Found 194 results
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1986
Authors: Brucker G. J., Herbert J., Stewart R., and Plus D.
Title: Sapphire Photocurrent Sources and Their Impact on RAM Upset
Abstract:

This paper reports on the transient photocurrent measurements made with test structures fabricated on sapphire substrates, and the computer simulation model which was developed to use the test results. Predictions of logic upset for a 4 K RAM CMOS/SOS compared with measured upset rates showed agreement within a factor of 2. The test structure results indicate that the sapphire photoconductance is 6.3 x 10 to the -19th mhos/(rads/s)-micron. The use of this value in the present simulation model will increase the predicted upset rate, and thus, increase the disagreement by more than a factor of two.


Date: 12/1986 Publisher: IEEE Transactions on Nuclear Science Pages: 1377 - 1380 DOI: 10.1109/TNS.1986.4334608 Available at: http://ieeexplore.ieee.org/document/4334608/http://xplorestaging.ieee.org/ielx5/23/4334557/04334608.pdf?arnumber=4334608
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2010
Authors: Mozer F. S., and Hull A.
Title: Scaling the energy conversion rate from magnetic field reconnection to different bodies
Abstract:

Magnetic field reconnection is often invoked to explain electromagnetic energy conversion in planetary magnetospheres, stellar coronae, and other astrophysical objects. Because of the huge dynamic range of magnetic fields in these bodies, it is important to understand energy conversion as a function of magnetic field strength and related parameters. It is conjectured theoretically and shown experimentally that the energy conversion rate per unit area in reconnection scales as the cube of an appropriately weighted magnetic field strength divided by the square root of an appropriately weighted density. With this functional dependence, the energy release in flares on the Sun, the large and rapid variation of the magnetic flux in the tail of Mercury, and the apparent absence of reconnection. . .
Date: 10/2010 Publisher: Physics of Plasmas Pages: 102906 DOI: 10.1063/1.3504224 Available at: http://aip.scitation.org/doi/10.1063/1.3504224http://aip.scitation.org/doi/pdf/10.1063/1.3504224
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Authors: Guo Yanping
Title: Solar Probe Plus: Mission design challenges and trades
Abstract:

NASA plans to launch the first mission to the Sun, named Solar Probe Plus, as early as 2015, after a comprehensive feasibility study that significantly changed the original Solar Probe mission concept. The original Solar Probe mission concept, based on a Jupiter gravity assist trajectory, was no longer feasible under the new guidelines given to the mission. A complete redesign of the mission was required, which called for developing alternative trajectories that excluded a flyby of Jupiter. Without the very powerful gravity assist from Jupiter it was extremely difficult to get to the Sun, so designing a trajectory to reach the Sun that is technically feasible under the new mission guidelines became a key enabler to this highly challenging mission. Mission design requirements and challen. . .
Date: 11/2010 Publisher: Acta Astronautica Pages: 1063 - 1072 DOI: 10.1016/j.actaastro.2010.06.007 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0094576510001980https://api.elsevier.com/content/article/PII:S0094576510001980?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0094576510001980?httpAccept=text/plain
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Authors: Ergun R. E., Malaspina D. M., Bale S. D., McFadden J. P., Larson D. E., et al.
Title: Spacecraft charging and ion wake formation in the near-Sun environment
Abstract:

A three-dimensional, self-consistent code is employed to solve for the static potential structure surrounding a spacecraft in a high photoelectron environment. The numerical solutions show that, under certain conditions, a spacecraft can take on a negative potential in spite of strong photoelectron currents. The negative potential is due to an electrostatic barrier near the surface of the spacecraft that can reflect a large fraction of the photoelectron flux back to the spacecraft. This electrostatic barrier forms if (1) the photoelectron density at the surface of the spacecraft greatly exceeds the ambient plasma density, (2) the spacecraft size is significantly larger than local Debye length of the photoelectrons, and (3) the thermal electron energy is much larger than the characterist. . .
Date: 07/2010 Publisher: Physics of Plasmas Pages: 072903 DOI: 10.1063/1.3457484 Available at: http://aip.scitation.org/doi/10.1063/1.3457484http://aip.scitation.org/doi/pdf/10.1063/1.3457484
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2011
Authors: Velli Marco, Lionello Roberto, Linker Jon A., and ć Zoran
Title: CORONAL PLUMES IN THE FAST SOLAR WIND
Abstract:

