Issue |
A&A
Volume 392, Number 2, September III 2002
|
|
---|---|---|
Page(s) | 699 - 712 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20020947 | |
Published online | 30 August 2002 |
Investigation of the Neupert effect in solar flares
I. Statistical properties and the evaporation model
1
Institute for Geophysics, Astrophysics and Meteorology, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
2
Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kačićeva 26, HR-10000 Zagreb, Croatia
3
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
Corresponding author: A. Veronig, asv@igam.uni-graz.at
Received:
11
April
2002
Accepted:
6
June
2002
Based on a sample of 1114 flares observed simultaneously in
hard X-rays (HXR) by the BATSE instrument and in soft X-rays (SXR) by
GOES, we studied several aspects of the Neupert effect and its interpretation in the
frame of the electron-beam-driven evaporation model. In particular,
we investigated the time differences () between the maximum of the
SXR emission and the end of the HXR emission, which are expected to occur at
almost the same time. Furthermore, we performed a detailed analysis of the SXR peak
flux – HXR fluence relationship for the complete set of events, as well as separately
for subsets of events which are likely compatible/incompatible with the timing
expectations of the Neupert effect. The distribution of the time
differences reveals a pronounced peak at
. About half of the events
show a timing behavior which can be considered to be consistent with the
expectations from the Neupert effect. For these events, a high correlation between
the SXR peak flux and the HXR fluence is obtained, indicative of
electron-beam-driven evaporation. However, there is also a significant
fraction of flares (about one fourth), which show strong deviations from
, with a prolonged increase of the SXR emission distinctly
beyond the end of the HXR emission. These results suggest that electron-beam-driven
evaporation plays an important role in solar flares. Yet, in a significant fraction
of events, there is also clear evidence for the presence of an additional
energy transport mechanism other than nonthermal electron beams,
where the relative contribution is found to vary with the flare importance.
Key words: Sun: flares / Sun: X-rays, gamma rays / Sun: corona / Sun: chromosphere / methods: statistical
© ESO, 2002
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