Found 123 results
Author Title Type [ Year(Asc)]
2019
Authors: Chhiber Rohit, Usmanov Arcadi V., Matthaeus William H., and Goldstein Melvyn L.
Title: Contextual Predictions for the Parker Solar Probe . I. Critical Surfaces and Regions
Abstract:

The solar corona and young solar wind may be characterized by critical surfaces—the sonic, Alfvén, and first plasma-β unity surfaces—that demarcate regions where the solar wind flow undergoes certain crucial transformations. Global numerical simulations and remote sensing observations offer a natural mode for the study of these surfaces at large scales, thus providing valuable context for the high-resolution in situ measurements expected from the recently launched Parker Solar Probe (PSP). The present study utilizes global three-dimensional magnetohydrodynamic (MHD) simulations of the solar wind to characterize the critical surfaces and investigate the flow in propinquitous regions. Effects of solar activity are incorporated by varying source magnetic dipole tilts and employing ma. . .
Date: 03/2019 Publisher: The Astrophysical Journal Supplement Series Pages: 11 DOI: 10.3847/1538-4365/ab0652 Available at: http://stacks.iop.org/0067-0049/241/i=1/a=11?key=crossref.5e73dbbb501083f4d606cdf21e74f766http://stacks.iop.org/0067-0049/241/i=1/a=11/
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Authors: Adhikari L., Zank G. P., and Zhao L.-L.
Title: Does Turbulence Turn off at the Alfvén Critical Surface?
Abstract:

The Parker Solar Probe (PSP) will eventually reach and cross the Alfvén point or surface as it provides us with direct in situ measurements of the solar atmosphere. The Alfvén surface is the location at which the large-scale bulk solar wind speed ${\boldsymbol{U}}$ and the Alfvén speed ${\boldsymbol{V}}$ A are equal, and thus it separates sub-Aflvénic coronal flow $| {\boldsymbol{U}}| \ll | {{\boldsymbol{V}}}_{{\rm{A}}}| $ from super-Alfv. . .
Date: Jan-05-2019 Publisher: The Astrophysical Journal Pages: 26 DOI: 10.3847/1538-4357/ab141c Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab141c
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Authors: Al-Haddad Nada, Lugaz Noé, Poedts Stefaan, Farrugia Charles J., Nieves-Chinchilla Teresa, et al.
Title: Evolution of Coronal Mass Ejection Properties in the Inner Heliosphere: Prediction for the Solar Orbiter and Parker Solar Probe
Abstract:

The evolution of the magnetic field and plasma quantities inside a coronal mass ejection (CME) with distance are known from statistical studies using data from 1 au monitors, planetary missions, Helios, and Ulysses. This does not cover the innermost heliosphere, below 0.29 au, where no data are yet publicly available. Here, we describe the evolution of the properties of simulated CMEs in the inner heliosphere using two different initiation mechanisms. We compare the radial evolution of these properties with that found from statistical studies based on observations in the inner heliosphere by Helios and MESSENGER. We find that the evolution of the radial size and magnetic field strength is nearly indistinguishable for twisted flux rope from that of writhed CMEs. The evolution of these pr. . .
Date: 10/2019 Publisher: The Astrophysical Journal Pages: 179 DOI: 10.3847/1538-4357/ab4126 Available at: https://iopscience.iop.org/article/10.3847/1538-4357/ab4126
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Authors: Telloni Daniele, Giordano Silvio, and Antonucci Ester
Title: On the Fast Solar Wind Heating and Acceleration Processes: A Statistical Study Based on the UVCS Survey Data
Abstract:

