University of Oulu

Kozlovsky, A., Shalimov, S., Oyama, S., Hosokawa, K., Lester, M., Ogawa, Y., & Hall, C. ( 2019). Ground echoes observed by the meteor radar and high‐speed auroral observations in the substorm growth phase. Journal of Geophysical Research: Space Physics, 124, 9278– 9292. https://doi.org/10.1029/2019JA026829

Ground echoes observed by the meteor radar and high-speed auroral observations in the substorm growth phase

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Author: Kozlovsky, A.1; Shalimov, S.2,3; Oyama, S.4,5,6;
Organizations: 1Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
2Institute of Physics of the Earth, Moscow, Russia
3Space Research Institute, Moscow, Russia
4Institute for Space‐Earth Environmental Research, Nagoya University, Nagoya, Japan
5Ionospheric Physics Unit, University of Oulu, Oulu, Finland
6National Institute of Polar Research, Tokyo, Japan
7Department of Communication Engineering and Informatics, University of Electro‐Communications, Tokyo, Japan
8Department of Physics and Astronomy, University of Leicester, Leicester, UK
9Tromsø Geophysical Observatory, The Arctic University of Norway, Tromsø, Norway
Format: article
Version: published version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe202002064686
Language: English
Published: American Geophysical Union, 2019
Publish Date: 2020-06-26
Description:

Abstract

Multi‐instrument observations by a meteor radar (MR), auroral cameras, ionosondes, and ground magnetometers were made in Northern Europe at auroral latitudes (between 64° and 72° corrected geomagnetic latitude) at 22–24 magnetic local time in the substorm growth phase. The southward drifting growth phase auroral arc was associated with enhanced electron density up to 2⋅1012 m‐3 (corresponding to a plasma frequency, foEs of about 13 MHz) at about 110‐km altitude. Such an enhanced E layer electron density caused bending toward the ground of the MR radio waves transmitted at a frequency, fr, of 36.9 MHz and at low elevation (el. < 25°), such that the radar received ground echoes characterized by a near‐zero Doppler shift. The amplitude of the echoes was modulated at a frequency of a few hertz, and a similar modulation was found in the auroral luminosity at 427.8 nm near the location of the bending of MR radio waves. The modulation was due to irregular (random) fluctuations of auroral precipitation. Although such a few‐hertz variation of the auroral precipitation cannot produce more than 1% modulation of the ionospheric electron density, even such a small modulation can lead to 50% modulation of the MR ground scatter provided foEs ≈ fr sin (el.). The ionosonde and MR data provide evidence that this condition was satisfied in the present case. Due to a high‐frequency (>2 Hz) amplitude modulation of the ground scatter, the MR erroneously accepts such signals as echoes from meteor trails.

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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: 11
Pages: 9278 - 9292
DOI: 10.1029/2019JA026829
OADOI: https://oadoi.org/10.1029/2019JA026829
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Subjects:
Funding: The data of the meteor radar, SGO ionosonde, and Abisko ASC were collected at SGO (http://www.sgo.fi/). The operation of the EMCCD camera at Tromsø has been supported by JSPS KAKENHI JP 15H05747 and the Arctic University of Norway (UiT). The data files are obtained from ERG‐Science Center operated by ISAS/JAXA and ISEE/Nagoya University (at https://ergsc.isee.nagoya‐u.ac.jp/data_info/ground.shtml.en). Data of the Digisonde were obtained from the Tromsø Geophysical Observatory of the Arctic University of Norway (http://geo.phys.uit.no/ionodata/index.html). Data of the IMAGE magnetometer network are available online (at http://space.fmi.fi/image/www/). We thank the institutes who maintain the IMAGE Magnetometer Array: Tromsø Geophysical Observatory of UiT the Arctic University of Norway (Norway), Finnish Meteorological Institute (Finland), Institute of Geophysics Polish Academy of Sciences (Poland), GFZ German Research Centre for Geosciences (Germany), Geological Survey of Sweden (Sweden), Swedish Institute of Space Physics (Sweden), Sodankylä Geophysical Observatory of the University of Oulu (Finland), and Polar Geophysical Institute (Russia). S. S. acknowledges support from the Academy of Finland via Grant 310348. M. L. acknowledges support from STFC Grants ST/S000429/1 and ST/N000749/1. A. K. acknowledges discussions within the International Space Science Institute (ISSI) Team 410 on New Features in the Meteor Radar Observations and Applications for Space Research.
Academy of Finland Grant Number: 310348
Detailed Information: 310348 (Academy of Finland Funding decision)
Copyright information: © 2019. American Geophysical Union. All Rights Reserved.