Estimation of Global Lightning Activity and Observations of Atmospheric Electric Field
Summary (2 min read)
1. INTRODUCTION
- The relationship between atmospheric currents and ionospheric potentials on a planetary scale is known as the global electric circuit.
- Many questions remain and even fundamental assertions are often contended.
- It is clear that the link between the DC phenomena of the equipotential global ionosphere and the AC phenomena of lightning discharges and their related effects are still poorly understood.
- Thus, although both LIS and OTD instruments provide extremely valuable long term averages of lightning frequency and distribution, they are unable to quantify lightning activity at any given instant.
2.1 ELF/VLF measurements and analysis
- Stanford University operates a network of global receiving sites that record data in the band from 300 Hz to 47 kHz using aircore magnetic field antennas.
- Cohen et al. (2009) provide a description of the receiver hardware.
2.3 Atmospheric electric field observations
- The fair weather atmospheric electric field (vertical electric field measured at the ground) Figure 4a, adapted from Fig. 5 of Kubicki et al. (2007), shows the normalized daily variation of electric field over select summer and winter days during the years 1965-2000.
- Since the conductivity and electric field exhibit an inverse relationship only for the late evening and night hours, diurnal observations of Ez at SW can be interpreted as measures of global ionospheric potential (Kubicki et al. 2007).
- For lightning detection networks, of which WWLLN is an example, the observable is the flash rate scaled by the detection efficiency α, which will depend on the location of receiving stations and the specifics of the algorithm employed.
- The high peak currents of lightning associated with the oceans and the maritime continent are expected predominantly to influence VLF observations, while the high charge moment strikes of the Congo Basin can be expected to be observed in Schumann resonance measurements.
3. OBSERVATIONS AND ANALYSIS
- Seven days each in the months of March and May 2007.the authors.
- During this time, ELF/VLF data were available from at least 3 sites and SR data were obtained for 31 March Brought to you by | Koc University Authenticated Download Date | 5/5/17 9:33 AM.
3.1 Data from 31 March and 20 May
- The days 31 March and 20 May were those for which the most measurements were available.
- The SR derived lightning activity for both of these days, as shown in Fig. 3, is found to exhibit a central peak between 10:00-18:00 UT, which is classically associated with lightning activity in the African sector as established by thunder days (Whipple and Scrase 1936).
- It is worth mentioning a recent study by Nieckarz et al. (2009) who examined two years of fair weather Ez data from SW with SR data using the identical receiving station (HY) and technique as the authors use here.
- An examination of data from the WWLLN network for 20 May 2007 corroborates this view.
- It is clear that increasing the observation station requirement causes the number of geolocated flashes attributed to the African sector to decrease more substantially than for the other two regions and thereby changes the shape of the diurnal world total flash detection curve.
3.4 Multi-day averages
- Figure 13 shows averages of ELF/VLF and Ez for the seven days in March and seven days in May separated by month.
- The ELF/VLF data were computed using the three sites, AD, CH and PA, which recorded data on all days of the study.
- The averaged ELF and VLF data for March and the VLF data for May exhibit resemblance to the classic Carnegie curve (Whipple and Brought to you by | Koc University Authenticated Download Date | 5/5/17 9:33 AM.
4. SUMMARY AND DISCUSSION
- The authors have analyzed widely spaced ELF, VLF, SR and Ez for select days in March and May 2007.
- A theme of their work has been the integration of different globally spaced measurements and investigating the regional differ- Brought to you by | Koc University Authenticated Download Date | 5/5/17 9:33 AM.
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Cites background from "Estimation of Global Lightning Acti..."
...An ELF station with a single antenna enables measuring electrical lightning activity in the storm centers at a broad range of distances, starting at 0.15 Mm [Nieckarz et al., 2009b; Gołkowski et al., 2011]....
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6 citations
References
176 citations
"Estimation of Global Lightning Acti..." refers methods in this paper
...M. GOŁKOWSKI et al. 184...
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...The attenuation calculation is carried out separately for the ELF and VLF bands using published frequency dependent daytime and nighttime attenuation rates (Watt 1967, p. 338)....
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163 citations
"Estimation of Global Lightning Acti..." refers methods in this paper
...Global lightning location networks in the VLF band have been constructed of which the World Wide Lightning Location Network (WWLLN) (Dowden et al. 2002, Lay et al. 2004, Rodger et al. 2006) is currently the most prominent example....
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154 citations
"Estimation of Global Lightning Acti..." refers background or methods in this paper
...Kartalev et al. (2006) propose that the location of lightning in relation to the magnetic dip equator plays an important role while other workers have suggested that the answer lies in electric rain showers which are dominant in South America (Williams and Sátori 2004)....
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...Kartalev, M.D., M.J. Rycroft, M. Füllekrug, V.O. Papitashvili, and V.I. Keremidarska (2006), A possible explanation for the dominant effect of South American thunderstorms on the Carnegie curve, J. Atmos....
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...Rycroft et al. (2007) employed circuit simulation software to conclude that lightning discharges only contribute to ~1% of ionospheric potential changes and Williams and Sátori (2004) emphasize the importance of electrified shower clouds....
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145 citations
"Estimation of Global Lightning Acti..." refers background in this paper
...On global scales, the value of α for WWLLN does not exceed 5% (of cloud to ground lightning) (Rodger et al. 2005)....
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...Sprites, on the other hand, are produced by the quasi-static electric fields (Pasko et al. 1997) which are associated with lightning charge moment....
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...However, WWLLN is only able to locate major storms accurately, the detection efficiency for cloud to ground lightning events is less than a few percent (Rodger et al. 2005)....
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...Acta Geophysica vol. 59, no. 1, Feb. 2011, pp. 183-204 DOI: 10.2478/s11600-010-0035-4 ________________________________________________ © 2010 Institute of Geophysics, Polish Academy of Sciences...
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111 citations
"Estimation of Global Lightning Acti..." refers methods in this paper
...Rycroft et al. (2007) employed circuit simulation software to conclude that lightning discharges only contribute to ~1% of ionospheric potential changes and Williams and Sátori (2004) emphasize the importance of electrified shower clouds....
[...]
...Acta Geophysica vol. 59, no. 1, Feb. 2011, pp. 183-204 DOI: 10.2478/s11600-010-0035-4 ________________________________________________ © 2010 Institute of Geophysics, Polish Academy of Sciences...
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