Magnetoacoustic and Alfvénic black holes

Gheibi, A.; Safari, Hossein; Innes, D. E.

doi:10.1140/epjc/s10052-018-6109-1

Cited by 2 publications

(4 citation statements)

References 44 publications

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“…An Alfvénic black hole may be created using a magnetic flux tube with a variable cross section and super-Alfvénic flow. Using the linearized MHD equations in the presence of super-Alfvénic plasma flow, a tensorial form of the Alfvén waves (with an accompanying metric) was obtained (Gheibi et al 2018). The resultant metric is singular at a point (horizon of black hole) where the local Alfvén speed is equal to flow speed.…”

Section: Numerical Resultsmentioning

confidence: 99%

Kappa-Maxwellian Electrons and Bi-Maxwellian Protons in a Two-fluid Model for Fast Solar Wind

Taran

Safari

Daei

2019

ApJ

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Modeling fast solar wind based on the kinetic theory is an important task for scientists. In this paper, we present a two-fluid model for fast solar wind with anisotropic Kappa-Maxwellian electrons and Bi-Maxwellian protons. In the simulation, the energy exchange between the plasma particles and low-frequency Alfvén waves is considered. A set of eleven coupled equations is derived by applying the zeroth-to fourth-order moments of the Vlasov equation and the modified electromagnetic Maxwell equations. A characteristic of the Kappa distribution (indicated by κ index) is explicit in the equation for the parallel component of the electron heat flux (parallel to the ambient magnetic field line) and differs from the equation derived for the proton heat flux due to the different nature of the distributions. Within the large κ index, the equations for the two-fluid model tend to the equations obtained by the Maxwellian distribution.Using an iterated Crank-Nicolson method, the coupled equations are numerically solved for the fast solar wind conditions. We show that at (0.3 -1) AU from the Sun, the electron density, components of temperature, and components of heat flux follow the power-law behavior. We also showed that near the Earth, the flow speed (electron or proton) increases with decreasing κ. We concluded that applying the small κ index (the non-MaxwellianCorresponding author: Hossein Safari safari@znu.ac.ir Taran, Safari, Daei distribution), the extraordinary nature of the solar atmosphere, with its temperature of several million kelvin temperature for electrons, has been captured.

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Section: Numerical Resultsmentioning

confidence: 99%

Kappa-Maxwellian Electrons and Bi-Maxwellian Protons in a Two-fluid Model for Fast Solar Wind

Taran

Safari

Daei

2019

ApJ

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“…In particular, we introduce a pair of canonical variables that specify the phase space of the underlying classical system and use the Dirac's canonical quantization prescription to write down the Alfvén wave velocity filed (or the corresponding plasma displacement vector) in terms of the creation and annihilation operators. This defines the concept of "Alphonons", the elementary excitations of the Alfvén wave velocity in a magnetized plasma that was first introduced in Gheibi et al (2018).…”

Section: Discussionmentioning

confidence: 99%

“…An immediate application of the concept of Alphonon was made by Gheibi et al (2018), who showed that in the horizon of an Alfvénic black hole, Alfvén waves will be trapped and emit Hawking radiation that comprises the Alphonons. Detecting the Hawking radiation from the gravitational black holes is an important task for scientists.…”

Section: Discussionmentioning

confidence: 99%

“…In a similar analysis, Gheibi, Safari, and Innes introduced the Alfvénic black hole based on the magnetohydrodynamics approach (Gheibi et al 2018). They showed that similar to sonic black holes, which trap phonons and emit Hawking radiation at the sonic horizon where the flow speed changes from super-to sub-sonic, in the horizon of Alfvénic black holes, the Alfvén waves will be trapped and emit Hawking radiation made of quantized vibrations similar to phonons, for which they coined the name "Alphonons".…”

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confidence: 99%

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Alphonons as the quanta of the Alfvén waves

Mohammadi,

Safari,

Zamani

2020

Preprint

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In a magnetized plasma, both the transverse and longitudinal Alfvén waves carry an average energy density that, for each mode of oscillation, resembles the classical energy of a harmonic oscillator with unit mass and angular frequency that depends on the background magnetic field and plasma density. We employ this fact to introduce a pair of canonical variables for the underlying classical system, and then use the canonical quantization procedure to express the Alfvén wave velocity (or the corresponding plasma displacement vector) in terms of creation and annihilation operators. We thus introduce the concept of "Alphonons" as the quanta for the Alfvén wave packets and study their characteristic features. The corresponding quanta (Alphonons) carry spin one for the transverse Alfvén wave and spin zero for the longitudinal Alfvén wave. We obtained behavior of thermodynamic quantities for an Alphonon system (e.g., free energy, entropy, specific heat). We showed that for the Alphonon system the spectral energy density obeys the Planck's black body radiation law.

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Magnetoacoustic and Alfvénic black holes

Cited by 2 publications

References 44 publications

Kappa-Maxwellian Electrons and Bi-Maxwellian Protons in a Two-fluid Model for Fast Solar Wind

Kappa-Maxwellian Electrons and Bi-Maxwellian Protons in a Two-fluid Model for Fast Solar Wind

Alphonons as the quanta of the Alfvén waves

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