# Research Highlights

A selection of highlights culled from publications by HAO staff.

### The topological nature of the Parker Magnetostatic Theorem

B. C. Low reviews the two-plate initial boundary-value problem of Parker, treating the relaxation of a 3D magnetic field prescribed with an arbitrary topology to a terminal force-free field in a cold, viscous, electrically perfect fluid-conductor. Anchored by their foot-points at the perfectly conducting rigid plates, the relaxing field preserves its topology.

### Pronounced suppression and X-pattern merging of equatorial ionization anomalies after the 2022 Tonga volcano eruption

Wenbin Wang, Liying Qian, et. al. investigate the crests variations and associated ionosphere-thermosphere disturbances following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter.

### A Machine Learning Enhanced Approach for Automated Sunquake Detection in Acoustic Emission Maps

Vanessa Mercea, Alin Razvan Paraschiv, Daniela Adriana Lacatus, Anca Marginean, Diana Besliu-Ionescu  introduce an acoustic holography processed dataset constructed from egression-power maps of solar active regions for Solar Cycles 23 and 24. They then present a pedagogical approach to the application of machine learning representation methods for sunquake detection using AutoEncoders, Contrastive Learning, Object Detection and recurrent techniques, which we enhance by introducing several custom domain-specific data augmentation transformations.

### The Ionospheric Connection Explorer - Prime Mission Review

Astrid Maute et. al., following the two-year prime mission of the NASA Ionospheric Connection Explorer (ICON) mission collected a key set of in-situ and remote sensing measurements that are, by virtue of a detailed mission design, uniquely comparable, ICON provides for new investigations of the mechanisms that control the behavior of the ionosphere-thermosphere system under both geomagnetically quiet and active conditions.

### Thermospheric Density Perturbations Produced by Traveling Atmospheric Disturbances during August 2005 Storm

K. H. Pham, W. Wang, H. Liu, D. Lin, M. Wiltberger, et al. discuss how during geomagnetic storms, increased activity within the geospace environment causes large scale plasma convection to occur and electrons to precipitate into the upper atmosphere. The enhanced heating of the thermosphere by the plasma convection and electron precipitation can produce large perturbations in the neutral density.

### An improved MHD simulation of the 2006 December 13 coronal mass ejection of active region NOAA 10930

Yuhong Fan presents an magnetohydrodynamic (MHD) simulation of the coronal mass ejection (CME) on 13 December 2006 in the emerging $\delta$-sunspot active region 10930, improving upon a previous simulation by Fan (2016). It is found that the kinematics of the erupting flux rope is significantly affected by the open magnetic fields and fast solar wind streams adjacent to the active region.

### The Impact of Assimilating COSMIC-2 Observations of Electron Density in WACCMX

N.M. Pedatella and J.L. Anderson present study investigates the impact of assimilating electron density profiles from the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) mission in a whole atmosphere data assimilation system. The observations are assimilated into the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCMX) using the Data Assimilation Research Testbed (DART) ensemble adjustment Kalman filter.

### Hemispherically Asymmetric Evolution of Nighttime Ionospheric Equatorial Ionization Anomaly in the American Longitude Sector

Xuguang Cai, Liying Qian, Wenbin Wang, Joseph M. McInerney, Han-Li Liu, Richard W. Eastes in JGR–Space Physics reveal that the Global-scale Observation of Limb and Disk (GOLD) mission observed distinct post-sunset, hemispherically asymmetric evolution of the equatorial ionization anomaly between 40° and 50°W on 19 November 2018, with the southern crest shifting poleward but the northern crest remaining in the same latitude region. The Whole Atmosphere Community Climate Model-eXtended captured this phenomenon.

### Ionosphere Variability During the 2020-2021 SSW: COSMIC-2 Observations and WACCM-X Simulations

Nicholas Pedatella investigates the variability in the ionosphere during the 2020-2021 sudden stratospheric warming (SSW) using a combination of Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) observations and Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) simulations. The unprecedented spatial-temporal sampling of the low latitude ionosphere afforded by COSMIC-2 enables investigating the short-term ($<$ 5 days) variability in the ionosphere during the SSW event