Response of the F-region Ionosphere to a Solar Eclipse

Flaherty, B. J.; Cho, H. R.; Yeh, K. C.

doi:10.1038/2261121a0

Cited by 6 publications

(5 citation statements)

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“…The geomagnetic storm may corrupt and cause a problem in detecting the ionospheric response to the solar eclipse [ Afraimovich et al , 2002]. The mixed storm‐eclipse‐TIDs solar eclipses events were also reported by several researchers [ Abdul Rashid et al , 2006; Musatenko et al , 2003; Arendt , 1971; Chimonas and Hines , 1971; Flaherty et al , 1970; N. Sato et al, Conjugate ionospheric disturbances affected by the 23 November 2003 solar eclipse, paper presented at XXVIII Open Science Conference, Scientific Committee on Antarctic Research, Bremen, Germany, 2004]. Most of these measurements were made for the 23 November 2003 total solar eclipse over Antarctica and the 7 March 1970 total solar eclipse over Mexico and the southern United States.…”

Section: Introductionmentioning

confidence: 95%

“…The partial or total blockage of solar radiation during solar eclipse produces various local effects. When the ultraviolet radiation from the Sun is blocked during solar eclipse the ions and electrons start to recombine, and therefore the number of electrons and ions decreases [ Chapman , 1932; Appleton and Chapman , 1935; Almeida and da Rosa , 1970; Bienstock et al , 1970; Flaherty et al , 1970; Klobuchar and Malik , 1970; Rishbeth , 1970]. The ionospheric effects during eclipse imply an increase of the effective reflection heights, reduction in the concentration of the F layer maximum, and decrease in total electron content (TEC) of the ionosphere [ Cohen , 1984; Afraimovich et al , 2000].…”

Section: Introductionmentioning

confidence: 99%

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Ionospheric and geomagnetic response to the total solar eclipse on 1 August 2008 over Northern Hemisphere

2010

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[1] The ionospheric and geomagnetic response to the total eclipse of the Sun on 1 August 2008 over Northern Hemisphere has been examined using 14 GPS, three ISR radar, and three magnetometer ground-based stations. Three different approaches were employed to examine the TEC depletion occurrence at the GPS stations: determination of the TEC depletion parameters during the solar eclipse with respect the quiet day TEC variations, comparison of the total TEC (STEC) during the solar eclipse period with respect to quiet day TEC measurements for the same period of time, and determination of the average daily TEC obtained from eight GPS stations and compares the values with the average quiet day TEC at these stations. The GPS observations indicate obvious TEC depression occurrence at all stations with the values was varying between 11% and 40%. The observations show that TEC depression at most GPS stations started on the neck of the first contact of the eclipse followed by deeper negative deviation while the area of optical disk obscured getting larger. Periods of TEC depletion were also observed before the first contact time of solar eclipse and after the fourth contact of solar eclipse due to earlier and later obscuration of the solar corona before and after the eclipse observation time. The incoherent scatter radar observations at Svalbard, Tromso, and Sondrestrom also show clear depletion occurrence in electron density, electron temperature, ion velocity, and plasma cutoff frequency during the solar eclipse passage at these stations. Radar measurements show obvious difference in the ionospheric response between the E and F layers of ionosphere and between ion and electron temperature in the F layer. The geomagnetic field response to the solar eclipse at CBB, RESO, and NUR stations was examined by using two different techniques, first by comparing the daily variations of geomagnetic field during the eclipse period with the variations on the day before and day after the eclipse, and second by determination the D magnetic field with respect to the average quiet geomagnetic field. The results show obvious decrease in the total field, X and Z components of geomagnetic field and obvious increase in the Y component at both CBB and RESO stations. The depletion in X, Z, and total field was in the range between 15 and 28 nT while the increase in the Y component was 18-22 nT.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Ionospheric and geomagnetic response to the total solar eclipse on 1 August 2008 over Northern Hemisphere

2010

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“…It has been found that the ionospheric response to the solar eclipse is generally manifested as a decrease in total electron content [ Afraimovich et al , 1998; Jakowski et al , 2008], an increase of the F layer minimum height and of the effective reflection heights [ Schodel et al , 1973; Cheng et al , 1992], and a density drop in the F layer maximum, which are the usual characteristics for the nightside ionosphere [ Flaherty et al , 1970; Boitman et al , 1999; Bamford , 2001; Farges et al , 2001]. Moreover, the cooling spot of the lunar shadow caused by the solar eclipse, which travels with supersonic speed in the lower atmosphere, would change the thermal structure near the eclipsed region and act as a continuous source of gravity waves that build up into a bow wave [ Chimonas , 1970; Chimonas and Hines , 1970, 1971].…”

Section: Introductionmentioning

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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“…During the eclipse period, the solar radiation is shadowed by the moon and the photochemical activity in the ionosphere decreases to almost reach the nighttime levels for a short period. In general, the ionospheric response to the solar eclipse is analogous to what happens after sunset, representing a decrease of electron density [ Flaherty et al ., ; Boitman et al ., ; Bamford , ; Farges et al ., ] and an increase of F‐layer altitude [ Schodel et al ., ; Cheng et al ., ]. However, at some occasions, there is a small increase of F2‐layer electron density instead of the expected reduction as the lunar shadow approaches.…”

Section: Introductionmentioning

confidence: 98%

Nighttime ionospheric enhancements induced by the occurrence of an evening solar eclipse

Chen

Ning

et al. 2013

JGR Space Physics

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[1] The solar eclipse on 15 January 2010 traversed Asia and completed its travel on the Shandong Peninsula in China at sunset. Two vertical incidence ionosondes at Wuhan and Beijing and the oblique incidence ionosonde network in North China were implemented to record the ionospheric response to the solar eclipse. Following the initial electron density decrease caused by the eclipse, the ionosphere was characterized by a strong premidnight enhancement, and a subsequent ionospheric decay, and a~10 h later postmidnight enhancement. Neither geomagnetic disturbance occurred during the eclipse day nor did obvious nighttime peak appear for the 10 day mean of the F2-layer critical frequency (foF2). The electron density profilogram of the Beijing ionosonde indicates that the two enhancements were the result of the plasma flux downward from the top ionosphere, possibly due to the steep decrease of the ionospheric electron density and plasma temperature during the solar eclipse. The two-dimensional differential foF2 maps present the regional variations of the nighttime electron density peaks and decay. Both the pre-and postmidnight enhancements initially appeared in a belt almost in parallel with the eclipse track and then drifted southward. The different magnitudes of greatest eclipse in the umbra and outside tend to account for the different occurrence times of the plasma flux. The ionospheric decay following the premidnight enhancement is also considered as a consequence of the eclipse shade.

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Response of the F-region Ionosphere to a Solar Eclipse

Cited by 6 publications

References 7 publications

Ionospheric and geomagnetic response to the total solar eclipse on 1 August 2008 over Northern Hemisphere

Ionospheric and geomagnetic response to the total solar eclipse on 1 August 2008 over Northern Hemisphere

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

Nighttime ionospheric enhancements induced by the occurrence of an evening solar eclipse

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