New pulsar radiation model

[ZX.Liang]

For decades, the lighthouse model has stood as the sole framework explaining the radiation mechanism of pulsars. We recently published a new model in the Monthly Notices of the Royal Astronomical Society (MNRAS). I will briefly introduce this model here and welcome interested friends to discuss it together.

We know the Sun’s magnetic field undergoes polarity reversal with a 22-year cycle. If the Sun were to collapse into a neutron star, would its magnetic field cease flipping? We argue its magnetic field would not stop reversing—instead, it would flip far more rapidly. When the magnetic field reversal cycle becomes very short, the induced electric field reaches extremely high magnitudes, triggering coherent pulsed radiation from electrons within the magnetosphere. This is our Magnetic-field Oscillation Model (MO Model).

The core distinction between the MO Model and the lighthouse model lies in their respective origins of pulse periodicity: the pulse period in the former corresponds to the magnetic field reversal cycle, while in the latter it matches the stellar rotation period.

The MO Model can account for all key observational radiation features of pulsars with minimal auxiliary assumptions. First proposed back in 2004, several predictions derived from this model have since been corroborated by subsequent astronomical observations:

1. Celestial bodies capable of emitting pulsed radiation are not limited to neutron stars (published).
2. Pulsed radiation is generated during the magnetic field’s zero-crossing phase (published).
3. The circular contribution of emission is positively correlated with the pulse radiation period (published).
4. The circular contribution of emission is negatively correlated with absolute luminosity (unpublished).

Section 4 of our paper also puts forward a prediction pending observational verification.

I am an amateur enthusiast of astrophysics and hope to connect with fellow aficionados sharing this research interest.



Our MNRAS Publications

1. Full model paper: Magnetic-field oscillation model of pulsar radio emission: prediction of an observable effect (https://doi.org/10.1093/mnras/stae909).
2. Model validation test paper: Testing the rotating lighthouse model with the double pulsar system PSR J0737-3039A/B (https://doi.org/10.1093/mnras/stu223).

 

[Matterwave]

You will have to forgive my ignorance as it has been many years since I've looked at stellar physics. What is the mechanism for magnetic pole reversal in the sun and why should that mechanism speed up in neutron stars?

It's easy for me to understand why neutron stars spin faster due to angular momentum conservation. But magnetic pole reversal is not obvious to me.

 

[ZX.Liang]

You will have to forgive my ignorance as it has been many years since I've looked at stellar physics. What is the mechanism for magnetic pole reversal in the sun and why should that mechanism speed up in neutron stars?

It's easy for me to understand why neutron stars spin faster due to angular momentum conservation. But magnetic pole reversal is not obvious to me.

The mechanism of solar magnetic field reversal is still unclear to us. However, according to Cowling's theorem (1933, MNRAS, 94, 39), no celestial body can maintain a steady and symmetrical magnetic field. From this, it can be inferred that any celestial body with a magnetic field must have an alternating magnetic field.

Based on Cowling's theorem, our hypothesis is that the magnetic fields of all celestial bodies are generated by self excited AC generators. The frequency of the alternating magnetic field depends on factors such as the capacitance, inductance, rotational speed, temperature, etc. of the celestial body itself, and is not related to internal turbulence. The volume of neutron stars is very small, and their capacitance and inductance are also very small, so the oscillation frequency is very high.

 

[ZX.Liang]

You will have to forgive my ignorance as it has been many years since I've looked at stellar physics. What is the mechanism for magnetic pole reversal in the sun and why should that mechanism speed up in neutron stars?

It's easy for me to understand why neutron stars spin faster due to angular momentum conservation. But magnetic pole reversal is not obvious to me.

Our model adopts Schuster–Wilson hypothesis (Schuster 1911 Proc. Phys. Soc. London, 24, 121; Wilson 1923 Proc. Roy. Soc. London, A, 104, 451). This hypothesis holds that any celestial body will generate a magnetic field as long as its equatorial velocity exceeds a certain threshold. We introduced Cowling's theorem on top of their hypothesis. Therefore, it can be concluded that any celestial body, as long as it rotates fast enough, will generate an alternating magnetic field. The magnetic fields of the sun and the earth are clearly alternating. The moon, Venus, and Mars do not have a magnetic field because their rotational speed is too low.

