The Community Coordinated Modeling Center (CCMC) at NASA Goddard Space Flight Center has developed comprehensive resources and initiatives to support the Heliophysics Big Year (HBY) during the approach to solar maximum. This paper details the CCMC’s extensive outreach efforts from October 2023 through December 2024, engaging diverse audiences including the general public, educators, and scientific communities. Key activities included partnerships with the Intrepid Museum and American Museum of Natural History, educational presentations reaching over 1,000 physics educators, and specialized workshops for high school teachers. The paper also highlights significant technological enhancements to the CCMC’s visualization capabilities, specifically the improved Integrated Space Weather Analysis (ISWA) system with its global synchronization features and specialized layout options. Additionally, we discuss the collaborative development of OpenSpace, a versatile 3D visualization tool that integrates data from observations, simulations, and space missions to support public engagement through planetarium shows and educational initiatives. Through these combined efforts, the CCMC has established multiple pathways for audiences to engage with heliophysics research and better understand space weather phenomena during this period of heightened solar activity.

The nonlinear development of ballooning instability and the subsequently induced plasmoid formation in the near-Earth magnetotail demonstrated in MHD simulations has been proposed as a potential trigger mechanism for substorm onset over the past decade, and their connections to the in situ satellite and ground all-sky auroral optical observations have been a subject of continued research. In this work, a set of THEMIS substorm onset events with good conjunction of auroral observations has been selected for comparative simulation study, whose pre-onset magnetotail configuration and conditions are inferred from in situ data and compared with the onset conditions of ballooning instability obtained in our MHD simulations. The evolution of the near-Earth magnetotail is followed, where the signatures of ballooning instability and the plasmoid formation are extracted from simulations and compared with the magnetic fields and flow patterns within the magnetotail region from observation data. The field-aligned current (FAC) density is evaluated at the Earth side boundary of the magnetotail domain of simulation, which is further mapped along magnetic field lines to the auroral ionosphere as input to the newly developed TREx-ATM model for auroral simulation. The comparison between the simulation and the THEMIS-ASI observation data on the auroral bead and arc has enabled the identification of their magnetotail origins. In particular, a scenario for the subsequent emergence of new poleward auroral arc above the substorm onset auroral beads has been proposed, which brings new understanding on how the ballooning induced plasmoid formation process may contribute to substorm onset and expansion.

Abstract Poleward boundary intensifications (PBIs) are one of the most common auroral disturbances and have been shown to play a key role in substorm dynamics. PBIs are commonly interpreted as the ionospheric signature of magnetotail reconnection, providing insight into X‐line evolution. While PBIs have been linked to ionospheric flow channels using line‐of‐sight observations, their two‐dimensional flow dynamics remain poorly understood. Using coordinated THEMIS All‐Sky Imager and SuperDARN observations, we present high‐resolution two‐dimension flows derived by the spherical elementary current systems (SECS) method in association with PBI morphology. AMPERE magnetic perturbation data are presented for one event to analyze the current system associated with a dawn‐cell PBI. Ionospheric flow channel observations are used to infer plasma inflow in the magnetotail, and our results show they play a determining role in PBI morphology, including spatial extent, number, and propagation. These results suggest that inflow properties strongly influence X‐line dynamics.

Meso-scale enhanced flow channels often extend across the polar cap from the dayside to the nightside auroral oval, where they enter the oval via localized reconnection and cause auroral oval disturbances. Examples here show such flows associated with azimuthally moving polar cap arcs that develop an equatorward portion that bends in the direction opposite to the arc's motion, becoming nearly parallel to the nightside auroral oval and possibly becoming an oval poleward boundary arc. The arcs then continue to move equatorward, and "lay down" along the auroral oval, leading to an explosive substorm onset (or expansion enhancement) that rapidly expands azimuthally with laying down of the arc, and later expands further with westward traveling surge sliding along the arc. This gives a longitudinally broad region of expansion-phase aurora, and a similarly broad magnetic depression, indicating large and broad substorm energy release. The surge sliding along the poleward boundary arc occurs at a higher latitude than the laydown portion of onset, so that sliding leads to later magnetic depressions at locations west of the initial onset and at higher latitudes. The polar cap arc appears to be pushed equatorward and westward (for By >0) by the flow of new plasma moving across the polar cap, the arc being like a weather front that demarcates an advancing boundary between plasma regimes along polar cap field lines. The onset and expansion of the activity appear to be driven by the flow of this new plasma from the polar cap to the region of expansion phase activity.

