A. Chasapis

MMS Observations of Ion-scale Magnetic Island in the Magnetosheath Turbulent Plasma

In this letter, first observations of ion-scale magnetic island from the Magnetospheric Multiscale mission in the magnetosheath turbulent plasma are presented. The magnetic island is characterized ...

Multispacecraft analysis of dipolarization fronts and associated whistler wave emissions using MMS data

Dipolarization fronts (DFs), embedded in bursty bulk flows, play a crucial role in Earths plasma sheet dynamics because the energy input from the solar wind is partly dissipated in their vicinity. This dissipation is in the form of strong low-frequency waves that can heat and accelerate energetic electrons up to the high-latitude plasma sheet. However, the dynamics of DF propagation and associated low-frequency waves in the magnetotail are still under debate due to instrumental limitations and spacecraft separation distances. In May 2015 the Magnetospheric Multiscale (MMS) mission was in a string-of-pearls configuration with an average intersatellite distance of 160 km, which allows us to study in detail the microphysics of DFs. Thus, in this letter we employ MMS data to investigate the properties of dipolarization fronts propagating earthward and associated whistler mode wave emissions. We show that the spatial dynamics of DFs are below the ion gyroradius scale in this region (∼500 km), which can modify the dynamics of ions in the vicinity of the DF (e.g., making their motion nonadiabatic). We also show that whistler wave dynamics have a temporal scale of the order of the ion gyroperiod (a few seconds), indicating that the perpendicular temperature anisotropy can vary on such time scales.

Electron Heating at Kinetic Scales in Magnetosheath Turbulence

We present a statistical study of coherent structures at kinetic scales, using data from the Magnetospheric Multiscale mission in the Earths magnetosheath. We implemented the multi-spacecraft part ...

Magnetospheric Multiscale Observation of Plasma Velocity-Space Cascade: Hermite Representation and Theory

Plasma turbulence is investigated using unprecedented high-resolution ion velocity distribution measurements by the Magnetospheric Multiscale mission (MMS) in the Earths magnetosheath. This novel observation of a highly structured particle distribution suggests a cascadelike process in velocity space. Complex velocity space structure is investigated using a three-dimensional Hermite transform, revealing, for the first time in observational data, a power-law distribution of moments. In analogy to hydrodynamics, a Kolmogorov approach leads directly to a range of predictions for this phase-space transport. The scaling theory is found to be in agreement with observations. The combined use of state-of-the-art MMS data sets, novel implementation of a Hermite transform method, and scaling theory of the velocity cascade opens new pathways to the understanding of plasma turbulence and the crucial velocity space features that lead to dissipation in plasmas.

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 (

High-resolution Statistics of Solar Wind Turbulence at Kinetic Scales Using the Magnetospheric Multiscale Mission

T_{\perp p}

Energy Conversion and Collisionless Plasma Dissipation Channels in the Turbulent Magnetosheath Observed by the Magnetospheric Multiscale Mission

and

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

T_{\parallel p}

In Situ Observation of Intermittent Dissipation at Kinetic Scales in the Earth's Magnetosheath

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