VIX
The VIX has been hovering around the 20-21 region so far today.
The VIX has been a great shibboleth for testing whether stocks will rise or fall and a quick barometer on the risk tone. If we move, and stay above 21, then expect equities to keep falling. If we move below, and stay below 20, expect stocks to rise.
VIX is the bottom right chart amongst a selection of global indices.