The Electromagnetic Characteristics of the Polar Ionosphere during a Moderately Disturbed Period

The distribution of the ionospheric conductivities, electric potential, ionospheric currents, filed-aligned current, Joule heating rate, and particle energy input rate by auroral electrons along with the characteristics of auroral particle spectrum are examined during moderately disturbed period by using the computer code developed by Kamide et al. (1981) and the ionospheric conductivity model developed by Ahm et al. (1995). Since the ground magnetic disturbance data are obtained from a single meridian chain of magnetometers(Alaska meridian chain) for an extended period of time (March 9 - April 27, 1978), they are expected to present to present the average picture of the electrodynamics over the entire polar ionosphere. A number of global features noted in this study are as follows: (1) The electric potential distribution is characterized by the so-called two cell convection pattern with the positive potential cell in the morning sector extending into the evening sector. (2) The auroral electrojet system is well developed during this time period with the signatures of DP-1 and DP-2 current systems being clearly discernable. It is also noted that the electric field seems to play a more important role than the ionospheric conductivity over the poleward half of the westward electrojet in the morning sector while the conductivity enhancement seems to be more important over its equatorward half. (3) The global field-aligned current distribution pattern is quite comparable with the statistical result obtained by Iijima and Potemra(1976). However, the current density of Region 1 is much higher than that of Region 2 current as pointed out by previous studies (e.g.;Kamide 1988). (4) The Joule heating occurs over a couple of island-like areas, one along the poleward side of the westward electrojet and the other over the eastward electrojet region in the afternoon sector. (5) The maximum average energy of precipitating electrons is found to be in the morning sector(07¡­08 MLT) while the maximum energy flux is regi! stered in the postmidnight sector (02 MLT). Thus auroral brightening and enhancement of ionospheric conductivity during disturbed period seem to be more closely associated with enhancement of particle flux rather than hardening of particle energy