The Ultraviolet Imager (UVI) is one of the four instruments onboard the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) satellite, a collaborative science mission between the Chinese Academy of Sciences (CAS) and the European Space Agency (ESA). The UVI will capture the terrestrial auroral images that depict the energy depositions in the solar wind-magnetosphere coupling system. The primary function of UVI is to image the entire auroral oval at characteristic wavelengths while effectively mitigating contamination from dayglow, achieving a spatial resolution of approximately 100 km or better. The co-axis four-mirror all-reflective optical system provides a circular field of view of 9.97°, enabling coverage of the entire polar region when the spacecraft’s geocentric distance exceeds 50,000 km. This capability allows UVI to continuously monitor the complete auroral oval for over 40 hours. UVI operates in the long wavelength range of the N2 Lyman-Birge-Hopfield (LBH) band, specifically between 160–180 nm. To achieve the required spectral response and significantly reject out-of-band stray light, multilayer coatings are applied to its mirrors. The detector utilized is an intensified charge-coupled device (ICCD), with photons emitted from the phosphor being coupled through a relay lens to the ICCD. By default, the CCD captures one frame (512 × 512 pixels) every two seconds; thus, thirty frames per minute are coadded to produce a single UVI image. This processing can be performed in orbit or on ground to compensate the possible satellite jitters. The detailed geometric and photometric calibration procedures for UVI are elaborated upon in the paper.

The SMILE mission, supported by the European Space Agency and the Chinese Academy of Sciences, is scheduled for launch in 2024. The mission is augmented by a substantial ground-based network of optical ASI's. Here, we report progress in developing a numerical model of UV emissions to aid interpretation of images collected by the SMILE UVI. The model calculates UV emissions produced by suprathermal electrons, accounting for prominent UV auroral and dayglow emission lines and bands, including OI 130.4/135.6nm, Lyman-Birge-Hopfield (LBH) and Vegard-Kaplan (VK) bands. It also calculates line-of-sight absorption and the integrated UV photon flux spectrum reaching each UVI-imager pixel. Photoelectron energy spectra for the UV emission module are generated using a Monte Carlo model of photoelectron propagation. This model accounts for 52 kinds of electron-neutral collisions as well as Coulomb collisions. Considering closed geomagnetic field lines in the night sector, and depending on Earth's position relative to the Sun, the model predicts the appearance of energetic photoelectrons coming from the day sector. Coulomb scattering prevents pthese hotoelectrons from reaching the opposite ionosphere [c.f., Khazanov et al, 1994]. To reveal the importance of Coulomb collisions, model photoelectron fluxes and related UV emissions were calculated with Coulomb collisions included and omitted for five locations along the orbit of the DMSP F16 satellite on UT0800 January 1, 2017, which observed anomalous UV emission induced by conjugate photoelectrons [Kil et al., 2020]. Omitting Coulomb collisions overestimates the photoelectron flux and the intensity of UV emission by up to 50% with the effect being more pronounced on longer field lines.Solar EUV photons also produce energetic photoelectrons which ionize neutrals, heat ambient electrons, and cause UV emission. These photoelectrons can penetrate into the nightside even when connected to the day sector by geomagnetic field lines. UV emission caused by such photoelectrons in the night sector is called anomalous UV emission. knowlege of which is important for the analysis of data from the SMILE UVI. The model development for SMILE includes a module that calculates propagation of photoelectrons and related UV emission. Results from the model are benchmarked against observations by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) of the DMSP F16 spacecraft. The spacecraft was in Earths shadow, and traveling towards the equatorial plane. The observed anomalous UV emission rapidly decreases as the spacecraft approaches lower latitudes where field lines are shorter and almost completely in the shadow. Values of the UV emission at wavelengths of 135.6 nm and 130.4 nm were calculated from the model at several locations along the spacecraft orbit. Calculations performed with a tilted dipole geomagnetic field gave values that were significantly larger than the observed ones. Calculations using the International Reference Geomagnetic Field (IGRF) provided much improved agreement between the model and the observation because the IGRF places the southern ends of geomagnetic field lines farther from the sunlit hemisphere. The improved agreement suggests the model development related to the SMILE mission will aid interpretation of the data.

