Why to determine the magnetic helicity in corona and interplanetary medium?

LUONI, M.L.; DASSO, S.; MANDRINI, C.H.; DÉMOULIN, P.; VAN DRIEL-GESZTELYI, L.

La Plata

Congreso; 46 Reunión de la Asociación Argentina de Astronomía; 2003

Asociación Argentina de Astronomía

Magnetic clouds are huge objects that travel in the interplanetary medium, transporting magnetic helicity (MH) produced by the Sun. Since the dissipation time of MH is much larger than the typical time associated with the dynamical processes in the solar corona and the heliosphere, MH is the natural magnetohydrodinamic (MHD) magnitude to compare interplanetary manifestations with the associated solar processes. In this work we study an active region that produced a coronal mass ejection (CME). We model the coronal magnetic field using a linear force free approach, and we calculate the magnetic flux and the variation of MH, before and after the ejection of the CME. We model also the magnetic field configuration of the associated interplanetary cloud, using several cylindrical models, and estimate the flux and the content of MH. Finally, we compare the coronal and the interplanetary values for the flux and the MH, and we find a very good agreement. The coronal flux is 1022Mx, while the magnetic flux for the cloud is around 1021Mx (? 10% of the coronal flux, as typically observed). The variation of the coronal MH turns out to be 3x1042Mx2, while we obtain that the MH contained in the magnetic cloud is in the range (2-8)x1042Mx2. Our results indicate that MH is a very useful tool to link phenomena in very different regimes and can be used to constrain both coronal and interplanetary models.