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A STEVE over Little Bow Resort, Alberta, in August 2015
A STEVE over Crossfield, Alberta, in March 2018 (around 12:30 a.m.)

STEVE is an atmospheric optical phenomenon that appears as a purple and green light ribbon in the night sky, named in late 2016 by aurora watchers from Alberta, Canada. The backronym later adopted for the phenomenon is the Strong Thermal Emission Velocity Enhancement. According to analysis of satellite data from the European Space Agency's Swarm mission, the phenomenon is caused by a 25 km (16 mi) wide ribbon of hot plasma at an altitude of 450 km (280 mi), with a temperature of 3,000 °C (3,270 K; 5,430 °F) and flowing at a speed of 6 km/s (3.7 mi/s) (compared to 10 m/s (33 ft/s) outside the ribbon). The phenomenon is not rare, but had not been investigated and described scientifically prior to that time.[1][2][3]

Discovery and naming

[edit]

The STEVE phenomenon has been observed by auroral photographers for decades.[3] Some evidence suggests that STEVE observations may have been recorded as early as 1705.[4] Notations resembling the phenomenon exist in some observations from 1911 to the 1950s by Carl Størmer.[5][6]

The first accurate determination of the nature of the phenomenon was not made, however, until after members of a Facebook group, Alberta Aurora Chasers, named it, attributed it to a proton aurora, and began calling it a "proton arc".[7] When physics professor Eric Donovan from the University of Calgary saw their photographs and suspected that their determination was incorrect because proton auroras are not visible,[8] he correlated the time and location of the phenomenon with Swarm satellite data and one of the Alberta Aurora Chaser photographers, Song Despins. She provided GPS coordinates from Vimy, Alberta, that helped Donovan link the data to identify the phenomenon.[1]

One of the aurora watchers, photographer Chris Ratzlaff,[9][10] suggested using the name "Steve" for the phenomenon, in reference to Over the Hedge, an animated comedy movie from 2006. The characters in the movie give the name to a hedge that appears overnight, in order to make it seem more benign.[11] Reports of the heretofore undescribed and unusual "aurora" went viral as an example of citizen science on Aurorasaurus.[12][13]

During the fall meeting of the American Geophysical Union in December 2016, Robert Lysak suggested using a backronym of "Steve" for the phenomenon that would stand for a "Strong Thermal Emission Velocity Enhancement".[14] That acronym, "STEVE", has been adopted by the team at NASA Goddard Space Flight Center that is studying the phenomenon.[15]

External media
Images
image icon Photograph of the phenomenon
image icon Gallery
Video
video icon Time-lapse phenomenon on YouTube

Occurrence and cause

[edit]

Location and timing

[edit]

STEVE phenomena may be spotted further from the poles than the aurora,[16] and as of March 2018, have been observed in the United Kingdom, Canada, Alaska, northern U.S. states, Australia, New Zealand[17] and Denmark.[18] The phenomenon appears as a very narrow arc extending for hundreds or thousands of kilometers, aligned east–west. It generally lasts for twenty minutes to an hour. As of March 2018, STEVE phenomena have only been spotted in the presence of an aurora. None were observed from October 2016 to February 2017, or from October 2017 to February 2018, leading NASA to believe that STEVE phenomena may only appear during certain seasons.[19] However, STEVE phenomena have since been reported and photographed in South Australia during a geomagnetic storm event on 11 October 2024.[20]

Research into cause

[edit]

A study published in March 2018 by Elizabeth A. MacDonald and co-authors in the peer-reviewed journal, Science Advances, suggested that the STEVE phenomenon accompanies a subauroral ion drift (SAID),[21] a fast-moving stream of extremely hot particles. STEVE marks the first observed visual effect accompanying a SAID.[19]

In August 2018, researchers determined that the skyglow of the phenomenon was not associated with particle precipitation (electrons or ions) and, as a result, could be generated in the ionosphere.[22]

One proposed mechanism for the glow is that excited nitrogen breaks apart and interacts with oxygen to form glowing nitric oxide.[23]

Association with picket-fence aurora

[edit]

Often, although not always, a STEVE phenomenon is observed above a green, "picket-fence" aurora according to a study published in Geophysical Research Letters.[24][25] Although the picket-fence aurora is created through precipitation of electrons, they appear outside the auroral oval and so their formation is different from traditional aurora.[26] The study also showed these phenomena appear in both hemispheres simultaneously. Sightings of picket-fence aurora have been made without observations of STEVE.[27]

