Reconnection nanojets associated with a prominence eruption observed with Solar Orbiter/EUI-HRI

ABSTRACT Magnetic reconnection is a proposed mechanism for nanojets associated with coronal heating. We investigate the characteristics of reconnection-driven nanojets just before and during a prominence eruption using the High Resolution Imager (HRI) of the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter during its perihelion on 2024 September 30. Extreme-ultraviolet (EUV) images at unprecedented high spatial and temporal resolution from HRIEUV were analysed. The dimensions and propagation speeds of nanojets were estimated and used to estimate the kinetic energies. Nanojet activity was compared with the Geostationary Operational Environmental Satellite (GOES) X-ray flux to assess its relation to flare evolution. The high spatial and temporal resolution in the EUV was found to be essential to fully capture the properties and numbers of reconnection nanojets. Approximately 120 nanojets were detected during the eruption, with 40 analysed in detail. Nanojets exhibited lengths of 200–5000 km, widths of 200–500 km, and durations of 2–12 s. Instant velocities ranged from 150–600 km s$^{-1}$ with kinetic energies reaching $1.56\times 10^{27}$ erg. These nanojets are faster, longer, more energetic, and more numerous compared to previous studies. We also find clear signatures of acceleration and deceleration, reflecting magnetic tension release, and reach of new equilibria. Reconnection events during the eruption were found to be more frequent and energetically intense. Pre-flare nanojet clustering indicates small-scale reconnection may precede large eruptive activity. These results suggest that nanojets also occur in fully ionized coronal plasma, playing a role in both quiescent and eruptive solar activity.