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Plasma sheet convection is a key element of storm‐time plasma dynamics in the magnetosphere. While decades of observations have advanced our understanding of convection in general, specifically storm‐time convection remains poorly understood. Using data from ISAS/NASA's Geotail and NASA's MMS, this study characterizes plasma sheet magnetic flux transport across the magnetotail during numerous storms (both recovery and main phases) and contrasts these observations with those from quiet times. Our findings confirm the well‐documented enhancement of the convection electric field during geomagnetic storms. Beyond that, our results reveal a significant dawn‐dusk asymmetry. At dawn, the elevated convection is realized via relatively faster flows while at dusk, through a stronger northward magnetic field. These findings suggest a complex feedback loop between plasma sheet convection and ring current buildup, whereby the latter asymmetrically inflates the magnetotail on the dusk side, shifting the reconnection site and subsequently enhanced earthward flows toward dawn. Strong solar activity creates major disruptions of the Earth's magnetic field known as geomagnetic storms. These major disturbances of near‐Earth space can impact essential technologies like GPS systems and power grids. Our research used data from two space missions, ISAS/NASA's Geotail and NASA's MMS, to study how particles and magnetic fields move in space around Earth during such storms. We compared storm periods to calm times and evaluated the differences. During geomagnetic storms, we found that charged particles transport more magnetic flux due to stronger electric field. We further noted a significant difference between the dawn (morning) and dusk (evening) sectors on the nightside of the near‐Earth space environment. During storm times, plasma moves faster on the dawn side, while the magnetic field is stronger on the dusk side. This discovery reveals that plasma movement and energy buildup during storms are more complex than we thought. The energy buildup on the dusk side pushes plasma movement more toward the dawn side. Understanding these details helps us better predict the impacts of geomagnetic storms on Earth's space environment, which can improve our ability to protect our technology and infrastructure. Convection electric field is elevated across the plasma sheet during storms, but convection properties are different between dawn and duskDawn magnetic flux transport during storm time is statistically associated with relatively faster flowsDusk magnetic flux transport during storm times is statistically associated with more dipolar magnetic fields Convection electric field is elevated across the plasma sheet during storms, but convection properties are different between dawn and dusk Dawn magnetic flux transport during storm time is statistically associated with relatively faster flows Dusk magnetic flux transport during storm times is statistically associated with more dipolar magnetic fields

Plasma Depletion Events (PDEs) are characterized by abrupt, localized reductions in ionospheric plasma density at least by an order of magnitude decrease. These events are observed over a limited range of altitudes, typically spanning a few tens of kilometers. We use Mars Atmosphere and Volatile Evolutionspacecraft data to investigate the properties and possible formation mechanism of daytime PDEs, typically observed at altitudes above 250 km. We show, using two example events and statistical analysis, that the depletion events are associated with electrostatic fluctuations and increased electron temperatures. The events are further accompanied by enhanced fluxes of suprathermal electrons and light energetic ions. These are indicative of local plasma heating, possibly mediated by the electrostatic fluctuations. The heated plasma may eventually escape from the depletion region through the ambipolar diffusion. The Martian ionosphere, consisting of ions and electrons, is embedded in the planet's thin atmosphere. Density variations in the ionosphere, occurring on both large and small scales, can significantly impact the atmospheric loss process on Mars. One particular type of these ionospheric anomalies involves sudden reductions in ion density, often by tenfold or more. Although we have a basic understanding of these depletion events, their detailed characteristics and origins are not yet fully understood. We use data from various instruments onboard the Mars Atmosphere and Volatile Evolutionspacecraft to investigate these phenomena, particularly on the dayside. We find that these depletion events are accompanied by increased electron temperatures and enhanced electric field fluctuations, while the magnetic field remains virtually unchanged. These observations suggest localized plasma heating within the depleted region. Furthermore, the fluxes of energetic light ions (mostly protons) and electrons are increased during the events. This increase in energetic particles could potentially serve as the energy source driving the heating process. We propose that the depletion events form when the heated ionospheric plasma escapes from the heated region. Large scale plasma density depletions in the Martian dayside ionosphere are linked with electrostatic fluctuationsIncreased electron temperatures, enhanced suprathermal electron fluxes, and energetic light ions are observed within the depleted regionsLocal plasma heating possibly drives electron escape, forming an ambipolar field and causing plasma depletions through ambipolar diffusion Large scale plasma density depletions in the Martian dayside ionosphere are linked with electrostatic fluctuations Increased electron temperatures, enhanced suprathermal electron fluxes, and energetic light ions are observed within the depleted regions Local plasma heating possibly drives electron escape, forming an ambipolar field and causing plasma depletions through ambipolar diffusion

