Lightning discharges between charged clouds and the Earth’s surface are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that laser-induced filaments—formed in the sky by short and intense laser pulses—can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was conducted on the Säntis mountain in north-eastern Switzerland during the summer of 2021 with a high-repetition-rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by very-high-frequency interferometric measurements, and the number of X-ray bursts detected during guided lightning events greatly increased. Although this research field has been very active for more than 20 years, this is the first field-result that experimentally demonstrates lightning guided by lasers. This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures.

Interest in exploring the meteorological conditions favoring upward lightning from tall man‐made structures has grown in recent years, largely due to the worldwide expansion of wind energy. To this end, instrumented towers existing around the world are the most suitable places to study upward lightning. In this context, an LMA network was deployed around the Säntis Mountain (northeast Switzerland) during the summer of 2017, in order to complement the long‐term measurements currently held at the Säntis telecommunications tower, a lightning hot spot in central Europe. This campaign allowed, for the first time, to gather a comprehensive set of observations of self‐initiated upward lightning emerging from the Tower. With the help of C‐band dual‐polarimetric radar data, the present work focuses on the meteorological conditions conductive to self‐initiated upward lightning from the Säntis. The analysis revealed that the upward propagating positively charged leaders spread mostly horizontal above the melting level, after an initial short vertical path from the tower tip. After this initial stage, the majority of upward leaders were followed by a sequence of negative return strokes. The inception upward lightning under a stratiform cloud shield would be favored by the low height of the charge structure. From the obtained results, it turns out that a key feature favoring self‐initiated upward lightning would be the proximity of the tower tip to the melting level.

Lightning is highly destructive due to its high power density and unpredictable character. Directing lightning away would allow to protect sensitive sites from its direct and indirect impacts (electromagnetic perturbations). Up to now, lasers have been unable to guide lightning efficiently since they were not offering simultaneously terawatt peak powers and kHz repetition rates. In the framework of the Laser Lightning Rod project, we develop a laser system for lightning control, with J-range pulses of 1 ps duration at 1 kHz. The project aims at investigate its propagation in the multiple filamentation regime and its ability to control high-voltage discharges. In particular, a field campaign at the Säntis mountain will assess the laser ability to trigger upward lightning.

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