Transverse structure of the Earth’s magnetotail and fluctuations of the tail magnetic field

The analysis is based on 5.46-min magnetic field averages measured by the IMP 3 satellite. The effect of the inclination χ of the earth's magnetic axis with respect to the Y, Z-plane of solar magnetospheric coordinates (perpendicular to the earth-sun line) is studied in detail, and a thick sheet of magnetic field depression is shown to exist around the neutral sheet at distances of 30 to 38 RE in the antisolar direction. The location of the region of magnetic field depression varies with the value of χ; the thickness of the depression region is about 10 RE in the central parts of the tail, Y≈0, and is probably higher for Y>10 RE. The region of magnetic field depression is identified with the plasma sheet. The sheet of magnetic field depression is characterized by very large, long time-scale fluctuations parallel to the average local magnetic field. A ‘flapping motion’ of the neutral sheet may be responsible for the large values of some of these fluctuations. The fluctuations perpendicular to local magnetic field are nearly independent of position in the magnetotail. Both types of fluctuations are enhanced during and/or after sudden storm commencements (ssc) and sudden impulses (si) observed at ground stations. The effect is more clearly seen in the perpendicular fluctuations. The information from the interaction between the magnetosphere and a discontinuity in the interplanetary medium is transferred mainly along the lines of force.