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Virtually all space probes that explore the sun from space view our star from the ecliptic. This is the plane in which the planets orbit the sun. Although this plane is slightly tilted relative to the sun's equator, the angle of about 7° is not enough to catch a clear view of our star's poles. Solar telescopes on Earth naturally have the same limited perspective.

Only Ulysses, a joint mission of the European and American space agencies ESA and NASA, flew over the sun's poles several times between 1990 and 2009, albeit from a much greater distance than Solar Orbiter and without imaging instruments on board. The sun's poles are of particular interest to researchers. The processes taking place there are likely to play a decisive role in the sun's activity cycle.

The sun's 'internal clock'

The sun is subject to an approximately 11-year cycle. Roughly every 11 years, it reaches its activity peak. During this period, as in recent months and currently, it is particularly active. Violent bursts of radiation and particles often occur during this time. In recent months, some of these have triggered impressive auroras that were visible even in central and southern Europe. In addition, many dark sunspots, areas with particularly high magnetic field strength, appear on the sun's visible surface during this period.

Between peaks of activity, the sun comes to rest: Eruptions occur seldomly, and sunspots often remain completely absent for several months at a time. The basis of the solar cycle, our star's "internal clock," is not yet understood. Researchers suspect that the crucial puzzle piece missing for a deeper understanding lies at the poles. Finding this piece of the puzzle is one of the most important mission objectives of the Solar Orbiter.

To this end, the probe used the momentum from its flyby of Venus on February 18 this year to leave the ecliptic. About a month later, on March 22, the probe looked at the sun from an angle of 17° for the first time. "We didn't know what exactly to expect from these first observations. The sun's poles are literally terra incognita," says Sami Solanki, director at the Max Planck Institute for Solar System Research (MPS) in Göttingen (Germany) and Principal Investigator of Solar Orbiter's Polarimetric and Helioseismic Imager (PHI).

A look at the surface, magnetic field, and corona

The images published today were taken on March 16 and 17 of this year, a few days before reaching the highest deflection from the ecliptic, from an angle of 15°. In addition to PHI, the Extreme Ultraviolet Imager (EUI) and the instrument Spectral Imaging of the Coronal Environment (SPICE) instruments also captured unique images. The MPS contributed sub-instruments and hardware components to EUI and SPICE; the PHI was developed under the leadership of the MPS.

While PHI captures the visible light of the sun and thus images the sun's surface and its magnetic field there, EUI and SPICE look at the higher layers of the sun up to the hot solar corona. The images from these instruments can help understand how the sun manages to fling the particles of the solar wind into space.

The images from PHI show the magnetic field at the solar south pole in a state of turmoil. In general, the sun's magnetic field is much more complex than that of Earth. Many small, variable, and highly complex magnetic structures, which occur in connection with sunspots or at the poles, generate the sun's large-scale, global magnetic field. During much of the solar cycle it resembles that of a bar magnet, with the poles of the sun roughly corresponding to the magnetic poles.

The global magnetic field reverses its polarity during the sun's maximum activity, approximately every 11 years. The small magnetic structures at the poles are likely to play an important role in this process.

Solar magnetic field in turmoil

Researchers expect the magnetic field at the poles to change significantly during the solar cycle. While one magnetic polarity is likely to predominate there during the minimum activity phase, the magnetic field should be significantly more complex during the maximum. This is confirmed by the latest observations. At the south pole, observational data from PHI reveal an intricate jumble of small areas with different polarities.

"Solar Orbiter has taken up its new observation position at exactly the right time," says MPS scientist and PHI operations scientist Johann Hirzberger. "PHI was able to map the magnetic field at the South Pole at a key moment," he adds. The team is now eager to follow the restructuring of the polar magnetic field over the coming months and years. Current forecasts indicate that solar activity will decrease slightly from its current high level.

By the end of 2026, Solar Orbiter will be able to observe the north and south poles of the sun three more times from an angle of 17°. Another flyby of Venus on December 24, 2026, will further tilt the probe's orbit to an angle of 23°, providing an even better view of the poles.