Equatorial Influence of Sunspot Number (SSN) on Total Electron Content (TEC) at the Moderate Phase of the Solar Cycle

Author

Yusuf Arzika Koko, Abbas Mustapha, Yusha’u Muhammad Sulaiman, Aminu Muhammad

Abstract

 The sunspot number (SSN) is a standard indicator of solar activity and a recognised driver of ionospheric Total Electron Content (TEC). This study assesses how strongly SSN is reflected in GPS-derived TEC at eight equatorial and low-latitude stations in the Northern Hemisphere (geomagnetic latitudes 1.12°N to 26.58°N) during 2013, a year of moderate activity in Solar Cycle 24 with a mean monthly SSN of 64.7. For each station, monthly mean TEC from the five international quietest days of every month was compared with monthly SSN through linear regression and the Pearson correlation coefficient (r). Seven stations show positive correlations (r = 0.12 to 0.36), while SHEB shows a negligible negative value (r = −0.09). The largest coefficients occur at NAMA (0.36), ASAB (0.30) and BDMT (0.30). Stations within 12° of the geomagnetic equator average r ≈ 0.22, compared with r ≈ 0.14 for those beyond 20°. In a year of moderate solar activity, SSN therefore leaves a weak to moderate, latitude-dependent imprint on equatorial TEC, alongside substantial local and seasonal influences.

Keywords

Sunspot number; Total Electron Content; equatorial ionization anomaly; moderate solar activity; GPS-TEC; Solar Cycle 24

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References

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