Over‐Darkening of Pulsating Aurora

Hosokawa, K.; Miyoshi, Yoshizumi; Oyama, S.; Ogawa, Y.; Kurita, Satoshi; Kasahara, Yoshiya; Kasaba, Yasumasa; Yagitani, Satoshi; Matsuda, Shoya; Ozaki, Mitsunori; Tsuchiya, Fuminori; Kumamoto, Atsushi; Takashima, Takeshi; Shinohara, I.; Fujii, Ryoichi

doi:10.1029/2020ja028838

Cited by 6 publications

(7 citation statements)

References 41 publications

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“…The original time resolution was 0.01 s, and post‐analysis was performed to provide images with a time resolution of 1 s. More detailed information on the camera system can be found in Hosokawa et al. (2023).…”

Section: Data Setmentioning

confidence: 99%

“…A conceptual drawing illustrated by Hernandez et al. (1982; Figure 7 in their publication) may be helpful in tracing the wind flow starting from the auroral oval. Molecular‐rich air transportation along the wind surge reduces the O/N 2 ratio (Cai et al., 2023; Immel et al., 2001; Miller et al., 1984; Strickland et al., 2001; Yu et al., 2022; Zhang et al., 2004), which depresses the ionospheric plasma density via the dissociative recombination process, that is, negative ionospheric storm (Strickland et al., 2001).…”

Section: Introductionmentioning

confidence: 99%

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Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry‐Perot Interferometer in Tromsø, Norway Since 2009

Oyama,

Vanhamäki,

Cai

et al. 2024

Space Weather

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Solar cycles 24–25 were quiet until a geomagnetic storm with a Sym‐H index of −170 nT occurred in late March 2023. On March 23–24, a Fabry‐Perot interferometer (FPI; 630 nm) in Tromsø, Norway, recorded the highest thermospheric wind speed of over 500 m/s since 2009. Comparisons with magnetometer readings in Scandinavia showed that a large amount of electromagnetic energy was transferred to the ionosphere‐thermosphere system. Total electron content maps suggested an enlarged auroral oval and revealed that the FPI observed winds near the polar cap instead of inside the oval for a long period during the storm main phase. The FPI wind had a strong equatorward component during the storm, likely because of the powerful anti‐sunward ionospheric plasma flow in the polar cap. The positive Y‐component of the IMF for 6 days before the storm caused a successive westward component of the FPI‐measured wind during the storm main phase. On March 24, the first day of the storm recovery phase, thermospheric wind disturbed and the ionospheric density decreased significantly at high latitudes. This density depression lasted for several days, and a large amount of electromagnetic energy during the storm modified the thermospheric dynamics and ionospheric plasma density.

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Section: Data Setmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry‐Perot Interferometer in Tromsø, Norway Since 2009

Oyama,

Vanhamäki,

Cai

et al. 2024

Space Weather

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“…Combining with the fact that a similar modulation (C. C. > 0.5) was also observed by BARREL-1Q and GOES-15 (Figure 1A), we conclude that the quasi-static breathing mode may have played a significant role in modulating the electron precipitation. Previous studies show high correlation between chorus waves and ASI auroral intensity when the electron precipitation is driven by chorus waves (Nishimura et al, 2011;Hosokawa et al, 2020). In those work, the observations were specifically chosen at latitudes with the highest correlation (corresponding to highest correlation L shell), within a narrow window of a few minutes.…”

Section: Modulation Of Waves and Electron Precipitationmentioning

confidence: 99%

Large-scale magnetic field oscillations and their effects on modulating energetic electron precipitation

Qin,

Li,

et al. 2024

Front. Astron. Space Sci.

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In this study, we present simultaneous multi-point observations of magnetospheric oscillations on a time scale of tens of minutes (forced-breathing mode) and modulated whistler-mode chorus waves, associated with concurrent energetic electron precipitation observed through enhanced BARREL X-rays. Similar fluctuations are observed in X-ray signatures and the compressional component of magnetic oscillations, spanning from ∼9 to 12 h in MLT and 5 to 11 in L shell. Such magnetospheric oscillations covering an extensive region in the pre-noon sector have been suggested to play a potential role in precipitating energetic electrons by either wave scattering or loss cone modulation, showing a high correlation with the enhancement in X-rays. In this event, the correlation coefficients between chorus waves (smoothed over 8 min), ambient magnetic field oscillations and X-rays are high. We perform an in-depth quasi-linear modeling analysis to evaluate the role of magnetic field oscillations in modulating energetic electron precipitation in the Earth’s magnetosphere through modulating whistler-mode chorus wave amplitude, resonance condition between chorus waves and electrons, as well as loss cone size. Model results further show that the modulation of chorus wave amplitude plays a dominant role in modulating the electron precipitation. However, the effect of the modulation in the resonant energy between chorus waves and energetic electrons due to the background magnetic field oscillations cannot be neglected. The bounce loss cone modulation, affected by the magnetic oscillations, has little influence on the electron precipitation modulation. Our results show that the low frequency magnetospheric oscillations could play a significant role in modulating the electron precipitation through modulating chorus wave intensity and the resonant energy between chorus waves and electron.

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“…Pulsating aurora is a type of diffuse aurora that exhibits intermittent modulation of luminosity whose period is typically several seconds. The precipitation of several to ~100 keV electrons scattered by the chorus waves causes the pulsating auroral emission in the Earth's auroral ionosphere [e.g., Miyoshi et al, 2010Miyoshi et al, , 2015bKasahara et al, 2018;Ozaki et al, 2019;Hosokawa et al, 2020]. A few Hz internal modulations are sometimes embedded in the main pulsation of the pulsating aurora.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Precipitation of Sub-Relativistic Electron Microburst and Pulsating Aurora Electrons

Namekawa

Mitani

Asamura

et al. 2023

Preprint

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We have identified for the first time an energy-time dispersion of precipitating electron flux in a pulsating aurora patch, ranging from 6.7 keV to 580 keV, through simultaneous in-situ observations of sub-relativistic electrons of microburst precipitations and lower-energy electrons using the LAMP sounding rocket launched from the Poker Flat Research Range in Alaska. Our observations reveal that precipitating electrons with energies of 180-320 keV were observed first, followed by 250-580 keV electrons 0-30 ms later, and finally, after 500-1000 ms, 6.7-14.6 keV electrons were observed. The identified energy-time dispersion is consistent with the theoretical estimation that the relativistic electron microbursts are a high-energy tail of pulsating aurora electrons, which are caused by chorus waves propagating along the field line.

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Over‐Darkening of Pulsating Aurora

Cited by 6 publications

References 41 publications

Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry‐Perot Interferometer in Tromsø, Norway Since 2009

Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry‐Perot Interferometer in Tromsø, Norway Since 2009

Large-scale magnetic field oscillations and their effects on modulating energetic electron precipitation

Simultaneous Precipitation of Sub-Relativistic Electron Microburst and Pulsating Aurora Electrons

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