Found 9 results
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2019
Authors: Chang Qing, Xu Xiaojun, Xu Qi, Zhong Jun, Xu Jiaying, et al.
Title: Multiple-point Modeling the Parker Spiral Configuration of the Solar Wind Magnetic Field at the Solar Maximum of Solar Cycle 24
Abstract:

By assuming that the solar wind flow is spherically symmetric and that the flow speed becomes constant beyond some critical distance r = R 0 (neglecting solar gravitation and acceleration by high coronal temperature), the large-scale solar wind magnetic field lines are distorted into a Parker spiral configuration, which is usually simplified to an Archimedes spiral. Using magnetic field observations near Mercury, Venus, and Earth during solar maximum of Solar Cycle 24, we statistically surveyed the Parker spiral angles and obtained the empirical equations of the Archimedes and Parker spirals by fitting the multiple-point results. We found that the solar wind magnetic field configurations are slightly different during different years. Archimedes and Parker spiral configuration. . .
Date: 10/2019 Publisher: The Astrophysical Journal Pages: 102 DOI: 10.3847/1538-4357/ab412a Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab412
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2018
Authors: Bourdin Philippe, Singh Nishant K., and Brandenburg Axel
Title: Magnetic Helicity Reversal in the Corona at Small Plasma Beta
Abstract:

Solar and stellar dynamos shed small-scale and large-scale magnetic helicity of opposite signs. However, solar wind observations and simulations have shown that some distance above the dynamo both the small-scale and large-scale magnetic helicities have reversed signs. With realistic simulations of the solar corona above an active region now being available, we have access to the magnetic field and current density along coronal loops. We show that a sign reversal in the horizontal averages of the magnetic helicity occurs when the local maximum of the plasma beta drops below unity and the field becomes nearly fully force free. Hence, this reversal is expected to occur well within the solar corona and would not directly be accessible to in situ measurements with the Parker Solar Probe or . . .
Date: 12/2018 Publisher: The Astrophysical Journal Pages: 2 DOI: 10.3847/1538-4357/aae97a Available at: http://stacks.iop.org/0004-637X/869/i=1/a=2?key=crossref.90fa7f41d90e2c8b57f8248c0437cc6b
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Authors: Hu Junxiang, Li Gang, Fu Shuai, Zank Gary, and Ao Xianzhi
Title: Modeling a Single SEP Event from Multiple Vantage Points Using the iPATH Model
Abstract:

Using the recently extended 2D improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, we model an example gradual solar energetic particle event as observed at multiple locations. Protons and ions that are energized via the diffusive shock acceleration mechanism are followed at a 2D coronal mass ejection-driven shock where the shock geometry varies across the shock front. The subsequent transport of energetic particles, including cross-field diffusion, is modeled by a Monte Carlo code that is based on a stochastic differential equation method. Time intensity profiles and particle spectra at multiple locations and different radial distances, separated in longitudes, are presented. The results shown here are relevant to the upcoming Parker Solar Probe mission.

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Date: 02/2018 Publisher: The Astrophysical Journal Pages: L19 DOI: 10.3847/2041-8213/aaabc1 Available at: http://stacks.iop.org/2041-8205/854/i=2/a=L19?key=crossref.3db06d37bee0fc065cdec82f4faaf3b7
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2017
Authors: Hill M. E., Mitchell D. G., Andrews G. B., Cooper S. A., Gurnee R. S., et al.
Title: The Mushroom: A half-sky energetic ion and electron detector
Abstract:

We present a time-of-flight mass spectrometer design for the measurement of ions in the 30 keV to 10 MeV range for protons (up to 40 MeV and 150 MeV for He and heavy ions, respectively) and 30 keV to 1 MeV range for electrons, covering half of the sky with 80 apertures. The instrument, known as the "Mushroom," owing to its shape, solves the field of view problem for magnetospheric and heliospheric missions that employ three-axis stabilized spacecraft, yet still require extended angular coverage; the Mushroom is also compatible with a spinning spacecraft. The most important new feature of the Mushroom is the method through which uncomplicated electrostatic optics and clean position sensing combine to permit many apertures to fit into a compact, low-mass sensor head (or wedge), several of. . .
Date: 02/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022614 Available at: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016JA022614
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2016
Authors: Klein K. G., and Howes G. G.
Title: MEASURING COLLISIONLESS DAMPING IN HELIOSPHERIC PLASMAS USING FIELD–PARTICLE CORRELATIONS
Abstract:

