Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001pbeio..37...46l&link_type=abstract
Astrophysics Reports. Publications of the Beijing Astronomical Observatory, No. 37, p. 46 - 54 (2001). In: Proceedings of the Ei
Astronomy and Astrophysics
Astrophysics
Solar Flares, Infrared, Line Profiles
Scientific paper
The HeI 10830 Å spectra observed during the 2N/X20 solar limb flare of 16 August 1989 show unusually broadened profiles in the impulsive phase, and most of the spectra are blueshifted and/or blue asymmetric with full-width-at-half-maximum (FWHM) greater than 10 Å. Contrary to prominences, weak post-flare loops and surges, the profiles of the flare cannot be simulated by Doppler broadening with a uniform flaring atmosphere model. Calculations show that only when the electron density is greater than 1016 cm-3 can Stark broadening produce obvious influence on He I 10830 Å profile. This indicates that it is not plausible that Stark broadening leads to the observed profiles even though the observed profiles can be fitted by Stark broadening. Alternatively, an expanding flaring atmosphere can perfectly simulate all the observed He I 10830 Å profiles. The expanding velocities are generally several-tens of km s-1 and the widest profile corresponds to an expanding velocity greater than 120 km s-1. This and other parameters vary with time and the observed area. The expanding flaring atmosphere model is a perspective candidate. It is the indication of the lateral expansion resulted from the rapid chromospheric heating by non-thermal electrons or thermal conduction, in addition to the upward chromospheric evaporation and downward chromospheric condensation.
Li Hui
You Jianqi
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