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Title:
Solar simple bursts observed with spectral resolution in the 18-23 GHz range
Authors:
Sawant, H. S.; Rosa, R. R.; Cecatto, J. R.; Gopalswamy, N.
Affiliation:
AA(Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP, B), AB(Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP, B), AC(Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP, B), AD(Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP, B)
Publication:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 90, no. 2, p. 693-695 (ApJS Homepage)
Publication Date:
02/1994
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
Nonthermal Radiation, Solar Flares, Solar Radio Bursts, Spectral Resolution, Decay Rates, Electron Density (Concentration), Frequency Distribution, H Alpha Line, Height, Magnetic Fields
DOI:
10.1086/191891
Bibliographic Code:
1994ApJS...90..693S

Abstract

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 13.7 m diameter antenna. Here, we investigate the microwave type 'simple low level (less than 10 SFU) bursts' associated with the impulsive phase of solar flares. Observed properties of these simple bursts are: rise time tr approximately 3 s, decay time td approximately 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 H(alpha). 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 approximately 2400 km), electron density (Nepsilon is less than 8.8 x 109/cu cm.), and magnetic field (B approximately 300 G).

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