Solar wind measurements by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission provide samples of the heliosphere at 1.38–1.67 AU, and of the upstream conditions that drive numerous processes in the near-Mars plasma environment. We reduce ion measurements from MAVEN’s Solar Wind Ion Analyzer (SWIA), using contextual magnetic field measurements, to 13 independent macroscopic plasma parameters by fitting a convolution of SWIA’s 3-dimensional response function and a superposition of phase-space bi-kappa distribution functions to each measured distribution using an iterative Poisson optimization scheme. This ensemble of parameters represents the solar wind H+ core, H+ beam, and He2+ (alpha) populations, effectively separating each population’s contribution to any measured distribution. Sporadic plasma frequency measurements from MAVEN’s Langmuir Probe and Waves (LPW) instrument are used to calibrate the SWIA measurements such that ion charge densities match LPW-derived electron charge densities. The resulting dataset is effectively ground-truthed, largely corrected for instrumental particularities, and provides a rich timeline of solar wind properties at Mars, including composition, velocities, temperature anisotropies, differential drifts, and degree of thermalization.

Over two decades ago, the first detection of electron cyclotron maser instability radio emission from a brown dwarf confirmed the presence of aurorally precipitating electrons on these objects. This detection established that brown dwarfs can exhibit magnetic activity that is planetary and auroral, rather than stellar in nature. This discovery motivated ongoing observational searches for the corresponding optical, ultraviolet, and infrared auroral emission expected based on solar system analogs. The continuing nondetection of such auroral emission indicates that important differences exist between auroral processes on brown dwarfs and solar system planets. In this work, we implement a Monte Carlo simulation of monoenergetic electron beams interacting with brown dwarf atmospheres as a step toward understanding the physics of brown dwarf auroral emission. We detail the algorithm and underlying assumptions and validate against previously published Jovian results. Our results agree well with the literature, with some discrepancies from our updated interaction cross sections. We demonstrate the applicability of our simulation across the range of surface gravities and effective temperatures of radio-emitting brown dwarfs. We present an analytic parameterization of interaction rates based on our finding that atmospheric column density governs the interaction profiles. We apply this parameterization to calculate the total volumetric interaction rates and energy deposition rate for representative electron beam energy spectra enabling future predictions for spectra of aurorally emitting brown dwarfs. Simulations of high-energy electron interactions with substellar hydrogen-dominated atmospheres will guide observational searches for multiwavelength auroral features beyond the solar system.

Detection of an atmosphere around a terrestrial exoplanet will be a major milestone in the field, but our observational capacities are biased towards tidally locked, close-in planets orbiting M dwarf stars. The atmospheres of these planets are vulnerable to atmospheric erosion and collapse due to condensation of volatiles on the nightside. However, these condensed volatiles constitute a stable reservoir that could be revaporized by meteorite impacts and reestablish the atmospheres. Through a simple energy balance model applied to atmospheric evolution simulations with stochastic impacts, we assess the viability and importance of this mechanism for CO _2 atmospheres. We find that moderate-sized impactors (5–10 km diameter) occurring at a frequency of 1–100 Gyr ^−1 can regenerate observable transient atmospheres on previously airless planets. We focus on specific targets from the James Webb Space Telescope Director’s Discretionary Time Rocky Worlds programme and compute the fraction of their evolution spent with a transient CO _2 atmosphere generated through this mechanism. We find this fraction can reach 70% for GJ 3929 b, 50% for LTT 1445 Ac, and 80% for LTT 1445 Ab at high impact rates and strong CO _2 outgassing over the planet’s lifetime. We also show that atmospheric collapse can shield volatiles from escape, particularly in the early, high X-ray and ultraviolet phase of M dwarf evolution. Overall, our work suggests that terrestrial planet atmospheres may not evolve monotonically but instead may be shaped by episodic external forcings.

