We investigate sharp changes in magnetic field that can produce Geomagnetically Induced Currents (GICs) which damage pipelines and power grids. We use one‐minute cadence SuperMAG observations to find the occurrence distribution of magnetic field “spikes.” Recent studies have determined recurrence statistics for extreme events and charted the local time distribution of spikes; however, their relation to solar activity and conditions in the solar wind is poorly understood. We study spike occurrence during solar cycles 23 and 24, roughly 1995 to 2020. We find three local time hotspots in occurrence: the pre‐midnight region associated with substorm onsets, the dawn sector often associated with omega band activity, and the pre‐noon sector associated with the Kelvin‐Helmholtz instability (KHI) occurring at the magnetopause. Magnetic field perturbations are mainly North‐South for substorms and KHI, and East‐West for omega bands. Substorm spikes occur at all phases of the solar cycle, but maximize in the declining phase. Omega‐band and KHI spikes are confined to solar maximum and the declining phase. Substorm spikes occur during moderate solar wind driving, omega band spikes during strong driving, and KHI spikes during quiet conditions but with high solar wind speed. We show that the shapes of these distributions do not depend on the magnitude of the spikes, so it appears that our results can be extrapolated to extreme events.

We investigate sharp changes in magnetic field that can produce Geomagnetically Induced Currents (GICs) which damage pipelines and power grids. We use one-minute cadence SuperMAG observations to find the occurrence distribution of magnetic field "spikes". Recent studies have determined recurrence statistics for extreme events and charted the local time distribution of spikes; however, their relation to solar activity and conditions in the solar wind is poorly understood. We study spike occurrence during solar cycles 23 and 24, roughly 1995 to 2020. We find three local time hotspots in occurrence: the pre-midnight region associated with substorm onsets, the dawn sector associated with omega band activity, and the pre-noon sector associated with the Kelvin-Helmholtz instability occurring at the magnetopause. Magnetic field perturbations are mainly North-South for substorms and KHI, and East-West for omega bands. Substorm spikes occur at all phases of the solar cycle, but maximise in the declining phase. Omega-band and KHI spikes are confined to solar maximum and the declining phase. Substorm spikes occur during moderate solar wind driving, omega band spikes during strong driving, and KHI spikes during quiet conditions but with high solar wind speed. We show that the shapes of these distributions do not depend on the magnitude of the spikes, so it appears that our results can be extrapolated to extreme events.

Upstream solar wind measurements from near the L1 Lagrangian point are commonly used to investigate solar wind‐magnetosphere coupling. The off‐Sun‐Earth line distance of such solar wind monitors can be large, up to 100 RE. We investigate how the correlation between measurements of the interplanetary magnetic field and associated ionospheric responses deteriorates as the off‐Sun‐Earth line distance increases. Specifically, we use the magnitude and polarity of the dayside region 0 field‐aligned currents (R0 FACs) as a measure of interplanetary magnetic field (IMF) BY‐associated magnetic tension effects on newly‐reconnected field lines, related to the Svalgaard‐Mansurov effect. The R0 FACs are derived from Advanced Magnetosphere and Planetary Electrodynamics Response Experiment measurements by a principal component analysis, for the years 2010–2016. We perform cross‐correlation analyses between time‐series of IMF BY, measured by the Wind spacecraft and propagated to the nose of the bow shock by the OMNI technique, and these R0 FAC measurements. Typically, in the summer hemisphere, cross‐correlation coefficients between 0.6 and 0.9 are found. However, there is a reduction of order 0.1–0.15 in correlation coefficient between periods when Wind is close to (within 45 RE) and distant from (beyond 70 RE) the Sun‐Earth line. We find a time‐lag of around 17 min between predictions of the arrival of IMF features at the bow shock and their effect in the ionosphere, irrespective of the location of Wind.

Magnetic reconnection occurring between the interplanetary magnetic field and the dayside magnetopause causes a circulation of magnetic flux and plasma within the magnetosphere, known as the Dungey cycle. This circulation is transmitted to the ionosphere via field-aligned currents (FACs). The magnetic flux transport within the Dungey cycle is quantified by the cross-polar cap potential (CPCP or transpolar voltage). Previous studies have suggested that under strong driving conditions the CPCP can saturate near a value of 250 kV. In this study we investigate whether an analogous saturation occurs in the magnitudes of the FACs, using observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). The solar wind speed, density and pressure, the Bz component of the interplanetary magnetic field, and combinations of these, were compared to the concurrent integrated current magnitude, across each hemisphere. We find that FAC magnitudes are controlled most strongly by solar wind speed and the orientation and strength of the interplanetary magnetic field. FAC magnitude increases monotonically with solar wind driving but there is a distinct knee in the variation around IMF Bz = -10 nT, above which the increase slows.

<p>The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) has revolutionized the way in which we can study the electrical current systems present over the poles of Earth. With high cadence measurements taken in both hemispheres, the data has proven invaluable in developing our understanding of the current systems that couple the magnetosphere and ionosphere and how they change in response to space weather. By employing the AMPERE data set, we aim to offer new insights into the complex and dynamic region 1 and region 2 current systems as they respond to the impact of solar wind disturbances on the magnetosphere and the driving of geomagnetic storms.</p><p>We investigate the relationship between the hemispherically-integrated current flowing into or out of each pole and upstream solar wind parameters to understand how these currents are driven.  As expected, current magnitude increases with increasing interplanetary magnetic field strength and solar wind speed.  A key aim of the analysis is to determine if current magnitude saturates under strongly driven conditions, in the same way that the cross-polar cap potential is known to saturate.  We present preliminary results, indicating a variety of behaviours at high driving, and discuss these in terms of theories of solar wind-magnetosphere coupling.</p>