1

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

2

Objective

To study the behavior of the ionospheric F

layer in equatorial and low latitude

regions during occurrences of:

- Geomagnetic Storms

2

3

INTRODUCTIONSolar cycle variation

Reference: NASA

3

Variation in the number of sunspots

Nu

mb

er

of

su

nsp

ots

YEARS

4Reference: Tsurutani e Gonzalez (1997)

Geomagnetic Storm

4

5

Reference: Banks (1973, p. 13)

apud Pimenta 2002.

Earth Ionosphere

5

Region F is ionized by

EUV radiation (26-34

nm) (KANE, 2006).

NUMERICAL DENSITY (cm-3)

6

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

Região F

-5,0x105 0,0 5,0x10

51,0x10

61,5x10

62,0x10

62,5x10

6

200

400

600

800

1000

1200

Solar Mínimo

Noite

Dia

Noite

Dia

Solar Máximo

AL

TIT

UD

E [

km

]

DENSIDADE ELETRÔNICA [Ne/cm3]

101

102

103

104

105

40

80

120

160

200

240

F

E

F

E

D

Log [Ne]

Day

Solar Maximum

Solar MinimumNight

Day

Night

ELECTRONIC DENSITY [Ne/cm3]

7

EQUATORIAL IONOSPHERIC IRREGULARITIES

Reference: Whalen (2002)

-20

-100

20

10

200

1200

1600

1600

1200

-20

-10 010

20

200

7

8

Illustration of the constellation of 24 satellites of the GPS system

Reference: Dana (2000) apud de Abreu (2007).8

INSTRUMENTATION

9

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):

TECzVTEC )́cos(

9

zsenzsenHmRm

Rm

'

(Ionosphere)

(Ionospheric point)

(surface of the Earth)

(Sub-ionospheric point)

10

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:

t

TECROT

10

1111

RESULTS

In this work the ionosphere response was investigated

during:

1) Two geomagnetic storms that occurred on 24/08/2005

and 14/12/2006

30

30

NORTH

SOUTH

GPS STATIONS

IMPZ

BRAZ

PARA

PPTE

BOMJ

SMAR

PDES

VBCA

Location Stationcode

Dip. Lat.

Imperatriz, Brasil IMPZ 02,4ºS

Bom Jesus da Lapa, Brasil BOMJ 11ºS

Brasília, Brasil BRAS 11,3ºS

Presidente Prudente,Brasil PPTE 14,6ºS

Curitiba, Brasil PARA 18,2ºS

Santa Maria, Brasil SMAR 19,6ºS

Bahia Blanca, Argentina VBCA 23,1ºS

Puerto Deseado, Argentina PDES 28,2ºS

EA

ST

WE

ST

1313

23 24 25 26

AUGUST 2005

Reference: de Jesus et al. (2012)

1414Reference: de Jesus et al. (2012)

0

10

20

30

40

50

26 AGO 200525 AGO 200524 AGO 200523 AGO 2005

SSC 06:14 UT

0

10

20

30

40

50

SMAR

PARA

BOMJ

VT

EC

0

10

20

30

40

50

0 4 8 12 16 20 240

10

20

30

40

50

240 4 8 12 16 20 24

0 4 8 12 16 20 24

0 4 8 12 16 20 240 0

IMPZ

UT

23 24 25 26

AUGUST 2005

1515

DECEMBER 2006

Reference: de Jesus et al. (2010)

1616

DECEMBER

2006

13 DEZ 2006 14 DEZ 2006 15 DEZ 2006 16 DEZ 2006

UT

NÚ

ME

RO

DO

SA

TÉ

LIT

E

13 DEZ 2006 14 DEZ 2006 15 DEZ 2006 16 DEZ 2006

UT

NÚ

ME

RO

DO

SA

TÉ

LIT

E

13 14 15 16

SA

TE

LL

ITE

NU

MB

ER

Reference:

de Jesus et al. (2010)

1717

13 DEZ 2006 14 DEZ 2006 15 DEZ 2006 16 DEZ 2006

UT

13 DEZ 2006 14 DEZ 2006 15 DEZ 2006 16 DEZ 2006

UT

13 14 15 16DECEMBER

2006

Reference:

de Jesus et al. (2010)

18

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.

18

1919

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