Re: neutron stars

From: Martin Brown (|||newspam|||_at_nezumi.demon.co.uk)
Date: 12/05/04 

Date: Sun, 05 Dec 2004 10:22:46 +0000

Fred Kasner wrote:

> Oscar Lanzi III wrote:
>
>> Uh, 10^20?
>>
>> A neutron star still has a small fraction of protons and electrons left
>> over.
>
> It can't have much of any charge. The pulsars (neutrons stars) were an
> anomoly at the time of their original discovery because of their rapid
> rotation. A charged body cannot rotate very rapidly with all that mass
> as Lenz's Law tells you that it would set up magnetic fields that would
> appose the motion. It was the rapid rotation that led to the hypothesis
> of the stars being almost pure neutrons.
> FK

Neutron stars inherit the magnetic field of the sun that they formed
from but are much smaller and since right up to the point it goes
approximately neutral the field is locked in the grip of a conducting
plasma these fields are enormous.

Ball park numbers are the sun ~ 2G, typical white dwarf 100000G
Biggest white dwarf 10^8 G

Upper bound on neutron star magnetic field ~ 10^14 G
(source Carol & Ostlie, Intro to Modern Astrophysics p606)

The electric field at the surface is around 10^11 V/m

Wierd things occur at the light cylinder where the magnetic field can no
longer drag charged particles round with the neutron star.

It is the interaction of the spinning dipole magnetic field that powers
their beamed pulsating emissions.

Regards,
Martin Brown

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