Ion Composition Measurements Research Articles

First results from the Solar Orbiter Heavy Ion Sensor

Aims. Solar Orbiter launched in February 2020 with the goal of revealing the connections between the Sun’s interior, atmosphere, and the heliosphere. The Solar Orbiter Heavy Ion Sensor (HIS) is a time-of-flight ion mass spectrometer dedicated to measuring heavy ions in the solar wind. Methods. We present an overview of the first measurements of heavy ion composition from HIS, reviewing the methods used to transform the spectra obtained on board into scientific data products and examining two solar wind case studies as well as the statistical properties of the heavy ion composition observed by HIS. We also carried out a comparison with prior measurements of heavy ions at L1. Results. The HIS data set provides the first mass- and charge-resolved heavy ion measurements in the inner heliosphere. Conclusions. These high temporal resolution data have the potential to transform our understanding of the connections between the solar wind and its origin at the Sun, as well as the interaction between the solar wind and the environment around planets, comets, and in the interstellar medium.

Mass spectroscopic measurement of time-varying ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma

The time dependence of the ion composition in pulse-modulated dual-frequency capacitively coupled plasma with Ar/C4F8/O2 was measured using a quadrupole mass spectrometer with an electrostatic energy analyzer. After turning on the pulse, Ar+ ions were preferentially generated, and then, the composition of C x F y + ions, such as C2F4 + and C3F5 + ions, increased. This phenomenon was discussed on the basis of the time variation of electron temperature and the resultant change in the ratio of the C4F8 ionization rate to that of Ar atoms.

Fe Ion Composition in Solar-Wind Streams in the Solar Corona and Heliosphere

Analysis of the distributions of Fe ions over the stages of ionization in solar-wind (SW) plasma provides valuable information on the formation of SW streams and plasma heating processes, as well as for identifying SW sources on the Sun. When passing SW plasma through the corona, its ion composition evolves and finally “freezes” at distances of the order of several solar radii from the solar surface, remaining further practically unchanged in the heliosphere. This makes it possible to obtain information about the physical conditions in its source and the solar corona from the SW charge state. Average charge QFe, which is usually used to characterize the distributions of Fe ions, does not take into account all the features of the evolution of the ion composition, which does not allow one to extract more detailed information about the state of SW plasma. In this study, to describe the charge state of Fe ions, three parameters q4, q8, and q12 are introduced, which characterize the relative fractions of ions with charges Z = 0–7, 8–11, and 12–20, respectively, and conditionally correspond to “cold,” “medium,” and “hot” SW plasma components. According to the measurements of the Fe ion composition in 2010 on the STEREO-A spacecraft, the characteristic values of these parameters for different types of SW streams are given. The problem of modeling ion distributions in SW plasma based on diagnostic data on the parameters of coronal sources is considered. Using the example of the event associated with coronal-mass ejection on August 18, 2010, it is shown that the parameters of the charge state of Fe ions calculated from the model distributions are in good agreement within errors with the measurement data.

Estimation of sulfuric acid concentration using ambient ion composition and concentration data obtained with atmospheric pressure interface time-of-flight ion mass spectrometer

Abstract. Sulfuric acid (H2SO4, SA) is the key compound in atmospheric new particle formation. Therefore, it is crucial to observe its concentration with sensitive instrumentation, such as chemical ionisation (CI) inlets coupled to atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometers. However, there are environmental conditions for which and physical reasons why chemical ionisation cannot be used, for example in certain remote places or during flight measurements with limitations regarding chemicals. Here, we propose a theoretical method to estimate the SA concentration based on ambient ion composition and concentration measurements that are achieved by APi-TOF alone. We derive a theoretical expression to estimate the SA concentration and validate it with accurate CI-APi-TOF observations. Our validation shows that the developed estimate works well during daytime in a boreal forest (R2=0.85); however, it underestimates the SA concentration in, e.g. the Antarctic atmosphere during new particle formation events where the dominating pathway for nucleation involves sulfuric acid and a base (R2=0.48).

