A comparison of the thick-target model with stereo data on the height structure of solar hard x-ray bursts

Solar Physics ◽  
1983 ◽  
Vol 88 (1-2) ◽  
Author(s):  
J.C. Brown ◽  
V.A. Carlaw ◽  
D. Cromwell ◽  
S.R. Kane
Keyword(s):  
Thick Target ◽  
X Ray ◽  
Target Model ◽  
Stereo Data

scholarly journals Analysis of Prognoz - 9 Solar Flare Hard X-ray Data-support for the Non-thermal thick target Model

1990 ◽  
Vol 142 ◽  
pp. 445-447
Author(s):  
R. R. Rausaria ◽  
Ranjana Bakaya ◽  
P.N. Khosa
Keyword(s):  
Solar Flare ◽  
Energy Range ◽  
Spectral Index ◽  
High Energy ◽  
Thick Target ◽  
Low Energy ◽  
X Ray ◽  
Target Model ◽  
Data Support ◽  
Peak Emission

Solar flare hard X-ray data obtained by Prognoz-9 spacecraft (Abrosimov et al 1988) in the energy range 10-200 keV are analysed. In examples of events which we consider here, high energy X-ray pulses appear earlier than low energy ones, which is contrary to many other events where the low energy X-ray peak emission takes place earlier. The variation of the spectral index was dynamical.

Rise Time of Hard X-Ray Bursts

1975 ◽  
Vol 68 ◽  
pp. 237-238
Author(s):  
Joan Vorpahl ◽  
Tatsuo Takakura
Keyword(s):  
Spectral Index ◽  
Rise Time ◽  
Empirical Relation ◽  
Impulsive Phase ◽  
Alternative Interpretation ◽  
Thick Target ◽  
Thin Target ◽  
X Ray ◽  
Target Model ◽  
Acceleration Rate

SummaryA study was made of the hard X-ray component in the impulsive phase of solar flares. In 36 randomly chosen events the value for the slope in the differential electron power spectrum E−δ electrons cm−2 s−1 keV−1, was related to the 20–32 keV spike rise time (e-folding) as trise = 0.56 exp (0.88δ) in the thin target model and tfrise = 0.10 exp (0.88δ) in the thick target picture. In the thin target model, the above empirical relation would imply that the acceleration of electrons can be longer when the acceleration rate is smaller. An alternative interpretation would be that an impulsive hard X-ray burst is a superposition of two components emitted from thin and thick targets; when the former predominates, the duration is longer and the photon spectral index is larger, while when the latter predominates, the duration is shorter and the photon spectral index is smaller; 3 ≲δ ≲4 is required (Figure 1). The uncertainty in δ is 0.5 while that in the rise time is 1 s.

Electron Acceleration in Collapsing Magnetic Traps during the Solar Flare on July 19, 2012: Observations and Models

2017 ◽  
Vol 13 (S335) ◽  
pp. 90-93
Author(s):  
P. A. Gritsyk ◽  
B. V. Somov
Keyword(s):  
Point Source ◽  
Solar Flares ◽  
High Efficiency ◽  
Reverse Current ◽  
Electron Acceleration ◽  
Thick Target ◽  
Two Dimensions ◽  
Magnetic Traps ◽  
Thin Target ◽  
X Ray

AbstractUsing the appropriate kinetic equation, we considered the problem of propagation of accelerated electrons into the solar corona and chromosphere. Its analytical solution was used for modelling the M7.7 class limb flare occurred on July 19, 2012. Coronal above-the-loop-top hard X-Ray source was interpreted in the thin-target approximation, the foot-point source - in the thick-target approximation with account of the reverse-current electric field. For the foot-point source we found a good accordance with the RHESSI observations. For the coronal source we also got very accurate estimate of the power-law spectral index, but significant differences between the modelled and observed hard X-ray intensities were noticed. The last discrepancy was solved by adding the coronal magnetic trap model to the thin target model. The former one implies that the trap collapses in two dimensions, locks and accelerates particles inside itself. In our report, we confirm an existence and high efficiency of the electron acceleration in collapsing magnetic traps during solar flares. Our new results represent (e.g. for RHESSI observations) the theoretical prediction of the double step particle acceleration in solar flares, when the first step is the acceleration in reconnection area and the second one – the acceleration in coronal trap.

On Proton and Electron Acceleration by Shock Waves during Large Solar Flares

1978 ◽  
Vol 3 (3) ◽  
pp. 236-238
Author(s):  
V. M. Gubchenko ◽  
V. V. Zaitsev
Keyword(s):  
Shock Waves ◽  
Total Energy ◽  
Satisfactory Agreement ◽  
Solar Flares ◽  
Interplanetary Medium ◽  
Thermal Processes ◽  
Proton Acceleration ◽  
X Ray ◽  
Target Model ◽  
Γ Ray

Lin and Hudson (1976) have recently analysed non-thermal processes in proton flares, using observations of a series of major events in August 1972. They concluded that the 10–100 keV electrons accelerated during the flash phase account for the bulk of the total energy of a large proton flare (about 1032 – 1033 ergs); that most protons are accelerated later than the 10 — 100 keV electrons; and that most energetic protons escape to the interplanetary medium. Their conclusions with regard to proton acceleration are supported firstly by the delay of the maximum of γ-ray emission by 3-5 minutes after the maximum of X-ray emission, and secondly by the satisfactory agreement between the 7-ray spectrum and the thin-target model of emission. The energetic protons contain a very small fraction of the total flare energy (of the order of 10-5).

scholarly journals III. Solar Maximum Mission Results

1985 ◽  
Vol 19 (1) ◽  
pp. 64-68
Author(s):  
M. E. Machado
Keyword(s):  
Impulsive Phase ◽  
Thick Target ◽  
Spectral Lines ◽  
The Novel ◽  
Line Broadening ◽  
Ongoing Research ◽  
X Ray ◽  
Chromospheric Evaporation ◽  
High Resolution Images ◽  
Beam Mechanism

The ongoing research carried out by the solar community has been reported in the proceedings of several recent symposia, seminars and workshops, as well as in scientific journals (Kane et al. 1983, Švestka et al. 1982a, Shea et al. 1984, Kundu S Woodgate 1984, Simon 1984). We summarize here some of the novel results with reference to flare research as far as SMM data analysis is concerned. Understanding of impulsive phase phenomena was one of the primary goals of the SMM. The early reports from the analysis of the first ever obtained high-resolution images in the <30 keV energy range stressed the fact that some flares showed hard x-ray (HXR) bright sources at the feet of coronal loops (Hoyng et al. 1981a, b, Machado et al. 1982, Duijveman et al. 1982), the so-called HXR “footpoints,” favoring the thick-target beam mechanism for the production of HXRs, and indicating acceleration efficiencies >20% during the early impulsive phase. This phenomenon was shown to be accompanied by soft x-ray (SXR) line broadening, indicative of strong turbulence, and the immediate appearance of blue shifted spectral lines, which shows that plasma heated to >10-1 K rises from the footpoints of loops with velocities to 300 km s-1 (Antonucci et al. 1982, Antonucci et al. 1984a). This result provides a strong indication of the chromospheric evaporation phenomenon, which has been confirmed in analyses of combined SXR and Ha observations (Acton et al. 1982, Gunkler et al. 1984).

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