E: Flares,
Gordon Holman (30)
Last Updated Fri Dec 5 16:24:42 2008
| 1: Marina Battaglia (battaglia@astro.phys.ethz.ch), ETH Zurich [D] |
| [soi] What can RHESSI teach us about particle acceleration and propagation in solar flares? I will show how RHESSI can help us understanding acceleration and propagation processes in solar flares and how we can improve existing models to explain RHESSI observations. Further, a RHESSI look at pre-flares will be made and their physics will be discussed. |
| [none] |
| 2: D. Shaun Bloomfield (shaun.bloomfield@tcd.ie), Trinity College Dublin [G] |
| [soi] I am interested in studying the statistics of solar soft X-ray (GOES) flares and their dependence on the physical properties of the active regions from which they originate (e.g., magnetic field strength and gradient, total spot area, Mt Wilson and McIntosh magnetic classifications), with the aim of improving our understanding of the physical conditions required for flare activity. The flaring distributions of parameter-grouped active region types will be developed into a near-realtime flare-prediction tool using Bayesian techniques, providing novel physically-motivated probability measures for future flare events. |
| [none] |
| 3: Amir Caspi (cepheid@ssl.berkeley.edu), Space Sciences Lab, UC Berkeley [D] |
| [soi] I am interested in the origins and evolution of super-hot thermal plasmas, as well as the total partition of thermal versus non-thermal energy (including the time history of such) and the correlations between maximum temperature, thermal energy density, and other flare parameters (e.g. flare size and/or coronal magnetic field strength). Currently, I am particularly interested in how and where super-hot thermal plasmas are heated, and in using the iron line complexes as diagnostics to constrain thermal parameters.If time permits, I may request to present an early version of my AGU talk, which focuses on using RHESSI to place constraints on the thermal parameters for chromospheric evaporation plasma in super-hot flares. |
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| 4: Jonathan Cirtain (Jonathan.W.Cirtain@nasa.gov), [I] |
| [soi] Hinode's draft plan on flare and AR long-term observations |
| [none] |
| 5: Lindsay Glesener (glesener@ssl.berkeley.edu), University of California, Berkeley [G] |
| [soi] I am interested in coronal sources -- specifically thin-target bremsstrahlung as a possible explanation for the HXR emission from these sources. I investigate this using occulted flares. |
| [poster] Hard X-ray Emission From Partially Occulted Solar Flares Most RHESSI flares exhibit strong HXR emission from bright flare loop footpoints, drowning out faint emission from higher in the corona. Partial occultation of flares by the solar disk obscures these bright footpoints, allowing for detailed observations of faint coronal HXR sources. It is therefore necessary to identify and characterize flares with high occultation heights. Here we present a technique for determining flare occultation heights by extrapolating the paths of active flare regions across the solar disk. A statistical study of 55 flares compares occultation heights to nonthermal flux. Compared with statistical results of on-disk flares, it is estimated that this coronal emission is at least 20 times fainter than the expected footpoint emission, confirming that partial occultation is crucial for the study of faint coronal sources. HXR images made by RHESSI are also compared with images at longer wavelengths from the TRACE, EIT, and STEREO instruments. |
| 6: Gordon Holman (Gordon.D.Holman@nasa.gov), NASA Goddard Space Flight Center [E] |
| [soi] Flares Group Leader |
| [none] |
| 7: Gordon Hurford (ghurford@ssl.berkeley.edu), SSL - UC Berkeley [G] |
| [soi] Application of hard x-ray and gamma-ray imaging spectroscopy and radio observations to solar flares. |
| [none] |
| 8: Haisheng Ji (jihs@pmo.ac.cn), Purple Mountain Observatory, China [D] |
| [soi] In the talk, I will present observational evidences for the reconnection between sheared flux ropes in the initial phase of solar flares. |
| [none] |
| 9: Eduard Kontar (eduard@astro.gla.ac.uk), University of Glasgow [D] |
| [soi] a) The role of plasma waves turbulence in the electron transport in solar flares. b) Chromospheric magnetic field and density structures in flaring loops c) Transport of solar flare energetic electrons in the heliosphere: onsets and spectra |
| [none] |
| 10: Sam Krucker (krucker@ssl.berkeley.edu), [E] |
| [soi] |
| [none] |
| 11: Wei Liu (weiliu@helio.gsfc.nasa.gov), NASA Goddard Space Flight Center [G] |
