David J. McComas

A two‐fluid, MHD coronal model

We describe first results from a numerical two-fluid MHD model of the global structure of the solar corona. The model is two-fluid in the sense that it accounts for the collisional energy exchange between protons and electrons. As in our single-fluid model, volumetric heat and momentum sources are required to produce high speed wind from coronal holes, low speed wind above streamers, and mass fluxes similar to the empirical solar wind. By specifying different proton and electron heating functions we obtain a high proton temperature in the coronal hole and a relatively low proton temperature above the streamer (in comparison with the electron temperature). This is consistent with inferences from SOHO/UltraViolet Coronagraph Spectrometer instrument (UVCS) [Kohl et al., 1997], and with the Ulysses/Solar Wind Observations Over the Poles of the Sun instrument (SWOOPS) proton and electron temperature measurements which we show from the fast latitude scan. The density in the coronal hole between 2 and 5 solar radii (2 and 5 R s ) is similar to the density reported from SPARTAN 201-01 measurements by Fisher and Guhathakurta [1994]. The proton mass flux scaled to 1 AU is 2.4 x 10 cm -2 s -1 , which is consistent with Ulysses observations [Phillips et al., 1995]. Inside the closed field region, the density is sufficiently high so that the simulation gives equal proton and electron temperatures due to the high collision rate. In open field regions (in the coronal hole and above the streamer) the proton and electron temperatures differ by varying amounts. In the streamer the temperature and density are similar to those reported empirically by Li et al. [1998], and the plasma β is larger than unity everywhere above ∼ 1.5 R s , as it is in all other MHD coronal streamer models [e.g., Steinolfson et al., 1982; also G. A. Gary and D. Alexander, Constructing the coronal magnetic field, submitted to Solar Physics, 1998].

The 2π charged particles analyzer: All-sky camera concept and development for space missions

Increasing the temporal resolution and instant coverage of velocity space of space plasma measurements is one of the key issues for experimentalists. Today the top-hat plasma analyzer appears to be the favorite solution due to its relative simplicity and the possibility to extend its application by adding a mass-analysis section and an electrostatic angular scanner. Similarly, great success has been achieved in MMS mission using such multiple top-hat analyzers to achieve unprecedented temporal resolution. An instantaneous angular coverage of charged particles measurements is an alternative approach to pursuing the goal of high time resolution. This was done with FONEMA 4-D and, to a lesser extent, by DYMIO instruments for Mars-96 and with the FIPS instrument for MESSENGER mission. In this paper we describe, along with precursors, a plasma analyzer with a 2π electrostatic mirror that was developed originally for the Phobos-Soil mission with a follow-up in the frame of the BepiColombo mission, and is under development for future Russian missions. Different versions of instrument are discussed along with their advantages and drawbacks.

Particle acceleration from reconnection in the geomagnetic tail

Acceleration of charged particles in the near geomagnetic tail, associated with a dynamic magnetic reconnection process, was investigated by a combined effort of data analysis, using Los Alamos data from geosynchronous orbit, MHD modeling of the dynamic evolution of the magnetotail, and test particle tracing in the electric and magnetic fields obtained from the MHD simulation.

Measuring the magnetic connectivity of the geosynchronous region of the magnetosphere

This is the final report of a three-year, Laboratory-Directed Research and Development (LDEtD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to determine the magnetic connectivity of the geosynchronous region of the magnetosphere to the auroral zone in the polar ionosphere in order to test and refine current magnetospheric magnetic field models. We used plasma data from LANL instruments on three geosynchronous satellites and from USAF instruments on three low-altitude, polar-orbiting, DMSP satellites. Magnetic connectivity is tested by comparing plasma energy spectra at DMSP and geosynchronous satellites when they are in near conjunction. The times of closest conjugacy (Le., best spectral match) are used to evaluate the field models. We developed the tools for each step of the process and applied them to the study of a one-week test set of conjunctions. We automated the analysis tools and applied them to four months of twosatellite observations. This produced a database of about 130 definitive magnetic conjunctions. We compared this database with the predictions of the widely-used Tsyganenko magnetic field model and showed that in most cases one of the various parameterizations of the model could reproduce the observed field line connection. Further, we explored various measurables (e.g., magnetospheric activity indices or the geosynchronous field orientation) that might point to the appropriate parameterization of the model for these conjunctions, and ultimately, for arbitrary times. 1. Background and Research Objectives One of the most urgent problems of magnetospheric research is that of magnetic field line mapping between the low-altitude ionosphere and atmosphere and the high-altitude *Principal investigator, e-mail: mthomsen@lad.gov