The 2021 Antarctic Total Eclipse: Ground Magnetometer and GNSS Wave Observations From the 40 Degree Magnetic Meridian

Abstract

Solar eclipses provide an opportunity to study ionospheric dynamics in a way unlike any other. The majority of the sun's direct energy link into Earth's atmosphere is rapidly turned off and on again, and the impact of such a modulation is profound. Anyone who has experienced an eclipse from under the track of totality in person can attest to the dramatic temperature swings that occur from the momentary absence of sunlight. From the perspective of the global atmospheric system, the effects are equally noteworthy. Not only does an eclipse directly affect the thermosphere (Li et al., 2021;McInerney et al., 2018), but the obscuration related reduction in photoioniza tion undoubtedly impacts the ionospheric composition (and therefore dynamics) as well (X. Chen et al., 2021;Dang et al., 2018). As a result of changes to the ionosphere's local total electron content (TEC), currents flowing within the ionosphere should also be modified by an eclipse. However, the exact physical description of how these currents are modified is an unsettled question, particularly in polar regions where data coverage is sparse and eclipses are relatively rare. It is therefore necessary for multi-point observations supported by modeling efforts to advance our understanding of eclipse related effects.Several studies have suggested that ionosphere-thermosphere (IT) dynamics will be altered during an eclipse. One of the main drivers of these modified dynamics (at least at mid to low latitudes) is expected to be changes in the neutral wind structure that create counteracting flows in opposition to the regular wind dynamo (Aa et al., 2020;Choudhary et al., 2011;St.-Maurice et al., 2011). Because of coupling between the ionosphere and thermosphere, the normal evolution of the ionospheric electrojets are likely to be impacted as well by deviations in neutral

Substorms and Solar Eclipses: A Mutual Information Based Study

“…Model results from previous studies have shown that conductivity can be reduced by nearly half under the region of totality. This rapid modification of conductivity on the dayside has been associated with magnetosphere-ionosphere waves observed in both hemispheres during a high latitude eclipse (Coyle et al, 2023). It is possible that these dayside magnetosphere waves couple to a fast-mode wave that travels toward the magnetotail.…”

“…It is likely that future modeling work may give us an insight into the plausibility of coupling energy from the dayside to the nightside in a manner that can trigger a substorm. Coyle et al (2023) presented a case study of an Antarctic total solar eclipse and used event data to simulate the amount of energy diverted from the ionosphere in a simple circuit model as in Boström (1974). This analysis yielded a result similar to the energy supposed by Akasofu (2021) necessary to initiate a substorm onset.…”

“…Coyle et al. (2023) presented a case study of an Antarctic total solar eclipse and used event data to simulate the amount of energy diverted from the ionosphere in a simple circuit model as in Boström (1974). This analysis yielded a result similar to the energy supposed by Akasofu (2021) necessary to initiate a substorm onset.…”

“…One avenue for untangling this dependence is by surveying periods of solar eclipse. It is well known that an eclipse can modify the ionospheric conductivity in the region of shadow (Chen et al., 2021), but a recent study (Coyle et al., 2023) have suggested that eclipse related ionospheric disturbances may also couple into the global magnetosphere. Eclipse related ionospheric modulation is a unique phenomenon with magnetospheric implications that cannot be replicated outside of a realistically coupled ionosphere‐magnetosphere model.…”

IonosphericTotal Electron Content Changes during the 15 February 2018 and 30 April 2022 Solar Eclipses over South America and Antarctica

“…The maximum TEC enhancement was at all sites after the eclipse day. Coyle et al [50] compared GPS TEC observations to the TIE-GCM model ionosphere. They used ground magnetometer observations located along the 40 • magnetic meridian between 69 • S and 79 • S and their magnetically conjugate counterpart.…”