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Eclipse‐Induced Changes to Topside Ion Composition and Field‐Aligned Ion Flows in the August 2017 Solar Eclipse: e‐POP Observations
Author(s) -
Yau Andrew W.,
Foss Victoria,
Howarth Andrew D.,
Perry Gareth W.,
Watson Christopher,
Huba Joseph
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl079269
Subject(s) - ion , eclipse , solar eclipse , physics , plasma , polar , outflow , photoionization , electron density , astrophysics , ionization , atmospheric sciences , astronomy , meteorology , quantum mechanics
We present in situ ion composition and velocity measurements during the August 2017 solar eclipse from the Enhanced Polar Outflow Probe (e‐POP), which crossed the path of totality at ~640‐km altitude within 10 min of totality passing. These measurements reveal two distinct H + ion populations, an ~40% decrease in topside plasma density, a similar drop in upward but not downward H + ion flux, and a downward O + ion velocity of ~100 m/s. These features are directly linked to changes in the H + /O + composition and in interhemispheric or field‐aligned light ion flow and to a reduction in the negative spacecraft potential. These observed features were absent on the preceding, noneclipse days and corroborate the reduction in F region plasma density and topside total electron content observed by the Global Positioning System receivers on board. They are attributed to the temporary reduction of photoionization in the eclipsed F region.