My muon detector, and a number of other people’s around the world, has shown significant dip in muon detector on 20 January 2026. A CME hit the atmosphere of Earth on 19 January 2026. Are the two related?

Dip in Muons detected on the UKRAA PicoMuon detector at LRO 20/1/2026:

Yes — they’re very likely related. Here’s why:

📡 What happened on 19–20 January 2026

• A full-halo coronal mass ejection (CME) associated with an X1.9 solar flare on 18 January 2026 hit Earth on 19 January. This triggered a severe (G4) geomagnetic storm and elevated radiation conditions that persisted into 20 January.

🌍 How CMEs affect cosmic rays and muon detectors

Cosmic rays reaching Earth are mostly high-energy galactic particles. When intense solar activity drives large CMEs and associated magnetic disturbances into interplanetary space, those structures modify the local magnetic field environment through which galactic cosmic rays travel. Two key effects occur:

1. Forbush decreases — A transient drop in observed cosmic ray (and hence muon) flux when a CME’s magnetic field and shock front sweep past Earth and shield or scatter incoming galactic cosmic rays. These decreases are widely observed in neutron monitor, muon telescope, and similar detector networks.
2. Ground Level Enhancements (GLEs) — Sometimes an increase in counts due to high-energy solar particles, but such enhancements depend on the energy and directionality of the solar event. GLEs were not reported for this event, and instead the dominant signature was the decrease.

🧪 Why your muon detector dip matches

The timing of the dip (20 January) aligns well with the CME’s arrival and geomagnetic disturbance. During the passage of the CME’s magnetic cloud and shock structure, the effective galactic cosmic ray flux at Earth’s atmosphere was temporarily reduced — this is exactly the Forbush decrease phenomenon seen in global cosmic-ray networks, including both neutron and muon channels.

In other words:

• The CME disturbed the heliospheric magnetic field.
• This disturbance acted as a barrier/modulator to galactic cosmic rays.
• Muon detectors (sensitive to secondary cosmic rays produced in the atmosphere) registered a significant dip as a consequence.

So, yes — the observed muon rate drop on 20 January is consistent with the effects established by space weather science for strong CMEs and geomagnetic storms.