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

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 (<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 Dst was less −130 nT. More specifically, the NDA occurred during recovery or the lowest Dst period for each intense storm. The magnetic latitudes of the NDA are between 45° and 55° ( L shell: 2.0–3.0). We found that the latitude location of the NDA is quasi‐linearly correlated with Dst . 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.