Combine first 6 ingredients in a small bowl. Cover and chill.
Cut off stems of artichokes; remove bottom leaves. Trim about 1/2 inch from tops of artichokes. Place artichokes, stem ends down, in a large Dutch oven filled two-thirds with water. Add 1 teaspoon orange rind and salt; bring to a boil. Cover, reduce heat, and simmer 40 minutes or until a leaf near the center of each artichoke pulls out easily.
Place artichokes in a large ice-filled bowl; cool. Place artichokes, stem sides up, on a rack to drain. Remove tough outer leaves and small inner leaves from artichokes; discard. Serve with yogurt dip.