9.The Connection Between Red and Blue Lightning
Although most people’s imagination is captured by red lightning, it is intimately tied to another amazing higher atmospheric phenomena: blue lightning. Rising-propagating discharges from the tops of thunderclouds, blue jets and giant jets seem as blue cones or columns of light. Often seen in concert with red sprites, these blue events create a fascinating interaction of colours in the upper atmosphere. Red and blue lightning differs mostly in colour from the altitude at which these discharges occur and the atmospheric composition at such heights. Usually starting at lower altitudes (between 20 and 30 km), blue jets favour the emission of blue light from nitrogen molecules by thicker atmosphere. The discharge may turn crimson as it moves upward into the less thick atmosphere, producing an amazing visual show. Red and blue lightning events give important new perspectives on the vertical structure of the atmosphere and the propagation of electrical discharges over several atmospheric layers. Suggesting a complicated chain of events in the evolution of upper atmospheric electrical events, some scientists speculate that blue jets may be precursors or triggers for red sprite creation. Developing thorough models of atmospheric electricity and solving the riddles of how energy is distributed across various parts of the Earth’s atmosphere depend on an awareness of the link between these vivid discharges.