Abstract. Using 3-D particle-in-cell (PIC) simulations we studied the structure and temporal behavior of electron holes (e-holes) in a magnetized plasma driven by an electron beam. When e-holes are fully evolved from high-frequency waves in a time of about a few tens of electron plasma periods, most of the wave energy in the plasma resides in them. Parallel to the ambient magnetic field Bo, the potential distribution of an ehole is approximately a Gaussian, and the scalelength gz is only a few Debye lengths when determined by the effective temperature of the beam-modified electron distribution function. Transverse to Bo, the potential distribution tends to have a flat top, which makes it difficult to fit a Gaussian distribution, but the scalelengths at which the potential decays in the transverse directions (gx and gz) are found to be only slightly longer than gz. The passages of electron holes monitored at several points in the simulation volume has the signature of bipolar parallel electric field and unipolar perpendicular electric-field pulses as measured from FAST and POLAR. The eventual decay of e-holes is accompanied by the generation of lower hybrid (gh) waves.

Abstract. Recent observations of electron holes (e-holes) in space plasma have led to theoretical and numerical studies which show that e-holes in a magnetized plasma are unstable nonlinear structures. Their decay generates plasma waves in the frequency bands of lower hybrid (LH) and electrostatic w_histler (EW) waves. An analysis is presented demonstrating that the e-holes are an effective radiator of plasma waves in the above frequency bands critically depending on their scalelength (eñ) transverse to the ambient magnetic field. In this sense, an e-hole acts like a radiating antenna. The results from 3-D numerical simulations are presented to examine the nonlinear consequences of the radiation from e-holes. When e-holes have long e•_ during the initial stage of their existence, they undergo a beading process. This involves radiation of spatial Fourier components corresponding to long scalelength in the structure of e-holes, leaving behind smaller structures. This divides the initially large e-hole structure into several fragments. The resulting smaller structures with e •_ -e, eventually dissipate by radiating transversely structured lower hybrid waves.

Abstract. We present here a systematic simulational study on electron beam driven waves and their consequences in terms of plasma electrodynamics. The study is performed by using three-dimensional particle-in-cell code, parallelized to simulate a large volume of plasma. Our simulation shows that an initial electron beam of finite radius with beam velocity along the ambient magnetic field triggers a series of events in the evolution of the waves and the plasma.

Particle filter techniques are common methods used to estimate the evolving state of nonlinear, non-Gaussian time-variant systems by utilizing a periodic sequence of noisy measurements. The accuracy of particle filter methods has often been shown to be superior to other state estimation techniques, such as the extended Kalman filter (EKF), for many applications. Unfortunately, the high computational cost and highly nondeterministic runtime behavior of particle filters often preclude their use in hard, real-time environments, where filter response must meet the strict timing requirements of the application. Particle filter algorithms are composed of three main stages: prediction, update, and resampling. General purpose graphics processing units (GPGPUs) have been successfully employed in previous research to accelerate the computation of both the prediction and update stages by exploiting their natural fine-grain parallelism. This research focuses on accelerating the resampling stage for GPGPU execution, which has been much more difficult to parallelize due to it's apparent inherent sequentially. This paper introduces a novel GPGPU implementation of the systematic and stratified resampling algorithms that exploit the monotonically increasing nature of the prefix-sum and the evolutionary nature of the particle weighting process to allow the re-indexing portion of the algorithms to occur in a two-phase, multi-threaded manner. This resulting measured factor of performance improvement for the systematic and stratified algorithms was 15x and 32x, respectively, over the serial implementations. INDEX TERMS Graphics processing units, parallel algorithms, parallel architectures, parallel programming, particle filters, state estimation, resampling.

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