University of Oulu

Miyamoto, T., Oyama, S.-i., Raita, T., Hosokawa, K., Miyoshi, Y., Ogawa, Y., & Kurita, S. (2021). Variations in cosmic noise absorption in association with equatorward development of the pulsating auroral patch: A case study to estimate the energy spectra of auroral precipitating electrons. Journal of Geophysical Research: Space Physics, 126, e2021JA029309.

Variations in cosmic noise absorption in association with equatorward development of the pulsating auroral patch : a case study to estimate the energy spectra of auroral precipitating electrons

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Author: Miyamoto, Taishiro1,2; Oyama, Shin-ichiro1,3; Raita, Tero4;
Organizations: 1Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan
2Now at Nippon Steel Corporation Nagoya Works, Tokai-shi, Japan
3National Institute of Polar Research, Tokyo, Japan
4Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
5Center for Space Science and Radio Engineering, University of Electro-Communications, Chōfu, Japan
6Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.9 MB)
Persistent link:
Language: English
Published: American Geophysical Union, 2021
Publish Date: 2022-03-04


This study focused on a pulsating aurora event associated with aurora morphological changes in Fennoscandia in the early morning on March 7, 2017. A high-speed sampling all-sky camera captured equatorward development of the pulsating auroral patch in association with a substorm centered over the Greenland/North America region. Of particular interest in this event is the interconnection between the auroral intensity and the cosmic noise absorption (CNA) derived from three riometers aligned meridionally in Finland (from north to south: Ivalo, Sodankylä, and Rovaniemi). The analysis was made by dividing optical measurements into two oscillation components: longer and shorter than 40 s, that is, nonpulsating and pulsating auroral modulations. The interrelation between the auroral brightness and CNA showed a linear correlation. The inclination of the regression line changed with time depending on latitudes, which was interpreted as hardening or softening of the precipitating electron spectrum. Especially in the case of the low-pass component, the inclination of the CNA-vs-intensity interrelation increased at the three riometer latitudes in the substorm recovery phase. On the other hand, for the high-pass component, the inclination decreased at Rovaniemi (lower latitude) but remained uniform at Sodankylä (higher latitude). These features suggest that the precipitating electron spectrum has softened in the low-pass or nonpulsating auroral component, but the spectrum has hardened in the high-pass or pulsating auroral component on the lower latitude part of the auroral patch region. This study proposes a new application of riometer-camera measurements to examine auroral particle precipitation.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 126
Issue: 9
Article number: e2021JA029309
DOI: 10.1029/2021JA029309
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This work was supported by JSPS KAKENHI JP 15H05747, 16H06286, 21H04518, and JPJSBP120194814. Part of the work by SO was supported by Academy of Finland 314664. This work was carried out by the joint research program of Planetary Plasma and Atmospheric Research Center, Tohoku University. The operation of the EMCCD camera at Sodankylä was supported by Sodankylä Geophysical Observatory (SGO). AMGeO is supported by NSF Earth Cube grants ICER 1928403 to the University of Colorado Boulder, ICER 1928327 to the Virginia Tech, and ICER 1928358 to the Johns Hopkins University Applied Physics Laboratory.
Academy of Finland Grant Number: 314664
Detailed Information: 314664 (Academy of Finland Funding decision)
Dataset Reference: The data files were obtained from the ERG-Science Center operated by ISAS/JAXA and ISEE/Nagoya University ( The SGO riometer quick look plots can be viewed at, and the data are available upon request.
Copyright information: © 2021. American Geophysical Union.