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The physics of high altitude lightning.

Valdivia, Juan Alejandro.

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The physics of high altitude lightning.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	The physics of high altitude lightning./
作者:	Valdivia, Juan Alejandro.
面頁冊數:	156 p.
附註:	Adviser: Dennis Papadopoulos.
Contained By:	Dissertation Abstracts International58-09B.
標題:	Physics, Astronomy and Astrophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9808675
ISBN:	9780591591064

The physics of high altitude lightning.
Valdivia, Juan Alejandro.

The physics of high altitude lightning. - 156 p.

Adviser: Dennis Papadopoulos.

Thesis (Ph.D.)--University of Maryland, College Park, 1997.

It has been very surprising to discover in recent years that some of the energy dissipated by lightning can couple upwards into the upper atmosphere driving the impressive high altitude lightning phenomena. To understand these phenomena requires modeling of nonlinear processes driven by high electric power densities. The objective of this thesis is to provide the physics framework within which some of the observed phenomena can be studied and quantitatively understood and modeled.

ISBN: 9780591591064Subjects--Topical Terms:

1019521
Physics, Astronomy and Astrophysics.

The physics of high altitude lightning.
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502 $a Thesis (Ph.D.)--University of Maryland, College Park, 1997.
520 $a It has been very surprising to discover in recent years that some of the energy dissipated by lightning can couple upwards into the upper atmosphere driving the impressive high altitude lightning phenomena. To understand these phenomena requires modeling of nonlinear processes driven by high electric power densities. The objective of this thesis is to provide the physics framework within which some of the observed phenomena can be studied and quantitatively understood and modeled.
520 $a The first part of the thesis deals with red sprites, the millisecond-long red optical flashes that stretch at altitudes between 50-90 km. In this thesis we set forth the hypothesis that the fractal nature of the lightning discharge is responsible for the presence of localized regions of high power density in the upper atmosphere while maintaining low average integrated power. Such inhomogeneous radiation pattern naturally reduces the required current threshold for sprites to values closer to measurements as compared with dipole type of models. To understand the radiation pattern generated by the tortuous structure of lightning, fractal antennae are studied in detail, with special emphasis on the dependency on the fractal characteristics--the fractal dimension--of the discharge.
520 $a The second part of the thesis addresses the issue of the generation of the observed $\gamma$-ray flashes. The $\gamma$-rays observed are consistent with the generation of a runaway discharge. Runaway discharges have been studied only in the absence of a magnetic field. The magnetic field effect on the runaway discharge may be important at heights consistent with HAL since the gyromotion becomes more important than the other $b = 0$ time scales, e.g. collisions, ionization, etc. We developed the theory of the runaway discharge for $b \not= 0$. Results indicate that the threshold conditions for the runaway discharge are changed radically in the presence of the Earth's magnetic for heights above 20 km constraining the electron acceleration between the ionizing collisions, hence inhibiting the discharge. Consequently, runaway discharges driven by static electric fields are a very unlikely source of $\gamma$-rays and red sprites, requiring extremely large electric fields with amplitudes at least 10 times larger than expected.
590 $a School code: 0117.
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