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Recent Submissions

Global heliospheric termination shock strength in the solar–interstellar interaction
(Springer Nature, 2025) Zirnstein, Eric J.; Kumar, R.; Shrestha, Bishwas L.; Swaczyna, Paweł; Dayeh, Maher A.; Heerikhuisen, Jacob; Szalay, J R.
A heliospheric termination shock (HTS) surrounds our Solar System at approximately 100 astronomical units from the Sun, where the expanding solar wind (SW) is compressed and heated before encountering the interstellar medium. HTS-accelerated particles govern the pressure balance with the interstellar medium, but little is known about the global properties of the HTS beyond in situ measurements from Voyager in only two directions of the sky. Here we fill this gap by extracting the HTS strength using particle-in-cell, test particle and magnetohydrodynamic simulations, constrained by Interstellar Boundary Explorer observations of energetic neutral atoms produced from HTS-accelerated particles. Our results reveal there is a higher compression near the poles during solar minimum compared with solar maximum due to the higher Mach number flow. North–south asymmetries arise from the disparate evolution of the polar coronal holes, while minimum compression near the flanks is probably due to SW slowing from mass loading over a greater distance to the HTS. The results imply a strong connection between the HTS strength and the SW and interstellar medium dynamics.
An exploratory report focused on the current and potential use of digital identity in digital trade
(Te Kotahi Research Institute, University of Waikato, 2026-05) Lucas, Danielle
This report is part of the Tauhokohoko research project. The Tauhokohoko research project aims: “to transform trade policy, measurement, and facilitation using Indigenous knowledge, methods, and values for the benefit of Māori and non-Māori people, communities, and enterprises in Aotearoa New Zealand, with application for Indigenous peoples elsewhere.” Mātauranga Māori and Māori data sovereignty are a key part of the project, in particular, as it relates to digital trade. This report contributes to the Tauhokohoko project by looking at the use of digital identity as a conduit for digital trade, to ensure the protection of people and taonga in digital trade. It hopes to help create “a future where Māori as tangata whenua and Te Tiriti partners can equitably participate in and benefit from New Zealand’s trade agreements.” This report builds on a previous report, done as part of the Tikanga in Technology research project, titled ‘Protecting the heartwood: how tikanga Māori and mātauranga Māori can inform the construction of digital identities in Aotearoa New Zealand.’
The leashed we can do: Effects of targeted conservation messaging on dog leashing behaviour
(The University of Waikato, 2026) Smith, Ashleigh; Blackmore, Tania
The current study investigated whether the viewing of posters conveying kiwi conservation or dog safety messaging would influence behaviour change in the form of reasons given to leash their dog: would participants leash their dog more for concerns about dog safety and welfare, or more for concerns related to kiwi conservation. The results showed that both Poster A (kiwi conservation message) and Poster B (dog welfare message) had a significant effect on how participants answered, “how likely are you to leash your dog in the bush?” with participants choosing both the kiwi conservation message and the dog welfare message more frequently post survey than they did pre survey. This finding supports previous NZ based research by Macdonald (2015) and Macaskill (2025) who both found that highlighting pet welfare was more effective at increasing conservation behaviour than highlighting the intended conservation behaviour.
A numerical model for the dynamics of pickup ions outside the heliopause and IBEX “ribbon” observation
(IOP, 2025) Huang, Yifan; Guo, Fan; Zirnstein, Eric J.; Noh, Sung Jun; Li, Hui; Reisenfeld, Daniel B.; Heerikhuisen, Jacob
The leading mechanism for the origin of the Interstellar Boundary Explorer (IBEX) “ribbon” of enhanced energetic neutral atoms (ENAs) from the outer heliosphere is the so-called secondary ENA process. In this mechanism, neutralized ions escape the heliosphere, and after several times of charge exchange collision,s some propagate back toward Earth in directions nearly perpendicular to the local interstellar magnetic field. However, the physical processes governing the distribution of the pickup ions (PUIs) outside the heliopause are still unclear. In this study, we build a new global model of the IBEX ribbon, where a key component is to calculate the dynamics of the PUIs outside the heliopause by solving the gyrophase-averaged focused transport equations on top of the background magnetohydrodynamic-kinetic model for the heliosphere-interstellar medium interaction. We discuss how the properties of the simulated ribbon change with different scattering parameters and show simulation results of the ENA sky maps, ribbon centers, ribbon profiles at several azimuthal slices, the ribbon ENA source region, and the velocity distribution of PUIs in the ENA source region for different scattering frequencies. Our results show that the model can provide reasonable ribbon sky maps comparable to the observed ribbon when the PUI mean free path is on the order of several thousand astronomical units.
Energetic neutral atom fluxes from the Voyager 1 and 2 directions
(IOP, 2025) Fuselier, Stephen A.; Zirnstein, Eric J.; Heerikhuisen, Jacob; Galli, André; Richardson, John D.; Reisenfeld, Daniel B.; Schwadron, Nathan A.; Dayeh, Maher A.; McComas, David J.; Funsten, Herbert O.; Sokół, Justyna M.; Opher, Merav; Kornbleuth, Marc Z.; Gasser, Jonathan
IBEX observes a globally distributed energetic neutral atom (ENA) flux from the heliosheath and very local interstellar medium (VLISM). Over a 14 yr period, Voyager 1 and Voyager 2 traversed the heliosheath from the termination shock to the heliopause. In situ observations from these spacecraft place important constraints on the parent ion populations of the ENAs from the heliosheath in two directions on the upwind side of the heliosphere, i.e., the direction of motion of the Sun in the local interstellar medium. In this study, an MHD model that is constrained by Voyager in situ observations is used to estimate the contribution from the heliosheath to the total ENA fluxes observed by IBEX. At energies greater than about 0.5 keV, the heliosheath provides a significant fraction of the observed ENA flux. However, at energies less than about 0.5 keV, the heliosheath provides an insignificant fraction of the observed ENA flux. These results are the same for both directions, and since the Voyager 1 and 2 directions are not particularly unique, the results are likely to be applicable for much of the upwind hemisphere. Fundamentally, it is the physics of the termination shock and the thickness of the heliosheath that determine the energy-dependent contributions to the observed ENA flux from this region. Because the heliosheath source is insignificant, most ENAs at energies less than about 0.5 keV probably come from the VLISM.