Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 21/12/2014 03:30:07

Title: Can magnetic fields snap?
Post by: thedoc on 21/12/2014 03:30:07

Wilf James  asked the Naked Scientists:
   
I have often heard in talks about the sun that sometimes magnetic fields
snap like breaking elastic bands.

I don't know where this simile comes from but I can't connect it with
any of my experiences with electricity and magnetism in 70 -odd years.
Then, after watching a series of talks and interviews on YouTube about
Richard Feynman I began to wonder if I had missed something.
Is it possible for your kitchen scientists to see if a magnetic field
can be broken like a failing elastic band?

Wilf
 
What do you think?

Title: Re: Can magnetic fields snap?
Post by: PmbPhy on 21/12/2014 05:30:01

Quote from: thedoc on 21/12/2014 03:30:07

Wilf James  asked the Naked Scientists:
   
I have often heard in talks about the sun that sometimes magnetic fields
snap like breaking elastic bands.

I don't know where this simile comes from but I can't connect it with
any of my experiences with electricity and magnetism in 70 -odd years.
Then, after watching a series of talks and interviews on YouTube about
Richard Feynman I began to wonder if I had missed something.
Is it possible for your kitchen scientists to see if a magnetic field
can be broken like a failing elastic band?

Wilf
 
What do you think?

I never heard of such a thing and don't think it exists. All that I can see being possible is a rapid change in a magnetic field which can be caused by a rapid change in an electric field.

Title: Re: Can magnetic fields snap?
Post by: evan_au on 21/12/2014 11:25:17

The usual terminology is "magnetic reconnection (http://en.wikipedia.org/wiki/Magnetic_reconnection)". 

A magnetic field is able to store energy - it takes more and more energy to increase the strength of a magnetic field.

There comes a point where the magnetic field can no longer be sustained, and it switches to a different configuration of the magnetic field which has lower magnetic energy - but the energy is now converted into mechanical, thermal and optical energy.

This is seen in Solar flares and coronal mass ejections on the Sun, and in Earth's magnetosphere, magnetic reconnection can trigger the aurora (northern & southern lights).

The most dramatic effects happen in plasmas, but if you have ever played with a stepper motor, you can apply more torque to the rotor, until it suddenly snaps into a different magnetic field configuration with a lower energy. You can achieve a similar effect by sliding a couple of fridge magnets past each other.

Title: Re: Can magnetic fields snap?
Post by: PmbPhy on 21/12/2014 11:28:04

Quote from: evan_au

The usual terminology is "magnetic reconnection (http://en.wikipedia.org/wiki/Magnetic_reconnection)".

Cool. That's very interesting evan. Thank you very much. :)

Title: Re: Can magnetic fields snap?
Post by: jeffreyH on 21/12/2014 16:57:10

Evan I am constantly surprised by the answers that you give. You are a mine of useful information.

Title: Re: Can magnetic fields snap?
Post by: acsinuk on 24/12/2014 14:44:16

The flux from the different magnets may entangle as they are going in the same direction but why reconnect ??

Title: Re: Can magnetic fields snap?
Post by: evan_au on 24/12/2014 20:02:03

Quote from: acsinuk

why reconnect ??

Because there is potential energy stored in those stretched magnetic fields. It moves to a state of lower potential energy if the magnetic fields can reconnect so the magnetic field is not so stretched.

Title: Re: Can magnetic fields snap?
Post by: A Davis on 28/12/2014 01:11:59

The electrons travelling along the suns magnetic field between two dark spots causes it to snap, most are pulled back to the sun but some are ejected with the magnetic field into space its not simple at all.