Publications by authors named "William H Matthaeus"

Reducing the form factor while retaining the radiation hardness and performance matrix is the goal of avionics. While a compromise between a transistor's size and its radiation hardness has reached consensus in microelectronics, the size-performance balance for their optical counterparts has not been quested but eventually will limit the spaceborne photonic instruments' capacity to weight ratio. Here, we performed space experiments of photonic integrated circuits (PICs), revealing the critical roles of energetic charged particles.

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  • A new method was developed to analyze data from the Magnetospheric Multiscale Mission, focusing on energy transfer in the Earth's magnetosheath.
  • This approach is unique because it operates in three dimensions, generates a high volume of data estimates from one source, and visualizes energy flow in turbulent plasma.
  • The technique named "lag polyhedral derivative ensemble" utilizes groups of tetrahedra in lag space and similar algorithms to those used in curlometer techniques.
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The solar wind, a continuous flow of plasma from the sun, not only shapes the near Earth space environment but also serves as a natural laboratory to study plasma turbulence in conditions that are not achievable in the lab. Starting with the Mariners, for more than five decades, multiple space missions have enabled in-depth studies of solar wind turbulence. Parker Solar Probe (PSP) was launched to explore the origins and evolution of the solar wind.

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A familiar problem in space and astrophysical plasmas is to understand how dissipation and heating occurs. These effects are often attributed to the cascade of broadband turbulence which transports energy from large scale reservoirs to small scale kinetic degrees of freedom. When collisions are infrequent, local thermodynamic equilibrium is not established.

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  • The study estimates the turbulent energy-cascade rate using a third-order law from Hall-magnetohydrodynamics (MHD) and analyzes both Hall and MHD contributions to energy flux.
  • By comparing Magnetospheric Multiscale (MMS) data from the magnetosheath and solar wind with simulation results, researchers confirm that MMS observations show a clear inertial range at large MHD scales, primarily influenced by the MHD flux.
  • The findings reveal that even at smaller scales, the MHD contribution to energy transfer is more significant than previously believed, with the Hall term's role becoming more pronounced in high plasma beta conditions.
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Based on the Langevin equation of Brownian motion, we present a simple model that emulates a typical mode in incompressible magnetohydrodynamic turbulence, providing a demonstration of several key properties. The model equation is consistent with von Kármán decay law and Kolmogorov's symmetries. We primarily focus on the behavior of inertial range modes, although we also attempt to include some properties of the large-scale modes.

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We investigate energy transfer across scales in three-dimensional compressible magnetohydrodynamic (MHD) turbulence, a model often used to study space and astrophysical plasmas. Analysis shows that kinetic and magnetic energies cascade conservatively from large to small scales in cases with varying degrees of compression. With more compression, energy fluxes due to pressure dilation and subscale mass flux are greater, but conversion between kinetic and magnetic energy by magnetic line stretching is less efficient.

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  • In helical hydromagnetic turbulence with a constant magnetic field, the usual magnetic helicity is not invariant under ideal conditions, but a generalized version exists.
  • This generalized magnetic helicity is not practical due to its lack of gauge invariance.
  • The study presents a model that tracks the evolution of the magnetic helicity relative to the imposed field, successfully predicting its behavior and confirming its results with simulations.
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