A study of auroral fine structure in the magnetic zenith

An auroral event which occurred over Spitsbergen at 17:25-17:30 UT on 26 January 2006 has been studied in detail. The instruments used to study the event include a high resolution echelle spectrograph, a white light television camera, photometers, and the EISCAT incoherent scatter radar. It is usually assumed that the magnetic zenith is fixed in a constant point above the observer when studying auroral data. By analysing rayed coronal aurora an accurate position for the magnetic zenith was found for portions of the event studied here. It was found that this auroral zenith moved by approximately 2 degrees on timescales of a few seconds. At times it moved outside of the main beam of the EISCAT radar entirely. The structure of the aurora within the region of the magnetic zenith was studied over the different stages of the event. By considering the auroral struc ture many features of the data recorded by the various instruments have been explained. This shows how important it is to use a variety of data inputs when studying the ionosphere. Auroral modelling of the 732.0 nm 0+ line and F region electron densities showed that it is important to consider contributions to the electron density from field lines which are not entirely within the field of view of the radar. In addition to the study of the 26 January 2006 event a new method for intensity calibrating a low-light spectrograph has been demonstrated and ver ified. This new method uses the measurements made of stars during a normal data run. It provides a good calibration with many advantages over the method employed in the past for calibration of the spectrograph used here.