Search Publications
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…
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…
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…
Scaling Laws of Turbulence and Heating of Fast Solar Wind: The Role of Density Fluctuations
Bruno, R.; Carbone, V.; Sorriso-Valvo, L. +2 more
Incompressible and isotropic magnetohydrodynamic turbulence in plasmas can be described by an exact relation for the energy flux through the scales. This Yaglom-like scaling law has been recently observed in the solar wind above the solar poles observed by the Ulysses spacecraft, where the turbulence is in an Alfvénic state. An analogous phenomeno…
Kinetic Alfvén Wave Turbulence and Transport through a Reconnection Diffusion Region
Acuna, M.; Reme, H.; Goldstein, M. L. +3 more
We demonstrate from observations that kinetic Alfvén waves may play an important role in facilitating magnetic reconnection. These waves radiate outwards from the diffusion region oblique to the magnetic field in a conelike pattern delimited by the X line separatrices with outward energy fluxes equivalent to that contained in the outstreaming ions…
Reconnection at High Latitudes: Antiparallel Merging
Escoubet, C. P.; Dunlop, M. W.; Fear, R. C. +5 more
New investigations have renewed the debate on the occurrence of magnetic reconnection of Earth’s dayside magnetopause. Here, we show for the first time strong evidence for a high-latitude reconnection site, located on initially closed field lines, where the magnetic field orientations inside and outside the magnetopause are close to antiparallel. …
Is There a Dark Matter Signal in the Galactic Positron Annihilation Radiation?
Rothschild, R. E.; Higdon, J. C.; Lingenfelter, R. E.
Assuming Galactic positrons do not go far before annihilating, a difference between the observed 511 keV annihilation flux distribution and that of positron production, expected from β+ decay in Galactic iron nucleosynthesis, was evoked as evidence of a new source and signal of dark matter. We show, however, that the dark matter sources…
Nonlinear Development of Shocklike Structure in the Solar Wind
Parks, G. K.; Lin, N.; Lee, E. +1 more
We report first in situ multispacecraft observations of nonlinear steepening of compressional pulses in the solar wind upstream of Earth’s bow shock. The magnetic field of a compressional pulse formed at the upstream edge of density holes is shown to suddenly break and steepen into a shocklike structure. During the early phase of development therm…