Omega bands are mesoscale auroral structures that emerge as eastward moving sinusoidal undulations of the poleward boundary of the equatorward oval in the post-midnight sector. They have been observed during the recovery phase of substorms and storms, and during periods of steady magnetospheric convection, but to date the statistical occurrence characteristics are unknown.While omega bands can be seen during stormtime events, their drivers and the magnetospheric conditions in which they appear are not well understood. Gaining insight into the geomagnetic conditions and solar wind drivers that give rise to omega bands could greatly benefit theoretical and simulation studies, ultimately enhancing our understanding of global magnetospheric dynamics. In this work, we perform a superposed epoch analysis of geomagnetic and solar wind parameters for omega band events identified using THEMIS ASI from 2006 to 2013. We use data from OMNI and SuperMAG to quantify the solar wind-magnetosphere-ionosphere system during these intervals. Since omega bands are known to have a near-Earth source, we hope to use this analysis to better understand their associated current systems and coupling mechanisms between the inner magnetosphere and ionosphere.

Abstract The vibrational‐translational (VT) excitation of nitrogen molecules led by collisions with fast ions in subauroral ion drifts (SAID) has been conceived as a potential underlying mechanism contributing to the formation of the Strong Thermal Emission Velocity Enhancement (STEVE) phenomenon (Harding et al., 2020, https://doi.org/10.1029/2020gl087102). In this study, we perform quantum calculations of the VT excitation rates of N2 led by fast‐drifting ions, and evaluate the resulting vibrational distribution of N2 with ionospheric/thermospheric parameters expected under intense SAID condition. We conclude that, while the VT energy transfer led by SAID plays a distinguishable role in the vibrational excitation of N2, it is incapable of populating the high vibrational levels to the required concentration (Harding et al., 2020, https://doi.org/10.1029/2020gl087102) to produce adequate nitric oxide density, and in turn the nitrogen‐dioxide continuum intensity, to account for the STEVE brightness.

The relationship between auroral, ground, and plasma sheet signatures in the late growth phase is crucial for understanding the sequence of events during a substorm expansion phase onset. Here we show conjugate ground-auroral-satellite observations of a substorm that occurred on 18 September 2021, between 04:45 and 05:00 UT, where four auroral activations were detected in the all-sky imagers. An initial activation showed the brightening of an equatorward arc within the cutoff of the 630 nm emissions, indicating activity on closed field lines well inside the open-closed field line boundary (OCFLB). During a second activation, auroral beads were observed on a brightening arc, equatorward and within the OCFLB, followed by the transformation from small-scale to large-scale vortices. The tail current sheet was highly disturbed during the auroral vortex evolution, including pressure and magnetic disturbances, an apparent broadening of a previously thin current sheet, and a breakdown of the frozen-in condition. Our observations clearly show late growth phase dynamics, including arc brightenings, the formation of auroral beads, and auroral vortex development, can occur well in advance of fast Earthward flows in the tail. Indeed, it is only during that later activity that auroral breakup and strong Earthward flows, which we associate with magnetic reconnection further down the tail, are observed together with strong magnetic bays on the ground. The sequence of events is consistent with an inside-to-outside model at substorm expansion phase onset, most likely via a shear-flow ballooning instability in the transition region from dipole to tail-like fields in the near-Earth plasma sheet. Substorm onset is associated with the explosive release of stored magnetic energy, which can be visualized as auroral activity in the ionosphere, magnetic-field disturbances in the ground-based magnetometers, and plasma sheet disturbances in the magnetosphere. Even though the processes that lead to energy storage are well known, the exact sequence of events and the triggering factors that lead to the release of this stored energy are poorly understood. In this study, we show conjugate auroral-ground-satellite observations of a substorm event that occurred on 18 September 2021. Four auroral activations were observed in the all-sky imagers, all of which can be associated with plasma sheet disturbances observed in the satellites. Our observations show an initial activation and bead-like structures on a brightening arc, followed by the formation and expansion of vortex-like auroral forms, all of which can be associated with magnetic field and pressure fluctuations in the near-Earth nightside magnetosphere on closed field lines. Auroral breakup and strong magnetic bays on the ground are only observed after the arrival of fast Earthward flows in the magnetosphere. Overall, this paper identifies disturbances in the near-Earth plasma environment which are the counterparts to the evolving auroral forms seen leading up to the substorm expansion phase onset. Plasma sheet dynamical counterparts are reported for an evolving sequence of late growth phase auroral forms Plasma sheet current disruption and ion kinetic scale perturbations occur in advance of fast Earthward flows and magnetic reconnection One-to-one correspondence between plasma sheet disturbances and auroral forms implies ballooning instability in advance of auroral breakup

