On the role of reverse current on the hard X-ray production in solar flares and time-lags between high- and low-energy photons

1992 ◽  
Vol 195 (2) ◽  
pp. 401-412
Author(s):  
Ranjana Bakaya ◽  
S. A. Chasti ◽  
R. R. Rausaria
Keyword(s):  
Solar Flares ◽  
Reverse Current ◽  
Low Energy ◽  
Time Lags ◽  
X Ray

Role of non-thermal electrons on the generation of X-ray and EUV lines in solar flares

1988 ◽  
Vol 148 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Ranjna Bakaya ◽  
R. R. Rausaria ◽  
P. N. Khosa
Keyword(s):  
Solar Flares ◽  
X Ray

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 the role of nonthermal electrons in EUV and X-ray line emissions from solar flares

1997 ◽  
Vol 18 (1) ◽  
pp. 57-71 ◽  
Author(s):  
Ranjna Bakaya ◽  
R. R. Rausaria
Keyword(s):  
Solar Flares ◽  
X Ray ◽  
Nonthermal Electrons

scholarly journals The First Results from “Solar X-ray Spectrometer (SOXS)” Mission

2005 ◽  
Vol 13 ◽  
pp. 622-622 ◽  
Author(s):  
Rajmal Jain ◽  
Hemant Dave ◽  
P. Sreekumar ◽  
A. B. Shah ◽  
N. M. Vadher ◽  
...  
Keyword(s):  
Solid State ◽  
Solar Flare ◽  
Energy Range ◽  
Solar Flares ◽  
High Energy ◽  
Low Energy ◽  
Energy Detector ◽  
X Ray ◽  
Phoswich Detector ◽  
First Results

Abstract“Solar X-ray Spectrometer (SOXS)” mission on-board GSAT-2 Indian spacecraft was launched on 08 May 2003 by GSLV-D2 and deployed in geostationery orbit to study the X-ray emission from solar flares with high spectral and temporal resolution. The SOXS consists of two independent payloads viz. SOXS Low Energy Detector (SLD) payload, and SOXS High Energy Detector (SHD) payload. The SLD consists of two solid state detectors Si PIN and CZT, which cover the energy range from 4-60 keV, while the SHD has NaI(Tl)/CsI(Na) sandwiched phoswich detector that covers energy range from 20 keV to 10 MeV. We present very briefly the science objectives and instrumentation of SLD payload. After the successful In-orbit Tests (IOT), the first light was fed into SLD payload on 08 June 2003 when the solar flare was already in progress. We briefly present the first results from the SLD payload.

scholarly journals Plasma Processes in Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 355-364
Author(s):  
V.M. Tomozov
Keyword(s):  
Solar Flares ◽  
Large Scale ◽  
Stark Effect ◽  
Active Regions ◽  
Theoretical Models ◽  
Radio Bursts ◽  
X Ray ◽  
Plasma Effects ◽  
Collective Plasma

A rationale is presented for a conception that appearance of flares in active regions is due to the interaction of large-scale convective elements. Such an interaction gives rise to shear motions in the vicinity of the inverse polarity line of the photospheric magnetic field which generate vortical motions leading to non-equilibrium state of the magnetic configuration. Modern concepts of manifestations of turbulent plasma processes are described in terms of theoretical models for solar flares. Plasma effects arising at propagation of electron beams and thermal fluxes in the solar atmosphere are considered. Their role in the interpretation of hard X-ray and type III radio bursts is pointed out. The role of the turbulent Stark effect for diagnostics of collective plasma processes in solar flares is emphasized.

