A nonlinear two dimensional fluid model of whistler turbulence is developed that nonlinearly couples wave magnetic field with electron density perturbations. This coupling leads essentially to finite compressibility effects in whistler turbulence model. Interestingly it is found from our simulations that despite strong compressibility effects, the density fluctuations couple only weakly to the wave magnetic field fluctuations. In a characteristic regime where large scale whistlers are predominant, the weakly coupled density fluctuations do not modify inertial range energy cascade processes. Consequently, the turbulent energy is dominated by the large scale (compared to electron inertial length) eddies and it follows a Kolmogorov-like $k^{-7/3}$ spectrum, where $k$ is a characteristic wavenumber. The weak coupling of the density fluctuations is explained on the basis of a whistler wave parameter that quantifies the contribution of density perturbations in the wave magnetic field.
Using the Parker Solar Probe FIELDS bandpass filter data and SWEAP electron data from Encounters 1 through 9, we show statistical properties of narrowband whistlers from ~16 Rs to ~130 Rs, and compare wave occurrence to electron properties including beta, temperature anisotropy and heat flux. Whistlers are very rarely observed inside ~28 Rs (~0.13 au). Outside 28 Rs, they occur within a narrow range of parallel electron beta from ~1 to 10, and with a beta-heat flux occurrence consistent with the whistler heat flux fan instability. Because electron distributions inside ~30 Rs display signatures…
AIM: Large amplitude narrowband obliquely propagating whistler-mode waves at frequencies of ~0.2 fce (electron cyclotron frequency) are commonly observed at 1 AU, and are most consistent with the whistler heat flux fan instability. We want to determine whether similar whistler-mode waves occur inside 0.2 AU, and how their properties compare to those at 1 AU. METHODS: We utilize the waveform capture data from the Parker Solar Probe Fields instrument to develop a data base of narrowband whistler waves. The SWEAP instrument, in conjunction with the quasi-thermal noise measurement form Fields, pro…
In the absence of efficient collisions, deviations from thermal equilibrium of plasma particle distributions are controlled by the self-generated instabilities. The whistler instability is a notorious example, usually responsible for the regulation of electron temperature anisotropy $A = T_{\perp}/T_\parallel>$ (with $\perp, \parallel$ respective to the magnetic field direction) observed in space plasmas, e.g., solar wind and planetary magnetospheres. Suprathermal electrons present in these environments change the plasma dispersion and stability properties, with expected consequences on the ki…
Resonances with electromagnetic whistler-mode waves are the primary driver for the formation and dynamics of energetic electron fluxes in various space plasma systems, including shock waves and planetary radiation belts. The basic and most elaborated theoretical framework for the description of the integral effect of multiple resonant interactions is the quasi-linear theory, that operates through electron diffusion in velocity space. The quasi-linear diffusion rate scales linearly with the wave intensity, D(QL) is proportional to Bw2, which should be small enough to satisfy the applicability c…
We investigate the kinetic properties of a typical fast-mode shock inside an interplanetary coronal mass ejection (ICME) observed on 1998 August 6 at 1 AU, including particle distributions and wave analysis with the in situ measurements from Wind. Key results are obtained concerning the shock and the shock-ICME interaction at kinetic scales: (1) gyrating ions, which may provide energy dissipation at the shock in addition to wave-particle interactions, are observed around the shock ramp; (2) despite the enhanced proton temperature anisotropy of the shocked plasma, the low plasma beta inside the…
The expansion of hot electrons in flaring magnetic loops is crucial to understanding the dynamics of solar flares. In this paper we investigate, for the first time, the transport of hot electrons in a magnetic mirror field based on a 1-D particle-in-cell (PIC) simulation. The hot electrons with small pitch angle transport into the cold plasma, which leads to the generation of Langmuir waves in the cold plasma and ion acoustic waves in the hot plasma. The large pitch angle electrons can be confined by the magnetic mirror, resulting in the different evolution time scale between electron parallel…