When charged particles are accelerated from Earth's magnetosphere and precipitate into the atmosphere, their impact with neutral gas creates the aurora. Structured electric fields drive the acceleration processes but they are also passed down to the ionosphere, meaning that turbulence can in part be embedded into the ionosphere rather than emerge through instability processes locally. Applying a point-cloud analysis technique adapted from observational cosmology, we show how observed turbulence in the ionosphere matches electrical current signatures in the pulsating aurora in a series of conjunctions between space- and ground-based instruments. We propose that the temporal spectrum of pulsations in the pulsating aurora is the driver of a clearly observed energy injection into the ionosphere's unstable bottomside. Precipitating electrons produce electric fields through charge deposition, and we observe wave characteristics that are present in this pattern. Next, the relative electron-ion drifts excite the Farley-Buneman instability, the distribution of whose waves are organized according to the local electric field. It is the temporal characteristics of chorus wave interactions in the magnetosphere that is imparted, via precipitating electrons, to the pulsating aurora, and so we propose that chorus wave interactions are capable of embedding turbulent structure into the ionosphere. This structure (now pressure gradients) dissipate energy in the E-region through turbulent processes, observed by the icebear coherent scatter radar. A study of multiple space-ground conjunctions that occurred during a strong pulsating aurora event There were identical turbulent properties in in-situ field-structuring and in E-region plasma turbulence We suggest that this structure is driven, or embedded, by electromagnetic waves, mediated by precipitating particles in the pulsating aurora

We suggest that the next era of Heliophysics should focus on the Sun-Heliosphere and Geospace as each a system-of-systems, and recommend a coordinated, deliberate, worldwide scientific effort to answer long-standing questions that will remain unanswered without a unified program. Many of the biggest unanswered science questions that remain across Heliophysics center around the interconnectivity of the different physical systems and the role of mesoscale dynamics in modulating, regulating, and controlling that interconnected behavior. Heliophysics has made key progress understanding both the large-scale dynamics and the microphysical processes that occur in these dynamic systems. Such understanding grew out of a systematic approach to study both limits of the system, from global, with the coordinated missions of the International Solar Terrestrial Physics (ISTP) program, to micro, with largely uncoordinated (albeit coincident) missions such as Cluster, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes, Magnetospheric Multiscale (MMS), Parker Solar Probe, and Solar Orbiter. We suggest that the international Heliophysics community should embark on a grand program to study these system-of-systems holistically, with coordinated, multipoint measurements. We particularly recommend an emphasis on resolving the mesoscale dynamics that links micro to global, and a whole-of-science approach that includes ground-based measurements and advanced numerical modeling. In effect, we propose a mesoscale ISTP type program that would consist of a system of Great Observatories capable of revealing the connections among systems from the solar interior to the top of Earth's atmosphere. The paradigm and specific approaches outlined in this paper could serve as a strategic imperative and overarching theme that binds our Solar and Space Physics communities together under a common scientific objective. By its very nature, the type of program we argue for would be large, with several coordinated elements, and international in scope. It would include space-borne missions and coordinated ground-based observatories, artificial intelligence/machine learning (AI/ML) methods of analyzing large and complex datasets, and next-generation numerical modeling. The need to coordinate and integrate these different elements is independent of any specific mission implementation. Hence, we suggest the Heliophysics community organize around an ISTP-type program, ISTPNext, with associated Heliophysics "Great Observatories".

