Convection And Substorms PDF Download

This paper reports multi-point observations of ionospheric convection made during the SUNDIAL 1987 campaign. Two specific intervals of varying interplanetary magnetic field, which also include several substorms, have been identified for detailed study. The two intervals differed considerably in both the input of energy from the solar wind to the magnetosphere prior to the substorm expansion phase onset and the response during the expansion phase. One substorm can be represented by the classical picture of growth phase, expansion phase and recovery phase. The other, which occurred during an interval of weak energy input from the solar wind to the magnetosphere, was more complex, in particular during the expansion phase. Observations of the earth's magnetic field in the midnight sector provide the timing of the expansion phase onset of substorms which allow the separation of ionospheric effects due to changes in IMF and substorms. The primary ionospheric effect of a change in IMF from positive Bsubz to negative Bsubz is an enhancement in plasma flow magnitude. Response time of the ionospheric convection to each southward turning varies from 15 minutes near 1800 MLT to 30 minutes near 2100 MLT and closer to an hour near midnight. In both instances, a growth phase can be identified as an increase in ionospheric convection following a southward turning of the IMF. The overall length of each growth phase was similar, about 90 minutes, despite the different prevailing solar wind and IMF conditions. Furthermore this time is somewhat longer than previous observations.