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Solar fundamental pulsation and the origin of the long period Alfvén waves observed in the solar wind

Published online by Cambridge University Press:  01 November 2006

Teimuraz V. Zaqarashvili
Affiliation:
Abastumani Astrophysical Observatory, Al. Kazbegi ave. 2a, 0160 Tbilisi, Georgia, email: temury@genao.org
Gaetano Belvedere
Affiliation:
Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Universitá di Catania, Via S.Sofia 78, I-95123 Catania, Italy email: gbelvedere@ct.astro.it
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Abstract

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Ulysses spacecraft discovered the long-period, outwardly propagating Alfvén waves in the solar polar regions (Balogh et al. 1995). Here we suggest that the waves may be generated in the solar interior due to the pulsation of the Sun in the fundamental radial mode or in low-frequency g-modes. The period of fundamental mode is about 1 hour, while the period of g-modes can be longer. The pulsation causes a periodical variation of density and large-scale magnetic field, this affecting the Alfvén speed in the solar interior. Consequently the Alfvén waves with the half frequency of pulsation (i.e. with the double period) can be parametrically amplified in the interior below the convection zone due to the recently suggested swing wave-wave interaction. Therefore the amplified Alfvén waves have periods of several hours. The waves can propagate upwards through the convection zone to the solar atmosphere and cause the observed long-period Alfvén oscillations in the solar wind.

Type
Contributed Papers
Copyright
© 2006 International Astronomical Union