Ions In Plume Research Articles

Ultra-low frequency discharge instability of a barium tungsten hollow cathode at lower self-sustaining margin

Development of low-orbiting constellations stimulated the demand for low-power Hall thrusters, as well as their accompanying low-current hollow cathodes. In this paper, such cathodes were tested on quite low currents to search their self-sustaining limit, and were found to exhibit an ultra-low frequency instability at lower current limit. The instability would grow fast when the cathode current was below 0.3A, and oscillate on 0.1Hz to a few Hz with a visibly blinking plume. At the same time, the emitter temperature was fluctuating with a 15 °C peak-to-peak amplitude. The instability was confirmed to originate from the cathode interior, as a result of depleted plasma heating. Then the thermionic cathode had to rely mainly on neutral gas to heat the emitter. Because thermionic emission was in exponential relation with emitter temperature, the temperature fluctuation was then amplified to cause larger fluctuation in total current as well as in total discharge power, which led to deeper fluctuation in temperature. Regarding the heating of both neutral gas and emitter, an instability model showed that multiple unnoticed factors could determine the onset of instability, including the thermal inertia of neutral gas and emitter, the heat transfer from discharging plasma to neutral gas, the heat loss of cathode and the response time of power supply. As a result of this instability, the plume ion energy was elevated from <50eV to 30∼120eV due to the fluctuating density on cathode exit and fluctuating discharge voltage. It was estimated that the increased ion energy could accelerate the keeper erosion by 4∼22 times.

Fabrication of Isotope-Enriched Nanostructures Using Ultrafast Laser Pulses under Ambient Conditions for Biomolecular Sensing.

Recent advances in the use of stable isotopes necessitate novel synthesis techniques for isotope separation and enrichment that are scalable and offer high throughput. Stable-isotope-enriched nanostructures can offer unique advantages as nanomedicines, safe tracers, and labels and are critical for applications in various industrial processes, metabolic research, and medicine. So far, there exists no method to synthesize miniature isotope-enriched materials at the nanoscale. In this study, an ultrafast Laser-induced isotope enrichment at nanoscale (LIIEN) is put forward to synthesize isotope-enriched nanostructures, eliminating the need for large equipment and expenses, thereby demonstrating a lab-scale isotope enrichment process. A significant isotope enrichment for Carbon nanostructures is observed. The isotope enrichment can be attributed to the redistribution of isotope ions in the plasma plume explained by the plasma centrifuge model. The LIIEN synthesized structures exhibit excellent Surface-Enhanced Raman Scattering (SERS)signal enhancement and reproducibility, making them potential candidates for SERS-based biomolecule sensing. This technique is an efficient method to fabricate nanosized isotope-enriched structures of characteristic properties by carefully tuning laser parameters at ambient conditions.

Effect of pulse frequency on discharge characteristics of Hall thruster under pulsating operation

In this study, the effect of pulse frequency on the discharge and plume characteristics of Hall thrusters under pulsating operation is investigated. The experimental results show that the discharge current and thrust decrease as the frequency increases to the range of 30–90 kHz. The efficiency of the thruster is negatively correlated with the pulse frequency, and the pulse frequency minimally affects the plume divergence angle and ion current. It is found that an increase in the pulse frequency decreases the secondary electron emission flux on the wall and the near-wall conduction rate of electrons in the channel, thus consequently decreasing the electron current. An increase in the electron current share improves the current-utilization efficiency. In addition, as the frequency increases, the ion power loss on wall increases and the ion acceleration becomes less effective, thus resulting in a decrease in thrust. The combined effect of these two factors results in an increase in the anode efficiency as the frequency increases.

The Energetic Oxygen Ion Beams in the Martian Magnetotail Current Sheets: Hints From the Comparisons Between Two Types of Current Sheets

AbstractUsing 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.

