We have analyzed SEP events that were observed in connection with flares and shock waves driven by coronal mass ejections (CMEs) including their in-situ counterparts when crossing the spacecraft. Altogether dozens of multi-spacecraft events have been cataloged, addressing T1, and case studies of best observed events have provided first answers to the science questions of SERPENTINE. We found that there are probably multiple reasons causing widespread SEP events in the heliosphere: broad sources (shock waves), transport perpendicular to the magnetic field, and multiple narrower sources operating at the same time, an even new scenario. SERPENTINE has also analyzed data from older missions leading to another catalog of SEP events based on the Helios mission (from mid 1970s to early 1980s).
Another dataset comes from the STEREO mission with two spacecraft orbiting the Sun approximately at Earth’s distance but at different positions relative to the Earth. We analyzed a comprehensive sample of events for which an analysis of the solar eruption associated with the event was performed earlier. Our study established a connection between the shock strength and the energetic electrons — a major step forward in our understanding of the role of coronal shocks in the acceleration of electrons to the highest energies and an answer to Q3. We also used the STEREO dataset to study shock acceleration of electrons in-situ and confirmed the role of the shocks in relativistic electron acceleration in several events.
The extensive in-situ instrument suite of Solar Orbiter has been particularly exploited by SERPENTINE. Using Solar Orbiter, the world’s most complete and up-to-date catalog of (interplanetary) shock waves in the inner heliosphere was built. The spacecraft was also used as an “outpost” upstream of Earth to elucidate the peculiar behavior of a strong shock wave as observed by a fleet of 6 spacecraft near-Earth. We found that the first stages of particle acceleration happen in an irregular fashion in space and time at interplanetary shock, a crucial ingredient to unveil their acceleration to the highest energies.
The project also produced and released several analysis tools, e.g. the Solar-MACH tool (
https://solar-mach.github.io/(si apre in una nuova finestra)) which shows the configuration of the heliospheric spacecraft and planets in their orbits around the Sun at any given time. Other tools gaining popularity, based on Jupyter Notebooks, provide easier access to data and time series analysis tools for the broad community, as well as tools for analyzing solar context observations, like CMEs and their shocks, ensuring the possibility of identification and characterization of events beyond the project aims and duration. SERPENTINE also contributed new datasets to existing analysis platforms and provided access to several catalogs of SEP events and shocks through a server operated at the University of Alcala.
The project results have been published in dozens of papers as well as presented in conferences and workshops. Key results have also been published as short and easy-to-understand News Items at the project website and advertised in Twitter / X.
