Solar Energetic Particles

The First Ground Level Enhancement Seen on Three Planetary Surfaces: Earth, Moon, and Mars

“…Both the event‐spectrum and the radiation impact of the GLE73 are modest compared to previous GLEs, which may be due to the fact that (a) the parent CME/flare acceleration is not as efficient as for other events with higher total doses, and/or (b) the magnetic connectivity between the observer and the SEP source region is suboptimal (e.g., C. M. S. Cohen et al., 2021, and references therein). More multi‐spacecraft observations of extreme types of SEPs would be helpful to better understand and predict the spatial distribution of the radiation environment in the inner‐heliosphere during the event.…”

“…The identified in‐situ arrivals of CME2 and CME8 (orange lines) are followed by enhanced flux of protons with energy below 10 MeV, especially upon CME8's arrival which corresponds to a much stronger in‐situ shock (Li et al., 2022). These so‐called energetic storm particles (ESPs) are believed to be accelerated by interplanetary shocks as they propagate outward (C. M. Cohen, 2006).…”

Modeling of Cosmogenic Cr Isotopes Produced in Lunar Rocks Compared With Existing Calculations and Measurements

“…They are mainly protons, electrons, and a small amount of heavier ions. The SCRs normally refer to Solar Energetic Particles (SEPs) which are accelerated during sporadic solar eruptive events and therefore, they have a very unstable flux which can vary greatly over time (e.g., Cohen et al, 2021). However, if we consider the time scales of several solar cycles or the exposure history of an extraterrestrial sample, the long-term average proton flux of SCRs has been estimated (R. C. Reedy & Arnold, 1972;Nishiizumi et al, 2009) as below:…”

“…They are mainly protons, electrons, and a small amount of heavier ions. The SCRs normally refer to Solar Energetic Particles (SEPs) which are accelerated during sporadic solar eruptive events and therefore, they have a very unstable flux which can vary greatly over time (e.g., Cohen et al., 2021). However, if we consider the time scales of several solar cycles or the exposure history of an extraterrestrial sample, the long‐term average proton flux of SCRs has been estimated (R. C. Reedy & Arnold, 1972; Nishiizumi et al., 2009) as below: $$$\frac{dI}{dR}=k\cdot {e}^{-\tfrac{R}{{R}_{0}}}.$$$ Here I is the proton flux in the unit of particles/cm 2 /s; R is the proton rigidity which is $$\sqrt{{E}_{p}^{2}+2{m}_{p}{c}^{2}{E}_{p}}$$ and has the units of MV, where E p is the kinetic energy and m p c 2 is the rest mass of a proton in the unit of MeV.…”

Observations of a Solar Energetic Particle Event From Inside and Outside the Coma of Comet 67P

“…SEP events which originate at CME shocks are referred to as “gradual” events because the particles are being accelerated and propagated outwards for a longer period of time and therefore cause more gradual intensity‐time profiles; their spread in the interplanetary medium tends to be much broader due to a larger acceleration area with many magnetic connections to a much wider range of destinations. Impulsive SEP events typically extend in a relatively narrow cone, approximately 30°–60° in solar longitude, while gradual events often extend over 100°–180° (Cohen et al., 2021 ; L. Wang et al., 2012 ). There is not always a clear distinction between the two types, and SEPs generated both at flare sites and CME shock fronts can be observed as part of the same SEP event (Cane et al., 2006 ).…”