This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Ī solar eclipse is a natural phenomenon that occurs when the moon appears between the Sun and the Earth, and the moon fully or partially blocks the Sun, casting a shadow over the Earth. 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. We found that the magnitude of TEC depletion is linearly dependent on the Sun’s obscuration function. 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 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. 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. After removing the negative storm effect, the eclipse-induced depletion amounts to about 30%, which is in agreement with previous observations. Therefore, the unusual high depletion is due to the negative bias of up to 20% already observed over Northern Europe before the eclipse occurred. However, the Maeclipse occurred during the recovery phase of a strong geomagnetic storm and the ionosphere was still perturbed and depleted. 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%. We analyzed the behavior of total ionospheric ionization over Europe by reconstructing total electron content (TEC) maps and differential TEC maps. 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. 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. * Corresponding author: solar eclipse on Mawas a fascinating event for people in Northern Europe. German Aerospace Center (DLR), Institute of Communications and Navigation, Kalkhorstweg 53, 17235 Mohammed Mainul Hoque *, Daniela Wenzel, Norbert Jakowski, Tatjana Gerzen, Jens Berdermann, Volker Wilken, Martin Kriegel, Hiroatsu Sato, Claudia Borries and David Minkwitz
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