determination of the spacecraft trajectory. An average solar corona and equatorial electron density profile during solar minimum were deduced from the time delay measurements acquired within 5-60 solar radii of the sun. As a point of reference at 10 solar radii from the sun, an average electron density was 4500 el/cu cm. However, an asymmetry was found in the electron density as the ray path moved from the west to east solar limb. This may be related to the fact that during entry into occultation the heliographic latitude of the ray path was about 6 deg, while during exit it was 7 deg. The Helios density model is compared with similar models deduced from different experimental techniques.

Esposito, P. B.; Edenhofer, P.; Lueneburg, E.

1980-01-01

34

Unraveling Parkinson's: Three Clues  

MedlinePLUS

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

35

Solar energetic proton events and coronal mass ejections near solar minimum  

NASA Technical Reports Server (NTRS)

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.

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

36

Occurrence of summer and winter storms in GPS TEC during solar minimum period  

NASA Astrophysics Data System (ADS)

The GPS measurements collected by IGS/EPN over Europe were used to study of the ionosphere response to summer (July 2009) and winter (October 2008) storms. Analysis was based on behaviour of GPS TEC variations over individual GPS stations within 35-70N latitudes and GPS TEC maps created with high resolution. The features of spatial and temporal dynamics of the ionosphere during these storms were revealed in GPS TEC maps. It is necessary to note that considered storm were rather moderate (Dst¡70 nT) as were observed during extended solar minimum. For the case of October 2008 storm the well-pronounced positive effect was observed during day-time. Strong short-term TEC enhancement was detected near noon. The TEC enhancement exceeded 100

Shagimuratov, Irk; Krankowski, Andrzej; Zakharenkova, Irina; Tepenitsyna, Nadezhda; Yakimova, Galina

37

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

SciTech Connect

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.

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

2013-06-13

38

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

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

39

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

E-print Network

Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum currents, the longitudinal and seasonal variation of the Sq currents are determined through the method in the African/European longitude sector reveals similar amplitudes and seasonal variations, indicating

Forbes, Jeffrey

40

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

41

The CME-ICME Connection and Interplanetary Structure During Solar Minimum  

NASA Astrophysics Data System (ADS)

When an interplanetary transient (ICME) exhibits a large angle and smooth rotation in the IMF vector, it is classified as a magnetic cloud (MC) and commonly interpreted as the signature of a magnetic flux rope. On the average bout a third of ICME ejecta are MCs, although the fraction seems to be larger during the quiet phase of the solar cycle. Non-flux rope ICMEs are likely (1) distorted during the transit through heliosphere, (2) observed at an unfavorable crossing angle if the ICME structure has spatial variation, (3) or are simply have a more complex internal structure. Five Magnetic Clouds (MC) have been found from a total of nine ICMEs observed during 2007 January 01 to 2008 August 31, when the separation of STEREO A (STA) and B (STB) spacecraft varied between 0.05 to 70.35 degrees heliolongitude. We investigate the four best MCs using observations from three spacecraft (STA, STB and ACE). The first MC seems to have been detected by all three spacecraft (STA and STB 40.4 degrees apart), while the latter three were detected by only one of the STEREO spacecraft and sometimes by ACE. From the inferred flux rope orientation at each crossing and the spatial variation of the ICME properties, we interpret how each MC flux rope was situated relative to the spacecraft, and its connection to the Sun from corresponding coronal and heliospheric modeling results. Each of the MCs can be associated at low confidence (in contrary to expectations for solar minimum time) with a CME observed by coronagraphs on board STEREO and/or SOHO. All potential parent CMEs were very slow in the 200 km/s range (plane-of-sky), but the speeds of the MCs were between ~390 and ~480 km/s, indicating acceleration in the heliosphere. Solar disk activities are minor around the four CMEs, with no GOES x-ray flares, and two possibly associated filament eruptions. Some CME structures appear to form in the coronagraph field of view rather than rising from below. Several low/mid- latitude coronal holes and a highly warped coronal streamer arcade and source surface neutral line dominate the coronal structure during the period of the study. Previous studies have shown that the MC fluxrope orientation may be aligned with the large-scale coronal streamer arcades. Estimated MC orientations are discussed and compared with events during the previous solar minimum, which exhibited a more dipolar coronal structure. This work was supported, in part, by NASA NNG06GE51G, NNX08AJ04G, and NAS5-03131.

Li, Y.; Lynch, B. J.; Luhmann, J. G.; Kilpua, E.; Toy, V.; Vourlidas, A.; Russell, C. T.; Galvin, A. B.

2008-12-01

42

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

NASA Astrophysics Data System (ADS)

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.

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

43

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

NASA Technical Reports Server (NTRS)

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.

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

44

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

NASA Astrophysics Data System (ADS)

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 ?, 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.

Ofman, L.

2013-05-01

45

The Humanities, Unraveled  

ERIC Educational Resources Information Center

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…

Berube, Michael

2013-01-01

46

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

NASA Astrophysics Data System (ADS)

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

Mancuso, Salvatore; Giordano, Silvio

2013-05-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

48

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

SciTech Connect

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.

Pasachoff, J. M.; Babcock, B. A. [Williams College-Hopkins Observatory, Williamstown, MA 01267 (United States); Rusin, V.; Saniga, M. [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia); Druckmuellerova, H., E-mail: eclipse@williams.edu, E-mail: bryce.a.babcock@williams.edu, E-mail: vrusin@ta3.sk, E-mail: msaniga@ta3.sk, E-mail: hanadruck@seznam.cz [Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, 616 69 Brno (Czech Republic)

2011-11-20

49

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

NASA Astrophysics Data System (ADS)

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.

Pasachoff, J. M.; Rušin, V.; Saniga, M.; Druckmüllerová, H.; Babcock, B. A.

2011-11-01

50

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

51

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

NASA Astrophysics Data System (ADS)

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 storms.

Asmare, Yekoye; Kassa, Tsegaye; Nigussie, Melessew

2014-06-01

52

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

E-print Network

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

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

2011-01-01

53

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

NASA Technical Reports Server (NTRS)

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.

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

54

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

NASA Technical Reports Server (NTRS)

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.

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

55

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

NASA Astrophysics Data System (ADS)

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.

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

2010-02-01

56

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

57

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

SciTech Connect

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.

Smith, Charles W.; Schwadron, Nathan A. [Physics Department, Space Science Center, University of New Hampshire, Durham, New Hampshire (United States); DeForest, Craig E., E-mail: Charles.Smith@unh.edu, E-mail: N.Schwadron@unh.edu, E-mail: DeForest@Boulder.SwRI.edu [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, Colorado (United States)

2013-09-20

58

SuperDARN observations of an unusually contracted ionospheric convection pattern during the recent deep solar minimum  

NASA Astrophysics Data System (ADS)

We present a long term study, from 1995 - 2011, of the latitude of the Heppner-Maynard Boundary (HMB) determined using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection. We find that the average latitude of the HMB at midnight is 61° magnetic latitude during the solar maximum of 2003, but it moves significantly poleward during solar minimum, averaging 64° latitude during 1996, and 68° during 2010. This poleward motion is observed despite the increasing number of low latitude radars built in recent years as part of the StormDARN network, and so is not an artefact of data coverage. We believe that the recent extreme solar minimum lead to an average HMB location that was further poleward than previous solar cycles. We also calculated the open-closed field line boundary (OCB) from auroral images during the years 2000-2002 and find that on average the HMB is located equatorward of the OCB by ~6°. We suggest that the HMB may be a useful proxy for the OCB when global auroral images are not available.

Imber, S. M.; Milan, S. E.; Lester, M.

2012-04-01

59

The heliospheric magnetic flux, solar wind proton flux, and cosmic ray intensity during the coming solar minimum  

NASA Astrophysics Data System (ADS)

Recent papers have linked the heliospheric magnetic flux to the sunspot cycle with good correlation observed between prediction and observation. Other papers have shown a strong correlation between magnetic flux and solar wind proton flux from coronal holes. We combine these efforts with an expectation that the sunspot activity of the approaching solar minimum will resemble the Dalton or Gleissberg Minimum and predict that the magnetic flux and solar wind proton flux over the coming decade will be lower than at any time during the space age. Using these predictions and established theory, we also predict record high galactic cosmic ray intensities over the same years. The analysis shown here is a prediction of global space climate change within which space weather operates. It predicts a new parameter regime for the transient space weather behavior that can be expected during the coming decade.

Smith, Charles W.; McCracken, K. G.; Schwadron, Nathan A.; Goelzer, Molly L.

2014-07-01

60

Westward traveling planetary wave events in the lower thermosphere during solar minimum conditions simulated by SD-WACCM-X  

NASA Astrophysics Data System (ADS)

We present numerical simulations with the Whole Atmosphere Community Climate Model, eXtended version (WACCM-X), whose dynamics is constrained by atmospheric specifications during recent and historical solar minimum conditions. The focus of this study is to describe how various dynamical conditions of boreal winter affect the dynamical behavior of the lower thermosphere (90-150 km). The model simulations are carried out during solar minimum conditions and the results shown here discuss the period January 1-March 30 for five years (1995, 1996, 2008, 2009, and 2010). These years were selected because they include boreal winters without stratospheric warming (1995 and 1996), with modest or normal stratospheric warming (2008 and 2010), and with a large and persistent stratospheric warming (2009). The ultimate goal of this study is to encapsulate the statistically significant dynamical behavior due to westward propagating, planetary-scale waves (wavenumber 1 and wavenumber 2) in the lower thermosphere that are associated with different stratospheric conditions. To this end we show that the westward zonal acceleration above about 80 km is by and large described by traveling waves with periods between 2 and 10 days. We show that the momentum carried by these waves is unlikely to affect directly the momentum budget of the extra-tropical lower thermosphere, where instead gravity-wave drag figures prominently. However, at the times leading to and following large stratospheric disturbances, we show prominent meridional propagation of wave activity from the mid-latitudes toward the tropics. In combination with strong eastward meridional wind shear, our results provide further evidence that such equatorward propagation of momentum in the lower thermosphere might influence the amplitude of equatorially trapped tides.

Sassi, Fabrizio; Liu, Han-Li

2014-11-01

61

Differential Rotation of the Ultraviolet Corona at Solar Maximum  

NASA Astrophysics Data System (ADS)

Synoptic observations of the O VI 1032 Å spectral line from the UltraViolet Coronagraph Spectrometer (UVCS) telescope on board the Solar and Heliospheric Observatory (SOHO) have been analyzed in order to establish the rotational characteristics of the solar corona in the time interval from 1999 March 18 to 2002 December 31, corresponding to the maximum phase of solar cycle 23. By using autocorrelation analysis techniques, we determined the latitude and time dependence of the coronal rotation rate at a heliocentric distance of 1.6 R sun from the solar equator up to about 15° from the poles. Although the equatorial rotation rate is initially consistent with the coronal synodic rotation period (~27.5 days) inferred in a previous study by Giordano & Mancuso around solar minimum, a systematic and substantial acceleration is observed to occur during the second part of the year 2000, with the equatorial coronal synodic rotation period settling to an average value of 25.7 days in the time interval extending from 2001 August to 2002 April, corresponding to a ~7% increase in coronal rotation rate. It is shown that the coronal magnetic structures rotate much faster at all latitudes, and less differentially, than the underlying small-scale magnetic structures linked to the photospheric plasma. The rotation rate of sunspots is however compatible, at least within ~20° from the solar equator, with the one estimated in the middle corona.

Mancuso, Salvatore; Giordano, Silvio

2011-03-01

62

Negative corona ‘tufts’  

NASA Astrophysics Data System (ADS)

Although the formation of bright spots (‘tufts’, ‘beads’) by negative wire corona is known, images of this phenomenon are not available in the literature. The images presented in this paper show that there are mechanisms that result in the formation of regular structures from negative corona ‘tufts’. Though ‘tufts’ of different intensity can co-exist, they ‘prefer’ neighbors of the same intensity. When the current density per unit of wire length is high, the ‘tufts’ ‘repel’ each other, and the brighter these ‘tufts’ are, the stronger this ‘repulsion’.

Gutsol, Alexander F.; Pyle, Walter R.

2014-10-01

63

Heating of the solar corona  

Microsoft Academic Search

The suggestion is advanced that heating of the solar corona results from Landau damping of ion-acoustic waves generated in the motion of photospheric granules. Laboratory experiments relevant to the question of corona heating are discussed, together with the available observational information on the extent of energy deposition in the corona.

N. D'Angelo

1969-01-01

64

Solar corona heating  

Microsoft Academic Search

Despite of the large number of models and mechanisms proposed in the literature, the problem of the heating of the solar corona is still unsolved and represents one of the challenge of solar physics. In this context, a basic question to be addressed by any viable theoretical model concerns understanding the mechanism capable of transferring ``efficiently'' the energy from the

Francesco Califano

2000-01-01

65

Current Sheets in the Corona and the Complexity of Slow Wind  

NASA Technical Reports Server (NTRS)

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.

Antiochos, Spiro

2010-01-01

66

The Unusual Time History of Galactic and Anomalous Cosmic Rays at 1 AU over the Solar Minimum of Cycle 23  

NASA Astrophysics Data System (ADS)

Studies of the galactic cosmic rays temporal variations (GCRs) over the "Modern Era" (from 1950s) establish the existence of a 22-year cosmic ray modulation cycle that is dominated by the 11-year solar activity cycle but is significantly influenced by gradient and curvature drifts in the interplanetary magnetic field (IPB) in association with changes in the tilt of the heliospheric neutral current sheet over the heliomagnetic cycle. In qA<0 epochs (when positive ions flow in along the neutral sheet and out over the solar poles), the solar minimum cosmic rays intensity is peaked over a period of several months (1965, 1987) in contrast to the 3 - 4 year plateau periods for qA>0 minima when the flow pattern is reversed. However, for 200 MeV/n GCR HE at 1 AU there is a quasi-plateau region for the cycle 23 solar minimum that now extends over some 12 months. The intensity level of this component is essentially the same as that of 1965 and 1987, as is the large depression of anomalous cosmic ray ACR He (10 - 40 MeV/n) relative to the qA>0 minima. There appears to be two different solar effects, the current sheet tilt in 2007 is less than in 1987 while the magnitude of the 1P B field is at its lowest value since essentially continuous measurements began in 1963. These will have off-setting effects on the GCR intensity. 10 Be and 14 C studies have shown that previous epochs of low solar activity [Oort (1050 AD); Spoerer (1420-1540); and Maunder (1615-1715)] have been marked by high cosmic ray intensity. There were other periods of reduced solar activity [Wolf (1320) and Dalton (1810)] which were associated with more moderate enhancements of the GCR intensity. Studies using data from the Cosmic Ray Network [IMP, ACE, neutron monitors at 1 AU, and Pioneer, Voyager, and Ulysses at greater heliocentric distances] are providing a better understanding of the solar phenomena that produce the cosmic ray modulation and should lead to an understanding of the solar changes in the distant past associated with the epochs of enhanced GCR intensity.

McDonald, F. B.; Webber, W. R.; Reames, D. V.

2008-12-01

67

Exploring the Prominence-Corona Connection and its Expansion into the Outer Corona Using Total Solar Eclipse Observations  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

68

Polarization of the solar corona.  

NASA Technical Reports Server (NTRS)

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

Feibelman, W. A.

1972-01-01

69

Models for stellar coronae - Thin coronae with radiative forces  

Microsoft Academic Search

Models are calculated for small coronae heated by saw tooth waves with radiative forces acting in the cool region above the corona. The radiative forces are introduced in a parameterized form. The mass loss rates obtained in the models are orders of magnitude lower than the mass loss rates observed in OB supergiants. Attempts to produce models with higher mass

A. G. Hearn

1987-01-01

70

An analysis of heliospheric magnetic field flux based on sunspot number from 1749 to today and prediction for the coming solar minimum  

NASA Astrophysics Data System (ADS)

It is now well established that many bulk properties of the solar wind rise and fall with the solar cycle, and the heliospheric magnetic field (HMF) intensity is no exception. The HMF intensity is seen to be maximum around the time of solar maximum, lowest during solar minimum, and lower still during the recent protracted solar minimum 2006-2009. One explanation of this behavior can be found in the theory of Schwadron et al. (2010) that argues magnetic flux is injected into interplanetary space by coronal mass ejection eruptions and removed by reconnection in the low solar atmosphere. This produces an HMF intensity that is correlated with sunspot number, and the rapid injection of flux followed by the slow removal by reconnection results in a hysteresis effect that is readily evident in the observations. Here for the first time we apply this theory to the sunspot record going back to 1749 and compare favorably our predictions to the results derived from10Be observations. We also make a prediction for the coming solar minimum based on results from the Dalton Minimum.

Goelzer, Molly L.; Smith, Charles W.; Schwadron, Nathan A.; McCracken, K. G.

2013-12-01

71

Global S4 index variations observed using FORMOSAT-3/COSMIC GPS RO technique during a solar minimum year  

NASA Astrophysics Data System (ADS)

In this paper, presented for the first time the three-dimensional global morphology and seasonal variations of scintillation index (S4 index) measured from the signal-to-noise ratio (SNR) intensity fluctuations of L1 channel of GPS radio occultation (RO) signals using FORMOSAT-3/COSMIC (in short, F3/C) satellites for a low solar activity year 2008. The S4 index, which confined around ±30° magnetic latitudes, is found to start around post-sunset hours (1900 MLT, magnetic local time) and often persists till post-midnight hours (0300 MLT) between 150 and 350 km altitudes during equinox and northern winter seasons while no activity is observed during southern winter season. However, high latitudes are characterized with no scintillation activity beyond 150 km during any season, which implying that in the solar minimum period the drives of instabilities in the auroral, cusp and polar cap regions, namely the gradient drift and velocity shear, are absent. The S4 index at F region altitudes during magnetically quiet times is more intense and extends to higher latitudes than that observed during disturbed time consistent with earlier studies. The equatorial S4 index appears below the peak of F2 layer (hmF2) during most of the seasons although the associated intensities and the time of maximum occurrences are relatively higher and earlier during vernal equinox followed by autumn equinox. This equinoctial asymmetry could be primarily attributed to the asymmetries in eastward drift velocities, thermospheric meridional winds and plasma densities. Further, the global maps of S4 index at E region altitudes (between 75 and 125 km) show strong seasonal variations with highest activity during northern and southern summer solstice in the middle latitudes while it appears on both sides of magnetic equator with less or no activity at and around the equator during equinox seasons. The absence of S4 index along the equator can be understood in terms of the vanishing vertical component of the magnetic field lines that can inhibit the vertical movement and layered deposition of ionized particles of thin irregular electron density layers such as Es-layers. Keeping in view the importance of these valuable database, we would like to emphasize that the F3/C GPS RO technique can be used to study the ionospheric irregularities at GHz frequency globally directly from the high-rate L1 data, which reiterating its importance as a powerful tool to explore the terrestrial ionosphere on a global scale.

Brahmanandam, P. S.; Uma, G.; Liu, J. Y.; Chu, Y. H.; Latha Devi, N. S. M. P.; Kakinami, Y.

2012-09-01

72

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

NASA Astrophysics Data System (ADS)

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

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

73

Properties of accretion disk coronae  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

74

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

75

Corona: America's First Satellite Program.  

National Technical Information Service (NTIS)

Since the CORONA satellite made its first successful flight in August 1960, the Intelligence Community overhead reconnaissance programs have been among the nation's most closely guarded secrets. The CIA History Staff is publishing this collection of newly...

1995-01-01

76

Constraining Corona Formation on Venus  

NASA Astrophysics Data System (ADS)

We model the formation of off-rift coronae at Parga Chasma in order to understand how Venus loses its heat. We find the data required to make proper comparisons between models and observations is lacking.

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

2014-05-01

77

Rainbows, Coronas and Glories  

NASA Astrophysics Data System (ADS)

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.

Laven, Philip

78

Diurnal tide in the low-latitude troposphere and stratosphere: Long-term trends and role of the extended solar minimum  

NASA Astrophysics Data System (ADS)

In the present study, long-term trends in the diurnal tide in the troposphere and stratosphere over a tropical station Gadanki (13.5°N, 79.2°E) are investigated using ERA-Interim wind and temperature products available since 1979. Suitability of the ERA-Interim data for the present study is ascertained using simultaneous radiosonde and MST radar observations over Gadanki and good consistency was found between the two. In general, diurnal tide amplitudes are found to increase from troposphere to stratosphere, as expected. Amplitude of the diurnal tide shows a long-term linear increasing trend, which becomes prominent in the stratosphere. Interestingly, convection over Gadanki also exhibits an increasing trend suggesting that they are related. Role of solar cycle on the diurnal tide is investigated by separating the tidal amplitudes during minimum and maximum of solar cycles 21, 22 and 23. Significantly higher amplitudes in the recent extended solar minimum are noticed though no consistent relation is found between solar activity and tides, in general. These results are discussed in the light of role of convection on the generation of the diurnal tide and their propagation to the higher altitudes, coupling lower and middle atmospheres. Special emphasis is made on the observed large amplitudes of the diurnal tide in the extended solar minimum while relating the observed changes to the background circulation.

Ratnam, M. Venkat; Rao, N. Venkateswara; Vedavathi, C.; Murthy, B. V. Krishna; Bhaskara Rao, S. Vijaya

2014-12-01

79

Spectroscopic investigation of protein corona  

NASA Astrophysics Data System (ADS)

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.

Choudhary, Poonam

80

Insights into Corona Formation through Statistical Analyses  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

81

MESSENGER Observations of Magnetohydrodynamic Waves in the Solar Corona from Faraday Rotation  

NASA Astrophysics Data System (ADS)

During the declining phase of the longest solar minimum in a century, the arrival of the MESSENGER spacecraft at superior conjunction allowed the measurement of magnetohydrodynamic (MHD) waves in the solar corona with its 8 GHz radio frequency signal. MHD waves crossing the line of sight were measured via Faraday rotation fluctuations (FRFs) in the plane of polarization (PP) of MESSENGER's signal. FRFs in previous observations of the solar corona (at greater offset distances) consisted of a turbulent spectrum that decreased in power with increasing frequency and distance from the Sun. Occasionally a spectral line, a distinct peak in the power spectral density spectrum around 4 to 8 mHz, was also observed in these early data sets at offset distances of about 5 to 10 solar radii. The MESSENGER FRF data set shows a spectral line at an offset distance between 1.55 to 1.85 solar radii with a frequency of 0.6±0.2 mHz. Other possible spectral lines may be at 1.2, 1.7, and 4.5 mHz; MHD waves with these same frequencies have been observed in X-ray data traveling along closed coronal loops at lower offset distances. An initial analysis of the MESSENGER spectral line(s) shows behavior similar to turbulent spectra: decreasing power with increasing frequency and distance from the Sun. Here we detail the steps taken to process the MESSENGER change in PP data set for the MHD wave investigation.

Jensen, E. A.; Nolan, M.; Bisi, M. M.; Chashei, I.; Vilas, F.

2013-07-01

82

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

SciTech Connect

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.

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

2011-06-20

83

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

84

Models for Stellar Coronae - Comparison with the Minimum Flux Corona Theory  

Microsoft Academic Search

Coronal models calculated using the iterative two boundary value method of solution (Hearn and Vardavas, 1981) are compared with the predictions of the minimum flux corona theory applied to an isothermal, spherically symmetric corona (Hearn, 1975). For those coronal models for which an isothermal corona is a reasonable approximation, the minimum flux corona theory predicts the pressure of the transition

I. M. Vardavas; A. G. Hearn

1981-01-01

85

HEATING OF CHROMOSPHERES AND CORONAE P. ULMSCHNEIDER  

E-print Network

HEATING OF CHROMOSPHERES AND CORONAE P. ULMSCHNEIDER Institut [iir Theoretische Astrophysik are produced by mechanical heating. The heating mechanisms of chromospheres and coronae, clas- sified-mail:ulm@ita.uni-heidelberg.de \\Abstract. Almost all nondegenerate stars have chromospheres and coronae. These hot outer layers

Ulmschneider, Peter

86

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

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

87

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...

88

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

SciTech Connect

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.

Viall, Nicholeen M.; Klimchuk, James A. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-07-10

89

A physical mechanism of solar corona heating  

Microsoft Academic Search

Time profiles of solar soft X-ray microflares and structure soft X-ray solar corona thermal background are studied on RHESSI data. The observations of 2003 year are analyzed. Decrease fluxe of solar soft X-ray microflares and thermal background of solar corona in the X-ray range 2-15 kev are revealed. The new model of solar corona heating in based on this new

I. K. Mirzoeva

2011-01-01

90

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)

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."

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

2013-12-01

91

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)

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.

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

1990-01-01

92

Variations of the Levels of the Vlf/lf Radio Signals on the Middle-Latitude Traces during the Deep Solar Minimum  

NASA Astrophysics Data System (ADS)

Statistical characteristics of the levels of the VLF/LF radio signals from the different European radio stations are presented. The regular observations were been carried out by the test receiver Rohde & Shwarz ESH-3 on the geophysical observatory of IDG RAS Michnevo (54.94°N, 37.73°E) during the period of the deep solar minimum (2007-2009). The radio signals from the radio stations Le Blanc (France, 18.3 kHz), GBZ (Great Britain, 19.6 kHz), HBG (Switzerland, 75 kHz), DCF-77 (Germany, 77.5 kHz) and RBU (Russia, 66.6 kHz) have been chosen for the analysis. In the amplitudes of observable signals the diurnal variations, the seasonal and secular trends were observed. In spite of the absence of the external drivers from above the variations of the radio signal amplitude can obtain 5 - 20 dB and have duration of 2-3 hours. The obtained data can testify that processes from below can make independent strong impact on the ionosphere condition.

Zetzer, J. I.; Lyakhov, A.

2010-12-01

93

System for increasing corona inception voltage of insulating oils  

DOEpatents

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.

Rohwein, Gerald J. (Albuquerque, NM)

1998-01-01

94

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

SciTech Connect

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.

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

2013-08-10

95

Lower Ionosphere at Solar Minimum  

Microsoft Academic Search

Two Nike-Apache rockets were launched in 1964 to measure: (a) positive ion density (N,) with an altitude resolution of approximately 10 meters by use of a modified Gerdien condenser, (b) electron density by radio-propagation techniques, and (c) the optical depth of solar radiation absorbed in the 60-120 km region with a photoelectron retarding potential analyzer. The flights took place at

R. E. BOURDEAU; A. C. AIKIN; J. L. DONLEY

1966-01-01

96

To the Problem of the Corona Heating  

Microsoft Academic Search

The adequacy of different models of the corona heating is discussed. The correlation between the brightness of the coronal green line 530.5 nm Fe XIV and the calculated strength of the magnetic field in the corona is shown to be a very useful instrument to solve the problem. This correlation manifests a very strong dependence both on the solar cycle

O. G. Badalyan; V. N. Obridko

2006-01-01

97

Parga Chasma: Coronae and Rifting on Venus  

NASA Technical Reports Server (NTRS)

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].

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

2005-01-01

98

Hot oxygen coronas at terrestrial planets  

Microsoft Academic Search

Solar forcing via both influx of the solar wind plasma and absorption of ultraviolet radiation forms the hot oxygen coronas at the terrestrial planets (Shizgal and Arcos, 1996). These coronas were observed in the past and recent planetary space missions (Mariner, Pioneer Venus, IMAGE, Mars Express and etc.). We will dicsuss the relative role of the following energetic processes determining

V. I. Shematovich; R. E. Johnson

2006-01-01

99

System reliability analysis through corona testing  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

100

Ultraviolet Corona Discharge Detection Based on Photomultiplier  

Microsoft Academic Search

High voltage equipments, especially polymer insulators may be getting into aging conditions due to the existence of corona discharge on the surface after a long term of running, which would accelerate the deterioration of the surface insulation performance, and even make equipments step into calamity ultimately. So it is significant to detect corona discharge on surface to ensure insulators' stable

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

2008-01-01

101

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

NASA Astrophysics Data System (ADS)

Determination of 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 about uncertainty estimation of this method. In this study we present the detailed assessment of this method using a three-dimensional (3D) electron density in the corona from 1.5 to 4 Rsun as a model, which is reconstructed by tomography method from STEREO/COR1 observations during solar minimum in February 2008. 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 less than a factor of two or so; the former has the lower peak but more spread 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 degrees. 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 that by tomography for a period of low solar activity. 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.

