Charged particle acceleration by intermittent electromagnetic turbulence

Abstract

[1] We studied the role of intermittency in the process of acceleration and transport of charged particles by electromagnetic turbulence. We propose a simple model of electromagnetic turbulence with a variable level of intermittency. The magnetic field is described as a superposition of an ensemble of magnetostatic plane waves and of spatially localized dynamic magnetic clouds. The amplitudes of magnetic clouds are distributed according to an intermittent map. The model approximates essential properties of turbulence observed 'in situ' in the neutral plane of the Earth's magnetotail. Numerical integration of charged particle trajectories in such a dynamic electromagnetic environment shows that, for the fixed time interval, the higher the level of intermittency, the higher the energy gain. Moreover, in a sufficiently intermittent turbulence, particle acceleration occurs without significant intensification of the spatial transport. Citation: Zelenyi, L. M., S. D. Rybalko, A. V. Artemyev, A.

Van Allen Probes observations of magnetic field dipolarization and its associated O+ flux variations in the inner magnetosphere at L < 6.6

“…The generation mechanism of the fluctuating magnetic and electric fields during dipolarization is considered to be the drift-driven electromagnetic ioncyclotron instability [e.g., Lui et al, 2008;Yoon et al, 2009;Mok et al, 2010;Huang et al, 2012;Nosé et al, 2014]. Numerical simulation studies reported that such electromagnetic fluctuations are very effective for particle acceleration [Artemyev et al, 2009;Zelenyi et al, 2011]. A statistical study using the Geotail data revealed that O + ions Journal of Geophysical Research: Space Physics 10.1002/2016JA022549 are nonadiabatically accelerated by the fluctuations whose frequencies are close to f G (O + ) and have larger energy densites than H + ions [Ono et al, 2009].…”

Generation of Alfvénic waves and turbulence in reconnection jets

“…It is also interesting to study the effect of the guide magnetic field B z on the streaming instabilities, because a global dynamical behavior of magnetic reconnection is known to be controlled by the guide magnetic field. In fact, the guide magnetic field in the magnetotail, which is the dawn-dusk magnetic field, is known to exist due to the penetration of the solar wind magnetic field [e.g., Cowley, 1981;Petrukovich, 2011;Rong et al, 2012]. Figure 8 are the growth rates of the standard tearing mode and the streaming tearing, sausage, and kink modes as a function of the initial guide magnetic field B z .…”

“…It has been argued that turbulence plays a crucial role in the dynamic evolution of magnetic reconnection and that the magnetic energy dissipation rate can be enhanced by turbulence [e.g., Matthaeus and Lamkin, 1986;Lazarian and Vishniac, 1999;Loureiro et al, 2009;Higashimori et al, 2013;Yokoi et al, 2013]. In addition to its role in the dynamic evolution of reconnection, turbulence is believed to play an essential role not only in thermal plasma heating but also in nonthermal particle production through the stochastic scattering of particles [e.g., Veltri et al, 1998;Greco et al, 2002;Zelenyi et al, 1998Zelenyi et al, , 2011Lazarian et al, 2012]. However, in previous studies, it was postulated that turbulence can be generated in the high β plasma sheet with a high magnetic Reynolds number, but the detailed mechanism required to generate Alfvénic waves and turbulence during the dynamic evolution of reconnection is not understood as yet.…”

Magnetic fluctuations embedded in dipolarization inside geosynchronous orbit and their associated selective acceleration of O+ ions

“…The magnetic fluctuations associated with dipolarization are commonly accompanied by the fluctuating inductive electric field [ Lui et al , ; Lopez et al , ; Ohtani et al , ] that can accelerate ions nonadiabatically [ Artemyev et al , ; Zelenyi et al , ]. Using Geotail data obtained in the near‐Earth plasma sheet, Ono et al [] found that O + ions have larger energy density and their energy spectrum becomes harder when magnetic fluctuations have larger power near .…”