The Solar Orbiter spacecraft crossed Comet Leonard’s ion tail on 2021 December 17 near 1 au. In and near the ion tail, significant amounts of singly charged oxygen (O ^+ ) ions were detected by the Heavy Ion Sensor on board the spacecraft. These ions are likely the result of outgassed water molecules from the comet that became ionized and disassociated into protons and O ^+ ions and that were then picked up by the interplanetary magnetic field and advected outward with the solar wind. At this time, the spacecraft was also located amidst the denser parts of the interstellar helium (He) neutrals that are focused here by their gravitational interaction with the Sun. Pickup He ^+ ions in greater numbers are also found in this region and form when neutrals interact with solar photons. Newly ionized ions can generate waves that propagate mainly along the background magnetic field before the waves scatter the ions toward isotropy. Spectral magnetic field analyses are employed to find mainly elliptically polarized waves associated with O ^+ and He ^+ from ring-beam instabilities. Waves associated with He ^+ are identified, but O ^+ waves are not seen. Visibility is concluded to be affected by the relative amplitude of the waves to turbulence, and the visibility increases when the sampling direction is more aligned with the background magnetic field.

Using recent in-situ Arase satellite observations during Solar Cycle 25, between March 2017 and December 2023, we perform a comprehensive statistical study of the inner magnetospheric ion (H + , He + , and O + ) distributions as a function of geomagnetic conditions and solar activity. The analysis employed the intercalibration method to combine two ion datasets (LEPi and MEPi) onboard the Arase satellite, covering an energy range of 0.03–187 keV/q. In this study, we found distinct ion populations on energy: (1) plasmaspheric population (E < 30 eV) at L < 5; (2) suprathermal population at energies of several tens of eV to several keV at L > 5 for H + and L < 5 for He + and O + ; (3) ring current population (E = 1 keV – several tens of keV) with the ion nose structures; and (4) high-energy ring current particles (E > 30 keV) with symmetric MLT distributions. Ion fluxes and partial number densities exhibited significant enhancements with increasing Kp levels and solar activity. The O + fraction increased dramatically during periods of elevated Kp and enhanced solar activity, becoming comparable to the H + contribution within the plasmasphere. From our observations, we suggest that ion behavior in the inner magnetosphere is strongly influenced by geomagnetic disturbance levels and solar activity. This ion behavior can provide the favorable conditions for understanding the major driver of various magnetospheric plasma waves.

The Heavy Ion Sensor in Solar Wind Analyser suite on Solar Orbiter has provided unprecedented high-resolution elemental and ionic signatures around the heliospheric current sheet (HCS) from a vantage point near the Sun. Its high cadence time-series observations are used to determine the magnetic connectivity and map these complex transitions, revealing embedded processes of the observed signatures around the HCS crossing at ∼0.3 au. Electron strahl dropouts observed before the HCS crossing are accompanied by distinct local drops in the oxygen–proton temperature ratio ( T _O / T _p ), while carbon and oxygen charge-state ratios remain nearly invariant, with at most slight reductions depending on the interval. In contrast, near the true sector boundary (TSB) the heavy-ion composition profiles remain nearly constant, despite marked changes in magnetic and strahl topology. These measurements show that small-scale HCS-related structures at 0.3 au can be systematically matched with their heavy-ion thermal and compositional signatures. A gradual decrease of the Fe/O ratio toward the TSB is observed, reaching a minimum of (4.54 ± 0.54) × 10 ^−2 at the sector boundary and recovering within a few hours, establishing a clear association between Fe/O depletion and the HCS. After the HCS crossing, T _O / T _p frequently exceeds the super-mass-proportional threshold and is positively correlated with O ^7+ /O ^6+ , while C ^6+ /C ^5+ shows a negative correlation, indicating distinct properties of fully striped carbon within the same sector. As these signatures undergo minimal distortion during radial propagation and evolution, the observations presented in this study offer critical insights into the plasma provenance and the underlying physical processes governing the HCS environment.

