Collective dynamics of bursty particle precipitation initiating in the inner and outer plasma sheet

Abstract

Abstract.Using multiscale spatiotemporal analysis of bursty precipitation events in the nighttime aurora as seen by the POLAR UVI instrument, we report a set of new statistical signatures of high-and low-latitude auroral activity, signaling a strongly non-uniform distribution of dissipation mechanism in the plasma sheet. We show that small-scale electron emission events that initiate in the equatorward portion of the nighttime auroral oval (scaling mode A 1 ) have systematically steeper power-law slopes of energy, power, area, and lifetime probability distributions compared to the events that initiate at higher latitudes (mode B). The low-latitude group of events also contain a small but energetically important subpopulation of substorm-scale disturbances (mode A 2 ) described by anomalously low distribution exponents characteristic of barely stable thermodynamic systems that are prone to large-scale sporadic reorganization. The high latitude events (mode B) can be accurately described by a single set of distributions exponents over the entire range of studied scales, with the exponent values consistent with globally stable self-organized critical (SOC) behavior. The lowand high latitude events have distinct inter-trigger time statistics, and are characterized by significantly different MLT distributions. Based on these results we conjecture that the inner and outer portions of the plasma sheet are associated with two (or more) mechanisms of collective dynamics that may represent an interplay between current disruption and magnetic reconnection scenarios of bursty energy conversion in the magnetotail.

Discerning a linkage between solar wind turbulence and ionospheric dissipation by a method of confined multifractal motions

“…This means that the similarity in multifractal structure of B z and AE represents strong evidence in favor of the existence of a physical mechanism that links the intermittency of solar wind turbulence and the corresponding intermittency of fluctuations in the ionospheric dissipation rate on these time scales. There is not necessarily a contradiction between existence of such a mechanism and the conjecture that the AE index fluctuations are formed by avalanching dynamics whose main scaling characteristics are of internal magnetospheric origin [ Uritsky et al , 2001, 2008, 2009; Klimas et al , 2010]. The ultimate drive of this avalanching is the solar wind, and even if the main scaling exponents for AE bursting and auroral emission events are of internal origin, the intermittency characteristics may be determined by the intermittency of the driver.…”

25 Years of Self-Organized Criticality: Solar and Astrophysics

“…14 and 20). Another anomaly that was found is the latitude dependence of the size distribution of auroral events (see Uritsky et al 2008 in Table 11), which indicates substantially different scaling regimes of bursty energy dissipation in the inner and outer portion of the geotail plasma sheet (Uritsky et al , 2009).…”

Role of turbulent transport in the evolution of the κ distribution functions in the plasma sheet

“…We propose that the transport of particles from the inner magnetosphere toward the tail could be related to the presence of the turbulence and eddy diffusion in the plasma sheet. The properties of such a turbulence can be studied using different techniques and kinds of measurements [ Zimbardo et al , ], for example, particle and magnetic field measurements on board the high‐altitude satellites [ Borovsky and Funsten , ], auroral intensities from Polar UVI images [ Uritsky et al , , ], and auroral absorption [ Stepanova et al , ]. For this study we will focus on the turbulent eddy diffusion as a mechanism of particle transport.…”