Effects of the solar wind electric field and ionospheric conductance on the cross polar cap potential: Results of global MHD modeling

Merkine, V. G.; Papadopoulos, K.; Milikh, G. M.; Sharma, A. S.; Shao, Xi; Lyon, J. G.; Goodrich, C. C.

doi:10.1029/2003gl017903

Cited by 62 publications

(96 citation statements)

References 9 publications

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“…These clusters of plots show three different ways in which saturation of the ionospheric CPCP has typically been shown: (1) the time series plots show that the Boyle et al (1997) estimation of the CPCP typically becomes larger than the AMIE CPCP when the IMF B z component becomes large and negative; (2) the upper scatter plot shows that the Boyle et al (1997) estimated CPCP is linear for large REFs, while the AMIE CPCP is significantly lower than this linear estimate; and (3) when the Boyle et al (1997) In most previous studies of the saturation of the cross polar cap potential (e.g. Russell et al, 2001;Merkine et al, 2003;Nagatsuma, 2002), they show plots such as Figs. 1-4, implying a relationship between an electric field and a potential.…”

Section: Resultsmentioning

confidence: 99%

A new formulation for the ionospheric cross polar cap potential including saturation effects

Ridley

2005

Ann. Geophys.

108

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Abstract. It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) B z becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12 mV/m at some time. When these events are examined as typically done in previous studies, all of them show some signs of saturation (i.e., over-prediction of the CPCP based on a linear relationship between the IMF and the CPCP). We show that by taking into account the size of the magnetosphere and the fact that the post-shock magnetic field strength is strongly dependent upon the solar wind Mach number, we can better specify the ionospheric CPCP. The CPCP ( ) can be expressed as =(10 −4 v 2 +11.7B(1−e −M a /3 ) sin 3 (θ/2))r ms /9 (where v is the solar wind velocity, B is the combined Y and Z components of the interplanetary magnetic field, M a is the solar wind Mach number, θ =acos(B z /B), and r ms is the standoff distance to the magnetopause, assuming pressure-balance between the solar wind and the magnetosphere). This is a simple modification of the original Boyle et al. (1997) formulation.

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Section: Resultsmentioning

confidence: 99%

A new formulation for the ionospheric cross polar cap potential including saturation effects

Ridley

2005

Ann. Geophys.

108

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“…This measured progression supports the finite grid-resolution underestimate picture. Note that other simulations see this difference between the magnetosphere and ionosphere [e.g., Merkine et al, 2003]. And note further that arguments have been made that there is a difference in potentials across the real ionosphere and real magnetosphere [Russell et al, 2001].…”

Section: à3mentioning

confidence: 99%

“…Some of the global MHD simulations in the literature have also explored polar cap saturation in this modestly driven regime [e.g., Fedder and Lyon, 1987;Siscoe et al, 2002a;Ridley et al, 2004]. Other simulations have explored polar cap saturation with very strong driving [e.g., Raeder et al, 2001;Merkin et al, 2005b;Raeder and Lu, 2005;Ridley et al, 2006] or have varied their solar wind parameters into the very strongly driven regime [e.g., Siscoe et al, 2002b;Merkine et al, 2003;Merkin et al, 2005a;Ridley, 2007;Lavraud and Borovsky, 2008].…”

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Polar cap potential saturation, dayside reconnection, and changes to the magnetosphere

2009

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[1] Global MHD simulations of the Earth's magnetosphere using the Block-AdaptiveTree Solarwind Roe Upwind Scheme code at the Community Coordinated Modeling Center are run with a high-resolution dayside magnetopause and variable-resolution nearEarth regions to study the phenomena of polar cap saturation. In the simulations a resistive spot is maintained on the moving magnetopause to ensure that the correct dayside reconnection rate is obtained. The solar wind parameters are held fixed, and the ionospheric Pedersen conductivity is varied. Strong reduction of the cross-polar cap potential is observed, with modest increases in the cross-polar cap current, and no changes in the local and global reconnection rates. Changes in the magnetosphere associated with the saturation of the polar cap are explored: these include a weakening of the dayside magnetic field strength, an equatorward shift of the cusps, a flattening in Z of the closed field line region of the dayside magnetosphere, and a taillike stretching of the dipole field lines at the terminator. Measurements of the currents and voltages of the polar cap indicate that the solar wind acts like a current-limited voltage generator. A simple circuit model is analyzed using measurements from the MHD simulations, and physically reasonable values for the circuit elements are obtained. Nine models for polar cap saturation are assessed against the findings of the present study.

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“…As a matter of fact, it was used to study the dependence of the MR voltage and transpolar potential on the solar wind electric field and ionospheric Pedersen conductance [4,5,13,14] and the paths of the FACs [12,15,16]. In particular, Guo et al [16] found that more than 50% of the region 1 FAC may come from the bow shock under strong southward IMF conditions.…”

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“…Note that here the ionosphere is not only a passive load for the M-I system, but plays a crucial role in the M-I coupling. It directly affects the transpolar potential and the FAC intensity, and exerts an indirect but important influence on the magnetosphere configuration, the magnetosheath flow, and the MR voltage [13,14]. Hence the effect of the ionospheric conductance must be included while studying the SW-M-I coupling.…”

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Response of the Earth's Magnetosphere and Ionosphere to Solar Wind Driver and Ionosphere Load: Results of Global MHD Simulations

Xiong

Zhong

et al. 2009

Chinese Phys. Lett.

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Three-dimensional global magnetohydrodynamic simulations of the solar wind -magnetosphere -ionosphere system are carried out to explore the dependence of the magnetospheric reconnection voltage, the ionospheric transpolar potential, and the field aligned currents (FACs) on the solar wind driver and ionosphere load for the cases with pure southward interplanetary magnetic field (IMF). It is shown that the reconnection voltage and the transpolar potential increase monotonically with decreasing Pedersen conductance (Σ P ), increasing southward IMF strength (B s ) and solar wind speed (v sw ). Moreover, both of the region 1 and the region 2 FACs increase when B s and v sw increase, whereas the two currents behave differently in response to Σ P . As Σ P increases, the region 1 FAC increases monotonically, but the region 2 FAC shows a non-monotonic response to the increase of Σ P : it first increases in the range of (0, 5) Siemens and then decreases for Σ P > 5 Siemens. Submitted to: Chinese Physics LettersThe solar wind -magnetosphere -ionosphere (SW-M-I) system is a multi-variable, multi-scale complex system [1], in which the solar wind serves as a driver and the ionosphere plays a role of load. It has been widely believed that magnetic reconnection (MR) between the geomagnetic and interplanetary fields on the dayside magnetopause leads to an efficient and rapid transfer of energy and momentum from the solar wind to the magnetosphere. The electrons may be temporarily trapped in the central reconnection region including electron diffusion region [2]. The MR takes place along the separatrix line, i.e., the MR line, which connects a pair of magnetic nulls lying on the magnetopause [3]. The total electric potential drop along the MR line (MR voltage) virtually represents the global MR rate [4,5] so as to be an important parameter characterizing the SW-M-I coupling. The ionospheric transpolar potential, named as

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Effects of the solar wind electric field and ionospheric conductance on the cross polar cap potential: Results of global MHD modeling

Cited by 62 publications

References 9 publications

A new formulation for the ionospheric cross polar cap potential including saturation effects

A new formulation for the ionospheric cross polar cap potential including saturation effects

Polar cap potential saturation, dayside reconnection, and changes to the magnetosphere

Response of the Earth's Magnetosphere and Ionosphere to Solar Wind Driver and Ionosphere Load: Results of Global MHD Simulations

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