Researchers identify eddy currents in the Sun, called Rossby waves, as mediating the tidal effects of Venus, Earth and Jupiter on the Sun's magnetic activity
Researchers at the HZDR and the University of Latvia have proposed the first comprehensive physical explanation for the sun's various cycles of activity. They identify eddy currents in the Sun, called Rossby waves, as mediating the tidal effects of Venus, Earth and Jupiter on the Sun's magnetic activity. This study presents a consistent model for solar cycles of different lengths and makes a strong argument in support of the previously controversial planetary hypothesis. The findings were published in the journal Solar Physics.
Although the Sun, being close to us, is the best-studied star, many questions about its physics have not been fully answered. Among them are the rhythmic fluctuations in solar activity. The most famous of them is that, on average, the sun reaches maximum radiation every eleven years - the experts call this the Schwab cycle. This cycle of activity occurs because the Sun's magnetic field changes during this cycle and eventually reverses polarity. This in itself is not unusual for a star - if not for the fact that the Schwab circulation is remarkably stable.
The Schwab cycle is covered by other, less prominent, fluctuations in activity ranging from a few hundred days to a few hundred years, and each of them is named after its discoverer. Although various attempts have been made to explain these cycles and mathematical calculations, there is still no comprehensive physical model.
For several years, Dr. Frank Stefani from the HZDR Institute for Flow Dynamics supported the "planetary hypothesis" because it is clear that the gravity of the planets exerts a tidal effect on the sun, similar to the effect of the moon on the earth. This effect is strongest every 11.07 years: when the three planets Venus, Earth and Jupiter are aligned with the Sun in a particularly prominent line, similar to tides and low tides with a maximal difference on the Earth at the new moon or full moon. It coincides prominently with the Schwab cycle.
The Sun's magnetic field is created by complex movements of the electrically conducting plasma within the Sun. "It can be compared to a huge dynamo. This solar dynamo creates an activity cycle of about 11 years on its own, but we think that the influence of the planets then intervenes in the operation of this dynamo, giving it a small push every now and then and thus imposing on the sun the unusually stable rhythm of 11.07 years", from Sapir Stefani.
A few years ago he and his colleagues discovered strong evidence for the existence of such a timed process in the existing observational data. They were also able to match different solar cycles and the movement of the planets only through mathematical methods. But at first it was impossible to explain the correlation satisfactorily from a physical point of view.
"Now we have found the underlying physical mechanism. We know how much energy is needed to synchronize the dynamo, and we know that this energy can be transmitted by Rossby waves. What's great is that now we can explain not only the Schwab cycle and longer solar cycles but also the shorter Rieger cycles that we didn't even think about before," says Stefani.
Rossby waves are eddy-shaped currents in the Sun similar to the large-scale wave motions in the Earth's atmosphere that dominate high and low pressure systems. The researchers calculated that the tidal forces during high tides with a maximum difference between each pair of the three planets Venus, Earth and Jupiter have the properties just right for triggering Rossby waves - an insight with many implications: First, these Rossby waves then attain speeds high enough to give the solar dynamo the driving force the necessary Second, it happens every 118, 193 and 299 days according to the observed Rieger cycles of the Sun. And third, all the additional solar cycles can be calculated on this basis.
This is where the math comes in: the merging of the three short Rieger cycles automatically creates the prominent Schwab cycle of 11.07 years. And the model even predicts long-term fluctuations of the sun because the movement of the sun around the center of gravity of the solar system causes a pulsation cycle of 193 years based on the Schwab cycle. This matches the order of magnitude of another observed cycle, the Sous-de-Pries cycle.
In this context, the scientists discovered an impressive correlation between the calculated 193-year cycle and periodic fluctuations in climate data. This is another strong argument in favor of the planets' hypothesis that "the sharp peak of Sousse-de-Paris after 193 years is almost impossible to explain without the stability of a show in the Schwab cycle, which is only in a timed process", Stefani estimates.
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