The Autumnal Equinox occurs today at 5:18 PM EDT. Today the sun will be across the Equator, giving the entire Earth approximately 12 hours of daylight and 12 hours of night (equinox is derived from the Latin words for equal night). At Indianapolis, sunrise on the 22nd is at 7:33 AM and sunset is at 7:42 PM. The Autumnal Equinox falls approximately on September 23 of each year. This year it falls late in the day of the 22nd.
Below is a picture which shows the Earth's orbit around the sun and the approximate dates of the solstices and equinoxes. (Image courtesy of NWS Jetstream)