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    Rights statement: This is the peer reviewed version of the following article:Berngardt, O. I., Ruohoniemi, J. M., St‐Maurice, J.‐P., Marchaudon, A., Kosch, M. J., Yukimatu, A. S., et al. ( 2019). Global diagnostics of ionospheric absorption during X‐ray solar flares based on 8‐ to 20‐MHz noise measured by over‐the‐horizon radars. Space Weather, 17, 907– 924. https://doi.org/10.1029/2018SW002130 which has been published in final form at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018SW002130 This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.

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Global Diagnostics of Ionospheric Absorption During X-Ray Solar Flares Based on 8- to 20-MHz Noise Measured by Over-the-Horizon Radars

Research output: Contribution to journalJournal article

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  • O.I. Berngardt
  • J.M. Ruohoniemi
  • J.-P. St-Maurice
  • A. Marchaudon
  • M.J. Kosch
  • A.S. Yukimatu
  • N. Nishitani
  • S.G. Shepherd
  • M.F. Marcucci
  • H. Hu
  • T. Nagatsuma
  • M. Lester
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<mark>Journal publication date</mark>1/06/2019
<mark>Journal</mark>Space Weather
Issue number6
Volume17
Number of pages18
Pages (from-to)907-924
Publication statusPublished
Early online date2/05/19
Original languageEnglish

Abstract

An analysis of noise attenuation during 80 solar flares between 2013 and 2017 was carried out at frequencies 8–20 MHz using 34 Super Dual Auroral Radar Network radars and the EKB ISTP SB RAS radar. The attenuation was determined on the basis of noise measurements performed by the radars during the intervals between transmitting periods. The location of the primary contributing ground sources of noise was found by consideration of the propagation paths of radar backscatter from the ground. The elevation angle for the ground echoes was determined through a new empirical model. It was used to determine the paths of the noise and the location of its source. The method was particularly well suited for daytime situations, which had to be limited for the most part to only two crossings through the D region. Knowing the radio path was used to determine an equivalent vertical propagation attenuation factor. The change in the noise during solar flares was correlated with solar radiation lines measured by GOES/XRS, GOES/EUVS, SDO/AIA, SDO/EVE, SOHO/SEM, and PROBA2/LYRA instruments. Radiation in the 1 to 8 Å and near 100 Å are shown to be primarily responsible for the increase in the radionoise absorption, and by inference, for an increase in the D and E region density. The data are also shown to be consistent with a radar frequency dependence having a power law with an exponent of −1.6. This study shows that a new data set can be made available to study D and E regions.

Bibliographic note

This is the peer reviewed version of the following article:Berngardt, O. I., Ruohoniemi, J. M., St‐Maurice, J.‐P., Marchaudon, A., Kosch, M. J., Yukimatu, A. S., et al. ( 2019). Global diagnostics of ionospheric absorption during X‐ray solar flares based on 8‐ to 20‐MHz noise measured by over‐the‐horizon radars. Space Weather, 17, 907– 924. https://doi.org/10.1029/2018SW002130 which has been published in final form at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018SW002130 This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.