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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Empirical modelling of auroral absorption during disturbed periods of interplanetary coronal mass ejection events
AU - Ogunmodimu, Olugbenga
AU - Honary, Farideh
AU - Rogers, Neil
AU - Richardson, Ian
AU - Nwankwo, Victor
AU - Adebisi, Bamidele
PY - 2020/6/20
Y1 - 2020/6/20
N2 - Energetic charged particle precipitation associated with solar wind perturbations causes enhanced high-frequency radiowave absorption in the high-latitude ionosphere. This study models 38.2 MHz cosmic noise absorption (CNA) by utilising measurements from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi, Finland obtained during solar cycle 23 (1996-2009) associated with the passage of interplanetary coronal mass ejections (ICMEs) past Earth; ICMEs are a major driver ofenhanced geomagnetic activity. Superposed epoch analysis suggests that the absorption vs. time profile depends on whether ICME arrival occurs in the day-time (10-14 MLT) or night-time (22-02 MLT) for IRIS, with peak absorption occurring ~2-3hours ahead of ICME arrival or ~4 hours after ICME arrival, respectively. We determine which combinations of solar wind and IMF parameters show the best correlation with the absorption associated with day-time or night-time arriving ICMEs using superposed epoch analysis and the least squares estimation method. Various combinations of solar wind parameters (including bulk velocity v, density n, and the interplanetary magnetic field north and south components Bz and the SYMH geomagnetic index), have been ranked to obtain the best coupling function for the absorption associated with day- and night-time arriving ICMEs. The absorption for day-time events is found to correlate closely with the solar wind dynamic pressure, SYMH, and the northward direction of the Bz while the absorption for night-time events is most closely related to the direction of the Bz and SYMH. The coupling functions are found to model the observed absorption successfully, with correlation coefficients of ~0.7-0.8 between the observed and modelled absorption.
AB - Energetic charged particle precipitation associated with solar wind perturbations causes enhanced high-frequency radiowave absorption in the high-latitude ionosphere. This study models 38.2 MHz cosmic noise absorption (CNA) by utilising measurements from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi, Finland obtained during solar cycle 23 (1996-2009) associated with the passage of interplanetary coronal mass ejections (ICMEs) past Earth; ICMEs are a major driver ofenhanced geomagnetic activity. Superposed epoch analysis suggests that the absorption vs. time profile depends on whether ICME arrival occurs in the day-time (10-14 MLT) or night-time (22-02 MLT) for IRIS, with peak absorption occurring ~2-3hours ahead of ICME arrival or ~4 hours after ICME arrival, respectively. We determine which combinations of solar wind and IMF parameters show the best correlation with the absorption associated with day-time or night-time arriving ICMEs using superposed epoch analysis and the least squares estimation method. Various combinations of solar wind parameters (including bulk velocity v, density n, and the interplanetary magnetic field north and south components Bz and the SYMH geomagnetic index), have been ranked to obtain the best coupling function for the absorption associated with day- and night-time arriving ICMEs. The absorption for day-time events is found to correlate closely with the solar wind dynamic pressure, SYMH, and the northward direction of the Bz while the absorption for night-time events is most closely related to the direction of the Bz and SYMH. The coupling functions are found to model the observed absorption successfully, with correlation coefficients of ~0.7-0.8 between the observed and modelled absorption.
KW - auroral absorption
KW - coronal mass ejection
KW - space weather
KW - riometer
U2 - 10.1016/j.jastp.2020.105364
DO - 10.1016/j.jastp.2020.105364
M3 - Journal article
JO - Journal of Atmospheric and Solar-Terrestrial Physics
JF - Journal of Atmospheric and Solar-Terrestrial Physics
SN - 1364-6826
ER -