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Confirmation of existence of the small‐scale field‐aligned currents in middle and low latitudes and an estimate of time scale of their temporal variation
Author(s) -
Iyemori Toshihiko,
Nakanishi Kunihito,
Aoyama Tadashi,
Yokoyama Yoshihiro,
Koyama Yukinobu,
Lühr Hermann
Publication year - 2015
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 - 10.1002/2014gl062555
Subject(s) - latitude , scale (ratio) , magnetic field , satellite , swarm behaviour , zonal and meridional , current (fluid) , physics , geology , variation (astronomy) , local time , middle latitudes , geophysics , atmospheric sciences , geodesy , astrophysics , astronomy , mathematical optimization , statistics , mathematics , quantum mechanics , thermodynamics
The magnetic data obtained by the SWARM (the Earth's Magnetic Field and Environment Explorers) satellites in middle or low latitudes during the initial 2 months after launch were analyzed, when they flew nearly on the same orbit with variable time separation ranging from 5 to 100 s. It was confirmed that the small‐scale magnetic fluctuations having period around 10–30 s are the manifestation of spatial structure of small‐scale field‐aligned currents along the orbits. From the statistical relation between correlation coefficients and two satellite separation in time, the typical time scale of temporal variation of the field‐aligned current system is estimated to be around 200 s for meridional component and 340 s for zonal components of the magnetic fluctuations, respectively. Existence of shorter time scale around 30–50 s was also found. These results suggest that the main source of current generation is the acoustic mode of atmospheric gravity waves.