The UltraViolet Coronagraph Spectrometer (UVCS) on board the SOlar and Heliospheric Observatory has almost continuously observed, throughout the whole solar cycle 23, the UV solar corona. This work addresses the first-ever statistical analysis of the daily UVCS observations, performed in the O VI channel, of the northern polar coronal hole, between 1.5 and 3 R , during the period of low solar activity from 1996 April to 1997 December. The study is based on the investigation, at different heights, of the correlation between the variance of the O VI 1031.92 Å spectral line and the O VI 1031.92, 1037.61 Å doublet intensity ratio, which are proxies of the kinetic temperature of the O5+ ions and of the speed of the oxygen component of the fast solar wind, respectiv. . .
Date: 08/2019 Publisher: The Astrophysical Journal Pages: L36 DOI: 10.3847/2041-8213/ab3731 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab3731
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Authors: Wu Honghong, Verscharen Daniel, Wicks Robert T., Chen Christopher H. K., He Jiansen, et al.
Title: The Fluid-like and Kinetic Behavior of Kinetic Alfvén Turbulence in Space Plasma
Abstract:

Kinetic Alfvén waves (KAWs) are the short-wavelength extension of the magnetohydrodynamics Alfvén-wave branch in the case of highly oblique propagation with respect to the background magnetic field. Observations of space plasma show that small-scale turbulence is mainly KAW-like. We apply two theoretical approaches, a collisional two-fluid theory and a collisionless linear kinetic theory, to obtain predictions for the KAW polarizations depending on β p (the ratio of the proton thermal pressure to the magnetic pressure) at the ion gyroscale in terms of fluctuations in density, bulk velocity, and pressure. We perform a wavelet analysis of Magnetospheric Multiscale magnetosheath measurements and compare the observations with both the. . .
Date: 01/2019 Publisher: The Astrophysical Journal Pages: 106 DOI: 10.3847/1538-4357/aaef77 Available at: http://stacks.iop.org/0004-637X/870/i=2/a=106?key=crossref.82a2db48f1fad21f326ef5e3fb4b795
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Authors: Pacheco D., Agueda N., Aran A., Heber B., and Lario D.
Title: Full inversion of solar relativistic electron events measured by the Helios spacecraft
Abstract:

Context. The Parker Solar Probe and the incoming Solar Orbiter mission will provide measurements of solar energetic particle (SEP) events at close heliocentric distances from the Sun. Up to present, the largest data set of SEP events in the inner heliosphere are the observations by the two Helios spacecraft.

Aims. We re-visit a sample of 15 solar relativistic electron events measured by the Helios mission with the goal of better characterising the injection histories of solar energetic particles and their interplanetary transport conditions at heliocentric distances <1 AU.

Methods. The measurements provided by the E6 instrument on board Helios provide us with the electron directional distributions in eight different sectors that we use t. . .
Date: 01/2019 Publisher: Astronomy & Astrophysics Pages: A3 DOI: 10.1051/0004-6361/201834520 Available at: https://www.aanda.org/10.1051/0004-6361/201834520/pdf
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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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Authors: Riley Pete, Downs Cooper, Linker Jon A., Mikic Zoran, Lionello Roberto, et al.
Title: Predicting the Structure of the Solar Corona and Inner Heliosphere during Parker Solar Probe 's First Perihelion Pass
Abstract:

NASA’s Parker Solar Probe (PSP) spacecraft reached its first perihelion of 35.7 solar radii on 2018 November 5. To aid in mission planning, and in anticipation of the unprecedented measurements to be returned, in late October, we developed a three-dimensional magnetohydrodynamic (MHD) solution for the solar corona and inner heliosphere, driven by the then available observations of the Sun’s photospheric magnetic field. Our model incorporates a wave-turbulence-driven model to heat the corona. Here, we present our predictions for the structure of the solar corona and the likely in situ measurements that PSP will be returning over the next few months. We infer that, in the days prior to first encounter, PSP was immersed in wind emanating from a well-established, positive-polarity north. . .
Date: 04/2019 Publisher: The Astrophysical Journal Pages: L15 DOI: 10.3847/2041-8213/ab0ec3 Available at: http://stacks.iop.org/2041-8205/874/i=2/a=L15?key=crossref.94a3f13ef95cab063c2cc60115d0f410http://stacks.iop.org/2041-8205/874/i=2/a=L15/pd
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Authors: Hein Andreas M., Perakis Nikolaos, Eubanks Marshall, Hibberd Adam, Crowl Adam, et al.
Title: Project Lyra: Sending a spacecraft to 1I/’Oumuamua (former A/2017 U1), the interstellar asteroid
Abstract:

