Investigating High-Latitude Sporadic E Layers Using Incoherent Scatter Radar

Investigating High-Latitude Sporadic E Layers Using Incoherent Scatter Radar Authors: Anaswara Sunil Kumar, Steve R. Kaeppler
Sporadic-E (Es) layers are characterized as thin layers (1-5 km) of enhanced electron density that occur between 90-120 km in altitude and are composed of metallic ions (Fe+, Mg+, Na+, Ca+). Sporadic-E at mid and low latitudes have a reasonably well-established climatology. In contrast, at high latitudes, fewer investigations have characterized the climatology of Sporadic-E occurrence using altitude-resolved measurements. Incoherent scatter radar provides altitude-resolved measurements of the E-region ionosphere with relatively high-altitude resolution. Since 2008, the Poker Flat Incoherent Scatter Radar (PFISR) has been operating in nearly continuous operations through a low-duty cycle mode, thus enabling observations of Es layers. The distinction between Es and auroral precipitation is detectable and is generally associated with the differences in structure height, with Es being, on average, smaller in altitudinal range and shorter time duration. This investigation aims to present observations of Es layers derived from this nearly continuous database of Alternating Code and along with high-resolution Barker code PFISR data spanning 2007-2023. Our results show that Sporadic-E (Es) events are most frequent during the summer months (June-August), with a secondary peak in winter (December-January) at high latitudes. Peak daily occurrence rates are observed around 12 UTC. The most common event duration is 2-3 hours, with occasional outliers lasting up to 18-19 hours, highlighting variability in event persistence. We also compare the IMF (Interplanetary Magnetic Field ) dependence of Sporadic E (Es) occurrence and whether there is a connection to plasma drifts in the F-region, consistent with previous investigation.