Thinkshop12

On Measurements of Optical Continuum Flux in Solar Flares

Pavel Kotrc (Astronomical Institute, Academy of Sciences of the Czech Republic)

Abstract. For a broad-band diagnostics of chromospheric flare plasma it is highly desirable to analyze spectra covering many spectral lines and various continuum features. While the flare spectra are well detected on the background of the solar disk, the detection of flare line emission from the Sun-as-a-star in optical is much more difficult due to a strong background radiation. Supposing the flare/background radiation contrast is strong enough to be detected, we developed a device for measuring the flux from a selected part of the flaring region. Here we present a technical description of the post-focus instrument installed at the horizontal solar telescope HSFA2 of the Ondřejov observatory. It consists of a system of diaphragms, imaging Hα telescope and a fast spectrometer with low dispersion (up to 3 pixel per Ångström) but with a cadence reaching up to 50 frames per second. The first solar flares observed recently by this novel technique provide quite interesting results which are presented and discussed.

Contributed Talk