Self‐consistent model of magnetospheric ring current and propagating electromagnetic ion cyclotron waves: Waves in multi‐ion magnetosphere

Abstract

[1] The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves (Khazanov et al., 2003) is presented. In order to adequately take into account wave propagation and refraction in a multi-ion magnetosphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate the spatial, temporal, and spectral evolution of the ring current and of electromagnetic ion cyclotron waves. To demonstrate the effects of EMIC wave propagation and refraction on the wave energy distribution and evolution, we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, owing to the density gradient at the plasmapause, the net wave refraction is suppressed, and He + -mode grows preferably at the plasmapause. This result is in total agreement with previous ray tracing studies and is very clearly found in presented B field spectrograms. Second, comparison of global wave distributions with the results from another ring current model reveals that this new model provides more intense and more highly plasmapause-organized wave distributions during the May 1998 storm period. Finally, it is found that He + -mode energy distributions are not Gaussian distributions and most important that wave energy can occupy not only the region of generation, i.e., the region of small wave normal angles, but all wave normal angles, including those to near 90°. The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping and subsequent downward heat transport and excitation of stable auroral red arcs.Citation: Khazanov, G. V., K. V. Gamayunov, D. L. Gallagher, and J. U. Kozyra (2006), Self-consistent model of magnetospheric ring current and propagating electromagnetic ion cyclotron waves: Waves in multi-ion magnetosphere,

Model of electromagnetic ion cyclotron waves in the inner magnetosphere

“…The function G ( , k, r) has roots for the EMIC eigenmodes only, i.e., G ( (k), k, r) = 0 at any point along the phase trajectory. An extensive verification of our ray tracing code against previously published results for different plasmaspheric density models and for all possible EMIC wave modes in a multi-ion magnetospheric plasma demonstrated a very good agreement between the results [Khazanov et al, 2006].…”

“…To model RC ions we use the same approach we used in our previous work [Khazanov et al, 2003[Khazanov et al, , 2006Gamayunov et al, 2009]. The RC ion module used in our code has been developed at the University of Michigan by Fok et al [1993] and Jordanova et al [1996].…”

“…A schematic of the reflected ray trajectories is similar to that shown in Figure 6 of the paper by Perraut et al [1984], except we do not consider here the wave tunneling through the O + -He + bi-ion latitudes. (Note that wave tunneling may be an important energy sink for the He + -mode EMIC waves when the O + fraction in plasma is less than about 1% [e.g., Khazanov et al, 2006].) All the ray trajectories that pass the O + -He + bi-ion latitudes propagating downward to the ionosphere eventually leave the simulation domain, and we neglect them.…”

Modeling the superstorm in November 2003

“…The loss cone loss (dark red curves) has only a very minor effect on the total energy budget for either species. The loss cone may play a more important role if pitch angle diffusion due to wave-particle interactions is considered [Jordanova et al, 1998[Jordanova et al, , 2001Khazanov et al, 2002Khazanov et al, , 2006. Charge exchange loss (magenta curves) is the dominant loss mechanism, especially for O + .…”

Study of Electromagnetic Ion-Cyclotron Instability in a Magnetoplasma

“…This leads to a frequency structure of wave growth ordered by the heavy ion gyro frequencies [6][7][8]. Recently a complete description of self consistent model of magnetospheric ring current interacting with EMIC wave has been represented on the basis of kinetic equation by Khazanov et al [9,10] and Kudrin et al [43].…”