Solar Origin of Bare Ion Anomalies in the Solar Wind and Interplanetary Coronal Mass Ejections

Abstract Previous studies of the solar wind and interplanetary coronal mass ejections (ICMEs) have shown periods throughout solar cycle 23 when heliospheric measurements of ion composition appear anomalous. In these cases, C6+ and other bare ion densities, i.e., fully stripped ions, are unusually low, leading it to be classified as the Outlier solar wind. However, its origin and solar source(s) remain largely uncertain. In this work, we further characterize the Outlier wind to connect its heliospheric structure to its solar source to constrain the conditions of its formation. Through an analysis of the plasma and magnetic field properties of each occurrence between 1998 and 2011, we find that the Outlier plasma occurs in the slow solar wind or interplanetary mass ejections (∼460 km s−1), and comprises distinct, high density events lasting less than 10 hr. The number of events is correlated with the solar cycle, indicating the process leading to the depletion of bare ions is strongly governed by the magnetic field. Additionally, the events exhibit a bi- or unidirectional suprathermal electron strahl that is concurrent with changes in the magnetic field direction. Moreover, the Outlier wind’s composition, entropy, Alfvén speed, and proton temperature suggest a helmet streamer or active region origin. Together, the properties exhibited by the Outlier wind suggest a strong connection to the heliospheric current sheet and that the solar wind events are smaller scale versions of those seen in ICMEs, such as small magnetic flux ropes. However, more work is necessary to determine the source and creation process in the vicinity of the Sun.

Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk‐Side Electromagnetic Ion Cyclotron Waves

AbstractAn extended interval of perturbed magnetospheric conditions in November 2016 supported increased convection and sunward transport of plasmaspheric material. During this period of time the Magnetospheric Multiscale satellites, with their apogees along Earth's dusk‐side outer magnetosphere, encountered several cold plasma density structures at the same time as plasma bulk flows capable of accelerating hidden cold plasma occurred. Investigating the charged particle and fields data during two subintervals showed that the satellites made direct measurements of cold plasmaspheric ions embedded within multicomponent hot plasmas as well as electromagnetic emissions consistent with electromagnetic ion cyclotron (EMIC) waves. The complex in situ ion composition measurements were applied to linear wave modeling to interpret the impacts of cold and hot ion species on wave growth and band structure. Although the waves for both intervals were predicted to have peak growth rate below ΩHe+, substantial differences were observed among all other dispersive properties. The modeling also showed EMIC waves generated in the presence of heavy ions had growth rates and unstable wave numbers always smaller than predicted for a pure proton‐electron plasma. The results provide implications for future investigation of EMIC wave generation with and without direct measurements of the cold and hot plasma composition as well as of subsequent wave‐particle interactions.

The Energetic Particle Detector

After decades of observations of solar energetic particles from space-based observatories, relevant questions on particle injection, transport, and acceleration remain open. To address these scientific topics, accurate measurements of the particle properties in the inner heliosphere are needed. In this paper we describe the Energetic Particle Detector (EPD), an instrument suite that is part of the scientific payload aboard the Solar Orbiter mission. Solar Orbiter will approach the Sun as close as 0.28 au and will provide extra-ecliptic measurements beyond ∼30° heliographic latitude during the later stages of the mission. The EPD will measure electrons, protons, and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of megaelectronvolts/nucleons. For this purpose, EPD is composed of four units: the SupraThermal Electrons and Protons (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the High-Energy Telescope (HET) plus the Instrument Control Unit that serves as power and data interface with the spacecraft. The low-energy population of electrons and ions will be covered by STEP and EPT, while the high-energy range will be measured by HET. Elemental and isotopic ion composition measurements will be performed by SIS and HET, allowing full particle identification from a few kiloelectronvolts up to several hundreds of megaelectronvolts/nucleons. Angular information will be provided by the separate look directions from different sensor heads, on the ecliptic plane along the Parker spiral magnetic field both forward and backwards, and out of the ecliptic plane observing both northern and southern hemispheres. The unparalleled observations of EPD will provide key insights into long-open and crucial questions about the processes that govern energetic particles in the inner heliosphere.

Natural isotopes support groundwater origin as a driver of mire type and biodiversity in Slitere National Park, Latvia

Slitere National Park in Latvia is home to rich fens with many endangered and threatened plant species. This study aims to address how the hydrological systems affect vegetation biodiversity (cf. Wolejko et al. 2019) in the mire systems of the National Park: the base-rich inter-dune mires and extremely base-rich calcareous fens. Groundwater samples from these areas were collected for measurements of ion composition and natural isotopes of C, H and O. Also, we simulated groundwater flow paths from the highest local topographical point (a nearby sandy plateau) to the sea, and calculated the residence times of these groundwater flows. The results show that the inter-dune mires are supplied by a mixture of local and regional groundwater systems. The groundwater supply at one of the inter-dune mires was dominated by local groundwater flow from adjacent dunes, but we also detected a small input of calcareous water. This dominance of local groundwater may have resulted from the presence of drainage ditches and a small stream that drains into the Baltic Sea. In contrast, the extremely base-rich fens were found to be solely dependent on regional groundwater which is likely to discharge at the plateau foothills due to the presence of fault structures. Thus, the mires in Slitere National Park are not as undisturbed as was previously believed. Drainage may have affected the original hydrological flow paths. Further research on the extent of these changes is recommended to preserve the endangered species and high biodiversity of these fens. Also, in order to trace the origin of groundwater flows, further investigation into the larger landscape beyond the plateau might be required.

