Space Geophysics Division

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Space Geophysics Division

MAGHEL – Magnetosphere & Heliosphere

Electrodynamical Phenomena Modeling

(http://www.inpe.br)

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Scientific Staff

Dra. Alícia L. Clúa de Gonzalez – [email protected]

Ms. Andrea Borgazzi – [email protected]

Dra. Aracy Mendes da Costa – [email protected]

Dra. Margarete Oliveira Domingues – [email protected]

Dr. Nalin Babulal Trivedi – [email protected]

Dr. Odim Mendes Jr. – [email protected]

Eng. Varlei Everton Menconi

Dr. Walter D. González Alarcon – [email protected] (leader)

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Main purposes

To characterize different processes that occur in the solar wind-magnetosphere-ionosphere coupling during magnetic storms.

To characterize magnetic storms taking into account the amount of energy transferred as transients, during the main phase of the storm.

To infer some properties of the magnetospheric dynamics involved in the energy transfer from higher to lower latitudes.

To search for peculiarities of the Earth’s magnetic field in the South Atlantic Geomagnetic Anomaly (SAMA) region.

Magnetogram analysis using wavelet singularities

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Experimental data

Moderate, intense or superintense magnetic storms

Horizontal component of the geomagnetic field (H)

Time resolution: with 1 min

Ground based magnetometers

Low latitude magnetic stations

Reference magnetic station: Kakioka (Japan) (KAK)Geomagnetic coordinates : 26.94; 208.29

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Wavelet technique (properties)

Wavelet transforms are a good tool to identify short-lived high-frequency phenomena, such as singularities in signal and transient structures.

Wavelets have time–frequency localization, being the time and frequency resolution, inversely proportional.

The magnitude of the wavelet coefficients are directly proportional to the local “smoothness” of the function they represent.

Wavelet coefficients are known as ‘‘details’’ because they represent the difference between the signal in two consecutive scale levels.

Daubechies wavelet family 4 is adequate to detect shock-like singularities, because it uses few coefficients and it is a good representation of low-order polynomials.

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Methodology steps

(1) To calculate the discrete wavelet transform of the magnetograms (wavelet signature).

(2) To analyze the wavelet coefficients of the decomposition levels dj

(j=1,2,3).

(3) To choose the wavelet coefficient thresholds that allow the singularity to be detected in the

magnetic disturbance.

(4) To count the wavelet coefficients above the defined threshold.

(5) To integrate the magnitude of the wavelet coefficients (a representation of the total energy accumulated by the signal in the storm period).

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Kakioka

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R1 = 0.75

R2 = 0.86

R3 = 0.84

The number of the wavelet coefficients and the sum of their magnitude are well correlated to Dst index.

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CNB

KDU

TIK

KAK

GUA

DRV

1st Application: North-South array of magnetometers along magnetic meridian 210o

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Magnetic stations location and Coordinates

Code Magnetic Satation

Geographic Coordinates

Geomagnetic Coordinates (1995)*

Lat. Long. Lat. Long

TIK Tixie Bay (Russia)

71.58 129.00 61.31 193.27

KAK Kakioka (Japan)

36.23 140.18 26.94 208.29

GUA Guam (USA) 13.58 144.87 4.89 215.26

KDU Kakadu (Australia)

-12.69 132.47 -22.43 205.29

CNB Canberra (Australia)

-35.30 149.00 -43.10 226.43

DRV Dumont d’ Urville (Antart)

-66.66 140.01 -74.70 231.94

Data Catalogue, 25, Oct. 1999, WDC for Geomagnetism, Kyoto (Japan), http://swdcwww.kugi.kyoto-u.ac.jp/

1219 20 21 22 23 24 25 26 27 28 29 30

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SAMA

SAMA region

Because of its peculiarities, the SAMA is seen as a natural sink for the energetic particles trapped in the van Allen radiation belt.

Total geomagnetic field contours as derived from NASA's Topography from Space Experiment satellite (TOPEX).

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2. Application: SAMAAugust 18, 2003 (Dst = –168 nT)

Vassouras Geog. Coor.(-22.40°S; 46.35°W)

São Martinho da Serra(-29.44°S; 53.82°W)

Kakioka (Japan)(-36.23° N; 140.18°E)

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The magnitude of the wavelet coefficients can be used to identify quiet and quiescent conditions.

The singularity patterns occur mostly in the main phase of the geomagnetic storms.

The wavelet signatures are characterized by the amplitude and the number of the wavelet coefficients above the thresholds considered.

Small magnitudes of wavelet coefficients mean that the energy transfer process is smooth, while the large amplitudes indicate that there are impulsive energy injections superposed to the smooth background process.

The wavelet technique has revealed to be a helpful tool in the study of magnetospheric phenomena such as the time localization of geomagnetic storms.

Summary of the resultsSummary of the results

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Cont.The sequence of transient field variations detected at auroral latitudes, have their counter part at lower latitudes, where the effects of the ring current dominate.

These results also show that these two regions are electrodynamically connected and the energy transport could be “followed” by ueing an array of at least six magnetometers.

The inclusion of more magnetometers in a similar array, would lead to a more detailed analysis concerning the processes involved in the energy transport from auroral to equatorial latitudes.

Common characteristics have been found in both stations located in the SAMA, and the relative position the stations in relation to the SAMA center does not make relevant difference.

The highest coefficients were found in the SAMA stations with about twice the values obtained at KAK, for both events.

A permanent magnetometer operating close to the center of the SAMA is fundamental to investigate the characteristics of the SAMA during quiet and disturbed periods.

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Odim Mendes Jr., Margarete Oliveira Domingues, Aracy Mendes da Costa, Alícia L. Clúa de Gonzalez. Wavelet analysis applied to magnetograms: Singularity detections related to geomagnetic storms, J. of Atmos. Solar Terr. Phys. 67(17-18), 1827-1836, 2005.

Odim Mendes Jr., Aracy Mendes da Costa, Margarete Oliveira Domingues. Introduction to planetary electrodynamics: A view of electric fields, currents and related magnetic fields, Adv. Space Res. 35(5), 812-828 , 2005.

Margarete Oliveira Domingues, Odim Mendes Jr., Aracy Mendes da Costa. On wavelet techniques in atmospheric sciences, Adv. Space Res. 35(5), 831-842 , 2005.

Recently published papers