Fifty Years of Solar Radio Astronomy

Abstract

An account is given of the history of solar radio astronomy, starting from the early failures to the serendipitous discovery of solar radio waves by Hey in 1942. Major advances in solar radio research at meter-decameter, kilometer-hectometer and centimeter wavelengths are discussed. Observations of flare associated radio bursts and their interpretations in terms of plasma and gyrosynchrotron radiations are discussed. In-situ measurements from space of plasma oscillations in association with type III bursts and of one-dimensional electron velocity distributions have confirmed their interpretation by plasma radiation. Radioheliograph measurements at meter-decameter wavelengths and spacecraft measurements at kilometer-hectometer wavelengthss of type III bursts have shown that the type III electron streams travel along dense coronal streamers and along archimedean spiral trajectories. High spatial resolution observations of active regions and bursts at centimeter wavelengths, using large arrays with arc second resolution have shown the power of such measurements in measuring coronal magnetic fields, understanding the physics of coronal loops, measuring the magnetic field topology in the vicinity of flares and thereby understanding the origin of solar flares.