Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999apj...510..474r&link_type=abstract
The Astrophysical Journal, Volume 510, Issue 1, pp. 474-484.
Astronomy and Astrophysics
Astronomy
3
Sun: Flares, Sun: Uv Radiation, Sun: X-Rays, Gamma Rays
Scientific paper
We have analyzed an active region which was observed in Hα (Multichannel Subtractive Double Pass Spectrograph), in UV lines (SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X-rays. Using an extrapolation based on the Fourier transform, we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find two different zones: (1) a high-shear region (>70 deg) where subflares occur, and (2) a low-shear region along the magnetic inversion line where UV bright points are observed. In these latter regions the magnetic topology is complex with a mixture of polarities. According to the velocity field observed in the Si IV lambda1402 line and the extrapolation of the magnetic field, we notice that each UV bright point is consistent with emission from low-rising loops with downflows at both ends. We notice some hard X-ray emissions above the bright-point regions with temperatures up to 8 x 10^6 K, which suggests some induced reconnection due to continuous emergence of new flux. This reconnection is also enhanced by neighboring subflares.
Démoulin Pascal
Hagyard Mona J.
Reichmann Edwin
Rovira Marta
Schmieder Brigitte
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