Climatological characteristics of the auroral ionosphere in terms of electric field and ionospheric conductance

Citation
Bh. Ahn et al., Climatological characteristics of the auroral ionosphere in terms of electric field and ionospheric conductance, J GEO R-S P, 104(A5), 1999, pp. 10031-10040
Citations number
42
Categorie Soggetti
Space Sciences
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
ISSN journal
21699380 → ACNP
Volume
104
Issue
A5
Year of publication
1999
Pages
10031 - 10040
Database
ISI
SICI code
0148-0227(19990501)104:A5<10031:CCOTAI>2.0.ZU;2-L
Abstract
The contributions of the north-south component of the electric field and th e Hall conductance to the auroral electrojet are examined separately. For t his purpose, 52 days of measurements from the Chatanika incoherent scatter radar, which was located near one of the standard AE stations, College, are utilized. A number of interesting characteristics of the amoral electrojet system and auroral electrojet indices are noted: (1) The electric field di stribution along the auroral region is roughly symmetric with respect to th e 1100-2300 magnetic local time meridian. (2) The electric field, particula rly the southward component, becomes a dominant feature along auroral latit udes with increasing magnetic activity. (3) The Hall conductance distributi on in the postnoon sector is mainly determined by the Sun, thus making the eastward electrojet and the AU index dependent upon season. On the other ha nd, the Hall conductance associated with the major part of the westward ele ctrojet in the midnight-postmidnight sector is controlled by precipitating electrons. (4) Since the Hall conductance of solar origin in the postnoon s ector can be estimated, it would be possible to monitor electric field enha ncements contributing to the eastward electrojet. By assuming the same elec tric field, except for the sign being applied to the westward electrojet, t he AL index can be used to estimate the contribution of the Hall conductanc e associated with particle precipitation. This is a clear indication that t he two indices, AU and AL, are governed by different physical processes. Th us it is recommended to use the two indices separately, rather than the com bined AE, in monitoring the auroral electrojet system. (5) The Harang disco ntinuity seems to be a boundary separating the region of precipitating ener getic particles on its northeast side from that of soft particles on its so uthwest side.