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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. 

The ability for traits to recover after exposure to stress varies depending on the magnitude, duration, or type of stressor. One such stressor is circadian rhythm disruption stemming from exposure to light at night. Circadian rhythm disruption may lead to long-term physiological consequences; however, the capacity in which individuals recover and display stress resilience is not known. Here, we exposed zebra finches (Taeniopygia castanotis) to constant light (24L:0D) or a regular light/dark cycle (14L:10D) for 23 days, followed by a recovery period for 12 days. We measured body mass, corticosterone, and glucose levels at multiple timepoints, and relative protein expression of glucocorticoid receptors at euthanasia. Body mass significantly increased over time in light-exposed birds compared to controls, but a 12-day recovery period reversed this increase. Baseline levels of circulating glucose decreased in light-exposed birds compared to controls, but returned to pretreatment levels after the 12-day recovery period. In contrast, the glucose stress response did not show a similar recovery trend, suggesting longer recovery is needed or that this is a persistent effect in light-exposed birds. Surprisingly, we did not detect any differences in baseline corticosterone or reactivity of the hypothalamic-pituitiary-adrenal (HPA) axis between groups throughout the experiment. Moreover, we did not detect differences between relative protein expression of glucocorticoid receptors or a relationship with HPA axis reactivity. Yet, we found a positive relationship between glucocorticoid receptors and the glucose stress response, but only in the light group. Our results indicate that physiological and morphological traits differ in their ability to recover in response to constant light and warrants further investigation on the mechanisms driving stress resilience under a disrupted circadian rhythm. 

A new version of the US National Science Foundation National Center forAtmospheric Research (NSF NCAR) thermosphere-ionosphere-electrodynamicsgeneral circulation model (TIEGCM) has been developed and released. Thispaper describes the changes and improvements of the new version 3.0since its last major release (2.0) in 2016. These include: 1) increasingthe model resolution in both the horizontal and vertical dimensions, aswell as the ionospheric dynamo solver; 2) upward extension of the modelupper boundary to enable more accurate simulations of the topsideionosphere and neutral density in the lower exosphere; 3) improvedparameterization for thermal electron heating rate; 4) resolvingtransport of minor species N(2D); 5) treating helium as a major species;6) parameterization for additional physical processes, such as SAPS andelectrojet turbulent heating; 7) including parallel ion drag in theneutral momentum equation; 8) nudging of prognostic fields near thelower boundary from external data; 9) modification to the NO reactionrate and auroral heating rate; 10) outputs of diagnostic analysis termsof the equations; 11) new functionalities enabling model simulations ofcertain recurrent phenomena, such as solar flares and eclipse. Wepresent examples of the model validation during a moderate storm andcompare simulation results by turning on/off new functionalities todemonstrate the related new model capabilities. Furthermore, the modelis upgraded to comply with the new computer software environment at NSFNCAR for easy installation and run setup and with new visualizationtools. Finally, the model limitations and future development plans arediscussed. 

Numerous numerical studies have been carried out in recent years that simulate different aspects of star-planet interactions. These studies focus mostly on hot Jupiters with sun-like stars. However, more realistic simulations require the inclusion of a wide range of stellar types in the study of stellar-planetary interactions. In this study, I use MHD simulations to model star-planet interactions assuming different stellar types and a Jovian exoplanet. 

Abstract The Starlink satellites launched on 3 February 2022 were lost before they fully arrived in their designated orbits. The loss was attributed to two moderate geomagnetic storms that occurred consecutively on 3–4 February. We investigate the thermospheric neutral mass density variation during these storms with the Multiscale Atmosphere‐Geospace Environment (MAGE) model, a first‐principles, fully coupled geospace model. Simulated neutral density enhancements are validated by Swarm satellite measurements at the altitude of 400–500 km. Comparison with standalone TIEGCM and empirical NRLMSIS 2.0 and DTM‐2013 models suggests better performance by MAGE in predicting the maximum density enhancement and resolving the gradual recovery process. Along the Starlink satellite orbit in the middle thermosphere (∼200 km altitude), MAGE predicts up to 150% density enhancement near the second storm peak while standalone TIEGCM, NRLMSIS 2.0, and DTM‐2013 suggest only ∼50% increase. MAGE also suggests altitudinal, longitudinal, and latitudinal variability of storm‐time percentage density enhancement due to height dependent Joule heating deposition per unit mass, thermospheric circulation changes, and traveling atmospheric disturbances. This study demonstrates that a moderate storm can cause substantial density enhancement in the middle thermosphere. Thermospheric mass density strongly depends on the strength, timing, and location of high‐latitude energy input, which cannot be fully reproduced with empirical models. A physics‐based, fully coupled geospace model that can accurately resolve the high‐latitude energy input and its variability is critical to modeling the dynamic response of thermospheric neutral density during storm time. 

