Eduardo Perez Macho
Career Stage
Student (postgraduate)
Poster Abstract
Scintillations are caused by ionospheric irregularities and can affect trans-ionospheric radio signals. One way to understand and predict such irregularities is through ionospheric climatology using scintillation indexes during different periods of times of solar cycle in different regions, including the Equatorial Ionospheric Anomaly (EIA) and the South Atlantic Magnetic Anomaly (SAMA) regions. In this work we are using amplitude scintillation index S4 during the full solar cycle 24 at South American sector. Preliminary results show a significant intensification of ionospheric fluctuation at northern and southern crest of EIA, especially during the southern hemisphere’s spring/summer seasons, with a higher increase during solar maximum. In the SAMA region, where the intensity of field magnetic lines is lower, the fluctuation is much higher during the spring/summer months of solar maximum.
Plain text summary
The ionosphere is a region of the atmosphere, from 70 to 1000 km of altitude, with a peak at 350 km, where the neutral gas is partially ionized by the solar radiation over 12 eV, which includes extreme ultraviolet and x-ray. However, this ionization is not homogeneous, there are regions with enhanced and depleted electron density. These irregularities affect the trans-ionospheric signals of Global Navigation Satellite System (GNSS), such as Global Positioning System (GPS), causing phase or amplitude scintillation. When amplitude scintillation happens, the intensity of the GNSS signal, that is already low, can be dropped to a level in which the receiver is unable to track it, causing navigation unavailability or reducing its accuracy.
Scintillation is expected to decrease during solar minimums and increase during solar maximums especially at certain latitudes and locations, such as Equatorial Ionospheric Anomaly (EIA), around 15-20º north and south of magnetic equator, and South Atlantic Magnetic Anomaly (SAMA), with peak at 20-30º south, where the weakest geomagnetic field on Earth allows precipitations of energetic particles. Thus, knowing how the scintillation behaves in different periods of solar cycle, as well as at different locations, can be a useful tool to forecast the accuracy of navigation systems and to predict when and where the tracking obstruction is likely to occur.
In this work, we investigate the amplitude scintillation at South American (SA) sector during the full solar cycle 24, using as tool, S4 index, in order to understand its behavior over a region affected both by EIA and SAMA at magnetic latitudes lower than 40º.
The just ended solar cycle 24 started in ~2009 and reached the maximum intensity in ~2014, as observed by the sunspot progression in first figure of page 2. To choose the GNSS stations, we considered the data availability for each year, and the dip angles of the locations of the stations. The dip angles are the magnetic field lines angles made with the horizontal plane, and varies according to the magnetic equator. The stations we used and the magnetic equator are shown in the second figure of page 2.
Page 3 shows the normalized S4 index taken every minute, of 3 selected stations during solar minimum (2019, right side) and maximum (2014, left side). It is possible to see that in 2019, S4 index barely surpass 0.2 (value that may cause navigation inaccuracy), with an average of 0.1. The station BOA has slightly higher S4 values than RBR because it is located in the norther crest of EIA, and DOU has even higher values because it is both affected by EIA southern crest and SAMA. In 2019, there is a significant scintillation increase, especially during spring in SA (September 22nd to December 21st) and summer (December 21st to March 20th), with some S4 values surpassing 0.7 or 0.8 (values that may cause navigation unavailability) at northern and southern crests of EIA.
Page 4 shows a general overview of the full solar cycle 24 indicating the percentage of occurrence of S4 over 0.2 (magnetic latitudes x Julian Days). In 2009, there are very few occurrences that can be noticed in few latitudes, but, from 2010 to 2014, these occurrences increase with more intensity in the EIA crests (at 15-20º north and south) and SAMA (with peak at 20-30º south). It is clear that the scintillation increases when the solar activity increases, with a stronger occurrence during spring and summer, when there is a greater occurrence of plasma bubbles. After 2015, when the solar activity starts to decrease, the scintillation decreases as well until 2019, end of cycle.
Scintillation is expected to decrease during solar minimums and increase during solar maximums especially at certain latitudes and locations, such as Equatorial Ionospheric Anomaly (EIA), around 15-20º north and south of magnetic equator, and South Atlantic Magnetic Anomaly (SAMA), with peak at 20-30º south, where the weakest geomagnetic field on Earth allows precipitations of energetic particles. Thus, knowing how the scintillation behaves in different periods of solar cycle, as well as at different locations, can be a useful tool to forecast the accuracy of navigation systems and to predict when and where the tracking obstruction is likely to occur.
In this work, we investigate the amplitude scintillation at South American (SA) sector during the full solar cycle 24, using as tool, S4 index, in order to understand its behavior over a region affected both by EIA and SAMA at magnetic latitudes lower than 40º.
The just ended solar cycle 24 started in ~2009 and reached the maximum intensity in ~2014, as observed by the sunspot progression in first figure of page 2. To choose the GNSS stations, we considered the data availability for each year, and the dip angles of the locations of the stations. The dip angles are the magnetic field lines angles made with the horizontal plane, and varies according to the magnetic equator. The stations we used and the magnetic equator are shown in the second figure of page 2.
Page 3 shows the normalized S4 index taken every minute, of 3 selected stations during solar minimum (2019, right side) and maximum (2014, left side). It is possible to see that in 2019, S4 index barely surpass 0.2 (value that may cause navigation inaccuracy), with an average of 0.1. The station BOA has slightly higher S4 values than RBR because it is located in the norther crest of EIA, and DOU has even higher values because it is both affected by EIA southern crest and SAMA. In 2019, there is a significant scintillation increase, especially during spring in SA (September 22nd to December 21st) and summer (December 21st to March 20th), with some S4 values surpassing 0.7 or 0.8 (values that may cause navigation unavailability) at northern and southern crests of EIA.
Page 4 shows a general overview of the full solar cycle 24 indicating the percentage of occurrence of S4 over 0.2 (magnetic latitudes x Julian Days). In 2009, there are very few occurrences that can be noticed in few latitudes, but, from 2010 to 2014, these occurrences increase with more intensity in the EIA crests (at 15-20º north and south) and SAMA (with peak at 20-30º south). It is clear that the scintillation increases when the solar activity increases, with a stronger occurrence during spring and summer, when there is a greater occurrence of plasma bubbles. After 2015, when the solar activity starts to decrease, the scintillation decreases as well until 2019, end of cycle.
Poster file
Poster Title
Ionospheric climatology at South American sector using amplitude scintillation S4 index
Url
edu_point@hotmail.com