Authors: Wenwen Wei(Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA), Christina O. Lee(Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA), N. Dresing(Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland), L. Y. Khoo(Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA), L. K. Jian(Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), J. G. Luhmann(Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA), C. M. S. Cohen(California Institute of Technology, Pasadena, CA 91125, USA), F. Fraschetti(Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA 02138, USA), B. Zhuang(Institute for the Study of Earth, Ocean, and Space, University of New Hampshire, Durham, NH 03824, USA), J. Huang(Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA), C. Owen(Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK), G. Nicolaou(Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK), L. Rodríguez-García(European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, E-28692 Villanueva de la Can˜ada, Madrid, Spain), E. Palmerio(Predictive Science Inc., San Diego, CA 92121, USA), I. C. Jebaraj(Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland), B. J. Lynch(Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA), F. Carcaboso(Postdoctoral Program Fellow, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA)

The anisotropy of solar energetic particles (SEPs) provides essential information to help resolve the underlying fundamental physics of the spatial distributions, injection, acceleration, and transport of energetic particles. In this work, we report an energetic ion enhancement that is characterized by very large and long-lasting anisotropies observed by STEREO A and Solar Orbiter. This ion enhancement appears at the rising phase of a widespread SEP event that was associated with the farside coronal mass ejection on 15 February 2022. Our analysis suggests the long-lasting anisotropy resulted from the continuous injections of energetic ions from a particle source located beyond STEREO A, together with the spacecraft’s good magnetic connectivity to that source. Furthermore, we suggest that large anisotropy tends to occur when the directional intensity difference is large, and there are relatively stable distributions with nearly field aligned pitch angles. Solar Orbiter also observed an interval of very large anisotropy dominated exclusively by sunward streaming ions, but with the additional implication that it detected the very early phase of ion injections onto magnetic field lines that were newly connected to the particle source. These results further illustrate how SEP anisotropy information, in particular from multiple observer locations, can be used to disentangle the sources and transport processes of energetic ions, even when their heliospheric context is not simple.