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Solar Supergranulation Revealed as a Superposition of Traveling Waves40 years ago two new solar phenomena were described: supergranulation and the five-minute solar oscillations. While the oscillations have since been explained and exploited to determine the properties of the solar interior, the supergranulation has remained unexplained. The supergranules, appearing as convective-like cellular patterns of horizontal outward flow with a characteristic diameter of 30 Mm and an apparent lifetime of 1 day, have puzzling properties, including their apparent superrotation and the minute temperature variations over the cells. Using a 60-day sequence of data from the MDI (Michelson-Doppler Imager) instrument onboard the SOHO (Solar and Heliospheric Observatory) spacecraft, we show that the supergranulation pattern is formed by a superposition of traveling waves with periods of 5-10 days. The wave power is anisotropic with excess power in the direction of rotation and toward the equator, leading to spurious rotation rates and north-south flows as derived from correlation analyses. These newly discovered waves could play an important role in maintaining differential rotation in the upper convection zone by transporting angular momentum towards the equator.
Document ID
20020081295
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Gizon, L.
(Stanford Univ. Stanford, CA United States)
Duvall, T. L., Jr.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Schou, J.
(Stanford Univ. Stanford, CA United States)
Oegerle, William
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Solar Physics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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