Stochastic growth of waves over Earth's polar cap

Details Stochastic growth of waves over Earth's polar cap Stochastic growth of waves over Earth's polar cap

Dec 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001jgr...10629515c&link_type=abstract

Journal of Geophysical Research, Volume 106, Issue A12, p. 29515-29530

Physics

Plasma Physics

15

Magnetospheric Physics: Auroral Phenomena, Magnetospheric Physics: Plasma Waves And Instabilities, Magnetospheric Physics: Polar Cap Phenomena, Space Plasma Physics: Wave/Particle Interactions

Scientific paper

Bursty waves with widely varying electric fields persist over a wide range of altitudes ~2-7RE at polar cap latitudes in Earth's inner magnetosphere. These ``PF'' waves have frequencies near expected values of the electron plasma frequency (PF), well below the electron gyrofrequency, and are believed to be generated by electron beams. Here it is demonstrated that stochastic growth theory (SGT) can account well for the detailed field statistics of the archetypal PF wave event, by showing that the observed distributions P(logE) of envelope electric fields E are well fitted by the lognormal function predicted by SGT. Weak evidence exists that a nonlinear wave process coexists with stochastic growth physics at large fields >~1 mV m-1 on the basis of fits of the observed P(logE) distribution to the SGT prediction that includes a nonlinear process at high fields and on the discovery of a class of low-frequency waves that may be produced by nonlinear decay of PF waves. An analytic model is developed for why the waves evolve to an SGT state, on the basis of waves driven by an electron beam in MHD density turbulence and the development of fluctuations in the electron beam due to wave growth occurring in localized regions. The model is viable for the polar cap plasma parameters considered, predicting that the wave burstiness should be of order that observed and that the beam fluctuations should have timescales ~10 ms that are below current detection capabilities. SGT thus accounts well for the burstiness and wave statistics, as well as the persistence of the waves and driving distribution. The consistency of the PF wave statistics with SGT also implies the presence of local electron beams over much of the polar cap, whose source is currently unknown. This application brings to five the number of contexts in which SGT applies, suggesting that SGT is widely applicable in space plasmas.

Affiliated with

Also associated with

No associations

Rating

Stochastic growth of waves over Earth's polar cap 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 Stochastic growth of waves over Earth's polar cap, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stochastic growth of waves over Earth's polar cap will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1104800