Modelling an Ion Thruster for a Small Spacecraft in Very Low Earth Orbit

A gridded ion thruster running on two different propellants (Xenon and Iodine) and sited within a 3U CubeSat satellite, is modelled in a Low-Earth-Orbit (altitude 400 km), using a Particle-in-Cell approach. Charged exchange collisions cause a plume backflow, which results in erosion or contamination of external spacecraft surfaces. In particular, this research is motivated by evaluating the risks to solar panel arrays from plume backflow. At low altitudes there is a wide range of ambient species able to interact electrostatically with the ion plume. In particular one must consider the plasma potential of the incoming particle flux at the solid boundaries as well as a sheath comparison and the temperature of the solar panel surfaces. This enables evaluation of the effect of temperature on the charged exchange region. A Particle-in-Cell is used, with a hybrid approach where electrons are treated as a fluid and the propellant as kinetic particles. Our results compare surface ablation for two propellants, focusing on solar panel arrays which are considered to be especially vulnerable to the backflow of ions from the plume expansion. It is found that the flux of incoming particles increases for lower satellite surface temperatures. Furthermore, Xenon results in having a lower overall effect on the sensitivity of the particle flux in comparison to Iodine.

Martian global current systems and related solar wind energy transfer: hybrid simulation under nominal conditions

ABSTRACT The magnetized solar wind drives a current system around Mars that maintains its induced magnetosphere. The solar wind also transfers its energy to the atmospheric ions, causing continuous atmospheric erosion, which has a profound impact on the planet’s evolution history. Here, we use Amitis, a Graphics Processing Unit (GPU)-based hybrid plasma model to first reproduce the global pattern of the net electric current and ion currents under an interplanetary magnetic field perpendicular to the solar wind flow direction. The resultant current distribution matches the observations and reveals more details. Using the electric field distribution characterized earlier with the same model, we calculate for the first time the spatial distribution of energy transfer rate to the plasmas in general and to different ion species at Mars. We find out that (1) the solar wind kinetic energy is the dominant energy source that drives Martian induced magnetosphere, (2) the energy flux of the shocked solar wind flows from the magnetic equatorial plane towards the plasma sheet in the induced magnetotail, (3) both the bow shock and the induced magnetospheric boundary are dynamos where plasma energy is transferred to the electromagnetic field, and (4) the planetary ions act as loads and gain energy from the electromagnetic field. The most intense load region is the planetary ion plume. The general pattern of the energy transfer rate revealed in this study is common for induced magnetospheres. Its variabilities with the upstream conditions can provide physical insight into the observed ion escape variabilities.

Performance and plasma diagnostics of the Air-breathing Microwave Plasma CAThode (AMPCAT) coupled to a cylindrical Hall thruster

The Air-breathing Microwave Plasma CAThode (AMPCAT) has been developed for air-breathing electric propulsion in very-low Earth orbit. In this study, the standalone AMPCAT plasma characteristics are analyzed by means of several diagnostic tools and operation on xenon is compared to a conventional hollow cathode. A transition of AMPCAT extracted current from a lower (&amp;lt;0.1 A) to higher-current (&amp;gt;0.5 A) mode, triggered by increasing the negative cathode bias voltage, is accompanied by a significant rise in internal electron density and external electron temperature. The AMPCAT is coupled with a cylindrical Hall thruster in the 100–300 W power-level running on 0.5–0.7 mg/s of xenon, and the thrust is directly measured for cathode operation with both xenon and air. Stable thruster operation is demonstrated for the AMPCAT running on both propellants. For xenon, the performance is compared to a hollow cathode, which reveals matching discharge current profiles but a significantly higher thrust for the AMPCAT at low discharge voltages, approximately two times higher at 200 V. Langmuir probe measurements highlight a 30–40 V lower plasma potential in the cathode vicinity for the AMPCAT with xenon compared to both the hollow cathode and AMPCAT with air. This indicates a significantly improved coupling of cathode electrons to the thruster discharge, yielding an increased degree of ionization. Faraday probe and Wien filter results show that a larger current utilization efficiency drives the observed performance difference at low discharge voltages, rather than a significant change in ion acceleration or plume divergence.

