  Using Hinode SP and G-band observations, we examined the relationship between
magnetic field structure and penumbral size as well as Evershed flow speed. The
latter two are positively correlated with magnetic inclination angle or
horizontal field strength within 1.5 kilogauss, which is in agreement with
recent magnetoconvective simulations of Evershed effect. This work thus
provides direct observational evidence supporting the magnetoconvection nature
of penumbral structure and Evershed flow in the presence of strong and inclined
magnetic field.
