Ionospheric absorption on October 24, 1995 solar eclipse

Abraham, Saji; Dhaka, S. K.; Nath, N.; Baluja, K. L.

doi:10.1029/98gl01781

Cited by 7 publications

(5 citation statements)

References 28 publications

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“…For the current eclipse, our GCP lied totally in the partial eclipse zone at an angle of 34° with respect to the path of totality and a large area of the Indian subcontinent was covered for the present study. It is also noted that the path lied totally under the equatorial ionization anomaly (EIA) region and few reports exist in literature over the Indian subcontinent [ Patel et al , 1986; Vyas et al , 1997; De and Sarkar , 1997; Abraham et al , 1998; Patra et al , 2009]. It is also interesting to note that the transmitter latitude 8.38°N was located almost near to the equatorial ionization trough region while our receiver was placed at 23.75°N latitude, which was near to the equatorial ionization crest region.…”

Section: Discussionmentioning

confidence: 64%

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Guha

Roy

et al. 2010

J. Geophys. Res.

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[1] Changes in equatorial D-region electron density are studied using subionospherically propagating VLF signal at 18.2 kHz over a distance of 2200 km during the total solar eclipse of 22 July 2009. There are very few studies about the eclipse's effects on the equatorial lower ionosphere in the scientific literature. In the light of that, the objective of the present work is to study the effects of the eclipse on the dynamics of the equatorial lower ionosphere during ionospheric sunrise transition period. In the present case, great circle path between VLF transmitter and receiver falls totally in partial eclipse zone, having a maximum solar obscuration of 90% and an average obscuration of 74%. Results show an average decrease of 3.2 dB in signal strength compared to control days during peak solar obscuration over the path. A comparison with previous studies shows an increase both in lower ionosphere virtual reflection height (H′) and Wait inverse scale height parameter , respectively. During maximum eclipse over the path, the model profile shows an average 80% drop in electron density at a height of 71 km at equatorial lower ionosphere. A nonlinear variation of lower ionosphere electron density with solar radiation is found as opposed to the model study proposed by previous workers.Citation: Guha, A., B. K. De, R. Roy, and A. Choudhury (2010), Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal,

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Section: Discussionmentioning

confidence: 64%

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Guha

Roy

et al. 2010

J. Geophys. Res.

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“…For the solar eclipse of 24 October 1995, measurements of absorption at 2.5 and 2.8 MHz at Ahmedabad showed a decrease that was associated with the eclipse (Lele et al, 1997a), and the field strength for the Colombo-Ahmedabad path (11.8 MHz) also showed an increase (Lele et al, 1997b). Ionspheric absorption measurements at 2.5 MHz at Delhi were also at a minimum during the eclipse of 24 October 1995 (Abraham et al, 1998). Thus, the ionosonde, LF/HF field strength and riometer measurements reveal an eclipse-associated decrease of ionization in the ionospheric D-, E-and F 1 -regions.…”

Section: Discussionmentioning

confidence: 88%

Ionospheric measurements during the total solar eclipse of 11 August 1999

et al. 2007

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A number of radio experiments were conducted at Ahmedabad (23• N, 73• E) with the aim of studying the ionospheric effects of the total solar eclipse of 11 August 1999. Rapid radio soundings from the ionosonde were made on the eclipse day and on control days. A riometer was operating at 30 MHz, and Àeld strength measurements along the three oblique incidence paths of Colombo-Ahmedabad (11905 kHz), Bombay-Ahmedabad (558 kHz) and Rajkot-Ahmedabad (810 kHz) were also made. A reduction of about 20% was observed in the minimum frequency of reÁection from the ionosonde (f min ), which indicates a reduction in D-region ionization. The critical frequency of the E-layer was not measurable beyond 1600 h IST on eclipse day due to the strong blanketing sporadic-E, but there is a 20% decrease in the critical frequency of the F 1 -layer. Although there was no change in the minimum virtual height of the F-layer on eclipse day, there appears to have been a decrease in the height of maximum ionization (h p F 2 ) during the eclipse, indicating a reduction in the thickness of the F-layer. The signal strength of the Colombo-Ahmedabad path shows an initial rapid increase with the start of the eclipse (indication of a decrease in ionization in the D-and lower E-regions), but subsequently decreases until the maximum of the eclipse (excessive deviative absorption because of the wave penetrating to the E-region). The Àeld strength measurements of the Bombay-Ahmedabad path show a large fading after sunset as the sky wave also appeared. On eclipse day the fading started about an hour earlier. Riometer recordings also show a higher signal during eclipse day, which again indicates an eclipse-associated decrease in ionization.

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“…Several studies using VLF/LF/MF transmitter signals have also examined the lower ionosphere during solar eclipses [e.g., Bracewell , 1952; Crary and Schneible , 1965; Lynn , 1981; Abraham et al , 1998; Clilverd et al , 2001; Guha et al , 2010; De et al , 2011]. Bracewell [1952] first reported solar eclipse effects on VLF transmitter signals, sent from Rugby (16 kHz) to Cambridge in the UK.…”

Section: Introductionmentioning

confidence: 99%

“…The peak of amplitude occurred 2–7 min before maximum solar obscuration, while the maximum phase changes occurred 1–7 min after maximum solar obscuration. Abraham et al [1998] reported using ionospheric radio wave absorption (2.5 MHz, A1 technique) that the absorption decreased by 18 dB at the totality during the solar eclipse of 24 October 1995. Clilverd et al [2001] found that the amplitude showed positive changes for path lengths <2,000 km and negative changes for path lengths >10,000 km using 17 paths (16–24 kHz).…”

Section: Introductionmentioning

confidence: 99%

Reflection height of daytime tweek atmospherics during the solar eclipse of 22 July 2009

Ohya¹,

Tsuchiya²,

Nakata³

et al. 2012

J. Geophys. Res.

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[1] We report multipoint observations of daytime tweek atmospherics during the solar eclipse of 22 July 2009. Sixteen and sixty-three tweek atmospherics were observed at Moshiri and Kagoshima, Japan, where the magnitudes of the solar eclipse were 0.458 and 0.966, respectively. This was the first observation of tweek atmospherics during a low-magnitude eclipse (0.458). The average and standard deviation of the reflection height were 94.9 AE 13.7 km at Moshiri and 87.2 AE 12.9 km at Kagoshima. The reflection height at Moshiri was almost the same as that for normal nighttime conditions in July (96.7 AE 12.6 km) in spite of the low magnitude of the eclipse. The reflection height at Kagoshima seems be divided into two parts: propagation across the total solar eclipse path and propagation in the partial solar eclipse path. During the eclipse, we also observed the phase variation in the LF transmitter signals. The average change in the phase delay of the LF signals was 109 for the paths that crossed the eclipse path and 27 for the paths that did not cross the eclipse path. Assuming a normal daytime height for LF waves of 65 km, a ray tracing analysis indicates that the variations in phase correspond to a height increase of 5-6 km for the paths across the eclipse and 1-2 km for partial eclipse paths. The wide range of estimated tweek reflection heights at Kagoshima also suggests a difference in electron density in the lower ionosphere between total and partial solar eclipses.

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Ionospheric absorption on October 24, 1995 solar eclipse

Cited by 7 publications

References 28 publications

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Ionospheric measurements during the total solar eclipse of 11 August 1999

Reflection height of daytime tweek atmospherics during the solar eclipse of 22 July 2009

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