Optical and particle observations of type B red aurora

Ebihara, Yusuke; Sakanoi, Takeshi; Asamura, Kazushi; Hirahara, Masafumi; Ieda, A.

doi:10.1029/2009gl041037

Cited by 4 publications

(4 citation statements)

References 28 publications

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“…Hereinafter we call this a smokelike aurora. The field of view of MAC was rather small (∼70 × 70 km) and the satellite moved rapidly, so that MAC could not keep observing the same part of the aurora more than ∼9 s. We confirm that the smokelike auroras maintained their shape at least for ∼9 s. That is, the smokelike aurora is clearly distinguished from the discrete, active aurora observed by Reimei/MAC [ Obuchi et al , 2008; Ebihara et al , 2009], pulsating aurora [ Røyrvik and Davis , 1977], and black aurora [ Davis , 1978].…”

Section: Data Presentationsupporting

confidence: 60%

Reimei observation of highly structured auroras caused by nonaccelerated electrons

et al. 2010

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[1] We present observations of highly structured, thin auroras cased by precipitation of nonaccelerated electrons on the basis of optical and particle measurements performed by the Reimei satellite near the equatorward edge of the main auroral oval. The aurora has the following characteristics: (1) A full width at half maximum (FWHM) value is as low as only ∼1.8 km from optical measurements, and ∼0.6 km from particle measurements at the ionospheric altitude, which is much smaller than previously determined. (2) The FWHM value of 0.6 km corresponds to 9 km in the equatorial plane, which is ∼10 times smaller than the gyroradius of typical protons trapped in the near-Earth plasma sheet. (3) At high energies greater than ∼1 keV, the velocity distribution function of precipitating electrons is comparable to that of the trapped ones and does not demonstrate any plateau or positive gradient in the distribution. (4) The aurora was observed in geomagnetically quiet condition. (5) A geosynchronous satellite observed a significant increase in the plasma pressure of hot electrons in comparison with that of hot ions. The structuring of the aurora may be attributed to scattering processes of hot electrons. If this were the case, hot electrons would be scattered by whistler mode chorus, or electrostatic electron cyclotron harmonic waves, and the structured aurora would be a visual manifestation of the highly structured, cold plasma that determines the growth of the waves scattering the hot electrons.Citation: Ebihara, Y., T. Sakanoi, K. Asamura, M. Hirahara, and M. F. Thomsen (2010), Reimei observation of highly structured auroras caused by nonaccelerated electrons,

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Section: Data Presentationsupporting

confidence: 60%

Reimei observation of highly structured auroras caused by nonaccelerated electrons

et al. 2010

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“…Narrow rays are known to exhibit a violet colour at the leading edge and a green colour behind owing to the lifetime of O( 1 S) being longer than that of excited N 2 + (Omholt, 1971, p. 126). The delay of the 557.7 nm [OI] emission is confirmed by simultaneous observations of aurora and precipitating electrons (Ebihara et al ., 2009). The pinkish or bluish colouration extending to higher altitudes is also attributed to nitrogen emissions (N 2 + ) in sunlit aurorae (Hunten, 2006; Shiokawa et al ., 2019).…”

Section: Summary and Discussionmentioning

confidence: 99%

A review for Japanese auroral records on the three extreme space weather events around the International Geophysical Year (1957–1958)

Hayakawa

Ebihara

Hata

2022

Geoscience Data Journal

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Solar Cycle 19 was probably the greatest solar cycle over the last four centuries and significantly disrupted the solar-terrestrial environments with a number of solar eruptions and resultant geomagnetic storms. At its peak, the International Geophysical Year (IGY: 1957(IGY: -1958 was organised by international collaborations and benefitted scientific developments, capturing multiple unique extreme space weather events including the third and fourth greatest geomagnetic storms in the space age. In this article, we review and analyse original records of Japanese auroral observations around the IGY. These observations were organised by Masaaki Huruhata in collaboration with professional observatories and citizen contributors. We have digitised and documented these source documents, which comprise significant auroral displays in March 1957 (minimum Dst = −255 nT), September 1957 (minimum Dst = −427 nT), and February 1958 (minimum Dst = −426 nT). These records allow us to visualise temporal and spatial evolutions of these auroral displays, reconstruct their equatorward auroral boundaries down to 41.4°, 38.3°, and 33.3° in invariant latitudes, and contextualise their occurrences following contemporary

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“…Highly rapid variations of the different types of auroral forms represented by curtains, rays, and vortices have been observed by a new type of simultaneous observations of both auroral imaging and in situ particle measurements made by high-time/spatial resolutions of the instruments on the Reimei satellite (Asamura et al, 2003;Sakanoi et al, 2003). Owing to the simultaneous image-particle observations with the high resolutions, Ebihara et al (2009) successfully derived a novel interpretation concerning the reddening of auroral arcs. Asamura et al (2009) and Saito et al (2011) reported a case study based on fine-scale observations of the auroral forms and particles for addressing the significance of the Alfvénic electron acceleration in the auroral arcs.…”

Section: Reimei Observations With High Resolutionsmentioning

confidence: 99%

“…Owing to the simultaneous image‐particle observations with the high resolutions, Ebihara et al. (2009) successfully derived a novel interpretation concerning the reddening of auroral arcs. Asamura et al.…”

Section: Introductionmentioning

confidence: 99%

Latitudinal Profiles of Auroral Forms/Motions and Plasma Properties Based on Simultaneous Image‐Particle Measurements by Reimei in the Midnight Auroral Oval

Hirahara,

Fukuda,

Ebihara

et al. 2024

JGR Space Physics

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We present the simultaneous and conjugated auroral emission and particle data obtained by a low‐altitude polar‐orbiting micro‐satellite, Reimei, for elucidating their latitudinal distributions and variations in the nightside auroral oval. Here are reported a few notable examples of the Reimei observations with high time and spatial resolutions, namely ∼120 msec. and ∼1.2 km × 1.2 km for multispectral auroral images and 40 msec. for energy‐pitch angle distributions of electrons and ions with energies of 10 eV–12 keV, respectively. The auroral images show various fine‐scale auroral activities characterized by the following types of auroral forms and variations: faint bands, streaming multiple arcs, shearing arcs, and vortices/curls, which are typical of the latitudinal properties of auroras. The particle analyzer simultaneously observed various properties of electron energy‐pitch angle and latitudinal distributions, and their temporal variations, each of which corresponds to a type of the auroral activities. Their features are summarized below. Reimei repetitively observed inverted‐V signatures of low‐energy (<1 keV) field‐aligned electrons in addition to the higher‐energy (several keV) diffuse electrons in low‐latitude auroral oval. In more active regions at higher latitudes, the dominant energy flux responsible for the multiple‐arc emissions was carried by the well‐known inverted‐V electron precipitation. The rapidly rotating vortices or so‐called curls of fine‐scale discrete auroras near the poleward boundary of the auroral oval were closely associated with the significant energy fluxes of spiky field‐aligned electron bursts with energy‐time dispersions produced by dispersive Alfvén waves.

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Optical and particle observations of type B red aurora

Cited by 4 publications

References 28 publications

Reimei observation of highly structured auroras caused by nonaccelerated electrons

Reimei observation of highly structured auroras caused by nonaccelerated electrons

A review for Japanese auroral records on the three extreme space weather events around the International Geophysical Year (1957–1958)

Latitudinal Profiles of Auroral Forms/Motions and Plasma Properties Based on Simultaneous Image‐Particle Measurements by Reimei in the Midnight Auroral Oval

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