| [soi] We present a detailed imaging and spectroscopic study of the conjugate hard X-ray (HXR) footpoints (FPs) observed with RHESSI in the 2003 October 29 X10 flare. The double FPs first move toward and then away from each other, mainly parallel and perpendicular to the magnetic neutral line, respectively. The transition of these two phases of FP unshearing motions coincides with the direction reversal of the motion of the loop-top (LT) source, and with the minima of the estimated loop length and LT height. The FPs show temporal correlations in HXR flux, spectral index, and magnetic field strength. The HXR flux exponentially correlates with the magnetic field strength which also anti-correlates with the spectral index before the maximum of the second HXR peak, suggesting that particle acceleration sensitively depends on the magnetic field strength and/or reconnection rate. Asymmetries are observed between the FPs: on average, the eastern FP is 2.2 times brighter in HXR flux and 1.8 times weaker in magnetic field strength, and moves 2.8 times faster away from the neutral line than the western FP; the estimated coronal column density to the eastern FP from the LT source is 1.7 times smaller. The two FPs have marginally different spectral indexes. The eastern-to-western FP HXR flux ratio and magnetic field strength ratio are anti-correlated only before the maximum of the second HXR peak. Neither magnetic mirroring nor column density alone can explain these observations when taken together, but their combination, together with other transport effects, may play a role. |
| [poster] In this poster, we first present data analysis and interpretation of an M1.4 class flare observed with RHESSI on 2002 April 30. This event, with its footpoints occulted by the solar limb, exhibits a rarely observed, but theoretically expected, double-source structure in the corona. The two coronal sources, observed over the 6-30 keV range, appear at different altitudes and show energy-dependent structures with the higher energy emission being closer together. Spectral analysis implies that the emission at higher energies in the inner region between the two sources is mainly nonthermal, while the emission at lower energies in the outer region is primarily thermal. The two sources are both visible for about 12 minutes and have similar light curves and power-law spectra above about 20 keV. These observations suggest that the magnetic reconnection site lies between the two sources. Bidirectional outflows of the released energy in the form of turbulence and/or particles from the reconnection site could be the source of the observed radiation. The spatially resolved thermal emission below about 15 keV, on the other hand, indicates that the lower source has a larger emission measure but a lower temperature than the upper source. This is likely the result of the differences in the magnetic field and plasma density of the two sources. Preliminary analysis of other flares showing similar double coronal source structures will also be presented, and their theoretical implications will be discussed. |
| 12: B. C. Low (low@ucar.edu), [E] |
| [soi] |
| [none] |
| 13: Anna Maria Massone (massone@ge.infm.it), CNR - INFM LAMIA, Genova [G] |
| [soi] I am interested in the use of computational methods for the analysis of RHESSI data. In particular, I currently work at the use of visibilities for solar flares X-ray imaging and imaging-spectroscopy |
| [poster] Count visibilities represent the purest measurements provided by RHESSI collimators. I will introduce a fast and reliable imaging method for flaring events applying an inverse FFT code to interpolated RHESSI count visibilities. I will also show that super-resolution effects can be obtained by utilizing a projected iterative algorithm. |
| 14: Satoshi Masuda (masuda@stelab.nagoya-u.ac.jp), STEL, Nagoya University [D] |
| [soi] I am interested in particle acceleration in solar flares. I would like to reveal it by using multi-wavelength observations such as RHESSI, Nobeyama Radio Heliograph, Hinode, and so on. |
