Thursday, June 25th 2020, 3:40 pm - SDO's constant vigil from orbit helps protect us from the impacts of space weather
NASA's Solar Dynamics Observatory as been aiming an unblinking eye at the Sun for a full decade now. Capturing millions of images over the past solar cycle, SDO has provided astounding insights into the Sun's behaviour, while keeping us alert to potentially dangerous activity.
February 2010 saw the launch of a new telescope into orbit around Earth. Its mission: to keep an unwavering watch over our parent star, in the hopes of teaching us new science about the universe, but also to provide us with a way of predicting the impacts of space weather on Earth and human civilization.
As of June 2020, SDO has now been continually observing the Sun for ten years - nearly an entire solar cycle.
According to NASA, SDO's Atmospheric Imaging Assembly (AIA) instrument captures images every 12 seconds, at 10 different wavelengths of light. The new 10-year time-lapse video from the mission features views captured using a filter that blocks out everything but the extremely intense ultraviolet light that is emitted from the Sun's corona. The temperature of the matter seen in these images is an astonishing 1 million degrees Kelvin.
Watch below: NASA presents nearly a full 11-year solar cycle of the Sun
The only things that have interrupted its watch have been those rare times when either the Moon or Earth passed directly through its field of view. Of particular note are the spectacular 'coronal loops' - arcs of flowing magnetic solar plasma that stretch outward to thousands of kilometres above the Sun's surface.
HIGHLIGHTS FROM THE LAST DECADE
This artist impression of the Solar Dynamics Observatory shows it maintaining its vigil from low-Earth orbit. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
The Solar Dynamics Observatory has captured many other fascinating phenomena over the past 10 years. Below is a list of the most amazing sights the spacecraft has shown us since its mission began.
Just two years after it was launched, SDO captured what can only be described as 'solar tornadoes'.
According to NASA, although these tornadoes resemble the ones we see here on Earth, they are not created by wind, but instead by solar plasma spinning around magnetic fields. Also, they stretch up to 13,000 kilometres above the surface and can rotate at speeds of nearly 300,000 kilometres per hour.
One of the most impressive sights revealed by SDO shows what are known as coronal loops.
Solar plasma rains down onto the surface of the Sun from these intensely heated coronal loops. An image of Earth is provided for scale. Credit: NASA/Goddard Space Flight Center
Seen here in images captured in July of 2012, arcs of superheated solar material stretch upwards from the surface, looped around powerful magnetic field lines. The image of Earth, provided for scale, reveals the truly immense proportions of these loops. From the brightest arc, plasma rains down from over 63,000 kilometres above the surface - five times the width of Earth - while the entire structure stretches to a height of more than 114,000 km (roughly the size of Saturn, without its rings).
Only two and a half years into its mission, SDO captured one of the most iconic images of solar activity that we have ever seen.
This immense coronal mass ejection erupted into space on August 31, 2012. Although it was not an Earth-directed CME, it dwarfed our tiny planet by comparison. Credit: NASA/Goddard Space Flight Center
On August 31, 2012, an immense filament of solar plasma, heated to tens of thousands of degrees, arched high above an active region on the Sun's surface. As it was held there by powerful magnetic fields, SDO captured a sequence of images, documenting this impressive display of our home star's power. When the filament finally stretched outwards and snapped, it propelled a cloud of hot plasma, weighing in at billions of tonnes, out into the solar system. This solar storm would eventually expand until three days later, one edge of it swept past Earth. Due to the energy, density and speed of the storm, it resulted in a vivid display of the Northern Lights.
Having now gone through nearly an entire solar cycle, from 2010 to 2019, SDO watched as solar activity ramped down from the twin peaks of 2011 and 2014. Even two years before the end of the cycle, though, when activity was nearing its minimum, the mission showed us that the Sun was still capable of intense activity.
A lone sunspot complex, labelled Active Region 2665, began crossing the Earth-facing side of the Sun in early July 2017. Towards the end of its journey across the face of the Sun, on July 14, 2017, it generated some intense coronal loops that bridged across the entire sunspot.
Sunspot AR2665 as viewed through SDO's 171 Angstrom filter, revealing the elegant coronal loop structures around the region. Credit: NASA
Weeks later, in early September 2017, another small sunspot named AR 2673 suddenly blossomed to ten times its original size. Developing into a chaotic sunspot complex surrounded by a cluster of tangled magnetic loops, it contained an immense amount of energy, just waiting to erupt. On September 6, the tangles abruptly snapped, producing the most powerful solar flare of the entire 11-year cycle!
This X9.3 flare blasted out from the Sun on September 6, 2017. It was the most potent solar flare seen from the Sun since 2005. Credit: NASA
Scientists studying the Sun have known for some time that our local star can still produce extreme activity even very late in a solar cycle. This proved to be an excellent example.
Overall, SpaceWeather.com ranked this flare as the 14th strongest ever seen since the mid-1970s. It was quite tame, though, compared to the Halloween storms of 2003 and the Carrington Event of 1859 (two of the strongest geomagnetic events ever recorded).
WHY DOES THIS MATTER?
Our Sun is an active star, with an 11-year cycle of increasing and decreasing activity.
A continuous stream of charged particles is emitted by the Sun into space, which we call the solar wind. The Sun also periodically blasts out powerful bursts of x-rays, known as solar flares, and it throws off immense eruptions of electrically-charged plasma, known as coronal mass ejections or 'solar storms'.
This graphic collects the various impacts of space weather. The inset plots the past 400 years of solar cycles, counting the numbers of sunspots per year to track solar maximums and solar minimums. Credits: NASA/Scott Sutherland
Scientists group this solar activity under the heading 'space weather', due to its effects on Earth, and the impacts it can have on our technologies - both in space and on the ground.
X-rays from solar flares cause radio blackouts on the daylight side of the planet. The stronger the flare, the more intense and long-lasting the outage. The timing of these events can be quite disruptive. When a series of solar flares went off in September 2017, the lengthy radio blackouts disrupted relief efforts in the wake of Hurricane Irma, and during Hurricane Jose. While most spacecraft and satellites in orbit are hardened against the effects of space weather, very intense X-rays can still have damaging impacts on them.
Changes in the flow of the solar wind, as well as the arrival of a solar storm, can both spark disturbances in Earth's magnetic field, known as geomagnetic storms. Spectacular displays of the auroras - the Northern and Southern Lights - are often seen during these storms. Still, there can be negative impacts as well. The fluctuations in Earth's magnetic field produced by particularly strong geomagnetic storms can cause electrical problems with spacecraft in low-Earth orbit. They can also induce electric currents through the ground that are capable of disrupting power grids, result in widespread blackouts.
This artist's drawing depicts the 1989 Quebec blackout, which was caused by an intense geomagnetic storm after a solar storm passed by Earth. Credit: NASA
SDO helps protect us against these space weather impacts by snapping images of the Sun in different wavelengths every 12 seconds. So far, as of June 2020, it has collected a total of over 425 million images, according to NASA.
We have no way of directly shielding ourselves against the impacts of solar flares or the geomagnetic effects of a solar storm. Having 'eyes' on the Sun does provide us with vital warnings. Forewarned about a potentially dangerous situation developing, we could take action, shutting down satellites and vulnerable power grids until the danger had passed.