Accession Number : ADP001437

Title :   Profiles of Coronal MHD (Magnetohydrodynamic) Disturbance Associated with the Solar Flare on April 27, 1979,

Corporate Author : PHYSICAL RESEARCH LAB AHMEDABAD (INDIA)

Personal Author(s) : Bhonsle,R. V. ; Degaonkar,S. S. ; Alurkar,S. K.

Report Date : 27 DEC 1982

Pagination or Media Count : 6

Abstract : A solar flare of importance 1B which occurred at 0636 UT on April 27, 1979 in region 1705 (McMath No. 15967) on the solar disk (N20, E16) produced intense radio bursts. An impulsive microwave event was also recorded at 2800 MHz at Ahmedabad, beginning at 0642 UT, and showing about 10-12 peaks in intensity in a time duration of 20 minutes. The most interesting feature of this event is the observation of a strong continuum radiation (Type IV) starting at 0653 UT and lasting for about 10 minutes as recorded by the wide band spectrograph operating in the 45 - 25 mhz range. This continuum radiation displayed sharp low frequency cut-off, which varied from about 40 to 30 MHz in a quasi-periodic manner. The sharp low frequency cut-off in the continuum radiation is attributed to 'Razin effect'. The perturbation of this cut-off frequency is interpreted as that induced by the passing MHD shock wave through the magnetic flux tube where the continuum radiation is generated by the synchrotron mechanism from trapped energetic electrons. Assuming a spherically symmetric electron density model and using the observed cut-off frequency, the magnitude of the coronal magnetic field around 2 solar radii above the photosphere had a value of about 6 gauss. (Author)

Descriptors :   *Solar disturbances, *Solar corona, *Solar flares, Magnetic fields, Burst transmission, Radio signals, Magnetohydrodynamics, Shock waves, Equations of motion, Electron density, Low frequency, India

Distribution Statement : APPROVED FOR PUBLIC RELEASE