Reason for the faster than predicted rotation of the inner solar system has been established

(ORDO NEWS) — The movement of a tiny number of charged particles could help solve a long-standing mystery of the rotation of gaseous disks around young stars, according to a new study.

These structures, called accretion disks, have existed for tens of millions of years and represent an early stage in the evolution of a star system. They contain only a fraction of the mass of the star they orbit. They are called accretion disks because the gas in these disks falls on the star, approaching it in a spiral path.

Scientists have long understood that with such a spiral fall of material, the inner part of the disk should rotate faster, which is due to the known law of conservation of angular momentum.

Indeed, observations show that the inner part of the disk rotates faster than the outer part – but more slowly than follows from the calculations made for the star system, based on the moment of conservation of angular momentum.

A number of hypotheses have been proposed to explain this discrepancy, including friction between the inner and outer disk, as well as the so-called “magneto-rotational instability”, which generates turbulent effects in a gas in a magnetic field.

However, all the hypotheses described do not give a clear explanation of the reasons for the slowdown in the rotation of the inner disk of the solar system.

In a new study led by a team led by Paul Bellan, Professor of Applied Physics at Caltech, USA, the trajectories of individual atoms, electrons and gas ions were modeled to address the issue of slowing the rotation of the inside of an accretion disk.

Detailed modeling showed that collisions between neutral atoms and much smaller numbers of charged particles caused positively charged ions, or cations, to spiral towards the center of the disk, while negatively charged particles, electrons, were pushed to the periphery.

Neutral particles, meanwhile, lost angular momentum and, like cations, moved in a spiral towards the center of the system. The detailed mathematical of this process showed.

According to the authors, for neutral particles the difference between the values ​​of the classical and canonical angular momenta is insignificant, while for charged particles the contribution of the component associated with magnetic fields becomes quite significant.

Since electrons have a negative charge, and electrons have a positive charge, the movement of cations inward while pushing the electrons outward increases the total canonical angular momentum of the system.

At the same time, neutral particles lose angular momentum as a result of collisions with charged particles and move inward, thus compensating for the increase in canonical angular momentum achieved by charged particles, the authors explained.


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