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Chen Zhou - One of the best experts on this subject based on the ideXlab platform.
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excitation of dayside chorus waves due to Magnetic Field Line compression in response to interplanetary shocks
Journal of Geophysical Research, 2015Co-Authors: Chen Zhou, W Li, R M Thorne, J Bortnik, Xin An, Xiaojia Zhang, V Angelopoulos, Binbin NiAbstract:© 2015 American Geophysical Union. All Rights Reserved. The excitation of magnetospheric whistler-mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008-2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of Magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background Magnetic Field configurations in the near-equatorial dayside magnetosphere; and therefore, the threshold of nonLinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geoMagnetic Field Line configuration plays a key role in the excitation of dayside chorus. Key Points Excitation of dayside chorus waves is observed These waves are in response to IP shocks IP shocks change the Magnetic Field Line configuration.
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excitation of dayside chorus waves due to Magnetic Field Line compression in response to interplanetary shocks
Journal of Geophysical Research, 2015Co-Authors: Chen Zhou, R M Thorne, J Bortnik, Xiaojia Zhang, V Angelopoulos, Zhengyu ZhaoAbstract:The excitation of magnetospheric whistler-mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008–2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of Magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background Magnetic Field configurations in the near-equatorial dayside magnetosphere; and therefore, the threshold of nonLinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geoMagnetic Field Line configuration plays a key role in the excitation of dayside chorus.
W H Matthaeus - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Line random walk and solar energetic particle path lengths stochastic theory and psp isois observation
Astronomy and Astrophysics, 2021Co-Authors: R Chhiber, W H Matthaeus, C M S Cohen, D Ruffolo, W Sonsrettee, P Tooprakai, A Seripienlert, P Chuychai, A V Usmanov, M L GoldsteinAbstract:We thank Junxiang Hu for useful discussions. This research is partially supported by the Parker Solar Probe mission and the IS IS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165). Additional support is acknowledged from the NASA Living With a Star (LWS) program (NNX17AB79G) and HSR program (80NSSC18K1210 & 80NSSC18K1648) and Thailand Science Research and Innovation (RTA6280002). The IS IS data and visualization tools are available to the community at https://spacephysics.princeton.edu/missions-instruments/isois; data are also available via the NASA Space Physics Data Facility. PSP was designed, built, and is now operated by the Johns Hopkins Applied Physics Laboratory as part of NASA’s LWS program (contract NNN06AA01C). Support from the LWS management and technical team has played a critical role in the success of the PSP mission.
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Magnetic Field Line random walk and solar energetic particle path lengths
'EDP Sciences', 2021Co-Authors: R Chhiber, W H Matthaeus, C M S Cohen, D Ruffolo, W Sonsrettee, P Tooprakai, A Seripienlert, P Chuychai, A V Usmanov, M L GoldsteinAbstract:Context. In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/IS⊙IS instrument suite at ≈0.35 AU from the Sun. From standard velocity-dispersion analysis, the apparent ion path length is ≈0.625 AU at the onset of each event. Aims. We develop a formalism for estimating the path length of random-walking Magnetic Field Lines to explain why the apparent ion path length at an event onset greatly exceeds the radial distance from the Sun for these events. Methods. We developed analytical estimates of the average increase in path length of random-walking Magnetic Field Lines, relative to the unperturbed mean Field. Monte Carlo simulations of Field Line and particle trajectories in a model of solar wind turbulence were used to validate the formalism and study the path lengths of particle guiding-center and full-orbital trajectories. The formalism was implemented in a global solar wind model, and the results are compared with ion path lengths inferred from IS⊙IS observations. Results. Both a simple estimate and a rigorous theoretical formulation are obtained for Field-Lines’ path length increase as a function of path length along the large-scale Field. From simulated Field Line and particle trajectories, we find that particle guiding centers can have path lengths somewhat shorter than the average Field Line path length, while particle orbits can have substantially longer path lengths due to their gyromotion with a nonzero effective pitch angle. Conclusions. The long apparent path length during these solar energetic ion events can be explained by (1) a Magnetic Field Line path length increase due to the Field Line random walk and (2) particle transport about the guiding center with a nonzero effective pitch angle due to pitch angle scattering. Our formalism for computing the Magnetic Field Line path length, accounting for turbulent fluctuations, may be useful for application to solar particle transport in general
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Magnetic Field Line random walk and solar energetic particle path lengths stochastic theory and psp isois observation