The green emissions in the picket fence aurora seem to be related to eddies in the supersonic flow of charged particles, similar to the eddies seen in a river that move more slowly than the water around them. Hence, the green bars in the picket fence are moving more slowly than the structures in the purple emissions and some scientists have speculated they could be caused by turbulence in the charged particles from space.[28]

Research

[edit]

2017

[edit]
  • "How I met Steve" - Eric Donovan's presentation to the 2017 ESA Earth Explorer Missions Science Meeting, March 20, 2017 (1:08:30 - 1:26:00)[29]
  • "On the location of Steve, the mysterious subauroral feature"[30]

2018

[edit]
  • "New Science in Plain Sight: Citizen scientists lead to the discovery of optical structure in the upper atmosphere"[21]
  • "On the Origin of STEVE: Particle Precipitation or Ionospheric Skyglow?"[31]
  • "Historical observations of STEVE"[32]
  • "What else can citizen science and 'amateur' observations reveal about STEVE?"[33]
  • "From the spark to the fire, reflections on five years of public participation in aurora research"[34]
  • "On the origin and geomagnetic conditions of STEVE's formation"[35]
  • "A Statistical Analysis of STEVE"[36]

2019

[edit]
  • "How Did We Miss This? An Upper Atmospheric Discovery Named STEVE"[37]
  • "First Observations From the TREx Spectrograph: The Optical Spectrum of STEVE and the Picket Fence Phenomena"[38]
  • "Color Ratios of Subauroral (STEVE) Arcs"[39]
  • "A new dataset of STEVE phenomenon related observations spanning multiple solar cycles"[40]
  • "Subauroral Green STEVE Arcs: Evidence for Low-Energy Excitation"[41]
  • "Magnetospheric Signatures of STEVE: Implications for the Magnetospheric Energy Source and Interhemispheric Conjugacy"[42]
  • "High-Latitude Ionospheric Electrodynamics Characterizing Energy and Momentum Deposition during STEVE Events Reported by Citizen Scientists"[43]
  • "Steve: The Optical Signature of Intense Subauroral Ion Drifts"[44]
  • "Optical Spectra and Emission Altitudes of Double-Layer STEVE: A Case Study"[45]
  • "The Vertical Distribution of the Optical Emissions of a Steve and Picket Fence Event"[46]
  • "Identifying STEVE's Magnetospheric Driver Using Conjugate Observations in the Magnetosphere and on the Ground"[47]
  • "STEVE and the Picket Fence: Evidence of Feedback-Unstable Magnetosphere-Ionosphere Interaction"[48]
  • "Possible Evidence of STEVE in Dynamics Explorer-2 Data"[49]

2020

[edit]
  • "Early Ground-Based Work by Auroral Pioneer Carl Størmer on the High-Altitude Detached Subauroral Arcs Now Known as "STEVE""[50]
  • "Early Evidence of Isolated Auroral Structures in the 100 km Height Regime Observed at Subauroral Latitudes by the Aurora Pioneer Carl Størmer"[51]
  • "Early Ground-Based Work by Auroral Pioneer Carl Størmer on the High-Altitude Detached Subauroral Arcs Now Known as "STEVE""[52]
  • "Magnetospheric Conditions for STEVE and SAID: Particle Injection, Substorm Surge, and Field-Aligned Currents"[53]
  • "Neutral Wind Dynamics Preceding the STEVE Occurrence and Their Possible Preconditioning Role in STEVE Formation"[54]
  • "A Mechanism for the STEVE Continuum Emission"[55]
  • "High-latitude Ionospheric Electrodynamics during STEVE Events"[56]
  • "Dynamics of Auroral Precipitation Boundaries Associated With STEVE and SAID"[57]
  • "The Apparent Motion of STEVE and the Picket Fence Phenomena"[58]
  • "Characteristics of fragmented aurora-like emissions (FAEs) observed on Svalbard"[59]
  • "Fragmented Aurora-like Emissions (FAEs) as a new type of aurora-like phenomenon"[60]

