Inertial-range Magnetic-fluctuation Anisotropy Observed from Parker Solar Probe’s First Seven Orbits

Solar wind turbulence is anisotropic with respect to the mean magnetic field. Anisotropy leads to ambiguity when interpreting in situ turbulence observations in the solar wind because an apparent change in the measurements could be due to either the change of intrinsic turbulence properties or to a simple change of the spacecraft sampling direction. We demonstrate the ambiguity using the spectral index and magnetic compressibility in the inertial range observed by the Parker Solar Probe during its first seven orbits ranging from 0.1 to 0.6 au. To unravel the effects of the sampling direction, we assess whether the wave-vector anisotropy is consistent with a two-dimensional (2D) plus slab turbulence transport model and determine the fraction of power in the 2D versus slab component. Our results confirm that the 2D plus slab model is consistent with the data and the power ratio between 2D and slab components depends on radial distance, with the relative power in 2D fluctuations becoming smaller closer to the Sun.

Design and first result of combined Langmuir-magnetic probe on J-TEXT tokamak

In order to measure boundary electrostatic and magnetic fluctuations simultaneously, a set of combined Langmuir-magnetic probe (CLMP) has been designed and built on Joint-Texas Experimental Tokamak (J-TEXT). The probe consists of 8 graphite probe pins and a 3D magnetic probe, driven by a mechanical pneumatic device. By means of simulation, the shielding effect of the graphite sleeve on the magnetic fluctuation signal is explored, and the influence of the eddy current was reduced by cutting the graphite sleeve. In the experiment, it has been verified that the mutual inductance of electromagnetic signals can be ignored. And a 70~90kHz electromagnetic mode is observed around the last closed magnetic surface (LCFS). The establishment of CLMP provides data for the exploration of the coupling of electrostatic and magnetic fluctuations.

Fermionic order by disorder in a van der Waals antiferromagnet

CeTe3 is a unique platform to investigate the itinerant magnetism in a van der Waals (vdW) coupled metal. Despite chemical pressure being a promising route to boost quantum fluctuation in this system, a systematic study on the chemical pressure effect on Ce3+(4f1) states is absent. Here, we report on the successful growth of a series of Se doped single crystals of CeTe3. We found a fluctuation driven exotic magnetic rotation from the usual easy-axis ordering to an unusual hard-axis ordering. Unlike in localized magnetic systems, near-critical magnetism can increase itinerancy hand-in-hand with enhancing fluctuation of magnetism. Thus, seemingly unstable hard-axis ordering emerges through kinetic energy gain, with the self-consistent observation of enhanced magnetic fluctuation (disorder). As far as we recognize, this order-by-disorder process in fermionic system is observed for the first time within vdW materials. Our finding opens a unique experimental platform for direct visualization of the rich quasiparticle Fermi surface deformation associated with the Fermionic order-by-disorder process. Also, the search for emergent exotic phases by further tuning of quantum fluctuation is suggested as a promising future challenge.

Reconstruction of the magnetic connection from Mercury to the solar corona

<p>The magnetic foot point of Mercury on the solar disk has been reconstructed for selected case studies, in order to better understand the interaction between the solar corona and the planet. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that gives a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a “local” diffusion coefficient, which is a function of the fluctuation level and magnetic field correlation lengths. The simulation is tailored to specific events by using the observed values of solar wind velocity and magnetic fluctuation levels. Magnetic data from MAG/MESSENGER have been considered to compute the magnetic fluctuation level, while, concerning proton fluxes, FIPS/MESSENGER data has been taken into account. A number of SEP events observed on Mercury during 2011 and 2012 have been analysed, studying, for each event, the magnetic connection from Mercury to the solar corona, and the position of the active region possibly source of the accelerated particles observed.</p>

Self-generated turbulence by plasmas and magnetic field collective interaction in 3D large temporal-spatial turbulent magnetic reconnection: I. The Basic Feature