To verify our hypothesis, we once cast a solid aluminum ball with a diameter of one meter and a weight of 1.5 tons. We plan to make its equatorial velocity reach that of the Earth's equator. Then measure whether there is a magnetic field present.
Unfortunately, due to excessive centrifugal force, the sphere exploded and the experiment failed. It also caused one person's death.

 

[Matterwave]

I have still just the very naive view of neutron stars. At the level of an undergraduate. So please see my comments as pure curiosity. I am not an expert in the field so I am unqualified to judge the actual physics here. However, reading parts of the paper, I do have some thoughts and comments.

The mechanism of solar magnetic field reversal is still unclear to us.

In the paper, in section 2 introduction to the MO model you introduce 4 assumptions.

1. The flip oscillation is common to all stars.
2. Oscillation frequency is positively correlated with rotation frequency.
3. Magnetic field strength is positively correlated with oscillation frequency.
4. Oscillating magnetic field induces oscillating electric field (seems valid to me from just Maxwell's eqns) and at the peak produces a radiation pulse.

My comment/thought for these assumptions is that they seem to be broadly generalizing properties of typical main sequence stars or other kind of "typical celestial objects" and imposing those properties onto a neutron star which, internally, looks very much NOT like any main sequence star.

My naive understanding of a neutron star is after some short time after formation its interior is roughly frozen in place. The magnetic flux is conserved and then trapped. So you get a very large magnetic field, but it's stuck there. Whatever internal mechanism in the Sun, for example, which leads to the reversal of the magnetic poles, I would not expect to happen analogously in the neutron star.

and is not related to internal turbulence.

I have a hard time understanding how this could be. Aren't all the magnetic fields in celestial bodies assumed to come from internal dynamics? Are you saying the magnetic field of a neutron star is somehow a surface-only field?

The volume of neutron stars is very small, and their capacitance and inductance are also very small, so the oscillation frequency is very high.

I don't see how the conclusion can be derived from the premises.

My final comment -- in the paper it is claimed in the abstract that remining data from observations of TVLM 513−46546 could help bolster the claims of this paper. Was that data remined and what were the results?

 

[Matterwave]

To verify our hypothesis, we once cast a solid aluminum ball with a diameter of one meter and a weight of 1.5 tons. We plan to make its equatorial velocity reach that of the Earth's equator. Then measure whether there is a magnetic field present.
Unfortunately, due to excessive centrifugal force, the sphere exploded and the experiment failed. It also caused one person's death.

This seems super dangerous... please don't do this again...

 

[Matterwave]

Also.. wouldn't the EM waves you have to radiate based on this magnetic dipole moment flipping so fast just take all the energy out of the system? There's some physical intuition on my end that's not jiving with this rapid oscillation of such a strong magnetic field.

 

[ZX.Liang]

My comment/thought for these assumptions is that they seem to be broadly generalizing properties of typical main sequence stars or other kind of "typical celestial objects" and imposing those properties onto a neutron star which, internally, looks very much NOT like any main sequence star.

Under the Schuster Wilson hypothesis and Cowing's theorem, the difference between neutron stars and other celestial bodies does not affect the output characteristics of the AC generator. This is similar to a generator made of copper wire and silver wire, with no significant difference.

 

[Baluncore]

This is similar to a generator made of copper wire and silver wire, with no significant difference.

I would question the EM skin depth of a neutron star, and ask how it is possible to flip hundreds of times per second.

 

[ZX.Liang]

My naive understanding of a neutron star is after some short time after formation its interior is roughly frozen in place. The magnetic flux is conserved and then trapped. So you get a very large magnetic field, but it's stuck there. Whatever internal mechanism in the Sun, for example, which leads to the reversal of the magnetic poles, I would not expect to happen analogously in the neutron star.

