New Perspectives on the Solar Corona Revealed with the First Detailed Measurements of the Magnetic Field, Essential for Understanding Solar Eruptions.

The study of the solar coronal magnetic field, its outer atmospheric layer, is crucial for understanding solar activity, which includes phenomena such as solar flares and space weather-related events. For years, scientists have faced the challenge of measuring this magnetic field, which drives much of the energy behind solar explosions.

Researchers led by Professor Tian Hui from Peking University, in collaboration with international experts, have achieved the first conventional measurements of the global coronal magnetic field. These results, published in an academic paper, provide new insights into the Sun's magnetic activity over an eight-month period.

The Sun's magnetic field acts as a reservoir of energy, which, when released, heats the plasma in the corona and causes solar flares. These flares can have significant impacts on space weather, affecting satellite operations, GPS systems, and even crewed space flights. However, the relatively weak nature of the coronal magnetic field compared to that of the solar surface has made its measurement difficult.

The ability to regularly monitor the coronal magnetic field will be key to enhancing our understanding of solar flares and protecting technological systems both on Earth and in space. Although routine measurements of the magnetic field in the photosphere have been carried out, the coronal field has largely remained unexplored, thus limiting the understanding of the three-dimensional structure of the magnetic field and dynamic processes in the solar atmosphere.

In 2020, Tian Hui's team developed a method called "two-dimensional coronal shocks," facilitating the first measurements of the global distribution of the coronal magnetic field. More recently, they refined this technique, allowing more accurate tracking of magnetohydrodynamic cut waves in the corona, which facilitated the diagnosis of coronal density and the determination of magnetic field intensity and direction.

Using the Enhanced Coronal Multi-Channel Polarimeter (UCoMP), the research team conducted detailed observations of the solar corona from February to October 2022, collecting a total of 114 magnetograms. This allowed them to study how the coronal magnetic field evolves at different altitudes and latitudes over multiple solar rotations. The results showed that the magnetic field intensity varied between 1.05 and 1.60 solar radii, with values ranging from less than 1 gauss to approximately 20 gauss.

With this data, they were able to create a global map of the magnetic field intensity in the solar corona, revealing its temporal and regional evolution. When comparing these findings with more advanced global coronal models, they noted that their measurements closely aligned with predictions in mid- and low-latitude regions, although greater discrepancies existed in high-latitude areas and active regions of the Sun.

These discoveries are fundamental for improving current models of solar magnetic activity and understanding the dynamics of solar flares. According to the lead author, these observations lay a crucial foundation for refining coronal models, which could lead to more accurate predictions of solar flares and their potential impacts on Earth's space environment.

This study represents a shift in solar physics, marking the beginning of a new era in the routine measurement of the coronal magnetic field. Tian Hui notes that this achievement is just the start, as the next goal is to develop techniques that allow for the measurement of the entire coronal magnetic field, including the solar disk. Achieving this will require the integration of other measurement methods and tools, which is a critical objective for the scientific community in the coming decades.