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Using data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we explore the plasma properties of Martian magnetotail current sheets (CS), to further understand the solar wind interaction with Mars and ion escape. There are some CS exhibit energetic oxygen ions that show narrow beam structures in the energy spectrum, which primarily occurs in the hemisphere where the solar wind electric field (Esw) is directed away from the planet. On average, these CS have a higher escaping flux than that of the CS without energetic oxygen ion beams, suggesting different roles in ion escape. The CS with energetic oxygen ion beams exhibits different proton and electron properties to the CS without energetic oxygen ion beams, indicating their different origins. Our analysis suggests that the CS with energetic oxygen ion beams may result from the interaction between the penetrated solar wind and localized oxygen ion plumes. Plain Language Summary: Ion escape into space, driven by solar wind interactions with Mars, plays a pivotal role in the evolution of the Martian atmosphere. An important escape channel of planetary oxygen ions is the current sheet in the nightside magnetotail. Yet, our existing understanding of plasma characteristics within this magnetic structure remains quite limited. Based on the MAVEN observations, we find the current sheets can be categorized into two distinct types according to the energy distribution patterns of oxygen ions: one is with the appearance of energetic oxygen ions with narrow beam structure, the other one is not. On average, the current sheets with energetic oxygen ion beams have a higher escaping flux than those without, suggesting different roles in ion escape. Furthermore, the two types of current sheets exhibit markedly distinct plasma properties, indicating that they have different origins. Here we suggest that the current sheet with energetic oxygen ion beams arise from the interaction between the penetrated solar wind and localized oxygen ion plumes. Key Points: Martian magnetotail current sheets occasionally exhibit energetic oxygen ions that show beam structures in the energy spectrumThe current sheets with energetic oxygen ion beam usually have a higher escaping flux than those withoutPlasma properties in current sheets differ significantly differences between those with and without energetic oxygen ion beams [ABSTRACT FROM AUTHOR]

Several techniques are under development for image-guidance in particle therapy. Positron (β+) emission tomography (PET) is in use since many years, because accelerated ions generate positron-emitting isotopes by nuclear fragmentation in the human body. In heavy ion therapy, a major part of the PET signals is produced by β+-emitters generated via projectile fragmentation. A much higher intensity for the PET signal can be obtained using β+-radioactive beams directly for treatment. This idea has always been hampered by the low intensity of the secondary beams, produced by fragmentation of the primary, stable beams. With the intensity upgrade of the SIS-18 synchrotron and the isotopic separation with the fragment separator FRS in the FAIR-phase-0 in Darmstadt, it is now possible to reach radioactive ion beams with sufficient intensity to treat a tumor in small animals. This was the motivation of the BARB (Biomedical Applications of Radioactive ion Beams) experiment that is ongoing at GSI in Darmstadt. This paper will present the plans and instruments developed by the BARB collaboration for testing the use of radioactive beams in cancer therapy. [ABSTRACT FROM AUTHOR]

Recent observations and particle‐tracing models have revealed a counterintuitive difference between the behaviors of magnetospheric protons and oxygen ions when they encounter the magnetopause. The oxygen ions usually meander around the magnetopause without a full escape to the magnetosheath, whereas the protons can more easily stream across the magnetopause despite their smaller gyroradii. Here, we analytically identify the mechanisms that cause this species dependence. As magnetospheric ions drift toward the magnetopause, the grazing angle of their magnetopause encounter is constrained within a narrow range near 0°, with its maximum being proportional to the square root of the ion gyroradius. It is the grazing angle that largely determines the follow‐up ion motion. The ions with larger grazing angles would meander around the magnetopause, whereas the meandering motion for ions with smaller grazing angles could be easily disrupted to enable their escape even if the normal magnetic field is very weak. Plain Language Summary: The Earth's magnetic field is constrained by the interplanetary field within a finite region named the magnetosphere. The boundary of this region, the magnetopause, separates the magnetospheric plasma from the cooler and denser population in the shocked solar wind. Some of the magnetospheric particles, however, can still penetrate the magnetopause and escape into the interplanetary space. One may expect that heavy ions, like singly charged oxygen ions, are more likely to escape than protons due to their larger gyroradii; however, the opposite trend has been identified in spacecraft observations. This counterintuitive feature, although reproduced in a particle‐tracing model, has not yet been fully understood. Here, we analyze the particle trajectories to identify the mechanism underlying the species dependence of the ion escape. When magnetospheric ions encounter the magnetopause, their grazing angles are constrained within a narrow range near 0°, with the maximum angle depending positively on ion gyroradius. We find that the ions with larger grazing angles would meander around the magnetopause without a full escape, whereas the meandering motion for those with smaller angles could be more easily disrupted by a weak normal magnetic field to enable their field‐aligned escape. Key Points: Despite their smaller gyroradii, protons are found more likely to escape from the magnetosphere than oxygen ionsA mechanism leading to the counterintuitive species dependence is analytically identified based on a simple modelThe model also explains the bifurcated gyrophase bunching of the oxygen ions observed in the magnetosheath [ABSTRACT FROM AUTHOR]

