Quasi-periodic fluctuations in electron content during a partial solar eclipse

Vaidyanathan, S.; Reddi, C. Raghava; Krishnamurthy, B.

doi:10.1038/271040b0

Cited by 4 publications

(5 citation statements)

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“…Spectral analysis of the variations of the ionospheric or atmospheric parameters can yield clues regarding the frequencies and amplitudes of gravity waves which the eclipse may have produced [ Vaidyanathan et al , 1978; Goodwin and Hobson , 1978]. The time‐frequency analysis technique was applied to the DFS sequences of the eclipse day shown in Figures 6 and 7 for investigation of the nature of the observed oscillations and for detection of quasi‐periodic fluctuations.…”

Section: Doppler Observationsmentioning

confidence: 99%

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

et al. 2010

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[1] The sporadic E (Es) frequently emerging in midlatitude during summer is a very special layer in the ionosphere, and its formation mechanism is different to from that of other layers. The total solar eclipse of 22 July 2009 provided a very unique opportunity to study the relationship of Es and solar radiation. During the solar eclipse day and the days before and after, the vertical incidence ionosonde was located in Wuhan to record the ionograms for this event. Two oblique incidence high-frequency radio systems were used to record the waves from Wuhan to Suzhou and from Wuhan to Huaian. The enhancement of Es during the eclipse period was observed in the vertical and oblique incidence ionograms. The quasi-periodic fluctuations in the critical frequency and Doppler frequency shift curves indicated the possible existence of the gravity waves, which may be responsible for the Es enhancement. However, we find that the enhancement occurred earlier than the appearance of gravity waves and consider that there may be other mechanisms which contribute to the observed enhancement in the ionosphere. A hypothesis is put forward that the cooling effect of the lunar shadow induced powerful airflow from the northern and southern limits of the shadow toward its center, which accelerated the irregularities in Es to produce the large-scale Doppler shift in the reflected waves and form the meridional windshear. Both the windshear and the gravity waves may affect the Es layer and increase the electron concentration. Many observed phenomena are in accordance with this.

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Section: Doppler Observationsmentioning

confidence: 99%

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

et al. 2010

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“…At Ootaeamund, Faraday rotation and group delay measurements were made at 40 MHz as well as at 140 MHz. The lower frequency being more sensitive to TEC changes, further analysis was done using measurements made at 40 MI-lz, in the same way as followed by Vaidyanathan et al (1978). Similar analysis was done for a day previous to the eclipse day also and the fluctuations are shown in figure 4 along with the times of first contact, the maximum phase and the last contact.…”

Section: Resultsmentioning

confidence: 99%

“…Similar analysis was done for a day previous to the eclipse day also and the fluctuations are shown in figure 4 along with the times of first contact, the maximum phase and the last contact. For comparison the results of Vaidyanathan et al (1978) are also included in figure 4. The eclipse start time for Ootacamund is about 10 min earlier than the start time at Trivandrum (figure 1).…”

Section: Resultsmentioning

confidence: 99%

“…In view of the conflicting reports about the detection of TIDs in the Faraday rotation measurements, due to eclipseinduced gravity waves, an attempt is made to examine the excellent coverage of data available for this eclipse from all the stations. Recently Vaidyanathan et al (1978) had reported quasi-periodic fluctuations of about 10 rain periodicities in the Faraday rotation and group delay measurements at 40 MHz, using radio beacons from ATS-6 at Trivandrum (dip 0" 6 ~ S). The amplitude of the fluctuations is estimated to be of the order of 0.5 x 10 TM el m -~.…”

Section: G Sethia H Chandra and M R Deshpandementioning

confidence: 99%

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On the effect of the partial solar eclipse of 29 April 1976 on electron content

1980

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Faraday rotation measurements made at a chain of stations and group delay measurements made at Ootacaraund from ATS-6 are examined for the partial solar eclipse event of 29 April 1976. There is no evidence of eclipse-induced gravity waves in these measurements extending from Ootacamund near dip equator to Patiala (dip45~ Eclipse-induced fluctuations wear however reported at Trivandrura, about 300 km south of Ootacamund.

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“…However, TIDs observed in a number of ionospheric experiments in United States during the same period were not conclusively attributed to the eclipse effect (Carlson et al 1970;Larford et a11972;Arendt 1972;Sears 1972). From observations of Faraday rotation and group delay measurements at 40 MHz using radio beacons from ATS-6 at Trivandrum, Vaidyanathan et al (1978) had reported quasi-periodic fluctuations of about l0 min periodicities during the partial eclipse of 29 April 1976. However, Sethia et al (1980) using the ATS-6 satellite data for a number of other locations for the same eclipse reported absence of travelling ionospheric disturbances at all these stations.…”

Section: Discussionmentioning

confidence: 99%

Temperature variation in the mesosphere during solar eclipse

Chakrabarty

Saha

1983

J Earth Syst Sci

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Rocket-borne observations of the extinction of solar hydrogen Lyman-alpha radiation made during the solar eclipses of 20 May 1966 at Karistos for normal and 44~ visibility and o f 7 March 1970 at East Quoddy for normal. 10ud ` and 0.6ud visibility have been used to study the variation of temperature in the mesosphere during these events. It is seen that near the mesopause the decrease of temperature at Karistos is by 20 ~ K for 44ud ,,isibility and at East Quoddy by 100O K for 0.6% visibility. Possible causes of these temperature variations visa -vis molecular oxygen and pressure variations have been briefly discussed.

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Quasi-periodic fluctuations in electron content during a partial solar eclipse

Cited by 4 publications

References 5 publications

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

On the effect of the partial solar eclipse of 29 April 1976 on electron content

Temperature variation in the mesosphere during solar eclipse

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