Some definitions first: VIX - expected 30-day volatility for the S&P 500 VXV - expected 3 month volatility for the S&P 500
So if VIX implies short term fear, VXV implies quarterly fear. To divide both of them as a spread can give an indication/direction of where both short term and a slightly longer term 'fear' is heading.
Looking at the chart this ratio of spread has some interesting spikes. I've drawn horizontal rays to show where the support and resistance levels are.
In addition, an exponential envelope shows when this ratio falls out or touches a 10% band. One can choose to take the Long view on SPY when this ratio spikes and hedge (go long VXX) should there be a divergence on MACD.