2021

[edit]
  • "Multi-Wavelength Imaging Observations of STEVE at Athabasca, Canada"[61]
  • "Registration of synchronous geomagnetic pulsations and proton aurora during the substorm on March 1, 2017"[62]
  • "First Simultaneous Observation of STEVE and SAR Arc Combining Data From Citizen Scientists, 630.0 nm All-Sky Images, and Satellites"[63]
  • "Proton Aurora and Optical Emissions in the Subauroral Region"[64]
  • "Robust techniques to improve high quality triangulations of contemporaneous citizen science observations of STEVE"[65]
  • "Comparison of the SAR arc, STEVE and Picket fence dynamics registered at the Maimaga subauroral station on March 1, 2017"[66]
  • "Improved Analysis of STEVE Photographs"[67]

2022

[edit]
  • "Rainbow of the Night: First Direct Observation of a SAR arc evolving into STEVE"[68]
  • "Auroral structures: Revealing the importance of meso-scale M-I coupling"[69]

2023

[edit]
  • "It's Not Easy Being Green: Kinetic Modeling of the Emission Spectrum Observed in STEVE's Picket Fence"[70]
  • "Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence"[71]

2024

[edit]
  • "Unexpected STEVE Observations at High Latitude During Quiet Geomagnetic Conditions"[72]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

STEVE

View on Grokipedia
from Grokipedia
STEVE (Strong Thermal Emission Velocity Enhancement) is a rare atmospheric optical phenomenon appearing as a narrow, east-west ribbon of mauve or purple light in the subauroral zone of the night sky in both hemispheres, typically equatorward of the auroral oval and often accompanied by vertical green ray-like structures called the "picket fence."[1][2] This glow, lasting about 1 hour, occurs at ionospheric altitudes of approximately 100–300 km during periods of geomagnetic activity, such as substorms, and is driven by intense westward flows of hot plasma rather than particle precipitation.[1][3] The phenomenon was first documented by citizen scientists, including aurora photographers from the Alberta Aurora Chasers group in Canada, who captured images of the unusual lights between 2015 and 2016 and playfully named it "STEVE" after a mysterious hedge character in the animated film Over the Hedge.[4][5] Scientific interest surged after these observations, leading to the formal acronym in a 2018 study that linked STEVE to subauroral ion drifts (SAID)—fast-moving streams of ionospheric plasma with velocities up to 5.5 km/s, electron temperatures exceeding 6,000 K, and plasma density depletions.[1] Unlike traditional auroras, which result from solar wind particles exciting atmospheric gases to produce primarily green emissions, STEVE arises from thermal emissions in a heated, depleted plasma region without significant energetic particle influx, though it frequently co-occurs with auroral displays during equinox seasons.[1][3] Ongoing research, including satellite data from ESA's Swarm mission and ground-based optical instruments, has revealed STEVE's fine-scale structures, such as westward-drifting rays connected to the picket fence, and its association with substorm energy releases in the magnetosphere.[1][3] Historical records suggest similar events may date back to the 19th century, but modern studies emphasize its rarity, peaking during moderate geomagnetic storms and providing insights into ionospheric dynamics and space weather.[3]

Discovery and Naming

Initial Observations

The initial observations of STEVE occurred in Alberta, Canada, beginning in August 2014, when aurora enthusiast Chris Ratzlaff captured a narrow, purplish strand of light while photographing the northern lights near Airdrie, initially mistaking it for an airplane contrail due to its linear form.[5] Over the following years, particularly in 2015 and 2016, amateur photographers such as Neil Zeller and Dave Markel documented similar occurrences, noting the phenomenon's distinctive purple or mauve arc that appeared south of traditional auroras, spanning east to west without the typical dancing motion.[6][7] These sightings were often recorded during subauroral conditions at lower latitudes than usual for auroral displays, leading observers to describe it as a stable, ribbon-like glow lasting up to an hour.[8] Early documentation revealed confusion with proton auroras, a rare type caused by proton precipitation that can produce diffuse, linear emissions visible at mid-latitudes, as STEVE's non-waving structure and southward position mirrored those traits but featured a more vivid purple hue absent in known proton events.[5] Photographers like Zeller shared images showing the arc's sharp boundaries and lack of spectral green dominance typical of electron auroras, prompting initial speculation that it represented an undocumented variant of proton activity.[9] The Alberta Aurora Chasers, a Facebook group founded in 2012 with thousands of members dedicated to tracking northern lights, played a pivotal role by facilitating the sharing of photos and videos from these sightings across the province.[10] Members, including Ratzlaff, used the group to discuss and compile evidence of the recurring purple arcs, which appeared sporadically during auroral activity but stood apart in form and color.[6] In late 2016, as the phenomenon gained attention within the community without a formal scientific name, the group adopted "Steve" as a placeholder, drawn from a humorous scene in the 2006 animated film Over the Hedge where characters arbitrarily name an unknown object "Steve" to reference it easily.[5] This informal moniker quickly spread through social media posts, amassing dozens of documented instances by 2016 and drawing initial curiosity from researchers.[11]