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: R Chhiber, W H Matthaeus, C M S Cohen, D Ruffolo, W Sonsrettee, P Tooprakai, A Seripienlert, P Chuychai, A V Usmanov, M L GoldsteinAbstract:Context:In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/ISoIS instrument suite at 0.35 AU from the Sun. From standard velocity-dispersion analysis, the apparent ion path length is 0.625 AU at the onset of each event. Aims:We develop a formalism for estimating the path length of random-walking Magnetic Field Lines, to explain why the apparent ion pathlength at event onset greatly exceeds the radial distance from the Sun for these events. Methods:We developed analytical estimates of the average increase in pathlength of random-walking Magnetic Field Lines, relative to the unperturbed mean Field. Monte Carlo simulations of FieldLine and particle trajectories in a model of solar wind turbulence are used to validate the formalism and study the path lengths of particle guiding-center and full-orbital trajectories. The formalism is implemented in a global solar wind model, and results are compared with ion pathlengths inferred from ISoIS observations. Results:Both a simple estimate and a rigorous theoretical formulation are obtained for FieldLines' pathlength increase as a function of pathlength along the large-scale Field. From simulated FieldLine and particle trajectories, we find that particle guiding centers can have pathlengths somewhat shorter than the average FieldLine pathlength, while particle orbits can have substantially larger pathlengths due to their gyromotion with a nonzero effective pitch angle. Conclusions:The long apparent path length during these solar energetic ion events can be explained by 1) a Magnetic Field Line path length increase due to the Field Line random walk, and 2) particle transport about the guiding center with a nonzero effective pitch angle. Our formalism for computing the Magnetic Field Line path length, accounting for turbulent fluctuations, may be useful for application to solar particle transport in general.
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in situ measurement of curvature of Magnetic Field in turbulent space plasmas a statistical study
The Astrophysical Journal, 2020Co-Authors: Riddhi Bandyopadhyay, W H Matthaeus, T N Parashar, A Chasapis, Yan Yang, C T Russell, R J Strangeway, R B Torbert, B L GilesAbstract:Using in situ data, accumulated in the turbulent magnetosheath by the Magnetospheric Multiscale (MMS) Mission, we report a statistical study of Magnetic Field curvature and discuss its role in the turbulent space plasmas. Consistent with previous simulation results, the Probability Distribution Function (PDF) of the curvature is shown to have distinct power-law tails for both high and low value limits. We find that the Magnetic-Field-Line curvature is intermittently distributed in space. High curvature values reside near weak Magnetic-Field regions, while low curvature values are correlated with small magnitude of the force acting normal to the Field Lines. A simple statistical treatment provides an explanation for the observed curvature distribution. This novel statistical characterization of Magnetic curvature in space plasma provides a starting point for assessing, in a turbulence context, the applicability and impact of particle energization processes, such as curvature drift, that rely on this fundamental quantity.
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Magnetic Field Line random walk for disturbed flux surfaces trapping effects and multiple routes to bohm diffusion
The Astrophysical Journal, 2011Co-Authors: M C Ghilea, D Ruffolo, W Sonsrettee, A Seripienlert, P Chuychai, W H MatthaeusAbstract:The Magnetic Field Line random walk (FLRW) is important for the transport of energetic particles in many astrophysical situations. While all authors agree on the quasiLinear diffusion of Field Lines for fluctuations that mainly vary parallel to a large-scale Field, for the opposite case of fluctuations that mainly vary in the perpendicular directions, there has been an apparent conflict between concepts of Bohm diffusion and percolation/trapping effects. Here computer simulation and non-perturbative analytic techniques are used to re-examine the FLRW in Magnetic turbulence with slab and two-dimensional (2D) components, in which 2D flux surfaces are disturbed by the slab fluctuations. Previous non-perturbative theories for D ⊥, based on Corrsin's hypothesis, have identified a slab contribution with quasiLinear behavior and a 2D contribution due to Bohm diffusion with diffusive decorrelation (DD), combined in a quadratic formula. Here we present analytic theories for other routes to Bohm diffusion, with random ballistic decorrelation (RBD) either due to the 2D component itself (for a weak slab contribution) or the total fluctuation Field (for a strong slab contribution), combined in a direct sum with the slab contribution. Computer simulations confirm the applicability of RBD routes for weak or strong slab contributions, while the DD route applies for a moderate slab contribution. For a very low slab contribution, interesting trapping effects are found, including a depressed diffusion coefficient and subdiffusive behavior. Thus quasiLinear, Bohm, and trapping behaviors are all found in the same system, together with an overall viewpoint to explain these behaviors.
