On the Origin and Morphology of Complex Hectometric Type III-like Radio Emissions Observed by Wind/WAVES

Michael J. Reiner

Abstract

Cane et al. (1981) identified a class of intense, complex, hectometric-kilometric  type III-like bursts (SA events) that  they believed to be produced by electrons accelerated by blast-wave shocks high in the solar corona. Verification of this hypothesis, however, was hampered by the lack of radio observations in the frequency range from ~2 to 20 MHz. Radio receivers  on the Wind spacecraft have recently provided observations in the region of this frequency  gap. In this talk, we review these new observations. Bougeret et al. (1998) observed one type III-like burst that appeared to originate from the backbone of a metric type II burst, which are believed to correspond to coronal shocks. This type III-like burst, which was not associated with any metric type III or decimetric radio emissions, was observed to extend through the kilometric wavelength regime. Reiner and Kaiser (1999) studied the morphological characteristics of intense, complex type III-like bursts in the frequency range from 1 to 14 MHz and found distinct differences above and below ~7 MHz, suggesting different origins. Finally, Reiner et al. (2000) studied a number of complex, hectometric-kilometric type III-like events that were associated with the simultaneous presence of decimeter wavelength radio emissions. From a comparison of the shape and duration of the burst profile at 1 MHz with that at decimetric wavelengths, they concluded that the complex type III-like bursts were likely generated by electrons accelerated by the primary flare energy release process.

Cane, H. V. et al., Geophys. Res. Lett., 12, 1285, 1981
Bougeret, J.-L. et al., Geophys. Res. Lett., 25, 2513, 1998
Reiner, M. J. and M. L. Kaiser, Geophys. Res. Lett., 26, 397, 1999
Reiner, M. J. et al., Astrophys. J., 530, xxx, 2000

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