Transfer of Ang.Momentum from contracting disk

[dougettinger]

I originally thought most of the infalling mass that could create overspin of the newly formed Sun was lost through polar jets of materials. Then I read that the HH objects resulting from these polar jets are only 1 to 20 Earth masses.

So how does the angular momentum of the material falling inward from as far as Jupiter or even farther away get transferred from the protostar back to the protoplanetary disk during the T Tauri stage ? If the protostar disk originally possessed the mass to produce the Sun then why is not the Sun spinning much faster in order to conserve angular momentum ? Are we ignoring a braking element caused by perhaps magnetism ?

Doug Ettinger
Pittsburgh, PA

[alter-ego]

Yes.

Magnetic breaking is considered a fundamental mechanism for transferring angular momentum in single and (close) multiple star systems. We don't really know the Sun's formation enviroment, but growth in a cluster can play a role too.

http://iopscience.iop.org/0004-637X/599 ... _1_516.pdf

[dougettinger]

Thanks for the reference. dbe

[neufer]

The Parker Spiral rotates with a constant period of 27 days;
this rotation rate exceeds the free orbital rotation rate at 0.176 AU.

Hence: any prograde orbiting conducting body beyond 0.176 AU
currently gains angular momentum at the expense of the sun.

<<As the Sun rotates, its magnetic field twists into a Parker spiral, a form of an Archimedean spiral, named after its discovery by Eugene Parker. Parker's spiral magnetic field was divided in two by a current sheet. As the spiraling magnetic sheet changes polarity, it warps into a wavy spiral shape that has been likened to a ballerina's skirt.Further dynamics have suggested that "The Sun with the heliosheet is like a bashful ballerina who is repeatedly trying to push her excessively high flaring skirt downward".


The Parker Spiral

The heliospheric current sheet rotates along with the Sun once every 27 days, during which time the peaks and troughs of the skirt pass through the Earth's magnetosphere, interacting with it. Near the surface of the Sun, the magnetic field produced by the radial electric current in the sheet is of the order of 5×10⁻⁶ T. The magnetic field at the surface of the Sun is about 10^-4 tesla. If the form of the field were a magnetic dipole, the strength would decrease with the cube of the distance, resulting in about 10^-11 tesla at the Earth's orbit. The heliospheric current sheet results in higher order multipole components so that the actual magnetic field at the Earth due to the Sun is 100 times greater.>>

[dougettinger]

Neufer, thanks for the graphics. This is a great aid to my mathematically deficient brain. Am I to presume that this could be the main method for transfer of angular momentum outward to the planets while they were forming ? Can this type of transfer explain the transfer needed to avoid over-spinning of the Sun as the protostar disk materials fell inward ?

Reference is made to a radial electric current in the heliospheric sheet that is shown. Does this current consist of electrons ? What "ground" are the charges flowing toward ? In other words, what is the circuit ?

Doug Ettinger
Pittsburgh, PA

Doug Ettinger
Pittsburgh, PA

[neufer]

Neufer, thanks for the graphics. This is a great aid to my mathematically deficient brain. Am I to presume that this could be the main method for transfer of angular momentum outward to the planets while they were forming ? Can this type of transfer explain the transfer needed to avoid over-spinning of the Sun as the protostar disk materials fell inward ?

It certainly needs to be considered for the situation when the sun & planets were still forming
and, especially, when there was a lot of plasma floating around.

Reference is made to a radial electric current in the heliospheric sheet that is shown.
Does this current consist of electrons ? What "ground" are the charges flowing toward ?
In other words, what is the circuit ?

The current consists of the solar wind plasma
(; i.e., electrons moving radially outward faster than protons within the sheet.)
---------------------------------------------------
MHD simulation of the three-dimensional structure of the heliospheric current sheet
P. L. Israelevich1 - T. I. Gombosi2 - A. I. Ershkovich1 - K. C. Hansen2 - C. P. T. Groth2 - D. L. DeZeeuw2 - K. G. Powell3

Interplanetary magnetic field lines and electric current lines in the solar wind near the heliospheric current sheet surface.

a) Solid lines show the magnetic field lines slightly above the surface, and dashed lines correspond to the field lines
slightly below the current sheet surface. Empty lines show the direction of the electric current in the sheet.

[dougettinger]

Neufer, thanks for the graphics. This is a great aid to my mathematically deficient brain. Am I to presume that this could be the main method for transfer of angular momentum outward to the planets while they were forming ? Can this type of transfer explain the transfer needed to avoid over-spinning of the Sun as the protostar disk materials fell inward ?

