Crucial role of ring current H⁺ in electromagnetic ion cyclotron wave dispersion relation: Results from global simulations

Abstract

[1] The effect of ring current (RC) H + in the real part of electromagnetic ion cyclotron (EMIC) wave dispersion relation is studied on the global magnetospheric scale. The simulations of the 2-3 May 1998 storm are done using our model of the He + -mode EMIC waves self-consistently interacting with RC ions. The wave model describes EMIC waves bouncing between the off-equatorial magnetic latitudes, which correspond to the bi-ion hybrid frequencies in conjugate hemispheres, along with tunneling across the reflection zones and subsequent strong absorption in the ionosphere. This model explicitly includes the EMIC wave growth/damping, propagation, refraction, reflection, and tunneling in a multi-ion magnetospheric plasma. An analysis of the wave observations is presented and strongly supports our wave model. The main findings from our simulations can be summarized as follows: First, RC H + only contributes a few percent to the total plasma density near the inner edge of the plasmasphere boundary layer, but it can dominate outside the plasmapause. About 90% of the RC H + density in the dawn MLT sector is formed by the suprathermal ions (]2 keV), while a major contribution in dusk comes from the 10-100 keV ions, allowing not more than 10-20% for the suprathermal ions. Second, RC H + in the real part of the wave dispersion relation increases local growth rate leading to a dramatic change in the wave global patterns. The ''new'' EMIC waves are generated not only on the plasmapause, as expected from previous global simulations, but also inside and outside the plasmapause consistent with the observations. Citation: Gamayunov, K. V., and G. V. Khazanov (2008), Crucial role of ring current H + in electromagnetic ion cyclotron wave dispersion relation: Results from global simulations,

Model of electromagnetic ion cyclotron waves in the inner magnetosphere

“…In the present study, we also included the RC H + and O + only in the imaginary part of the EMIC wave dispersion relation but neglected it in the real part. (The effect of RC H + in the real part of wave dispersion relation was previously discussed, for example, by Gamayunov and Khazanov [2008].) As follows from Figure 3 in the paper by Gamayunov et al [2009], the cross polar cap potential (CPCP) drop grows from about 50 kV up to about 275 kV during approximately 2 h from 74 to 76.…”

Self‐consistent model of magnetospheric electric field, ring current, plasmasphere, and electromagnetic ion cyclotron waves: Initial results

“…The second model is governed by a coupled system of the RC kinetic equation and the wave kinetic equation. This model self‐consistently treats a mesoscale electrodynamic coupling of RC and EMIC waves, and determines the evolution of the EMIC wave power spectral density [ Gamayunov and Khazanov , 2008]. The RC‐EMIC wave model explicitly includes the wave growth/damping, propagation, refraction, reflection, and tunneling in a multi‐ion magnetospheric plasma.…”

“…As such, the main purpose of this paper is to present a new self‐consistent model of the magnetospheric electric field, RC, plasmasphere, and EMIC waves along with initial results from the model simulations. The results presented in this study were obtained from simulations of the 2–4 May 1998 geomagnetic storm, that we previously analyzed using an analytical formulation of the Volland‐Stern electric field [ Khazanov et al , 2006, 2007b; Gamayunov and Khazanov , 2008].…”

Circulation of Heavy Ions and Their Dynamical Effects in the Magnetosphere: Recent Observations and Models

“…In a hydrogen plasma there is one frequency band (hydrogen band) where waves can be observed, while in a multi-ion plasma EMIC waves are observed in three separate bands. A number of modeling studies explored the role of H + , He + , and O + ions on the excitation and propagation properties of EMIC waves (e.g., Gamayunov and Khazanov 2008;Omidi et al 2013, and references therein). Omidi et al (2013) using hybrid simulations (kinetic for ions and fluid for electrons) showed that EMIC waves are generated in the near equatorial region and propagate parallel or anti-parallel to the magnetic field directly towards the ionosphere where they are absorbed when the O + concentration is lower than 7 %.…”