To examine the temporal and spatial evolution of cold ions within the inner magnetosphere during geomagnetic storms, we conducted superposed epoch analyses on the electron density (N-e) and the partial ion densities of H+, He+, and O+ within the instrument frame energy range of 1-10 eV, using data obtained from the Van Allen Probes. The analyses were performed on a set of 14 large storms (SYM-H < -100 nT) over a 5-year period from 2013 to 2017. We found that the electron density and cold H+ and He+ densities outside the plasmasphere decrease as large storms develop. However, the cold O+ density outside the plasmasphere remains largely unchanged during the storm's main and early recovery phases. Based on these observations, we suggest that the less-dense cold population outside the plasmasphere during storm activities contains more cold O+ ions. Plain Language Summary This paper examines the spatial and temporal variations of cold O+ ions (with energies less than 10 eV at the instrument frame) in the inner magnetosphere during geomagnetic storms. These ions originate from the Earth's ionosphere and are believed to be energized in the polar ionosphere, subsequently flowing out along the Earth's magnetic field. This outflow of cold O+ ions is enhanced during geomagnetic storms. This study shows that storm-associated cold O+ ions are found outside the plasmapause, with a bidirectional field-aligned population, suggesting that the cold ions drift into the inner magnetosphere from the tail during storms.

This is the summary of findings by ISSI topical team on the molecular and metallic ions in the magnetosphere.Heavy molecular and metallic ions with mass ≥ 27 (Al+, N2+, NO+, O2++, Fe+, Cu+, Ti+, etc) in the magnetosphere provide independent information on the ion sources and entry route to the magnetosphere from traditional four components (H+, He++, He+, O+). There are four ultimate sources of these heavy molecular and metallic ions: the solar wind (high charge-state metallic ions), the ionosphere (mainly molecular ions), the atmospheric metal layers (low charge-state metallic ions and metal-rich molecular ions that ultimately originating from ablation of meteoroids and possibly space debris), and the surface and exosphere go the Moon (low charge-state metallic and molecular ions). The lunar origin low charge-state metallic ions, if separated from the ionospheric origin, give independent information on the entry route into the magnetosphere for ions of much larger gyroradius than the solar wind ions. The atmospheric-origin molecular ions are essential in understanding energization, ionization altitudes, and upward transport in the ionosphere during various ionospheric and magnetospheric conditions. These ions are also important when considering the evolution of the Earth's atmosphere on the geological timescale. So far, we cannot dismiss any of four possible sources with the existing data because only a few terrestrial missions have been equipped with instrumentation dedicated to separate these molecular and metallic ions, within only a limited energy range (cold ions of < 50 eV and energetic ions of ~100 keV or more) and a limited mass range (mainly ≤ 40 amu). This is far too limited to make any quantitative discussion on the very heavy ions in the magnetosphere. Under this circumstance, it is worth to re-examine, using available tools, the existing data from the past and on-going missions, including those not designed for the required mass separation, to search for these ions. We synthesised these patchy observations and combining all sources with updated models. With such knowledge, we re-examined available data and model that actually provided important indications of the sources of these heavy ions and their amounts that have been overlooked to date. Finally, we note the possible future contamination of specific masses by ablated space debris (Al, but also Li, Fe, Ni, Cu, Ti, and Ge) in the coming decades.

The Heavy Ion Instrument (HIS) onboard Solar Orbiter measures mass, charge, and full 3-D velocities of ions in the energy/charge range 0.5-75keV/charge. Using the data from HIS we study how interplanetary events like shocks or CME fronts create suprathermal tails in the velocity distribution and how those tails change with time. HIS observed the passage of three interplanetary shocks during the period October 2021 - May 2022. The three events were characterized by the acceleration of plasma from the solar wind energy regime (~1keV per amu/charge) to higher energies (5-75 keV), commonly referred to as suprathermal ions; later during the events, energetic particles (100keV and above) were measured by the EPD instrument. This energization process was characterized by a clear dependence upon mass/charge, and found consistent with preferential acceleration of ions present in the high energy tails of solar wind distributions, the seed population. Details of the distribution functions during the three events are presented and contrasted to each other.

