Recurrent ionospheric storms during solar minimum

We present a comprehensive analysis of perturbations in the lowand mid-latitude ionosphere during moderate recurrent geomagnetic storms (RGSs) in 2007-2008 solar minimum. It is shown that during socalled recurrentionospheric storms (RIS), the heliospheric magnetospheric ionospheric thermospheric coupling remains highly efficient even during solar minimum. Analysis of global ionospheric maps of vertical total electron content (VTEC) derived on the base of GPS network showed that VTEC has a tendency to decrease and negative ionospheric storms occur right before the onset and on the late recovery phase of RGS. A positive ionospheric storm is developed 2 to 4 days after, i.e.,on the recovery phase of RGS produced by high intensity longdurationcontinuous auroral activity. The ionospheric response to heliospheric and geomagnetic drivers reveals prominent longitudinal and local time variations. Such effects as penetrating electric fields of interplanetary andmagnetospheric origin, disturbance dynamo electric fields, neutral winds and thermospheric chemical composition changesare considered as possible mechanisms responsible for the observed recurrent ionospheric storms.