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Multiple polar cap arcs: Akebono (Exos D) observations
Author(s) -
Obara T.,
Mukai T.,
Hayakawa H.,
Tsuruda K.,
Matsuoka A.,
Nishida A.,
Fukunishi H.,
Zhu L.,
Sojka J.,
Crain D.
Publication year - 1996
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/96rs00435
Subject(s) - ionosphere , polar cap , magnetosphere , polar , arc (geometry) , physics , geophysics , conductance , electron , current (fluid) , computational physics , atmospheric sciences , geology , plasma , geometry , condensed matter physics , astronomy , mathematics , quantum mechanics , thermodynamics
Akebono (Exos D) observations demonstrate that polar cap arcs sometimes have a fine structure, that is, multiple (double or triple) arcs with spacing of a few tens of kilometers. The multiple polar cap arcs are dominantly observed in the nightside polar cap region, suggesting that low background conductance favors the appearance of the structured arcs. A relationship between the spacing and the average energy of the precipitating electrons is investigated. Results show that a higher energy leads to a wider spacing. Akebono observations also show the existence of a downward current region embedded between upward current regions (arcs). Comparison of the observations with results from a coupled magnetosphere‐ionosphere Sun‐aligned arc model is made, which shows good qualitative agreement between the modeling and observational results on the spacing‐energy dependence and the effect of background ionospheric conductance.