The distribution of charged particles in the heliosphere covers more than 16 orders of magnitude in particle flux and more than 6 orders of magnitude in energy. While the majority of these particles are ionized hydrogen (protons) and fully ionized helium (alpha particles), heavier ions are also present. Because of the large parameter space that must be covered, different instruments are required and these instruments must be optimized to specific energy and particle flux ranges. They must also be designed to target specific ion species. To properly characterize the means by which different energy ranges are populated, the observations from these different instruments must be intercalibrated. We present initial progress intercalibrating observations from Solar Orbiter’s Heavy Ion Sensor (HIS) and Suprathermal Ion Spectrograph (SIS). HIS is a heavy ion composition experiment that targets the solar wind through the low energy range of suprathermal energies with mass and charge state resolution. SIS covers the suprathermal and low range energetic particles with high mass resolution but without charge state resolution. Together, these two sensors cover heavy ion composition from solar wind to suprathermal energies. During advantageous conditions, proton distributions across both instruments are also available. Properly intercalibrated observations across these instruments enable studies of charged particle energization across the energy ranges, which is essential for characterizing a wide range of phenomena in heliosphere.

The Interstellar Mapping and Acceleration Probe (IMAP) is a NASA heliophysics science mission that provides new coordinated and comprehensive observations of the inner and outer heliosphere. The IMAP observatory orbits at the Sun-Earth L1 Lagrange point, which is an ideal location for observing the space weather conditions upstream of Earth. Thus, in addition to providing new and groundbreaking heliophysics science observations, five in-situ instruments on IMAP make measurements that are critical for advancing space weather research and operational forecasting. These measurements are continuously telemetered in near real-time as part of the IMAP Active Link for Real-Time (I-ALiRT) space weather data system. I-ALiRT is based on the Real-Time Solar Wind (RTSW) data system from the NASA Advanced Composition Explorer (ACE) mission and provides similar space weather data products at enhanced cadences as well as additional new data products. This paper describes the I-ALiRT instruments and measurements, real-time data flow architecture, and publicly available space weather data products.

To study the average contributions of the cusp outflow through the lobes and of the nightside auroral outflow to the O+ in the plasma sheet (PS), we performed a statistical study of tailward streaming O+ in the lobes, plasma sheet boundary layer|the plasma sheet boundary layer (PSBL) and the PS, using MMS/Hot Plasma Composition Analyzer (HPCA) data from 2017 to 2020. Similar spatial patterns illustrate the entry of cusp‐origin O+ from the lobes to the PS through the PSBL. There is an YGSM‐dependent energy pattern for the lobe O+, with low‐energy O+ streaming closer to the tail center and high energy (1–3 keV) O+ streaming near the flanks. Low energy (1–100 eV) O+ from the nightside auroral oval is identified in the near‐Earth PSBL/PS with high‐density (>0.02 cm−3), and energetic (>3 keV) streaming O+ with similar density (∼0.013 cm−3) is observed further out on the duskside of the PSBL/PS. The rest of the nightside auroral O+ in the PSBL is mixed with O+ coming in from the lobe, making it difficult to distinguish the source. We estimated the contributions of the different sources of H+ and O+ ions through the PS between 7 and 17 RE, using estimates from this work and data extracted from previous studies. We conclude that, during quiet times, the majority of the near‐Earth PS H+ are from the cusps, the polar wind and Earthward convection from the distant tail. Similarly, while the O+ in the same region has a mixed source, cusp origin outflow provides the highest contribution.

Abstract Previous simulations have suggested that O+ outflow plays a role in driving the sawtooth oscillations. This study investigates the role of O+ by identifying the differences in ionospheric outflow between sawtooth and non‐sawtooth storms using 11 years of FAST/Time of flight Energy Angle Mass Spectrograph (TEAMS) ion composition data from 1996 through 2007 during storms driven by coronal mass ejections. We find that the storm's initial phase shows larger O+ outflow during non‐sawtooth storms, and the main and recovery phases revealed differences in the location of ionospheric outflow. On the pre‐midnight sector, a larger O+ outflow was observed during the main phase of sawtooth storms, while non‐sawtooth storms exhibited stronger O+ outflow during the recovery phase. On the dayside, the peak outflow shifts significantly toward dawn during sawtooth storms. This strong dawnside sector outflow during sawtooth storms warrants consideration.

We analyzed time-of-flight (TOF) data from the Arase satellite to investigate temporal variations of O2+, NO+, and N2+ at 19.2 keV/q in the inner magnetosphere for 6.5 years from the solar declining to rising phases. Molecular ion counts were estimated by subtracting the background contamination of oxygen counts. While the number of clear molecular events was small, the estimated molecular ion counts exhibited good correlation with the solar wind dynamic pressure and SYM-H index. Long-term variations of molecular ions were different from that of oxygen ions. Additionally, we discuss the importance of the solar wind dynamic pressure in causing the escape of molecular ions into the magnetosphere through an increase in the convection electric field, which causes different evolutions of oxygen ions and molecular ions.

