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Statistics of High Latitude Sporadic E Layer Occurrence derived using Incoherent Scatter Radar Observations
  • Andrew Pepper,
  • Austin Smith,
  • Stephen Kaeppler
Andrew Pepper
Clemson University
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Austin Smith
Clemson University

Corresponding Author:asmit35@g.clemson.edu

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Stephen Kaeppler
Clemson University
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Abstract

Sporadic-E (Es) layers are characterized as thin layers (1-5 km) of enhanced electron density that occur between 90-120 km in altitude. Sporadic E at mid- and low-latitudes has a reasonably well established climatology, while at high latitudes there have been fewer investigations that have characterized the climatology of sporadic E occurrence using altitude resolved measurements. Incoherent scatter radar provides direct 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 sporadic E. 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. The purpose of this investigation is to present observations of sporadic E derived from this nearly continuous database of alternating code and Barker code PFISR data spanning the years from 2007-2021. We visually identified the sporadic E layers and have found approximately 300 events. We present statistical results of the occurrence, duration, and characteristics of high latitude sporadic E derived from these events. The preponderance of events manifested within 95 to 120 km, typically lasted 1 to 3 hours, and mostly occurred during May through September with observance peaking in July. In addition, the trends indicated a potential disconnect between sporadic-E events and auroral activity, which was previously considered the primary driving force behind high latitude sporadic-E events. The climatology of high latitude sporadic E is an important contribution that must be considered in future high latitude models of the ionosphere.