Forecasting GPS Scintillations For Low Latitude Stations, in Brazil, using Real-Time Space Weather Data. Enivaldo Bonelli Federal University of Rio Grande do Norte (UFRN) - Brazil SA13A-07

Definitions S4 : Scintillation index on the satellite signal. : Average scintillation index, on the signal of all satellites at a given night (2100 through 0500 UT.)  K P : Sum of 3-hour estimated index of magnetic activity, K P, from 0 through 21 UT.

We plan to show that magnectic storms inhibt GPS scintillations at low magnetic latitudes. For this reason we do the following, in this paper: Select indices of magnectic activity Calculate averages of the Scintillation Index for each day for some months. Check for correlation between the two.

A qualitative example for the October 2003 storm. The next figure shows a detail of the NOAA-SEC alerts time-line. This information is provided in real-time, so we can use it, at sunset, to predict the amount of scintillation at night.

NOAA/SEC ALERTS & WARNINGS OF MAGNETIC STORMS(Detail,) STORM DAYS OCT 2003.

Paths of satellites. Size of the circles represent the scintillation intensity. Note that the first storm night (29 October) had few scintillations. Plot software by Ted Beach = = 0.31

Calm versus Active night, in terms of Scintillations. WBP of same satellite, for October 28, 2003(calm) and Oct, 29(storm)

Behavior of Scintillations for October/2003. Notice the “Halloween Storm at end of month”

Scintillations and  kP, versus day, for November, 2003

Scintillations and  kP, versus day, for January, 2005

Scintillations and  kP, versus day, for October, 2004

An alternative way to have real- time information on storm: The GOES geostationary satellites can measure, among other quantities, the component of the magnetic field paralell to the earth´s axis, Hp. See the consistency between the next figure and the alerts above.

GOES North component of the geomagnetic field as a parameter for forecasting scintillations

Still GOES Hp

CONCLUSIONS The magnetic storm forecast from several sources NOAA-SEC ALERTS, GOES HP, ESTIMATED KP FROM SEC, can be used, at local sunset to forecast scintillations for the whole night. The average S4 for the whole night seems to be a suitable parameter from which to estimate the amount of scintillations. The inverse correlation between Kp and seems to work even when we do not have storms.

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