Nav: Home

The sun follows the rhythm of the planets

May 27, 2019

One of the big questions in solar physics is why the Sun's activity follows a regular cycle of 11 years. Researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), an independent German research institute, now present new findings, indicating that the tidal forces of Venus, Earth and Jupiter influence the solar magnetic field, thus governing the solar cycle. The team of researchers present their findings in the journal Solar Physics (10.1007/s11207-019-1447-1).

In principle, it is not unusual for the magnetic activity of a star like the Sun to undergo cyclic oscillation. And yet past models have been unable to adequately explain the very regular cycle of the sun. The HZDR research team has now succeeded in demonstrating that the planetary tidal forces on the Sun act like an outer clock, and are the decisive factor behind its steady rhythm. To accomplish this result, the scientists systematically compared historical observations of solar activity from the last thousand years with planetary constellations, statistically proving that the two phenomena are linked. "There is an astonishingly high level of concordance: what we see is complete parallelism with the planets over the course of 90 cycles," enthused Frank Stefani, lead author of the study. "Everything points to a clocked process."

As with the gravitational pull of the Moon causing tides on Earth, planets are able to displace the hot plasma on the Sun's surface. Tidal forces are strongest when there is maximum Venus-Earth-Jupiter alignment; a constellation that occurs every 11.07 years. But the effect is too weak to significantly perturb the flow in the solar interior, which is why the temporal coincidence was long neglected. However, the HZDR researchers then found evidence of a potential indirect mechanism that may be able to influence the solar magnetic field via tidal forces: oscillations in the Tayler instability, a physical effect that, from a certain current, can change the behavior of a conductive liquid or of a plasma. Building on this concept, the scientists developed their first model in 2016; they have since advanced this model in their new study to present a more realistic scenario.

Small trigger with a major impact: tides utilize instability

In the hot plasma of the Sun, the Tayler instability perturbs the flux and the magnetic field, itself reacting very sensitively to tiny forces. A small thrust of energy is enough for the perturbations to oscillate between right-handed and left-handed helicity (the projection of the spin onto the direction of momentum). The momentum required for this may be induced by planetary tidal forces every eleven years - ultimately also setting the rhythm at which the magnetic field reverses the polarity of the Sun.

"When I first read about ideas linking the solar dynamo to planets, I was very skeptical," Stefani recalled. "But when we discovered the current-driven Tayler instability undergoing helicity oscillations in our computer simulations, I asked myself: What would happen if the plasma was impacted on by a small, tidal-like perturbation? The result was phenomenal. The oscillation was really excited and became synchronized with the timing of the external perturbation."

Solar dynamo with an added touch

In the standard scenario of a dynamo, the rotation of the Sun and the complex motion of the solar plasma create a cyclically changing magnetic field. Two effects interact here: the plasma rotates more quickly at the Sun's equator than at the poles. This leads to the omega effect: the magnetic field lines frozen in the plasma stretch around the Sun and convert the magnetic field into a field aligned almost parallel to the Sun's equator. The alpha effect describes a mechanism that twists magnetic field lines, forcing the magnetic field back into a north-south direction.

What exactly causes the alpha effect, however, is a subject of dispute. Stefani's model indicates that the Tayler instability is partly responsible for this. The researchers consider the most plausible scenario to be one in which a classic solar dynamo is combined with the modulations excited by the planets. "Then the Sun would be a completely ordinary, older star whose dynamo cycle, however, is synchronized by the tides," summarized Stefani. "The great thing about our new model is that we are now easily able to explain effects that were previously difficult to model, such as 'false' helicities, as observed with sunspots, or the well-known double peak in the Sun's activity curve."

Besides influencing the 11-year cycle, planetary tidal forces may also have other effects on the Sun. For example, it is also conceivable that they change the stratification of the plasma in the transition region between the interior radiative zone and the outer convection zone of the Sun (the tachocline) in such a way that the magnetic flux can be conducted more easily. Under those conditions, the magnitude of activity cycles could also be changed, as was once the case with the Maunder Minimum, when there was a strong decline in solar activity for a longer phase.

