University of Oulu

Heino, E., Verronen, P. T., Kero, A., Kalakoski, N., & Partamies, N. ( 2019). Cosmic noise absorption during solar proton events in WACCM‐D and riometer observations. Journal of Geophysical Research: Space Physics, 124, 1361– 1376.

Cosmic noise absorption during solar proton events in WACCM‐D and riometer observations

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Author: Heino, Erkka1,2; Verronen, Pekka T.3; Kero, Antti4;
Organizations: 1Department of Arctic Geophysics, The University Centre in Svalbard, Longyearbyen, Norway
2Department of Physics and Technology, University of Tromsø, Tromsø, Norway
3Space and Earth Observation Centre, Finnish Meteorological Institute, Helsinki, Finland
4Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
5Birkeland Centre for Space Science, Bergen, Norway
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.5 MB)
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Language: English
Published: American Geophysical Union, 2019
Publish Date: 2019-03-21


Solar proton events (SPEs) cause large‐scale ionization in the middle atmosphere leading to ozone loss and changes in the energy budget of the middle atmosphere. The accurate implementation of SPEs and other particle ionization sources in climate models is necessary to understand the role of energetic particle precipitation in climate variability. We use riometer observations from 16 riometer stations and the Whole Atmosphere Community Climate Model with added D region ion chemistry (WACCM‐D) to study the spatial and temporal extent of cosmic noise absorption (CNA) during 62 SPEs from 2000 to 2005. We also present a correction method for the nonlinear response of observed CNA during intense absorption events. We find that WACCM‐D can reproduce the observed CNA well with some need for future improvement and testing of the used energetic particle precipitation forcing. The average absolute difference between the model and the observations is found to be less than 0.5 dB poleward of about 66° geomagnetic latitude, and increasing with decreasing latitude to about 1 dB equatorward of about 66° geomagnetic latitude. The differences are largest during twilight conditions where the modeled changes in CNA are more abrupt compared to observations. An overestimation of about 1° to 3° geomagnetic latitude in the extent of the CNA is observed due to the fixed proton cutoff latitude in the model. An unexplained underestimation of CNA by the model during sunlit conditions is observed at stations within the polar cap during 18 of the studied events.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 124
Issue: 2
Pages: 1361 - 1376
DOI: 10.1029/2018JA026192
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: The work of E. H., P. T. V., and N. K. was supported by the Academy of Finland through the project 276926 (SECTIC: Sun‐Earth Connection Through Ion Chemistry). This work of A. K. is a part of the Tenure Track Project in Radio Science at Sodankylä Geophysical Observatory. This work of N. P. was supported by the Research Council of Norway under CoE contract 223252.
Copyright information: © 2019. American Geophysical Union. All Rights Reserved.