Enhanced energization of plume ions around Mars from interplanetary shocks

Heavy ions escaping Mars along the solar wind electric field direction are often referred to as an “ion plume”. This phenomenon represents one of the major ion escape channels on Mars. Spacecraft observations have indicated that the global average of escaping ion fluxes, derived with the aid of models, can be increased by an order of magnitude or more in response to strong solar events. In particular, it has been reported that interplanetary (IP) shocks produce high-energy escaping ion plumes. However, the ion acceleration mechanisms associated with the shock arrival have not yet been fully elucidated. During the passage of an IP shock on Mars on March 3, 2015, the plume O+ ions continuously entered the narrow field of view (FoV) of STATIC on board the MAVEN spacecraft, thanks to favorable FoV configurations. This event provides a unique opportunity to identify plume ion energization processes associated with the shock arrival. Our analysis suggests that the enhanced energization of the plume O+ ions is mainly due to the enhanced convection electric field caused by the IP shock compression. This finding provides a crucial clue towards the understanding of how IP shocks facilitate ion escape through the plume.

IMPROVEMENT LIFETIME OF THE HALL THRUSTER THROUGH MAGNETIC SYSTEM OPTIMIZATION

The object of research in this work is electromagnetic processes in the anode of a Hall thruster. The expansion of the requirements for the total impulse of Hall thrusters emphasizes the need to develop high-performance Hall thrusters, the operational life of which is determined by the amount of time during which the thruster can operate before the plasma in the channel damages the magnetic system. After complete erosion of the dielectric output from the discharge channel, the ion plume interacts with the inner and outer magnetic poles and causes progressive erosion of the magnetic conductor. A new magnetic topology called "magnetic shielding" has been described to reduce channel erosion. The purpose of the work is to increase the lifetime of the Hall thrusters by optimizing the parameters and topology of the magnetic field in the thruster.&#x0D; The use of modern programs makes it possible to determine the azimuthal distribution and configuration of the magnetic field in the acceleration channel and in the peripheral zone of the thruster, as well as obtain results that are close to real ones. In this regard, in this work, the method of mathematical modeling was chosen as a research method for conducting research on the magnetic field of the Hall thruster. The quantitative relationship between the magnitude and configuration of the magnetic field, thruster operation parameters, length, and the position of the ionization and acceleration layer in the discharge channel of the Hall thruster, which determines the boundaries of the erosion zones of the walls of the discharge chamber, was determined, namely: - it was established that the boundaries of the erosion zones on the outer and inner walls of the discharge chamber from the anode side are at the intersection of one "boundary" line of force of the magnetic field with the walls, the discharge voltage, the shape of the magnetic lens, the amount of induction and the material of the discharge chamber; - the position of this "limit" line of force is determined by the value along the middle line of the discharge chamber.

Effects of ion composition on escape and morphology on Mars

Abstract. We refine a recently presented method to estimate ion escape from non-magnetized planets and apply it to Mars. The method combines in situ observations and a hybrid plasma model (ions as particles, electrons as a fluid). We use measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission and Mars Express (MEX) for one orbit on 1 March 2015. Observed upstream solar-wind conditions are used as input to the model. We then vary the total ionospheric ion upflux until the solution fits the observed bow shock location. This solution is a self-consistent approximation of the global Mars–solar-wind interaction at the time of the bow shock crossing for the given upstream conditions. We can then study global properties, such as the heavy-ion escape rate. Here, we investigate in a case study the effects on escape estimates of assumed ionospheric ion composition, solar-wind alpha-particle concentration and temperature, solar-wind velocity aberration, and solar-wind electron temperature. We also study the amount of escape in the ion plume and in the tail of the planet. Here, we find that estimates of total heavy-ion escape are not very sensitive to the composition of the heavy ions or to the number and temperature of the solar-wind alpha particles. We also find that velocity aberration has a minor influence on escape but that it is sensitive to the solar-wind electron temperature. The plume escape is found to contribute 29 % of the total heavy-ion escape, in agreement with observations. Heavier ions have a larger fraction of escape in the plume compared to the tail. We also find that the escape estimates scale inversely with the square root of the atomic mass of the escaping ion species.

