Correlating Trapped Waves in Electron Density Profiles to a Geomagnetic Storm in the F Region of the Ionosphere

Abstract:

Geomagnetic storms influence different ionospheric regions and can result in either increase or decrease in the electron density concentrations. A strong magnetic disturbance was recorded on 5-6 Aug 2011, where the DST index dropped to -200 nT. This study investigates the response of this geomagnetic disturbance on the E and F region of the ionosphere. The purpose of this research is to determine the coupling mechanism responsible for this behavior through numerical analysis of periodic components of data. The Incoherent Scatter Radar data, which was used for this analysis, was gathered in August of 2011 by the Arecibo line feed radio antenna. Extensive data analysis was performed that included removal of unwanted white noise, and data gaps. The procedure involved use of polynomial fit after rejection of spurious spikes through the implementation of Butterworth low-pass-filter with a cutoff frequency of 0.05 hr^-1. Once the data file had been cleaned, several data analysis techniques were executed to determine the presence of waves. Maximum electron density values and their respective altitudes of occurrence were extracted from the data file, as well as values 10-20 kilometers above and below this level. Further calculations of electron density gradients were used to evaluate any wave signatures that may be present in the data. A Fourier transform was applied to data across it’s temporal axis to determine the dominant periodicity present at each altitude. Gradient calculation revealed the presence of a descending wave of dominant period 2.5 hours between hours 16 and 31. This became trapped at 300km, while waves with periodicities of 4.5 hours extended down into the E region, and waves of periodicity 6.5 hours were present at every level.