Jan 29, 2010

LIS science: global electricicty


Global electric circuit and lightning

Lightning is not an event isolated within the confines of a thunderstorm. It is part of a massive electrical circuit that literally covers the globe. The voltage difference between ground and ionosphere is 200,000 to 500,000 volts (200 to 500 kV). Even in fair weather, a slight current of 2 pA (picoamps, or 0.0000000000001 A) flows from every square meter of ground upward to the ionosphere. Thunderstorms alone send 1 A of current skyward. Indeed, the flash rate for a storm is directly related to its current flow.

While this view is widely accepted, it has not been proven by hard data. The LIS, and a Lightning Mapping Sensor, would clear up many of the uncertainties about the global electrical circuit. Lightning images would enhance data from ground-based lightning networks by catching the cloud-to-cloud flashes that ground networks miss.

The resolution of LIS and of the planned Lightning Mapping Sensor will be higher (it will see smaller events and shorter intervals) than those of other space sensors which miss a lot of the lightning that could be observed from space.

Ultimately, data from LIS and LMS will give scientists hard numbers to plug into computer models of the Earth's climate.

Back to the Lighting Imaging Sensor story.