Available JWST observations of the TRAPPIST-1 system have suggested that several of the planets are likely airless, or possess a very tenuous atmosphere. However, the high atmospheric escape rates expected for these planets suggest that any tenuous atmosphere must be replenished by constant outgassing, and past studies on modeling potential atmospheres for the planets have not widely considered surface pressures << 1 bar. Here, we show that tenuous atmospheres on the TRAPPIST-1 planets are likely possible, supported by constant plausible rates of water and/or CO2 outgassing against assumed high escape rates (up to similar to 10(30) s(-1)). We use a coupled photochemical-climate model and sample from a broad phase space of outgassing, surface deposition, and top-of-atmosphere escape rates to test hundreds of atmospheres per planet. Critically, our model also allows the surface pressure to vary based on the balance of sources and sinks. We find that six different compositional archetypes are generated via H2O and/or CO2 outgassing across our phase space, and atmospheres commonly fall between 10(-4) and 1 bar. We find that potentially habitable surface environments are possible for TRAPPIST-1 d and e at pressures between 0.05-2 bar and 0.5-1 bar, respectively. Where possible, we compare our models to JWST observational data of TRAPPIST-1 b, c, d, and e; all atmospheres found in this study for these planets match the available transmission data to <3 sigma. However, the emission data are consistent with atmospheric outcomes constrained to thin O-2-dominated compositions for TRAPPIST-1 b (less than or similar to 0.01 bar) and c (less than or similar to 0.2 bar), which may or may not contain trace SO2.

Shortly after the solar wind was first measured by the Second Soviet Cosmic Rocket (Luna 2) in 1959, planetary scientists immediately began wondering if it might be a source of mass for terrestrial atmospheres; perhaps even providing the Earth with all of the hydrogen needed for its oceans (De Turville 1961). This particular idea has been shown not to hold water, moreover, it is now known that the solar wind can drive escape from planetary atmospheres in the form of pick up ions. This presentation highlights an unresolved question: does the solar wind represent a net source or sink of mass for the terrestrial planets? We approach the problem using an ion-kinetic quasi-neutral hybrid (QNH) particle-in-cell (PIC) code called Rhybrid. We simulate the interaction of the solar wind with non-magnetized and weakly-magnetized terrestrial-type planets ranging in size from Mars to super Earth (1.5 RE). We also vary the ion production rate and dipole moment strength in order to explore the relevant parameter space. We quantify the escape rate of planetary ions (H+ and O+), as well as the accretion rate of solar hydrogen, and present the net mass flux for the different modeled scenarios.

As a weakly magnetized planet, Mars interacts directly with the highly variable solar wind, where small-scale and short-duration structures are ubiquitous. Among solar wind parameters, dynamic pressure, as the dominant external pressure, plays a key role in shaping the pressure level and structures in the downstream induced magnetosphere. In this study, a multispecies global magnetohydrodynamic model is used to investigate Mars’s response to a series of idealized solar wind dynamic pressure enhancements with varying durations and magnitudes, aiming to capture responses in different plasma regions and isolate the effects of dynamic pressure. For the subsolar region, the simulations reveal a sequence of response phases, each exhibiting distinct temporal characteristics. Beyond the subsolar region, the terminator ionosphere and global ion escape show prolonged disturbances. These results highlight the importance of short-term upstream variability in shaping both local and global features of the Martian plasma environment and provide context for interpreting spacecraft observations that sample only limited regions of the system.

Mars, being a small planet with a tenuous atmosphere, does not have a sharp boundary between regions dominated by solar wind plasma and planetary plasma. Instead, this transition is typically extended, allowing the interplanetary magnetic field (IMF) to penetrate into the Martian ionosphere. However, the depth of this penetration is not well understood. Using 6 years of MAVEN data, we statistically assess locations where a transition exists between the dominance of magnetic versus cold (< 1 eV), thermal plasma pressure to better understand the reach of the IMF. We identify the presence or absence of pressure transitions from 200 to 800 km altitude for each MAVEN orbit and find a clear transition in similar to 55% of cases. The pressure transition locations are mapped in different coordinate systems that provide insight into the solar and planetary driving conditions that cause a detected transition region. Transitions are more likely to occur under weak-to-nominal solar wind conditions, away from strong crustal magnetic fields, near the terminator, on the dusk side of the planet compared to the dawn side, and in the negative solar wind motional electric field hemisphere. We speculate on possible causes for asymmetries that arise in the mapped locations of these pressure transitions and the effect that penetrated IMF may have on driving plasma dynamics in the Martian ionosphere.