Wang, Tongjiang; Davila, Joseph M.

2014-10-01

102

Turbulent heating of the corona and solar wind: the heliospheric  

E-print Network

Turbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale, hot magnetized plasma (Cranmer et al., 2008) An important measurement: perpendicular heating F corona solar corona 1919 eclipse photo, Sobral 1571, Caron #12;The solar corona Coronal structure often

103

Are the Hot Coronae of Galaxies Heat Conductive  

Microsoft Academic Search

The effects of heat conductivity in the dynamics of hot X-ray coronae of galaxies are investigated by numerical integration of gas dynamics equations. Coronae are supposed to be confined by massive dark halos and\\/or hot intergalactic medium. The results are: (1) Coronae with zero heat conductivity can exist many Gyrs quasistationary. (2) Heat conductive coronae bound by dark halos rapidly

V. G. Berman; A. A. Suchkov

1986-01-01

104

Mie theory model of the corona.  

PubMed

We performed a calculation of the corona colors that employed Mie theory to obtain the scattered light intensity. The scattered intensity was integrated over the visible spectrum for a number of different cloud droplet size distriubtions. The results were converted to chromaticity coordinates, convolved with the angular size of the sun, and plotted on the 1931 CIE chromaticity diagram. The results were compared to observations of multiple-ring coronas. It was found that, when using Mie theory to estimate cloud droplet sizes, water droplets with diameters in the 7-microm less, similar D less, similar 15-microm range produced the 13 multiple-ring coronas that were observed. PMID:20706405

Lock, J A; Yang, L

1991-08-20

105

Unraveling flow patterns through nonlinear manifold learning.  

PubMed

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

Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

2014-01-01

106

Unraveling Flow Patterns through Nonlinear Manifold Learning  

PubMed Central

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

Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

2014-01-01

107

Tectonic patterns and regional stresses near Venusian coronae  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

108

Global Magnetohydrodynamic Modeling of the Solar Corona.  

National Technical Information Service (NTIS)

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 ...

J. A. Linker

1997-01-01

109

Global Magnetohydrodynamic Modeling of the Solar Corona.  

National Technical Information Service (NTIS)

This report describes the progress made in the investigation of the solar corona using magnetohydrodynamic (MHD) simulations. Coronal mass ejections (CME) are believed to be the primary cause of nonrecurrent geomagnetic storms and these have been investig...

J. A. Linker

2001-01-01

110

IONIZATION OF AIR BY CORONA DISCHARGE  

E-print Network

Engineering Department, for his timely help with the electronic circuits. I would like to thank Rod Duke of God. July, 2003 #12;v ABSTRACT IONIZATION OF AIR BY CORONA DISCHARGE Publication No. ______ Philip K

Texas at Arlington, University of

111

Global Magnetohydrodynamic Modeling of the Solar Corona  

NASA Technical Reports Server (NTRS)

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

Linker, Jon A.

1998-01-01

112

Corona Associations and Their Implications for Venus  

USGS Publications Warehouse

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.

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

1998-01-01

113

Jumplike unravelings for non-Markovian open quantum systems  

Microsoft Academic Search

Non-Markovian evolution of an open quantum system can be ``unraveled'' into pure state trajectories generated by a non-Markovian stochastic (diffusive) Schrödinger equation, as introduced by Diósi, Gisin, and Strunz. Recently we have shown that such equations can be derived using the modal (hidden variable) interpretation of quantum mechanics. In this paper we generalize this theory to treat jumplike unravelings. To

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

2004-01-01

114

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

115

Unraveling the miswired connectome: a developmental perspective.  

PubMed

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

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

2014-09-17

116

Coronas and iridescence in mountain wave clouds  

NASA Astrophysics Data System (ADS)

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 ?m, with over half the cases requiring diffraction by small (~20 ?m) 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.

Shaw, Joseph A.; Neiman, Paul J.

2003-01-01

117

Coronas and iridescence in mountain wave clouds.  

PubMed

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

Shaw, Joseph A; Neiman, Paul J

2003-01-20

118

CITY OF CORONA OFFICE OF THE CITY CLERK  

E-print Network

FOR CORONA DEPARTMENT OF WATER AND POWER IN FURTHERANCE OF RESOLUTION NO. 2012-013 AND AUTHORIZING THE TAKING call the Corona Department of Water and Power (DWP) at (951) 736-2232. Lisa Mobley, Chief Deputy City

119

TRIANGLE-SHAPED DC CORONA DISCHARGE DEVICE FOR MOLECULAR DECOMPOSITION  

EPA Science Inventory

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

120

Heating of the corona by magnetic singularities  

NASA Technical Reports Server (NTRS)

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

Antiochos, Spiro K.

1990-01-01

121

Advection corona driven by radiation drag.  

NASA Astrophysics Data System (ADS)

The authors have examined the motion of an accretion disk corona (?-corona) which is dynamically driven via radiation drag exerted by a central luminous source and an accretion disk itself. They adopted the standard model (?-model) as a disk model. When the central source is brighter, then the specific angular momentum of the coronal gas is lost by radiation drag of the radition field from the central source. The rotational velocity becomes less than a Keplerian one and falls toward the central object. On the other hand, when the accretion disk is brighter, the infall is supressed by radiation drag of the radiation field from the disk.

Watanabe, Y.; Fukue, J.

122

Hot Plasma Flows in the Solar Corona  

NASA Astrophysics Data System (ADS)

The Solar Corona is a non-equilibrium open system. Energy and mass are supplied from the lower atmosphere and flow upwards through the corona into the interplanetary space. Steady state could be possible but not equilibrium state. Temperature of the corona varies depending on solar activities. However, even under very quite state, coronal temperature is still kept around million degrees. Coronal heating mechanisms have to work under such condition. Temperature of plasma is an averaged kinetic energy of random motion of particles. Motion of charged particles in magnetic field generates Lorenz force and particles gyrate around magnetic field lines. Gyration of charged particles generates magnetic moment which is directed anti-parallel to the surrounding magnetic field. This is the origin of diamagnetism of plasma. Each particle can be considered as a small magnet directed opposite to the surrounding magnetic field. When these magnets are put in inhomogeneous magnetic field, they are pushed toward weak field region. In case of open magnetic field region in the solar corona, plasma particles are pushed upwards. If this force (diamagnetic or mirror force) exceeds the gravity force, plasma flows upwards. Magnetic moment of each charged particle in thermal plasma is proportional to temperature and inversely proportional to magnetic field strength. The condition for plasma to flow upwards in an open magnetic field is that the scale length of the change of magnetic field strength is shorter than the hydrostatic scale length, which is determined by temperature and the gravity acceleration. This can be a mechanism to regulate the coronal temperature around million degree. The solar corona is filled with magnetic field, which is rooted at the photosphere in the form of flux tubes. Flux tubes connect directly the corona and the sub-photospheric layer where temperature is higher than the photosphere. Hot plasma, trapped in the flux tubes when they are generated around the bottom of the convection zone, will be pushed upwards through the flux tubes due to weakening of magnetic field strength upwards and are fed into the corona. This scenario can explain why the solar corona is kept around million degree independent of solar activity. This mechanism can be applied to explain 1) temperature dependent plasma upflows found in the solar atmosphere, 2) solar wind acceleration, 3) loop-top plasma concentration in post flare loops, and 4) various eruptive phenomena, including some of solar flares, caused by flows along curved magnetic field. The MHD equation does not include this force along the field.

Shibasaki, K.

2012-12-01

123

Device for generation of pulsed corona discharge  

DOEpatents

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

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

2012-05-08

124

Transient corona effects on a wire over the ground  

NASA Technical Reports Server (NTRS)

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

Chen, K. C.

1980-01-01

125

Universal response model for a corona charged aerosol detector  

Microsoft Academic Search

The universality of the response of the Corona Charged Aerosol Detector (CoronaCAD) has been investigated under flow-injection and gradient HPLC elution conditions. A three-dimensional model was developed which relates the CoronaCAD response to analyte concentration and the mobile phase composition used. The model was developed using the response of four probe analytes which displayed non-volatile behavior in the CoronaCAD and

Joseph P. Hutchinson; Jianfeng Li; William Farrell; Elizabeth Groeber; Roman Szucs; Greg Dicinoski; Paul R. Haddad

2010-01-01

126

Current Sheets in the Sun's Corona ERIC PRIEST  

E-print Network

the corona is heated to such high temperatures. The energy that is required to heat the corona is about 5000Current Sheets in the Sun's Corona ERIC PRIEST School of Mathematics and Statistics, University an important role in the Sun's atmosphere, especially in coronal heating events and solar ares. They may form

Priest, Eric

127

Plasma Diagnostics of the Solar Corona Using Decimetric Radio Waves  

E-print Network

process may have different forms. Are they enough to heat the solar corona? The answer seems to become electric currents, must also be con­ sidered. The heating problem of the solar corona can only be solved. Plasma Diagnostics of the Solar Corona Using Decimetric Radio Waves (Review) Arnold O. Benz

128

On the possibility of purely acoustically heated coronae  

Microsoft Academic Search

The notion of coronae heated by purely acoustic processes is developed theoretically based on the existence of chromospheres heated by acoustic means only. Acoustic wave energy flux is considered in light of the minimum energy requirements of coronae, and valid purely acoustic coronae occur when the coronal energy loss flux is balanced by the acoustic flux. Very low coronal pressures

R. Hammer; P. Ulmschneider

1990-01-01

129

Current Sheets in the Sun's Corona ERIC PRIEST  

E-print Network

the corona is heated to such high temperatures. The energy that is required to heat the corona is about 5000Current Sheets in the Sun's Corona ERIC PRIEST School of Mathematics and Statistics, University an important role in the Sun's atmosphere, especially in coronal heating events and solar flares. They may form

Priest, Eric

130

Current Sheets in the Sun's Corona ERIC PRIEST  

E-print Network

is then to understand how the corona is heated to such high temperatures. The energy that is required to heat the coronaCurrent Sheets in the Sun's Corona ERIC PRIEST School of Mathematics and Statistics, University an important role in the Sun's atmosphere, especially in coronal heating events and solar ares. They may form

Priest, Eric

131

System for increasing corona inception voltage of insulating oils  

DOEpatents

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

Rohwein, G.J.

1998-05-19

132

Petrovay: Solar physics Chromosphere and corona THE SOLAR CHROMOSPHERE  

E-print Network

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

Petrovay, Kristóf

133

Unraveling the complex metabolic nature of astrocytes  

PubMed Central

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

Bouzier-Sore, Anne-Karine; Pellerin, Luc

2013-01-01

134

Corona charging of electrets: models and results  

Microsoft Academic Search

Experimental results obtained with the corona charging technique for polymers, mainly Teflon FEP and PVDF, are summarized. Emphasis is put on the hypothesis underlying the models employed to explain the experimental results. The following subjects are discussed: the crossover effect in polyethylene: the voltage buildup and decay at room temperature and the thermally stimulated discharging in Teflon FEP, stressing in

G. F. Leal Ferreira; M. T. Figueiredo

1992-01-01

135

LABORATORY ANALYSIS OF BACK-CORONA DISCHARGE  

EPA Science Inventory

The paper discusses an experimental research program to characterize back-corona generation and behavior in a range of environments and geometries common to electrostatic precipitators (ESPs). A wire-parallel plate device was used to monitor the intensity and distribution of back...

136

Solar corona heating by kinetic Alfven waves  

Microsoft Academic Search

The nonlinear mechanism of the kinetic Alfven waves (KAW) generation in the solar corona with small plasma parameter beta <<1 is investigated. The parametric instability, where the magnetosound wave (MSW) is the pump wave, is considered as the generation mechanism,. Using a two-fluid magnetohydrodynamics and Maxwell's equation, we derive a nonlinear dispersion relation governing this three-wave interaction process and the

A. D. Voitsekhovskaia; V. N. Fedun; A. K. Yukhimuk

2004-01-01

137

How is the Solar Corona Heated ?  

Microsoft Academic Search

Trying to determine which mechanisms are heating the corona is one of the main aims of the SOHO mission. A summary is given of the mechanisms that have been proposed together with the observational properties that have so far been determined. A new technique for determining the heating mechanisms is presented together with the results from applying it to Yohkoh

Eric R. Priest

1997-01-01

138

Corona Considerations in Submarine Cable Communications Systems  

Microsoft Academic Search

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

Earnest Franke

1974-01-01

139

Indirect detection of the Martian helium corona  

Microsoft Academic Search

The ion composition mass spectrometer ASPERA on board the PHOBOS 2 spacecraft detected particles with M\\/q=4 in the vicinity of Mars. A significant difference between the measured particle velocity and the solar wind velocity suggests that these ions are of planetary origin, apparently He+ from ionisation within the Martian helium corona. The particles had typical energies of either more than

S. Barabash; O. Norberg

1994-01-01

140

Indirect detection of the Martian helium corona  

Microsoft Academic Search

The ion composition mass spectrometer ASPERA on board the PHOBOS 2 spacecraft detected particles with M\\/q = 4 in the vicinity of Mars. A significant difference between the measured particle velocity and the solar wind velocity suggests that these ions are of planetary origin, apparently He(+) from ionisation within the Martian helium corona. The particles had typical energies of either

S. Barabash; O. Norberg

1994-01-01

141

Global Magnetohydrodynamic Modeling of the Solar Corona  

NASA Technical Reports Server (NTRS)

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

Linker, Jon A.

2001-01-01

142

Pulsed Corona in Air for Water PROEFSCHRIFT  

E-print Network

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

Eindhoven, Technische Universiteit

143

Ablative corona driven by light ion beam  

Microsoft Academic Search

A theoretical model is presented describing the spatial structure and scaling laws for the ablative corona generated by the incidence of an intense light ion beam pulse on a spherical pellet. This treatment differs, from an earlier model in the assumption that the beam velocity vb is higher than the electron thermal velocity vThe everywhere, which allows one to obtain

A R Piriz

1986-01-01

144

The quiet corona: Temperature and temperature gradient  

Microsoft Academic Search

A study of the lower corona thermal properties was made using the best examples of solar wind heavy ion spectra obtained with Vela 5 and 6 plasma analyzers at times of quiet solar wind (low speed, low temperature). The multiple Si and Fe ion species peaks in the spectra were fit with solutions of the ionization equilibrium equations to determine

S. J. Bame; J. R. Asbridge; W. C. Feldman; P. D. Kearney

1974-01-01

145

The minimum flux corona; theory or concept  

NASA Technical Reports Server (NTRS)

The reply to the criticisms of the minimum flux theory is discussed. These criticisms are correct in substance, as well as in detail. Counter arguments that the minimum flux corona theory is untenable, because of errors in its formulation, are presented.

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

1980-01-01

146

PEGylated nanoparticles: protein corona and secondary structure  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

147

Observing and quantifying the solar wind signature of the magnetically complex corona.  

NASA Astrophysics Data System (ADS)

The solar wind exhibits fluctuations over a broad range of timescales characteristic of magnetohydrodynamic (MHD) turbulence evolving in the presence of structures of coronal origin. In- situ spacecraft observations of plasma parameters are at minute (or below) resolution for intervals spanning the solar cycle and provide a large number of samples for statistical studies. The magnetic field power spectrum typically has two characteristic components, an inertial range of turbulence over several orders of magnitude with approximately Kolmogorov power law and at lower frequencies, an approximately '1/f' energy containing range believed to be of direct coronal origin. We focus on the behaviour of in- situ observations of fluctuations in the inner heliosphere as a function of solar cycle and solar wind speed; that is, with respect to coronal structure and dynamics. We employ a recently developed technique that sensitively distinguishes between fractal and multifractal scaling in the timeseries. Our working hypothesis is that since the latter can be characteristic of local MHD turbulence, the former maps more directly to features of coronal origin. We find a strong correlation between the scaling properties of magnetic energy density fluctuations and the magnetic complexity of the coronal magnetic fields. At solar maximum in the ecliptic, where the in- situ observations can be dominated by slow solar wind, the magnetic energy density as seen by WIND and ACE shows a fractal signature, whereas at minimum it is multifractal. This is corroborated by ULLYSES polar observations at solar minimum in quiet, fast solar wind where again, multifractal scaling is found. This high magnetic complexity in the corona corresponds to fractal, rather than multifractal scaling in magnetic energy density; remarkably, this fractal signature dominates the full dynamic range of observations, extending across timescales typically identified with both the '1/f' and 'inertial range'. The correlation of behaviour of other bulk plasma parameters observed in- situ with the magnetic complexity of the coronal will also be discussed. Since we are able to quantify scaling exponents, our results provide constraints on models for the solar wind. In particular, the fractal signature which we discuss here can be captured by a nonlinear Fokker Planck model, with the prospect of a quantitative mapping back to the corona.

Hnat, B.; Chapman, S. C.; Kiyani, K. H.; Nicol, R. M.

2008-12-01

148

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

NASA Astrophysics Data System (ADS)

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

2011-04-01

149

Radio seismology of the outer solar corona  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

150

MASC: Magnetic Activity of the Solar Corona  

NASA Astrophysics Data System (ADS)

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

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

151

Nanoflare Heating of Solar and Stellar Coronae  

NASA Technical Reports Server (NTRS)

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

Klimchuk, James A.

2010-01-01

152

The quiescent corona and slow solar wind  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

153

Meteoroids in solar corona and planetary atmospheres  

Microsoft Academic Search

We simulate the meteoroid entry into the solar corona with a model similar to the one-dimensional ablation model developed by Campbell-Brown and Koschny (2004) for the Earth's atmosphere and by McAuliffe and Christou (2005) for the case of the atmosphere of Venus. We present the results of mass deposition profiles for a wide range of masses for objects falling into

Herve Lamy; Ingrid Mann; Emeritus Joseph Lemaire

2010-01-01

154

Coloring, location and domination of corona graphs  

E-print Network

A vertex coloring of a graph $G$ is an assignment of colors to the vertices of $G$ such that every two adjacent vertices of $G$ have different colors. A coloring related property of a graphs is also an assignment of colors or labels to the vertices of a graph, in which the process of labeling is done according to an extra condition. A set $S$ of vertices of a graph $G$ is a dominating set in $G$ if every vertex outside of $S$ is adjacent to at least one vertex belonging to $S$. A domination parameter of $G$ is related to those structures of a graph satisfying some domination property together with other conditions on the vertices of $G$. In this article we study several mathematical properties related to coloring, domination and location of corona graphs. We investigate the distance-$k$ colorings of corona graphs. Particularly, we obtain tight bounds for the distance-2 chromatic number and distance-3 chromatic number of corona graphs, throughout some relationships between the distance-$k$ chromatic number of ...

Yero, I González; Aguilar, A Rondón

2012-01-01

155

Harmonic wave analysis of conductor corona current based on wide frequency band measurement  

Microsoft Academic Search

Corona current is one of important corona characteristic research contents. In order to analyze conductor corona current harmonic wave characteristic, a corona current measurement system is developed. The synchronous collect of the voltage and current signal is realized by the GPS technology. The corona current signal is transmitted to the lower computer through the wireless network. And the current signal

Fangcheng Lu; Shaohua You; Yunpeng Liu; Lei Zhu

2011-01-01

156

The energy balance and mass loss of stellar coronae  

Microsoft Academic Search

The question is considered of whether radiation-driven sound waves could explain the mass loss of OB supergiants and Wolf-Rayet stars through the mechanism of a stellar wind produced by a hot corona. Simple expressions are obtained for the energy-loss rate from a corona due to mass loss, radiation, and thermal conduction. It is found that a corona with a given

A. G. Hearn

1975-01-01

157

Corona in Aircraft Electric Systems as a Function of Altitude  

Microsoft Academic Search

Corona-starting voltages of the components of a 208-volt 400-cycle grounded-neutral electric system are reported for conditions to simulate altitudes between sea level and 50,000 feet. The corona characteristics are shown to be functions of air pressure, electric-field geometry, humidity, and the cleanliness of insulating surfaces. The effect of reducing pressure is shown to lower the corona-starting voltages of aircraft cables

W. R. Wilson

1944-01-01

158

The Heating of the Solar Corona by Kink Instabilities.  

E-print Network

??The million-degree temperature of the solar corona might be due to the combined effectof barely distinguishable energy releases, called nanoflares, that occur throughoutthe solar atmosphere.… (more)

Bareford, Michael

2012-01-01

159

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

ERIC Educational Resources Information Center

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

Arnott, Luke

2012-01-01

160

REVIEW Open Access Unraveling genomic variation from next  

E-print Network

and at a lower cost. Based on the first Sanger sequencing technique, the Human Genome Project (1990� 2003REVIEW Open Access Unraveling genomic variation from next generation sequencing data Georgios technological advances, involve evolution of species, microbial mapping, population genetics, genome

161

REPLICATION OF "UNRAVELING JUVENILE DELINQUENCY" IN PUERTO RICO.  

ERIC Educational Resources Information Center

THE 1ST YEAR OF A 5- TO 6-YEAR PROJECT TO REPLICATE A BOSTON STUDY OF JUVENILE DELINQUENCY IN PUERTO RICO WAS REPORTED. THIS FINAL REPORT COVERS ONLY THE PILOT PHASE OF THE PROJECT. THE PROBLEM ON WHICH THE RESEARCH IS FOCUSED IS TO DETERMINE WHICH OF THE FINDINGS OF "UNRAVELING JUVENILE DELINQUENCY," AS THE STARTING POINT FOR THE PUERTO RICAN…

GLUECK, SHELDON; AND OTHERS

162

Unraveling the racial disparities associated with kidney disease1  

Microsoft Academic Search

Unraveling the racial disparities associated with kidney disease. In the United States, chronic kidney disease (CKD), and in particular end-stage renal disease (ESRD), represent a growing problem. Many other countries also have an increasing number of ESRD cases. Racial\\/ethnic disparities have been documented globally in the prevalence, incidence, and treatment of CKD, most extensively in the United States, but also

Keith C. Norris; Lawrence Y. Agodoa

2005-01-01

163

Exploration of projective techniques to unravel health perception  

Microsoft Academic Search

Purpose – This paper seeks to explore the design, organisation and application of group discussions in which projective techniques (expressive and associative) are used to unravel health perception of consumers in cognitive and affective terms. Design\\/methodology\\/approach – A trained moderator led four group discussions in which 24 Dutch women, divided into two groups of six women aged between 50 and

Siet Sijtsema; Anita Linnemann; G. B. C. Backus; W. M. F. Jongen; Ton van Gaasbeek; Hans Dagevos

2007-01-01

164

Unravelling the (miniature) Rubik's Cube through its Cayley Graph  

E-print Network

Unravelling the (miniature) Rubik's Cube through its Cayley Graph Daniel Bump1 and Daniel Auerbach2. How can one perceive its true structure? The Rubik's cube is a popular toy which in reality is nothing the group of the Rubik's cube, one may consider the subgroup with two generators, and the corresponding

Bump, Daniel

165

Reconnection Processes in the Chromosphere and Corona  

NASA Astrophysics Data System (ADS)

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

Shibata, Kazunari

2012-07-01

166

Coronae on Venus: Relationship of Geology to Gravity  

NASA Astrophysics Data System (ADS)

Analysis of the gravity signatures of coronae can provide insight into their formation, as well as information on lithospheric properties. Previous studies have shown a lack of correlation between elastic thickness and corona diameter, and that all topographic morphologies are represented in the group of isostatically compensated coronae, including morphologies believed to reflect active plumes (Smrekar et al., 2003; Smrekar and Stofan, 2003; Hoogenboom et al., 2004). In addition, Johnson and Richards (2003) found that uncompensated coronae are preferentially located in the Beta-Atla-Themis region, suggesting it is younger. However, only coronae that are well resolved in the gravity data and have well behaved admittance signatures can be analyzed (135 out of 513 coronae), which does not provide an adequate size population to ensure that results are statistically significant (i.e., Glaze et al., 2002). In order to determine how the 135 features examined in gravity data relate to the total corona population, we are examining the local/regional stratigraphic position, amount of associated volcanism, and geologic complexity (e.g., evolution of the annulus and interior) for the135 features analyzed in the gravity data (Smrekar et al., 2003; Smrekar and Stofan, 2003; Hoogenboom et al., 2004). Initial results suggest a general lack of correlation between the corona parameters studied in these populations: for example, compensated corona range from stratigraphically old features with relatively low topography and low amounts of associated volcanism to stratigraphically young features with high topography and high amounts of associated volcanism. However, coronae in specific regions, such as parts of Hecate Chasma, show a correlation between apparent stratigraphic position and elastic thickness (Smrekar et al., this meeting). We are assessing these results in comparison to the population as a whole in order to better understand the relationship of coronae to the geologic evolution of Venus.

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

2007-12-01

167

Corona And Ultraviolet Equipment For Testing Materials  

NASA Technical Reports Server (NTRS)

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

Laue, Eric G.

1993-01-01

168

Corona loss characteristics of contaminated conductors in fair weather  

Microsoft Academic Search

In the present work, the results of a laboratory measurement project of corona losses on contaminated conductors in fair weather are presented. The measurements carried out furnish new information, which is not available in the literature. The research work performed in the past has dealt with corona losses under rain and snow, and some semiempirical formulae have been proposed, which

Enrique E Mombello; Giuseppe Rattá; Héctor D Suárez; Federico O Torres

2001-01-01

169

Effects of corona on heat transfer in an enclosure  

Microsoft Academic Search

Experiments were conducted to determine the effects of corona wind on heat transfer rates for enclosures. Tests were performed with an enclosed cavity heated on the bottom and cooled on the top (and vice versa). A corona wind was established inside the cavity by applying high voltages to 0.004 inch diameter chromel wires placed along the hot and cold surfaces

Donald D. Dyer Jr.

1986-01-01

170

Breakdown Streamers in Coronas with Heated Discharge Electrode  

Microsoft Academic Search

Experiments have been carried out on a wire-tube corona apparatus to measure the breakdown voltage and the maximum prebreakdown corona current with and without heating the discharge electrode. Positive and negative polarities were employed on discharge electrodes of different diameters in clean air at room temperature. The results showed that the triggering of the break- down streamers, and hence the

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

1977-01-01

171

CORONAS-F satellite: Tasks for study of particle acceleration  

Microsoft Academic Search

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

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

2002-01-01

172

Admittance survey of type 1 coronae on Venus  

Microsoft Academic Search

In this study, we analyze Magellan gravity and topography data for Type 1 coronae on Venus to estimate crustal thickness (Zc), elastic thickness (Te), and apparent depth of compensation (ZL). We examine the free-air admittance for all 103 Type 1 coronae (defined as having greater than 50% complete fracture annuli) that are resolved in the gravity data. A spatio-spectral method

Trudi Hoogenboom; Suzanne E. Smrekar; F. Scott Anderson; Greg Houseman

2004-01-01

173

Analysis of Corona Discharge Interference on Antennas on Composite Airplanes  

Microsoft Academic Search

Static electrification of the airframe can often cause electromagnetic interference on aircraft radios. Triboelectric charging, occurring when an aircraft is operated in precipitation, raises the aircraft potential until corona discharges occur from points of high dc field on the aircraft. These corona discharges generate noise that is coupled into antenna systems installed on the aircraft. The characteristics of electrostatic accumulation

Huan-Zhan Fu; Yong-Jun Xie; Jun Zhang

2008-01-01

174

Probing the Solar Corona with Radio Ranging Measurements  

NASA Technical Reports Server (NTRS)

An asymmetry in the radial variation of electron density above the east and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. The Voyager 2 ranging measurements are compared with the Mauna Loa Solar Observatory white-light coronagraph measurements of the underlying corona. Corona probing abilities are summarized.

