Nightside detached auroras due to precipitating protons/ions during intense magnetic storms

<p>Nightside detached auroras (NDA) during intense magnetic storms are studied by using FUV image data from Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED)/Global Ultraviolet Imager (GUVI), Imager for Magnetopause-to-Aurora Global Exploration (IMAGE)/FUV, and particle data from DMSP/SSJ/4 instruments. We found that NDA are caused by proton/ion precipitation only. Thin arc-shaped NDA are very likely due to soft (\&lt;1 keV) proton/ion precipitation. Thick or patch-shaped NDA are caused by energetic (\~10 keV) proton/ion precipitation. All the cases indicate that the NDA were observed when\&nbsp;<em>Dst</em>\&nbsp;was less -130 nT. More specifically, the NDA occurred during recovery or the lowest\&nbsp;<em>Dst</em>\&nbsp;period for each intense storm. The magnetic latitudes of the NDA are between 45\textdegree and 55\textdegree (<em>L</em>shell: 2.0\textendash3.0). We found that the latitude location of the NDA is quasi-linearly correlated with\&nbsp;<em>Dst</em>. The magnetic local time (MLT) of the NDA ranges from 1930 to 0300. All the facts indicate that the source of the NDA is the trapped protons/ions in the ring current. Precipitation of the trapped protons/ions is caused by an interaction between the perpendicularly heated ring current particles and the cold/dense plasma at the plasmapause.</p>