Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Energetic particle precipitation leads to ionization in the Earth's atmosphere, initiating the formation of active chemical species which destroy ozone and have the potential to impact atmospheric composition and dynamics down to the troposphere. We report on one exceptionally strong high-energy electron precipitation event detected by balloon measurements in geomagnetic midlatitudes on 14 December 2009, with ionization rates locally comparable to strong solar proton events. This electron precipitation was possibly caused by wave–particle interactions in the slot region between the inner and outer radiation belts, connected with still poorly understood natural phenomena in the magnetosphere. Satellite observations of odd nitrogen and nitric acid are consistent with widespread electron precipitation into magnetic midlatitudes. Simulations with a 3D chemistry–climate model indicate the almost complete destruction of ozone in the upper mesosphere over the region where high-energy electron precipitation occurred. Such an extraordinary type of energetic particle precipitation can have major implications for the atmosphere, and their frequency and strength should be carefully studied.

Highlights

  • We report on one exceptionally strong high-energy electron precipitation event detected by balloon measurements in middle latitudes on 14 December 2009 with ionization rates locally comparable to strong solar proton events

  • Energetic particle precipitation into the atmosphere initiates a chain of reactions starting with atmospheric ionization, leading to large changes in middle atmosphere composition, including the formation of hydrogen and nitric oxides followed by ozone loss in the stratosphere and mesosphere over ∼30-80 km, and with potential relevance even for tropospheric weather 15 systems and regional climate (e.g. Seppälä et al, 2009; Mironova et al, 2015; Arsenovic et al, 2016; Sinnhuber and Funke, 2019)

  • The effect of high latitude electron precipitation (EEP) on atmospheric composition and ozone is confirmed by various observations (e.g. Newnham et al, 2011; Andersson et al, 2014; Newnham et al, 2013; Sinnhuber et al, 2016; Randall et al, 2006) and 3D chemistry-climate models (e.g. Rozanov et al, 2012; Arsenovic et al, 2016; Verronen et al, 2016; Sinnhuber et al, 2018) that account for EEP induced ionization

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Summary

Introduction

Energetic particle precipitation into the atmosphere initiates a chain of reactions starting with atmospheric ionization, leading to large changes in middle atmosphere composition, including the formation of hydrogen and nitric oxides followed by ozone loss in the stratosphere and mesosphere over ∼30-80 km, and with potential relevance even for tropospheric weather 15 systems and regional climate (e.g. Seppälä et al, 2009; Mironova et al, 2015; Arsenovic et al, 2016; Sinnhuber and Funke, 2019). The effect of high latitude EEP on atmospheric composition and ozone is confirmed by various observations (e.g. Newnham et al, 2011; Andersson et al, 2014; Newnham et al, 2013; Sinnhuber et al, 2016; Randall et al, 2006) and 3D chemistry-climate models (e.g. Rozanov et al, 2012; Arsenovic et al, 2016; Verronen et al, 2016; Sinnhuber et al, 2018) that account for EEP induced ionization. Model studies with the 1D atmospheric chemistry model ExoTIC (Herbst et al, 2019) and the 3D chemistry-climate model HAMMONIA (Schmidt et al, 2006; Meraner et al, 2016) using the ionization rates derived from the balloon observations demonstrate formation and loss rates of a wide range of neutral species and ozone in the upper mesosphere

Balloon observations
POES observations
Geomagnetic disturbances
Satellite observations of trace gases (MLS and MIPAS)
HAMMONIA chemistry-climate model results
Findings
Discussion and Conclusions

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