A solenoid has a core made of material with relative permeability 400 . The magnetic field produced in the interior of solenoid is 1.0 T . The magnetic intensity in SI units is $\alpha \times 10^5$. The value of $\alpha$ is $\_\_\_\_$ . (Free space permeability $\mu_0=4 \pi \times 10^{-7} \mathrm{SI}$ units.)