Questions tagged [plasma-physics]
Theory, lab and space experiments, and calculations related the physics of plasmas, i.e., matter constituted by ionized atoms.
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Why is the electric field time independent in the induction equation of the magnetohydrodynamics?
Why does the induction equation of the magnetohydrodynamics assume the electric field $E$ is time $t$ independent or $\frac{\partial E}{\partial t}=0$?
Note: I am querying about the general case ...
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In a tokamak, is there a density-dependent limit on plasma current?
In a tokamak, the kink limit places an upper bound on the magnitude of the plasma current. For example, Parisi and Ball (2019) write this limit as (p. 246)
$$I\lesssim\frac{1}{q}\frac{2\pi}{\mu_0}\...
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How to deduce the 2d Fermi integral with drift velocity?
I read the article https://arxiv.org/abs/2106.01296, and i see in the eq. (3) an expression for the local electron density using a 2D Dirac distribution with drift velocity,
$$f_{\alpha 0} (r,p,t) = \...
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What is the typical range of the percentage of energy conversion in magnetic reconnection?
I want to determine a suitable range for the efficiency energy conversion of magnetic energy to thermal energy in usual magnetic reconnection because usually it is said that this process is highly ...
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MHD plasma regime clarification
Could you give an intuition about why does MHD requires the following condition in time and spatial scales, please? Thanks.
At scales much larger than the mean free path and gyroradius, and time ...
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What is this anode discolouration in plasma tube?
I made a argon plasma tube with 954 bronze aluminum bronze electrodes. After running for some time the anode (left) face is a silver colour. The cathode is on the right.
Does anyone know what this is? ...
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Statistical mechanics of a mixture that can form clusters
I am not sure how to look for references for the following problem. Imagine having a collection of 2 kinds of particles of density $n_1$ and $n_2$ that can arrange themselves in "clusters" (...
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Magnetic reconnection in MHD theory [closed]
What does the MHD theory predict when two regions with magnetic field of opposed polarization interact? When we take in account the resistivity then we can observe a rearrangement of the topology due ...
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Explanation of why Kinetic Energy Increases when Particle Reaches the End of the Magnetic Bottle?
I don't understand how to explain why kinetic energy increases using Faraday's Law as a charged particle reaches the end of a magnetic bottle.
I know that along the field line in the bottle, the ...
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Why is there plasma near the inlet when Voltage is increased to higher Voltage? What can I do to eliminate this?
We built this plasma jet reactor with a side inlet of helium at 2 slm. My question is why is there plasma generated near the inlet where in it should only be at the bottom part. You can check the ...
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Why is aurora borealis circular in shape when viewed from space?
These are some false color images of the northern lights captured by NASA's satellite Dynamics Explorer-1.
Image credits: Dynamics Explorer - 1 (DE-1)
Spin-Scan Auroral Imaging (SAI)
Photo Gallery
It'...
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Cold plasma approximation leads to infinite coupling
In plasma physics, there is an approximation called cold plasma approximation according to which, the temperature of a plasma species in an electron-ion plasma, say ions ( $T_i$ ) is assumed to be ...
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Unexpected generation of plasma far from HV rod electrode. Why is plasma being generated near the encircled part wherein there shouldn't be?
we have built a kHz jet plasma reactor and we are generating plasma at the inlet side every time we increase input voltage to more than 3 kV. Working gas used was argon at 1 slm entering at the side. ...
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Solving $2\frac{\partial S}{\partial z}+\left(\frac{\partial S}{\partial r}\right)^2=0$ [migrated]
I have been trying to solve this PDE $$2\frac{\partial S}{\partial z}+\left(\frac{\partial S}{\partial r}\right)^2=0$$ The solution of this equation corresponding to a spherical wave of radius of ...
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Phase space density behavior in finite volume
I am trying to develop better intuition for the single-particle phase space density $f(x,v,t)$ and I am confused by the tendency of $f(x,v,t)$ to become wiggly in velocity space. Consider the simplest ...
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Plasma composition [closed]
Good day all,
I am looking for a way to estimate the composition of a thermal plasma formed by flowing gas between two charged electrodes.
I understand that when plasma is formed this way, it would be ...
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How can I calculate plasma temperature from particle density per energy histogram?
