How do sunspots reveal the Sun’s magnetic fields?

Sunspots serve as visible indicators of the Sun’s intense magnetic activity, revealing the presence and structure of magnetic fields through several key characteristics:

• Magnetic Field Strength: Sunspots are regions of extremely strong magnetic fields, typically ranging from 2,000 to 4,000 gauss, compared to Earth’s magnetic field of approximately 1 gauss.12
• Spectral Analysis: Astronomers identify these fields using the Zeeman effect, which causes spectral lines of light to split into multiple components when emitted from a region with a magnetic field. This technique allows scientists to measure the strength and orientation of the Sun's magnetic fields.3
• Structural Configuration: Sunspots often appear in pairs or groups of opposite magnetic polarity, representing where magnetic flux loops intersect the solar surface. The dark central core, or umbra, is where magnetic flux emerges vertically, while the surrounding penumbra is where the field spreads horizontally.12
• Suppression of Convection: The strong magnetic fields within sunspots suppress convective motions that would otherwise bring heat from the solar interior, causing the spots to be significantly cooler—and thus darker—than the surrounding photosphere.1