A Statistical Survey of E-Region Anomalous Electron Heating Using Poker Flat Incoherent Scatter Radar Observations

This work presents an algorithm for automatic detection of anomalous electron heating (AEH) events in the auroral E-region ionosphere using data from the Poker Flat Incoherent Scatter Radar (PFISR). The algorithm considers both E-region electron temperature and magnetically conjugate electric field measurements. Application of this algorithm to 14 years of PFISR data spanning 2010 through 2023 detected 505 AEH events. Measured electron temperatures increase linearly with plasma drift speeds. Statistical trends of AEH occurrence as a function of space weather indices (AE and F10.7) demonstrate correlations with the solar cycle and geomagnetic activity levels. The magnetic local time occurrence rates show preferences for dusk and dawn with most events in the dusk sector. Observed AEH events tend to appear in regions of relatively low electron density and do not appear inside intense auroral arcs with high electron density. Furthermore, AEH detection requires a higher electric field than predicted by the threshold for a positive growth rate of the Farley-Buneman instability (FBI), according to linear fluid theory. The implications of these findings for kinetic theories of FBI and AEH are discussed. The ionized portion of the upper atmosphere, known as the ionosphere, can conduct electrical currents. In cases where those currents are so large that the relative motion of the electrons and ions exceeds a critical threshold, the ionosphere becomes unstable. The resulting instability rapidly heats electrons in the lower ionosphere, producing what are known as anomalous electron heating (AEH) events. We use ionospheric data from a radar facility in Alaska to detect AEH events. Our detection algorithm identified 505 AEH events in 14 years of data (2010-2023). The occurrence rates of AEH are strongly correlated with the 11-year solar cycle and indicators of auroral activity. Furthermore, AEH events preferentially occur at times near dawn and dusk, with the highest number of events in the dusk sector. The elevated electron temperatures increase linearly with the magnitude of the ionospheric electric field. A novel detection algorithm for identifying anomalous electron heating events primarily based on plasma flow velocities is presented Analysis of Poker Flat Incoherent Scatter Radar data from 2010 to 2023 detected 505 events Statistical analysis of occurrence rates revealed a strong relationship with geomagnetic activity over the 11-year solar cycle