Metric radio emission associated with X-ray plasmoid ejections

In this paper we report the first detection of metric/decimetric radio emis sion associated with two soft X-ray plasmoid ejecta events that occurred du ring two limb flares observed by the Yohkoh SXT. In the first event a loop started to rise slowly (similar to 10 km s(-1)) before the beginning of the hard X-ray impulsive phase of the flare. At about the onset of the impulsi ve flare, there was acceleration of the ejecta, resulting in a speed of 130 km s(-1) and finally to similar to 200 km s(-1). The associated radio emis sion was observed with the Nancay radioheliograph (NRH) in the frequency ra nge of 230-450 MHz. It was an unpolarized continuum that lasted 8-10 minute s. The 410 MHz source was located close to the height where the plasmoid wa s last identified in the SXT images. In the second event an eruption result ed in the expansion of a large-scale, looplike feature and the development of two plasmoid ejecta which moved in different directions. The speed of th e ejecta was 60-100 km s(-1). In this event, the associated radio emission was a long-lasting (about 2 hr) continuum observed from 450 to 164 MHz. The onset of the low-frequency emission was delayed with respect to the onset of the high-frequency emission. In both cases the radio sources were locate d above the soft X-ray ejecta in the general direction of the prolongation of the ejecta movement. In both cases the radio emission comes from nonther mal electrons which are accelerated in close relationship with the propagat ion of the X-ray plasmoid: as the plasmoid reaches higher altitudes, it int eracts with increasingly more extended magnetic field lines and new coronal sites of production of nonthermal electrons are created.