Definition of our coordinate system. The termination shock and the astropause in the (B, V) plane (model 1: V = 2 km s⁻¹, B = 3 µG case) are outlined. The x- and y-axes lie on the (B, V) plane. The x-axis is directed along the ISM inflow. The z-axis (not shown) completes the right-handed system. The angle ϕ (the astrospheric longitude) is counted from the x-axis. The astrospheric latitude θ is counted from the (B, V) plane. Dash-dotted lines show the limits in longitude of the R, L, and T sectors.