Solar flare hard X-rays measured by spectrometer “IRIS”: spectral and temporal characteristics

Abstract

Sub-second time structure of hard X-rays observed during solar flares by spectrometer "IRIS" on a board of CORONAS satellite are discussed. The burst duration of 80ms and FWHM about 30ms are recorded in powerful flare of

Stationary and impulsive injection of electron beams in converging magnetic field

“…4.1. This timescale agrees closely with observations (Charikov et al 2004). Further simulations show that as long as δt e δt hxr , the hard X-ray timescale depends only on the atmosphere parameters and does not depend on the length of the initial electron impulse.…”

“…The early SMM (Kiplinger et al 1983) and CORONAS/IRIS (Charikov et al 2004) observations identify millisecond impulses in the hard X-ray emission from solar flares. Furthermore, the electron acceleration time in a reconnecting current sheet was shown by Siversky & Zharkova (2009) to be as short as 10 −5 s. The timescale of a beam of accelerated electrons should therefore be rather short.…”

“…The temporal intervals of impulsive increases in HXR emission also vary from very short tens of milliseconds (Kiplinger et al 1983;Charikov et al 2004) to tens of minutes as often observed by RHESSI (Holman et al 2003). This encouraged us to revise the electron transport models and consider solutions of a time-dependent Fokker-Planck equation for different timescales of beam injection (milliseconds, seconds, and minutes).…”

Solar flare hard X-rays measured by spectrometer “IRIS”: spectral and temporal characteristics

“…The most direct evidence of magnetic reconnection processes in solar flares is a fast time structure of hard X-rays. Sub-second pulses detected in nonthermal hard X-rays are generally interpreted as bremsstrahlung from electrons accelerated in low corona (Kiplinger et al 1983;Aschwanden 2001). "IRIS" spectrometer employs scintillation and proportional counters with large-sized windows.…”

Evolution of electron beam pulses of short duration in the solar corona

“…The evolution of an electron beam pulse is studied by launching a pulse of short duration from the top of a magnetic loop into the solar corona. Based on the observations of Xray emission from precipitating electron beams, the duration of the pulse is of the order of 10 −3 s [Charikov et al (2004); Siversky and Zharkova (2009)]. The pulse is injected at a height of 10 9 cm from the photosphere and the evolution is followed to a distance of about 3 × 10 11 cm.…”