Solar rotation and polar flows of the Sun as deduced from measurements by the Michelson Doppler Imager (MDI) instrument onboard SOHO. The left side of the image represents the difference in rotation speed between various areas on the Sun. Red-yellow is faster than average and blue is slower than average. The light orange bands are zones that are moving slightly faster than their surroundings. The new SOHO observations indicate that these extend down approximately 20,000 km into the Sun. Sunspots, caused by disturbances in the solar magnetic field, tend to form at the edge of these bands. The cutaway reveals rotation speed inside the Sun. The large dark red band is a massive fast flow of hot, electrically charged gas called plasma beneath the solar equator. Additionally, a newly discovered, but much more subtle, plasma stream+ can be seen in the cutaway at the poles. They are the light blue areas embedded in the slower moving dark blue regions. Finally, the blue lines in the cutaway at the right represent the surface flow from the equator to the poles of the Sun which, as SOHO observations have revealed for the first time, extends to a depth of at least 26,000 km (4% of the solar radius), so that it is likely to be an important factor in solar dynamics, although the flow speed (10-20 m/s) is small compared to random motions at the surface (1 km/s). The return flow indicated at the bottom of the convection zone is from a simple model and has not been observed yet.

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