Benefiting from a large orbit and high sensitivity, the Emirates Mars mission EMUS instrument has provided the first opportunity to synoptically and regularly image Mars’ discrete FUV auroral oxygen emission at 130.4 and 135.6 nm. Over 15-20 minutes, EMUS produces a) images by slewing its aperture slit across the disk or b) “movies” of narrow regions by staring continuously.Discrete aurora are observed primarily where the magnetic topology is open (i.e. connected to the collisional atmosphere at one end), which occurs where Mars’ crustal magnetic fields are either very weak or primarily vertical. Discrete aurora show a strong local time dependence, with occurrence % decreasing with increasing solar zenith angle. The highest occurrences are generally found in the post-dusk sector, before 10 PM SLT, though a few regions (e.g. 60°-70° S, 120°-150° E) are brightest between midnight and 3 AM. Sinuous discrete auroras (SDA) are enigmatic, sharply-defined filamentary emissions identified in approximately 3% of observations. These emissions intersect Mars' UV terminator, aligning generally away from the Sun, tending to cluster into groups oriented to the north, south, east, and west. The occurrence of SDAs increases with higher solar wind pressure. SDAs have a tendency to form toward the direction of the solar wind convection electric field (i.e., forming in the +E hemisphere). Depending on whether they originate near dusk or dawn, there is a moderate clockwise or counterclockwise "twist" observed in the average orientation of SDAs, respectively. Based on these characteristics, we infer a connection between SDAs and Mars' magnetotail current sheet, suggesting that the emission may be a result of energized electrons within this sheet.Lastly, near the dawn and dusk terminators, discrete aurora often display a preference for formation in regions of either positive or negative crustal magnetic field, depending on IMF direction. This preference can be used to determine whether a dayside (magnetosheath or photoelectron) or nightside (magnetotail) source of electrons is dominant. Overall, nightside sources dominate over dayside by 20-40%, although individual radial crustal fields can show strong preferences for day or night sources. This tells us that local magnetic geometry plays a role in global precipitation patterns.With more than 3000 nightside images and 400 aurora movies collected (totaling more than 12 million pixels) since April 2021, we now have a powerful tool to understand Martian aurora morphologies, variability, and dependence on internal and external drivers.

We investigate Martian electron aurora utilizing 130.4 nm auroral observations from the Emirates Mars Ultraviolet Spectrograph and IMF clock angle measurements and estimates from MAVEN. Analysis reveals that more than 5 R aurora occurrence in a given region can vary by up to a factor of seven with IMF orientation, generally highest for southward IMF and lowest for westward IMF, with higher auroral occurrence post-dusk, decreasing toward and past midnight before increasing again toward dawn. A broad diversity of IMF and local time dependence of aurora occurrence is observed across Mars' crustal magnetic fields. The polarity of a given crustal field determines whether its field lines preferentially magnetically connect to dayside ionospheric or nightside magnetotail electron sources in the post-dusk or pre-dawn sectors. We thus establish a "source preference metric", that is, the excess likelihood of aurora when likely magnetically connected to the nightside versus dayside. A wide range of source preferences are observed across the crustal field features, with some showing higher occurrence for night sources, day sources, or neither, often differently when in the post-dusk or pre-dawn sectors. A generally stronger nightside source preference is found for radially inward crustal fields in the predawn sector, and for weaker outward crustal fields in the post-dusk sector. These results highlight the complex and dynamic nature of Mars' magnetic topology in controlling auroral electron access. Future studies integrating in situ electron measurements with synoptic and limb auroral imaging will further constrain the relative contributions of dayside and magnetotail electron populations to Mars' auroral processes.

Planetary magnetic fields are important indicators of planetary processes and evolution, from a planet's outer core to its surface (if it possesses one) to its atmosphere and near-space environment. Magnetic fields are most directly measured in situ, and determining whether distant planetary objects possess magnetic fields can be challenging. At present we have no unambiguous measurements of magnetic fields on exoplanets. Nevertheless, it would be surprising if at least some exoplanets did not generate a magnetic field, like many planetary bodies in the solar system. This chapter provides an overview of the current understanding of exoplanetary magnetic fields and their consequences. In the next section we review the current understanding of planetary dynamo generation as it applies to solar system objects and discuss the implications for exoplanetary magnetic field generation. Following this, we describe seven methods for determining the existence and strength of an exoplanetary magnetic field and discuss the near-term prospects for each method. We close by highlighting four main consequences of exoplanetary magnetic fields for a planet and its evolution.

