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

Abstract

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.

Ionospheric Response to the 21 May 2012 Annular Solar Eclipse Over Taiwan

“…On the other hand, the observed VLF signal reduces during the eclipse period. Both enhancement and reduction of VLF amplitudes were reported in previous literature (e.g., Chakrabarti et al, ; Clilverd et al, ; Hoque et al, ), since the VLF waves are propagated in the ground‐ionosphere waveguide and wave mode theory is valid for VLF waves here (Wait, ). However, we have different conditions of propagation path and obscuration rate during the eclipse, which could not be fully explained or substituted by the previous literature.…”

Short‐ and Long‐Wavelength TIDs Generated by the Great American Eclipse of 21 August 2017

“…The magnitude of the TEC depletion produced by the Moon's shadow was already studied in the past and was found to depend on the latitude . Other studies confirmed this effect: for total solar eclipses the TEC depletion can reach 30-40% at midlatitudes with a delay of 5-20 min after the passing of the Moon's shadow (Jakowski et al, 2008); (Ding et al, 2010), 10-30% at high latitudes (Afraimovich et al, 1998); (Momani et al, 2010); (Hoque et al, 2016), whereas for the equatorial latitudes it can reach more than 40% due to the increased RESEARCH ARTICLE 10.1029/2019JA026919 Key Points:…”

Ionospheric Total Electron Content Response to the Great American Solar Eclipse of 21 August 2017

“…During a solar eclipse, reduce in solar EUV flux results in thermosphere‐ionosphere cooling, electron density decrease at E / F 1 / F 2 regions and decrease in the total electron content (TEC), integrated up to 20,000 km. For total eclipse that occurred at midlatitudes, TEC depletion can reach 30–40% with time delay of 5–20 min (Ding et al, ; Jakowski et al, ), for high latitudes TEC decreased by 10–30% (Afraimovich et al, ; Hoque et al, ; Momani et al, ). TEC response to total eclipses at equatorial latitudes is complicated by equatorial anomaly and can reach more than 30–40% (Tsai & Liu, ).…”