Ionospheric Effects During the Total Solar Eclipse Over Southeast Asia‐Pacific on 9 March 2016: Part 1. Vertical Movement of Plasma Layer and Reduction in Electron Plasma Density

Abstract

We report our investigation of ionospheric effects that occurred during a total solar eclipse over the Southeast Asia-Pacific region on 9 March 2016. In particular, here we examine rapid uplift of the ionospheric F-layer during the eclipse, and reductions of ionospheric plasma density in areas around the eclipse totality. This study used data from ionosondes at Biak and Guam, as well as data from a bistatic HF radio link (∼1300 km apart, cutting across the eclipse totality trajectory) between Biak and Manado. Gridded total electron content (TEC) data from the Madrigal Database were also used for a cross-comparison. The ionosonde measurements indicate an upward vertical drift velocity in the range of 21−40 m/s in the ionospheric F-region during the eclipse. Over Biak, f oF2 decreased from 10 MHz to 6 MHz (a 40% reduction) during the eclipse. Meanwhile, f oF2 over Guam during the eclipse was suppressed for a few hours; lower than the 7-day average normal level by 3 MHz. The Madrigal GPS TEC data corroborate these ionosonde measurements. Finally, data from the Biak-Manado HF radio link indicate that the D-region ionosphere had diminished substantially during the eclipse.

Coordinated Ground‐Based and Space‐Borne Observations of Ionospheric Response to the Annular Solar Eclipse on 26 December 2019

“…Combined with the curl‐free requirement for the electric field, this would produce a corresponding zonal electric field as an edge effect and would drive an enhanced PRE‐like vertical drift (Eccles, 1998; Rishbeth, 1971b, 1971a). Both our results in Figure 10b, along with previous observations and numerical simulations, have verified that solar eclipses can generate a considerable enhancement of the equatorial eastward electric field and upward plasma drift, especially in the heading (eastern) region of obscuration (Chen et al, 1971a; Dear et al, 2020; Goncharenko et al, 2018; Tsai & Liu, 1999). Under these conditions, the enhanced electric field and upward plasma drift would amplify the equatorial fountain effect and more rapidly evacuate the lower part of the F region (Tomás et al, 2007).…”

“…For example, how does the equatorial dynamo change due to the impact of a solar eclipse? In particular, the electrodynamics of the ionospheric fountain mechanism could be complicated by solar eclipse due to conductivity variations, since the magnitude of eclipse‐associated TEC depletion at equatorial latitudes can reach more than 40%, larger than those at midlatitudes (Dear et al, 2020; Huang et al, 1999; Tsai & Liu, 1999). Moreover, to what degree is the equatorial ionization anomaly (EIA) modified by a solar eclipse?…”

Enhancement of Electron Density in the Ionospheric F2 Layer Near the First Contact of the Total Solar Eclipse on 21 August 2017

“…The corresponding Ne diffusivity is 6.25 𝐴𝐴 × 10 12 electrons/m 2 s −1 (10 16 electrons/m 2 𝐴𝐴 × 1.5 TECU/3,600 s). Numerous studies reported the layer uplift or occurrence of strong vertical drift during solar eclipses (e.g., Dear et al, 2020;Pradipta et al, 2018;Verhulst et al, 2016;W. Wang et al, 2019).…”

Ionospheric Responses at Low Latitudes to the Annular Solar Eclipse on 21 June 2020

“…Besides the neutral wind transport, the eclipse‐induced ionospheric equatorial electric field perturbations can also possibly affect the ionospheric variation. Previous observations and numerical simulations suggested that solar eclipses can induce a considerable increase in the eastward equatorial electric field, which then modifies the ionospheric variations by the upward E × B drifts (Chen et al, 2019; Dear et al, 2020; Goncharenko et al, 2018; St‐Maurice et al, 2011; Tsai & Liu, 1999). As shown in Figure 9, the h m F 2 at Guam which is close to the magnetic equator evidently increased from 300 to 350 km around the onset of the eclipse and then decreased rapidly during the eclipse, which was different as compared with that before and after the eclipse day and the reference.…”