Speaker
Theodoros Sarris
(Democritus University of Thrace)
Description
In studies of particles' radial diffusion processes in the magnetosphere it is well known that Ultra-Low Frequency (ULF) waves of frequency m*ω_d can resonantly interact with particles of drift frequency ω_d, where m is the azimuthal mode number of the waves; however due to difficulties in estimating m an over-simplifying assumption is often made in radial diffusion simulations, namely that all ULF wave power is located at m=1 or, in some cases, m=2. In the present work, a technique is presented for extracting information on the distribution of ULF wave power in a range of azimuthal mode numbers, through calculations of the cross-power and phase differences between a number of azimuthally aligned pairs of magnetometers, either in space or on the ground, including estimates of the corresponding phase velocities; subsequently, through integrating the power of the ULF fluctuations at only particular ranges of phase differences that would correspond to a particular mode number, we provide an order of magnitude estimate of the fraction of the total power at each phase difference range or mode number. We find that the temporal evolution of power at each mode number gives unique insight into the temporal evolution of ULF waves during a storm as well as a more accurate characterization of broadband ULF waves that could be used in more accurate radial diffusion simulations.
Primary author
Theodoros Sarris
(Democritus University of Thrace)
