Final answer:
Glowing loops of hydrogen seen over the solar limb during totality are known as prominences, which are huge loops of plasma that extend from the sun's surface into the corona, often observed as red features during a solar eclipse.
Step-by-step explanation:
The loops of glowing hydrogen seen hanging over the solar limb during totality are known as prominences. These structures are essentially huge loops of plasma, predominantly composed of hydrogen that extends outward from the sun's surface and into the corona. These prominences originate near sunspots and can be observed during a solar eclipse, appearing as red features that rise above the sun and reach into its atmosphere. Quiescent prominences can remain stable for several hours or even days, while eruptive prominences can move rapidly, sometimes reaching speeds of up to 1300 kilometers per second, and stretch over significant distances above the photosphere. The red glow of these prominences is due to hydrogen gas emitting light at specific wavelengths as electrons move to lower energy levels.