Tianwen-1 and MAVEN observations of Martian oxygen ion plumes

There is a significant Martian ion escape channel called the “plume”. Due to the lack of multi-point, high-resolution field and particle detections, the energization mechanism and source region identification of ion plumes by in situ measurements remain unclear. China's first Mars exploration mission, Tianwen-1, provides us an opportunity to study ion escape owing to the high altitude of its apoapsis (∼3 RM, RM is Mars radius). In this study, we take advantage of the joint observations of Tianwen-1 and Mars Atmosphere and Volatile EvolutioN (MAVEN) to study oxygen ion plumes. Our statistical results confirm the convection electric field acceleration as the energization mechanism of plume ions (up to >15 keV) in a more direct way than ever before. Our estimation suggests that most ion plumes originate from middle and low MSE (Mars Solar Electric) latitude of the northern dayside Martian ionosphere. This work improves our understanding of the pick-up process of the Martian escaping ions.

Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

In the Martian induced magnetosphere, the motion of planetary ions is significantly controlled by the ambient electric fields, which can be decomposed into three components: the motional, Hall, and ambipolar electric fields. Each of them is dominant in different regions and provides the ion acceleration with a particular effectiveness. Therefore, it is necessary to characterize the global distribution of these electric field components. In this study, a global multifluid Hall-MHD model is applied, which considers the motional, Hall, and ambipolar electric fields in ion transport and magnetic induction equations to self-consistently investigate the morphology of the electric fields in the Martian space environment. Numerical results suggest that the motional electric field is dominant in the upstream of the bow shock and in the magnetosheath along the Z MSE direction, leading to the formation of the ion plume escape channel. At the bow shock, the ambipolar electric field points outward, to decelerate and deflect the solar wind plasma flow. In the magnetosheath region, the ambipolar and motional electric fields with inward direction tend to reaccelerate the solar wind ions. However, along the magnetic pileup boundary, the Hall electric field pointing outward prevents the solar wind ions from penetrating the Martian induced magnetosphere, which also prevails in the Martian magnetotail region, to accelerate the ions’ tailward escape. This is the first systematic investigation of the global distribution of electric fields, which is helpful to understand the processes of ion acceleration/deceleration and escape within the Mars–solar wind interaction.

Ion expansion dynamics of laser induced multi-elemental plasmas

Ablation of multi-elemental materials by nanosecond lasers is often used to deposit oxide thin films. Understanding the ablation plume dynamics is of utmost importance to gain a detailed insight into thin film growth of materials with a complex composition. In this study, the plume expansion dynamics of several compound materials (AuCu, La0.33Ca0.67MnO3, and LiMn2O4) were characterized by measuring the angular-dependent kinetic energy (KE) distributions of ionic plasma species produced by KrF- and XeCl-excimer laser ablation in vacuum. The distributions of the lightest plume ions were found to differ fundamentally from those of other ions. The latter are similar to the energy distributions observed in single-component plumes and represent a low-energy peak and high-energy tail, while those for the lightest ions consist of at least two distinct peaks. These observations can be explained by assuming the formation of a dynamic double layer (DL) at the front of the plasma giving rise to different acceleration rates for light and heavier ions. As a consequence, heavier elements stay longer within the dynamic DL and gain larger KEs that leads to the observed ion separation. Extending these considerations into three dimensions yields an anisotropic acceleration concept for the plasma ions with high acceleration rates and longer presence within the DL normal to the target surface and lower acceleration rates and shorter time in the parallel direction.

Solar Control of the Pickup Ion Plume in the Dayside Magnetosheath of Venus

AbstractUsing the 8.5‐year Venus Express measurements, we demonstrate the asymmetric plasma distributions in the Venusian magnetosheath. An escaping plume is formed by pickup oxygen ions in the hemisphere where the motional electric field points outward from Venus, while the velocity of solar wind protons is faster in the opposite hemisphere. The pickup O+ escape rate is estimated to be (3.6 ± 1.4) × 1024 s−1 at solar maximum, which is comparable to the ion loss rate through the magnetotail, and (1.3 ± 0.4) × 1024 s−1 at solar minimum. The increase of O+ fluxes with extreme ultraviolet (EUV) intensity is significant upstream of the bow shock, partially attributed to the increase of exospheric neutral oxygen density. However, the solar wind velocity just has a slight effect on the pickup O+ escape rate in the magnetosheath, while the effect of solar wind density is not observed. Our results suggest the pickup O+ escape rate is mainly controlled by EUV radiation.

