What is the solar term for the direct northward movement of the southern hemisphere?

When the earth revolves around the sun, the axis of the earth and the orbital plane form a fixed inclination of 66.5, which makes the direct point of the sun's rays move regularly between the tropic of cancer in a year.

When the sun's rays move from the southern hemisphere to the equator, it is the vernal equinox in the northern hemisphere (about March 2 1); When the direct point of the sun is on the tropic of cancer, there will be extreme daylight in the Arctic Circle.

So the answer is: vernal equinox; March 2 1 or so; An extreme day.