During magnetic reconnection in collisionless plasma strong electron jets often emanate from the electron diffusion region (EDR). Given the results of the influential Sweet‐Parker reconnection model (derived for a collisional plasma), it is commonly assumed that these electron jets are driven by the reconnection electric field. In contrast, kinetic models and simulations have suggested that...
Collisionless shocks are among the most fundamental nonlinear processes in plasmas. Generated by violent interactions of supersonic plasma flows with the interstellar medium or planetary magnetospheres, collisionless shocks are inferred to heat the plasma, amplify magnetic fields, and accelerate electrons and protons to highly relativistic speeds. However, the exact mechanisms that control...
Recent advancements in the state-of-the-art modelling of relativistic astrophysical plasma via numerical simulations are presented. In particular, I will focus on a novel implementation of a genuinely 4th-order accurate finite volume scheme for the solution of the relativistic MHD equations in the presence of a finite conductivity. The method has been successfully implemented and validated in...
Space plasma simulations are typically categorized into fluid and kinetic models, which are employed for modeling macroscopic and microscopic phenomena, respectively. Fluid models consider only lower-order moments (usually up to the second order), whereas kinetic models have degrees of freedom that are more than one order of magnitude larger. This introduces a significant gap between the two...
Recent decades have seen great progress in the experimental investigation of fundamental processes that are relevant to geophysical and astrophysical fluid dynamics. For such studies, liquid metals have proven particularly suited, partly owing to their small Prandtl numbers which are comparable to those in planetary cores and stellar convection zones, partly due to their high electrical...
The transport of energy and momentum and the heating of plasma particles by waves and turbulence are key ingredients in many problems at the frontiers of heliospheric and astrophysics research. This includes the heating and acceleration of the solar wind, the observational appearance of black-hole accretion flows on event-horizon scales, and the properties of the hot, diffuse plasmas that fill...
We investigate nonlinear processes in the generation of whistler-mode chorus emissions in the Earth's inner magnetosphere by a series of electron hybrid code simulations. We also study propagation properties of chorus emissions under the presence of duct structure in the magnetosphere. Chorus emissions are coherent whistler-mode waves with varying frequencies in the typical frequency range of...
In many scientific, industrial, and economical applications, knowledge of fields, quantities that vary as a function of position, is essential.
Inferring a physical field from data, however, is an ill posed problem, as the finite data can not alone constrain the infinite number of degrees of freedom of a function over continuous space. Domain knowledge has to regularize the set of possible...
NASA’s Magnetospheric Multiscale mission (MMS) has provided and continues to provide heretofore unimaginable insight into the kinetic machinery of the magnetic reconnection process. These successes are based on innovative combinations of extreme-precision observations of magnetic reconnection at the Earth’s magnetopause and inside the nightside magnetotail, with concurrent theoretical analyses...
With the advent of Ultra-High Energy gamma-ray astronomy (photons above 100 TeV energies) it is at last possible to directly probe the most extreme particle accelerators in our galaxy. Two source classes have emerged as highly prominent producers of the cosmic rays above PeV energies, namely massive stellar clusters and microquasars, adding a new dimension to the long held supernova remnant...
Magnetic reconnection serves as a crucial mechanism for generating various sources of free energy for waves and instabilities, including pressure gradients, temperature anisotropies, and large electric currents. In this talk, we focus on recent observations of waves in laboratory reconnection experiments, particularly in the Magnetic Reconnection Experiment (MRX).
Whistler waves, originating...
Here we report the particle acceleration and heating of magnetic reconnection under the influence of high guide field in the merging spherical tokamak formation experiments in ST40 and TS-6. In addition to the extension of ion heating scaling $\Delta T_i\propto B_{rec}^2$ in keV range, our recent experiments explored the following 3 new findings using 96CH/320CH ion Doppler tomography and...
Numerical schemes that preserve the structure of the underlying kinetic
equations can provide new insights into the long time behavior of plasmas. Implicit schemes offer the possibility to simulate large scale systems where the characteristic plasma parameters, skin depth and plasma frequency, are underresolved. A very efficient semi-implicit energy-conserving scheme can be derived for the...
The Basic Plasma Science Facility (BaPSF) at UCLA is a collaborative research facility for studies of fundamental processes in magnetized plasmas, supported by US DOE and NSF. The centerpiece of the facility is the Large Plasma Device (LAPD), a 20m long, magnetized linear plasma device. The LAPD is used to study a number of fundamental processes, including: collisionless shocks; dispersion...
Interaction between the solar wind and upper atmosphere facilitates various atmospheric escape processes from terrestrial planets. The escape rate depends on various conditions such as the distance from the Sun, solar activities, planetary size, atmospheric composition, and intrinsic magnetic field. The atmosphere retention is one of necessary conditions for habitable terrestrial exoplanets....
Axial merging of two torus plasmas is utilized to form a high ion temperature plasma in fusion devices through energy conversion by magnetic reconnection. In a spherical tokamak merging experiment [1] in which the guide magnetic field is more than ten times larger than the reconnecting magnetic field, the inductive reconnection electric field is almost parallel to the magnetic field...
As Quantum Computing systems continue their maturation, their addition to the spectrum of HPC accelerators slowly becomes more viable. For them to be usable, though, we require substantial efforts to integrate the quantum and the HPC ecosystem. On the hardware side, the needed efforts seem straightforward - integrating the quantum control system with lowest possible latency into the HPC...
High fidelity numerical simulations are necessary to drive design choices for future fusion devices, e.g. the ITER tokamak. XGC is a gyrokinetic Particle-in-Cell (PIC) application optimized for modeling the edge region plasma. The Coulomb collision operator is one of the more computationally expensive components of XGC. It requires linear solutions for a large number of small matrices with an...
The 'picket fence' is a captivating visual phenomenon characterized by vibrant green streaks in the subauroral sky, often appearing below a rare purpleish-white arc called STEVE (Strong Thermal Emission Velocity Enhancement). Recent studies suggest that, despite its aurora-like appearance, the picket fence may be driven NOT by magnetospheric particle precipitation but instead by local...
Two-dimensional full particle-in-cell simulations of pickup ion mediated oblique shocks were conducted with unprecedentedly long simulation times (over 100 times the inverse ion gyro frequency) and large system sizes (2000 times the ion inertial length) along the shock normal direction. An oblique shock refers to a shock where the angle between the shock normal direction and the upstream...
Magnetic reconnection has long been known to be the most important mechanism not only for the mixing of plasmas by changing the magnetic field topology, but also for the release of magnetic field energy into plasma kinetic energy. In addition, part of the heated plasma can be accelerated to energies much higher than the thermal energy during reconnection. So far, the energy partitioning of...
The grand challenge being pursued by the APEX (A Positron Electron eXperiment) Collaboration is to create and study cold, confined, strongly magnetized, matter-antimatter “pair plasmas” in the laboratory. This unusually simple, symmetric type of plasma has been the subject of theory/simulation predictions, in part motivated by astrophysical e+e- pair plasmas, going back over four decades; we...
