Abstract
Special magnetic emissions were found below 10Hz at Lulin ELF station by analyzing observational data from October 2009 to September 2010. The events are especially for the frequency-shift events between 4 and 6 Hz. All the frequency-shift occurred within one day, and can last for several days, according to the f-t spectrograms plotted on monthly base. (Ho et al., 2013).To understand the source of the phenomena of frequency-shift and the associated emissions, this thesis investigates the frequency-shift phenomena in detail based on single-day f-t spectrograms.
The Mean’s method is adopted to define the polarized direction of the incoming signals. The polarization of any wave fields can be characterized in terms of the coherency matrix elements and then we can use the above information to estimate the trait of signal and the direction of polarization axis. At the same time, we analyze the direction of magnetic fields using FFT (Fast Fourier Transform).
Finally, the weather condition of the Observatory as well as the nearby activity from measurement team of atmospheric chemistry are compared with the occurrences of frequency-shift events. The possible sources of these signals and reasons for frequency shifts are discussed.
| Date of Award | 2014 |
|---|---|
| Original language | English |
| Supervisor | Bing-Chih Chen (Supervisor) |
Keywords
- ELF-emissions
- frequency-shift
- polarization parameters
- directional angles