PFISR and ROPA observations of pulsating aurora

Jones, S. L.; Lessard, M.; Fernandes, P. A.; Lummerzheim, D.; Semeter, J. L.; Heinselman, C. J.; Lynch, K. A.; Michell, R.; Kintner, P. M.; Stenbaek‐Nielsen, H. C.; Asamura, Kazushi

doi:10.1016/j.jastp.2008.10.004

Cited by 41 publications

(65 citation statements)

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“…It is often reported that the electron precipitations resulting in pulsating auroras typically range from a few keV up to a few tens of keV [ Sandahl et al ., ; Yau et al ., ; Jones et al ., ; Miyoshi et al ., ]. Under such a notion, a main contribution to the red‐line aurora may be from the secondary electrons and/or the cascading process depicted in equation .…”

Section: Discussionmentioning

confidence: 99%

“…We, however, note that the existence of low‐energy electron precipitation during pulsating auroral intervals was previously reported by, e.g., Jones et al . [], Liang et al . [], and Samara et al .…”

Section: Discussionmentioning

confidence: 99%

“…A pulsating aurora is a repetitive modulation of auroral luminosity with quasiperiods typically within ~3–30 s [ Johnstone , ; Yamamoto , ]. It is often reported that the precipitating electrons resulting in pulsating auroras typically range from a few keV up to a few tens of keV [ Sandahl et al ., ; Yau et al ., ; Jones et al ., ; Lessard , ; Miyoshi et al ., ]. This is also in line with the result that the pulsating auroral electron precipitation was often found to be driven by a quasiperiodic oscillation of lower band whistler‐mode chorus [ Nishimura et al ., , ], whose minimum resonant energy is usually more than several keV in the inner magnetosphere [e.g., Ni et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

et al. 2016

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In this study, we present observations of red‐line (630 nm) pulsating auroras using the camera system of Red‐line Emission Geospace Observatory (REGO), during a geomagnetic storm interval. We also develop a time‐dependent model to simulate the 630 nm auroral pulsations in response to modulated precipitation inputs and compare the model outputs with REGO observations. Key results are as follows. (1) Notwithstanding the long radiative timescale of the 630 nm emission, red‐line auroras can still be modulated by pulsating electron precipitations and feature noticeable oscillations, which constitute the red‐line pulsating auroral phenomena. (2) In a majority of cases, the oscillation magnitude of red‐line pulsating auroras is substantially smaller than that of the concurrent pulsating auroras seen on Thermal Emission Imaging System whitelight images (generally dominated by 557.7 nm green‐line emissions). Under certain circumstances, e.g., when the characteristic energy of the precipitation is very high, some of the pulsating auroras may not show discernible imprints on red line. (3) The altitude range contributing most to the red‐line pulsating aurora is systematically lower than that of the steady‐state red‐line aurora, since the slower O(1D) loss rate at higher altitudes tends to suppress the oscillation range of the 630 nm emission rate. (4) We find that some pulsating auroral patches are characterized by enhanced red‐to‐green color ratio during their on time, hinting that the percentage increase of the red‐line auroral component exceeds that of the green‐line auroral component for those patches. We suggest that those special patches might possibly be associated with lower energy (<1 keV) electron precipitations.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

et al. 2016

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“…Ionospheric density enhancements occur very rapidly in response to energetic electron precipitation [Bösinger et al, 1996;Jones et al, 2008;Hosokawa et al, 2010]. While much of the enhanced density is confined to 100-120 km altitude, modest density enhancements can be seen up to the highest-altitude limit (200 km) shown by Jones et al [2008].…”

Section: 1002/2015ja021330mentioning

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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“…As with previous observations for the height‐resolved electron density profile associated with pulsating auroras, Jones et al . [], using the Poker Flat Incoherent Scatter Radar, showed that significant electron density enhancement appears at an altitude of 90 km which indicates precipitation of ~20 keV electrons [ Semeter and Kamalabadi , ]. Oyama et al .…”

Section: Introductionmentioning

confidence: 99%

Energetic electron precipitation associated with pulsating aurora: EISCAT and Van Allen Probe observations

et al. 2015

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Pulsating auroras show quasi-periodic intensity modulations caused by the precipitation of energetic electrons of the order of tens of keV. It is expected theoretically that not only these electrons but also subrelativistic/relativistic electrons precipitate simultaneously into the ionosphere owing to whistler mode wave-particle interactions. The height-resolved electron density profile was observed with the European Incoherent Scatter (EISCAT) Tromsø VHF radar on 17 November 2012. Electron density enhancements were clearly identified at altitudes >68 km in association with the pulsating aurora, suggesting precipitation of electrons with a broadband energy range from~10 keV up to at least 200 keV. The riometer and network of subionospheric radio wave observations also showed the energetic electron precipitations during this period. During this period, the footprint of the Van Allen Probe-A satellite was very close to Tromsø and the satellite observed rising tone emissions of the lower band chorus (LBC) waves near the equatorial plane. Considering the observed LBC waves and electrons, we conducted a computer simulation of the wave-particle interactions. This showed simultaneous precipitation of electrons at both tens of keV and a few hundred keV, which is consistent with the energy spectrum estimated by the inversion method using the EISCAT observations. This result revealed that electrons with a wide energy range simultaneously precipitate into the ionosphere in association with the pulsating aurora, providing the evidence that pulsating auroras are caused by whistler chorus waves. We suggest that scattering by propagating whistler simultaneously causes both the precipitations of subrelativistic electrons and the pulsating aurora.

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PFISR and ROPA observations of pulsating aurora

Cited by 41 publications

References 42 publications

On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

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

Energetic electron precipitation associated with pulsating aurora: EISCAT and Van Allen Probe observations

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