Radio and X-Ray Imaging Observations of a Continuum Burst

We study a metric continuum burst observed on 1993 February 18, and its X-ray signatures from imaging observations in radio and X-rays using the Nançay radioheliograph and the Yohkoh Soft X-Ray Telescope (SXT). The event in question was associated with weak type III bursts; these were detected at only one frequency (164 MHz), except for one burst (at 10:58:05 UT), which was observed over a broad frequency range (164-435 MHz). We believe that the early metric continuum burst is an extension of the microwave continuum which was observed at frequencies as high as 5 GHz, and its onset at ~10:50 UT is associated with the development of an X-ray-emitting diffuse loop system which appears to advance with a speed of ~50-100 km s^-1. The observed type III bursts seem to correspond to the repeated occurrence/appearance of a collimated jet emanating from the loop system that is responsible for the continuum burst. A few minutes prior to the main continuum onset there is a soft X-ray ejection from the main flare region. The main continuum has a brightness temperature greater than 10⁸ K; it is unpolarized, and it shows dispersion in position with frequency and moves with speeds of ~50 km s^-1 at 236-410 MHz. The SXT images reveal that this initially ejected soft X-ray-emitting hot plasma seems to gradually fill up the loop system with hot material. This hot plasma must contain enough energetic electrons of energy greater than several tens of keV, which are responsible for producing the metric continuum burst by plasma radiation mechanism.