Anisotropic Heating and Cooling within Interplanetary Coronal Mass Ejection Sheath Plasma
The Astrophysical Journal2024
This study is the first to comprehensively explore the relationship between heating and cooling, temperature anisotropy, turbulence, and collisional age within ICME sheaths. Using Wind spacecraft data from 333 ICME sheaths observed at 1 au (1995–2015), we found that plasma unstable to proton-cyclotron (PC) and firehose instabilities is significantly hotter—by a factor of 5 to 10—than stable plasma. Additionally, these unstable regions exhibit higher magnetic fluctuations and lower collisional ages, especially at low proton beta (βₚ ≤ 2). Our findings highlight that heating dominates over cooling in producing temperature anisotropy within ICME sheaths, with collisional age and magnetic fluctuations playing key roles in maintaining plasma conditions.
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Space-qualifying silicon photonic modulators and circuits
Science Advances2024
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. The year-long cosmic radiation exposure does not change carrier mobility but reduces free carrier lifetime, resulting in unchanged electro-optic modulation efficiency and well-expanded optoelectronic bandwidth. The diversity and statistics of the tested PIC modulator indicate the minimal requirement of shielding for PIC transmitters with small footprint modulators and complexed routing waveguides toward lightweight space terminals for terabits communications and intersatellite ranging.
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HelioSwarm: A Multipoint, Multiscale Mission to Characterize Turbulence
Space Science Reviews2023
HelioSwarm (HS) is a NASA Medium-Class Explorer mission of the Heliophysics Division designed to explore the dynamic three-dimensional mechanisms controlling the physics of plasma turbulence, a ubiquitous process occurring in the heliosphere and in plasmas throughout the universe. This will be accomplished by making simultaneous measurements at nine spacecraft with separations spanning magnetohydrodynamic and sub-ion spatial scales in a variety of near-Earth plasmas. In this paper, we describe the scientific background for the HS investigation, the mission goals and objectives, the observatory reference trajectory and instrumentation implementation before the start of Phase B. Through multipoint, multiscale measurements, HS promises to reveal how energy is transferred across scales and boundaries in plasmas throughout the universe.
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Regulation of Proton–α Differential Flow by Compressive Fluctuations and Ion-scale Instabilities in the Solar Wind
The Astrophysical Journal2023
Large-scale compressive slow-mode-like fluctuations can cause variations in the density, temperature, and magnetic-field magnitude in the solar wind. In addition, they also lead to fluctuations in the differential flow U p α between α -particles and protons (p), which is a common source of free energy for the driving of ion-scale instabilities. If the amplitude of the compressive fluctuations is sufficiently large, the fluctuating U p α intermittently drives the plasma across the instability threshold, leading to the excitation of ion-scale instabilities and thus the growth of corresponding ion-scale waves. The unstable waves scatter particles and reduce the average value of U p α . We propose that this “fluctuating-drift effect” maintains the average value of U p α well below the marginal instability threshold. We model the large-scale compressive fluctuations in the solar wind as long-wavelength slow-mode waves using a multi-fluid model. We numerically quantify the fluctuating-drift effect for the Alfvén/ion-cyclotron and fast-magnetosonic/whistler instabilities.
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The Future of Heliophysics Research through Targeted use of Constellations
Bulletin of the American Astronomical Society2023
This white paper seeks to outline the benefits and challenges of constellations, ranging from the Heliophysics System Observatory, to constellations consisting of a small number of spacecraft, to large-number constellations. In moving toward this constellation era, investments are required by our sponsors to best enable our continued scientific advancement in Solar and Space Physics.
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The Solar Wind at Mesoscales — Revealing the Missing Link
Bulletin of the American Astronomical Society2023
To address the fundamental gap in our knowledge of the heliosphere at mesoscales, new dedicated mesoscale missions are required in the next decade. This white paper outlines the current gaps in our understanding resulting from limited measurements at this critical scale and the need for an asserted effort in addressing these gaps.
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The Trans-Heliospheric Survey
Astronomy & Astrophysics (A&A)2023
Context. Though the solar wind is characterized by spatial and temporal variability across a wide range of scales, long-term averages of in situ measurements have revealed clear radial trends: changes in average values of basic plasma parameters (e.g., density, temperature, and speed) and a magnetic field with a distance from the Sun.
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