Influence of collisions on ion dynamics in the inner comae of four comets.

Collisions between cometary neutrals in the inner coma of a comet and cometary ions that have been picked up into the solar wind flow and return to the coma lead to the formation of a broad inner boundary known as a collisionopause. This boundary is produced by a combination of charge transfer and chemical reactions, both of which are important at the location of the collisionopause boundary. Four spacecraft measured ion densities and velocities in the inner region of comets, exploring the part of the coma where an ion-neutral collisionopause boundary is expected to form. The aims are to determine the dominant physics behind the formation of the ion-neutral collisionopause and to evaluate where this boundary has been observed by spacecraft. We evaluated observations from three spacecraft at four different comets to determine if a collisionopause boundary was observed based on the reported ion velocities. We compared the measured location of the ion-neutral collisionopause with measurements of the collision cross sections to evaluate whether chemistry or charge exchange are more important at the location where the collisionopause is observed. Based on measurements of the cross sections for charge transfer and for chemical reactions, the boundary observed by Rosetta appears to be the location where chemistry becomes the more probable result of a collision between H2O and H2O+ than charge exchange. Comparisons with ion observations made by Deep Space 1 at 19P/Borrelly and Giotto at 1P/Halley and 26P/Grigg-Skjellerup show that similar boundaries were observed at 19P/Borrelly and 1P/Halley. The ion composition measurements made by Giotto at Halley confirm that chemistry becomes more important inside of this boundary and that electron-ion dissociative recombination is a driver for the reported ion pileup boundary.

Statistical Properties of Molecular Ions in the Ring Current Observed by the Arase (ERG) Satellite

AbstractMolecular ions in the magnetosphere can be a tracer of fast ion outflows from the deep ionosphere. Statistical properties of molecular ions (O2+/NO+/N2+) in the ring current are investigated based on ion composition measurements (<180 keV/q) by medium‐energy particle experiments‐electron analyzer and low‐energy particle experiments‐ion mass analyzer instruments on board the Arase (Exploration of energization and Radiation in Geospace, ERG) satellite. The investigated period from late March to December 2017 includes 11 geomagnetic storms with the minimum Dst index less than −40 nT. The molecular ions are observed in the region of L = 2.5–6.6 and clearly identified at energies above ~12 keV during most magnetic storms. During quiet times, molecular ions are not observed. The average energy density ratio of the molecular ions to O+ is ~3%. The ratio tends to increase with the size of magnetic storms. Existence of molecular ions even during small magnetic storms suggests that the fast ion outflow from the deep ionosphere occurs frequently during geomagnetically active periods.

On the response of Martian Ionosphere to the Passage of a Corotating Interaction Region: MAVEN Observations

AbstractThe response of Martian ionosphere to the passage of corotating interaction region (CIR) of June 2015 is studied using observations from several instruments aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. An intense CIR arrived at Mars on 22 June 2015, during which the upstream solar wind and interplanetary magnetic field conditions were monitored by the Solar Wind Ion Analyzer (SWIA), Solar Wind Electron Analyzer (SWEA), Solar Energetic Particle (SEP), and Magnetometer (MAG) instruments aboard MAVEN. The CIR event was characterized by enhancements in solar wind density, velocity, and dynamic pressure, and increased and fluctuating interplanetary magnetic field and was associated with enhanced fluxes of Solar Energetic Particles. The Langmuir Probe and Waves (LPW) instrument onboard MAVEN provided the ionospheric observations such as electron density and electron temperature during this period. The dayside ionosphere is significantly compressed only near the peak of solar wind dynamic pressure enhancement (∼14 nPa). In contrast, on the nightside, the electron density remains depleted for a longer period of time. The electron temperatures are also enhanced during the period of electron depletion on the nightside. The Suprathermal and Thermal Ion Composition (STATIC) measurements show enhanced fluxes of suprathermal heavy ions in the Martian exosphere during CIR period, and evidences for enhanced tailward flow of these pickup ions. The analysis suggests that the nightside ionosphere is primarily controlled by the precipitating Solar Energetic Particles and pickup ions transported across the Martian terminator and depletes significantly when the heavy ion flux in the exosphere enhances.

