Rohit Chhiber

Charged particle diffusion in isotropic random magnetic fields

The investigation of the diffusive transport of charged particles in a turbulent magnetic field remains a subject of considerable interest. Research has most frequently concentrated on determining the diffusion coefficient in the presence of a mean magnetic field. Here we consider diffusion of charged particles in fully three-dimensional isotropic turbulent magnetic fields with no mean field, which may be pertinent to many astrophysical situations. We identify different ranges of particle energy depending upon the ratio of the Larmor radius of the charged particle to the characteristic outer length scale of the turbulence. Two different theoretical models are proposed to calculate the diffusion coefficient, each applicable to a distinct range of particle energies. The theoretical results are compared with those from computer simulations, showing good agreement.

GENERATING SYNTHETIC MAGNETIC FIELD INTERMITTENCY USING A MINIMAL MULTISCALE LAGRANGIAN MAPPING APPROACH

The Minimal Multiscale Lagrangian Mapping procedure developed in the context of neutral fluid turbulence is a simple method for generating synthetic vector fields. Using a sequence of low-pass filtered fields, fluid particles are displaced at their rms speed for some scale-dependent time interval, and then interpolated back to a regular grid. Fields produced in this way are seen to possess certain properties of real turbulence. This paper extends the technique to plasmas by taking into account the coupling between the velocity and magnetic fields. We examine several possible applications to plasma systems. One use is as initial conditions for simulations, wherein these synthetic fields may efficiently produce a strongly intermittent cascade. The intermittency properties of the synthetic fields are also compared with those of the solar wind. Finally, studies of cosmic ray transport and modulation in the test particle approximation may benefit from improved realism in synthetic fields produced in this way.

Solar Wind Turbulence Studies Using MMS Fast Plasma Investigation Data

Studies of solar wind turbulence traditionally employ high-resolution magnetic field data, but high-resolution measurements of ion and electron moments have been possible only recently. We report the first turbulence studies of ion and electron velocity moments accumulated in pristine solar wind by the Fast Particle Investigation instrument onboard the Magnetospheric Multiscale (MMS) Mission. Use of these data is made possible by a novel implementation of a frequency domain Hampel filter, described herein. After presenting procedures for processing of the data, we discuss statistical properties of solar wind turbulence extending into the kinetic range. Magnetic field fluctuations dominate electron and ion velocity fluctuation spectra throughout the energy-containing and inertial ranges. However, a multi-spacecraft analysis indicates that at scales shorter than the ion-inertial length, electron velocity fluctuations become larger than ion velocity and magnetic field fluctuations. The kurtosis of ion velocity peaks around few ion-inertial lengths and returns to near gaussian value at sub-ion scales.

MMS Observations of Beta-dependent Constraints on Ion Temperature Anisotropy in Earth’s Magnetosheath

Protons (ionized hydrogen) in the solar wind frequently exhibit distinct temperatures (

SOLAR WIND COLLISIONAL AGE FROM A GLOBAL MAGNETOHYDRODYNAMICS SIMULATION

T_{\perp p}

Cosmic-Ray Diffusion Coefficients throughout the Inner Heliosphere from a Global Solar Wind Simulation

and

Kinetic range spectral features of cross-helicity using MMS.

T_{\parallel p}

Contextual Predictions for Parker Solar Probe I: Critical Surfaces and Regions

) perpendicular and parallel to the plasmas background magnetic-field. Numerous prior studies of the interplanetary solar-wind have shown that, as plasma beta (

Incompressive Energy Transfer in the Earth’s Magnetosheath: Magnetospheric Multiscale Observations

\beta_{\parallel p}

The Steady Global Corona and Solar Wind: A Three-dimensional MHD Simulation with Turbulence Transport and Heating

) increases, a narrower range of temperature-anisotropy (