Geomagnetically induced currents (GICs) represent a significant space weather issue for power grid and pipeline infrastructure, particularly during severe geomagnetic storms. In this study, magnetometer data collected from around the world are analyzed to investigate the GICs caused by the 2015 St. Patrick's Day storm. While significant GIC activity in the high‐latitude regions due to storm time substorm activity is shown for this event, enhanced GIC activity was also measured at two equatorial stations in the American and Southeast Asian sectors. This equatorial GIC activity is closely examined, and it is shown that it is present both during the arrival of the interplanetary shock at the storm sudden commencement (SSC) in Southeast Asia and during the main phase of the storm ∼10 h later in South America. The SSC caused magnetic field variations at the equator in Southeast Asia that were twice the magnitude of those observed only a few degrees to the north, strongly indicating that the equatorial electrojet (EEJ) played a significant role. The large equatorial magnetic field variations measured in South America are also examined, and the coincident solar wind data are used to investigate the causes of the sudden changes in the EEJ ∼10 h into the storm. From this analysis it is concluded that sudden magnetopause current increases due to increases in the solar wind dynamic pressure, and the sudden changes in the resultant magnetospheric and ionospheric current systems, are the primary drivers of equatorial GICs.

The definite identification of the characteristics of the geomagnetic response to solar wind pressure changes represents an interesting element of magnetospheric dynamics that is also important in the Space Weather context. In the present analysis the aspects of the global response in ground‐based observations have been examined for three case events, discriminating between magnetospheric and ionospheric contributions in ground manifestations of sudden impulses (SI). The separation between the magnetospheric and ionospheric contributions is obtained by a comparison between the observations at geostationary orbit and the predictions of the Tsyganenko and Sitnov (2005) model for the different magnetospheric current systems (from the magnetopause, ring current, tail current, etc.). The magnetopause current is the key element for the SI variation observed at geosynchronous orbit in a wide local time sector and practically represents the DL field of magnetospheric origin. The expected DL field is then subtracted, at each ground station, from the experimental measurements, in order to obtain a confident estimate of the residual DP field at different latitudes and local times. After evaluating the contribution of the field‐aligned currents, we estimate the ionospheric current flow pattern of the preliminary and main impulses (PIIC and MIIC). The patterns of PIIC and MIIC fields are consistent with those proposed by Araki (1994). Some “anomalous” ground manifestations can be interpreted in terms of the combined effect of the irregular configuration of the boundary of the vortices of the ionospheric currents, of the rapid temporal evolution of the entire pattern, and of the station rotation beneath the pattern.

Many real‐life signals and, in particular, in the space physics domain, exhibit variations across different temporal scales. Hence, their statistical momenta may depend on the time scale at which the signal is studied. To identify and quantify such variations, a time‐frequency analysis has to be performed on these signals. The dependence of the statistical properties of a signal fluctuation on the space and time scales is the distinctive character of systems with nonlinear couplings among different modes. Hence, assessing how the statistics of signal fluctuations vary with scale will be of help in understanding the corresponding multiscale statistics of such dynamics. This paper presents a new multiscale data analysis technique, the adaptive local iterative filtering (ALIF), which allows to describe the multiscale nature of the geophysical signal studied better than via Fourier transform, and improves scale resolution with respect to discrete wavelet transform. The example of geophysical signal, to which ALIF has been applied, is ionospheric radio power scintillation on L band. ALIF appears to be a promising technique to study the small‐scale structures of radio scintillation due to ionospheric turbulence.

An analysis of sudden impulses (SI) at geosynchronous orbit (2000–2004) confirms a general dependence of the SI amplitude on the variation of the square root of the solar wind pressure, together with an explicit LT dependence, with greater responses at satellites located closer to noon meridian. In the dayside hemisphere the magnetospheric response, which mostly influences the Bz component, is well consistent with the magnetic field jump expected for changes of the magnetopause current alone, driven by changes of the solar wind pressure. In the dark hemisphere, where the changes of the Bx component are often relevant, the competing contributions of several current systems (from the magnetopause, cross‐tail current, ring current, Birkeland current) determine a large variety of responses that cannot be interpreted in a statistical sense. Depending on the solar wind conditions, different situations emerge for nightside events. We present a case in which a remarkable magnetospheric compression determined field variations which can be interpreted in terms of a strongly dominant contribution of the magnetopause current even in the midnight sector, while in other cases the observed features are consistent with the predictions of the global current system. We also speculated that additional elements (such as the geocentric distance of the hinging point, the separation point between closed and open field lines in the geomagnetic tail) might play a crucial role in determining the aspects of the magnetospheric response. The correspondence between model predictions and observations persists even in cases of moderate Southward orientations of the IMF.

A full-halo coronal mass ejection left the sun on June 21, 2015 from the active region NOAA 12371 encountering Earth on June 22, 2015, generating a G3 strong geomagnetic storm. The CME was associated with an M2 class flare observed at 01:42 UT, located near the center disk (N12E16). Using satellite data from solar, heliospheric, magnetospheric missions and ground-based instruments, we performed a comprehensive Sun-to-Earth analysis. In particular, we analyzed the active region evolution using ground-based and satellite instruments (BBSO, IRIS, HINODE, SDO/AIA, RHESSI --Halpha, EUV, UV, X), the AR magnetograms, using data from SDO HMI, the relative particle data, using PAMELA instruments and the effects of interplanetary perturbation on cosmic ray intensity. We also evaluated the