Astronomers have made a significant advancement in solar physics by creating precise maps of the magnetic fields in the Sun’s corona. This important development is set to improve our comprehension of the Sun’s atmosphere and how its variations influence our technology-based society on Earth. The corona, which is the outer layer of the Sun’s atmosphere, plays a key role in governing solar winds and space weather events such as solar flares and coronal mass ejections. However, quantifying the magnetic forces that drive these phenomena and the corona itself has proven to be quite difficult.
The U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope, the strongest solar telescope globally, developed, constructed, and operated by the NSF National Solar Observatory (NSO), has made a groundbreaking achievement in solar physics by directly mapping the strength of the magnetic field in the solar corona, which is the Sun’s outer atmosphere visible during a total eclipse. This milestone enhances our grasp of space weather and its repercussions for our technology-reliant world.
The Corona: The Source of Space Weather
The Sun’s magnetic field creates regions within its atmosphere, often connected to sunspots, that contain immense energy responsible for explosive solar storms and space weather. The corona, the outer atmosphere of the Sun, is superheated and where these magnetic enigmas occur. Understanding and predicting space weather necessitates mapping the coronal magnetic fields, which is essential for safeguarding our technologies both on Earth and in space.
Why It’s Important
The magnetic field of Earth provides protection from solar winds, shielding our atmosphere and enabling life as we know it. However, the electromagnetic fields and energetic particles released during intense solar eruptions can interfere with satellites, power grids, and other essential systems in our increasingly technology-centered society. Comprehending these dynamic interactions, which can change over periods from days to centuries, is vital for ensuring the protection of our infrastructure and lifestyle.
For a long time, astronomers have faced the challenge of measuring the magnetic properties of the corona due to technological limits. The Inouye Solar Telescope, now the most advanced facility dedicated to studying the corona, has taken a significant step forward by producing its first maps of the coronal magnetic field — the most detailed we’ve seen so far.
The Inouye Solar Telescope’s Initial Maps of the Corona’s Magnetic Field
Since the 1950s, research in solar physics has included mapping magnetic fields on the Sun’s surface, providing important data. However, mapping the magnetic fields above the surface, particularly in the corona — the origin of solar storms — has been a long-desired goal. The Inouye, situated near the peak of Hawaii’s Haleakalā, now offers the capabilities necessary to fulfill this critical need.
The Inouye has created its first detailed maps of the solar corona’s magnetic fields using the Zeeman Effect, a technique that assesses magnetic properties through the observation of spectral line splitting. Spectral lines, which appear at unique wavelengths in the electromagnetic spectrum, indicate the light absorbed or emitted by atoms or molecules. These distinctive lines serve as “fingerprints” that reveal the chemical makeup and physical characteristics of celestial entities. When these lines come into contact with a magnetic field, like the Sun’s, they split, providing insights into the object’s magnetic characteristics. Earlier efforts to detect these signals, the last of which were reported two decades ago (Lin et al. 2004), did not possess the detail or consistency necessary for extensive scientific research. Today, the Inouye’s unparalleled capabilities permit detailed and organized studies of these vital signals.
A Technological Wonder
Generally, the Sun’s corona, which is a million times dimmer than the solar disk, can only be viewed during a total solar eclipse, when most of the Sun’s light is obscured, plunging Earth into darkness. The Inouye, however, utilizes a method called coronagraphy to simulate artificial eclipses, allowing it to detect extremely faint polarized signals — a billion times fainter than the solar disk — showcasing its exceptional sensitivity and establishing its role as a unique portal to our home star.
The Inouye accomplishes this through its Cryogenic Near-Infrared Spectropolarimeter (Cryo-NIRSP), one of the primary instruments designed to analyze the corona and map its magnetic fields, developed by the University of Hawaii’s Institute for Astronomy.
Looking Ahead
This achievement heralds a new epoch in solar physics. The Inouye’s ability to map the Sun’s coronal magnetic fields reinforces its goals and opens up new avenues for comprehending the Sun’s effect on space weather.
“Just like detailed maps of Earth’s surface and atmosphere have improved weather forecasting, this exceptionally comprehensive map of the Sun’s corona magnetic fields will enhance our ability to forecast solar storms and space weather,” says Dr. Carrie Black, NSF program director for the NSO. “These invisible yet immensely powerful forces illustrated in this map will propel solar physics for the next century and beyond.”
Christoph Keller, director of the NSO, states that “Mapping the magnetism in the corona constitutes a fundamental breakthrough not only for solar science but for astronomy as a whole.” He believes, “This marks the beginning of a new era where we will comprehend how the magnetic fields of stars influence planets, both in our solar system and in the thousands of exoplanetary systems we have discovered.”
Ongoing and future studies will refine diagnostic tools and methods, yielding deeper insights into the Sun’s magnetic landscape and its effects on Earth and our solar system.