Magnetic holes are plasma structures that trap a large number of particles in a magnetic field that is weaker than the field in its surroundings. The unprecedented high time-resolution observations by NASA's Magnetospheric Multi-Scale (MMS) mission enable us to study the particle dynamics in magnetic holes in the Earth's magnetosheath in great detail. We reveal the local generation mechanism of whistler waves by a combination of Landau-resonant and cyclotron-resonant wave-particle interactions of electrons in response to the large-scale evolution of a magnetic hole. As the magnetic hole conver…
Thermalization and heating of plasma flows at shocks result in unstable charged-particle distributions which generate a wide range of electromagnetic waves. These waves, in turn, can further accelerate and scatter energetic particles. Thus, the properties of the waves and their implication for wave-particle interactions are critically important for modeling energetic particle dynamics in shock environments. Whistler-mode waves, excited by the electron heat flux or a temperature anisotropy, arise naturally near shocks and foreshock transients. As a result, they can often interact with supra-the…
Large amplitude whistler waves at frequencies of 0.2 to 0.4 times electron cyclotron frequency are frequently observed in the solar wind. The waves are obliquely propagating close to the resonance cone, with significant electric fields parallel to the background magnetic field, enabling strong interactions with electrons. Propagation angles are distinctly different from whistlers usually observed in the solar wind, and amplitudes are significantly larger. Waves occur most often in association with stream interaction regions (SIRs), and are often close-packed. 68 percent of the 54 SIRs had narr…
Heat flux suppression in collisionless plasmas for a large range of plasma $β$ is explored using two-dimensional particle-in-cell simulations with a strong, sustained thermal gradient. We find that a transition takes place between whistler-dominated (high-$β$) and double-layer-dominated (low-$β$) heat flux suppression. Whistlers saturate at small amplitude in the low beta limit and are unable to effectively suppress the heat flux. Electrostatic double layers suppress the heat flux to a mostly constant factor of the free streaming value once this transition happens. The double layer physics is …
We present STEREO observations within 1500 proton gyroradii of 12 interplanetary shocks, with long-duration burst mode electric field acquisition by S/WAVES enabling observation of the evolution of waves throughout the entire ramp of interplanetary shocks. The shocks are low Mach number ($M_{f} \sim $1--5), quasi-perpendicular ($θ_{Bn} \geq 45^{\circ}$), with beta ($β$) $\sim $0.2--1.8. High variability in frequency, amplitude, and wave mode is observed upstream, downstream, and in shock ramps. Observations in every region include ion acoustic-like waves, electron cyclotron drift instability d…
The heat transport in the solar wind is dominated by the suprathermal electron populations, i.e., a tenuous halo and a field-aligned beam/strahl, with high energies and antisunward drifts along the magnetic field. Their evolution may offer plausible explanations for the rapid decrease of the heat flux with the solar wind expansion, typically invoked being the self-generated instabilities, or the so-called heat flux instabilities (HFIs). The present paper provides a unified description of the full spectrum of HFIs, as prescribed by the linear kinetic theory for high beta conditions ($β_e \gg 0.…
Reduced fluid models for collisionless plasmas including electron inertia and finite Larmor radius corrections are derived for scales ranging from the ion to the electron gyroradii. Based either on pressure balance or on the incompressibility of the electron fluid, they respectively capture kinetic Alfvén waves (KAWs) or whistler waves (WWs), and can provide suitable tools for reconnection and turbulence studies. Both isothermal regimes and Landau fluid closures permitting anisotropic pressure fluctuations are considered. For small values of the electron beta parameter $β_e$, a perturbative co…
Collisionless, phase-mixed, dispersive, Gaussian Alfven pulse in transversely inhomogeneous plasma
在以前的作品谐波，相位混合，阿尔芬波动力学被认为是在动力学和磁流体动力学制度。到目前为止，只有磁流体动力学，相位混合，高斯阿尔芬脉冲进行了研究。在目前的工作中，我们扩展到动力学制度。这里相位混合，高斯阿尔芬脉冲的研究，这是更适合于太阳耀斑，比谐波，因为耀斑是脉冲的性质。利用粒子模拟和解析模型研究了横向非均匀等离子体中无碰撞、相位混合、色散高斯阿尔芬脉冲。脉冲是在惯性制度与等离子体β小于电子-离子质量比，并具有12离子惯性长度的空间宽度。线性分析模型预测，脉冲幅度的下降是由线性Korteweg de Vries（KdV）方程描述。线性KdV方程的数值解和解析解产生脉冲幅度随时间减小为$t^{-1}$。后者的标度律证实了完整的PIC模拟。结果表明，脉冲振幅的减小是由于色散效应，而电子加速是由于相位混合波的朗道阻尼。作为$t^{-1}$确定的振幅随时间降低与$t^{-3/2}$的MHD标度不同。这可以归因于色散效应导致与MHD相比的不同缩放，其中电阻效应导致阻尼，进而通过不均匀性增强。降低背景等离子体温度和增加离子质量产生更有效的粒子加速。
