I The Role of magnetic field during the formation of small to medium scale stars

[Harsha Avinash Tanti]

Hi, I would like to raise a question about Role of magnetic field while formation of small to medium scale stars emerging from nebula ?

 

[berkeman]

Hi, I would like to raise a question about Role of magnetic field while formation of small to medium scale stars emerging from nebula ?

Welcome to the PF.

Can you post links to the reading you have been doing so far? Also, you have used the "A" prefix for this thread, which means you want to discuss it at a PhD level. Would you prefer that we change the prefix to "I" for a more undergraduate-level discussion, or do you still prefer "A"?

Thanks!

 

[davenn]

Hi, I would like to raise a question about Role of magnetic field while formation of small to medium scale stars emerging from nebula ?

Can you post links to the reading you have been doing so far?

indeed

But as a starting point, I would consider that gravity is the overwhelmingly predominant force

 

[Harsha Avinash Tanti]

These are the papers which I was referring to-


https://doi.org/10.1111/j.1365-2966.2007.11621.x
http://iopscience.iop.org/article/10.1086/305230/pdf
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?db_key=AST&bibcode=1962AnAp...25...18S&letter=0&classic=YES&defaultprint=YES&whole_paper=YES&page=20&epage=20&send=Send+PDF&filetype=.pdf
https://doi.org/10.1093/mnras/221.2.319

And I would prefer this topic at Phd level

And as we know basically how stars are born but how the magnetic field emerge in that process and what role it play while star formation that I want to discuss.

 

[JMz]

Please clarify: Are you asking if magnetic fields influence the formation of medium- & low-mass stars? Or if the fields influence their emergence from the proto-stellar nebula (Herbig-Haro stage, for instance)?

 

[Harsha Avinash Tanti]

Please clarify: Are you asking if magnetic fields influence the formation of medium- & low-mass stars? Or if the fields influence their emergence from the proto-stellar nebula (Herbig-Haro stage, for instance)?

I am intrigued that you clearly understood what I was talking about.

I am Concerned about the magnetic fields influence on the formation of medium and low mass star. And also searching is there any relation between fields influence on the star and there emergence from the nebula.

 

[JMz]

In most situations, magnetic fields "come along for the ride", especially during the collapse of a gas cloud into a proto-star. In particular, if the molecular cloud collapses to form any stars at all, then my understanding is that gravity is typically a much bigger effect than magnetic fields, except perhaps very locally. (E.g., the immediate vicinity of a pulsar would not be a likely place for a proto-star to form. However, the magnetic field isn't the only reason for that.)

I have seen hypotheses that magnetic fields are important for clearing the proto-stellar nebula (and shutting down planet formation), though I don't know the current state of research on that. There are multiple mechanisms to form jets near the proto-star, not only magnetic fields. However, the fields do seem to be important for HH objects, which are themselves a normal part of low-mass star formation: see https://en.wikipedia.org/wiki/Herbig–Haro_object.

 

[Harsha Avinash Tanti]

In most situations, magnetic fields "come along for the ride", especially during the collapse of a gas cloud into a proto-star. In particular, if the molecular cloud collapses to form any stars at all, then my understanding is that gravity is typically a much bigger effect than magnetic fields, except perhaps very locally. (E.g., the immediate vicinity of a pulsar would not be a likely place for a proto-star to form. However, the magnetic field isn't the only reason for that.)

I have seen hypotheses that magnetic fields are important for clearing the proto-stellar nebula (and shutting down planet formation), though I don't know the current state of research on that. There are multiple mechanisms to form jets near the proto-star, not only magnetic fields. However, the fields do seem to be important for HH objects, which are themselves a normal part of low-mass star formation: see https://en.wikipedia.org/wiki/Herbig–Haro_object.

I see your hypotheses seems fair enough but I have another one as we have known the existence of magnetic properties of elements from last few decades, I think that its the electromagnetic forces that brings together few of the particle together in a nebula after which the gravitational contraction begins as gravity plays its role due to which the cluster of particle gets a spin as other particle hits it and joins it due to this constant bombardment heat is produced which some how creates a magnetic field and according to me the magnetic helps the form of star as this " It stops the charged particles (possibly electron clouds), due to which stable atoms gets attracted and the heat due to bombardment and rotation kicks off fusion".

My thought seems childish but its got its own merit as by my hypotheses one can explain the accumulated electron clouds near medium and low mass star.

 

[davenn]

I see your hypotheses seems fair enough but I have another one as we have known the existence of magnetic properties of elements from last few decades, I think that its the electromagnetic forces that brings together few of the particle together in a nebula after which the gravitational contraction begins as gravity plays its role due to which the cluster of particle gets a spin as other particle hits it and joins it due to this constant bombardment heat is produced which some how creates a magnetic field and according to me the magnetic helps the form of star as this " It stops the charged particles (possibly electron clouds), due to which stable atoms gets attracted and the heat due to bombardment and rotation kicks off fusion".

please provide links to reputable papers on this
personal theories are against PF rules

 

[Harsha Avinash Tanti]

please provide links to reputable papers on this
personal theories are against PF rules

