## 1. IntroductionThe observation of millisecond microwave spikes from the Sun has
been interpreted as gyrosynchrotron maser emission since the late
1970`s (Wu & Lee 1979; Holman et al. 1980). Melrose and Dulk
(1982) have used the semi-relativistic approximation to derive
approximate formulae for the frequency of the largest growth rate, and
for the growth rate. Aschwanden (1990a,1990b) followed the evolution
of the ECM numerically, and gives frequencies and angles of largest
growth. All previous studies concentrated on the © European Southern Observatory (ESO) 1999 Online publication: July 16, 1999 |