Re: [Phys-l] surfing

[Carl Mungan <mungan@usna.edu>]

> I wouldn't have said that.  The motion of the wave is not the 
> motion of the medium!  To demonstrate this, set up a rope,
> clothesline style.  Tie a ribbon onto it somewhere.  Whack
> the rope to set up a transverse wave.  The wave moves along
> the rope, but the ribbon moves (mostly) perpendicular to the 
> rope.

Yup, you and Jeffrey are right, my bad.

> > Next question: How does plasma wakefield acceleration (which is also 
> > often described as "surfing") work? 

>  http://en.wikipedia.org/wiki/Plasma_acceleration
>
> If that isn't what you wanted to know, please ask a more specific
> question.

That page is a start, but still doesn't make it clear exactly what the forces are. The wiki page claims it is the electric field of the laser pulse that pushes the electrons forward. Isn't the electric field of an optical pulse transverse and not in the forward direction?

Also there is no clear discussion of what kinds of drag forces (if any) might be limiting the electron acceleration. How far can we push the surfer analogy - is there something akin to water drag/air resistance? (What speed do the electrons attain - are they really moving at the speed of the light pulse?) -Carl