Conjugate Ionospheric Perturbation During the 2017 Solar Eclipse

Abstract

We report new findings of total electron content (TEC) perturbations in the southern hemisphere at conjugate locations to the northern eclipse on August 21, 2017. We identified a persistent conjugate TEC depletion by 10%–15% during the eclipse time, elongating along magnetic latitudes with at least ∼5° latitudinal width. As the Moon's shadow swept southward, this conjugate depletion moved northward and became most pronounced at lower magnetic latitudes (>−20°N). This depletion was coincident with a weakening of the southern crest of the equatorial ionization anomaly (EIA), while the northern EIA crest stayed almost undisturbed or was slightly enhanced. We suggest these conjugate perturbations were associated with dramatic eclipse initiated plasma pressure reductions in the flux tubes, with a large portion of shorter tubes located at low latitudes underneath the Moon's shadow. These short L‐shell tubes intersect with the F region ionosphere at low and equatorial latitudes. The plasma pressure gradient was markedly skewed northward in the flux tubes at low and equatorial latitudes, as was the neutral pressure. These effects caused a general northward motion tendency for plasma within the flux tubes, and inhibited normal southward diffusion of equatorial fountain plasma into the southern EIA region. We also identified posteclipse ionospheric disturbances likely associated with the global propagation of eclipse‐induced traveling atmospheric disturbances in alignment with the Moon's shadow moving direction.

Traveling Ionospheric Disturbances in the Vicinity of Storm‐Enhanced Density at Midlatitudes

“…Such constraints are eased if meridional polarization electric fields are embedded in TIDs to drive zonal plasma motion, or if the ion density is low, or if waves have short periodicities. Some of these electric fields embedded in TIDs have been recently confirmed at midlatitudes during quiet time postsunrise hours with significant TID zonal propagation for a few hours (Zhang, Erickson, Gasque, et al., 2021).…”

“…GWs near the terminator have often been observed, for example, Zhang, Erickson, Gasque, et al. (2021) identified eastward propagating electrified TIDs during postsunrise hours, and Figure 6 shows MSTIDs near the sunset terminator at 01:30 UT on 2018‐08‐26 (marked as T4). To provide further contrasts of MSTIDs between storm/substorm and non‐storm/substorm conditions, Figure 13 depicts sample non‐storm/non‐substorm MSTIDs close to the periods of the four storm events studied here.…”

Ionospheric Behavior during the 10 June 2021 Annular Solar Eclipse and Its Impact on GNSS Precise Point Positioning

“…The decrease in foF2 and hmF2 is notorious at stations near the anomaly's crest (RA, FZ, CP); however, it is not very significant in the stations at the magnetic equator (SL). Moreover, similar ionospheric effects were seen in distant regions in the moon's shadow [16][17][18][19][20][51][52][53][54][55][56]. Differences between foF2 and TEC may be due to the fact that foF2 was the result of the original autoscaled records, and also that TEC was calculated from a spatial average.…”

Modeling Solar Eclipses at Extreme Ultra Violet Wavelengths and the Effects of Nonuniform Eclipse Shadow on the Ionosphere‐Thermosphere System

“…Interestingly, the southern crest was first slightly negative (panel c) followed by a positive bay afterward. TEC observations from the southern hemisphere reported TEC depletion at low‐latitudes (Zhang et al., 2021) and both depletion and increase at higher latitudes (He et al., 2018). These results reinforce the TEC data assimilation results indicating early reduction followed by the relative increase in the southern equatorial ionization anomaly (EIA) crest (Chen et al., 2019).…”