Energetic proton precipitation from the magnetosphere plays an important role in the magnetosphere-ionosphere-thermosphere coupling and energy transfer. Proton precipitation causes hydrogen emissions, such as H beta (486.1 nm), and also triggers the excitation of other emission lines such as the blue-line (427.8 nm) and the green-line (557.7 nm). In light of the growing availability of ground-based proton auroral measurements in recent years, we revisit the proton auroral modeling in this study, with more focus on the application for interpreting ground observations. An accurate simulation of these optical emissions requires a comprehensive understanding of particle transport and collisions in the upper atmosphere, where the simultaneous consideration of precipitating protons, newly generated energetic hydrogen atoms, and secondary electrons is critical. For this purpose, we couple a 3D Monte-Carlo proton transport model and an electron transport model. The integrated model framework can compute the emission rates of most major auroral emission lines/bands resulting from proton precipitation, along with self-consistent calculation of the ionospheric electron density variations. The model results show improved agreement with ground optical observations in terms of the H beta yield and the green-to-H beta ratio compared to previous model studies. Our new model is a valuable tool for quantifying excitation and ionization due to proton aurora. It has the potential to leverage ground observations to infer precipitating conditions at high altitudes and even for studying magnetospheric activity. The terrestrial auroral display is caused by the collision of energetic particles from space with the Earth's atmosphere. Both energetic electrons and protons can enter the atmosphere and cause auroras, but their transport processes are different. The proton can exchange its charge with atmospheric neutral particles in a collision and become a neutral hydrogen atom, and the hydrogen atom can become a proton again in another collision with atmospheric particles. Both the protons and the hydrogens can ionize the atmospheric neutrals and produce secondary electrons. To model the proton-induced auroras, the three components, protons, hydrogens, and secondary electrons, must be considered together with their different trajectories and transport in the atmosphere. In this study, we present such a coupled proton-hydrogen-electron transport model and simulate the resulting proton auroral intensities. The model results show reasonable agreement with existing ground-based observations. We present a model of coupled proton-hydrogen-electron transport in the atmosphere and the resulting auroral excitation and ionization The model results show improved agreement with the Hbeta yield reported in existing observations compared to previous models Our model can simulate the 557.7 nm emission in proton auroras. The modeled green-to-Hbeta ratio is compatible with the existing observation

Patterns of ionospheric luminosity provide a unique window into our complex, coupled space environment. The aurora, for example, indicates plasma processes occurring thousands of km away, depositing immense amounts of energy into our polar ionospheres. Here we show observations of structured continuum emission associated with the dynamic aurora. The presence of weak ambient continuum emission has long been recognized. However, studies of its relationship to aurora are scarce and limited by observational constraints. We use spectrally resolved measurements to analyze these previously unexplained emissions, adding critical information about spatial structure, characteristic spectra, and location within auroral dynamics. Our findings demonstrate that the coupling among auroral processes, the plasma, and the neutral atmosphere can unfold at meso-scales and is more complex than previously reported. We suggest that the meso-scale auroral precipitation may, under certain circumstances, effectively couple to atmospheric chemistry and conditions to produce the continuum structure.

Although Strong Thermal Emission Velocity Enhancement (STEVE) and subauroral ion drifts (SAID) are often considered in the context of geomagnetically disturbed times, we found that STEVE and SAID can occur even during quiet times. Quiet-time STEVE has the same properties as substorm-time STEVE, including its purple/mauve color and occurrence near the equatorward boundary of the pre-midnight auroral oval. Quiet-time STEVE and SAID emerged during a non-substorm auroral intensification at or near the poleward boundary of the auroral oval followed by a streamer. Quiet-time STEVE only lasted a few minutes but can reappear multiple times, and its latitude was much higher than substorm-time STEVE due to the contracted auroral oval. The THEMIS satellites in the plasma sheet detected dipolarization fronts and fast flows associated with the auroral intensification, indicating that the transient energy release in the magnetotail was the source of quiet-time STEVE and SAID. Particle injection was weaker and electron temperature was lower than the events without quiet-time STEVE. The plasmapause extended beyond the geosynchronous orbit, and the ring current and tail current were weak. The interplanetary magnetic field (IMF) Bz was close to zero, while the IMF Bx was dominant. We suggest that the small energy release in the quiet magnetosphere can significantly impact the flow and field-aligned current system.

