3-D Force-balanced Magnetospheric Configurations

Abstract

Abstract. The knowledge of plasma pressure is essential for many physics applications in the magnetosphere, such as computing magnetospheric currents and deriving mag-netosphere-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. 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 J × B = ∇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 = ∇ψ × ∇α. The pressure distribution, P = P (ψ, α), is prescribed in the equatorial plane and is based on satellite measurements. In addition, computational boundary conditions for ψ surfaces are imposed using empirical field models. Our results provide 3-D distributions of magnetic field, plasma pressure as well as parallel and transverse currents for both quiet-time and disturbed magnetospheric conditions.

The effects of dynamic ionospheric outflow on the ring current

“…The other half of RAM‐SCB is the 3‐D force balance magnetic field model [ Zaharia et al , 2004; Zaharia , 2008]. This model balances the J × B force with the divergence of the general pressure tensor to calculate the magnetic field configuration within its domain.…”

Self-consistent geomagnetic storm simulation: The role of the induced electric fields

“…As the full details are discussed elsewhere (e.g., Jordanova et al, 1997Jordanova et al, , 2006Zaharia et al, 2004Zaharia et al, , 2005Zaharia et al, , 2006, here we only briefly summarize the method.…”

“…Our 3-D equilibrium code is an extension (Zaharia et al, 2004) of the isotropic pressure case (Cheng, 1995;Zaharia and Cheng, 2003), and solves the equation…”

“…For a unique solution one needs P ? and P k at one point on each field line, as well as boundary conditions for the magnetic flux a [usually obtained (Zaharia et al, 2004) from empirical B-field models].…”

On the Transition Between the Inner and Outer Plasma Sheet in the Earth's Magnetotail

“…The average properties of the plasma sheet have been extensively studied from various points of view for decades, based on in situ observations (e.g., Baumjohann et al, ; Huang & Frank, ; Kaufmann et al, , ; Lennartsson & Shelley, ; Paterson et al, ; Tsyganenko & Mukai, ; Wang et al, , , ), equatorial mapping of low‐altitude observations (e.g., Wing & Newell, ), and numerical modeling (e.g., Wang et al, , ; Zaharia et al, ). Nevertheless, a fundamental issue concerning the plasma sheet structure that still leaves room for discussion is the transition between the inner and outer plasma sheet.…”