Pitch‐Angle Scattering of Inner Magnetospheric Electrons Caused by ECH Waves Obtained With the Arase Satellite

Fukizawa, Mizuki; Sakanoi, Takeshi; Miyoshi, Yoshizumi; Kazama, Y.; Katoh, Yutai; Kasahara, Yoshiya; Matsuda, Shoya; Matsuoka, A.; Kurita, Satoshi; Motomizu, Shoji; Teramoto, Masaaki; Imajo, Shun; Sinohara, Iku; Wang, S. Y.; Tam, Sunny Wing-Yee; Chang, T. F.; Wang, B. J.; Jun, Chae‐Woo

doi:10.1029/2020gl089926

Cited by 9 publications

(13 citation statements)

References 32 publications

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“…Previous studies demonstrated that the contribution of ECH waves to approaching strong diffusion is relatively small compared with LBC and UBC waves (Khazanov et al, 2015;Tao et al, 2011;Thorne et al, 2010; 2021) identified that both LBC and UBC waves contribute to the electron PA scattering close to the equator via Arase observations. On the other hand, the PA scattering of keV electrons in a loss cone by ECH waves had been reported using ground-based all-sky imager and Arase satellite observations (Fukizawa et al, 2018(Fukizawa et al, , 2020. Although these previous studies are based on case studies, our study is based on statistical analyses of data obtained with a relatively high-angular-resolution electron instrument onboard the Arase satellite.…”

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confidence: 86%

Statistical Study of Approaching Strong Diffusion of Low‐Energy Electrons by Chorus and ECH Waves Based on In Situ Observations

et al. 2022

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Inner magnetospheric electrons are precipitated in the ionosphere via pitch‐angle (PA) scattering by lower band chorus (LBC), upper band chorus (UBC), and electrostatic electron cyclotron harmonic (ECH) waves. However, the PA scattering efficiency of low‐energy electrons (0.1–10 keV) has not been investigated via in situ observations because of difficulties in flux measurements within loss cones at the magnetosphere. In this study, we demonstrate that LBC, UBC, and ECH waves contribute to PA scattering of electrons at different energy ranges using the Arase (ERG) satellite observation data and successively detected the moderate loss cone filling, that is, approaching strong diffusion. Approaching strong diffusion by LBC, UBC, and ECH waves occurred at ∼2–20 keV, ∼1–10 keV, and ∼0.1–2 keV, respectively. The occurrence rate of the approaching strong diffusion by high‐amplitude LBC (>50 pT), UBC (>20 pT), and ECH (>10 mV/m) waves, respectively, reached ∼70%, ∼40%, and ∼30% higher than that without simultaneous wave activity. The energy range in which the occurrence rate was high agreed with the range where the PA diffusion rate of each wave exceeded the strong diffusion level based on the quasilinear theory.

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Section: Summary and Discussionmentioning

confidence: 86%

Statistical Study of Approaching Strong Diffusion of Low‐Energy Electrons by Chorus and ECH Waves Based on In Situ Observations

et al. 2022

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“…These relatively high-energy precipitating electrons cannot produce the enhancement of electron density in the F region. We suggest that the electron density enhancement in the F region with electron temperature increase would be caused by precipitating electrons with energies lower than 1 keV, and these low-energy electrons are generated by UBC and/or ECH waves and the backscattered primary and secondary electrons in the opposite hemisphere (Evans et al, 1987;Fukizawa et al, 2020Fukizawa et al, , 2018Inan et al, 1992;Khazanov et al, 2014;Miyoshi et al, 2015). Figure 10b indicates that the electron density enhancements in the E and F regions have a positive correlation.…”

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confidence: 92%

Statistical Study of Electron Density Enhancements in the Ionospheric F Region Associated With Pulsating Auroras

et al. 2021

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When a substorm occurs, various plasma waves are excited in the inner magnetosphere by temperature anisotropies and loss cone distribution of the plasma injected from the magnetospheric tail. Immediately after auroral breakups, auroras start to blink quasi-periodically on a time scale of a few seconds to tens of seconds (Yamamoto, 1988). These auroras, called pulsating auroras (PsAs), are believed to be driven by precipitating electrons of energies from a few kiloelectron volts (keV) to tens of keV that are scattered into a loss cone through cyclotron resonance with lower band chorus (LBC) waves near the magnetic equator (e.g., Kasahara et al., 2019Kasahara et al., , 2018Nishimura et al., 2010).Electron precipitation of energies from tens of eV to a few keV associated with PsAs was observed by sounding rockets and low-altitude satellites accompanied by energetic electron precipitation (e.g.,

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“…The occurrence rate of Diffuse peaked in the morning sector, which is also consistent with previous studies 4 , 14 , 27 , 32 , 33 . Diffuse auroras could originate due to magnetospheric waves, such as chorus 34 – 37 and electrostatic electron cyclotron harmonic (ECH) waves 38 , 39 , the former often being widely distributed from the midnight to noon sector 40 and the latter from the pre-midnight to morning sector 41 . In panel (e), the occurrence rate of diffuse auroras decreased in the morning sector owing to the effect of sunlight, but their occurrence over a wide range of UT was generally consistent with the distribution of the magnetospheric waves.…”

Section: Discussionmentioning

confidence: 99%

An automated auroral detection system using deep learning: real-time operation in Tromsø, Norway

Nanjo

Nozawa

Yamamoto

et al. 2022

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The activity of citizen scientists who capture images of aurora borealis using digital cameras has recently been contributing to research regarding space physics by professional scientists. Auroral images captured using digital cameras not only fascinate us, but may also provide information about the energy of precipitating auroral electrons from space; this ability makes the use of digital cameras more meaningful. To support the application of digital cameras, we have developed artificial intelligence that monitors the auroral appearance in Tromsø, Norway, instead of relying on the human eye, and implemented a web application, “Tromsø AI”, which notifies the scientists of the appearance of auroras in real-time. This “AI” has a double meaning: artificial intelligence and eyes (instead of human eyes). Utilizing the Tromsø AI, we also classified large-scale optical data to derive annual, monthly, and UT variations of the auroral occurrence rate for the first time. The derived occurrence characteristics are fairly consistent with the results obtained using the naked eye, and the evaluation using the validation data also showed a high F1 score of over 93%, indicating that the classifier has a performance comparable to that of the human eye classifying observed images.

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Pitch‐Angle Scattering of Inner Magnetospheric Electrons Caused by ECH Waves Obtained With the Arase Satellite

Cited by 9 publications

References 32 publications

Statistical Study of Approaching Strong Diffusion of Low‐Energy Electrons by Chorus and ECH Waves Based on In Situ Observations

Statistical Study of Approaching Strong Diffusion of Low‐Energy Electrons by Chorus and ECH Waves Based on In Situ Observations

Statistical Study of Electron Density Enhancements in the Ionospheric F Region Associated With Pulsating Auroras

An automated auroral detection system using deep learning: real-time operation in Tromsø, Norway

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