The role of magnetic loops in solar flares

1991 ◽  
Vol 336 (1643) ◽  
pp. 389-400 ◽  
Keyword(s):  
Solar Flare ◽  
Spatial Structure ◽  
Spatial Resolution ◽  
Solar Flares ◽  
Solar Maximum ◽  
Magnetic Topology ◽  
Solar Maximum Mission ◽  
X Ray ◽  
Ultraviolet Observations

X -ray and ultraviolet observations of flares have provided much important information on their spatial structure and magnetic topology. The early observations from Skylab emphasized the role of simple loops and loop arcades, but later observations from the Solar Maximum Mission have greatly complicated this picture. Flares appear in a multitude of loops with complex spatial and temporal interrelations. In many cases, interactions between different loops appear to play a crucial role. The inferred magnetic topology of solar flares will be reviewed with emphasis on the implications for processes of energy release and transfer. It will be shown that the spatial resolution of the observations obtained so far is still inadequate for solving many basic questions of solar flare research.

Energetic particles in solar flares: theory and diagnostics

1991 ◽  
Vol 336 (1643) ◽  
pp. 413-424 ◽  
Keyword(s):  
Solar Flares ◽  
Gamma Ray ◽  
Low Energy ◽  
Emission Data ◽  
Energetic Electrons ◽  
X Ray ◽  
Electrons And Ions ◽  
Low Energy Ions ◽  
Impact Polarization ◽  
Major Progress

Recent progress and future prospects in diagnostics of energetic electrons and ions in the flares are reviewed, together with the roles they play in the flare as a whole. Most of the discussion centres on hard X-ray and gamma-ray and thermal plasma emission data, rather than on radio sources. Since Solar Maximum Mission and Hinotori there has been major progress in all areas of flare electron diagnostics. Electron spectra are now recoverable with some precision, electrons with energies above 10 MeV are known to be highly anisotropic, and indications are available of the spatial distribution of electrons at 20 keV. Timescales of electron acceleration are now known to be shorter than 0.1 s. Energetic electrons are believed to carry much of the flare power. Ion diagnostics are more limited. For greater than 1 MeV ions the flux, spectrum and acceleration timescale are now quite well known. Low energy ions are hard to diagnose but have been invoked as a flare heating mechanism alternative to electron beams. The problems with beam heating models are discussed with special attention to the problems of the low energy proton model and its only direct diagnostic, Hα impact polarization. Finally, theoretical problems associated with return currents and with accelerator requirements are discussed and attention is drawn to the possible importance of entropy as well as energy considerations.

scholarly journals Recent Observations of Energetic Electrons in Solar Flares

1980 ◽  
Vol 91 ◽  
pp. 227-230
Author(s):  
S. R. Kane
Keyword(s):  
Spatial Resolution ◽  
Solar Flares ◽  
Electron Distribution ◽  
Energetic Electron ◽  
Low Energy ◽  
Thermal Source ◽  
X Rays ◽  
Energetic Electrons ◽  
X Ray ◽  
Wide Range

SummaryIt has been apparent for the last few years that a large fraction of the total energy released during a solar flare appears initially in the form of energetic electrons accelerated during the impulsive phase. An estimate of the energy of these electrons is based on the observed hard x-ray spectra as well as the assumed form (thermal or non-thermal) of the electron distribution. Even after the basic form of the electron distribution is assumed, additional assumptions, such as the low energy cut-off in the case of the power law energy spectrum or existence of a multi-thermal source in the case of the thermal spectrum, are usually required. In order to test these assumptions, measurements of the hard x-ray spectrum with spatial resolution and covering a wide range of x-ray energy are essential. In absence of good spatial resolution, as is the case with most of the presently available hard x-ray observations, the impulsive x-ray emission at energies hv ≲ 10 keV is often unobservable because of the presence of a large background of relatively intense gradual emission associated with most flares. Observations made in the past suffered either because of the lack of a clearly identifiable impulsive x-ray emission at low energies (Peterson et al, 1973) or an adequate spectral resolution (Kahler, 1973). Thus so far it has not been possible to measure unambiguously the spectrum of impulsive x-rays ≲ 10 keV and hence to deduce a possible low energy cut-off in the energetic electron spectrum. Here we report briefly such an observation made with the ISEE-3 x-ray spectrometer experiment and its implications with regard to the characteristics of energetic electrons in solar flares.

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