Abstract
Abstract The rotational temperature and number density of molecular nitrogen (N2) in the lower thermosphere were measured by the N2 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.
Highlights
The dissipation of energy originating in the magnetosphere and lower atmosphere plays an important role in the energy budget controlling the temperature of the polar lower thermosphere (Fujiwara et al, 2004)
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
The neutral temperatures derived from the look directions closest to the rocket correspond to the rotational temperature measured at an altitude of 120 km
Summary
The dissipation of energy originating in the magnetosphere and lower atmosphere plays an important role in the energy budget controlling the temperature of the polar lower thermosphere (Fujiwara et al, 2004). In spite of the importance of temperature observation in the lower thermosphere, it is difficult to obtain reliable temperatures from both in situ and remote sensing measurements. The effective emission altitude of the auroral green line varies depending on the precipitating electron energy. 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. One of the objectives of the Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) campaign was to measure temperatures by a rocket-borne instrument, ground-based FPIs, and the European Incoherent Scatter (EISCAT) radar during the auroral disturbances. This paper reports the in situ observations of the rotational temperature and number density of atmospheric molecular nitrogen (N2 ) by the N2 temperature instrument (NTV) onboard the sounding rocket. KURIHARA et al.: OBSERVATIONS OF NEUTRAL TEMPERATURE AND DENSITY perature measurements
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