VLA (Very Large Array) observations of a solar-noise storm
The first Very Large Array (VLA) observations of the Sun at 92-cm wavelength (328 MHz) are presented. A solar-noise storm, which lasted at least 3 hr, was detected at this wavelength; it consisted of burstlike spikes superposed on a slowly varying background, and both components were 95% + or - 5% right-hand circularly polarized. A long-duration soft x-ray event preceded the radio radiation by 30 minutes, suggesting a disturbance moving outward at a velocity of v=78 km/s. The 92-cm noise storm was resolved with an angular resolution 9 arc sec for time intervals as short as 13 s. Snapshot maps revealed a persistent elongated source at successive peaks, with a scatter in the source position. A systematic position shift of Delta Theta > or = 15 can be produced by the Earth's ionosphere, but these effects can be removed by frequent observations of a nearby calibrator source. Previously reported trends are confirmed for a decrease in source size at higher frequencies. The new VLA results are also consistent with previous observations of noise-storm polarization and height. The VLA can potentially resolve both the burst and continuum components of noise storms, while also detecting the effects of anisotropic scattering in the corona. The high angular resolution and large collecting area of the VLA may lead to the detection of the second harmonic of the storm plasma frequency or establish important limits to it.
- Research Organization:
- Tufts Univ., Medford, MA (USA)
- OSTI ID:
- 5162807
- Report Number(s):
- AD-A-189301/5/XAB
- Resource Relation:
- Other Information: Pub. in The Astrophysical Journal, Vol. 319, No. 1, Pt. 1, 514-519(1 Aug 1987)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
SOLAR ACTIVITY
BACKGROUND NOISE
SOLAR RADIO BURSTS
SOLAR X-RAY BURSTS
ANISOTROPY
CALIBRATION
DETECTION
DISTURBANCES
POLARIZATION
SCATTERING
SHORT WAVE RADIATION
SOLAR RADIATION
STORMS
DISASTERS
ELECTROMAGNETIC RADIATION
NOISE
RADIATIONS
RADIOWAVE RADIATION
STELLAR RADIATION
640104* - Astrophysics & Cosmology- Solar Phenomena