Naming and Public Awareness

In late 2016, members of the Alberta Aurora Chasers Facebook group, a community of amateur aurora photographers based in western Canada, informally named the unexplained ribbon-like atmospheric phenomenon "Steve" after observing it during their regular sky-watching sessions.[1] The group selected the simple, non-technical name as a lighthearted reference to a character from the animated film Over the Hedge, distinguishing it from more complex scientific terms and making it easier to discuss among enthusiasts.[5] This naming arose directly from initial sightings that puzzled the chasers, who had documented similar events since 2015 but lacked an official classification.[1] In 2017, scientists collaborating with the aurora chasers formalized the name by coining the backronym STEVE, standing for Strong Thermal Emission Velocity Enhancement, based on preliminary satellite data indicating associations with heated, fast-moving ionospheric flows in the sub-auroral region.[7] Researchers, including Elizabeth MacDonald from NASA's Goddard Space Flight Center, adopted the acronym to honor the citizen scientists' original moniker while aligning it with emerging observational evidence from instruments like the European Space Agency's Swarm satellites.[1] The phenomenon's public profile surged in the following years through widespread media coverage, including a 2017 CBC News feature that highlighted the Alberta group's discoveries and a 2019 episode of The Nature of Things hosted by David Suzuki, which explored STEVE's mysteries and featured interviews with key observers.[11][12] NASA further amplified interest with a 2018 visualization and article describing STEVE as a "thin purple ribbon of light," prompting global reports in outlets like The New York Times.[13] This viral attention spurred citizen science initiatives, notably through the Aurorasaurus app—a NASA- and National Science Foundation-funded platform—where users worldwide submitted photos and reports of STEVE events, contributing over 100 validated sightings by 2020 and aiding professional research.[14]

Physical Characteristics

Appearance and Morphology

STEVE manifests as a narrow, ribbon-like arc of light in the night sky, typically appearing as a stable, non-pulsating glow oriented in an east-west direction. This structure is often 20–30 km wide and can extend up to 1,000 km or more in length, forming an elongated band or arch that remains relatively stationary during its occurrence.[15][16] The primary coloration of STEVE is purple-white or mauve, appearing as a bright, uniform luminosity to the naked eye, sometimes with subtle tinges of pink or yellow. It is frequently accompanied by occasional green, vertical emissions along its lower edge, resembling a "picket fence" structure composed of discrete, elongated streaks. Unlike traditional auroras, which exhibit dynamic pulsations and a broader range of colors, STEVE maintains a consistent, steady appearance throughout its duration, which typically lasts about 1 hour.[1][17][14] Spectrally, the phenomenon's characteristic mauve hue arises primarily from a broadband continuum emission, with faint contributions from atomic oxygen at 630.0 nm; it lacks the prominent nitrogen emissions (such as N₂⁺ first positive bands around 400–500 nm) that are typical of auroral displays. The associated green picket-fence structures are primarily due to molecular oxygen emissions at 557.7 nm.[1][16][17]

Location, Timing, and Visibility

STEVE is primarily observed in sub-auroral zones at mid-latitudes between approximately 45° and 65° N, appearing equatorward of the typical auroral oval. Sightings have been documented across Canada, including Alberta and eastern regions, as well as in northern U.S. states like Michigan and Alaska, and parts of northern Europe such as the United Kingdom and Scotland.[1][18][14] Rare occurrences in the Southern Hemisphere, referred to as "southern STEVE," have been reported in New Zealand and Australia, such as in South Australia, though these are infrequent and typically tied to intense geomagnetic events.[14][19] The phenomenon predominantly manifests in the premidnight sector, often post-sunset or pre-dawn, and is most frequent during equinox periods in September–October and March–April, coinciding with geomagnetic substorms that enhance auroral activity.[1][18] Events typically last about 1 hour, with documented cases from 2008 to 2016 showing patterns aligned with seasonal auroral enhancements.[1] STEVE sightings are expected to peak during solar maximum phases of the 11-year solar cycle, as increased solar activity drives more frequent substorms; the maximum occurred in 2024–2025.[20][21] Optimal visibility requires clear, dark skies far from urban light pollution, as STEVE's faint emissions are often subtle to the naked eye and best captured via long-exposure photography during predicted auroral nights.[1][22] Brighter instances may be discernible without aids, but the structure's narrow east-west extent—spanning over 1,000 km but only tens of kilometers wide—necessitates low-light conditions for full appreciation.[18][13]