The expansion of a coronal hole filled with a discrete number of higher density coronal plumes is simulated using a time-dependent two-dimensional code. A solar wind model including an exponential coronal heating function and a flux of Alfvén waves propagating both inside and outside the structures is taken as a basic state. Different plasma plume profiles are obtained by using different scale heights for the heating rates. Remote sensing and solar wind in situ observations are used to constrain the parameter range of the study. Time dependence due to plume ignition and disappearance is also discussed. Velocity differences of the order of 50 km s-1, such as those found in microstreams in the high-speed solar wind, may be easily explained by slightly different heat depositio. . .
Date: 07/2011 Publisher: The Astrophysical Journal Pages: 32 DOI: 10.1088/0004-637X/736/1/32 Available at: http://stacks.iop.org/0004-637X/736/i=1/a=32?key=crossref.9f21641f557225a36ce23f05fa1256f6http://stacks.iop.org/0004-637X/736/i=1/a=32/pdf
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Authors: Lario D., and Decker R. B.
Title: Estimation of solar energetic proton mission-integrated fluences and peak intensities for missions traveling close to the Sun
Abstract:

A method to estimate both solar energetic particle mission-integrated fluences and solar energetic particle peak intensities for missions traveling through the innermost part of the heliosphere (r < 1 AU) is presented. By using (1) an extensive data set of particle intensities measured at 1 AU over the last three solar cycles, (2) successive launch dates for the mission traveling close to the Sun over the time interval spanned by our data set, and (3) appropriate radial dependences to extrapolate fluences and peak intensities measured at 1 AU to the heliocentric radial distance of the mission at each specific time, we generate distributions of both mission-integrated fluences and maximum peak intensities. From these distributions we extract the values of mission-integrated fluence an. . .
Date: 11/2011 Publisher: Space Weather Pages: n/a - n/a DOI: 10.1029/2011SW000708 Available at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011SW000708
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Authors: Eck J., Sans J.-L., and Balat-Pichelin M.
Title: Experimental study of carbon materials behavior under high temperature and VUV radiation: Application to Solar Probe+ heat shield
Abstract:

The aim of the Solar Probe Plus (SP+) mission is to understand how the solar corona is heated and how the solar wind is accelerated. To achieve these goals, in situ measurements are necessary and the spacecraft has to approach the Sun as close as 9.5 solar radii. This trajectory induces extreme environmental conditions such as high temperatures and intense Vacuum Ultraviolet radiation (VUV). To protect the measurement and communication instruments, a heat shield constituted of a carbon material is placed on the top of the probe. In this study, the physical and chemical behavior of carbon materials is experimentally investigated under high temperatures (1600-2100 K), high vacuum (10-4 Pa) and VUV radiation in conditions near those at perihelion for SP+. Thanks to several in si. . .
Date: 02/2011 Publisher: Applied Surface Science Pages: 3196 - 3204 DOI: 10.1016/j.apsusc.2010.10.139 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0169433210015059https://api.elsevier.com/content/article/PII:S0169433210015059?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0169433210015059?httpAccept=text/plain
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2012
Authors: Lario D.
Title: Estimation of the solar flare neutron worst-case fluxes and fluences for missions traveling close to the Sun
Abstract:

A method to estimate the total fluence of solar flare neutrons at a spacecraft traveling in the innermost part of the heliosphere (at heliocentric radial distances of <1 AU) is presented. The results of the neutron production and emissivity codes of Hua and Lingenfelter (1987a, 1987b) scaled to one of the largest solar neutron events ever observed at the Earth are used to derive a conservative estimate of the energy spectrum of neutrons emitted from the Sun after a large solar flare. By taking into account the survival probability of a neutron to reach a certain heliocentric distance, we evaluate the observed time-integrated spectrum of solar neutrons as a function of the heliocentric distance of the observer. By considering (1) a working relationship between the soft X-ray class of . . .
Date: 03/2012 Publisher: Space Weather Pages: n/a - n/a DOI: 10.1029/2011SW000732 Available at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011SW000732
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Authors: Lipatov Alexander S., Jr. Edward C. Sittler, Hartle Richard E., and Cooper John F.
Title: Short wavelength electromagnetic perturbations excited near the Solar Probe Plus spacecraft in the inner heliosphere: 2.5D hybrid modeling
Abstract:

