South Africa #10: Science Time

A one figure summary of my thesis on low energy ions from satellite observations
So I confess - I had a totally non-adventurous week in South Africa this past week. I had a sinus infection earlier this week (yummy!) followed by a lot of work (epic!) to prepare for Nadine and I's trip the next two weeks. In my 'extra' time this week, I week on a book binge and read something ridiculous like 10 books. So, no penguins or epic hikes this week...

However, I am going to take this week to talk about my research here in South Africa on a high-level (so understandable hopefully to everyone!) and why I am here. I hope you all accept my peace offering as satisfactory ;)

A PhD is a not a license of general knowledge, it's a title of specialization. Your Innocent Heroine here specialization looks something like this:
Physics -> Astronomy -> Space Science -> Magnetospheric Physics -> Earth -> Satellite Observations -> Plasmasphere -> Inner Plasmasphere -> Low Energy Ions
And in South Africa, my specialization has changed to:
Physics -> Astronomy -> Space Science -> Ionospheric Physics -> Earth -> Ground Based Observations -> F Region -> Electron Density
Saskatoon SuperDARN Radar (photo credit someone else)

EISCAT Incoherent Scatter Radar at Tromso (photo cred: me!)
This is a pretty major switch from what I normally do, and it's required a lot of background reading and delving into things I'd never considered before (i.e. how does a plasma heater work? How do you generate the waves for a plasma heater?) But I've really loved it... it's challenging work, it requires me to think deeply about the physics behind what's occurring in conjunction with a large engineering component.

The goal of my project is to see if it's possible to calculate electron number densities using SuperDARN coherent scatter radars. A coherent scatter radar sends out a 'weak' signal and can only receive signals from large amplitude (re: high density) patches aligned with Earth's magnetic field. SuperDARN radars do not measure electron number densities directly; instead, they measure bulk velocity, power of backscatter signal, and spectral width of the received signal (think of it as an indicator of how good the signal is).

Coherent = SuperDARN, Incoherent = EISCAT. Ne = electron number densities, and the y axis is height
We care about electron number densities because they affect all signal propagation through the ionosphere. This is why your radio works better at night than during the day (Hey! We're getting Chicago stations now! Thanks Ionosphere!). More seriously though, electron number densities can seriously affect GPS and HF frequency communication. Our ability to measure, predict, and understand electron number densities is critical for stable communication maintenance.

A few years ago, a group in Canada came up with a reasonable theory that is mathematically sound for calculating electron densities using changes in signal frequency from the radar and measured velocity. Without going into too much detail, the essence of their idea is kind of like shining a flash light into a pond and seeing how deep the pond is by how much the light bends (index of refraction). They did some statistical comparison, but Mike Kosch (South African advisor- http://www.mikekosch.com/) came up with an experiment to test success with a case study using the Hankasalmi SuperDARN radar and the EISCAT incoherent scatter radar at Tromso (hey! Those other blog posts at Norway make sense now!)

Why compare with EISCAT? EISCAT is much more powerful signal, can look in any direction and can (through a procedure) calculate accurate and verified electron number densities at known heights. EISCAT is reliable, and the Hankasalmi SuperDARN radar field of view (where we will have measurements) overlooks the EISCAT radar. Perfect, right?
Ray Trace (black lines) from Hankasalmi to Tromso. The Black Star is the EISCAT radar, and the purple line is the magnetic field. 

SuperDARN only measures irregularities, so turning on the EISCAT heater (which issues a wave that heats the plasma, much like your microwave), we create artificial irregularities over EISCAT at Tromso that SuperDARN can see. However, depending on how dense the ionosphere is, the signal propagates differently from Hankasalmi. Using a model, we traced "rays" (re: signals at specific frequencies) from Hankasalmi to get an estimate which gates correspond to the EISCAT heater.

Obviously, many problems arise. Namely that SuperDARN data is tough because you have no idea where it is. It's kind of light going into your basement, turning on a high beam flashlight, and trying to count dust particles. You can kind of tell how far they are away, but not really. We're constantly trying to constrain the data while still saying something meaningful.  [cue rant] For all the 'climate change deniers' this is how science works, and when you have 95% agreement across an enormous community, that's a well constrained and accurate statement.  I guarantee if I presented my results tomorrow, I would have at least 50% disagreement in the community  despite the fact that the success of my project would mean more funding for SuperDARN radar project. [end rant]
The colored dots = SuperDARN number densities / EISCAT number densities. SuperDARN is all over the place

 In this study, we found that SuperDARN number densities did not agree with the EISCAT ones. I know the first thought is "But Lo, I'm attached to SuperDARN now because you talked about it so much... what if EISCAT is wrong". EISCAT isn't wrong here... please trust me. The method should work but it has some inherent flaws (dividing by small differences) that cause it to produce enormous variability.

We've submitted this study for review and publication. Mike and I have been hard at work though... we've also done another study on using SuperDARN to calculate Neutral thermospheric densities and another determining backscatter locations for the South African SuperDARN radar at SANAE in Antarctica. Lots of good stuff, but I just wanted to give you all an insight into what I'm doing here and why, which I should add...

Who is paying for all this? 

Haha, great question, because it's not the South African National Space Agency. In 2014, I won an NSF Graduate Research Fellowship (https://www.nsfgrfp.org/) which is an extremely competitive fellowship for STEM field researchers that pays for 3 full years of graduate tuition and stipend. 2000 awards are made each year from bioengineering to mathematics. Within the NSF GRF program, there is another fellowship that we can apply for called GROW - the Global Research Opportunities World wide.

The GROW fellowship is a coordination between NSF and the Science Foundations of other countries to send GRFP students abroad to work on part of their thesis. Usually the host country pays for most of the expenses and NSF chips in a bit. However, there exists a subset within GROW called the US-AID, which is the US Agency for International Development,  project which supports NSF Fellows who want to research abroad in countries that can't afford to host NSF fellows, so NSF pays for all of it in conjunction with the US-AID program. The South African National Space Agency requested a researcher with a space science background... and I matched that call. It was a match made in heaven.



In the Fall of 2014, I wrote an extensive proposal (> 40 pages all together, budget and everything) to collaborate with Mike Kosch at SANSA. In April of 2015, it was approved, so here I am now :) The moral of the story is: 1st year graduate students, take your NSF Fellowship application seriously... it leads to opportunities you can only begin to imagine.

Next week, I will be *skipping* a blog post because Nadine and I will traveling. Stay tuned for the following week, I'll do 2 posts to make up for it :)

Lo

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