Low-latitude circulation in three-circle circulation

This should be related to air pressure.

Because there is more heat near the equator than in the mid-latitude area, the hot air rises and the pressure near the ground decreases, so the equatorial low pressure area is formed. Note that the low pressure mentioned here is near the ground, while the sky far from the ground is high pressure. The high pressure moves to the north and south mid-latitudes and falls to the mid-latitudes (the ground pressure in the mid-latitudes should be less than the high pressure over the equator), so the mid-latitudes form a subtropical high pressure area.

This should have nothing to do with geostrophic deflection.