The present study reports a gas‐phase photoelectrochemical (GPEC) system in which photoanode and photocathode materials are coated on each side with a pellet of the oxygen‐ion conductor yttria‐stabilized zirconia (YSZ), where light irradiation is feasible on both sides. As a model gas‐phase reaction, we chose dry reforming of methane (DRM), which converts greenhouse gases into valuable syngas. Consequently, the stoichiometric DRM reaction proceeded in our GPEC system, indicating that the oxygen ions in a YSZ pellet act as mediators to link the redox reactions. It was also noted that UV light irradiation on the anodic side was more effective than that on the cathodic side, suggesting that the photogenerated holes in the anodic YSZ side activate methane molecules, while photogenerated electrons are injected into Rh nanoparticles to cause carbon dioxide reduction in the cathodic side. Our GPEC system converts greenhouse gases into valuable syngas by light irradiation. [ABSTRACT FROM AUTHOR]

Ionospheric outflow is an important plasma source that feeds the near‐Earth magnetotail with heavy oxygen ions. Because these ions can significantly alter the structure and stability of the magnetotail current sheet, the characteristics of this outflow are important for accurate magnetosphere modeling, including modeling of substorms—a key element of magnetosphere dynamics. Using Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements in the magnetotail (around the plasma sheet boundary), we investigate characteristics oxygen outflows observed during substorm growth phases. The observed oxygen ion temperature and flow energy indicate that the outflow is marginally stable to ion acoustic wave generation: The oxygen temperature is slightly lower than the electron temperature and slightly higher than the oxygen flow energy. Moreover, the observed outflows are accompanied by low frequency electrostatic waves that may contribute to outflow thermalization. The oxygen bulk velocity has a significant component directed toward the equatorial plane, originating from the cross‐field drift in the convection electric field. The estimated radial distances at which oxygen ions reach the plasma sheet are ∼20–40RE downtail, that is, outflows during substorm growth phases can alter current sheet characteristics around the potential magnetic reconnection region. Key Points: We present observations of ionospheric oxygen outflow during the substorm growth phaseTypical oxygen outflow is marginally stable to ion acoustic wave generationOxygen ions drift toward the equatorial plane because of convection electric field [ABSTRACT FROM AUTHOR]