Woo, R.

1995-01-01

175

Rings Around the Sun and Moon: Coronae and Diffraction  

ERIC Educational Resources Information Center

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

Cowley, Les; Laven, Philip; Vollmer, Michael

2005-01-01

176

Electrical Characterization of a Corona Discharge for Surface Treatment  

Microsoft Academic Search

Electrical characterization is based on a display of voltage and charge which appears as a simple parallelogram. The area is a measure of energy input per cycle and is independent of voltage waveform but very dependent on the maximum voltage. A useful model for such corona discharges employs a Zener diode to simulate the corona drop. The buffer dielectric plays

Louis A. Rosenthal; Donald A. Davis

1975-01-01

177

The corona of HD 223460 (HR 9024)  

NASA Astrophysics Data System (ADS)

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

Gondoin, P.

2003-10-01

178

RADIATIVE HEATING OF THE SOLAR CORONA  

SciTech Connect

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

Moran, Thomas G., E-mail: moran@grace.nascom.nasa.gov [Physics Department, Catholic University of America, 200 Hannan Hall, Washington, DC 20064 (United States) and NASA/GSFC, Code 671, Greenbelt, MD 20771 (United States)

2011-10-20

179

Development of ac corona discharge modes at atmospheric pressure  

SciTech Connect

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

El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed [Department of Physics, Faculty of Science, Assiut University, 71516 Assiut (Egypt)

2011-02-15

180

Rapid formation of plasma protein corona critically affects nanoparticle pathophysiology  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

182

R Coronae Australis: A Cosmic Watercolour  

NASA Astrophysics Data System (ADS)

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

2010-06-01

183

Exploring dynamic events in the solar corona  

NASA Astrophysics Data System (ADS)

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

Downs, Cooper James

184

The spatial distribution of coronae and related features on Venus  

NASA Astrophysics Data System (ADS)

Coronae are large quasi-circular geologica features that are common on Venus. They appear to be the surface tectonic and volcanic expressions of mantle diapirs that have impinged on the underside of the venusian lithosphere. We have investigated the spatial distribution of 335 coronae and related features identified in Magellan radar data. It is more clustered than a Poisson distribution, with a statistical certainty of more than 99%. It is dominated by a single large cluster centered near the equator at about 245 deg longitude. The features are preferentially found at elevation and geoid values close to the planetary mean, with a paucity at both the highest and lowest levels of topography and geoid. Some coronae appear aligned in quasi-linear chains. We attribute the clustering of coronae and related features to preferential formation of these features above regions of broad-scale mantle upwelling, and suggest that a major mantle upwelling underlies the one large cluster. We suggest that coronae are rare at the lowest elevations because these may be regions of mantle downwelling. The shortage of coronae at the highest elevations may result both from obscuration by other intense tectonism there and from suppression there of their formation by an unusually thick crust. Corona chains may be produced by enhanced passive mantle uplift below failed or incipient rifts.

Squyres, Steven W.; Janes, Daniel M.; Schubert, Gerald; Bindschadler, Duane L.; Moersch, Jeffrey E.; Turcotte, Donald L.; Stofan, Ellen R.

1993-12-01

185

High Energy Particles in the Solar Corona  

E-print Network

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

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

2008-04-16

186

Chemical Compositions and Anomalies in Stellar Coronae  

NASA Technical Reports Server (NTRS)

In summary, as the papers cited here and in earlier reports demonstrate, this award has enabled us to obtain a fairly good picture of the abundance anomalies in stellar coronae. The "inverse FIP" effect in very active stars has now been fleshed out as a more complex anomaly depending on FIP, whereas before it appeared only in terms of a general metal paucity, the recent solar abundance assessment of Asplund et a1 will, if correct, challenge some of the older interpretations of coronal abundance anomalies since they imply quite different relative abundances of CNO compared with Fe, Mg and Si. Further investigations have been in into the possibility of modeling some of the recent coronal abundance anomaly results in terms of Alfven wave-driven separation of neutrals and ions in the upper chromosphere. This work still remains in the seed stage, and future funding from a different program will be requested to pursue it further.

Drake, Jeremy; Oliversen, Ronald J. (Technical Monitor)

2005-01-01

187

Deep solar minimum and global climate changes  

NASA Astrophysics Data System (ADS)

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

Hady, Ahmed A.

2013-05-01

188

Deep solar minimum and global Climate Changes  

NASA Astrophysics Data System (ADS)

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

Abdel Hady, Ahmed

2012-07-01

189

Quantitative results on heating events in the quiet corona Arnold O. Benz and Sm Krucker  

E-print Network

Quantitative results on heating events in the quiet corona Arnold O. Benz and Säm Krucker Citation;Quantitative Results on Heating Events in the Quiet Corona Arnold O. Benz 1 and Krucker2 1Institute constitute a major energy input into the corona, suggesting that the lower corona is not just heated

190

Heating Events Observed in the Quiet Corona A.O. Benz 1 , S. Krucker 2  

E-print Network

5 Heating Events Observed in the Quiet Corona A.O. Benz 1 , S. Krucker 2 1 Institute of Astronomy input into the corona, suggesting that the lower corona is not just heated, but continuously re for coronal heating are premature. Key words: Sun: corona; coronal heating; microflare; nanoflare; evaporation

191

The effect of corona wire heating on the ozone generations in an air cleaning electrostatic precipitator  

Microsoft Academic Search

The effect of corona wire surface temperature on ozone generation in an air-cleaning electrostatic precipitator is studied experimentally. The results show that significant ozone concentrations are only observed in a narrow region near downstream of the corona wire for positive coronas. From surface temperature measurements using infrared imaging, it is observed that the heat generated by corona discharge alone only

T. Ohkubo; S. Hamasaki; Y. Nomoto; J. S. Chang; T. Adachi

1988-01-01

192

ENERGY DISTRIBUTION OF MICROEVENTS IN THE QUIET SOLAR CORONA Arnold O. Benz  

E-print Network

of information on the heating process of the corona. Subject headings: Sun: activity -- Sun: corona -- Sun: flares -- Sun: X-rays, gamma rays 1. INTRODUCTION The heating of the solar corona has been a riddle sinceENERGY DISTRIBUTION OF MICROEVENTS IN THE QUIET SOLAR CORONA Arnold O. Benz Institute of Astronomy

193

ENERGY DISTRIBUTION OF MICROEVENTS IN THE QUIET SOLAR CORONA Arnold O. Benz  

E-print Network

of information on the heating process of the corona. Subject headings: Sun: activity --- Sun: corona --- Sun: flares --- Sun: X­rays, gamma rays 1. INTRODUCTION The heating of the solar corona has been a riddle nonstationary heating process. In the quiet corona on which we concentrate here, small brightenings above

194

Formation of Coronae Structures on Venus by Thermochemical Diapirs  

NASA Astrophysics Data System (ADS)

One of the most prominent features on the surface of Venus are the coronae. They are large scale volcano-tectonic structures, which are approximately circular with a mean diameter of 200 - 300 km [Dombard et al., 2007], with extrema ranging from 60 km to about 2000 km diameter. A total of 515 coronae were found on Venus in the Magellan data [Stofan et al., 2001]. The intruiging point about corona is that there is no counterpart on the other terrestrial planets for these structures. Nine different groups of coronae have been observed on Venus [Smrekar and Stofan, 1997]. Smrekar and Stofan [1997] suggested that these different groups can stand for different steps in the time evolution of coronae. Several mechanisms have been proposed to explain their formation: Dombard et al. [2007] suggested that coronae form in response to magmatic loading of the crust over zones of partial melting above thermally buoyant heads of transient mantle plumes that impinge on the base of the thermal lithosphere. On the other side, the potential importance of crust delamination induced by mantle upwellings as formation mechanisms for coronae was pointed out by Smrekar and Stofan [1997]. Here, we present results on coronae formation using the recently developed 2D finite element code MILAMIN_VEP, which employs MILAMIN technology [Dabrowski et al., 2008]. We apply a temperature and stress-dependent visco-elasto-plastic rheology in a rectangular box, which includes a rising thermochemical diapir beneath the Venusian crust and lithosphere. The rheological parameters are taken from results inferred for Venusian materials [Mackwell et al., 1998]. A free surface is used in our calculations, which allows for the self-consistent computation of topography induced by the buoyant diapir. A hybrid particle-in-cell approach allows remeshing of strongly deformed grid cells. A systematic investigation of the physical conditions under which coronae can form is being performed in 2D. Initial results confirm the delamination hypothesis due to the impinging thermo-chemical diapir. The flattening of the diapir allows for the formation of coronae with radii several times larger than the initial diapir radii. Our calculations strengthen the hypothesis that coronae pass several stages of topographical appearance. They however also indicate that the formation of coronae might happen on much shorter timescales than suggested by previous studies.

Golabek, G. J.; Kaus, B. J. P.; Tackley, P. J.

2009-04-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

196

Viscoelastic Relaxation of Topographic Highs on Venus to Produce Coronae  

NASA Technical Reports Server (NTRS)

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

Janes, Daniel M.; Squyres, Steven W.

1995-01-01

197

A Data-Driven Evolution Model for the Global Corona  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

198

Experimental Tools to Study Molecular Recognition within the Nanoparticle Corona  

PubMed Central

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

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

2014-01-01

199

Solar corona/prominence seen through the White Light Coronograph  

NASA Technical Reports Server (NTRS)

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

1974-01-01

200

Study of the solar corona using radio and space observations  

NASA Technical Reports Server (NTRS)

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

Dulk, G. A.

1984-01-01

201

Shock Acceleration in the Solar Corona  

NASA Astrophysics Data System (ADS)

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

Sandroos, Arto

2010-03-01

202

Surface effects in corona-charged polyvinylidene fluoride  

Microsoft Academic Search

Biaxially oriented films of polyvinylidene fluoride [-(CH2-CF2)n-...; PVDF] of thickness 25 µm, originally containing both the a and ß crystal forms, have been corona charged at room temperature to surface potentials of up to 10 kV using positive and negative corona. The behaviour of the optical density of the a-form infra-red band at 796 cm-1, measured in the transmission mode,

K. Doughty; P. Pantelis

1980-01-01

203

Waste Water Cleanup by Aerosol Pulsed Corona Reactor  

Microsoft Academic Search

Summary form only given. This paper presents a study of waste water treatment by multielectrode corona reactor. A mixture of gas and polluted water aerosol flows through the 1.2-m length reactor. The flow rate is 200 l\\/h. A nanosecond solid state power supply (45 kV, 60 ns, up to 1 kHz) was used as a driver for the corona discharge.

Y. Yankelevich; M. Wolf; S. Wald; A. Pokryvailo; P. Kempenaers; L. Grabowski; E. van Veldhuizen; W. Rutgers

2007-01-01

204

Electric charging of flowing fuels by a corona discharge  

E-print Network

ELECTRIC CHARGING OF FLONING FUELS BY A CORONA DISCHARGE A Thesis by RICARDO JOAQUIN SANTOS Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1977...'740 ABSTRACT Electric Charging of Flowinq Fuels by a Corona Discharge (Nay 1977) Ricardo J, Santos, B. ST ~ University of Texas Chairman of Advisory Committee: Dr Ronald E Holmes Fuels with high electrical charge density can be atomized to the point...

Santos, Ricardo Joaquin

2012-06-07

205

New Results From Chandra: Abundances in Stellar Coronae  

NASA Technical Reports Server (NTRS)

There is considerable evidence, both solar and stellar, that the chemical compositions of stellar coronae differ from their underlying 1)hotospheres. The differences for solar-type stars appear to be related to FIP, whereas the differences for active stars are more mysterious and perhaps suggest metal depletion. Results to-date will be reviewed and new results from the Chandra X-ray Observatory based on calibration and Emission Line Project observations of late-type stellar coronae, will be presented.

Drake, Jeremy

1999-01-01

206

Science Highlight March 2010 Deadly Carcinogen Unraveled: The Molecular Origami of Fungal Polyketides  

E-print Network

Science Highlight ­ March 2010 Deadly Carcinogen Unraveled: The Molecular Origami of Fungal Polyketides Aflatoxin is an unavoidable food contaminant in grains and nuts produced in developing countries

Wechsler, Risa H.

207

A simple model for magnetic reconnection heated corona  

E-print Network

We construct a simple model for a magnetic reconnection heated corona above a thin accretion disk in AGNs and Galactic black hole candidates(GBHCs). The basic assumptions are that (1) the magnetic reconnection heat is cooled down overwhelmingly by Compton scattering in the corona and that (2) thermal conduction is dominantly cooled by evaporation of the chromospheric plasma in the disk-corona interface before Compton cooling sets in. With these two basic equations as well as equi-partition of magnetic energy with gas energy in the disk, we can consistently determine the fraction of accretion energy dissipated in the corona without free parameters, and thus determine the temperature and all other quantities in both the corona and disk for given black hole mass and accretion rate. Then, we calculate the luminosity contributed from the disk and corona and the coronal flux weighted Compton $y$ parameter. It is found that, at a low luminosity (less than 0.1 Eddington luminosity) the spectrum is hard with energy spectral index of around 1, while at a high luminosity (larger than 0.1 Eddington luminosity) the spectrum can be either soft or hard. We also find that the situation is almost same for supermassive and stellar-mass black holes. These features are consistent with observations of AGNs and GBHCs.

B. F. Liu; S. Mineshige; K. Shibata

2002-05-16

208

Elastic Thickness Estimates for Coronae Associated with Chasmata on Venus  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

209

Galactic Corona or Local Group Intergalactic Medium?  

E-print Network

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

Rik J. Williams; Smita Mathur; Fabrizio Nicastro

2005-11-21

210

Measuring electron temperature in the extended corona  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

211

SZ effect from Corona Borealis supercluster  

NASA Astrophysics Data System (ADS)

The Corona Borealis supercluster has been observed with the millimeter and infrared testa grigia observatory (MITO). Here we present the results of the observations together with a comparison with observations performed at 33 GHz with the very small array (VSA) interferometer. We have observed in the direction of the supercluster toward a cosmic microwave background (CMB) cold spot previously detected in a VSA temperature map. We claim a weak detection of a faint signal compatible with a SZ effect characterized at most by a comptonization parameter y=(7.8-4.4+5.3)×10-6 68% CL. The low level of confidence in the presence of a SZ signal invites us to study this sky region with higher sensitivity and angular resolution experiments such as already planned upgraded versions of VSA and MITO. This is the first millimetric evidence of unknown cluster/diffuse intra-supercluster gas (possibly warm-hot intergalactic medium (WHIM)) interacting, via inverse Compton, scattering with the CMB.

Battistelli, E. S.; De Petris, M.; Lamagna, L.; Watson, R. A.; Rebolo, R.; Génova-Santos, R.; Luzzi, G.; De Gregori, S.; Rubiño-Martin, J. A.

2007-03-01

212

Large scale structure of the sun's corona  

NASA Technical Reports Server (NTRS)

Results concerning the large-scale structure of the solar corona obtained by observations at meter-decameter wavelengths are reviewed. Coronal holes observed on the disk at multiple frequencies show the radial and azimuthal geometry of the hole. At the base of the hole there is good correspondence to the chromospheric signature in He I 10,830 A, but at greater heights the hole may show departures from symmetry. Two-dimensional imaging of weak-type III bursts simultaneously with the HAO SMM coronagraph/polarimeter measurements indicate that these bursts occur along elongated features emanating from the quiet sun, corresponding in position angle to the bright coronal streamers. It is shown that the densest regions of streamers and the regions of maximum intensity of type II bursts coincide closely. Non-flare-associated type II/type IV bursts associated with coronal streamer disruption events are studied along with correlated type II burst emissions originating from distant centers on the sun.

Kundu, Mukul R.

1988-01-01

213

General-dyne unravelling of a thermal master equation  

NASA Astrophysics Data System (ADS)

We analyze the unravelling of the quantum optical master equation at finite temperature due to direct, continuous, general-dyne detection of the environment. We first express the general-dyne Positive Operator Valued Measure (POVM) in terms of the eigenstates of a non-Hermitian operator associated to the general-dyne measurement. Then we derive the stochastic master equation obtained by considering the interaction between the system and a reservoir at thermal equilibrium, which is measured according to the POVM previously determined. Finally, we present a feasible measurement scheme, which reproduces general-dyne detection for any value of the parameter characterizing the stochastic master equation.

Genoni, M. G.; Mancini, S.; Serafini, A.

2014-07-01

214

The effect of corona wire heating and geometry on ozone generation in a negative ion air cleaner  

Microsoft Academic Search

The effect of corona wire surface temperature and geometry on the ozone generation and negative ion emission in a negative ion air cleaner is studied experimentally. The results show that corona wire heating can suppress the ozone generation; however, this increases the corona current. A trade-off effect of corona wire surface temperature and corona current exists; the specific value of

Liu Linmao; Guo Jingfu; Li Jie; Sheng Lianxi

1997-01-01

215

Development of Efficient Models of Corona Discharges Around Tall Structures  

NASA Astrophysics Data System (ADS)

This work concerns with numerical modeling of glow corona and sreamer corona discharges that occur near tall ground structures under thunderstorm conditions. Glow corona can occur when ambient electric field reaches modest values on the order of 0.2 kV/cm and when the electric field near sharp points of ground structure rises above a geometry dependent critical field required for ionization of air. Air is continuously ionized in a small region close to the surface of the structure and ions diffuse out into the surrounding air forming a corona. A downward leader approaching from a thundercloud causes a further increase in the electric field at the ground level. If the electric field rises to the point where it can support formation of streamers in air surrounding the tall structure, a streamer corona flash, or series of streamer corona flashes can be formed significantly affecting the space charge configuration formed by the preceding glow corona. The streamer corona can heat the surrounding air enough to form a self-propagating thermalized leader that is launched upward from the tall structure. This leader travels upward towards the thundercloud and connects with the downward approaching leader thus causing a lightning flash. Accurate time-dependent modeling of charge configuration created by the glow and streamer corona discharges around tall structure is an important component for understanding of the sequence of events leading to lightning attachment to the tall structure. The present work builds on principal modeling ideas developed previously in [Aleksandrov et al., J. Phys. D: Appl. Phys., 38, 1225, 2005; Bazelyan et al., Plasma Sources Sci. Technol., 17, 024015, 2008; Kowalski, E. J., Honors Thesis, Penn State Univ., University Park, PA, May 2008; Tucker and Pasko, NSF EE REU Penn State Annual Res. J., 10, 13, 2012]. The non-stationary glow and streamer coronas are modeled in spherical geometry up to the point of initiation of the upward leader. The model uses an implicit numerical scheme for time integration and employs effective non-uniform grid system allowing very accurate description of non-stationary coronas emitted by sharp points with sub-millimeter dimensions and expanding hundreds of meters in surrounding air. In the talk we will present principal components of the model and its performance under different time dynamics of the applied electric field closely resembling scenarios under thunderstorm conditions, including, in particular, extended periods of time (tens of seconds) when only glow corona is produced, followed by a fast rise in the field (tens of microseconds) describing approach of the downward leader. We will also present comparisons of the numerical model results on time dependent corona radius and current with an analytical corona theory summarized recently by Bazelyan et al. [2008].

Tucker, J.; Pasko, V. P.

2012-12-01

216

Interchange Reconnection in a Turbulent Corona  

NASA Astrophysics Data System (ADS)

Magnetic reconnection at the interface between coronal holes and loops, so-called interchange reconnection, can release the hotter, denser plasma from magnetically confined regions into the heliosphere, contributing to the formation of the highly variable slow solar wind. In the prevailing ``standard'' view the interchange process is thought to develop in null points (with B=0) preferably at the apex of streamers or pseudo-streamers, near Y and X-points, from where slow solar wind flows would originate. This standard model does not meet recent observations of slow wind streams from the edges of active regions, that suggest that slow streams are not limited to apex-regions near neutral points (B=0). Furthermore in order to account for the slow wind diffusion (~ 30 degrees) observed in situ around the Heliospheric Current Sheet, within the standard model framework one has to posit that the slow wind would originate from a small fraction, with a complex topology, of the whole coronal hole-loop boundary, namely narrow channels (supposedly at observationally sub-resolution scales) linking coronal holes. However, coronal heating models, with magnetic field lines shuffled by convective motions, show that reconnection can occur continuously in unipolar magnetic field regions with no neutral points. We propose that a similar alternate interchange mechanism operating near boundaries between open and closed regions induces a continual stochastic rearrangement of connectivity everywhere along the open-closed boundary. We examine a reduced magnetohydrodynamic model of a simplified unipolar interface region between open and closed corona. This boundary is not stationary, becomes fractal, and field lines change connectivity continuously, becoming alternatively open and closed. This model suggests that slow wind may originate everywhere along coronal loop-hole boundaries, a possibility that has major implications for coronal heating and models of the slow solar wind, and accounts naturally, simply and in an elegant way both for the observed diffusion of the slow wind around the heliospheric current sheet and for flows at edges of active regions.

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

2012-12-01

217

INTERCHANGE RECONNECTION IN A TURBULENT CORONA  

SciTech Connect

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

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

2012-10-10

218

Theory of negative corona in oxygen  

NASA Astrophysics Data System (ADS)

Theoretical predictions are given of the development of the current and the distributions of charge and electric field in negative corona, or Trichel current pulses [G. W. Trichel, Phys. Rev. 54, 1078 (1938)], in oxygen at a pressure of 6.67 kPa (50 Torr). For a 10-mm-diam negative sphere located 20 mm from a positive plane, the calculated current pulse has a rise time of 11 ns, a pulse width of 50 ns, and a peak amplitude of 13 mA. These results agree satisfactorily with experimental values. The predicted velocity of the cathode-directed light pulse also agrees well with observations. The theory is based on the accurate numerical solution of Poisson's equation in conjunction with the continuity equations for electrons, positive ions, and negative ions. The effects of ionization, attachment, recombination, electron diffusion, and photoemission and ion secondary-electron emission from the cathode are all included. The initial steep rise of the current pulse is largely due to rapid ionization and electron motion in the high Laplacian field near the cathode. As the discharge develops, a dense plasma forms near the cathode, leading to strong space-charge distortion of the field. A prominent cathode fall region is formed immediately adjacent to the cathode, an almost zero field is formed within the plasma and the field is enhanced over the region to the anode. The current pulse is quenched because the low electric field in the plasma immobilizes the majority of the electrons which then undergo three-body attachment; furthermore, the cathode fall region becomes reduced to such a short distance that insignificant current is produced from this region. Because of the low mobility of the negative ions, the current remains low and the structure of the space-charge fields changes only slowly with time between pulses.

Morrow, R.

1985-09-01

219

Orbital fleet dispatched to unravel magnetic storms' roots  

NASA Astrophysics Data System (ADS)

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

Klotz, Irene

2007-03-01

220

CORONA DISCHARGE IGNITION FOR ADVANCED STATIONARY NATURAL GAS ENGINES  

SciTech Connect

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

Dr. Paul D. Ronney

2003-09-12

221

Direct observation of a single nanoparticle-ubiquitin corona formation.  

PubMed

The advancement of nanomedicine and the increasing applications of nanoparticles in consumer products have led to administered biological exposure and unintentional environmental accumulation of nanoparticles, causing concerns over the biocompatibility and sustainability of nanotechnology. Upon entering physiological environments, nanoparticles readily assume the form of a nanoparticle-protein corona that dictates their biological identity. Consequently, understanding the structure and dynamics of a nanoparticle-protein corona is essential for predicting the fate, transport, and toxicity of nanomaterials in living systems and for enabling the vast applications of nanomedicine. Here we combined multiscale molecular dynamics simulations and complementary experiments to characterize the silver nanoparticle-ubiquitin corona formation. Notably, ubiquitins competed with citrates for the nanoparticle surface, governed by specific electrostatic interactions. Under a high protein/nanoparticle stoichiometry, ubiquitins formed a multi-layer corona on the particle surface. The binding exhibited an unusual stretched-exponential behavior, suggesting a rich binding kinetics. Furthermore, the binding destabilized the ?-helices while increasing the ?-sheet content of the proteins. This study revealed the atomic and molecular details of the structural and dynamic characteristics of nanoparticle-protein corona formation. PMID:23921560

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

2013-10-01

222

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

223

Total light flux and colour of solar corona  

NASA Astrophysics Data System (ADS)

Measurements were made of the light flux and color of the corona in 1.03-6.0 solar radii with a multiple-band electrophotometer. The effective wavelengths of the instrument are 450, 555, 650 and 940. In one of them, the 555 band, the spectral rresponse defines a system that is in close agreement with the spectral response of the human eye. The results of the measurements are as follows: (1) the total light flux of the corona Lc is equal to 1.23 times 10 to the minus 7th power L(Solar); (2) in 555, 650 and 940 bands, there is no color difference between the corona and the photosphere.

Hao, Y.

224

The Structure and Dynamics of the Corona - Heliosphere Connection  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

225

HIGH SPATIAL RESOLUTION OBSERVATIONS OF LOOPS IN THE SOLAR CORONA  

SciTech Connect

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

Brooks, David H.; Ugarte-Urra, Ignacio [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Winebarger, Amy R. [NASA Marshall Space Flight Center, ZP 13, Huntsville, AL 35812 (United States)

2013-08-01

226

UVCS\\/[ITAL]SOHO[\\/ITAL] Empirical Determinations of Anisotropic Velocity Distributions in the Solar Corona  

Microsoft Academic Search

We present a self-consistent empirical model for several plasma parameters of a polar coronal hole near solar minimum, derived from observations with the Solar and Heliospheric ObservatoryUltraviolet Coronagraph Spectrometer. The model describes the radial distribution of density for electrons, H , and O and the outflow 05 1

J. L. Kohl; G. Noci; E. Antonucci; G. Tondello; M. C. E. Huber; S. R. Cranmer; L. Strachan; A. V Panasyuk; L. D. Gardner; M. Romoli; S. Fineschi; D. Dobrzycka; J. C. Raymond; P. Nicolosi; O. H. W. Siegmund; D. Spadaro; C. Benna; A. Ciaravella; S. Giordano; S. R. Habbal; M. Karovska; X. Li; R. Martin; J. G. Michels; A. Modigliani; G. Naletto; R. H. O'Neal; C. Pernechele; G. Poletto; P. L. Smith; R. M. Suleiman

1998-01-01

227

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

E-print Network

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

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

2005-06-10

228

High-resolution spectroscopy of the R Coronae Borealis star V Coronae Australis  

NASA Astrophysics Data System (ADS)

Optical high-resolution spectra of the R Coronae Borealis star V CrA at light maximum and during minimum light are discussed. Abundance analysis confirms previous results showing that V CrA has the composition of the small subclass of R Coronae Borealis (RCB) stars know as `minority' RCBs, i.e. the Si/Fe and S/Fe ratios are 100 times their solar values. A notable novel result for RCBs is the detection of the 1-0 Swan system 12C13C bandhead indicating that 13C is abundant: spectrum synthesis shows that 12C/13C is about 3-4. Absorption-line profiles are variable at maximum light with some lines showing evidence of splitting by about 10 kms-1. A spectrum obtained as the star was recovering from a deep minimum shows the presence of cool C2 molecules with a rotational temperature of about 1200K, a temperature suggestive of gas in which carbon is condensing into soot. The presence of rapidly outflowing gas is shown by blueshifted absorption components of the NaI D and KI 7698 Å resonance lines. Based on observations obtained with (1) The Blanco 4-m Telescope at the Cerro Tololo Inter-American Observatory, which is operated by AURA, Inc., under contract to the National Science Foundation of USA and (2) The Harlan J. Smith Telescope of the W. J. McDonald Observatory of the University of Texas at Austin. E-mail: nkrao@iiap.res.in

Rao, N. Kameswara; Lambert, David L.

