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Fine‐Scale Structures of STEVE Revealed by 4K Imaging
We utilized a 4K imaging to examine properties of fine‐scale structures of Strong Thermal Emission Velocity Enhancement (STEVE) near the magnetic zenith. Its high spatial (0.09 km at 200 km altitude) and temporal (24 Hz) resolution provided unprecedented details of fine‐scale structures in the subau...
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| Published in: | Journal of geophysical research. Space physics 2023-12, Vol.128 (12), p.n/a |
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| creator | Nishimura, Y. Dyer, A. Donovan, E. F. Angelopoulos, V. |
| description | We utilized a 4K imaging to examine properties of fine‐scale structures of Strong Thermal Emission Velocity Enhancement (STEVE) near the magnetic zenith. Its high spatial (0.09 km at 200 km altitude) and temporal (24 Hz) resolution provided unprecedented details of fine‐scale structures in the subauroral ionosphere. Although the STEVE emission was seen as a homogeneous purple/mauve arc in the all‐sky images, the high‐speed imaging revealed that STEVE contained substantial multi‐scale structures. The characteristic wavelength and period were 12.4 ± 7.4 km and 1.4 ± 0.8 s, and they drifted westward at 8.9 ± 0.7 km/s. The speed is comparable to the reported magnitude of the intense subauroral ion drifts (SAID), suggesting that the fine‐scale structures are an optical manifestation of the E × B drift in the intense SAID. A spectral analysis identified multiple peaks at >10, 4, 2, 1.1, and 83, 33, 16, 9, and |
| doi_str_mv | 10.1029/2023JA032008 |
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Plain Language Summary
Strong Thermal Emission Velocity Enhancement (STEVE) is often perceived as a homogeneous arc with a purple or mauve color. However, this notion is based on photographs with a long exposure time. We conducted a 4K video observation of STEVE with unprecedentedly high spatial and temporal resolution. The video revealed that STEVE is not a homogeneous arc but consists of rich fine‐scale structures that could not be seen in regular photographs. The fine‐scale structures had wavelengths of 1–10 s of km with multiple spectral peaks. The fine‐scale structures moved westward at 8.9 km/s. We suggest that the fine‐scale structures of STEVE correspond to fine‐scale plasma structures in the fast plasma streams in the upper atmosphere. However, it is challenging to explain how the upper atmospheric glow can form the fine‐scale structure because of the long chemical reaction time.
Key Points
Citizen scientist photographs revealed fine‐scale structures of Strong Thermal Emission Velocity Enhancement
The fine‐scale structures extend down to a 9 km size, possibly even below a 1 km size. They propagate at 8.9 km/s westward
The power law spectrum with a slope of −1 suggests a shear flow turbulence by the intense subauroral ion drifts</description><identifier>ISSN: 2169-9380</identifier><identifier>EISSN: 2169-9402</identifier><identifier>DOI: 10.1029/2023JA032008</identifier><language>eng</language><publisher>Washington: Blackwell Publishing Ltd</publisher><subject>Cascade flow ; Chemical reactions ; citizen scientist observations ; Drift ; Emissions ; fine‐scale structure ; Imaging ; Ionosphere ; Reaction time ; Shear flow ; Spectral analysis ; Spectrum analysis ; STEVE, SAID and SAPS ; substorm ; Temporal resolution ; THEMIS, DMSP and spectrograph ; Thermal emission ; Thermosphere ; turbulence in the subauroral ionosphere and thermosphere ; Upper atmosphere ; Velocity ; Wavelengths</subject><ispartof>Journal of geophysical research. Space physics, 2023-12, Vol.128 (12), p.n/a</ispartof><rights>2023. American Geophysical Union. All Rights Reserved.</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c3071-bee919ed1ab0ec7e6c31e084993f562952eab9be5bb9da53363c60a37b2b05c13</citedby><cites>FETCH-LOGICAL-c3071-bee919ed1ab0ec7e6c31e084993f562952eab9be5bb9da53363c60a37b2b05c13</cites><orcidid>0000-0001-7024-1561 ; 0000-0002-7639-9463 ; 0000-0003-3126-4394 ; 0000-0002-8557-4155</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27922,27923</link.rule.ids></links><search><creatorcontrib>Nishimura, Y.</creatorcontrib><creatorcontrib>Dyer, A.</creatorcontrib><creatorcontrib>Donovan, E. F.</creatorcontrib><creatorcontrib>Angelopoulos, V.</creatorcontrib><title>Fine‐Scale Structures of STEVE Revealed by 4K Imaging</title><title>Journal of geophysical research. Space physics</title><description>We utilized a 4K imaging to examine properties of fine‐scale structures of Strong Thermal Emission Velocity Enhancement (STEVE) near the magnetic zenith. Its high spatial (0.09 km at 200 km altitude) and temporal (24 Hz) resolution provided unprecedented details of fine‐scale structures in the subauroral ionosphere. Although the STEVE emission was seen as a homogeneous purple/mauve arc in the all‐sky images, the high‐speed imaging revealed that STEVE contained substantial multi‐scale structures. The characteristic wavelength and period were 12.4 ± 7.4 km and 1.4 ± 0.8 s, and they drifted westward at 8.9 ± 0.7 km/s. The speed is comparable to the reported magnitude of the intense subauroral ion drifts (SAID), suggesting that the fine‐scale structures are an optical manifestation of the E × B drift in the intense SAID. A spectral analysis identified multiple peaks at >10, 4, 2, 1.1, and <1/5 s period (>83, 33, 16, 9, and <1.7 km wavelength). Although most of the fine‐scale structures were stable during the drift across the field of view, some of the structures dynamically evolved within a few tens of km. The fine‐scale structures have a power law spectrum with a slope of −1, indicating that shear flow turbulence cascade structures to smaller scales. The fine‐scale structures pose a challenge to the subauroral ionosphere‐thermosphere interaction about how the ionosphere creates such fine‐scale structures and how the thermosphere reacts much faster than expected from a typical chemical reaction time.
