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

Abstract

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.

Combined ground-based optical support for the aurora (DELTA) sounding rocket campaign

“…When we consider these changes in temperature in the context of the EISCAT ion temperature measurements we see that the likely altitude of the green line emission prior to the rocket launch is likely to be closer to 115 km than either 120 km or 110 km. The DELTA rocket in-situ measurements (see Kurihara et al, 2006), however, would suggest that the green line emission neutral temperatures are closer to an altitude of around 120 km. The error bars attributable to the individual measurements, combined to the lack of a direct overlap in the individually sampled volumes make it difficult to draw any more detailed estimate than the 115 km to 120 km range as being the most probable emission altitude in the 0000 UT to 0100 UT period.…”

“…IMAGE magnetometers are located close to each of these locations. Figure 1 in Kurihara et al (2006), this issue, shows the progress of the auroral activity during the rocket flight in great detail.…”

“…Cloud free conditions were apparent at the Andoya, Skibotn and Keops optical sites with the auroral arc visible at each site, as presented earlier. Kurihara et al (2006) report neutral temperatures at 120 km close to 500 K from the NTV instrument on board the DELTA rocket. It is not intended to repeat the results presented in this paper but it is important to point out that this provides very good agreement with the FPI and EISCAT measurements presented here.…”

Daytime twin-peak structures observed at southern African and European middle latitudes on 8–13 April 2012

“…Also the uncertainties of neutral parameters derived from neutral atmospheric model, such as neutral densities and temperatures derived from MSIS, have an impact on the discrepancy of the derived vertical component of the equivalent winds. Studies show that even during quiet geomagnetic conditions, these models still fail to reproduce realistic neutral densities (Grossmann et al, 2000;Kurihara et al, 2006). However due to the lack of direct measurements of neutral winds in the regions under study these methods are the best that can be used in an effort to understand the dynamics of the twin-peak structures in relation to neutral winds.…”

Sheath capacitance observed by impedance probes onboard sounding rockets: Its application to ionospheric plasma diagnostics

“…The second arc around 124-131 km altitude was within the range of sheath analysis. We should also mention that observations by the N 2 temperature instrument (NTV), which emitted the arti cial electron beam (Kurihara et al, 2006), onboard the rocket affected the electron densities and the probe potentials below about 115 km altitude in the ascent (see Wakabayashi and Ono, 2006).…”