The 7 degrees solar paradox: Astronomers believe they are closer to solving the “impossible” rotation of the Sun

Those who thought the Sun was well studied have most likely never heard of the mystery of its differential rotation: the equator of our star rotates much faster than its poles. How is this possible?

For a long time this was explained by temperature differences. But only now physicists from the Max Planck Institute for Solar System Research were able to accurately determine this difference and finally at least somewhat resolve the “solar paradox.”

Over decades of observation, it has been calculated that the Sun’s equator completes one revolution every approximately 24 days. This could be taken as a constant “sunny day”, if not for one “but”: the poles of the star require as many as 34 days for a full rotation.

The only explanation for this geometrically impossible phenomenon was the slight difference between the temperature of the Sun at the poles and at the equator. But it was not clear how to measure it. However, German physicists came up with a way: based on observations of long-period oscillations of the Sun.

In this they found useful data collected by the Solar Dynamics Observatory (a research probe launched 14 years ago) from 2017 to 2021. Then global oscillations of the solar surface were discovered and carefully documented, reminiscent of huge inertial vortices that shook the surface of the Sun for months.

The results of observations of these oscillations were incorporated into a series of large-scale three-dimensional simulations on one of the Institute’s powerful computers. And the result lived up to expectations: it was these vortices, as it turned out, that transfer huge amounts of heat from the poles of the Sun to its equator. Thus, the temperature difference was previously measured to be less than 7 degrees Celsius. However, even such a tiny difference (against the background of thousands and millions of degrees in different layers of the star) can be more than enough:

“This very small temperature difference between the poles and the equator controls the balance of angular momentum on the Sun and is thus an important feedback mechanism for its global dynamics,” explained Institute Director Dr. Laurent Gizon.

Thus, the oscillations of the Sun’s surface at high latitudes resemble the tropical cyclones that regulate the Earth’s climate, although the details differ: 

“If the Sun’s pole is about seven degrees hotter than the equator, then this is enough for the vortices to reach speeds of about 70 kilometers per hour over a large part of the surface stars,” said one of the co-authors of the article, Dr. Robert Cameron.

7 degrees

7 degrees at a surface temperature of 6000 and a difference of thousands of degrees between spots cannot make a noticeable contribution to rotation. Even 70 km/h cannot explain such a difference in rotation speed.

There is another question; what and where were the scientific measurements made? For example, in the area of the dark spot, when it appears, the temperature will be less and much more than 7 degrees.

It is also surprising that theorists and astronomers have not yet realized that the polar regions “live” on their own and have their own magnetic field. If we consider the official point of view, then there are convective currents in the interior, which should create the magnetic fields of the Sun. But the fact of the matter is that the rotation is differential and the magnetic fields cannot be homogeneous!

There are two options here: The convection tubes rotate in unison with the photosphere and in all spatial directions, since the total temperature of the FS is the same over the entire surface. Everyone knows that to rotate anything, you need energy and the Sun is no exception.

However, differential rotation is far from the only mystery of our star. For example, why was gamma radiation distributed unevenly across the surface of the Sun during the burst of activity ten years ago ? Not to mention the fact that rays emanating from the polar regions were orders of magnitude brighter than theoretical predictions promised.

Nevertheless, right now is a good time to dot the i’s – scientists hope that the flaring solar maximum, which will last until 2026, thanks to new observation technologies, will become a turning point in revealing many of the Sun’s secrets.