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TitleLong-term variations in the intensity of polar cap plasma flows inferred from SuperDARN
AuthorKoustov, A V; Fiori, R A D; Abooali zadeh, Z
SourceJournal of Geophysical Research, Space Physics vol. 120, issue 11, 2015 p. 9722-9737,
Alt SeriesEarth Sciences Sector, Contribution Series 20160036
PublisherJohn Wiley & Sons, Inc
Mediaon-line; digital; paper
File formathtml; pdf
AreaEarth's ionosphere
Subjectsextraterrestrial geology; solar cycles; solar variations
ProgramNorthern Canada Geohazards Project, Public Safety Geoscience
AbstractMultiyear (1995-2013) velocity data collected by the Super Dual Auroral Network (SuperDARN) HF radars are considered to investigate the diurnal, seasonal, and solar cycle variation of the polar cap plasma flow speed. By considering monthly data sets, we show that the flows are systematically faster in the dawn/prenoon sector. The effect is particularly strong for interplanetary magnetic field (IMF) Bz < 0, By > 0 and in summer months. For Bz < 0, the flow speed increases with intensification of the IMF transverse component Bt at a rate of 20-30 m/s/nT during near noon summer hours. The dependence is weaker for other seasons and away from noon. For IMF Bz > 0, the flow speed response to the increase in Bt is weak. Despite the general sensitivity of the flow speed to Bt intensity and season, the speed for specific IMF bins and seasons or the speed averaged over a year does not change much over the solar cycle. Overall, the velocity is reduced during years of lowest solar activity, but a progression of the effect throughout the solar cycle was not observed. Inferred diurnal and seasonal trends of the polar cap flow speed are generally consistent with variations in the occurrence of VHF echoes whose onset depends on the strength of the ionospheric electric field or equivalently the magnitude of the plasma flow speed.
Summary(Plain Language Summary, not published)
Space weather refers to the dynamic conditions on the Sun and in the space environment, in particular, in the near-Earth environment, that can affect critical infrastructure. NRCan operates the Canadian Space Weather Forecast Centre and conducts research into space weather effects on power systems, pipelines, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. Ionospheric plasma flow is ultimately driven by the interaction between the solar wind, interplanetary magnetic field, and the geomagnetic field. The intensity of plasma flow over the polar cap can be thought of as both the degree to which the solar wind couples to the magnetosphere, and as an indicator for the amount of energy flowing into and throughout the magnetosphere-ionosphere system. This paper presents the long-term variation in the intensity of the polar cap plasma flows inferred from the Super Dual Auroral Radar Network (SuperDARN).