I want to know the temperature of electron plasma whose data has been generated via particle in cell simulation. My professor said if I have histogram of electron density by kinetic energy, then I can ...
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Why can't you measure the ion temperature with a Langmuir probe?
From the I-V curve of a Langmuir probe, the curvature in the ion saturation region (negative voltage) is due to the electron temperature (assuming maxwellian distribution). Similarly in Merlino's ...
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Why Euler equation in Ideal MHD is not identically zero?
In Ideal MHD, we assume the plasma to be force-free:
$$\vec{E} = - \frac{1}{c}\left(\vec{v}\times \vec{B}\right)$$
But the Euler equation of motion is written as:
$$\rho \frac{d\vec{u}}{dt} = \vec{j}\...
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Curvature Drift In Plasma Derivation - But Centrifugal Force does not exist in inertial reference frame?
In the textbook 'Introduction to Plasma Physics and Controlled Fusion' (F. Chen) the Curvature Drift of a particle in a magnetic field with constant radius of curvature is derived like this:
A ...
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Group velocity vector in spherical coordinates
I am trying to understand a derivation from the textbook Radiation Processes in Plasmas by G. Bekefi (p. 14).
Start with the group velocity vector
$$\mathbf{w}=\frac{\partial \omega}{\partial \mathbf{...
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Derive the drift velocity from drifting Maxwellian distribution
Having a drifting Maxwellian (Maxwell-Boltzmann) distribution:
$$f(\vec v) = n \left(\dfrac{m}{2\pi k_B T}\right)^\frac{3}{2}\exp\left({-\dfrac{m[(v_x-a)^2+v_y^2 + v_z^2]}{2k_BT}}\right)
$$
where $a$ ...
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Is nonlinearity a denser encoding of information?
At the microscopic level, an $n$-particle system in 3D can be described by the Liouville equation, which governs the evolution of the distribution function in a $6n$-dimensional phase space.
Going ...
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Plasma Linear Tearing Mode Theory Fitzpatrick
I've been looking through Richard Fitzpatrick's book on plasma physics on the section on linear tearing mode theory (shown below) and there are a few equations I haven't been able to replicate, except ...
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The Debye length and the Vlasov-Poisson-Fokker-Planck system
I'm a math student and I studies PDEs which come from plasma physics, and especially the Vlasov-Poisson-Fokker-Planck system. The system can be found in this article, page 2:
https://arxiv.org/abs/...
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Larmor radius in magnetic bottle/increasing magnetic field
I am confused about how Larmor radius changes in an increasing magnetic field.
The Larmor radius means the radius of a charged particle’s circular motion in a magnetic field, its formula is
$r_{L} = {{...
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Deriving the number density of electrons distributed by bi-kappa distribution in plasmas [closed]
Can anyone explain the derivation of the number density of electrons distributed by the following bi-kappa distribution function commonly observed in space plasmas:
\begin{equation}
f_e(V_\perp,V_\...
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Why is there no electron-positron plasma around proton?
When electric field approaches Schwinger limit:
$$
E_{cr}=\frac{m_e^2c^3}{e\hbar}\approx 1.32\times10^{18}~\text{V/m},
$$
in the presence of such field electron-positron pairs will be spontaneously ...
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Determing for particle density of many particle species in plasma
For quasi-neutrality plasma of many species, the relation of electron density and ion density said that
\begin{equation}
n_{\text{e}} = \sum_{s}Z_{\text{i},s}n_{\text{i},s},
\end{equation}
where $n_{\...
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What are some practical problems with static electrical confinement of plasma?
Plasma and fusion physics experts, help me with this one: Suppose we have a D-T plasma with net positive electrical charge inside a positively charged metal sphere. As the containment sphere's net ...
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How to get Absorption cross section of Gaseous Ions for photons?
How or where can I find the Absorption cross-section of Gaseous Ions? I have looked over the internet and can only find it for neutral atoms. Does it increase or decrease for ions?
I have found ...
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Is it true that particle-in-cell (PIC) simulation apply both Lagranian/Eulerian method in?
I'm learning about particle-in-cell (PIC simulation) of plasma and I'm having some questions on the description of PIC method. I still have somes questions how PIC simulation works with Eulerian and ...
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Plasma globe - circular fringes
why there are dark bright fringes (multiple of them very similar to newton rings) around each arc path where arc is connected to the inner electrode?