A 2.5D numerical plasma model of the interaction of the solar wind (SW) with the Solar Probe Plus spacecraft (SPPSC) is presented. These results should be interpreted as a basic plasma model derived from the SW interaction with the spacecraft (SC), which could have consequences for both plasma wave and electron plasma measurements on board the SC in the inner heliosphere. Compression waves and electric field jumps with amplitudes of about 1.5 V/m and (12-18) V/m were also observed. A strong polarization electric field was also observed in the wing of the plasma wake. However, 2.5D hybrid modeling did not show excitation of whistler/Alfvén waves in the upstream connected with the bi-directional current closure that was observed in short-time 3D modeling SPPSC and near a tether in the io. . .
Date: 03/2012 Publisher: Planetary and Space Science Pages: 61 - 68 DOI: 10.1016/j.pss.2011.12.008 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0032063311003527https://api.elsevier.com/content/article/PII:S0032063311003527?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0032063311003527?httpAccept=text/plain
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Authors: Rohner U, Saul L, Wurz P, Allegrini F, Scheer J, et al.
Title: A simple 3D plasma instrument with an electrically adjustable geometric factor for space research
Abstract:

We report on the design and experimental verification of a novel charged particle detector and an energy spectrometer with variable geometric factor functionality. Charged particle populations in the inner heliosphere create fluxes that can vary over many orders of magnitude in flux intensity. Space missions that plan to observe plasma fluxes, for example when travelling close to the Sun or to a planetary magnetosphere, require rapid particle measurements over the full three-dimensional velocity distribution. Traditionally, such measurements are carried out with plasma instrumentation with a fixed geometrical factor, which can only operate in a limited range of flux intensity. Here we report on the design and testing of a prototype sensor, which is capable of measuring particle flux wit. . .
Date: 02/2012 Publisher: Measurement Science and Technology Pages: 025901 DOI: 10.1088/0957-0233/23/2/025901 Available at: http://stacks.iop.org/0957-0233/23/i=2/a=025901?key=crossref.d9b288ad2aedebf79cadcdbcf703f854http://stacks.iop.org/0957-0233/23/i=2/a=025901/pdf
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2013
Authors: Bastian T. S.
Title: AIP Conference ProceedingsA view from the ground: Next generation instrumentation for solar and heliospheric physics
Abstract:

The solar and space physics community has recently completed its second decadal survey under the auspices of the National Research Council. An integrated strategy for ground and space based studies of the Sun and space physics has been recommended, with specific recommendations made regarding new instrumentation, programs, and facilities. The ground based component of these recommendations is briefly reviewed here: the Advanced Technology Solar Telescope (ATST), the Frequency Agile Solar Radiotelescope (FASR), and the Coronal Solar Magnetism Observatory (COSMO). Although not considered as part of the decadal portfolio, but of which the community should nevertheless be aware, are the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array (VLA). Several additi. . .
Date: 07/2013 Publisher: AIP DOI: 10.1063/1.4811080 Available at: http://aip.scitation.org/doi/abs/10.1063/1.4811080
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Authors: Wicks Robert T., Matteini Lorenzo, Horbury Timothy S., Hellinger Petr, and Roberts Aaron
Title: AIP Conference ProceedingsTemperature anisotropy instabilities; combining plasma and magnetic field data at different distances from the Sun
Abstract:

We present a new data analysis method enabling the observation of magnetic field fluctuations associated with temperature anisotropy instabilities using the Ulysses spacecraft. The movement of the spacecraft away from the Sun causes the observed plasma conditions, turbulent fluctuation amplitude, magnetic field strength and important physical scales to change. We normalize wavelet power spectra of the magnetic field using local values for the proton gyroscale and large scale magnetic field fluctuation amplitude to remove the effects of varying heliocentric distance. We recover the enhancement of magnetic fluctuations where temperature anisotropy instability growth rates are large, as seen by previous studies in the ecliptic at 1 AU. This method can be applied to any spacecraft data that. . .
Date: 07/2013 Publisher: AIP DOI: 10.1063/1.4811048 Available at: http://aip.scitation.org/doi/abs/10.1063/1.4811048
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Authors: Reid Hamish A. S., and Kontar Eduard P.
Title: Evolution of the Solar Flare Energetic Electrons in the Inhomogeneous Inner Heliosphere
Abstract:

