Dynamical processes in the mesopause region from OH-airglow and meteor echoes above Longyearbyen

• Main Author: Isaksen, Magnus Johan
• Format: Master Thesis
• Language: English
• Published: 2018
• Subjects: Arctic; Svalbard; Longyearbyen
• Online Access: http://hdl.handle.net/10852/63457; http://urn.nb.no/URN:NBN:no-66013

During the winter season in the high arctic above Svalbard the sun is below the horizon not contributing to heating of the mesosphere and lower thermosphere (MLT) region (50-100 km). In this region there are no direct mesurments of temperature, neutral air density and wind speeds, the only way of getting these parameters are to infer them indirectly by measuring thing such as airglow and metor ablations. The OH-airglow temperature is assumed to have a central emission layer at 87 km while the peak meteor ablation region is at about 90km, both of them are in what is called the mesopause region and relativly close together. Because they are so close toghether they are assumed to be influenced by the same type of dynamics, such as planetary waves and up/downwelling over the pole. The meteor height is used together with a model NRLMSISE-00 in order to find the temperature. The OH-airglow and meteor height are compared to see if they move hand in hand.\\ The temperatures were seemingly following the same development, but the correlation were below 0,15 for 4 of 6 seasons studied. The end of season of 2008-09 and 2011-12 were found to have a correlation of 0.66 and 0.40 respectively. Both seasons show a stable and denser air-mass after a sudden stratospheric warming, as seen by the meteor height being around 87 km for 2008-09 and around 89 km for 2011-12 for an extended period of time after the event and thing return to normal. Typically there was a cooling observed from November until January, cooling by around 20 K for the OH-airglow temperature and around 10 K for the meteor heights. There were larger variations observed in the OH-airglow temperature by 20-30 K compared to the variations in meteor height temperature 10 K. The OH-airglow variations were also changing quicker, and the meteor height and model used a couple of days to catch up to the rapid changes observed in OH-airglow. The model also did not respond as much to the events of SSW as the OH-airglow. The rapid changes in temperature compared to the meteor heights is most likely the reason for the low correlation. The moving meteor height is also thought to compensate for changes in temperature, density and other factors, while the OH-airglow is assumed stationary and therefore lacking the compensation mechanism generating the large difference seen in temperature.