University of Groningen
Atmospheric electric fields during thunderstorm conditions measured by LOFAR
Trinh, Thi Ngoc Gia
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Publication date: 2018
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Trinh, T. N. G. (2018). Atmospheric electric fields during thunderstorm conditions measured by LOFAR. University of Groningen.
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ISBN (printed version): 978-94-034-0815-6 ISBN (electronic version): 978-94-034-0816-3
Cover: An air shower develops through a thundercloud and reaches the LOFAR ‘Superterp’. Pictures are taken from Ref. [1] and Ref. [2].
Atmospheric electric fields during thunderstorm
conditions measured by LOFAR
PhD thesis
to obtain the degree of PhD at the University of Groningen
on the authority of the Rector Magnificus Prof. E. Sterken
and in accordance with the decision by the College of Deans. This thesis will be defended in public on
Monday 9 July 2018 at 11.00 hours
by
Thi Ngoc Gia Trinh born on April 30, 1986
Supervisors Prof. O. Scholten Prof. A. M. van den Berg Prof. U. Ebert
Assessment committee Prof. J. Dwyer
Prof. T. Huege
Table of contents
1 Introduction 1
1.1 Cosmic rays . . . 1
1.2 Extensive air showers . . . 2
1.3 Radio emission from air showers in fair weather . . . 5
1.4 LOFAR, LORA and data analysis . . . 7
1.4.1 LOFAR - The Low Frequency Array . . . 7
1.4.2 LORA - The LOFAR Radbound Air Shower Array . . . 8
1.4.3 Data analysis . . . 9
1.5 Thunderstorm charge structure and cloud electrification . . . 10
1.5.1 Thunderstorm charge structure . . . 10
1.5.2 Cloud electrification . . . 11
1.6 This thesis . . . 13
1.6.1 Radio emission from air showers in thunderstorm conditions 14 1.6.2 Measurements at LOFAR and the method to probe electric fields during thunderstorm conditions . . . 16
1.6.3 Full analysis . . . 18
2 Influence of atmospheric electric fields on the radio emission from ex-tensive air showers 19 2.1 Introduction . . . 20
2.2 Radio emission simulations . . . 23
2.2.1 Parallel electric field . . . 27
Table of contents
2.3 Interpretation . . . 30
2.3.1 Energy-loss time of electrons . . . 32
2.3.2 Trailing distance . . . 34
2.3.3 Influence of E∥ . . . 36
2.3.4 Influence of E⊥ . . . 43
2.3.5 Effects of electric fields in the low-frequency domain . . . . 49
2.3.6 Adapting distance of the effects of E-fields . . . 52
2.4 Conclusion . . . 54
Appendix 2.A CORSIKA . . . 55
3 Probing atmospheric electric fields in thunderstorms through radio emis-sion from cosmic-ray induced air showers 57 4 Thunderstorm electric fields probed by extensive air showers through their polarized radio emission 65 4.1 Introduction . . . 66
4.2 LOFAR and data analysis . . . 67
4.3 Modeling . . . 71
4.4 Probing the structures of atmospheric electric fields . . . 76
4.5 Conclusion . . . 84
5 Electric fields in thunderstorms measured by LOFAR 85 5.1 Introduction . . . 86
5.2 LOFAR and data analysis . . . 88
5.3 Reconstruction technique . . . 90
5.4 Electric field determination . . . 95
5.5 Discussion . . . 101
5.5.1 Charge structure . . . 101
5.5.2 Electric fields . . . 105
5.5.3 Tomography of electric fields . . . 105
5.5.4 Tomography of events 1, 2, and 3 . . . 108
5.5.5 Tomography of events 6, 7, and 8 . . . 110
5.5.6 Comparison with lightning location data . . . 110
5.6 Conclusion . . . 111 vi
Table of contents Appendix 5.A . . . 112 5.A.1 December 14th, 2011 . . . 112 Appendix 5.B April 26th, 2012 . . . 119 Appendix 5.C July 28th, 2012 . . . 122 Appendix 5.D August 26th, 2012 . . . 125
Appendix 5.E December 30th, 2012 . . . 132
Appendix 5.F July 26th, 2013 . . . 135
Appendix 5.G June 27th, 2014 . . . 138
6 Outlook 141
References 145