Solar flare accelerated electrons escaping into the interplanetary space and seen as type III solar radio bursts are often detected near the Earth. Using numerical simulations we consider the evolution of energetic electron spectrum in the inner heliosphere and near the Earth. The role of Langmuir wave generation, heliospheric plasma density fluctuations, and expansion of magnetic field lines on the electron peak flux and fluence spectra is studied to predict the electron properties as could be observed by Solar Orbiter and Solar Probe Plus. Considering various energy loss mechanisms we show that the substantial part of the initial energetic electron energy is lost via wave-plasma processes due to plasma inhomogeneity. For the parameters adopted, the results show that the electron spect. . .
Date: 07/2013 Publisher: Solar Physics Pages: 217 - 232 DOI: 10.1007/s11207-012-0013-x Available at: http://link.springer.com/10.1007/s11207-012-0013-xhttp://link.springer.com/content/pdf/10.1007/s11207-012-0013-x
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2014
Authors: Goelzer Molly L., Schwadron Nathan A., and Smith Charles W.
Title: An analysis of Alfvén radius based on sunspot number from 1749 to today
Abstract:

The Solar Probe Plus mission now under construction will provide the first in situ measurements from inside the orbit of Mercury. The most critical part of that mission will be measurements from inside the Alfvén radius where the Alfvén speed exceeds the wind speed and the physics of the solar wind changes fundamentally due, in part, to the multidirectionality of wave propagation. In this region waves from both sunward and antisunward of the observation point can effect the local dynamics including the turbulent evolution, heating, and acceleration of the plasma. While the location of this point can change with solar wind conditions, we ask the question of whether there is a systematic dependence on the solar cycle that moves the average Alfvén radius to different locations depending. . .
Date: 01/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 115 - 120 DOI: 10.1002/2013JA019420 Available at: http://doi.wiley.com/10.1002/2013JA019420http://onlinelibrary.wiley.com/wol1/doi/10.1002/2013JA019420/fullpdf
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Authors: Marchand R., Miyake Y., Usui H., Deca J., Lapenta G., et al.
Title: Cross-comparison of spacecraft-environment interaction model predictions applied to Solar Probe Plus near perihelion
Abstract:

Five spacecraft-plasma models are used to simulate the interaction of a simplified geometry Solar Probe Plus (SPP) satellite with the space environment under representative solar wind conditions near perihelion. By considering similarities and differences between results obtained with different numerical approaches under well defined conditions, the consistency and validity of our models can be assessed. The impact on model predictions of physical effects of importance in the SPP mission is also considered by comparing results obtained with and without these effects. Simulation results are presented and compared with increasing levels of complexity in the physics of interaction between solar environment and the SPP spacecraft. The comparisons focus particularly on spacecraft floating po. . .
Date: 06/2014 Publisher: Physics of Plasmas Pages: 062901 DOI: 10.1063/1.4882439 Available at: http://aip.scitation.org/doi/10.1063/1.4882439http://aip.scitation.org/doi/pdf/10.1063/1.4882439
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Authors: Li T. C., Drake J. F., and Swisdak M.
Title: DYNAMICS OF DOUBLE LAYERS, ION ACCELERATION, AND HEAT FLUX SUPPRESSION DURING SOLAR FLARES
Abstract:

Observations of flare-heated electrons in the corona typically suggest confinement of electrons. The confinement mechanism, however, remains unclear. The transport of coronal hot electrons into ambient plasma was recently investigated by particle-in-cell (PIC) simulations. Electron transport was significantly suppressed by the formation of a highly localized, nonlinear electrostatic potential in the form of a double layer (DL). In this work large-scale PIC simulations are performed to explore the dynamics of DLs in larger systems where, instead of a single DL, multiple DLs are generated. The primary DL accelerates return current electrons, resulting in high velocity electron beams that interact with ambient ions. This forms a Buneman unstable system that spawns more DLs. Trapping of hea. . .
Date: 09/2014 Publisher: The Astrophysical Journal Pages: 7 DOI: 10.1088/0004-637X/793/1/7 Available at: http://stacks.iop.org/0004-637X/793/i=1/a=7?key=crossref.1ff276d1b5e9632b2d52ebb5720bc5e6
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Authors: Balat-Pichelin M., Eck J., Heurtault S., and énat H.
Title: Experimental study of pyrolytic boron nitride at high temperature with and without proton and VUV irradiations
Abstract:

