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Abstract We combine wavelet analysis and data fusion to investigate geomagnetically induced currents (GICs) on the Mäntsälä pipeline and the associated horizontal geomagnetic field, BH, variations during the late main phase of the 17 March 2013 geomagnetic storm. The wavelet analysis decomposes the GIC and BH signals at increasing “scales” to show distinct multi‐minute spectral features around the GIC spikes. Four GIC spikes >10 A occurred while the pipeline was in the dusk sector—the first sine‐wave‐like spike at ∼16 UT was “compound.” It was followed by three “self‐similar” spikes 2 hr later. The contemporaneous multi‐resolution observations from ground‐(magnetometer, SuperMAG, SuperDARN), and space‐based (AMPERE, Two Wide‐Angle Imaging Neutral‐atom Spectrometers) platforms capture multi‐scale activity to reveal two magnetospheric modes causing the spikes. The GIC at ∼16 UT occurred in two parts with the negative spike associated with a transient sub‐auroral eastward electrojet that closed a developing partial ring current loop, whereas the positive spike developed with the arrival of the associated mesoscale flow‐channel in the auroral zone. The three spikes between 18 and 19 UT were due to bursty bulk flows (BBFs). We attribute all spikes to flow‐channel injections (substorms) of varying scales. We use previously published MHD simulations of the event to substantiate our conclusions, given the dearth of timely in‐situ satellite observations. Our results show that multi‐scale magnetosphere‐ionosphere activity that drives GICs can be understood using multi‐resolution analysis. This new framework of combining wavelet analysis with multi‐platform observations opens a research avenue for GIC investigations and other space weather impacts. 

Abstract We review observations of solar activity, geomagnetic variation, and auroral visibility for the extreme geomagnetic storm on 1872 February 4. The extreme storm (referred to here as the Chapman–Silverman storm) apparently originated from a complex active region of moderate area (≈ 500μsh) that was favorably situated near disk center (S19° E05°). There is circumstantial evidence for an eruption from this region at 9–10 UT on 1872 February 3, based on the location, complexity, and evolution of the region, and on reports of prominence activations, which yields a plausible transit time of ≈29 hr to Earth. Magnetograms show that the storm began with a sudden commencement at ≈14:27 UT and allow a minimum Dst estimate of ≤ −834 nT. Overhead aurorae were credibly reported at Jacobabad (British India) and Shanghai (China), both at 19.°9 in magnetic latitude (MLAT) and 24.°2 in invariant latitude (ILAT). Auroral visibility was reported from 13 locations with MLAT below ∣20∣° for the 1872 storm (ranging from ∣10.°0∣–∣19.°9∣ MLAT) versus one each for the 1859 storm (∣17.°3∣ MLAT) and the 1921 storm (∣16.°2∣ MLAT). The auroral extension and conservative storm intensity indicate a magnetic storm of comparable strength to the extreme storms of 1859 September (25.°1 ± 0.°5 ILAT and −949 ± 31 nT) and 1921 May (27.°1 ILAT and −907 ± 132 nT), which places the 1872 storm among the three largest magnetic storms yet observed. 

Abstract In 1972, early August, a series of interplanetary shocks were observed in the heliosphere from 0.8 to 2.2 au. These shocks were attributed to a series of brilliant flares and plasma clouds since at that time coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) were unknown to the scientific community. This paper aims to reinterpret the interplanetary data in light of the current understanding about interplanetary transients and to track the evolution of the ICMEs, taking advantage of the alignment of Pioneers 9 and 10 spacecraft. For this purpose, we reanalyze in situ data from these two Pioneers and also from Heos, Prognoz 1 and 2, and Explorer 41 spacecraft searching for ICMEs and high-speed streams. Then we assemble the interplanetary transients and solar activity and analyze the propagation of the ejections through the heliosphere. The evolution of four ICMEs and a high-speed stream from a low-latitude coronal hole is followed using the multipoint in situ observations. The first three ICMEs show clear signatures of ICME–ICME interaction in the interplanetary medium, suggesting the first observations of an ICME which developed into an ICME-in-the-sheath. For a non-perturbed ICME event, we obtain the evolution parameter,ζ, related to the local expansion of ICMEs, getting similar values for Pioneer 9 (ζ= 0.80) and Pioneer 10 (ζ= 0.78). These results support previous findings ofζbeing independent of the heliocentric distance and the magnetic field strength decreasing asr^−2ζ. 

The continental United States is well instrumented with facilities for mid‐latitude upper atmosphere research that operate on a continuous basis. In addition, citizen scientists provide a wealth of information when unusual events occur. We combine ionospheric total electron content (TEC) data from distributed arrays of GNSS receivers, magnetometer chains, and auroral observations obtained by citizen scientists, to provide a detailed view of the intense auroral breakup and westward surge occurring at the peak of the 10–11 May 2024 extreme geomagnetic storm. Over a 20‐min interval, vertical TEC (vTEC) increased at unusually low latitude (∼45°) and rapidly expanded azimuthally across the continent. Individual receiver/satellite data sets indicate sharp bursts of greatly elevated of vTEC (∼50 TECu). Intense red aurora was co‐located with the leading edge of the equatorward and westward TEC enhancements, indicating that the large TEC enhancement was created by extremely intense low‐energy precipitation during the rapid substorm breakup.