Time of flight mass spectrometry with direct extraction of a uranium plasma

We demonstrate a Wiley-McClaren Time of Flight Mass Spectrometer modified to allow direct extraction of ions from a laser-induced plasma. Unlike many other methods that utilize mass spectrometry to investigate laser-induced plasmas, no collisional cooling or further ionization of the plasma is required prior to acceleration, allowing measurements of the plasma ion composition to be obtained directly. Furthermore, we show using the laser ablation of gadolinium as an example that we are able to obtain the translational energy distribution of the plasma directly and infer information about the relative composition of ions within different regions of the plasma plume. The approach is then applied to laser ablation of a uranium sample as a step toward probing the chemistry under conditions relevant to a nuclear fireball for nuclear forensics applications.

Eclipse‐Induced Changes to Topside Ion Composition and Field‐Aligned Ion Flows in the August 2017 Solar Eclipse: e‐POP Observations

AbstractWe present in situ ion composition and velocity measurements during the August 2017 solar eclipse from the Enhanced Polar Outflow Probe (e‐POP), which crossed the path of totality at ~640‐km altitude within 10 min of totality passing. These measurements reveal two distinct H+ ion populations, an ~40% decrease in topside plasma density, a similar drop in upward but not downward H+ ion flux, and a downward O+ ion velocity of ~100 m/s. These features are directly linked to changes in the H+/O+ composition and in interhemispheric or field‐aligned light ion flow and to a reduction in the negative spacecraft potential. These observed features were absent on the preceding, noneclipse days and corroborate the reduction in F region plasma density and topside total electron content observed by the Global Positioning System receivers on board. They are attributed to the temporary reduction of photoionization in the eclipsed F region.

Dominance of high‐energy (>150 keV) heavy ion intensities in Earth's middle to outer magnetosphere

AbstractPrevious observations have driven the prevailing assumption in the field that energetic ions measured by an instrument using a bare solid state detector (SSD) are predominantly protons. However, new near‐equatorial energetic particle observations obtained between 7 and 12 RE during Phase 1 of the Magnetospheric Multiscale mission challenge the validity of this assumption. In particular, measurements by the Energetic Ion Spectrometer (EIS) instruments have revealed that the intensities of heavy ion species (specifically oxygen and helium) dominate those of protons at energies 150–220 keV in the middle to outer (>7 RE) magnetosphere. Given that relative composition measurements can drift as sensors degrade in gain, quality cross‐calibration agreement between EIS observations and those from the SSD‐based Fly's Eye Energetic Particle Spectrometer (FEEPS) sensors provides critical support to the veracity of the measurement. Similar observations from the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instruments aboard the Van Allen Probes spacecraft extend the ion composition measurements into the middle magnetosphere and reveal a strongly proton‐dominated environment at but decreasing proton intensities at . It is concluded that the intensity dominance of the heavy ions at higher energies (>150 keV) arises from the existence of significant populations of multiply‐charged heavy ions, presumably of solar wind origin.

Generation of Boron-Rich Plasma by a Pulsed Vacuum Arc With Lanthanum Hexaboride Cathode

We report on the generation of boron-rich plasma by a pulsed vacuum arc with lanthanum hexaboride cathode. Two different ranges of arc current pulse duration and amplitude were investigated: the first one has pulse duration of 5–20 $\mu \text{s}$ and arc current of 100–700 A and the second one has pulse duration of 300 $\mu \text{s}$ and arc current of 140 A. The ion mass-to-charge spectrum of the plasma was investigated by both time-of-flight spectrometry and magnetic analysis. The results of measurements of the plasma ion composition for different arc parameters are presented and discussed. For all arc parameters considered, the fractional composition of boron and lanthanum ions agrees well with the stoichiometric composition of these elements into the lanthanum hexaboride cathode.

An investigation of ionospheric upper transition height variations at low and equatorial latitudes deduced from combined COSMIC and C/NOFS measurements

In this study we propose the combination of topside in-situ ion density data from the Communication/Navigation Outage Forecast System (C/NOFS) along with the electron density profile measurement from Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) satellites Radio Occultation (RO) for studying the spatial and temporal variations of the ionospheric upper transition height (hT) and the oxygen ion (O+) density scale height. The latitudinal, local time and seasonal distributions of upper transition height show more consistency between hT re-calculated by the profile of the O+ using an α-Chapman function with linearly variable scale height and that determined from direct in-situ ion composition measurements, than with constant scale height and only the COSMIC data. The discrepancy in the values of hT between the C/NOFS measurement and that derived by the combination of COSMIC and C/NOFS satellites observations with variable scale height turns larger as the solar activity decreases, which suggests that the photochemistry and the electrodynamics of the equatorial ionosphere during the extreme solar minimum period produce abnormal structures in the vertical plasma distribution. The diurnal variation of scale heights (Hm) exhibits a minimum after sunrise and a maximum around noon near the geomagnetic equator. Further, the values of Hm exhibit a maximum in the summer hemisphere during daytime, whereas in the winter hemisphere the maximum is during night. Those features of Hm consistently indicate the prominent role of the vertical electromagnetic (E×B) drift in the equatorial ionosphere.