Scientific Explanation

Underlying Mechanisms

The underlying mechanism of STEVE involves enhanced subauroral ion drifts (SAID), where intense westward flows of ions in the ionosphere, driven by strong electric fields, reach velocities exceeding 3 km/s, placing them in the top 5% of observed SAID events.[23] These supersonic ion flows, occurring equatorward of the auroral oval during the recovery phase of magnetospheric substorms, result from magnetosphere-ionosphere coupling that enhances convective electric fields in the inner magnetosphere.[1] The frictional collisions between these fast-moving ions and ambient neutral particles are proposed to heat the neutrals to disturbed temperatures around 2000 K, exciting atomic and molecular species without requiring energetic particle precipitation.[24] This heating is thought to populate excited states in neutral oxygen and nitrogen species, leading to thermal emissions that may dominate STEVE's optical signature. The emission intensity for such thermally excited lines, such as the green [OI] 557.7 nm line, is governed by the Boltzmann distribution, where the population of excited states scales with temperature:
I∝nexp⁡(−ΔEkT) I \propto n \exp\left(-\frac{\Delta E}{kT}\right)
Here, II is the emission intensity, nn is the neutral density, ΔE\Delta E is the energy difference between ground and excited states (e.g., ~4.17 eV for the relevant oxygen transition), kk is Boltzmann's constant, and TT is the neutral temperature.[24] For the purple continuum component, one proposed mechanism involves vibrational excitation of N₂ molecules by ion-neutral collisions, which enhances production of NO and contributes broadband emission through subsequent chemical reactions producing NO₂.[24] However, the exact processes remain under investigation.[3] In distinction from traditional auroras, STEVE lacks significant electron or proton precipitation, as evidenced by low plasma densities (~10¹⁰ m⁻³) and minimal field-aligned currents; instead, the phenomenon arises purely from these in situ ionospheric dynamics and thermal processes.[1] The narrow, ribbon-like visual appearance of STEVE serves as observational evidence for this localized heating and emission mechanism.[23]

Relation to Auroras and Picket-Fence Structures

STEVE differs fundamentally from traditional auroras, as it lacks the energetic particle precipitation characteristic of auroral displays. Whereas auroras result from charged particles, primarily electrons, colliding with atmospheric atoms and molecules to produce discrete spectral emissions, STEVE arises from thermal heating of the ionosphere without such precipitation.[1] This non-auroral nature positions STEVE equatorward of the main auroral oval, typically at magnetic latitudes around 58°–62°, during periods of enhanced geomagnetic activity such as substorms.[1] Observations confirm no significant electron or proton fluxes associated with STEVE events, distinguishing it further from auroral processes.[18] A key feature accompanying STEVE is the picket-fence structure, consisting of green, vertical rays that frequently border or appear beneath the purple arc. These rays emit predominantly at the 557.7 nm wavelength, corresponding to the forbidden transition of atomic oxygen, and propagate at speeds of about 400–600 m/s, often westward.[25] The picket fence has been interpreted in different ways; one explanation links it to the same subauroral ion drift (SAID) mechanism driving STEVE, involving plasma turbulence or eddies in the ionosphere that enhance green emissions, while other studies suggest involvement of energetic electron precipitation similar to auroral processes.[26][27] The origin remains debated, with picket-fence structures observed in most documented STEVE events, often emerging after the initial STEVE arc and persisting longer.[6] Recent observations have revealed variants extending STEVE's associations, including the 2024 discovery of its "dawn-side twin," a similar purple arc observed in the post-midnight sector. This counterpart appears poleward of green auroras during substorm recovery, driven by eastward ion flows of around 2.5 km/s rather than the westward drifts of classic STEVE.[15] While primarily documented in northern high latitudes, symmetric ionospheric dynamics suggest analogous manifestations in southern latitudes, potentially involving variations in ion species contributing to the emission spectrum.[28] These findings highlight STEVE's integration into broader ionospheric phenomena without overlapping auroral precipitation mechanisms.[15]