In situ exploration of Uranus has been limited to a single flyby encounter by the Voyager 2 spacecraft in January 1986. Nonetheless, new investigation has led to significant questions about the origin of energetic ions observed in the region between its moons Miranda and Ariel. Radial and pitch angle diffusion modeling suggests that typical magnetospheric sources cannot explain the observed characteristics of these energetic ions. We suggest that these are likely being introduced by a source from one of these moons and give rise to waves that could result in the observed particle distribution characteristics. This may reveal that internal plasma sources in the system may be important for Uranus' magnetospheric dynamics and may contribute to its unexpectedly strong radiation belts. Uranus is an oddity in the solar system for a variety of reasons, but mostly as a result of its perpendicular rotation relative to the rest of the planets in the solar system. During its approximately 3‐day flyby of Uranus in 1986, Voyager 2 captured the only in situ observations of the planet and its system. New analysis of these three‐decade‐old observations have revealed a mysterious source of energetic ions in the planet's magnetosphere. These ions were originally explained by dynamics of the system, but new understanding suggests that this is probably unlikely. New simple modeling of the expected behavior of such energetic particles show that sustaining such a population requires a very strong source and specific energization mechanism. Both would potentially be consistent with the ions originating from either Miranda or Ariel. This potentially hints that the Uranian magnetosphere may harbor an ocean world like those known or believed to exist at the other Giant Planets. Analysis of Voyager 2 observations revealed a localized source of energetic ions in the region between the moons Miranda and ArielDiffusive transport modeling suggests that typical magnetospheric sources cannot explain the observed characteristics of the energetic ionsAdditional in situ ion composition and plasma wave observations are necessary to confirm whether these ions are coming from an active moon Analysis of Voyager 2 observations revealed a localized source of energetic ions in the region between the moons Miranda and Ariel Diffusive transport modeling suggests that typical magnetospheric sources cannot explain the observed characteristics of the energetic ions Additional in situ ion composition and plasma wave observations are necessary to confirm whether these ions are coming from an active moon

We present the first investigation and quantification of the photoionization loss process to Mercury's sodium exosphere from spacecraft and ground‐based observations. We analyze plasma and neutral sodium measurements from NASA's MESSENGER spacecraft and the THEMIS telescope. We find that the sodium ion (Na+) content and therefore the significance of photoionization varies with Mercury's orbit around the Sun (i.e., true anomaly angle: TAA). Na+production is affected by the neutral sodium solar‐radiation acceleration loss process. More Na+was measured on the inbound leg of Mercury's orbit at 180°–360° TAA because less neutral sodium is lost downtail from radiation acceleration. Calculations using results from observations show that the photoionization loss process removes ∼1024atoms/s from the sodium exosphere (maxima of 4 × 1024atoms/s), showing that modeling efforts underestimate this loss process. This is an important result as it shows that photoionization is a significant loss process and larger than loss from radiation acceleration. Mercury has a thin sodium collision‐less atmosphere (i.e., an exosphere). A variety of processes add or subtract sodium particles to and from the exosphere. Photoionization is a loss process, and we investigate it in this paper by analyzing data from NASA's MESSENGER spacecraft and ground‐based observations made by the THEMIS telescope. Mercury has an eccentric (noncircular) orbit, which means the planet's distance from the Sun changes throughout its orbit. This, first of all, affects how much sodium is lost due to acceleration of neutral sodium by radiation (i.e., how much sodium is accelerated away from Mercury by radiation from the Sun). This subsequently affects how much sodium is left to be photoionized. Therefore, the amount of sodium lost due to photoionization varies throughout a Mercury‐year. We calculate that ∼1024atoms/s of sodium are lost due to photoionization, and that it is a significant loss process in comparison to acceleration by radiation. Photoionization can be a significant loss process to the sodium exosphere with peak loss estimates of 4 × 1024atoms/sThe photoionization loss process of Mercury's sodium exosphere varies throughout the planet's orbit around the SunMore sodium is lost due to photoionization on the inbound leg (true anomaly angle of 180°–360°) of Mercury's orbit than the outbound leg Photoionization can be a significant loss process to the sodium exosphere with peak loss estimates of 4 × 1024atoms/s The photoionization loss process of Mercury's sodium exosphere varies throughout the planet's orbit around the Sun More sodium is lost due to photoionization on the inbound leg (true anomaly angle of 180°–360°) of Mercury's orbit than the outbound leg