Puissantes éruptions solaires enregistrées par la caméra ultraviolet extrême EUI de la sonde européenne Solar Orbiter lors de son passage rapproché le 27/03/2022. Crédits : ESA & NASA/Solar Orbiter/EUI Team.
Un curieux « hérisson » solaire
What breathtaking pictures! The European Solar Orbiter probe, launched in 2020, made its first close approach to the Sun—or perihelion—on 26 March. This is when its orbit passes very close to our star, at just 0.32 AU (astronomical units), i.e. about 48 million kilometres for this approach. There will be more during the course of the mission.
On this occasion, the probe’s 10 instruments recorded unique data of powerful flares, clear views of the Sun’s polar regions and an unusual, eye-catching feature nicknamed the ‘hedgehog’. Solar Orbiter’s main science goal is to explore the connection between the Sun and heliosphere, the elongated ‘bubble’ of space filled with the electrically charged particles continuously streaming from the Sun that form the solar wind.
Solar ‘hedgehog’ observed by Solar Orbiter’s EUI instrument on 30 March. ESA & NASA/Solar Orbiter/EUI Team.
The European Solar Orbiter probe was sent into space in 2020. Credits: ESA/ATG medialab.
Solar Orbiter’s main science goal is to explore the connection between the Sun and heliosphere, the elongated ‘bubble’ of space filled with the electrically charged particles that form the solar wind. Credits: NASA.
Joining the dots between what the probe sees and ‘feels’
Joining the dots between what the probe sees and ‘feels’The crux of the matter now for the mission’s science team is to trace back the data from the in-situ instruments analysing the probe’s immediate environment, bathed in the energetic particles sweeping across the spacecraft, to the events recorded by the remote-sensing instruments observing the Sun’s activity: in other words, to ‘join the dots’ between what the probe sees and ‘feels’.
Highest-ever-resolution image of the Sun’s south pole, acquired by Solar Orbiter on 30 March. Credits: ESA & NASA/Solar Orbiter/EUI Team.
As luck would have it, a few days before perihelion, on 21 March, a cloud of energetic particles swept over the spacecraft. The Energetic Particle Detector (EPD) recorded the event, the most energetic particles arriving first. The Radio and Plasma Waves (RPW) instrument, assembled at CNES, also picked up the strong characteristic sweep of radio frequencies produced when accelerated particles—mostly electrons—spiral outwards along the Sun’s magnetic field lines. The Extreme Ultraviolet Imager (EUI) and Spectrometer/Telescope for Imaging X-rays (STIX) also both observed solar events that could have been responsible for the release of the particles, but the science team will have to analyse the data more closely before reaching any conclusions.
A boon for ‘space weather’ forecasting
A boon for ‘space weather’ forecastingOne of the surprises of the close approach on 26 March discovered by the team working with David Berghmans, EUI Principal Investigator from the Royal Observatory of Belgium, is a feature in the solar corona they have nicknamed the ‘hedgehog’, as it stretches 25,000 kilometres and has a multitude of spikes of hot and colder gas reaching out in all directions. “The images are really breathtaking,” says Berghmans . “Even if Solar Obiter stopped taking data tomorrow, I would be busy for years trying to figure all this stuff out.”
Desi Raulin, Solar Orbiter project leader at CNES
The perihelion of 26 March has proved a great success for Solar Orbiter. “The French science teams are delighted with the results, as they’ve been able to harvest huge amounts of data,” says Desi Raulin , Solar Orbiter project leader at CNES. “All the instruments are working perfectly despite a technical hitch encountered with the Solar Wind Analyser (SWA) affecting the first observations. It’s a huge relief the probe’s instruments have acquired so much data and at such good resolution. At CNES, we’ll be continuing to support the French scientific community involved in this mission over the next five years, which is how long the main science phase is scheduled to last.”
What’s more, all of these observations are a gold mine for ‘space weather’ forecasting. Ultimately, the idea is to have a precise and reliable system able to predict solar events likely to damage power grids on Earth and even pose a threat to astronaut crews. For example, on 10 March a coronal mass ejection (CME) hit Solar Orbiter. The Magnetometer instrument (MAG) was able to predict the CME would reach Earth 18 hours later, leaving time to take mitigating action. This event therefore gave a taste of what’s to come. The next perihelion of Solar Orbiter will be on 13 October, this time setting a new record of 0.29 AU.
Locations of Solar Orbiter’s instruments on the spacecraft. RPW, the instrument assembled at CNES, is composed of three antennas on either side of the probe and a magnetic sensor (SCM for Search Coil Magnetic) on the boom to the rear. Credits: ESA.
Solar Orbiter’s perihelia
- 15/06/2020 (0,52 UA)
- 10/02/2021 (0,49 UA)
- 12/09/2021 (0,59 UA)
- 26/03/2022 (0,32 UA) – 1st close perihelion
- 13/10/2022 (0,29 UA)
France shines on Solar Orbiter
Solar Orbiter is an international space mission of the European Space Agency (ESA) and NASA. France, through CNES, seven research laboratories at CNRS, universities and CEA, contributed to six of the ten instruments on the spacecraft. CNES supplied the RPW instrument (pictured) and oversaw other contributions, providing its technical expertise to mission partners. For the Proton-Alpha Sensor (PAS), CNES was in charge of thermal engineering and several component and material tests, as well as electrostatic discharge analyses, electromagnetic compatibility expertise and magnetic testing.