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Statistical Characteristics of Polar Cap Patches Observed by RISR‐C
Author(s) -
Ren Jiaen,
Zou Shasha,
Gillies Robert G.,
Donovan Eric,
Varney Roger H.
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja025621
Subject(s) - noon , latitude , polar , atmospheric sciences , electron density , altitude (triangle) , flux (metallurgy) , physics , ion , incoherent scatter , f region , electron temperature , geodesy , astrophysics , ionosphere , geology , plasma , materials science , geophysics , astronomy , mathematics , geometry , quantum mechanics , metallurgy
Polar cap “patches” are ~100 to 1,000 km islands of high‐density plasma at polar latitudes, which can cause scintillation to communication and navigation signals. An automatic algorithm for patch identification has been developed and applied to the observations from the Resolute Bay Incoherent Scatter Radar‐Canada during January to March and September to December, 2016. Four hundred thirty‐seven patches have been identified, and their statistical characteristics have been studied, including their occurrence rate as a function of magnetic local time (MLT) and statistical profiles of plasma parameters at different MLT sectors. About 60% of the patches are observed between 1200 and 2400 MLT, consistent with earlier observations near this latitude (~82° MLat) using different instruments. Superposed epoch analysis has been used to study the vertical profiles of electron density and temperature, ion temperature, vertical velocity, and flux measured within the patches where the density peaks. The patch median density is higher than the sector median with a ratio of ~1.8–2.1 at the altitude of F‐region density peak. Meanwhile, the patch electron temperature is typically lower than the sector median between ~200 and 450 km with the largest difference near noon (~380 K). In contrast, the ion temperature profile of the patches does not show obvious differences except in the noon sector, where the ion temperature is about 150 K higher than the sector median at ~360 km. Additionally, downward ion fluxes with peak exceeding ~10 13 m −2 s −1 are found in the patches between ~200 and 400 km at all MLT sectors.