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We present ten young ($\lesssim$10 Myr) late-K and M dwarf stars observed inK2 Campaign 2 that host protoplanetary disks and exhibit quasi-periodic oraperiodic dimming events. Their optical light curves show $\sim$10-20 dips influx over the 80-day observing campaign with durations of $\sim$0.5-2 days anddepths of up to $\sim$40%. These stars are all members of the $\rho$ Ophiuchus($\sim$1 Myr) or Upper Scorpius ($\sim$10 Myr) star-forming regions. Toinvestigate the nature of these "dippers" we obtained: optical andnear-infrared spectra to determine stellar properties and identify accretionsignatures; adaptive optics imaging to search for close companions that couldcause optical variations and/or influence disk evolution; andmillimeter-wavelength observations to constrain disk dust and gas masses. Thespectra reveal Li I absorption and H$\alpha$ emission consistent with stellaryouth (<50 Myr), but also accretion rates spanning those of classical andweak-line T Tauri stars. Infrared excesses are consistent with protoplanetarydisks extending to within $\sim$10 stellar radii in most cases; however, thesub-mm observations imply disk masses that are an order of magnitude belowthose of typical protoplanetary disks. We find a positive correlation betweendip depth and WISE-2 excess, which we interpret as evidence that the dipperphenomenon is related to occulting structures in the inner disk, although thisis difficult to reconcile with the weakly accreting aperiodic dippers. Weconsider three mechanisms to explain the dipper phenomenon: inner disk warpsnear the co-rotation radius related to accretion; vortices at the inner diskedge produced by the Rossby Wave Instability; and clumps of circumstellarmaterial related to planetesimal formation.

Young "Dipper" Stars in Upper Sco and $\rho$ Oph Observed by K2