We analyze a database of Dynamics Explorer-1 (DE-1) Retarding Ion Mass Spectrometer densities and temperatures to yield the first explicit measure of how cold ion concentration depends on temperature. We find that cold H+ and He+ concentrations have very weak dependence on temperature, but cold O+ ion concentration increases steeply as these ions become warmer. We demonstrate how this result can aid in analyzing composition data from other satellites without spacecraft potential mitigation, by applying the result to an example using data from the Van Allen Probes mission. Measurement of light ion concentrations above 1 electron volt (eV) are a reasonable proxy for the concentrations of colder (eV) ions. Warmer O+ ion concentrations may be extrapolated to colder temperatures using our fit to the statistical distribution versus temperature.

Nearly 35 years ago direct observations of cold plasmaspheric ions found enhanced O(+), O(++), and even N(+) densities in the outer plasmasphere, in particular during storm recovery conditions. Enhancements were seen inside or just outside of the plasmapause at all magnetic local times. Whereas nominal O(+) concentrations were found to be 1% or less inside the plasmasphere, enhanced O(+) in the vicinity of the plasmapause was found to reach densities comparable to H(+). Enhanced ion outflow (including oxygen) from high latitudes has also become part of our picture of storm-time phenomena. More recently it has become apparent that high latitude outflow is a source of inner magnetospheric warm ions that convect into morning and afternoon local times, to form what we now call the warm plasma cloak. Low to middle latitude ionospheric outflow and high latitude outflow are thought to result from very different processes and can be expected to contribute differently as a function of conditions and locations to the dynamic processes of energy and particle transport in the inner magnetosphere. Given the apparent proximity of their delivery to the vicinity of the plasmapause during plasmaspheric refilling conditions it becomes worthwhile to question the origin of the oxygen torus and its role in this region. While the observations do not yet exist to settle this question, there are measurements that contribute to the discussion in the new emerging context of cold plasma in the inner magnetosphere. In this paper we present and discuss DE 1 RIMS derived ion densities and temperatures that contribute to answering these outstanding questions about the origin and dynamics of the oxygen torus.

The Global Core Plasma Model (GCPM) is the first empirical model for thermal inner magnetospheric plasma designed to integrate previous models and observations into a continuous in value and gradient representation of typical total densities. New information about the plasmasphere, in particular, makes possible significant improvement. The IMAGE Mission Radio Plasma Imager (RPI) has obtained the first observations of total plasma densities along magnetic field lines in the plasmasphere and polar cap. Dynamics Explorer 1 Retarding Ion Mass Spectrometer (RIMS) has provided densities in temperatures in the plasmasphere for 5 ion species. These and other works enable a new more detailed empirical model of thermal in the inner magnetosphere that will be presented.

This chapter contains sections titled: Introduction Data Sources Observations Discussion Summary

Thermal plasmaspheric densities and temperatures for five ion species have recently become available, even though these quantities were derived some time ago from the Retarding Ion Mass Spectrometer onboard the Dynamics Explorer 1 satellite over the years 1981-1984. The quantitative properties will be presented. Densities are found to have one behavior with lessor statistical variation below about L=2 and another with much greater variability above that Lshell. Temperatures also have a behavior difference between low and higher L-values. The density ratio He++/H+ is the best behaved with values of about 0.2% that slightly increase with increasing L. Unlike the He+/H+ density ratio that on average decreases with increasing Lvalue, the O+/H+ and O++/H+ density ratios have decreasing values below about L=2 and increasing average ratios at higher L-values. Hydrogen ion temperatures range from about 0.2 eV to several 10s of eV for a few measurements, although the bulk of the observations are of temperatures below 3 eV, again increasing with L-value. The temperature ratios of He+/H+ are tightly ordered around 1.0 except for the middle plasmasphere between L=3.5 and 4.5 where He+ temperatures can be significantly higher. The temperatures of He++, O+, and O++ are consistently higher than H+.

In order to understand the effect of the charging environment on and around structures on the lunar surface, we have exposed basic structural shapes to electrons and Vacuum Ultra-Violet (VUV) radiation. The objects were, in separate runs, isolated, grounded, and placed on dielectric surfaces. In this presentation, the effects of electron energy, VUV flux, and sample orientation, on the charging of the objects will be examined. The potential of each of the object surfaces was monitored in order to determine the magnitude of the ram and wake effects under different orientations relative to the incoming beams (solar wind). This is a part of, and complementary to, the study of the group at USC under Dr. J. Wang, the purpose of which is to model the effects of the charging environment on structures on the lunar surface.

The NASA Dust Management Project has been established to address relevant high priority needs for lunar dust mitigation technologies to be used during lunar surface operations. (1) (2) A key task of the project is to support the assessment of test planning and test facility requirements for dust mitigation technology evaluation and demonstration. The overall objectives of the assessment include a) delineation of testing philosophy and needs and b) the identification and evaluation of the capabilities of available and suitable NASA and non-NASA test facilities to identify potential gaps between testing needs and current operational testing capabilities. The approach, methodology and initial results of this ongoing assessment are described in this paper.

