EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

HEPPA III intercomparison experiment on electron precipitation impacts:  Estimated ionization rates during a geomagnetic active period in April 2010

Hilde Nesse Tyssøy1, Miriam Sinnhuber2, Timo Asikainen3, Stefan Bender4, Mark A. Clilverd5, Bernd Funke6, Max van de Kamp7, Joshua Pettit8, Cora Randall8, Thomas Reddmann2, Craig J. Rodger9, Eugene Rozanov10,11, Christine Smith-Johnsen1, Timofei Sukhodolov10,11, Pekka T. Verronen3,7, Jan Maik Wissing12, and Olesya Yakovchuk11,12,13
Hilde Nesse Tyssøy et al.
  • 1Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, Norway (
  • 2Karlsruhe Institute of Technology, Germany
  • 3University of Oulu, Finland
  • 4Birkeland Centre for Space Science, Norwegian University of Science and Technology, Trondheim, Norway
  • 5British Antarctic Survey (UKRI-NERC), Cambridge, England
  • 6Instituto de Astrofisica de Andalucia, CSIC, Granada, Spain
  • 7Space and Earth Observation Centre, Finnish Meteorological Institute, Finland
  • 8LASP, University of Colorado, Boulder, Colorado, USA
  • 9University of Otago, New Zealand
  • 10PMOD/WRC, Davos, Switzerland
  • 11Department of Physics of Earth, Faculty of Physics, St. Petersburg State University, St. Petersburg, Russia
  • 12University of Rostock, Germany
  • 13Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia

Precipitating auroral and radiation belt electrons are considered an important part of the natural forcing of the climate system.  Recent studies suggest that this forcing is underestimated in current chemistry-climate models. The HEPPA III intercomparison experiment is a collective effort to address this point. Here, eight different estimates of medium energy electron (MEE) (>30 keV) ionization rates are assessed during a geomagnetic active period in April 2010.  The objective is to understand the potential uncertainty related to the MEE energy input. The ionization rates are all based on the Medium Energy Proton and Electron Detector (MEPED) on board the NOAA/POES and EUMETSAT/MetOp spacecraft series. However, different data handling, ionization rate calculations, and background atmospheres result in a wide range of mesospheric electron ionization rates. Although the eight data sets agree well in terms of the temporal variability, they differ by about an order of magnitude in ionization rate strength both during geomagnetic quiet and disturbed periods. The largest spread is found in the aftermath of the geomagnetic activity.  Furthermore, governed by different energy limits, the atmospheric penetration depth varies, and some differences related to latitudinal coverage are also evident. The mesospheric NO densities simulated with the Whole Atmospheric Community Climate Model driven by highest and lowest ionization rates differ by more than a factor of eight. In a follow-up study, the atmospheric responses are simulated in four chemistry-climate models and compared to satellite observations, considering both the model structure and the ionization forcing.

How to cite: Nesse Tyssøy, H., Sinnhuber, M., Asikainen, T., Bender, S., Clilverd, M. A., Funke, B., van de Kamp, M., Pettit, J., Randall, C., Reddmann, T., Rodger, C. J., Rozanov, E., Smith-Johnsen, C., Sukhodolov, T., Verronen, P. T., Wissing, J. M., and Yakovchuk, O.: HEPPA III intercomparison experiment on electron precipitation impacts:  Estimated ionization rates during a geomagnetic active period in April 2010, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5287,, 2021.

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