We report the first simultaneous observations of total electron content (TEC), radio signal scintillation, and precise point positioning (PPP) variation associated with Strong Thermal Emission Velocity Enhancement (STEVE) emissions during a 26 March 2008 storm-time substorm. Despite that the mid-latitude trough TEC decreases during the substorm overall, interestingly, we found an unexpected TEC enhancement (by similar to 2 TECU) during STEVE. Enhancement of vertical TEC and phase scintillation was highly localized to STEVE within a thin latitudinal band of 1 degrees. As STEVE shifted equatorward, TEC enhancement was found at and slightly poleward of the optical emission. PPP exhibited enhanced variation across a 3 degrees latitudinal range around STEVE and indicated increased GNSS positioning error. We suggest that TEC enhancement during STEVE creates local TEC structures in the ionosphere that degrade Global Navigation Satellite Systems (GNSS) signals and PPP performance. The TEC enhancement may be created by particle precipitation, Pedersen drift across STEVE, neutral wind, or plasma instability.

Flow channels can extend across the polar cap from the dayside to the nightside auroral oval, where they lead to localized reconnection and auroral oval disturbances. Such flow channels can persist within the polar cap >1½ hours, can move azimuthally with direction controlled by IMF By, and may affect time and location of auroral oval disturbances. We have followed a polar cap arc as it moved duskward from Canada to Alaska for ∼2 h while connected to the oval. Two-dimensional ionospheric flows show an adjacent flow channel that moved westward with the arc and was a distinct feature of polar cap convection that locally impinged upon the outer boundary of the auroral oval. The flow channel’s interaction with the oval appears to have triggered two separate substorms during its trip across western Canada and Alaska, controlling the onset location and contributing to subsequent development of substorm activity within the oval. The first substorm (over Canada) occurred during approximately equatorward polar cap flow, whereas the second substorm (over Alaska) occurred as the polar cap arc and flow channel bent strongly azimuthally and appeared to “lay down” along the poleward boundary. The oval became unusually thin, leading to near contact between the polar cap arc and the brightening onset auroral arc within the oval. These observations illustrate the crucial role of polar cap flow channels in the time, location, and duration of space weather activity, and the importance of the duration and azimuthal motion of flow channels within the nightside polar cap.

An approach for creating continental-scale, multi-scale plasma convection maps in the nightside high-latitude ionosphere using the spherical elementary current systems technique has been developed and evaluated. The capability to reconstruct meso-scale flow channels improved dramatically, and the velocity errors were reduced by similar to 30% compared to the spherical harmonic fitting method. Uncertainties of velocity vectors estimated by varying the model setup was also low. Convection maps for a substorm event revealed multiple flow channels in the polar cap, dominating the convection in the quiet time and early growth phase. The meso-scale flows extended toward the nightside auroral oval and had continuous flow channels over >20 degrees of latitude, and the flow channels dynamically merged and bifurcated. The substorm onset occurred along one of the flow channels, and the azimuthal extent of the enhanced flows coincided with the initial width of the auroral breakup. During the expansion phase, the meso-scale flows repetitively crossed the oval poleward boundary, and some of them contributed to subauroral polarization streams enhancements. Increased flows extended duskward, along with the westward traveling surge. Then, flows near midnight weakened and evolved to the Harang flow shear. The meso-scale flow channels had significant (similar to 10%-40% on average) contributions to the total plasma transport. The meso-scale flows were highly variable on similar to 10 min time scales and their individual maximum contributions reached upto 73%. These results demonstrate the capability of specifying realistic convection patterns, quantifying the contribution of meso-scale transport, and evaluating the relationship between meso-scale flows and localized auroral forms.

