HR: 16:15h
AN: SM54A-02 INVITED    [Abstracts]
TI: The observed scaling properties of fluctuations in the solar wind and in geomagnetic indices: intermittent turbulence and coronal driver.
AU: * Chapman, S C
EM: S.C.Chapman@warwick.ac.uk
AU: Hnat, B
EM: B.Hnat@warwick.ac.uk
AF: Centre for Fusion, Space and Astrophysics, Physics Dept., Univ. of Warwick, Coventry, CV4 7AL, United Kingdom
AU: Kiyani, K
EM: K.Kiyani@warwick.ac.uk
AF: Centre for Fusion, Space and Astrophysics, Physics Dept., Univ. of Warwick, Coventry, CV4 7AL, United Kingdom
AU: Watkins, N
EM: nww@bas.ac.uk
AF: Physical Sciences, British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB1 1UJ, United Kingdom
AB: The solar wind provides a natural laboratory for observations of MHD turbulence over extended temporal scales. We quantify the ‘macroscopic' scaling seen in extended intervals of solar wind by testing for scaling in the Probability Density Functions (PDF) of fluctuations in the timeseries both directly and via structure function analysis. In practice there are statistical limitations presented by a finite length time series which we will first discuss. The anisotropic nature of solar wind fluctuations can be accessed by decomposing the vector velocity linearly into two coexistent components perpendicular and parallel to the local average magnetic field. These show distinct scaling. That of the perpendicular fluctuations is consistent with recent predictions for anisotropic MHD. That of the parallel fluctuations is close to the scaling which we find in the number and magnetic energy density, and Poynting flux. One interpretation of the co- existence of these scalings in the solar wind is that they reflect both local and nonlocal phenomenologies, with implications for our understanding of the evolving solar wind. Intriguingly, a more detailed analysis of magnetic energy density reveals a solar cycle dependence, and at solar maximum, self affine rather than multifractal scaling, suggesting the scaling is of solar origin. To see how these fluctuations impact on magnetospheric activity, we consider the same analysis performed on fluctuations of the AU and AL geomagnetic indices that provide a measure of magnetospheric activity, and of the epsilon parameter which is a measure of the solar wind driver.
DE: 2159 Plasma waves and turbulence
DE: 2164 Solar wind plasma
DE: 2784 Solar wind/magnetosphere interactions
DE: 7536 Solar activity cycle (2162)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting