Vertical phase and group velocities of internalgravity waves derived from ionograms during the solareclipse of 24 October 1995

Liu, J.Y; Hsiao, Chao-Chih; Tsai, Lung Chih; Liu, C.H; Kuo, F. S.; Lue, H. Y.; Huang, Chun‐Kai

doi:10.1016/s1364-6826(98)00103-5

Cited by 58 publications

(64 citation statements)

References 14 publications

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“…The sources of gravity waves were proposed to be the thermosphere where molecular oxygen heating begins (Chimonas, 1970), the stratosphere where ozone layer heating takes place (Fritts and Luo, 1993;Zerefos et al, 2000) and the troposphere where water vapor IR absorption and ground cooling occurs (Chimonas and Hines, 1971;Chimonas, 1973). Modeling studies supported the idea of eclipse-induced gravity wave generation in the thermosphere (Ridley et al, 1984;Roble et al, 1986;Muller-Wodarg et al, 1998), which is also supported by measurements (Liu et al, 1998;Altadill et al, 2001;Sauli et al, 2006). Zerefos et al (2007) reported waves with periods ranging from 30 to 40 min associated with thermal stratospheric ozone forcing.…”

Section: Introductionmentioning

confidence: 71%

Ionospheric response to total solar eclipse of 22 July 2009 in different Indian regions

Kumar

Singh

2013

Ann. Geophys.

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The variability of ionospheric response to the total solar eclipse of 22 July 2009 has been studied analyzing the GPS data recorded at the four Indian low-latitude stations Varanasi (100% obscuration), Kanpur (95% obscuration), Hyderabad (84% obscuration) and Bangalore (72% obscuration). The retrieved ionospheric vertical total electron content (VTEC) shows a significant reduction (reflected by all PRNs (satellites) at all stations) with a maximum of 48% at Varanasi (PRN 14), which decreases to 30% at Bangalore (PRN 14). Data from PRN 31 show a maximum of 54% at Kanpur and 26% at Hyderabad. The maximum decrement in VTEC occurs some time (2–15 min) after the maximum obscuration. The reduction in VTEC compared to the quiet mean VTEC depends on latitude as well as longitude, which also depends on the location of the satellite with respect to the solar eclipse path. The amount of reduction in VTEC decreases as the present obscuration decreases, which is directly related to the electron production by the photoionization process. The analysis of electron density height profile derived from the COSMIC (Constellation Observing System for Meteorology, Ionosphere & Climate) satellite over the Indian region shows significant reduction from 100 km altitude up to 800 km altitude with a maximum of 48% at 360 km altitude. The oscillatory nature in total electron content data at all stations is observed with different wave periods lying between 40 and 120 min, which are attributed to gravity wave effects generated in the lower atmosphere during the total solar eclipse

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Section: Introductionmentioning

confidence: 71%

Ionospheric response to total solar eclipse of 22 July 2009 in different Indian regions

Kumar

Singh

2013

Ann. Geophys.

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“…Thus, the ionospheric depletion signatures may be heavily disturbed by electrodynamic forces in equatorial regions (e.g., Cheng et al 1992;Tsai & Liu 1999) and by space weather effects, such as particle precipitation, at high latitudes (e.g., Rashid et al 2006;Pitout et al 2013). As reported by Chimonas & Hines (1970) and others, the rapidly moving cooling spot can act as a continuous source of travelling ionospheric disturbance (TID) like gravity waves (e.g., Liu et al 1998;Altadill et al 2001;Jakowski et al 2008). On the other hand, the origin of TIDs observed during eclipses often remains unclear due to enhanced geomagnetic activity or other perturbations like strong weather fronts in the troposphere (Jakowski et al 2001(Jakowski et al , 2008.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric response over Europe during the solar eclipse of March 20, 2015