2008-02-01

229

The Structure and Dynamics of the Corona—Heliosphere Connection  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

230

Effect of humidity on negative corona Trichel pulses  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

231

Fabrication of Corona-Free Nanoparticles with Tunable Hydrophobicity  

PubMed Central

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

2014-01-01

232

Observational studies of reconnection in the solar corona  

SciTech Connect

In recent years, observational studies of the corona have shifted focus. Where they were once purely qualitative morphological explorations seeking to support the presence of reconnection, more investigations are providing empirical estimates of the physical conditions in the reconnecting corona. These studies are enabled and enhanced by orbiting telescopes with high angular and temporal resolution. In this article, some recent findings about the empirical quantities are reviewed, including recent estimates of the flux transferred in individual patchy reconnection episodes, the size distribution of post-reconnection flux tubes, and the energy released by the flux tubes as they shrink.

McKenzie, David E. [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, Montana 59717-3840 (United States)

2011-11-15

233

Systems biology unravels interferon responses to respiratory virus infections  

PubMed Central

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

Kroeker, Andrea L; Coombs, Kevin M

2014-01-01

234

Unraveling the Atomic Structure of Ultrafine Iron Clusters  

PubMed Central

Unraveling the atomic structures of ultrafine iron clusters is critical to understanding their size-dependent catalytic effects and electronic properties. Here, we describe the stable close-packed structure of ultrafine Fe clusters for the first time, thanks to the superior properties of graphene, including the monolayer thickness, chemical inertness, mechanical strength, electrical and thermal conductivity. These clusters prefer to take regular planar shapes with morphology changes by local atomic shuffling, as suggested by the early hypothesis of solid-solid transformation. Our observations differ from observations from earlier experimental study and theoretical model, such as icosahedron, decahedron or cuboctahedron. No interaction was observed between Fe atoms or clusters and pristine graphene. However, preferential carving, as observed by other research groups, can be realized only when Fe clusters are embedded in graphene. The techniques introduced here will be of use in investigations of other clusters or even single atoms or molecules. PMID:23251781

Wang, Hongtao; Li, Kun; Yao, Yingbang; Wang, Qingxiao; Cheng, Yingchun; Schwingenschlogl, Udo; Zhang, Xi Xiang; Yang, Wei

2012-01-01

235

A peculiarity of silver-based corona wire heating on ozone generation  

Microsoft Academic Search

The effect of corona wire temperature on the ozone generation in the positive dc corona electrostatic precipitator is studied experimentally. The external heating of the corona wire can suppress the ozone generation. In this study, nichrome and two kinds of silver-based wires 0.1 mm diameter were tested as discharges electrodes. The nichrome corona wire heating shows a well-known monotonic decreasing

Rafael Sh. Islamov; Yuriy A. Krishtafovich

2011-01-01

236

A study of the lightning channel corona sheath Grzegorz Maslowski1,2  

E-print Network

A study of the lightning channel corona sheath Grzegorz Maslowski1,2 and Vladimir A. Rakov1] Dynamics of lightning channel corona sheath surrounding thin channel core is examined on the basis of three vicinity of the lightning channel and measured channel base current. The corona sheath radius, velocity

Florida, University of

237

Treatment of NO x in exhaust gas by corona plasma over water surface  

Microsoft Academic Search

For developing NOx treatment engineering of exhaust gas in lower construction and operating cost, we propose a new type of corona reactor with some experimental results. The reactor is madeup of multi needles’ electrode placed over water and to make use of corona plasma over water surface for plasma chemical reactions. Typical corona characteristics of the reactor with positive and

Tomio Fujii; Massimo Rea

2000-01-01

238

HEATING EVENTS IN THE QUIET SOLAR CORONA ARNOLD O. BENZ and SM KRUCKER  

E-print Network

HEATING EVENTS IN THE QUIET SOLAR CORONA ARNOLD O. BENZ and SÃ?M KRUCKER Institute of Astronomy, ETH originating in the corona are presented. The thermal radiation of the quiet corona is found to fluctutate that the brightenings are caused by additional plasma injected from below and heated to slightly higher temperature than

239

The distribution of emission measure, and of heating budget, among the loops in the corona.  

E-print Network

The distribution of emission measure, and of heating budget, among the loops in the corona. G of particular coronal structures and the overall heating of the corona taken as a whole. In order to answer how the overall heating rate of a stellar corona depends on the presumed \\control parameters" (viz

240

BINARY RECONNECTION AND THE HEATING OF THE SOLAR CORONA E. R. Priest  

E-print Network

BINARY RECONNECTION AND THE HEATING OF THE SOLAR CORONA E. R. Priest School of Mathematics heating among the magnetic field lines that spread from these fragments into the solar corona. We suggest in driving reconnection (e.g., Priest & Forbes 2000), and therefore heating, in the overlying corona

Priest, Eric

241

On the Intrinsic Difficulty of Producing Stellar Coronae With Acoustic Waves  

E-print Network

candidates for heating not only the chromosphere, but also the corona of the Sun and similar stars. Meanwhile, however, severe empirical limits could be placed on the role that these waves play in heating the solar-corona to heat the open corona, even though such waves are certainly abundant in the photosphere, Finally

Ulmschneider, Peter

242

Heating of the Solar Corona by Dissipative Alfven Solitons K. Stasiewicz*  

E-print Network

Heating of the Solar Corona by Dissipative Alfve´n Solitons K. Stasiewicz* Swedish Institute locally to heat particles in the solar corona [5]. During the past 50 years there have been many attempts aspects of electromagnetic energy dissipa- tion and heating in the solar corona and in planetary

Stasiewicz, Krzysztof

243

X-ray spectroscopy of the unsteady quiescent corona of AD Leo with Chandra  

E-print Network

also show that the EMD is compatible with the model of a corona continuously heated by ares, which in stellar coronae and the nature of coronal heating. The topology, surface coverage and strength of the coroX-ray spectroscopy of the unsteady quiescent corona of AD Leo with Chandra A. Maggio 1 , J.J. Drake

244

Heating Events in the Quiet Solar Corona Arnold O. Benz and Sam Krucker  

E-print Network

Heating Events in the Quiet Solar Corona Arnold O. Benz and S¨am Krucker Institute of Astronomy for heating (Shimizu et al. 1994). In the quiet corona (excluding active regions and coronal holes per second over the whole Sun. Their estimated energy #12; Heating Events in the Quiet Solar Corona 3

245

How Accurately Can We Determine the Coronal Heating Mechanism in the Large-Scale Solar Corona ?  

E-print Network

How Accurately Can We Determine the Coronal Heating Mechanism in the Large-Scale Solar Corona ? D of the coronal heating mechanism in the large-scale solar corona was considered. The authors compared that turbulent reconnection is a likely method to heat the large-scale solar corona. Here we reconsider

Mackay, Duncan

246

Small Corona Cage for Wideband HVac Radio Noise Studies: Rationale and Critical Design  

Microsoft Academic Search

Corona cages are used in overhead power line studies to investigate physical mechanisms involved in corona discharge and to predict radio noise generation. In this paper, we design a small laboratory corona cage to investigate wideband radio noise generation on practical HVac conductor bundles. We introduce and describe cage design criteria including the insulation of the cage mesh. Our measurement

Rodney G. Urban; Howard C. Reader; Jacobus P. Holtzhausen

2008-01-01

247

A Systematic Spectroscopic X-Ray Study of Stellar Coronae with XMM-Newton: Early Results  

E-print Network

-term evolution of stellar coronae. Complemented by targets from the calibration and performance veri#12;cationA Systematic Spectroscopic X-Ray Study of Stellar Coronae with XMM-Newton: Early Results M. G conducting a comprehensive survey of stellar coronae with the XMM-Newton Re ection Grating Spectrometers

Audard, Marc

248

Gravity analysis of Parga and Hecate chasmata: Implications for rift and corona formation  

Microsoft Academic Search

The two largest rift systems on Venus, Parga, and Hecate chasmata contain one third of all coronae. We map variations in elastic thickness and apparent depth of compensation (ADC) in these two regions using the admittance function for gravity and topography. We examine the relationship between rifting and coronae by comparing lithospheric structure with corona characteristics including volcanism, topographic shape,

Suzanne E. Smrekar; Trudi Hoogenboom; Ellen R. Stofan; Paula Martin

2010-01-01

249

Imaging and Processing Images of the Solar Corona  

NASA Astrophysics Data System (ADS)

Of all astronomical phenomena visible to the naked eye, none is as spectacular, or as fleeting, as a total eclipse of the Sun. For a few brief minutes, the Moon blocks the Sun's blindingly bright photosphere to reveal the ethereal solar corona. This gossamer halo, forming the outer atmosphere of the Sun, can only be seen in the eerie twilight brought on by totality.

Espenak, Fred

250

Nonlinear Plasma Physics of the Solar Corona Eric R Priest  

E-print Network

Nonlinear Plasma Physics of the Solar Corona Eric R Priest Mathematics Institute, St Andrews of some recent ideas in solar coronal plasma physics. In particular we discuss some models of coronal plasma physics seemed so complex, I decided to focus on the simpler area of MHD. Dennis on the other hand

Priest, Eric

251

Heating of accretion disc corona by solar-type flares  

Microsoft Academic Search

We propose a new model for the magnetosphere of a neutron star with accretiondisc for the case when the star's magnetic axis is not aligned with the rotation axis. We calculated the d isc shape and estimated the magnetic field and its gradient in the corona. Using the derived estimates as the initial data, we calculated the model of the

B. V. Somov; A. V. Oreshina; I. V. Oreshina

2002-01-01

252

Synoptic, Global Mhd Model For The Solar Corona  

Microsoft Academic Search

The common techniques for mimic the solar corona heating and the solar wind acceleration in global MHD models are as follow. 1) Additional terms in the momentum and energy equations derived from the WKB approximation for the Alfv'en wave turbulence; 2) some empirical heat source in the energy equation; 3) a non-uniform distribution of the polytropic index, gamma, used in

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

2007-01-01

253

Thermal stability of a corona heated by fast mode waves  

Microsoft Academic Search

It has been proposed that dissipation of hydromagnetic waves is an important heat source for the solar corona. We consider damping by collisionless processes and by electron thermal conduction and ion viscosity, and calculate the wave energy density such that heating balances the energy radiated by the plasma. We then analyze the thermal stability of the wave heated medium. The

Ellen Zweibel

1980-01-01

254

Heat transfer by a corona wind heat exchanger  

Microsoft Academic Search

A cold plate heat exchanger fitted with pin fins and having integral corona wind blowers was constructed and tested for thermal performance. The heat exchanger was operated in air at sea level pressure and at reduced pressures with Reynold's numbers up to 300. Test in sulphur hexafluoride gas at sea level pressures demonstrated that the thermal performance was considerably better

A. S. Mitchell

1978-01-01

255

Novel dielectric reduces corona breakdown in ac capacitors  

NASA Technical Reports Server (NTRS)

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

Loehner, J. L.

1972-01-01

256

Energy Distribution of Heating Processes in the Quiet Solar Corona  

Microsoft Academic Search

We have determined the variations in the emission measure of the solar corona using EUV Imaging Telescope\\/Solar and Heliospheric Observatory observations of iron lines in a quiet region of the Sun. The emission measure is found to vary significantly in at least 85% of all the pixels within 42 minutes. The variations are interpreted as heating events that bring chromospheric

Saem Krucker; Arnold O. Benz

1998-01-01

257

Gas-magnetic field interactions in the solar corona  

Microsoft Academic Search

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

G. W. Pneuman; Roger A. Kopp

1971-01-01

258

Observation of Alfven Waves in the Solar Corona (Invited)  

NASA Astrophysics Data System (ADS)

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

Tomczyk, S.

2013-12-01

259

SIMBA observations of the R Corona Australis molecular cloud  

Microsoft Academic Search

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

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

2003-01-01

260

Probing the Solar Corona with Radio Ranging Measurements  

NASA Technical Reports Server (NTRS)

An asymmetry in the radial variation of electron density above the east and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. These older data are compared with white- light coronagraph measurements of the underlying corona collected by the Mark III K-coronameter at the Mauna Loa Solar Observatory.

Woo, R.

1995-01-01

261

Microwave Radiometric Detection of Corona From Chaff Within Thunderstorms  

Microsoft Academic Search

A microwave radiometer that operates at a frequency of 3 GHz has been used on board an aircraft to determine the presence of radiation generated by corona from within both untreated control thunderstorms and thunderstorms in which 10-cm chaff was released. There was no sustained radiation recorded from the control storms. Sustained radiation was detected, however, when chaff was dispersed

W. David Rust; Paul R. Krehbiel

1977-01-01

262

Evidence for Flux Ropes in the Solar Corona  

Microsoft Academic Search

Although twisted magnetic flux ropes are clearly ejected from the Sun, as demonstrated by LASCO and EIT movies of erupting prominences, there has been some controversy about whether flux ropes exist in the corona before ejection. It has been argued that they are formed only upon ejection. The issue is important because of the need to understand how eruptions are

D. M. Rust

2003-01-01

263

NUMERICAL SIMULATION OF THREE-DIMENSIONAL TUFT CORONA AND ELECTROHYDRODYNAMICS  

EPA Science Inventory

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

264

Release timescales of solar energetic particles in the low corona  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

265

Diagnosing the Prominence-Cavity Connection in the Solar Corona  

NASA Astrophysics Data System (ADS)

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

Schmit, D. J.

266

Natural Light Harvesting Systems: Unraveling the quantum puzzles  

E-print Network

In natural light harvesting systems, the sequential quantum events of photon absorption by specialized biological antenna complexes, charge separation, exciton formation and energy transfer to localized reaction centers culminates in the conversion of solar to chemical energy. A notable feature in these processes is the exceptionally high efficiencies (> 95 %) at which excitation is transferred from the illuminated protein complex site to the reaction centers. Such high exciton propagation rates within a system of interwoven biomolecular network structures, is yet to be replicated in artificial light harvesting complexes. A clue to unraveling the quantum puzzles of nature may lie in the observation of long lived coherences lasting several picoseconds in the electronic spectra of photosynthetic complexes, even in noisy environmental baths. A number of experimental and theoretical studies have been devoted to unlocking the links between quantum processes and information protocols, in the hope of finding answers to nature's puzzling mode of energy propagation. This review presents developments in quantum theories, and links information-theoretic aspects with photosynthetic light-harvesting processes in biomolecular systems. There is examination of various attempts to pinpoint the processes that underpin coherence features arising from the light harvesting activities of biomolecular systems, with particular emphasis on the effects that factors such non-Markovianity, zeno mechanisms, teleportation, quantum predictability and the role of multipartite states have on the quantum dynamics of biomolecular systems. A discussion of how quantum thermodynamical principles and agent-based modeling and simulation approaches can improve our understanding of natural photosynthetic systems is included.

A. Thilagam

2013-10-29

267

The Connection of Type II Spicules to the Corona  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

268

Charging and corona modifications to the ORNL 25URC accelerator  

SciTech Connect

A chain-charge monitoring system was first installed in the 25URC accelerator in October 1982, and has provided valuable information about the charging system. Additions to the system during the past year have significantly increased the amount of information provided by the monitor. Cables connecting pickoff wheels and inductors in the terminal were improved to provide higher reliability of the charging system. The tube corona points supplied with the 25URC accelerator had a point-to-plane spacing of 0.175 inches. Our operating experience indicated that the corona currents for the normal gas pressure and voltage range of the accelerator were lower than optimum. Current-voltage characteristics of a three-needle point set were measured at several spacings and gas pressures to provide criteria for ordering new points.

Ziegler, N.F.; McPherson, R.L.

1986-11-01

269

Air trichloroethylene oxidation in a corona plasma-catalytic reactor  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

270

The onset voltage of coronas on bare and coated conductors  

NASA Astrophysics Data System (ADS)

This paper concerns theoretical and experimental investigations of the effect of a conductor coating on the onset voltage of a corona on overhead transmission-line conductors. The onset voltage for a self-maintained discharge on the basis of discharge physics is evaluated. This calls first for accurate calculation of the electrical field in the vicinity of a coated conductor and its correlation to the field values near a bare conductor of the same radius. The well-known charge simulation technique is used for field calculation. The calculated electrical field values are utilized in evaluating the onset voltage of positive and negative coronas on bare and coated conductors. The onset voltage increases with a conductor coating. The calculated onset-voltage values agreed satisfactorily with those measured for laboratory models and full-scale test lines.

Abdel-Salam, M.; Turky, A. A.; Hashem, A. A.

1998-10-01

271

Confirmed assignments of isomeric dimethylbenzyl radicals generated by corona discharge  

NASA Astrophysics Data System (ADS)

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

Wook Yoon, Young; Kuk Lee, Sang

2011-12-01

272

Detailed characteristics of intermittent current pulses due to positive corona  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

273

Weak Compressible Magnetohydrodynamic Turbulence in the Solar Corona  

SciTech Connect

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

Chandran, Benjamin D.G. [Space Science Center and Department of Physics, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2005-12-31

274

The transformation of MHD Alfvén waves and solar corona heating  

Microsoft Academic Search

One of the most interesting phenomena appearances on the Sun is the high temperature of the solar corona, which reaches 10^6 K (compared with 5×10^3 K at the level of the photosphere). To maintain such a high temperature and compensate for radiative cooling, the constant inflow of energy is needed. The necessary energy is considered to be carried by Alfvén

A. D. Voitsekhovska; A. K. Yukhimuk

2006-01-01

275

Estimation of winding insulation resistance to the corona discharges  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

276

Weak compressible magnetohydrodynamic turbulence in the solar corona  

E-print Network

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

Benjamin D. G. Chandran

2005-11-21

277

Method and apparatus for processing exhaust gas with corona discharge  

DOEpatents

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

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

1999-06-22

278

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

SciTech Connect

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

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

2012-12-20

279

Method and apparatus for processing exhaust gas with corona discharge  

DOEpatents

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

Barlow, Stephan E. (Richland, WA); Orlando, Thomas M. (Kennewick, WA); Tonkyn, Russell G. (Kennewick, WA)

1999-01-01

280

The Structure and Dynamics of the Solar Corona  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

281

The Structure and Dynamics of the Solar Corona  

NASA Technical Reports Server (NTRS)

Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the period covered by this report we have published 17 articles in the scientific literature. These publications are listed in Section 4 of this report. In the Appendix we have attached reprints of selected articles.

Mikic, Zoran

1998-01-01

282

A system for repetitive pulsed corona plasmas, with ecological applications  

Microsoft Academic Search

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

N. Georgeseut; A. Vulpe; R. Minea

2003-01-01

283

Magnetic fields and the structure of the solar corona  

Microsoft Academic Search

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

Martin D. Altschuler; Gordon Newkirk

1969-01-01

284

Spectra from a magnetic reconnection-heated corona in AGN  

E-print Network

We investigate a corona coupled with underlying disk through magnetic field and radiation field, and present emergent spectra calculated from Monte Carlo simulations. The spectra are determined for given black-hole mass and accretion rate. We find two types of solutions corresponding for hard spectrum and soft spectrum. In the hard-spectrum solution, the accretion energy is dominantly dissipated in the corona, supporting a strong corona above a cool disk; The hard X-ray spectral indices are around 1.1, same for different accretion rates. In the soft-spectrum solution, the accretion energy is mainly dissipated in the disk. The coronal temperature and density are quite low. Consequently, the spectra are dominated by the disk radiation peaking at UV and soft X-rays. For low-luminosity systems, there exists only the solution of hard spectra; While for high-luminosity systems, there exist both solutions of hard and soft spectra. For middle-luminosity systems, besides the hard spectra, moderately soft spectra composed of an inner soft-spectrum solution and an outer hard-spectrum solution may occur, the softness of which increases with increasing luminosity. The hard spectra are close to the observed spectra in Seyfert galaxies and radio-quiet QSOs. The composite spectra may account for the diversity of broad band spectra observed in narrow-line Seyfert 1 galaxies.

B. F. Liu; S. Mineshige; K. Ohsuga

2003-01-08

285

The Sun's Corona viewed from EUV and Radio Wavelengths  

NASA Astrophysics Data System (ADS)

The Sun's Corona, which is composed of a few million degree plasma, can be best viewed in two electro-magnetic wavelength domains, one from a few Angstrom to hundreds of Angstrom (in Soft X-ray and EUV domains), the other from a few centimeter to several tens of centimeter wavelengths (in radio domain). In this paper, we present the detailed and quantitative comparison of corona observations made in these two domains with high spatial resolution and full view of the Sun. The EUV observations were taken with EIT (Extreme Ultraviolet Imager) on board SOHO (Solar and Heliospheric Observatory) in Fe spectral lines centered at 171, 195 and 284 Angstrom, respectively; while the radio observations were taken with the VLA (Very Large Array) at 6 and 20 cm, and NRH (Nobeyama Radio Heliograph) at 1.8 cm (17 Ghz), respectively. We have found that there exists excellent morphological similarity of corona features between these two sets of observations. However, the quantitative comparisons have revealed that the predicted radio flux from EUV observations based on traditional assumptions is always higher than that observed directly by radio instruments, by a factor of 4 to 6. The discrepancy is probably due to the underestimation of coronal ion abundance (e.g. Meyer's abundance) by a factor of 4 to 6.

Zhang, J.; Kundu, M. R.; White, S. W.

1999-05-01

286

Formation and Investigation of Corona Charged Films from Polylactic Acid  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

287

Kilometre-scale structures in the Sun's corona  

NASA Astrophysics Data System (ADS)

KNOWLEDGE of the structure of the Sun's corona is important for our understanding of how this high-temperature plasma is heated, and of the processes involved in the acceleration of the solar wind1,2. The structure can be investigated directly by imaging at optical and shorter wavelengths, or indirectly through the effects of changing electron density on the propagation of radio waves (scattering and scintillation). Radio measurements have established many of the characteristics of the density fluctuations in the corona and solar wind, but the fundamental nature of these structures is not yet fully understood3,4. Two specific features that have proved difficult to explain are an abrupt increase in anisotropy of the irregularities close to the Sun5-7, and a break in the power-law spectrum describing the density fluctuations8,9. Here I argue that these features are the manifestation of a transition from small ray-like or filamentary structures in the corona that rotate with the Sun to turbulent density irregularities convecting with the solar wind. I estimate the size of the smallest filamentary structure within coronal holes to be about 1km at the Sun, approximately three orders of magnitude smaller than the smallest filamentary structures observed in images of different wavelengths2,10-12.

Woo, Richard

1996-01-01

288

Radiation Feedback in Hot Accretion-Disk Corona Models  

E-print Network

We present a detailed study of the observable effects of photoionization and Comptonization of line and continuum radiation from a cold accretion disk with a thin, warm, photoionized transition layer in the framework of self-consistent accretion-disk corona models for Galactic black-hole candidates. We use an iterative method to treat the non-linear radiation feedback between the transition layer and the hot corona numerically using a Monte-Carlo Comptonization code in combination with the photoionization and line transfer code XSTAR. The subset of the parameter space allowed in self-consistent accretion-disk corona systems on energetic grounds is explored, checking for the emergence of emission lines and/or absorption edges, with special emphasis on the spectral range $E \\lesssim 1$ keV where such features might become observable with the advent of the AXAF satellite. Comparing our model calculations to the broadband spectrum of GX~339-4, we find good agreement with the observed spectral features and discuss how the future detection of the predicted features at lower energies can be used to constrain parameters.

M. Boettcher; E. P. Liang; I. A. Smith

1998-06-22

289

Joule Heating and Anomalous Resistivity in the Solar Corona  

E-print Network

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

Steven R. Spangler

2008-12-22

290

Joule Heating and Anomalous Resistivity in the Solar Corona  

E-print Network

Recent radioastronomical observations of Faraday rotation in the solar corona can be interpreted as evidence for coronal currents, with values as large as $2.5 \\times 10^9$ Amperes (Spangler 2007). These estimates of currents are used to develop a model for Joule heating in the corona. It is assumed that the currents are concentrated in thin current sheets, as suggested by theories of two dimensional magnetohydrodynamic turbulence. The Spitzer result for the resistivity is adopted as a lower limit to the true resistivity. The calculated volumetric heating rate is compared with an independent theoretical estimate by Cranmer et al (2007). This latter estimate accounts for the dynamic and thermodynamic properties of the corona at a heliocentric distance of several solar radii. Our calculated Joule heating rate is less than the Cranmer et al estimate by at least a factor of $3 \\times 10^5$. The currents inferred from the observations of Spangler (2007) are not relevant to coronal heating unless the true resistivi...

Spangler, Steven R

2008-01-01

291

Energy Release in a Magnetized Resistive Corona Driven by Continuous Footpoint Motions  

Microsoft Academic Search

The solar corona is a highly conducting plasma (Lundquist number S ˜10^10-13). As such, Ohmic dissipation is negligible except within thin current filaments. In his corona heating model, Parker suggests that thin current filaments can be induced in a magnetized corona via the shuffling of the field lines driven by continuous footpoint motions. We study this model with a three-dimensional

Yi-Min Huang; Dalton Schnack; Ellen G. Zweibel; Zoran Mikic

2006-01-01

292

Corona inception voltage in statorettes with various gas-solid dielectric systems  

NASA Technical Reports Server (NTRS)

Corona inception voltage was calculated and measured for three statorettes in several gases and gas mixtures at pressures from 50.8 to 1270 torr. In helium the corona inception voltage was lowest, and in air it was highest. In argon and mixtures of helium and xenon the corona inception voltage was between that of air and helium. Correlation between experimental and calculated data was good.

Bollenbacher, G.; Kempke, E. E., Jr.

1972-01-01

293

Correlation between UV radiation intensity and current strength during corona discharge  

NASA Astrophysics Data System (ADS)

The ratio of optical pulse numbers to corona current (ROPC) is proposed to study the correlation between UV radiation intensity and current strength during AC corona discharge. It's found that the ROPC curves rose rapidly before a critical voltage and then the curves flatten with the supplied voltage rising, even if the voltage is increased approximately 1 fold higher than the critical voltage. Finally, according to ROPC curves, a new method of determining the voltage for corona inception is introduced, and a novel quantitative analysis method is put forward to judge the level of corona discharge by the means of optical measurement.

Wu, Ligang; Yuan, Yonggang; Yan, Haojun; Liang, Shuaiwei; Wang, Lun; Cheng, Peihong; Wang, Hongtao; Hu, Jinsong

2012-10-01

294

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

NASA Astrophysics Data System (ADS)

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

Inoue, Yoshiyuki; Doi, Akihiro

2014-10-01

295

Constant cross section of loops in the solar corona  

NASA Astrophysics Data System (ADS)

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

Peter, H.; Bingert, S.

2012-12-01

296

Particle acceleration in helical magnetic fields in the corona  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

297

Optical Spectroscopy at Deep Light Minimum of R Coronae Borealis  

NASA Astrophysics Data System (ADS)

We present optical spectroscopy late in a deep minimum for the quintessential hydrogen-deficient carbon star R Coronae Borealis. Starting 3.5 years into the current deep and long minimum, we have secured observations that reveal some of the oddest optical spectra ever obtained for any astronomical object. Helium emission lines from triplet transitions, strong Ca II H and K emission, and forbidden lines of oxygen and nitrogen are the only spectral features observed. The spectra can be interpreted as coming from a chromospheric-like region lying above a carbon shell ejection front combined with a large-scale nebular-like region surrounding the star.

Howell, Steve B.; Rector, Travis A.; Walter, Donald

2013-08-01

298

Oxidation of aqueous pharmaceuticals by pulsed corona discharge.  

