Field Experiments Using Femtosecond Laser Filamentation

5 Field Experiments Using Femtosecond Laser Filamentation 

Because the laser is fired independently from the electric activity in the clouds, and because natural electric activity in clouds is a random process, temporal correlations between the electric events detected by the LMA and the laser operation were used as an evidence for an effect of the laser. At each location, the events synchronized (within 2 ms) with the laser have been identified. The probability async that these events may have been obtained by chance among random events, rather than being due to an effect of the laser, was estimated. async can be understood as the risk of error when concluding that the observed pulses are related with the laser pulses. This corresponding confidence level is therefore 1 — async- 

Similar results have been obtained during the second thunderstorm [31]. In contrast, no effect was observed when the electric field was low or negative. Therefore, these results suggest that a small fraction (0.24% of the laser pulses, i.e., d event/minute) of the plasma filaments have initiated electric events in a strong positive (upward pointing) electric field [31]. 

Plasma filaments generated in the atmosphere by ultrashort laser pulses therefore appear to be able to trigger electric events in thunderclouds under high positive electric field. This result constitutes a first step towards laser-controlled lightning. 

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