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Sudden f/sub min/ enhancements and sudden cosmic noise absorptions associated with solar X-ray flares

Journal Article:

Abstract

Sudden fsub(min) enhancements (SFsub(m)E's) and sudden cosmic noise absorptions (SCNA's) associated with increments of X-ray fluxes during solar flares are studied on the basis of X-ray flux data measured by SOLRAD 9 and 10 satellites. Some statistical analyses on SFsub(m)E's observed at five observatories in Japan, corresponding to increased X-ray fluxes in the 1-8 A band are made for 50 solar flare events during the period January 1972 to December 1973, and value of fsub(min) is expressed as functions of cos x(x; solar zenith angle) and 1-8 A band X-ray flux. Similar study is also made for SCNA's observed by 30 MHz riometer at Hiraiso for 15 great solar flare events during the same period, together with 27.6 MHz riometer data reported by Schwentek (1973) and 18 MHz data published by Deshpande and Mitra (1972b). It is found that fsub(min) value (MHz) and SCNA value (L, dB) of a radio wave with frequency f(MHz) are related to X-ray flux (F/sub 0/, erg cm/sup -2/ sec/sup -1/) in the 1-8 A band and to cos x, by following approximate expressions, fsub(min)(MHz)=10F/sub 0/sup(1/4) cossup(1/2) x, and L(dB)=4.37x10/sup 3/f/sup -2/F/sub 0/sup(1/2) cos x, respectively. Blackout seems to occur for F/sub 0/ values causing  More>>
Authors:
Sato, T [1] 
  1. Hyogo Coll. of Medicine, Hyogo (Japan). Dept. of Physics
Publication Date:
Jan 01, 1975
Product Type:
Journal Article
Reference Number:
AIX-07-272884; EDB-77-033455
Resource Relation:
Journal Name: J. Geomagnet. Geoelec.; (Japan); Journal Volume: 27:2
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; SOLAR X-RAY BURSTS; SUDDEN IONOSPHERIC DISTURBANCE; ABSORPTION; IONOSPHERE; MHZ RANGE 01-100; RADIO NOISE; SOLAR FLARES; X RADIATION; DISTURBANCES; EARTH ATMOSPHERE; ELECTROMAGNETIC RADIATION; FREQUENCY RANGE; IONIZING RADIATIONS; IONOSPHERIC STORMS; MHZ RANGE; NOISE; RADIATIONS; RADIOWAVE RADIATION; SOLAR ACTIVITY; 640201* - Atmospheric Physics- Auroral, Ionospheric, & Magetospheric Phenomena
OSTI ID:
7132971
Country of Origin:
Japan
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: JGEGA
Submitting Site:
INIS
Size:
Pages: 95-112
Announcement Date:

Journal Article:

Citation Formats

Sato, T. Sudden f/sub min/ enhancements and sudden cosmic noise absorptions associated with solar X-ray flares. Japan: N. p., 1975. Web.
Sato, T. Sudden f/sub min/ enhancements and sudden cosmic noise absorptions associated with solar X-ray flares. Japan.
Sato, T. 1975. "Sudden f/sub min/ enhancements and sudden cosmic noise absorptions associated with solar X-ray flares." Japan.
@misc{etde_7132971,
title = {Sudden f/sub min/ enhancements and sudden cosmic noise absorptions associated with solar X-ray flares}
author = {Sato, T}
abstractNote = {Sudden fsub(min) enhancements (SFsub(m)E's) and sudden cosmic noise absorptions (SCNA's) associated with increments of X-ray fluxes during solar flares are studied on the basis of X-ray flux data measured by SOLRAD 9 and 10 satellites. Some statistical analyses on SFsub(m)E's observed at five observatories in Japan, corresponding to increased X-ray fluxes in the 1-8 A band are made for 50 solar flare events during the period January 1972 to December 1973, and value of fsub(min) is expressed as functions of cos x(x; solar zenith angle) and 1-8 A band X-ray flux. Similar study is also made for SCNA's observed by 30 MHz riometer at Hiraiso for 15 great solar flare events during the same period, together with 27.6 MHz riometer data reported by Schwentek (1973) and 18 MHz data published by Deshpande and Mitra (1972b). It is found that fsub(min) value (MHz) and SCNA value (L, dB) of a radio wave with frequency f(MHz) are related to X-ray flux (F/sub 0/, erg cm/sup -2/ sec/sup -1/) in the 1-8 A band and to cos x, by following approximate expressions, fsub(min)(MHz)=10F/sub 0/sup(1/4) cossup(1/2) x, and L(dB)=4.37x10/sup 3/f/sup -2/F/sub 0/sup(1/2) cos x, respectively. Blackout seems to occur for F/sub 0/ values causing fsub(min)'s greater than about 5 MHz. It is shown that these expressions can be derived from a brief theoretical calculation of radio wave absorption in the lower ionosphere. Also it is suggested that threshold X-ray fluxes in the 1-8 A band which may produce a minimum SFsub(m)E (2 MHz), blackout and minimum SCNA (0.27-0.36 dB for 30 MHz noise) are 1.6x10/sup -3/, 6.2x10/sup -2/ and (3-8) x 10/sup -3/ erg cm/sup -2/ sec/sup -1/, respectively, for cos x=1.}
journal = {J. Geomagnet. Geoelec.; (Japan)}
volume = {27:2}
journal type = {AC}
place = {Japan}
year = {1975}
month = {Jan}
}