FLARE MULTI-LINE 2D-SPECTROSCOPY

Abstract

A small flare was observed at the Teide Observatory on October 5, 1994. Simultaneous data were obtained at the German Vacuum Tower Telescope (VTT) with the MSDP spectrograph providing high-resolution imaging spectroscopy in two chromospheric lines, and the Gregory Coudé Telescope (GCT) providing information about the magnetic field. Basic flare characteristics are:

The area of the flare kernel (≤ 2 x 2 arc sec) is similar in Hα and Caii 8542 Å.

The early phase of the flare is characterized by a blue asymmetry in Hα and a red one in Caii 8542 Å line.

The evolutions of line profiles are different; the red asymmetry observed in the Caii line is detected a few seconds later in Hα.

The maximum asymmetry of the Caii line does not coincide with the maximum brightness.

The flare occurs in a region of a strong horizontal gradient of the line-of-sight component of the magnetic field.

Brightness and asymmetry in Hα and Caii are discussed in the context of standard flare models and velocity fields. Our observations suggest that a magnetic reconnection could occur at low levels of the solar atmosphere.