Abstract
A search for ultraviolet (UV) emissions in satellite data during known
STEVE (Strong Thermal Emission Velocity Enhancement) events found that
simultaneous subauroral UV arcs (SUA) were not always present in the
Southern Hemisphere despite coverage of the conjugate STEVE location.
Over the years 2005 to 2020 a total of 108 SUA and STEVE cases were
found. A theory is presented in which MeV solar protons guided by the
interplanetary magnetic field (IMF) produce these arcs along with STEVE
as they precipitate into the atmosphere. Numerous aspects of STEVE and
SUA are explained by this theory.