HR: 0830h
AN: SH21B-0155    [PDF]
TI: Induced electric field and cross helicity in solar wind fluctuations
AU: Breech, B
EM: breech@eecis.udel.edu
AF: Bartol Research Institute, University of Delaware, Newark, DE 19716 United States
AU: * Matthaeus, W
EM: whm@udel.edu
AF: Bartol Research Institute, University of Delaware, Newark, DE 19716 United States
AU: Milano, L
EM: lmilano@bartol.udel.edu
AF: Bartol Research Institute, University of Delaware, Newark, DE 19716 United States
AU: Smith, C
EM: Charles.Smith@unh.edu
AF: Institute for Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AB: Solar wind turbulence at 1 AU exhibits, on the one hand, a frequent high degree of Alfvenicity (or, cross helicity) and on the other hand, indications of a strong magnetohydrodynamic (MHD) cascade. The former is associated with a high degree of correlation of velocity and magnetic field -- in the limiting case they would be aligned -- while the latter requires nonzero values of ${\bf v} \times {\bf b}$ so that the cascade is suppressed when the fluctuation fields are aligned. Here we examine the statistics of the induced MHD-scale electric field at 1AU, to demonstrate how the degree of Alfvenicity is consistent with the observed induced electric field. The statistics support the view (Roberts et al, JGR, 92, 12023, 1987) that there remains at 1 AU some preference for an Alfvenicity associated with outward traveling fluctuations. However there is a dominance of non-Alfvenic turbulence that is sufficient to account for the observed distribution of induced electric field. A generic result is obtained that explains the sin(v,b) distribution, which is observed to peak at values corresponding to 90 degrees, even when some Alfvenic fluctuations ("0 degrees" or "180 degrees") are present. This helps to understand how Alfvenic fluctuations and turbulence can coexist in the solar wind.
DE: 2149 MHD waves and turbulence
DE: 2159 Plasma waves and turbulence
DE: 7863 Turbulence
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting