Double hard X-ray peaks inRHESSIflares as evidence of chromospheric evaporation and implications for modifying the Neupert effect

2009 ◽  
Vol 9 (10) ◽  
pp. 1155-1164 ◽  
Author(s):  
You-Ping Li ◽  
Wei-Qun Gan ◽  
Yang Su
1994 ◽  
Vol 144 ◽  
pp. 275-277
Author(s):  
M. Karlický ◽  
J. C. Hénoux

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.


1985 ◽  
Vol 19 (1) ◽  
pp. 64-68
Author(s):  
M. E. Machado

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).


2002 ◽  
Vol 580 (1) ◽  
pp. L73-L76 ◽  
Author(s):  
Manuel Güdel ◽  
Marc Audard ◽  
Stephen L. Skinner ◽  
Matthias I. Horvath

2004 ◽  
Vol 219 ◽  
pp. 249-253
Author(s):  
Rachel A. Osten ◽  
Suzanne L. Hawley ◽  
Joel Allred ◽  
Christopher M. Johns-Krull ◽  
Christine Roark ◽  
...  

We report on a large, multi-wavelength campaign to observe variability across the electromagnetic spectrum in the M dwarf flare star EV Lacertae, in 2001 September. The campaign involved X-ray (Chandra ACIS-S+HETG), UV (HST/STIS), and optical (McDonald) spectra, as well as optical photometry and multi-frequency radio (VLA) observations. EV Lac demonstrated both frequent and extreme variability during the course of the two day intensive recordings. Dispersed X-ray spectra confirm the metal underabundance seen in other active stars. The increase in continuum fluxes at short X-ray wavelengths during flare intervals compared to quiescent intervals signals the creation of high temperature plasma, a signature of the flare process. Multi-wavelength comparisons reveal interesting trends: X-ray flare frequencies are within the range predicted by optical observations, yet there is no correspondence between X-ray flares and optical flares in our data. Two UV flares occur during the rise stages of X-ray flares; a major radio flare is accompanied by a large optical flare, which has no apparent counterpart in the X-ray. The results give conflicting evidence for the applicability of the Neupert effect interpretation in stellar coronae.


2020 ◽  
Vol 10 ◽  
pp. 64
Author(s):  
Ruhann Steyn ◽  
Du Toit Strauss ◽  
Frederic Effenberger ◽  
Daniel Pacheco

The acceleration and injection of solar energetic particles (SEPs) near the Sun is one of the major unsolved problems in contemporary SEP transport modeling efforts. Here, we establish a new approach to the injection problem by utilizing a correlation between the soft X-ray thermal emission in solar flares, and their hard X-ray counterpart, the so-called Neupert effect, which is indicative of the presence of non-thermal particles. We show that the resulting injection function, in the initial phase of the flare, is similar to those inferred from inverting the transport problem based on in-situ observations. For few cases, we find early injections with no in-situ correspondence, that can be caused by particles accelerated before there is a magnetic connection between the source and the spacecraft. The method has limitations for long-duration injections, since it is not applicable to the decay phase of the flare where particle trapping might play a role. For a sample of SEP events in 1980, observed with the Helios-1 and IMP8 spacecraft, we show the results of a 2D SEP transport model based on this approach. We discuss that, with this method, a physics-based, real-time operational SEP now-cast model for the heliosphere is feasible.


Author(s):  
Alexey Kirichenko ◽  
Sergey Kuzin ◽  
Sergey Shestov ◽  
Artem Ulyanov ◽  
Andrey Pertsov ◽  
...  

We present a description of the recent advances in the development of the KORTES assembly—the first solar oriented mission designed for the Russian segment of the International Space Station. KORTES consists of several imaging and spectroscopic instruments collectively covering a wide spectral range extending from extreme ultraviolet (EUV) wavelengths to X-rays. The EUV telescopes inside KORTES will trace the origin and dynamics of various solar phenomena, e.g., flares, CMEs, eruptions etc. EUV spectra provided by grazing-incidence spectroheliographs will enable precise DEM-diagnostics during these events. The monochromatic X-ray imager will observe the formation of hot plasma in active regions and outside them. The SolpeX module inside KORTES will offer an opportunity to measure fluxes, Doppler shifts and polarization of soft X-ray emission both in lines and continuum. SolpeX observations will contribute to studies of particle beams and chromospheric evaporation. The instrumentation of KORTES will employ a variety of novel multilayer and crystal optics. The deployment of KORTES is planned for 2024.


2016 ◽  
Vol 12 (S327) ◽  
pp. 103-108
Author(s):  
V. M. Sadykov ◽  
A. G. Kosovichev ◽  
I. N. Sharykin ◽  
I. V. Zimovets ◽  
S. Vargas Dominguez

AbstractInitiation and development of a M 1.0 class flare of June 12, 2014, was observed by space and ground-based telescopes, including EUV and X-ray imaging spectroscopy by IRIS and RHESSI, and high-resolution optical imaging by 1.6 m New Solar Telescope (NST). Analyzing the NST data, we found small-scale loop-like structures in the region of the magnetic field Polarity Inversion Line (PIL), the emergence and interaction of which caused photospheric brightenings temporarily coinciding with hard X-ray impulses. Detailed studies of the PIL region reveal signatures of photospheric plasma downflows and dissipation of electric currents. The reconstructed magnetic field topology shows a bundle of lines connecting the PIL region with the flare ribbons which were places of chromospheric evaporation observed by IRIS. The observations suggest a scenario with the primary energy release processes located in the low atmospheric layers of the PIL, energizing the overlying large-scale magnetic structure and causing “gentle” chromospheric evaporation.


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