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.

scholarly journals Production of Different Non-Thermal Electron Groups in Small Solar Flares

1972 ◽  
Vol 14 ◽  
pp. 822-823
Author(s):  
S. R. Kane
Keyword(s):  
Electron Emission ◽  
Solar Flares ◽  
Electron Acceleration ◽  
X Rays ◽  
Thermal Electron ◽  
X Ray ◽  
Type Iii

Using the measurements of impulsive solar X-rays made with the OGO-5 satellite to identify the flash phase electron acceleration in solar flares of Hα-importance ≲ 1, the satellite and ground based observations are analyzed to study the origin of the different groups of non-thermal electrons responsible for the impulsive X-ray, impulsive microwave, type III radio and interplanetary electron emission.

scholarly journals Radiation Hydrodynamics in Solar Flares

1986 ◽  
Vol 89 ◽  
pp. 53-74
Author(s):  
George H. Fisher
Keyword(s):  
Heating Rate ◽  
Transition Region ◽  
Solar Flares ◽  
Thermal Model ◽  
Thermal Conduction ◽  
Thick Target ◽  
Pressure Increase ◽  
Electromagnetic Spectrum ◽  
X Ray ◽  
Upper Limit

AbstractSolar flares are currently understood as the explosive release of energy stored in the form of stressed magnetic fields. In many cases, the released energy seems to take the form of large numbers of electrons accelerated to high energies (the nonthermal electron “thick target” model), or alternatively plasma heated to very high temperatures behind a rapidly moving conduction front (the “thermal” model). The transport of this energy into the remaining portion of the atmosphere results in violent mass motion and strong emission across the electromagnetic spectrum. Radiation processes play a crucial role in determining the ensuing plasma motion.One important phenomenon observed during flares is the appearance in coronal magnetic loops of large amounts of upflowing, soft X-ray emitting plasma at temperatures of 1−2×107 [K]. It is believed that this is due to chromospheric evaporation, the process of heating cool (T - 104[K]) chromospheric material beyond its ability to radiate. Detailed calculations of thick target heating show that if nonthermal electrons heat the chromosphere directly, then the evaporation process can result in explosive upward motion of X-ray emitting plasma if the heating rate exceeds a threshold value. In such a case, upflow velocities approach an upper limit of roughly 2.35 cs as the heating rate is increased beyond the threshold, where cs is the sound speed in the evaporated plasma. This is known as explosive evaporation. If the flare heating rate is less than the threshold, evaporation takes place indirectly through thermal conduction of heat deposited in the corona by the energetic electrons. Upflows in this case are roughly 10 to 20% of the upper limit. Evaporation by thermal model heating always takes place through thermal conduction, and the computed upflow speeds seem to be about 10% to 20% of the upper limit, independent of the energy flux.The pressure increase in the evaporated plasma for either the thick target or thermal model leads to a number of interesting phenomena in the flare chromosphere. The sudden pressure increase initiates a downward moving “chromospheric condensation”, an overdense region which gradually decelerates as it accretes material and propagates into the gravitationally stratified chromosphere. Solutions to an equation of motion for this condensation shows that its motion decays after about one minute of propagation into the chromosphere. When the front of this downflowing region is supersonic relative to the atmosphere ahead of it, a radiating shock will form. If the downflow is rapid enough, the shock strength should be sufficient to excite UV radiation normally associated with the transition region, and furthermore, the radiating shock will be brighter than the transition region. These results lead to a number of observationally testable relationships between the optical and ultraviolet spectra from the condensation and radiating shock.

Localization of electron acceleration in solar flares based on the spectrum analysis of hard X-ray time delays

2015 ◽  
Vol 55 (7) ◽  
pp. 1000-1007 ◽  
Author(s):  
Yu. E. Charikov ◽  
V. I. Globina ◽  
A. N. Shabalin ◽  
E. Elfimova
Keyword(s):  
Spectrum Analysis ◽  
Solar Flares ◽  
Time Delays ◽  
Electron Acceleration ◽  
X Ray

scholarly journals Return Current Instability in Flares

1989 ◽  
Vol 104 (2) ◽  
pp. 313-316
Author(s):  
D. Cromwell ◽  
P. McQuillan ◽  
J.C. Brown
Keyword(s):  
Solar Flares ◽  
Small Area ◽  
Thick Target ◽  
Target Electron ◽  
Return Current ◽  
Ion Acoustic Wave ◽  
X Ray ◽  
Acoustic Wave Generation ◽  
Bremsstrahlung Emission ◽  
Current Instability

AbstractWe consider the problem of ion-acoustic wave generation, and resultant anomalous Joule heating, by a return current driven unstable by a small-area thick-target electron beam in solar flares. We find that, contrary to the usual assumption, the hard X-ray bremsstrahlung emission may actually be enhanced in comparison to conventional thick-target models. This present paper is a summary of the work of Cromwell, McQuillan and Brown (1988).

scholarly journals Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares

2011 ◽  
pp. 107-166 ◽  
Author(s):  
G. D. Holman ◽  
M. J. Aschwanden ◽  
H. Aurass ◽  
M. Battaglia ◽  
P. C. Grigis ◽  
...  
Keyword(s):  
Solar Flares ◽  
Electron Acceleration ◽  
X Ray
Sign in / Sign up

Export Citation Format

Share Document