Long-term Solar Activity Studies using Microwave Imaging Observations and Prediction for Cycle 25.

Area of Science:

• Solar physics and space weather research.
• Heliophysics and solar activity monitoring.

Background:

• Long-term solar activity studies are crucial for space weather prediction.
• Understanding solar magnetic field evolution and its impact on solar wind is key.
• Polar magnetic field reversals and north-south asymmetry influence solar cycle dynamics.

Purpose of the Study:

• To utilize microwave imaging for long-term solar activity analysis.
• To establish proxies for polar magnetic fields and active regions using brightness temperatures.
• To predict solar cycle strength and investigate polar field reversal asymmetry.

Main Methods:

• Analysis of 17 GHz microwave imaging data from the Nobeyama Radioheliograph.
• Using polar and low-latitude brightness temperatures as proxies for magnetic fields and active regions.
• Employing prominence eruption locations to track filament evolution and combining with historical data.

Main Results:

• Polar microwave brightness temperature strongly correlates with polar magnetic field strength and fast solar wind speed.
• A lag of approximately half a solar cycle exists between polar and low-latitude microwave brightness.
• Predicted smoothed sunspot numbers for cycle 25 are 89 (south) and 59 (north), indicating similar strength to cycle 24.
• Analysis of historical data reveals a quasi-periodicity of 3-5 cycles in the north-south asymmetry of polar sign reversal.

Conclusions:

• Microwave brightness temperatures serve as effective proxies for key solar activity indicators.
• The observed correlations allow for reliable prediction of solar cycle strength.
• The study provides insights into the long-term behavior and asymmetry of solar polar magnetic field reversals.