The Solar Dynamics Observatory launched last week for the thrilled scientists and engineers who have worked for years on this mission, some happy #SDOisGO TweetUp participants, and countless other space fans around the world. (The who? The wha? Oh, pretty!)
SDO’s EVE instrument (Extreme-ultraviolet Variability Experiment) is particularly interesting to me since these EUV photons from the sun are what drives the Earth’s ionosphere. The ionosphere is the outermost layer of the Earth’s atmosphere and consists of ionized, or charged particles. As new low frequency radio telescope capabilities have been coming online at the VLA, GMRT, LOFAR, LWA, MWA, and, my home, PAPER*, the ionosphere is gaining more attention, and not the good kind. Just as the lower levels of the atmosphere cause all kinds of scintillation and “twinkling” to annoy visible light observers, the ionosphere refracts and distorts light coming in at low radio frequencies. (Well, low for astronomers, that is… less than a few 100 MHz!) This is particularly troubling since all of these telescopes are interferometers, or systems of multiple radio antennas linked together to make one telescope. Images are made by measuring the difference between the arrival of light at different antennas, and this difference can be skewed by a turbulent ionosphere. And the ionosphere changes in density and turbulence, based on the solar output! See, it all ties together.
I have to admit, of course, there are more pressing concerns than radio astronomy. The ionosphere will also have an effect on GPS signals. As we start the upswing in the solar cycle, more turbulence in the ionosphere will mean larger position errors and even times when the signals cannot propagate at all. Monitoring systems can do their best to account for changes in the ionosphere, but an early warning system will help those who have to make very precise GPS measurements (not just you and your TomTom) plan their activities. EVE will measure the extreme-ultraviolet output of the sun on 10-second time scales, 30 times better than previous instruments could. Therefore, solar physicists will be able to better understand the signs and signals of a sun that is about to make our ionosphere dance around.
That’s it, for now, for my sciencey SDO posts. I can’t wait to see what new discoveries start rolling in when science operations begin. I’ll probably have one more SDO post soon, about the TweetUp itself!