We believe that freezing magnetic field lines inside neutron stars to achieve the concept of magnetic flux conservation is questionable. The interior of the sun is also highly ionized and highly conductive, and can also be considered an ideal conductor. But the magnetic field inside the sun is obviously not conserved. There will be a magnetic flux zero crossing and polarity reversal every 11 years. Therefore, there is no reason to believe that the magnetic flux inside neutron stars is conserved. The principle of magnetic freezing has seriously affected people's research on the magnetic field of celestial bodies. Alvin, the inventor of the principle of magnetic freezing, twice opposed the use of the concept of magnetic freezing in his later years, believing that it would be misleading. A few years ago, we published two papers that denied the principle of magnetic freezing through theoretical analysis and three sets of experiments.

 

[ZX.Liang]

I have a hard time understanding how this could be. Aren't all the magnetic fields in celestial bodies assumed to come from internal dynamics? Are you saying the magnetic field of a neutron star is somehow a surface-only field?

The interior of a neutron star has a magnetic field, but like the magnetic field of the sun, it is not conserved, but an alternating magnetic field. Their interiors are all ideal conductors. It is a certain fact that the magnetic field inside the sun is not conserved. Isn't it a good inference that the magnetic field inside a neutron star is not conserved?

 

[ZX.Liang]

My final comment -- in the paper it is claimed in the abstract that remining data from observations of TVLM 513−46546 could help bolster the claims of this paper. Was that data remined and what were the results?

I once requested data from three author teams to verify our prediction, but they did not answer, so the prediction has not been verified. I believe that as long as they provide us with data, we can overturn their model.
In fact, the initial version of our paper had two prophecies, the first of which was' The circular contribution of emission is positively correlated with the pulse radiation period '. During the review process, the reviewer provided us with three datasets. Using those datasets, we directly confirmed our first prediction. That is the correlation shown in Figure 2. Due to the direct confirmation of the first prediction during the review period, demonstrating the predictive ability of the new model, our paper was successfully published.

 

[ZX.Liang]

This seems super dangerous... please don't do this again...

Later, we conducted a second experiment. To ensure safety, a basement was specifically built.
The diameter of the aluminum ball in the second experiment is 30+ centimeters. The final rotational speed reached 30000 r/m, and the equatorial velocity of the ball reached the equatorial velocity of the Earth. But the expected magnetic field was not detected. Later on, there were three possible reasons for the failure analysis.
1.The threshold for triggering the magnetic field is not directly proportional to the linear velocity, so the rotational speed is still too low.
2. The sensitivity of the instrument is insufficient.
3. The vacuum chamber outside the sphere is made of iron material, which suppresses the generation of alternating magnetic fields.

 

[ZX.Liang]

Also.. wouldn't the EM waves you have to radiate based on this magnetic dipole moment flipping so fast just take all the energy out of the system? There's some physical intuition on my end that's not jiving with this rapid oscillation of such a strong magnetic field.

Our idea is that energy is periodically converted between magnetic energy and electrical energy, and when magnetic energy crosses zero, electrical energy reaches its peak. This phenomenon is very common in the field of electrical engineering. Only a small amount of energy is radiated out in each cycle. Then the rotational energy will continuously replenish electromagnetic energy. The final result is that the rotational speed of the celestial body continuously decreases.

 

[ZX.Liang]

I would question the EM skin depth of a neutron star, and ask how it is possible to flip hundreds of times per second.

We still don't know the entire process of magnetic field reversal. However, in our model, the oscillation frequency is negatively correlated with the capacitance and inductance of the celestial body itself. The capacitance and inductance of neutron stars are much lower than those of the Sun, so their magnetic field oscillation frequency is much higher than that of the Sun.

 

[ZX.Liang]

I would question the EM skin depth of a neutron star, and ask how it is possible to flip hundreds of times per second.

Our model is far from mature, and there are still many problems waiting to be solved. But in another paper, we provided a gold standard for model validation. Using our published method, we can ultimately determine which model is the correct one.