Observational Studies of Photonuclear Reactions Triggered by Lightning Discharges (Springer Theses)

Supervisor’s Foreword
Preface
Parts of this thesis have been published in the following journal articles:
Acknowledgements
Contents
About the Author
1 Introduction
	References
2 Observational and Theoretical Overview of High-Energy Atmospheric Physics
	2.1 Terrestrial Gamma-Ray Flash
		2.1.1 Gamma-Ray Observations with Space-Borne Detectors
		2.1.2 Radio-Frequency Observations of TGF-Associated Lightning Discharges
		2.1.3 Downward TGFs Observed at Ground Level
	2.2 Lightning-Associated X-Ray Emissions
	2.3 Gamma-Ray Glow
	2.4 Neutron Production in the Atmosphere
	2.5 Theories of Electron Acceleration in Thunderstorms
		2.5.1 Relativistic Runaway Electron Avalanche
		2.5.2 Relativistic Feedback Processes
		2.5.3 Thermal Runaway Process
		2.5.4 Modification of Spectra
	2.6 Basics of Neutron Physics
		2.6.1 Elastic Scattering
		2.6.2 Inelastic Scattering
		2.6.3 Neutron Capture
		2.6.4 Charged-Particle Production
	References
3 Instrumentation and Observation
	3.1 Winter Thunderstorms
	3.2 Detector Development
		3.2.1 Scintillation Crystals
		3.2.2 Data Acquisition System
		3.2.3 Compact Detectors
		3.2.4 Stationary Detectors in Kashiwazaki
	3.3 Detector Deployment
	3.4 Detector Calibration and Responses
	3.5 Monitoring Posts
	3.6 Radio-Frequency Measurement
	References
4 Photonuclear Reactions in Lightning
	4.1 Overview of Short Bursts in Two Winter Seasons
	4.2 Short-Burst Event 2 on 2017 February 6th
		4.2.1 Observational Results
		4.2.2 Scenarios to Produce Positrons
		4.2.3 Atmospheric Interactions of Neutrons
		4.2.4 Initial Flash Triggering Photonuclear Reactions
	4.3 Interpretation of All Detected Events
		4.3.1 Event 1
		4.3.2 Event 3
		4.3.3 Event Summary
	References
5 Positrons from Proton-Rich Radionuclides
	5.1 Channels of Photonuclear Reactions in the Atmosphere
	5.2 Monte-Carlo Simulations with Geant4
		5.2.1 Three-Stage Simulation
		5.2.2 Distribution of β+-Decay Nuclei
		5.2.3 Spacial Distribution and Energy Spectrum of Annihilation Emissions
		5.2.4 Comparison with Observation
	References
6 Atmospheric Reactions of Photoneutrons
	6.1 Monte-Carlo Simulations of Neutron Propagation
		6.1.1 Photoneutron Spectrum by Terrestrial Gamma-Ray Flashes
		6.1.2 Neutron Thermalization in the Ground
		6.1.3 Full Simulation of Photoneutrons in the Atmosphere
	6.2 Neutron Detection with GSO Scintillators
		6.2.1 Responses of GSO Scintillators to Thermal Neutrons
		6.2.2 Neutron Flux in Event 3
	6.3 Comparison Between Observations and Simulations
		6.3.1 Model Construction
		6.3.2 Fitting Results
	References
7 Downward Terrestrial Gamma-Ray Flash
	7.1 Verification of Dose Measurements with Monitoring Posts
	7.2 Monte-Carlo Simulation of Radiation Doses at the Ground
	7.3 Fitting of Radiation Doses at Multiple Monitoring Posts
	References
8 Discussions
	8.1 Properties of Downward TGFs
		8.1.1 Event 1
		8.1.2 Event 2
		8.1.3 Event 3
		8.1.4 Summary of Analysis
	8.2 Origin of Possible Systematic Uncertainties
	8.3 Comparison with Previous Upward and Downward TGFs
	8.4 Suggestions for Future Observations
	8.5 Radiation Exposures to Downward TGFs
	8.6 Isotope Production by Photonuclear Reactions
	References
9 Conclusion
Appendix A Wind Estimation with XRAIN
Appendix B Short-Burst Events in Kanazawa
Appendix C Cross Section Correction of Geant4
Appendix D Neutron Spectrum with JENDL/PD-2016
Appendix E Correlation Between TGFs and LF Pulses