Eckart Marsch | PubMed Health

PubMed2006

Coronal waves: propagation in the multi-fluid description.

We study wave propagation in the low-beta coronal plasma using a collisionless multi-fluid model. Neglecting the electron inertia, this model allows us to take into account ion-cyclotron wave effects that are absent in the magnetohydrodynamics model. To accomplish this, we perform a Fourier plane-wave perturbation analysis. Solving numerically the dispersion relations obtained from a two- and three-fluid model, dispersion curves for representative parameters of the solar corona are presented. The results reveal the presence of resonance frequencies that might play a role in coronal heating.

Journal Article↗

PubMed2005

Solar wind origin in coronal funnels.

The origin of the solar wind in solar coronal holes has long been unclear. We establish that the solar wind starts flowing out of the corona at heights above the photosphere between 5 megameters and 20 megameters in magnetic funnels. This result is obtained by a correlation of the Doppler-velocity and radiance maps of spectral lines emitted by various ions with the force-free magnetic field as extrapolated from photospheric magnetograms to different altitudes. Specifically, we find that Ne7+ ions mostly radiate around 20 megameters, where they have outflow speeds of about 10 kilometers per second, whereas C3+ ions with no average flow speed mainly radiate around 5 megameters. Based on these results, a model for understanding the solar wind origin is suggested.

Journal Article↗