We present the first observations of the dayside coronal oxygen emission in far ultraviolet (FUV) measured by the Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM). The high sensitivity of EMUS is providing an opportunity to observe the tenuous oxygen corona in FUV, which is otherwise difficult to observe. Oxygen resonance fluorescence emission at 130.4 nm provides a measurement of the upper atmospheric and exospheric oxygen. More than 500 oxygen corona profiles are constructed using the long-exposure time cross-exospheric mode (OS4) of EMUS observations. These profiles range from similar to 200 km altitude up to several Mars radii (>6 R-M) across all seasons and for two Mars years. Our analysis shows that OI 130.4 nm is highly correlated with solar irradiance (solar photoionizing and 130.4 nm illuminating irradiances) as well as changes in the Sun-Mars distance. The prominent short term periodicity in oxygen corona brightness is consistent with the solar rotation period (quasi-27-day). A comparison between the perihelion seasons of Mars Year (MY) 36 and MY 37 shows interannual variability with enhanced emission intensities during MY 37, due to the rise of Solar Cycle 25. These observations show a highly variable oxygen corona, which has significant implications on constraining the photochemical escape of atomic oxygen from Mars.

We examine the newly discovered phenomena of sinuous aurora on the nightside of Mars, using images of 130.4 and 135.6 nm oxygen emission measured by the Emirates Mars Mission EMUS ultraviolet spectrograph, and upstream measurements from the MAVEN and Mars Express spacecraft. They are detected in similar to 3% of observations, totaling 73 clear detections. These emissions are narrow, elongated (1,000-6,000 km), cross Mars' UV terminator, and are oriented generally toward the anti-solar point, clustering into north, south, east, and west-oriented groups. Diverse morphologies are observed, though some spatial features, such as broad curves, may in some cases be due to temporal aliasing of aurora motion as each image is built up over 15-20 min. Sinuous aurora form away from Mars' strongest crustal magnetic fields and can be interrupted by moderate crustal fields. Sinuous aurora occurrence increases strongly with solar wind pressure, though brightness shows only a weak positive dependence on pressure. Interplanetary magnetic field (IMF) clock angle affects their occurrence and orientation: sinuous aurora show a broad range of orientations centered on the solar wind convection electric field (Econv) direction and forming in the +Econv hemisphere, although with moderate clockwise and counterclockwise average "twists" for westward and eastward IMF, respectively. From these features we infer a link between sinuous aurora and electron energization in Mars' magnetotail current sheet, where field geometry on the +Econv side of the sheet is more organized and symmetric. Determination of specific triggering conditions for sinuous aurora requires further investigation. Sinuous aurora are narrow, extended patterns of UV emission caused by long, thin channels of energized electrons striking Mars' nightside upper atmosphere. We study images of these aurora taken by the Emirates Mars Mission EMUS instrument. 73 cases of sinuous auroras were found (similar to 3% occurrence rate) with lengths ranging from 1,000 to 6,000 km. These auroras usually cross Mars' day-night boundary and extend in the direction opposite to the Sun. They tend to cluster into groups oriented toward the north, south, east, and west directions with a diverse array of shapes. Sinuous aurora generally form away from Mars' strongest crustal magnetic fields. They occur more frequently for higher solar wind pressure. Their orientations are affected by the interplanetary magnetic field (IMF), displaying a broad range of orientations centered on the direction of the electric field in the solar wind, and forming in the hemisphere to which this electric field points, although with moderate counterclockwise and clockwise average "twists" for eastward and westward IMF, respectively. From these features we infer a link between sinuous aurora and a sheet of current in Mars magnetic tail, wherein the aurora-causing electrons may be energized before falling into the upper atmosphere to produce aurora. These narrow emission features form away from strong crustal fields, oriented anti-sunward, cross the terminator, are detected in 3% observations Occurrence increases with solar wind pressure, certain interplanetary magnetic field orientations, and in the positive motional electric field hemisphere Sinuous aurora may be related to magnetotail asymmetry and electron energization processes occurring in the tail current sheet

Multi-spacecraft missions after 2000 (Cluster II, THEMIS, Van Allen Probes, and MMS) have revolutionized our understanding of the causes, patterns and variability of a wide array of plasma phenomena in the terrestrial magnetospheric environment. ESCAPADE is a twin-spacecraft Mars mission concept that will similarly revolutionize our understanding of how solar wind momentum and energy flows throughout Mars’ magnetosphere to drive ion and sputtering escape, two processes which have helped shape Mars’ climate evolution over solar system history. ESCAPADE will measure magnetic field strength and topology, ion plasma distributions (separated into light and heavy masses), as well as suprathermal electron flows and thermal electron and ion densities, from coordinated elliptical, 200 km x ~7000 km orbits. ESCAPADE are small spacecraft (

