@InProceedings{BonelliCuevPaul:2009:GPScTw,
author = "Bonelli, E. and Cueva, R. Y. L. C. and Paula, Eurico Rodrigues
de",
affiliation = "{Universidade Federal do Rio Grande do Norte} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)}",
title = "GPS scintillation at two low magnetic latitude stations in Brazil
during the 2008-2009 prolonged solar minimum",
booktitle = "Proceedings...",
year = "2009",
organization = "Iaga, 2009.",
keywords = "ionospheric scintillation, ionospheric irregularities, gps
scintillation.",
abstract = "GPS scintillations are caused by irregularities in the ionospheric
plasma density. At low magnetic latitudes, irregularities occur
mostly just after sunset, due to an increase in the eastward
electric field, the pre-reversal enhancement electric field, a
phenomenon due to the ionospheric dynamo. This intense eastward
electric field drives the plasma up fast and usually causes the
formation of plasma density irregularities. These plasma
irregularities cause ionospheric scintillations, which are
fluctuations in radio signals received from artificial satellites
or natural sources like stars and galaxies. Scintillations are
intense during periods of maximum solar activity. Now, however,
they are very weak, especially in GPS signals, since the Sun has
stationed around a minimum of activity. It is believed that plasma
bubbles originate at the magnetic equator and then propagate
through higher latitudes by moving up and diffusing along magnetic
field lines. For this reason, only very low latitudes show
scintillations, now. We have chosen two low latitude stations,
almost aligned with the same magnetic meridian, S{\~a}o Luis (dip
-4.5°, at 300 km) and Natal (dip -28°, at 300 km) both with a -20°
declination. Scintillations were recorded at both stations at the
rate of 50 samples per second per satellite, for the period of
September/2008 through March/2009. To compare the scintillations
at both stations the S4 index is averaged first hourly, for all
satellites, and then for the whole night for all satellites. A
surprising result is that it is not clear from the data that the
irregularities are being produced at the lower latitude station
and then moving to the higher latitude station. Some results show
an increase of scintillations in Natal, which does not occur in
S{\~a}o Luis. These results are discussed in terms of production
of irregularities at Natal, at S{\~a}o Luis, and at other sites,
estwards, and then moving west to these stations.",
conference-location = "Sopron, Hungary",
conference-year = "23-30 Aug.",
language = "en",
urlaccessdate = "05 maio 2024"
}