Magnetic Rossby waves in the solar tachocline and Rieger-type periodicities - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




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Abstract: Apart from the 11-year solar cycle, another periodicity around 155-160 dayswas discovered during solar cycle 21 in high energy solar flares, and itspresence in sunspot areas and strong magnetic flux has been also reported. Thisperiodicity has an elusive and enigmatic character, since it usually appearsonly near the maxima of solar cycles, and seems to be related with a periodicemergence of strong magnetic flux at the solar surface. Therefore, it isprobably connected with the tachocline, a thin layer located near the base ofthe solar convection zone, where strong dynamo magnetic field is stored. Westudy the dynamics of Rossby waves in the tachocline in the presence of atoroidal magnetic field and latitudinal differential rotation. Our analysisshows that the magnetic Rossby waves are generally unstable and that the growthrates are sensitive to the magnetic field strength and to the latitudinaldifferential rotation parameters. Variation of the differential rotation andthe magnetic field strength throughout the solar cycle enhance the growth rateof a particular harmonic in the upper part of the tachocline around the maximumof the solar cycle. This harmonic is symmetric with respect to the equator andhas a period of 155-160 days. A rapid increase of the wave amplitude could giveplace to a magnetic flux emergence leading to observed periodicities in solaractivity indicators related with magnetic flux.



Autor: T.V. Zaqarashvili, M. Carbonell, R. Oliver, J.L. Ballster

Fuente: https://arxiv.org/







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