Mars once had a dense atmosphere enabling liquid water existing on its surface, however, much of that atmosphere has since escaped to space. We examine how incoming solar and solar wind energy fluxes drive escape of atomic and molecular oxygen ions (O+ and O2+) at Mars. We use MAVEN data to evaluate ion escape from February 1, 2016 through May 25, 2022. We find that Martian O+ and O2+ both have increased escape flux with increased solar wind kinetic energy flux and this relationship is generally logarithmic. Increased solar wind electromagnetic energy flux also corresponds to increased O+ and O2+ escape flux, however, increased solar wind electromagnetic energy flux seems to first dampen ion escape until a threshold level is reached, at which point ion escape increases with increasing electromagnetic energy flux. Increased solar irradiance (both total and ionizing) does not obviously increase escape of O+ and O2+. Our results suggest that the solar wind electromagnetic energy flux should be considered along with the kinetic energy flux as an important driver of ion escape, and that other parameters should be considered when evaluating solar irradiance’s impact on O+ and O2+ escape.

We present a comprehensive study of the nightside aurora phenomenon on Mars, utilizing observations from EMUS onboard EMM. The oxygen emission at 130.4 nm is by far the brightest FUV auroral emission line observed at Mars. Our statistical analysis reveals geographic, solar zenith angle, local time, and seasonal dependencies of auroral occurrence. Higher occurrence of aurora is observed in regions of open magnetic topology, where crustal magnetic fields are either very weak or both strong and vertical. Aurora occurs more frequently closer to the terminator and is more likely on the dusk side than on the dawn side of the night hemisphere. A pronounced auroral feature appears close to midnight local times in the southern hemisphere, consistent with the spot of energetic electron fluxes previously identified in the MGS data. This auroral spot is more frequent after midnight than before. Additionally, some regions on Mars are “aurora voids” where essentially no aurora occurs. Aurora exhibits a seasonal dependence, with a major enhancement near perihelion. Non-crustal field aurora additionally shows a secondary enhancement near Ls 30°. This seasonal variability is a combination of the variability in ionospheric photoelectrons and thermospheric atomic oxygen abundance. Auroral occurrence also shows an increase with the rise of Solar Cycle 25. The brightest auroral pixels are observed during space weather events such as CMEs and SIRs. These observations not only shed light on where and when Martian aurora occurs, but also add to our understanding of Mars’ magnetic environment and its interaction with the heliosphere.

We explore the ability of an unmagnetized planet to retain an atmosphere as a function of its radius. We use a particle-in-cell hybrid code to simulate the global plasma interaction of unmagnetized terrestrial planets at 1 au under average solar wind conditions. We vary the radius of the planet (R-p) from Mars-sized (3390 km) to super-Earth-sized (9390 km). We inject hydrogen and oxygen ion outflows from the ionosphere and quantify how the ion escape, recirculation, solar wind deposition, and net atmospheric mass flux vary as a function of planetary radius. We find that as the radius and the corresponding ionospheric outflow rate are varied, the fraction of outflowing H+ that escapes remains at 15.5 +/- 1.0 percent, while the rest recirculates back towards the planet. The fraction of produced O+ that escapes from a Mars-sized planet is 27 +/- 1 percent, and decreases to 7 +/- 1 percent for super-Earth, suggesting that smaller planets are less able to retain heavy ions. We find, however, that larger planets have lower solar wind deposition fractions because their bow shocks are at greater distances from the surface of the planet. The ionospheric outflow rate at which mass deposition is equal to mass escape is found to be proportional to R-p(2). Lastly, we propose that the bulk gyration of the solar wind at the induced magnetosphere can lead to differential escape trajectories of light and heavy ions.

