Authors: Haotian Da (University of Maryland), Marc Swisdak (University of Maryland)

Anomalous Cosmic Rays (ACRs) primarily originate from neutral interstellar atoms that are ionized and subsequently accelerated within the heliosphere. One theory for the source, diffusive shock acceleration, posits that it occurs through interactions with the solar wind termination shock. However, Voyager spacecraft observation showed that ACRs continued to gain energy beyond the shock the shock region, suggesting alternative acceleration mechanisms or acceleration locations within the heliosheath may be relevant. One possibility is magnetic reconnection, specifically that occurring due to the pile-up of the sectored heliospheric magnetic field as it approaches the heliopause.

To simulate this process, we use the new computational model, k-global. It is a hybrid MHD/particle model that excludes all kinetic scales and has been developed to explore particle energization in macroscale reconnecting systems. Excluding the small scale is physically legitimate since Fermi reflection is the dominant drive mechanism for energetic particles, rather than parallel electric fields in kinetic-scale boundary layers. To explore ACR energization, we have added initial mono-energetic population of pickup ions to the usual Maxwellian-distributed ions and electrons to simulate the reconnection happening in the outer heliosphere. Preliminary results show that the pickup and Maxwellian ion distributions exhibit significant evolution during the reconnection, with the energy peak of pickup ions broadening significantly.  Next steps include fitting the model with more realistic parameters and comparing our results with the observations of the energization of pickup ions in the heliosphere.