People in North America can gaze up at the sky tonight (with protective glasses) to watch the total solar eclipse. Streamed by NASA and across the news, many will be able to see the world plunged into dark as the moon covers the sun, but there is something else that will be happening at the same time: the Sounding Rocket Launches.
As part of a project known as the Atmospheric Perturbations around the Eclipse Path (helpfully shortened to APEP), rockets will be launching from the Wallops NASA facility and can be watched here. But why, when the eclipse is a natural phenomenon in its own right, are NASA launching rockets up at the darkness?
Part 1: The Ionosphere
To start understanding why NASA are doing this, we need to understand a niche area of our atmosphere known as the ionosphere. The Ionosphere is the top layer of the atmosphere, and the first barrier between Earth and Space. It's the part of the atmosphere that first feels the suns rays, and so the particles that are within it get all charged and affected by the sun's rays. This area is around 50-400 miles above ground, according to NASA, and because it is influenced so much by the sun's rays, it changes constantly, even as often as day and night where the lack of rays in the night can allow particles to 'relax' and become neutral again.
Part 2: The party in the sky
Knowing that the Ionosphere exists is only half the story, the other half, or majority I should say, comes from what's IN the Ionosphere and what it does, which brings us to the party of atoms up there, and what they get up to.
Photoionisation...it's a word that's difficult to spell, and harder to say, but has a relatively simple definition. This word refers to how light energy can cause ionisation- or the change of an atom into an ion, usually occuring by changing the number of electrons. This means that atoms up in the ionosphere are hit with energy from the sun, and their electron number is changed, forming ions. In the F1 region of the Ionosphere (the Ionosphere is split into layers, D, E, F1 and F2), Oxygen molecules (your O2), Oxygen atoms (O) and nitrogen (N2) are affected by photoionisation.
What this means, is you end up with all these charged ions in the atmosphere, which will then pair up with atoms and form new molecules and then these can do a number of things such as Recombinate, Diffuse, or Adsorb, which are different movement and transformation mechanisms that chemicals can experience, explained in more detail here.
But anyway, focussing back on Space and NASA. The Ionosphere, as we've very briefly touched upon, is a highly changing space, affected a lot by the sun's rays. There are patterns in the way the ionosphere can behave, some of which correlate to the time of day and how much air the sun has to get through to reach the atmosphere, with specific layers WITHIN the ionosphere displaying their own individual trends over a day.
3: What about a lack of sun???
So, the activity in the ionosphere changes often with the sun, but what about in the event of no sun...or a covered sun? As NASA points out, it's difficult to track short term changes in the ionosphere during an eclipse, which makes sense given how many changes occur on a normal day! When an eclipse casts its shadow, the effect on not just the ionosphere, but the atmosphere, is like a short little sunset, causing changes even to radio frequencies, and gathering data on what happens helps us understand it, and even adapt to it.
So...back to NASA...what are they up to again?
On the 8th April 2024, NASA will be launching the APEP rockets, which will reach 260 miles (right up in that Ionosphere), to measure the charged and neutral particle density. They will also be launching balloons, and a collaboration team will be operating radars to take measurements. They will be measuring these with respect to measurements taken in 2023, during the annualar solar eclipse, to see how and if the results change.
I wonder what they will find, and how it will influence our understanding of atmospheric chemistry, and the influence it has on our lives!
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