On the location of Steve, the mysterious subauroral feature

Over the past year, there has been an exciting development in auroral research with the finding of a new subauroral phenomenon called Steve. Although Steve has been documented by amateur night sky watchers for decades, this is a new phenomenon about which scientists know very little. From optical observations including images from amateur photographers, Steve is a luminous arc that is narrow in north-south extent, and thousands of kilometers in east-west extent. We use auroral images from the ground-based THEMIS all-sky imagers and the Redline Geospace Observatory (REGO) array to identify Steve events. In addition, we use data from Meridian Scanning Photometers (NORSTAR and FESO) that measure brightness of H-β proton auroral emission at 4861Å. We surveyed data from December 2007 up to May 2017. Our observations suggest that Steve is always located equatorward of the proton aurora, and thus is not a traditional electron auroral arc, a feature which is always poleward of the peak in proton auroral brightness. Further, we have developed a picture of the magnetospheric region which is magnetically conjugate to Steve, and the magnetospheric conditions which give rise to the feature.