Research Developments

Early Investigations (2016–2018)

Following initial sightings reported by citizen scientists in Alberta, Canada, a collaboration emerged in 2016 between amateur aurora photographers from the Alberta Aurora Chasers group and researchers at the University of Calgary, including Bea Gallardo-Lacourt.[29][1] This partnership leveraged citizen-submitted images to identify recurring east-west arcs during subauroral conditions, prompting the use of satellite data to investigate underlying ionospheric dynamics.[1] In 2016–2017, Gallardo-Lacourt's team analyzed data from the European Space Agency's Swarm satellites, which revealed strong westward ion drifts exceeding 5 km/s associated with these arcs, alongside elevated electron temperatures around 6000 K and ion density depletions.[1] These findings linked the phenomenon to subauroral ion drifts (SAIDs), a known but optically elusive process, marking the first instrumental confirmation of its atmospheric signature.[1] A pivotal advancement came in 2018 with the publication of a study in Science Advances by Gallardo-Lacourt et al., which formalized STEVE—backronymed as Strong Thermal Emission Velocity Enhancement—as a distinct optical structure driven by thermal emissions from heated ionospheric plasma.[1] The research ruled out proton aurora as an explanation, noting the absence of expected Balmer-alpha spectral lines (typically from proton precipitation) and STEVE's occurrence at lower latitudes (~59.5° magnetic latitude), equatorward of typical proton auroral zones (~65° MLAT).[1] Instead, the model emphasized kinetic heating from SAID flows, producing purple emissions through non-equilibrium processes involving nitric oxide ions, without requiring particle precipitation.[1] This work established STEVE's independence from traditional auroral mechanisms, shifting focus to electrodynamic instabilities in the subauroral ionosphere.[1] Ground-based observations during this period relied on all-sky cameras from the Redline Emission Geospace Observatory (REGO) network in Canada, capturing STEVE events such as one on 25 July 2016 lasting over an hour in premidnight hours.[1][30] A statistical analysis of seven events from 2014–2017, published in 2018, showed STEVE occurring amid moderate geomagnetic disturbances, with the planetary Kp index rising from ~2 to ~3.5 approximately 12 hours prior to onset, often following substorm activity indicated by an AL index decrease of ~300 nT.[30] These imagers documented STEVE's narrow latitudinal width (~32 km on average) and equatorward displacement (~74 km from the auroral oval), providing visual corroboration of satellite-detected drifts during enhanced convection.[30]

Mid-Period Advances (2019–2022)

In 2019, researchers advanced the understanding of STEVE through integrated optical and radar observations. These studies demonstrated associations between STEVE events and subauroral polarization streams (SAPS), as well as intense subauroral ion drifts (SAID).[31] Such multi-instrument approaches refined early models by demonstrating how SAPS and SAID enhance ion-neutral coupling in the subauroral ionosphere, providing a more precise linkage to STEVE's dynamic morphology.[31] During 2020 and 2021, remote sensing techniques, bolstered by satellite missions, further elucidated STEVE's triggers amid reduced ground-based observations due to global restrictions. Analysis of Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite data correlated STEVE occurrences with magnetotail reconnection processes, showing that duskward shifts in the reconnection site lead to enhanced electron injections (up to 100 keV) into the premidnight inner magnetosphere.[32] These findings indicated that substorm surges, driven by reconnection in the magnetotail, facilitate the conditions for STEVE by narrowing the ion-electron precipitation boundaries and intensifying field-aligned currents.[33] This period's emphasis on space-based correlations marked a shift toward comprehensive magnetosphere-ionosphere modeling for STEVE events. By 2022, observations expanded STEVE's known distribution with the first confirmed sightings in the Southern Hemisphere, captured at Casey Station in Antarctica on August 17.[34] These events mirrored Northern Hemisphere STEVE characteristics, appearing as luminous arcs at altitudes of 130–270 km with hot plasma flows reaching up to 6 km/s, often alongside picket-fence auroras during the rising phase of Solar Cycle 25.[35] The Antarctic detections, visible to the naked eye and documented through time-lapse photography, underscored STEVE's global symmetry and its independence from solar wind-driven precipitation, contributing to hemispheric comparisons of subauroral dynamics.