The first definitely interstellar object 1I/'Oumuamua (previously A/2017 U1) observed in our solar system provides the opportunity to directly study material from an other star system. Can such objects be intercepted? The challenge of reaching the object within a reasonable timeframe is formidable due to its high heliocentric hyperbolic excess velocity of about 26 km/s; much faster than any vehicle yet launched. This paper presents a high-level analysis of potential near-term options for a mission to 1I/'Oumuamua and potential similar objects. Reaching 1I/'Oumuamua via a spacecraft launched in a reasonable timeframe of 5-10 years (launch in 2022-2027) requires an Earth departure hyperbolic excess velocity between 33 and 76 km/s for mission durations between 30 and 5 years, respectively.. . .
Date: 08/2019 Publisher: Acta Astronautica Pages: 552 - 561 DOI: 10.1016/j.actaastro.2018.12.042 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0094576518317004
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Authors: Yoon Peter H., Hwang Junga, Kim Hyangpyo, and Seough Jungjoon
Title: Quasi Thermal Noise Spectroscopy for Van Allen Probes
Abstract:

Quasi thermal fluctuations in the Langmuir/upper-hybrid frequency range are pervasively observed in space plasmas including the radiation belt and the ring current region of inner magnetosphere as well as the solar wind. The quasi thermal noise spectroscopy may be employed in order to determine the electron density and temperature as well as to diagnose the properties of energetic electrons when direct measurements are not available. However, when employing the technique, one must carefully take the spacecraft orientation into account. The present paper takes the upper-hybrid and multiple harmonic—or (n + 1/2)fce—emissions measured by the Van Allen Probes as an example in order to illustrate how the spacecraft antenna geometrical factor can be incorporated into the theore. . .
Date: 04/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA026460 Available at: https://onlinelibrary.wiley.com/doi/abs/10.1029/2019JA026460
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Authors: Ratmaya Widya, Soudant Dominique, Salmon-Monviola Jordy, Plus Martin, Cochennec-Laureau Nathalie, et al.
Title: Reduced phosphorus loads from the Loire and Vilaine rivers were accompanied by increasing eutrophication in the Vilaine Bay (south Brittany, France)
Abstract:

The evolution of eutrophication parameters (i.e., nutrients and phytoplankton biomass) during recent decades was examined in coastal waters of the Vilaine Bay (VB, France) in relation to changes in the Loire and Vilaine rivers. Dynamic linear models were used to study long-term trends and seasonality of dissolved inorganic nutrient and chlorophyll a concentrations (Chl a) in rivers and coastal waters. For the period 1997-2013, the reduction in dissolved riverine inorganic phosphorus (DIP) concentrations led to the decrease in their Chl a levels. However, while dissolved inorganic nitrogen (DIN) concentrations decreased only slightly in the Vilaine, they increased in the Loire, specifically in summer. Simultaneously, phytoplankton in the VB underwent profound changes with increase in bio. . .
Date: 04/2019 Publisher: Biogeosciences Pages: 1361 - 1380 DOI: 10.5194/bg-16-1361-201910.5194/bg-16-1361-2019-supplement Available at: https://www.biogeosciences.net/16/1361/2019/https://www.biogeosciences.net/16/1361/2019/bg-16-1361-2019.pdfhttps://www.biogeosciences.net/16/1361/2019/bg-16-1361-2019-supplement.pdf
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Authors: Le Fur I, De Wit R, Plus M, Oheix J, Derolez V, et al.
Title: Re-oligotrophication trajectories of macrophyte assemblages in Mediterranean coastal lagoons based on 17-year time-series
Abstract:

No abstract


Date: 01/2019 Publisher: Marine Ecology Progress Series Pages: 13 - 32 DOI: 10.3354/meps12814 Available at: https://www.int-res.com/abstracts/meps/v608/p13-32/https://www.int-res.com/articles/meps_oa/m608p013.pdf
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Authors: Parashar T. N., Cuesta M., and Matthaeus W. H.
Title: Reynolds Number and Intermittency in the Expanding Solar Wind: Predictions Based on Voyager Observations
Abstract:

The large-scale features of the solar wind are examined in order to predict small-scale features of turbulence in unexplored regions of the heliosphere. The strategy is to examine how system size, or effective Reynolds number Re, varies, and then how this quantity influences observable statistical properties, including intermittency properties of solar wind turbulence. The expectation based on similar hydrodynamics scalings is that the kurtosis, of the small-scale magnetic field increments, will increase with increasing Re. Simple theoretical arguments as well as Voyager observations indicate that effective interplanetary turbulence Re decreases with increasing heliocentric distance. The decrease of scale-dependent magnetic increment kurtosis with increasing heliocentric distance is ver. . .
Date: 10/2019 Publisher: The Astrophysical Journal Pages: L57 DOI: 10.3847/2041-8213/ab4a82 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab4a82
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Authors: Pecora Francesco, Greco Antonella, Hu Qiang, Servidio Sergio, Chasapis Alexandros G., et al.
Title: Single-spacecraft Identification of Flux Tubes and Current Sheets in the Solar Wind
Abstract:

A novel technique is presented for describing and visualizing the local topology of the magnetic field using single-spacecraft data in the solar wind. The approach merges two established techniques: the Grad─Shafranov (GS) reconstruction method, which provides a plausible regional two-dimensional magnetic field surrounding the spacecraft trajectory, and the Partial Variance of Increments (PVI) technique that identifies coherent magnetic structures, such as current sheets. When applied to one month of Wind magnetic field data at 1 minute resolution, we find that the quasi-two-dimensional turbulence emerges as a sea of magnetic islands and current sheets. Statistical analysis confirms that current sheets associated with high values of PVI are mostly located between and within the GS mag. . .
Date: 08/2019 Publisher: The Astrophysical Journal Pages: L11 DOI: 10.3847/2041-8213/ab32d9 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab32d9
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Authors: Yoon P. H., Seough J., Salem C. S., and Klein K. G.
Title: Solar Wind Temperature Isotropy
Abstract:

Reliable models of the solar wind in the near-Earth space environment may constrain conditions close to the Sun. This is relevant to NASA's contemporary innerheliospheric mission Parker Solar Probe. Among the outstanding issues is how to explain the solar wind temperature isotropy. Perpendicular and parallel proton and electron temperatures near 1 AU are theoretically predicted to be unequal, but in situ observations show quasi-isotropy sufficiently below the instability threshold condition. This has not been satisfactorily explained. The present Letter shows that the dynamical coupling of electrons and protons via collisional processes and instabilities may contribute toward the resolution of this problem.


Date: 10/2019 Publisher: Physical Review Letters DOI: 10.1103/PhysRevLett.123.145101 Available at: https://link.aps.org/doi/10.1103/PhysRevLett.123.145101http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.123.145101/fulltexthttps://link.aps.org/article/10.1103/PhysRevLett.123.145101
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Authors: Pavan J., and Viñas A. F.
Title: Temperature Fluctuation at the Sun and Large-scale Electric Field in Solar Wind: A Challenge for the Parker Solar Probe Mission
Abstract:

