Radial position of the ribbon in the Io plasma torus observed by the Tohoku University 60-cm telescope (T60).The time period of the data is from 2014-12-15 to 2017-05-18. The ribbon is a distinct structure in the Io plasma torus where the Io-originated plasma spreads along the magnetic field lines. Images of Io plasma torus were taken by Visible Imager and SPectrograph with a coronagraph (VISP) installed at the Coude focus of T60. The IPT images are integrated over 3 RJ (Jupiter's radius) along the north-south direction, and the ribbon radial position was defined as the radial distance of the maximum brightness.