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Ion Velocity and Temperature Variation Around Topside Nighttime Irregularities: Contrast Between Low‐ and Mid‐Latitude Regions
Author(s) -
Park Jaeheung,
Heelis Roderick,
Chao Chi Kuang
Publication year - 2021
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028810
Subject(s) - ionosphere , latitude , geomagnetic latitude , middle latitudes , geology , atmospheric sciences , low latitude , local time , context (archaeology) , f region , geodesy , geophysics , earth's magnetic field , physics , magnetic field , paleontology , statistics , mathematics , quantum mechanics
Studies on low‐/mid‐latitude ionospheric irregularities have a long history, but ion temperature and drift velocity variations within the irregularities have been rarely investigated, especially at mid‐latitudes. To fill this knowledge gap, we statistically investigate ion temperature and velocity of mid‐latitude ionospheric irregularities and compare them to those of low‐latitude ones. This study mainly relies on in situ plasma moment data from the newly launched Ionospheric Connection Explorer (ICON) satellite and is supplemented by Republic of China Satellite 1 (ROCSAT‐1) data in 2000–2004. At low latitudes (|MLAT|<10°) plasma density irregularities encountered by ICON have the following properties: lower‐density regions have cooler ions and more poleward/westward/outward velocity than the ambient plasma, which agrees with previous reports on equatorial plasma bubbles. At mid‐latitudes (|MLAT| = 10°∼30°), the opposite trends are observed: lower‐density regions have hotter ions and more equatorward/eastward/inward drift than the ambient, which is a new finding in this study. The mid‐latitude observations can be put into the context of Medium‐Scale Traveling Ionospheric Disturbance (MSTID) properties reported previously, which evidences that topside irregularities at nighttime mid‐latitudes generally represent MSTIDs. ROCSAT‐1 data support the contrast between low‐ and mid‐latitude ionospheric irregularities.