Inaug.-diss.--Göttiagen. / Lebenslauf. Folds of table numbered as p. 13-16. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 122-125).

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy / The work presented in this thesis extends and contributes to research in the field of lightning injury mechanisms. Six mechanisms have been described in the literature about lightning injury. This thesis takes an in-depth look at the sixth injury mechanism. The sixth mechanism may be thought of as a ‘pressure-shock wave’ which is directly proportional to the current of the lightning discharge, and which is present immediately surrounding lightning’s luminous channel. A literature review, case studies and two novel experiments helped confirm the sixth mechanism’s existence. The medical data and the lightning data were then aligned. Two main questions were addressed, namely within what range is a human at risk; and what is the risk of lightning’s pressure shock wave. This ‘pressure-shock wave’ may explain some of the more curious lightning injury patterns seen on lightning-strike victims. Knowledge and insight into the sixth mechanism may have direct and indirect applications to those working in the fields of lightning injury and lightning protection. This thesis represents a contribution to the literature in both medicine and engineering.

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The Maxwell current density (J(s)), electric field (E), and positive and negative air conductivities were measured simultaneously under several thunderstorms at the NASA Kennedy Space Center (KSC), Florida, during the summer of 1981. The components of J(m) include displacement current as well as field-dependent (J(s)) and convection (J(c)) currents. The measurements under active storms show that: (a) J(m) is usually dominated by displacement currents when E is close to zero, (b) J(m) is steady with time in the intervals between lightning discharges, (c) J(m) is usually not altered significantly by lightning, and (d) the average values of J(m) change slowly over time scales that are comparable to those required for storm development. Field-mill data have been used to derive estimates of the time-average J(m), ‘J(m), under a number of storms at KSC in the years 1976-1978 and 1981. Maps of ‘J(m) are consistent with the locations of radar echoes and lightning charges, and the patterns of ‘J(m) develop and change shape slowly with time. Maximum values of ‘J(m) for large storms are typically on the order of 10 to 15 na/m², and those for small storms are 2 to 4 na/m². Since J(m) is a solenoidal vector, area-integrals of the ‘J(m) maps (‘I) on the ground provided at least a lower limit to the total storm current aloft. Maximum values of ‘I for small convective storms are on the order of 0.1 to 0.5 A, and the maximum values for large storms are at least 3 to 5 times larger. Attempts to infer the location, magnitude, and geometry of the current sources aloft from the field-derived estimates of ‘J(m) have been hampered by a 10-20% variance in the values of ‘J(m). These errors prevent a unique characterization of the current sources aloft unless other data can be included in the analysis. Polar conductivities have been found to be highly variable in a thunderstorm environment, but the total conductivity often remains comparable to that found in fair weather. Conductivities derived from Maxwell current estimates of Jₑ vs. E are about an order of magnitude larger than the direct measurements; therefore, the Jₑ vs. E method of estimating σ may not be valued.