Minimum Variance Analysis of Interplanetary Coronal Mass Ejections Around Solar Cycle 23 Maximum (1998–2002) |
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Authors: | E Echer W D Gonzalez M V ALVES |
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Institution: | 1. Instituto Nacional de Pesquisas Espaciais (INPE), POB 515, ZIP: 12201-970, S?o José dos Campos, SP, Brazil
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Abstract: | The minimum variance analysis of interplanetary coronal mass ejections (ICMEs) observed close to the Earth's orbit around
solar cycle 23 maximum (1998–2002) was performed. The ICMEs were classified in three categories: magnetic clouds (MC), undefined
ejecta (UE), and complex ejecta (CE). An analysis of the full ICMEs set shows that the average of minimum variance direction
inclination angle is 1.6°± 24.8° in relation to the ecliptic plane, with more than 33% of the events presenting inclination
angles lower than 10°. The average of minimum variance direction azimuthal angle (in relation to the Sun–Earth line) was 56°.
However, around 60% of the ICMEs presented an azimuthal angle lower than 30°, close to the radial direction. It was also observed
that the MC set had lower axial (intermediate variance) inclinations relative to the ecliptic plane than the UE and CE events.
The intermediate variance axis is close to 90° to the Sun–Earth line. The results obtained in the present analysis were also
compared with previous works, permitting a comparison of the ICMEs orientations in solar cycle 23 with previous sor cycles. |
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