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Aims. We model the energetic storm particle (ESP) event of 14 July 2012 using the energetic particle acceleration and transport model named PArticle Radiation Asset Directed at Interplanetary Space Exploration'(PARADISE), together with the solar wind and coronal mass ejection (CME) model named EUropean Heliospheric FORcasting Information Asset'(EUHFORIA). The simulation results illustrate both the capabilities and limitations of the utilised models. We show that the models capture some essential structural features of the ESP event; however, for some aspects the simulations and observations diverge. We describe and, to some extent, assess the sources of errors in the modelling chain of EUHFORIA and PARADISE and discuss how they may be mitigated in the future. Methods. The PARADISE model computes energetic particle distributions in the heliosphere by solving the focused transport equation in a stochastic manner. This is done using a background solar wind configuration generated by the ideal magnetohydrodynamic module of EUHFORIA. The CME generating the ESP event is simulated by using the spheromak model of EUHFORIA, which approximates the CME's flux rope as a linear force-free spheroidal magnetic field. In addition, a tool was developed to trace CME-driven shock waves in the EUHFORIA simulation domain. This tool is used in PARADISE to (i) inject 50 keV protons continuously at the CME-driven shock and (ii) include a foreshock and a sheath region, in which the energetic particle parallel mean free path, λ¥, decreases towards the shock wave. The value of λ¥ at the shock wave is estimated from in situ observations of the ESP event. Results. For energies below ∼ 1 MeV, the simulation results agree well with both the upstream and downstream components of the ESP event observed by the Advanced Composition Explorer. This suggests that these low-energy protons are mainly the result of interplanetary particle acceleration. In the downstream region, the sharp drop in the energetic particle intensities is reproduced at the entry into the following magnetic cloud, illustrating the importance of a magnetised CME model., We acknowledge the use of ACE data from the ACE Science Center and of SOHO/ERNE data from sepem.eu and of the SEPEM Reference Data Set version 2.00, European Space Agency (2016). N.W. acknowledges funding from the Research Foundation – Flanders (FWO – Vlaanderen, fellowship no. 1184319N). A.A. and B.S. acknowledge the support by the Spanish Ministerio de Ciencia e Innovación (MICINN) under grant PID2019-105510GB-C31 and through the “Centre of Excellence María de Maeztu 2020–2023” award to the ICCUB (CEX2019-000918-M). C.S. acknowledges the NASA Living With a Star Jack Eddy Postdoctoral Fellowship Program, administered by UCAR’s Cooperative Programs for the Advancement of Earth System Science (CPAESS) under award no. NNX16AK22G. D.L. acknowledges support from NASA Living With a Star (LWS) programs NNH17ZDA001N-LWS and NNH19ZDA001N-LWS, and the Goddard Space Flight Center Heliophysics Innovation Fund (HIF) program. The work in the University of Turku was performed under the umbrella of Finnish Centre of Excellence in Research of Sustainable Space. This project has received funding from the European Union’s Horizon 2020 research and innovation programs under grant agreement No. 870405 (EUHFORIA 2.0). These results were also obtained in the framework of the ESA project “Heliospheric modelling techniques” (Contract No. 4000133080/20/NL/CRS). Computational resources and services used in this work were provided by the VSC (Flemish Supercomputer Centre), funded by the FWO and the Flemish Government-Department EWI.

