New insights into the Sun's corona emerge from the first successful detailed magnetic field measurements – crucial for understanding solar eruptions

Peking University team achieves milestone in solar physics by mapping the coronal magnetic field

News By Efosa Udinmwen published 17 October 2024

The Sun’s corona, its outermost atmospheric layer, holds the key to understanding solar activity, including phenomena like solar flares and space weather events. For decades, scientists have grappled with the challenge of measuring the Sun’s coronal magnetic field, as this field drives much of the energy that leads to solar eruptions.

Now, in a groundbreaking achievement, Professor Tian Hui's research team from Peking University, in collaboration with international experts, has made the first conventional measurements of the global coronal magnetic field. Their findings, published in the journal Science (Volume 386, No 6717), offer new insights into the Sun’s magnetic activity over a period of eight months.

The Sun’s magnetic field is responsible for storing and releasing energy, which heats the plasma in the corona and triggers solar eruptions. These eruptions, in turn, can have significant impacts on space weather, potentially affecting satellite operations, GPS systems, and even human spaceflight. However, due to the relatively weak nature of the coronal magnetic field compared to the magnetic field on the Sun’s surface (the photosphere), measuring this field has proven to be a significant challenge.

The importance of coronal magnetic field measurements

As the Sun rotates, there are variations in the magnetic fields and the ability to regularly monitor the Sun’s coronal magnetic field will improve our understanding of solar eruptions and help protect high-tech systems on Earth and in space.

Over the years, there have been routine measurements of the photospheric magnetic field, but the coronal field has remained elusive. This limitation has impeded scientists' ability to fully understand the three-dimensional magnetic field structure and the dynamic processes that occur in the Sun’s atmosphere.

In 2020, Tian Hui's team developed a method called “two-dimensional coronal shocks,” which enabled the first measurements of the global distribution of the coronal magnetic field. This was a major milestone, marking a crucial step towards the goal of routine coronal magnetic field measurements.

More recently, Tian's team refined this method further, allowing them to track magnetohydrodynamic shear waves in the corona with greater precision. This made it possible to diagnose the distribution of coronal density and, as a result, determine both the strength and direction of the magnetic field.

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