[Paper Review] Parity of the Solar Magnetic Fields and Related Astrophysical Phenomena

G. Gopkumar, T. E. Girish|arXiv (Cornell University)|Dec 16, 2010

Solar and Space Plasma Dynamics3 citations

TL;DR

This study analyzes the parity (odd or even) of solar magnetic fields using spherical harmonic coefficients of photospheric magnetic fields from 1959 to 1985. It reveals that the dominant parity alternates between odd and even over each sunspot cycle, with a shift from even to odd dominance during the past 12 cycles, correlating with solar activity trends and phenomena like polar field reversals and interplanetary magnetic field strength.

ABSTRACT

The cumulative contribution of odd (Bo) and even (BE) parity zonal magnetic multipoles to the solar magnetic fields is calculated using spherical harmonic coefficients of the photospheric magnetic field for the years 1959-1985. The dominant parity of the solar magnetic field is shown to change from odd to even during every sunspot cycle. The association of variations of Bo and BE with different astrophysical phenomena such as magnetic reversal of solar polar magnetic fields, north-south asymmetry in sunspot activity and strength of the interplanetary magnetic field will be also discussed. Using solar observations we could infer that dominant parity of the solar magnetic field is changing from even to odd during the past 12 solar cycles when the solar activity is showing an increasing trend during this period.

Motivation & Objective

• To determine the dominant parity (odd or even) of the solar magnetic field over time using photospheric magnetic field data.
• To investigate how parity variations correlate with astrophysical phenomena such as polar magnetic field reversals and interplanetary magnetic field strength.
• To examine the relationship between parity changes and the north-south asymmetry in sunspot activity.
• To assess the long-term trend in parity dominance over the past 12 solar cycles.

Proposed method

• Spherical harmonic decomposition is applied to photospheric magnetic field data from 1959 to 1985 to extract odd (Bo) and even (BE) parity zonal multipoles.
• The cumulative contributions of Bo and BE are calculated to determine the dominant parity at each time point.
• Time-series analysis of parity dominance is performed across solar cycles to identify periodic transitions.
• Correlations between parity transitions and observed solar phenomena—such as polar field reversals and interplanetary magnetic field variations—are evaluated.

Experimental results

Research questions

• RQ1 How does the dominant parity of the solar magnetic field evolve over individual sunspot cycles?
• RQ2 What is the relationship between parity transitions and the reversal of the solar polar magnetic fields?
• RQ3 How do variations in odd and even parity multipoles relate to the north-south asymmetry in sunspot activity?
• RQ4 Is there a long-term trend in parity dominance over the past 12 solar cycles, and how does it correlate with increasing solar activity?

Key findings

• The dominant parity of the solar magnetic field alternates between odd and even every sunspot cycle, with a transition from odd to even dominance observed per cycle.
• A shift from even to odd dominance is identified over the past 12 solar cycles, coinciding with an increasing trend in solar activity.
• The cumulative contributions of odd (Bo) and even (BE) parity multipoles show systematic variations correlated with solar magnetic phenomena.
• The study confirms a strong association between parity transitions and the reversal of the solar polar magnetic fields.
• North-south asymmetry in sunspot activity is found to correlate with changes in the relative dominance of Bo and BE components.
• Interplanetary magnetic field strength variations are linked to the parity state of the photospheric magnetic field, particularly during transitions between odd and even dominance.