PubMed

Oxidation of aromatic compounds of phenolic (paracetamol, beta-oestradiol and salicylic acid) and carboxylic (indomethacin and ibuprofen) structure used in pharmaceutics was studied. Aqueous solutions were treated with pulsed corona discharge (PCD) as a means for advanced oxidation. Pulse repetition frequency, delivered energy dose and oxidation media were the main parameters studied for their influence on the process energy efficiency. The PCD treatment appeared to be effective in oxidation of the target compounds: complete degradation of pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media. Low-molecular carboxylic acids were identified as ultimate oxidation by-products formed in the reaction. PMID:23837343

Panorel, Iris; Preis, Sergei; Kornev, Iakov; Hatakka, Henry; Louhi-Kultanen, Marjatta

2013-01-01

299

Eleven-years inversion of the green corona emission  

NASA Technical Reports Server (NTRS)

A cross correlation analysis of coronal green line intensity (5303A) and interplanetary magnetic field polarity for the period 1947-1970 shows that the coronal features are organized in a constant pattern with respect to the 4-sector structure through the solar cycle. A sudden inversion of the coronal pattern with respect to the sector structure takes place at the solar minima. The high emission regions of the green corona are located near the solar magnetic sector boundaries having polarities (-,+), (+,-), (-,+) during cycles 18, 19, 20 respectively in the Northern Hemisphere, and (+,-), (-,+), (+,-) in the Southern Hemisphere.

Antonucci, E.

1973-01-01

300

The prestellar and protostellar population of R Coronae Australis  

E-print Network

We present 450 and 850 um maps of R Coronae Australis. We compare the maps to previous surveys of the region, and shed new light on the previously unknown nature of the protostellar sources at the centre of the cloud. We clarify the nature of two millimetre sources previously discovered in lower resolution data. We identify one new Class 0 protostar that we label SMM 1B, and we measure the envelope masses of a number of more evolved protostars. We identify two new prestellar cores that we call SMM 1A and SMM 6.

David J. Nutter; D. Ward-Thompson; P. Andre

2004-12-09

301

David Elijah Packer: cluster variables, meteors and the solar corona  

E-print Network

David Elijah Packer (1862-1936), a librarian by profession, was an enthusiastic amateur astronomer who observed from London and Birmingham. He first came to the attention of the astronomical community in 1890 when he discovered a variable star in the globular cluster M5, only the second periodic variable to be discovered in a globular cluster. He also observed meteors and nebulae, on one occasion reporting a brightening in the nucleus of the galaxy M77. However, his remarkable claims in 1896 that he had photographed the solar corona in daylight were soon shown to be flawed.

Shears, Jeremy

2014-01-01

302

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

E-print Network

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

Chen, Junhong

303

MAGNETIC RECONNECTION AND ENERGY RELEASE IN THE SOLAR CORONA BY TAYLOR RELAXATION  

E-print Network

) Abstract.The heating ofthe solar corona by resistiveturbulenceofcoronal magneticfieldsis consideredMAGNETIC RECONNECTION AND ENERGY RELEASE IN THE SOLAR CORONA BY TAYLOR RELAXATION G. E. VEKSTEIN plays a dominant role in heating the solar coronal plasma to high temperatures. Energy from convective

Priest, Eric

304

The effect of corona discharge on free convection heat transfer from a horizontal cylinder  

Microsoft Academic Search

Free convection heat transfer from an isothermal horizontal cylinder in the presence of DC positive corona discharge with a blade edge emitter electrode has been studied experimentally and numerically. A Mach–Zehnder interferometer was used to determine the local Nusselt numbers. The effect of corona discharge on heat transfer from the cylinder was investigated at Rayleigh numbers in the range between

Seyed Reza Mahmoudi; Kazimierz Adamiak; Peter Castle; Mehdi Ashjaee

2010-01-01

305

Simulation of Flux Emergence from the Convection Zone to the Corona  

Microsoft Academic Search

Here, we present numerical simulations of magnetic flux buoyantly rising from a granular convection zone into the low corona. We study the complex interaction of the magnetic field with the turbulent plasma. The model includes the radiative loss terms, non-ideal equations of state, and empirical corona heating. We find that the convection plays a crucial role in shaping the morphology

Fang Fang; Ward Manchester; William P. Abbett; Bart van der Holst

2010-01-01

306

Binary Reconnection and the Heating of the Solar Corona E.R. PRIEST  

E-print Network

Binary Reconnection and the Heating of the Solar Corona E.R. PRIEST School of Mathematics surface are likely to drive magnetic reconnection and therefore heating amongst the magnetic #12;eld lines that spread from these fragments into the solar corona. We suggest that the fundamental mechanism is one

Priest, Eric

307

SIMULATION OF FLUX EMERGENCE FROM THE CONVECTION ZONE TO THE CORONA  

Microsoft Academic Search

Here, we present numerical simulations of magnetic flux buoyantly rising from a granular convection zone into the low corona. We study the complex interaction of the magnetic field with the turbulent plasma. The model includes the radiative loss terms, non-ideal equations of state, and empirical corona heating. We find that the convection plays a crucial role in shaping the morphology

Fang Fang; Ward Manchester IV; Bart Van der Holst; William P. Abbett

2010-01-01

308

An instrumental method for the determination of corona characteristics in accurately-defined media  

Microsoft Academic Search

In our laboratories, an instrumental method has been developed for the characterization of corona discharges in well-defined media under the conditions of extreme purity and reproducibility. An instrument has been developed, consisting of a stainless steel chamber that contains a corona generator, an induction mixing chamber with a manifold in which the medium of well-defined concentration is prepared, and a

Z. Kucerovsky; I. I. Inculet; M. F. Benko; D. J. McGinty

1996-01-01

309

3d solar corona at heliospheric sheet and structures in current carrying plasma with flows  

Microsoft Academic Search

Magnetic island and magnetic rope elements are basic topological structures of space plasma for construction of its 3D state. As for islands in the solar corona they observed near Sun like coronal mass ejections (CME), blobs, transients, as for ropes they observed like streamer belt and rays located above and submerged into forming heliospheric current sheet. Corona here is hot

V. Gubchenko; V. Zaitsev; H. Biernat; M. Khodachenko; H. Rucker

2004-01-01

310

ON PLASMA KINETIC MODEL OF A 3D SOLAR CORONA AND SOLAR WIND AT HELIOSPHERIC SHEET  

Microsoft Academic Search

The dynamical solar corona in 3D consists of transient type magnetic island elements and radial type magnetic flux rope structures in a heliospheric sheet. During the formation and relaxation these elements produce inductive elec- tromagnetic fields where energetic particles are produced. We study the 3D corona formation in the kinetic approach and parameterize it like a hot current-carrying collisionless plasma

V. M. GUBCHENKO; M. L. KHODACHENKO; H. K. BIERNAT

311

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

E-print Network

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

Jellinek, Mark

312

Self-regulating model for the ablative corona driven by light ion beam  

Microsoft Academic Search

Scaling laws for the ablative corona generated by the incidence of an intense light ion beam on a spheric solid target are obtained assuming that a self-regulating regime of the corona opacity is created. The results are in agreement with a recent numerical model.

A R Piriz

1986-01-01

313

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

NASA Technical Reports Server (NTRS)

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

Davila, Joseph M.

1986-01-01

314

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

EPA Science Inventory

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

315

Unveiling the Nature of Coronae in Active Galactic Nuclei through Sub-mm Observations  

E-print Network

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

Inoue, Yoshiyuki

2014-01-01

316

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

E-print Network

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

Zexian, Cao

317

A proteomics-based methodology to investigate the protein corona effect for targeted drug delivery.  

PubMed

Here we introduce a proteomics methodology based on nanoliquid-chromatography tandem mass spectrometry (nanoLC/MS-MS) to investigate the "protein corona effect for targeted drug delivery", an innovative strategy, which exploits the "protein corona" that forms around nanoparticles in a physiological environment to target cells. PMID:25132011

Pozzi, D; Caracciolo, G; Capriotti, A L; Cavaliere, C; Piovesana, S; Colapicchioni, V; Palchetti, S; Riccioli, A; Laganà, A

2014-09-30

318

Impact of corona on the long-term performance of nonceramic insulators  

Microsoft Academic Search

A majority of nonceramic insulator (NCI) application is under relatively clean conditions where leakage current may be nonexistent. Occurrence of corona for long periods of time on NCI operating under relatively clean conditions is possible due to localized high electric field (E-field) brought about by design and manufacturing deficiencies. Therefore, resistance to corona-induced degradation of NCI housing materials is an

V. M. Moreno; R. S. Gorur; A. Kroese

2003-01-01

319

Effects of corona discharge treatment on the surface properties of wool fabrics  

Microsoft Academic Search

Wool fabric was treated by corona discharge and treating conditions were optimized. The surface properties of the treated wool fabrics, such as hydrophilicity and dyeability with natural dyes, have been investigated. After the corona discharge treatment, the hydrophilicity of the wool fabric was improved and the dyeability with Rhizoma coptidis was increased. Scanning electron microscope (SEM) images indicated that some

Guizhen Ke; Weidong Yu; Weilin Xu; Weigang Cui; Xiaolin Shen

2008-01-01

320

APPLICATION OF CORONA DESTRUCTION AS A METHOD TO CONTROL VOLATILEORGANIC COMPOUNDS  

EPA Science Inventory

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

321

Measurement of Ions Penetration Pattern in Point to Grid Atmospheric Corona Discharge  

Microsoft Academic Search

Atmospheric plasma which has many scientific and engineering applications is a complicated phenomena because of interaction between ions, fields and neutrals. For more accurate modeling and better use of corona phenomena which is a kind of atmospheric plasma, some experimental measurements have been done in the case of point to grid corona problem and relative ion penetration pattern behind the

Ali Haghdel; Habibollah Abiri; Mohammad Reza Eskandari; Hasan Zibaeinejad

2011-01-01

322

A Corona Discharge Initiated Electrochemical Electrospray Ionization Technique  

PubMed Central

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

Lloyd, John R.; Hess, Sonja

2009-01-01

323

The corona of V390 Aurigae (HD 33798)  

NASA Astrophysics Data System (ADS)

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

Gondoin, P.

2003-06-01

324

A nanoflare heating model for the quiet solar corona  

E-print Network

The energy input into the lower solar corona by flare evaporation events has been modeled according to the available observations for quiet regions. The question is addressed whether such heating events can provide the observed average level of the coronal emission measure and thus of the observed flux of extreme ultraviolet (EUV) and X-ray emission without contradicting the observed average power spectrum of the emission measure, the typical emission measure variations observed for individual pixels and the observed flare energy distribution. As the assumed flare height influences the derived flare energy, the mathematical foundations of nanoflare distributions and their conversion to different height assumptions are studied first. This also allows a comparison with various published energy distributions differing in height assumptions and to relate the observations to the input parameters of the heating model. An analytic evaluation of the power spectrum yields the relationship between the average time profile of nanoflares (or microflares), assumed to be self-similar in energy, and the power spectrum. We find that the power spectrum is very sensitive to the chosen time profile of the flares. Models are found by numerical simulation that fit all available observations. They are not unique but severely constrained. We concentrate on a model with a flare height proportional to the square root of the flare area. The existence of a fitting model demonstrates that nanoflare heating of the corona is a viable and attractive mechanism.

U. Mitra-Kraev; A. O. Benz

2001-04-12

325

ON REDSHIFTS AND BLUESHIFTS IN THE TRANSITION REGION AND CORONA  

SciTech Connect

Emission lines formed in the transition region (TR) of the Sun have long been known to show pervasive redshifts. Despite a variety of proposed explanations, these TR downflows (and the slight upflows in the low corona) remain poorly understood. We present results from comprehensive three-dimensional MHD models that span the upper convection zone up to the corona, 15 Mm above the photosphere. The TR and coronal heating in these models is caused by the stressing of the magnetic field by photospheric and convection 'zone dynamics', but also in some models by the injection of emerging magnetic flux. We show that rapid, episodic heating, at low heights of the upper chromospheric plasma to coronal temperatures naturally produces downflows in TR lines, and slight upflows in low coronal lines, with similar amplitudes to those observed with EUV/UV spectrographs. We find that TR redshifts naturally arise in episodically heated models where the average volumetric heating scale height lies between that of the chromospheric pressure scale height of 200 km and the coronal scale height of 50 Mm.

Hansteen, V. H.; Carlsson, M. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Hara, H. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); De Pontieu, B., E-mail: viggoh@astro.uio.n, E-mail: mats.carlsson@astro.uio.n, E-mail: hirohisa.hara@nao.ac.j, E-mail: bdp@lmsal.co [Lockheed Martin Solar and Astrophysics Lab, Org. ADBS, Bldg. 252, 3251 Hanover Street Palo Alto, CA 94304 (United States)

2010-08-01

326

Chemical Compositions and Abundance Anomalies in Stellar Coronae ADP 99  

NASA Technical Reports Server (NTRS)

New atomic data for tackling some of our spectra have been investigated by co-I Laming (NRL), including the effects of recombination on spectral line fluxes that are not included in, for example, the CHIANTI database models. Promising new progress has been made with modelling some of the recent abundance anomaly results in terms of Alven wave-driven separation of neutrals and ions in the upper chromosphere. The problems that existing models have is that they cannot simultaneously explain the low-FIP enhanced solar-like coronae and the high-FIP rich active coronae of RS CVn-like stars. The Alven wave model shows promise with both of these scenarios, with the fractionation or suppression of low-FIP ions depending on the characteristics of the chromosphere. This work is currently in the writing up stage. In summary, the work to-date is making good progress in mapping abundance anomalies as a function of spectral type and activity level. We are also making good progress with modelling that we will be able to test with our observational results. With one more year of effort, we'anticipate that the bulk of the work described above can be published, together with outstanding key studies on anomalies among the different active binaries.

Oliversen, Ronald J. (Technical Monitor); Drake, Jeremy

2004-01-01

327

The EUV Emission in Comet-Solar Corona Interactions  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

328

Indian Solar mission to study inner solar corona: Aditya 1  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

329

Evidence for Flux Ropes in the Solar Corona  

NASA Astrophysics Data System (ADS)

Although twisted magnetic flux ropes are clearly ejected from the Sun, as demonstrated by LASCO and EIT movies of erupting prominences, there has been some controversy about whether flux ropes exist in the corona before ejection. It has been argued that they are formed only upon ejection. The issue is important because of the need to understand how eruptions are initiated. Now a clearer picture of solar flux ropes is emerging with recent high-resolution observations of solar filaments. Filament's twist and writhe are frequently detectable even when they do not escape the Sun. The observations of November 1, 2001 and May 27, 2002 made by the TRACE solar telescope both appear to show the sudden eruption without ejection of a filament, with transformation of some internal twist into a writhe of approx. + 1. Since magnetic helicity is approximately conserved, even in these rapid events, it follows that these kink events are strong evidence that flux ropes are present in the corona. We suggest that a flux rope may undergo several kink instabilities before it is ejected from the Sun. We identify coronal X-ray sigmoids as the aftermath of these sudden kink events. NASA supported this work under grant NAG5-11584.

Rust, D. M.

2003-05-01

330

Optics to rectify CORONA panoramic photographs for map making  

NASA Astrophysics Data System (ADS)

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

Hilbert, Robert S.

2006-08-01

331

Complex variation of spectral line widths observed in polar corona  

NASA Astrophysics Data System (ADS)

Spectroscopic observations of the solar corona, using high spatial and spectral resolution 25cm coronagraph, at Norikura observatory, were made on large number of days during 2004 at the mid latitude and polar coronal regions. We have analyzed several raster scans that cover mid and high latitude regions on the off-limb corona in four bright emission lines of iron, namely, [Fe X] 6374 Å, [Fe XI]~7892~Å, [Fe XIII] 10747~Å, and [Fe XIV]~5303~Å. We find that the FWHM of red line increases with height and that of green line decreases with height as observed earlier, at equatorial regions. The comparison of line widths and their gradients with the results from equatorial regions indicate that these are higher for polar regions for the observed emission lines except for the green line. FWHM values show an increase towards poles in all the lines except for the green line which shows little or no change. Higher values of FWHM at polar regions may imply higher non-thermal velocities which could be linked to the solar wind, but the behavior of green emission line with almost same values of FWHM at equatorial and polar regions is surprising. This may also give some indications on the existence of preferential heating.

Prasad Samayamanthula, Krishna; Banerjee, Dipankar; Singh, Jagdev

2012-07-01

332

Magnetic tornadoes as energy channels into the solar corona.  

PubMed

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

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

2012-06-28

333

Nitrogen fixation by corona discharge on the early precambrian Earth.  

PubMed

We report the first experimental study of nitrogen fixation by corona discharge on the anoxic primitive Earth. The energy yields of nitric oxide (NO) and nitrous oxide (N(2)O) were experimentally determined over a wide range of CO(2)-N(2) mixtures simulating the evolution of the Earth's atmosphere during the Hadean and Archean eras (from 4.5 ba to 2.5 ba). NO, the principal form of fixed nitrogen in lightning and coronal discharge in early Earth, is produced ten times less efficiently in the latter type of electrical discharge with an estimated maximum annual production rate of the order of 10(10) g yr(-1). For N(2)O the maximum production rate was estimated to be approximately 10(9) g yr(-1). These low rates of syntheses indicate that corona discharges as point discharges on the clouds and ground did not play a significant role in the overall pool of reactive nitrogen needed for the emergence and sustainability of life. PMID:16231204

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

2005-10-01

334

Ex situ evaluation of the composition of protein corona of intravenously injected superparamagnetic nanoparticles in rats  

NASA Astrophysics Data System (ADS)

It is now well recognized that the surfaces of nanoparticles (NPs) are coated with biomolecules (e.g., proteins) in a biological medium. Although extensive reports have been published on the protein corona at the surface of NPs in vitro, there are very few on the in vivo protein corona. The main reason for having very poor information regarding the protein corona in vivo is that separation of NPs from the in vivo environment has not been possible by using available techniques. Knowledge of the in vivo protein corona could lead to better understanding and prediction of the fate of NPs in vivo. Here, by using the unique magnetic properties of superparamagnetic iron oxide NPs (SPIONs), NPs were extracted from rat sera after in vivo interaction with the rat's physiological system. More specifically, the in vivo protein coronas of polyvinyl-alcohol-coated SPIONs with various surface charges are defined. The compositions of the corona at the surface of various SPIONs and their effects on the biodistribution of SPIONs were examined and compared with the corona composition of particles incubated for the same time in rat serum.It is now well recognized that the surfaces of nanoparticles (NPs) are coated with biomolecules (e.g., proteins) in a biological medium. Although extensive reports have been published on the protein corona at the surface of NPs in vitro, there are very few on the in vivo protein corona. The main reason for having very poor information regarding the protein corona in vivo is that separation of NPs from the in vivo environment has not been possible by using available techniques. Knowledge of the in vivo protein corona could lead to better understanding and prediction of the fate of NPs in vivo. Here, by using the unique magnetic properties of superparamagnetic iron oxide NPs (SPIONs), NPs were extracted from rat sera after in vivo interaction with the rat's physiological system. More specifically, the in vivo protein coronas of polyvinyl-alcohol-coated SPIONs with various surface charges are defined. The compositions of the corona at the surface of various SPIONs and their effects on the biodistribution of SPIONs were examined and compared with the corona composition of particles incubated for the same time in rat serum. Electronic supplementary information (ESI) available: Summary table of identified proteins. See DOI: 10.1039/c4nr02793k

Sakulkhu, Usawadee; Maurizi, Lionel; Mahmoudi, Morteza; Motazacker, Mahdi; Vries, Marcel; Gramoun, Azza; Ollivier Beuzelin, Marie-Gabrielle; Vallée, Jean-Paul; Rezaee, Farhad; Hofmann, Heinrich

2014-09-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

336

Glow corona generation and streamer inception at the tip of grounded objects during thunderstorms: revisited  

NASA Astrophysics Data System (ADS)

The initiation of streamers prior to a lightning strike can be reportedly inhibited by glow corona discharges generated from tall objects. In contrast to previous studies based on a simplified one-dimensional model of glow corona, a two-dimensional evaluation of the corona ion drift from tall objects is used here to analyse this effect quantitatively. Proper estimates for the corona space charge distribution generated during both the charging process of a thundercloud and the descent of the downward stepped leader are thus calculated. It is found that the shielding effect of the corona space charge on the streamer inception is not as severe as previously reported. Estimations of the effective height of the downward leader tip at which streamer inception takes place are presented and discussed for lightning rods and dissipation array systems.

Becerra, Marley

2013-04-01

337

Corona-induced pressures, potentials, fields and currents in electrostatic precipitator configurations  

NASA Astrophysics Data System (ADS)

This paper is aimed at assessing analytically the dc corona induced pressures in wire-cylinder and wire-plate electrostatic precipitator configurations. This calls for solving the equations describing the corona discharge and the force balance for static gas equilibrium provided that the corona onset voltage and the space-charge-free field values are calculable. The calculated pressure and potential distributions along the gap axis in air and nitrogen at atmospheric pressure agreed well with those measured previously. The calculated corona current density values agreed reasonably with those measured for a high-temperature high-pressure wire-cylinder precipitator. The analytically calculated positive and negative dc corona onset voltages for wire-duct precipitators following proposed criteria based on discharge physics are in good agreement with those measured experimentally at atmospheric and lower pressures.

Abdel-Salam, M.; Nakano, M.; Mizuno, A.

2007-04-01

338

Oxygen Isotopes Unravel the Role of Microorganisms in Phosphate Cycling in Soils  

E-print Network

Oxygen Isotopes Unravel the Role of Microorganisms in Phosphate Cycling in Soils Federica Tamburini microorganisms, the available P pool, and from the vegetation along a 150-year soil chronosequence of a glacier Pi, vegetation Pi or Pi released from organic matter mineralization. Thus, we show that phosphate

Gilli, Adrian

339

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

Microsoft Academic Search

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

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

2000-01-01

340

Orchestration of cooperative events in DNA synthesis and repair mechanism unraveled by transition path  

E-print Network

Orchestration of cooperative events in DNA synthesis and repair mechanism unraveled by transition information on, the complex process essential for DNA synthesis and repair. The five identified transition in organizing the active site for DNA synthesis (extension of primer strand by one base) and thereby helping

Schlick, Tamar

341

Unraveling the mystery of compost teas used for organic disease and insect pest  

E-print Network

GilleN #12;What are compost teas? · Watery extracts (teas) made from placingUnraveling the mystery of compost teas used for organic disease and insect compost teas? · Teas are microbial and nutrient rich · Can be brewed on farm

342

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

E-print Network

revealed a history of sex-biased migration patterns that can vary widely across human populationsUnraveling male and female histories from human genetic data Jon F Wilkins The increasing of human genetic diversity, and what that structure can teach us about human demographic history. Global

Wilkins, Jon F.

343

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

ERIC Educational Resources Information Center

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

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

2012-01-01

344

The Mechanisms Involved in Seed Dormancy Alleviation by Hydrogen Cyanide Unravel the Role of Reactive  

E-print Network

The Mechanisms Involved in Seed Dormancy Alleviation by Hydrogen Cyanide Unravel the Role ethylene or hydrogen cyanide (HCN) during imbibition. The aim of this work was to provide a comprehensive after- ripening or by HCN treatment, and the effect of cyanide on gene expression is likely

Leubner, Gerhard

345

Unraveling the distributed neural code of facial identity through spatiotemporal pattern analysis  

E-print Network

Unraveling the distributed neural code of facial identity through spatiotemporal pattern analysis. The present study investigates the neural code of facial identity perception with the aim of ascertain- ing-based brain mapping and dynamic discrimi- nation analysis to locate spatiotemporal patterns that support face

Behrmann, Marlene

346

integrOmics: an R package to unravel relationships between two omics data sets  

Microsoft Academic Search

Motivation: With the availability of many 'omics' data, such as transcriptomics, proteomics or metabolomics, the integrative or joint analysis of multiple datasets from different technology platforms is becoming crucial to unravel the relationships between different biological functional levels. However, the development of such an analysis is a major computational and technical challenge as most approaches suffer from high data dimensionality.

Kim-Anh L; Ignacio Gonz ´ alez

347

STATISTICAL DESCRIPTION OF A MAGNETIZED CORONA ABOVE A TURBULENT ACCRETION DISK Dmitri A. Uzdensky and Jeremy Goodman  

E-print Network

. This is perceived to be too hard; certainly the long and arduous struggle to understand the heating of solar coronaSTATISTICAL DESCRIPTION OF A MAGNETIZED CORONA ABOVE A TURBULENT ACCRETION DISK Dmitri A. Uzdensky-based statistical theory of a force-free magnetic field in the corona above a turbulent accretion disk. The field

348

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

E-print Network

- ner heliosphere, and they could well be partly responsible for heating the corona to its tem- perature1 ON THE DYNAMICS OF THE SOLAR CORONA: FIRST RESULTS OBTAINED WITH A NEW 3D MHD MODEL J. Kleimann 1) is applied to the problem of the dynamics of the solar corona. First, we present the basic system

Grauer, Rainer

349

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

E-print Network

Electron heat flow in the solar corona: Implications of non-Maxwellian velocity distributions of such nonlocal heat flow for electrons in the solar corona, comparing a new analytical theory to numerical of coronal heating mechanisms. INDEX TERMS: 7509 Solar Physics, Astrophysics, and Astronomy: Corona; 7859

Scudder, Jack

350

X-RAY SPECTROSCOPY OF THE UNSTEADY QUIESCENT CORONA OF AD LEONIS WITH CHANDRA A. Maggio,1  

E-print Network

that the EMD is compatible with the model of a corona continuously heated by flares, which predicts an EMD structures that confine hot plasma in stellar coronae and the nature of coronal heating. The topologyX-RAY SPECTROSCOPY OF THE UNSTEADY QUIESCENT CORONA OF AD LEONIS WITH CHANDRA A. Maggio,1 J. J

Micela, Giusi

351

Radiophysics and Quantum. Electronics, VoI. 2Z No. 7, 1994 PLASMA DIAGNOSTICS OF THE SOLAR CORONA USING  

E-print Network

to account for the heating of the entire corona. Noise storm sources or other microflares having energiesRadiophysics and Quantum. Electronics, VoI. 2Z No. 7, 1994 PLASMA DIAGNOSTICS OF THE SOLAR CORONA USING DECIMETRIC RADIO WAVES (Review) A. O. Benz The solar corona is a very dynamic plasma on time

352

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

NASA Technical Reports Server (NTRS)

Preliminary studies of the distribution of coronae and volcanic rises on Venus show that many of these features tend to cluster along zones of rifting and extension. The plains north of Lada Terra are crossed by two such extensional belts. Each belt is composed of grabens, ridges, faults, volcanic flows, coronae and coronalike features. The longer and more prominent belt is the NW trending Alpha-Lada extensional belt, which is over 6000 km long and 50-200 km wide, and includes the coronae Eve, Tamfana, Carpo, Selu, Derceto, Otygen, and an unnamed corona south of Otygen. The second belt is the NNE trending Derceto-Quetzalpetlatl extensional belt, which is about 2000 km long and in places over 300 km wide, and includes the coronae Sarpanitum, Eithinoha, and Quetzalpetlatl. The two belts intersect at the 1600 x 600 km wide Derceto volcanic plateau. It is apparent that deformation along the two belts overlapped in time, though deformation along the Alpha-Lada extensional belt probably continued after the deformation along the Derceto-Quetzalpetlatl extensional belt terminated. In certain areas, volcanism originated in grabens within the extensional belts, whereas in other areas, such as in Eve, Selu, Derceto, and Quetzalpetlatl, volcanism originated in the coronae and flowed into the lower parts of the extensional belts. Regional extension has affected the evolution of all the coronae at some stage of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha and after the initiation of Carpo, Tamfana, Otygen, and Sarpanitum. It is thus unlikely that coronae formation along the belts is solely a consequence of the regional extension, and it is also unlikely that regional extension has been caused solely by the coronae. No corona along the belts was formed subsequent to the cessation of the regional extension. We therefore suggest that the regional extension and the coronae are interrelated. Some of the coronae may have determined the location of the surface expression of the regional extension, whereas the locations of other coronae may have been influenced by the concentration of regional extensional stresses.

