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Solar wind drives magnetospheric dynamics through coupling with the geospace system at the magnetopause. While upstream fluctuations correlate with geomagnetic activity, their impact on the magnetopause energy transfer is an open question. In this study, we examine three‐dimensional global magnetospheric simulations using the Geospace configuration of the Space Weather Modeling Framework. We examine the effects of solar wind fluctuations during a substorm event by running the model with four different driving conditions that vary in fluctuation frequency spectrum. We demonstrate that upstream fluctuations intensify the energy exchange at the magnetopause increasing both energy flux into and out of the system. The increased energy input is reflected in ground magnetic indices. Moreover, the fluctuations impact the magnetopause dynamics by regulating the energy exchange between the polar caps and lobes and energy transport within the magnetotail neutral sheet. Plain Language Summary Earth's magnetic field shields the near‐Earth space plasma environments from the direct influence of solar wind. Solar wind however drives the magnetosphere when physical processes at the magnetopause boundary enable the transfer of energy between the plasmas. The coupling has global consequences in the magnetosphere system and its efficiency is particularly dependent on the orientation of interplanetary magnetic field and its magnitude but also on magnetic field fluctuation power. We capture the impact of upstream fluctuations on magnetopause energy exchange and nightside magnetotail dynamics by analyzing magnetohydrodynamic simulations of the global magnetosphere using various upstream driving conditions. We discover that more energy flows out from and into the system at the magnetopause when the upstream solar wind plasma include magnetic field fluctuations. The upstream fluctuation power is moreover reflected in nightside magnetotail, where flow patterns at the neutral sheet are regulated, as well as to ground indices with fluctuations driving a stronger geomagnetic response. Key Points Solar wind magnetic field ULF fluctuations (2–8 mHz) increase energy transfer at the magnetopause boundary and into the inner magnetosphere The upstream fluctuations regulate the lobe dynamics and plasma flows at the magnetotail neutral current sheet The varying lobe and nightside dynamics are reflected in ground indices with solar wind fluctuations driving a stronger geomagnetic response

A new observational phenomenon, named Simultaneous Global Ionospheric Density Disturbance (SGD), is identified in GNSS total electron content (TEC) data during periods of three typical geospace disturbances: a Coronal Mass Ejection‐driven severe disturbance event, a high‐speed stream event, and a minor disturbance day with a maximum Kp of 4. SGDs occur frequently on dayside and dawn sectors, with a ∼1% TEC increase. Notably, SGDs can occur under minor solar‐geomagnetic disturbances. SGDs are likely caused by penetration electric fields (PEFs) of solar‐geomagnetic origin, as they are associated with Bz southward, increased auroral AL/AU, and solar wind pressure enhancements. These findings offer new insights into the nature of PEFs and their ionospheric impact while confirming some key earlier results obtained through alternative methods. Importantly, the accessibility of extensive GNSS networks, with at least 6,000 globally distributed receivers for ionospheric research, means that rich PEF information can be acquired, offering researchers numerous opportunities to investigate geospace electrodynamics. Plain Language Summary Electric fields of solar wind and geomagnetic disturbance origin can penetrate into the low latitude upper atmosphere, influencing the ionospheric dynamics and electron density variations. This study employs a new method that utilizes global and continuous GNSS total electron content (TEC) observations to investigate the electric field effects. The analysis focuses on three geospace disturbance events of different intensities and solar‐terrestrial conditions. The study identifies a novel phenomenon named Simultaneous Global Ionospheric Density Disturbance (SGD), primarily occurring on the sunlit portion of the Earth's ionosphere and also near dawn hours with 1% or larger amplitudes of the background TEC, or a few tenths of a TEC unit (1016 m3). The remarkable global extent of ionospheric responses to minor solar‐geomagnetic conditions is noteworthy. The solar wind magnetic field directed southward is highly correlated with most SGDs, lasting for up to 30 min. The findings present an effective approach for continuously monitoring electric field penetration and ionospheric impacts, leading to an improved understanding of space weather and its technological implications. Key Points Simultaneous global ionospheric disturbances (SGDs) are often observed even during minor solar and geomagnetic disturbances SGDs occur predominately on dayside and are related to penetration electric fields (PEFs) of solar wind and geomagnetic disturbance origin Global GNSS networks offer a novel and effective technique for continuous PEF monitoring, providing rich data sets for further study

