Understanding Mie Scattering: Exploring Angle Dependent Formulae and Functions

[khdani]

Hello,

I do a research concerning Mie scattering. The Mie formulae are angle dependent, but I need a function from which I'll get the scatterd angle (as a function of some dependent parameter), can someone please direct me in the right way ?

 

[mormonator_rm]

Hello,

I do a research concerning Mie scattering. The Mie formulae are angle dependent, but I need a function from which I'll get the scatterd angle (as a function of some dependent parameter), can someone please direct me in the right way ?

What is Mie Scattering? I don't remember ever hearing the name "Mie" anywhere before. Please explain.

 

[malawi_glenn]

That is the processes that make reddening when light passes trhough the interstellar media. It is scattering of molecules. Should be posted in atomic physics forum.

 

[mormonator_rm]

That is the processes that make reddening when light passes trhough the interstellar media. It is scattering of molecules. Should be posted in atomic physics forum.

Ok, I think I understand. It is the scattering process of particles and light traveling through the cosmic microwave background? Is this the process that restricts all "conventional" cosmic rays to < 6x10^19 eV?

 

[malawi_glenn]

no, Mie is just scattering of light of light molecules such as NH4 etc. Gas in the interstellar media that makes stars lying behind them a little bit redder.

The effect you are talking about is called GZK cutoff, that high energy particles interact with cosmic background radiation and makes it very unlikley for very high energy cosmic rays to survive long distances (many thousands of light years).

 

[khdani]

Mie scattering is a complete analytical solution of Maxwell's equations for the scattering of electromagnetic radiation by spherical particles. Mie scattering is important for understanding phenomenae as haze, cloud scattering, apperance of milk, oil concentration in polluted water, and more...

 

[mormonator_rm]

no, Mie is just scattering of light of light molecules such as NH4 etc. Gas in the interstellar media that makes stars lying behind them a little bit redder.

The effect you are talking about is called GZK cutoff, that high energy particles interact with cosmic background radiation and makes it very unlikley for very high energy cosmic rays to survive long distances (many thousands of light years).

Okay, now I see. I should have known better than to confuse the GZK cut-off with Mie Scattering... especially seeings I just started working with a UHECR project last month. I got a little confused there.

So, it sounds to me like Mie Scattering would be particularly important when you have young stars that may still be bounded by nebulae. Or maybe also when you are looking at a star through a gas shroud?

 

[malawi_glenn]

Okay, now I see. I should have known better than to confuse the GZK cut-off with Mie Scattering... especially seeings I just started working with a UHECR project last month. I got a little confused there.

So, it sounds to me like Mie Scattering would be particularly important when you have young stars that may still be bounded by nebulae. Or maybe also when you are looking at a star through a gas shroud?

Yes Mie scattering is important in Stellar astrophysics, and also galatic cosmology. Because you want the right spectra. But this should not be mixed by doppler reddening. Doppler SHIFTS all the wavelenghts to larger, Interstellar redding just decreases the intensity of the blue part of spectra.

 

[JeffKoch]

There are entire books devoted to Mie scattering, it's a mathematical heaven or hell depending on your aptitude - as I recall, it's quite complicated to solve exactly. There are some references in http://en.wikipedia.org/wiki/Mie_scattering.

 

[mormonator_rm]

Yes Mie scattering is important in Stellar astrophysics, and also galatic cosmology. Because you want the right spectra.

Certainly. This effect would need to be compensated for in the visual spectrum images.

But this should not be mixed by doppler reddening. Doppler SHIFTS all the wavelenghts to larger, Interstellar redding just decreases the intensity of the blue part of spectra.

So, the Mie Scattering has a more pronounced affect in deflecting light of higher frequency? Or is the reduction in the blue light the result of absorption?

 

[malawi_glenn]

Certainly. This effect would need to be compensated for in the visual spectrum images.



So, the Mie Scattering has a more pronounced affect in deflecting light of higher frequency? Or is the reduction in the blue light the result of absorption?

It is called Mie Scattering, so the process is that bluish ligt scatters more when continuous light enters a gas cloud. The blue light then leaves the clouds at almost any directions, but the red light don't scatters as much, so it basically just passes through.

http://images.google.se/imgres?imgu...terstellar+reddening&svnum=10&um=1&hl=sv&sa=N

And Mie scattering is one of the processes responsible for this. Same as Ratleigh scattering makes sky on Earth blue.

 

[JeffKoch]

There is some confusion here.

Mie scattering is the formal solution to scattering by spherical particles.

Rayleigh scattering refers to the limit where the size of the particles is much smaller than the light wavelength. Rayleigh scattering is strongly wavelength-dependent, and explains the blue sky (scattered sunlight) as well as the red sunset (what's left after the blue light scatters).

Mie scattering can also refer to the opposite limit, scattering by particles comparable to or larger than the light wavelength. This scattering is not strongly wavelength-dependent, and is the scattering process responsible (for example) for the milky whiteness of clouds and fog.

 

[mormonator_rm]

There is some confusion here.

Mie scattering is the formal solution to scattering by spherical particles.

Rayleigh scattering refers to the limit where the size of the particles is much smaller than the light wavelength. Rayleigh scattering is strongly wavelength-dependent, and explains the blue sky (scattered sunlight) as well as the red sunset (what's left after the blue light scatters).

Mie scattering can also refer to the opposite limit, scattering by particles comparable to or larger than the light wavelength. This scattering is not strongly wavelength-dependent, and is the scattering process responsible (for example) for the milky whiteness of clouds and fog.

Ah... very good, thank you. This is all making much better sense now.