Rainbow of the Night: First Direct Observation of a SAR Arc Evolving Into STEVE

Martinis, C. R.; Griffin, I. P.; Gallardo‐Lacourt, B.; Wroten, J.; Nishimura, Y.; Baumgardner, Jeffrey; Knudsen, D. J.

doi:10.1029/2022gl098511

Cited by 26 publications

(50 citation statements)

References 34 publications

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“…The electron flux above a few tens of keV for the 2:46 UT event was substantially higher than that for the other injections (Figure 3K). This event supports the finding by Nishimura et al, (2020b) that the strong electron injection to the dusk side magnetosphere could be the driver for intense subauroral 3 Fine-scale structures of STEVE STEVE, in some images, appears as a homogeneous arc with little structure along the arc [e.g., Archer et al, 2019b;Martinis et al, 2022;Parnikov et al, 2022]. Wilson (1891) and Stormer (1935) perceived STEVE-like emissions as a luminous band such as a comet tail and homogeneous arc.…”

Section: Occurrence Characteristicssupporting

confidence: 82%

“…The fine-scale structures of STEVE drift westward along the arc, and the speed seems to correspond to the intense SAID flow speed (Gillies et al, 2020). The exposure time may affect the detectability of fine-scale structures in photographs, but the photographs by Martinis et al (2022) and Figures 1 and 4, have similar exposure times (10, 13, and 10 s). There may also be conditions in the magnetosphere−ionosphere system that create fine-scale structures of STEVE.…”

Section: Occurrence Characteristicsmentioning

confidence: 96%

“…The two photographs were taken only 6 min apart, but the picket fence was not present earlier at 5:16 UT. Typically, STEVE appears first, and then the picket fence, if it exists, emerges during the course of STEVE (Yadav et al, 2021;Anderson and Anderson, 2021;Martinis et al, 2022). The picket fence can remain after STEVE disappears.…”

Section: Introductionmentioning

confidence: 99%

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Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Nishimura

Dyer

Kangas³

et al. 2023

Front. Astron. Space Sci.

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This paper reviews key properties and major unsolved problems about Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence. We first introduce the basic characteristics of STEVE and historical observations of STEVE-like emissions, particularly the case on 11 September 1891. Then, we discuss major open questions about STEVE: 1) Why does STEVE preferentially occur in equinoxes? 2) How do the solar wind and storm/substorm conditions control STEVE? 3) Why is STEVE rare, despite that STEVE does not seem to require extreme driving conditions? 4) What are the multi-scale structures of STEVE? 5) What mechanisms determine the properties of the picket fence? 6) What are the chemistry and emission mechanisms of STEVE? 7) What are the impacts of STEVE on the ionosphere−thermosphere system? Also, 8) what is the relation between STEVE, stable auroral red (SAR) arcs, and the subauroral proton aurora? These issues largely concern how STEVE is created as a unique mode of response of the subauroral magnetosphere−ionosphere−thermosphere coupling system. STEVE, SAR arcs, and proton auroras, the three major types of subauroral emissions, require energetic particle injections to the pre-midnight inner magnetosphere and interaction with cold plasma. However, it is not understood why they occur at different times and why they can co-exist and transition from one to another. Strong electron injections into the pre-midnight sector are suggested to be important for driving intense subauroral ion drifts (SAID). A system-level understanding of how the magnetosphere creates distinct injection features, drives subauroral flows, and disturbs the thermosphere to create optical emissions is required to address the key questions about STEVE. The ionosphere−thermosphere modeling that considers the extreme velocity and heating should be conducted to answer what chemical and dynamical processes occur and how much the STEVE luminosity can be explained. Citizen scientist photographs and scientific instruments reveal the evolution of fine-scale structures of STEVE and their connection to the picket fence. Photographs also show the undulation of STEVE and the localized picket fence. High-resolution observations are required to resolve fine-scale structures of STEVE and the picket fence, and such observations are important to understand underlying processes in the ionosphere and thermosphere.

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Section: Occurrence Characteristicssupporting

confidence: 82%

Section: Occurrence Characteristicsmentioning

confidence: 96%

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Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Nishimura

Dyer

Kangas³

et al. 2023

Front. Astron. Space Sci.

