In early February, 2010, the US space agency NASA launched a mission called the Solar Dynamics Observatory, or SDO. It carries instruments to take frequent and detailed images of our sun. EarthSky spoke with Tom Woods, principal investigator of the Extreme Ultraviolet Variability Experiment on NASA’s SDO.
Tom Woods: SDO is a new NASA mission to study the details of solar variability and with special emphasis on the solar storms that drive our space weather here on Earth.
Space weather, explained Woods, is weather that happens in the outer atmosphere instead of near Earth’s surface, and it affects satellites.
Tom Woods: The solar storms are especially important because they end up depositing lots of energy and particles in our upper atmosphere that impact a lot of our technologies, such as communication, GPS, navigation systems. And one of the key goals for SDO is to understand better the causes for these solar storms and how to better forecast these storms.
Dr. Woods said that the sun goes through an 11-year cycle of activity, and he expects the sun to be at maximum activity by around 2013. When that happens, there could be an increase of solar flares that affect people on Earth.
Tom Woods: An example might be during the big Halloween storm of 2003, it disrupted GPS navigation as far south as Florida. There are also some benefits. People as far south as Mexico saw the aurora for the first time in their lives.
NASA’s Solar Dynamics Observatory is expected to keep its eye on the sun through 2015 and beyond. Dr. Woods spoke about the Extreme Ultraviolet Variability Experiment, or EVE, on board NASA’s Solar Dynamics Observatory.
Tom Woods: EVE is one of the three instruments aboard SDO. EVE will be measuring the solar extreme ultraviolet radiation, or EV, with unprecedented accuracy and spectral resolution and temporal coverage than what we’ve been currently able to measure. And it consists of three spectrographs to make these measurements. Spectrographs for us include diffraction gratings that sort out the wavelengths, or colors. And then we use special EV sensitive CCD cameras to measure the brightness of each of the EV emissions. We’ll be measuring this 24/7, with about 10 second cadence, 0.1 nanometer resolution, spectral resolution. There are also other instruments on board SDO to measure images of the sun, in extreme ultraviolet as well as in the visible, to help understand magnetic interactions of the different activities on the sun.
The SDO will capture images of the sun in resolutions far beyond those of High Definition television, said Woods.
Tom Woods: It’s probably ten times more than high-definition television. The images that are coming out will be 4,000 by 4,000, and there’ll be about 15 unique images every ten seconds.
Dr. Woods talked to EarthSky about the science questions that NASA’s SDO will attempt to answer.
Tom Woods: The SDO mission is designed to last for at least five years. One of the goals of having a long mission is to study the solar activity throughout its eleven-year solar cycle. We’re currently in a solar minimum period now, where we have low activity. In approximately three years, four years, we’ll be at its peak of activity. We call that solar maximum. So we’re hoping that it will last longer than that and be able to see a full solar cycle. Some of the early science results of SDO will be related to understanding what causes the solar storms, these flares and coronal mass ejections of particles. We know that the solar magnetic activity is a key driver for these solar storms, but we don’t really fully understand how the solar magnetic field rises up from the interior of the sun. And once they’re above the surface of the sun, how do they interact to produce bright flares? Why are some flares larger than others? They have similar magnetic field structures. Why are there coronal mass ejections, these particles that are associated with some flares but not other flares, those type questions I think, by having 24/7 coverage in looking over the entire disc of the sun, we’ll be able to start addressing these questions early in the mission.
EarthSky asked Dr. Woods what he thought was most important about NASA’s Solar Dynamics Observatory.
Tom Woods: I think the most important thing to recognize about SDO is maybe its slogan, “our eye on the sun.” And that’s because we’ll be providing 24/7 coverage of the sun. This continuous coverage is ideal for seeing all solar storms. By being able to observe all these storms with great detail that we haven’t had before, we plan to advance our understanding of solar variability, which in turn will lead to more reliable space weather predictions.