Investigation into the Initial Electric Field Change of Lightning Flashes

Chapman, Ryan (2015) Investigation into the Initial Electric Field Change of Lightning Flashes. Undergraduate thesis, under the direction of Thomas Marshall from Physics and Astronomy, The University of Mississippi.

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Abstract

Previously, an initial electric field change (IEC) was found occurring before initial breakdown (IB) pulses by sensors within the reversal distance of 36 lightning flashes [Marshall et al. 2014]. The E-change for a CG flashes was positive within reversal distance, and the E-change for an IC flashes was negative. With this data in mind, an IEC is best defined as occurring from zero slope to gradual increase in E-change at the beginning of a lightning flash, and it ends with the first IB pulse. The purpose of this thesis is to extend said findings to further understand the characteristics of IECs as well as look at instances of unique IECs not categorized as either intracloud (IC) or cloud-to-ground (CG) flashes. In order to find the IECs, electric field change (E-change) sensors were spread across east central Florida in the summers of 2010 and 2011. The 2nd generation Lightning Detection And Ranging system (LDAR2) was used for location data of the IECs by locating impulsive lightning events [Murphy et al. 2008]. Vertical point dipole moments were also calculated for IECs with LDAR2 locations in order to normalize the E-change data for IECs at different distances from sensors. A total of 55 lightning flashes with IECs were recorded (14 CG flashes, 38 IC flashes, and 3 two-start flashes). 43 of the 57 flashes in the August 1, 2010, storm were analyzed in this study (the 3 two-start flashes had 2 IECs). 10 flashes from August 1, were previously analyzed for IECs by Marshall et al. [2014]. All 13 flashes from the August 17, 2010, were analyzed for IECs (6 from Marshall et al. [2014]). Only 1 out of 92 flashes (combined with Marshall et al. [2014]) was found without an IEC by a sensor within the reversal distance. This could be because the flash was located near the reversal distance or because the IEC had a very strong initiation. The two-start flashes had higher altitudes, longer durations, and greater point dipole moments than other IECs.

Item Type: Thesis (Undergraduate)
Creators: Chapman, Ryan
Student's Degree Program(s): B.A. in Physics and Psychology
Thesis Advisor: Thomas Marshall
Thesis Advisor's Department: Physics and Astronomy
Institution: The University of Mississippi
Subjects: Q Science > QC Physics
Depositing User: Ryan Chapman
Date Deposited: 12 May 2015 17:49
Last Modified: 12 May 2015 17:49
URI: http://thesis.honors.olemiss.edu/id/eprint/461

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