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Drifting field‐aligned density structures in the night‐side polar cap
Author(s) -
Santolík O.,
Persoon A. M.,
Gurnett D. A.,
Décréau P. M. E.,
Pickett J. S.,
Maršálek O.,
Maksimovic M.,
CornilleauWehrlin N.
Publication year - 2005
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 - 10.1029/2004gl021696
Subject(s) - physics , dusk , polar , ionosphere , hiss , electric field , geophysics , transverse plane , computational physics , spacecraft , field line , polar cap , geology , geodesy , plasma , astronomy , electron , engineering , structural engineering , quantum mechanics
Spatio‐temporal properties of density irregularities in the night‐side polar cap are inferred from multi‐point observations of auroral hiss at a radial distance of 5 Earth radii. In this case study, we use high resolution data of the wave instruments onboard the four Cluster spacecraft to estimate the local plasma density, obtaining values close to 1 cm −3 with density depletions decreasing down to 0.15 cm −3 . Combined analysis in different points in space conclusively shows for the first time that these density structures are field‐aligned and that they predominantly drift in the anti‐sunward direction at speeds of a few km/s. This corresponds to a dawn‐to‐dusk convection electric field of approximately 1 mV/m. The transverse dimension of the observed density depletions, mapped down to the ionospheric heights, is of the order of a few tens of km. Their lifetime is probably longer than tens of seconds.