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Table 3 Summary of characteristics of Venus electrical activity

From: Lightning detection on Venus: a critical review

Property Estimate and confidence Support Comment
Rate of bursts 15/h
~ 1/min
~ 18/h
PV E-field bursts [30 s] (Scarf et al. 1987)
Venera 11 bursts 13–17 km
Venus Express bursts (see text)
 
Rate of pulses (during burst) ~ 0.14/s
~ 0.1–0.7/s
2–20/s
PV E-field pulses (Ho et al. 1990)
Venera 14 descent pulses (> 200 μV/m/Hz0.5)
Venera 11 descent pulses (unknown threshold)
 
Duration of burst events Well-determined: 5–100 s • Venera 12 surface burst > 8 s, less than 3–6 min
• VEx magnetometer bursts 6 s to > 60 s
• Venera 9 burst 70 s
• PV E-field bursts
Overlaps between bursts on Veneras 11–14 descent do not constrain burst duration
Flash duration Unclear • Venera 9 claims ~ 250 ms (long for terrestrial lightning) but instrument response?
• Hansell ground-based detections < 100 ms (but 5-frame running mean bias subtraction reduces sensitivities to flashes > 50 ms, and discards transients > 250 ms altogether)
• Veneras 11–14 pulses 10–60/s, means up to ~ 8–50 ms long
Venus Express, Pioneer Venus ELF signatures longer than “flash” due to propagation delay, so no constraint (see Fig. 5 bottom panel)
Geographic distribution Global? • PV OEFD detections mostly mid-latitude (claimed association with highlands specifically was not substantiated by data, but not excluded either
• VEx MAG detections only made near north pole (low altitude required for observation)
• Venera lander detections made at low latitude, but long detection range gives little localization
 
Source region size < few hundred kilometers • Spin modulation of Venera 11 source
• PV, VEx cover ~ 600 km in 60 s
• Hansell flashes cover 3–15 pixels (2.2 arcsec pixels each ~ 600 km across)
 
Local time distribution Strongest observed in evening (18–24 h). But few dayside observations • Strongly indicated by distribution of PV OEFD and VEx MAG bursts
• Statistics of optical detections too poor to provide useful constraints
Evening cooling of cloud-tops drives convection?