Search Publications
Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades in Magnetized Weakly Collisional Plasmas
Quataert, E.; Howes, G. G.; Schekochihin, A. A. +4 more
This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turb…
Evidence of a Cascade and Dissipation of Solar-Wind Turbulence at the Electron Gyroscale
Sahraoui, F.; Khotyaintsev, Yu. V.; Goldstein, M. L. +1 more
We report the first direct determination of the dissipation range of magnetofluid turbulence in the solar wind at the electron scales. Combining high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectrum of turbulence and found two distinct breakpoints in the magnetic spectrum at 0.4 and 35 Hz, which corre…
Universality of Solar-Wind Turbulent Spectrum from MHD to Electron Scales
Saur, J.; Alexandrova, O.; Schwartz, S. J. +4 more
To investigate the universality of magnetic turbulence in space plasmas, we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spec…
Energetic electron response to ULF waves induced by interplanetary shocks in the outer radiation belt
Zong, Q. -G.; Daly, P. W.; Baker, D. N. +7 more
Strong interplanetary shock interactions with the Earth's magnetosphere have great impacts on energetic particle dynamics in the magnetosphere. An interplanetary shock on 7 November 2004 (with the maximum solar wind dynamic pressure of ∼70 nPa) was observed by the Cluster constellation to induce significant ULF waves in the plasmasphere boundary, …
Nonlinear mechanisms of lower-band and upper-band VLF chorus emissions in the magnetosphere
Katoh, Yuto; Omura, Yoshiharu; Hikishima, Mitsuru +2 more
We develop a nonlinear wave growth theory of magnetospheric chorus emissions, taking into account the spatial inhomogeneity of the static magnetic field and the plasma density variation along the magnetic field line. We derive theoretical expressions for the nonlinear growth rate and the amplitude threshold for the generation of self-sustaining ch…
Radial evolution of nonthermal electron populations in the low-latitude solar wind: Helios, Cluster, and Ulysses Observations
Maksimovic, Milan; Štverák, Štěpán; Marsch, Eckart +3 more
We have performed a statistical study of a substantial amount of solar wind electron velocity distribution functions (eVDFs). In our data set, we combine measurements acquired onboard three spacecrafts (Helios, Cluster II, and Ulysses) in the low ecliptic latitudes covering the heliocentric distance from 0.3 up to 4 AU. In this study, we focus on …
Global Scale-Invariant Dissipation in Collisionless Plasma Turbulence
Sahraoui, F.; Dunlop, M. W.; Khotyaintsev, Yu. V. +2 more
A higher-order multiscale analysis of the dissipation range of collisionless plasma turbulence is presented using in situ high-frequency magnetic field measurements from the Cluster spacecraft in a stationary interval of fast ambient solar wind. The observations, spanning five decades in temporal scales, show a crossover from multifractal intermit…
Ion heating resulting from pickup in magnetic reconnection exhausts
Lin, R. P.; Phan, T. D.; Lepri, S. T. +6 more
The heating of ions downstream of the x-line during magnetic reconnection is explored using full-particle simulations, test particle simulations, and analytic analysis. Large-scale particle simulations reveal that the ion temperature increases sharply across the boundary layer that separates the upstream plasma from the Alfvénic outflow. This boun…
Observations of Turbulence Generated by Magnetic Reconnection
Eastwood, J. P.; Bale, S. D.; Phan, T. D. +1 more
Spacecraft observations of turbulence within a magnetic reconnection (guide field ∼0) ion diffusion region are presented. In the inertial subrange, electric and magnetic fluctuations both followed a -5/3 power law; at higher frequencies, the spectral indices were -1 and -8/3, respectively. The dispersion relation was found to be consistent with fa…
Supermagnetosonic Jets behind a Collisionless Quasiparallel Shock
Vainio, R.; Vaivads, A.; Lucek, E. A. +7 more
The downstream region of a collisionless quasiparallel shock is structured containing bulk flows with high kinetic energy density from a previously unidentified source. We present Cluster multispacecraft measurements of this type of supermagnetosonic jet as well as of a weak secondary shock front within the sheath, that allow us to propose the fol…