Séminaire "Sprites" | 16 janvier 2013
Thunderstorms, Lightning and Sprites on Earth and other Planets,
Pr. Yoav YAIR,
Department of Life and Natural Sciences, The Open University of Israel
Lightning is the manifestation of electrical breakdown, occurring within convective clouds after microphysical charge separation processes build strong enough electric fields. On Earth, the global flash rate is 45 flashes per second, mostly over the continents in tropical and mid-latitudes. This lightning activity sustains a global electrical circuit between the planet’s surface and the ionosphere, and can be remotely sensed from large distances, enabling tracking and forecasting severe weather. Lightning leaves chemical effects in the atmosphere in the form of NOx and ozone, which may have had a significant role in the emergence of organic compounds in Earth’s early atmosphere (as shown in the Miller-Urey experiments, 1951). The effects of lightning-induced electric fields sometimes spread into the mesosphere, generating transient luminous events (e.g. sprites, elves, jets) which last several milliseconds and have a global rate of 1-10 per minute. Spacecrafts and ground-based measurements detected lightning activity on Jupiter, Saturn and possibly on Venus, Uranus and Neptune, offering a probe into these planets meteorology and cloud microphysics. This talk will review the latest results on terrestrial and planetary thunderstorms and associated electrical phenomena.
Mercredi 16 janvier 2013 à 16h
IPAG, bâtiment PhITEM-D, salle Oisans