The D‐shaped ion velocity distribution generated by the time‐of‐flight (ToF) effect can be considered as an important characteristic of reconnection exhausts in the magnetopause and magnetotail reconnection processes. In this study, we reported the D‐shaped velocity distribution of O+ ions produced by the ToF effect in the magnetotail reconnection exhaust based on the observations from the Cluster spacecraft. The observed cutoff velocity of O+ ions is smaller than that of H+ ions at the same time, which is different from the previous theoretical prediction. We suggested that the difference between the two cutoff velocities is probably due to O+ ions having a larger reconnection diffusion region than H+ ions. We also demonstrated a remote‐sensing method to estimate the spatial scale ratio between the O+ and H+ diffusion regions and the distance from the observation site to the center of the magnetotail reconnection region. Plain Language Summary: The reconnection processes at the Earth's magnetopause and magnetotail can convert the magnetic energy into the kinetic energy of the plasma, thus producing high‐speed reconnection exhausts. The exhausting ions usually show a D‐shaped velocity distribution caused by the time‐of‐flight effect. Previous works usually focused only on exhausting protons from the reconnection site, while O+ ions could also be abundant during geomagnetic active times. In this study, we analyzed a reconnection event to investigate the behaviors of O+ and H+ ions in the magnetotail reconnection exhaust region using the observations from the Cluster spacecraft. It is suggested that different behaviors of H+ and O+ ions are probably due to O+ ions having a larger reconnection diffusion region than H+ ions. In addition, we proposed a remote‐sensing method to estimate the spatial scale ratio between the O+ and H+ diffusion regions and the distance from the observation site to the center of the magnetotail reconnection region. Key Points: The time‐of‐flight effect of O+ ions in magnetotail reconnection exhaust was observed by the Cluster spacecraftThe observed cutoff velocity of O+ is smaller than that of H+, indicating that O+ may have a larger diffusion region than H+A remote‐sensing method to estimate the spatial scale ratio between O+ and H+ diffusion regions is introduced [ABSTRACT FROM AUTHOR]

Cluster observed two intermittent oxygen ion (O+) flux enhancements with energy dispersions in a dipolarizing flux bundle, which is known as a region of enhanced northward magnetic field (Bz) embedded in the earthward high‐speed flow. The flux enhancements of O+ show clear pitch angle dependences, which are termed as butterfly distributions. Two corresponding flux enhancements of field‐aligned protons (H+) are also shown in its spectrum, but they are weaker and emerge later (~10 s) than those of O+. Simulation shows that both enhanced ion species are the counterstreaming populations. They originated from the lobe region and were driven into the center plasma sheet by the dawn‐dusk electric field (Ey). Backward tracing test‐particle simulations reproduce the butterfly O+ and the counterstreaming H+ distribution. The differences between O+ and H+ are because of their different gyroradii. The lobe O+ can arrive at the magnetic equatorial plane in less than one gyromotion due to its large gyroradius, and O+ with a larger field‐aligned velocity can arrive at the equatorial plane earlier, leading to the energy and pitch angle dependence. While H+ with similar energy can drift into dipolarizing flux bundle through electric field drift (E × B motion) and arrive at the equatorial plane through adiabatic motion, which consequently forms the field‐aligned flux enhancements in dipolarizing flux bundle, that is, the Bz‐dominant region. The simulation further confirms that intermittent increases of Ey component can produce the two intermittent flux enhancements, as indicated in the in situ observation. Key Points: Two intermittent butterfly O+ and counterstreaming H+ flux enhancements are observed in a dipolarizing flux bundleO+ enhancements are more intense and emerge earlier than those of H+Convection electric field plays a key role in the formation of butterfly O+ and counterstreaming H+ [ABSTRACT FROM AUTHOR]

We present a statistical study of magnetotail flows that change direction from earthward to tailward using Cluster spacecraft. More precisely, we study 318 events of particle flux enhancements in the O+ data for which the pitch angle continuously changes with time, either from 0° to 180° or from 180° to 0°. These structures are called "Pitch Angle Slope Structures" (PASSes). PASSes for which the pitch angle changes from 0° to 180° are observed in the Northern Hemisphere while those for which the pitch angle changes from 180° to 0° are observed in the Southern Hemisphere. These flux enhancements result in a reversal of the flow direction from earthward to tailward regardless of the hemisphere where they are observed. Sometimes, several PASSes can be observed consecutively which can therefore result in oscillatory velocity signatures in the earth‐tail direction. The PASS occurrence rate increases from 1.8% to 3.7% as the AE index increases from ∼0 to ∼600 nT. Also, simultaneously to PASSes, there is typically a decrease in the magnetic field magnitude due to a decrease (increase) of the sunward component of the magnetic field in the Northern (Southern) Hemisphere. Finally, based on the 115 (out of 318) PASSes that show energy‐dispersed structures, the distance to the source from the spacecraft is estimated to be typically <25RE along the magnetic field line. This study is important as it sheds light on one of the causes of tailward velocities in Earth's magnetotail. Key Points: Flow reversals from earthward to tailward can be due to an enhanced flux of earthward moving particles which move tailward after mirroringFlow reversals can be flux enhancements for which the pitch angle changes from 0° (180°) to 180° (0°) in the Northern (Southern) HemisphereThe particles forming the flow reversals have typically traveled <25RE from the apparent source to the spacecraft [ABSTRACT FROM AUTHOR]

