IGPP Seminar Series

Correlative Scale, Taylor Scale, and Effective Magnetic Reynolds Number Determination from Plasma Sheet and Solar Wind Magnetic Field Fluctuations

by James Weygand
IGPP, UCLA

Abstract

Cluster data from many different intervals in the magnetospheric plasma sheet are employed to determine the magnetic correlative scale and the Taylor microscale from simultaneous multiple point measurements. For this study we define the correlative scale as the exponential decay constant of the correlation coefficient as a function of spacecraft separation and the Taylor scale as the radius of curvature of the correlation coefficient values at zero separation. The present determination of the Taylor scale makes use of a novel extrapolation technique to derive a statistically stable estimate from a range of measurements at small spatial separations. In the plasma sheet the correlative scale length is found to be largest (about 20,000 km) in the direction parallel to the magnetic field and smallest (about 10,000 km) in the direction perpendicular to the magnetic field. Similar results have been determined in the slow solar wind using Cluster and several other spacecraft. The effective magnetic Reynolds number can be expressed in terms of the correlative scale and the Taylor scale. Knowledge of the effective magnetic Reynolds number may be useful in magnetohydrodynamic modeling of the magnetosphere and the solar wind and may provide constraints on kinetic theories of dissipation in space plasmas.
Tuesday, 20 November 2007
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM