MAGNETIC ROSSBY WAVES IN THE SOLAR TACHOCLINE AND RIEGER-TYPE PERIODICITIES

Journal Article · Mon Feb 01 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/2/749· OSTI ID:21392299

Zaqarashvili, Teimuraz V ^[1]; Carbonell, Marc ^[2]; Oliver, Ramon

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1. Abastumani Astrophysical Observatory at Faculty of Physics and Mathematics, Ilia Chavchavadze State University, Chavchavadze Ave 32, 0179 Tbilisi (Georgia)
2. Departament de Matematiques i Informatica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

Apart from the eleven-year solar cycle, another periodicity around 155-160 days was discovered during solar cycle 21 in high-energy solar flares, and its presence in sunspot areas and strong magnetic flux has been also reported. This periodicity has an elusive and enigmatic character, since it usually appears only near the maxima of solar cycles, and seems to be related with a periodic emergence of strong magnetic flux at the solar surface. Therefore, it is probably connected with the tachocline, a thin layer located near the base of the solar convection zone, where a strong dynamo magnetic field is stored. We study the dynamics of Rossby waves in the tachocline in the presence of a toroidal magnetic field and latitudinal differential rotation. Our analysis shows that the magnetic Rossby waves are generally unstable and that the growth rates are sensitive to the magnetic field strength and to the latitudinal differential rotation parameters. Variation of the differential rotation and the magnetic field strength throughout the solar cycle enhance the growth rate of a particular harmonic in the upper part of the tachocline around the maximum of the solar cycle. This harmonic is symmetric with respect to the equator and has a period of 155-160 days. A rapid increase of the wave amplitude could give rise to a magnetic flux emergence leading to observed periodicities in solar activity indicators related to magnetic flux.

• OSTI ID: 21392299
• Journal Information: Astrophysical Journal, Vol. 709, Issue 2; Other Information: DOI: 10.1088/0004-637X/709/2/749; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETOHYDRODYNAMICS
ROTATION
SOLAR CYCLE
SOLAR FLARES
SUN
SUNSPOTS
THIN FILMS
FILMS
FLUID MECHANICS
HYDRODYNAMICS
MAIN SEQUENCE STARS
MECHANICS
MOTION
SOLAR ACTIVITY
STARS
STARSPOTS
STELLAR ACTIVITY
STELLAR FLARES