On the first day or fall or spring, the sun is perpendicular (directly above) the equator on the equinox. On the equinox, there are twelve hours of daylight and twelve hours of darkness at all points on the earth’s surface on each of the two equinoxes. Sunrise is at 6 a.m. and sunset is at 6 p.m. local (solar) time for most points on the earth’s surface.
At the North Pole the sun is on the horizon at the North Pole on the September Equinox in the morning. The sun sets at the North Pole at noon on the September Equinox and the North Pole remains dark until the March Equinox.
On the Arctic Circle, there is are hours of daylight and 12 hours of darkness. The sun is 66.5 degrees off of the zenith or 23.5 degrees above the horizon.
On the Tropic of Cancer there are 12 hours of daylight and 12 hours of darkness. The sun is 23.5 degrees off of the zenith.
The sun is directly overhead the equator at noon on the equinox. On both equinoxes (which means "equal nights" in Latin), the sun is directly over the equator at noon.
On the Tropic of Capricorn there are 12 hours of daylight and 12 hours of darkness. The sun is 23.5 degrees off of the zenith.
On the Antarctic Circle there are 12 hours of daylight and 12 hours of darkness.
The sun rises at the South Pole after the Pole having been dark for the past six months (since the March Equinox). The sun rises to the horizon and it remains light at the South Pole for six months. Each day, the sun appears to rotate around the South Pole at the same declination angle in the sky.
The beginning of fall or spring often represents a mild transitional climate between the extremes of summer and winter. The areas between the Tropic of Cancer in the north and the Tropic of Capricorn in the south effectively do not have seasons because the sun is always high in the sky and thus there is a large amount of solar radiation received throughout the year. Seasonal changes primarily impact the higher latitudes (those above 23.5 degrees).