The role of magnetic handedness in magnetic cloud propagation
We investigate the propagation of magnetic clouds (MCs) through the inner heliosphere using 2.5-D ideal magnetohydrodynamic (MHD) simulations. A numerical solution is obtained on a spherical grid, either in a meridional plane or in an equatorial plane, by using a Roe-type approximate Riemann sol...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2010-05-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/28/1075/2010/angeo-28-1075-2010.pdf |
| Summary: | We investigate the propagation of magnetic clouds (MCs) through the
inner heliosphere using 2.5-D ideal magnetohydrodynamic (MHD)
simulations. A numerical solution is obtained on a spherical grid,
either in a meridional plane or in an equatorial plane, by using a
Roe-type approximate Riemann solver in the frame of a finite volume
approach. The structured background solar wind is simulated for a
solar activity minimum phase. In the frame of MC propagation,
special emphasis is placed on the role of the initial magnetic
handedness of the MC's force-free magnetic field because this
parameter strongly influences the efficiency of magnetic
reconnection between the MC's magnetic field and the interplanetary
magnetic field. Magnetic clouds with an axis oriented perpendicular
to the equatorial plane develop into an elliptic shape, and the
ellipse drifts into azimuthal direction. A new feature seen in our
simulations is an additional tilt of the ellipse with respect to the
direction of propagation as a direct consequence of magnetic
reconnection. During propagation in a meridional plane, the initial
circular cross section develops a concave-outward shape. Depending
on the initial handedness, the cloud's magnetic field may reconnect
along its backside flanks to the ambient interplanetary magnetic
field (IMF), thereby losing magnetic flux to the IMF. Such a process
in combination with a structured ambient solar wind has never been
analyzed in detail before. Furthermore, we address the topics of
force-free magnetic field conservation and the development of
equatorward flows ahead of a concave-outward shaped MC. Detailed
profiles are presented for the radial evolution of magnetoplasma and
geometrical parameters. The principal features seen in our MHD
simulations are in good agreement with in-situ measurements
performed by spacecraft. The 2.5-D studies presented here may serve
as a basis under more simple geometrical conditions to understand
more complicated effects seen in 3-D simulations. |
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| ISSN: | 0992-7689 1432-0576 |