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Observations and Modeling of the Ionospheric Topside Response to the Moon's Shadow During Solar Eclipses
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  • Marc Hairston,
  • Sebastijan Mrak,
  • William Coley,
  • Joshua Semeter
Marc Hairston
University of Texas at Dallas

Corresponding Author:[email protected]

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Sebastijan Mrak
Boston University
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William Coley
Univ. of Texas at Dallas
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Joshua Semeter
Boston Univ
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In previous work (Hairston et al., GRL doi 10.1029/2018GL077381, 2018) we showed the topside F-layer (~850 km) electron temperatures measured by two DMSP spacecraft as they flew through the Moon’s shadow during the 21 August 2017 eclipse exhibited a series of non-uniform, banded decreases rather than a broad and smooth temperature decrease. We found that making a “mask” of the shadow of the Moon eclipsing the existing active regions on the sun’s surface created a pattern on the ionosphere showing where the gradient of the EUV from the active regions was greatest. The complex pattern of these areas from the mask at the F-peak altitude at 300 km corresponded to the areas in the topside F-layer where the DMSP observed the bands of cooled electrons. We have expanded this work to examine about a dozen other eclipses including the most recent 21 June 2020 eclipse. We repeatedly observed the same banded pattern in the electron temperatures in almost all the DMSP eclipse passes, thus demonstrating this is a repeatable phenomenon. Since the DMSP series of spacecraft form a constellation of four operational satellites with the same plasma instrument package making multiple measurements of the shadow at different local times, and sometimes within 10-15 minutes of each other, we can use these observations to map the shape and evolution of these cooling band patterns as the eclipse’s shadow passes over the Earth’s ionosphere. Here we will present our first detailed analysis of the two eclipses that occurred on 20-21 May 2012 and 2 July 2019. Both these eclipses have passes through the duskside by two spacecraft within a few minutes of each other, thus allowing us to examine the evolution of the pattern. We are using these events to determine the empirical patterns seen in the electron temperature decreases during eclipses and to explore the mechanism causing the cooling of the plasma and how it is transported from the F-peak region to the topside ionosphere.