Behavior of zonal ion drifts in low and middle latitude ionosphere.

摘要

The Earth's environment consists of a neutral and an ionized atmosphere. The neutral atmosphere can be divided by its temperature profile into the troposphere (0-12 km), the stratosphere (12-45 km), the mesosphere (45-85 km), the thermosphere (85-1000 km) and exosphere (>1000 km). The Earth's ionized atmosphere is typically divided by density and composition into the ionosphere (70-1000 km), the plasmasphere (1000 km to 4 Re for MLAT less than 60°), and the magnetosphere extending to nearly 8 Re on the dayside and to approximately 1000 Re on the nightside. The Earth's ionosphere does not get direct energy from the solar wind because it is shielded by its magnetic field. The region of geospace is dominated by Earth's magnetic field is called the magnetosphere and outermost edge of the magnetosphere, called the magnetopause is maintained by the charged particles from the solar wind flowing along the boundary. The largest energy transfer from the solar wind to the magnetosphere is driven by an electric field directed dawn to dusk.;This limited study shows that during large magnetic storms, ion drifts driven by the magnetosphere penetrate to latitudes as low as the dip equator on the dusk side and extend a few degrees equatorward of the auroral zone on the dawn side. A description of the evolution of the auroral precipitation and the zonal ion drifts at high latitudes during times of extreme storm activity is produced by applying some quantitative definitions that allow us to identify the expansion and penetration of the high-latitude zonal ion drifts to middle and low latitudes in the ionosphere. Times are identified when ion drifts driven from the magnetosphere exist at latitudes inside the plasmasphere and when regions below the auroral zone may be influenced by a disturbance dynamo. The resolved boundaries in the ion drifts and the electron precipitation allow us to distinguish penetration events from sub-auroral polarization fields. This limited study also shows that during large magnetic storms in the northern hemisphere dusk sector at 1800 MLT the equatorward extent of the region-2 current signature extends to as low as 39° MLAT. We have also figured out that at low and middle latitudes small variations in the magnetic perturbations that are removed as a baseline may represent reproducible storm-time signatures.