Imbalances between storm clouds and the ground cause lightning to form. A momentous lightning bolt that flashed above a network of radio telescopes in the Netherlands in 2018 was captured and revealed that lightning does start inside a thundercloud.
The detailed recordings of the network of thousands of small radio telescopes called Low Frequency Array (LOFAR) settle a long-standing debate about what causes lightning, which is the first step in understanding the mysterious process of how bolts arise, grow, and propagate to the ground.
What Causes Lightning? Low Radio Frequency Telescope Captures in Detail What Happens Behind Thunderstorms
Low Frequency Array Used to Observe the Universe
A first of its kind, the LOFAR is a radio interferometer that observes the universe in low frequencies, from 90 to 200MHz, which is close to the FM radio band. According to the University College London, LOFAR can observe objects in many directions simultaneously to allow for a multi-user operation so scientists can use it to look at the entire sky simultaneously, not like most telescopes.
LOFAR's main base is in the Netherlands, while its other stations can be found in France, the UK, and Germany. One of the critical projects that the team operating LOFAR is hunting signals from an epoch where the universe was re-ionized by probing the redshifted transition of the hyperfine structure in neutral hydrogen that has a frequency of 1.4GHz.
LOFAR Captures in Detail What Triggers Lightning
LOFAR has solved the issue of observing lightning in clouds to know what exactly happens behind thunderstorms. Before this technology, scientists had little choice but to venture into the storm by sending weather balloons and rockets that offered snapshots of the interior. They observed that its presence only interfered with the data because they created artificial sparks.
In the new paper, titled "The Spontaneous Nature of Lightning Initiation Revealed," published in the journal Geophysical Research Letters, researchers reported that LOFAR tunes its antennas to detect the millions of radio pulses that came from the lightning flash that passes through thick clouds.
The use of radio detectors is not a new concept because purpose-built antennas were also used before in observing storms in New Mexico. However, those were low-resolution or in two dimensions. On the other hand, Quanta Magazine reported that the state-of-the-art astronomical telescope LOFAR could create a detailed map of lightning in 3D to give scientists a clear picture of what triggers them.
What Triggers Lightning?
Researchers also employed an algorithm to create the 3D lightning image. They found that the radio pulses from the 2018 lightning flash all came from a 70-meter-wide region deep inside a thunderstorm cloud.
They infer that the pulses could be explained by one of two theories about a common type of lightning, Quanta Magazine. They said that it begins with a cluster of ice crystals inside the cloud and turbulent collisions between them trigger electrons and cause one end of each ice crystal to become positively charged. In contrast, the other end becomes negatively charged.
The positive end of the molecules draws more electrons that flow in from air molecules farther away to form streamers or ribbons of ionized air that extend from each ice crystal tip. Then each of these ice crystal tips forms new streamers and branch off again and again, increasing the temperature of the surrounding air and pulling electrons from the air so that a larger electric current flows into the ice crystals.
Until a streamer becomes too hot and conductive that it channels along with a fully-fledged streak of lightning that travels through the air.
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