Using the 8.5‐year Venus Express measurements, we demonstrate the asymmetric plasma distributions in the Venusian magnetosheath. An escaping plume is formed by pickup oxygen ions in the hemisphere where the motional electric field points outward from Venus, while the velocity of solar wind protons is faster in the opposite hemisphere. The pickup O+ escape rate is estimated to be (3.6 ± 1.4) × 1024 s−1 at solar maximum, which is comparable to the ion loss rate through the magnetotail, and (1.3 ± 0.4) × 1024 s−1 at solar minimum. The increase of O+ fluxes with extreme ultraviolet (EUV) intensity is significant upstream of the bow shock, partially attributed to the increase of exospheric neutral oxygen density. However, the solar wind velocity just has a slight effect on the pickup O+ escape rate in the magnetosheath, while the effect of solar wind density is not observed. Our results suggest the pickup O+ escape rate is mainly controlled by EUV radiation. Plain Language Summary The atmospheric evolution and water escape of Venus might be influenced by the solar wind‐Venus interaction. The atoms outside the induced magnetosphere are ionized by the solar radiation and accelerated to the escape velocity by solar wind electric field. In this way, the oxygen ions are picked up by solar wind and lost from the atmosphere to space. We use the data from Venus Express spacecraft to analyze the distribution of pickup oxygen ions in the vicinity of the planet. The planetary oxygen ions form a strong escaping plume, indicating the pickup process is an efficient escape channel removing the atmospheric particles. With an enhanced solar extreme ultraviolet radiation, the escape rate through this channel would be higher because more ions are produced and then picked up. This indicates an enhanced ion loss billions of years ago since the young Sun is more active, which might be a reason for the disappearance of a presumably‐existed ocean. Key Points The pickup O+ escape rate at Venus increases with solar activity, and it is comparable to the ion loss rate through the magnetotail The solar wind velocity has a slight effect on the pickup O+ escape rate in the magnetosheath The neutral oxygen density upstream of the bow shock might increase by a factor of two from solar minimum to maximum

The Martian bow shock stands as the first defense against the solar wind and shapes the Martian magnetosphere. Previous studies showed the correlation between the Martian bow shock location and solar wind parameters. Here we present direct evidence of solar wind effects on the Martian bow shock by analyzing Tianwen‐1 and MAVEN data. We examined three cases where Tianwen‐1 data show rapid oscillations of the bow shock, while MAVEN data record changes in solar wind plasma and magnetic field. The results indicate that the bow shock is rapidly compressed and then expanded during the dynamic pressure pulse in the solar wind, and is also oscillated during the IMF rotation. The superposition of variations in multiple solar wind parameters leads to more intensive bow shock oscillation. This study emphasizes the importance of joint observations by Tianwen‐1 and MAVEN for studying the real‐time response of the Martian magnetosphere to the solar wind. Plain Language Summary The Martian bow shock is a standing shock wave that forms ahead of Mars due to the interaction with the solar wind, where the supersonic solar wind flow drops sharply to subsonic. The bow shock plays a crucial role in shaping the Martian magnetosphere and controlling the energy, mass, and momentum exchange between the solar wind and the Martian atmosphere. Previous research has shown that the position of Mars' bow shock is related to the solar wind. This research presents two‐spacecraft observations of how the solar wind affects the Martian bow shock. By analyzing data obtained by two orbiters, Tianwen‐1 and MAVEN, we find that the bow shock quickly contracts when the solar wind dynamic pressure rises or when the interplanetary magnetic field direction turns radial. When there are multiple changes in the solar wind at the same time, the bow shock moves around even more. This study shows how important it is to look at data from Tianwen‐1 and MAVEN at the same time to understand how Mars' magnetosphere reacts to the solar wind. Key Points First observations of the real‐time response of the Martian bow shock to changes in the upstream solar wind Direct evidence of the compression of the Martian bow shock under increased solar wind dynamic pressure Direct evidence of motion of the Martian bow shock caused by the rotation of the interplanetary magnetic field

