In the down residential market, New York City developers are catching auction fever. The Solaria condominium in the Bronx’s Riverdale neighborhood is the latest new building in the region to use an auction to spur interest — the Saffron condo in Jersey City recently used an auction to kick off sales and Greenpoint’s the Locale sold off units at auction earlier this month for 44 percent below asking — hosting an auction yesterday afternoon. The tactic seemed to pan out well for both buyers and Arc Development, which has been struggling to move units. By the auction’s end, 54 condos sold, with the average winning bids hitting 35 to 45 percent below what the asking prices were on the units. [Crain’s] and