The joint European Space Agency (ESA) and NASA Solar Orbiter spacecraft has made groundbreaking observations by tracking electrons traveling at nearly the speed of light back to the sun. This remarkable achievement has unveiled that these electrons, known as Solar Energetic Electrons (SEEs), originate from different types of solar outbursts. The Solar Orbiter detected these high-energy particles in space, aiding researchers in pinpointing their sources and enhancing our understanding of the sun's physics.
Through its observations, the Solar Orbiter has revealed two distinct types of SEEs, each with unique origins. One group of electrons is associated with solar flares that erupt from smaller areas of the sun, while the other group is linked to larger and more powerful phenomena known as coronal mass ejections (CMEs). According to Alexander Warmuth, team leader and researcher at the Leibniz Institute for Astrophysics Potsdam (AIP), there is a clear distinction between what he describes as 'impulsive' particle events and 'gradual' ones. Impulsive events are characterized by energetic electrons that burst off the sun’s surface during solar flares, whereas gradual events are associated with CMEs that release a broader wave of particles over an extended period.
Prior to this study, scientists had recognized the existence of two families of SEEs, but the Solar Orbiter's observations have finally allowed them to differentiate between their origins. Warmuth stated that the team was able to identify and understand these two groups by observing hundreds of events at varying distances from the sun, something that only the Solar Orbiter can achieve. By venturing close to our star, the spacecraft could measure particles in a 'pristine' early state, accurately determining when and where they originated on the sun.
The Solar Orbiter's ability to detect SEEs at various distances from the sun has enabled researchers to investigate how these particles behave as they travel through the solar system. One of the key goals was to understand the time lag often observed between the eruption of a solar flare or CME and the subsequent release of SEEs into space. Surprisingly, this lag can be attributed to multiple factors related to the electrons' journey through space. Laura Rodríguez-García, an ESA Research Fellow, noted that the delay could either be due to the lag in release or a lag in detection. As the electrons navigate through turbulent space and encounter scattering, their detection becomes less immediate, and these effects compound as they move further from the sun.
The path that SEEs take through the solar system is heavily influenced by the solar wind, which is a stream of charged particles emanating from the sun. This solar wind carries the sun's magnetic field along with it, effectively confining and scattering the charged particles like SEEs. The research conducted by the Solar Orbiter team underscores the spacecraft's revolutionary capabilities in studying the sun and its environment. As Daniel Müller, ESA Project Scientist for Solar Orbiter, stated, “Thanks to Solar Orbiter, we're getting to know our star better than ever.”
In its first five years of operation, the Solar Orbiter has observed a vast array of SEE events, enabling detailed analyses and the creation of a unique database for the global scientific community. This research holds significant implications for our understanding of space weather and its effects on spacecraft operating around Earth. Particularly, the SEEs produced by CMEs, which carry higher energy levels, pose a greater risk to technology. Consequently, distinguishing between the two types of SEEs could greatly enhance the accuracy of space weather forecasts.
Müller emphasized that the insights gained from Solar Orbiter will be instrumental in protecting future spacecraft by improving our understanding of the energetic particles from the sun that threaten astronauts and satellites. The collaborative effort between European scientists, instrument teams from various ESA Member States, and colleagues from the US has made this research possible, showcasing the power of teamwork in advancing scientific knowledge.
Looking ahead, scientists anticipate gaining an even clearer understanding of solar outbursts with the upcoming launch of the ESA's Smile mission in 2026. This mission aims to measure the solar wind and its interactions with Earth's magnetic field, known as the magnetosphere. Additionally, in 2031, the ESA plans to launch the Vigil mission, which will focus on examining the sun's limb to identify potentially damaging solar events before they impact Earth. This initiative is expected to significantly enhance space weather predictions by allowing scientists to assess the power, direction, and impact potential of solar outbursts.
The team's findings were published on September 1 in the journal Astronomy & Astrophysics, marking a significant milestone in solar research and our quest to understand the sun's behavior and its effects on our planet.
