What is the Alfvén speed?
The Alfvén speed ranges from 5–14 km s−1, mainly 6–11 km s−1. The plasma-β is established to be 0.3–1.6. The density inside the umbral photosphere ranges from (1–10) × 10−4 kg m−3, which gives the number density ~1016–1017 cm−3.
How do you calculate Alfvén speed?
The Alfvén velocity calculator helps you compute the velocity of a magnetohydrodynamic wave, a type of a plasma wave….Alfvén velocity calculator
- B [T] is the magnetic field,
- μ0 = 4 * π * 10^(-7) [T * m / A] is the magnetic permeability of free space,
- ρ [kg/m³] is the density of ions,
- v [m/s] is the Alfvén velocity.
What is Alfvén radius?
The Alfvén radius is a distance where the magnetic energy density is equal to the kinetic energy density, or bulk velocity equals the Alfvén velocity. For magnetized planets a concept of Alfvén radius is important as for the interaction with the solar/stellar wind, either for the inter-magnetospheric processes.
What is Alfven wave in plasma?
Definition. An Alfvén wave in a plasma is a low-frequency (compared to the ion cyclotron frequency) travelling oscillation of the ions and the magnetic field. The motion of the ions and the perturbation of the magnetic field are in the same direction and transverse to the direction of propagation.
What is kinetic Alfven waves?
The transverse shear Alfvén wave (SAW) is a fundamental anisotropic electromagnetic oscillation in plasmas with a finite background magnetic field. Any initial perturbation of SAW structures will, thus, evolve eventually into short-wavelength structures; termed as kinetic Alfvén wave (KAW).
What is plasma pressure?
Plasma pressure consists of many parameters; they are plasma density (ne,i), plasma temperature (Te,i), impurity (Zeff), and fast beam ions. Among these parameters, ion density (ni) and fast beam ions can not be measured directly in practice.
Are Alfvén waves transverse?
A variant is the “kinetic” Alfvén wave which is transverse, with strong magnetic field variation perpendicular to the wave motion, so can trade energy between the different frequencies which might propagate through a plasma.
What is MHD equation?
A self-consistent set of MHD equations connects the plasma mass density ρ, the plasma velocity V, the thermodynamic (also called gas or kinetic) pressure P and the magnetic field B. also called the Euler equation. The vector j is the electric current density which can be expressed through the magnetic field B.
Who discovered Alfven waves?
Hannes Alfvén
In 1942 (Alfvén 1942), Hannes Alfvén discovered that if a perfectly conducting medium (e.g., a fully ionized gas; i.e., a plasma) is immersed in a finite background magnetic field \varvec{B}_0; electromagnetic waves can then propagate within it.
What does the Debye length describe?
The Debye length is a characteristic distance over which ions and electrons can be separated in a plasma (Chen et al., 1984) and is equal to the ratio of the electron thermal velocity divided by the plasma frequency.
What is Thomas Fermi screening length?
It is a special case of the more general Lindhard theory; in particular, Thomas–Fermi screening is the limit of the Lindhard formula when the wavevector (the reciprocal of the length-scale of interest) is much smaller than the fermi wavevector, i.e. the long-distance limit. …