C C Chaston - One of the best experts on this subject based on the ideXlab platform.
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ion temperature effects on magnetotail alfven wave propagation and electron energization ion temperature effects on alfven waves
Journal of Geophysical Research, 2015Co-Authors: P A Damiano, C C Chaston, Jay R JohnsonAbstract:A new 2-D self-consistent hybrid gyrofluid-kinetic electron model in dipolar coordinates is presented and used to simulate dispersive-scale Alfven wave pulse propagation from the equator to the ionosphere along an L = 10 Magnetic Field Line. The model is an extension of the hybrid MHD-kinetic electron model that incorporates ion Larmor radius corrections via the kinetic fluid model of Cheng and Johnson (1999). It is found that consideration of a realistic ion to electron temperature ratio decreases the propagation time of the wave from the plasma sheet to the ionosphere by several seconds relative to a ρi=0 case (which also implies shorter timing for a substorm onset signal) and leads to significant dispersion of wave energy perpendicular to the ambient Magnetic Field. Additionally, ion temperature effects reduce the parallel current and electron energization all along the Field Line for the same magnitude perpendicular electric Field perturbation.
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megavolt parallel potentials arising from double layer streams in the earth s outer radiation belt
Physical Review Letters, 2013Co-Authors: F S Mozer, S D Bale, J W Bonnell, C C Chaston, I Roth, J R WygantAbstract:Huge numbers of double layers carrying electric Fields parallel to the local Magnetic Field Line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth's outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230,000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1,000,000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a Magnetic Field Line in about 15 s and the orbital motion of the spacecraft perpendicular to the Magnetic Field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single Magnetic Field Line was the order of tens of kilovolts. Electrons on the Field Line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100 km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects.
J Bortnik - One of the best experts on this subject based on the ideXlab platform.
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excitation of dayside chorus waves due to Magnetic Field Line compression in response to interplanetary shocks
Journal of Geophysical Research, 2015Co-Authors: Chen Zhou, W Li, R M Thorne, J Bortnik, Xin An, Xiaojia Zhang, V Angelopoulos, Binbin NiAbstract:© 2015 American Geophysical Union. All Rights Reserved. The excitation of magnetospheric whistler-mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008-2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of Magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background Magnetic Field configurations in the near-equatorial dayside magnetosphere; and therefore, the threshold of nonLinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geoMagnetic Field Line configuration plays a key role in the excitation of dayside chorus. Key Points Excitation of dayside chorus waves is observed These waves are in response to IP shocks IP shocks change the Magnetic Field Line configuration.
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excitation of dayside chorus waves due to Magnetic Field Line compression in response to interplanetary shocks
Journal of Geophysical Research, 2015Co-Authors: Chen Zhou, R M Thorne, J Bortnik, Xiaojia Zhang, V Angelopoulos, Zhengyu ZhaoAbstract:The excitation of magnetospheric whistler-mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008–2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of Magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background Magnetic Field configurations in the near-equatorial dayside magnetosphere; and therefore, the threshold of nonLinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geoMagnetic Field Line configuration plays a key role in the excitation of dayside chorus.
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ray tracing of penetrating chorus and its implications for the radiation belts
Geophysical Research Letters, 2007Co-Authors: J Bortnik, R M Thorne, Nigel P Meredith, O SantolikAbstract:Using ray tracing and suprathermal electron distributions from CRRES, the final propagation latitudes of typical chorus rays are calculated as a function of L, MLT, AE, and initial wave normal angle. Rays initiated within a certain range of wave normals ψ P ∼ −0.8ψ G to −0.6ψ G (where ψ G is the Gendrin angle) propagate to very high latitudes, largely avoiding Landau damping whilst remaining roughly Field-aligned for large portions of their propagation paths. The relative wave power of such penetrating chorus may increase above its initial value due to the low damping rates and Magnetic Field Line convergence. By considering 4 representative rays with f = 0.3f ce , and calculating the resonant energies at the edge of the loss-cone, it is shown that penetrating chorus readily interacts with electrons in the >1 MeV energy range, and may thus contribute to the previously reported relativistic electron microbursts.
