Although here, on earth, we, as humans, perceive the sun as this element with an apparent constant behavior, taking a closer and sharper look, with tools that gather data that humans by themselves can’t, we realize this is not true. The Sun shows an approximate 11-year dynamic cycle of behavior, with periods of more or less activity in this time span. During the active period, extreme phenomena, which release a lot of energy to the heliosphere, like solar flares, and Coronal Mass Ejections (CMEs), are observed more often. Although we know what’s the energy/matter constitution of these phenomena, and many aspects of the sun’s behavior and “anatomy”, many questions remain unanswered: What drives the Sun’s 11-year cycle of rising and subsiding magnetic activity? How does the solar wind form, and what accelerates it to speeds of hundreds of kilometers per second? What heats up the corona, the sun’s upper atmosphere layer, to millions of degrees Celsius? What are the sources of high-energy solar particles? To answer these questions, NASA, and collaboratively ESA and NASA, have launched, respectively, two spacecrafts that will study the Sun closer than ever before: The Parker Solar Probe, and the Solar Orbiter.
NASA’s Parker Solar Probe was built with the purpose of “touching the Sun”. With a capacity of facing brutal heat and radiation, and every orbit bringing it closer to the Sun’s surface, it’s the first spacecraft to fly through the corona. Parker Solar Probe will give humanity its first-ever sampling of a star’s atmosphere and answers to long-standing questions like, e.g.: Why is the corona much hotter than the photosphere? And how does the solar wind accelerate? Answers which will be key to understanding space weather . The probe contains four instrument suites designed to study magnetic fields, plasma , energetic particles, and to image the solar wind. It will fly more than seven times closer to the Sun than any spacecraft, and over seven years will complete 24 orbits around the Sun. It can withstand temperatures reaching nearly 1377 oC. On December 14th, 2021, it was announced, in a press conference, that, for the first time in history, a spacecraft had touched the Sun, having the Parker Solar Probe flown through the Sun’s upper atmosphere (the corona), and sampled particles and magnetic fields there.
The other spacecraft, ESA’s and NASA’s Solar Orbiter, is the most complex scientific laboratory ever to have been sent to the Sun, taking images of our star from closer than any spacecraft before. It’s also the first spacecraft to look at its polar regions. With ten instruments onboard, it’s intended to answer similar and complementary questions to those of Parker Solar Probe’s. For that reason, both missions, as we’ll see, have already worked together to complement each other’s observations and measures.
The Solar Orbiter spacecraft is made of instruments capable of remote and in-situ measurements, with the remote instruments being also able to provide contextual information to Parker Solar Probe’s in-situ measurements, given that no current technology could look at the Sun from that close and survive. Regarding Solar Orbiter’s own way of functioning, the in-situ instruments measure the solar wind plasma and magnetic field around the spacecraft, while the remote sensing instruments take images and other data of the Sun itself. Given that it takes some time for the solar wind particles to reach the spacecraft, and that the cameras provide images of the Sun as it appears in the moment, an online software tool called “The Magnetic Connectivity Tool” is used to link the two datasets and, therefore, provide more insightful information.
On April 2024, both spacecrafts were at a special positioning regarding to each other, because at some point in their orbits, the Solar Orbiter had its instruments pointed towards a region on the Sun where the solar wind produced would, a few hours later, hit the Parker Solar Probe. This would allow scientists to compare the data collected by both missions, and, since Parker Solar Probe orbits much closer to the Sun, it was able to directly measure properties of the solar wind, like its temperature and density, closer to its birthplace, before these properties change as they got distant from the Sun. If a CME was observed by Solar Orbiter in these conditions, scientists could then see the restructuring of the Sun’s outer atmosphere during the CME in great detail, and compare it to the structure seen in-situ by the Parker Solar Probe. This complementary work between missions was possible, because remote sensing detects light waves coming from the Sun, which took 2.5 minutes to reach Solar Orbiter’s in this position in orbit, while the in-situ instruments at Parker Solar Probe sense the particles and fields in the immediate vicinity of the spacecraft, travelling these particles away from the Sun 500 times slower than the speed of light.
As we’ve seen, efforts have been made to understand the nature of the extreme phenomena that happen in the Sun throughout its life cycle. Missions involving extremely resistant technology allowed us to get closer than ever before, and might give us important answers to questions that have been standing unanswered for many years. But the work doesn’t stop here, and although understanding the Sun’s extreme phenomena is important, monitoring it in order to protect our space assets and infrastructure on the ground might be even more important. With that purpose, a new spacecraft, named Vigil, to be launched in 2031, will be looking to the “side” of the Sun, looking for potentially hazardous solar activity, before it rolls into view from Earth. This way, Vigil’s purpose is to give us advanced warning of oncoming solar storms and, therefore, help us preserve our infrastructure in Space and on Earth.
Read more:
https://science.nasa.gov/mission/parker-solar-probe/
https://www.esa.int/Science_Exploration/Space_Science/Solar_Orbiter
https://www.esa.int/Space_Safety/Vigil
https://www.esa.int/ESA_Multimedia/Videos/2022/02/Introducing_ESA_Vigil
