An EUV Model of Solar Eclipses using SDO-AIA Images and the Impacts on
Ionosphere-Thermosphere System
Abstract
Solar eclipses cause profound effects on ionosphere-thermosphere
dynamics due to the abatement of solar Extreme Ultra Violet (EUV)
irradiance. The reduced EUV flux cause relative reduction of ionospheric
plasma density and temperature, and well as it reduces thermospheric
temperature, and alters neutral winds. Numerical simulations are used to
understand and characterize the ionosphere-thermosphere response to
solar eclipses and to compare the model results with observations. The
models have traditionally implemented simplified solar eclipses,
assuming spherically symmetric models with the maximum eclipse
(obscuration) set to ~15%. We present a realistic model
of solar eclipses, using Solar Dynamic Observatory (SDO) Atmospheric
Imaging Assembly (AIA) images of the solar corona. This model computes
the eclipse occultation factors as a function of geolocation and time
for a chosen SDO AIA wavelength. The model includes an interface to
retrieve raw high-resolution SDO AIA, the model includes horizon
computation for a smooth and accurate transition at the terminators. The
model is 100% pythonic, featuring parallel execution. We present
observations and numerical simulations of the ionosphere-thermosphere
system bolstering the importance of the accurate EUV eclipse
description. We present use 21 August 2017, and 10 June 2021 solar
eclipses as examples to show the effects of realistic EUV flux and
transient gradients within the penumbra, and compare it with simulations
using symmetric penumbra. We integrated the EUV penumbra in the Global
Ionosphere Thermosphere Model (GITM), and show that the difference
between EUV and symmetric eclipse amounts to as much as plus-minus 1
TECu.