Simulating Giant Sound Waves on Mars

Hello, again!

It’s time for another installment of “a day in the life of an awesome physics student at Embry-Riddle.”

Well the summer is in full swing; I had my first exam on Thursday, which was also my first exam of grad school, as the class I’m taking is my first master’s class for the accelerated degree. I was really confident, which means I either aced the exam or bombed it – you never really know until you get your results back. I’ve never taken summer classes before, but so far I think it’s pretty awesome. The material moves at a quick yet manageable pace, and it’s nice to only have one class to worry about after the last four semesters of 16-17 credits. My only complaint about summer classes is the “summer” part – why is it so hot outside? It’s unnatural. I really wasn’t born to live in the south; I can handle a -20º wind-chill, but as soon as the thermometer climbs above 90º that’s when I give up and hide inside. Not to mention it rains so much! (I promise I won’t complain about the weather in every entry.)

I’ve had a lot of free time, which is unusual for me, so it’s been nice. Lately I’ve been learning some new acoustic guitar songs, watching old seasons of Buffy the Vampire Slayer, and leveling a blood elf warlock. And let me just take a moment to talk about how much I love living in my own apartment off campus. Everything is finally clean, unpacked, and decorated to my liking, and I can listen to loud music in any room at any time and nobody complains about my volume, musical tastes, or singing. It’s great. I live only two minutes from campus, so it’s a nice, short commute every day. Once I figure out how to reduce my electric bill everything will be perfect!

Image of Mars’ Gale Crater from Google Earth. This location was used to generate the profile used in our acoustic wave simulations. Gale Crater was the landing site of NASA’s Curiosity rover, which landed last year.

My days are spent sitting up in the Lehman Building’s Space Physics Research Lab (which will henceforth be referred to as “SPRL”) working on my project for the CEDAR conference in late-June. I mentioned it briefly in the last entry, but I think I should elaborate, since that’s what got me this gig as a blogger. CEDAR (which stands for “Coupling, Energetics, and Dynamics of Atmospheric regions”) is an NSF-sponsered yearly atmospheric sciences meeting that focuses on instrumentation and modeling of the middle and upper atmosphere. I am working with Dr. Snively in the Department of Physical Sciences to adapt his atmospheric wave model to Martian conditions so that we can see how atmospheric acoustic and gravity waves, which are a bit like ocean waves, but in the atmosphere, propagate on Mars in comparison to Earth (if you’re interested, my project abstract is here).

Some plots of relevant atmospheric data on Mars generated by the profile used in our simulations.

We are using MarsGRAM (Mars Global Reference Atomic Model) data provided by NASA’s Marshall Space Flight Center to specify many different properties of the atmosphere, which has proven very interesting! This data is then used to generate a profile, which essentially shows the temperature, density, pressure, etc. as you travel up through the atmosphere (it’s really just a big table of numbers), and then the profile is loaded into the wave dynamics model. The model produces a simulation based on some inputs, such as frequency, amplitude, etc., and we watch how the wave behaves as it moves upward.

Animation of a nonlinear acoustic wave traveling up through the Martian atmosphere. The one-dimensional simulation is laid over the two-dimensional simulation in order to determine that the results of each are valid. This wave has a frequency of 0.032 Hz, which corresponds to a wavelength of about 31 km. (Click on thumbnail to watch animation.) Note that the axes correspond to the 2-D results (and are in meters – please disregard the error in the labeling.)

This past week we successfully simulated an acoustic wave in both a one-dimensional and two-dimensional model and confirmed that the results agreed. Acoustic waves are really cool – they are essentially giant sound waves that move up through the atmosphere until the air becomes too sparse and viscous, causing them to dissipate. We’ve found that this happens really quickly on Mars compared to Earth, due to the increasing viscosity at higher altitudes. The waves we have been simulating have frequencies of about 0.03 Hz. For perspective, note that the average human can hear frequencies ranging from 20-20,000 Hz, so these waves are much larger and lower-frequency than ordinary sound waves.

The next phase of the project is to simulate two-dimensional gravity waves, which I will talk about in my next entry!

Before I close out this entry, I wanted to touch back on what I said last time about going where life takes you. I came into Riddle as an Aerospace Engineering student, but was converted to Engineering Physics after my first semester due to the fact that I love physics and space and don’t really care about designing airplanes (blasphemy, I know.) Deep down I definitely feel like an EP student, and never once regret my change. In fact, the more I go through my coursework, the more I find myself leaning towards physics and research and away from actual engineering – I took the “gauntlet” (solids, dynamics, and fluids, which are engineering sciences classes you take your sophomore year), and pretty much hated them (though I did like fluids, but that was because professor Davids is awesome!) Plus I am loving what I am doing here in SPRL. I’ve been thinking a lot about what I’m going to do after Riddle, and, while my plan had always been BS then MS then Work in engineering then PhD maybe later, I am thinking more about going straight onto my PhD and getting involved in space and astrophysics research.

Tune in next week, I’ll have some really cool Mars stuff to share with y’all! (Yeah, I’m becoming a southerner. I say that now.) Be sure to email me if there’s anything you’d like me to write about Riddle, otherwise I’ll just keep rambling on about my life in every entry.

-Lynsey
schroel2@my.erau.edu

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