The midlatitude F2 layer during solar eclipses: Observations and modeling

Le, Huijun; Liu, Libo; Yue, Xinan; Wan, Weixing

doi:10.1029/2007ja013012

Cited by 52 publications

(77 citation statements)

References 47 publications

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“…Figure 9a shows that the delay time of the ionization decrease increases with height from foE to foF2 in agreement with earlier observations (e.g., Jakowski et al 2008) and simulation results (e.g. Le et al 2008).…”

Section: Vertical Sounding Datasupporting

confidence: 81%

“…As a result, it is reasonable to assume that the E layer was further depleted at around the time of the maximum obscuration at the Dourbes station. Based on simulation studies, Le et al (2008) discussed the eclipse effects on electron density and corresponding delay time considering control factors such as the background hmF2, local time and solar zenith angle, solar cycle, and dip angle. According to their study, an eclipse will produce a relatively smaller change in NmF2 associated with a higher time delay if the hmF2 is higher.…”

Section: Vertical Sounding Datamentioning

confidence: 99%

“…Since most solar eclipses occur in mid-and low latitudes (e.g., Jakowski et al 1983Jakowski et al , 2001Jakowski et al , 2008Cheng et al 1992;Fritts & Luo 1993;Mueller-Wodarg et al 1998;Krankowski et al 2008;Le et al 2008Le et al , 2009Le et al , 2010, the number of publications considering high-latitude eclipses is rather low (e.g., Rashid et al 2006;Pitout et al 2013). Le et al (2009) investigated the latitudinal dependence of the ionospheric response to solar eclipses and found that eclipse effects are larger at middle latitudes than at low latitudes.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Vertical Sounding Datasupporting

confidence: 81%

Section: Vertical Sounding Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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 F2 region behavior may be quite different accompanied with various amplitudes of decrease or even a small increase in the electron concentration. Combining the measurements and four controlled case simulations, Le et al (2008b) found that most of the observed differences in the behavior of the peak electron density of the F2 layer (NmF2) during eclipses can be attributed to the differences in O + loss rates brought about by the background differences in the neutral molecular densities. Despite many studies on the eclipse effects of the ionosphere over the eclipse region, there are still rarely studies on the ionospheric disturbances in the magnetically conjugate regions.…”

Section: Introductionmentioning

confidence: 99%

The ionospheric behavior in conjugate hemispheres during the 3 October 2005 solar eclipse

Liu

Yue

et al. 2009

Ann. Geophys.

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Abstract.We investigate the ionospheric behavior in conjugate hemispheres during the 3 October 2005 solar eclipse, on the basis of observations of electron temperature (T e ) from the Defense Meteorological Satellites Program (DMSP) spacecraft, F2 layer critical frequency (foF2) and F2 layer peak height (hmF2) at the Grahamstown ionosonde station, and total electron content (TEC) from the Global Positioning System (GPS) station SUTH. The observations show that when the eclipse occurred in the Northern Hemisphere, there was a decrease in T e , an increase in foF2 and TEC, and an uprising in hmF2 in its conjugate region compared with their reference values. We also simulated the ionosphere behavior during this eclipse using a mid-and low-latitude ionospheric model. The simulations agree well with the observations. Because of the eclipse effect, there are far fewer photoelectrons travelling along the magnetic field lines from the eclipse region to the conjugate region, resulting in reduced photoelectron heating in the conjugate hemisphere which causes a drop in electron temperature and subsequent disturbances in the region.

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“…Study of the ionospheric response to a solar eclipse has been in place for decades, and extensive studies have been made with various experimental techniques, such as ionosondes, incoherent scatter radar, rockets, Faraday rotation measurements, global positioning system and satellite measurements (Evans, 1965a, b;Klobuchar and Whitney, 1965;Rishbeth, 1968;Hunter et al, 1974;Oliver and Bowhill, 1974;Cohen, 1984;Salah et al, 1986;Cheng et al, 1992;Farges et al, 2001;Tomas et al, 2007) as well as theoretical modeling (Le at al., 2008a, and references therein). Both the measurements and simulations show that the eclipse effect is larger in the midday than in the morning and afternoon, and also the decrease in electron concentration is greater in the F1 region than in the E region (Le at al., 2008a). The eclipse effect in the F2 region is larger at high solar activity than at low solar activity.…”

Section: Introductionmentioning

confidence: 99%

The equatorial ionospheric response over Tirunelveli to the 15 January 2010 annular solar eclipse: observations

et al. 2012

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Abstract. In this paper we present a case study of the annular solar eclipse effects on the ionization of E and F regions of equatorial ionosphere over Tirunelveli [77.8 • E, 8.7 • N, dip 0.4 • N] by means of digital ionosonde on 15 January 2010. The maximum obscuration of the eclipse at this station was 84 % and it occurred in the afternoon. The E and F1 layers of the ionosphere showed very clear decrease in their electron concentrations, whereas the F2 layer did not show appreciable changes. A reduction of 30 % was observed in the foF1 during the maximum phase of the eclipse. During the beginning phase of the eclipse, an enhancement of 0.97 MHz was observed in the foF2 as compared to that of the control days. But the foF2 decreased gradually as the eclipse progressed and a decrease of 0.59 MHz was observed towards the end phase of the eclipse. Observed variations in the h F2 and hmF2 showed lower values than the control days, although hmF2 was found to increase a bit during the eclipse. Observed variability in the E, F1 and F2 layer ionospheric parameters on the eclipse day and their departure from the control days are discussed as the combined effect of annular eclipse and presence of counter equatorial electrojet (CEEJ).

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The midlatitude F2 layer during solar eclipses: Observations and modeling

Cited by 52 publications

References 47 publications

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

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

The ionospheric behavior in conjugate hemispheres during the 3 October 2005 solar eclipse

The equatorial ionospheric response over Tirunelveli to the 15 January 2010 annular solar eclipse: observations

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