Plain Language Summary
Strong Thermal Emission Velocity Enhancement (STEVE) is often perceived as a homogeneous arc with a purple or mauve color. However, this notion is based on photographs with a long exposure time. We conducted a 4K video observation of STEVE with unprecedentedly high spatial and temporal resolution. The video revealed that STEVE is not a homogeneous arc but consists of rich fine‐scale structures that could not be seen in regular photographs. The fine‐scale structures had wavelengths of 1–10 s of km with multiple spectral peaks. The fine‐scale structures moved westward at 8.9 km/s. We suggest that the fine‐scale structures of STEVE correspond to fine‐scale plasma structures in the fast plasma streams in the upper atmosphere. However, it is challenging to explain how the upper atmospheric glow can form the fine‐scale structure because of the long chemical reaction time.
Key Points
Citizen scientist photographs revealed fine‐scale structures of Strong Thermal Emission Velocity Enhancement
The fine‐scale structures extend down to a 9 km size, possibly even below a 1 km size. They propagate at 8.9 km/s westward
The power law spectrum with a slope of −1 suggests a shear flow turbulence by the intense subauroral ion drifts</description><subject>Cascade flow</subject><subject>Chemical reactions</subject><subject>citizen scientist observations</subject><subject>Drift</subject><subject>Emissions</subject><subject>fine‐scale structure</subject><subject>Imaging</subject><subject>Ionosphere</subject><subject>Reaction time</subject><subject>Shear flow</subject><subject>Spectral analysis</subject><subject>Spectrum analysis</subject><subject>STEVE, SAID and SAPS</subject><subject>substorm</subject><subject>Temporal resolution</subject><subject>THEMIS, DMSP and spectrograph</subject><subject>Thermal emission</subject><subject>Thermosphere</subject><subject>turbulence in the subauroral ionosphere and thermosphere</subject><subject>Upper atmosphere</subject><subject>Velocity</subject><subject>Wavelengths</subject><issn>2169-9380</issn><issn>2169-9402</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2023</creationdate><recordtype>article</recordtype><recordid>eNp9kMFOAjEQhhujiQS5-QCbeHV12tnubo-EAIIkJoBem7bMkiXAYstKuPkIPqNP4ho08eR_mT__fJlJfsauOdxxEOpegMBxF1AA5GesJXiqYpWAOP_1mMMl64SwgkZ5E3HZYtmg3NLn-8fMmTVFs72v3b72FKKqiGbz_ks_mtIbNbtFZI9R8hiNNmZZbpdX7KIw60Cdn9lmz4P-vPcQT56Go153EjuEjMeWSHFFC24skMsodcgJ8kQpLGQqlBRkrLIkrVULIxFTdCkYzKywIB3HNrs53d356rWmsNerqvbb5qUWChKpMBOioW5PlPNVCJ4KvfPlxvij5qC_29F_22lwPOGHck3Hf1k9Hk67MueK4xdxkmO1</recordid><startdate>202312</startdate><enddate>202312</enddate><creator>Nishimura, Y.</creator><creator>Dyer, A.</creator><creator>Donovan, E. F.</creator><creator>Angelopoulos, V.</creator><general>Blackwell Publishing Ltd</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>8FD</scope><scope>H8D</scope><scope>KL.</scope><scope>L7M</scope><orcidid>https://orcid.org/0000-0001-7024-1561</orcidid><orcidid>https://orcid.org/0000-0002-7639-9463</orcidid><orcidid>https://orcid.org/0000-0003-3126-4394</orcidid><orcidid>https://orcid.org/0000-0002-8557-4155</orcidid></search><sort><creationdate>202312</creationdate><title>Fine‐Scale Structures of STEVE Revealed by 4K Imaging</title><author>Nishimura, Y. ; Dyer, A. ; Donovan, E. F. ; Angelopoulos, V.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c3071-bee919ed1ab0ec7e6c31e084993f562952eab9be5bb9da53363c60a37b2b05c13</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2023</creationdate><topic>Cascade flow</topic><topic>Chemical reactions</topic><topic>citizen scientist observations</topic><topic>Drift</topic><topic>Emissions</topic><topic>fine‐scale structure</topic><topic>Imaging</topic><topic>Ionosphere</topic><topic>Reaction time</topic><topic>Shear flow</topic><topic>Spectral analysis</topic><topic>Spectrum analysis</topic><topic>STEVE, SAID and SAPS</topic><topic>substorm</topic><topic>Temporal resolution</topic><topic>THEMIS, DMSP and spectrograph</topic><topic>Thermal emission</topic><topic>Thermosphere</topic><topic>turbulence in the subauroral ionosphere and thermosphere</topic><topic>Upper atmosphere</topic><topic>Velocity</topic><topic>Wavelengths</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Nishimura, Y.</creatorcontrib><creatorcontrib>Dyer, A.</creatorcontrib><creatorcontrib>Donovan, E. F.</creatorcontrib><creatorcontrib>Angelopoulos, V.