Purpose: The main advantages of charged particle radiotherapy compared to conventional X-ray external beam radiotherapy are a better tumor conformality coupled with the capability of treating deep-seated radio-resistant tumors. This work investigates the possibility to use oxygen beams for hadron therapy, as an alternative to carbon ions. Materials and Methods: Oxygen ions have the advantage of a higher relative biological effectiveness (RBE) and better conformality to the tumor target. This work describes the mixed radiation field produced by an oxygen beam in water and compares it to the one produced by a therapeutic carbon ion beam. The study has been performed using Geant4 simulations. The dose is calculated for incident carbon ions with energies of 162 MeV/u and 290 MeV/u, and oxygen ions with energies of 192 MeV/u and 245 MeV/u, and hence that the range of the primary oxygen ions projectiles in water was located at the same depth as the carbon ions. Results: The results show that the benefits of oxygen ions are more pronounced when using lower energies because of a slightly higher peak-to-entrance ratio, which allows either providing higher dose in tumor target or reducing it in the surrounding healthy tissues. It is observed that, per incident particle, oxygen ions deliver higher doses than carbon ions. Conclusions: This result coupled with the higher RBE shows that it may be possible to use a lower fluence of oxygen ions to achieve the same therapeutic dose in the patient as that obtained with carbon ion therapy. [ABSTRACT FROM AUTHOR]

Oxygen (O+) enhancements in the inner magnetosphere are often observed during geomagnetically active times, such as geomagnetic storms. In this study, we quantitatively examine the difference in ring current dynamics with and without a substantial O+ ion population based on almost 6 years of Van Allen Probes observations. Our results have not only confirmed previous finding of the role of O+ ions to the ring current but also found that abundant O+ ions are always present during large storms when sym‐H < −60 nT without exception, while having the pressure ratio (ℛ) between O+ and proton (H+) larger than 0.8 and occasionally even larger than 1 when L < 3. Simultaneously, the pressure anisotropy decreases with decreasing sym‐H and increasing L shell. The pressure anisotropy decrease during the storm main phase is likely related to the pitch angle isotropization processes. In addition, we find that ℛ increases during the storm main phase and then decreases during the storm recovery phase, suggesting faster buildup and decay of O+ pressure compared to H+ ions, which are probably associated with some species dependent source and/or energization as well as loss processes in the inner magnetosphere. Plain Language Summary: The behavior of the ionospheric O+ ions in the Earth's ring current should be carefully examined in order to advance our understanding of the role of ion composition in ring current dynamics. This problem has been extensively studied using past spacecraft missions. In this study, we revisit this problem based on almost 6 years of high‐quality data from the Van Allen Probes and have confirmed previous finding about the role of O+ ions to the ring current. For example, more O+ ions contribute to the ring current as sym‐H decreases, and O+ and total plasma pressures dramatically build up during storm time. Besides, our statistical results also provide evidence that without exception, ionospheric O+ ions make a significant contribution to the ring current during active time and their relative contribution to the ring current increases during the storm main phase and then decreases during the storm recovery phase compared to those of H+ ions, suggesting a faster buildup and decay of O+ pressure. In addition, the decrease of pressure anisotropy during the storm main phase is related to the pitch angle isotropization, which is probably caused by current sheet scattering or wave‐particle interaction. Key Points: We quantitatively examine how the total plasma pressure and pressure anisotropy changes with and without a substantial O+ ion populationO+ ions always make a nonnegligible contribution to the ring current when sym‐H < ‐60 nT with ℛ > 0.8The decrease of pressure anisotropy during storm main phase is related to pitch angle isotropization [ABSTRACT FROM AUTHOR]

