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Abstract Penetrating and disturbed electric fields develop during geomagnetic storms and are effective in driving remarkable changes in the nightside low latitude ionosphere over varying time periods. While the former arrive nearly instantaneously with the changes in the solar wind electric field, the latter take more time, requiring auroral heating to modify upper atmospheric winds globally, leading to changes in the thermospheric wind dynamo away from the auroral zones. Such changes always differ from the quiet time state where the winds are usually patterned after daytime solar heating. We use the Multiscale Atmosphere‐Geospace Environment model (MAGE) and observations from the NASA Ionospheric Connection Explorer (ICON) mission to investigate both during the 7–8 July 2022 geomagnetic storm event. The model was able to simulate the penetrating and disturbed electric fields. The simulations showed enhanced westward winds and the wind dynamo induced upward ion drift confirmed by the ICON zonal wind and ion drift observations. The simulated zonal wind variations are slightly later in arrival at the low latitudes. We also see the penetrating electric field opposes or cancels the disturbed electric field in the MAGE simulation. 

Abstract Ultra low frequency (ULF; 1 mHz ‐ several Hz) waves are key to energy transport within the geospace system, yet their contribution to Joule heating in the upper atmosphere remains poorly quantified. This study statistically examines Joule heating associated with ionospheric ULF perturbations using Super Dual Auroral Radar Network (SuperDARN) data spanning middle to polar latitudes. Our analysis utilizes high‐time‐resolution measurements from SuperDARN high‐frequency coherent scatter radars operating in a special mode, sampling three “camping beams” approximately every 18 s. We focus on ULF perturbations within the Pc5 frequency range (1.6–6.7 mHz), estimating Joule heating rates from ionospheric electric fields derived from SuperDARN data and height‐integrated Pedersen conductance from empirical models. The analysis includes statistical characterization of Pc5 wave occurrence, electric fields, Joule heating rates, and azimuthal wave numbers. Our results reveal enhanced electric fields and Joule heating rates in the morning and pre‐midnight sectors, even though Pc5 wave occurrences peak in the afternoon. Joule heating is more pronounced in the high‐latitude morning sector during northward interplanetary magnetic field conditions, attributed to local time asymmetry in Pedersen conductance and Pc5 waves driven by Kelvin‐Helmholtz instability. Pc5 waves observed by multiple camping beams predominantly propagate westward at low azimuthal wave numbers , while high‐m waves propagate mainly eastward. Although Joule heating estimates may be underestimated due to assumptions about empirical conductance models and the underestimation of electric fields resulting from SuperDARN line‐of‐sight velocity measurements, these findings offer valuable insights into ULF wave‐related energy dissipation in the geospace system. 

Abstract The 3D freeze printing (3DFP) of nanocellulose aerogels are demonstrated with large‐scale aligned pore orientations as a sustainable alternative to current acoustical materials. In contrast with the unidirectional pore network orientations obtained from current 3DFP techniques, a bidirectional orientation is achieved by using an inhomogeneous printing substrate to alter the thermal gradient within the print volume. The microstructural morphology shows that bidirectional printing results in a 2D pore orientation, with comparatively thinner pore walls and larger pore widths. Acoustic measurements reveal that altering the pore network characteristics significantly affects the acoustical behavior of the printed CNC aerogels; the wider pores allow the bidirectional CNC aerogels to provide higher sound absorption performance at lower frequencies than the unidirectional samples. Notably, both 3D Freeze printed CNC aerogels provide substantially higher sound transmission loss performance as compared to current acoustical materials. The unidirectional pore structure results in CNC aerogels with higher stiffness and improved energy absorption performance, with both 3D freeze printed CNC aerogels outperforming other CNC aerogel materials in their stiffness‐to‐density ratios. The ability to simultaneously control their pore orientation and macrostructural geometry paves the way for printing complex shaped CNC aerogel structures for multifunctional noise control applications. 

Abstract This research advances the field of additive manufacturing (AM) of silicon carbide (SiC) ceramics by integrating spark plasma sintering (SPS) to enhance material density, mechanical strength, and thermal properties. Traditional AM techniques struggle to achieve the high‐density SiC required for demanding applications, such as aerospace engineering, where high thermal conductivity and mechanical strength are paramount. Our study addresses these challenges by incorporating SPS as a post‐processing step, achieving near‐theoretical maximum densities and significantly reducing porosity, thereby resulting in outstanding thermal conductivity in SiC ceramics. We developed a specialized SiC ink optimized for 3D printing, ensuring structural integrity after deposition through tailored rheological properties. The application of SPS facilitates rapid, uniform sintering, essential for attaining superior density, mechanical properties, and thermal performance. Our experimental results, confirmed through scanning electron microscopy analysis, demonstrate significant microstructural properties, mechanical strength, and thermal conductivity, showcasing the effectiveness of integrating SPS in AM processes. This innovative approach not only expands the capabilities of AM in producing complex, high‐density ceramic structures but also broadens the potential applications of SiC in demanding environments. 

Abstract The offset between Earth's magnetic and rotational axes introduces a diurnal dependence in the high‐latitude EUV exposure of the northern hemisphere (NH) and southern hemisphere (SH). This variation raises the question: Does the Universal Time (UT) of geomagnetic storm onset impact its geospace consequences? To address this question, we used the Multiscale Atmosphere‐Geospace Environment (MAGE) model to simulate the 10 October 2024, geomagnetic storm—the year's second strongest (SYM‐H minimum of −346 nT). Since the storm occurred near equinox, we did not expect, but found, significant interhemispheric asymmetries in magnetosphere‐ionosphere‐thermosphere (M‐I‐T) coupling parameters such as the cross‐polar cap potential, hemispherically integrated field‐aligned current, and hemispheric power of electron precipitation. Controlled simulations show that interplanetary magnetic field (IMF) and solar wind have negligible effects on these asymmetries, whereas the EUV variation arising from the diurnal dipole tilt produces noticeable interhemispheric differences. Coincidentally, during this storm, IMFB_zturned southward when the SH was tilted toward the Sun, and it maintained this orientation for 12 hr. A controlled simulation with storm onset shifted by 12 hr exhibits a substantial reduction in interhemispheric asymmetry. Differences in integrated Joule heating power and the SML/SMU indices also occurred with the shifted onset, underscoring the importance of UT in stormtime magnetosphere‐ionosphere coupling.