Open AccessMagnetic merging line and reconnection voltage versus IMF clock angle: Results from global MHD simulations
Author(s) -
Hu Y. Q.,
Peng Z.,
Wang C.,
Kan J. R.
Publication year - 2009
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009ja014118
Subject(s) - physics , magnetic reconnection , field line , interplanetary magnetic field , magnetosphere , computational physics , magnetohydrodynamics , electric field , geophysics , magnetic field , solar wind , ionosphere , dipole , magnetic dipole , line (geometry) , geometry , mathematics , quantum mechanics
This paper proposes diagnosis methods to trace the magnetic merging line and to calculate the electric potential along it for Earth's magnetospheric magnetic fields obtained by global magnetohydrodynamic (MHD) simulations of the solar wind‐magnetosphere‐ionosphere (SMI) system. The points with minimum magnetic field strength along last closed magnetic field lines and properly selected closed field lines are combined to trace the whole merging line, and the radial ray integration of convectional electric field is used to calculate the electric potential on the merging line. The diagnosis methods are then applied to magnetospheric magnetic fields associated with different interplanetary magnetic field (IMF) clock angles, and a preliminary analysis is presented on the clock angle response of the geometry of the merging line and the associated reconnection voltage. The merging line is found to be similar in geometry to that of the compound field superposed by the Earth's dipole field and the IMF, whereas the reconnection voltage is approximately fitted by sin 3/2 (θ IMF /2) for its response to the IMF clock angle θ IMF . The ionospheric transpolar potential and the voltage along the polar cap boundary show different dependence from that of the reconnection voltage, so it is not justified to take them as substitutes for the reconnection voltage. The length of the sunward merging line between the two peaks of reconnection potential shows a nonmonotonic variation in response to θ IMF , peaked at θ IMF = 90°, so it is also not justified to take electric fields along the merging line, however defined they may be, to characterize the total reconnection rate and the coupling strength between the solar wind and the magnetosphere. The reconnection nearby magnetic nulls closest to the subsolar point is found to be negligible, which gives support to the component reconnection hypothesis for dayside reconnection of quasi‐steady states of the SMI system.