Review of Magnetic Field Observations

Abstract

Detailed magnetic field observations are now routinely conducted on satellites mapping the magnetosphere and its boundaries. Sufficiently comprehensive spatial, temporal, and high time resolution observations have improved the morphological description of the structure of and fluctuations in the magnetosphere, magnetosheath, plasma sheet and bow shock. Large scale distortion of the magnetospheric structure is detectable in the magnetic field data during and following major geomagnetic and substorm disturbances. Recent observations in previously unexplored regions of the magnetosphere, particularly in the polar cusp region, compliment and reinforce emphasis on particle access to the plasma sheet via the polar neutral points. Significant distortions of the geomagnetic field in the polar cusp region suggest field aligned currents at large geocentric distances which can be related to low altitude polar cap phenomena. Studies of the microstructure of the field reversal region of the plasma sheet imbedded in the geomagnetic tail suggest a periodic structure of more complexity than earlier assumed simplified single neutral-line models. No significant solar cycle variation of magnetospheric structure has been detected. This review highlights the salient features of the more recent observations of the magnetic field in the magnetosphere and identifies critical experimental and data areas for further study and theoretical analysis and interpretation.