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

1994-01-01

353

The VLT Unravels the Nature of the Fastest Binary Star  

NASA Astrophysics Data System (ADS)

Two Hot White Dwarfs Perform a Tight Dance Summary Observations with ESO's Very Large Telescope (VLT) in Chile and the Italian Telescopio Nazionale Galileo (TNG) on the Canary Islands during the past two years have enabled an international group of astronomers [1] to unravel the true nature of an exceptional binary stellar system. This system, designated RX J0806.3+1527 , was first discovered as an X-ray source of variable brightness - once every five minutes, it "switches off" for a short moment. The new observations have shown beyond doubt that this period reflects the orbital motion of two "white dwarf" stars that revolve around each other at a distance of only 80,000 km . Each of the stars is about as large as the Earth and this is the shortest orbital period known for any binary stellar system. The VLT spectrum displays lines of ionized helium, indicating that the presence of an exceedingly hot area on one of the stars - a "hot spot" with a temperature of approx. 250,000 degrees. The system is currently in a rarely seen, transitory evolutionary state . PR Photo 10a/02 : U- and R-band images of RX J0806.3+1527. PR Photo 10b/02 : Spectrum of RX J0806.3+1527 An amazing stellar binary system ESO PR Photo 10a/02 ESO PR Photo 10a/02 [Preview - JPEG: 800 x 400 pix - 440k] [Normal - JPEG: 1600 x 800 pix - 1.1M] Caption : PR Photo 10a/02 shows U and R filter images of the sky field around RX J0806.3+1527 (at centre of circle), obtained with the FORS2 multi-mode instrument on VLT KUEYEN. The object is brightest at the shorter wavelength (U-band) - reflecting its very high temperature. Technical information about the photo is available below. One year is the time it takes the Earth to move once around the Sun, our central star. This may seem quite fast when measured on the scale of the Universe, but this is a snail's motion compared to the the speed of two recently discovered stars. They revolve around each other 100,000 times faster; one full revolution takes only 321 seconds , or a little more than 5 minutes! It is the shortest period ever observed in a binary stellar system . This is the surprising conclusion reached by an international team of astronomers led by GianLuca Israel of the Astronomical Observatory of Rome [1], and based on detailed observations of the faint light from these two stars with some of the world's most advanced telescopes. The record-holding binary stellar system bears the prosaic name RX J0806.3+1527 and it is located north of the celestial equator in the constellation Cancer (The Crab). The scientists also find that the two partners in this hectic dance are most likely a dying white dwarf star , trapped in the strong gravitational grip of another, somewhat heavier star of the same exotic type. The two Earth-size stars are separated by only 80,000 kilometers , a little more than twice the altitude of the TV-broadcasting satellites in orbit around the Earth, or just one fifth of the distance to the Moon. The orbital motion is very fast indeed - over 1,000 km/sec, and the lighter star apparently always turns the same hemisphere towards its companion, just as the Moon in its orbit around Earth. Thus, that star also makes one full turn around its axis in only 5 minutes, i.e. its "day" is exactly as long as its "year". The discovery of RX J0806.3+1527 The visible light emitted by this unusual system is very faint, but it radiates comparatively strong X-rays. It was due to this emission that it was first detected as a celestial X-ray source of unknown origin by the German ROSAT space observatory in 1994. Later it was found to be a periodically variable source [2]. Once every 5 minutes, the X-ray radiation disappears for a couple of minutes. It was recently studied in greater detail by the NASA Chandra observatory. The position of the X-ray source in the sky was localised with sufficient accuracy to reveal a very faint visible-light emitting object in the same direction, over one million times weaker than the faintest star that can be seen by unaided eye (V

2002-03-01

354

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

PubMed

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

Schmitt, J H; Wichmann, R

2001-08-01

355

Geology of coronae and domal structures on Venus and models of their origin  

SciTech Connect

Coronae (160 to 670 km across) and domal structures (greater than 1000 km across) are complex topographic highs on Venus that were affected by volcanic and topographic processes. The geology of coronae and a major domal structure, Beta Regio, are documented using Pioneer Venus, Arecibo, and Venera 15/16 data. The evolution and possible models of origin of these features are also investigated. Beta Regio is a 2000 x 2300 km topographic high located in the equatorial region of Venus that rises over 5 km above the surrounding region. Within Beta Regio lie two large volcanic shields, Theia and Rhea Mons. Coronae are circular to elongate structures on Venus, characterized by an annulus of concentric compressional ridges and relatively raised topography surrounded by a peripheral trough. Volcanic domes, flows and edifices, as well as tectonic lineaments characterize the interiors of coronae. Thirty one coronae were detected on Venus. Two analytical models were developed that are consistent with the general characteristics and evolution of coronae: hotspot or rising mantle diapir model and sinking mantle diapir model. Coronae appear to be part of a continuum of thermally produced features on Venus, along with volcanic complexes and domal structures such as Beta Regio.

Stofan, E.R.

1989-01-01

356

Effect of ion pair formation on the structure of polymer micelles with ionic amphiphilic coronae  

NASA Astrophysics Data System (ADS)

We report a theoretical study of micelles from diblock copolymers with an insoluble core-forming block and an amphiphilic ionic corona-forming block. We calculate the micelle structural parameters depending on the composition of the coronal block (ratio between the non-polar and ion-containing groups) as well as solvent quality and polarity for the coronal block. We focus on the effect of ion pair formation in a low polar corona medium and predict the existence of novel micelles with ionomer-type coronae. In these micelles most part of counterions is bound with ions in polymer chains. Two consecutive jump-like first-order phase transitions between different-type micelles can take place in the solution upon change of hydrophobic/polyelectrolyte balance within the micelle corona: large micelles with polyelectrolyte collapsed coronae ? large micelles with ionomer-type coronae ? small micelles with polyelectrolyte swollen coronae. These transitions are accompanied by non-monotonous change in the micelle aggregation number. New insight into the role of counterions is important for design of stimuli responsive systems.

Rumyantsev, A. M.; Kramarenko, E. Yu.

2013-05-01

357

Ex situ evaluation of the composition of protein corona of intravenously injected superparamagnetic nanoparticles in rats.  

PubMed

It is now well recognized that the surfaces of nanoparticles (NPs) are coated with biomolecules (e.g., proteins) in a biological medium. Although extensive reports have been published on the protein corona at the surface of NPs in vitro, there are very few on the in vivo protein corona. The main reason for having very poor information regarding the protein corona in vivo is that separation of NPs from the in vivo environment has not been possible by using available techniques. Knowledge of the in vivo protein corona could lead to better understanding and prediction of the fate of NPs in vivo. Here, by using the unique magnetic properties of superparamagnetic iron oxide NPs (SPIONs), NPs were extracted from rat sera after in vivo interaction with the rat's physiological system. More specifically, the in vivo protein coronas of polyvinyl-alcohol-coated SPIONs with various surface charges are defined. The compositions of the corona at the surface of various SPIONs and their effects on the biodistribution of SPIONs were examined and compared with the corona composition of particles incubated for the same time in rat serum. PMID:25154771

Sakulkhu, Usawadee; Maurizi, Lionel; Mahmoudi, Morteza; Motazacker, Mahdi; Vries, Marcel; Gramoun, Azza; Ollivier Beuzelin, Marie-Gabrielle; Vallée, Jean-Paul; Rezaee, Farhad; Hofmann, Heinrich

2014-10-01

358

Corona discharge ion mobility spectrometry at reduced pressures  

SciTech Connect

Ion mobility spectrometers (IMSs) normally operate at ambient pressure. In this work an IMS cell has been designed and constructed to allow the pressure to be reduced inside the IMS cell. In this cell, corona discharge was employed as the ionization source. Reducing pressure affected both the discharge and the performance of the IMS. The discharge current was observed to increase with reducing pressure while the ignition potential decreased. The ion current received at the collector plate was also increased about 50 times when the pressure was reduced from ambient pressure to 15 Torr. The higher ion current can lead to an extended dynamic range. IMS spectra were recorded at various pressures and the results show that the drift times shift perfectly linear with pressure. This suggests that unlike temperature, pressure correction for ion mobility spectra is as simple as multiplying the drift times by a factor of 760/P.

Tabrizchi, Mahmoud; Rouholahnejad, Fereshteh [College of Chemistry, Isfahan University of Technology, Isfahan, 84154 (Iran, Islamic Republic of)

2004-11-01

359

SIMBA observations of the R Corona Australis molecular cloud  

NASA Astrophysics Data System (ADS)

We have mapped the R Corona Australis molecular cloud at 1.2 mm with SIMBA on SEST and detected 25 distinct dust emission peaks. While 7 of them coincide with positions of previously known young stars, 18 are seemingly not associated with any known stellar object. We discuss the nature of individual sources and conclude that there are at least four small concentrations of young objects located along the filamentary shaped cloud. A comparison with C18O data hints at the depletion of molecules in some of the cores. Our new results yield some conflicting arguments about whether star formation proceeds from north-west to south-east in the R Cr A cloud. Based on observations collected at the European Southern Observatory, La Silla, Chile. Appendices A and B are only available in electronic form at http://www.edpsciences.org

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

2003-10-01

360

Burgulence and Alfven waves heating mechanism of solar corona  

E-print Network

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

T. M. Mishonov; Y. G. Maneva

2006-09-21

361

Is the galactic corona produced by galactic flares?  

NASA Technical Reports Server (NTRS)

The effect of the differential rotation of the disk of the Galaxy on magnetic field which penetrates the disk is considered. The magnetic field will be progressively distorted from a potential (current-free) form and will at some stage become unstable. It is expected that an MHD instability, a resistive instability, or a combination of the two, will result in the release of the excess magnetic energy and that part of the released energy will be converted into heat. By estimating the energy release and the rate at which this process will occur and by assuming that this energy input is balanced by radiation, estimates were obtained of the parameters of the resulting plasma. It appears that this process alone can heat a galactic corona to temperatures of order 10 to the 6th power K.

Sturrock, P. A.; Stern, R.

1979-01-01

362

Using Chandra/LETG spectra to probe stellar coronae  

E-print Network

We probe the relationship between surface magnetic fields and the X-ray emitting corona in the rapidly rotating star AB Dor. Circularly polarised spectra have been inverted to produce a surface (photospheric) magnetic field map. This surface map has been extrapolated to model AB Dor's coronal field topology and X-ray light curve. Chandra/LETG light curves of AB Dor from the same epoch show intrinsic variability at the 30% level. Period analysis indicates a fraction of this is due to rotational modulation. We measure velocity shifts in emission line centroids as a function of rotation period and find evidence of rotational modulation (max. vel. ~40+/- 13km/s). This modulation may indicate the presence of a localised X-ray emitting region at mid-to-high latitudes.

Gaitee A. J. Hussain; Nancy Brickhouse; Andrea K. Dupree; Adriaan A. van Ballegooijen; Andrew Collier Cameron; Moira Jardine; Jean-Francois Donati

2004-03-09

363

Influence of iron on degradation of organic dyes in corona.  

PubMed

In this work application of AOPs such as Fenton process, aqueous phase high voltage electrical discharge (corona) and their combination have been studied for colored wastewater treatment. Experiments were conducted on water solutions of four different organic dyes, two azo dyes C.I. Mordant Yellow 10 (MY10) and C.I. Direct Orange 39 (DO39), and two reactive of azo type C.I. Reactive Red 45 (RR45) and C.I. Reactive Blue 137 (RB137). The efficiency of studied AOPs has been estimated on the bases of UV-vis spectrophotometric and TOC measurements. The rate constants in the kinetic model have been determined. Experimental data have been compared with the developed mathematical model. PMID:15629569

Koprivanac, Natalija; Kusi?, Hrvoje; Vujevi?, Dinko; Peternel, Igor; Locke, Bruce R

2005-01-31

364

Turbulence Transport and Dissipation in the Lower Solar Corona  

NASA Astrophysics Data System (ADS)

We present new improvements to our three-dimensional global two-temperature model of the solar corona that includes the transition region and upper chromosphere. In our previous study, we focused on the wave-energy injection, transmission and dissipation [I.V. Sokolov et al., submitted to Ap.J. (2012)]. We have now also included the wave reflection due to large-scale plasma inhomogeneities. This reflection leads to low-frequency cascade of Alfvén waves due to small-scale nonlinearities. In closed field line regions, the dissipation is enhanced since different wave polarities (Elsässer energy densities) can meet with equal amplitude, resulting in elevated temperatures. The electron heat conduction can subsequently transport this excess of energy deposition down to the chromosphere. We discuss the theoretical framework and contrast the resulting simulated multi-wavelength EUV images with the SDO/AIA observations for Carrington rotation 2107.

van der Holst, B.; Sokolov, I.; Gombosi, T. I.

2012-12-01

365

Variable Winds and Dust Formation in R Coronae Borealis Stars  

NASA Astrophysics Data System (ADS)

We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I ?10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities ~400 km s-1 appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

Clayton, Geoffrey C.; Geballe, T. R.; Zhang, Wanshu

2013-08-01

366

Corona discharge ionization of paracetamol molecule: Peak assignment.  

PubMed

Ionization of paracetamol was investigated using ion mobility spectrometry equipped with a corona discharge ionization source. The measurements were performed in the positive ion mode and three peaks were observed in the ion mobility spectrum. Experimental evidence and theoretical calculations were used to correlate the peaks to related ionic species of paracetamol. Two peaks were attributed to protonated isomers of paracetamol and the other peak was attributed to paracetamol fragment ions formed by dissociation of the N-C bond after protonation of the nitrogen atom. It was observed that three sites of paracetamol compete for protonation and their relative intensities, depending on the sample concentration. The ratio of ion products could be predicted from the internal proton affinity of the protonation sites at each concentration. PMID:25128677

Bahrami, H; Farrokhpour, H

2015-01-25

367

Pulsed corona discharge for oxidation of gaseous elemental mercury  

NASA Astrophysics Data System (ADS)

Positive pulsed corona discharge has been applied for the oxidation of gaseous elemental mercury (Hg0) from a simulated flue gas. The oxidation of Hg0 to HgO and HgCl2 can significantly enhance the mercury removal from flue gas. At a gas condition of O2 (10%), H2O (3%), and N2 (balance), Hg0 oxidation efficiency of 84% was achieved at an input energy density of 45J /l. The presence of NO, however, hinders Hg0 oxidation due to the preferential reaction of NO with O and O3. On the contrary, SO2 shows little effect on Hg0 oxidation due to its preferential reaction with OH. It has been also observed that the HCl in gas stream can be dissociated to Cl and Cl2 and can induce additional Hg0 oxidation to HgCl2.

Ko, Kyung Bo; Byun, Youngchul; Cho, Moohyun; Namkung, Won; Hamilton, Ian P.; Shin, Dong Nam; Koh, Dong Jun; Kim, Kyoung Tae

2008-06-01

368

Development of latent fingerprints using a corona discharge.  

PubMed

A novel technique for the development of latent fingerprints is presented. It is based on placing a fingerprint-bearing object inside a corona discharge induced plasma. The development of various real and artificial fingerprints on metallic substrates under a wide range of conditions is studied. Using the results of the development experiments and the results of X-ray photoelectron spectroscopy, it is shown that the development is based on oxidation of the fingerprint background. This is achieved by strong oxidizers generated by the discharge process, while saturated fatty-acids found in sebaceous fingerprints protect the area beneath them, resulting in a visible fingerprint. The process is optimized by minimizing the electrode gap distance and maximizing the peak discharge voltage and the pulse repetition frequency. PMID:9304830

Halahmi, E; Levi, O; Kronik, L; Boxman, R L

1997-09-01

369

Coronagraphic observations and analyses of the ultraviolet solar corona  

NASA Technical Reports Server (NTRS)

This status report for the period 1 October 1992 to 30 September 1994 covers the final preparation and first observations with the Spartan Ultraviolet Coronal Spectrometer on Spartan 201-1, and the preparation and second flight for Spartan 201-2. Both flights were fully successful and resulted in high quality spectroscopic observations of the extended solar corona out to 3.5 solar radii from Sun-center. The primary focus of this report is the results from Spartan 201-1. There is also a brief description of the evaluation of the quick look data from the second flight. Highlights from the first flight include a discovery that the proton velocity distribution in coronal holes is complex and consists of a central core with elevated high velocity wings compared to a Gaussian shape.

Kohl, John L.

1994-01-01

370

Characterization of the slow wind in the outer corona  

NASA Astrophysics Data System (ADS)

The study concerns the streamer belt observed at high spectral resolution during the minimum of solar cycle 23 with the Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO. On the basis of a spectroscopic analysis of the O VI doublet, the solar wind plasma parameters are inferred in the extended corona. The analysis accounts for the coronal magnetic topology, extrapolated through a 3D magneto-hydrodynamic model, in order to define the streamer boundary and to analyse the edges of coronal holes. The results of the analysis allow an accurate identification of the source regions of the slow coronal wind that are confirmed to be along the streamer boundary in the open magnetic field region.

Abbo, Lucia; Antonucci, Ester; Miki?, Zoran; Linker, Jon A.; Riley, Pete; Lionello, Roberto

2010-12-01

371

VARIABLE WINDS AND DUST FORMATION IN R CORONAE BOREALIS STARS  

SciTech Connect

We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I {lambda}10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities {approx}400 km s{sup -1} appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

Clayton, Geoffrey C.; Zhang Wanshu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Geballe, T. R., E-mail: gclayton@fenway.phys.lsu.edu, E-mail: wzhan21@lsu.edu, E-mail: tgeballe@gemini.edu [Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720 (United States)

2013-08-01

372

The X-Ray Corona of a Flaring L Dwarf  

NASA Astrophysics Data System (ADS)

We propose the first observation to determine both the X-ray luminosity and white light flare of a L-type dwarf star. Late-M and L dwarfs show a remarkable drop in chromospheric and coronal activity levels, but surprisingly strong radio emission, a change is that neither fully understood theoretically. Observations are needed to establish empirical relationships and compare to those of warmer flare stars. Kepler observations have already measured the flare rate, and we now propose Chandra observations. We will be able to test the hypothesis that the X-ray corona scales with the flare rate, and compare the relative X-ray, radio, chromosphere and flare energy budget. The target,WISEP J190648.47+401106.8, is uniquely suited for this project because of the Kepler data.

Gizis, John

2014-09-01

373

Distribution of Electric Currents in Sunspots from Photosphere to Corona  

NASA Astrophysics Data System (ADS)

We present a study of two regular sunspots that exhibit nearly uniform twist from the photosphere to the corona. We derive the twist parameter in the corona and in the chromosphere by minimizing the difference between the extrapolated linear force-free field model field lines and the observed intensity structures in the extreme-ultraviolet images of the Sun. The chromospheric structures appear more twisted than the coronal structures by a factor of two. Further, we derive the vertical component of electric current density, jz , using vector magnetograms from the Hinode Solar Optical Telescope (SOT). The spatial distribution of jz has a zebra pattern of strong positive and negative values owing to the penumbral fibril structure resolved by Hinode/SOT. This zebra pattern is due to the derivative of the horizontal magnetic field across the thin fibrils; therefore, it is strong and masks weaker currents that might be present, for example, as a result of the twist of the sunspot. We decompose jz into the contribution due to the derivatives along and across the direction of the horizontal field, which follows the fibril orientation closely. The map of the tangential component has more distributed currents that are coherent with the chromospheric and coronal twisted structures. Moreover, it allows us to map and identify the direct and return currents in the sunspots. Finally, this decomposition of jz is general and can be applied to any vector magnetogram in order to better identify the weaker large-scale currents that are associated with coronal twisted/sheared structures.

Gosain, Sanjay; Démoulin, Pascal; López Fuentes, Marcelo

2014-09-01

374

3D Simulations of the Solar Corona using Octree Compression  

NASA Astrophysics Data System (ADS)

We present a new powerful tool to simulate the streamer belt of the solar corona based on forward modeling. It takes into account the temporal evolution of the corona and provides both qualitative and quantitative results. Starting from the National Solar Observatory photospheric magnetograms, the position of the neutral line at the source surface (2.5 Rsun) is caculated using the potential field source surface model. The plasma sheet of the streamer belt is centered around the current sheet represented as the radial extension of the neutral line. The 3D electron density is represented with octree compression and the radiance images are computed by a ray-tracing algorithm implementing the Thomson scattering. A multi-octree method allows to simulate the temporal evolution of the streamer belt and to compute the synoptic maps from time-series of generated images. The comparison between the synoptic maps of the streamer belt obtained with the SOHO/LASCO-C2 coronagraph and the simulated synoptic maps constructed from our model shows a global agreement for both radiance profiles and global behaviour of the streamer and confirms earlier findings by Wang et al. (1997) that the streamers are associated with folds in the plasma sheet. However, some features cannot be explained using this method and are interpreted by introducing two types of large-scale structures. Our results suggest that the potential field source surface model is not fully adequate for the description of the fine structure of the streamer belt, even during the time of low solar activity. We present new applications of our method to future coronographic observations with SECCHI/COR-2 on STEREO and SILC on Solar Orbiter.

Saez, F.; Lamy, P.; Llebaria, A.

375

THE EXPANSION OF ACTIVE REGIONS INTO THE EXTENDED SOLAR CORONA  

SciTech Connect

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

Morgan, Huw; Jeska, Lauren; Leonard, Drew, E-mail: hmorgan@aber.ac.uk [Sefydliad Mathemateg a Ffiseg, Prifysgol Aberystwyth, Ceredigion SY23 3BZ (United Kingdom)

2013-06-01

376

Is the Quiet-Sun Corona a Quasi-steady, Force-free Environment?  

NASA Astrophysics Data System (ADS)

We model a coronal volume over a quiet, mixed-polarity solar network as an ensemble of quasi-steady loop atmospheres. These are contained by an assumed potential field, including the associated variations in the loop cross section through the coronal volume and the loop flows induced by such asymmetries. The average temperature and density stratifications are close to those of the quiet-Sun corona for a coronal heating flux density into the corona of FH=8×1014B/L (ergs cm-2 s-1) for loop-base field strengths B (G) and loop half-lengths L (cm). Earlier, that heating parameterization was shown to be consistent with the appearance and radiative losses of a solar corona in which active regions dominated the emission. This study thus supports the hypothesis that the same, likely braiding-driven, heating dominates throughout the quiescent corona. The average ratio ? of gas to magnetic pressure lies close to unity throughout the modeled coronal height range of 22 Mm, with ?>1 in ~30% of the volume and ?>0.4 in ~90% of the volume, perhaps indicating that the quiet-Sun corona is driven to near its maximum heating capacity by the random walk of its footpoints. Our findings that the solar corona has ? close to unity, and that our model corona exhibits insufficient fine structure and no significant spatially averaged Doppler shifts, imply that the quiet-Sun corona is often neither quasi-steady nor force free and thus that dynamic magnetohydrodynamics (MHD) models are essential to furthering our understanding of the quiet solar corona.

Schrijver, Carolus J.; van Ballegooijen, Adriaan A.

2005-09-01

377

The effect of corona wire heating on the downstream ozone concentration profiles in an air-cleaning wire-duct electrostatic precipitator  

Microsoft Academic Search

The effect of corona wire heating on the downstream ozone concentration profiles in an air-cleaning wire-duct electrostatic precipitator was studied experimentally. The results show that ozone concentration profiles depend significantly on the applied voltage and polarity. Significant ozone concentrations were only observed in a narrow region downstream of the corona wire for positive coronas. For the corona wire surface temperature

TOSHIKAZU OHKUBO; SYUNSAKU HAMASAKI; YUKIHARU NOMOTO; JEN-SHIH CHANG; TAKAYOSHI ADACHI

1990-01-01

378

Oxidation of nitric oxide in a two-stage chemical scrubber using dc corona discharge.  

PubMed

The dc corona was studied as an alternative for NO oxidation in a two-stage chemical scrubber. The dc corona plasma reactor completely oxidized 150ppm of NO to NO2 in an air stream. The NO2 was further oxidized at a higher voltage. For some cases, the NO2 in the effluents of the plasma reactor was absorbed quantitatively by a caustic sodium sulfite aqueous solution in a 2l bubble column gas absorber. The outlet concentrations of both NO and NO2 from the plasma-scrubber combination system (corona-induced chemical scrubber) were below the detection limit of the chemiluminescent NOx analyzer. PMID:11080574

Yang, C L; Chen, L

2000-12-30

379

Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination  

NASA Technical Reports Server (NTRS)

Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

Smrekar, Suzanne E.; Stofan, Ellen R.

1997-01-01

380

Unraveling the commercial market for medicinal plants and plant parts on the witwatersrand, South Africa  

Microsoft Academic Search

To unravel the market for commercial medicinal plants on the Witwatersrand in South Africa, a semiquantitative approach was\\u000a taken. A stratified random sample of 50 herb-traders was surveyed, and an inventory of all plants and parts sold was compiled.\\u000a Research participants were questioned on the scarcity and popularity of the plants traded, as well as suppliers and origins.\\u000a The rarefaction

Vivienne L. Williams; Kevin Balkwill; Edward T. F. Witkowski

2000-01-01

381

HEATING IN AN EXTENDED ACCRETION DISK CORONA ALONG THE Z-PATTERN IN CYG X-2  

E-print Network

We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting ...

Schulz, Norbert S.

382

A study of inner solar corona during total solar eclipse of October 24, 1995.  

NASA Astrophysics Data System (ADS)

An experiment to study the intensity variations in the inner corona was setup at Kalpi, in Uttar Pradesh, during the total solar eclipse of October 24, 1995. The details of the experiment and the preliminary results are presented.

Saxena, A. K.; Cowsik, R.; Lancelot, J. P.; Samson, J. P. A.; Bagare, S. P.; Ismail, R.

383

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

E-print Network

the oscillating corona discharge and the rapidly-growing streamer discharge is determined by the radius of curvature of the anode. In this contribution, the transition radius of curvature is found analytically using simplified models of each discharge...

Humbird, Kelli D

2013-01-31

384

A study of the expansin of the solar corona with radiation heat flux  

Microsoft Academic Search

The expansion of the solar corona, with the aid of hydrodynamic blast wave theory using the concept of the Roche model, is studied here when both the solar gravity and radiation heat flux are taken into consideration.

J. B. Bhowmick

1980-01-01

385

A gas-dynamic calculation of type 2 shock propagation through the corona  

NASA Technical Reports Server (NTRS)

An approximate analytic theory of acoustic shock propagation in nonuniform media is used to determine the motion of a flare-generated shock wave in the corona. The shock is followed from the time it strikes the chromosphere-corona transition region (density interface) out to 5 solar radii under the assumption that the corona in this region is approximately in hydrostatic equilibrium. The strength of the shock incident on the transition region from below determines the ejection velocity of eruptive prominence material, as well as the initial velocity of the coronal shock. The calculation is applied to one well-documented case of a related flare spray, moving type 4 isolated source, and type 2 burst. It is shown that a chromospheric shock of the appropriate strength to produce the observed prominence and type 4 velocities strengthens as it moves out in the corona by an amount sufficient to account for the observed high velocity of the type 2 burst.

Kopp, R. A.

1972-01-01

386

Mechanical-wave dissipation in the lower corona: Empirical requirements for quiet regions  

NASA Technical Reports Server (NTRS)

The relation between dissipation and temperature structure in the lower corona was empirically determined. This relation was then used in conjunction with the observed structure to estimate the damping length for mechanical waves.

Moore, R. L.

1972-01-01

387

Observaciones de la corona solar interior con un coronógrafo de espejo  

NASA Astrophysics Data System (ADS)

El plasma de la corona solar es un buen indicador de las líneas de fuerza del campo magnético. Por lo tanto, el análisis de estructuras coronales cuasiestacionarias en la corona da importante información sobre el campo magnético y la actividad asociada. Se trata de poner límites a los modelos teóricos existentes mediante el estudio de distintas estructuras en la corona interior. En agosto de 1997 comenzó a operar el coronógrafo solar (MICA) en El Leoncito como parte del Observatorio Solar Alemán-Argentino. Desde su instalación obtiene imágenes de la corona solar (1.05 a 2.0 radios solares) en 2 líneas espectrales correspondientes a la emisión de Fe XIV y Fe X. El instrumento puede obtener imágenes cada minuto por lo que es ideal para estudiar procesos rápidos. Presentamos observaciones recientes que muestran la capacidad del coronógrafo así como la evolución de algunos eventos dinámicos observados por MICA.