It certainly needs to be considered for the situation when the sun & planets were still forming
and, especially, when there was a lot of plasma floating around.

Reference is made to a radial electric current in the heliospheric sheet that is shown.
Does this current consist of electrons ? What "ground" are the charges flowing toward ?
In other words, what is the circuit ?

The current consists of the solar wind plasma
(; i.e., electrons moving radially outward faster than protons within the sheet.)
---------------------------------------------------
MHD simulation of the three-dimensional structure of the heliospheric current sheet
P. L. Israelevich1 - T. I. Gombosi2 - A. I. Ershkovich1 - K. C. Hansen2 - C. P. T. Groth2 - D. L. DeZeeuw2 - K. G. Powell3

Interplanetary magnetic field lines and electric current lines in the solar wind near the heliospheric current sheet surface.

a) Solid lines show the magnetic field lines slightly above the surface, and dashed lines correspond to the field lines
slightly below the current sheet surface. Empty lines show the direction of the electric current in the sheet.

Nuefer, I like these ideas, but I am wondering whether the maximum circuit was overlooked because it has not been simulated yet. I am stealing an idea from one of our friends, Mr. Faraday, and his invention the Faraday dynamo. The charged plasma follows the magnetic field lines on the heliospheric plasmic sheet into the forming star and then outward along the polar field lines from each end of the spin axis which then return to the perimeters of the protostar disk to complete the circuit. The protostar evolves into a stronger and stronger dipole magnet as it keeps taking away the angular momentum energy and thus braking its own rotational velocity. What are your thoughts ? Thanks so much for sharing your information.

Doug Ettinger
Pittsburgh, PA

[neufer]

I am stealing an idea from one of our friends, Mr. Faraday, and his invention the Faraday dynamo. The charged plasma follows the magnetic field lines on the heliospheric plasmic sheet into the forming star and then outward along the polar field lines from each end of the spin axis which then return to the perimeters of the protostar disk to complete the circuit. The protostar evolves into a stronger and stronger dipole magnet as it keeps taking away the angular momentum energy and thus braking its own rotational velocity. What are your thoughts ? Thanks so much for sharing your information.

The main energy source for the sun's magnetic dynamo is probably fusion generated convection cells just as the main energy source for the earth's magnetic dynamo is probably fission generated convection cells. Understanding the details of all this is way above my pay grade, Doug.

[dougettinger]

I am just looking for anyone's personal thoughts ( not to end up in any scientific journal ) on why most of the angular momentum of the solar system resides in the outer planets; and, why the Sun spins so slowly after supposely having its own material spiral inward from a disk reaching outward at least to the Oort Cloud.

Doug Ettinger

[neufer]

I am just looking for anyone's personal thoughts ( not to end up in any scientific journal ) on why most of the angular momentum of the solar system resides in the outer planets; and, why the Sun spins so slowly after supposely having its own material spiral inward from a disk reaching outward at least to the Oort Cloud.

Well then, you already got my idea: magnetic fields pushing around electrical conductors.

Magnetic fields can also induce currents in electrical conductors
which can then feed back into more magnetic fields
...but all that makes my head spin.

[bystander]

Most of the angular momentum of the solar system resides in the outer planets because that is where most of the mass is (sans sun).

[dougettinger]

Most of the angular momentum of the solar system resides in the outer planets because that is where most of the mass is (sans sun).

Most of the mass for the planetary bodies is in the outer planet, but the Sun by far possesses the most mass of the entire rotating system.

DBE

[Chris Peterson]

Most of the mass for the planetary bodies is in the outer planet, but the Sun by far possesses the most mass of the entire rotating system.

But despite the great mass of the Sun, the angular momentum of the Solar System is dominated by the outer planets. It is the four of them that largely determine the invariant plane (which helps explain why the Sun can easily be tilted several degrees with respect to that plane).

[bystander]

Most of the mass for the planetary bodies is in the outer planet, but the Sun by far possesses the most mass of the entire rotating system.

The angular momentum of a planetary system is determined by the planets. The central star is not considered.

http://asterisk.apod.com/vie ... 65#p119965

edit: I see Chris beat me to it.

[Chris Peterson]

The angular momentum of a planetary system is determined by the planets. The central star is not considered.

