The microwave subsecond pulse of September 17, 2001: The spectrum, location and size of the source

Abstract

We examine simultaneous observations of microwave subsecond pulses with high temporal, spatial and spectral resolution from the Siberian Solar Radio Telescope (5.7 GHz, 14 ms resolution) and from the spectropolarimeters (5.2-7.6 GHz, 6 ms) of the National Astronomical Observatories. The September 17, 2001 flare is discussed in detail. The subsecond pulse (SSP) was observed in the initial phase of the flare, and its HWFH duration was 40 ms. The pulse was accompanied by a rapid change of the dynamic spectrum whose width was about 1%, and the degree of polarization made up 35%. The time profile at the SSRT frequency depends substantially on the SSP's spectral features. The SSP was observed by both the NS (North-South) and EW (East-West) arms (in two interference orders in the latter case). SSP sources locations in burst structures were determined. We also find that the source was not a point-like one, but its apparent size was about the beam width (15 arcsec) for the NS scanning direction. In the EW direction the SSP was less than 10 arcsec in size.