Question

How do solstice's and equinox's affect solar energy reaching the Earth's surface?

Answer 1

The angle of incidence of radiation is latitude at equinoxes and latitude `+-23.4^o` at solstices. .Accordingly, there is quantitative periodic variation, in reception of solar energy.

Explanation:

The angle of incidence of solar rays is their inclination to the vertical

(radius from the center of the Earth to the place), at the location.

At an equinox instant (about 21st March (vernal equinox) and 23rd

September (autumnal equinox)), the angle of incidence (`alpha`) of

solar rays is exactly the latitude `(theta`), everywhere.

At summer solstice (about June 21), it is '`theta +23.4 ^o'`, for

northern latitudes, and '`theta-23.4^o` ', for southern latitudes.

It is vice versa , on winter solstice (around December 21).

This oscillatory variation '`alpha in [theta-23.4^o, theta+23.4^o]`

with period 1 year, affects quantitatively the reception of solar

energy, everywhere.