| [poster] Title: GEMSIS-Sun: Modeling of Particle Acceleration and Transport in Solar Flares Authors: S. Masuda, T. Minoshima, T. Yamamoto, Y. Miyoshi (STEL, Nagoya Univ.), S. Inoue, and K. Kusano (JAMSTEC) Abstract: GEMSIS (Geospace Environment Modeling System for Integrated Studies) is one of projects in Solar-Terrestrial Environment Laboratory, Nagoya University. Its final goal is to build a geospace-environment model based on various (satellite and ground-based) observational facts in order to understand the dynamic energy-transport-processes taking place in geospace. In the first three years (2007.4 - 2010.3), we set a few individual scientific targets as fundamental elements/information for the final model. One of them is to know how particles are accelerated, transported, and lose their energies in solar flares. It is evident from many observations such as X-rays, gamma-rays, and microwaves that a large amount of high-energy particles are produced in solar flares. However, the dynamics of these particles is not completely understood so far. The GEMSIS-Sun group approaches this research topic through integrated studies, i.e., an empirical modeling of particle dynamics and analyses of various data observed with Hinode, RHESSI, Nobeyama Radioheliograph, and so on. It is widely believed that a solar flare is a consequence of magnetic reconnection. Based on the magnetic reconnection model, we are developing a numerical model for particle acceleration and transport in the flare region. Since the temporal and spatial scales of particles are much shorter than the flare scale (roughly by ten to the six for ions), the full-particle approach is yet unrealistic for the empirical understanding. We therefore employ the guiding-center kinetic equation of particles so that we can perform the calculation in the coronal actual parameter range. By the direct comparison between observations and the calculation, we will empirically discuss the acceleration and transport mechanisms of particles in solar flares. |
| 15: James McTiernan (jimm@ssl.berkeley.edu), Space Sciences Lab/Univ. of California [C] |
| [soi] I am interested in flare X-ray spectroscopy. |
| [poster] RHESSI/GOES Xray Solar Flare Multitemperature plus Power law Spectra: We present spectral fits for RHESSI and GOES solar flare data that include both a Differential Emission Measure for thermal emission and a power law fit for nonthermal emission. This improvement over the traditional isothermal approximation for thermal flare emission is intended to help to resolve the ambiguity in the range where the thermal and nonthermal components may have similar photon fluxes. This "crossover" range can be anywhere from 10 to 30 keV for medium to large solar flares. It is also expected that the low energy cutoff of the nonthermal electron spectrum lurks in this enery range, or below, but is obscured by thermal emission. |
| 16: Ryan Milligan (ryan.o.milligan@nasa.gov), NASA/GSFC [G] |
| [soi] It is widely assumed that the process of chromospheric evaporation is responsible for much of the EUV and X-ray emission observed during solar flares. Until now, many previous studies have relied primarily on the detection of blueshifts of a single, high-temperature emission line (e.g.'Ca XIX on Yohkoh/BCS, Fe XIX on SOHO/CDS). With the launch of Hinode, the EUV Imaging Spectrometer (EIS) now offers us the opportunity to diagnose this fundamental process across a multitude of emission lines, at high spatial, spectral and temporal resolution. As part of this workgroup I shall present new findings from joint observations between RHESSI and EIS, which allow a much more comprehensive comparison with the long-accepted theories. In particular I shall discuss how upflow and downflow velocities vary as a function of temperature during the impulsive phase and how the division of energy between direct heating in the corona and particle acceleration can affect a flares temperature. Some factors of these results are inconsistent with the standard model of chromospheric evaporation and could have implications on flare heating models and interpretation of observations during the upcoming solar cycle. |
| [poster] The GOES solar flare catalog is the largest, self-consistent listing currently available covering three complete solar cycles - #21, 22, and 23 - from 1975 to the present. The two-channel X-ray fluxes recorded every 3 s allow several basic parameters of the high-temperature flare plasma to be derived (e.g. temperature, emission measure, radiative loss rate, etc.) as well as the timescales on which they change. In this study, after accounting for variations in the X-ray background, we attempt to systematically derive such parameters for all flares in the GOES catalog. The relationships between peak temperature, peak emission measure, and peak X-ray flux will be presented for each solar cycle. |
| 17: Ronald Murphy (murphy@ssd5.nrl.navy.mil), Naval Research Laboratory [D] |
