PPPL-3783 is available in <a href="PPPL-3783.pdf">pdf</a> format (2.7 MB).

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<b>3-D Force-balanced Magnetospheric Configurations</b>
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<b>Authors:</b> Sorin Zaharia, C.Z. Cheng, and K. Maezawa
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<b>Date of PPPL Report:</b> February 2003
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<b>Published in:</b> Annales Geophysicae <b>22</b> (January 2004) 251-265.</p>


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The knowledge of plasma pressure is essential for many physics applications in the magnetosphere, such as computing magnetospheric currents and deriving magnetosphere-ionosphere coupling. A thorough knowledge of the 3-D pressure distribution has, however, eluded the community, as most in-situ pressure observations are either in the ionosphere or the equatorial region of the magnetosphere. With the assumption of pressure isotropy there have been attempts to obtain the pressure at different locations by either (a) mapping observed data (e.g., in the ionosphere) along the field lines of an empirical magnetospheric field model, or (b) computing a pressure profile in the equatorial plane (in 2-D) or along the Sun-Earth axis (in 1-D) that is in force balance with the magnetic stresses of an empirical model. However, the pressure distributions obtained through these methods are not in force balance with the empirical magnetic field at all locations.<BR><BR> In order to find a global 3-D plasma pressure distribution in force balance with the magnetospheric magnetic field, we have developed the MAG-3D code that solves the 3-D force balance equation <B>J</B> x <B>B</B> = <IMG SRC = "./upside_down_delta.jpg" width = "10" height = "10" VALIGN = "bottom" ALT = "upside down delta symbol">P computationally. Our calculation is performed in a flux coordinate system in which the magnetic field is expressed in terms of Euler potentials as <B>B</B> = <IMG SRC = "./upside_down_delta.jpg" width = "10" height = "10" VALIGN = "bottom" ALT = "upside down delta symbol"><font face ="symbol">y </font> x<IMG SRC = "./upside_down_delta.jpg" width = "10" height = "10" VALIGN = "bottom" ALT = "upside down delta symbol"><font face ="symbol">a</font>. The pressure distribution, P = P(<font face ="symbol">y,a</font>), is prescribed in the equatorial plane and is based on satellite measurements. In addition, computational boundary conditions for y surfaces are imposed using empirical field models. Our results provide 3-D distributions of magnetic field and plasma pressure as well as parallel and transverse currents for both quiet-time and disturbed magnetospheric conditions.




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