During geomagnetic storms, the increase in energy input into the ionosphere in the form of Poynting flux and electron precipitation leads to an enhanced ionospheric outflow that results in an increase of the O+ content in the magnetosphere. Using different missions and instrumentation, two main ionospheric sources have been identified for the oxygen ions reaching the inner magnetosphere during geomagnetic storms: the dayside cusp, and the night side auroral region. Evidence of both pathways have been presented in the literature. However, the relative contribution of each of these pathways to the enhancement of O+ observed in near-Earth plasma sheet, as well as the dynamics involved during the development of geomagnetic storms remains an open question. Here, we present the first statistical study to date to address this question, in the form of a superposed epoch analysis of O+ and H+ moments obtained by the Magnetospheric Multiscale (MMS) mission throughout the main phase of 90 geomagnetic storms with a minimum SYM-H of at least -50 nT. The results show a clear increase in the oxygen density in the near-Earth plasma sheet, with values further from Earth remaining low. Temperature values for both species show an increase with the progress of the storms. These results combined suggest that, during the main phase of geomagnetic storms, most of the oxygen ions observed in the near-Earth plasma sheet are traveling directly from the nightside auroral region.

The approximately 11-year solar cycle has been shown to impact the heavy ion composition of the solar wind, even when accounting for streams of differing speeds; however, the heavy ion composition observed between the same specific phases of a past solar cycle and the current cycle has rarely, if ever, been compared. Here, we compare the heavy ion composition of the solar wind, as measured in situ during the solar cycle 23 and 25 ascending phases. We examine the mean iron and oxygen charge state composition and the O7+/O6+ ratio in multiple ranges of associated bulk wind speeds. Then, we compare the iron and oxygen charge state composition and relative abundance of iron to oxygen in the traditionally defined fast and slow solar wind. Finally, to determine the impact of individual ion contributions on the solar wind iron abundance, we examine individual ratios of iron and oxygen ions. Although the charge state composition remained broadly similar between these two ascending phases, both the O7+/O6+ ratio and iron fractionation in fast-speed streams were higher in the solar cycle 25 ascending phase than they were during the solar cycle 23 ascending phase, suggesting that equatorial coronal hole fields more frequently reconnected with helmet streamers or active regions in the latter of the two ascending phases; however, more work will need to be done to connect these observations back to their coronal origins. The individual ion ratios used in this work provided a spectrum to analyze the aggregate elemental abundances, and this work, as a whole, is an important step in determining how conditions in the corona may vary between solar cycles between the same phases.

In order to determine the extent to which a global magnetic field is required for a planet to be habitable at its surface, expertise is required from diverse communities, some of which have diverged from each other over the past several decades. For example, modelers and observers of the terrestrial magnetosphere have limited overlap and interaction with modelers and observers of unmagnetized planets or the giant planets in our solar system. There is relatively limited interaction between any of the above communities and those who study exoplanets, though efforts are increasing to bridge the solar system and exoplanet communities. We describe a NASA Heliophysics DRIVE Science Center selected to answer the central question of this session: “Do Habitable Worlds Require Magnetic Fields”. This Center, named MACH (Magnetic Fields, Atmospheres, and the Connection to Habitability) includes scientists who study atmospheric escape from Earth, unmagnetized planets, and exoplanets. Over the next several years MACH will construct a framework that enables the evaluation of atmospheric loss from an arbitrary rocky planet, given information about the planet and its host star. The MACH Center hosted a community-wide workshop in June 2021 centered around this topic, and is seeking to grow their interactions with interested scientists from relevant disciplines.

