Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009jgra..11404203p&link_type=abstract
Journal of Geophysical Research, Volume 114, Issue A4, CiteID A04203
Astronomy and Astrophysics
Astrophysics
1
Magnetospheric Physics: Solar Wind/Magnetosphere Interactions, Magnetospheric Physics: Magnetosphere/Ionosphere Interactions (2431), Solar Physics, Astrophysics, And Astronomy: Magnetic Reconnection (2723, 7835), Magnetospheric Physics: Numerical Modeling
Scientific paper
The ionospheric transpolar potential (V pc) and the magnetospheric reconnection voltage (V r) of the Earth are investigated in terms of global MHD simulations of the solar wind-magnetosphere-ionosphere (SMI) system. A spherical shell approximation is used for the ionosphere with a uniform Pedersen conductance and a zero Hall conductance, the interplanetary magnetic field is due southward, and quasi-steady solutions are obtained for the system. Each solution is characterized by the following four parameters: the ionospheric Pedersen conductance ΣP, the solar wind electric field E sw, ram pressure P sw, and Alfvén Mach number M A. More than 100 cases are treated separately and V pc and V r are calculated in each case. It is found that both V pc and V r increase monotonically with increasing P sw and decreasing M A regardless of the magnitude of E sw. The simulation results are well organized by a combined parameter f = E sw P sw M A -1/2 and approximately fitted by functions of f and ΣP. When the units are S for ΣP, kV for V pc and V r, mV/m for E sw, and nPa for P sw, the functions are found to be V pc = 2.3 × 103 (f + 0.8)(ΣP + 2)-1/(f + 8.2) and V r = 1.8 × 103[f + 0.45(ΣP 1/2 + 1.2)] (ΣP 1/2 + 0.45)-1/(f + 15.5). Three conclusions are made as follows: (1) Both V pc and V r saturate with respect to the increase of f; any variation of the interplanetary conditions in favor of the increase of f may cause the saturation. (2) The saturation point is found to be f c = 6.6 for V pc and f c = 14.4 - 0.9ΣP 1/2 for V r, whereas the value of ΣP controls the saturation levels. (3) The two potentials, V pc and V r, stem from the SMI coupling and exhibit similar saturation behaviors. They are positively correlated because of sharing the same driving source and the close coupling between the ionosphere and the magnetosphere.
Hu Yong-Qing
Lai H. R.
Peng Zhe
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