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Observation of non‐drifting radio emissions associated with the intense solar activity in March 1991
Author(s) -
Reiner M. J.,
Stone R. G.,
Fainberg J.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/92gl00338
Subject(s) - physics , solar radio , sawtooth wave , astrophysics , frequency drift , radio frequency , spacecraft , plasma , radio wave , astronomy , optics , nuclear physics , telecommunications , phase locked loop , quantum mechanics , computer science , phase noise , computer vision
Three very unusual radio bursts, separated in time by 4 hours and 35 minute‐intervals were observed on March 28, 1991 by the radio and plasma wave (URAP) experiment on the Ulysses spacecraft. Although they are preceded by drifting type III bursts at high frequencies, they show no frequency drift at frequencies from 52 kHz down to 16 kHz. In addition, they have extraordinary sawtooth‐like profiles; they have a very rapid exponential rise of about 20 minutes independent of frequency and a much longer nonexponential decay which increases with decreasing frequency. The bursts are interpreted as due to synchrotron emission, which seems to fit many of their characteristics. This radio emission appears to be associated with an expanding source region. However, the observed intensity may be somewhat higher than expected and the possible role of the precursor type III radio bursts in triggering the low frequency non‐drifting emission remains unanswered.