MHD reconstruction of a magnetic cloud in the solar wind

We use for the first time the two-dimensional (2-D), magneto-hydrodynamic (MHD) reconstruction technique to examine a magnetic cloud structure in the solar wind. The MHD reconstruction technique is based upon the initial-value integration of the steady, 2-D, ideal MHD equations to generate the cross section of field and plasma of a structure seen by a spacecraft. On 15 May, 2005, a super-intense geomagnetic storm was triggered by a magnetic cloud, which was observed by the Advanced Composition Explorer (ACE) spacecraft in the solar wind at 1 AU. Here AU is the astronomical unit (~1.5 × 10⁸ km). A size of ~0.20 AU (length) × ~0.15 AU (width) of a left-handed magnetic flux rope structure is reconstructed for the magnetic cloud. The axial orientation of the magnetic flux rope is directed to [-0.433, 0.744, 0.509] in Geocentric Solar Magnetospheric (GSM) coordinates system. The distance of the spacecraft from the center of the flux rope is ~0.05 AU. The maximum axial magnetic field of the flux rope is ~59 nT for which the axial current density is estimated of ~5 pA/m².