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Micrometeorological measurements in Nigeria during the total solar eclipse of 29 March, 2006

The photometrical flattening index of the solar corona a+b is defined according to Ludendorff. In this paper we have investigated how the flattening index varies with respect to the phase of solar activity and the sunspot number. We have compiled 170 values of the flattening index using the data on 60 total solar eclipses from 1851 to 2010. We have found that the flattening index takes values from 0 to 0.4, and is anticorrelated with solar activity. The value of the flattening index at the beginning of solar cycle 24 was used as a precursor to forecast the amplitude of the cycle. It was found that the amplitude of solar cycle 24 will be about 95 in terms of the smoothed monthly sunspot numbers.

Flattening Index of the Solar Corona and the Solar Cycle

Flattening Index of the Solar Corona and the Sun’s Magnetic Field

The global structure of solar corona observed in optical window is governed by the global magnetic field with different characteristics over solar activity cycle. Ludendorff flattening index becomes a popular measure of the global structure of solar corona as observed during eclipse. In this study, 15 digital images of solar corona from 1991 to 2016 were analyzed in order to construct the coronal flattening profiles as a function of radius. In most of the cases, the profile can be modeled with 2nd order polynomial function so that the radius with maximum flattening index ($R_{\text{max}}$) can be determined. Along with this value, Ludendorff index ($a+b$) was also calculated. Both Ludendorff index and $R_{\text{max}}$ show anti-correlation with monthly sunspot number, though the $R_{\text{max}}$ values are more scattered. The variation of $R_{\text{max}}$ can be regarded as the impact of changing coronal brightness profile over equator.

Shape Parameters of 1991 to 2016 Solar Corona

Ludendorff coronal flattening index of the Total Solar Eclipse (TSE) on March 9, 2016, was calculated at various distances in solar radius As a result, we obtained the coronal flattening index $\left(\epsilon =a+b\right)$ at a distance of 2 solar radii is 016 The $24^{th}$ solar cycle phase based on the 2016 TSE event obtained -064 which showed the corona is pre-minimum type Resulted coronal flattening index value gives a predicted maximum amplitude of the monthly sunspot number ($W_{max}$) for the $25^{th}$ solar cycle to be $70\pm65$ Therefore, the solar activity for $25^{th}$ solar cycle predicted to be lower than the current solar cycle, which has a maximum sunspot number value of 146 in February 2014

N. Stoyanov

Papers

Investigation of the white light coronal structure during the total solar eclipse on March 29, 2006