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Alfvén Mach number and IMF clock angle dependencies of sunward flow channels in the magnetosphere
Author(s) -
Eriksson S.,
Rastätter L.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50307
Subject(s) - physics , magnetosphere , interplanetary magnetic field , ionosphere , poynting vector , solar wind , mach number , flux (metallurgy) , geophysics , coronal mass ejection , magnetohydrodynamics , magnetic reconnection , interplanetary spaceflight , astrophysics , magnetic field , computational physics , mechanics , materials science , quantum mechanics , metallurgy
Interplanetary coronal mass ejections associated with strong interplanetary magnetic field (IMF) By have been shown to enhance the neutral density in low Earth orbit. The enhancement has been linked to strong downward Poynting fluxes embedded within ionospheric channels of significant sunward E x B drift (2000–3000 m/s). Here we present MHD results describing the magnetospheric counterpart of the ionospheric flow channel that Defense Meteorological Satellite Program (DMSP) encountered on 15 May 2005. It is shown that the clock angle of maximum sunward flow (θ FC ) depends on the IMF clock angle θ FC = α * θ IMF − 1.3° with α = (0.30, 0.38, 0.43, 0.45) at X = (4, 2, 0, −2) R E . This is poleward of the magnetic null point region. The flow also depends on the solar wind Alfvén Mach number Vx = Vx0 − δv * M A . The critical M A = Vx0 / δV for Vx = 0 decreases from M A = 3.42 (X = 4 R E ) to M A = 2.40 (X = −2 R E ). The low M A and θ IMF conditions that characterized the X = 2 R E flow and resulted in strong Poynting flux occurred for 16% of all 167 h in 1998–2008 with Dst < −180 nT.