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G P Zank - One of the best experts on this subject based on the ideXlab platform.
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the evolution of Interplanetary Shocks propagating into the very local interstellar medium
Journal of Physics: Conference Series, 2018Co-Authors: P Mostafavi, G P ZankAbstract:Voyager 1 has made in situ measurements of the very local interstellar medium (VLISM) since August 2012 and its magnetometer and plasma wave instrument have detected several VLISM Shock Waves. Interplanetary Shocks propagate through the supersonic solar wind and then through the inner heliosheath after colliding with the heliospheric termination Shock (HTS). Interplanetary Shock Waves are transmitted partially across the heliopause (HP) into the VLISM and partially reflected back into the inner heliosheath. Previous studies showed that the in situ VLISM Shocks observed by Voyager 1 were very weak and remarkably broad and had properties different than Shocks inside the heliosphere [1, 2]. We model the first VLISM Shock observed by Voyager 1 and compare with observations. We calculate the collisionality of the thermal particles and the dissipation terms such as heat conduction and viscosity that are associated with Coulomb collisions in the VLISM. The VLISM is collisional with respect to the thermal plasma and the VLISM Shock structure is determined by thermal proton-proton collisions, which is the dominant thermal collisional term. The VLISM Shock is controlled by particle collisions and not mediated by PUIs since they do not introduce significant dissipation through the Shock transition. As a result, we find that the extremely broadness of the weak VLISM Shock is due to the thermal collisionality.
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analytic forms of the perpendicular cosmic ray diffusion coefficient for an arbitrary turbulence spectrum and applications on transport of galactic protons and acceleration at Interplanetary Shocks
Astrophysics and Space Science, 2010Co-Authors: A. Shalchi, G P ZankAbstract:We investigate cosmic ray scattering in the direction perpendicular to a mean magnetic field. Unlike in previous articles we employ a general form of the turbulence wave spectrum with arbitrary behavior in the energy range. By employing an improved version of the nonlinear guiding center theory we compute analytically the perpendicular mean free path. As shown, the energy range spectral index, has a strong influence on the perpendicular diffusion coefficient. If this parameter is larger than one we find for some cases a perpendicular diffusion coefficient that is independent of the parallel mean free path and particle energy. Two applications are considered, namely transport of Galactic protons in the solar system and diffusive particle acceleration at highly perpendicular Interplanetary Shock Waves.
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a forecast of the heliospheric termination Shock position by three dimensional mhd simulations
The Astrophysical Journal, 2007Co-Authors: H Washimi, G P Zank, Takashi Tanaka, K MunakataAbstract:The effects of heliospheric disturbances on the position of the termination Shock (TS) are examined using a three-dimensional MHD model. Variations in the solar wind ram pressure due to the Interplanetary Shock Waves drive the TS away from its steady state equilibrium position and emit Shocks and Waves downstream. Transmitted/emitted disturbances propagating from the TS to the heliopause (HP) are partially reflected at the HP, and the reflected Waves return and collide with the TS. Thus, besides upstream solar wind disturbances, the TS location RTS changes in response to incident downstream disturbances associated with Waves reflected from the HP produced by earlier supersonic solar wind disturbances. To determine the time-varying RTS, we incorporate Voyager 2 (V2) plasma data as a boundary condition into our 3D MHD simulations, which allows us to forecast the termination Shock movement for nearly a year after the present V2 data. Our simulations indicate that the TS was at ~90 AU along the Sun-V1 line on 2007 August 14, the last tentative available date of the V2 data. After this, our simulation forecasts that RTS will decrease to a minimum distance in late 2007 or early 2008. This decrease will be mainly caused by the heliosheath returned pulse driven by the 2006 March event. Whether V2 will cross the TS or not in this period depends on the future solar wind ram pressure and also on the degree of the north-south asymmetry of the heliospheric structure. Some quantitative discussions are given.
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particle acceleration and coronal mass ejection driven Shocks Shocks of arbitrary strength
Journal of Geophysical Research, 2003Co-Authors: W K M Rice, G P ZankAbstract:[1] There is substantial evidence suggesting that energetic particles observed in “gradual” solar energetic particle events are accelerated at Shock Waves driven out of the corona by coronal mass ejections (CMEs). We present a model of particle acceleration at Interplanetary Shock Waves, assumed to be driven by CMEs, in which the upstream wave intensity, driven by the accelerated particles, is calculated self-consistently using the steady-state solution to the wave growth equation. This then allows for the self-consistent calculation of the momentum dependent spatial diffusion coefficient which ultimately governs both the acceleration and subsequent evolution of the energetic particles. The model is consequently applicable to Shock Waves of arbitrary strength, a significant improvement on previous models which were generally only valid for very strong Shock Waves. The model is able to calculate minimum and maximum particles energies as the Shock propagates out into the solar wind and can determine time-dependent downstream spectra. The spectra of particles escaping into the relatively undisturbed upstream medium is also calculated and in future will be used as input to a detailed transport model to determine upstream spectra and intensity profiles. Although we do not compare the results with any individual observations, the model is able to reproduce some of the observed features of “gradual” SEP events. The self-consistent calculation of the upstream wave intensity will in future allow this model to be extended to consider the acceleration of particles of various charge states and masses.