Hoque

Wenzel

Jakowski

et al. 2016

J. Space Weather Space Clim.

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The solar eclipse on March 20, 2015 was a fascinating event for people in Northern Europe. From a scientific point of view, the solar eclipse can be considered as an in situ experiment on the Earth's upper atmosphere with a well-defined switching off and on of solar irradiation. Due to the strong changes in solar radiation during the eclipse, dynamic processes were initiated in the atmosphere and ionosphere causing a measurable impact, for example, on temperature and ionization. We analyzed the behavior of total ionospheric ionization over Europe by reconstructing total electron content (TEC) maps and differential TEC maps. Investigating the large depletion zone around the shadow spot, we found a TEC reduction of up to 6 TEC units, i.e., the total plasma depletion reached up to about 50%. However, the March 20, 2015 eclipse occurred during the recovery phase of a strong geomagnetic storm and the ionosphere was still perturbed and depleted. Therefore, the unusual high depletion is due to the negative bias of up to 20% already observed over Northern Europe before the eclipse occurred. After removing the negative storm effect, the eclipse-induced depletion amounts to about 30%, which is in agreement with previous observations. During the solar eclipse, ionospheric plasma redistribution processes significantly affected the shape of the electron density profile, which is seen in the equivalent slab thickness derived by combining vertical incidence sounding (VS) and TEC measurements. We found enhanced slab thickness values revealing, on the one hand, an increased width of the ionosphere around the maximum phase and, on the other, evidence for delayed depletion of the topside ionosphere. Additionally, we investigated very low frequency (VLF) signal strength measurements and found immediate amplitude changes due to ionization loss at the lower ionosphere during the eclipse time. We found that the magnitude of TEC depletion is linearly dependent on the Sun's obscuration function. By modelling TEC depletion and knowing the Sun's obscuration function in advance, Global Navigation Satellite System (GNSS) operators may improve the broadcast ionospheric correction during a solar eclipse day.

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“…The passage of solar terminator is another main in situ source of GWs. Several studies have shown wave-like signatures (WLS)/GWs in E and F regions of ionosphere during SEs using Ionosonde and GPS total electron content (TEC) measurements [Liu et al, 1998;Altadill et al, 2001;Zerefos et al, 2007;Kumar et al, 2013;Yadav et al, 2013], but very few studies have attempted WLS/GWs in the Mesosphere/D region ionosphere [Bošková and Laštovička, 2001;Chernogor, 2010;Ratnam et al, 2012]. The probing of D region ionosphere is difficult as its altitude is too low for satellites and too high for balloons and due to low electron MAURYA ET AL.…”

Section: Introductionmentioning

confidence: 99%

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Maurya¹,

Phanikumar

Singh³

et al. 2014

JGR Space Physics

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We present first report on the periodic wave-like signatures (WLS) in the D region ionosphere during 22 July 2009 total solar eclipse using JJI, Japan, very low frequency (VLF) navigational transmitter signal (22.2 kHz) observations at stations, Allahabad, Varanasi and Nainital in Indian Sector, Busan in Korea, and Suva in Fiji. The signal amplitude increased on 22 July by about 6 and 7 dB at Allahabad and Varanasi and decreased by about 2.7, 3.5, and 0.5 dB at Nainital, Busan, and Suva, respectively, as compared to 24 July 2009 (normal day). The increase/decrease in the amplitude can be understood in terms of modal interference at the sites of modes converted at the discontinuity created by the eclipse intercepting the different transmitter-receiver great circle paths. The wavelet analysis shows the presence of WLS of period~16-40 min at stations under total eclipse and of period~30-80 min at stations under partial eclipse (~85-54% totality) with delay times between~50 and 100 min at different stations. The intensity of WLS was maximum for paths in the partially eclipsed region and minimum in the fully eclipsed region. The features of WLS on eclipse day seem almost similar to WLS observed in the nighttime of normal days (e.g., 24 July 2009). The WLS could be generated by sudden cutoff of the photo-ionization creating nighttime like conditions in the D region ionosphere and solar eclipse induced gravity waves coming to ionosphere from below and above. The present observations shed additional light on the current understanding of gravity waves induced D region ionospheric perturbations.

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Vertical phase and group velocities of internalgravity waves derived from ionograms during the solareclipse of 24 October 1995

Cited by 58 publications

References 14 publications

Ionospheric response to total solar eclipse of 22 July 2009 in different Indian regions

Ionospheric response to total solar eclipse of 22 July 2009 in different Indian regions

Ionospheric response over Europe during the solar eclipse of March 20, 2015

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

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