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Astron. Astrophys. 342, 583-591 (1999)

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Yohkoh observations of the Neupert effect

M. Tomczak

Astronomical Institute, Wrocaw University, Kopernika 11, PL-51-622 Wrocaw, Poland (e-mail: tomczak@astro.uni.wroc.pl)

Received 18 February 1998 / Accepted 4 November 1998


A Neupert effect is a well-known observational aspect of dynamics of many solar flares during their impulsive phase. Imaging capabilities of the Yohkoh satellite provide a new perspective in an investigation of this effect. In this paper it has been shown that impulsive soft X-ray brightenings are a direct cause of some soft X-ray excess resulting as the Neupert effect. An additional observational confirmation is presented that the impulsive phase of flares showing the Neupert effect is dominated by non-thermal electron beams. The importance of relatively soft (below 10 keV) non-thermal electrons in the production of soft X-ray brightenings is suggested.

Key words: Sun: X-rays, gamma rays – Sun: flares – Sun: corona

© European Southern Observatory (ESO) 1999

Online publication: February 22, 1999