The remote sensing technique of measuring the magnetic field was applied first to sunspots by Hale (1908). Later Babcock (1961) showed that the solar surface magnetic field on a global scale is a dipole in first-order approximation and that this dipole field reverses once every solar cycle. The Wilcox Solar Observatory (WSO) supplies the spherical harmonics coefficients of the solar corona magnetic field of each Carrington Rotation, calculated based on the remotely-sensed photospheric magnetic field of the solar surface. To infer the internal current system producing the global solar coronal magnetic field structure and evolution of the Sun, we calculate the multipole components of the solar magnetic field using the WSO data from 1976 to 2019. The prominent cycle components over the last 4 solar activity cycles are axis-symmetric fields of the dipole and octupole. This implies that the current inversion driving the solar magnetic field reversal originates from the equatorial region and spreads to the whole globe. Thus, a more accurate solar dynamo model must include an explanation of the origin and evolution of such solar internal current dynamics.

Abstract
1. Introduction
2. Data and Methods
    2.1. Multipole Magnetic Field of Spherical Harmonics
    2.2. Axis-Symmetric and Non-Axis-Symmetric Terms ofMagnetic Field Components (Dipole, Quadrupole,and Octupole)
3. Results
    3.1. Annual Variation of Multipole Components SolarCorona Magnetic Field
    3.2. Axis-Symmetric Magnetic Field Reversal Mechanism
4. Discussion & Conclusion
Acknowledgments
References

• Bogyeong Kim(Institute of Natural Sciences, Chungnam National University, Yuseong-gu, Daejeon 34134, Republic of Korea)
• Yu Yi(Department of Astronomy, Space Science and Geology, Chungnam National University, Yuseong-gu, Daejeon 34134, Republic of Korea) Corresponding Author