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
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.