HR: 0800h
AN: SH31B-03    [Abstracts]
TI: Intermittency Analysis and Spatial Dependence of Magnetic Field Disturbances in the Fast Solar Wind
AU: Yang, Y
EM: yhyang@pssc.ncku.edu.tw
AF: 1Plasma and Space Science Center, National Cheng Kung University, Tainan, 70101, Taiwan
AU: * Tam, S W
EM: sunwytam@pssc.ncku.edu.tw
AF: 2Institute of Space, Astrophysical and Plasma Sciences, National Cheng Kung University, Tainan, 70101, Taiwan
AU: * Tam, S W
EM: sunwytam@pssc.ncku.edu.tw
AF: 1Plasma and Space Science Center, National Cheng Kung University, Tainan, 70101, Taiwan
AB: The intermittency properties of the magnetic field fluctuations in the fast solar wind are investigated here at various heliocentric distances based on the Helios measurements from 0.29 to 1.0 AU during 1974-1981. Seven quantities of normalized PDF (Probability Distribution Function) associated with the magnetic field and its disturbances and the magnetic energy are utilized to characterize the intermittency by fitting the PDF with a Castaing distribution and by using the idea of ˇ§Flatnessˇ¨. The magnetic field fluctuations are found to be more intermittent at farther distances from the sun and at smaller time scales. For all the quantities considered, the intermittency decreases with increasing time scales, with their PDF eventually approaching Gaussian distributions. Such a transition occurs at a relatively small time scale for the perpendicular component of the perturbed magnetic field in particular. Moreover, the increase in the degree of intermittency with decreasing time scale is more obvious farther from the sun. Based on the finding of a good power-law relationship between the magnetic energies of the perturbed and mean fields and the feature of lower mean magnetic field at a larger heliocentric distance, the trend of spatial variation of magnetic energy is found to have a power-law scaling at different time scales. By considering the ion cyclotron resonance condition for the Helios measurements presented here, we suppose that the perturbed magnetic fields in the fast solar wind in the frequency range considered are mainly affected by cross-scale redistribution of the wave energy.
DE: 2134 Interplanetary magnetic fields
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
SC: SPA: Solar and Heliospheric Physics [SH]
MN: 2009 Joint Assembly