Magnetospheric substorms: Some problems and controversies

This description of the present status of work on magnetospheric substorms is based on the talks and discussions that occurred at the Rice University-AGU Conference on Magnetospheric Substorms. Various types of new data were presented, including, for example, Isis 2 scanning photometer observations of the aurora from above and lunar shadowing observations made from the Apollo 15 subsatellite. The subject of greatest controversy at the conference was the substorm growth phase: gaps in the network of ground magnetometer stations can result in the expansion phase of one substorm being mistaken for the growth phase of another, and there was considerable debate over whether this observational ambiguity could invalidate popular ideas about the growth phase and its signatures. Correlations between magnetospheric phenomena and the direction of the interplanetary magnetic field constituted another area of considerable discussion: the picture appears complicated, with different magnetospheric phenomena correlating with different components of the interplanetary magnetic field. Two areas in which previous controversies have been closed for some time now are the question of whether the magnetosphere is open or closed and the general pattern of the average magnetospheric electric field: it now seems generally agreed that there is direct connection between interplanetary and magnetospheric magnetic field lines, although the details of the connection process remain uncertain, and electric-field measurements from balloons and satellites have convincingly verified the existence of systematic magnetospheric convection, with dawn-to-dusk electric fields over the polar caps. A variety of theoretical approaches to the substorm problem are being pursued, with, as yet, no commonly accepted unifying concept.