In the frame of future exploration missions such as Solar Probe Plus (NASA) and PHOIBOS (ESA), research was carried out to study pyrolytic BN material envisaged as coating for their heat shields. The physico-chemical behavior of CVD pBN at very high temperature with or without hydrogen ions and VUV (Vacuum Ultra-Violet) irradiations was studied in high vacuum together with the in situ measurement of the thermal radiative properties conditioning the thermal equilibrium of the heat shield. Experimental results obtained on massive pBN samples are presented through in situ mass spectrometry and mass loss rate, and post-test microstructural characterization by XRD, SEM, AFM and nano-indentation techniques, some of them leading to mechanical properties. It could be concluded that synergistic . . .
Date: 09/2014 Publisher: Applied Surface Science Pages: 415 - 425 DOI: 10.1016/j.apsusc.2014.07.007 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0169433214015219https://api.elsevier.com/content/article/PII:S0169433214015219?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0169433214015219?httpAccept=text/plain
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Authors: DeForest C. E., Howard T. A., and McComas D. J.
Title: INBOUND WAVES IN THE SOLAR CORONA: A DIRECT INDICATOR OF ALFVÉN SURFACE LOCATION
Abstract:

The tenuous supersonic solar wind that streams from the top of the corona passes through a natural boundary—the Alfvén surface—that marks the causal disconnection of individual packets of plasma and magnetic flux from the Sun itself. The Alfvén surface is the locus where the radial motion of the accelerating solar wind passes the radial Alfvén speed, and therefore any displacement of material cannot carry information back down into the corona. It is thus the natural outer boundary of the solar corona and the inner boundary of interplanetary space. Using a new and unique motion analysis to separate inbound and outbound motions in synoptic visible-light image sequences from the COR2 coronagraph on board the STEREO-A spacecraft, we have identified inbound wave motion in the outer co. . .
Date: 06/2014 Publisher: The Astrophysical Journal Pages: 124 DOI: 10.1088/0004-637X/787/2/124 Available at: http://stacks.iop.org/0004-637X/787/i=2/a=124?key=crossref.8ca79a982204ddd2b4922cc108364616
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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: Lawrence David J., Feldman William C., Gold Robert E., Goldsten John O., and McNutt Ralph L.
Title: The neutron, gamma-ray, X-ray spectrometer (NGXS): A compact instrument for making combined measurements of neutrons, gamma-rays, and X-rays
Abstract:

The Neutron, Gamma ray, and X-ray Spectrometer (NGXS) is a compact instrument designed to detect neutrons, gamma-rays, and hard X-rays. The original goal of NGXS was to detect and characterize neutrons, gamma-rays, and X-rays from the Sun as part of the Solar Probe Plus mission in order to provide direct insight into particle acceleration, magnetic reconnection, and cross-field transport processes that take place near the Sun. Based on high-energy neutron detections from prompt solar flares, it is estimated that the NGXS would detect neutrons from 15 to 24 impulsive flares. The NGXS sensitivity to 2.2 MeV gamma rays would enable a detection of ̃50-60 impulsive flares. The NGXS is estimated to measure ̃120 counts/s for a GOES C1-type flare at 0.1 AU, which allows for a large dynamic ra. . .
Date: 01/2014 Publisher: Acta Astronautica Pages: 524 - 529 DOI: 10.1016/j.actaastro.2012.06.017 Available at: https://linkinghub.elsevier.com/retrieve/pii/S009457651200255Xhttps://api.elsevier.com/content/article/PII:S009457651200255X?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S009457651200255X?httpAccept=text/plain
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Authors: Vainio Rami, önni Arttu, Battarbee Markus, Koskinen Hannu E. J., Afanasiev Alexandr, et al.
Title: A semi-analytical foreshock model for energetic storm particle events inside 1 AU
Abstract:

We have constructed a semi-analytical model of the energetic-ion foreshock of a CME-driven coronal/interplanetary shock wave responsible for the acceleration of large solar energetic particle (SEP) events. The model is based on the analytical model of diffusive shock acceleration of Bell (1978), appended with a temporal dependence of the cut-off momentum of the energetic particles accelerated at the shock, derived from the theory. Parameters of the model are re-calibrated using a fully time-dependent self-consistent simulation model of the coupled particle acceleration and Alfvén-wave generation upstream of the shock. Our results show that analytical estimates of the cut-off energy resulting from the simplified theory and frequently used in SEP modelling are overestimating the cut-off . . .
Date: 02/2014 Publisher: Journal of Space Weather and Space Climate Pages: A08 DOI: 10.1051/swsc/2014005 Available at: http://www.swsc-journal.org/10.1051/swsc/2014005http://www.swsc-journal.org/10.1051/swsc/2014005/pdf
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Authors: Howes G. G., Klein K. G., and TenBarge J. M.
Title: VALIDITY OF THE TAYLOR HYPOTHESIS FOR LINEAR KINETIC WAVES IN THE WEAKLY COLLISIONAL SOLAR WIND
Abstract:

