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Dual Frequency Variability Study of an Active Region

Published online by Cambridge University Press:  19 July 2016

R. K. Shevgaonkar  and
M. R. Kundu
R. K. Shevgaonkar
Affiliation:
1 Electrical Engineering Department, Indian Institute of Technology, Powai, Bombay 400 076, India
M. R. Kundu
Affiliation:
2 Astronomy Program, University of Maryland, College Park, Maryland 20742, USA

Abstract

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A short-time variability study of a solar active region simultaneously at 6 and 2 cm wavelengths was carried out using the VLA. The observations show interesting uncorrelated brightness temperature variation at the two wavelengths. The observed low brightness temperatures indicate that the emission is mainly originating from the chromosphere - corona transition region.

A transition region model with constant pressure and power-law temperature variation as a function of height has been assumed to analyse the data. The uncorrelated variation of the observed brightness temperature at the two wavelengths suggest different dominant emission mechanisms (bremsstahlung at 2cm and gyro-resonance at 6cm) operative at the two wavelengths. It is shown that an independent variation of a few percent in the magnetic field (900 ±45 G) and a factor of two variation in the density (2 to 4 × 1010 cm−3) over a time scale of few hours is required to explain the uncorrelated brightness temperature variations at the two wavelengths.

Type
IX. Solar Radio Emission
Information
Symposium - International Astronomical Union , Volume 142: Basic Plasma Processes on the Sun , 1990 , pp. 489 - 493
Copyright
Copyright © Kluwer 1990 

References

4. REFERENCES

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Shevgaonkar, R.K. and Kündu, M.R. (1989) ‘Time variability of solar active regions at centimeter wavelengths’, Astrophys. J., 342, p. 586.CrossRefGoogle Scholar