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G. Lapenta (Los Alamos National Laboratory)
We present a new class of magnetic configurations that present analogy with solitons. And we ask if they can be an idealization of the real configuration of jets emitted from active galactic nuclei (AGN). The magnetic configuration of jets can be obtained studying equilibrium solutions of the MHD model. MHD equilibrium can be cast in a convenient form called Grad-Shafranov equation. Traditionally various classes of solutions have been obtained using self-similarity techniques and using the analogy between the Grad-Shafranov equation and the classic Helmholtz problem. Here we present a new class of solutions obtained using a different (and previously undiscovered) mathematical analogy: between the Grad-Shafranov equation and the cubic Schrödinger equation for solitons. The solutions we obtain are exact and can be derived analytically. The new class of soliton-like solutions of the Grad-Shafranov equation represents legitimate magnetic equilibria. Being legitimate equilibria does not automatically make the soliton-like solutions realistic representations of astrophysics jets. However, several features of the new solutions make them attractive candidates. First, the soliton-like solutions display a repetitive series of plasma blobs very reminiscent of the knotty structure of many jets (several observed jets can be shown as examples). Second, the soliton-like solutions naturally imply the presence of reconnection, a feature that has been suggested to explain the observed synchrotron radiation. Third, the generation of soliton-like solutions relies on processes that have been already proven by simulations conducted on similar configurations of the Sun’s corona. Finally, and most importantly, unlike solutions suggested in the existing literature, solitons can remain collimated indefinitely, providing an explanation for the observed collimation of jets on the kpc scale.
Bulletin of the American Astronomical Society,
35#2
© 2003. The American Astronomical Soceity.