[1] Two vortex-like plasma flow structures have been observed at the outer radiation belt and/or the ring current region on 11 April 2002, from 0415 to 0635 UT, when the Cluster fleet entered (in the Southern Hemisphere) and exited (in the Northern Hemisphere) the boundary layer of the inner magnetosphere near 2130 MLT. On 11 April 2002 during the period of interest, the solar wind speed was high, and the geomagnetic activity was moderate. These two vortices have opposite rotation directions and are characterized by bipolar signatures in the flow V x components with peak-to-peak amplitudes of about 40 km/s. The inflection points of the plasma flow coincide precisely with the local maxima of the duskward core flow V y (30 km/s) which exceed the surrounding flow by 3-4 times in magnitude for both vortices. A pair of bidirectional current sheets and bipolar electric fields (E y ) are found to be closely associated with these vortices. Whereas magnetic field disturbances are observed only in B x and B y components, the magnetic magnitude stays almost unchanged. Vortices observed both inbound and outbound at the boundary of the radiation belt at nearly the same location (L shell and latitude), suggesting they may last for more than 140 min. The scale sizes of the two vortices are about 810 km and 1138 km, respectively. Interestingly, it is found that Earth's ionospheric singly charged oxygen are precipitating in the vortex dynamic process, having energies less than 1 keV and having a strong field-aligned pitch angle distribution. These plasma flow vortices are suggested to be formed at the interface between the enhanced ionospheric outflow stream from the polar ionosphere and a sudden braking and/or azimuthal deflection of bursty bulk flows generated by the tail reconnection. These observed flow vortices provide a link among the inner magnetosphere, the tail plasma sheet, and the Earth's ionosphere by coupling magnetic shear stresses and plasma flow momentum.

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<p>Whistler mode chorus waves play a vital role in the Earth’s outer radiation belt dynamics through the cyclotron resonant pitch angle diffusion.     Recent numerical studies have shown that the temporal and spatial variability of wave growth parameters have universal importance for the diffusion process, which should be much larger than those in the traditional averaged diffusion model.       In the present study, we analyzed both the temporal and spatial coherence of chorus wave in a statistical method using data from the EMFISIS instrument onboard the Van Allen Probes A&B from November 2012 to July 2019. In total, we find 3,875 chorus wave events to calculate the correlation of wave amplitudes between Van Allen Probes A&B.      The results show that both the spatial and temporal correlation of chorus waves decrease significantly with increasing spacecraft separation and time lag, and the spatial and temporal coherence of chorus wave only last ~433 km and ~12 s. We also find that the spatial coherence of chorus waves is higher at L>6, on the dayside, or with a lower geomagnetic index (AL*), while the temporal coherence of chorus waves does not depend on the L-shell, geomagnetic index (AL*) or magnetic local time (MLT). Our results will increase the accuracy of modeling wave-particle interactions due to chorus waves.</p>

In this study the nonlinear behavior of a buck converter was simulated and the responses of Phases 1 and 2 and the chaotic phase were investigated using changes of input voltage. After a dynamic system model had been acquired using basic electronic circuit theory, Matlab and Pspice simulations were used to study system inductance, resistance, and capacitance. The characteristic changes of input voltage, and phase plane traces from simulation and experiments showed nonlinear behavior in Phases 1 and 2, as well as a chaotic phase. PID control and Integral Absolute Error (IAE) were used as adaption coefficients to control chaotic behavior, and particle swarm optimization (PSO) and the genetic algorithm were used to find the optimal gain parameters for the PID controller. Simulation results showed that the control of chaotic phenomena could be achieved and errors were close to zero. Fuzzy control was also used effectively to prevent chaos. The experimental results also showed nonlinear behavior from Phases 1 and 2 as well as the chaotic phase. Laboratory experiments conducted using both PID and fuzzy control echoed the simulation results. The fuzzy control results were somewhat better than those obtained with PID.

Abstract. Ultra-low-frequency (ULF) waves are ubiquitous in the magnetosphere. Previous studies mostly focused on ULF waves in the dayside or near-Earth region (with radial distance R<12 RE). In this study, using the data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission during the period from 2008 to 2015, the Pc5–6 ULF waves in the tail region with XGSM∗<0, 8 RE<R<32 RE (mostly on the stretched magnetic field lines) are studied statistically. A total of 1089 azimuthal oscillating events and 566 radial oscillating events were found. The statistical results show that both the azimuthal and radial oscillating events in the magnetotail region (12 RE<R<32 RE) are more frequently observed in the post-midnight region. The frequency decreases with increasing radial distance from Earth for both azimuthal oscillating events (8 RE<R<16 RE) and radial oscillating events (8 RE<R<14 RE), which is consistent with the field line resonances theory. About 52 % of events (including the azimuthal and radial oscillating events) are standing waves in the region of 8–16 RE, while only 2 % are standing waves in the region of 16–32 RE. There is no obvious dawn–dusk asymmetry of ULF wave frequency for events in 8 RE<R<32 RE, which contrasts with the obvious dawn–dusk asymmetry found by previous studies in the inner magnetosphere (4 RE<R<9 RE). An examination for possible statistical relationships between the ULF wave parameters and substorm occurrences is carried out. We find that the wave frequency is higher after the substorm onset than before it, and the frequency differences are more obvious in the midnight region than in the flank region.