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We examined rapid variations in the electron zebra stripe patterns, specifically at L = 1.5, over a three‐month duration, using twin Van Allen Probes within Earth's inner magnetosphere. During geomagnetically quiet intervals, these stripes exhibit a peak‐to‐valley ratio (Δj) ∼1.25 in detrended electron fluxes. However, during geomagnetic storms, they became highly prominent, with Δj > 2.5. The correlation between Δj and net field‐aligned currents (FACs) is observed to be high (0.70). Global magnetohydrodynamic (MHD) simulation results indicate that the westward electric field at midnight at low latitudes in the deep inner magnetosphere correlates well with net FACs. An increase in net FACs could amplify the dawn‐to‐dusk electric field in the deep inner magnetosphere, thereby causing the inward transport of electrons. Given that FACs are linked to the interaction between solar wind and the magnetosphere, our findings emphasize the importance of solar wind‐magnetosphere coupling in the deeper regions of the inner magnetosphere. Plain Language Summary: The intensity of hundreds of keV electron fluxes displays a distinctive pattern in the energy versus L‐value spectrogram, characterized by periodic valleys and peaks, commonly referred to as zebra stripes. These patterns have been observed in the magnetospheres of multiple planets, including Earth, Jupiter, and Saturn. Our study reveals that during geomagnetically quiet intervals, Earth's inner magnetospheric zebra stripes exhibit well‐defined banded features. However, these bands become highly pronounced during geomagnetic storms. The peak‐to‐valley ratio (Δj) of detrended electron fluxes shows a correlation with net field‐aligned currents (FACs), and these FACs, in turn, align with the westward component of the electric field at midnight. Consequently, FACs play a significant role in controlling electron flux dynamics deep within the inner magnetosphere. This research illuminates the solar wind‐magnetosphere‐ionosphere couplings. Key Points: Electron zebra stripes are a persistent feature in Earth's inner magnetosphere, although they become intensified during geomagnetic stormsPeak‐valley ratio (Δj) in detrended electron flux within the zebra stripes enhances by ≥1 factor at L = 1.5 during three geomagnetic stormsΔj is well correlated with the net field‐aligned current (FAC) in polar region, suggesting the dominant role of convection driven by FAC [ABSTRACT FROM AUTHOR]

The Whole Heliosphere and Planetary Interactions initiative was established to leverage relatively quiet intervals during solar minimum to better understand the interconnectedness of the various domains in the heliosphere. This study provides an expansive mosaic of observations spanning from the Sun, through interplanetary space, to the magnetospheric response and subsequent effects on the ionosphere‐thermosphere‐mesosphere (ITM) system. To accomplish this, a diverse set of observational datasets are utilized from 2019 July 26 to October 16 (i.e., over three Carrington rotations, CR2220, CR2221, and CR2222) with connections of these observations to the more focused studies submitted to this special issue. Particularly, this study focuses on two long‐lived coronal holes and their varying impact in sculpting the heliosphere and driving of the magnetospheric system. As a result, the evolution of coronal holes, impacts on the inner heliosphere solar wind, glimpses at mesoscale solar wind variability, magnetospheric response to these evolving solar wind drivers, and resulting ITM phenomena are captured to reveal the interconnectedness of this system‐of‐systems. Plain Language Summary: The field of Heliophysics research spans a large range of plasma regimes and disciplines that are all linked through the complex interactions each system has with one another. To better explore the interconnected nature of the heliosphere, this study combines observations from across the sub‐domains of Heliophysics to construct snapshots of the Sun, solar wind, and the magnetospheric and ionospheric systems at Earth over three revolutions of the Sun. This allows for a unique vantage point to put these systems in perspective of one another and understand how they impact one another. Key Points: The evolution and impacts of two coronal holes are investigated over three Carrington rotationsThe evolution of the coronal hole led to changes in the solar wind throughout the inner solar systemSubsequent geospace response differed with each passage due to both changes in the solar wind and preconditioning within the systems [ABSTRACT FROM AUTHOR]

An extended interval of perturbed magnetospheric conditions in November 2016 supported increased convection and sunward transport of plasmaspheric material. During this period of time the Magnetospheric Multiscale satellites, with their apogees along Earth's dusk-side outer magnetosphere, encountered several cold plasma density structures at the same time as plasma bulk flows capable of accelerating hidden cold plasma occurred. Investigating the charged particle and fields data during two subintervals showed that the satellites made direct measurements of cold plasmaspheric ions embedded within multicomponent hot plasmas as well as electromagnetic emissions consistent with electromagnetic ion cyclotron (EMIC) waves. The complex in situ ion composition measurements were applied to linear wave modeling to interpret the impacts of cold and hot ion species on wave growth and band structure. Although the waves for both intervals were predicted to have peak growth rate below ûHe+, substantial differences were observed among all other dispersive properties. The modeling also showed EMIC waves generated in the presence of heavy ions had growth rates and unstable wave numbers always smaller than predicted for a pure proton-electron plasma. The results provide implications for future investigation of EMIC wave generation with and without direct measurements of the cold and hot plasma composition as well as of subsequent wave-particle interactions. Plain Language Summary Electromagnetic ion cyclotron (EMIC) waves occur throughout our solar system. The waves have been observed near Earth and are more likely to achieve large amplitudes in the magnetized plasma that exists in a region of space called Earth's dusk-side magnetosphere. Multiple plasma populations exist in this region that can be organized into groups of cold or hot plasmas. Although the hot plasmas can be measured most of the time, the cold plasmas are usually hidden from plasma sensors due to positive spacecraft charging issues; cold plasmas are therefore usually unavailable to help provide a detailed understanding of why dusk-side EMIC waves are generated. The purpose of our study was to investigate measurements made by the NASA Magnetospheric Multiscale satellites to during a time period when the cold plasma species were not hidden and apply these measurements to improve understanding of these dusk-side EMIC waves. The results showed why comprehensive measurements are needed to continue advancing our understanding of EMIC waves as seen by other spacecraft in different regions in Earth's magnetosphere, and how these waves impact other plasma populations. [ABSTRACT FROM AUTHOR]

