Solar spectral fine structure in 18-23 GHz band

On 30th June 1989 high sensitivity-spectral resolution observations of sola r radio bursts were carried out in the frequency range of 18 - 23 GHz. The burst observed at 17:46 UT was different from the 60 bursts observed so far in the sense that it exhibited a frequency fine structure superimposed on the ongoing burst in its rising phase, i.e. an additional enhancement of th e Aux density of the order of 10 SFU, observed only in the 21 and 22 GHz fr equency channels, lasting for about 4 s. Interaction of an emerging loop wi th an adjacent loop accelerated particles in that loop from which the broad band burst was emitted due to the gyrosynchrotron emission. The observed fi ne structure is interpreted as due to thermal gyro-emission at 6th harmonic of the gyrofrequency originated from a hot kernel with short lifetime loca ted at the top of emerging loop. We derived the hot kernel source parameter s, the temperature as 8 x 10(7) K, the magnetic field as similar or equal t o 1250 G and the density as similar or equal to 5 x 10(12) cm(-3).