In the long term, a more precise model of the solar dynamo would help scientists to quantify climate-relevant processes such as space weather more effectively, and perhaps even to improve climate predictions one day. The new model calculations also mean that, besides tidal forces, potentially other, hitherto neglected mechanisms would have to be integrated into the solar dynamo theory, mechanisms with weak forces that can nevertheless - as researchers now know - have a major impact. To be able to investigate this fundamental question in the laboratory, too, the researchers are currently setting up a new liquid metal experiment at HZDR.
-end-
Publication: F. Stefani, A. Giesecke, T. Weier: A model of a tidally synchronized solar dynamo, in Solar Physics, 2019, DOI: 10.1038/s41467-019-09071-7

More information:
Dr. Frank Stefani
Institute of Fluid Dynamics at HZDR
Phone +49 351 260-3069| E-Mail: f.stefani@hzdr.de

Media contact:
Dr. Christine Bohnet | Press officer and head of HZDR communications group
Phone +49 351 260-2450 | E-Mail: c.bohnet@hzdr.de
Helmholtz-Zentrum Dresden-Rossendorf | Bautzner Landstr. 400 | 01328 Dresden / Germany | http://www.hzdr.de

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs - as an independent German research center - research in the fields of energy, health, and matter. We focus on answering the following questions:
  • How can energy and resources be utilized in an efficient, safe, and sustainable way?
  • How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
  • How do matter and materials behave under the influence of strong fields and in smallest dimensions?
To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the High-Magnetic Field Laboratory Dresden, and the ELBE Center for High-Power Radiation Sources.

HZDR is a member of the Helmholtz Association and has five sites (Dresden, Freiberg, Grenoble, Leipzig, Schenefeld near Hamburg) with almost 1,200 members of staff, of whom about 500 are scientists, including 150 Ph.D. candidates.

Helmholtz-Zentrum Dresden-Rossendorf

Related Magnetic Field Articles:

Global magnetic field of the solar corona measured for the first time
An international team led by Professor Tian Hui from Peking University has recently measured the global magnetic field of the solar corona for the first time.
Magnetic field of a spiral galaxy
A new image from the VLA dramatically reveals the extended magnetic field of a spiral galaxy seen edge-on from Earth.
How does Earth sustain its magnetic field?
Life as we know it could not exist without Earth's magnetic field and its ability to deflect dangerous ionizing particles.
Scholes finds novel magnetic field effect in diamagnetic molecules
The Princeton University Department of Chemistry publishes research this week proving that an applied magnetic field will interact with the electronic structure of weakly magnetic, or diamagnetic, molecules to induce a magnetic-field effect that, to their knowledge, has never before been documented.
Origins of Earth's magnetic field remain a mystery
The existence of a magnetic field beyond 3.5 billion years ago is still up for debate.
New research provides evidence of strong early magnetic field around Earth
New research from the University of Rochester provides evidence that the magnetic field that first formed around Earth was even stronger than scientists previously believed.
Massive photons in an artificial magnetic field
An international research collaboration from Poland, the UK and Russia has created a two-dimensional system -- a thin optical cavity filled with liquid crystal -- in which they trapped photons.
Adhesive which debonds in magnetic field could reduce landfill waste
Researchers at the University of Sussex have developed a glue which can unstick when placed in a magnetic field, meaning products otherwise destined for landfill, could now be dismantled and recycled at the end of their life.
Earth's last magnetic field reversal took far longer than once thought
Every several hundred thousand years or so, Earth's magnetic field dramatically shifts and reverses its polarity.
A new rare metals alloy can change shape in the magnetic field
Scientists developed multifunctional metal alloys that emit and absorb heat at the same time and change their size and volume under the influence of a magnetic field.
More Magnetic Field News and Magnetic Field Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.