Ionospheric Response to the Solar Eclipse of 21 August 2017 in Millstone Hill (42N) Observations

Abstract

This study examines the ionospheric changes associated with the solar eclipse of 21 August 2017. The effects associated with the passage of the eclipse shadow were observed more than 1,000 km away from the totality at midlatitudes using the Millstone Hill incoherent scatter radar and digisonde. There was a 30–40% decrease in electron density, a 100‐ to 220‐K decrease in electron temperature, and a 50‐ to 140‐K decrease in ion temperature. Surprisingly, the greatest decrease in electron density occurred above 200 km. The most unexpected effect was a large 20‐ to 40‐m/s upward vertical drift observed in the topside ionosphere right after the local maximum obscuration. We suggest that this drift led to a posteclipse increase in the topside electron density.

Multispectral and Multi‐instrument Observation of TIDs Following the Total Solar Eclipse of 21 August 2017

“…Perturbations are also seen immediately prior to the start of geomagnetic disturbances (0 UTC on 22 August 2017). These premidnight perturbations might be associated with the aftereffect of the eclipse, as Goncharenko et al () also reported enhanced plasma density over MH around 21 UTC (21 August) based on radar measurements. Goncharenko et al () attributed these enhancements to the eclipse's aftereffect.…”

“…These premidnight perturbations might be associated with the aftereffect of the eclipse, as Goncharenko et al () also reported enhanced plasma density over MH around 21 UTC (21 August) based on radar measurements. Goncharenko et al () attributed these enhancements to the eclipse's aftereffect. On the other hand, the postmidnight DTEC, red and green line brightnesses and MUF dynamics were more likely associated with the TIDs generated due to an increase in auroral currents as a result of enhanced geomagnetic activity.…”

“…Previous studies have observed disturbances in the IT system well after the eclipse and far away from its path (e.g., Harding et al, ; Verhulst & Stankov, ). Goncharenko et al () reported enhanced electron density (>50–150%) starting from 21 UTC, 21 August 2017 to at least midnight UTC (22 August) based on radar measurements at MH hours after the eclipse. The authors attributed this enhancement in electron density to the downward flux of plasma from the plasmasphere that was initially filled by upwelling of plasma immediately following the eclipse.…”

The Response of the Ionosphere‐Thermosphere System to the 21 August 2017 Solar Eclipse

“…Millstone Hill experienced a partial eclipse starting at 17:27 UT, maximizing at 18:46 UT at nearly 63% obscuration, and ending at 19:59 UT. The observed response was obtained using 22 August 2017 as the reference day, following Goncharenko et al (2018). The latter three variables are only shown up to 400-km altitude, as results obtained for higher altitudes are considered less reliable, while electron density is shown up to 550 km altitude.…”

“…Figure 10 shows the response in electron density, electron and ion temperature, and vertical drift as simulated by GITM and as observed by the radar. There are arguments to be made for either of these days to be the most appropriate (see Coster et al, 2017;Goncharenko et al, 2018), so we follow here the methods used by the experts on the data sets in their respective publications. The observed response was obtained using 22 August 2017 as the reference day, following Goncharenko et al (2018).…”