<p>The role of turbulence is one of key issues for understanding the magnetic and plasma energy conversion, plasma heating and high energy particles acceleration in large temporal-spatial scale turbulent magnetic reconnection (LTSTMR; observed current sheet thickness to characteristic electron length, Larmor radius for low-beta and electron inertial length for high-beta, ratios on the order of ten to the power of ten or higher; observed evolution time to electron cyclotron time ratios on the order of ten to the power of ten or higher) . Solar atmosphere activities (e.g., limbs, flares, coronal mass ejections, solar winds and so on), which are the most important phenomenon in the solar and Sun-Earth space systems, are typical LTSTMRs.</p><p>Here we used our newly developed RHPIC-LBM algorithm[*]  to perform the role of  turbulence in the magnetic fluctuation-induced self-generating-organization  (MF-ISGO), the turbulence in the plasma turbulence-induced self-feeding-sustaining (PT-ISFS), and the interaction of turbulence between MF-ISGO and PT-ISFS in the continuous kinetic-dynamic-hydro fully coupled LTSTMR. </p><p>First, we find that the self-generated turbulence by magnetic field and plasma motion collective interaction include two fully coupled processes of 1) fluid vortex induced magnetic reconnection (MR) and 2) MR induced fluid vortex. The Biermann battery effect and  alpha-effect can not only generate magnetic fields, but can server them to trigger MR, the Spitzer resistance and turbulence resistance (beta-effect)  can not only generate magnetic eddies, but can server  them to trigger fluid turbulence.  </p><p>Then, we find that these interaction leads to vortex splitting and phase separating instabilities, and there are four species instabilities coexist in the evolution process. 1) Vortex separation interface instabilities. 2)Magnetic fluctuation-induced self-generating-organization instabilities. 3) Plasma turbulence-induced self-feeding-sustaining instabilities. 4) Vortex shedding instabilities.</p><p>Finally, the nuanced details of the magnetic topological structure and the topological characterization of flow structures in plasma of the simulated 3D LTSTMR are also presented.</p><p>The characterization of turbulence anisotropy and the turbulence acceleration of the LTSTMR are presented in Part II and Part III of this three-paper series study.</p><p>*Techniques and algorithms for RHPIC-LBM have been developed in previous studies (e.g.,Zhu2020a, Zhu2020b)</p><p>References</p><p>Zhu, B. J., Yan, H., Zhong, Y., et al. 2020a, Appl Math Model, 78, 932, doi: 10.1016/j.apm.2019.09.043</p><p>Zhu, B. J., Yan, H., Zhong, Y., et al. 2020b, Appl Math Model, 78, 968,doi: 10.1016/j.apm.2019.05.027</p>

Pressure-induced Lifshitz transition in FeSe$_{0.88}$S$_{0.12}$ probed via $^{77}$Se-NMR

Recently, FeSe$_{1-x}$S$_x$ systems have received much attention because of the unique pressure-temperature phase diagram. We performed $^{77}$Se-NMR measurements on a single crystal of FeSe$_{0.88}$S$_{0.12}$ to investigate its microscopic properties. The shift of $^{77}$Se spectra exhibits anomalous enhancement at $1.0~\mathrm{GPa}$, suggesting a topological change in the Fermi surfaces, so-called Lifshitz transition, occurs at $1.0~\mathrm{GPa}$. The magnetic fluctuation simultaneously changes its properties, which implies a change in the dominant nesting vector. Edited by: A. Goñi, A. Cantarero, J. S. Reparaz

Characteristic of Magnetic Fluctuation of Underground Passing Pig Labeled with Magnets

During the pigging process, a pig labeled with magnets can be effectively detected by monitoring the magnetic fluctuation (MF) introduced when the pig passes by. In order to analyze the influence of various factors on the MF, the principle for magnetic fluctuation detection (MFD) is described, and a detection model is established here. The influence of model parameters, such as pipeline geometries, geomagnetic characteristics, as well as permeability of pipeline, on the magnetic anomaly distribution along the measured line is analyzed. The study reveals that with the increase in pipeline parameters (thickness, permeability, and outer diameter), the MF detected decreases. The pipeline length will have little influence on the MF. With an increased number of magnets, the MF increases while remaining almost unchanged at two ends of the measuring line. Attention should be paid to the installation of magnets to ensure the consistency of the magnetic moments. With the increase in geomagnetic intensity and declination, the MF will be almost unaffected, while the change of geomagnetic inclination will introduce an obvious change to the MF. In field application, measuring points can be set along and above the pipeline with a certain interval. From the magnetic anomaly measured, it can be determined whether the pig has passed by the point or not.