Types of pulsating aurora: comparison of model and EISCAT electron density observations

Fasil Tesema,Noora Partamies,Daniel K Whiter,Yasunobu Ogawa

doi:10.5194/angeo-40-1-2022

Abstract

Abstract. Energetic particle precipitation associated with pulsating aurora (PsA) can reach down to lower mesospheric altitudes and deplete ozone. It is well documented that pulsating aurora is a common phenomenon during substorm recovery phases. This indicates that using magnetic indices to model the chemistry induced by PsA electrons could underestimate the energy deposition in the atmosphere. Integrating satellite measurements of precipitating electrons in models is considered to be an alternative way to account for such an underestimation. One way to do this is to test and validate the existing ion chemistry models using integrated measurements from satellite and ground-based observations. By using satellite measurements, an average or typical spectrum of PsA electrons can be constructed and used as an input in models to study the effects of the energetic electrons in the atmosphere. In this study, we compare electron densities from the EISCAT (European Incoherent Scatter scientific radar system) radars with auroral ion chemistry and the energetics model by using pulsating aurora spectra derived from the Polar Operational Environmental Satellite (POES) as an energy input for the model. We found a good agreement between the model and EISCAT electron densities in the region dominated by patchy pulsating aurora. However, the magnitude of the observed electron densities suggests a significant difference in the flux of precipitating electrons for different pulsating aurora types (structures) observed.

Highlights

Pulsating aurora (PsA) is a diffuse type of aurora with distinctive structures as arcs, bands, arc segments, and patches that are blinking on and off independently within a period of few seconds (Royrvik and Davis, 1977; Yamamoto, 1988)
Combining all-sky camera (ASC) data, EISCAT electron density measurements, electron density output from auroral model, and PsA energy spectra from Polar Operational Environmental Satellite (POES) measurements, we investigate the characteristics of precipitating PsA electrons and their ionization effects during three PsA events, as follows
The ASC data showed PsA drifting into the EISCAT field of view (FOV), where it stayed until 04:43 UT

Summary

Introduction

Pulsating aurora (PsA) is a diffuse type of aurora with distinctive structures as arcs, bands, arc segments, and patches that are blinking on and off independently within a period of few seconds (Royrvik and Davis, 1977; Yamamoto, 1988). Pulsating aurora is often observed after midnight, during the recovery phase of a substorm, and at the equatorward part of the auroral oval (Lessard, 2012; Nishimura et al, 2020), and it can persist for more than 2 h (Jones et al, 2011; Partamies et al, 2017; Bland et al, 2019; Tesema et al, 2020a). PsA is often observed between 56 and 77◦ of magnetic latitude (Grono and Donovan, 2020; Oguti et al, 1981). PsA is very common, with an occurrence rate of about 30 % around magnetic midnight (Oguti et al, 1981) and above 60 % in the morning sector (Oguti et al, 1981; Bland et al, 2019)

Results

Discussion

Conclusion