Ionospheric Radiation Absorption

[Wannabeagenius]

Hi All,

I've read the reason for longer radio waves being absorbed by the ionosphere more than shorter waves and the argument goes like this:

The longer waves cause the ions in the ionosphere to travel a longer distance during a typical RF cycle because the time subjected to the electric field on each half of the cycle is longer. This longer distance causes more ions to crash into each other and the crashing into each other is the reason for more energy being absorbed.

It seems to me that the crashing of particles into each other has nothing to do with the additional absorption of energy. The ions, being subjected to a longer time in the electric field, attain a higher velocity and it is this increase in kinetic energy that the particles attain on each cycle which is responsible for the increased absorption and not the crashing of the particles into each other.

As I see it, once a particle takes energy from a wave it doesn't matter what happens to the particle. The crashing only changes the direction of the particle and any energy the particle has is simply shared with its neighbors into which they are crashing.

Is my logic correct?

Thank you,

Bob

 

[eljose79]

Hello Bob,

Thank you for your question. Your logic is partially correct, but there are some additional factors that contribute to the absorption of longer radio waves by the ionosphere.

Firstly, you are correct that the increase in kinetic energy of the ions due to the longer time in the electric field is a major factor in the absorption of energy. However, the crashing of particles into each other also plays a significant role.

When ions collide with each other, they transfer some of their kinetic energy to one another. This leads to an increase in the overall temperature of the ionosphere, which in turn affects the absorption of radio waves. Higher temperatures lead to greater ionization and therefore a higher density of ions in the ionosphere, which results in increased absorption.

Additionally, the collisions between ions can also cause them to lose their energy through radiation, which contributes to the absorption of longer radio waves.

In summary, both the increase in kinetic energy and the collisions between ions contribute to the absorption of longer radio waves by the ionosphere. I hope this helps clarify the concept for you.

 

[astrokreng]

I understand your reasoning and it is partially correct. The longer radio waves do cause the ions in the ionosphere to travel a longer distance during a typical RF cycle, which can lead to collisions between particles. However, it is not just the collisions that cause the increased absorption of energy. As you mentioned, the longer time in the electric field also leads to an increase in kinetic energy for the ions. This increase in kinetic energy is what ultimately causes the absorption of energy from the radio waves.

Additionally, the collisions between particles can also lead to the creation of new ions and the breaking apart of existing ions, which can also contribute to the absorption of energy. So while the crashing of particles may not directly absorb energy, it can still play a role in the overall absorption process.

Overall, your logic is mostly correct. The increase in kinetic energy for the ions is the main reason for the increased absorption of longer radio waves in the ionosphere. However, it is important to consider the role of collisions in this process as well.