# Frequency higher then plasma frequency

• Thierry12
Dielectrics are non-metallic and do not have a fixed frequency, so they can oscillate with the electromagnetic wave.

#### Thierry12

Electromagnetic wave with higher frequency then plasma frequency are barely attenuated. I always hear that the reason is the electrons can't oscillate fast enought... how does that actually work? (how can an electron not be able to oscillate at the same speed?)

Because the behavior of a plasma is non-linear. Take a look at the "Convective Derivative." A normal force equation, assuming constant mass, is just $$m\frac{\partial \mathbf{v}}{\partial t}$$ but when we talk about plasma, there is an extra term that arises resulting in the force being $$m\left[\frac{\partial \mathbf{u}}{\partial t} + \left(\mathbf{u}\cdot \nabla \right)\mathbf{u} \right]$$. This non-linearity gives rise to the ponderamotive force and other effects that will affect the propagation. In addition, electrons have mass and thus will time-lag the electric feld due to their inertia. If the frequency is low enough, the lag is negligible but at very very high frequencies they cannot keep up with the oscillations. This is a common assumption with the ions but it can apply to the electrons too.

At the plasma frequency and above, dielectrics behave as ideal metals, with electron gas behavior.

I thought 'plasma frequency' referred to conductors not dielectrics.

Plasma frequency applies to many things. It is not necessarily tied to one type of material and is derived based upon plasma physics, an ionized gas. So anytime that you can achieve a plasma in a material, the plasma frequency can arise to describe various phenomenon. A lot of materials, when subjected to a very high frequency electromagnetic wave, will behave like a plasma. Conductors will do this, I believe silver's plasma frequency is in the terahertz, but it does not surprise me that it can occur in dielectrics too.

## What is frequency higher than plasma frequency?

Frequency higher than plasma frequency is a term used in plasma physics to describe electromagnetic waves with a frequency that is higher than the natural frequency of oscillations of the plasma particles. This frequency is typically in the range of radio or microwave frequencies.

## How is frequency higher than plasma frequency generated?

Frequency higher than plasma frequency is usually generated by an external source, such as a radio antenna, that excites the plasma particles and causes them to oscillate at a higher frequency than their natural frequency. This is known as the plasma resonance effect.

## What are the properties of frequency higher than plasma frequency?

Frequency higher than plasma frequency has several unique properties, including the ability to penetrate through plasma without being significantly absorbed or reflected. It also has a longer wavelength compared to the plasma wavelength and can be used to study the properties of plasma.

## Why is frequency higher than plasma frequency important in research?

Frequency higher than plasma frequency is important in research because it allows scientists to study the properties and behavior of plasma, which is a fundamental state of matter that makes up most of the visible universe. Understanding plasma is crucial in fields such as astrophysics, fusion energy, and materials science.

## What are some practical applications of frequency higher than plasma frequency?

Frequency higher than plasma frequency has several practical applications, including plasma heating and diagnostics in fusion research, plasma processing in industrial and medical applications, and radio communication through plasma, such as in satellite communication. It also has potential uses in advanced technologies, such as plasma-based propulsion systems for spacecraft.