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Solar Simple Bursts Observed with High Spectral Resolution in the 18-23 GHz Range

Published online by Cambridge University Press:  12 April 2016

H. S. Sawant ,
R. R. Rosa ,
J. R. Cecatto  and
N. Gopalswamy
H. S. Sawant
Affiliation:
Instituto Nacional de Pesquisas Espaciais (INPE), Cx. Postal 515, 12201-970, São José dos Campos, SP, Brazil
R. R. Rosa
Affiliation:
Instituto Nacional de Pesquisas Espaciais (INPE), Cx. Postal 515, 12201-970, São José dos Campos, SP, Brazil
J. R. Cecatto
Affiliation:
Instituto Nacional de Pesquisas Espaciais (INPE), Cx. Postal 515, 12201-970, São José dos Campos, SP, Brazil
N. Gopalswamy
Affiliation:
University of Maryland, College Park, Md 20742

Abstract

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For the first time, solar bursts in the frequency range of (18-23) GHz have been observed with high-time (0.6-1.2 s) and high-frequency resolution (1 GHz), by using the Itapetinga 13.7m diameter antenna. Here, we investigate the microwave type “simple low level (< 10 SFU) bursts” associated with the impulsive phase of solar flares. Observed properties of these simple bursts are: rise time tr ~3 s, decay time td ~ 5 s and spectral index ranging between −1 and −4. These bursts were found to be associated with SF or SN flares as seen in Hα. The above properties suggest that they are likely to be a microwave counterpart of elementary flare bursts. In the majority of the cases the spectral evolution is soft-hard-soft. This suggests a nonthermal gyrosynchrotron mechanism for generating these elementary flare bursts. Estimated parameters of these simple burst sources are height (h ~ 2400 km), electron density (Nє < 8.8 × 109 cm−3 ), and magnetic field (B ~ 300 G).

Subject headings: radiation mechanisms: nonthermal — Sun: radio radiation

Type
Poster Papers
Information
International Astronomical Union Colloquium , Volume 142: Particle Acceleration Phenomena in Astrophysical Plasmas , 1994 , pp. 693 - 695
Copyright
Copyright © The American Astronomical Society 1994

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