The Ion/Electron Temperature Characteristics of Polar Cap Classical and Hot Patches and their Influence on Ion Upflow

The term of “polar cap hot patch” is a newly identified high-density plasma irregularity at high latitudes, which is associated with high electron temperature and particle precipitation, while a classical polar cap patch has lower electron temperature. To investigate characteristics of hot patches versus classical patches, five years of in situ database of plasma observations from the DMSP satellites was analyzed. For the first time, we show how the ion/electron temperature ratio (or temperature difference) can be used to distinguish between classical and hot patches. For classical patches (Ti/Te > 0.8 or Te Ti + 600 K), the vertical ion flux is generally upward. The highest upflow occurrence was found near the polar cap boundary, associated with hot patches, particle precipitation, strong convection speed, and localized field-aligned currents. This result shows that the polar cap hot patches may play a very important role in solar wind-magnetosphere-ionosphere coupling processes. ©2018. American Geophysical Union. All Rights Reserved.