Distribution of the SEP associated flare longitude in the cases with inferred radio association. The red dash-dotted and blue dashed lines correspond to different well-connected magnetic flux tubes, according to Parker’s model of the interplanetary magnetic field, with their longitudes calculated from Eq. (2) using different solar wind velocities (υ_sw). The red lines correspond to 50°–60° western longitude (υ_sw ~ 415–500 km s^-1). The right blue dashed line corresponds to longitude φ₀ = 80° (~312 km s^-1) and the left blue dashed line corresponds to φ₀ = 30° (~832 km s^-1). We also label the 50°–60° longitudes as “Well-Connected Region”.