Observations and present knowledge of heavy ions with mass ≥ 27 in the magnetosphere are reviewed. There are four ultimate sources of these heavy ions: the solar wind (mainly high charge-state atomic ions), the ionosphere (mainly molecular ions), the atmospheric metal layers that originate ultimately from ablation of meteoroids and possibly space debris (low charge-state metallic ions and metal-rich molecular ions), and lunar surface and exosphere (low charge-state metallic and molecular ions). The upstream heavy ions (solar wind origin and lunar origin) give independent information on the ion entry routes to the magnetosphere from proton (H+) and alpha particles (He++): with similar mass-per-charge (m/q) values, or gyroradius, for the solar wind origin, and much larger gyroradius for the lunar origin. The lunar origin ions also give independent insights from laboratory observations on the sputtering processes. The atmospheric origin molecular and metallic ions are essential in understanding energization, ionization altitudes, and upward transport in the ionosphere during various ionospheric and magnetospheric conditions. These ions are also important when considering the evolution of the Earth’s atmosphere on the geological timescale. Only a few terrestrial missions have been equipped with instrumentation dedicated to separate these molecular and metallic ions, within only a limited energy range (cold ions of < 50 eV and energetic ions of ∼ 100 keV or more) and a limited mass range (mainly ≤ 40 amu). This is far too limited to make any quantitative discussion on the very heavy ions in the magnetosphere. For example, the existing data are far from sufficient for determining the dominant contributor from the four possible sources, or even to rule out any of the possible sources as a substantial contributor. Under this circumstance, it is worth to re-examine, using available tools, the existing data from the past and on-going missions, including those not designed for the required mass separation, to search for these ions. The purpose of this review is to summarize the availability of these datasets and tools. This review also shows some examples of combinations of different datasets that provide important indications of the sources of these heavy ions and their amounts that have been overlooked to date. Finally, we note the possible future contamination of specific masses (mainly aluminum (Al), but also lithium (Li), iron (Fe), nickel (Ni), copper (Cu), titanium (Ti) and germanium (Ge)) by the ablation of re-entering human-made objects in space (debris and alive satellites) in the coming decades. This possibility argues the need for dedicated observations of magnetospheric and ionospheric metallic ions before these metallic ions of space debris origin start to dominate over the natural contribution. The required observations can be performed with the available designs of space instrumentation and available ground-based instruments.

The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on both the Van Allen Probes spacecraft is a time-of-flight versus total energy instrument that provided ion composition data over the ring current energy (∼7 keV to ∼1 MeV), and electrons over the energy range ∼25 keV to ∼1 MeV throughout the duration of the mission (2012 – 2019). In this paper we present instrument calibrations, implemented after the Van Allen Probes mission was launched. In particular, we discuss updated rate dependent corrections, possible contamination by “accidentals” rates, and caveats concerning the use of certain products. We also provide a summary of the major advances in ring current science, obtained from RBSPICE observations, and their implications for the future of inner magnetosphere exploration.

&lt;p&gt;Geomagnetic storms are the main component of space weather. Enhancement of the ring current is a typical feature of the geomagnetic storm and a global decrease in the &lt;em&gt;H&lt;/em&gt; component of the geomagnetic field is observed during the main phase of the geomagnetic storm. &amp;#160;The ring current represents a diamagnetic current driven by the plasma pressure in the inner magnetosphere. The plasma pressure is mainly dominated by protons in an energy range of a few to a few hundred keVs during quiet times. The O&lt;sup&gt;+&lt;/sup&gt; contribution is also important, and sometimes dominates more than H&lt;sup&gt;+&lt;/sup&gt; during intense geomagnetic storms. However, electron contribution to the ring current is not studied well. Recently, we showed that the electron pressure also contributes to the depression of ground magnetic field during the November 2017 CIR-driven storm by comparing &lt;strong&gt;R&lt;/strong&gt;ing current&amp;#160;&lt;strong&gt;A&lt;/strong&gt;tmosphere interactions&amp;#160;&lt;strong&gt;M&lt;/strong&gt;odel with&amp;#160;&lt;strong&gt;S&lt;/strong&gt;elf&amp;#160;&lt;strong&gt;C&lt;/strong&gt;onsistent magnetic field (RAM-SCB) simulation, Arase in-situ plasma/particle data, and ground-based magnetometer data [Kumar et al., 2021]. Arase satellite observed 26 geomagnetic storms driven by Corotating Interaction Regions (CIR) during 2017-2021. In this study, we examine statistically the spatial and temporal distribution of ions (H&lt;sup&gt;+&lt;/sup&gt;, He&lt;sup&gt;+&lt;/sup&gt;, O&lt;sup&gt;+&lt;/sup&gt;) and electrons pressure as a function of magnetic local time, L shell and wide range of energies during prestorm, main phase, early recovery and late recovery phase for 26 CIR storms using in situ plasma/particle data obtained by Arase. The results indicate that the electrons (20-50 keV) contribution to the ring current pressure is non-negligible.&lt;/p&gt;