The Mini Induced Magnetospheres at Mars

AbstractWe report on observations made by the Mars Atmosphere and Volatile EvolutioN spacecraft at Mars, in the region of the ion plume. We observe that in some cases, when the number density of oxygen ions is comparable to the density of the solar wind protons interaction between both plasmas leads to formation in the magnetosheath of mini induced magnetospheres possessing all typical features of induced magnetospheres typically observed at Mars or Venus: a pileup of the magnetic field at the head of the ion cloud, magnetospheric cavity, partially void of solar wind protons, draping of the interplanetary magnetic field around the mini obstacle, formation of a magnetic tail with a current sheet, in which protons are accelerated by the magnetic field tensions. These new observations may shed a light on the mechanism of formation of induced magnetospheres.

Sputtered atom transport calculation via Radiosity View Factor Model and particle data compression

Sputter deposition calculation adds a major cost to a complete electric propulsion plume simulation due to the significantly lower velocities of sputtered atoms compared to plume ions. Simulation time is reduced considerably by decoupling the sputtered atom transport from the full plume simulation and solving sputter deposition via the non-Maxwellian Radiosity View Factor model. In order to do this, the incident ion or sputtered atom particle data are compressed on the fly and used in the subsequent simulation to construct the velocity distribution functions of the outgoing sputtered atoms in an interpolatable form. This paper explores several different methods enabling this approach and demonstrates the benefit in terms of accuracy, speed, and memory usage.

Formation and fragmentation of 2-hydroxyethylhydrazinium nitrate (HEHN) cluster ions: a combined electrospray ionization mass spectrometry, molecular dynamics and reaction potential surface study.

The 2-hydroxyethylhydrazinium nitrate ([HOCH2CH2NH2NH2]+NO3-, HEHN) ionic liquid has the potential to power both electric and chemical thrusters and provide a wider range of specific impulse needs. To characterize its capabilities as an electrospray propellant, we report the formation of HEHN cluster ions in positive electrospray ionization (ESI) and their collision-induced dissociation. The experiment was carried out using ESI guided-ion beam mass spectrometry which mimics an electrospray thruster in terms of ion emission, injection into a vacuum and fragmentation in space. Measurements include compositions of primary ions in the electrospray plume and their individual dissociation product ion cross sections and threshold energies. The results were interpreted in light of theoretical modeling. To determine cluster structures that are comprised of [HE + H]+ and NO3- constituents, classical mechanics simulations were used to create initial guesses; and for clusters that are formed by reactions between ionic constituents, quasi-classical direct dynamics trajectory simulations were used to mimic covalent bond formation and structures. All candidate structures were subject to density functional theory optimization, from which global minimum structures were identified and used for construction of reaction potential energy surface. The comparison between experimental values and calculated dissociation thermodynamics was used to verify the structures for the emitted species [(HEHN)nHE + H]+, [(HEHN)n(HE)2 + H]+, [(HE)n+1 + H]+ and [(HE)nC2H4OH]+ (n = 0-2), of which [(HE)1-2 + H]+ dominates. Due to the protic nature of HEHN, cluster fragmentation can be rationalized by proton transfer-mediated elimination of HNO3, HE and HE·HNO3, and the latter two become dominant in larger clusters. [(HE)2 + H]+ and [(HE)nC2H4OH]+ contain H-bonded water and consequently are featured by water elimination in fragmentation. These findings help to evaluate ion formation and fragmentation efficiencies and their impacts on electrospray propulsion.