We use the magnetohydrodynamic (MHD) with embedded particle‐in‐cell model (MHD‐EPIC) to study the Geospace Environment Modeling (GEM) dayside kinetic processes challenge event at 01:50–03:00 UT on 18 November 2015, when the magnetosphere was driven by a steady southward interplanetary magnetic field (IMF). In the MHD‐EPIC simulation, the dayside magnetopause is covered by a PIC code so that the dayside reconnection is properly handled. We compare the magnetic fields and the plasma profiles of the magnetopause crossing with the MMS3 spacecraft observations. Most variables match the observations well in the magnetosphere, in the magnetosheath, and also during the current sheet crossing. The MHD‐EPIC simulation produces flux ropes, and we demonstrate that some magnetic field and plasma features observed by the MMS3 spacecraft can be reproduced by a flux rope crossing event. We use an algorithm to automatically identify the reconnection sites from the simulation results. It turns out that there are usually multiple X‐lines at the magnetopause. By tracing the locations of the X‐lines, we find that the typical moving speed of the X‐line endpoints is about 70 km/s, which is higher than but still comparable with the ground‐based observations. Key Points: The MHD‐EPIC simulation magnetic fields and plasma data match MMS3 observations well during the magnetopause crossingThere are usually multiple X‐lines at the magnetopause in the MHD‐EPIC simulationThe MHD‐EPIC simulation shows complex movement and spreading of the X‐lines [ABSTRACT FROM AUTHOR]

Field‐aligned currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) were combined with simultaneous and coincident observations of ionospheric conductivities made by the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska for 20 geomagnetically active days. The height‐integrated conductivities (conductances) were determined from the electron densities measured by the radar between 80 and 200 km altitude. Binning and averaging the data by field‐aligned current density and magnetic local time, we find that the currents correlate with conductances in both upward and downward current regions over some magnetic local times. The strongest correlation is seen in the late evening and morning sectors, with the Hall conductances two to three times larger than the Pedersen conductances for the same values of the field‐aligned current. The observed correlations reflect the mean energy of auroral precipitation, the contributions from electrons and protons to producing enhanced conductances, and the availability of charge carriers on auroral field lines. We apply linear fitting and smoothing to the correlations to construct an empirical model for specifying auroral conductances globally from AMPERE field‐aligned current maps. The energy fluxes from precipitating particles derived from the model conductances compare well with those derived using AMPERE data combined with satellite‐based measurements of far ultraviolet emissions, suggesting the results obtained at Poker Flat may be applicable to all high latitude locations. The ability to estimate conductances from AMPERE field‐aligned current maps provides the means to develop a global conductance model for the auroral ionosphere. Key Points: Simultaneous and coincident field‐aligned current and conductance data are used to study correlations between the two quantitiesThe correlations between parallel currents and conductances are strongest from late evening to morning magnetic local timesThe correlations can be used to model auroral conductances from field‐aligned current measurements [ABSTRACT FROM AUTHOR]

The development of large‐scale Birkeland currents is examined using the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), which measures global Birkeland currents continuously on 10‐min time scales. The integrated current was used to identify onsets of at least 1 MA preceded by periods of quiescence lasting at least 3 hr. The Region 1 currents do not fully form without Region 2. Rather, they develop together, first on the dayside, then on the nightside, and lastly, they fill in and intensify at all local times to form the nominal statistical pattern. The onsets are closely correlated with enhancements of magnetospheric forcing as indicated by the solar wind electric field and the orientation of the interplanetary magnetic field. Nightside onsets correspond to intensifications of the auroral electrojet as reflected in the AE index; they are delayed by ~40 min relative to the increase of the dayside current and are 2.8 times more rapid than the dayside current increase. After nightside onset, Birkeland currents expand toward dawn and dusk and merge with the dayside currents while also intensifying at all local times. The dayside current pattern depends on the sign of the interplanetary magnetic field BY. The nightside current distributions are the same for positive and negative BY and display a Harang discontinuity independent of the sign of BY. The predominant development and intensification of Birkeland currents occur after nightside onset at all local times with roughly 75% of the total current, both Regions 1 and 2, appearing after nightside onset. Plain Language Summary: This study uses data from the 66 Iridium Communications satellites to track the development of electric currents that drive aurora. These currents can turn on in less than about an hour. However, the currents can only be measured from satellites orbiting the Earth above the atmosphere, and in those orbits, satellites take about 100 min to orbit the Earth. With the Iridium constellation, we remeasure these currents every 10 min and are able to track where they start and how they grow. This happens in two steps: Currents appear first in the day where they remain. About 30 min later, new currents start near midnight and then spread toward dawn and dusk and increase until they completely encircle the poles in an oval pattern. The total current finally reaches millions of Amperes. The two‐step process implies that explosive dynamics in the magnetic tail of the Earth play a key role in creating and generating the auroral currents. This study shows that the effects they have on the temporal sequence of activity onset need to be included to predict the effects of the solar wind and solar storms on the Earth's ionosphere and upper atmosphere. Key Points: Analysis of Birkeland current growth following extended intervals of low current reveals the development sequence of the global systemCurrents begin on the dayside with both Regions 1 and 2 and do not appear on the nightside until a sudden onset about 30 min laterAt onset, nightside Regions 1 and 2 appear together, intensify, and expand to the dayside forming the complete system after about an hour [ABSTRACT FROM AUTHOR]