University of Oulu

Verronen, P. T., Marsh, D. R., Szeląg, M. E., and Kalakoski, N.: Magnetic-local-time dependency of radiation belt electron precipitation: impact on ozone in the polar middle atmosphere, Ann. Geophys., 38, 833–844,, 2020.

Magnetic-local-time dependency of radiation belt electron precipitation : impact on ozone in the polar middle atmosphere

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Author: Verronen, Pekka T.1,2; Marsh, Daniel R.3,4; Szeląg, Monika E.2;
Organizations: 1Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
2Space and Earth Observation Centre, Finnish Meteorological Institute, Helsinki, Finland
3Atmospheric Chemistry Observations and Modeling, National Center for Atmospheric Research, Boulder, CO, USA
4Priestley International Centre for Climate, University of Leeds, Leeds, UK
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 8.2 MB)
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Language: English
Published: Copernicus Publications, 2020
Publish Date: 2020-09-03


The radiation belts are regions in the near-Earth space where solar wind electrons are captured by the Earth’s magnetic field. A portion of these electrons is continuously lost into the atmosphere where they cause ionization and chemical changes. Driven by the solar activity, the electron forcing leads to ozone variability in the polar stratosphere and mesosphere. Understanding the possible dynamical connections to regional climate is an ongoing research activity which supports the assessment of greenhouse-gas-driven climate change by a better definition of the solar-driven variability. In the context of the Coupled Model Intercomparison Project Phase 6 (CMIP6), energetic electron and proton precipitation is included in the solar-forcing recommendation for the first time. For the radiation belt electrons, the CMIP6 forcing is from a daily zonal-mean proxy model. This zonal-mean model ignores the well-known dependency of precipitation on magnetic local time (MLT), i.e. its diurnal variability. Here we use the Whole Atmosphere Community Climate Model with its lower-ionospheric-chemistry extension (WACCM-D) to study effects of the MLT dependency of electron forcing on the polar-ozone response. We analyse simulations applying MLT-dependent and MLT-independent forcings and contrast the resulting ozone responses in monthly-mean data as well as in monthly means at individual local times. We consider two cases: (1) the year 2003 and (2) an extreme, continuous forcing. Our results indicate that the ozone responses to the MLT-dependent and the MLT-independent forcings are very similar, and the differences found are small compared to those caused by the overall uncertainties related to the representation of electron forcing in climate simulations. We conclude that the use of daily zonal-mean electron forcing will provide an accurate ozone response in long-term climate simulations.

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Series: Annales geophysicae
ISSN: 0992-7689
ISSN-E: 1432-0576
ISSN-L: 0992-7689
Volume: 38
Issue: 4
Pages: 833 - 844
DOI: 10.5194/angeo-38-833-2020
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This research has been supported by a National Science Foundation award for “Collaborative Research: CEDAR – Quantifying the Impact of Radiation Belt Electron Precipitation on Atmospheric Reactive Nitrogen Oxides (NOx) and Ozone (O3)” (grant no. 1650918).
Copyright information: © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.