UMD Plasma Seminar

Plasma Physics Seminar

Fall 2022 Schedule

September 7th, Wed. 3:30PM Location TBD	Open
September 14th, Wed. 3:30PM Location TBD	Open
September 21st, Wed. 3:30PM Location TBD	Open
September 28th, Wed. 3:30PM ERF 1207, Large Conference Room	Kirill Lezhnin, PPPL Laser ion acceleration from tailored solid targets with micron-scale channels Laser ion acceleration is a promising concept for the generation of fast ions using a compact laser-solid interaction setup. In this study, we theoretically investigate the feasibility of ion acceleration from the interaction of petawatt-scale laser pulses with a structured target that embodies a micron-scale channel filled with relativistically transparent plasma. Using 2D and 3D Particle-In-Cell (PIC) simulations and theoretical estimates, we show that it is possible to generate GeV protons with high volumetric charge and quasi-monoenergetic features in the energy spectrum. Optimal parameters of the target are obtained using 2D PIC simulations and interpreted on the basis of an analytical two-stage ion acceleration model. 3D PIC simulations and realistic preplasma profile runs with 2D PIC show the feasibility of the presented laser ion acceleration scheme for the experimental implementation at the currently available petawatt laser facilities.
October 5th, Wed. 3:30PM Location TBD	Open
October 12th, Wed. 3:30PM ERF 1207, Large Conference Room	Julie Vievering, APL Investigating the Nature of Energy Release during Solar Eruptive Events Solar flares are some of the most energetic events in the solar system, producing bursts of radiation across the electromagnetic spectrum and often resulting in significant space weather hazards at Earth. Measurements of high-energy emission from the earliest phases of flares (e.g., pre-flare, impulsive phases) contain key physics about how reconnection and energy release are triggered, how flares develop, and how energy is transferred into accelerated particles and hot plasma. In the first part of this presentation, we leverage simultaneous measurements of flare hard X-ray (HXR) emission, magnetic reconnection, and coronal mass ejection (CME) acceleration using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), the Solar Dynamics Observatory (SDO), and the Solar TErrestrial RElations Observatory (STEREO) to study the evolution of 12 eruptive events. We analyze the relative timing of these phenomena, focusing on event onset and fast-varying features, or "bursts," in the HXR and reconnection rate profiles to improve our understanding of the particle acceleration mechanisms and the connections between flare and CME energization. Further insight into early flare physics will be enabled by improvements in instrumentation (e.g., finer spatial/temporal resolution, greater sensitivity) and observational coverage across the electromagnetic spectrum throughout the duration of the events. In the second part of this presentation, we present a concept for real-time solar flare predictions: a tool that rapidly aggregates near-real-time signatures of flare onset, including X-ray and extreme ultraviolet (EUV) irradiance measurements, to provide early prediction of the magnitude and duration of ensuing solar eruptive events. Such a tool will enable triggered observations of solar transients, which is particularly important for observatories targeting flare physics that are restricted in field of view and/or observing time, including novel solar instruments onboard sounding rockets. We present preliminary analyses of early flare signatures from the Geostationary Observational Environmental Satellite (GOES) X-ray Sensor (XRS) and EUV Sensor (EUVS), exploring their predictive value for such an application.
October 19th, Wed. 3:30PM	APS DPP Meeting
October 26th, Wed. 3:30PM ERF 1207, Large Conference Room	Bo Miao, Jaron Shrock, Ela Rockafellow, University of Maryland Multi-GeV electron bunches from an all-optical laser wakefield accelerator with optical guiding of high intensity laser pulses Conventional RF electron accelerators are limited by breakdown potentials to ~100 MeV/m. This poses significant economic and practical obstacles for the construction of new, high energy particle accelerators which can be used as advanced light sources, or as colliders to probe new fundamental physics regimes. Laser Wakefield accelerators (LWFAs), which can achieve acceleration gradients 1000 times greater, offer a promising alternative for the next generation of accelerators. LWFAs use the plasma waves (wakes) driven by an ultra-intense laser pulse to accelerate electron bunches to near luminal