The central star's angular momentum certainly does contribute to the angular momentum of the entire system. In some systems, the angular momentum of the star certainly must dominate. In our own system, the angular momentum of the four gas giants dominates, but the angular momentum of the Sun is not insignificant in its contribution to the total angular momentum of the Solar System.

[dougettinger]

Most of the mass for the planetary bodies is in the outer planet, but the Sun by far possesses the most mass of the entire rotating system.

But despite the great mass of the Sun, the angular momentum of the Solar System is dominated by the outer planets. It is the four of them that largely determine the invariant plane (which helps explain why the Sun can easily be tilted several degrees with respect to that plane).

The issue is not what is. The issue is the question as to why the Sun should not possess most of the angular momentum since the majority of the mass fell inward to create the Sun. If you contract a spinning mass inward like a spinning skater bringing in their arms to increase spin, why does not the Sun spin in likewise fashion at a ridiculously high rotational velocity ? Scientists have made the calculations, but I do not have the resulting value of angular velocity at my fingertips.

Doug Ettinger
Pittsburgh, PA

[Chris Peterson]

The issue is not what is. The issue is the question as to why the Sun should not possess most of the angular momentum since the majority of the mass fell inward to create the Sun. If you contract a spinning mass inward like a spinning skater bringing in their arms to increase spin, why does not the Sun spin in likewise fashion at a ridiculously high rotational velocity? Scientists have made the calculations, but I do not have the resulting value of angular velocity at my fingertips.

Understood. But as has been pointed out, there are mechanisms that transfer angular momentum completely from the system, such as jets during early formation, as well as mechanisms that transfer it within the system, such as magnetic and fluid dynamic forces. Also, it is not at all clear that most of the mass fell inward to create the Sun. Most of the mass was probably blown out of the system once fusion was initiated in the primordial Sun- another opportunity for the system to lose angular momentum.

[dougettinger]

The issue is not what is. The issue is the question as to why the Sun should not possess most of the angular momentum since the majority of the mass fell inward to create the Sun. If you contract a spinning mass inward like a spinning skater bringing in their arms to increase spin, why does not the Sun spin in likewise fashion at a ridiculously high rotational velocity? Scientists have made the calculations, but I do not have the resulting value of angular velocity at my fingertips.

Understood. But as has been pointed out, there are mechanisms that transfer angular momentum completely from the system, such as jets during early formation, as well as mechanisms that transfer it within the system, such as magnetic and fluid dynamic forces. Also, it is not at all clear that most of the mass fell inward to create the Sun. Most of the mass was probably blown out of the system once fusion was initiated in the primordial Sun- another opportunity for the system to lose angular momentum.

Thank you for your dilegence and patience. To my surprise I recently read that Herbig-Haro objects at the end of the early HH jets are estimated to only be 1 to 20 Earth masses. To date, there is no mention of the amount of energy expelled by these early jets and their relative significance in removing energy to slow the Sun's rotation. In the later T Tauri phase when T-Tauri winds are blowing outward and evacuating the remainder of the protostar disk, the Sun has already gathered its solar mass to join other stars on the Hertzsprung-Russell main sequence and fuse hydrogen in its core. The high velocities attained at that time would have blown apart the star before it could started fusing hydrogen and releasing outwardly angular momentum energy. That leaves only magnetic and fluid dynamic forces to do the job of transfer. I believe by fluid dynamic forces you refer to the compressive forces of a column of fluid or gas created by gravity.

Obviously, the angular momentum energy was transferred by some means when the prostar disk collapsed.

Doug Ettinger
Pittsburgh, PA

[Chris Peterson]

Thank you for your dilegence and patience. To my surprise I recently read that Herbig-Haro objects at the end of the early HH jets are estimated to only be 1 to 20 Earth masses. To date, there is no mention of the amount of energy expelled by these early jets and their relative significance in removing energy to slow the Sun's rotation...

This is a very technical area, and I don't pretend to be an expert. To get some real understanding would require the diligent analysis of a good many dense scientific papers. I haven't seen a good Wikipedia-level treatment that summarizes things effectively. But I would suggest that there are a number of models used to study stellar system formation, and they don't seem to have any problem with producing stars that spin so fast they don't hold together. This seems like something that would be obvious to the researchers, so I'm inclined to believe that the distribution of angular momentum is actually well understood.

I believe by fluid dynamic forces you refer to the compressive forces of a column of fluid or gas created by gravity.

I'm referring to the dynamics associated with the fact that the accretion disc behaves as a viscous fluid. Fluid dynamics is the primary theory used to describe accretion discs.