Ionospheric Response to Two Intense Geomagnetic Storms Over South American Using GPS Measurements

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Ionospheric response to two intense geomagnetic storms over South American using GPS measurements

R. de Jesus, I.S. Batista, A.J. de Abreu, P.R. Fagundes

1 Objective

To study the behavior of the ionospheric F layer in equatorial and low latitude regions during occurrences of:

- Geomagnetic Storms

2 INTRODUCTION Solar cycle variation

Reference: NASA

Variation in the number of sunspots Number of sunspots Number

3 YEARS Geomagnetic Storm

Reference: Tsurutani e Gonzalez (1997) 4 Earth Ionosphere

Region F is ionized by EUV radiation (26-34 nm) (KANE, 2006).

Reference: Banks (1973, p. 13) apud Pimenta 2002.

NUMERICAL DENSITY (cm-3) 5

1200 240

200 F 1000 F 160

120 E 800 80 E D SolarSolar Máximo Maximum40 1 2 3 4 5 600 10 10 10 10 10 Log [Ne] Região F SolarSolar MinimumMínimo ALTITUDE [km] ALTITUDE 400 NoiteNight NoiteNight DayDia 200 DayDia

-5,0x105 0,0 5,0x105 1,0x106 1,5x106 2,0x106 2,5x106 3 ELECTRONICDENSIDADE ELETRÔNICA DENSITY [Ne/cm [Ne/cm3] ]

The vertical profile of the ionospheric layers D, E and F on conditions of maximum (day and night) and minimum (day and night) solar activity (results obtained with the International Reference Ionosphere model, IRI- 2001). 6 EQUATORIAL IONOSPHERIC IRREGULARITIES

1600

1200

200 0 -10 10 -20 20

1600

1200

200

-10 0 10 -20 20

7 Reference: Whalen (2002) INSTRUMENTATION

Illustration of the constellation of 24 satellites of the GPS system

Reference: Dana (2000) apud de Abreu (2007). 8 Total Electron Content (TEC) – Conteúdo Total de Elétrons

The TEC is related to the electron density contained in a cylindrical column that extends from the receiving antenna (R) to the satellite (S), where the base area is unitary. The TEC can be given by (KLOBUCHAR, 1991):

(Ionospheric point)

(Ionosphere)

VTEC  cos(z´)TEC (surface of the Earth)

Rm (Sub-ionospheric point) sen z' RmHm senz 9 Rate of TEC (ROT) or phase fluctuations

The rate of change of TEC (ROT) is useful for tracing the presence of the ionospheric irregularities of the order of kilometers (Aarons et al., 1996). The ROT is defined as:

TEC ROT  t

10 RESULTS

In this work the ionosphere response was investigated during:

1) Two geomagnetic storms that occurred on 24/08/2005 and 14/12/2006

11 Location Station Dip. Lat. code Imperatriz, Brasil IMPZ 02,4ºS Bom Jesus da Lapa, Brasil BOMJ 11ºS NORTH 30 Brasília, Brasil BRAS 11,3ºS Presidente Prudente,Brasil PPTE 14,6ºS Curitiba, Brasil PARA 18,2ºS Santa Maria, Brasil SMAR 19,6ºS IMPZ Bahia Blanca, Argentina VBCA 23,1ºS BOMJ Puerto Deseado, Argentina PDES 28,2ºS

BRAZ EAST

WEST PPTE PARA SMAR

VBCA PDES

GPS STATIONS

30 SOUTH AUGUST 2005 23 24 25 26

13 Reference: de Jesus et al. (2012) AUGUST 2005

23 AGO23 2005 24 25 AGO 25 2005 26 AGO 26 2005 50 24 AGO 2005 40 IMPZ 30 20 10 0

50 40 BOMJ 30 20 10 0

VTEC 50 40 PARA 30 20 10 0

SSC 06:14 UT 50 40 SMAR 30 20 10 0 0 4 8 12 16 20 24240 4 8 12 16 20 240 4 8 12 16 20 240 4 8 12 16 20 24 UT 14 Reference: de Jesus et al. (2012) DECEMBER 2006

15 Reference: de Jesus et al. (2010) 13 DEZ13 2006 14 DEZ 14 2006 15 DEZ 15 2006 1 6 DEZ 16 2006 DECEMBER 2006

NÚMERO DO SATÉLITENÚMERO SATELLITE NUMBER SATELLITE

Reference: de Jesus et al. (2010)

16 UT 13 DEZ13 2006 14 DEZ 14 2006 15 DEZ 15 2006 1 6 DEZ 16 2006 DECEMBER 2006

Reference: de Jesus et al. (2010)

17 UT CONCLUSIONS

The effects observed during the geomagnetic storms were varied in the ionosphere. The observed effects include:

- Positive ionospheric storm (VTEC) in GPS stations associated with major changes in the circulation of winds.

- Negative ionospheric storm in the South American sector, probably due to changes in the O / N2 rate in this sector.

- Generation of equatorial ionospheric irregularities in the F region.

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