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north
2005-Mar-01, 12:27 AM
just wondering, since a supernova, class 2, is the star that becomes a blackhole and since ALL spining masses have a magnetic field, why would not a blackhole signature be the evidence of an extremely powerful magnetic field? which at this point has not been shown to be the case. the smaller the mass becomes the stronger its magnetic field becomes.

wstevenbrown
2005-Mar-01, 12:56 AM
This may be a word game. Since the electromagnetic force is carried by photons, and no photons can escape from within the event horizon (nor any other particles), the 'object' inside the event horizon cannot be said to have a magnetic field.

Objects orbiting the BH can generate and manifest a field. It is thought that BH's that are feeding (absorbing surrounding matter quickly) expel charged particles from their poles (called bipolar jets) as a result of the accretion disc's magnetic field. While scientists are usually careful about this distinction, the lay press is sometimes not. Best regards-- Steve

north
2005-Mar-01, 02:24 AM
i don't quite understand. what then would be the mechanisim that would change the magnetic field of a star , from drawing in plasmas , to a magnetic that would spew out matter? is this known. also how do we know that the jets are moving matter out , rather than drawing them in?

GOURDHEAD
2005-Mar-01, 04:38 AM
The mass of the plasma is attracted to the BH by gravity. The magnetic field of the orbiting plasma in the accretion disk causes the plasma to be expelled at the magnetic poles of the BH.

north
2005-Mar-01, 05:33 AM
Originally posted by GOURDHEAD@Mar 1 2005, 04:38 AM
The mass of the plasma is attracted to the BH by gravity. The magnetic field of the orbiting plasma in the accretion disk causes the plasma to be expelled at the magnetic poles of the BH.

fair enough, but

but since in the begining, the supernova, had a magnetic field that was the same as the Suns which had a magnetic field direction inward toward its poles, and if the mass of a supernova started to collapse inwards, along with this collapse so would the supernova's magnetic field, which would become stronger the more the star collapsed into its self. to the point i think that it would resist any further collapse.

this is because magnetic field would become very dense. so that not even gravity of the internal mass could overwhelm(become more powerful than the magnetic field) the magnetic field.

what would be the mechanism that could change all this?

and how do we know the direction of the polar jets(whether they are spewing out or bringing in matter,plasmas or energy)?

Svemir
2005-Mar-01, 07:34 AM
the smaller the mass becomes the stronger its magnetic field becomes
I don't know where do you get it from.
First of all, how do you make mass smaller?
Objects with greater mass (Sun) usually have stronger magnetic field (Earth).
It also depends on mechanism that causes magnetic field.
I think you wanted to say : "the smaller the object becomes the stronger its magnetic field."

As I understand that, magnetic field of black holes is generated from surrounding plasma and has the shape of homopolar motor, which in turns generate outgoing jets.
This link from EU debate:
http://www.es.ucl.ac.uk/research/planetary...grev/magtoc.htm (http://www.es.ucl.ac.uk/research/planetaryweb/undergraduate/dom/magrev/magtoc.htm)
is wonderful reading about magnetic fields.
Second, there is no law of conservation of magnetic field, so magnetic field of parrent star can be complitely different from magnetic field of it's remnant.

wstevenbrown
2005-Mar-01, 12:12 PM
and how do we know the direction of the polar jets(whether they are spewing out or bringing in matter,plasmas or energy)?

First, bear it in mind that what we are seeing is a 2D projection of a 3D process. When an outgoing jet of energetic particles encounters the surrounding medium, the force of the jet compresses the medium, and heats it. In return, the material of the jet is slowed and cooled. What we observe is a bow shock, so called because of its resemblance to the wave that motion of the bow of a boat creates in the water before it. If the jet passes thru successive layers of alternating dense and thin material, we see several such heating events, and the thermal signatures clearly show the decreasing power of the jet. If you try to read this process backwards, as infalling material encountering resistance, but accelerating anyhow, the velocities will not reconcile with the inverse-square law. Second, there is no known selection process which would account for an infalling flow only attracting a very narrow cone of material-- gravitation attracts everything, and EMF attracts (at minimum) a wide fan of oppositely charged material.


