What is the largest recorded lightning strike

Storm: Mega lightning bolt in Baden-Württemberg sets a new record

A village in the Swabian Alb has held an unofficial record since Wednesday. The strongest known lightning bolt in Germany so far fell there. Only: it was too strong for reliable measurements.

The stage for the spectacular event is extremely unspectacular: It was a field north of the last houses in the village of Dürrenstetten, where the strongest lightning so far in Germany was measured at 8:35:51 p.m. 685,000 amperes were reported by BLIDS, the lightning information service from Siemens with a Europe-wide measuring network. But its expert Stephan Thern considers the value to be excluded.

For comparison: In the household, currents between a few milliamperes and 10 to 15 amperes generally flow, high-voltage lines carry a few hundred amperes - and the around one million lightning bolts in Germany each year are on average 15,000 to 20,000 amperes, i.e. 15 to 20 kilo-amperes (not specified). The mega-lightning bolt from the Swabian Alb would have been more than 30 times as powerful. This was also noticed by meteorologist Jörg Kachelmann's team:

Last summer, Kachelmann also created an overview of the "strongest mega-lightning flashes of the past few years". The strongest so far was recorded at 480,000 amperes. But BLIDS expert Stephan Thern does not consider this value realistic either. "In science it is assumed that lightning will not be stronger than 350,000 to 400,000 amperes," said Thern to t-online.de.

After three years of dealing with the topic, the German Reactor Safety Commission also disclosed its calculations in 2016: A percentage of lightning strikes would be 200,000 amperes or stronger - the natural, realistic upper limit in moderate latitudes, however, is 300,000 amperes.

Lightning strength is calculated from electromagnetic fields

The problem with the rare mega-lightning strikes is that there are insufficiently reliable direct measurements of impacts. This means that there are also no reference values ​​to adjust strength calculations. If lightning does not strike a measuring point directly, the strength can be extrapolated from the change in electromagnetic fields.

Every lightning bolt anywhere in Germany is registered by up to 30 antennas. Using the various data, the impact location can be determined with an accuracy of 50 meters: In this case, the field between Ulm and Reutlingen near Dürrenstetten, a district of Münsingen with 85 inhabitants.

The strength is automatically extrapolated from the field strength using a complicated formula. One factor in this is the rate at which the current flows during the main discharge. This can be a third of the speed of light, but the current can also reach two thirds of the speed of light - depending on the humidity, for example.

Half the speed of light is assumed for the calculation, which is also correct on average. Experts assume that the formula can, however, give a value that is also half or twice as strong as the real one.

There are reliable comparative values ​​for normal lightning. They do not exist for the mega-flashes, with today's knowledge they are too strong for the exact determination by the system. This is why BLIDS does not keep a list of the strongest lightning strikes.

The lightning from the Swabian Alb was probably only half as strong. Even with a real value of 300,000 amperes, it would still be the largest bundle of energy among lightning bolts in Germany. Nobody can prove the opposite to him.