  A large fraction of known Jupiter like exoplanets are inflated as compared to
Jupiter. These "hot" Jupiters orbit close to their parent star and are
bombarded with intense starlight. Many theories have been proposed to explain
their radius inflation and several suggest that a small fraction of the
incident starlight is injected in to the planetary interior which helps to puff
up the planet. How will such energy injection affect the planetary dynamo? In
this Letter, we estimate the surface magnetic field strength of hot Jupiters
using scaling arguments that relate energy available in planetary interiors to
the dynamo generated magnetic fields. We find that if we take into account the
energy injected in the planetary interior that is sufficient to inflate hot
Jupiters to observed radii, then the resulting dynamo should be able generate
magnetic fields that are more than an order of magnitude stronger than the
Jovian values. Our analysis highlights the potential fundamental role of the
stellar light in setting the field strength in hot Jupiters.
