2026-09-20T15:23:32Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/179842026-06-06T01:04:38Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023
Earle Williams.
Surana, Kunal K. (Kunal Krishna), 1979-
Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
2005-06-02T19:30:39Z
2005-06-02T19:30:39Z
2004
2004
http://hdl.handle.net/1721.1/17984
57189479
Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Includes bibliographical references (leaves 93-96).
The waveguide cutoff phenomenon provides information about the height of a waveguide. This cutoff for the earth-ionosphere waveguide is illuminated by lightning sferics and is used to monitor the change in ionosphere height through the day-night boundary. The observed ionospheric heights are found to be dependent on the three kinds of source-receiver paths: daytime, nighttime and mixed. Accurate locations for individual events are obtained from the National Lightning Detection Network (NLDN) to enable the analysis. Tweek sferics, which asymptote towards the transverse resonance frequency of the waveguide, predominate in the night path giving the most precise information about ionospheric heights. Weak dispersion and steep transitions in one-dimensional spectra provide information about daytime heights. Propagation over mixed paths reveals both daytime and nighttime signatures. Nighttime observations are also compared against theoretical predictions (Porrat et al, 2001). Agreement is best for large peak current events ( > 100) kA). Some indication of a residual daytime effect in a nighttime ionosphere is also observed.
by Kunal K. Surana.
M.Eng.
S.B.
106 leaves
4803755 bytes
4816280 bytes
application/pdf
application/pdf
eng
Massachusetts Institute of Technology
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http://dspace.mit.edu/handle/1721.1/7582
Electrical Engineering and Computer Science.
Sferic propagation in the cutoff region of the earth-ionosphere waveguide
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<Abstract>The waveguide cutoff phenomenon provides information about the height of a waveguide. This cutoff for the earth-ionosphere waveguide is illuminated by lightning sferics and is used to monitor the change in ionosphere height through the day-night boundary. The observed ionospheric heights are found to be dependent on the three kinds of source-receiver paths: daytime, nighttime and mixed. Accurate locations for individual events are obtained from the National Lightning Detection Network (NLDN) to enable the analysis. Tweek sferics, which asymptote towards the transverse resonance frequency of the waveguide, predominate in the night path giving the most precise information about ionospheric heights. Weak dispersion and steep transitions in one-dimensional spectra provide information about daytime heights. Propagation over mixed paths reveals both daytime and nighttime signatures. Nighttime observations are also compared against theoretical predictions (Porrat et al, 2001). Agreement is best for large peak current events ( > 100) kA). Some indication of a residual daytime effect in a nighttime ionosphere is also observed.</Abstract>
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