We investigated, for the first time, the impact of the disappearing solar wind (DSW) event [26–28 December 2022] on the deep nightside ionospheric species using MAVEN data sets. An enhanced plasma density has been observed in the Martian nightside ionosphere during extreme low solar wind density and pressure periods. At a given altitude, the electron density surged by ∼2.5 times, while for ions (NO+, O2+, CO2+, C+, N+, O+, and OH+), it enhanced by > 10 times, respectively, compared to their typical average quiet‐time periods. This investigation suggests that an upward ionospheric expansion likely took place in a direct consequence to the contrasting low dynamic/magnetic pressure and relatively higher nightside ionospheric pressure (by 1–2 orders) causing an increased ionospheric density. Moreover, the day‐to‐night plasma transport may also be a contributing factor to the increased plasma density. Thus, this study offers a new insight about planetary atmosphere/ionosphere during extreme quiescent solar wind periods. Plain Language Summary The evolution of the Mars climate over time depends upon the solar wind‐Mars interactions. The varying activity over the Sun intermittently produce extreme low density solar wind or also called as disappearing Solar Wind (DSW), which can affect the planetary environment in many ways. Beyond Earth, the effect of DSW on other planetary atmospheres is not well studied. In order to understand this aspect, we have explored the behavior of Martian nightside plasma environment (species: e−, NO+, O2+, CO2+, C+, N+, O+, and OH+) during the DSW event. A dense ionosphere is observed during DSW compared to non‐DSW periods. During DSW, the magnitude of peak nightside electron and ions density are increased by ∼2.5 and more than 10 times, respectively compared to their typical average quiet‐time scenario. The higher plasma density could be due to an expansion from the lower to the topside ionosphere, in consequence to the higher ionospheric pressure as compared to the low solar wind pressure. Furthermore, it could also be enhanced by the transport of plasma from dayside to nightside. Hence, this study, for the first instance, guides us to a new understanding of the impact of a rarest solar wind phenomenon on the Martian ionosphere. Key Points An increased plasma density is observed in the nightside ionosphere during the disappearing solar wind periods around Mars The electron and ions abundance surged by a factor of ∼2.5 and >10 respectively, compared to the average quiet‐time periods The contrast between the higher nightside ionospheric pressure and the dynamic/magnetosheath pressure led to increased plasma densities

When the solar wind speed falls below the local Alfvén speed, the magnetotail transforms into an Alfvén wing configuration. A Grid Agnostic Magnetohydrodynamics for Extended Research Applications (GAMERA) simulation of Earth's magnetosphere using solar wind parameters from the 24 April 2023 sub‐Alfvénic interval is examined to reveal modifications of Dungey‐type magnetotail reconnection during sustained sub‐Alfvénic solar wind. The simulation shows new magnetospheric flux is generated via reconnection between polar cap field lines from the northern and southern hemisphere, similar to Dungey‐type magnetotail reconnection between lobe field lines mapping to opposite hemispheres. The key feature setting the Alfvén wing reconnection apart from the typical Dungey‐type is that the majority of new magnetospheric flux is added to the polar cap at local times 1–3 (21‐23) in the northern (southern) hemisphere. During most of the sub‐Alfvénic interval, reconnection mapping to midnight in the polar cap generates relatively little new magnetospheric flux. Plain Language Summary Similar to how a shock wave forms around a supersonic plane, the supersonic plasma emanating from the sun forms a shock wave around Earth. However, the speed of sound through the plasma depends on different parameters that vary substantially based on the origin and evolution of solar material flowing into interplanetary space. In some coronal mass ejections, the characteristics of the plasma are such that the flow is sub‐sonic, leaving the magnetosphere in a unique state. Determining whether there are any space weather impacts associated with the sub‐sonic flow has been difficult due to lack of observations, but a recent event has ignited interest. This study examines the global structure and dynamics of the magnetosphere in a simulation representative of the sub‐sonic flow interval of the April 2023 geomagnetic storm. Key Points On 24 April 2023, Earth's magnetosphere experienced an interval of sustained sub‐Alfvénic solar wind driving Sub‐Alfvénic driving suppresses typical Dungey‐type magnetotail reconnection but polar cap expansion is still limited Global simulations have strong Earthward flows localized ∼10 RE tailward of theterminator, where most new magnetospheric flux is generated

