Statistical mechanics of dust charging in a multi-ion plasma with negative and positive ionic species

Mishra, S. K.; Misra, Shikha

doi:10.1063/1.4907664

Cited by 4 publications

(6 citation statements)

References 45 publications

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“…can be regarded as a "multistep process", a generalized notion of the one-step process [1], where jumps can also occur between non-adjacent sites. The change of the grain charge by multiple units as a result of collecting multiply charged ions [21] is an example of a jump between non-adjacent sites [6,7,9]. The other example is when multiple secondary electrons are emitted when a primary electron impacts the grain [6,9].…”

Section: First Passage Time In Multistep Processesmentioning

confidence: 99%

“…The ME of the dust charging system admits different forms where the functionality of the transition probability rates in terms of the charge state depends on the mechanisms that are responsible for charging. These forms are previously constructed when the charging mechanisms are the collisional collection of electrons and singly charged positive ions [2][3][4][5], the collisional collection of electrons and multiply charged ions [6,7], and the collisional collection of ions and electrons combined with the secondary emission of electrons (SEE) from the grain [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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First passage time in multistep stochastic processes with applications to dust charging

Shotorban

2020

Phys. Rev. E

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An approach was developed to describe the first passage time (FPT) in multistep stochastic processes with discrete states governed by a master equation (ME). The approach is an extension of the totally absorbing boundary approach given for calculation of FPT in one-step processes (Van Kampen 2007) to include multistep processes where jumps are not restricted to adjacent sites. In addition, a Fokker-Planck equation (FPE) was derived from the multistep ME, assuming the continuity of the state variable. The developed approach and an FPE based approach (Gardiner 2004) were used to find the mean first passage time (MFPT) of the transition between the negative and positive stable macrostates of dust grain charge when the charging process was bistable. The dust was in a plasma and charged by collecting ions and electrons, and emitting secondary electrons.The MFPTs for the transitioning of grain charge from one macrostate to the other were calculated by the two approaches for a range of grain sizes. Both approaches produced very similar results for the same grain except for when it was very small. The difference between MFPTs of two approaches for very small grains was attributed to the failure of the charge continuity assumption in the FPE description. For a given grain, the MFPT for a transition from the negative macrostate to the positive one was substantially larger than that for a transition in a reverse order. The normalized MFPT for a transition from the positive to the negative macrostate showed little sensitivity to the grain radius. For a reverse transition, with the increase of the grain radius, it dropped first and then increased. The probability density function of FPT was substantially wider for a transition from the positive to the negative macrostate, as compared to a reverse transition. *

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Section: First Passage Time In Multistep Processesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First passage time in multistep stochastic processes with applications to dust charging

Shotorban

2020

Phys. Rev. E

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“…Dust grains with radius can be major charge carriers in the interstellar medium in general, and in protoplanetary disks in particular. Dust grain charging is studied in the field of plasma physics (Mishra & Misra 2015).…”

Section: Dust Grain Chargingmentioning

confidence: 99%

Radiation thermo-chemical models of protoplanetary disks

Thi

Lesur

Woitke

et al. 2019

A&A

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Context. Disks around pre-main-sequence stars evolve over time by turbulent viscous spreading. The main contender to explain the strength of the turbulence is the magnetorotational instability model, whose efficiency depends on the disk ionization fraction. Aims. Our aim is to compute self-consistently the chemistry including polycyclic aromatic hydrocarbon (PAH) charge chemistry, the grain charging, and an estimate of an effective value of the turbulence α parameter in order to find observational signatures of disk turbulence. Methods. We introduced PAH and grain charging physics and their interplay with other gas-phase reactions in the physico-chemical code PRODIMO. Non-ideal magnetohydrodynamics effects such as ohmic and ambipolar diffusion are parametrized to derive an effective value for the turbulent parameter αeff. We explored the effects of turbulence heating and line broadening on CO isotopologue submillimeter lines. Results. The spatial distribution of αeff depends on various unconstrained disk parameters such as the magnetic parameter βmag or the cosmic ray density distribution inside the protoplanetary disk s. The inner disk midplane shows the presence of the so-called dead zone where the turbulence is almost inexistent. The disk is heated mostly by thermal accommodation on dust grains in the dead zone, by viscous heating outside the dead zone up to a few hundred astronomical units, and by chemical heating in the outer disk. The CO rotational lines probe the warm molecular disk layers where the turbulence is at its maximum. However, the effect of turbulence on the CO line profiles is minimal and difficult to distinguish from the thermal broadening. Conclusions. Viscous heating of the gas in the disk midplane outside the dead zone is efficient. The determination of α from CO rotational line observations alone is challenging.

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“…Description of intrinsic charge fluctuations of grains was the subject of a number of studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Cui and Goree [2] studied the fluctuations through a Monte Carlo approach and concluded that they are most important for small grains.…”

Section: Introductionmentioning

confidence: 99%

“…They concluded that Z rms ∝ | Z | is valid for these situations as well. Lately, Mishra and Misra [15] studied the fluctuations in multi-component plasma through a population balance equation resembling the master equation. They also included the influence of photoemission from dust through irradiation by laser light in their study.…”

Section: Introductionmentioning

confidence: 99%

Bistable intrinsic charge fluctuations of a dust grain subject to secondary electron emission in a plasma

Shotorban¹

2015

Phys. Rev. E

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A master equation was formulated to study intrinsic charge fluctuations of a grain in a plasma as ions and primary electrons are attached to the grain through collisional collection, and secondary electrons are emitted from the grain. Two different plasmas with Maxwellian and non-Maxwellian distributions were considered. The fluctuations could be bistable in either plasma when the secondary electron emission is present, as two stable macrostates, associated with two stable roots of the charge net current, may exist. Metastablity of fluctuations, manifested by the passage of the grain charge between two macrostates, was shown to be possible. *

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Statistical mechanics of dust charging in a multi-ion plasma with negative and positive ionic species

Cited by 4 publications

References 45 publications

First passage time in multistep stochastic processes with applications to dust charging

First passage time in multistep stochastic processes with applications to dust charging

Radiation thermo-chemical models of protoplanetary disks

Bistable intrinsic charge fluctuations of a dust grain subject to secondary electron emission in a plasma

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