Pickup ion-mediated plasma physics of the outer heliosphere and very local interstellar medium

Zank, G. P.

doi:10.1186/s40562-016-0055-2

Cited by 24 publications

(18 citation statements)

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“…Pitch-angle scattering introduces both a collisionless heat flux and a non-isotropic pressure tensor, or a collisionless viscosity tensor into the transport equations describing the energetic particles Zank 2016).…”

Section: The Multi-component Model and The Simplified Singlefluid-likmentioning

confidence: 99%

“…Although our focus is on the role that PUIs and SEPs play in determining the structure of heliospheric shocks, the model equations developed by Zank et al (2014Zank et al ( , 2016 and Zank (2016) are strikingly similar to the so-called galactic cosmic ray two-fluid model (Drury & Völk 1981;Axford et al 1982). A surprising result obtained from the galactic cosmic ray twofluid model was that the steady-state analysis shows that multivalued downstream solutions exist for a fixed upstream state.…”

Section: Introductionmentioning

confidence: 96%

“…As discussed originally by Earl et al (1988), Jokipii & Williams (1992), and Webb (1989) in their description of the cosmic ray transport equation, the inclusion of higher-order terms introduces a form of cosmic ray viscosity. For the case of PUIs, this was revisited recently by Zank et al (2014Zank et al ( , 2016 and Zank (2016), who developed a collisionless form of Chapman-Enskog expansion for a multi-component plasma comprising thermal electrons, protons, and energetic particles (such as PUIs, ACRs, or SEPs). Zank et al (2014Zank et al ( , 2016 showed that their model was structurally identical to the two-fluid model used by Drury & Völk (1981) and Axford et al (1982), but now including viscosity that is introduced by energetic particles.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we use the Zank et al (2014) model, extended in Zank et al (2016) and Zank (2016), to investigate the structure of shock waves in the presence of PUIs, SEPs, and ACRs by neglecting the magnetic field. In the case of the outer heliosphere and the IHS, the plasma beta is large  ( ) 1 by virtue of the pressure of PUIs and ACRs.…”

Section: Introductionmentioning

confidence: 99%

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Structure of Energetic Particle Mediated Shocks Revisited

Mostafavi

Zank

Webb

2017

ApJ

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The structure of collisionless shock waves is often modified by the presence of energetic particles that are not equilibrated with the thermal plasma (such as pickup ions [PUIs] and solar energetic particles [SEPs]). This is relevant to the inner and outer heliosphere and the Very Local Interstellar Medium (VLISM), where observations of shock waves (e.g., in the inner heliosphere) show that both the magnetic field and thermal gas pressure are less than the energetic particle component pressures. Voyager 2 observations revealed that the heliospheric termination shock (HTS) is very broad and mediated by energetic particles. PUIs and SEPs contribute both a collisionless heat flux and a higher-order viscosity. We show that the incorporation of both effects can completely determine the structure of collisionless shocks mediated by energetic ions. Since the reduced form of the PUI-mediated plasma model is structurally identical to the classical cosmic ray two-fluid model, we note that the presence of viscosity, at least formally, eliminates the need for a gas sub-shock in the classical two-fluid model, including in that regime where three are possible. By considering parameters upstream of the HTS, we show that the thermal gas remains relatively cold and the shock is mediated by PUIs. We determine the structure of the weak interstellar shock observed by Voyager 1. We consider the inclusion of the thermal heat flux and viscosity to address the most general form of an energetic particle-thermal plasma two-fluid model.

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Section: The Multi-component Model and The Simplified Singlefluid-likmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure of Energetic Particle Mediated Shocks Revisited

Mostafavi

Zank

Webb

2017

ApJ

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“…The Voyager Interstellar Mission (VIM) has recently crossed the outer boundary of the heliosphere or heliospheric termination shock (HTS) and entered the interstellar medium. Zank (2016) reports the observations of plasma and turbulence in the supersonic and subsonic solar wind in HTS and beyond made by VIM. These observations reveal that the plasma in the outer heliosphere and very local interstellar medium (VLISM) is composed of distinct thermal proton and electron and super-thermal pickup ions.…”

Section: Outer Heliospherementioning

confidence: 99%

Introduction to the special issue on history development of solar terrestrial sciences including auroral sub-storms

et al. 2016

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Solar terrestrial (ST) sciences started centuries ago and branched into different disciplines. Starting with naked eye to highly sophisticated novel experimental techniques, observations have revealed the secrets of the Sun, heliosphere, magnetosphere, plasmasphere, and ionosphere-atmosphere components of the ST system. Theories and theoretical models have been developed for the different components independently and together. World-wide efforts under different umbrella are being persuaded to understand the challenges of the ST system. The onset problem and role of O + ions in sub-storm physics are two issues that are hotly debated. The onset problem is whether sub-storm is triggered by magnetic reconnection in the tail region at 15-20 Re or by a current disruption at ~12 Re. The issue on O + role is whether O + ions affect the dynamics of sub-storms under magnetic storm and non-storm conditions differently. This special issue of Geoscience Letters contains a collection of 15 papers on the history and development of solar terrestrial sciences including auroral sub-storms. Over half of the papers are based on the presentations in a session on the same topic organized at the AOGS (Asia Oceania geosciences Society) General Assembly held in Singapore during 02-07 August 2015. The rest of the papers from outside the assembly also falls within the theme of the special issue. The papers are organized in the order of history and development of ST coupling, sub-storms, and outer heliosphere.

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Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields

et al. 2017

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Publication resulting from an International ISSI Team of the same name. Submitted to Space Science ReviewsInternational audienceThis paper summarizes the results obtained by the team "Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields" supported by the International Space Science Institute in Bern, Switzerland. We focus on the physical processes occurring in the outer heliosphere, especially at its boundary called the heliopause (HP), and in the LISM. The importance of magnetic field, charge exchange between atoms and ions, and solar cycle on the heliopause topology and observed heliocentric distances to different heliospheric discontinuities are discussed. It is shown that time-dependent boundary conditions are necessary to describe the heliospheric asymmetries detected by the Voyager spacecraft. We also discuss the structure of the HP, especially due to its instability and magnetic reconnection. It is demonstrated that the Rayleigh-Taylor instability of the nose of the HP creates consecutive layers of the interstellar and heliospheric plasma which are magnetically connected to different sources. This may be a possible explanation of abrupt changes in the galactic and anomalous cosmic ray fluxes observed by Voyager 1 when it was crossing the HP structure for a period of about one month in the summer of 2012. This paper also discusses the plausibility of fitting simulation results to a number of observational data sets obtained by in situ and remote measurements. The distribution of magnetic field in the vicinity of the HP is discussed in the context of Voyager measurements. We discuss the transport of energetic particles in the inner and outer heliosheath, concentrating on the anisotropic spatial diffusion diffusion tensor and the pitch-angle dependence of perpendicular diffusion and demonstrate that the latter can explain the observed pitch-angle anisotropies of both the anomalous and galactic cosmic rays in the outer heliosheath

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Pickup ion-mediated plasma physics of the outer heliosphere and very local interstellar medium

Cited by 24 publications

References 69 publications

Structure of Energetic Particle Mediated Shocks Revisited

Structure of Energetic Particle Mediated Shocks Revisited

Introduction to the special issue on history development of solar terrestrial sciences including auroral sub-storms

Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields

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