D. V. Reames - One of the best experts on this subject based on the ideXlab platform.
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the two sources of solar energetic particles
Space Science Reviews, 2013Co-Authors: D. V. ReamesAbstract:Evidence for two different physical mechanisms for acceleration of solar energetic particles (SEPs) arose 50 years ago with radio observations of type III bursts, produced by outward streaming electrons, and type II bursts from coronal and Interplanetary Shock Waves. Since that time we have found that the former are related to “impulsive” SEP events from impulsive flares or jets. Here, resonant stochastic acceleration, related to magnetic reconnection involving open field lines, produces not only electrons but 1000-fold enhancements of 3He/4He and of (Z>50)/O. Alternatively, in “gradual” SEP events, Shock Waves, driven out from the Sun by coronal mass ejections (CMEs), more democratically sample ion abundances that are even used to measure the coronal abundances of the elements. Gradual events produce by far the highest SEP intensities near Earth. Sometimes residual impulsive suprathermal ions contribute to the seed population for Shock acceleration, complicating the abundance picture, but this process has now been modeled theoretically. Initially, impulsive events define a point source on the Sun, selectively filling few magnetic flux tubes, while gradual events show extensive acceleration that can fill half of the inner heliosphere, beginning when the Shock reaches ∼2 solar radii. Shock acceleration occurs as ions are scattered back and forth across the Shock by resonant Alfven Waves amplified by the accelerated protons themselves as they stream away. These Waves also can produce a streaming-limited maximum SEP intensity and plateau region upstream of the Shock. Behind the Shock lies the large expanse of the “reservoir”, a spatially extensive trapped volume of uniform SEP intensities with invariant energy-spectral shapes where overall intensities decrease with time as the enclosing “magnetic bottle” expands adiabatically. These reservoirs now explain the slow intensity decrease that defines gradual events and was once erroneously attributed solely to slow outward diffusion of the particles. At times the reservoir from one event can contribute its abundances and even its spectra as a seed population for acceleration by a second CME-driven Shock wave. Confinement of particles to magnetic flux tubes that thread their source early in events is balanced at late times by slow velocity-dependent migration through a tangled network produced by field-line random walk that is probed by SEPs from both impulsive and gradual events and even by anomalous cosmic rays from the outer heliosphere. As a practical consequence, high-energy protons from gradual SEP events can be a significant radiation hazard to astronauts and equipment in space and to the passengers of high-altitude aircraft flying polar routes.
Hairston Marc - One of the best experts on this subject based on the ideXlab platform.
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Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm
2017Co-Authors: Chandler, Michael O., Sazykin Stan, Minow Joseph, Coffey Victoria, Anderson, Brian J., Hairston MarcAbstract:The magnetic storm that commenced on June 22-23, 2015 was one of the largest storms in our current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated Interplanetary Shock Waves. On June 22 at 18:36 UT the magnetosphere was impacted by the Shock wave on the magnetosphere. Observations from several spacecraft observed the dynamic response of the magnetosphere and ionosphere. MMS observatories in the near earth tail These low altitude measurements are correlated in the magnetosphere with particle flux dropouts measured by MMS We follow the timing of this storm in the ionosphere with the density depletions throughout the ISS orbits, DMSP drift velocities, and enhanced AMPERE Birkland currents. Together these observations and simulation results will be assembled to provide each region's context to the global dynamics and time evolution of the storm. The models during these event support and flesh out the puzzle of the global dynamics
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Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm
2017Co-Authors: Hairston Marc, Sazykin Stan, Minow Joseph, Chandler Michael, Anderson Brian, Coffey VictoriaAbstract:The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated Interplanetary Shock Waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge Shock wave and a sheath carrying a large and highly variable Interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasmasheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasmasheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe
Coffey Victoria - One of the best experts on this subject based on the ideXlab platform.
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Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm
2017Co-Authors: Chandler, Michael O., Sazykin Stan, Minow Joseph, Coffey Victoria, Anderson, Brian J., Hairston MarcAbstract:The magnetic storm that commenced on June 22-23, 2015 was one of the largest storms in our current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated Interplanetary Shock Waves. On June 22 at 18:36 UT the magnetosphere was impacted by the Shock wave on the magnetosphere. Observations from several spacecraft observed the dynamic response of the magnetosphere and ionosphere. MMS observatories in the near earth tail These low altitude measurements are correlated in the magnetosphere with particle flux dropouts measured by MMS We follow the timing of this storm in the ionosphere with the density depletions throughout the ISS orbits, DMSP drift velocities, and enhanced AMPERE Birkland currents. Together these observations and simulation results will be assembled to provide each region's context to the global dynamics and time evolution of the storm. The models during these event support and flesh out the puzzle of the global dynamics
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Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm
2017Co-Authors: Hairston Marc, Sazykin Stan, Minow Joseph, Chandler Michael, Anderson Brian, Coffey VictoriaAbstract:The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated Interplanetary Shock Waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge Shock wave and a sheath carrying a large and highly variable Interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasmasheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasmasheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe
Sazykin Stan - One of the best experts on this subject based on the ideXlab platform.
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Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm
2017Co-Authors: Chandler, Michael O., Sazykin Stan, Minow Joseph, Coffey Victoria, Anderson, Brian J., Hairston MarcAbstract:The magnetic storm that commenced on June 22-23, 2015 was one of the largest storms in our current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated Interplanetary Shock Waves. On June 22 at 18:36 UT the magnetosphere was impacted by the Shock wave on the magnetosphere. Observations from several spacecraft observed the dynamic response of the magnetosphere and ionosphere. MMS observatories in the near earth tail These low altitude measurements are correlated in the magnetosphere with particle flux dropouts measured by MMS We follow the timing of this storm in the ionosphere with the density depletions throughout the ISS orbits, DMSP drift velocities, and enhanced AMPERE Birkland currents. Together these observations and simulation results will be assembled to provide each region's context to the global dynamics and time evolution of the storm. The models during these event support and flesh out the puzzle of the global dynamics
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Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm
2017Co-Authors: Hairston Marc, Sazykin Stan, Minow Joseph, Chandler Michael, Anderson Brian, Coffey VictoriaAbstract:The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated Interplanetary Shock Waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge Shock wave and a sheath carrying a large and highly variable Interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasmasheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasmasheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe
