Christine Gabrielse

This study demonstrates the intriguing and complex interplay among auroral precipitation, enhanced TEC, density irregularities, and amplitude scintillations observed during the November 2025 superstorm. For the first time, we present observations of strong amplitude scintillation across continental United States (CONUS)—nearly from coast to coast—caused by small‐scale irregularities distributed over mid‐latitude regions, impacting GNSS applications for hours. While mid‐latitude phase scintillation associated with the storm‐time equatorward expansion of the auroral oval occurs frequently, strong mid‐latitude amplitude scintillation spanning a wide range of longitudes has never been reported before. During the storm main phase, an east–west elongated band of intense auroral brightness expanded equatorward and produced a horizontally extended strip of strong density gradients. These conditions favored the development of small‐scale irregularities and consequently triggered pronounced amplitude scintillations (S ₄ > 0.5) and caused significant positioning errors exceeding 10 m—large enough to disrupt precision agriculture and autonomous transportation industries across CONUS.

Bursty bulk flows, injections, and related flows are a key component of plasma energy and flux transport during substorms. Mixed observational features require researchers to carefully define their quantitative criteria in studies of such events, a process that requires presuming some quantity of the output events. In this work we present a novel supervised random forest classification model for identifying substorm related flows in the plasma sheet. Our model allows a more complete view of event variety, and avoids the presumptive nature of data‐derived quantitative classification. We observe no correlation between event velocities and geomagnetic activity, however an uneven formation of large‐scale dipolarization in the tail region during strong substorms is statistically present in our data. A bi‐modality also appears in the event occurrence location during strong substorms. Some model limitations and future work is discussed.

On 10 May 2024, Earth was hit by a CME that drove the largest geomagnetic storm in 20 years. Multi‐spacecraft observations previously showed that the ∼100 nT north‐south IMF variation was driven by Kelvin‐Helmholtz waves with wavelength ∼250 and reconnection jets in the ‐direction (Nykyri, 2024a, https://doi.org/10.1029/2024gl110477 ). Here we show that Magnetospheric Multiscale (MMS), located upstream of the Earth's bow shock at , detected additional reconnection jets not seen by ARTEMIS at lunar orbit ∼60 away, perpendicular to CME propagation. One jet coincided with high‐energy ions and electrons streaming anti‐parallel to the magnetic field. The ions showed dispersion followed by apparent counter‐dispersion, whereas electrons above 100 keV arrived nearly simultaneously. Strong electromagnetic wave activity between these phases is consistent with magnetosonic‐Whistler waves, suggesting that MMS traversed very near the particle acceleration region.

Bursty bulk flows (BBFs) are fast flows of plasma in the tail and are responsible for much of the energy flux transport earthward from the tail into the inner magnetosphere despite being relatively short‐lived. BBFs are often accompanied by injections in which particles that have been accelerated to 10–100s of keV are transported earthward. We quantify kinetic energy transport by both the thermal plasma of the BBF and the energetic particles of the injections to see how significantly injections contribute. We studied three different cases. In the first, a BBF with no observed injections, we found that the thermal ion population was responsible for almost all the kinetic energy transport. In the second, a BBF with only an electron injection, the thermal ions were again dominant, suggesting that neither electron population is a major contributor to energy transport. Finally, the third event contained an ion injection. This time, the energetic ions transported a comparable amount of energy as the thermal ions. The energy transport from the thermal ions alone is similar to the other events and the total energy transport is higher, suggesting that the ion injection is adding extra energy transport to the process. Global magnetospheric modeling shows that this is a straightforward reconnection event, so unique conditions are not necessary for energetic ions to be a significant contributor to earthward kinetic energy transport during a BBF. Therefore, an energy transport calculation assuming a solely thermal flow can lead to an underestimate if there is a concurrent ion injection.

Auroral transport models (ATMs) play an important role in quantitative studies of optical auroras, their driving mechanisms, and their effects on the ionosphere and thermosphere. TREx‐ATM was initially developed as the support model for the Transition Region Explorer (TREx) mission, and has gained increasing applications in the community in recent years. In this paper, we introduce the recently updated TREx‐ATM V2.0. We compare the modeled emission intensities and ratios with those from two other commonly used ATMs, B3C and GLOW, and address the reasons for the moderate discrepancies among them. We articulate the recent model extension to relativistic energy ranges and the associated cross‐sections. We compare our modeled ionization rates under high‐energy electron precipitation with those computed using the existing fast calculation method and fixed branching ratios in Whole Atmosphere Community Climate Model. We also introduce the model's capability, albeit with certain limitations in the open version, to compute the profiles of ionospheric plasma density and electron temperature under auroral precipitation. Support for proton auroral ionization is also partly offered in TREx‐ATM V2.0. Finally, we describe our algorithm to invert the electron precipitation parameters, as well as the oxygen correction factor, from four‐wavelength optical data, and exemplify the inversion procedure via both numerical tests and realistic TREx data. We also demonstrate the auroral conductance data sets based on the inversion. With these updated capabilities, TREx‐ATM may offer a convenient and versatile tool for quantitative studies of auroras and magnetosphere‐ionosphere‐thermosphere‐mesosphere coupling processes.

Techniques developed in the past few years enable the derivation of multiscale ion convection and particle precipitation patterns from high‐resolution ground‐based observations, and it has been shown in previous studies that such multiscale geomagnetic forcing can contribute significantly to ionospheric and thermospheric disturbances. In this work, the global ionosphere–thermosphere model (GITM) is utilized to simulate the 27 March 2014 substorm event. Simulations are driven by both the original and spatially smoothed multiscale Super Dual Auroral Radar Network electric potential patterns, and the differences between the two sets of simulations are used to evaluate the effects of mesoscale (500 km) and mesoscale (<500 km) structures. Data‐model comparisons show that, while GITM captures large‐scale wind variations reasonably well, it underestimates the magnitudes of mesoscale winds. Both mesoscale ion convection and precipitation are found to substantially enhance the simulated mesoscale neutral winds. Quantitative analyses at a fixed location and over two vortex regions reveal that F‐region neutral wind variations (at ∼270 km) typically lag mesoscale ion drift enhancements by a few to ∼30 min. The maximum magnitude of mesoscale ion drifts is consistently ∼6 times larger than that of the associated neutral wind changes.

Identifying the primary physical mechanisms and associated secondary processes (e.g., different plasma wave modes, instabilities and magnetic reconnection), that are responsible for plasma heating at the planetary magnetospheres and astrophysical plasmas is often difficult with a single spacecraft or even with a constellation of spacecraft within a single‐plasma scale. Here, we present a statistical study using data from four Magnetospheric Multiscale (MMS) satellites to characterize the cross‐scale plasma‐heating distributions associated with Kelvin‐Helmholtz instability (KHI) and drift mirror instability (DMI). We find that characteristic heating frequency (CHF) distributions follow distinct tail‐scaling regimes: KHI events exhibit low‐ power‐law‐like tails, whereas DMI events occupy larger‐ regimes closer to quasi‐Gaussian behavior. Comparison of a KHI event with Particle‐in‐Cell (PIC) simulations yields consistent tail‐scaling, supporting the physical interpretation. We also analyze an event with periodic encounters of diamagnetic cavities (DMCs) at the Earth's dayside magnetopause, and find that the CHF scaling together with KH growth‐rate analysis is consistent with KHI modulation of reconnection. These results establish statistical discrimination between KHI‐ and DMI‐associated heating, and can be used in future works to establish an automated identification of primary mesoscale processes driving cross‐scale non‐adiabatic heating in collisionless plasmas.

Auroral transport models (ATMs) play an important role in quantitative studies of optical auroras, their driving mechanisms, and their effects on the ionosphere and thermosphere. TREx-ATM was initially developed as the support model for the Transition Region Explorer (TREx) mission, and has gained increasing applications in the community in recent years. In this paper, we introduce the recently updated TREx-ATM V2.0. We compare the modeled emission intensities and ratios with those from two other commonly used ATMs, B3C and GLOW, and address the reasons for the moderate discrepancies among them. We articulate the recent model extension to relativistic energy ranges and the associated cross-sections. We compare our modeled ionization rates under high-energy electron precipitation with those computed using the existing fast calculation method and fixed branching ratios in WACCM. We also introduce the model’s capability, albeit with certain limitations in the open version, to compute the profiles of ionospheric plasma density and electron temperature under auroral precipitation. Support for proton auroral ionization is also partly offered in TREx-ATM V2.0. Finally, we describe our algorithm to invert the electron precipitation parameters, as well as the oxygen correction factor, from four-wavelength optical data, and exemplify the inversion procedure via both numerical tests and realistic TREx data. We also demonstrate the auroral conductance datasets based on the inversion. With these updated capabilities, TREx-ATM may offer a convenient and versatile tool for quantitative studies of auroras and magnetosphere-ionosphere-thermosphere-mesosphere coupling processes

This study investigates energy dissipation in small‐scale solar wind turbulence using a novel approach to autocorrelation function analysis leveraging high‐resolution data from the Magnetospheric Multiscale Mission (MMS). We analyze magnetic field fluctuations at ion dissipation scales, focusing on short 20‐s intervals to isolate dissipation‐scale dynamics. Using MMS's fluxgate magnetometer, fast plasma investigation, and energetic particle detector, we compute normalized correlation functions as functions of the interplanetary magnetic field cone angle. Our results show that turbulence is correlated over short spatial scales (100–1,000 km), with shorter correlation lengths in the compressional component compared to the transverse components. We find that the transverse correlation lengths differ most when the interplanetary magnetic field is nearly perpendicular to the solar wind flow (cone angle ), and that they vary approximately as the inverse sine of the cone angle. The characteristics of the correlation length suggest that the turbulence observed is primarily two‐dimensional. These findings highlight the anisotropic nature of dissipation‐scale turbulence and its dependence on solar wind conditions, providing insights into energy transfer in space plasmas.