Role in RTL3D
Three monitor sites record gamma dose rate and energy spectra during storms across the Straits of Malacca network. Data complement electric-field mills and LF/VHF imaging when validating thundercloud electrification.
What is observed?
Thunderstorm ground enhancements (TGE) — short-lived gamma-ray bursts from relativistic electrons. Radon progeny radiation — longer-lived low-energy gamma from uplifted aerosols in strong near-surface fields.
Why it matters
Enhanced electron and photon fluxes in thunderstorm electric fields may contribute to air ionization, conductivity growth, and lightning initiation — a key research thread from Japan’s winter-thunderstorm studies to tropical Malaysia.
Physical processes
From winter TGE discoveries to radon–field coupling — four concepts explained.
Monitoring characteristics
- Network sites
- 3 monitors
- Detector type
- NaI / scintillation
- TGE duration
- Seconds–minutes
- High-energy γ
- Up to several MeV
- Radon daughters
- ²¹⁴Pb, ²¹⁴Bi
- Rn decay tail
- ~20–90 min
- Coupled sensors
- E-field, LF
- Winter TGE dose
- Up to ~0.1 mGy
- Field threshold
- Strong NSEF
- Lightning link
- Often terminates TGE
Key research & references
- Torii, Takeishi & Hosono (2002) — gamma-ray dose increases up to ~0.1 mGy during winter thunderstorms in Japan; continuous spectrum to several MeV consistent with bremsstrahlung from energetic electrons (J. Geophys. Res., doi:10.1029/2001JD000938).
- Torii et al. (2005) — Monte Carlo study showing electron and photon fluxes increase greatly where field strength exceeds ~280 P(z) kV/m; cosmic-ray muon secondary electrons are a key source; radon-progeny beta/gamma also discussed.
- TGE bursts often precede or coincide with lightning; a return stroke can abruptly terminate the high-energy component while radon-derived low-energy gamma may persist for hours after the near-surface field relaxes.