Multi-Platform Analysis of Aurora

Research was funded by SNSA (Swedish National Space Agency) contract no. RS 2020-00154

Abstract

This thesis presents a multi-platform investigation of auroral processes, combining in situ measurements, satellite-based optical observations, and satellite-receiver signal analysis.

First, data collected by the SPIDER-2 sounding rocket and its deployed subsystems are analysed to examine the properties of pulsating aurora, providing detailed insight into its altitude, densities, pulsating frequencies and modulation. Combined measurements of Langmuir probes and a wave propagation experiment reveal the altitude profile of the electron density, revealing the peak electron densities of the order of 10¹¹ m^-3 at about 100 km altitude. An ion chemistry model allows to derive the energy profile of the precipitating electrons, which is found to peak at about 19 keV. In addition, ion probe and photometer measurements resolve individual pulsations with characteristic periods of about 2 s.

Second, limb observations from the Swedish MATS satellite are used to conduct a statistical study of a particularly poorly understood auroral emission, the O₂ atmospheric band at 762 nm. The results reveal a dependence between the geomagnetic activity and magnetic latitude, between the peak emission altitude and the magnetic local time, and between the intensity of the emissions and the emission altitude, providing new information on the characteristics of this auroral emission across both hemispheres.

Third, disturbances in Global Navigation Satellite System (GNSS) signals are shown to correlate with intensity variations in pulsating aurora, and a novel large-scale statistical analysis of this phenomenon is performed. The study, based on 14 years of data from Swedish receiver stations at auroral latitudes, demonstrates that total electron content (TEC) variations with periods of 33 s and shorter exhibit dependencies consistent with auroral activity in terms of solar cycle, seasonal, and diurnal behaviour. By identifying events associated with pulsating aurora, new relationships are established, including the dependence of pulsation period on magnetic local time, geomagnetic activity, and solar wind conditions, as well as a scaling between TEC fluctuation power and geomagnetic activity.

In summary, this work presents three complementary approaches to studying aurora: a sounding rocket case study, a statistical analysis from satellite limb observations, and an investigation based on GNSS signal disturbances. Together, they bridge small-scale in situ measurements and large-scale observations, advancing the understanding of pulsating aurora and the O₂ auroral emission.

Link to DiVA