Formation and disruption of current filaments in a flow-driven turbulent magnetosphere

Abstract

[1] Recent observations have established that the magnetosphere is a system of natural complexity. The coexistence of multiscale structures such as auroral arcs, turbulent convective flows, and scale-free distributions of energy perturbations has lacked a unified explanation, although there is strong reason to believe that they all stem from a common base of physics. In this paper we show that a slow but turbulent convection leads to the formation of multiscale current filaments reminiscent of auroral arcs. The process involves an interplay between random shuffling of field lines and dissipation of magnetic energy on sub-MHD scales. As the filament system reaches a critical level of complexity, local current disruption can trigger avalanches of energy release of varying sizes, leading to scale-free distributions over energy perturbation, power, and event duration. A long-term memory effect is observed whereby the filament system replicates itself after each avalanche. The results support the view that that the classical and inverse cascades operate simultaneously in the magnetosphere. In the former, the high Reynolds number plasma flow disintegrates into turbulence through successive breakdowns; in the latter, the interactions of small-scale flow eddies with the magnetic field can self-organize into elongated current filaments and large-scale energy avalanches mimicking the substorm.

Kinetic-scale magnetic turbulence and finite Larmor radius effects at Mercury

“…The fluid component of the magnetospheric turbulence can be reliably identified only during the near‐Mercury portion of the flyby, namely during the first diamagnetic decrease encountered in the inner magnetosphere [ Slavin et al , 2008], gray line in Figure 4f. Based on the analysis of a similar region in the terrestrial magnetosphere [ Uritsky et al , 2010b; Liu et al , 2011; Panov et al , 2010], these fluctuations can manifest transient velocity and magnetic field shears due to reconnection‐driven sunward flow bursts in the plasma sheet. The flows are expected to stir turbulent vortices at the inner edge of the plasma sheet where the sunward convecting plasma sheet ions encounter the stronger planetary dipole magnetic field and are quickly decelerated [ Shiokawa et al , 1998].…”

Correlation as a global measure of geomagnetic activity: Phase boundaries and a precedent line of nodes

“…This persistent feature began to form hours before the disturbance, as evidenced by the 0.7 mHz pulsations with the same line of nodes, and continued to be associated with energy release all through the subsequent varied evolution. The persistence of the line of nodes suggests the feature of memory found in SOC modeling of the CPS by Liu et al [2011].…”

Period doubling in magnetospheric convection cycle

“…Self‐organization means that microscopically random processes yield macroscopically multiscale structures and scale‐free distributions after integration. Examples of this approach as applied to the magnetosphere include works by Chapman et al [1998], Klimas et al [2000, 2004], Liu et al [2006, 2011], and Valli è res‐Nollet et al [2010]. Our present theory is fundamentally dissimilar to this approach, and no further contrast is drawn.…”