Investigating the Hot Zone Developed Under Short‐Circuiting Conditions and the Coupled Magnetosphere‐Ionosphere (M‐I) System for the Subauroral Arc's Inner‐Magnetosphere Generation Environment

Based on correlated magnetosphere‐ionosphere (M‐I) conjugate observations of seven events, we study the hot zone developed under short‐circuiting conditions leading (a) to the development of outward Subauroral Polarization Streams (SAPS) or Subauroral Ion Drifts (SAID) electric (E) field and (b) to the various subauroral arcs' absence or presence. Results show (a) the close relations of the hot zone earthward extent and peak ion temperature (Ti) to the magnitude of outward SAPS/SAID E field and (b) the hot zone's high Ti (∼11,000 eV) developed under enhanced plasma turbulence that was (c) generated by the amplified narrow hot ion and electron plasma density peaks, (d) sometimes in plasmaspheric plumes, and that was (e) sometimes further enhanced by the strong auroral kilometric radiation (AKR) waves (f) leading to the development of enhanced SAPS/SAID E field. From these (a–f) findings we conclude for the seven events investigated that (a) the hot zone's development under short‐circuiting conditions was regulated by the kinetic energy of mesoscale plasma flows and that (b) the hot zone created the favorable inner‐magnetosphere conditions during short circuiting (c) for stable auroral red (SAR) arc development by plasma turbulence, which is the common source of heat/suprathermal particles accelerated downward, and (d) in the plasmaspheric plume scenario for SAR arc and Strong Thermal Emission Velocity Enhancement (STEVE) arc development by the plumes' enhanced cold plasma populations leading to strong shear flows and thus shear‐flow instabilities well‐known associated with the SAPS/SAR arc and recently regarded as a potential driver mechanism of the STEVE arc.