Abstract Solar eruptions cause geomagnetic storms in the near‐Earth environment, creating spectacular aurorae visible to the human eye and invisible dynamic changes permeating all of geospace. Just equatorward of the aurora, radars and satellites often observe intense westward plasma flows called subauroral polarization streams (SAPS) in the dusk‐to‐midnight ionosphere. SAPS occur across a narrow latitudinal range and lead to intense frictional heating of the ionospheric plasma and atmospheric neutral gas. SAPS also generate small‐scale plasma waves and density irregularities that interfere with radio communications. As opposed to the commonly observed duskside SAPS, intense eastward subauroral plasma flows in the morning sector were recently discovered to have occurred during a super storm on 20 November 2003. However, the origin of these flows termed “dawnside SAPS” could not be explained by the same mechanism that causes SAPS on the duskside and has remained a mystery. Through real‐event global geospace simulations, here we demonstrate that dawnside SAPS can only occur during major storm conditions. During these times, the magnetospheric plasma convection is so strong as to effectively transport ions to the dawnside, whereas they are typically deflected to the dusk by the energy‐dependent drifts. Ring current pressure then builds up on the dawnside and drives field‐aligned currents that connect to the subauroral ionosphere, where eastward SAPS are generated. The origin of dawnside SAPS explicated in this study advances our understanding of how the geospace system responds to strongly disturbed solar wind driving conditions that can have severe detrimental impacts on human society and infrastructure. 

Abstract An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field‐aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<∼1 min) response of the ionosphere‐thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ∼6 s resolution Super Dual Auroral Radar Network ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ∼1 min before moving upward. By contrast, the post‐midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversedvertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC. 

Abstract Characterizing the azimuthal mode number,m, of ultralow‐frequency (ULF) waves is necessary for calculating radial diffusion of radiation belt electrons. A cross‐spectral technique is applied to the compressional Pc5 ULF waves observed by multiple pairs of GOES satellites to estimate the azimuthal mode structure during the 28‐31 May 2010 storm. We find that allowing for both positive and negativemis important to achieve a more realistic distribution of mode numbers and to resolve wave propagation direction. During the storm commencement when the solar wind dynamic pressure is high, ULF wave power is found to dominate at low‐mode numbers. An interesting change of sign inmoccurred around noon, which is consistent with the driving of ULF waves by solar wind buffeting around noon, creating antisunward wave propagation. The low‐mode ULF waves are also found to have a less global coverage in magnetic local time than previously assumed. In contrast, during the storm main phase and early recovery phase when the solar wind dynamic pressure is low and the auroral electrojet index is high, wave power is shown to be distributed over all modes from low to high. The high‐mode waves are found to cover a wider range of magnetic local time than what was previously assumed. Furthermore, to reduce the 2nπambiguity in resolvingm, a cross‐pair analysis is performed on satellite field measurements for the first time, which is demonstrated to be effective in generating more reliable mode structure of ULF waves during high auroral electrojet periods. 

Abstract The role of diffuse electron precipitation in the formation of subauroral polarization streams (SAPS) is investigated with the Multiscale Atmosphere‐Geospace Environment (MAGE) model. Diffuse precipitation is derived from the distribution of drifting electrons. SAPS manifest themselves as a separate mesoscale flow channel in the duskside ionosphere, which gradually merges with the primary auroral convection toward dayside as the equatorward auroral boundary approaches the poleward Region‐2 field‐aligned currents (FACs) boundary. SAPS expand to lower latitudes and toward the nightside during the main phase of a geomagnetic storm, associated with magnetotail earthward plasma flows building up the ring current and intensifying Region‐2 FACs and electron precipitation. SAPS shrink poleward and sunward as the interplanetary magnetic field turns northward. When diffuse precipitation is turned off in a controlled MAGE simulation, ring current and duskside Region‐2 FACs become weaker, but subauroral zonal ion drifts are still comparable to auroral convection. However, subauroral and auroral convection manifest as a single broad flow channel without showing any mesoscale structure. SAPS overlap with the downward Region‐2 FACs equatorward of diffuse precipitation, where poleward electric fields are strong due to a low conductance in the subauroral ionosphere. The Region‐2 FACs extend to latitudes lower than the diffuse precipitation because the ring current protons penetrate closer to the Earth than the electrons do. This study reproduces the key physics of SAPS formation and their evolution in the coupled magnetosphere‐ionosphere during a geomagnetic storm. Diffuse electron precipitation is demonstrated to play a critical role in determining SAPS location and structure.