Total gamma dropped by 87M to -0.6M today. Traders bought downside protection at 1100 (-11M to -9M d/d), 1095 (-5.7M to -10M), 1000 (-6.9M to -5.3M) and especially at 950 (-7.1M to 8.5M). Should the downtrend persist tomorrow, then the negative gamma environment will lead to higher vol and maybe to a self reflexive spiral.