Calibrated, Multiband Radiometric Measurements of the Optical Radiation from Lightning

Persistent Link:
http://hdl.handle.net/10150/325230
Title:
Calibrated, Multiband Radiometric Measurements of the Optical Radiation from Lightning
Author:
Quick, Mason G.
Issue Date:
2014
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Calibrated, multiband radiometric measurements of the optical radiation emitted by rocket-triggered lightning (RTL) have been made in the ultraviolet (UV, 200-360 nm), the visible and near infrared (VNIR, 400-1000 nm), and the long wave infrared (LWIR, 8-12 µm) spectral bands. Measurements were recorded from a distance of 198 m at the University of Florida International Center for Lightning Research and Testing (ICLRT) during the summers of 2011 and 2012. The ICLRT provided time-correlated measurements of the current at the base of the RTL channels. Following the onset of a return stroke, the dominant mechanism for the initial rise of the UV and VNIR waveforms was the geometrical growth of the channel in the field-of-view of the sensors. The UV emissions peaked about 0.7 µs after the current peak, with a peak spectral power emitted by the source per unit length of channel of 10 ± 7 kW/(nm-m) in the UV. The VNIR emissions peaked 0.9 µs after the current peak, with a spectral power of at 7 ± 4 kW/(nm-m). The LWIR emissions peaked 30-50 µs after the current peak, and the mean peak spectral power was 940 ± 380 mW/(nm-m), a value that is about 4 orders of magnitude lower than the other spectral band emissions. In some returns strokes the LWIR peak coincides with a secondary maximum in the VNIR band that occurs during a steady decrease in channel current. Examples of the optical waveforms in each spectral band are shown as a function of time and are discussed in the context of the current measured at the channel base. Source power estimates in the VNIR band have a mean and standard deviation of 2.5 ± 2.2 MW/m and are in excellent agreement with similar estimates of the emission from natural subsequent strokes that remain in a pre-existing channel which have a mean and standard deviation of 2.3 ± 3.4 MW/m. The peak optical power emitted by RTL in the UV and VNIR bands are observed to be proportional to the square of the peak current at the channel base. The same trend was found for natural lightning using peak currents estimates provided by the National Lightning Detection Network. Ratios of the optical power to the electromagnetic power emitted at the time of peak current suggest the radiative efficiency in the VNIR band is a few percent during the early onset of a return stroke. The majority of return strokes in RTL are found to emit most of their optical energy during the initial impulse phase.
Type:
text; Electronic Dissertation
Keywords:
Photo-Electric Detector; Plasma; Radiative Transfer; Radiometry; Thermodynamics; Atmospheric Sciences; Lightning
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Atmospheric Sciences
Degree Grantor:
University of Arizona
Advisor:
Krider, E. Philip; Betterton, Eric A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleCalibrated, Multiband Radiometric Measurements of the Optical Radiation from Lightningen_US
dc.creatorQuick, Mason G.en_US
dc.contributor.authorQuick, Mason G.en_US
dc.date.issued2014-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractCalibrated, multiband radiometric measurements of the optical radiation emitted by rocket-triggered lightning (RTL) have been made in the ultraviolet (UV, 200-360 nm), the visible and near infrared (VNIR, 400-1000 nm), and the long wave infrared (LWIR, 8-12 µm) spectral bands. Measurements were recorded from a distance of 198 m at the University of Florida International Center for Lightning Research and Testing (ICLRT) during the summers of 2011 and 2012. The ICLRT provided time-correlated measurements of the current at the base of the RTL channels. Following the onset of a return stroke, the dominant mechanism for the initial rise of the UV and VNIR waveforms was the geometrical growth of the channel in the field-of-view of the sensors. The UV emissions peaked about 0.7 µs after the current peak, with a peak spectral power emitted by the source per unit length of channel of 10 ± 7 kW/(nm-m) in the UV. The VNIR emissions peaked 0.9 µs after the current peak, with a spectral power of at 7 ± 4 kW/(nm-m). The LWIR emissions peaked 30-50 µs after the current peak, and the mean peak spectral power was 940 ± 380 mW/(nm-m), a value that is about 4 orders of magnitude lower than the other spectral band emissions. In some returns strokes the LWIR peak coincides with a secondary maximum in the VNIR band that occurs during a steady decrease in channel current. Examples of the optical waveforms in each spectral band are shown as a function of time and are discussed in the context of the current measured at the channel base. Source power estimates in the VNIR band have a mean and standard deviation of 2.5 ± 2.2 MW/m and are in excellent agreement with similar estimates of the emission from natural subsequent strokes that remain in a pre-existing channel which have a mean and standard deviation of 2.3 ± 3.4 MW/m. The peak optical power emitted by RTL in the UV and VNIR bands are observed to be proportional to the square of the peak current at the channel base. The same trend was found for natural lightning using peak currents estimates provided by the National Lightning Detection Network. Ratios of the optical power to the electromagnetic power emitted at the time of peak current suggest the radiative efficiency in the VNIR band is a few percent during the early onset of a return stroke. The majority of return strokes in RTL are found to emit most of their optical energy during the initial impulse phase.en_US
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectPhoto-Electric Detectoren_US
dc.subjectPlasmaen_US
dc.subjectRadiative Transferen_US
dc.subjectRadiometryen_US
dc.subjectThermodynamicsen_US
dc.subjectAtmospheric Sciencesen_US
dc.subjectLightningen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAtmospheric Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorKrider, E. Philipen_US
dc.contributor.advisorBetterton, Eric A.en_US
dc.contributor.committeememberKrider, E. Philipen_US
dc.contributor.committeememberBetterton, Eric A.en_US
dc.contributor.committeememberCummins, Kenneth L.en_US
dc.contributor.committeememberDereniak, Eustace L.en_US
dc.contributor.committeememberRitchie, Elizabeth A.en_US
dc.contributor.committeememberWeidman, Charles D.en_US
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