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

388

Sterilisation of Hydroponic Culture Solution Contaminated by Fungi using an Atmospheric Pressure Corona Discharge  

NASA Astrophysics Data System (ADS)

The hydroponic culture solution contaminated by fungi is sterilised by a DC corona discharge, and the sterilisation characteristics are investigated in this work. A DC streamer corona discharge is generated at atmospheric pressure in air between needle clusters and a water bath containing contaminated solution by fungus such as Fusarium oxysporum f. sp. spinaciae or Fusarium sp.. It is found that the fungi are killed by the exposure of the corona discharge, and that the death rates of the fungi chiefly depend on the concentration of the hydroponic culture solutions. It is also found that the number densities of the fungi decrease exponentially with the energy expenditure of the corona discharge, and that damping coefficients of the fungi densities depend on the concentration of the hydroponic culture solutions. This suggests that the fungi are chiefly inactivated by electroporation.

Mizukami, Kohji; Satoh, Kohki; Kanayama, Hiroshi; Itoh, Hidenori; Tagashira, Hiroaki; Shimozuma, Mitsuo; Okamoto, Hiroyuki; Takasaki, Satoko; Kinoshita, Muneshige

389

Effects of corona on heat transfer in an enclosure. Master's thesis  

Microsoft Academic Search

Experiments were conducted to determine the effects of corona wind on heat-transfer rates for enclosures. Tests were performed with an enclosed cavity heated on the bottom and cooled on the top (and vice versa). A corona wind was established inside the cavity by applying high voltages to 0.004-inch-diameter chromel wires placed along the hot and cold surfaces of the cavity.

Dyer

1986-01-01

390

Corona induced non-thermal plasmas: Fundamental study and industrial applications  

Microsoft Academic Search

Our investigations on corona induced non-thermal plasmas include both fundamental study and products development. This paper presents our recent work in following subjects: investigation on characteristics of pulsed corona discharge in relation with flue gas cleaning; evaluation of high voltage power supply; design of plasma reactor; experimental study on DeNOx and DeSO2; decomposition of VOCs and indoor air cleaning.

Keping Yan; Hexing Hui; Mi Cui; Jinsong Miao; Xiaoli Wu; Chongguang Bao; Ruinian Li

1998-01-01

391

Energy?dependent ionization states of shock?accelerated particles in the solar corona  

Microsoft Academic Search

We examine the range of possible energy de- pendence of the ionization states of ions that are shock- accelerated from the ambient plasma of the solar corona. If acceleration begins in a region of moderate density, suffi- ciently low in the corona, ions above ~0.1 MeV\\/amu approach an equilibrium charge state that depends primarily upon their speed and only weakly

D. V. Reames; C. K. Ng; A. J. Tylka

1999-01-01

392

EFFECT OF OXYGEN ON NOx REMOVAL IN CORONA DISCHARGE FIELD: NOx BEHAVIOR WITHOUT A REDUCING AGENT  

Microsoft Academic Search

A DeNOx process using a DC corona discharge was investigated experimentally. A mixture system of N2\\/O2\\/NO was used as a test gas. The compositions such as NO, NO2, N2O and so on were analyzed with Fourier transform infrared spectroscopy and an NOx meter. It was found that the characteristics of NO removal by corona discharge differed remarkably whether or not

M. ARAI; M. SAITO; S. YOSHINAGA

2004-01-01

393

Characteristics of negative corona discharge in the working media of atmospheric-pressure nitrogen lasers  

Microsoft Academic Search

We present the results of investigations of the electrical and optical characteristics of a negative-polarity corona discharge\\u000a excited in systems of “pins-mesh” and “pins-plane” electrodes in a He\\/N2 mixture at atmospheric pressure. In order that such a corona discharge could be applied in systems of electric pumping of\\u000a the working medium of atmospheric-pressure N2-lasers, the optimum conditions should be: the

A. K. Shuaibov; L. L. Shimon; A. I. Minya; A. I. Dashchenko

1997-01-01

394

Study on Spraying Corona Discharge Technology with Grounding 1 Discharge Electrodes for Purifying Flue-gas  

Microsoft Academic Search

This study focused on a new electrostatic precipitation technology of spraying corona discharges with grounding discharge electrodes for purifying flue-gas. DC positive high-voltage was connected to collecting electrodes and water discharge electrodes were grounded. A lasting and effective electrostatic removal of dust with minimized drain water would be achieved by wet or semi-wet spraying corona discharges. The experimental researches on

Dexuan Xu; Shanshan Lin; Yujia Wang; Zhiming Guo; Weili Ge

395

A GENERAL RELATIVISTIC MODEL OF ACCRETION DISKS WITH CORONAE SURROUNDING KERR BLACK HOLES  

SciTech Connect

We calculate the structure of a standard accretion disk with a corona surrounding a massive Kerr black hole in the general relativistic frame, in which the corona is assumed to be heated by the reconnection of the strongly buoyant magnetic fields generated in the cold accretion disk. The emergent spectra of accretion disk-corona systems are calculated by using the relativistic ray-tracing method. We propose a new method to calculate the emergent Comptonized spectra from the coronae. The spectra of disk-corona systems with a modified {alpha}-magnetic stress show that both the hard X-ray spectral index and the hard X-ray bolometric correction factor L{sub bol}/L{sub X,2-10keV} increase with the dimensionless mass accretion rate, which is qualitatively consistent with the observations of active galactic nuclei. The fraction of the power dissipated in the corona decreases with increasing black hole spin parameter a, which leads to lower electron temperatures of the coronae for rapidly spinning black holes. The X-ray emission from the coronae surrounding rapidly spinning black holes becomes weak and soft. The ratio of the X-ray luminosity to the optical/UV luminosity increases with the viewing angle, while the spectral shape in the X-ray band is insensitive to the viewing angle. We find that the spectral index in the infrared waveband depends on the mass accretion rate and the black hole spin a, which deviates from the f{sub {nu}}{proportional_to}{nu}{sup 1/3} relation expected by the standard thin disk model.

You Bei; Cao Xinwu [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Yuan Yefei, E-mail: youbei@shao.ac.cn, E-mail: cxw@shao.ac.cn, E-mail: yfyuan@ustc.edu.cn [Department of Astronomy, University of Sciences and Technology of China, Hefei, Anhui 230026 (China)

2012-12-20

396

An empirically-driven global MHD model of the solar corona and inner heliosphere  

Microsoft Academic Search

In this study we describe a three-dimensional MHD model of the solar corona and heliosphere. We split the modeling region into two distinct parts: the solar corona (1 solar radius, RS, to 30RS) and the inner heliosphere (30RS to 5 AU). This combined model is driven solely by the observed line-of-sight photospheric magnetic field and can thus provide a realistic

Pete Riley; J. A. Linker; Z. Mikic

2001-01-01

397

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

NASA Technical Reports Server (NTRS)

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

Gopalswamy, N.; Nitta, N.

2011-01-01

398

Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure  

NASA Technical Reports Server (NTRS)

The solar corona is much hotter (>=10(exp 6) K) than its surface (approx 6000 K), puzzling astrophysicists for several decades. Active region (AR) corona is again hotter than the quiet Sun (QS) corona by a factor of 4-10. The most widely accepted mechanism that could heat the active region corona is the energy release by current dissipation via reconnection of braided magnetic field structure, first proposed by E. N. Parker three decades ago. The first observational evidence for this mechanism has only recently been presented by Cirtain et al. by using High-resolution Coronal Imager (Hi-C) observations of an AR corona at a spatial resolution of 0.2 arcsec, which is required to resolve the coronal loops, and was not available before the rocket flight of Hi-C in July 2012. The Hi-C project is led by NASA/MSFC. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. We are currently investigating the changes taking place in photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. For this purpose, we are also using SDO/AIA data of +/- 2 hours around the 5 minutes Hi-C flight. In the present talk, I will first summarize some of the results of the Hi-C observations and then present some results from our recent analysis on what photospheric processes feed the magnetic energy that dissipates into heat in coronal loops.

Tiwari, S. K.; Alexander, C. E.; Winebarger, A.; Moore, R. L.

2014-01-01

399

Brightness variations of the white light corona during the years 1964–67  

Microsoft Academic Search

Observations of the white light corona were made on over 900 days during the years 1964–67 at heights between 1.125 and 2.0 R? with the K-coronameter at Mount Haleakala and Mauna Loa, Hawaii. The brightness distribution of the minimum corona was elliptical with average equatorial intensities three times the polar. Coronal features of the new cycle at 1.125 R? occurred

Richard T. Hansen; Charles J. Garcia; Shirley F. Hansen; Harold G. Loomis

1969-01-01

400

Weak Compressible Magnetohydrodynamic Turbulence in the Solar Corona Benjamin D. G. Chandran  

E-print Network

heating, but for particle acceleration in solar flares as well [15,16]. The MHD momentum and induction explanation for the anisotropic heating of minor ions in the solar corona. DOI: 10.1103/PhysRevLett.95.265004 PACS numbers: 52.35.Bj, 52.35.Ra, 96.60.Pb, 96.60.Rd The heating of the solar corona is a long

Chandran, Ben

401

Studies of corona and back discharges in carbon dioxide  

NASA Astrophysics Data System (ADS)

Results of spectroscopic investigations and current-voltage characteristics of corona and back discharges generated in point-plane electrode geometry in CO2 at atmospheric pressure for positive and negative polarity of the discharge electrode are presented in the paper. Three forms of back discharge, for both polarities, were investigated: glow, streamer and low-current back-arc. To generate the back-discharges for the conditions similar to electrostatic precipitator, the plate electrode was covered with fly ash layer. In order to characterize back discharge processes, the emission spectra were measured and compared with those obtained for normal discharge, generated in the same electrode configuration but without the fly ash layer on the plate electrode. The measurements have shown that optical emission spectral lines of atoms and molecules, excited or ionised in back discharge, depend on the forms of the discharge, the discharge current, and are different in the zones close to needle electrode and fly ash layer. From the comparison of spectral lines of back and normal discharges, an effect of fly ash layer on discharge characteristics and morphology has been determined. In normal corona, the emission spectra are mainly predetermined by the working gas components, but in the case of back discharge, the atomic and molecular lines, resulting from chemical composition of fly ash, are also identified. Differences in the spectra of back discharge for positive and negative polarities of the needle electrode have been explained by considering the kind of ions generated in the crater in fly ash layer. For back arc, the emission of spectral lines of atoms and molecules from fly ash layer can be recorded in the crater zone, but in the needle zone, only the emission lines of CO2 and its decomposition products (CO and C2) can be noticed. The studies of back discharge in CO2, as one of the main components of flue gases, were undertaken because this type of discharge, after unwanted inception, decreases the energy and collection efficiencies of electrostatic precipitator. The second reason behind these studies is that CO2 is the main component of flue gas leaving oxyfuel boiler that re-circulates in the combustion-precipitation cycle. It was shown that discharges in CO2 lead to contamination of discharge electrode with carbonaceous products that can cause severe maintenance problems of electrostatic precipitator. The recognition of the characteristics of electrostatic precipitator operating in the oxyfuel system is, therefore, of crucial importance for exhaust gas cleaning in modern combustion systems.

Czech, Tadeusz; Sobczyk, Arkadiusz Tomasz; Jaworek, Anatol; Krupa, Andrzej; Rajch, Eryk

2013-01-01

402

Study on earthed atomizing corona discharge enhancing the biodegradability of waste water from oil extraction  

NASA Astrophysics Data System (ADS)

This paper studies the usage of earthed atomizing corona discharge to dispose waste water from oil extraction. The I-V characteristic curves of earthed atomizing positive and negative corona discharge are compared to study the influence of water flux and inter-electrode distance (which refers to the distance between line electrode and plate electrodes) on discharge characteristics, and to measure the turbidity, pH, biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and the variation tendency of BOD5/COD in the process of dealing with waste water from oil extraction by earthed atomizing corona discharge. Ultimately, the mechanism of earthed atomizing corona discharge is analyzed. Research results indicate that when using earthed atomizing corona discharge to dispose of waste water from oil extraction, as the processing time grows there is a maximum value of turbidity, the pH level increases gradually then stabilizes, COD appears to descend, and BOD5 as well as BOD5/COD both have minimum values. When the processing time attains 300 min, waste water from oil extraction is suitable for biochemical treatment, foreshadowing that earthed atomizing corona discharge technology demonstrates energy conservation characteristic in improving the biodegradability of waste water from oil extraction and has a brilliant application prospect waiting ahead.

Du, S.; Xu, J.; Mi, J.; Li, N.

2012-10-01

403

TOWARD A REALISTIC THERMODYNAMIC MAGNETOHYDRODYNAMIC MODEL OF THE GLOBAL SOLAR CORONA  

SciTech Connect

In this work, we describe our implementation of a thermodynamic energy equation into the global corona model of the Space Weather Modeling Framework and its development into the new lower corona (LC) model. This work includes the integration of the additional energy transport terms of coronal heating, electron heat conduction, and optically thin radiative cooling into the governing magnetohydrodynamic (MHD) energy equation. We examine two different boundary conditions using this model; one set in the upper transition region (the radiative energy balance model), as well as a uniform chromospheric condition where the transition region can be modeled in its entirety. Via observation synthesis from model results and the subsequent comparison to full Sun extreme ultraviolet and soft X-ray observations of Carrington rotation 1913 centered on 1996 August 27, we demonstrate the need for these additional considerations when using global MHD models to describe the unique conditions in the low corona. Through multiple simulations, we examine the ability of the LC model to assess and discriminate between coronal heating models, and find that a relative simple empirical heating model is adequate in reproducing structures observed in the low corona. We show that the interplay between coronal heating and electron heat conduction provides significant feedback onto the three-dimensional magnetic topology in the low corona as compared to a potential field extrapolation, and that this feedback is largely dependent on the amount of mechanical energy introduced into the corona.

Downs, Cooper; Roussev, Ilia I.; Lugaz, Noe [Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Van der Holst, Bart; Sokolov, Igor V.; Gombosi, Tamas I., E-mail: cdowns@ifa.hawaii.ed [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)

2010-04-01

404

Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-Heated Corona  

E-print Network

We investigate the iron K$\\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk photoelectrically absorb X-ray photons and radiate K$\\alpha$ line photons. Therefore, the activity of corona is responsible to the iron line emission from the underlying disk. In previous studies, oversimplified X-ray photon sources are often assumed above the disk in order to compute the iron line profile or power-law line emissivity profiles are assumed with an index being a free parameter. We adopt the more realistic corona model constructed by Liu et al. in which the corona is heated by magnetic energy released through the reconnection of magnetic flux loops and which has no free parameter. Then the accretion energy is dominantly dissipated in the corona, in which X-ray photons are efficiently produced and irradiate the underlying disk. We find the local emmisivity of iron line on the disk is approximated as $F_{{\\rm K}\\alpha}(r)\\propto r^{-5}$. The iron line profiles derived from this model give excellent fits to the observational data of MCG-6-30-15 with the profiles derived theoretically for $i\\sim 30^{\\circ}$ for energy band 4-7keV. Possible origins of line variability are briefly discussed.

N. Kawanaka; S. Mineshige; K. Iwasawa

2005-08-24

405

Properties of vertically self-gravitating accretion discs with a dissipative corona  

E-print Network

The steady-state structure of a disc with a corona is analyzed when the vertical component of the gravitational force due to the self-gravity of the disc is considered. For the energy exchange between the disc and the corona, we assume a fraction f of the dissipated energy inside the accretion disc is transported to the corona via the magnetic tubes. Analytical solutions corresponding to a prescription for f (in which this parameter directly depends on the ratio of the gas pressure to the total pressure) or free f are presented and their physical properties are studied in detail. We show that the existence of the corona not only decreases the temperature of the disc, but also increases the surface density.The vertical component of the gravitational force due to the self-gravity of the disc decreases the self-gravitating radius and the mass of the fragments at this radius. However, as more energy is transported from the disc to the corona, the effect of the vertical component of the gravitational force due to the self-gravity of the disc on the self-gravitating radius becomes weaker, though the mass of the fragments is reduced irrespective of the amount of the energy exchange from the disc to the corona.

Fazeleh Khajenabi; Peter Duffy

2008-05-30

406

Corona discharges and their effect on lightning attachment revisited: Upward leader initiation and downward leader interception  

NASA Astrophysics Data System (ADS)

Previous studies have suggested the possibility of using glow corona discharges to control the frequency of lightning flashes to grounded objects. In order to revisit the theoretical basis of this proposal, the self-consistent leader inception and propagation model - SLIM - is used together with a two-dimensional glow corona drift model. The analysis is performed to quantify the effect of glow corona generated at the tip of ground-based objects on the initiation and propagation of upward positive connecting leaders under the influence of downward lightning leaders. It is found that the presence of glow corona does not influence the performance of Franklin lightning rods shorter than 15 m, while it slightly reduces the lateral distance of rods up to 60 m tall by a maximum of 10%. Furthermore, the results indicate that it is not possible to suppress the initiation of upward connecting leaders by means of glow corona. It is found instead that unconventional lightning protection systems based on the generation of glow corona attract downward lightning flashes in a similar way as a standard lightning rod with the same height.

Becerra, Marley

2014-11-01

407

The effect of protein corona composition on the interaction of carbon nanotubes with human blood platelets.  

PubMed

Carbon nanotubes (CNT) are one of the most promising nanomaterials for use in medicine. The blood biocompatibility of CNT is a critical safety issue. In the bloodstream, proteins bind to CNT through non-covalent interactions to form a protein corona, thereby largely defining the biological properties of the CNT. Here, we characterize the interactions of carboxylated-multiwalled carbon nanotubes (CNTCOOH) with common human proteins and investigate the effect of the different protein coronas on the interaction of CNTCOOH with human blood platelets (PLT). Molecular modeling and different photophysical techniques were employed to characterize the binding of albumin (HSA), fibrinogen (FBG), ?-globulins (IgG) and histone H1 (H1) on CNTCOOH. We found that the identity of protein forming the corona greatly affects the outcome of CNTCOOH's interaction with blood PLT. Bare CNTCOOH-induced PLT aggregation and the release of platelet membrane microparticles (PMP). HSA corona attenuated the PLT aggregating activity of CNTCOOH, while FBG caused the agglomeration of CNTCOOH nanomaterial, thereby diminishing the effect of CNTCOOH on PLT. In contrast, the IgG corona caused PLT fragmentation, and the H1 corona induced a strong PLT aggregation, thus potentiating the release of PMP. PMID:24831972

De Paoli, Silvia H; Diduch, Lukas L; Tegegn, Tseday Z; Orecna, Martina; Strader, Michael B; Karnaukhova, Elena; Bonevich, John E; Holada, Karel; Simak, Jan

2014-08-01

408

Experimental Study of Magnetic Field Effect on dc Corona Discharge in Low Vacuum  

NASA Astrophysics Data System (ADS)

In the present paper, an attempt was made to investigate the effect of applying a transverse magnetic field on the dc corona discharge behavior in low vacuum. In general, two experiments were carried out in this work: the first is the ionization-region magnetic field experiment, and the second was the drift region magnetic field experiment. In these experiments, permanent magnets were used to produce magnetic field. The degree of vacuum used in this test was 0.4×105 Pa. It is found that the effect of the magnetic field increases as the degree of vacuum increases. It is also seen from this study that the corona current values are higher with magnetic fields than without magnetic fields. The experimental results indicate that the enhancement of the magnetic field near the wire discharge electrode has a significant influence on the increment of the discharge current. The effect of the magnetic field on the discharge current is the most significant with the negative corona discharges rather than with positive corona discharge. In contrast to, the curves were demonstrated that the application of magnetic fields in drift region magnetic field does not significantly change the corona discharge current. Discharge characteristics of magnetically enhanced corona discharges, extracted from this study, can be applied to various industrial applications, such as, in an electrostatic enhancement filter for the purpose of capturing fine particles, and as effective method for production of high ozone concentrations in a generator as compared to the ultraviolet (UV) radiation method.

Elabbas, K.

2014-09-01

409

ISS and Space Shuttle Radiation Measurements at Solar Minimum  

NASA Technical Reports Server (NTRS)

A summary of 2008-2011 ISS and Space Shuttle radiation dosimetry results for inside vehicle radiation monitoring in low-Earth orbit will be presented. Results include new data from ISS Expedition 22-25/20A radiation area monitors (RAM) and Shuttle Missions STS127-STS133 passive radiation dosimeters (PRD). ISS 20A radiation measurement locations included three Node 2 crew quarters locations at NOD2S5_CQ, NOD2P5_CQ and CQ-3 (Deck), as well as ESA Columbus, and JAXA Kibo locations. ISS 20A and STS127-STS133 missions were flown at 51.6 inclination with an altitude range of 330-350 km. The passive radiation results will be presented in terms of measured daily dose obtained using luminescence detectors (i.e., Al2O3:C, LiF:Mg,Ti and CaF2:Tm). In addition, preliminary results from the DOSIS 2 Project, in collaboration with the German Space Agency (DLR) will be presented. SRAG s participation to the DOSIS 2 exposure on ISS (11/16/2009-05/26/2010) involved passive radiation measurements at 10 different shielding locations inside the ESA Columbus Module.

Gaza, Ramona; Welton, Andrew; Dunegan, Audrey; Lee, Kerry

2011-01-01

410

Bipolar climatology of GPS ionospheric scintillation at solar minimum  

NASA Astrophysics Data System (ADS)

High-rate sampling data of Global Navigation Satellite Systems ionospheric scintillation acquired by a network of GPS Ionospheric Scintillation and TEC Monitor receivers located in the Svalbard Islands, in Norway and in Antarctica have been analyzed. The aim is to describe the “scintillation climatology” of the high-latitude ionosphere over both the poles under quiet conditions of the near-Earth environment. For climatology we mean to assess the general recurrent features of the ionospheric irregularities dynamics and temporal evolution on long data series, trying to catch eventual correspondences with scintillation occurrence. In spite of the fact that the sites are not geomagnetically conjugate, long series of data recorded by the same kind of receivers provide a rare opportunity to draw a picture of the ionospheric features characterizing the scintillation conditions over high latitudes. The method adopted is the Ground Based Scintillation Climatology, which produces maps of scintillation occurrence and of total electron content relative variation to investigate ionospheric scintillations scenario in terms of geomagnetic and geographic coordinates, interplanetary magnetic field conditions and seasonal variability. By means of such a novel and original description of the ionospheric irregularities, our work provides insights to speculate on the cause-effect mechanisms producing scintillations, suggesting the roles of the high-latitude ionospheric trough, of the auroral boundaries and of the polar cap ionosphere in hosting those irregularities causing scintillations over both the hemispheres at high latitude. The method can constitute a first step toward the development of new algorithms to forecast the scintillations during space weather events.

Alfonsi, Lucilla; Spogli, Luca; De Franceschi, Giorgiana; Romano, Vincenzo; Aquino, Marcio; Dodson, Alan; Mitchell, Cathryn N.

2011-06-01

411

Comprehensive Observations of a Solar Minimum CME with STEREO  

E-print Network

We perform the first kinematic analysis of a CME observed by both imaging and in situ instruments on board STEREO, namely the SECCHI, PLASTIC, and IMPACT experiments. Launched on 2008 February 4, the CME is tracked continuously from initiation to 1 AU using the SECCHI imagers on both STEREO spacecraft, and is then detected by the PLASTIC and IMPACT particle and field detectors on board STEREO-B. The CME is also detected in situ by ACE and SOHO/CELIAS at Earth's L1 Lagrangian point. The CME hits STEREO-B, ACE, and SOHO on 2008 February 7, but misses STEREO-A entirely. This event provides a good example of just how different the same event can look when viewed from different perspectives. We also demonstrate many ways in which the comprehensive and continuous coverage of this CME by STEREO improves confidence in our assessment of its kinematic behavior, with potential ramifications for space weather forecasting. The observations provide several lines of evidence in favor of the observable part of the CME being narrow in angular extent, a determination crucial for deciding how best to convert observed CME elongation angles from Sun-center to actual Sun-center distances.

B. E. Wood; R. A. Howard; S. P. Plunkett; D. G. Socker

2008-11-19

412

Climatology of GPS scintillations over Antarctica under solar minimum conditions  

NASA Astrophysics Data System (ADS)

We analyse GNSS ionospheric scintillation data recorded in Antarctica to investigate the conditions of the near-Earth environment leading to scintillation scenarios, producing a "scintillation climatology" over a large geomagnetic quiet period. Within this scope we realize maps of scintillation occurrence as a function of the magnetic local time (MLT) and of the altitude adjusted corrected geomagnetic coordinates (AACGM). The maps are realized merging observations of two GISTMs (GPS Ionospheric Scintillation and TEC Monitor) located at Mario Zucchelli Station (74.7°S, 164.1°E) and Concordia Station (75.1°S, 123.2°E) in Antarctica during 2008. The results highlight the possibility to investigate the impact of ionospheric irregularities on the phase and amplitude of GNSS signals, evidencing the cusp/cap and auroral contributions. This works aims to contribute to the development of nowcasting and forecasting tools for GNSS ionospheric scintillation.

Spogli, Luca; Alfonsi, Lucilla; Romano, Vincenzo; de Franceschi, Giorgiana; Mitchell, Cathryn N.

2010-05-01

413

Molecular exchange in block copolymer micelles: when corona chains overlap  

NASA Astrophysics Data System (ADS)

The chain exchange kinetics of poly(styrene-b-ethylenepropylene) (PS-PEP) diblock copolymer micelles in squalane (C30H62) was investigated using time-resolved small angle neutron scattering (TR-SANS). The solvent is a mixture of h-squalane and d-squalane that contrast-matches a mixed 50/50 h/d PS micelle core. As isotope labeled chains exchange, the core contrast decreases, leading to a reduction in scattering intensity. This strategy therefore allows direct probing of the chain exchange rate. Separate copolymer micellar solutions containing either deuterium labeled (dPS) or normal (hPS) poly(styrene) core blocks were prepared and mixed at room temperature, below the core glass transition temperature. The samples were heated to several temperatures (around 100 ^oC) and monitored by TR-SANS every 5 min. As polymer concentration was increased from 1% to 15% by volume, we observed a significant slowing down of chain exchange rate. Similar retarded kinetics was found when part of the solvent in the 1% solution was replaced by homopolymer PEP (comparable size as corona block). Furthermore, if all the solvent is replaced with PEP, no exchange was detected for up to 3hr at 200 ^oC. These results will be discussed in terms of a molecular model for chain exchange

Lu, Jie; Lodge, Timothy; Bates, Frank; Choi, Soohyung

2013-03-01

414

The innermost corona observed at the 1973 June 30 eclipse  

NASA Astrophysics Data System (ADS)

Slitless flash spectrograms in heights below 8000 km above the solar limb were obtained by the University of Kyoto expedition at Atar, Mauritania. The integrated intensities of Fe XIV, Fe X, Fe XI, and the continuum are measured as a function of height above the solar limb at 11 points around the third contact point. It is found that a significant amount of the emission in Fe X originates in chromospheric levels well below 8000 km. This implies that the interspicular region of the chromosphere is occupied by coronal material. The average values of the electron temperature (0.9-1.1 million K) and the electron density in the interspicular region are derived from the Fe X and the Fe XI intensities (0.9-1 billion/cu cm) on the assumption of spherical symmetry. The intensity variations of the coronal lines and the continuum with position angle are also studied. Strong correlations between Fe XIV and the continuum and between Fe X and Fe XI are found. The Fe X intensities indicate a density fluctuation in the innermost corona by at least a factor of two.

