Abstract. The global core plasma model (GCPM) provides empirically derived core plasma density as a function of geomagnetic and solar conditions throughout the inner magnetosphere. It is continuous in value and gradient and is composed of separate models for the ionosphere, plasmasphere, plasmapause, trough, and polar cap. The relative composition of plasmaspheric H +, He +, and O + is included in the GCPM. A blunt plasmaspheric bulge and rotation of the bulge with changing geomagnetic conditions is included. The GCPM is an amalgam of density models intended to serve as a framework for continued improvement as new measurements become available and are used to characterize core plasma density, composition, and temperature.

The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on SolarProbe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.

[1] The objectives of this paper are twofold: first, to report our estimates of the meter-todecameter-scale topography and slopes of candidate landing sites for the Phoenix mission, based on analysis of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images with a typical pixel scale of 3 m and Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) images at 0.3 m pixel À1 and, second, to document in detail the geometric calibration, software, and procedures on which the photogrammetric analysis of HiRISE data is based. A combination of optical design modeling, laboratory observations, star images, and Mars images form the basis for software in the U.S. Geological Survey Integrated Software for Imagers and Spectrometers (ISIS) 3 system that corrects the images for a variety of distortions with single-pixel or subpixel accuracy. Corrected images are analyzed in the commercial photogrammetric software SOCET SET ( 1 BAE Systems), yielding digital topographic models (DTMs) with a grid spacing of 1 m (3-4 pixels) that require minimal interactive editing. Photoclinometry yields DTMs with single-pixel grid spacing. Slopes from MOC and HiRISE are comparable throughout the latitude zone of interest and compare favorably with those where past missions have landed successfully; only the Mars Exploration Rover (MER) B site in Meridiani Planum is smoother. MOC results at multiple locations have root-mean-square (RMS) bidirectional slopes of 0.8-4.5°at baselines of 3-10 m. HiRISE stereopairs (one per final candidate site and one in the former site) yield 1.8-2.8°s lopes at 1-m baseline. Slopes at 1 m from photoclinometry are also in the range 2-3°a fter correction for image blur. Slopes exceeding the 16°Phoenix safety limit are extremely rare.

Wave-particle instabilities driven by departures from local thermodynamic equilibrium have been conjectured to play a role in governing solar wind dynamics. We calculate the statistical variation of linear stability over a large subset of Helios I and II observations of the fast solar wind using a numerical evaluation of the Nyquist stability criterion, accounting for multiple sources of free energy associated with protons and helium including temperature anisotropies and relative drifts. We find that 88% of the surveyed intervals are linearly unstable. The median growth rate of the unstable modes is within an order of magnitude of the turbulent transfer rate, fast enough to potentially impact the turbulent scale-to-scale energy transfer. This rate does not significantly change with radial distance, though the nature of the unstable modes, and which ion components are responsible for driving the instabilities, does vary. The effect of ion-ion collisions on stability is found to be significant; collisionally young wind is much more unstable than collisionally old wind, with very different kinds of instabilities present in the two kinds of wind.

Funnel‐shaped, low‐frequency radiation, as observed in frequency time spectrograms, are frequently found at the Earth's magnetic equator. At the equator the radiation often extends from the proton cyclotron frequency up to the lower hybrid frequency. Ray‐tracing calculations can qualitatively reproduce the observed frequency‐time characteristics of these emissions if the waves are propagating in the fast magnetosonic mode starting with wave normal angles of ∼88° at the magnetic equator. The funnel‐shaped emissions are consistent with generation by protons with a ring‐type velocity space distribution. A ring‐shaped region of positive slope in the velocity space density distribution of protons is observed near the Alfvén velocity, indicating that the ring protons strongly interact with the waves. Ray‐tracing calculations show that for similar equatorial wave normal angles lower‐frequency fast magnetosonic waves are more closely confined to the magnetic equator than higher‐frequency fast magnetosonic waves. For waves refracted back toward the equator at similar magnetic latitudes, the lower‐frequency waves experience stronger damping in the vicinity of the equator than higher‐frequency waves. Also, wave growth is restricted to higher frequencies at larger magnetic latitudes. Wave damping at the equator and wave growth off the equator favors equatorial wave normal angle distributions which lead to the funnel‐shaped frequency time characteristic.