Recent Findings (2023–2025)

During the peak of Solar Cycle 25 in 2023, STEVE sightings increased significantly due to heightened geomagnetic activity, with citizen scientists contributing reports through Aurorasaurus that highlighted more frequent occurrences across mid-latitudes.[36][37] Researchers advanced modeling of plasma instabilities associated with STEVE, emphasizing intermittency and multi-scale structuring in ionospheric flows to better explain its thermal emission characteristics.[26] In 2024, an Eos-highlighted study documented rare STEVE events occurring post-substorm, revealing strong ionospheric flows under disturbed conditions that deviated from typical quiet-time observations.[38][39] Observations also identified a purple-hued variant resembling "STEVE's twin," characterized by patchy arcs and emissions potentially linked to excited nitrogen ions in post-midnight sectors during geomagnetic disturbances.[15] Preliminary 2025 reports from Svalbard captured fragmented STEVE-like emissions near the poleward auroral boundary, suggesting extensions driven by localized plasma dynamics and potentially accompanied by small arcs.[40] In July 2025, the first observations of continuum emissions resembling STEVE were reported in the dayside aurora over Svalbard, featuring white, pale pink, or mauve colors at the poleward boundary, linked to plasma heating and velocity shear following particle precipitation.[41] Ongoing data from NASA's ICON satellite mission continue to provide detailed velocity profiles of ionospheric winds and drifts, aiding interpretations of these variants' kinematics.[42]

References

  1. New science in plain sight: Citizen scientists lead to the discovery of optical structure in the upper atmosphere
  2. https://www.frontiersin.org/articles/10.3389/fspas.2023.1087974/full
  3. The Aurora Named STEVE - NASA
  4. Meet the aurora chaser who named an atmospheric phenomenon ...
  5. Aurora-Chasing Citizen Scientists Help Discover A New Feature of ...
  6. An Aurora Named Steve - National Geographic Education Blog
  7. An Aurora Called 'Steve'? Strange Sky Phenomenon Investigated
  8. The weird sky glow called STEVE is really confusing scientists
  9. That Ghostly, Glowing Light Above Canada? It's Just Steve
  10. Meet Steve, the curious ribbon of purplish light discovered in Alberta ...
  11. Alberta man nets NASA award for work on 'new type of auroral ...
  12. The Aurora Named STEVE - NASA Scientific Visualization Studio
  13. NASA Needs Your Help to Find Steve and Here's How
  14. [PDF] HISTORICAL OBSERVATIONS OF STEVE - arXiv
  15. Optical Spectra and Emission Altitudes of Double‐Layer STEVE: A ...
  16. Post-midnight purple arc and patches appeared on the high latitude ...
  17. The Mysterious Green Streaks Below STEVE - AGU Journals - Wiley
  18. On the Origin of STEVE: Particle Precipitation or Ionospheric Skyglow?
  19. What is STEVE, and how is it different from the aurora? - Space
  20. When is an aurora not an aurora? Phenomena called 'Steve' and ...
  21. STEVE - An Entirely New Celestial Phenomenon - SciTechDaily
  22. Steve: The Optical Signature of Intense Subauroral Ion Drifts - 2019
  23. A Mechanism for the STEVE Continuum Emission - Harding - 2020
  24. The Apparent Motion of STEVE and the Picket Fence Phenomena
  25. Frontiers | Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence
  26. Swarm helps discover Steve's long-lost twin - ESA
  27. Meet STEVE, The Mysterious Lights In The Sky Puzzling Scientists
  28. A Statistical Analysis of STEVE - Gallardo‐Lacourt - AGU Journals
  29. SuperDARN Observations During Geomagnetic Storms ...
  30. Dynamics of Auroral Precipitation Boundaries Associated With ...
  31. Magnetospheric Conditions for STEVE and SAID: Particle Injection ...
  32. 2020 Publications on THEMIS Results - UCLA
  33. When Barry met Steve: aurora watcher captures rare hot glow over ...
  34. Rare celestial phenomenon observed in Antarctica | Polar Journal
  35. Aurorasaurus - Reporting Auroras from the Ground Up
  36. Steve: The aurora-like light show you can help research - CNN
  37. Unusual Occurrence of STEVE: An Aurora-Like Glow - Eos.org
  38. Unexpected STEVE Observations at High Latitude During Quiet ...
  39. https://theauroraguy.com/blogs/blog/what-are-fragmented-aurora-like-emissions
  40. Characteristics of fragmented aurora-like emissions (FAEs ... - ANGEO
  41. The Ionospheric Connection Explorer - Prime Mission Review
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