Sorry! I don't know the rules well here as I am new.
I currently studying the outflow by the proto stars in star formation process, I don't have any proofs regarding my theory. But here are some papers which lead me to this thought and a Phd topic proposed by ESO by Dr. Markus Schöller which is "Spectropolarimetric observations of Herbig Ae/Be stars indicate that magnetic fields are important ingredients of intermediate mass star formation. To properly understand the physics involved in the intermediate mass star formation process, it is particularly important to know the origin of the magnetic fields in these stars. However, current theories are not able to present a consistent scenario of how the magnetic fields in Herbig Ae/Be stars are generated or how these fields interact with the circumstellar environment, presenting a combination of disk, wind, accretion, and jets. Understanding the interaction between the central stars, their magnetic fields, and protoplanetary disks is crucial to reconstruct the Solar System's history, and to account for the diversity of exoplanetary systems." .

https://arxiv.org/pdf/1603.08385.pdf
https://link.springer.com/chapter/10.1007/978-1-4020-6935-2_31

 

[JMz]

I see your hypotheses seems fair enough but I have another one as we have known the existence of magnetic properties of elements from last few decades, I think that its the electromagnetic forces that brings together few of the particle together in a nebula after which the gravitational contraction begins as gravity plays its role due to which the cluster of particle gets a spin as other particle hits it and joins it due to this constant bombardment heat is produced which some how creates a magnetic field and according to me the magnetic helps the form of star as this " It stops the charged particles (possibly electron clouds), due to which stable atoms gets attracted and the heat due to bombardment and rotation kicks off fusion".

My thought seems childish but its got its own merit as by my hypotheses one can explain the accumulated electron clouds near medium and low mass star.

Two things to keep in mind: (1) For practical purposes, the nature of the atoms does not matter -- for instance, iron and hydrogen are about equally irrelevant: Both nuclei are much more massive than electrons (though iron may ionized more easily, producing free electrons). Magnetic fields in gases and plasmas are caused by macroscopic electrical currents, mostly free electrons.
(2) The collapse of a gas cloud is initially caused by (a) collision with another cloud or (b) cooling until its pressure is weaker than its gravity or (c) radiation pressure on one side, causing a build-up of density on the opposite side. Electromagnetic effects (except for the photons in (c)) have nothing to do with starting the collapse.

 

[JMz]

Sorry! I don't know the rules well here as I am new.
I currently studying the outflow by the proto stars in star formation process, I don't have any proofs regarding my theory. But here are some papers which lead me to this thought and a Phd topic proposed by ESO by Dr. Markus Schöller which is "Spectropolarimetric observations of Herbig Ae/Be stars indicate that magnetic fields are important ingredients of intermediate mass star formation. To properly understand the physics involved in the intermediate mass star formation process, it is particularly important to know the origin of the magnetic fields in these stars. However, current theories are not able to present a consistent scenario of how the magnetic fields in Herbig Ae/Be stars are generated or how these fields interact with the circumstellar environment, presenting a combination of disk, wind, accretion, and jets. Understanding the interaction between the central stars, their magnetic fields, and protoplanetary disks is crucial to reconstruct the Solar System's history, and to account for the diversity of exoplanetary systems." .

https://arxiv.org/pdf/1603.08385.pdf
https://link.springer.com/chapter/10.1007/978-1-4020-6935-2_31

In terms of my last response, note that (a) this abstract deals with magnetic fields in proto-stars that have already formed, not fields in gas clouds, and (b) stars and proto-stars are plasmas.

It may help to realize that, if magnetic flux is conserved (i.e., the currents never meet and cancel with large release of heat), then a Sun-sized star's magnetic field will be >~ 10^15 times as large as in the cloud. (A molecular cloud may typically have ~ 1 solar mass per cubic light year, and 1 LY ~ 10^7 solar diameters.) Thus, the mere fact that the plasma collapsed from a light year to a solar diameter means than the field is compressed enormously. It does not necessarily mean that the field influenced the collapse significantly.

You may find the abstract here http://iopscience.iop.org/article/10.1086/318290 to be helpful.

 

[alantheastronomer]

There's a problem in the theory of protostellar collapse, and that is that angular momentum precludes the collapse from proceeding. Efforts have been made to solve this problem by means of what's called "ambipolar diffusion" - the decoupling of molecular hydrogen from the plasma that it's collisionally coupled to - and a concept called "flux freezing" - where the magnetic field of the protostar is "frozen" in the surrounding disk. The orbital velocity of the disk being smaller than the rotational velocity of the protostar, the disk slows down the protostar by way of the frozen magnetic field, the disk gaining angular momentum as the star loses it.

 

[Harsha Avinash Tanti]

There's a problem in the theory of protostellar collapse, and that is that angular momentum precludes the collapse from proceeding. Efforts have been made to solve this problem by means of what's called "ambipolar diffusion" - the decoupling of molecular hydrogen from the plasma that it's collisionally coupled to - and a concept called "flux freezing" - where the magnetic field of the protostar is "frozen" in the surrounding disk. The orbital velocity of the disk being smaller than the rotational velocity of the protostar, the disk slows down the protostar by way of the frozen magnetic field, the disk gaining angular momentum as the star loses it.

Sir, Will you be able to refer me some articles regarding this.

 

[alantheastronomer]

I don't have anything specific, but if you search "ambipolar diffusion" on "adsabs.harvard.edu" you may find what you're looking for - good luck!

 

[Nikolay Larin]

[QUOTE = "Harsha Avinash Tanti, сообщение: 5970831, участник: 641677"] Sir, Will you be able to refer me some articles regarding this. [/ QUOTE]
http://hydrogen-future.com/en/list-c-larin-en/68-hydridicearthfrompolarpublishing-en.html
https://arxiv.org/abs/1208.2909

 

[alantheastronomer]

Also search "adsabs.harvard.edu" for "magnetic braking"!

 

[alantheastronomer]

P.S. - Use the "beta" format