Upwards lightning caught on film

Scientists have photographed "upwards lightning", a rarely-seen phenomenon where electricity from storms flows into the upper atmosphere.

During last year's Tropical Storm Cristobal, lightning reached more than 60km (40 miles) up.

Also known as "gigantic jets", these events are just as powerful as cloud-to-ground lightning bolts.

The US team of researchers also took radio measurements of the electrical charge.

The phenomenon was photographed from a field site near Duke University in Durham, North Carolina.

Their work, published in Nature Geoscience, gives scientists a better understanding of this form of lightning.

Gigantic jets do not occur during every storm and scientists do not yet know what types of storm are conducive to their formation.