More Like this

1. Mapping Solutions for Geomagnetic Conjugate Observations in the Arctic and Antarctic (iPoster/Lightning Presentation)

   https://doi.org/10.5281/zenodo.14574877  

   Collins, Kristina; Hartinger, Michael; Salzano, Michelle; Zimmerman, Kelsey (December 2024, Zenodo)

   Access the original poster here: https://agu24.ipostersessions.com/default.aspx?s=56-AC-77-47-70-EA-25-74-40-80-19-49-D4-CA-D6-A7 Link to conference program: https://agu.confex.com/agu/agu24/meetingapp.cgi/Paper/1538608 This is an interactive poster, which was presented at AGU24 as a Lightning presentation. To view HTML files, download locally and open in browser. Abstract: The polar regions are uniquely valuable in geospace science, in part because much of the solar wind's energy enters the system in polar regions and their magnetospheric, ionospheric, and atmospheric connections are markedly different from the lower latitudes. Geomagnetic conjugate points in the northern and southern hemispheres – i.e., points linked by Earth's magnetic field, including both points connected by closed magnetic field lines and points in open-field line regions that are in similar magnetic domains – have been shown to alter each other’s environment on the order of minutes. Space weather conditions in Antarctica, therefore, influence and are influenced by the conditions in the northern hemisphere. This has been observed in the formation of auroral structures. However, the magnetic conjugate relationship is not straightforward to visualize with many common mapping tools, which commonly focus on midlatitude-oriented map projections. Related visualization difficulties also arise from the counterintuitive vertical scale of the geospace environment. Here, we present Python-based tools for mapping multiple instrumentation networks, including ground-based instruments, radars and satellites, to observe geospace events such as the polar eclipses of 2021, and discuss approaches to make the data presentation more flexible and intuitive. In particular, we highlight regions of potential interest for future instrument deployments. 

   more » « less
2. conjugate_map: A Python package for calculating geomagnetic conjugate points

   https://doi.org/10.1016/j.softx.2025.102354  

   Collins, Kristina; Hartinger, Michael; Zimmerman, Kelsey; Salzano, Michelle; Burrell, Angeline (September 2025, SoftwareX)

   The Earth’s magnetic field is dominated by the dipole moment, which magnetically connects the northern and southern hemispheres. Because ionospheric and magnetospheric plasmas preferentially move along magnetic field lines, local processes that affect the ionosphere or magnetosphere in one hemisphere can cause changes in the opposite hemisphere. The polar regions are uniquely valuable in geospace science, in part because much of the solar wind’s energy enters the system in polar regions and their magnetospheric, ionospheric, and atmospheric connections are markedly different from the lower latitudes. Geomagnetic conjugates are points in the northern and southern hemispheres linked by Earth’s magnetic field, including both points connected by closed magnetic field lines and points in open-field line regions that are in similar magnetic domains. Conjugate locations are both affected asymmetrically by external factors and have also been shown to alter each other’s environment on the order of minutes, which makes interhemispheric comparisons crucial to understanding the full dynamics of the geospace system. Here, we present conjugate_map, a Python library for flexible geomagnetic coordinate conversions that was designed to facilitate interhemispheric comparisons of geospace events and deployment of polar geospace instruments. As the fifth International Polar Year approaches in 2032–33, this work will help researchers to incorporate interhemispheric geospace investigations into the instrument planning process. 

   more » « less
3. Large critical fields in superconducting Ti4Ir2O from spin-orbit coupling

   https://doi.org/10.1103/PhysRevB.111.184506  

   Wu, Hao; Shishidou, Tatsuya; Weinert, Michael; Agterberg, Daniel F (May 2025, Physical Review B)

   The recently synthesized η-carbide-type superconductors exhibit large critical fields. A notable example is Ti4Ir2O, for which the upper critical field strongly violates the Pauli paramagnetic limit, a behavior that is unusual for cubic materials that preserve inversion symmetry. Here, by combining density functional theory (DFT) and analytic modeling, we provide an explanation for this enhanced Pauli limiting field. We show that the nonsymmorphic Fd3m symmetry implies that the electronic states near the X points exhibit strong spin-orbit coupling (SOC), which leads to a vanishing effective g factor and enables the enhanced Pauli limiting field. Furthermore, our DFT results reveal a Van Hove singularity peak near the X points, accounting for ∼65% of the total density of states (DOS), occurring near the chemical potential. We propose that the strong SOC and enhanced DOS in the vicinity of the X points provide the origin of the observed enhancement of the critical field. This leads to a prediction that the magnetic field will lead to a strongly momentum-dependent gap suppression. The gap due to electronic states away from (near to) the X points will be rapidly (slowly) suppressed by fields. 

   more » « less
4. Angle-dependent switching in a magnetic tunnel junction containing a synthetic antiferromagnet

   https://doi.org/10.1063/5.0093044  

   Chen, Hao; Parks, Brad; Zhang, Qiang; Fang, Bin; Zhang, Xixiang; Majetich, Sara A. (May 2022, Applied Physics Letters)

   The angle dependence of field-induced switching was investigated in magnetic tunnel junctions with in-plane magnetization and a pinned synthetic antiferromagnet reference layer. The 60 × 90 nm2 elliptical nanopillars had sharp single switches when the field was applied along the major axis of the ellipse, but even with small (20°) deviations, reversal occurred through an intermediate state. The results are interpreted with a model that includes the external applied field and the effective fields due to shape anisotropy and the fringe field of the synthetic antiferromagnet and used to extract the magnetization direction at various points in the magnetoresistance loop. The implications for faster spintronic probabilistic computing devices are discussed. 

   more » « less
5. Wavelet-based ULF pulsation indices and their application to geomagnetically conjugate ULF pulsation studies at high latitudes

   Xu, Z; Clauer, C; Hartinger, M; Kim, H; Weimer, D (March 2024, CHINESE JOURNAL OF POLAR RESEARCH)

   He, Jian_Jun (Ed.)

   Geomagnetic Ultra Low Frequency (ULF) are terrestrial manifestations of the propagation of very low frequency magnetic fluid waves in the magnetosphere, and it is critical to develop near real-time space weather products to monitor these geomagnetic disturbances. A wavelet-based index is described in this paper and applied to study geomagnetic ULF pulsations observed in Antarctica and their magnetically conjugate locations in West Greenland. Results showed that (1) the index is effective for identification of pulsation events in the Pc4–Pc5 frequency range, including transient events, and measures important characteristics of ULF pulsations in both the temporal and frequency domains. (2) Comparison between conjugate locations reveals the similarities and differences between ULF pulsations in northern and southern hemispheres during solstice conditions, when the largest asymmetries are expected. Results also showed that the geomagnetic pulsations at conjugate locations respond differently according to the Interplanetary Magnetic Field condition, magnetic field topology, magnetic latitude of the observation, and other conditions. The actual magnetospheric and ionospheric configurations and driving conditions in the case need to be further studied. 

   more » « less