The 17 March 2013 storm: Synergy of observations related to electric field modes and their ionospheric and magnetospheric Effects

The main phase of the 17 March 2013 storm had excellent coverage from groundâ based instruments and from lowâ and highâ altitude spacecraft, allowing for evaluation of the relations between major storm time phenomena that are often considered separately. The shock impact with its concurrent southward interplanetary magnetic field (IMF) immediately drove dramatic poleward expansion of the poleward boundary of the auroral oval (implying strong nightside reconnection), strong auroral activity, and strong penetrating midlatitude convection and ionospheric currents. This was followed by periods of southward IMF driving of electric fields that were at first relatively smooth as often employed in storm modeling but then became extremely bursty and structured associated with equatorward extending auroral streamers. The auroral oval did not expand much further poleward during these two latter periods, suggesting a lower overall nightside reconnection rate than that during the first period and approximate balance with dayside reconnection. Characteristics of these three modes of driving were reflected in horizontal and fieldâ aligned currents. Equatorward expansion of the auroral oval occurred predominantly during the structured convection mode, when electric fields became extremely bursty. The period of this third mode also approximately corresponded to the time of largest equatorward motion of the ionospheric trough, of apparent transport of high total electron content (TEC) features into the auroral oval from the polar cap, and of largest earthward injection of ions and electrons into the ring current. The enhanced responses of the aurora, currents, TEC, and the ring current indicate a common driving of all these storm time features during the bursty convection mode period.Key PointsStorm had excellent ground/space data coverage, allowing evaluation of relations between major storm phenomena often considered separatelyIdentified three southward IMF electric fields driving modes that were reflected in the aurora and ionospheric and fieldâ aligned currentsThe third mode was extremely bursty, giving common driving of auroral and current structures, TEC changes, and ring current injectionPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135355/1/jgra53033_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135355/2/jgra53033.pd

New Science in Plain Sight : Citizen Scientists Lead to Discovery of Optical Structure in the Upper Atmosphere

A glowing ribbon of purple light running east-west in the night sky has recently been observed by citizen scientists. This narrow, subauroral, visible structure, distinct from the traditional auroral oval, was largely undocumented in the scientific literature and little was known about its formation. Amateur photo sequences showed colors distinctly different from common types of aurora and occasionally indicated magnetic field–aligned substructures. Observations from the Swarm satellite as it crossed the arc have revealed an unusual level of electron temperature enhancement and density depletion, along with a strong westward ion flow, indicating that a pronounced subauroral ion drift (SAID) is associated with this structure. These early results suggest the arc is an optical manifestation of SAID, presenting new opportunities for investigation of the dynamic SAID signatures from the ground. On the basis of the measured ion properties and original citizen science name, we propose to identify this arc as a Strong Thermal Emission Velocity Enhancement (STEVE)

Exploring the relationship between STEVE and SAID during three events observed by SuperDARN

The phenomenon known as strong thermal emission velocity enhancement (STEVE) is a narrow optical structure that may extend longitudinally for thousands of kilometers. Initially observed by amateur photographers, it has recently garnered researchers’ attention. STEVE has been associated with a rapid westward flow of ions in the ionosphere, known as subauroral ion drift (SAID). In this work, we investigate three occurrences of STEVE, using data from one of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) ground-based all-sky imagers (ASIs) located at Pinawa, Manitoba, and from the Super Dual Auroral Radar Network (SuperDARN). This approach allows us to verify the correlation between STEVE and SAID, as well as analyze the temporal variation of SAID observed during STEVE events. Our results suggest that the SAID activity starts before the STEVE, and the magnitude of the westward flow decreases as the STEVE progresses toward the end of its optical manifestation

External triggering of substorms identified using modern optical versus geosynchronous particle data

