Final answer:
Sunspots are cooler, darker regions on the Sun's surface created by magnetic loops, where magnetic field lines from within the Sun rise up and sink back down. These magnetic fields inhibit convection, leading to lower temperatures. Helioseismology has helped to understand the underlying dynamics of these spots, which involves a continuous cycle of cooling and sinking gas.
Step-by-step explanation:
A loop of gas following the magnetic field lines around sunspots is explained by the impact that magnetic fields have on these cooler and darker regions on the Sun's surface. Sunspots form where magnetic field lines emerge from and re-enter the Sun, creating loops. The leading and trailing sunspots in an active region usually have opposite polarity; the leading sunspot matches one end of the magnetic loop and the trailing one matches the other end.
Moreover, these magnetic fields play a crucial role in why sunspots are cooler than their surroundings. The movement of hot gas is inhibited by the strong magnetic field, which prevents the efficient transport of heat from the Sun's interior to its surface by convection. This results in a cooling effect, and thus, sunspots are seen as darker areas. Measurements of the Zeeman effect have confirmed that sunspot regions harbor strong magnetic fields.
In a process revealed by helioseismology, material beneath a sunspot sinks while being pulled inward, maintaining the necessary strong magnetic field for sunspot formation. This cycle of cooling and sinking material is self-sustaining, enabling sunspots to last for several weeks. Additionally, the uneven spin of the Sun, which rotates faster at the equator than near the poles, causes magnetic field lines to wind up and form loops over time, further influencing sunspots' structure and behavior.