</creatorcontrib><collection>CrossRef</collection><collection>Meteorological & Geoastrophysical Abstracts</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Meteorological & Geoastrophysical Abstracts - Academic</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>Journal of geophysical research. Space physics</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Nishimura, Y.</au><au>Dyer, A.</au><au>Donovan, E. F.</au><au>Angelopoulos, V.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Fine‐Scale Structures of STEVE Revealed by 4K Imaging</atitle><jtitle>Journal of geophysical research. Space physics</jtitle><date>2023-12</date><risdate>2023</risdate><volume>128</volume><issue>12</issue><epage>n/a</epage><issn>2169-9380</issn><eissn>2169-9402</eissn><abstract>We utilized a 4K imaging to examine properties of fine‐scale structures of Strong Thermal Emission Velocity Enhancement (STEVE) near the magnetic zenith. Its high spatial (0.09 km at 200 km altitude) and temporal (24 Hz) resolution provided unprecedented details of fine‐scale structures in the subauroral ionosphere. Although the STEVE emission was seen as a homogeneous purple/mauve arc in the all‐sky images, the high‐speed imaging revealed that STEVE contained substantial multi‐scale structures. The characteristic wavelength and period were 12.4 ± 7.4 km and 1.4 ± 0.8 s, and they drifted westward at 8.9 ± 0.7 km/s. The speed is comparable to the reported magnitude of the intense subauroral ion drifts (SAID), suggesting that the fine‐scale structures are an optical manifestation of the E × B drift in the intense SAID. A spectral analysis identified multiple peaks at >10, 4, 2, 1.1, and <1/5 s period (>83, 33, 16, 9, and <1.7 km wavelength). Although most of the fine‐scale structures were stable during the drift across the field of view, some of the structures dynamically evolved within a few tens of km. The fine‐scale structures have a power law spectrum with a slope of −1, indicating that shear flow turbulence cascade structures to smaller scales. The fine‐scale structures pose a challenge to the subauroral ionosphere‐thermosphere interaction about how the ionosphere creates such fine‐scale structures and how the thermosphere reacts much faster than expected from a typical chemical reaction time.
Plain Language Summary
Strong Thermal Emission Velocity Enhancement (STEVE) is often perceived as a homogeneous arc with a purple or mauve color. However, this notion is based on photographs with a long exposure time. We conducted a 4K video observation of STEVE with unprecedentedly high spatial and temporal resolution. The video revealed that STEVE is not a homogeneous arc but consists of rich fine‐scale structures that could not be seen in regular photographs. The fine‐scale structures had wavelengths of 1–10 s of km with multiple spectral peaks. The fine‐scale structures moved westward at 8.9 km/s. We suggest that the fine‐scale structures of STEVE correspond to fine‐scale plasma structures in the fast plasma streams in the upper atmosphere. However, it is challenging to explain how the upper atmospheric glow can form the fine‐scale structure because of the long chemical reaction time.
Key Points
Citizen scientist photographs revealed fine‐scale structures of Strong Thermal Emission Velocity Enhancement
The fine‐scale structures extend down to a 9 km size, possibly even below a 1 km size. They propagate at 8.9 km/s westward
The power law spectrum with a slope of −1 suggests a shear flow turbulence by the intense subauroral ion drifts</abstract><cop>Washington</cop><pub>Blackwell Publishing Ltd</pub><doi>10.1029/2023JA032008</doi><tpages>11</tpages><orcidid>https://orcid.org/0000-0001-7024-1561</orcidid><orcidid>https://orcid.org/0000-0002-7639-9463</orcidid><orcidid>https://orcid.org/0000-0003-3126-4394</orcidid><orcidid>https://orcid.org/0000-0002-8557-4155</orcidid></addata></record> |
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| subjects | Cascade flow Chemical reactions citizen scientist observations Drift Emissions fine‐scale structure Imaging Ionosphere Reaction time Shear flow Spectral analysis Spectrum analysis STEVE, SAID and SAPS substorm Temporal resolution THEMIS, DMSP and spectrograph Thermal emission Thermosphere turbulence in the subauroral ionosphere and thermosphere Upper atmosphere Velocity Wavelengths |
| title | Fine‐Scale Structures of STEVE Revealed by 4K Imaging |
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