Atmospheric turbulence
Air contains interacting eddies over an enormous range of sizes. How can their combined effect on heat, momentum, and pollutants be predicted reliably?
Fluids and plasmas
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Coronal heating problem
The Sun’s outer atmosphere is much hotter than its visible surface. Which processes deliver and dissipate enough energy to maintain it?
Turbulence intermittency
Turbulent motion concentrates into rare, intense bursts. Can the fluid equations predict how those bursts scale?
Relativistic Vlasov–Maxwell global regularity
Can smooth three-dimensional collisionless plasma equations develop a singularity from regular initial data?
Saturn’s tidal dissipation
Saturn transfers spin to its moons, moving them outward. The strength and frequency pattern of this transfer point to unusually effective internal energy loss. Which interior processes set those rates and their evolution?
Magnetotail reconnection energy partition
When Earth’s stretched magnetic field reconnects, released energy heats particles and creates fast-moving tails in their energy distributions. What determines the ion/electron and thermal/nonthermal shares under measured magnetotail conditions?
Roughness-induced hypersonic transition
A rough patch on a hypersonic heat shield can change a smooth boundary layer into turbulent flow and increase heating. How can engineers predict the onset and heat load from the actual roughness geometry and flight conditions?
Gamma-ray burst prompt emission
The first flash of a long gamma-ray burst reveals an ultra-relativistic jet releasing energy. Which radiation processes produce the photons, and how do their contributions change during the burst?