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X-radiation /E greater than 10 keV/, H-alpha and microwave emission during the impulsive phase of solar flares.A study has been made of the variation in hard (E greater than 10 keV) X-radiation, H-alpha and microwave emission during the impulsive phase of solar flares. Analysis shows that the rise-time in the 20-30-keV X-ray spike depends on the electron hardness. The impulsive phase is also marked by an abrupt, very intense increase in H-alpha emission in one or more knots of the flare. Properties of these H-alpha kernels include: (1) a luminosity several times greater than the surrounding flare, (2) an intensity rise starting about 20-30 sec before, peaking about 20-25 sec after, and lasting about twice as long as the hard spike, (3) a location lower in the chromosphere than the remaining flare, (4) essentially no expansion prior to the hard spike, and (5) a position within 6000 km of the boundary separating polarities, usually forming on both sides of the neutral line near both feet of the same tube of force. Correspondingly, impulsive microwave events are characterized by: (1) great similarity in burst structure with 20-32 keV X-rays but only above 5000 MHz, (2) typical low frequency burst cutoff between 1400-3800 MHz, and (3) maximum emission above 7500 MHz.
Document ID
19730032239
Document Type
Reprint (Version printed in journal)
Authors
Vorpahl, J. A. (California, University Berkeley, Calif., United States)
Date Acquired
August 7, 2013
Publication Date
October 1, 1972
Publication Information
Publication: Solar Physics
Volume: 26
Subject Category
SPACE RADIATION
Report/Patent Number
NSSDC-ID-68-014A-04-PS
Funding Number(s)
CONTRACT_GRANT: NGL-05-003-017
CONTRACT_GRANT: NAS5-9094
CONTRACT_GRANT: NSF GA-31587
Distribution Limits
Public
Copyright
Other