What is Ion Bernstein Wave Heating?

[palol]

Hi Everyone! I am working in a plasma propulsion lab this summer, and am trying to get a better understanding of IBW heating. Very few papers on the academic databases actually describe what an IBW is, and how it heats, so I was hoping to open up a discussion about the topic.

Here's what I know so far: An IBW is a type of wave generated in a plasma by injecting a high frequency EM wave. The injected wave becomes the IBW as the ions and electrons in the plasma influence its propagation. The ions in the plasma hit some sort of resonance (not necessarily equal to the ion cyclotron frequency) and are heated. This process relies on something called the finite Larmor radius effect.

Here are some of my questions:
- Is my explanation on the right track? What do I need to know to improve my understanding of this phenomenon?
- How does this compare to ion cyclotron heating?
- How do you calculate this Larmor radius (or am I misunderstanding it?)
- It seems like you need to hit a specific frequency/wavelength ratio to get net heating, but how is that ratio maintained with the increasing gyration radius?

I'm excited to hear from the more knowledgeable members of the forum. Thanks for taking the time to participate in this discussion!

 

[AndyW]

Hi there, great to hear that you are working in a plasma propulsion lab this summer! IBW heating is definitely an interesting topic and I'm happy to help clarify some of your questions.

Your explanation of IBW heating is on the right track. IBWs, or ion Bernstein waves, are a type of electromagnetic wave generated in a plasma by injecting a high frequency wave. These waves are generated through a process called mode conversion, where the injected wave converts to an IBW as it interacts with the plasma. The ions in the plasma then absorb the energy from the IBW, leading to heating.

In comparison to ion cyclotron heating, IBW heating is more efficient in heating ions with lower energies. Ion cyclotron heating, on the other hand, is more efficient in heating ions with higher energies. Additionally, IBW heating can be used in plasmas with lower magnetic fields, whereas ion cyclotron heating requires a strong magnetic field.

The Larmor radius is the average radius of the circular motion of a charged particle in a magnetic field. It can be calculated using the equation r = mv/qB, where m is the mass of the particle, v is its velocity, q is its charge, and B is the magnetic field strength. This radius is important in IBW heating because it affects the resonance condition for the ions to absorb the energy from the IBW. As the Larmor radius increases, the resonance condition changes and the heating efficiency decreases.

Maintaining the correct frequency/wavelength ratio is crucial for efficient IBW heating. This is achieved through precise control of the injected wave frequency and the plasma density. The ratio must be maintained within a certain range for the wave to efficiently interact with the plasma and generate IBWs.

I hope this helps improve your understanding of IBW heating. Keep researching and asking questions, and good luck with your work in the plasma propulsion lab!