Magnetic field configuration in the magnetotail near 60RE

Abstract

The magnetic field line configuration in the geomagnetic tail near 60 RE is examined on the basis of nearly 3 years of magnetometer data from the lunar-orbiting Explorer 35 satellite. The magnetotail field line characteristics inside the plasma sheet and in the high-latitude tail, i.e., outside the plasma sheet, are separately examined. In the high-latitude tail the magnetic field lines systematically diverge in both longitudinal (east-west) and latitudinal (north-south) directions; the divergence angle between field lines near the dusk flank and those near the dawn flank is about 14°, but the divergence along the Z direction is only about 8°. The degree of divergence is found to be greater in the evening side than in the morning side and greater in the northern tail than in the southern tail. Inside the plasma sheet the field lines deviate by about 19° from the sun-earth line, and the spatial distribution of the field line deviation does not have any systematic tendency. The average longitudinal and latitudinal deviation is about 20° and 17°, corresponding to the average |BY| and |Bz| of 1.9 γ and 1.7 γ, respectively. The geomagnetic activity dependence of the field line configuration is also examined, and no drastic difference is found during different Kp periods.