Kollhoff, A., et al., Context. On 2020 November 29, the first widespread solar energetic particle (SEP) event of solar cycle 25 was observed at four widely separated locations in the inner (≲ 1 AU) heliosphere. Relativistic electrons as well as protons with energies > 50 MeV were observed by Solar Orbiter (SolO), Parker Solar Probe, the Solar Terrestrial Relations Observatory (STEREO)-A and multiple near-Earth spacecraft. The SEP event was associated with an M4.4 class X-ray flare and accompanied by a coronal mass ejection and an extreme ultraviolet (EUV) wave as well as a type II radio burst and multiple type III radio bursts. Aims. We present multi-spacecraft particle observations and place them in context with source observations from remote sensing instruments and discuss how such observations may further our understanding of particle acceleration and transport in this widespread event. Methods. Velocity dispersion analysis (VDA) and time shift analysis (TSA) were used to infer the particle release times at the Sun. Solar wind plasma and magnetic field measurements were examined to identify structures that influence the properties of the energetic particles such as their intensity. Pitch angle distributions and first-order anisotropies were analyzed in order to characterize the particle propagation in the interplanetary medium. Results. We find that during the 2020 November 29 SEP event, particles spread over more than 230° in longitude close to 1 AU. The particle onset delays observed at the different spacecraft are larger as the flare-footpoint angle increases and are consistent with those from previous STEREO observations. Comparing the timing when the EUV wave intersects the estimated magnetic footpoints of each spacecraft with particle release times from TSA and VDA, we conclude that a simple scenario where the particle release is only determined by the EUV wave propagation is unlikely for this event. Observations of anisotropic particle distributions at SolO, Wind, and STEREO-A do not rule out that particles are injected over a wide longitudinal range close to the Sun. However, the low values of the first-order anisotropy observed by near-Earth spacecraft suggest that diffusive propagation processes are likely involved., The CAU Kiel team acknowledges support from the German Federal Ministry for Economic Affairs and Energy, the German Space Agency (Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR) under grants 50OT0901, 50OT1202, 50OT1702, and 50OT2002. A.K. acknowledges financial support from the ANR COROSHOCK project (ANR-17-CE31-0006-01). D.L. acknowledges support from NASA-HGI grant NNX16AF73G and the NASA Program NNH17ZDA001N-LWS. This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004159 (SERPENTINE). The U. Turku team acknowledges funding by the Academy of Finland (Grant No. 336809). The UAH team acknowledges financial support by the Spanish Ministerio de Ciencia, Innovación y Universidades FEDER/MCIU/AEI Projects ESP2017-88436-R and PID2019-104863RB-I00/AEI/10.13039/501100011033. [...] The Swedish National Space Agency, ESA-PRODEX and all the participating institutes. I.G.R. acknowledges support from NASA programs NNH19ZDA001N-HSR and NNH19ZDA001N-LWS, and the STEREO mission. IRFU team acknowledges support from the Swedish National Space Agency grant 20/136. A.A. acknowledges the support of the Spanish Ministerio de Ciencia e Innovación (MICINN) under grant PID2019- 105510GB-C31 and through the ‘Center of Excellence María de Maeztu 2020-2023’ award to the ICCUB (CEX2019-000918- M). F.C. acknowledges the financial support by the Spanish MINECO-FPI-2016 predoctoral grant with FSE. E.A. would like to acknowledge the financial support by the Academy of Finland (Postdoctoral Grant No 322455). V.K. acknowledges the support by NASA under grants 18-2HSWO218_2-0010 and 19-HSR-19_2-0143. Solar Orbiter magnetometer operations are funded by the UK Space Agency (grant ST/T001062/1). T.S.H. is supported by STFC grant ST/S000364/1. T.L. and S.D. acknowledge support from the UK Science and Technology Facilities Council (STFC; grant ST/R000425/1).

We study the near‐relativistic (NR; >30 keV) electron event observed on 2000 February 18 by the Advanced Composition Explorer spacecraft. Highly collimated pitch‐angle distributions were observed during the first ∼2 h of the event. Roel of (2008) explained this event by assuming that the propagation of NR electrons is essentially “scatter‐free” in the inner heliosphere and that beyond 1 AU, particles are “back‐scattered” by magnetic field compressions and irregularities. We use Monte Carlo simulations to explore this approach. We fit observational sectored intensities to assure that the directional information contained in the data is used in full. We conclude that the event cannot be explained without assuming a back‐scatter region beyond 1 AU and that NR electrons propagated under weak‐scattering conditions in the inner heliosphere.