| [soi] We will discuss recent improvements to our computer codes for calculating expected gamma-ray spectra and neutron production in solar flares. The new calculations will be applied to satellite data (such as from the SMM gamma ray spctrometer) to derive information about the flaring atmosphere and the particles accelerated and interacting at the Sun. The derived accelerated particle parameters can be compared with parameters of particles observed in interplanetary space. |
| [none] |
| 18: Michele Piana (michele.piana@univr.it), Informatica Universita di Verona [G] |
| [soi] I am interested in the use of computational methods for the analysis of RHESSI data. In particular, I currently work at the use of visibilities for solar flares X-ray imaging and imaging-spectroscopy |
| [talkposter] Electron visibilities with corresponding electron maps of solar flares can be obtained from X-ray RHESSI count visibilities by utilizing regularization techniques. Processing such electron visibilities I will show how to infer information on the physics of solar flares like the evolution of electron spectral indices, the flare location as a function of electron energy and the effects of albedo on the recorded emission. |
| 19: Marco Prato (marco.prato@unimore.it), Universita di Modena e Reggio Emilia [G] |
| [soi] I am interested in the use of computational methods for the analysis of RHESSI data. In particular, I currently work at the use of visibilities for solar flares X-ray imaging and imaging-spectroscopy |
| [none] |
| 20: Fatima Rubio da Costa (f.rubiodacosta@astro.gla.ac.uk), University of Glasgow [H] |
| [soi] I am interested in how the particles are accelerated and the plasma is heated during the flare process. |
| [none] |
| 21: Pascal Saint-Hilaire (shilaire@ssl.berkeley.edu), SSL, UC Berkeley [D] |
| [soi] I will present observations of an unusual coronal source that lasted more than 12 hours (as seen in X-rays with RHESSI at 1.3Rs), thought to be at the base of a current sheet observed by SOHO/UVCS for 2.3 days at 1.7Rs, including energy budget and long-integration imaging. |
| [none] |
| 22: Gerald Share (share@astro.umd.edu), University of Maryland [H] |
| [soi] I will discuss application of new theoretical tools to the study of gamma-ray spectra from solar flares. This provides the capability for determining the ambient composition in the chromosphere where the flare particles interact, the spectrum and composition of accelerated particles. |
| [none] |
| 23: Albert Shih (ayshih@ssl.berkeley.edu), SSL, UC Berkeley [D] |
| [soi] I am interested using gamma-ray observations to measure flare ion acceleration, compare how it correlates with electron acceleration and SEPs, and determine the strength and characteristics of that correlation at different energies. |
| [poster] The new balloon-borne Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) instrument will provide a near-optimal combination of high-resolution imaging, spectroscopy, and polarimetry of solar-flare gamma-ray/hard X-ray emissions from ~20 keV to >~10 MeV. The spectrometer/polarimeter consists of sixteen 3D position-sensitive germanium detectors (3D-GeDs), where each energy deposition is individually recorded with an energy resolution of a few keV FWHM and a spatial resolution to within <0.1 mm^3. Imaging is accomplished by a single multi-pitch rotating modulator (MPRM), a 2-cm thick tungsten grid with pitches that range quasi-continuously from 1 to 13 mm. With the MPRM situated 8 meters from the spectrometer, this instrument will provide excellent image quality and unparalleled angular resolution at gamma-ray energies (12.5 arcsec FWHM), sufficient to separate the 2.2 MeV footpoint sources for almost all flares. Polarimetry is accomplished by analyzing the anisotropy of reconstructed Compton scattering in the 3D-GeDs (i.e. as an active scatterer), with an estimated minimum detectable polarization of a few percent at 150--650 keV in an X-class flare. GRIPS will address questions relevant to particle acceleration and energy release that have been raised by recent solar flare observations, such as: What causes the spatial separation between energetic electron producing hard X-rays and energetic ions producing gamma-ray lines? How anisotropic are the accelerated electrons, and why do relativistic electron dominate in the corona? How does the composition of accelerated and ambient material vary with space and time, and why? |
| 24: Yang Su (yangsu@helio.gsfc.nasa.gov), NASA Goddard Space Flight Center [H] |
| [soi] flares and related phenomena,non-thermal electrons,sunspot |