DETERMINATION OF THE FORCE IMPACT OF AN ION THRUSTER PLUME ON AN ORBITAL OBJECT VIA DEEP LEARNING

The subject of research is the process of creating a neural network model (NNM) for determining the force impact of an ion thruster (IT) plume on an orbital object during non-contact space debris removal. The work aims to develop NNMs and study the influence of various factors on the accuracy of determining the force transmitted by the ion plume of the thruster to a space debris object (SDO). The tasks to resolve are to choose the structures of the NNMs, form a data set and use this data to train and validate the NNMs, and to explore the influence of the model structure and optimizer parameters on the accuracy of force determination. The methods used are plasma physics, computer simulation, deep learning, and optimization using an improved version of stochastic gradient descent. As a result of research, three NNMs have been developed, which differ in the number of hidden layers and neurons in hidden layers. For training and validation of the NNMs, a data set was generated for an SDO approximated by a cylinder using an autosimilar description of the ion plasma propagation. The data set was obtained for various relative positions and orientations of the object in the process of its removal from an orbit. Using this data set, the NNM parameters were optimized with the supervised learning method. The optimizer and its parameters are selected, providing a small error at the stage of validating learning outcomes. It was found that the accuracy of determining the force depends on the relative position and orientation of the SDO, as well as the architecture of the NNM, and the features of this influence were identified. The approach applied allows us to obtain the possibility of using methods of deep learning to determine the force impact of the IT plume on the SDO. The proposed models provide the accuracy of the force impact determination, which is sufficient for solving the considered class of problems. At the same time, NNM makes it possible to obtain results much faster in comparison with the methods used previously. This fact makes the NNMs promising to use both on-board and in mathematical modeling of missions to remove space debris.

High-Throughput Sizing, Counting, and Elemental Analysis of Anisotropic Multimetallic Nanoparticles with Single-Particle Inductively Coupled Plasma Mass Spectrometry.

Nanoparticles (NPs) have wide applications in physical and chemical processes, and their individual properties (e.g., shape, size, and composition) and ensemble properties (e.g., distribution and homogeneity) can significantly affect the performance. However, the extrapolation of information from a single particle to the ensemble remains a challenge due to the lack of suitable techniques. Herein, we report a high-throughput single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS)-based protocol to simultaneously determine the size, count, and elemental makeup of several thousands of (an)isotropic NPs independent of composition, size, shape, and dispersing medium with atomistic precision in a matter of minutes. By introducing highly diluted nebulized aqueous dispersions of NPs directly into the plasma torch of an ICP-MS instrument, individual NPs are atomized and ionized, resulting in ion plumes that can be registered by the mass analyzer. Our proposed protocol includes a phase transfer step for NPs synthesized in organic media, which are otherwise incompatible with ICP-MS instruments, and a modeling tool that extends the measurement of particle morphologies beyond spherical to include cubes, truncated octahedra, and tetrahedra, exemplified by anisotropic Cu NPs. Finally, we demonstrate the versatility of our method by studying the doping of bulk-dilute (<1 at. %) CuAg nanosurface alloys as well as the ease with which ensemble composition distributions of multimetallic NPs (i.e., CuPd and CuPdAg) can be obtained providing different insights in the chemistry of nanomaterials. We believe our combined protocol could deepen the understanding of macroscopic phenomena involving nanoscale structures by bringing about a statistics renaissance in research areas including, among others, materials science, materials chemistry, (nano)physics, (nano)photonics, catalysis, and electrochemistry.

Formation Mechanisms of the Molecular Ion Polar Plume and Its Contribution to Ion Escape From Mars

AbstractWe investigated the formation mechanism of a molecular ion plume and its contribution to ion escape based on Mars Atmosphere and Volatile EvolutioN (MAVEN) observations from November 2014 to October 2019 and numerical models. Here, we report a CO2+‐rich plume event and a statistical study of the molecular ion plume. MAVEN observed a CO2+‐rich plume event, in which the maximum CO2+ escape flux is approximately 4.2 × 106 cm−2s−1, on 28 August 2015 under strong solar wind dynamic pressure conditions. A numerical simulation using strong solar wind dynamic pressure conditions from the event suggested that the molecular ion plume is formed by deep penetration of the solar wind‐induced electric field, which is caused by strong solar wind dynamic pressure. A statistical study showed that CO2+ plume events tend to be observed under high solar wind dynamic pressure and strong electric field conditions. This tendency is consistent with the formation mechanism of the molecular ion plume suggested by the event study. The O2+ plume does not show the same tendency. This is because O2+ ions are abundant in the high‐altitude ionosphere, and O2+ plumes can be formed even under weak solar wind conditions. The subsolar crustal magnetic fields tend to prevent the formation of the molecular ion plume by shielding the ionosphere from the solar wind. The escape rate ratio is approximately 45:53:3 during the whole statistical survey period, suggesting that a molecular ion plume from the ionosphere is a non negligible ion escape channel from Mars.