Radio emission from lightning on Earth has been seen at frequencies from the kilohertz to gigahertz range. Previous spacecraft visiting Jupiter have found that the radio emission from lightning cuts off atkHz frequencies, which has been somewhat puzzling. The explanation could be that the lightning at Jupiter differs from that on Earth, or that the radio signals were cut off due to effects in Jupiter’s ionosphere. The Juno spacecraft, which arrived at Jupiter on 2016 July 4, after a five-year trip, was equipped with detectors to determine precisely what the explanation is. Shannon Brown ofJPL, and his collaborators from around the world, found the radio signature of lightning at 600 MHz (see the 2018 June 7 issue of Nature). They conclude that the lightning is not so different from earthly lightning. But rather surprisingly, the distribution of lightning shows a distinct asymmetry—it is far more prevalent in Jupiter’s northern hemisphere than the southern, and most common north of 40 degrees north latitude, with a concentration around the poles. Because lightning is related to moist convection (think the towering summer thunderstorms on Earth), Brown and collaborators conclude that increased convection near the poles, carrying energy from the deep atmosphere, is most consistent with what they see.
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