The Effect of Forbush Decreases on the Polar-Night HOx Concentration Affecting Stratospheric Ozone

Irina Mironova,Eugene Rozanov,Arseniy Karagodin-Doyennel

doi:10.3389/feart.2020.618583

Abstract

It is well-known that energetic particle precipitations during solar proton events increase ionization rates in the middle atmosphere enhancing the production of hydrogen oxide radicals (HOx) involved in the catalytic ozone destruction cycle. There are many studies where the contribution of energetic particles to the formation of hydrogen oxide radicals and ozone loss has been widely investigated. However, until now, there was no solid evidence that the reduction in galactic cosmic ray fluxes during a magnetic storm, known as Forbush-effect, directly and noticeably affects the polar-night stratospheric chemistry. Here, the impact of the Forbush decrease on the behavior of hydrogen oxide radicals was explored using the chemistry-climate model SOCOLv2. We found that hydrogen oxide radical lost about half of its concentration over the polar boreal night stratosphere owing to a reduction in ionization rates caused by Forbush decreases after solar proton events occurred on 17 and 20 of January 2005. The robust response in ozone was not found. There is not any statistically significant response in (NOx) on Forbush decrease events as well as over summer time in the southern polar region. The results of this study can be used to increase the veracity of ozone loss estimation if stronger Forbush events can have place.

Highlights

Occurring strong increases in the intensity of energetic particles precipitation (EPP) can sufficiently enhance the ionization of the Earth polar atmosphere leading to the additional production of the odd hydrogen (HOx H + OH + HO2) and odd nitrogen (NOx N + NO + NO2) species (Crutzen et al, 1975; Solomon et al, 1981)
The Forbush decrease-related effects on hydrogen oxide radicals (HOx) were obtained during the polar-night with a statistical significance of more than 95%
Our analysis demonstrates a substantial decline in HOx concentration (∼50%) during both Forbush decreases occur on the 18th and 21st of January 2005 accounting for about half of its total concentration at heights affected by Forbush events

Summary

INTRODUCTION

Occurring strong increases in the intensity of energetic particles precipitation (EPP) can sufficiently enhance the ionization of the Earth polar atmosphere leading to the additional production of the odd hydrogen (HOx H + OH + HO2) and odd nitrogen (NOx N + NO + NO2) species (Crutzen et al, 1975; Solomon et al, 1981). We focus on determining the response in the chemical composition of the polar atmosphere, namely the odd hydrogen (HOx H + OH + HO2) and ozone during Forbush events in January 2005. During the second half of January 2005, several solar energetic particle events and Forbush decreases of galactic cosmic rays were observed. A rapid decrease in the observed galactic cosmic ray intensity followed a coronal mass ejection and SEP events. Forbush decreases caused by an interplanetary disturbance on the January 18, 2005, was a strong 15% decrease of galactic cosmic ray flux and January 21, 2005 Forbush decrease was about 10% (Papaioannou et al, 2010) Atmospheric ionization during these SEP events and Forbush decreases was discussed in great detail by Usoskin et al (2011). The Forbush-related effect on the behavior of HOx radicals and ozone was explored using the chemistry-climate model SOCOLv2

THE CCM SOCOL DESCRIPTION AND EXPERIMENTS SET-UP

Findings

DISCUSSION AND SUMMARY