The relationship between dispersive Alfvén waves (DAWs), magnetospheric activity, and O+ ion outflow/energy density is examined using measurements from the Van Allen Probes. We show that correlated DAW activity and O+ outflow/energization is a characteristic feature of the inner magnetosphere during active conditions and during storms persists for several hours over large L‐shell and azimuthal ranges of the plasma sheet. Though enhanced during substorm and storm active periods, these correlated features are most intense during geomagnetic storms. Comparisons show a linear relationship between DAW electric (and magnetic) field energy density and outflowing O+ energy. Statistical measurements from a large number of storms also reveal a linear relationship between DAW energy density and gross enhancements in energetic O+ energy densities. These observations support the notion that DAWs play an important role in the energization of O+ ions into and within the inner magnetosphere. Plain Language Summary: Geomagnetic storms are major disturbances in the Earth's magnetosphere, during which the particle content and pressure in the magnetosphere increase considerably. Much of the pressure increase is due to singly charged oxygen ions that come from the ionosphere. How this happens is not clear. Analyzing satellite observations, we found evidence suggesting that a particular type of low‐frequency electromagnetic wave called a dispersive Alfvén wave may be playing a key role. These waves are found to be more prevalent and intense in the magnetosphere during storms. Oxygen ion energies are shown to increase with increasing intensities of these waves. The oxygen ion contribution to pressure also increases in association with intensified wave activity. These observations support the notion that the waves energize and heat oxygen ions into and within the magnetosphere over extended periods of time, which leads to significant magnetospheric pressure increases. Key Points: Dispersive Alfven wave energy density is enhanced during substorms and geomagnetic stormsOxygen ion outflow energy and energy density are correlated with dispersive Alfven wave energy densityObservations support modeling that dispersive Alfven waves enhance oxygen ion energy density in the inner magnetosphere [ABSTRACT FROM AUTHOR]

Ion transport from the plasma sheet to the ring current is the main cause of the development of the ring current. Energetic (>150 keV) ring current ions are known to be transported diffusively in several days. A recent study suggested that energetic oxygen ions are transported closer to the Earth than protons due to the diffusive transport caused by a combination of the drift and drift‐bounce resonances with Pc 3–5 ultralow frequency waves during the 24 April 2013 magnetic storm. To understand the occurrence conditions of such selective oxygen increase (SOI), we investigate the phase space densities (PSDs) between protons and oxygen ions with the first adiabatic invariants (μ) of 0.1–2.0 keV/nT measured by the Radiation Belt Storm Probes Ion Composition Experiment instrument on the Van Allen Probes at L ~ 3–6 during 90 magnetic storms in 2013–2017. We identified the SOI events in which oxygen PSDs increase while proton PSDs do not increase during a period of ~9 hr (one orbital period). Among the 90 magnetic storms, 33% were accompanied by the SOI events. Global enhancements of Pc 4 and Pc 5 waves observed by ground magnetometers during the SOI events suggest that radial transport due to combination of the drift‐bounce resonance with Pc 4 oscillations and the drift resonance with Pc 5 oscillations can be the cause of SOIs. The contribution of the SOI events to the magnetic storm intensity is roughly estimated to be ~9% on average. Key Points: Increases of >150‐keV oxygen ions without proton increases are observed in the inner magnetosphere during 30 magnetic storms out of 90The selective oxygen increases occur simultaneously with global enhancements of Pc 4 and Pc 5 ULF waves at L > 4 and L > 3, respectivelyStatistical results suggest that the selective oxygen increases are caused by the combination of drift and drift‐bounce resonances [ABSTRACT FROM AUTHOR]

