Monthly counts of flux ropes with the yearly change. The top panel shows the monthly counts with different Walén slope thresholds (0.5 and 0.1) and monthly average sunspot number from the Sunspot Index and Long-term Solar Observations (SILSO), marked by blue, dark orange, and gray curves, respectively. The bottom panel shows the HGI latitudes and radial distances of the Ulysses spacecraft orbit around the Sun. The pairs of blue and dark orange dashed lines enclose the three fast latitudinal scans of the Ulysses orbit when the solar activity nearly reached its minimum and maximum levels.