EDP Sciences
Free access
Volume 387, Number 2, May IV 2002
Page(s) 678 - 686
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20020454

A&A 387, 678-686 (2002)
DOI: 10.1051/0004-6361:20020454

Chromospheric models of a solar flare including velocity fields

A. Falchi1 and P. J. D. Mauas2

1  Osservatorio Astrofisico di Arcetri, 50125 Firenze, Italy
2  Instituto de Astronomía y Física del Espacio, Buenos Aires, Argentina
    e-mail: pablo@iafe.uba.ar

(Received 14 December 2001 / Accepted 25 March 2002 )

We study the chromospheric structure of a small flare, before, during and after the first hard X-ray spike. We construct 5 semiempirical models for different times, which will reproduce the profiles of the H $_{\delta}$, Ca II K and Si I 3905 lines during the flare evolution. In order to reproduce the intensity and the main characteristics of the line asymmetry, we introduce the velocity fields in the profile calculations. We find that the whole chromosphere undergoes a strong upward motion within 1 s of the maximum of the first hard X-ray spike, when the temperature and the density begin to rapidly increase. This seems the first chromospheric response to the energy deposition and/or release. Only 6 s after the hard X-ray peak, a strong downflow begins in the low chromosphere and its velocity continues to increase even during the cooling phase.

Key words: Sun: chromosphere -- Sun: flares

Offprint request: A. Falchi, falchi@arcetri.astro.it

© ESO 2002