AbstractOmega bands are mesoscale auroral structures emerging as eastward moving quasi‐periodic poleward protrusions well within the closed field line region of the auroral oval. Neither specific conditions of their appearance nor their causes are well understood. We perform a superposed epoch analysis of OMNI and SuperMAG measurements taken during 28 omega band events recorded by auroral all‐sky imager observations from 2006 to 2013 to identify their solar wind drivers. We find local enhancements in the solar wind flow speed, magnetic field, pressure, and proton density at the time of the omega band observation. In the magnetosphere‐ionosphere, we see enhancements in the ring current, partial ring current, and auroral electrojets. These features are consistent with geomagnetic activity caused by stream interaction regions (SIRs). 19 of our events overlap with SIRs from published event catalogs. Our findings suggest that omega bands are driven by compression regions commonly associated with SIR events.

Following the auroral substorm onset, the active aurora undergoes expansion, which can vary in spatial and temporal extent. The spatiotemporal development of the expansion phase active aurora is controlled by new auroral intensifications that often follow the initial onset. Using seven examples, we investigate the nature of these new auroral intensifications and address a question: are they new auroral onsets, that is, "successive onsets" or poleward-boundary intensifications (PBIs) and ensuing auroral streamers? We observed events that included both types of auroral features-successive onsets and PBIs-and their combinations. For multiple-onset substorms, successive onsets may occur eastward, westward, and poleward of the initial onset, resulting in a diverse range of expansion phase spatial extent and durations. Single-onset substorms show only one auroral onset, but their spatiotemporal development can resemble that of multiple-onset substorms. However, the additional activations are mainly PBIs and subsequent streamers. In some cases, PBIs undergo explosion, leading to a rapid poleward and azimuthal expansion of the aurora, resembling the auroral substorm onset. A prolonged sequence of PBIs and its longitudinal extension can contribute significantly to the spatiotemporal development of substorms expansion phase. Results suggest that post-onset flow channels drive the spatiotemporal development of the substorm expansion phase by (a) triggering successive onsets and (b) inducing bursts of PBIs and their prolonged sequence. We speculate that post-onset flow channels likely originate from the polar cap, but more evaluation is required. Our findings highlight the significance of examining imager data before solely relying on magnetometers to identify substorm onsets.

The spectacular visual displays from the aurora come from curtains of excited atoms and molecules, impacted by energetic charged particles. These particles are accelerated from great distances in Earth's magnetotail, causing them to precipitate into the ionosphere. Energetic particle precipitation is associated with currents that generate electric fields, and the end result is a dissipation of the hundreds of gigawatts to terrawatts of energy injected into Earth's atmosphere during geomagnetic storms. While much is known about how the aurora dissipates energy through Joule heating, little is known about how it does so via small-scale plasma turbulence. Here we show the first set of combined radar and optical images that track the position of this turbulence, relative to particle precipitation, with high spatial precision. During two geomagnetic storms occurring in 2021, we unambiguously show that small-scale turbulence (several meters) is preferentially created on the edges of auroral forms. We find that turbulence appears both poleward and equatorward of auroral forms, as well as being nestled between auroral forms in the north-south direction. These measurements make it clear that small scale auroral plasma turbulence is an integral part of the electrical current system created by the aurora, in the sense that turbulent transport around auroral forms enhances ionospheric energy deposition through Joule heating while at the same time reducing the average strength of the electric field. The aurora continuous to amaze the inhabitants and travelers of Earth's polar regions. Bright shifting folds of light extend down from the nightsky, appearing as green, red, or faint-blue curtains. During geomagnetic storms the are particularly bright and dynamic, often visible in large parts of the inhabited globe. However, far from being simple displays of light, the aurora can wreak havoc on the thin gas of Earth's upper atmosphere. There, gigantic swirls of electric turbulence are excited in response to the energy that is being pumped into the atmosphere by the aurora. This plasma turbulence is detrimental to satellite communication, such as the principle operation of the GPS network, and future efforts are sorely needed to understand the when and how this turbulence appears. We present a series of photographical and radar-based images of the aurora and its plasma turbulence, shedding light on the complex relationship between the two phenomena. The images and videos we present are accessible and interesting to a public readership. Small-scale auroral plasma turbulence is created preferably outside of but not far from optical auroral forms Turbulence appears both poleward and equatorward of auroral arcs Strong electric fields that trigger meter-size E region turbulence are sometimes seen before the onset of optical aurora