M L Goldstein - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Line random walk and solar energetic particle path lengths stochastic theory and psp isois observation
Astronomy and Astrophysics, 2021Co-Authors: R Chhiber, W H Matthaeus, C M S Cohen, D Ruffolo, W Sonsrettee, P Tooprakai, A Seripienlert, P Chuychai, A V Usmanov, M L GoldsteinAbstract:We thank Junxiang Hu for useful discussions. This research is partially supported by the Parker Solar Probe mission and the IS IS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165). Additional support is acknowledged from the NASA Living With a Star (LWS) program (NNX17AB79G) and HSR program (80NSSC18K1210 & 80NSSC18K1648) and Thailand Science Research and Innovation (RTA6280002). The IS IS data and visualization tools are available to the community at https://spacephysics.princeton.edu/missions-instruments/isois; data are also available via the NASA Space Physics Data Facility. PSP was designed, built, and is now operated by the Johns Hopkins Applied Physics Laboratory as part of NASA’s LWS program (contract NNN06AA01C). Support from the LWS management and technical team has played a critical role in the success of the PSP mission.
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Magnetic Field Line random walk and solar energetic particle path lengths
'EDP Sciences', 2021Co-Authors: R Chhiber, W H Matthaeus, C M S Cohen, D Ruffolo, W Sonsrettee, P Tooprakai, A Seripienlert, P Chuychai, A V Usmanov, M L GoldsteinAbstract:Context. In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/IS⊙IS instrument suite at ≈0.35 AU from the Sun. From standard velocity-dispersion analysis, the apparent ion path length is ≈0.625 AU at the onset of each event. Aims. We develop a formalism for estimating the path length of random-walking Magnetic Field Lines to explain why the apparent ion path length at an event onset greatly exceeds the radial distance from the Sun for these events. Methods. We developed analytical estimates of the average increase in path length of random-walking Magnetic Field Lines, relative to the unperturbed mean Field. Monte Carlo simulations of Field Line and particle trajectories in a model of solar wind turbulence were used to validate the formalism and study the path lengths of particle guiding-center and full-orbital trajectories. The formalism was implemented in a global solar wind model, and the results are compared with ion path lengths inferred from IS⊙IS observations. Results. Both a simple estimate and a rigorous theoretical formulation are obtained for Field-Lines’ path length increase as a function of path length along the large-scale Field. From simulated Field Line and particle trajectories, we find that particle guiding centers can have path lengths somewhat shorter than the average Field Line path length, while particle orbits can have substantially longer path lengths due to their gyromotion with a nonzero effective pitch angle. Conclusions. The long apparent path length during these solar energetic ion events can be explained by (1) a Magnetic Field Line path length increase due to the Field Line random walk and (2) particle transport about the guiding center with a nonzero effective pitch angle due to pitch angle scattering. Our formalism for computing the Magnetic Field Line path length, accounting for turbulent fluctuations, may be useful for application to solar particle transport in general
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Magnetic Field Line random walk and solar energetic particle path lengths stochastic theory and psp isois observation
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: R Chhiber, W H Matthaeus, C M S Cohen, D Ruffolo, W Sonsrettee, P Tooprakai, A Seripienlert, P Chuychai, A V Usmanov, M L GoldsteinAbstract:Context:In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/ISoIS instrument suite at 0.35 AU from the Sun. From standard velocity-dispersion analysis, the apparent ion path length is 0.625 AU at the onset of each event. Aims:We develop a formalism for estimating the path length of random-walking Magnetic Field Lines, to explain why the apparent ion pathlength at event onset greatly exceeds the radial distance from the Sun for these events. Methods:We developed analytical estimates of the average increase in pathlength of random-walking Magnetic Field Lines, relative to the unperturbed mean Field. Monte Carlo simulations of FieldLine and particle trajectories in a model of solar wind turbulence are used to validate the formalism and study the path lengths of particle guiding-center and full-orbital trajectories. The formalism is implemented in a global solar wind model, and results are compared with ion pathlengths inferred from ISoIS observations. Results:Both a simple estimate and a rigorous theoretical formulation are obtained for FieldLines' pathlength increase as a function of pathlength along the large-scale Field. From simulated FieldLine and particle trajectories, we find that particle guiding centers can have pathlengths somewhat shorter than the average FieldLine pathlength, while particle orbits can have substantially larger pathlengths due to their gyromotion with a nonzero effective pitch angle. Conclusions:The long apparent path length during these solar energetic ion events can be explained by 1) a Magnetic Field Line path length increase due to the Field Line random walk, and 2) particle transport about the guiding center with a nonzero effective pitch angle. Our formalism for computing the Magnetic Field Line path length, accounting for turbulent fluctuations, may be useful for application to solar particle transport in general.
