ACE/Wind multispacecraft analysis of anisotropic solar wind fluctuations

DASSO, S.; MATTHAEUS, W.H.; WEYGAND J.M.; CHUYCHAI P.; MILANO, L.J.; SMITH, C.W.; KIVELSON M.G.

Mérida, Mexico

Conferencia; Proc. of the 30th International Cosmic Ray Conference (ICRC); 2007

The propagation of galactic and solar cosmic rays in the solar wind (SW) can be stronglyinfluenced by the SW fluctuations properties. Magnetohydrodynamic scale fluctuations in the solar windare usually highly anisotropic, and have also been found to exhibit different properties in regions ofhigh and low solar wind speed. Previous studies analyzed the anisotropy properties of the solar windmagnetic fluctuations at scales of the order of (105 106) km (inertial range) using two times – singlepoint measurements (assuming the Taylor frozen-in hypothesis), and found that the fluctuations in thefast solar wind tend to reside in wave vectors with their parallel component (to the mean magnetic field)larger than the perpendicular one, while the fluctuations in the slow wind present the opossite trend. Inthe present study we compare the magnetic autocorrelation function in the solar wind obtained with twotimes – single point observations (from a single spacecraft) with the same quantity obtained from singletime – two points measurements (from simultaneous observations of two spacecraft, observing the purespatial structures). We preliminarily compare also previous results of the anisotropy of the solar windfluctuations, obtained from a single spacecraft, with our new multispacecraft analysis using combiningobservations from the ACE and Wind spacecraft.