Asymmetries in Mars' Exosphere: Implications for X-ray and ENA Imaging

Observations and simulations show that Mars' atmosphere has large seasonal variations. Total atmospheric density can have an order of magnitude latitudinal variation at exobase heights. By numerical simulations we show that these latitude variations in exobase parameters induce asymmetries in the hydrogen exosphere that propagate to large distances from the planet. We show that these asymmetries in the exosphere produce asymmetries in the fluxes of energetic neutral atoms (ENAs) and soft X-rays produced by charge exchange between the solar wind and exospheric hydrogen. This could be an explanation for asymmetries that have been observed in ENA and X-ray fluxes at Mars.Comment: Submitted to Space Science Review. v2: Minor changes in text and figure

Characteristics of proton velocity distribution functions in the near-lunar wake from Chandrayaan-1/SWIM observations

Due to the high absorption of solar wind plasma on the lunar dayside, a large scale wake structure is formed downstream of the Moon. However, recent in-situ observations have revealed the presence of protons in the near-lunar wake (100 km to 200 km from the surface). The solar wind, either directly or after interaction with the lunar surface (including magnetic anomalies), is the source of these protons in the near-wake region. Using the entire data from the SWIM sensor of the SARA experiment onboard Chandrayaan-1, we analysed the velocity distribution of the protons observed in the near-lunar wake. The average velocity distribution functions, computed in the solar wind rest frame, were further separated based on the angle between the upstream solar wind velocity and the IMF. Several proton populations were identified from the velocity distribution and their possible entry mechanism were inferred based on the characteristics of the velocity distribution. These entry mechanisms include (i) diffusion of solar wind protons into the wake along IMF, (ii) the solar wind protons with finite gyro-radii that are aided by the wake boundary electric field, (iii) solar wind protons with gyro-radii larger than lunar radii from the tail of the solar wind velocity distribution, and (iv) scattering of solar wind protons from the dayside lunar surface or from magnetic anomalies. In order to gain more insight into the entry mechanisms associated with different populations, backtracing is carried out for each of these populations. For most of the populations, the source of the protons obtained from backtracing is found to be in agreement with that inferred from the velocity distribution. There are few populations that could not be explained by the known mechanisms and remain unknown.Comment: 8 figures, paper accepted in Icarus (2016), http://dx.doi.org/10.1016/j.icarus.2016.01.03

Flow of forces and couples to the cylindrical solids through system asymmetry thin-walled elements of varying stiffness

Задача про передачу силового і моментного навантаження до криволінійного отвору нескінченної ізотропної пластинки через систему несиметричних відносно серединної площини тонкостінних елементів змінної жорсткості зведена до системи чотирьох сингулярних інтегрально– диференціальних рівнянь з ядрами Гільберта. Методом колокації досліджується вплив на напружений стан пластинки несиметричності підсилень, способу їх розміщення на контурі отвору.The problem of flow of forces and couples to the curvilinear hole in a infinite isotropic plate through system of asymmetrical by a middle plane the thin-walled elements of varying stiffness reduce to the system of four singular integral-differential equations with cores of Hilbert. The effect of asymmetry strengthens and location mode by method of collocation does investigate

Economic incentives for preserving biodiverse semi-natural pastures with calves from dairy cows

Economical profitability of pasture-based beef production is necessary for continued maintenance of semi-natural pastures. In a situation of decreased cattle stocks, there is a potential to castrate male calves from dairy cows and raise them as grazing steers instead of intact bulls reared indoors, which is the common way in the Nordic countries. We examined the profitability in model enterprises with either grazing steers or indoor bulls. Within the two genders (steer and bull), there were animals of two breed types (pure dairy breed and dairy x beef crossbreed), which were divided into an intensive or extensive production system. The intensive steer system had one summer on grass and slaughter at 21 months of age whereas the extensive steer system had two summers on grass and slaughter at 28 months of age. All bulls were reared indoors and slaughtered at 15 or 18 months of age. The profitability was calculated as contribution margin (CM; sigma revenues - sigma variable costs) in three different herd sizes (50, 100 and 150 slaughtered animals per year) and in three different regions in Sweden (the southern forest districts Gsk, the southern plain districts Gns, and the lower parts of the northern Nn). In the basic calculation, CM for all steers in large herds with 150 slaughtered animals per year was above zero for all cases in Gns, and for one case in Nn and in Gsk respectively. However, all steer cases had lower CM than the comparable bull system in the basic calculation. Sensitivity analyses demonstrate several possible ways of increasing the competitiveness of the grazing steers, compared to the bulls. Utilization of buildings without opportunity cost resulted in a CM above zero for all cases. Increasing the proportion of semi-natural pastures rendering high agrienvironmental payment and support was another effective mean. Decreasing the winter feed cost and labour demand on pasture reduced the costs, whereas producing premium-price certified pasture beef increased the revenue, all measures further contributing to an improved profitability. Pasture-based beef production from dairy-born steers can be economically viable, especially in large herds and with extensive production systems. Thereby, we conclude this system to has a potential to graze large areas of semi-natural pastures and thereby conserve their biodiversity and cultural values

Baseline Pro-Inflammatory Cytokine Levels Moderate Psychological Inflexibility in Behavioral Treatment for Chronic Pain

Background: The medical and scientific communities struggle to understand chronic pain and find effective treatments. Multimodal approaches are encouraging but show significant individual differences. Methods: Seventy-eight persons (56 women) with chronic pain received Acceptance and Commitment Therapy and provided blood samples before and after treatment. The participants completed surveys with the blood sampling. Blood plasma was analyzed for IL-6 and TNF-α levels with the Olink Inflammation Panel (Olink Bioscience Uppsala, Sweden). The treatment effects and moderating effects of low-grade inflammation on changes in outcomes were analyzed using linear mixed models. Results: Pain interference (p < 0.001) and psychological inflexibility (p < 0.001) improved significantly during treatment, but pain intensity did not (p = 0.078). Cytokine levels did not change over the course of the treatment (IL-6/TNF-α p = 0.086/0.672). Mean baseline levels of IL-6 and TNF-α moderated improvement in psychological inflexibility during the course of treatment (p = 0.044), but cytokine levels did not moderate changes in pain interference (p = 0.205) or pain intensity (p = 0.536). Conclusions: Higher baseline inflammation levels were related to less improvement in psychological inflexibility. Low-grade inflammation may be one factor underlying the variability in behavioral treatment in chronic pain.publishedVersio

Extremely high reflection of solar wind protons as neutral hydrogen atoms from regolith in space

We report on measurements of extremely high reflection rates of solar wind particles from regolith-covered lunar surfaces. Measurements by the Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft in orbit around the Moon show that up to 20% of the impinging solar wind protons are reflected from the lunar surface back to space as neutral hydrogen atoms. This finding, generally applicable to regolith-covered atmosphereless bodies, invalidates the widely accepted assumption that regolith almost completely absorbs the impinging solar wind.Comment: 2 figure

Three-Dimensional Modeling of Callisto's Surface Sputtered Exosphere Environment

We study the release of various elements from Callisto's surface into its exosphere by plasma sputtering. The cold Jovian plasma is simulated with a 3D plasma-planetary interaction hybrid model, which produces 2D surface precipitation maps for magnetospheric H+ , O+ , O++ , and S++ . For the hot Jovian plasma, we assume isotropic precipitation onto the complete spherical surface. Two scenarios are investigated: One where no ionospheric shielding takes place and accordingly full plasma penetration is implemented ('no ionosphere' scenario), and one where an ionosphere lets virtually none of the cold plasma but all of the hot plasma reach Callisto's surface ('ionosphere' scenario). In the 3D exosphere model, neutral particles are sputtered from the surface and followed on their individual trajectories. The 3D density profiles show that whereas in the 'no ionosphere' scenario the ram direction is favored, the 'ionosphere' scenario produces almost uniform density profiles. In addition, the density profiles in the 'ionosphere' scenario are reduced by a factor of ~2.5 with respect to the 'no ionosphere' scenario. We find that the Neutral gas and Ion Mass spectrometer, which is part of the Particle Environment Package on board the JUICE mission, will be able to detect the different sputter populations from Callisto's icy surface and the major sputter populations from Callisto's non-icy surface. The chemical composition of Callisto's exosphere can be directly linked to the chemical composition of its surface, and will offer us information not only on Callisto's formation scenario but also on the building blocks of the Jupiter system.Comment: Published in JGR: Space Physic

Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Micro-Channel Plates

A Micro-Channel Plate (MCP) is a widely used component for counting particles in space. Using the background counts of MCPs on Mars Express and Venus Express orbiters operated over 17 years and 8 years, respectively, we investigate the galactic cosmic ray (GCR) characteristics in the inner solar system. The MCP background counts at Mars and Venus on a solar cycle time scale exhibit clear anti-correlation to the sunspot number. We conclude that the measured MCP background contain the GCR information. The GCR characteristics measured using the MCP background at Mars show features that are consistent with the ground-based measurement in solar cycle 24. The time lag between the sunspot number and the MCP background at Mars is found ~9 months. The shorter-term background data recorded along the orbits (with a time scale of several hours) also show evident depletion of the background counts due to the absorption of the GCR particles by the planets. Thanks to the visible planetary size change along an orbit, the GCR contribution to the MCP background can be separated from the internal contribution due to the \b{eta}-decay. Our statistical analysis of the GCR absorption signatures at Mars implies that the effective absorption size of Mars for the GCR particles have a >100 km larger radius than the solid Martian body.Comment: Submitted to ApJ (2022-03-19

First observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms

The Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft has produced for the first time an image of a lunar magnetic anomaly in backscattered hydrogen atoms. The image shows that a partial void of the solar wind, a mini-magnetosphere, is formed above the strong magnetic anomaly near the Crisium antipode. The mini-magnetosphere is 360 km across at the surface and is surrounded by a 300-km-thick region of enhanced plasma flux that results from the solar wind flowing around the mini-magnetosphere. The mini-magnetosphere is visible only in hydrogen atoms with energy exceeding 150 eV. Fluxes with energies below 100 eV do not show corresponding spatial variations. While the high-energy atoms result from the backscattering process, the origin of the low-energy component is puzzling. These observations reveal a new class of objects, mini-magnetospheres, and demonstrate a new observational technique to study airless bodies, imaging in backscattered neutral atoms.Comment: 17 pages, 3 figure

Mars Express science highlights and future plans

21st EGU General Assembly, EGU2019, proceedings from the conference held 7-12 April, 2019 in Vienna, Austria, id.11100After 15 years in orbit Mars Express remains one of ESA's most scientifically productive Solar System missions whose publication record now exceeds 1200 papers. Characterization of the geological processes on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent results suggest episodic geological activity as well as the presence of large bodies of liquid water in several provinces (e.g. Eridania Planum, Terra Chimeria) in the early and middle Amazonian epoch and formation of vast sedimentary plains north of the Hellas basin. Mars Express observations and experimental teams provided essential contribution to the selection of the Mars-2020 landing sites. Recent discovery of subglacial liquid water underneath the Southern polar cap has proven that the mission science potential is still not exhausted. More than a decade-long record of the atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO2 clouds distribution, collected by SPICAM, PFS, OMEGA, HRSC and VMC together with subsequent modeling have provided key contributions to our understanding of the martian climate. Recent spectroscopic monitoring of the 2018 dust storm revealed dust properties, their spatial and temporal variations and atmospheric circulation. More than 10,000 crossings of the bow shock by Mars Express allowed ASPERA-3 to characterize complex behavior of the magnetic boundary topology as function of the solar EUV flux. Observations of the ion escape during complete solar cycle revealed important dependencies of the atmospheric erosion rate on parameters of the solar wind and EUV flux and established global energy balance between the solar wind and escaping ion flow. The observations showed that ion escape can be responsible for removal of about 10 mbar over the Mars history that implies existence of other more effective escape channels. The structure of the ionosphere sounded by the MARSIS radar and the MaRS radio science experiment was found to be significantly affected by the solar activity, the crustal magnetic field, as well as by the influx of meteorite and cometary dust. MARSIS and ASPERA-3 observations suggest that the sunlit ionosphere over the regions with strong crustal fields is denser and extends to higher altitudes as compared to the regions with no crustal anomalies. Several models of the upper atmosphere and plasma environment are being developed based on and in support of the collected experimental data. The models aim at creating user-friendly data base of plasma parameters similar to the Mars Climate Database that would be of great service to the planetary community. A significant recent achievement was the flawless transition to the >gyroless> attitude control and operations mode on the spacecraft, that would allow mitigating the onboard gyros aging and extending the mission lifetime. In November 2018 ESA's Science Programme Committee (SPC) confirmed the mission operations till the end of 2020 and notionally approved its extension till the end of 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans focusing on synergistic science with TGO