velocities. For maximal energy gain, the wave needs to be driven over tens of centimeters in a low-density (~1 x 10^17 cm^-3) plasma. This poses a natural problem since an ultra-high intensity laser pulse will diffract on a much shorter scale, reducing the intensity below that required to drive a wake in the plasma. In this talk we will discuss a new method for optically generating plasma waveguides to enable meter scale LWFAs and the first successful implementation of the technique to accelerate electron bunches up to 5 GeV in a 20 cm all-optical LWFA. We will present transverse plasma interferometry, guided mode images and optical spectra, electron beam profiles, and electron spectra collected during experimental campaigns on the ALEPH laser at CSU, as well as particle in cell simulations to supplement the physical picture of the acceleration process.
November 2nd, Wed. 3:30PM ERF 1207, Large Conference Room	Manaure Francisquez, PPPL One-dimensional gyrokinetics of an HTS mirror High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields to compress loss cones and enhance confinement, and may offer cheaper, more compact candidates for fusion power plants. This new class of devices may exhibit largely unexplored interchange and gradient-driven modes, which can be studied using gyrokinetics given the strong magnetization and prevalence of kinetic effects. Our present focus is to: a) determine if oft-used gyrokinetic models for open field lines produce the (Pastukhov) electrostatic potential confining electrons; b) examine and address challenges faced by modern gyrokinetic codes in studying an HTS mirror. We show that a one-dimensional limit of said models self-consistently develops a potential that meets the analytically-approximated Pastukhov minimum. Additionally, we describe computational challenges of studying HTS mirrors with open field line gyrokinetic solvers, and propose a force-softening technique to mitigate small time steps needed by time integration in colossal magnetic field gradients produced by HTS coils. Force-softening attains speed ups of 16X.
November 9th, Wed. 3:30PM Location TBD	Open
November 16th, Wed. 3:30PM ERF 1207, Large Conference Room	Jaye Verniero, Goddard Space Flight Center Toward a trans-disciplinary framework for tracing cosmic energy flow Heliophysics is inherently interdisciplinary, connecting multiple sub-disciplines within the space sciences, to achieve an enhanced understanding of the way the Sun influences its surrounding space-environment. The uniting theme is energy transfer: how is it generated and where does it go? The subject of kinetic-scale wave-particle interactions is often studied independently from macroscale contexts. In this talk, we first approach the problem within the framework of turbulent energy dissipation mechanisms. We overview what we have learned about the nature of energy transfer in the inner heliosphere as seen by Parker Solar Probe's initial orbits around the Sun. Specifically, we present observations of asymmetric particle velocity distribution functions synchronous with electromagnetic fields measurements. We conclude with a discussion of generalizing the language of energy dynamics within the framework of mathematics, working toward a trans-disciplinary approach to heliophysics.
November 23rd, Wed. 3:30PM Location TBD	Technically open, but during UMD's Thanksgiving recess so extremely unlikely
November 30th, Wed. 3:30PM Postponed until 2023 ERF 1207, Large Conference Room	Mel Abler, Space Science Institute Laboratory Study of Residual Energy Generation in Strong Alfven Wave Interactions The solar wind is a classic example of a turbulent plasma. At moderate scales (larger than ion-kinetic scales) turbulent fluctuations in the solar wind are often Alfvenic in character, meaning that their magnetic and flow velocity fluctuations are proportional to each other. However, observations of the solar wind have shown that there is a significant difference in the energy in the velocity fluctuations and the normalized magnetic field fluctuations. This difference, called the residual energy, should be zero for linear Alfven waves, but is consistently observed to be negative in the solar wind, with magnetic fluctuations dominating. This work investigates the energy partition of strong three-wave interactions as a building block of interactions in the turbulent cascade. Preliminary results from an experimental campaign on LAPD studying three-wave interactions of Alfven waves in an MHD-like regime will be presented.
December 7th, Wed. 3:30PM Location TBD	Open

Contact Information: Marc Swisdak or Ian Abel