Electric potential variations on the International Space Station (ISS) structure in low Earth orbit are dominated by contributions from interactions of the United States (US) 160 volt solar arrays with the relatively high density, low temperature plasma environment and inductive potentials generated by motion of the large vehicle across the Earth?s magnetic field. The Floating Potential Measurement Unit (FPMU) instrument suite comprising two Langmuir probes, a plasma impedance probe, and a floating potential probe was deployed in August 2006 for use in characterizing variations in ISS potential, the state of the ionosphere along the ISS orbit and its effect on ISS charging, evaluating effects of payloads and visiting vehicles, and for supporting ISS plasma hazard assessments. This presentation summarizes observations of ISS frame potential variations obtained from the FPMU from deployment in 2006 through the current time. We first describe ISS potential variations due to current collection by solar arrays in the day time sector of the orbit including eclipse exit and entry charging events, potential variations due to plasma environment variations in the equatorial anomaly, and visiting vehicles docked to the ISS structure. Next, we discuss potential variations due to inductive electric fields generated by motion of the vehicle across the geomagnetic field and the effects of external electric fields in the ionosphere. Examples of night time potential variations at high latitudes and their possible relationship to auroral charging are described and, finally, we demonstrate effects on the ISS potential due to European Space Agency and US plasma contactor devices.

The dominant charging processes in various astrophysical environments are considered to be by photoelectric emissions with radiation from nearby stars and secondary electron emissions (SEE) by impact of electrons in a medium with sufficiently high energies. The charging of bulk materials with planar surfaces by SEE with electron impact appears to be well understood with theoretical expressions as well as by experimental techniques. However, the charging of submicron/micron-size dust grains by SEE with sufficiently high-energy electrons is a complex process, and is a function of electron energies, the electron current, and the grain size, and the charge or the surface potential. Development of viable theoretical models and acquisition of experimental data for charging properties of micron-size dust grains are still in the early stages. This paper focuses on SEE charging properties of individual micron-size dust grains by low-energy electron impact, obtained from laboratory measurements on an experimental facility based on an electrodynamic balance. The measurements of SEE yields of positively charged dust grains indicate the yields increase with decreasing grain size and the equilibrium surface potentials showing generally linear size dependence. These experimental results are generally in agreement with several independent experimental and analytical model studies in the literature, with the exception of a recently published paper which is in fundamental conflict with our studies as well as with several other experimental and theoretical studies. The sources and causes of this conflict are critically examined and discussed in this paper.

In a previous paper, we discussed a theory for the Rapid -Charging Events (RCEs) seen by the Floating Potential Measurement Unit (FPMU) on the International Space Station (ISS). The theory involves electro n collection by the ISS high voltage solar arrays before coverglass charging limits their collection. While describing the maximum amounts of charging seen on ISS with two active solar arrays, the theory fails to describe the average events, which are of lower magnitude. Several reasons for this deficiency were given in the previous paper. Two of the reasons that can be tested are examined in this paper. The first is the effect of magnetic latitude. When ISS exits eclipse at high magnetic latitudes, the magnetic induction effect across the ISS truss is greatest, and so the potential at the site of the FPMU is influenced by this effect. In this paper, we investigate the effects of magnetic latitude on RCE peak potential and amplitude. The second effect is that of weather at eclipse-exit. If ISS enters sunlight at a clear horizon, the charging voltage on the solar arrays is turned on by the near -infrared sunlight before the ultraviolet sunshine can activate the discharging photoelectric effect on ISS surfaces, and the RCEs should be of large r amplitude. On cloudy eclipse exits, the infrared and ultraviolet first impinge on ISS essentially simultaneously, and some of the electron collection is negated by electrons lost due to photoemission. At these t imes, the RCEs should be of lower amplitude. It has also been found in this study that when partly cloudy conditions prevail at eclipse exit, complex RCEs usually result, perhaps because of intermittent illumination of ISS solar arrays by light passing through the clouds along the line of sight to the sun. In this paper, we thus investigate the influence of weather at eclipse exit on the amplitude of charging and RCE structure. Finally, a more complete picture of RCE amplitude emerges, including effects due to weather and magnetic latitude as well as plasma density and temperature.

With the negative grounding of the 160V Photovoltaic (PV) arrays, the International Space Station (ISS) can experience varied and interesting charging events. Since August 2006, there has been a multi-probe p ackage, called the Floating Potential Measurement Unit (FPMU), availa ble to provide redundant measurements of the floating potential of th e ISS as well as the density and temperature of the local plasma environment. The FPMU has been operated during intermittent data campaigns since August 2006 and has collected over 160 days of information reg arding the charging of the ISS as it has progressed in configuration from one to three PV arrays and with various additional modules such as the European Space Agency?s Columbus laboratory and the Japan Aeros pace Exploration Agency's Kibo laboratory. This paper summarizes the charging of the ISS and the local environmental conditions that contr ibute to those charging events, both as measured by the FPMU.

The Floating Potential Measurement Unit (FPMU) has detected high negative amplitude rapid charging events (RCEs) on the International Space Station (ISS) at the morning terminator. These events are larger and more rapid than the ISS morning charging events first seen by the Floating Potential Probe (FPP) on ISS in 2001. In this paper, we describe a theory for the RCEs that further elucidates the nature of spacecraft charging in low Earth orbit (LEO) in a non-equilibrium situation. The model accounts for all essential aspects of the newly discovered phenomenon, and is amenable to testing on-orbit. Predictions of the model for the amplitude of the ISS RCEs for the full set of ISS solar arrays and for the coming solar cycle are given, and the results of modeling by the Environments WorkBench (EWB) are compared to the observed events to show that the phenomenon can be explained by solar array driven charging. The situation is unique because the coverglasses have not yet reached equilibrium with the surrounding plasma during the RCEs. Finally, a prescription for further use of the ISS for investigating fundamental plasma physics in LEO is given. Already, plasma and charging monitoring instruments on ISS have taught us much about spacecraft interactions with the dense LEO plasma, and we expect they will continue to yield more valuable science when the Japanese Experiment Module (JEM) is in place.