Observations of Filaments at Centimeter and Millimeter Wavelengths

Abstract

At cm and mm wavelengths, the quiescent prominences seen on the disk appear as depressions in brightness temperature that are well correlated with Ha dark filaments. In a large number of cases, the sizes of the radio and optical filaments are similar. However, in some cases, the radio filaments have been found to be broader and to persist longer than their optical counterparts. Undisputed examples of broadening have been provided by Kundu and McCullough (1972) at 9 mm (2;5 arc size compared to Ha size of 0;5), and by Kundu et al. (1978) at 5 wavelengths between 0.4 and 11 cm (with half-power beam widths of 017-5’) of a filament whose undeconvolved angular size, 2;2 × 2;7, greatly exceeded the 0;5 × 0;5 nize of the enclosed Ha filament. Specific examples of persistance have been provided by Kundu (1972) and by Kundu and Lantos (1977) who observed 3.5 mm ‘disparition bursque’ events. In the two events, Ha filaments were observed to lie. within the contours of a radio depression; after the Ha filaments disintegrated, the radio depression persisted, though with reduced contrast The depressions reach temperatures below the background of up to 400 K at mm-λ and ~ 1000-5000 K at cm-λ. These values correspond to brightness temperatures of ~ 6000 K at mm-λ and 7000-14000 K at cm-λ.