Coordinated Radio, Electron, and Waves Experiment (CREWE) for the NASA Comet Rendezvous and Asteroid Flyby (CRAF) instrument

The Coordinated Radio, Electron, and Waves Experiment (CREWE) was designed to determine density, bulk velocity and temperature of the electrons for the NASA Comet Rendezvous and Asteroid Flyby Spacecraft, to define the MHD-SW IMF flow configuration; to clarify the role of impact ionization processes, to comment on the importance of anomalous ionization phenomena (via wave particle processes), to quantify the importance of wave turbulence in the cometary interaction, to establish the importance of photoionization via the presence of characteristic lines in a structured energy spectrum, to infer the presence and grain size of significant ambient dust column density, to search for the theoretically suggested 'impenetrable' contact surface, and to quantify the flow of heat (in the likelihood that no surface exists) that will penetrate very deep into the atmosphere supplying a good deal of heat via impact and charge exchange ionization. This final report provides an instrument description, instrument test plans, list of deliverables/schedule, flight and support equipment and software schedule, CREWE accommodation issues, resource requirements, status of major contracts, an explanation of the non-NASA funded efforts, status of EIP and IM plan, descope options, and Brinton questions

The Origin of Persistently Nonthermal Solar Wind Electrons: the Steady Electron Runaway Model's Demonstration of Dreicer Bifurcation using Measured and Ion–Electron Coulomb Drag

The Steady Electron Runaway Model (SERM) develops the hypothesis that the solar wind’s observed ubiquitous nonthermal electron velocity distribution functions (eVDFs) are caused by Dreicer's velocity space bifurcation in the strong dimensionless ${{\mathbb{E}}}_{\parallel }$ required by quasi-neutrality. SERM’s predicted partitions for the pressure and density are contrasted with appropriately adapted eVDF properties from the Wind 3DP experiment (1995–1998), based on in situ observations of ${{\mathbb{E}}}_{\parallel }$ . The observed number fraction of electrons in runaway, δ ^3DP , follows a thousandfold decline of Dreicer’s predicted fraction, δ , across the observed tenfold reduction of ${{\mathbb{E}}}_{\parallel }$ , satisfying δ ^3DP ≃ δ ^0.89 . SERM’s predictions are shown to reproduce the observed variations with ${{\mathbb{E}}}_{\parallel }$ of the electron partial pressure and excess kurtosis, ${{ \mathcal K }}_{e}$ . ${{ \mathcal K }}_{e}$ and ${{\mathbb{E}}}_{\parallel }$ are positively correlated across 4 yr, as expected by the SERM–Dreicer origin of the suprathermals. SERM quantitatively explains the observed 50 yr anticorrelation between δ ^3DP and the partition slope temperature ratios. This documentation quantitatively establishes Coulomb runaway physics as the missing determinant of the ubiquitous nonthermal solar wind eVDF. Astrophysical plasmas, like stellar winds, are unavoidably inhomogeneous, requiring ${{\mathbb{E}}}_{\parallel }$ to enforce quasi-neutrality. Between the stars ${{\mathbb{E}}}_{\parallel }$ is expected to be sufficiently large that measurable runaway density fractions (0.1%–30%) will occur, producing widespread leptokurtic eVDFs. Using inhomogeneous two-fluid information, SERM predicts spatially dependent leptokurtic eVDF profiles consonant with Coulomb collisions and the fluid’s E _∥ ( r ). SERM can also comment on its eVDFs’ consistency with Maxwellians presumed in the Spitzer–Härm closure. The solar wind profile shows the implied strong radial gradient of the plasma eVDF’s transformation from near thermal to strongly leptokurtic across 1.5–6 R _⊙

Interactions of the heliospheric current and plasma sheets with the bow shock: Cluster and Polar observations in the magnetosheath

On 12 March 2001, the Polar and Cluster spacecraft were at subsolar and cusp latitudes in the dayside magnetosheath, respectively, where they monitored the passage by Earth of a large-scale planar structure containing the high-density heliospheric plasma sheet (HPS) and the embedded current sheet. Over significant intervals, as the magnetic hole of the HPS passed Cluster and Polar, magnetic field strengths ∣B∣ were much smaller than expected for the shocked interplanetary magnetic field. For short periods, ∣B∣ even fell below values measured by ACE in the upstream solar wind. Within the magnetic hole the ratio of plasma thermal and magnetic pressures (plasma β) was consistently \u3e100 and exceeded 1000. A temporary increase in lag times for identifiable features in B components to propagate from the location of ACE to those of Cluster and Polar was associated with the expansion (and subsequent compression) of the magnetic field and observed low ∣B∣. Triangulation of the propagation velocity of these features across the four Cluster spacecraft configuration showed consistency with the measured component of ion velocity normal to the large-scale planar structure. B experienced large-amplitude wave activity, including fast magnetosonic waves. Within the low ∣B∣ region, guiding center behavior was disrupted and ions were subject to hydrodynamic rather than magnetohydrodynamic forcing. Under the reported conditions, a significant portion of the interplanetary coupling to the magnetosphere should proceed through interaction with the low-latitude boundary layer. Data acquired during a nearly simultaneous high-latitude pass of a Defense Meteorological Satellites Program satellite are consistent with this conjecture

Pulsed power hydrodynamics : a new application of high magnetic fields.

Pulsed Power Hydrodynamics is a new application of high magnetic fields recently developed to explore advanced hydrodynamics, instabilities, fluid turbulences, and material properties in a highly precise, controllable environment at the extremes of pressure and material velocity. The Atlas facility at Los Alamos is the world's first and only laboratory pulsed power system designed specifically to explore this relatively new family of megagauss magnetic field applications. Constructed in 2000 and commissioned in August 2001, Atlas is a 24-MJ high-performance capacitor bank delivering up to 30 MA with a current risetime of 5-6 {micro}sec. The high-precision, cylindrical, imploding liner is the tool most frequently used to convert electrical energy into the hydrodynamic (particle kinetic) energy needed to drive the experiments. For typical liner parameters including initial radius of 5 cm, the peak current of 30 MA delivered by Atlas results in magnetic fields just over 1 MG outside the liner prior to implosion. During the 5 to 10-{micro}sec implosion, the field outside the liner rises to several MG in typical situations. At these fields the rear surface of the liner is melted and it is subject to a variety of complex behaviors including: diffusion dominated andor melt wave field penetration and heating, magneto Raleigh-Taylor sausage mode behavior at the liner/field interface, and azimuthal asymmetry due to perturbations in current drive. The first Atlas liner implosion experiments were conducted in September 2000 and 10-15 experiments are planned in the: first year of operation. Immediate applications of the new pulsed power hydrodynamics techniques include material property topics including: exploration of material strength at high rates of strain, material failure including fracture and spall, and interfacial dynamics at high relative velocities and high interfacial pressures. A variety of complex hydrodynamic geometries will be explored and experiments will be designed to explore uristable perturbation growth and transition to turbulence. This paper will provide an overview of the range of problems to which pulsed power hydrodynamics can be applied and the issues associated with these techniques. Other papers at this Conference will present specifics of individual experiments and elaborate on the liner physics issues

Material science experiments on the Atlas Facility

Three material properties experiments that are to be performed on the Atlas pulsed power facility are described; friction at sliding metal interfaces, spallation and damage in convergent geomety, and plastic flow at high strain and high strain rate. Construction of this facility has been completed and experiments in high energy density hydrodynamics and material dynamics will begin in 2001