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D. E. Gary (New Jersey Institute of Technology), V. F. Melnikov (Radiophysical Research Institute (NIRFI)), G. M. Nita (New Jersey Institute of Technology)
We have investigated the dynamical behavior of the radio spectrum of more than 300 microwave bursts observed with the Owens Valley Solar Array in the range 1.2-18 GHz. For this talk, we concentrate on the evolution of the peak frequency of the spectrum as measured throughout the bursts. We find that in most bursts the evolution fits the expected behavior for gyrosynchrotron emission, moving to higher frequencies on the rise and falling back on the decay of the burst. However, for some 35% of bursts we find that this expected behavior is modified during part or all of the burst by the presence of Razin Suppression, which is expected in sources with higher than usual ambient density. Looking at other aspects of the spectral evolution, we deduce several measures that occur together to uniquely distinguish the presence of Razin Suppression. The presence of Razin Suppression has historically been associated only with the presence of a steeper than usual low frequency spectral slope, but this traditional diagnostic is valid only for homogeneous sources and can be completely masked in the typical case of inhomogeneous or multiple sources. Our new diagnostics of Razin Suppression reveal its presence even for inhomogeneous sources, and hence has a wider range of validity. The new diagnostics will be especially useful with the high resolution imaging microwave spectroscopy that will be provided by the proposed FASR array. This work is supported by NSF grant AST-0307670 to New Jersey Institute of Technology.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.