Velocity distributions of particles are key elements in the study of solar wind. The physical mechanisms that regulate their many features are a matter of debate. The present work addresses the subject with a fully analytical method in order to establish the shape of particle velocity distributions in solar wind. The method consists of solving the steady-state kinetic equation for particles and the related fluid equations, with spatial profiles for density and temperature that match general observational data. The model is one-dimensional in configuration-space and two-dimensional in velocity-space, and accounts for large-scale processes, namely, advection, gravity, magnetic mirroring, and the large-scale ambipolar electric field. The findings reported add to the general understanding o. . .
Date: 09/2019 Publisher: The Astrophysical Journal Pages: 28 DOI: 10.3847/1538-4357/ab2fcd
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Authors: Perrone Denise, Stansby D, Horbury T S, and Matteini L
Title: Thermodynamics of pure fast solar wind: radial evolution of the temperature–speed relationship in the inner heliosphereABSTRACT
Abstract:

A strong correlation between speed and proton temperature has been observed, across many years, on hourly averaged measurements in the solar wind. Here, we show that this relationship is also observed at a smaller scale on intervals of a few days, within a single stream. Following the radial evolution of a well-defined stream of coronal-hole plasma, we show that the temperature-speed (T-V) relationship evolves with distance, implying that the T-V relationship at 1 au cannot be used as a proxy for that near the Sun. We suggest that this behaviour could be a combination of the anticorrelation between speed and flux-tube expansion factor near the Sun and the effect of a continuous heating experienced by the plasma during the expansion. We also show that the cooling index for the radial evo. . .
Date: 09/2019 Publisher: Monthly Notices of the Royal Astronomical Society Pages: 2380 - 2386 DOI: 10.1093/mnras/stz1877 Available at: https://academic.oup.com/mnras/article/488/2/2380/5530769http://academic.oup.com/mnras/article-pdf/488/2/2380/28979632/stz1877.pdfhttp://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/stz1877/28924256/stz1877.pdf
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2018
Authors: Witze Alexandra
Title: Death-defying NASA mission will make humanity’s closest approach to the Sun
Abstract:

The Parker Solar Probe will dive into the sizzling solar corona to explore its mysteries.


Date: 07/2018 Publisher: Nature Pages: 452 - 453 DOI: 10.1038/d41586-018-05741-6 Available at: http://www.nature.com/articles/d41586-018-05741-6http://www.nature.com/articles/d41586-018-05741-6.pdfhttp://www.nature.com/articles/d41586-018-05741-6http://www.nature.com/articles/d41586-018-05741-6.pdf
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Authors: Stansby D, Horbury T S, and Matteini L
Title: Diagnosing solar wind origins using in situ measurements in the inner heliosphere
Abstract:

Robustly identifying the solar sources of individual packets of solar wind measured in interplanetary space remains an open problem. We set out to see if this problem is easier to tackle using solar wind measurements closer to the Sun than 1 au, where the mixing and dynamical interaction of different solar wind streams is reduced. Using measurements from the Helios mission, we examined how the proton core temperature anisotropy and cross-helicity varied with distance. At 0.3 au there are two clearly separated anisotropic and isotropic populations of solar wind that are not distinguishable at 1 au. The anisotropic population is always Alfvénic and spans a wide range of speeds. In contrast the isotropic population has slow speeds, and contains a mix of Alfvénic wind with constant mass f. . .
Date: 01/2019 Publisher: Monthly Notices of the Royal Astronomical Society Pages: 1706 - 1714 DOI: 10.1093/mnras/sty2814 Available at: https://academic.oup.com/mnras/article/482/2/1706/5142296http://academic.oup.com/mnras/article-pdf/482/2/1706/26330049/sty2814.pdf
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Authors: Yoon Peter H., Hwang Junga, ópez Rodrigo A., Kim Sunjung, and Lee Jaejin
Title: Electromagnetic Thermal Noise in Upper-Hybrid Frequency Range
Abstract:

