Current distribution and transient magnetic fields in an observatory of TOKYO SKYTREE

•Detailed model of TOKYO SKYTREE is constructed using FDTD.•Transient magnetic fields in an observatory of TOKYO SKYTREE become obvious.•Current distributions in an observatory of TOKYO SKYTREE become obvious.•The wrap-around sashes applied to the observatory are effective for lightning protection.

TOKYO SKYTREE is the tallest free-standing antenna tower; whose height is 634 m. However, the number of lightning strikes to a tall structure increases in proportion to the structure height. Therefore, it is important to establish lightning protection methods for facilities in and around such tall antenna tower.There is a possibility that comparatively large magnetic fields occur inside an observatory by the current flowing through steel columns composing the TOKYO SKYTREE. This paper presents simulation results of lightning current distribution and magnetic fields around the observatory. Simulated results are from the finite-difference time-domain (FDTD) method which is one of the most widely used numerical electromagnetic analysis methods. The knowledge of these current distribution characteristics and magnetic fields would be very useful for lightning protection of TOKYO SKYTREE.