scholarly journals Features of K-Changes Observed in Sri Lanka in the Tropics

2018 ◽  
Author(s):  
Sankha Nanayakkara ◽  
Mahendra Fernando ◽  
Vernon Cooray
Keyword(s):  
Fine Structure ◽  
Sri Lanka ◽  
Small Step ◽  
Return Stroke ◽  
Pulse Burst ◽  
Regular Pulse ◽  
The Tropics

General characteristics of K changes together with their fine structure associated with ground flashes in Sri Lanka in the tropics are presented. It is found that on average there are about 2 K changes associated with each return stroke. Analysis of the fine structure of the K changes shows that the K change is a chaotic pulse burst. Some of these chaotic pulse bursts start and the others end as a regular pulse bursts. Sometimes the chaotic part occurs in between two regular pulse bursts. This is in agreement with the recent published results that claim that chaotic pulse bursts are a random superposition of regular pulse bursts. The results show that the small step fields identified in the literature as K changes are the static fields associated with these pulse bursts.

scholarly journals Features of K-Changes Observed in Sri Lanka in the Tropics

Atmosphere ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 141
Author(s):  
Sankha Nanayakkara ◽  
Mahendra Fernando ◽  
Vernon Cooray
Keyword(s):  
Fine Structure ◽  
Sri Lanka ◽  
Pulse Train ◽  
Geometric Mean ◽  
Time Interval ◽  
Small Step ◽  
Time Duration ◽  
Pulse Trains ◽  
Regular Pulse ◽  
The Tropics

General characteristics of K-changes, including their duration and probability of occurrence associated with ground flashes in Sri Lanka in the tropics, together with their fine structure, are presented. In 98 ground flashes where the small step changes associated with K-changes are clearly visible, there were about two K-changes per flash on average. The mean K-change time duration observed in this study is 0.38 ms. In 53 of the ground flashes, there were 120 consecutive K-changes. In these cases, the geometric mean of the time interval between K-changes was 12 ms. Analysis of the fine structure of the K-changes reveals the K-changes are always associated with either a chaotic pulse train or a combination of chaotic and regular pulse trains. The results suggest that the small step-like static electric fields identified in the literature as K-changes are the step-like static fields associated with the processes that generate chaotic or a combination of chaotic and regular pulse trains. Thus, at larger distances where the static fields are negligible, K-changes may appear as a chaotic pulse train or a combination of chaotic and regular pulse trains.

scholarly journals Fine Structure Signatures in Ground Flashes as a Source for HF Radiation

2013 ◽  
Vol 20 ◽  
pp. 91-104
Author(s):  
Mahesh Edirisinghe ◽  
Vernon Cooray
Keyword(s):  
Fine Structure ◽  
Arithmetic Mean ◽  
Return Stroke ◽  
Radiation Fields ◽  
Initiation Process ◽  
Natural Resonance ◽  
Strong Source ◽  
Average Rise ◽  
The Tropics ◽  
Negative Field

Lighting radiation fields below 10 MHz are of considerable interest since these frequencies correspond to the natural resonance of structures with dimensions of a few meters to tens of meters. In this paper we present the fine structure signatures of sub-microsecond range pulses appeared at the leader phase and after the return stroke in negative ground flashes which act as a source for HF radiations at 10 MHz, 5 MHz and 3 MHz observed in Sri Lanka, in the tropics. Of the total sub-microsecond range pulses analyzed, 298 were due to positive field changes and 228 were due to negative field changes. The average rise time of those pulses for both polarities is 127 ns and it was found to be varying from 110-160 ns. The peak amplitude is in the range of 0.65-2.19 V/m. For the total 526 pulses analyzed for this study, the FWHM was between 190-310 ns with an arithmetic mean of 238 ns. Signatures of these pulses are similar to the leader like electric field pulses which acted as a strong source for HF radiations at 10 MHz, 5 MHz and 3 MHz. The initiation process of pulses reported in this study could be similar to the initiation process of leader like pulses.

Urban shading-a design option for the tropics? A study in Colombo, Sri Lanka

2007 ◽  
Vol 27 (14) ◽  
pp. 1995-2004 ◽  
Author(s):  
R. Emmanuel ◽  
H. Rosenlund ◽  
E. Johansson
Keyword(s):  
Sri Lanka ◽  
Design Option ◽  
The Tropics

scholarly journals Species Composition and Visiting Frequencies of Flower Visitors ofChromolaena odoratain a Dry Zone Forest Patch of Sri Lanka

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
D. G. R. M. M. Kaushalya Rathnayake ◽  
W. M. G. Asanga S. T. B. Wijetunga
Keyword(s):  
Sri Lanka ◽  
Plant Species ◽  
Invasive Plant ◽  
Secondary Forest ◽  
Major Theme ◽  
Forest Patch ◽  
Flower Visitors ◽  
Dry Zone ◽  
Animal Interaction ◽  
The Tropics

Plant-animal interaction has been a major theme in ecology as it has helped ecologists to rule out different patterns they observed in the surrounding environments.Chromolaena odoratais another plant species that is studied extensively as it has become a major troublesome weed in many parts of the tropics. But, handful of studies are available on pollination of this invasive plant species in dry forests and its function as a pollinator sink in these environments. The current study was carried out in a dry zone secondary forest patch in North-Central Sri Lanka to assess the diversity, abundance, and pollination strength of flower visitors associated with theC. odorata. The results suggest that the diversity of Hymenoptera and Lepidoptera is higher than the other insect orders that visitedC. odorata, but all species exerted equal pollination strength on the plant. The attraction of large numbers of insects is concluded to as one of the factors that contribute to the reproductive success ofC. odoratain dry zone forests.

The fine structure of lightning return stroke wave forms

1978 ◽  
Vol 83 (C12) ◽  
pp. 6239 ◽  
Author(s):  
Charles D. Weidman ◽  
E. Philip Krider
Keyword(s):  
Fine Structure ◽  
Return Stroke ◽  
Wave Forms

scholarly journals THE DISTRIBUTION, IMPORTANCE, BIOLOGY AND CONTROL, OF CHROMOLAENA ODORATA (L.) K.& R.A MAJOR WEED SPECIES OF COCONUT PLANTATION IN SRI LANKA

CORD ◽  
1995 ◽  
Vol 11 (02) ◽  
pp. 34
Author(s):  
T.G.L.G. Gunasekara
Keyword(s):  
Sri Lanka ◽  
Control Measures ◽  
Chromolaena Odorata ◽  
Weed Species ◽  
Seed Biology ◽  
History Of ◽  
Biological Methods ◽  
The Tropics ◽  
And Control ◽  
Asteraceae Family

Chromolaena odorata (1.) K. & R. is a tropical peren­nial weed species qf the Asteraceae family that has be­come a serious problem in coconut plantations in Sri Lanka and in the tropics of Asia and Africa. The history of distribution, habitat and economic importance is summarized The botanical features and seed biology of this species are presented in this review Finally in­formation on the control measures such as mechanical, cultural, chemical and biological methods is discussed.

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