The observation of Ground Level Enhancement GLE 77 by the neutron detectors of the Experimental Complex NEVOD
On November 11, 2025, the Experimental Complex NEVOD's neutron detectors, originally designed for extensive air shower studies but recently modernized with additional flux measurement channels, recorded Ground Level Enhancement event GLE 77, marking the first time such an event was captured by this specific type of detector array.
Original paper dedicated to the public domain under CC0 1.0 (http://creativecommons.org/publicdomain/zero/1.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
🌟 The Big Picture: Catching a Solar "Super-Blast"
Imagine the Sun as a giant, sometimes grumpy, campfire. Usually, it just crackles and pops. But every now and then, it lets out a massive, violent sneeze—a Solar Flare. When this happens, it shoots a huge cloud of invisible, high-speed particles (mostly protons) toward Earth.
When these particles hit our atmosphere, they crash into air molecules and create a "shower" of secondary particles, including neutrons. These neutrons rain down to the ground, and when they hit our detectors, they cause a spike in the numbers we see. This spike is called a Ground Level Enhancement (GLE).
GLE #77 was a particularly loud sneeze from the Sun that happened on November 11, 2025.
🏗️ The Unlikely Detectives: The NEVOD Lab
Usually, scientists use special, giant "weather stations" (called Neutron Monitors) to catch these solar sneezes. But this paper is about a different kind of team.
The NEVOD Experimental Complex in Moscow is primarily a giant underwater lab designed to study Extensive Air Showers (EAS). Think of it like a giant net cast in the sky (and underground) to catch the debris of cosmic rays.
- The Old Setup: For years, this lab was like a camera set to "Night Mode." It was great at seeing the big, bright flashes of cosmic rays, but it wasn't tuned to count the tiny, individual "dust motes" (neutrons) floating around.
- The Upgrade: In 2024, the scientists gave the lab a software and hardware makeover. They added new "ears" to listen specifically to the neutron chatter. They turned the lab from a "Night Mode" camera into a "High-Speed Counter."
🚨 The Big Moment: November 11, 2025
At 10:15 AM (Universal Time), the Sun unleashed an X5.1 class flare. This is like a Category 5 hurricane of radiation.
- The Arrival: About 20 minutes later, the "sneezed" particles hit Earth's atmosphere.
- The Detection: The two main detector arrays at NEVOD—PRISMA-36 (located inside the building) and URAN (located on the roof)—suddenly went wild.
- PRISMA-36 saw its particle count jump by about 20%.
- URAN saw an even bigger jump, about 25%.
It was the first time this specific type of lab (designed for air showers) successfully caught a GLE event. It's like a fire department that usually puts out forest fires suddenly using its hoses to successfully put out a house fire, proving they can handle both.
🔍 How They Knew It Was Neutrons
You might ask, "How do you know it wasn't just random noise or a glitch?"
The scientists used a clever trick called Pulse-Shape Discrimination.
- The Analogy: Imagine you are in a dark room and you hear a sound.
- A charged particle (like a regular cosmic ray) is like a sharp, quick click (like a twig snapping).
- A neutron is like a slower, heavier thud (like a bowling ball dropping).
- Because the detectors are sensitive to the "shape" of the electrical signal, they could ignore the "clicks" and only count the "thuds." This confirmed that the spike was indeed caused by neutrons from the Sun.
📊 The Results: A Perfect Match
The scientists compared their new data with the "gold standard" station nearby (the Moscow Neutron Monitor).
- The Verdict: The graphs looked almost identical. The timing, the shape of the spike, and the size of the jump matched perfectly.
- The Classification: Based on how sharp and narrow the spike was, they classified this as a "Classic (Narrow) GLE." It was a quick, intense burst, not a long, drawn-out drizzle.
🚀 Why This Matters
This paper is a big deal for two reasons:
- New Tools for Old Jobs: It proves that the NEVOD lab, with its 108 detectors spread over a large area, is now a fully capable "Solar Weather Station." They can now monitor solar storms just as well as the dedicated global network.
- A New Network Member: Because they have so many detectors working together, they are now a strong candidate to join the Global Neutron Monitor Network. This means scientists around the world will have one more reliable pair of eyes watching the Sun, helping us predict space weather that could affect satellites and power grids.
In short: The Sun sneezed, and a lab that usually studies cosmic rainbows successfully caught the sneeze, proving they are ready to join the global team of solar watchers.
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