10:45 AM - 12:15 PM
[PEM12-P13] Calculation and Analysis for S4-index in Southern Taiwan
Keywords:S4-index, ionospheric irregularities, FORMOSAT-7
Global Navigation Satellite System ( GNSS ) satellites are crucial for map plotting, location service and navigation. When it comes to signal deviations and interference, “irregularities” from the ionosphere are usually the ones to blame. They not only cause errors for satellites during distance measuring, which thus affects its ability of positioning, but also result in both signal scintillation and amplitude instability.
In this experiment, we analyze data from a Global Positioning System ( GPS ) receiver at Eluanbi Elementary School in Pingtung, Taiwan. We chose the GPS L1 C/A band to calculate its S4-index, in order to observe the scintillations. The S4-index is defined as the ratio of a “signal’s amplitude deviation to its average amplitude”, where the signal amplitude denotes the “signal to noise ratio” on that band. A scintillation indicates an occurrence of signal amplitude fluctuation while the signal is being received. This is due to the existence of irregularities in the ionosphere such as Sporadic E and Spread F, that tend to cause the diffraction of a signal. Normally, if the S4-index were to be greater than 0.3, it implies that there might be irregularities around the ionosphere piercing point, so we focus on the variation and occurrence of such strong scintillation events.
In addition to the work above, we also compare the ground data to the electron density data yielded from FORMOSAT-7 / COSMIC-2 during similar time periods to get a better insight of this phenomenon and to see how these two factors are related.
In this experiment, we analyze data from a Global Positioning System ( GPS ) receiver at Eluanbi Elementary School in Pingtung, Taiwan. We chose the GPS L1 C/A band to calculate its S4-index, in order to observe the scintillations. The S4-index is defined as the ratio of a “signal’s amplitude deviation to its average amplitude”, where the signal amplitude denotes the “signal to noise ratio” on that band. A scintillation indicates an occurrence of signal amplitude fluctuation while the signal is being received. This is due to the existence of irregularities in the ionosphere such as Sporadic E and Spread F, that tend to cause the diffraction of a signal. Normally, if the S4-index were to be greater than 0.3, it implies that there might be irregularities around the ionosphere piercing point, so we focus on the variation and occurrence of such strong scintillation events.
In addition to the work above, we also compare the ground data to the electron density data yielded from FORMOSAT-7 / COSMIC-2 during similar time periods to get a better insight of this phenomenon and to see how these two factors are related.