The sun's magnetic field is a powerful force that can launch massive jets of plasma called coronal mass ejections (CMEs) into space. When these CMEs collide with Earth, they can disrupt power grids and damage satellites. Despite its significance, scientists still have much to learn about how magnetic fields are generated and amplified within the sun. However, a recent study published in Nature Astronomy has provided insights into this complex process, potentially aiding in the prediction of major solar events and allowing for better preparation time.
The generation of the sun's magnetism is attributed to the solar dynamo, which comprises two main components: the large-scale dynamo and the small-scale dynamo. Scientists have yet to fully model either of these components, and there is uncertainty regarding the existence and impact of a small-scale dynamo under the conditions found within the sun. Resolving this uncertainty is crucial because a small-scale dynamo could significantly influence solar dynamics.
To address this question, researchers from Aalto University and the Max Planck Institute for Solar System Research undertook extensive computer simulations using petascale supercomputers in Finland and Germany. The combined computational power allowed the team to simulate whether a small-scale dynamo could exist in the sun.
“By employing one of the most powerful computing simulations currently available, we have achieved the most realistic representation to date for modeling this dynamo,” explains Maarit Korpi-Lagg, the leader of the astroinformatics group and associate professor at Aalto University's Department of Computer Science. “Our findings demonstrate not only the feasibility of a small-scale dynamo but also its increased likelihood as our model more closely resembles the sun.”
Previous studies had suggested that the conditions found in stars like the sun, characterized by a very low magnetic Prandtl number (PrM), might not support a small-scale dynamo. The magnetic Prandtl number is a measure used in fluid and plasma physics to compare the rate at which variations in the magnetic field and velocities even out. Korpi-Lagg's research team modeled turbulence conditions with remarkably low PrM values and discovered that, contrary to previous beliefs, a small-scale dynamo can indeed occur under such conditions.
“This finding represents a significant advancement in understanding magnetic field generation in the sun and other stars,” states Jörn Warnecke, a senior postdoctoral researcher at MPS. “It brings us closer to unraveling the mystery of CME formation, which is crucial for developing protective measures against hazardous space weather for Earth.”
The research group is currently expanding their study to investigate even lower magnetic Prandtl number values using GPU-accelerated code on the state-of-the-art pan-European pre-exascale supercomputer, LUMI. Additionally, they plan to explore the interaction between the small-scale dynamo and the large-scale dynamo, which drives the 11-year solar cycle.
Source: Aalto University