The Emirates Mars Ultraviolet Spectrometer (EMUS), aboard the Emirates Mars Mission (EMM), has been conducting observations of ultraviolet emissions within the Martian exosphere. Taking advantage of the distinctive orbit of the EMM around Mars, EMUS utilizes a dedicated strafe observation strategy to scan the illuminated Martian exosphere at tangential altitudes ranging from 130 to over 20,000 km. To distinguish between emissions of Martian origin and those from the interplanetary background, EMUS conducts specialized background observations by looking away from the planet. This approach has allowed us to investigate the radial and seasonal variations in Martian coronal emission features at H Lyman-alpha, beta and gamma wavelengths. Our analysis supports the previous studies indicating that Martian exospheric hydrogen Lyman emission brightness attains its highest levels around the southern summer solstice and reaches its lowest levels when Mars is near aphelion. Additionally, a secondary peak emission at all altitudes is observed after perihelion during Martian Year (MY) 36, which can be attributed to a Class C dust storm. Our study establishes a strong correlation between solar flux and coronal brightness for these emissions, highlighting the impact of solar activity on the visibility of Martian corona. In addition, we have examined interannual variability and found that emission intensities in MY 37 surpassed those in MY 36, primarily due to increased solar activity. These observations help to understand potential seasonal patterns of exospheric hydrogen, which is driven by underlying mechanisms in the lower atmosphere and solar activity, eventually suggesting an impact on water loss in the Martian atmosphere. Atomic hydrogen primarily forms as a product when Martian water undergoes various photochemical reactions. These hydrogen atoms encircle Mars and become illuminated by solar radiation, leading to the creation of Martian hydrogen corona. The Emirates Mars Ultraviolet Spectrometer (EMUS), on the Emirates Mars Mission spacecraft, is currently studying the Martian atmosphere using the ultraviolet light emissions of different atoms and molecules on Mars. In this study, we have analyzed EMUS observations and determined that atomic hydrogen emission intensities increase during the Martian southern summer and decrease as Mars moves farther away from the Sun. Furthermore, we have compared the hydrogen brightness between two consecutive Martian years and have found that the hydrogen brightness is higher in the most recent year primarily due to increased solar radiation. These observations help us understand possible patterns that occur during different seasons on Mars and the mechanisms underlying water loss in the Martian atmosphere. We present the variability in Martian atomic hydrogen brightness from early Martian year (MY) 36 to the first quarter of MY 37 Martian exospheric H Ly-beta and gamma emissions reach their peak brightness during the southern summer of MY 36 Martian corona is much brighter at H Ly-beta wavelength in MY 37 compared to the previous year due to increased solar irradiance

On 26-27 December 2022, Mars experienced an extremely low-density solar wind stream, which was encountered first by Earth because of the radial alignment of the two planets (i.e., Mars opposition). During this event, two important properties of the ionospheric and magnetospheric states changed significantly in response to the low solar wind ram pressure, as inferred from the superthermal electron observations from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission. The interface between the ionosphere and magnetosphere expanded to thousands of kilometers, outside of the nominal bow shock locations, coinciding with the expansion of the cold planetary ions. Meanwhile, the ambipolar electrostatic potential arising from the ionospheric electron pressure gradient increased from the nominal similar to -0.7 to similar to -2 V (relative to the lower ionosphere). This enhanced ambipolar potential likely facilitated the observed ionosphere expansion. This study characterizes Mars's magnetospheric and ionospheric response to the disappearing solar wind event in December 2022 During the event, open and closed field lines extend beyond the nominal bow shock location, just as the planetary cold ions The ionospheric ambipolar potential drop is enhanced from the nominal similar to -0.7 to similar to -2 V, likely facilitating the ionosphere expansion

AbstractMars once had a dense atmosphere enabling liquid water existing on its surface, however, much of that atmosphere has since escaped to space. We examine how incoming solar and solar wind energy fluxes drive escape of atomic and molecular oxygen ions (O+ and ) at Mars. We use MAVEN data to evaluate ion escape from 1 February 2016 through 25 May 2022. We find that Martian O+ and both have increased escape flux with increased solar wind kinetic energy flux and this relationship is generally logarithmic. Increased solar wind electromagnetic energy flux also corresponds to increased O+ and escape flux, however, increased solar wind electromagnetic energy flux seems to first dampen ion escape until a threshold level is reached, at which point ion escape increases with increasing electromagnetic energy flux. Increased solar irradiance (both total and ionizing) does not obviously increase escape of O+ and . Our results suggest that the solar wind electromagnetic energy flux should be considered along with the kinetic energy flux as an important driver of ion escape, and that other parameters should be considered when evaluating solar irradiance's impact on O+ and escape.

Charles Bowers, James Slavin, Gina DiBraccio, Gang Kai Poh, Shaosui Xu, David Brain, Jared Espley, and David Mitchell Department of Climatology and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA (@umich.edu) NASA Goddard Space Flight Center, Greenbelt, MD, USA (@nasa.gov) University of California, Berkeley, CA, USA (@berkeley.edu) Laboratory of Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA (@colorado.edu