The Lifetimes of Plasma Structures at High Latitudes

Magnus F Ivarsen,Andres Spicher,Wojciech Miloch,Yaqi Jin,Lasse B N Clausen

doi:10.1029/2020ja028117

Abstract

AbstractWe present an investigation of polar cap plasma structure lifetimes. We analyze both simulated data from ionospheric models (International Reference Ionosphere model and Mass Spectrometer Incoherent Scatter model) and in situ data from the Swarm satellite mission (the 16 Hz Advanced Plasma Density dataset). We find that the theoretical prediction that E‐region conductance is a predictor of F‐region polar cap plasma structure lifetimes is indeed supported by both in situ‐based observations and by ionospheric models. In situ plasma structure lifetimes correlate well with the ratio of F‐ to E‐region conductance. We present explicit predictions of small scale (∼1 km) structure lifetimes, which range from less than 1 h during local summer to around 3 h during local winter. We highlight a large discrepancy between the observational and theoretical scale‐dependency of decay due to diffusion.

Highlights

In the high-latitude ionosphere, the primary source regions for plasma structuring tend to be located in the dayside cusp and the nightside auroral oval, where electron precipitation is abundant (Kelley et al, 1982)
We present an investigation of polar cap plasma structure lifetimes
We find that the theoretical prediction that E-region conductance is a predictor of F-region polar cap plasma structure lifetimes is supported by both in situ-based observations and by ionospheric models

Summary

Introduction

In the high-latitude ionosphere, the primary source regions for plasma structuring tend to be located in the dayside cusp and the nightside auroral oval, where electron precipitation is abundant (Kelley et al, 1982). The occurrence of plasma irregularities in the high-latitude regions is in general subject to strong seasonal dependencies (Ghezelbash et al, 2014; Heppner et al, 1993; Jin et al, 2018; Prikryl et al, 2015). The occurrence rate for the large-scale polar cap patches is higher during local winter (Coley & Heelis, 1998; Foster, 1984; Schunk & Sojka, 1987; Spicher et al, 2017; Wood & Pryse, 2010), though conflicting evidence exists for the southern hemisphere (Chartier et al, 2018; Noja et al, 2013). Ivarsen et al (2019) found clear evidence for the seasonal dependency plasma structure diffusion, on average for scales

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