Reiff, P.H.Daou, A.G.Sazykin, S.Y.Nakamura, R.Hairston, M.R.Coffey, V.Chandler, M.O.Anderson, B.J.Russell, C.T.Welling, D.Fuselier, S.A.Genestreti, K.J.2017-08-212017-08-212016Reiff, P.H., Daou, A.G., Sazykin, S.Y., et al.. "Multispacecraft observations and modeling of the 22/23 June 2015 geomagnetic storm." <i>Geophysical Research Letters,</i> 43, no. 14 (2016) Wiley: 7311-7318. https://doi.org/10.1002/2016GL069154.https://hdl.handle.net/1911/97377The magnetic storm of 22–23 June 2015 was one of the largest in the current solar cycle. We present in situ observations from the Magnetospheric Multiscale Mission (MMS) and the Van Allen Probes (VAP) in the magnetotail, field-aligned currents from AMPERE (Active Magnetosphere and Planetary Electrodynamics Response), and ionospheric flow data from Defense Meteorological Satellite Program (DMSP). Our real-time space weather alert system sent out a “red alert,” correctly predicting Kp indices greater than 8. We show strong outflow of ionospheric oxygen, dipolarizations in the MMS magnetometer data, and dropouts in the particle fluxes seen by the MMS Fast Plasma Instrument suite. At ionospheric altitudes, the AMPERE data show highly variable currents exceeding 20 MA. We present numerical simulations with the Block Adaptive Tree-Solarwind - Roe - Upwind Scheme (BATS-R-US) global magnetohydrodynamic model linked with the Rice Convection Model. The model predicted the magnitude of the dipolarizations, and varying polar cap convection patterns, which were confirmed by DMSP measurements.engThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Journal articleMultispacecraft_observationshttps://doi.org/10.1002/2016GL069154