Previous works on substorm triggering have shown that more than 50% of the substorms are triggered by a northward turning of the IMF Bz; However, recent studies have found a much lower percentage. We have examined triggering using three different onset lists: The THEMIS All Sky Image (ASI) list, substorm onsets from IMAGE-FUV, and events with large geosynchronous injections. We analyzed these onset lists with three different triggering criteria: (1) a criteria based on Lyons et al. criteria; (2) a relaxation of the Lyons et al. criteria based on the visual criteria proposed by Hsu et al.; and (3) a further relaxation of the Lyons et al. criteria, requiring the same conditions proposed in the visual criteria by Hsu et al. but without the growth phase southward IMF requirements. Appling the Lyons et al. criteria we find that only 17% and 22% of the substorms are triggered in the THEMIS ASIs and IMAGE-FUV onset lists respectively, consistent with the recent studies. However, the percentage reached nearly 50% when we applied relaxed criteria, suggesting that it is possible that the Lyons et al. criteria are too strict to identify all IMF triggered events. The triggering percentage for the events with large injections reached up to 60% applying the relaxed criteria, a result suggesting the possibility that triggers are more easily identified, or that triggering is more common for larger than for smaller substorm events. We have also found evidence that larger substorms may be more likely to be non-triggered under mostly southward IMF conditions than for other IMF conditions

Physical Processes of Meso-Scale, Dynamic Auroral Forms

Meso-scale auroral forms, such as poleward boundary intensifications, streamers, omega bands, beads and giant undulations, are manifestations of dynamic processes in the magnetosphere driven, to a large part, by plasma instabilities in the magnetotail. New observations from ground- and space-based instrumentation and theoretical treatments are giving us a clearer view of some of the physical processes behind these auroral forms. However, questions remain as to how some of these observations should be interpreted, given uncertainties in mapping auroral features to locations in the magnetotatil and due to the significant overlap in the results from a variety of models of different plasma instabilities. We provide an overview of recent results in the field and seek to clarify some of the remaining questions with regards to what drives some of the largest and most dynamic auroral forms

New Insight Into the Transition From a SAR Arc to STEVE

Abstract In this study, we present an analysis of the spectral transition of a Stable Auroral Red (SAR) arc to Strong Thermal Emission Velocity Enhancement (STEVE) emission observed by the Transition Region Explorer (TREx) Spectrograph on the night of 10 April 2022, recorded overhead in Lucky Lake, Saskatchewan. On this night, we see an unusually bright (∼2 kR) SAR arc with enhanced ionospheric flow channels in the conjugate southern hemisphere. Over a short time, on the order of minutes, we observe the spectra change from the typical SAR arc pure redline (630 and 636 nm) emission to the air glow continuum, a broadband enhancement across all wavelengths, characteristic of STEVE. We propose the presence of threshold conditions required for the SAR arc to evolve into STEVE. In addition, we present parameters such as transition times, luminosities, and arc motion to be applied to ionospheric models

Solar Wind Drivers of Auroral Omega Bands

Abstract Omega 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

Steve : The Optical Signature of Intense Subauroral Ion Drifts

Little is currently known about the optical phenomenon known as Steve. The first scientific publication on the subject suggests that Steve is associated with an intense subauroral ion drift (SAID). However, additional inquiry is warranted as this suggested relationship as it is based on a single case study. Here we present eight occurrences of Steve with coincident or near-coincident measurements from the European Space Agency's Swarm satellites and show that Steve is consistently associated with SAID. When satellite observations coincident with Steve are compared to that of typical SAID, we find the SAID associated with Steve to have above average peak ion velocities and electron temperatures, as well as extremely low plasma densities

DataSheet1_AuroraX, PyAuroraX, and aurora-asi-lib: A user-friendly auroral all-sky imager analysis framework.PDF

Within the context of the Heliophysics System Observatory, optical images of the aurora are emerging as an important resource for exploring multi-scale geospace processes. This capability has never been more critical as we are on the cusp of a new era of geospace research, by which we mean studying the overall system as a system of systems. Historically, the patchwork of ground-based instrumentation has required customized solutions for accessing data, assessing data relevance, and then ultimately using each individual network alongside other assets. Here we introduce a new and comprehensive approach for data discovery and utilization for one type of data, namely auroral images. The AuroraX project (https://aurorax.space/) is a cyberinfrastructure platform for the discovery of scientific opportunities with access to optical auroral data. The program has broad objectives, so we focus on one key thread. In particular, we focus on describing the AuroraX platform and its API and web-based tools for all-sky imager (ASI) data. As a practical example, we demonstrate how to identify conjunctions using the AuroraX conjunction finder or PyAuroraX, a Python library that interfaces with the AuroraX platform. We then demonstrate how aurora-asi-lib, a Python library for interacting with and analyzing high-resolution ASI data, can be used for detailed conjunction analysis on a personal computer. Together, these tools enable a rapid and streamlined end-to-end exploration of auroral data.</p