Non-thermal Electron Energization During the Impulsive Phase of an X9.3 Flare Revealed by Insight-HXMT

AbstractSpectral line intensities observed by the Extreme Ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) during 2012 March 9 M6.3 flare were used to diagnose a presence of a non-thermal electron distribution represented by a κ-distribution. The diagnosed electron densities ($\approx 2 \times {10^{11}}{\rm{c}}{{\rm{m}}^{ - 3}}$) are affected only a little by the presence of the non-thermal distribution, and are within the uncertainties of observation. On the other hand, the temperature diagnostics based on the line ratios involving different ionization degrees is strongly affected by the type of the electron distribution. The distribution functions diagnosed from relative Fe line intensities demonstrate the presence of strongly non-thermal distributions during the impulsive phase of the flare and later their gradual thermalization.

Download Full-text

Plasma heating in the initial phase of solar flares

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309992791 ◽

2009 ◽

Vol 5 (S264) ◽

pp. 282-284

Author(s):

P. Rudawy ◽

M. Siarkowski ◽

R. Falewicz

Keyword(s):

Solar Flares ◽

Energy Transport ◽

Electron Beams ◽

Plasma Heating ◽

Impulsive Phase ◽

Thermal Electron ◽

Flare Loop ◽

X Ray ◽

Heating Source ◽

Rise Phase

AbstractIn this paper we analyze soft and hard X-ray emission of the 2002 September 20 M1.8 GOES class solar flare observed by RHESSI and GOES satellites, where soft X-ray emission precedes the onset of the main bulk hard X-ray emission by ~5 min. This suggests that an additional heating mechanism may be at work at the early beginning of the flare. However RHESSI spectra indicate presence of the non-thermal electrons also before impulsive phase. So, we assumed that a dominant energy transport mechanism during rise phase of solar flares is electron beam-driven evaporation. We used non-thermal electron beams derived from RHESSI spectra as the heating source in a hydrodynamic model of the analyzed flare. We showed that energy delivered by non-thermal electron beams is sufficient to heat the flare loop to temperatures in which it emits soft X-ray closely following the GOES 1–8 Å light-curve.

Download Full-text

Type II Solar Radio Bursts over Solar Cycle 21

International Astronomical Union Colloquium ◽

10.1017/s025292110002546x ◽

1994 ◽

Vol 144 ◽

pp. 283-284

Author(s):

G. Maris ◽

E. Tifrea

Keyword(s):

Solar Radio ◽

Interplanetary Space ◽

Impulsive Phase ◽

Radio Bursts ◽

Type Ii ◽

Solar Radio Bursts ◽

Strong Energy ◽

Mass Ejection ◽

Geophysical Effect ◽

Radio Event

The type II solar radio bursts produced by a shock wave passing through the solar corona are one of the most frequently studied solar activity phenomena. The scientific interest in this type of phenomenon is due to the fact that the presence of this radio event in a solar flare is an almost certain indicator of a future geophysical effect. The origin of the shock waves which produce these bursts is not at all simple; besides the shocks which are generated as a result of a strong energy release during the impulsive phase of a flare, there are also the shocks generated by a coronal mass ejection or the shocks which appear in the interplanetary space due to the supplementary acceleration of the solar particles.

Download Full-text

Recent developments in low-voltage SEM of polymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150162 ◽

1993 ◽

Vol 51 ◽

pp. 866-867

Author(s):

S.J. Krause ◽

W.W. Adams

Keyword(s):

Low Voltage ◽

Chromatic Aberration ◽

Thermal Electron ◽

Analytical Technique ◽

Recent Developments ◽

Beam Currents ◽

New Generation ◽

First Time ◽

Voltage Scanning ◽

Beam Damage

Over the past decade low voltage scanning electron microscopy (LVSEM) of polymers has evolved from an interesting curiosity to a powerful analytical technique. This development has been driven by improved instrumentation and in particular, reliable field emission gun (FEG) SEMs. The usefulness of LVSEM has also grown because of an improved theoretical and experimental understanding of sample-beam interactions and by advances in sample preparation and operating techniques. This paper will review progress in polymer LVSEM and present recent results and developments in the field.In the early 1980s a new generation of SEMs produced beam currents that were sufficient to allow imaging at low voltages from 5keV to 0.5 keV. Thus, for the first time, it became possible to routinely image uncoated polymers at voltages below their negative charging threshold, the "second crossover", E2 (Fig. 1). LVSEM also improved contrast and reduced beam damage in sputter metal coated polymers. Unfortunately, resolution was limited to a few tenths of a micron due to the low brightness and chromatic aberration of thermal electron emission sources.

Download Full-text