Created By : Abhinandan Kumar

Reviewed By : Phani Ponnapalli

Last Updated : May 17, 2023

The Alfvén velocity calculator can be used to determine the velocity of a magnetohydrodynamic wave, which is a form of the plasma wave. This type of wave can be found in the corona of the Sun or the ionosphere. All you need to do is enter the inputs in the calculator tool and then tap on the calculate button to get output.

Magnetic Field Strength (B)
Permeability Of Free Space (μ0)
Plasma Mass Density (ρ)

What is meant by a Wave of Magnetohydrodynamics (Plasma Wave)?

A plasma wave is a form of Alfvén wave. Plasma is an ionized gas, as you may know. This indicates that it is made up of charged particles. The magnetohydrodynamic wave known as the Alfvén wave is one of the few forms of waves that can propagate in plasma. 

The Alfvén waves are visible when plasma is placed in an external magnetic field. They are the result of a delicate balancing act between two variables. One is plasma particle inertia, while the other is the magnetic field's restoring force. Plasma consists of charged particles that are constantly moving. This means they are affected by the Lorentz force of the external magnetic field. The Lorentz force resists the particle's inertia and acts as a restorative force. For additional information on the Lorentz force, use the Lorentz force calculator.

Alfvén Velocity Formula

The Alfvén velocity formula is as follows: v = B / √ (μ0 * ρ),

  • Where, B [T] = magnetic field,
  • μ0 = magnetic permeability of free space (4 * π * 10^(-7) [T * m / A]) 
  • ρ = density of ions [kg/m³]
  • v = Alfvén velocity [m/s].

For example, The Earth's ionosphere is made up of plasma with a density of roughly ρ = 10Γü╗¹Γü╡ kg/m³. B = 10 μT is the magnetic field in the ionosphere. The Alfvén velocity as a result is v = 282.1 km/s.

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FAQs on Alfvén Velocity Calculator

1. What is the Alfvén critical surface?

The commencement of the sun's outer edge is marked by the Alfvén critical surface, below which the solar wind is directly regulated by the sun's gravitational and magnetic forces. According to various experts, this region is thought to be the source of magnetic field switchbacks in the sun.

2. What is the Radius of Alfvén?

The Alfvén radius is the distance at which the magnetic energy density equals the kinetic energy density, or when bulk velocity equals Alfvén velocity. The idea of Alfvén radius is significant for magnetized planets, both for interactions with the solar/stellar wind and for inter-magnetospheric processes.

3. What is the origin of Alfvén Waves?

Alfvén waves are created by shaking magnetic field lines, similar to how waves on a string are created by shaking the thread. The Earth's magnetic field is shaken by the solar wind in several ways, including solar plasma eruptions and the stretching out of the geomagnetic field by the passing solar wind.

4. What is the significance of Alfvén?

The poloidal velocity equals the Alfven speed in magnetized disc models. The magnetic energy density prevails within this spot, forcing the gas to move along the field lines.

5. What is the significance of Alfvén Waves?

The importance of these waves is greater for stars with larger magnetic fields. As with sound-wave-driven winds, the dissipation of momentum and energy connected with Alfvén waves can cause a wind to accelerate.