Search Publications
Gyrokinetic Simulations of Solar Wind Turbulence from Ion to Electron Scales
Quataert, E.; Howes, G. G.; Schekochihin, A. A. +4 more
A three-dimensional, nonlinear gyrokinetic simulation of plasma turbulence resolving scales from the ion to electron gyroradius with a realistic mass ratio is presented, where all damping is provided by resolved physical mechanisms. The resulting energy spectra are quantitatively consistent with a magnetic power spectrum scaling of k-2.8
Plasma Jet Braking: Energy Dissipation and Nonadiabatic Electrons
André, M.; Vaivads, A.; Owen, C. J. +2 more
We report in situ observations by the Cluster spacecraft of wave-particle interactions in a magnetic flux pileup region created by a magnetic reconnection outflow jet in Earth’s magnetotail. Two distinct regions of wave activity are identified: lower-hybrid drift waves at the front edge and whistler-mode waves inside the pileup region. The whistle…
Electron Temperature Gradient Scale at Collisionless Shocks
Krasnoselskikh, Vladimir; Schwartz, Steven J.; Henley, Edmund +1 more
Shock waves are ubiquitous in space and astrophysics. They transform directed flow energy into thermal energy and accelerate energetic particles. The energy repartition is a multiscale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. While large scale features of ion heating are known, the…
Kinetic Structure of the Electron Diffusion Region in Antiparallel Magnetic Reconnection
Egedal, J.; Daughton, W.; Chen, L. -J. +2 more
Strong electron pressure anisotropy has been observed upstream of electron diffusion regions during reconnection in Earth’s magnetotail and kinetic simulations. For collisionless antiparallel reconnection, we find that the anisotropy drives the electron current in the electron diffusion region, and that this current is insensitive to the reconnect…
Anisotropic Third-Moment Estimates of the Energy Cascade in Solar Wind Turbulence Using Multispacecraft Data
Dasso, S.; Matthaeus, W. H.; Wan, M. +2 more
The first direct determination of the inertial range energy cascade rate, using an anisotropic form of Yaglom’s law for magnetohydrodynamic turbulence, is obtained in the solar wind with multispacecraft measurements. The two-point mixed third-order structure functions of Elsässer fluctuations are integrated over a sphere in magnetic field-aligned …
Jet Deflection by Very Weak Guide Fields during Magnetic Reconnection
Goldman, M. V.; Newman, D. L.; Lapenta, G. +2 more
Previous 2D simulations of reconnection using a standard model of initially antiparallel magnetic fields have detected electron jets outflowing from the x point into the ion outflow exhausts. Associated with these jets are extended “outer electron diffusion regions.” New PIC simulations with an ion to electron mass ratio as large as 1836 (an H
New Ion-Wave Path in the Energy Cascade
Perrone, Denise; Califano, Francesco; Valentini, Francesco +2 more
We present the results of kinetic numerical simulations that demonstrate the existence of a novel branch of electrostatic nonlinear waves driven by particle trapping processes. These waves have an acoustic-type dispersion with phase speed comparable to the ion thermal speed and would thus be heavily Landau damped in the linear regime. At variance …
Altitude Distribution of the Auroral Acceleration Potential Determined from Cluster Satellite Data at Different Heights
Karlsson, Tomas; Fazakerley, Andrew; Nilsson, Hans +6 more
Aurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by electron beams hitting the upper atmosphere, after being accelerated by quasistatic electric fields at 1-2 RE altitudes, or by wave electric fields. Although aurora was studied by man…
Nonaxisymmetric Anisotropy of Solar Wind Turbulence
Chapman, S. C.; Hnat, B.; Turner, A. J. +2 more
A key prediction of turbulence theories is frame-invariance, and in magnetohydrodynamic (MHD) turbulence, axisymmetry of fluctuations with respect to the background magnetic field. Paradoxically the power in fluctuations in the turbulent solar wind are observed to be ordered with respect to the bulk macroscopic flow as well as the background magne…
Mirror Mode Expansion in Planetary Magnetosheaths: Bohm-like Diffusion
Tsurutani, Bruce T.; Hasegawa, Akira
Observed scale sizes of mirror modes in planetary magnetosheaths tend to be equal or larger than those that correspond to the maximum growth rate of the mirror instability: 9 ρp (proton gyroradius). These phenomena can be accounted for by introducing a diffusion process (Bohm) that shifts the spectra to lower wave numbers as the mode co…