Observations by the LOFAR radio telescope of a fast negative leader propagation mode

Abstract

<p>We report on recent observations made by the LOFAR radio-telescope of a fast propagation mode in negative leaders we named Rapid Negative Leader (RNL).<br>The RNL has a variety of properties that make them clearly distinct from negative leaders or dart leaders, such as -- fast propagation, -- emission of strong broad-band pulses, -- emission of very high VHF power, -- a reduced density of located sources, and -- terminating with the spawning of a large number of negative leaders in a small area. RNLs are almost always observed in the initial stage of a lightning flash, but may also occur much later. They may occur repeatedly in a certain part of the cloud.</p><p>We interpret a RNL as negative leader developing in strong electric field due to a relatively small highly-charged cloud, probably created by a local turbulence, with a typical size of order 5 km<sup>2</sup>.  The strong field will lead to a larger than usual charge at the leader tip resulting in an increased propagation velocity as well as a strongly enhanced emission of VHF power.<br>Since for the initiation of a lightning flash strong ambient electric fields are required, it is thus no surprise that the initial leader is in fact a RNL. </p><div> <div> <div></div> <div>What do you want to do ?</div> New mail</div> </div><div> <div> <div></div> <div>What do you want to do ?</div> New mail</div> </div>