Observation of Traveling Ionospheric Disturbances by the Doppler Technique with Spaced Transmitters
Observation of Traveling Ionospheric Disturbances by the Doppler Technique with Spaced Transmitters

Author: John Emory Jones

Publisher:

Published: 1969

Total Pages: 478

ISBN-13:

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This report describes a radio investigation of traveling ionospheric disturbances carried out near Boulder, Colorado, over a 1-year period from June 1967 to June 1968. The three-dimensional motions of F2 layer disturbances were measured by the high frequency Doppler technique with spaced transmitters and at several probing frequencies. Horizontal motions were determined by cross-correlating three signals on frequencies near 5 MHz, whose reflection points were approximately at the corners of a horizontal equilateral triangle with 40-km sides. Vertical motions were determined from cross-correlation of signals on frequencies of 3.3, 4.0, and 5.1 MHz, whose reflection points were aligned vertically.

Contribution of X-ray and Extreme Ultraviolet Radiation of Solar Flares to Sudden Frequency Deviations
Contribution of X-ray and Extreme Ultraviolet Radiation of Solar Flares to Sudden Frequency Deviations

Author: Richard Frank Donnelly

Publisher:

Published: 1969

Total Pages: 52

ISBN-13:

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High time and intensity resolution satellite measurements of X-ray and extreme ultraviolet (EUV) radiation during solar flares are studied to determine the wavelength dependence of the flare radiation responsible for sudden frequency deviations (SFD). SFD's measure the flare-induced effects in the E and F1 regions of the ionosphere and are in effect like a broadband (1-1030 Å) detector for impulsive flare enhancements. He II 303.8 Å, O V 629.7 Å, H Ly [upsilon] 972.5 Å, C III 977.0 Å, and H Ly [alpha] 1215.7 Å were found to have essentially the same time dependence as the total ionizing radiation producing SFD's, except that they decay faster than the net 1-1030 Å radiation. Flare enhancements of Fe XV 284.1 Å, Fe XVI 335.3 Å, Si XII 499.3 Å. Mg X 625.3 Å, and Ne VIII 770.4 Å, which are normally coronal lines, appear to have a much slower time dependence than the radiation responsible for SFD's. X-rays in the 0.5-3 Å range are slightly slower than the radiation responsible for SFD's during the decay stage; 1-8 Å X-ray flares are slower, especially during the decay stages; and 8-20 Å flare radiation enhancements are slower throughout the entire SFD.

ATS Observations of Sudden Increases of Total Electron Content Induced by EUV and X-ray Burst of Solar Flares
ATS Observations of Sudden Increases of Total Electron Content Induced by EUV and X-ray Burst of Solar Flares

Author: Richard Frank Donnelly

Publisher:

Published: 1975

Total Pages: 48

ISBN-13:

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ATS-satellite observations of sudden increases in total electron content (SITECs) produced by extreme-ultraviolet (EUV) and X-ray bursts of solar flares are presented quantitatively and interpreted qualitatively. Large SITECs for the white-light flare of July 4, 1974, and for the large flares on July 5, September 10, and September 19, 1974, are illustrated. The time rate of change of total electron content dN (subscript)T/dt was directly compared with SFD (Sudden Frequency Deviations) measurements. The ATS-6 dN(subscript)T/dt measurements are essentially transionospheric SFD measurements. The main difference with respect to ground-based SFD measurements is that, in addition to the 100 to 200 km altitude range where ionospheric electron loss rates are high, the ATS-6 measurements also observe the low loss-rate F2 region. Because of this low ionization loss rate, dN(subscript)T/dt includes more of the slow radiation effects and proceeds to a negative decay phase much later than the ground-based SFDs.