The Dependence of Cold and Hot Patches on Local Plasma Transport and Particle Precipitation in Northern Hemisphere Winter. Issue 12 (18th June 2022) - Zhang, Duan
Abstract: By using a database of 4, 634 cold patches (high density and low electron temperature) and 4, 700 hot patches (high density and high electron temperature) from Defense Meteorological Satellite Program F16 in 2005–2018 winter months (October–March), we present a statistical survey of the distributions of polar cap patches for different interplanetary magnetic field (IMF) orientations and ionospheric convection geometries. We investigate the dependence of cold and hot patches on local plasma transport and soft‐electron precipitation. Our results indicate that: in winter, (a) more cold and hot patches occur in the stronger anti‐sunward flow organized by different IMF orientations. (b) cold patches are frequent near the central polar cap, while hot patches are closer to the auroral oval. (c) enhanced anti‐sunward flow ( E × B drift) mainly contributes to cold patch occurrence under Bz < 0, and soft‐electron precipitation contributes to hot patch occurrence both under southward and northward IMF. Plain Language Summary: Polar cap patches are common phenomena in the polar ionosphere and consist of high‐density plasma. We use 4, 634 cold patches and 4, 700 hot patches observed by the Defense Meteorological Satellite Program to investigate the distributions of polar cap patches for different interplanetary magnetic field (IMF) orientations and ionospheric convection geometries. We find that more cold and hot patches are distributed in areas of stronger anti‐sunward flow in winter. The hot patches are more frequent at lower magnetic latitudes, and located closer to the auroral oval than cold patches. Furthermore, in winter months, higher anti‐sunward flow velocity mainly contributes to a higher occurrence of cold patches under southward IMF, and stronger soft‐electron precipitation mainly contributes to a higher occurrence of hot patches both under southward and northward IMF. Key Points: The spatial distributions of cold and hot patches respond well to the convection pattern for different interplanetary magnetic field orientations The hot patches are more frequent at lower magnetic latitudes than cold patches, and located closer to the auroral oval Enhanced anti‐sunward flow promotes cold patch occurrence under Bz < 0, and soft‐electron precipitation promotes hot patch occurrence