skip to main content


Title: The Effects of Upper‐Hybrid Waves on Energy Dissipation in the Electron Diffusion Region
Abstract

Using a two‐dimensional particle‐in‐cell simulation, we investigate the effects and roles of upper‐hybrid waves (UHW) near the electron diffusion region (EDR). The energy dissipation via the wave‐particle interaction in our simulation agrees withJ · Emeasured by magnetospheric multiscale (MMS) spacecraft. It means that UHW contributes to the local energy dissipation. As a result of wave‐particle interactions, plasma parameters which determine the larger‐scale energy dissipation in the EDR are changed. They‐directional current decreases while the pressure tensorPyzincreases/decreases when the agyrotropic beam density is low/high, where(x, y, z)‐coordinates correspond the(L, M, N)‐boundary coordinates. Because the reconnection electric field comes fromPyz/z, our result implies that UHW plays an additional role in affecting larger‐scale energy dissipation in the EDR by changing plasma parameters. We provide a simple diagram that shows how the UHW activities change the profiles of plasma parameters near the EDR comparing cases with and without UHW.

 
more » « less
Award ID(s):
1842643
NSF-PAR ID:
10374441
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Geophysical Research Letters
Volume:
47
Issue:
19
ISSN:
0094-8276
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Here we have determined the nature of turbulent flow associated with oceanic nonbreaking waves, which are on average much more prevalent than breaking waves in most wind conditions. We found this flow to be characterized by a low turbulence microscale Reynolds number of30 < Reλ < 100. We observed that the turbulent kinetic energy dissipation rate associated with nonbreaking wavesϵ, ranged to3 · 10−4 W/kg for a wave amplitude 50 cm. Theϵ, under nonbreaking waves, was consistent with;Sijis the large‐scale (energy‐containing scales) wave‐induced mean flow stress tensor. The turbulent Reynolds stress associated with nonbreaking waves was consistent with experimental data when parameterized by an amplitude independent constant turbulent eddy viscosity, 10 times larger than the molecular value. Given that nonbreaking waves typically cover a much larger fraction of the ocean surface (90–100%) than breaking waves, this result shows that their contribution to wave dissipation can be significant.

     
    more » « less
  2. Abstract

    The nature of the 3‐s ultralow frequency (ULF) wave in the Earth's foreshock region and the associated wave‐particle interaction are not yet well understood. We investigate the 3‐s ULF waves using Magnetospheric Multiscale (MMS) observations. By combining the plasma rest frame wave properties obtained from multiple methods with the instability analysis based on the velocity distribution in the linear wave stage, the ULF wave is determined to be due to the ion/ion nonresonant mode instability. The interaction between the wave and ions is analyzed using the phase relationship between the transverse wave fields and ion velocities and using the longitudinal momentum equation. During the stage when ULF waves have sinusoidal waveforms up to |dB|/|B0| ~ 3, wheredBis the wave magnetic field andB0is the background magnetic field, the wave electric fields perpendicular toB0do negative work to solar wind ions; alongB0, a longitudinal electric field develops, but theV × Bforce is stronger and leads to solar wind ion deceleration. During the same wave stage, the backstreaming beam ions gain energy from the transverse wave fields and get deceleration alongB0by the longitudinal electric field. The ULF wave leads to electron heating, preferentially in the direction perpendicular to the local magnetic field. Secondary waves are generated within the ULF waveforms, including whistler waves near half of the electron cyclotron frequency, high‐frequency electrostatic waves, and magnetosonic whistler waves. The work improves the understanding of the nature of 3‐s ULF waves and the associated wave‐particle interaction.

     
    more » « less
  3. Abstract

    Two‐dimensional hybrid particle‐in‐cell (PIC) simulations are carried out on a constantL‐shell (or drift shell) surface of the dipole magnetic field to investigate the generation process of near‐equatorial fast magnetosonic waves (a.k.a equatorial noise; MSWs hereafter) in the inner magnetosphere. The simulation domain on a constantL‐shell surface adopted here allows wave propagation and growth in the azimuthal direction (as well as along the field line) and is motivated by the observations that MSWs propagate preferentially in the azimuthal direction in the source region. Furthermore, the equatorial ring‐like proton distribution used to drive MSWs in the present study is (realistically) weakly anisotropic. Consequently, the ring‐like velocity distribution projected along the field line by Liouville's theorem extends to rather high latitude, and linear instability analysis using the local plasma conditions predicts substantial MSW growth up to±27° latitude. In the simulations, however, the MSW intensity maximizes near the equator and decreases quasi‐exponentially with latitude. Further analysis reveals that the stronger equatorward refraction at higher latitude due to the larger gradient of the dipole magnetic field strength prevents off‐equatorial MSWs from growing continuously, whereas MSWs of equatorial origin experience little refraction and can fully grow. Furthermore, the simulated MSWs exhibit a rather complex wave field structure varying with latitude, and the scattering of energetic ring‐like protons in response to MSW excitation occurs faster than the bounce period of those protons so that they do not necessarily follow Liouville's theorem during MSW excitation.

     
    more » « less
  4. Abstract

    We present a global kinetic plasma simulation of an axisymmetric pulsar magnetosphere with self-consistente±pair production. We use the particle-in-cell method and log-spherical coordinates with a grid size 4096 × 4096. This allows us to achieve a high voltage induced by the pulsar rotation and investigate pair creation in a young pulsar far from the death line. We find the following: (1) The energy release ande±creation are strongly concentrated in the thin, Y-shaped current sheet, with a peak localized in a small volume at the Y-point. (2) The Y-point is shifted inward from the light cylinder by ∼15% and “breathes” with a small amplitude. (3) The densee±cloud at the Y-point is in ultrarelativistic rotation, which we call superrotation, because it exceeds corotation with the star. The cloud receives angular momentum flowing from the star along the poloidal magnetic field lines. (4) Gamma-ray emission peaks at the Y-point and is collimated in the azimuthal direction, tangent to the Y-point circle. (5) The separatrix current sheet between the closed magnetosphere and the open magnetic field lines is sustained by the electron backflow from the Y-point cloud. Its thickness is self-regulated to marginal charge starvation. (6) Only a small fraction of dissipation occurs in the separatrix inward of the Y-point. A much higher power is released in the equatorial plane, including the Y-point where the created densee±plasma is spun up and intermittently ejected through the nozzle between the two open magnetic fluxes.

     
    more » « less
  5. Abstract

    Models invoking magnetic reconnection as the particle acceleration mechanism within relativistic jets often adopt a gradual energy dissipation profile within the jet. However, such a profile has yet to be reproduced in first-principles simulations. Here we perform a suite of 3D general relativistic magnetohydrodynamic simulations of post–neutron star merger disks with an initially purely toroidal magnetic field. We explore the variations in both the microphysics (e.g., nuclear recombination, neutrino emission) and system parameters (e.g, disk mass). In all of our simulations, we find the formation of magnetically striped jets. The stripes result from the reversals in the poloidal magnetic flux polarity generated in the accretion disk. The simulations display large variations in the distributions of stripe duration,τ, and power, 〈PΦ〉. We find that more massive disks produce more powerful stripes, the most powerful of which reaches 〈PΦ〉 ∼ 1049erg s−1atτ∼ 20 ms. The power and variability that result from the magnetic reconnection of the stripes agree with those inferred in short-duration gamma-ray bursts. We find that the dissipation profile of the cumulative energy is roughly a power law in both radial distance,z, andτ, with a slope in the range of ∼1.7–3; more massive disks display larger slopes.

     
    more » « less