Type II flare continuum in the corona and solar wind

A solar radio type II/type IV event with exceptionally low frequency flare continuum radiation was observed on May 2, 1998 with title Wind spacecraft. This flare continuum, associated with the type II burst (FCII), descended to 7.5 Mhz (2.5-3 solar radii), the lowest frequency ever observed for this type of emission. It; lasted for >2 hours at 13.8 Mhz. Simultaneous observations were made with ground-teased radiospectrographs, and with the Extreme Ultraviolet Imaging Telescope (EIT) and Large Angle and Spectrometric Coronagraph (LASCO) telescopes. The radio event consists of a group of intense type III bursts observed from 1000 MHz down to 0.03 MHz, the plasma frequency at 1 AU. The type II burst was recorded from 45 MHz down to 0.4 MNz, and an interplanetary shock was observed at 1 AU on May 4 at 0500 UT. The type II shock commenced within a few minutes of the flash phase of the flare and of the liftoff time of a coronal mass ejection (CME) observed by EIT and LASCO. The derived speeds of the type II shock, the CME in the plane of the sky, and the shock from the Sun to 1 AU are all approximate to 1000 km s(-1). After estimating the liftoff time and radial speed of the CME front, we find that the type II shock and flare continuum were in the wake of the CME. This event shows evidence of acceleration of electrons in the corona out to 3 R-S for greater than or similar to 2 hours. Theoretical implications on the generation of the flare continuum radiation and its relation to the observed brightness temperature are considered. The source model of type II-flare continuum of Robinson [1985], in which electrons are accelerated by the shock wave tra,versing CME expanding loops, is discussed in view of these observation.