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Ionospheric VTEC dynamics during late declining phase of the solar cycle

In the late declining phase of the solar cycle, solar wind high-speed streams (HSSs) that originate from equatorial coronal holes (CHs) and the associated co- rotating interacting regions (CIRs) formed in front of HSSs are the major driver of medium-level, but long-lasting geomagnetic activity. Coronal mass ejections can strongly affect the ionosphere, but near the minimum of solar cycle activity their number is reduced and therefore the influence of HSSs to the ionosphere can be better distinguished. In this study we investigate the connection between the CH characteristics, HSS parameters, geomagnetic activity and the ionospheric activity, characterized by ionospheric vertical total electron content (VTEC). VTEC is derived from Global Navigation Satellite Systems (GNSS) reference stations data. We will discuss the efficiency of heliospheric-magnetospheric-ionospheric coupling during the CIR/HSS periods. The timing and phases of ionospheric responses obtained by applying the cross-correlation analyses will be derived. Results of this study could contribute to better space weather forecasting.

geomagnetic activity, ionospheric vertical total electron content, high speed streams, space weather

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