Distribution of the observational lengths in the L direction (R_L, red circle) and the M–N plane (R_MN, blue circle) with respect to θ, the angle between the L direction and the trajectory of the spacecraft. The units of the y axes are the ion (a) and electron (b) gyroradii. The cyan (orange) curves indicate the relation between R_L and θ determined by an assumption of an elliptical (uniform) geometry in the plane including the axis of the magnetic hole.