University of Oulu

Virtanen, I.I., B. Gustavsson, A.T. Aikio, A. Kero, K. Asamura, and Y. Ogawa. (2018), Electron energy spectrum and auroral power estimation from incoherent scatter radar measurements, J. Geophys. Res. Space Physics, 123.

Electron energy spectrum and auroral power estimation from incoherent scatter radar measurements

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Author: Virtanen, Ilkka I.1; Gustavsson, Björn2; Aikio, Anita1;
Organizations: 1Ionospheric Physics Research Unit, University of OuluOulu, Finland
2UiT – t he Arctic University, Tromsø, Norway
3Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
4Japan Aerospace Exploration Agency, Japan
5National Institute of Polar Research, Tokyo, Japan
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.8 MB)
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Language: English
Published: American Geophysical Union, 2018
Publish Date: 2019-01-23


Differential energy flux of electrons precipitating into the high‐latitude ionosphere can be estimated from incoherent scatter radar (ISR) observations of the ionospheric electron density profile. We present a method called ELSPEC for electron spectrum estimation from ISR measurements, which is based on integration of the electron continuity equation and spectrum model selection by means of the Akaike information criterion. This approach allows us to use data with almost arbitrary time resolutions, enables spectrum estimation with dense energy grids, avoids noise amplifications in numerical derivatives, and yields statistical error estimates for all the output parameters, including the number and energy fluxes and upward field‐aligned currents carried by the precipitating electrons. The technique is targeted for auroral energies, 1–100 keV, which ionize the atmosphere mainly between 80 and 150 km altitudes. We validate the technique by means of a simulation study, which shows that Maxwellian, kappa, and mono‐energetic spectra, as well as combinations of those, can be reproduced. Comparison study for two conjugate satellite measurements to the EISCAT UHF radar are shown, for Reimei and Swarm, showing an agreement with the results. Finally, an example of a two‐hour measurement by the EISCAT radar is shown, during which we observe a variety of precipitation characteristics, from soft background precipitation to mono‐energetic spectra with peak energies up to 60 keV. The upward field‐aligned current varies from zero to 10 μAm⁻² and the total energy flux from zero to 250 mWm⁻².

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 123
Issue: 8
Pages: 6865 - 6887
DOI: 10.1029/2018JA025636
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Ilkka Virtanen is funded by the Academy of Finland, application number 285474. Ilkka Virtanen thanks the Vilho, Yrjö and Kalle Väisälä Foundationof the Finnish Academy of Science and Letters for financial support. EISCAT is an international association supported by research organisations in China (CRIRP), Finland(SA), Japan (NIPR and STEL), Norway (NFR), Sweden (VR), and the United Kingdom (NERC).
Academy of Finland Grant Number: 285474
Detailed Information: 285474 (Academy of Finland Funding decision)
Dataset Reference: The European Space Agency (ESA) is acknowledged for providing the Swarm data. The EISCAT data are available for download from the EISCAT web page,
Copyright information: ©2018. American Geophysical Union. All Rights Reserved