Very Large Array Observations of Solar Active Regions. IV. Structure and Evolution of Radio Bursts from 20 cm Loops.
TUFTS UNIV MEDFORD MA DEPT OF PHYSICS
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The Very Large Array VLA has been used to study the structure and evolution of six solar bursts near 20 cm wavelength. In most cases the burst emission has been resolved into looplike structures with total lengths, approx, 3 x 10 to the minus 9th power cm, brightness temperatures approx. 10 to the 7th to 8th power K and degress of circular polarization approx. or 90. Changes in the total intensity and circular polarization of the bursts occur on timescales as short as ten seconds. The individual peaks of one multiple component burst originated in different locations within a magnetically complicated region. Preburst heating and circular polarizaton changes respectively occurred minutes before the onset of the impulsive phase of two bursts. In one case a loop system emerged in the vicinity of the impulsive source, and two adjacent loop systems may have emerged and triggered the burst.