Morphology of evening sector aurorae in λ557.7‐nm Doppler temperatures

Holmes, J. M.; Conde, M.; Deehr, C. S.; Lummerzheim, D.

doi:10.1029/2004gl021553

Cited by 15 publications

(13 citation statements)

References 23 publications

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“…The characteristic energy, E 0 , of precipitating particles can be estimated from the SDI green line temperature measurements, using the method described by Holmes et al () and Hecht et al (). Because temperature varies significantly with altitude in the E region, green line temperature measurements can act as a proxy for altitude when compared to a temperature profile generated by the NRLMSISE‐00 model (Picone et al, ).…”

Section: Observationsmentioning

confidence: 99%

Measurements of Ion‐Neutral Coupling in the Auroral F Region in Response to Increases in Particle Precipitation

et al. 2018

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Neutral winds are a key factor in the dynamics of the ionosphere‐thermosphere system. Previous observations have shown that neutral and ion flows are strongly coupled during periods of auroral activity when ion drag forcing can become the dominant force driving neutral wind flow. This is primarily due to increases in ion density due to enhanced particle precipitation as well as associated increases the strength of the electric fields that drive ion motions. Due to this strong coupling, numerical simulations of neutral dynamics have difficulty reproducing neutral wind observations when they are driven by modeled precipitation and modeled convection. It is therefore desirable whenever possible to have concurrent coincident measurements of auroral precipitation and ion convection. Recent advancements in high‐resolution fitting of Super Dual Auroral Radar Network ion convection data have enabled the generation of steady maps of ion drifts over Alaska, coinciding with several optics sites. The Super Dual Auroral Radar Network measurements are compared with scanning Doppler imager neutral wind measurements at similar altitude, providing direct comparisons of ion and neutral velocities over a wide field and for long periods throughout the night. Also present are a digital all‐sky imager and a meridian spectrograph, both of which provide measurements of auroral intensity on several wavelengths. In this study, we combine these data sets to present three case studies that show significant correlation between increases in F region precipitation and enhancements in ion‐neutral coupling in the evening sector. We investigate the time scales over which the coupling takes place and compare our findings to previous measurements.

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Section: Observationsmentioning

confidence: 99%

Measurements of Ion‐Neutral Coupling in the Auroral F Region in Response to Increases in Particle Precipitation

et al. 2018

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“…[29] It should also be noted that the large downward winds in excess of À20 m s À1 were observed during 22:50 -23:30 UT. Although large downward winds in the lower and upper thermosphere have often been observed at the equatorward side of an auroral arc [Crickmore et al, 1991;Innis et al, 1997;Ishii et al, 2001], there is no plausible explanation for the large downward winds [Ishii et al, 2001]. There may be a simple explanation that upward winds must be compensated by downward winds to keep the atmosphere from disappearing.…”

Section: Vertical Windsmentioning

confidence: 99%

Temperature enhancements and vertical winds in the lower thermosphere associated with auroral heating during the DELTA campaign

et al. 2009

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[1] A coordinated observation of the atmospheric response to auroral energy input in the polar lower thermosphere was conducted during the Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) campaign. N 2 rotational temperature was measured with a rocket-borne instrument launched from the Andøya Rocket Range, neutral winds were measured from auroral emissions at 557.7 nm with a Fabry-Perot Interferometer (FPI) at Skibotn and the KEOPS, and ionospheric parameters were measured with the European Incoherent Scatter (EISCAT) UHF radar at Tromsø. Altitude profiles of the passive energy deposition rate and the particle heating rate were estimated using data taken with the EISCAT radar. The local temperature enhancement derived from the difference between the observed N 2 rotational temperature and the MSISE-90 model neutral temperature were 70-140 K at 110-140 km altitude. The temperature increase rate derived from the estimated heating rates, however, cannot account for the temperature enhancement below 120 km, even considering the contribution of the neutral density to the estimated heating rate. The observed upward winds up to 40 m s À1 seem to respond nearly instantaneously to changes in the heating rates. Although the wind speeds cannot be explained by the estimated heating rate and the thermal expansion hypothesis, the present study suggests that the generation mechanism of the large vertical winds must be responsible for the fast response of the vertical wind to the heating event.

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“…Since vertical temperature gradients in the lower thermosphere are generally steep, there are difficulties in quantitative analysis of the neutral temperature derived from the auroral green line measurement by the FPI. However, the green line temperature measurement is potentially useful in estimating an auroral energy deposition (Holmes et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Observations of the lower thermospheric neutral temperature and density in the DELTA campaign

et al. 2006

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The rotational temperature and number density of molecular nitrogen (N 2 ) in the lower thermosphere were measured by the N 2 temperature instrument onboard the S-310-35 sounding rocket, which was launched from Andøya at 0:33 UT on 13 December 2004, during the Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) campaign. The rotational temperature measured at altitudes between 95 and 140 km, which is expected to be equal to neutral temperature, is much higher than neutral temperature from the Mass Spectrometer Incoherent Scatter (MSIS) model. Neutral temperatures in the lower thermosphere were observed using the auroral green line at 557.7 nm by two Fabry-Perot Interferometers (FPIs) at Skibotn and the Kiruna Esrange Optical Platform System site. The neutral temperatures derived from the look directions closest to the rocket correspond to the rotational temperature measured at an altitude of 120 km. In addition, a combination of the all-sky camera images at 557.7 nm observed at two stations, Kilpisjärvi and Muonio, suggests that the effective altitude of the auroral arcs at the time of the launch is about 120 km. The FPI temperature observations are consistent with the in situ rocket observations rather than the MSIS model.

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Morphology of evening sector aurorae in λ557.7‐nm Doppler temperatures

Cited by 15 publications

References 23 publications

Measurements of Ion‐Neutral Coupling in the Auroral F Region in Response to Increases in Particle Precipitation

Measurements of Ion‐Neutral Coupling in the Auroral F Region in Response to Increases in Particle Precipitation

Temperature enhancements and vertical winds in the lower thermosphere associated with auroral heating during the DELTA campaign

Observations of the lower thermospheric neutral temperature and density in the DELTA campaign

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