Date of Award

Fall 2003

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Applied Physics - (Ph.D.)

Department

Federated Physics Department

First Advisor

Dale E. Gary

Second Advisor

Ken K. Chin

Third Advisor

Philip R. Goode

Fourth Advisor

Haimin Wang

Fifth Advisor

Louis J. Lanzerotti

Sixth Advisor

Zhen Wu

Abstract

The peak flux distribution of 40 years of solar radio burst data recorded by NOAA, as a function of frequency and time over a wide range of frequencies, was investigated to quantify the potential impact of radio bursts on wireless systems. Tables of fit parameters, which can be used to find burst occurrence rates in a number of frequency ranges, are presented. The typical power-law index of number density distribution, -1.8, is similar to that found in many hard X-ray studies. Significant changes were found in power-law index with frequency. The results may be useful for designers of current and future wireless systems.

A set of 412 flares detected by OVSA during 2001-2002 was analyzed. Distributions of the spectral parameters were investigated and the correlations between them discussed, adding to the understanding of particle acceleration and flare energetics. The observed microwave bursts were classified according to their spectral and temporal characteristics, and the natural limits of different emission mechanisms were empirically inferred.

An analysis of spectral peak evolution of microwave bursts found that, generally, the peak frequency is very well correlated with the intensity of microwave bursts, in agreement with theoretical predictions following from the gyrosynchrotron selfabsorption origin of the low frequency turnover of the spectrum. However, for some events the peak frequency increase is much smaller than expected or even absent. It was found that the peak frequency almost always increases on the late decay phase of strong long duration events. For 60% of the cases, the spectral dynamics of peak frequency around the peak time is caused by gyrosynchrotron self-absorption, but in 70% of cases, Razin suppression is dominant at some time during the burst, especially on the early rise and late decay phases.

The properties of decimetric spike bursts occurring simultaneously with microwave gyrosynchrotron continuum bursts were analyzed. The spike cluster flux density was found to be tightly correlated with the high-frequency spectral index of the microwave continuum for each event, while the flux-to-flux correlation may not be present. It was concluded that the findings strongly support the electron cyclotron maser mechanism of spike emission.

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