We analyzed correlations between solar, interplanetary-medium parameters, and geomagnetic-activity proxies in 27-day averages (a Bartels rotation) for the 2009 – 2016 time interval. We considered two new proxies: I) Bzs GSM (Geocentric Solar Magnetic), calculated as the daily percentage of the IMF southward component along the GSM z-axis and then averaged every 27 days; ii) four magnetospheric indices (T-indices), calculated from the local north-south (X) contributions of the magnetosphere’s cross-tail (TAIL), the symmetric ring current (SRC), the partial ring current (PRC), and the Birkeland current (FAC), derived from the Tsyganenko and Sitnov (J. Geophys. Res. 110, A03208, 2005: TS05) semi-empirical magnetospheric model. Our results suggest, among the parameters tested here, solar facular areas, interplanetary-magnetic field intensity and new proxies derived here could be taken into account in an empirical model, with a 27-day resolution, to explain geomagnetic activity felt on the Earth’s surface in terms of solar surface features and the IMF condition. We further retrieve a clear annual oscillation in series of 27-day-mean values of toward/away asymmetries of geomagnetic-activity indices, which can be interpreted in the light of the Russell–McPherron hypothesis for the semiannual variation of geomagnetic activity (Russell, C.T., and R. L. McPherron (1973), J. Geophys. Res., 78, 92 – 108).

The solar quiet variation (Sq) observed at observatories near the latitude of the Sq vortex focus is difficult to assess because it is affected by both the geomagnetic activity level and the dynamics of the ionosphere and the upper atmosphere resulting in changes of the Sq ionospheric vortex shape and position. The use of only geomagnetically quiet days (QD) to calculate Sq for a given month can, to a certain extent, remove the effect of geomagnetic disturbances; however, the effect of the atmospheric dynamics still needs to be taken into account. The Sq vortex shape and position can be acquired from the horizontal vector of the geomagnetic field measured at geomagnetic observatories located in the European-African sector between 10ºN and 60ºN using vector rotation or calculating equivalent currents. Here we present results of a comparative analysis of two methods to extract Sq variations from the observations of the earth geomagnetic field. The analyzed data are measurements of the geomagnetic field done between 2007 and 2017 at the Coimbra Geomagnetic Observatory (COI, Portugal) located near 40ºN.The principal component analysis (PCA) based Sq curves are compared with the standard ones obtained using 5 international QD per month. For most of the analyzed years for the X component, the second PCA mode was identified as Sq variation whereas for the Y and Z components for all analyzed data sets the first PCA mode was identified as Sq variation. We studied differences and similarity of the PCA and IQD based Sq in relation to (1) the average geomagnetic activity level and (2) Sq vortex shape and position relatively to COI.

The total electron content (TEC) over the Iberian Peninsula was modeled using a PCA-based models based on the decomposition of the observed TEC series using the principal component analysis (PCA) and reconstruction of the daily modes’ amplitudes either by a multiple linear regression model (MRM) or neural networks (NN) using several types of space weather parameters as regressors/predictors: proxies for the solar UV and XR fluxes, number of the solar flares of different types, parameters of the solar wind and of the interplanetary magnetic field, and geomagnetic indices. Lags of 1 and 2 days between the TEC and space weather parameters are used. The general performance of the PCA-MRM and PCA-NN models is tested for different months and in different space weather conditions.

We present the results of the analysis of the reliability of ionosphere TEC values produced by the GNSS receiver installed at the Lisbon airport (Portugal), since 2015. The installed equipment is a NovAtel EURO4 with a JAVAD Choke-Ring antenna. The installed firmware (SCINDA) is specific for scintillation detection. We did a comparison of the SCINDA line-of-sight TEC values with the observed vertical TEC data collected (using ionosonde) by the Ebro Observatory in Spain, and with the vertical TEC values produced using the software developed in the Royal Observatory of Belgium. The differences between the ionosonde-based and GNSS-based TEC and sources of these differences are discussed. In this study special attention was paid to the epochs accompanied by significant Space Weather events strongly affected the ionosphere and the quality of the GNSS positioning.