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Saint-Hilaire Pascal von Praun Christoph Stolte Etzard Alonso Gustavo Benz Arnold O. Gross Thomas 《Solar physics》2002,210(1-2):143-164
The RHESSI Experimental Data Center (HEDC) at ETH Zürich aims to facilitate the use of RHESSI data. It explores new ways to
speed up browsing and selecting events such as solar flares. HEDC provides pre-processed data for on-line use and allows basic
data processing remotely over the Internet. In this article, we describe the functionality and contents of HEDC, as well as
first experiences by users. HEDC can be accessed at http://www.hedc.ethz.ch. Additional graphical material and color versions of most figures are available on the CD-ROM accompanying this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022413302246 相似文献
2.
We present the first in-depth statistical survey of flare source heights observed by RHESSI. Flares were found using a flare-finding
algorithm designed to search the 6 – 10 keV count-rate when RHESSI’s full sensitivity was available in order to find the smallest
events (Christe et al. in Astrophys. J.
677, 1385, 2008). Between March 2002 and March 2007, a total of 25 006 events were found. Source locations were determined in the 4 – 10 keV,
10 – 15 keV, and 15 – 30 keV energy ranges for each event. In order to extract the height distribution from the observed projected
source positions, a forward-fit model was developed with an assumed source height distribution where height is measured from
the photosphere. We find that the best flare height distribution is given by g(h)∝exp (−h/λ) where λ=6.1±0.3 Mm is the scale height. A power-law height distribution with a negative power-law index, γ=3.1±0.1 is also consistent with the data. Interpreted as thermal loop-top sources, these heights are compared to loops generated
by a potential-field model (PFSS). The measured flare heights distribution are found to be much steeper than the potential-field
loop height distribution, which may be a signature of the flare energization process. 相似文献
3.
Arnold?O.?BenzEmail author Paolo?C.?Grigis André?Csillaghy Pascal?Saint-Hilaire 《Solar physics》2005,226(1):121-142
The radio emission during 201 selected X-ray solar flares was surveyed from 100 MHz to 4 GHz with the Phoenix-2 spectrometer of ETH Zürich. The selection includes all RHESSI flares larger than C5.0 jointly observed from launch until June 30, 2003. Detailed association rates of radio emission during X-ray flares are reported. In the decimeter wavelength range, type III bursts and the genuinely decimetric emissions (pulsations, continua, and narrowband spikes) were found equally frequently. Both occur predominantly in the peak phase of hard X-ray (HXR) emission, but are less in tune with HXRs than the high-frequency continuum exceeding 4 GHz, attributed to gyrosynchrotron radiation. In 10% of the HXR flares, an intense radiation of the above genuine decimetric types followed in the decay phase or later. Classic meter-wave type III bursts are associated in 33% of all HXR flares, but only in 4% are they the exclusive radio emission. Noise storms were the only radio emission in 5% of the HXR flares, some of them with extended duration. Despite the spatial association (same active region), the noise storm variations are found to be only loosely correlated in time with the X-ray flux. In a surprising 17% of the HXR flares, no coherent radio emission was found in the extremely broad band surveyed. The association but loose correlation between HXR and coherent radio emission is interpreted by multiple reconnection sites connected by common field lines. 相似文献
4.
P. Saint-Hilaire G. J. Hurford G. Keating G. C. Bower C. Gutierrez-Kraybill 《Solar physics》2012,277(2):431-445
We present the first observations of the Sun with the Allen Telescope Array (ATA). We used up to six frequencies, from 1.43 to 6 GHz, and baselines from 6 to 300 m. To our knowledge, these are the first simultaneous multi-frequency full-Sun maps obtained at microwave frequencies without mosaicing. The observations took place when the Sun was relatively quiet, although at least one active region was present each time. We present multi-frequency flux budgets for each of the sources on the Sun. Outside of active regions, assuming optically thin bremsstrahlung (free–free) coronal emission on top of an optically thick ≈?10?000 K chromosphere, the multi-frequency information can be condensed into a single, frequency-independent, “coronal bremsstrahlung contribution function” \([\mathrm{EM}/\sqrt{T}]\) map. This technique allows the separation of the physics of emission as well as a measurement of the density structure of the corona. Deviations from this simple relationship usually indicate the presence of an additional gyroresonance-emission component, as is typical in active regions. 相似文献
5.
We investigate temporal and spatial correlations in solar flares of hard X-rays (HXR) and decimetric continuum emissions,
ejecta, and CMEs. The focus is on three M-class flares, supported by observations from other flares. The main conclusions
of our observations are that (1) major hard X-ray flares are often associated with ejecta seen in soft X-rays or EUV. (2)
Those ejecta seem to start before HXR or related decimetric radio continua (DCIM emission). (3) DCIM occurring nearly simultaneously
with the first HXR peak are located very close to the HXR source. Later in the flare, DCIM generally becomes stronger, drifts
to lower frequency and occurs far from the HXR source. Thus the positions at high frequency are generally closer to the HXR
source. DCIM emission consists of pulses that drift in frequency. The very high and sometimes positive drift rate suggests
spatially extended sources or type III like beams in an inhomogeneous source. Movies of selected flares used in this study
can be found on the CD-ROM accompanying this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1026194227110 相似文献
6.
The impulsive phase of the 23 July 2002 2B/X4.8 proton flare with a classical two-ribbon structure was observed with the Irkutsk
Large Solar Vacuum Telescope (LSVT) in spectropolarimetric mode, with high spatial, spectral, and time resolution. On the
basis of 49 spectrograms and 1200 spectral cuts across the flare ribbons, evidence for Hα line impact polarization has been obtained. A systematic change of the Stokes Q and U parameters has been detected across the ribbons for different flare regions measured with a scanning step of 0.85″. In the
eastern side of the ribbons, the degree of polarization is 4 – 8%; its plane is oriented toward the solar disk center (radial
direction). In the western side, the polarization degree runs up to 25%, and its plane is perpendicular to the disk center
direction (tangential direction). A comparison of these results with hard X-ray data (RHESSI) allows us to conclude that high-energy
electron beams reached the chromosphere during this flare. The observed changes of the direction of polarization and the vanishing
polarization within the ribbons mean that, at the chromospheric level, the energy of electrons remaining in the beam is about
200 eV. A shift of the peak position of polarization relative to the intensity maximum in the ribbons may result from the
inclination of the electron beam axis with respect to the solar surface. 相似文献
7.
We present the analysis of a compact flare that occurred on 26 February 2002 at 10:26 UT, seen by both RHESSI and TRACE. The
size of the nearly circular hard X-ray source is determined to be 5.6 (±0.8)′′, using different methods. The power-law distribution
of non-thermal photons is observed to extend down to 10 keV without flattening, and to soften with increasing distance from
the flare kernel. The former indicates that the energy of the precipitating flare electron population is larger than previously
estimated: it amounts to 2.6 (±0.8)×1030 erg above 10 keV, assuming thick-target emission. The thermal energy content of the soft X-ray source (isothermal temperature
of 20.8 (±0.9) MK) and its radiated power were derived from the thermal emission at low energies. TRACE has observed a low-temperature
ejection in the form of a constricted bubble, which is interpreted as a reconnection jet. Its initial energy of motion is
estimated. Using data from both satellites, an energy budget for this flare is derived. The kinetic energy of the jet bulk
motion and the thermal and radiated energies of the flare kernel were more than an order of magnitude smaller than the derived
electron beam energy. A movie is available on the CD-ROM accompanying this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022478300679 相似文献
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