Correlations between the very low frequency chorus and pulsating aurora observed by low-light-level television at

Tsuruda, K.; Machida, S.; Oguti, Takasi; Kokubun, S.; Hayashi, K.; Kitamura, Teitaro; Saka, O.; Watanabe, T.

doi:10.1139/p81-137

Cited by 41 publications

(34 citation statements)

References 6 publications

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“…Koons (1981) shows, using SCATHA satellite data, that the VLF chorus emissions very often start from the frequencies inside the ELF frequency range and that the chorus emissions could be generated by natural stochastic processes occurring in strongly structured bands of ELF-hiss in the outer magnetosphere. Tsuruda et al (1981) report only six cases of peak to peak correlation between chorus elements and pulses of auroral patches during more than one hour of observation. Hansen and Scour®eld (1990) have shown that the range of delay times between VLF waves and corresponding optical pulsations is consistent with electron cyclotron source region located near the equatorial plane.…”

Section: Introductionmentioning

confidence: 92%

Auroral pulsations and accompanying VLF emissions

et al. 1999

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Abstract. Results of simultaneous TV observations of pulsating auroral patches and ELF-VLF-emissions in the morning sector carried out in SodankylaÈ (Finland) on February 15, 1991 are presented. Auroral pulsating activity was typical having pulsating patches with characteristic periods of about 7 s. Narrow-band hiss emissions and chorus elements at intervals of 0.3±0.4 s formed the main ELF-VLF activity in the frequency range 1.0±2.5 kHz at the same time. The analysis of auroral images with time resolution of 0.04 s allowed perfectly separate analysis of spatial and temporal variations in the auroral luminosity. Mutual correspondence between the behaviour of the luminous auroral patches and the appearance of ELF noise type hiss emissions and VLF chorus trains was found in two intervals chosen for analysis. While the hiss emissions were associated with the appearance of luminosity inside a limited area close to the zenith, the structured VLF emissions were accompanied by rapid motion of luminosity inside the area. The spatial dimension of the pulsating area was about 45±50 km and luminosity propagated inside it with velocity of about 10±12 kms. We discuss a new approach to explain the 5±15 s auroral pulsation based on the theory of¯owing cyclotron maser and relaxation characteristics of ionosphere.

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Section: Introductionmentioning

confidence: 92%

Auroral pulsations and accompanying VLF emissions

et al. 1999

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“…Chorus waves have been considered as one of the candidate wave modes that drive pulsating aurora, based on correlations between ELF/VLF intensity and auroral luminosity [Tsuruda et al, 1981;Johnstone, 1983;Tagirov et al, 1999]. Although it has been rare to observe equatorial and auroral regions simultaneously and to precisely treat magnetic field line modeling, recent studies by Nishimura et al [2010Nishimura et al [ , 2011 determined magnetic field mapping and identified uniquely that lower band chorus is responsible for driving pulsating aurora.…”

Section: Introductionmentioning

confidence: 99%

Chorus intensity modulation driven by time‐varying field‐aligned low‐energy plasma

Nishimura

Bortnik

et al. 2015

JGR Space Physics

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Recent studies have shown that chorus waves are responsible for scattering and precipitating the energetic electrons that drive the pulsating aurora. While some of the chorus intensity modulation events are correlated with <~100 eV electron density modulation, most of the chorus intensity modulation events in the postmidnight sector occur without apparent density changes. Although it is generally difficult to measure evolution of low‐energy (<~20 eV) electron fluxes due to constraints imposed by the spacecraft potential and electrostatic analyzer (ESA) energy range limit, we identified using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite data that low‐energy ions of ~100 eV show density modulation that is correlated with chorus intensity modulation. Those low‐energy ions and electrons are field‐aligned with major peaks in 0° (for northern hemisphere winter event) and 180° (for northern hemisphere summer event) pitch angle, indicating that outflowing plasma from the sunlit hemisphere is the source of the low‐energy plasma density modulation near the equator. Plasma sheet plasma density, and ambient electric and magnetic fields do not show modulations that are correlated with the chorus intensity modulation. Assuming charge neutrality, the low‐energy ions can be used to represent cold plasma density in wave growth rate calculations, and the enhancements of the low‐energy plasma density are found to contribute most effectively to chorus linear growth rates. These results suggest that chorus intensity modulation is driven by a feedback process where outflowing plasma due to energetic electron precipitation increases the equatorial density that drives further electron precipitation.

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“…These waves interact with high-energy (10-100 keV) electrons and cause modulation of spectacular pulsating auroras [e.g., Tsuruda et al, 1981;Nishimura et al, 2010;Miyoshi et al, 2010;Lessard, 2012;Li et al, 2012;Ozaki et al, 2012]. ELF/VLF chorus emissions can also interact with relativistic electrons in the radiation belts, contributing to their acceleration and dissipation in the inner magnetosphere [e.g., Miyoshi et al, 2003Miyoshi et al, , 2007Katoh and Omura, 2007;Kasahara et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

Ground‐based ELF/VLF chorus observations at subauroral latitudes—VLF‐CHAIN Campaign

et al. 2014

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We report observations of very low frequency (VLF) and extremely low frequency (ELF) chorus waves taken during the ELF/VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) of 17-25 February 2012 at subauroral latitudes at Athabasca (L = 4.3), Canada. ELF/VLF waves were measured continuously with a sampling rate of 100 kHz to monitor daily variations in ELF/VLF emissions and derive their detailed structures. We found quasiperiodic (QP) emissions whose repetition period changes rapidly within a period of 1 h without corresponding magnetic pulsations. QP emissions showed positive correlation between amplitude and frequency sweep rate, similarly to rising-tone elements. We found an event of nearly simultaneous enhancements of QP emissions and Pc1/electromagnetic ion cyclotron wave intensities, suggesting that the temperature anisotropy of electrons and ions developed simultaneously at the equatorial plane of the magnetosphere. We also found QP emissions whose intensity suddenly increased in association with storm sudden commencement without changing their frequency. Falling-tone ELF/VLF emissions were observed with their rate of frequency change varying from 0.7 to 0.05 kHz/s over 10 min. Bursty-patch emissions in the lower and upper frequency bands are often observed during magnetically disturbed periods. Clear systematic correlation between these various ELF/VLF emissions and cosmic noise absorption was not obtained throughout the campaign period. These observations indicate several previously unknown features of ELF/VLF emissions in subauroral latitudes and demonstrate the importance of continuous measurements for monitoring temporal variations in these emissions.

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Correlations between the very low frequency chorus and pulsating aurora observed by low-light-level television at

Cited by 41 publications

References 6 publications

Auroral pulsations and accompanying VLF emissions

Auroral pulsations and accompanying VLF emissions

Chorus intensity modulation driven by time‐varying field‐aligned low‐energy plasma

Ground‐based ELF/VLF chorus observations at subauroral latitudes—VLF‐CHAIN Campaign

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