VI. Solar Radiophysics

Abstract

The past 3 years since the last solar maximum have witnessed an unprecedented number (>200) of published scientific papers on many aspects of solar radiophysics. These contributions are the result of an intense research effort mounted during the first Solar Maximum Mission of 1980 and continued until the present. Excellent x-ray, EUV, and visible light observations of the disturbed corona and transition region have been obtained from the SMM, Hinotori, P78-1, and ISEE-3 spacecraft. ISEE-3 also has provided very low-frequency radio observations of solar bursts in the interplanetary medium. Ground-based radio support for space experiments has been provided by many observatories throughout the world. In particular, many collaborative studies using x-ray and radio observations of solar flares have been reported. The outstanding radio instrument during this period has been the VLA, operating at 2, 6, and 20 cm with a time resolution of 10 s and both modes of circular polarization. The two-dimensional spatial resolution of the radio images is a few seconds of arc, almost as good as the best resolution obtained so far at any wavelength in the solar spectrum. To complement the rather poor time resolution of the VLA one-dimensional arrays such as the WSRT at 6 cm wavelength and the Nobeyama interferometer at 17 GHz have been used successfully. In addition, a number of very-high-time resolution radiometers have been built at different locations. At meter wavelengths two-dimensional arrays at Clark Lake, Culgoora, and Nancay and a one-dimensional array at Nobeyama have been employed. The little known region of the solar spectrum at decimeter wavelengths is being investigated by the Zurich spectrograph. It is pleasing to see Chinese participation in solar radiophysics.

Radio Emission of Flares and Coronal Mass Ejections

“…Moving type IVs (IVm) are outward-moving radio blobs associated with CMEs. They occur rarely and include isolated plasmoids (Wagner et al, 1981), expanding arches, and advancing fronts (Stewart, 1985). We note that plasma emission is not the only possible emission mechanism for IVm bursts.…”

A Highly Circularly Polarized Solar Radio Emission Component Observed at Hectometric Wavelengths

“…The radiation from these moving type IV radio bursts is known to drift slowly to lower frequencies, to be highly circularly polarized (≥90%), to often exhibit quasi-periodic pulsations, and to be comparatively rare (Stewart, 1985). It is intriguing therefore to speculate that this polarized hectometric radio event may be a rare interplanetary manifestation of a moving type IV burst.…”

A model for the coherent emission of solar radio moving type IV bursts

“…These radio bursts appear in the metric wavelength range (< 300 MHz) and possess broad spectra [1]. As revealed by white-light coronagraphic observations [ 2], the source of the moving type IV radio bursts is associated with a magnetic arc that extends slowly (~200--1600km/s) toward the higher coronal layers and lower frequencies [1,3] . The most noteworthy characteristics of these bursts are high brightness temperature, which sometimes exceeds 109 K, and high degree of polarization [3,4].…”