Ver 1.0
A plain-language summary of my Ph.D. dissertation on "Remote sensing of Energetic Electron Precipitation"
Source: Sivadas 2020 Ph.D. Thesis
Problem: My Ph.D. was on understanding the source and effects of energetic electrons in the polar regions. Auroras are produced by electrons and protons streaming down from space, and interacting with the Earth's upper atmosphere. The video shows a curtain of aurora seen from the International Space Station. The visible part is generated by what I'd call the auroral electrons. Right below that curtain, at a height below 100 km, there are electrons of higher energy interacting with the atmosphere (you cannot really see them much in visible light). They emit faint blue light and also cause UV and X-ray emission. I wanted to know where these electrons are coming from and the extent of their effect on our upper atmosphere.
[The aurora from the International Space Station. The red and green optical emissions are produced by auroral electrons which have lower energy than the energetic electrons that interact with the upper atmosphere below them. Source: https://go.nasa.gov/2IGGpk2; Credits: NASA and ISS. ](https://s3-us-west-2.amazonaws.com/secure.notion-static.com/033095ab-02cc-4158-9836-8af691414f1a/aurora_1_3.mp4)
The aurora from the International Space Station. The red and green optical emissions are produced by auroral electrons which have lower energy than the energetic electrons that interact with the upper atmosphere below them. Source: https://go.nasa.gov/2IGGpk2; Credits: NASA and ISS.
Results:
The night-side dipolar transition region, located at a distance of 8-12 RE from the center of the Earth. Source: Sivadas et al., 2019; Sivadas 2020.
Therefore, these energetic electrons seem to have a sizable impact on the upper atmosphere in the polar regions. We now know that they can contribute to the depletion of ozone in the polar regions and affect average atmospheric temperatures. They can enhance the upper atmosphere's conductivity, thereby increasing the amount of large electric currents that pass through the upper atmosphere. They also cause disruptions in high-frequency radio communications in the arctic and harm humans and solid-state electronics that are on its way.
Beyond now and here: Energetic electrons seem to play a significant role in the near-space environments of other planets in the solar system. Here is a video of ultra-violet aurora produced in Jupiter by energetic particles. The size of the Jovian energetic aurora, is as big as our entire planet. Just take a moment, and let that sink in. Whole moons of Jupiter end up being bathed in these energetic electrons. Thousand years from now, humans or other beings might live and work around these planets. Here the knowledge of the dynamics of energetic electrons learned from our world might help them be safer. And they might find ways to use these energetic electrons to harness energy - especially on planets much farther away from their star where solar energy is minimal.
[Jupiter's ultra-violet aurora caused by energetic particles, photograph taken by the Hubble space telescope. Source: NASA YouTube Link; Credit: NASA, ESA, J. Nichols (University of Leicester), and G. Bacon (STScI); Acknowledgment: A. Simon (NASA/GSFC) and the OPAL team](https://s3-us-west-2.amazonaws.com/secure.notion-static.com/670ec24b-4556-4acf-ae0a-329e26ba3b10/jupiter_aurora.mp4)
Jupiter's ultra-violet aurora caused by energetic particles, photograph taken by the Hubble space telescope. Source: NASA YouTube Link; Credit: NASA, ESA, J. Nichols (University of Leicester), and G. Bacon (STScI); Acknowledgment: A. Simon (NASA/GSFC) and the OPAL team