Ambipolar Diffusion

Zweibel, Ellen G.

doi:10.1007/978-3-662-44625-6_11

Cited by 12 publications

(7 citation statements)

References 82 publications

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“…Roughly speaking it works provided that the plasma's inertia is negligible compared to that of the neutral fluid, the coupling between charged and neutral species is strong, and the recombination time is short. Zweibel [451] gives an accessible account of the conditions necessary for a valid single-fluid description. Although some of the early analytic and numerical work on the MRI in weakly-ionized disks utilized a two-fluid approach [68,174], in many protoplanetary disk situations a single fluid model is both justified [31] and substantially simpler.…”

Section: Non-ideal Mhdmentioning

confidence: 99%

Physical Processes in Protoplanetary Disks

Armitage

2019

Saas-Fee Advanced Course

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This review, based on lectures given at the 45th Saas-Fee Advanced Course "From Protoplanetary Disks to Planet Formation", introduces physical processes in protoplanetary disks relevant to accretion and the initial stages of planet formation. After a brief overview of the observational context, I introduce the elementary theory of disk structure and evolution, review the gas-phase physics of angular momentum transport through turbulence and disk winds, and discuss possible origins for the episodic accretion observed in Young Stellar Objects. Turning to solids, I review the evolution of single particles under aerodynamic forces, and describe the conditions necessary for the development of collective gas-particle instabilities. Observations show that disks can exhibit pronounced large-scale structure, and I discuss the types of structures that may form from gas and particle interactions at ice lines, vortices and zonal flows, prior to the formation of large planetary bodies. I conclude with disk dispersal.

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Section: Non-ideal Mhdmentioning

confidence: 99%

Physical Processes in Protoplanetary Disks

Armitage

2019

Saas-Fee Advanced Course

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“…Ion-neutral interactions can lead to increased resistivity and an increase in the effective ion mass, with consequent reduction in the Alfvén speed, steepening of current sheets, heating of the inflow and exhaust regions of reconnection sites, and enhancement of the plasmoid instability (e.g. Zweibel, 1989;Chiueh, 1998;Zweibel et al, 2011;Leake et al, 2012;Mei et al, 2012;Murphy et al, 2012;Zweibel, 2015;Ni et al, 2020). These in turn have important implications for solar phenomena, likely being responsible for increased damping of MHD waves (De Pontieu, Martens, and Hudson, 2001), increased current dissipation and heating of the solar chromosphere (Khomenko and Collados, 2012;Martínez-Sykora, De Pontieu, and Hansteen, 2012), increased flux emergence rates into the corona, reduced Alfvén wave flux from photospheric foot-point motion, and changes in the structure of MHD shocks, prominences, and quiet-Sun magnetic features (see Anan, Ichimoto, and Hillier, 2017, and the references therein).…”

Section: What Is the Three-dimensional Geometry Of The Magnetic Field Near Reconnection Sites? What Roles Do Ion-neutral Collisions Currementioning

confidence: 99%

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

Rast¹,

González²,

Rubio³

et al. 2021

Sol Phys

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The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute.

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“…In partially ionized media such as interstellar medium, MCs and protoplanetary discs, MHD equations must be modified to account for non-ideal MHD effects namely ohmic dissipation, Hall effect and ambipolar diffusion, according to the degree of ionization and the strength of magnetic field. In the literature, two approaches are usually exploited for formulation of non-ideal MHD (see Zweibel 2015, for a review). In the first approach the tensor conductivity is used to replace the current density in the induction equation.…”

Section: Mhd Equations With Admentioning

confidence: 99%

Gravitational instability of filamentary molecular clouds, including ambipolar diffusion; non-isothermal filament

Hosseinirad

Abbassi

Roshan

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Recent observations of the filamentary molecular clouds show that their properties deviate from the isothermal equation of state. Theoretical investigations proposed that the logatropic and the polytropic equations of state with negative indexes can provide a better description for these filamentary structures. Here, we aim to compare the effects of these softer non-isothermal equation of states with their isothermal counterpart on the global gravitational instability of a filamentary molecular cloud. By incorporating the ambipolar diffusion, we use the non-ideal magnetohydrodynamics framework for a filament that is threaded by a uniform axial magnetic field. We perturb the fluid and obtain the dispersion relation both for the logatropic and polytropic equations of state by taking the effects of magnetic field and ambipolar diffusion into account. Our results suggest that, in absence of the magnetic field, a softer equation of state makes the system more prone to gravitational instability. We also observed that a moderate magnetic field is able to enhance the stability of the filament in a way that is sensitive to the equation of state in general. However, when the magnetic field is strong, this effect is suppressed and all the equations of state have almost the same stability properties. Moreover, we find that for all the considered equations of state, the ambipolar diffusion has destabilizing effects on the filament.

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Ambipolar Diffusion

Cited by 12 publications

References 82 publications

Physical Processes in Protoplanetary Disks

Physical Processes in Protoplanetary Disks

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

Gravitational instability of filamentary molecular clouds, including ambipolar diffusion; non-isothermal filament

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