The Path to Solar Weather Forecasts Is Paved with Drops in Cosmic Rays

Why It Matters

Accurate CME tracking protects satellites, astronauts and terrestrial power grids, reducing costly disruptions. Leveraging existing spacecraft instruments expands monitoring coverage without new hardware investments.

Key Takeaways

• Forbush decreases reveal CME structure via cosmic‑ray drops.
• Three spacecraft captured same 2022 CME from different angles.
• Repurposed health monitors became effective cosmic‑ray detectors.
• Multipoint data builds three‑dimensional CME evolution models.
• Continuous monitoring improves space‑weather forecasting reliability.

Pulse Analysis

Coronal mass ejections are massive bursts of plasma and magnetic field that can travel billions of kilometres, striking Earth’s magnetosphere and disrupting satellite operations, navigation systems, and even terrestrial power grids. Traditional space‑weather monitoring relies on a limited fleet of dedicated solar observatories, which often have narrow fields of view and finite mission lifespans. As the frequency of high‑impact CMEs rises with solar activity, the industry demands a more resilient, continuous observation network that can provide early warnings and detailed information about a storm’s trajectory and intensity.

The new study exploits the Forbush decrease—a temporary dip in galactic cosmic‑ray intensity caused by a CME’s magnetic shield—to track eruptions with unprecedented spatial resolution. In March 2022, ESA’s Solar Orbiter, JAXA‑ESA’s BepiColombo, and a near‑Earth probe were serendipitously aligned, allowing researchers to compare cosmic‑ray counts, magnetic field data, and solar‑wind parameters from three distinct vantage points. By calibrating a routine spacecraft health sensor on BepiColombo as a cosmic‑ray detector, the team demonstrated that even non‑science hardware can generate high‑quality space‑weather data.

Embedding this multipoint, repurposed‑instrument approach into the growing constellation of interplanetary probes could transform forecasting accuracy, giving operators of satellites, crewed missions, and ground‑based infrastructure more lead time to implement protective measures. The methodology also reduces reliance on costly, mission‑specific instruments, making continuous monitoring economically viable. As agencies plan new missions to the Sun‑Earth Lagrange points and beyond, integrating cosmic‑ray sensors into standard telemetry packages will likely become a best practice, ushering in a new era of proactive space‑weather resilience.