Both solar wind and ionospheric sources contribute to the magnetotail plasma sheet, but how their contribution changes during a geomagnetic storm is an open question. The source is critical because the plasma sheet properties control the enhancement and decay rate of the ring current, the main cause of the geomagnetic field perturbations that define a geomagnetic storm. Here we use the solar wind composition to track the source and show that the plasma sheet source changes from predominantly solar wind to predominantly ionospheric as a storm develops. Additionally, we find that the ionospheric plasma during the storm main phase is initially dominated by singly ionized hydrogen (H + ), likely from the polar wind, a low energy outflow from the polar cap, and then transitions to the accelerated outflow from the dayside and nightside auroral regions, identified by singly ionized oxygen (O + ). These results reveal how the access to the magnetotail of the different sources can change quickly, impacting the storm development.

The life cycle of core plasma, from its sources in the ionosphere through the magnetosphere-and its evolution and impacts along the way-is a truly critical aspect of geospace dynamics.Core plasma is initially cold (<10 eV) but becomes heated and energized (to tens of eV on the day side, and up to keV on the night side) as it permeates the entire magnetosphere.Because of the cross-scale, cross-regime, and cross-energy nature of this multi-step circulation and energization, and because it is a challenge to measure the lowest-energy ions, the core plasma life cycle remains poorly constrained by observation.The reward for closing this knowledge gap is enormous, however, both for understanding the geospace system, and for the fundamental physics of atmosphere-ionosphere-magnetosphere (and solar-wind/ atmosphere) interactions at other solar system bodies and exoplanets.Core plasma's enormous contribution to the major energetics of geospace is truly a system-level problem that requires a cross-scale, cross-energy solution.This white paper proposes the Synchronized Observations of Upflow, Redistribution, Circulation, and Energization (SOURCE) mission concept, a constellation of imaging & in situ observatories.SOURCE is a systems-level mission that targets the full life cycle of core plasma, from its ionospheric origin to its magnetospheric energization and impact.SOURCE fills critical gaps in our knowledge of geospace physics with a comprehensive remote and in situ constellation.Imaging quantifies the distribution, composition, system-level transport, and dynamics of core plasma.In situ measurements capture the local transport and physical processes that are responsible for creating highly structured core plasma distributions of the plasmasphere, dense O + torus, and warm cloak.SOURCE comprises five (5) spacecraft (SC).M1 and M2 are identical low-altitude in situ observatories to measure how core plasma escapes the ionosphere.Imager M3 measures global-to-regional refilling, erosion, evolution, and circulation pathways of core ions in the plasmasphere and oxygen torus.Imager M3 also measures crucial exospheric variability in the refilling source region, and images low energy neutral atoms in the plasma sheet and ring current to determine the transformation and macroscale stormtime impact of recirculated, heated/energized core plasma.In situ observer M4 measures cold ion refilling, energization, composition, and transport in the near-equatorial plasmasphere, oxygen torus, and trough.In situ SC M5 measures how outflowing ions are energized and transported in the tail lobes to help create the plasma sheet, warm cloak, and ring current (RC).The orbits from these 5 SC are optimized to provide frequent alignments with synchronized measurements covering the same set of flux tubes-maximizing the ability to quantify the mechanisms that transport and energize initially cold plasma, throughout geospace to help create the cloak, plasma sheet, and ring current.All SC use a common Millennium Space Systems (MSS) Altair bus and standard subsystems.

Ion mass-per-charge and shock geometry determine both shock injection and the number of times a charged particle is reflected across a shock. As such, they govern charged particle acceleration and heating at shock. Solar Obiter’s Heavy Ion Sensor (HIS) observed a quasi-parallel CME-driven shock on March 11, 2022. HIS has sufficient time, mass, and charge resolution that it measured individual distributions of iron 8+ through 12+ on the variable timescale of 2 to 5 minutes. Using these 1D velocity distribution functions (VDFs), we report that the thermal portion of the Fe distribution heats across the shock, that this heating increases with Q/M, and the heating increases with distance downstream from the shock.