Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000apj...541..489z&link_type=abstract
The Astrophysical Journal, Volume 541, Issue 1, pp. 489-494.
Astronomy and Astrophysics
Astronomy
13
Interplanetary Medium, Magnetohydrodynamics: Mhd, Sun: Solar Wind, Sun: Magnetic Fields, Turbulence
Scientific paper
A new characterization of interplanetary magnetohydrodynamic (MHD) turbulence over the polar regions of the Sun is presented. The pickup of interstellar ions in the supersonic solar wind is thought to generate significant levels of magnetic field fluctuations, which can then scatter the ions toward isotropy in the solar wind frame. Wave generation by pickup ions in the outer polar heliosphere is observed infrequently. Furthermore, pickup ion protons and helium distributions are found to exhibit pronounced anisotropies in quasi-radial magnetic field regions of the solar wind. A stochastic growth model is developed here for the growth of MHD waves driven by pickup ion instabilities in the polar solar wind. This is closely related to stochastic growth theories developed in other contexts. By considering temporal and spatial variations in the local interplanetary magnetic field (IMF) we compute the mean wave growth rate and variance of pickup ion excited MHD waves. It is found that the mean wave growth rate can be very small (and even negative), but the variance can be large in the polar solar wind, indicating that localized regions experience significant wave growth in a stochastic fashion. This suggests that pickup ion driven turbulence in the outer polar heliosphere has a bursty or intermittent character, occurring in clumps, which makes the detection of individual wave growth events rare. The stochastic growth model is shown to be self-consistent, predicting very bursty wave growth by numerous long-lived beamlike fluctuations in the pickup ions during characteristic wave growth times, and justifying qualitatively the persistence of beamlike anisotropies in the observed pickup ion distribution. Such a picture presents an entirely different characterization of low-frequency MHD turbulence driven by the pickup of interstellar atoms in the polar regions of the solar wind from that of homogeneous MHD turbulence.
Cairns Iver H.
Zank Gary P.
No associations
LandOfFree
Pickup Ion-driven Turbulence in the Polar Heliosphere: A Stochastic Growth Model does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Pickup Ion-driven Turbulence in the Polar Heliosphere: A Stochastic Growth Model, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pickup Ion-driven Turbulence in the Polar Heliosphere: A Stochastic Growth Model will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1524463