HR: 17:35h
AN: SH34A-06    [Abstracts]
TI: Using PEACE, FGM, and CIS Data from the Four Cluster Spacecraft to Measure Cross Helicity, Compressibility, and Vorticity in the Solar Wind
AU: Gurgiolo, C
EM: chris@gurgiolo.com
AF: Bitterroot Basic Research, Bitterroot Basic Research 837 Westside Rd, Bitterroot, MT 59840-9369, United States
AU: * Goldstein, M L
EM: melvyn.l.goldstein@nasa.gov
AF: Goddard Space Flight Center, NASA Goddard Space Flight Center Code 673, Greenbelt, MD 20771, United States
AU: Fazakerley, A N
EM: anf@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, Mullard Space Science Laboratory University College London, Holmbury St. Mary, RH5 6NT, United Kingdom
AU: Lahiff, A D
EM: adl@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, Mullard Space Science Laboratory University College London, Holmbury St. Mary, RH5 6NT, United Kingdom
AU: Lucek, E
EM: e.lucek@imperial.ac.uk
AF: Imperial College, Space and Atmospheric Physics Group Imperial College, London, SW7 2BZ, United Kingdom
AU: Parks, G
EM: parks@ssl.berkeley.edu
AF: University of California, Berkeley, University of California, Berkeley Space Science Laboratory, Berkeley, CA 94720-7450, United States
AU: Mozer, F
EM: fmozer@ssl.berkeley.edu
AF: University of California, Berkeley, University of California, Berkeley Space Science Laboratory, Berkeley, CA 94720-7450, United States
AU: Decreau, P
EM: pdecreau@cnrs-orleans.fr
AF: CNRS, Laboratoire de Physique et Chimie/CNRS, Orleans, F-45071, France
AB: Determinations of compressibility and vorticity in the solar wind require a set of multi-point measurements that encompass a volume of space over which finite differences can be defined in analogy to computing divergences and cross products in finite difference numerical calculations. Because Cluster cannot provide four-point data of the ion velocity and density moments, it is of interest to try to make such measurements using the four-point thermal electron data provided by the PEACE instruments. PEACE provides an opportunity to compute the velocity and density moments and from them construct the divergence and curl of the velocity, thereby obtaining both a measure of the compressibility and the vorticity. From those moments, and together with the FGM magnetic field data, we have also constructed spectra of the cross helicity (the correlation between the fluctuating velocity and magnetic fields). We present early results in that project, including strong velocity shears associated with a Hot Flow Anomaly encountered by the four spacecraft in 2007. The analysis makes use of the Taylor frozen-in-flow approximation to artificially vary the spacecraft separation in the GSE -x direction in the solar wind.
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 6050 Plasma and MHD instabilities (2149, 2752, 7836)
DE: 7836 MHD waves and instabilities (2149, 2752, 6050)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting