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Lightning flashes on Titan could provide additional energy for the formation of various chemical trace species, including prebiotic molecules in the troposphere, where other chemical processes are inactive. Lightning strokes typically produce a transient hot channel in which high-temperature chemistry takes place. The sudden heating initiates dissociation of bonded molecules. The atoms and ions are in equilibrium as long as the channel is hot, but as the lightning channel begins to cool down by mixing with the surrounding air and expands, various new molecules are formed by recombination of ions and atoms. Such molecules remain in excess of the equilibrium concentration during the cooling because the rates of depletion reactions are greatly reduced. This process is usually called "freeze-out" of molecules. The significance of lightning-generated organic chemistry in Titan's atmosphere is highly dependent on the global lightning frequency, which is currently under study here.
Electrical parameters of Titan’s atmosphere were measured in-situ with the HASI instrument onboard the Huygens probe. Additionally we investigate the propagation, absorption and reflection characteristics of electromagnetic waves - which may have their origin in lightning - through the ionosphere by a stratified medium model.
So far, the existence of lightning on Titan is still controversial. The HASI instrument detected some impulsive radio signals, but their origin is not clear. The RPWS instrument could not detect any radio signals attributed to lightning during numerous close flybys of Cassini at Titan.
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