We study the solar wind helium-to-hydrogen abundance’s ( A He ) relationship to solar cycle onset. Using OMNI/Lo data, we show that A He increases prior to sunspot number (SSN) minima. We also identify a rapid depletion and recovery in A He that occurs directly prior to cycle onset. This A He shutoff happens at approximately the same time across solar wind speeds ( v sw ) and the time between successive A He shutoffs is typically on the order of the corresponding solar cycle length. In contrast to A He ’s v sw -dependent phase lag with respect to SSN (Alterman and Kasper, 2019 ), A He shutofff’s concurrence across v sw likely implies it is independent of solar wind acceleration and driven by a mechanism near or below the photosphere. Using brightpoint (BP) measurements to provide context, we infer that A He shutoff is likely related to the overlap of adjacent solar cycles and the equatorial flux cancelation of the older, extended solar cycle during solar minima.

We use Δ SYM-H to capture the variation in the SYM-H index during the main phase of a geomagnetic storm. We define great geomagnetic storms as those with Δ SYM-H ≤ − 200  nT. After analyzing the data that were not obscured by solar winds, we determined that 17 such storms occurred during Solar Cycles 23 and 24. We calculated time integrals for the southward interplanetary magnetic field component I ( B s ) , the solar wind electric field I ( E y ) , and a combination of E y and the solar wind dynamic pressure I ( Q ) during the main phase of a great geomagnetic storm. The strength of the correlation coefficient (CC) between Δ SYM-H and each of the three integrals I ( B s ) (CC = 0.73), I ( E y ) (CC = 0.86), and I ( Q ) (CC = 0.94) suggests that Q , which encompasses both the solar wind electric field and the solar wind dynamic pressure is the main driving factor that determines the intensity of a great geomagnetic storm. The results also suggest that the impact of B s on the great geomagnetic storm intensity is much more significant than that of the solar wind speed and the dynamic pressure during the main phase of an associated great geomagnetic storm. The better estimation of the intensity of an extreme geomagnetic storm intensity based on solar wind parameters is also discussed.

Geomagnetic storms represent a critical yet sometimes overlooked factor affecting the reliability of modern power systems. This study examines the relationship between geomagnetic storm activity—characterized by the Dst index and categorized into weak, moderate, strong, severe, and extreme intensities—and reported power outages of unknown or unusual origin in the United States from 2006 to 2023. Outage data come from the DOE OE-417 Annual Summaries, while heliospheric and solar wind parameters (including proton density, plasma speed, and the interplanetary magnetic field) were obtained from NASA’s OMNIWeb database. Results indicate that years with a higher total count of geomagnetic storms, especially those featuring multiple strong or severe events, exhibit elevated incidences of unexplained power interruptions. Correlation analyses further reveal that increasingly negative Dst values, enhanced solar wind velocity, and higher alpha/proton ratios align with greater numbers of outages attributed to unknown causes, underscoring the pivotal role of solar wind–magnetosphere coupling. A simple regression model confirms that storm intensity and average magnetic field strength are statistically significant predictors of unexplained outages, more so than broad indicators such as sunspot number alone. These findings highlight the importance of monitoring high-intensity geomagnetic storms and associated heliospheric variables to mitigate potential risks. Greater attention to space weather impacts and improved reporting of outage causes could bolster grid resilience, helping operators anticipate and manage disruptions linked to geomagnetic disturbances.