Typically, there is an inverse relationship between the movement of a volatility index and it’s corresponding market index or etf ($VIX & $SPX or $SPY, $VXN & $NDX or $QQQ, $VXD & $DJI or $DIA). At times, though, there is a direct relationship. (Like today between $VXD & $DIA on the weekly chart).
What is happening for the market to, at times, create a direct relationship between a volatility index and a market index or etf?