The interpretation of single-point spacecraft measurements of solar wind turbulence is complicated by the fact that the measurements are made in a frame of reference in relative motion with respect to the turbulent plasma. The Taylor hypothesis—that temporal fluctuations measured by a stationary probe in a rapidly flowing fluid are dominated by the advection of spatial structures in the fluid rest frame—is often assumed to simplify the analysis. But measurements of turbulence in upcoming missions, such as Solar Probe Plus, threaten to violate the Taylor hypothesis, either due to slow flow of the plasma with respect to the spacecraft or to the dispersive nature of the plasma fluctuations at small scales. Assuming that the frequency of the turbulent fluctuations is characterized by th. . .
Date: 07/2014 Publisher: The Astrophysical Journal Pages: 106 DOI: 10.1088/0004-637X/789/2/106 Available at: http://stacks.iop.org/0004-637X/789/i=2/a=106?key=crossref.25a7683ba86c87973ee983db364c5e6f
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Authors: Klein K. G., Howes G. G., and TenBarge J. M.
Title: THE VIOLATION OF THE TAYLOR HYPOTHESIS IN MEASUREMENTS OF SOLAR WIND TURBULENCE
Abstract:

Motivated by the upcoming Solar Orbiter and Solar Probe Plus missions, qualitative and quantitative predictions are made for the effects of the violation of the Taylor hypothesis on the magnetic energy frequency spectrum measured in the near-Sun environment. The synthetic spacecraft data method is used to predict observational signatures of the violation for critically balanced Alfvénic turbulence or parallel fast/whistler turbulence. The violation of the Taylor hypothesis can occur in the slow flow regime, leading to a shift of the entire spectrum to higher frequencies, or in the dispersive regime, in which the dissipation range spectrum flattens at high frequencies. It is found that Alfvénic turbulence will not significantly violate the Taylor hypothesis, but whistler turbulence wil. . .
Date: 08/2014 Publisher: The Astrophysical Journal Pages: L20 DOI: 10.1088/2041-8205/790/2/L20 Available at: http://stacks.iop.org/2041-8205/790/i=2/a=L20?key=crossref.9873bcfbec22617b78b4a7d0cb1dbb95
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2015
Authors: de Patoul Judith, Foullon Claire, and Riley Pete
Title: 3D ELECTRON DENSITY DISTRIBUTIONS IN THE SOLAR CORONA DURING SOLAR MINIMA: ASSESSMENT FOR MORE REALISTIC SOLAR WIND MODELING
Abstract:

Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar reg. . .
Date: 11/2015 Publisher: The Astrophysical Journal Pages: 68 DOI: 10.1088/0004-637X/814/1/68 Available at: http://stacks.iop.org/0004-637X/814/i=1/a=68?key=crossref.845557cfda4b2a3786588c8b62dbb093
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Authors: Comişel H. ̧, Motschmann U., üchner J., Narita Y., and Nariyuki Y.
Title: ION-SCALE TURBULENCE IN THE INNER HELIOSPHERE: RADIAL DEPENDENCE
Abstract:

The evolution of the ion-scale plasma turbulence in the inner heliosphere is studied by associating the plasma parameters for hybrid-code turbulence simulations to the radial distance from the Sun via a Solar wind model based mapping procedure. Using a mapping based on a one-dimensional solar wind expansion model, the resulting ion-kinetic scale turbulence is related to the solar wind distance from the Sun. For this purpose the mapping is carried out for various values of ion beta that correspond to the heliocentric distance. It is shown that the relevant normal modes such as ion cyclotron and ion Bernstein modes will occur first at radial distances of about 0.2-0.3 AU, i.e., near the Mercury orbit. This finding can be used as a reference, a prediction to guide the in situ measurements . . .
Date: 10/2015 Publisher: The Astrophysical Journal Pages: 175 DOI: 10.1088/0004-637X/812/2/175 Available at: http://stacks.iop.org/0004-637X/812/i=2/a=175?key=crossref.a9d511ae127248e735f11254de6e3bb9
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Pages