Equatorial longitude and local time variations of topside magnetic field‐aligned ion drifts at solar minimum

Abstract

In the topside ionosphere, the high mobility of the plasma along the magnetic field allows field‐aligned ion drifts to occur readily as a result of field‐aligned gravitational forces, collisional forces, or pressure gradients. Therefore, variations in the field‐aligned ion drifts can be used to explore the influence of thermospheric, electrodynamic, and chemical processes on the ionosphere. Longitude and local time variations in the field‐aligned ion drifts near the magnetic equator are presented using observations from the Coupled Ion Neutral Dynamics Investigation on board the Communications/Navigation Outage Forecast System satellite. These observations were obtained during the period of extremely low solar activity present in 2008 and 2009, allowing the seasonal, local time, and longitudinal variations to reveal the relative importance of the processes responsible for topside field‐aligned plasma drifts during solar minimum. This investigation found that the low‐altitude winds and tides, the net ionization or loss, and the meridional E×B drift were all influential in creating longitudinal and local time variations in the field‐aligned drift, though the strength of the influence seen by each driver was found to vary with season, local time, and longitude.