Dr Michelle Dickinson: How does lightning begin?

Scientists have debated over two main theories of how lightning starts for years. 

Some say it's due to a build up of static electricity between particles in clouds, whereas others say cosmic rays are involved in the process.

Dr Michelle Dickinson joins Francesca Rudkin to breakdown these two leading theories. 

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Episode Transcript

Speaker 1 (00:06):
You're listening to the Sunday Session podcast with Francesca Rudgin
from News Talks EDB.

Speaker 2 (00:13):
It is time to talk science, and doctor Michelderkinson joins us.

Speaker 3 (00:15):
Now, good morning, Good morning.

Speaker 2 (00:17):
I am completely, nutterly fascinated by the study that you
have for us today about lightning. I thought we knew
quite a bit about lightning. Apparently we know very little
about lightning. And I had no idea.

Speaker 3 (00:27):
It was so cool, it's so cool, and I just
figured we knew how lightning began. Like we've all sat
and watched lightning storms. I didn't go, oh, nobody really
knows how that happens. But apparently, until today, this is true.
So if you want to read about this study, it's
in the Journal of Geophysical Research Atmospheres. And basically, we've

(00:49):
all watched a lightning string and gone, oh, that's so pretty,
that's so cool. But actually, scientists have been debating two
different theories for how lightning begins. And here are the
two theories. So number one theory number one, and I
think this is what I learned at school. I didn't
realize it was improved, but basically, theory number one is
that in storm clouds are basically little ice particles, and

(01:11):
when those ice particles run rubbed together, you get a
static electricity build up, and so that separates negatively charge
electrons from atoms, and eventually you get enough electrons that
are built up in the stat electricity that you get
the lightning.

Speaker 2 (01:25):
Yep, that's my tychon.

Speaker 3 (01:26):
It it was my tychon. I'm pretty sure that's what
I learned at school. Apparently nonsense. So the other theory
that's out there is that you get this initial ionization
achieved by cosmic rays, which sounds cool. And then I
had to go hold on motocosmic rays. So cosmic rays,
if you don't know, are these high energy sub atomic
particles that come from outer space. Typically they come from

(01:48):
the Sun and they strike our upper atmosphere. Now that
just I mean, it sounds cool anyway, And then I
was like, hold on, I didn't know there was this
other theory. I'd never heard of that before. But I
like the fact that it's got cosmic ray, So let's
go deeper into this study. So what they did is
they basically took a whole bunch of models, and they
basically took some ground sensors and they started measuring lightning

(02:10):
on what they could measure, and what they found is
actually they are able to approve of these two competing theories,
one of them is the winner, and it's the cosmic
ray one, which is like, yay, I don't know why
I want the cosmic race to win. But what they
found is that lightning starts when these cosmic rays from
outer space enter atmosphere and they create these high energy electrons,

(02:31):
and these electrons, because they're already supercharged, they get an
extra boost from our thunderclouds electric field, which is already electric,
and then they slam into molecules in the clouds such
as nitrogen and oxygen, and it's this violent collision that
produces X rays and even more high energy particles, and
it basically escalates in this chain reaction to create what

(02:52):
we call a runaway cascade known as the photo electric
feedback discharge, and that builds rapidly until lightning is triggered.
So lightning is kind of like the last stage of it.
Like all of this build energy and then eventually casta
release and it releases as lightning. And what's cool is
they found that actually there's a pre lightning show that

(03:14):
happens in secret that we can't see and we're not
aware of where Some of these energetic bursts, which are
called terrestrial gamma ray flashing that's cool, actually happen without
visible lightning or thunder, but they do release X rays
and radio waves that are really intense, and we can't
see them and we can't hear them, but we do
have senses now on the ground that can measure them,

(03:37):
which is why scientists know that before a lightning storm
that we can see all of this terrestral gammay flashes
are actually happening. So they took computer models and compared
them to the real world data that they were collecting
on satellites, planes and ground sensors, and they're able to
actually model how lightning starts right down to the individual
molecular level.

Speaker 2 (03:57):
Wow.

Speaker 3 (03:58):
And not only is this caol that no I know
how lightning starts, but also it's really helpful with better
weather prediction aviation safety. Right you look at so many
airports have to be shut down due to lightning threat
and even thinking about how you shield spacecraft and plane
maybe from lightning straits. But the most important thing is
it finally solves one of Earth's longest running scientific mysteries

(04:19):
that I didn't know hadn't been solved. Love it.

Speaker 2 (04:21):
Thank you so much, Michelle. We'll talk next week.

Speaker 1 (04:24):
For more from the Sunday session with Francesca Rudkin, listen
live to News Talks it'd be from nine am Sunday,
or follow the podcast on iHeartRadio