Compact Dual Ion Composition Experiment for space plasmas—CoDICE

AbstractThe Compact Dual Ion Composition Experiment—CoDICE—simultaneously provides high‐quality plasma and energetic ion composition measurements over six decades in energy in a wide variety of space plasma environments. CoDICE measures two critical ion populations in space plasmas: (1) Elemental and charge state composition, and 3‐D velocity distributions of <10 eV/q–40 keV/q plasma ions; and (2) Elemental composition, energy spectra, and angular distributions of ∼30 keV–>10 MeV energetic ions. CoDICE uses a novel, integrated, common time‐of‐flight subsystem that provides several advantages over the commonly used separate plasma and energetic ion sensors currently flying on several space missions. These advantages include reduced mass and volume compared to two separate instruments, reduced shielding in high‐radiation environments, and simplified spacecraft interface and accommodation requirements. This paper describes the operation principles, electro‐optic simulation results and applies the CoDICE concept for measuring plasma and energetic ion populations in Jupiter's magnetosphere.

The Pickup Ion Composition Spectrometer

AbstractObservations of newly ionized atoms that are picked up by the magnetic field in the expanding solar wind contain crucial information about the gas or dust compositions of their origins. The pickup ions (PUIs) are collected by plasma mass spectrometers and analyzed for their density, composition, and velocity distribution. In addition to measurements of PUIs from planetary sources, in situ measurements of interstellar gas have been made possible by spectrometers capable of differentiating between heavy ions of solar and interstellar origin. While important research has been done on these often singly charged ions, the instruments that have detected many of them were designed for the energy range and ionic charge states of the solar wind and energized particle populations, and not for pickup ions. An instrument optimized for the complete energy and time‐of‐flight characterization of pickup ions will unlock a wealth of data on these hitherto unobserved or unresolved PUI species. The Pickup Ion Composition Spectrometer (PICSpec) is one such instrument and can enable the next generation of pickup ion and isotopic mass composition measurements. By combining a large‐gap time‐of‐flight–energy sensor with a −100 kV high‐voltage power supply for ion acceleration, PUIs will not only be above the detection threshold of traditional solid‐state energy detectors but also be resolved sufficiently in time of flight that isotopic composition can be determined. This technology will lead to a new generation of space composition instruments, optimized for measurements of both heliospheric and planetary pickup ions.

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas.

We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ∼10 eV/q-40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ∼30 keV-10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs' singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

Experimental test of the ρ(1-α) evolution for rotational discontinuities: cluster magnetopause observations

Abstract. Rotational discontinuities (RDs) are governed by two relations: the Walén relation predicting that the plasma velocity observed in the deHoffmann–Teller frame equals the local Alfvén velocity and another relation that connects the variation in plasma mass density, ρ, to variations in the pressure anisotropy factor, α, defined as α: ≡(p∥ − p⊥) μ0/B2, so that ρ(1 − α) is constant. While the Walén relation has become a standard tool for classifying magnetopause crossings as RDs , the ρ(1 − α)= const. condition has never been directly verified at the same time, largely due to problems with determining ρ when no ion composition measurements were available. In fact, to overcome the lack of composition information, the validity of the relation has often been assumed and the Walén relation reformulated so that variations in ρ are replaced by variations in α. In this paper we exploit the availability of high-time-resolution composition measurements on the Cluster spacecraft to directly test the ρ (1− α)= const. condition for three magnetopause crossings, identified as RDs from the application of the Walén relation to measurements of plasma ions and magnetic field by the CIS (Cluster Ion Spectrometry) and FGM (flux-gate magnetometer) instruments, respectively. We find that the relation is not fulfilled in either case. In one event, with a fairly large content of oxygen ions, the Walén test improved when the contribution from these ions was taken into account. Through comparisons of the measured ion densities with simultaneously measured total electron densities by the Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation (WHISPER) instrument, we were able to exclude the possibility that ion populations hidden to the CIS instrument because of their very low energies could have changed ρ to match the ρ(1 − α)= const. condition. We also excluded the possibility that energetic ions above the CIS energy range could have sufficiently changed the true α. It thus appears that the ρ(1 − α)= const. condition, for reasons not presently understood, is not valid for the kind of RD-like structures we observe.