For dressing, in a glass bowl whisk together vinegar, sugar, the 1 teaspoon kosher salt, and black pepper until sugar is dissolved. Let dressing stand while preparing salad.
For salad, cut corn kernels from cobs. In a large bowl toss corn and remaining ingredients except sea salt and arugula leaves.
To serve, transfer salad to large serving bowl. Season with the 1/2 tsp. sea salt. Add the dressing; gently thread in arugula leaves. Serve immediately. (Cucumbers and tomatoes will begin to break down.) Makes 8 servings
Wear kitchen gloves when handling hot peppers, such as jalapenos to avoid burning skin and eyes with volatile oils. When hands touch peppers, wash immediately in warm sudsy water.