Hope this helps. Best regards-- Steve

north
2005-Mar-01, 03:10 PM
Originally posted by Svemir@Mar 1 2005, 07:34 AM

the smaller the mass becomes the stronger its magnetic field becomes
I don't know where do you get it from.
First of all, how do you make mass smaller?
Objects with greater mass (Sun) usually have stronger magnetic field (Earth).
It also depends on mechanism that causes magnetic field.
I think you wanted to say : "the smaller the object becomes the stronger its magnetic field."

As I understand that, magnetic field of black holes is generated from surrounding plasma and has the shape of homopolar motor, which in turns generate outgoing jets.
This link from EU debate:
http://www.es.ucl.ac.uk/research/planetary...grev/magtoc.htm (http://www.es.ucl.ac.uk/research/planetaryweb/undergraduate/dom/magrev/magtoc.htm)
is wonderful reading about magnetic fields.
Second, there is no law of conservation of magnetic field, so magnetic field of parrent star can be complitely different from magnetic field of it's remnant.

Svemir

thanks for the response and the site. i've briefly went through it, i'll read more latter.

yes, i meant the mass of the star(object) is becoming smaller.

north
2005-Mar-01, 03:14 PM
Originally posted by wstevenbrown@Mar 1 2005, 12:12 PM

and how do we know the direction of the polar jets(whether they are spewing out or bringing in matter,plasmas or energy)?

First, bear it in mind that what we are seeing is a 2D projection of a 3D process. When an outgoing jet of energetic particles encounters the surrounding medium, the force of the jet compresses the medium, and heats it. In return, the material of the jet is slowed and cooled. What we observe is a bow shock, so called because of its resemblance to the wave that motion of the bow of a boat creates in the water before it. If the jet passes thru successive layers of alternating dense and thin material, we see several such heating events, and the thermal signatures clearly show the decreasing power of the jet. If you try to read this process backwards, as infalling material encountering resistance, but accelerating anyhow, the velocities will not reconcile with the inverse-square law. Second, there is no known selection process which would account for an infalling flow only attracting a very narrow cone of material-- gravitation attracts everything, and EMF attracts (at minimum) a wide fan of oppositely charged material.


Hope this helps. Best regards-- Steve

wbtevenbrown

thanks for your response aswell, it gives me something to think about!!

north
2005-Mar-12, 04:28 AM
Originally posted by wstevenbrown@Mar 1 2005, 12:56 AM
This may be a word game. Since the electromagnetic force is carried by photons, and no photons can escape from within the event horizon (nor any other particles), the 'object' inside the event horizon cannot be said to have a magnetic field.

Objects orbiting the BH can generate and manifest a field. It is thought that BH's that are feeding (absorbing surrounding matter quickly) expel charged particles from their poles (called bipolar jets) as a result of the accretion disc's magnetic field. While scientists are usually careful about this distinction, the lay press is sometimes not. Best regards-- Steve

wstevenbrown

this is not a word game.

nowhere in the definition of a blackhole is the magnetic field, from the supernovas core , mentioned in the dynamics of a blackhole. and yet the magnetic field is 10 to the 36th power stronger than gravity alone.

so show that the magnetic field is inconsequential. and why!

photons are not the carrier of the magnetic field(this actually makes no sense). plasmas are.

antoniseb
2005-Mar-12, 08:57 AM
Originally posted by north@Mar 12 2005, 04:28 AM
photons are not the carrier of the magnetic field(this actually makes no sense). plasmas are.
??? Are you saying that the magnet on my fridge cannot hold up my daughter's report card without plasma to carry the magnetic force. Likewise, I dispute that photons are involved.

north
2005-Mar-12, 01:33 PM
Originally posted by antoniseb+Mar 12 2005, 08:57 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb @ Mar 12 2005, 08:57 AM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-north@Mar 12 2005, 04:28 AM
photons are not the carrier of the magnetic field(this actually makes no sense). plasmas are.
??? Are you saying that the magnet on my fridge cannot hold up my daughter&#39;s report card without plasma to carry the magnetic force. Likewise, I dispute that photons are involved. [/b][/quote]

i got a little carried away with plasmas there&#33;&#33;

wstevenbrown
2005-Mar-13, 10:01 PM
Objects orbiting the BH can generate and manifest a field.

Was I unclear? S