A dipolarization front (DF) is known as the leading edge of an earthward high‐speed flow with a sharp enhancement in the northward magnetic field (Bz). Analysis of an event observed by Cluster shows that the behavior of oxygen ions (O+) around the DF is very different from protons (H+). After the crossing of the DF, the O+ density decreases more gradually than H+. The distance between the density minimum of O+ and the DF layer is ~4 times longer than that of H+, which is close to their gyroradii ratio with the same energy. A flux dropout is observed in the O+ energy spectrum, whose energy dependence indicates that ions with higher energies can reach locations farther tailward of the DF. Similar variations are also seen in studies of 22 events in which a common pattern of ion properties is obtained by performing a superposed epoch analysis. Finally, using backward tracing test‐particle simulations, we reproduce the characteristics of the flux dropout and verify that the time dependence of the dropout is highly correlated with the gyromotion of different energy O+ behind the DF. All these results provide a further understanding of ion dynamics associated with DFs and suggest that the observed O+ ions are reflected within a half gyromotion in the central plasma sheet. Key Points: The reflection of oxygen ions at the dipolarization front is studied in both observations and simulationsA flux dropout could be observed in the O+ spectrum, whose contour is energy dependent and highly correlated with the gyromotion of different energy O+O+ can extend to a further position after the DF due to its larger gyro‐radius than that of H+ with the same energy [ABSTRACT FROM AUTHOR]

Enlargement of memory window through forming compliance current was demonstrated in Gd:SiO2 resistive random access memory (RRAM) with a gadolinium (Gd) electrode. Lower forming compliance current for Gd:SiO2 RRAM with a Gd electrode results in larger memory window as compared with the RRAM with a Pt electrode. Through analyses on the current conduction mechanism, we demonstrate that a lower forming compliance current leads to a thinner conductive filament forming and less oxygen ions penetrating into Gd electrode, which caused higher on current and lower off current. Furthermore, a possible resistive switching model was proposed to explain the effect of Gd electrode on RRAM device. [ABSTRACT FROM AUTHOR]

A model of oxygen ion transport in molten V2O5 is proposed. Within the framework of this model, the values of the parabolic rate constant of the catastrophic oxidation of copper in contact with VO and oxygen flux through an ion transport membrane with liquid-channel grain-boundary structure on the basis of VO are calculated as k′′ = 2.4 × 10 kg/(m s) and J = 2.7 × 10 mol/(m s) at 700°C. These values are in agreement with the experimental data in order of magnitude, indicating the agreement between theory and experiment. [ABSTRACT FROM AUTHOR]

One of the most fundamental important issues in the space physics is to understand how solar wind energy transports into the inner magnetosphere. Ultra low frequency (ULF) wave in the magnetosphere and its impact on energetic particles, such as the wave-particle resonance, modulation, and particle acceleration, are extremely important topics in the Earth’s radiation belt dynamics and solar wind—magnetospheric coupling. In this review, we briefly introduce the recent advances on ULF waves study. Further, we will explore the density structures and ion compositions around the plasmaspheric boundary layer (PBL) and discuss its possible relation to the ULF waves. [ABSTRACT FROM AUTHOR]

Measurements of XPS survey, core levels (N 1s, O 1s, Pb 4f, I 3d), and valence band (VB) spectra of CH3NH3PbI3 (MAPbI3) hybrid perovskite prepared on different substrates (glass, indium tin oxide (ITO), and TiO2) aged under different light-soaking conditions at room temperature are presented. The results reveal that the photochemical stability of MAPbI3 depends on the type of substrate and gradually decreases when glass is replaced by ITO and TiO2. Also, the degradation upon exposure to visible light is accompanied by the formation of MAI, PbI2, and Pb0 products as shown by XPS core levels spectra. According to XPS O 1s and VB spectra measurements, this degradation process is superimposed on the partial oxidation of lead atoms in ITO/MAPbI3 and TiO2/MAPbI3, for which Pb–O bonds are formed due to the diffusion of the oxygen ions from the substrates. This unexpected interaction leads to additional photochemical degradation. [ABSTRACT FROM AUTHOR]