An innovative field-particle correlation technique is proposed that uses single-point measurements of the electromagnetic fields and particle velocity distribution functions to investigate the net transfer of energy from fields to particles associated with the collisionless damping of turbulent fluctuations in weakly collisional plasmas, such as the solar wind. In addition to providing a direct estimate of the local rate of energy transfer between fields and particles, it provides vital new information about the distribution of that energy transfer in velocity space. This velocity-space signature can potentially be used to identify the dominant collisionless mechanism responsible for the damping of turbulent fluctuations in the solar wind. The application of this novel field-particle co. . .
Date: 08/2016 Publisher: The Astrophysical Journal Pages: L30 DOI: 10.3847/2041-8205/826/2/L30 Available at: http://stacks.iop.org/2041-8205/826/i=2/a=L30?key=crossref.1f33350dac6f20e78faa0a9e9d852985http://stacks.iop.org/2041-8205/826/i=2/a=L30/pdfhttp://stacks.iop.org/2041-8205/826/i=2/a=L30?key=crossref.1f33350dac6f20e78faa0a9e9d852985
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2015
Authors: Klein Kristopher G., Perez Jean C., Verscharen Daniel, Mallet Alfred, and Chandran Benjamin D. G.
Title: A MODIFIED VERSION OF TAYLOR’S HYPOTHESIS FOR SOLAR PROBE PLUS OBSERVATIONS
Abstract:

The Solar Probe Plus (SPP) spacecraft will explore the near-Sun environment, reaching heliocentric distances less than 10 {{R}}. Near Earth, spacecraft measurements of fluctuating velocities and magnetic fields taken in the time domain are translated into information about the spatial structure of the solar wind via Taylor’s “frozen turbulence” hypothesis. Near the perihelion of SPP, however, the solar-wind speed is comparable to the Alfvén speed, and Taylor’s hypothesis in its usual form does not apply. In this paper, we show that under certain assumptions, a modified version of Taylor’s hypothesis can be recovered in the near-Sun region. We consider only the transverse, non-compressive component of the fluctuations at length scales exceeding the proton gyrora. . .
Date: 03/2015 Publisher: The Astrophysical Journal Pages: L18 DOI: 10.1088/2041-8205/801/1/L18 Available at: http://stacks.iop.org/2041-8205/801/i=1/a=L18?key=crossref.c92a2bde23ce9cdd58185dec581d5a09
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2014
Authors: Rasca A. P., Oran R., and ányi M.
Title: Mass loading of the solar wind by a sungrazing comet
Abstract:

Collisionless mass loading was suggested by Biermann et al. (1967) for describing interactions between the solar wind and cometary atmospheres. Recent observations have led to an increased interest in coronal mass loading due to sungrazing comets and collisional debris of sunward migrating interplanetary dust particles. In a previous paper, we presented a 3-D MHD model of the solar corona based on the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme code which includes the interaction of dust with the solar wind. We have shown the impact on the solar wind from abrupt mass loading in the coronal region. We apply the model to a sungrazing cometary source, using ejected dust dynamics to generate tail-shaped mass-loading regions. Results help predict the effects on the solar wind acceleratio. . .
Date: 08/2014 Publisher: Geophysical Research Letters Pages: 5376 - 5381 DOI: 10.1002/2014GL060990 Available at: http://doi.wiley.com/10.1002/2014GL060990http://onlinelibrary.wiley.com/wol1/doi/10.1002/2014GL060990/fullpdfhttps
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Authors: Kombiadou Katerina, Ganthy Florian, Verney Romaric, Plus Martin, and Sottolichio Aldo
Title: Modelling the effects of Zostera noltei meadows on sediment dynamics: application to the Arcachon lagoon
Abstract:

A three-dimensional model has been modified to describe the complex interactions between hydrodynamics, sediment dynamics and biological parameters in the presence of Zostera noltei. The model treats seagrass leafs as flexible blades that bend under hydrodynamic forcing and alter the local momentum and turbulence fluxes and, therefore, the benthic shear conditions; these changes cause related changes to the mass balance at the boundary of the bed, in turn affecting the suspended matter in the column and ultimately primary productivity and the growth of the dwarf-grass. Modelling parameters related to the impact of Z. noltei to the local flow and to erosion and deposition rates were calibrated using flume experimental measurements; results from the calibration of the model are presented . . .
Date: 10/2014 Publisher: Ocean Dynamics Pages: 1499 - 1516 DOI: 10.1007/s10236-014-0754-1 Available at: http://link.springer.com/10.1007/s10236-014-0754-1http://link.springer.com/content/pdf/10.1007/s10236-014-0754-1
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2003
Authors: Plus M
Title: Modelling of oxygen and nitrogen cycling as a function of macrophyte community in the Thau lagoon
Abstract:

A three-dimensional model coupling physical and biological processes for the whole Thau lagoon (Mediterranean coast of France) was developed in order to assess the relationships between macrophytes and the oxygen and nitrogen cycles. Ten species have been inserted as forcing variables in the model. Plankton dynamics, shellfish cultivation impact and mineralization of organic matter are also considered, as well as nutrient and oxygen exchanges between the sediment and the water column. Simulations with and without the macrophytes have shown that the system can be characterized as having a highly structured pattern involving lagoon nitrogen and oxygen cycles. This pattern is created by the combined influence of macrophytes, watershed and oyster farming. The model has been also used to ass. . .
Date: 11/2003 Publisher: Continental Shelf Research Pages: 1877 - 1898 DOI: 10.1016/j.csr.2003.03.001 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0278434303001511https://api.elsevier.com/content/article/PII:S0278-4343(03)00151-1?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0278-4343(03)00151-1?httpAccept=text/plain
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