Evidence that polar cap arcs occur on open field lines
Abstract
The characteristics of polar cap arc occurrence are reviewed to show that the assumption of a closed magnetospheric magnetic field topology at very high latitudes when the IMF Bz is strongly northward is difficult to reconcile with a wide variety of observational and theoretical considerations. In particular, consideration is given to the implications of observations of particle entry for high and low energy electrons, magnetic flux conservation between the near and far tail, the time sequencing in polar cap arcs events, and the hemispherical differences in polar cap arc observations. These points can be explained either by excluding the need for a major topological magnetic field change from explanations of polar cap arc dynamics or by assuming a longtailed magnetosphere for all IMF orientations in which magnetic field lines eventually merge with solar wind field lines in either a smooth or a patchy fashion.
 Publication:

Journal of Geomagnetism and Geoelectricity
 Pub Date:
 1990
 DOI:
 10.5636/jgg.42.737
 Bibcode:
 1990JGG....42..737G
 Keywords:

 Auroral Arcs;
 Boundary Layer Plasmas;
 Magnetic Field Configurations;
 Magnetosheath;
 Polar Caps;
 Geomagnetism;
 Interplanetary Magnetic Fields;
 Magnetic Flux;
 Particle Precipitation