Dynamics of the Dissipation Range for Solar Wind Magnetic Fluctuations

Robert J. Leamon, Norman F. Ness, Charles W. Smith and Hung K. Wong

Solar Wind 9 (1999)

Abstract:

The dissipation range of interplanetary magnetic field (IMF) fluctuations is perhaps the least-studied aspect of the IMF. This is undoubtedly due, at least in part, to the large volume of data required to perform thorough studies of the high-frequency spectrum. We examine the properties of the dissipation range at 1 AU as observed by the WIND spacecraft, which include: (1) a general steepening of the power spectrum at spacecraft-frame frequencies comparable to, but greater than, the proton cyclotron frequency; (2) magnetic fluctuations that are largely transverse to the mean magnetic field, but less transverse than is seen in the high-frequency extent of the inertial range; (3) significant, but not maximal helicity and polarization signatures that indicate that ion-resonant dissipation is contributing to the magnetic spectrum; (4) a dominant fraction of the total magnetic energy is associated with wavevectors at large angles to the mean magnetic field; and(5) strong plasma $\beta$ effects in the above results. In addition, we present a comparison of the observed onset of dissipation with a theory based on Kinetic Alfven waves.