Browsing by Author "Daou, A.G."

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    Magnetospheric Multiscale Dayside Reconnection Electron Diffusion Region Events
    (Wiley, 2018) Webster, J.M.; Burch, J.L.; Reiff, P.H.; Daou, A.G.; Genestreti, K.J.; Graham, D.B.; Torbert, R.B.; Ergun, R.E.; Sazykin, S.Y.; Marshall, A.; Allen, R.C.; Chen, L.-J.; Wang, S.; Phan, T.D.; Giles, B.L.; Moore, T.E.; Fuselier, S.A.; Cozzani, G.; Russell, C.T.; Eriksson, S.; Rager, A.C.; Broll, J.M.; Goodrich, K.; Wilder, F.
    We use high‐resolution data from dayside passes of the Magnetospheric Multiscale (MMS) mission to create for the first time a comprehensive listing of encounters with the electron diffusion region (EDR), as evidenced by electron agyrotropy, ion jet reversals, and j • E′ > 0. We present an overview of these 32 EDR or near‐EDR events, which demonstrate a wide variety of observed plasma behavior inside and surrounding the reconnection site. We analyze in detail three of the 21 new EDR encounters, which occurred within a 1‐min‐long interval on 23 November 2016. The three events, which resulted from a relatively low and oscillating magnetopause velocity, exhibited large electric fields (up to ~100 mV/m), crescent‐shaped electron velocity phase space densities, large currents (≥2 μA/m2), and Ohmic heating of the plasma (~10 nW/m3). We include an Ohm's law analysis, in which we show that the divergence of the electron pressure term usually dominates the nonideal terms and is much more turbulent on the magnetosphere versus the magnetosheath side of the EDR.
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    Multispacecraft observations and modeling of the 22/23 June 2015 geomagnetic storm
    (Wiley, 2016) 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.
    The 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.