Daniel Clarkson was poring over radio signals from the Parker Solar Probe when he noticed something strange—half of the solar radio bursts he studied didn’t follow the expected path outward from the Sun. Instead, their trajectories bent sharply, as if tugged by invisible hands. These bursts, known as interplanetary type III radio bursts, are produced by high-speed electrons racing along magnetic field lines, and their signals act like cosmic breadcrumbs, revealing the hidden structure of the solar wind. What Clarkson and his team discovered, published in The Astrophysical Journal, is that 50% of the 24 bursts analyzed showed clear signs of veering off course—evidence pointing to massive magnetic kinks in space known as switchbacks.
Switchbacks are sudden, large-scale reversals in the Sun’s magnetic field, first detected by the Parker Solar Probe in 2018. They appear as S-shaped bends in the magnetic field lines that stretch millions of kilometers into space. Until now, direct observations were limited to in-situ measurements. But Clarkson’s work shows these structures leave a distinct fingerprint in radio data, offering a new way to map them from afar. By analyzing the frequency drift of radio bursts—how their pitch changes over time—the team could trace the path of the electrons and infer the shape of the magnetic landscape they traveled through.
The data came from one week of observations by the Parker Solar Probe’s FIELDS instrument, which captures radio emissions in the inner heliosphere. When the researchers converted burst frequencies into distance from the Sun, they found 12 of the 24 bursts deviated from a radial path by more than 0.57 solar radii—the threshold for real disturbances, not instrument noise. On average, these deviations measured 1.1 solar radii, corresponding to magnetic field deflections between 23 and 88 degrees across regions spanning 1.8 to 6.4 solar radii. Four bursts even mirrored the exact patterns seen in simulations of electrons moving through switchbacks.
The implications are profound. For decades, type III bursts have been used to study solar electron acceleration and plasma conditions. Now, they’ve become remote probes of magnetic architecture in the inner solar system. This means scientists can begin reconstructing the Sun’s magnetic skeleton without needing spacecraft to fly through every twist and turn. As the Parker Solar Probe continues its record-breaking dives toward the Sun, these radio signatures could help predict how switchbacks influence solar wind turbulence and space weather.
“We’re seeing the Sun’s magnetic field in a whole new way,” says Clarkson. “These bursts aren’t just noise—they’re messages written in radio waves, telling us where the field bends, breaks, and flips. And we’re finally learning how to read them.”