Variations of nitric oxide in the mesosphere and lower thermosphere over Antarctica associated with a magnetic storm in April 2012

Isono, Yasuko; Mizuno, Akira; Nagahama, Tomoo; Miyoshi, Yoshizumi; Nakamura, Takuji; Kataoka, Ryuho; Tsutsumi, Masaki; Ejiri, Mitsumu K.; Fujiwara, Hitoshi; Maezawa, Hiroyuki

doi:10.1002/2014gl059360

Cited by 15 publications

(17 citation statements)

References 25 publications

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“…The full‐width half‐maximum of the Gaussian fit is 503(11) kHz. This indicates that thermal, Doppler‐broadened NO emission from altitudes above ~65 km dominates the observed signal, as was found in measurements from Syowa station, Antarctica, during 2012–2013 (Isono et al, , ).…”

Section: Resultssupporting

confidence: 76%

Observations and Modeling of Increased Nitric Oxide in the Antarctic Polar Middle Atmosphere Associated With Geomagnetic Storm‐Driven Energetic Electron Precipitation

et al. 2018

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Nitric oxide (NO) produced in the polar middle and upper atmosphere by energetic particle precipitation depletes ozone in the mesosphere and, following vertical transport in the winter polar vortex, in the stratosphere. Medium‐energy electron (MEE) ionization by 30–1,000 keV electrons during geomagnetic storms may have a significant role in mesospheric NO production. However, questions remain about the relative importance of direct NO production by MEE at altitudes ~60–90 km versus indirect NO originating from auroral ionization above 90 km. We investigate potential drivers of NO variability in the southern‐hemisphere mesosphere and lower thermosphere during 2013–2014. Contrasting geomagnetic activity occurred during the two austral winters, with more numerous moderate storms in the 2013 winter. Ground‐based millimeter‐wave observations of NO from Halley, Antarctica, are compared with measurements by the Solar Occultation For Ice Experiment (SOFIE) spaceborne spectrometer. NO partial columns over the altitude range 65–140 km from the two observational data sets show large day‐to‐day variability and significant disagreement, with Halley values on average 49% higher than the corresponding SOFIE data. SOFIE NO number densities, zonally averaged over geomagnetic latitudes −59° to −65°, are up to 3 × 108/cm3 higher in the winter of 2013 compared to 2014. Comparisons with a new version of the Whole Atmosphere Community Climate Model, which includes detailed D‐region ion chemistry (WACCM‐SIC) and MEE ionization rates, show that the model underestimates NO in the winter lower mesosphere whereas thermospheric abundances are too high. This indicates the need to further improve and verify WACCM‐SIC with respect to MEE ionization, thermospheric NO chemistry, and vertical transport.

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Section: Resultssupporting

confidence: 76%

Observations and Modeling of Increased Nitric Oxide in the Antarctic Polar Middle Atmosphere Associated With Geomagnetic Storm‐Driven Energetic Electron Precipitation

et al. 2018

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“…It is worth noting that such energetic electron precipitation down to mesospheric altitudes is important with regard to the cause of significant ionization as well as the enhancement of NO x [e.g., Isono et al, 2014;Andersson et al, 2014]. We expect that subrelativistic electron precipitation, being concomitant with pulsating auroras, would have significant impact on the variation of the upper atmosphere composition.…”

Section: 1002/2014ja020690mentioning

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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“…Furthermore, Swider and Narcisi [1970] suggested that the R value is increased by an enhanced NO or N concentration in the E region. Isono et al [2014] showed that the high energetic particle precipitation may cause an enhancement of NO x gases. Brown [1968] suggested that N is enhanced in auroras.…”

Section: Numbermentioning

confidence: 99%

Depletion of mesospheric sodium during extended period of pulsating aurora

et al. 2017

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We quantitatively evaluated the Na density depletion due to charge transfer reactions between Na atoms and molecular ions produced by high‐energy electron precipitation during a pulsating aurora (PsA). An extended period of PsA was captured by an all‐sky camera at the European Incoherent Scatter (EISCAT) radar Tromsø site (69.6°N, 19.2°E) during a 2 h interval from 00:00 to 02:00 UT on 25 January 2012. During this period, using the EISCAT very high frequency (VHF) radar, we detected three intervals of intense ionization below 100 km that were probably caused by precipitation of high‐energy electrons during the PsA. In these intervals, the sodium lidar at Tromsø observed characteristic depletion of Na density at altitudes between 97 and 100 km. These Na density depletions lasted for 8 min and represented 5–8% of the background Na layer. To examine the cause of this depletion, we modeled the depletion rate based on charge transfer reactions with NO+ and normalO2+ while changing the R value which is defined as the ratio of NO+ to normalO2+ densities, from 1 to 10. The correlation coefficients between observed and modeled Na density depletion calculated with typical value R = 3 for time intervals T1, T2, and T3 were 0.66, 0.80, and 0.67, respectively. The observed Na density depletion rates fall within the range of modeled depletion rate calculated with R from 1 to 10. This suggests that the charge transfer reactions triggered by the auroral impact ionization at low altitudes are the predominant process responsible for Na density depletion during PsA intervals.

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Variations of nitric oxide in the mesosphere and lower thermosphere over Antarctica associated with a magnetic storm in April 2012

Cited by 15 publications

References 25 publications

Observations and Modeling of Increased Nitric Oxide in the Antarctic Polar Middle Atmosphere Associated With Geomagnetic Storm‐Driven Energetic Electron Precipitation

Observations and Modeling of Increased Nitric Oxide in the Antarctic Polar Middle Atmosphere Associated With Geomagnetic Storm‐Driven Energetic Electron Precipitation

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

Depletion of mesospheric sodium during extended period of pulsating aurora

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