Abstract - Lightning strikes to the Toronto CN Tower have
been observed since 1978. Since 1991, the lightning current
derivative resulting from strikes to the CN Tower and the
corresponding electromagnetic field have been measured
using systems with high resolution and broad bandwidths.
This paper focuses on the establishment of comprehensive
statistics concerning the characteristics of the lightning
current, measured at the CN Tower during ten years (1992-
2001). For negative lightning, two very distinguished current
impulses are characterized: impulses with fast wavefronts,
representing the overwhelming majority of CN Tower
lightning current impulses, and impulses with substantially
slower wavefronts and larger current peaks. These slow
negative impulses or strokes are found to either occur in
single-stroke flashes or to represent first strokes in multiplestroke flashes, suggesting that they belong to downwardinitiated lightning to the CN Tower. The paper also includes
a comparison between the current characteristics of the
ordinary, fast-rising wavefront, negative impulses and
positive impulses. The statistical analysis illustrates that
there is a substantial difference in wavefront characteristics
between the ordinary negative impulses and the rarely
measured positive impulses occurring in positive flashes. On
the other hand, no considerable difference is found when
comparing wavefront characteristics of ordinary negative
current impulses and the rarely measured positive impulses
occurring in bipolar flashes.
Abstract - Lightning strikes to the Toronto CN Tower have
been observed since 1978. Since 1991, the lightning current
derivative resulting from strikes to the CN Tower and the
corresponding electromagnetic field have been measured
using systems with high resolution and broad bandwidths.
This paper focuses on the establishment of comprehensive
statistics concerning the characteristics of the lightning
current, measured at the CN Tower during ten years (1992-
2001). For negative lightning, two very distinguished current
impulses are characterized: impulses with fast wavefronts,
representing the overwhelming majority of CN Tower
lightning current impulses, and impulses with substantially
slower wavefronts and larger current peaks. These slow
negative impulses or strokes are found to either occur in
single-stroke flashes or to represent first strokes in multiplestroke flashes, suggesting that they belong to downwardinitiated lightning to the CN Tower. The paper also includes
a comparison between the current characteristics of the
ordinary, fast-rising wavefront, negative impulses and
positive impulses. The statistical analysis illustrates that
there is a substantial difference in wavefront characteristics
between the ordinary negative impulses and the rarely
measured positive impulses occurring in positive flashes. On
the other hand, no considerable difference is found when
comparing wavefront characteristics of ordinary negative
current impulses and the rarely measured positive impulses
occurring in bipolar flashes.
การแปล กรุณารอสักครู่..