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“…Recently, the interest in SAID has been refreshed by the recognition and observations of the Strong Thermal Emission Velocity Enhancement (STEVE) optical phenomena. While the STEVE generation mechanism remains unclear to date, it is now well established that STEVE is collocated with intense SAID channels (Archer et al., 2019; Chu et al., 2019; MacDonald et al., 2018; Martinis et al., 2022; Nishimura et al., 2019; Nishimura, Donovan, et al., 2020). The STEVE‐related SAID channels have larger flow speeds (in excess of 4 km/s), hotter electrons with temperatures up to ∼10 4 K, and density troughs deeper than 10 4 cm −3 in the F region.…”

Section: Introductionmentioning

confidence: 99%

Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

2022

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During geomagnetically active intervals, latitudinally narrow channels of fast westward ion drifts were at times observed in the subauroral region. They are termed the “subauroral ion drifts” (SAID). The Strong Thermal Emission Velocity Enhancement (STEVE), a subauroral optical phenomenon, is intrinsically related to intense SAID. Recently, we had developed a two‐dimensional (2D) time‐dependent model to study the self‐consistent variations of the ionosphere under intense SAID. The present study further advances the model to a current generator scenario of SAID. By assuming magnetospheric field‐aligned current (FAC) inputs based on existing knowledge and observations, we model the self‐consistent variations of the ionosphere, with focus on the dynamic changes of the plasma density, the Pedersen conductance, and the electric field. We can reproduce the self‐consistent evolution of an intense SAID and its associated ionospheric dynamics such as extreme heating and depletion. We illustrate that the ion Pedersen drifts can cause dynamic density variations in the lower ionosphere. Positive feedback is found to exist between the self‐consistent variations of the electric field and the conductance: the ion Pedersen transport associated with the electric field leads to density depletion in the lower ionosphere, thus reducing the Pedersen conductance and further enhancing the electric field there. We conclude that such positive feedback is key to the formation of intense SAID's in the ionosphere.

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“…MacDonald et al (2018) reported for the first time on the connection of this phenomenon with SAID. Follow-on studies, several of them utilizing citizen science images, reveal a multitude of previously unknown aurora-untypical characteristics (spectral composition, height, not-field aligned structures, location), see reference list: Archer et al (2019aArcher et al ( , 2019b, Chu et al (2020), Harding et al (2020), Gallardo-Lacourt et al (2018a, 2018b, Gillies et al (2019Gillies et al ( , 2020, Liang et al (2019), Martinis et al ( 2021Martinis et al ( , 2022, Mende & Turner (2019), Mende et al (2019), Nishimura et al (2019Nishimura et al ( , 2020, and Semeter et al (2020).…”

Section: Steve (Strong Thermal Emission Velocity Enhancement) Is a Su...mentioning

confidence: 99%

Interoperable Database for Citizen Science Observations of STEVE

Hunnekuhl

MacDonald

2022

Preprint

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Days with STEVE observations per year for the Southern Hemisphere, North America, and EuropeThe monthly observation rates show seasonal variations similar to those known for at least intense geomagnetic storms and SAIDs. However, STEVE is not coupled to geomagnetic storms but to substorm activity and fast SAIDs and can occur under conditions where the DST index is close to zero e.g., in the case of the impressive STEVE observed over Alberta, Saskatchewan, and Manitoba in Canada on 29/30 August 2022.The ratio of days with STEVE observations in the equinox months (March, April, September, and October) and the days with STEVE observations in the solstice months (June, July, December, and January) is ~4, comparable with the analog ratio for SAIDs reported by He et al. (2014). The analog ratio of geomagnetic storms (1957-2008) with DSTp ≤ -100 nT is ~2.3 (Echer et al., 2011). The rate of STEVE observations and SAIDs per month both show a deep December minimum that is less pronounced for geomagnetic storms with DSTp ≤ -100 nT.

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Rainbow of the Night: First Direct Observation of a SAR Arc Evolving Into STEVE

Cited by 26 publications

References 34 publications

Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

Interoperable Database for Citizen Science Observations of STEVE

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