The inner magnetosphere including the radiation belt and ring current environment is replete with high-frequency fluctuations with peak intensity occurring near upper-hybrid frequency and/or multiple harmonic electron cyclotron frequencies above and below the upper-hybrid frequency. Past and contemporary spacecraft missions, including the Van Allen Probes, were designed to detect the electric field spectrum only for these high-frequency fluctuations. Making use of the recently formulated generalized theory of electromagnetic spontaneous emission in thermal magnetized plasmas, it is shown that upper-hybrid/multiple harmonic electron cyclotron emissions are characterized by a significant magnetic field component, even in the high-frequency regime. Such a prediction may potentially be test. . .
Date: 07/2018 Publisher: Journal of Geophysical Research: Space Physics Pages: 5356 - 5363 DOI: 10.1029/2018JA025459 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1029/2018JA025459/fullpdf
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Authors: Stenborg Guillermo, Stauffer Johnathan R., and Howard Russell A.
Title: Evidence for a Circumsolar Dust Ring Near Mercury’s Orbit
Abstract:

To test a technique to be used on the white-light imager onboard the recently launched Parker Solar Probe mission, we performed a numerical differentiation of the brightness profiles along the photometric axis of the F-corona models that are derived from STEREO Ahead Sun Earth Connection Heliospheric Investigation observations recorded with the HI-1 instrument between 2007 December and 2014 March. We found a consistent pattern in the derivatives that can be observed from any S/C longitude between about 18° and 23° elongation with a maximum at about 21°. These findings indicate the presence of a circumsolar dust density enhancement that peaks at about 23° elongation. A straightforward integration of the excess signal in the derivative space indicates that the brightness increase over. . .
Date: 11/2018 Publisher: The Astrophysical Journal Pages: 74 DOI: 10.3847/1538-4357/aae6cb Available at: http://stacks.iop.org/0004-637X/868/i=1/a=74?key=crossref.819ea43bc5d8ac7ce2e4d9090800ae03
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Authors: Owens Mathew J., Lockwood Mike, Barnard Luke A., and MacNeil Allan R.
Title: Generation of Inverted Heliospheric Magnetic Flux by Coronal Loop Opening and Slow Solar Wind Release
Abstract:

In situ spacecraft observations provide much-needed constraints on theories of solar wind formation and release, particularly the highly variable slow solar wind, which dominates near-Earth space. Previous studies have shown an association between local inversions in the heliospheric magnetic field (HMF) and solar wind released from the vicinity of magnetically closed coronal structures. We here show that in situ properties of inverted HMF are consistent with the same hot coronal source regions as the slow solar wind. We propose that inverted HMF is produced by solar wind speed shear, which results from interchange reconnection between a coronal loop and open flux tube, and introduces a pattern of fast─slow─fast wind along a given HMF flux tube. This same loop-opening process is tho. . .
Date: 11/2018 Publisher: The Astrophysical Journal Pages: L14 DOI: 10.3847/2041-8213/aaee82 Available at: http://stacks.iop.org/2041-8205/868/i=1/a=L14?key=crossref.317335516eaf9fd091c127050a2fecdd
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Authors: Graham G. A., Rae I. J., Owen C. J., and Walsh A. P.
Title: Investigating the Effect of IMF Path Length on Pitch-angle Scattering of Strahl within 1 au
Abstract:

Strahl is the strongly field-aligned, beam-like population of electrons in the solar wind. Strahl width is observed to increase with distance from the Sun, and hence strahl electrons must be subject to in-transit scattering effects. Different energy relations have been both observed and modeled for both strahl width and the width increase with radial distance. Thus, there is much debate regarding what mechanism(s) scatter strahl. In this study, we use a novel method to investigate strahl evolution within 1 au by estimating the distance traveled by the strahl along the interplanetary magnetic field (IMF). We do this by implementing methods developed in previous studies, which make use of the onset of solar energetic particles at ̃1 au. Thus, we are able to obtain average strahl broadeni. . .
Date: 03/2018 Publisher: The Astrophysical Journal Pages: 40 DOI: 10.3847/1538-4357/aaaf1b Available at: http://stacks.iop.org/0004-637X/855/i=1/a=40?key=crossref.ef4d8c88b914db7976655ab16f8f792a
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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.

. . .
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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