TY - JOUR

T1 - EFFECTS OF THE DAYSIDE FIELD-ALIGNED CURRENTS IN LOCATION AND STRUCTURE OF POLAR CUSPS

AU - TSYGANENKO, NA

AU - USMANOV, AV

PY - 1984

Y1 - 1984

N2 - We have studied the dayside magnetosphere structure and its Kp, AE and IMF-dependence using the magnetic data from IMP and HEOS satellites obtained during 1966–1972. An analysis of the field line configurations has been done on the basis of results of a least squares fitting of the model coefficients to the data subsets. The plots of the magnetopause subsolar point distance and of the polar cusp latitude vs Kp and AE have been obtained. A detailed study of the model field distribution has revealed a substantial difference in the polar cusp field line geometry between the cases of weak and strong geomagnetic activity. We find that this results in a considerable longitudinal extension of the isointensity contours of particle precipitation at ionospheric heights during disturbed periods with Kp ⩾ 3 or AE ≳ 300 nT. The same effect has been detected for the data subsets corresponding to the IMF Bz < 0. In contrast, at quiet times the precipitation isolines are much closer to circles. We conclude therefore that the cleft-like structure of polar cusps pertains only to active periods and can be explained by a magnetic effect of enhanced Birkeland currents.

AB - We have studied the dayside magnetosphere structure and its Kp, AE and IMF-dependence using the magnetic data from IMP and HEOS satellites obtained during 1966–1972. An analysis of the field line configurations has been done on the basis of results of a least squares fitting of the model coefficients to the data subsets. The plots of the magnetopause subsolar point distance and of the polar cusp latitude vs Kp and AE have been obtained. A detailed study of the model field distribution has revealed a substantial difference in the polar cusp field line geometry between the cases of weak and strong geomagnetic activity. We find that this results in a considerable longitudinal extension of the isointensity contours of particle precipitation at ionospheric heights during disturbed periods with Kp ⩾ 3 or AE ≳ 300 nT. The same effect has been detected for the data subsets corresponding to the IMF Bz < 0. In contrast, at quiet times the precipitation isolines are much closer to circles. We conclude therefore that the cleft-like structure of polar cusps pertains only to active periods and can be explained by a magnetic effect of enhanced Birkeland currents.

KW - magnetosphere

KW - polar cusps

KW - geomagnetic field

KW - magnetopause

KW - Birkeland currents

U2 - 10.1016/0032-0633(84)90045-X

DO - 10.1016/0032-0633(84)90045-X

M3 - Article

VL - 32

SP - 97

EP - 104

JO - Planetary and Space Science

JF - Planetary and Space Science

SN - 0032-0633

IS - 1

ER -