Electrostatic Electron Cyclotron Harmonic Waves as a Candidate to Cause Pulsating Auroras

Fukizawa, Mizuki; Sakanoi, Takeshi; Miyoshi, Yoshizumi; Hosokawa, K.; Katoh, Yutai; Kazama, Y.; Kumamoto, A.; Tsuchiya, F.; Miyashita, Yukinaga; Tanaka, Yoshimasa; Kasahara, Yoshiya; Ozaki, Mitsunori; Matsuoka, A.; Matsuda, Shoya; Hikishima, Mitsuru; Oyama, Shin‐ichiro; Ogawa, Y.; Kurita, Satoshi; Fujii, Ryoichi

doi:10.1029/2018gl080145

Cited by 36 publications

(43 citation statements)

References 42 publications

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“…The ultimate source of pulsating aurora is generally accepted to be magnetospheric electrons with energies of a few to tens of keV (Bryant et al, 1971;Sandahl et al, 1980). Recent studies have further shown that the precipitation is driven by wave-particles interactions (e.g., Fukizawa et al, 2018;Liang et al, 2010;Nishimura et al, 2010); however, the mechanism that determines the pulsation period and the shape of patches has not been determined. Previous studies of the optical emissions associated with pulsating aurora found that the emissions typically come from 110-km altitude (Davidson, 1990;Johnstone, 1978).…”

Section: Introductionmentioning

confidence: 99%

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

Yang

Spanswick

Liang

et al. 2019

Geophysical Research Letters

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A recent study (Grono & Donovan, 2018, https://doi.org/10.5194/angeo-36-891-2018) reported two distinct categories of pulsating aurora: patchy pulsating aurora (PPA) and amorphous pulsating aurora (APA). In this study we compare the auroral intensity of five PPA events and seven APA events monitored by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) All‐Sky Imagers with co‐located cosmic noise absorption (CNA) from the Geospace Observatory wide‐beam riometers. Our results show significant correlations between CNA and the auroral intensity of the APA events but no correlation between CNA and the auroral intensity of the PPA events. Analysis of conjunctions with the electron flux data obtained from the FAST satellite, we found that electrons responsible for APA may extend to higher energy range than those for PPA.

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Section: Introductionmentioning

confidence: 99%

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

Yang

Spanswick

Liang

et al. 2019

Geophysical Research Letters

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“…The resonance energy of LBC reaches 9 keV at the MLAT of −3° in this event. Although ECH and LBC waves were concurrently excited for this event, it can be considered that the difference between their cyclotron resonance energies differentiated their contributions to the pitch‐angle scattering of inner magnetospheric electrons (Fukizawa et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

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

Fukizawa

Sakanoi

Miyoshi

et al. 2020

Geophysical Research Letters

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Electrostatic electron cyclotron harmonic (ECH) waves are generally excited in the magnetic equator region, in the sector from nightside to dayside during geomagnetically active conditions, and cause the pitch angle scattering by cyclotron resonance. The scattered electrons precipitate into the Earth's atmosphere and cause auroral emission. However, there is no observational evidence that ECH waves actually scatter electrons into the loss cone in the magnetosphere. In this study, from simultaneous wave and particle observation data obtained by the Arase satellite equipped with a high-pitch angular resolution electron analyzer, we present evidence that the ECH wave intensity near the magnetic equator is correlated with an electron flux inside the loss cone with an energy of about 5 keV. The simulation suggests that this electron flux contributes to the auroral emission at 557.7 nm with an intensity of about 200 R.

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“…Recent statistical observations and theoretical predictions support the importance, and even dominance, of the whistler chorus in scattering energetic electrons out of the plasma sheet for L shells ≤8 (Li et al, 2005;Santolik et al, 2009;Thorne et al, 2010). Other observed statistics support the dominant scattering effect of electron cyclotron harmonic (ECH) waves at L shells > 8 (Liang et al, 2010;Ni, Thorne, Liang, et al, 2011;Zhang et al, 2015) and an association between intense auroral forms and ECH waves at about L = 6 (Fuzikawa et al, 2018). Other observed statistics support the dominant scattering effect of electron cyclotron harmonic (ECH) waves at L shells > 8 (Liang et al, 2010;Ni, Thorne, Liang, et al, 2011;Zhang et al, 2015) and an association between intense auroral forms and ECH waves at about L = 6 (Fuzikawa et al, 2018).…”

Section: Introductionmentioning

confidence: 87%

Source of the Bursty Bulk Flow Diffuse Aurora: Electrostatic Cyclotron Harmonic and Whistler Waves in the Coupling of Bursty Bulk Flows to Auroral Precipitation

et al. 2019

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Electron cyclotron harmonic (ECH) and whistler chorus waves are recognized as the two mechanisms responsible for the resonant wave‐particle interactions necessary to precipitate plasma sheet electrons into the ionosphere, producing the diffuse Aurora. Previous work has demonstrated ECH waves dominate electron scattering at L shells >8, while whistler chorus dominates scattering at L shells L < 8. However, we find from Time History of Events and Macroscale (THEMIS) Interactions during Substorms observations of fast flows at L = 12 that oblique whistler chorus emissions play the dominant role in scattering electrons. Previous works have identified whistler‐mode waves within fast flows that are produced by an electron temperature anisotropy Te,⊥/Te,||> 1, consistent with electron betatron acceleration. Here, however, we find whistler chorus emissions throughout an interval of fast flows where Te,⊥/Te,||< 1. Parallel electron beams account for the enhanced parallel electron temperature and serve as the instability mechanism for the whistler chorus. The parallel electron beams and associated cigar‐shaped distributions are consistent with Fermi acceleration at dipolarizations in fast flows. We demonstrate that the scattering efficiency of the whistler chorus exceeds that of ECH waves, which THEMIS also detects during the fast flows. The obliquity of the whistler waves permits efficient scattering of lower‐energy electrons into the diffuse aurora. We conclude that Fermi acceleration of electrons provides one important free‐energy source for the wave‐particle interactions responsible for coupling plasma sheet electrons into the diffuse aurora during substorm conditions.

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Electrostatic Electron Cyclotron Harmonic Waves as a Candidate to Cause Pulsating Auroras

Cited by 36 publications

References 42 publications

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

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

Source of the Bursty Bulk Flow Diffuse Aurora: Electrostatic Cyclotron Harmonic and Whistler Waves in the Coupling of Bursty Bulk Flows to Auroral Precipitation

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