Abstract
Abstract. Several possible mechanisms for the production of sporadic sodium layers have been discussed in the literature, but none of them seem to explain all the accumulated observations. The hypotheses range from direct meteoric input, to energetic electron bombardment on meteoric smoke particles, to ion neutralization, to temperature dependent chemistry. The varied instrumentation located on Andøya and near Tromsø in Norway gives us an opportunity to test the different theories applied to high latitude sporadic sodium layers. We use the ALOMAR Weber sodium lidar to monitor the appearance and characteristics of a sporadic sodium layer that was observed on 5 November 2005. We also monitor the temperature to test the hypotheses regarding a temperature dependent mechanism. The EISCAT Tromsø Dynasonde, the ALOMAR/UiO All-sky camera and the SKiYMET meteor radar on Andøya are used to test the suggested relationships of sporadic sodium layers and sporadic E-layers, electron precipitation, and meteor deposition during this event. We find that more than one candidate is eligible to explain our observation of the sporadic sodium layer.
Highlights
A sporadic sodium layer, called a sudden sodium layer, is a narrow layer in which a sudden increase of sodium (Na) is observed
We will use sodium density measurements from the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) Weber Na lidar located at Andøya in Norway (She et al, 2002) to monitor the appearance and characteristics of a sporadic Na layer
Molecules and ions on their surface. If such smoke particles are concentrated into a narrow layer by appropriate dynamical conditions, e.g. a vertical shear in the horizontal winds assuming that the particles are charged, auroral particles might be responsible for the observed sporadic Na layer. von Zahn et al (1987) suggested that this mechanism could explain the correlation between sporadic Na layers and low sporadic E-layers, because impact of energetic electrons on smoke particles would be responsible for the release of metallic ions
Summary
A sporadic sodium layer, called a sudden sodium layer, is a narrow layer in which a sudden increase of sodium (Na). We will limit our investigation and discussion of sporadic Na layers to auroral latitudes. We will use sodium density measurements from the ALOMAR Weber Na lidar located at Andøya in Norway (She et al, 2002) to monitor the appearance and characteristics of a sporadic Na layer. Most case studies trying to identify the production mechanism of sporadic Na layers seem to focus on only one of the proposed theories H. Nesse et al.: A case study of a sporadic sodium layer instrumentation at and near Andøya gives us, an opportunity to test several different theories applied to highlatitude sporadic Na layers. We should stress that a single case study will not constitute a definitive result, but a simultaneous evaluation of the different theories is important when considering whether or not there is more than one mechanism at work.
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