| [poster] Solar Hard X-ray (HXR) spectra during flares often show a broken power-law spectrum. A possible explanation for this spectral break is nonuniform ionization in the emission region. We have developed a thick-target model using the full Bethe-Heitler bremsstrahlung cross section and an ionization model that increases linearly from zero to 100% ionization. We compare spectra computed from this model with those obtained by Kontar, Brown and McArthur (2002) using a step-function ionization model and the Kramer's cross section. The model is applied to a statistical sample of RHESSI flares from 2002 to 2004 to determine whether thick-target nonuniform ionization can explain the breaks in the flare HXR spectra. We will present the results of this study for discussion. |
| 25: ShiChao TANG (sctang@ssl.berkeley.edu), Space Sciences Lab, UC Berkeley [G] |
| [soi] Heating of photosphere in flares, positron production and annihilation. Statistics of nanoflare profiles. |
| [none] |
| 26: Gerard Trottet (gerard.trottet@obspm.fr), Observatoire de Paris, LESIA [D] |
| [soi] Discuss joint observations in hard X-ray, gamma-ray and submm waves: possible emission processes and diagostics of relativistic leptons produced during flares. In this context, the interest of performing observations in the 1-10 THz domain, as planned for the SMESE french-chinese mission will be emphasized. |
| [none] |
| 27: Nicole Vilmer (nicole.vilmer@obspm.fr), LESIA- Paris Observatory [G] |
| [soi] Combined observations of a flare observed by Hinode/RHESSI and the Nan'ay Radioheliograph Observations of flares and constraints on particle acceleration in flares |
| [posternone] X-ray and radio observations of the 3 June 2007 flare |
| 28: Kyoko Watanabe (watanabe.kyoko@isas.jaxa.jp), ISAS/JAXA [E] |
| [soi] particle (especially ions) acceleration in solar flares |
| [poster] We are searching for the white light flares from Hinode/SOT G-band observation, and found 8 events until now. white light emission was seen even if its from C-class flare. These white light emissions came from almost the center of Ca II H emission, and are related with X-ray emission. In this presentation, we present these white light flare events, and discuss the relationship with the particle acceleration. |
| 29: Tetsuya Watanabe (watanabe@uvlab.mtk.nao.ac.jp), NAOJ [G] |
| [soi] The EIS instrument is very capable of seeing iron emission lines at its various ionization stages appearing in the EUV wavelengths. A few example of successful observations of small flares observed during the solar minimum show new views of heating and motions of flaring plasmas. FeXXIII line at 263.76 A shows completely blue-shifted line profiles at the foot points during the impulsive phase, while coronal plasmas below 2 MK show no significant plasma motions at the same time and at the same position. Radid fill up of high-temperature plasmas along the flaring loop can be traced by the FeXXIII/FeXXIV line intensity ratio. |
| [none] |
| 30: Brian Welsch (welsch@ssl.berkeley.edu), SSL, UC Berkeley [D] |
| [soi] |
| [poster] Is there any relationship between photospheric flows and flares? by B.T. Welsch[1], Y. Li[1], P.W. Schuck[2], & G.H. Fisher[1] Coupling between magnetic fields in the solar photosphere and corona implies that flows at the photosphere --- the only atmospheric layer where the magnetic field is routinely measured --- can inject magnetic energy and helicity into the coronal field. Fluxes of magnetic energy and helicity into the corona might play an important role in flares and coronal mass ejections (CMEs). Some flow patterns --- including shear flows, converging flows, and rotational flows --- have been proposed as particularly important processes leading to flares and CMEs. How common are these flow patterns? Which flows, if any, are statistically associated with flares? To answer these questions and others, we estimated photospheric flows using the FLCT and DAVE methods, from sequences of MDI full-disk magnetograms, with a nominal 96-minute cadence, from 46 active regions (ARs) that were tracked while within 45 degrees of disk center. Our AR sample includes both regions that produced many flares and CMEs, and regions that produced little activity. Based upon our preliminary analysis, we have not identified any flow properties that are as significantly correlated with average flare power as other AR properties: total unsigned flux; flux emergence; and previous flare activity. Hence, we conclude there is no simple or obvious relationship between photospheric flows and flares. [1] Space Sciences Lab, Univ. of California, Berkeley, CA [2] Plasma Physics Div., Naval Research Lab, Washington, DC |
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