YOHKOH OBSERVATION OF THE SOURCE REGIONS OF SOLAR NARROW-BAND, MILLISECOND SPIKE EVENTS

The source regions of metric spike events are investigated on Yohkoh s oft X-ray (SXR) maps. The spikes are identified by the spectrometer Ph oenix between 300 MHz and 360 MHz and are associated with groups of ty pe III bursts at lower frequencies reaching also the decametric range. The Very Large Array (VLA) provides simultaneously spatial informatio n at 333 MHz, 1446 MHz and 4866 MHz. Similar to the previous VLA obser vation of a metric spike event, the new data are consistent with a hig h altitude of the spike sources of about 5.10(10) cm above the photosp here. The additionally available SXR data for one of the presented eve nts give the following new informations: (i) The spike sources occur n ear open field lines and near regions of a slightly enhanced SXR flux relative to the ambient plasma. (ii) Contrary to SXR observations of t ype III bursts without metric spike activity, no SXR jet is observed. (iii) At low altitude, a weak SXR enhancement occurs, peaking about 60 s after the spike event. The SXR source and the spike sources can be connected by potential field lines. The observations corroborate a mod el in which a metric spike event is attributed to an energy release re gion at high altitude, while upwards propagating electrons produce typ e III bursts and downward moving electrons are responsible for SXR emi ssion of heated plasma.