The Goat, an Ancient Indo-European Solar Symbol

"The Goat typified the reproductive powers of the sun, and is given to various solar and atmospheric gods. Thor, the Scandinavian god of thunder and lightning, is depicted in a chariot drawn by goats."[Ancient Pagan Symbols, Elisabeth Goldsmith, 1929]

"The high gods have the lion, bull, goat, eagle, falcon, symbols of solar creative energy. Thor, the god of thunder, is depicted in a chariot drawn by goats."[Goldsmith]

Thor`s goats were called Tanngnjostr[`Tooth-cracker`] and Tanngrisnr[`Tooth-gnasher`]. It is not only the Germanic Thunder God whose chariot was pulled by goats:

"Perkunas. Lithuanian. The thunder god, the equivalent in LITHUANIA of PERKONS, PERKONIS, PERUN and PYERUN. Perkunas was perceived as a vigorous red-bearded man brandishing an axe who was drawn rattling, across the sky in a chariot drawn by a billy goat. "[European Myth & Legend, Mike Dixon-Kennedy, 1997]

In the case of Indra His chariot was pulled not by goats but by deer. However both animals appear to be associated closely with each other and the deer is likewise a solar animal. Both are horned animals and horns are often associated with Sun Gods and solar heroes. With the onset of xtian dominance from the early Middle Ages the head of the goat became a symbol of Lucifer-confused with the xtian and semitic `devil`.
Lucifer we should recall is an ancient solar deity, his name meaning `light` from the Latin lucis, the genetive of lux-`light`.

In the Eddas Thor is known to have used His goats as food and then revived them in the morning by consecrating their bones which were carefully laid on their skins with His hammer. Rudolf Simek[Northern Mythology] suggests that there is a link between this and the boar, Saehrimnir which likewise is eaten everday in Walhalla and then revived. There could be echoes of sacrificial rites connected to ancient shamanic practices in these myths.

I have always felt a strong connection with Thunor/Donar. My mother`s maiden name was Bock which is German for `he-goat`. In times past this surname became associated with houses that bore the sign of the goat, which could indicate an affiliation with and service to the German Thunder God, Donar.
My mother told me that the Harz mountains where she came from experienced very loud thunder storms and there is a whole body of lore associated with this. However instead of associating thunder and lightning with Donar like our post-conversion ancestors she instead associated it with giants. This is an interesting concept as Thor in the Eddas is frequently found combating giants and the thunder is reckoned to be an echo of these struggles.