I know why electrons form these paths but I can't ...
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What is the difference between Lagrangian and Eulerian description in Plasma?
I'm going to study plasma characteristics by using Particle-In-Cell (PIC) method and I know that plasma has fluid behaviour and can also consider as particle behaviour also. To understand a basic of ...
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Does any of the atoms actually "survive" in plasma?
Or does this state of matter detach electrons from all the atoms?
Thank you.
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What's wrong with solar wind?
As you know, the sun emits into the surrounding space the so-called "solar wind", consisting of plasma. In turn, plasma is a mixture of charged particles.
According to the laws of physics, ...
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How to determine Plasma Cleaning process completeness?
I'm trying to optimize plasma cleaning process to be signal driven instead of fixed time.
I have a vacuum chamber with hydrocarbon contaminants, I use air plasma for cleaning. Is there an option to ...
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Why it is not possible to reach the sun if we are able to create plasma? [closed]
if we are able to create plasma in isolated environment possessing temperature much more than temperature of sun then why are we not able to create something that can go to the sun?
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Difficulty in choosing which RF 13.56 Mhz Plasma Jet configuration to use
Can anybody explain why we can't use Molecular gases as our operating gas when we choose figure 1? Is it possible to use figure 1 using molecular gases such as O2 and Air or should we stick to the ...
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The phase and group velocity in plasma when calculating optical path difference
I know that in plasma, phase velocity $v_{p}$ is faster than light and group velocity $v_{g}$ is slower than light, for the refractive index of plasma $n<1$. When calculating optical path ...
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Conservation laws for particle in an axisymmetric electromagnetic field
I have a massive particle moving with position $X = X(t)\in \mathbb{R}^3$ and "velocity" $V = V(t)\in \mathbb{R}^3$, which satisfy the ODEs
$$\begin{align} \dot{X} &= \hat{V}\\ \dot{V} &...
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Kinetic equation material derivative
I am reading through Raizer's Gas Discharge Physics textbook, and I cannot figure out a bit of the math he used to get from one stage to the next. The subject is the how the distribution function ...
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What are the light emissions from an ion engine?
Consider an ion thruster like a DS4G (Dual-Stage 4 Grid) thruster. Gas is released, ionized, and accelerated. Assume it's in a vacuum, be it a chamber or space. Also assume the propellant is Xenon.
...
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Finding velocity field components from electric and magnetic field components in ideal MHD
How can I determine the components of the velocity field ($V_x, V_y, V_z$) using the components of the electric field $(E_x, E_y, E_z)$ and magnetic field $(B_x, B_y, B_z)$, assuming the ideal ...
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What are the observable emissions from an ion engine? What percent of input power ends up as heat, UV, or other emissions?
I'm wondering what would be observable to an astronomer if one knew where to look for a distant space craft with a powerful ion engine such as a Dual-Stage 4-Grid (DS4G) electrostatic thruster. In the ...
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Is there an intuitive picture for quasi-isodynamic versus quasi-axisymmetric versus quasi-helically symmetric flow in stellarators?
I recently read a paper in which Alan Boozer says,
The W7-X stellarator was made quasi-isodynamic rather than
quasi-symmetric in order to minimize the parallel currents as well as
the ripple-trapped ...
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I'm struggling with a collisionless plasma textbook problem. Calculating the longitudinal dielectric function from the distribution
The problem is:
Given the distribution of the electrons
$$
f_0(\mathbf{p}) = \frac{1}{\pi^2}\frac{mun_e}{(p^2 + m^2u^2)^2}
$$
find longitudinal dielectric function and the dispersion equation for ...
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How can I concentrate ions in a very small area?
I am interested in concentrating ions in a very small area, so the ion density of that region is elevated above normal levels.
What is the field of study, or term, that describes what I am talking ...
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Dense plasma focus at ambient air pressure
About a year ago I read a paper stating that a Dense Plasma Focus (DPF) could operate at ambient air pressure. But I can't find the paper anymore and what I've found in online journals seems ...
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How to decompose Plasma ion Drag Force on a particle moving through it?
Almost all papers on plasma mentioned that plasma ions drag on a particle is in the direction is opposite to the velocity of the particle. But no one said anything about the other two components; are ...
