Solar Dynamo and Magnetic Self-Organization
2010
It is well established that magnetic fields exist in astronomical objects of all scales, in planets, stars,galaxies and clusters of galaxies. Magnetic fields play a crucial role in star formation, solar and stel-lar activity, pulsars, magnetars, accretion disks, formation and stability jets, origin of cosmic rays,and stability of galactic disks. It is generally accepted that cosmic magnetic fields are producedby dynamo processes operating on various scales. In these processes the magnetic field is main-tained against Ohmic dissipation by turbulent motions, and despite the turbulent nature it showsremarkable self-organization properties, forming sunspots and starspots, magnetic loop structures,magnetic spiral arms etc. These phenomena show striking similarity suggesting that the basic phys-ical mechanisms are essentially the same.The Sun is our Rosetta stone when it comes to magnetic-field studies in the entire Universe. Thesolar magnetism is studied in great details, from global fields of the interior by helioseismology,to the smallest resolved and even unresolved scales by new large ground-based telescopes (SST,GREGOR, BBSO NST) and from space (SOHO, RHESSI, STEREO, Hinode, and SDO (scheduledfor launch in 2009). In addition, significant progress has been made in realistic numerical MHDsimulations. This progress in observations and modeling provides a good basis for solving theproblem of the solar dynamo and formation of self-organized magnetic structures during the nextdecade. This will have tremendous impact in many fields of astrophysics.However, this new science opportunity requires focused coordinated efforts in observations,modeling and theory. This opportunity can be realized with relatively modest investments, mostly,for supporting the projects that already exist or are under development. The Sun is the only objectthat can be observed to the level of details sufficient for investigation of the basic physical processesin a magnetized astrophysical plasma. These processes are a cornerstone of modern astrophysics.A key element of this opportunity is the understanding of interlinks between small-scale turbu-lent properties of magnetized plasma and large-scale dynamo processes. It has been long assumedthat the turbulent properties, such as turbulent diffusivity and helicity, define the large-scale behaviorof the magnetized plasma with some simple back-reaction, but recent plasma experiments and theo-retical studies showed that the large-scale flows and structures may significantly alter the turbulence,and that this may cause large-scale organization in plasma
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