Re: comet tails and wind

[Lew Haddad <lhaddad@dawsoncollege.qc.ca>]

Ken: There are two kinds of comet tails, a dust tail and a gas or plasma
tail. The former is affected by radiation pressure of sunlight and has a
somewhat curved appearance. The plasma tail is affected by the solar wind
and is much less curved. The solar wind is itself a plasma of positive ions
(mainly protons) and electrons and causes the plasma tail (via the magnetic
field that the solar wind drags along with it) to point much more directly
away from the sun. In a similar way, because of its very high conductivity,
the solar wind distorts the outer part of the earth's magnetic field so
that the resulting magnetosphere has an extended `downstream' shape along
the flow of the solar wind. The high conductivity essentially prevents
magnetic field lines from crossing the flow of the plasma (and vice versa)
in accordance with Faraday's Law. Induced currents and the resultant forces
on them essentially force the two (solar wind flow lines and the  earth's
magnetic field lines) to take on the same flow pattern.

Lew


At 10:24 PM 4/11/97 -0600, you wrote:
> I really have two questions today:
> 1. I understand that the solar wind is a stream of particles emanating from
> the Sun. I have learned that it is responsible for the tail of the comet
> pointing away from the sun. Does radiation pressure play any appreciable
> part in the tail formation?
>
> 2. In reading about the solar wind, in my own effort to answer this, I find
> statements that the wind displaces our magnetic field. This is puzzling to
> me. Can anyone give a basic explanation of how this happens?
>
> BTW, The comments about magnetic shielding were wonderful!
>
> Thanks,
Lew Haddad 
Physics Department
Dawson College
3040 Sherbrooke W.
Montreal QC
H3Z 1A4

(lhaddad@dawsoncollege.qc.ca)