One of the solar system's most mysterious landmarks, the giant storm on the surface of the gas planet should have disappeared centuries ago -- at least given what scientists understand about fluid dynamics.
"Based on current theories, the Great Red Spot should have disappeared after several decades," Pedram Hassanzadeh, a postdoctoral fellow at Harvard University, said. "Instead, it has been there for hundreds of years."
Many processes normally combine to dissipate vortices like the Red Spot, he explained; the turbulence and waves in and around the Red Spot sap the energy of its winds, it loses energy by radiating heat, and it sits between two strong jet streams that flow in opposite directions and should slow down its spinning.
Hassanzadeh and Philip Marcus, a professor of fluid dynamics at the University of California, have built a new computer model that takes into account forces they say most previous models didn't take into account -- vertical flows within the vortices.
"In the past, researchers either ignored the vertical flow because they thought it was not important, or they used simpler equations because it was so difficult to model," Hassanzadeh said.
However, the two researchers said, the vertical motion turns out to hold the key to the Red Spot's persistence. As the vortex loses energy, they said, the vertical flow transports hot gases from above and cold gases from below the vortex toward its center, restoring part of its lost energy.
The same vertical flow phenomenon could explain why oceanic vortices on Earth, such as those formed near the Straits of Gibraltar, can last for years in the Atlantic Ocean, Hassanzadeh said.
Hassanzadeh will present the research at the annual meeting of the American Physical Society's Division of Fluid Dynamics in Pittsburgh Nov. 25.