the spike each day is from the momentum of the market move. yesterday, the move to the downside was so fast, that is why the vix was spiking. but then at the end of the day, it was actually coming back, so it killed the vix. if the market keep going down and going down fast and stays down, Vix will stay high. we will see what happen today. vix was down yesterday, but VXX was up still. that means, people are still have fear, especially in the near future.