The Sun is governed by a strict rhythm. The Sun's magnetic activity exhibits cyclical changes, peaking approximately every 11 years. The speed of this rhythm is set by two giant plasma circulation rings – one in each hemisphere of the star. Near the surface, plasma flows carry field lines from the equator to the poles; At the depths of the Sun, plasma flows back toward the equator, forming a circulation that covers the entire hemisphere.
The important details of this “magnetic conveyor belt” are still not well understood. Precise processes at the Sun's poles may play an important role. From Earth, we see them passing by, at an angle; Most spacecraft have similar limitations.
“To understand the Sun's magnetic cycle, we lack knowledge about what happens at its poles. Solar orbiter Sami Solanki, director of the Max Planck Institute for Solar System Research (MPS), said it could provide that missing piece of the puzzle.
Since February 2020, this European Space Agency apparatus has been moving in elongated ellipses around our star. In March this year this is his first time leaves the plane where the planets and most other space probes orbit the Sun. From its 17-degree orbit, Solar Orbiter now has a better view of the star's polar regions.
In a new study in Astrophysical Journal Letters Analytical results from the polarimetric and helioseismic instrument (PHI) as well as the ultraviolet camera (EUI) on board Solar Orbiter. PHI data as of March 21 of this year; The EUI data cover the period from March 16 to 24. These measurements provide information about the direction of plasma flow and magnetic fields on the solar surface.
The information obtained reveals for the first time a more refined picture of the superparticle and the solar magnetic field network at the south pole. Superparticles are hot plasma cells two to three times the size of Earth that densely cover the Sun's surface. Their horizontal surface currents “wash” the magnetic field lines toward their edges, creating a magnetic field network – a strong magnetic field network.
To their surprise, the researchers found that the magnetic field was drifting toward the poles at an average speed of about 10 to 20 meters per second – almost as fast as at lower latitudes. Previous studies based on observations from the ecliptic plane have shown that the drift of the magnetic field closer to the poles is much slower. The movements of the superparticles provide important clues about the global circulation of plasma and magnetic fields on the Sun.
“The superparticles at the poles act as a kind of tracer,” said the head of the research team at the University of Chicago. “They make the polar component of the global solar cycle visible for the first time in 11 years.” MPS Lakshmi Pradeep Chitta, first author of the study.
It remains unclear whether the star's “magnetic conveyor belt” really does not slow down at the poles. The data obtained cover only a short period of the entire solar cycle. Furthermore, longer observation is required.