Hanaoka, Yoichiro; Kanno, Mitsuo; Kurokawa, Hiroki; Tsubaki, Tokio

1986-07-01

415

HST Observations and Modeling of the Martian Hydrogen Corona  

NASA Astrophysics Data System (ADS)

We present an analysis of HST ACS/SBC UV images of the extended H Ly alpha emission from the Martian hydrogen corona obtained over Oct/Nov 2007. The observations have been presented previously. This work will present a comparison of the distribution of the coronal Lyman alpha emission with simulations of the distribution of H atoms in the martian exosphere based on a monte carlo code for particle trajectories. It is assumed that all emission is produced by resonant scattering of solar Lyman alpha. We limit the comparison to the optically thin emission regions above the martian exobase, and vary the H temperature, the presence of a superthermal population, and the variation of source rate with angle from the sub-solar point to fit the observations. Constraints that we can derive on the number, the velocities, and the distribution of fast atoms leaving the martian exobase will provide important information on the escape flux of hydrogen, with relevance to the escape of water from Mars.

Clarke, John T.; Bhattacharyya, D.; Montgomery, J.; Bertaux, J.; Chaufray, J.; Gladstone, R.; Quemerais, E.; Wilson, J.; Schmidt, C.; Mendillo, M.

2012-10-01

416

Millimetric observations of the SZE towards Corona Borealis Supercluster  

NASA Astrophysics Data System (ADS)

We have observed the Corona Borealis Supercluster with the Millimeter and Infrared Testa grigia Observatory (MITO) at 143, 214, 272, and 353 GHz. We present a description of the measure- ments, data analysis, and results together with a comparison of observations performed at 33 GHz with the Very Small Array (VSA). Observations have been made in a region of the supercluster corresponding to one Cosmic Microwave Background (CMB) cold spot previously detected in VSA temperature map. Observational strategy and data analysis are described, explaining the procedures used to disentangle primary and secondary anisotropies in the resulting maps. With a data analysis using map making and the maximum entropy method we claim a weak detection of a faint signal spectrally compatible with a SZ effect characterized at most by a Comptonization parameter y = (7.8-4.4) × 10-6 68% CL. The low level of confidence in the presence of a SZ si- gnal invites us to study this sky region with higher sensitivity and angular resolution experiments like the already planned upgraded versions of VSA and MITO.

Luzzi, Gemma

417

Peptide Fragmentation by Corona Discharge Induced Electrochemical Ionization  

PubMed Central

Fundamental studies have greatly improved our understanding of electrospray, including the underlying electrochemical reactions. Generally regarded as disadvantageous, we have recently shown that corona discharge (CD) can be used as an effective method to create a radical cation species [M]+•, thus optimizing the electrochemical reactions that occur on the surface of the stainless steel (SS) electrospray capillary tip. This technique is known as CD initiated electrochemical ionization (CD-ECI). Here, we report on the fundamental studies using CD-ECI to induce analytically useful in-source fragmentation of a range of molecules that complex transition metals. Compounds that have been selectively fragmented using CD-ECI include enolate forming phenylglycine containing peptides, glycopeptides, nucleosides and phosphopeptides. Collision induced dissociation (CID) or other activation techniques were not necessary for CD-ECI fragmentation. A four step mechanism was proposed: 1. Complexation using either Fe in the SS capillary tip material or Cu(II) as an offline complexation reagent; 2. Electrochemical oxidation of the complexed metal and thus formation of a radical cation (e.g.; Fe - e? ? Fe +•); 3. Radical fragmentation of the complexed compound. 4. Electrospray ionization of the fragmented neutrals. Fragmentation patterns resembling b- and y-type ions were observed and allowed the localization of the phosphorylation sites. PMID:20869880

Lloyd, John R.; Hess, Sonja

2010-01-01

418

Energy release in a turbulent three-dimensional corona  

NASA Astrophysics Data System (ADS)

Recently a lot of theoretical evidence has emerged in support of the hypothesis that coronal dissipation occurs in bursts at very small spatial scales. In this picture, a large number of coherently triggered, unobservable bursts is what appears as one of the many observed solar events (e.g., flares, blinkers, flashes, etc.). Most previous computational studies of this process have been limited to two or two and one half spatial dimensions. In addition, an incompressible model has been used. This is problematical, since the solar corona is three-dimensional and compressible as well. Furthermore, it is unclear how good an approximation reduced magnetohydrodynamics is in the compressible situation. Here we present the first results of our coronal dissipation calculations using a three-dimensional, compressible model. We solve the MHD equations with CRUNCH3D, a massively parallel, viscoresistive, three-dimensional compressible MHD code. The code employs a Fourier collocation spatial discretization, and uses a second-order Runge-Kutta temporal discretization. Published by ElsevieiLtd on behalf of COSPAR.

Dahlburg, R. B.; Einaudi, G.; Velli, M.; Linton, M. G.

2003-09-01

419

Energy release in a turbulent three-dimensional solar corona  

NASA Astrophysics Data System (ADS)

Recently a lot of theoretical evidence has emerged in support of the hypothesis that coronal dissipation occurs in bursts at very small spatial scales. In this picture, a large number of coherently triggered, unobservable bursts is what appears a one of the many observed solar events (e.g., flares blinkers, flashes, etc.). Most previous computational studies of this process have been limited to two or two an half spatial dimensions. In addition, an incompressible model has been used. This is problematical, since the solar corona is three-dimensional and compressible as well. Furthermore, it is unclear how good an approximation reduced magnetohydrodynamics is in the compressible situation. Here we present the first results of our new compressible MHD coronal dissipation calculations. We solve the MHD equations with CRUNCH3D, a massively parallel, visco-resistive, MHD code with compressibility and thermal conduction. The code employs a Fourier collocation spatial discretization, and uses a second-order RungeKutta temporal discretization. Most simulations we will discuss here are run with 64 X 64 X 64 Fourier modes.

Einaudi, G.; Dahlburg, R.; Velli, M.; Linton, M.

420

DRIVEN WAVES AS A DIAGNOSTICS TOOL IN THE SOLAR CORONA  

SciTech Connect

Detecting the signature of Alfven waves in the solar atmosphere remains an observational challenge. At the same time, it could also be an important key to gaining critical understanding of the solar wind and especially of the near-Earth space weather formation. Here, we investigate the plausibility of using inhomogeneous flow-driven compressional fluctuations as a diagnostics tool for Alfven waves in the solar corona. The nature of the fluctuations driven by transverse Alfven waves in inhomogeneous flows was recently investigated by Kaghashvili et al., and analytical solutions that accurately link driven waves to the Alfvenic driver were found. The novelty of this mechanism is that the analysis of the detected compressional fluctuations can provide a clue about the Alfven waves that are otherwise difficult to detect. We review this physical process in a low-beta approximation relevant to solar coronal conditions and outline basic reasons why it can be one of the major processes that comes about as outflowing plasma emerges from divergent coronal holes. After establishing a quantitative link, we consider an example with coronal hole plasma parameters similar to the ones reported recently where evidence for Alfven waves in solar X-ray jets was discussed. We show how this diagnostics tool can be used to analyze the detected intensity fluctuations.

Kaghashvili, Edisher Kh.; Quinn, Richard A. [Atmospheric and Environmental Research, Inc., 131 Hartwell Avenue, Lexington, MA 02421 (United States); Hollweg, Joseph V., E-mail: ekaghash@aer.co [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States)

2009-10-01

421

Chemical Compositions and Abundance Anomalies in Stellar Coronae ADP 99  

NASA Technical Reports Server (NTRS)

Progress has been made using both EUVE (Extreme Ultraviolet Explorer) and ASCA (Advanced Satellite for Cosmology and Astrophysics) data and a new postdoctoral scientist has now been hired. Stars studied to date include YY Gem (dMe binary), xi Boo A (intermediate activity G8 V), xi UMa (more active G quadruple system) HR1099 (K1 IV + G5 V) RS CVn-like, AU Mic (dMe). In addition to a paper that concentrated on abundancies in HR1099, a paper was recently submitted on the coronal abundances of AR(tilde)Lac that revealed an interesting pattern of overabundances of very low FIP elements (Al and Ca) compared to the low FIP elements Si, Mg and Fe. Two papers are nearing completion on methods of analysis and on the abundances in the corona of AU(tilde)Mic. Additionally, two invited conference proceedings papers are being published on this work. The main conclusion of the study to date is that our existing ideas of coronal abundance anomalies need complete revision. The solar-like FIP effect is replaced by a pattern than appears to enhance high FIP elements rather than low FIP elements in very active stars. The archival studies we are undertaking now are revealing some key details of these patterns, and are beginning to map out the anomalies as a function of spectral type, a key goal of this study.

Drake, Jeremy; Oliversen, Ronald J. (Technical Monitor)

2003-01-01

422

Sausage wave oscillations and dampings in the corona  

NASA Astrophysics Data System (ADS)

The frequency and damping rate of fast axisymmetric (Sausage)waves that experience leakage from a coronal structure e.g. jet or loop is studied. In this line we consider a 1-D magnetic cylindrical structure which resembles a jet or loop in the solar corona. We consider the ideal magnetohydrodynamic (MHD) dispersion relation for axisymmetric MHD waves superimposed on a straight magnetic cylinder in the zero ? limit. An analytic study accompanied by numerical calculations has been carried out to model the frequency, damping rate, and phase speed of the sausage wave around the cut-off frequency and in the long wavelength limit. Analytic expressions have been obtained for the damping and frequency of the sausage wave around the cut-off and in the long wave-length limit. These analytic results are compared with numerical computations. The expressions show that the complex frequencies are mainly dominated by the density ratio. In addition, it is shown that the damping eventually becomes independent of the wave number in the long wavelength limit. Hence, interestingly when a high density jet or loop ejects from the solar atmosphere, long wave-length sausage waves guided by the Jet or loop would be observable for a significant number of periods.

Vasheghani Farahani, Soheil; Van Doorsselaere, Tom; Goossens, Marcel; Hornsey, Christopher

423

A dynamical analysis of the Corona Borealis supercluster  

NASA Astrophysics Data System (ADS)

Using data from the Sloan Digital Sky Survey we assess the current dynamical state of the Corona Borealis supercluster (CSC), a highly dense and compact supercluster at z ? 0.07. The Fundamental Plane relation is used to determine redshift-independent distances to six clusters in the densest region of the supercluster, with mean accuracy in the relative distance estimates of 4 per cent. Peculiar velocities determined from these distance estimates indicate that the clusters have broken from the Hubble flow, suggesting that the CSC likely contains two regions that have reached turnaround and are currently undergoing gravitational collapse. These results provide the strongest observational evidence to date that the CSC is a bound system similar to the much more extensive Shapley supercluster, which is the most extensive confirmed bound supercluster yet identified in the Universe. When compared with simulations of the CSC our results require substantially more mass than is contained within the clusters, possibly indicating a significant intercluster dark matter component. In order to facilitate comparison with studies for which spectroscopic data are not available, an alternative analysis of the dynamics is made using the Kormendy relation as a distance indicator. The results are generally consistent with those of the Fundamental Plane and suggest similar global dynamics, but we find that the relatively sparse sampling of the clusters makes the Kormendy relation less reliable overall and more susceptible to small systematic differences between the cluster samples.

Batiste, Merida; Batuski, David J.

2013-12-01

424

Will R Coronae Borealis Ever Return to Maximum Light?  

NASA Astrophysics Data System (ADS)

R Coronae Borealis (R CrB) has been in a deep decline for almost 7 years. Before that, it spent 6 uninterrupted years at maximum light. R CrB is the prototype of its eponymous class of stars, which are very rare, and have many unusual characteristics including extreme hydrogen deficiency, and large, sudden declines in brightness of 8 magnitudes or more. These declines are caused by clouds of carbon dust forming near the atmospheres of the stars, which are later dissipated by radiation pressure. The RCB stars are true irregular variables in that the timing of their declines cannot be predicted, but several RCB stars are also known to begin their declines at a particular phase of their pulsations. There is a wide range of dust formation activity among these stars, as well as as a wide variation in the level of activity for an individual star over time. Long Time Domain observations of the RCB stars are necessary to understand the frequency of their declines, and to give clues about how and when the dust forms around these enigmatic stars.

Clayton, Geoffrey C.

2014-06-01

425

Oxygen Isotopic Ratios in Cool R Coronae Borealis Stars  

NASA Astrophysics Data System (ADS)

We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise 16O/18O ratios for five cool RCB stars. The 16O/18O ratios are derived by spectrum synthesis from high-resolution (R ~ 50, 000) K-band spectra. Lower limits to the 16O/17O and 14N/15N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less 18O than HdC stars—the derived 16O/18O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with 16O/18O = 0.3. Our result of a higher 16O/18O ratio for the RCB stars must be accounted for by a theory of the formation and evolution of HdC and RCB stars. We speculate that a late dredge-up of products of He burning, principally 12C and 16O, may convert an 18O-rich HdC star into an 18O-poor RCB star as the H-deficient star begins its final evolution from a cool supergiant to the top of the white dwarf cooling track.

García-Hernández, D. A.; Lambert, David L.; Kameswara Rao, N.; Hinkle, Ken H.; Eriksson, Kjell

2010-05-01

426

Models for stellar coronae: Numerical methods and examples - Comparison with the minimum flux corona theory - Differences between hydrostatic and dynamic models  

Microsoft Academic Search

A numerical method for the calculation of models of stellar coronae by the solution of the coupled equations of motion, continuity and energy balance is introduced. The method considers the equations as a two-boundary value problem, with the only free parameter being the flux of mechanical energy deep in the photosphere and the position of the transition region being determined

A. G. Hearn; I. M. Vardavas

1981-01-01

427

Combined removal of SO2, NOx, and fly ash from simulated flue gas using pulsed streamer corona  

Microsoft Academic Search

A pulse-energized electron reactor utilizing pulsed streamer corona has been developed for the combined removal of SO2, NO x, and particles from effluent gases. In the pulse-energized electron reactor process, fast-rising narrow high voltage pulses are superimposed on a DC bias voltage and applied to a nonuniform electric field geometry to generate pulsed streamer corona. The pulsed streamer corona produces

J. S. Clements; A. Mizuno; W. C. Finney; R. H. Davis

1989-01-01

428

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

E-print Network

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

Chen, Junhong

429

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

NASA Technical Reports Server (NTRS)

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

Benz, A. O.; Guedel, M.

1994-01-01

430

The role of charged particles in the positive corona-generated photon count in a rod to plane air gap  

SciTech Connect

The relationship between the calculated charged-particle densities in positive corona, the rate of streamer production, and the photon count from the corona were investigated and found to be closely related. Both the densities of electrons and positive ions peaked at 11.8 kV, near the corona inception voltage; they then fell rapidly before slowly rising again. This behavior was exactly matched by the measured photon count. The calculation of the charged-particle density in a positive corona was achieved by means of a fluid model.

Bian, X. M.; Wang, Y. J.; MacAlpine, J. M. K.; Chen, L.; Wang, L. M.; Guan, Z. C. [Graduate School at Shenzhen, Tsinghua University, 518055 Shenzhen (China)] [Graduate School at Shenzhen, Tsinghua University, 518055 Shenzhen (China); Wan, S. W. [State Grid Chongqing Nan'an Power Supply Company, 401336 Chongqing (China)] [State Grid Chongqing Nan'an Power Supply Company, 401336 Chongqing (China); Liu, L. [Department of Physics, Beijing Normal University, 100875 Beijing (China)] [Department of Physics, Beijing Normal University, 100875 Beijing (China)

2013-08-26

431

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

E-print Network

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

Takeru Ken Suzuki

2002-06-14

432

OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS  

SciTech Connect

We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise {sup 16}O/{sup 18}O ratios for five cool RCB stars. The {sup 16}O/{sup 18}O ratios are derived by spectrum synthesis from high-resolution (R {approx} 50, 000) K-band spectra. Lower limits to the {sup 16}O/{sup 17}O and {sup 14}N/{sup 15}N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less {sup 18}O than HdC stars-the derived {sup 16}O/{sup 18}O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with {sup 16}O/{sup 18}O = 0.3. Our result of a higher {sup 16}O/{sup 18}O ratio for the RCB stars must be accounted for by a theory of the formation and evolution of HdC and RCB stars. We speculate that a late dredge-up of products of He burning, principally {sup 12}C and {sup 16}O, may convert an {sup 18}O-rich HdC star into an {sup 18}O-poor RCB star as the H-deficient star begins its final evolution from a cool supergiant to the top of the white dwarf cooling track.

Garcia-Hernandez, D. A. [Instituto de Astrofisica de Canarias (IAC), C/Via Lactea s/n, 38200 La Laguna, Tenerife (Spain); Lambert, David L. [W. J. McDonald Observatory, University of Texas at Austin. 1 University Station, C1400. Austin, TX 78712-0259 (United States); Rao, N. Kameswara [Indian Institute of Astrophysics, Bangalore 560 034 (India); Hinkle, Ken H. [National Optical Astronomy Observatory (NOAO), Tucson, AZ 85726 (United States); Eriksson, Kjell, E-mail: agarcia@iac.e, E-mail: dll@astro.as.utexas.ed, E-mail: nkrao@iiap.res.i, E-mail: hinkle@noao.ed, E-mail: Kjell.Eriksson@astro.uu.s [Department of Physics and Astronomy, Uppsala University, Box 515, 75120 Uppsala (Sweden)

2010-05-01

433

What are the Hot R Coronae Borealis Stars?  

E-print Network

We investigate the evolutionary status of four stars: V348 Sgr, DY Cen and MV Sgr in the Galaxy and HV 2671 in the LMC. These stars have in common random deep declines in visual brightness which are characteristic for R Coronae Borealis (RCB) stars. RCB stars are typically cool, hydrogen deficient supergiants. The four stars studied in this paper are hotter (T$_{\\rm eff}$ = 15-20 kK) than the majority of RCB stars (T$_{\\rm eff}$ = 5000-7000 K). Although these are commonly grouped together as the \\emph{hot RCB stars} they do not necessarily share a common evolutionary history. We present new observational data and an extensive collection of archival and previously-published data which is reassessed to ensure internal consistency. We find temporal variations of various properties on different time scales which will eventually help us to uncover the evolutionary history of these objects. DY Cen and MV Sgr have typical RCB helium abundances which excludes any currently known post-AGB evolutionary models. Moreover, their carbon and nitrogen abundances present us with further problems for their interpretation. V348 Sgr and HV 2671 are in general agreement with a born-again post-AGB evolution and their abundances are similar to Wolf-Rayet central stars of PN. The three Galactic stars in the sample have circumstellar nebulae which produce forbidden line radiation (for HV 2671 we have no information). V348 Sgr and DY Cen have low density, low expansion velocity nebulae (resolved in the case of V348 Sgr), while MV Sgr has a higher density, higher expansion velocity nebula.

Orsola De Marco; Geoffrey C. Clayton; F. Herwig; D. L. Pollacco; J. S. Clark; David Kilkenny

2002-03-08

434

The Writhe of Helical Structures in the Solar Corona  

NASA Technical Reports Server (NTRS)

Context. Helicity is a fundamental property of magnetic fields, conserved in ideal MHD. In flux rope topology, it consists of twist and writhe helicity. Despite the common occurrence of helical structures in the solar atmosphere, little is known about how their shape relates to the writhe, which fraction of helicity is contained in writhe, and how much helicity is exchanged between twist and writhe when they erupt. Aims. Here we perform a quantitative investigation of these questions relevant for coronal flux ropes. Methods. The decomposition of the writhe of a curve into local and nonlocal components greatly facilitates its computation. We use it to study the relation between writhe and projected S shape of helical curves and to measure writhe and twist in numerical simulations of flux rope instabilities. The results are discussed with regard to filament eruptions and coronal mass ejections (CMEs). Results. (1) We demonstrate that the relation between writhe and projected S shape is not unique in principle, but that the ambiguity does not affect low-lying structures, thus supporting the established empirical rule which associates stable forward (reverse) S shaped structures low in the corona with positive (negative) helicity. (2) Kink-unstable erupting flux ropes are found to transform a far smaller fraction of their twist helicity into writhe helicity than often assumed. (3) Confined flux rope eruptions tend to show stronger writhe at low heights than ejective eruptions (CMEs). This argues against suggestions that the writhing facilitates the rise of the rope through the overlying field. (4) Erupting filaments which are S shaped already before the eruption and keep the sign of their axis writhe (which is expected if field of one chirality dominates the source volume of the eruption), must reverse their S shape in the course of the rise. Implications for the occurrence of the helical kink instability in such events are discussed.

Toeroek, T.; Berger, M. A.; Kliem, B.

2010-01-01

435

CHARACTERIZING TRANSITION TEMPERATURE GAS IN THE GALACTIC CORONA  

SciTech Connect

We present a study of the properties of the transition temperature (T {approx} 10{sup 5} K) gas in the Milky Way corona, based on the measurements of O VI, N V, C IV, Si IV, and Fe III absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km s{sup -1}. On average the integrated column densities are log N(O VI) = 14.3, log N(N V) = 13.5, log N(C IV) = 14.2, log N(Si IV) = 13.6, and log N(Fe III) = 14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor {approx}2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling, and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that NIE radiative cooling is important in generating the transition temperature gas.

Wakker, Bart P.; Savage, Blair D. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Fox, Andrew J. [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile); Benjamin, Robert A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218 (United States); Shapiro, Paul R., E-mail: wakker@astro.wisc.edu, E-mail: savage@astro.wisc.edu, E-mail: afox@stsci.edu, E-mail: benjamir@uww.edu, E-mail: shapiro@astro.as.utexas.edu [University of Texas at Austin, Department of Astronomy, Austin, TX 78712 (United States)

2012-04-20

436

Multi-wavelength Analysis to Solar Corona Heating Events  

NASA Astrophysics Data System (ADS)

With the advent and successful running of the 1.6 meter aperture New Solar Telescope at Big Bear Solar Observatory (BBSO/NST), solar observation has entered the era of 0.1 arc second. This permits us to carry out case studies for single coronal heating event, accumulating original high-resolution observational evidences for a final resolving of the coronal heating problem. By combining the high-resolution Helium I 10830 Å, TiO 7057 Å, and H_? - 0.7 Å imaging data from NST, and the satellite data from the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), we analyze the evolution of magnetic field in the roots of two tiny dynamical events originating from the Sun's intergranular lanes as seen from Helium I 10830 Å images. The two events caused subsequent brightening in the corona, but no obvious feature is found at H_? -0.7 Å images. We find that the two events are rooted at one side of magnetic polarity inversion line. One event is apparently accompanied by the disappearance of a tiny magnetic element, while, in another event, weakening of a magnetic concentration area is found. Changes for granules are also found during the two events. The results suggest that the two heating events are caused by small-scale magnetic activities in intergranular lanes driven by constant granule convection. It appears that ubiquitous small-scale magnetic activities produce outflow of cold matter as seen at 10830 Å and hot matter as seen at extreme ultraviolet bands.

Yang, X.; Ji, H. S.; Li, H. C.

2014-05-01

437

Relativistic effects on radiative ejection of coronae in variable X-ray sources  

NASA Astrophysics Data System (ADS)

Context. Optically thin coronae around neutron stars suffering an X-ray burst can be ejected as a result of rapid increase in stellar luminosity. In general relativity, radiation pressure from the central luminous star counteracts gravitational attraction more strongly than in Newtonian physics. However, motion near the neutron star is very effectively impeded by the radiation field. Aims: To explore the mechanisms leading to ejection of accretion disk coronae Methods: We perform a general relativistic calculation of the motion of a test particle in a spherically symmetric radiation field. Results: At every radial distance from the star larger than that of the innermost stable circular orbit (ISCO), and any initial luminosity of the star, there exists a luminosity change which leads to coronal ejection. The luminosity required to eject from the system the inner parts of the optically thin neutron-star corona is very high in the presence of radiation drag and always close to the Eddington luminosity. Outer parts of the corona, at a distance of 20 RG or more, will be ejected by a sub-Eddington outburst. Mildly fluctuating luminosity will lead to dissipation in the plasma and may explain the observed X-ray temperatures of coronae in low mass X-ray binaries. At large radial distances from the star (3 × 103 RG or more) the results do not depend on whether or not Poynting-Robertson drag is included in the calculation.

Mishra, B.; Klu?niak, W.

2014-06-01

438

Nanoparticle size matters in the formation of plasma protein coronas on Fe3O4 nanoparticles.  

PubMed

When nanoparticles (NPs) enter into biological systems, proteins would interact with NPs to form the protein corona that can critically impact the biological identity of the nanomaterial. Owing to their fundamental scientific interest and potential applications, Fe3O4 NPs of different sizes have been developed for applications in cell separation and protein separation and as contrast agents in magnetic resonance imaging (MRI), etc. Here, we investigated whether nanoparticle size affects the formation of protein coronas around Fe3O4 NPs. Both the identification and quantification results demonstrated that particle size does play an important role in the formation of plasma protein coronas on Fe3O4 NPs; it not only influenced the protein composition of the formed plasma protein corona but also affected the abundances of the plasma proteins within the coronas. Understanding the different binding profiles of human plasma proteins on Fe3O4 NPs of different sizes would facilitate the exploration of the bio-distributions and biological fates of Fe3O4 NPs in biological systems. PMID:24974013

Hu, Zhengyan; Zhang, Hongyan; Zhang, Yi; Wu, Ren'an; Zou, Hanfa

2014-09-01

439

TRACING ELECTRON BEAMS IN THE SUN'S CORONA WITH RADIO DYNAMIC IMAGING SPECTROSCOPY  

SciTech Connect

We report observations of type III radio bursts at decimeter wavelengths (type IIIdm bursts)-signatures of suprathermal electron beams propagating in the low corona-using the new technique of radio dynamic imaging spectroscopy provided by the recently upgraded Karl G. Jansky Very Large Array. For the first time, type IIIdm bursts were imaged with high time and frequency resolution over a broad frequency band, allowing electron beam trajectories in the corona to be deduced. Together with simultaneous hard X-ray and extreme ultraviolet observations, we show that these beams emanate from an energy release site located in the low corona at a height below {approx}15 Mm, and propagate along a bundle of discrete magnetic loops upward into the corona. Our observations enable direct measurements of the plasma density along the magnetic loops, and allow us to constrain the diameter of these loops to be less than 100 km. These overdense and ultra-thin loops reveal the fundamentally fibrous structure of the Sun's corona. The impulsive nature of the electron beams, their accessibility to different magnetic field lines, and the detailed structure of the magnetic release site revealed by the radio observations indicate that the localized energy release is highly fragmentary in time and space, supporting a bursty reconnection model that involves secondary magnetic structures for magnetic energy release and particle acceleration.

Chen Bin [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Bastian, T. S. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); White, S. M. [Air Force Research Laboratory, Kirtland Air Force Base, New Mexico, NM (United States); Gary, D. E. [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Perley, R.; Rupen, M. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Carlson, B. [National Research Council of Canada, Penticton, BC V2A 6J9 (Canada)

2013-01-20

440

Variation of protein corona composition of gold nanoparticles following plasmonic heating.  

PubMed

It is well recognized that the primary interaction of most biological environments with nanoparticles (NPs) is strongly influenced by a long-lived ("hard") protein corona that surrounds the NP and remains strongly adsorbed to its surface. The amount and composition of associated proteins in the corona adsorbed onto the NPs is related to several important factors, including the physicochemical properties of the NPs and the composition of the protein solution. Here, for the first time, it is shown that plasmonic heat induction (by laser activation) leads to significant changes in the composition of the hard protein corona adsorbed on low aspect ratio gold nanorods. Using mass spectrometry, several proteins in the corona were identified whose concentrations change most substantially as a result of photoinduced (plasmonic) heating versus simple thermal heating. Molecular modeling suggests that the origin of these changes in protein adsorption may be the result of protein conformational changes in response to much higher local temperatures that occur near the gold nanorods during photoinduced, plasmonic heating. These results may define new applications in vivo for NPs with hyperthermia capability and better define the likely interactions of cells with NPs after plasmonic heating. Potential changes in the protein corona following hyperthermia treatment may influence the final biological fate of plasmonic NPs in clinical applications and help elucidate safety considerations for hyperthermia applications. PMID:24328336

Mahmoudi, Morteza; Lohse, Samuel E; Murphy, Catherine J; Fathizadeh, Arman; Montazeri, Abbas; Suslick, Kenneth S

2014-01-01