Radio-Astronomical Evidence for Magneto-Hydrodynamical Pulsations in the Corona

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Abstract
At Utrecht Observatory a 60-channel solar radiospectrograph has been in regular operation since the fall of 1968, in the bandwidth 160–320 MHz, with a time resolution of 0s.03 (DeGroot and Van Nieuwkoop, 1968). In addition to all generally known and classified emissions as noise storms, type IV bursts, type III bursts, type IV continua, a number of unclassified emissions have been observed. The spectrograph is particularly well suited to study short time scale fluctuations, even of small amplitude. One striking feature is an often recurring broad band (> 80 MHz) weak, quasiperiodic fluctuation superimposed on a type IV-like continuum (Figure 1). Since no interferometric measurements were available, it is not known whether it is a stationary or a moving type IV burst. However, due to the sometimes very long duration, we expect it to be a stationary type IV.