Journal ArticleDOI
Dynamic variations at the base of the solar convection zone
R. Howe,Jørgen Christensen-Dalsgaard,Frank Hill,Rudolf Komm,R. M. Larsen,Jesper Schou,Michael Thompson,Juri Toomre +7 more
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TLDR
Changes in the rotation of the sun near the base of its convective envelope are detected, including a prominent variation with a period of 1.3 years at low latitudes, which may generate the 22-year cycles of magnetic activity.Abstract:
We have detected changes in the rotation of the sun near the base of its convective envelope, including a prominent variation with a period of 1.3 years at low latitudes. Such helioseismic probing of the deep solar interior has been enabled by nearly continuous observation of its oscillation modes with two complementary experiments. Inversion of the global-mode frequency splittings reveals that the largest temporal changes in the angular velocity Ω are of the order of 6 nanohertz and occur above and below the tachocline that separates the sun's differentially rotating convection zone (outer 30% by radius) from the nearly uniformly rotating deeper radiative interior beneath. Such changes are most pronounced near the equator and at high latitudes and are a substantial fraction of the average 30-nanohertz difference in Ω with radius across the tachocline at the equator. The results indicate variations of rotation close to the presumed site of the solar dynamo, which may generate the 22-year cycles of magnetic activity.read more
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Journal ArticleDOI
Detectability of large-scale flows in global helioseismic data: A numerical experiment
Markus Roth,R. Howe,Rudolf Komm +2 more
TL;DR: In this article, the authors search for large-scale, long-lived structures in the convection zone by using global helioseismol- ogy results combined with quasi-degenerate perturbation the- ory and numerical simulations.
Journal ArticleDOI
Periodicity analysis of galactic cosmic rays using Fourier, Hilbert, and higher-order spectral methods
TL;DR: In this article, the effects of modulation are continuously measured by the well-established world-wide neutron monitor network and the characteristic features of nonlinear coupling and complex phase relationships between various harmonics present in GCRs and solar activity proxies are analyzed.
Probing the solar surface: the oblateness and astrophysical consequences
TL;DR: Based on accurate space-and ground-based observations, the authors argued that the oblateness of the Sun is time dependent, i.e., at high activity, only the dipolar moment c 2 has a significant effect, but at the time of low activity, c 4 is predominant.
Journal ArticleDOI
Short-Term Variations in the Equatorial Rotation Rate of Sunspot Groups
J. Javaraiah,L. Bertello +1 more
TL;DR: In this article, the authors compared the results from the fast Fourier transform (FFT), the maximum entropy method (MEM), and the Morlet wavelet power-spectra of the solar equatorial rotation rates determined from SOON and DPD sunspot-group data during the period 1986-to-2007 with those of the Mount Wilson Doppler-velocity data, during the same period determined by Javaraiah et al.
Journal ArticleDOI
Phase and amplitude asymmetry in the quasi-biennial oscillation of solar Hα flare activity
TL;DR: In this article, the phase and amplitude asymmetry of solar QBO of H alpha flare activity in the northern and southern hemispheres is studied by the ensemble empirical mode decomposition, the cross-correlation analysis, and the wavelet transform technique.
References
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Journal ArticleDOI
Abundances of the elements: Meteoritic and solar
Edward Anders,Nicolas Grevesse +1 more
TL;DR: In this article, new abundance tables have been compiled for C1 chondrites and the solar photosphere and corona, based on a critical review of the literature to mid-1988.
Journal ArticleDOI
The Solar Oscillations Investigation - Michelson Doppler Imager
Philip H. Scherrer,R. S. Bogart,R. I. Bush,J. T. Hoeksema,Alexander G. Kosovichev,Jesper Schou,W. Rosenberg,L. Springer,T. D. Tarbell,A. M. Title,C. J. Wolfson,I. Zayer +11 more
TL;DR: The Michelson Doppler Imager (MDI) as mentioned in this paper was used to probe the interior of the Sun by measuring the photospheric manifestations of solar oscillations, revealing the static and dynamic properties of the convection zone and core.
Book ChapterDOI
The Solar Oscillations Investigation — Michelson Doppler Imager
Philip H. Scherrer,R. S. Bogart,R. I. Bush,J. T. Hoeksema,Alexander G. Kosovichev,Jesper Schou,W. Rosenberg,L. Springer,T. D. Tarbell,A. M. Title,C. J. Wolfson,I. Zayer +11 more
TL;DR: The Solar Oscillations Investigation (SOI) as mentioned in this paper uses the Michelson Doppler Imager (MDI) instrument to probe the interior of the Sun by measuring the photospheric manifestations of solar oscillations.
Journal ArticleDOI
Helioseismic Studies of Differential Rotation in the Solar Envelope by the Solar Oscillations Investigation Using the Michelson Doppler Imager
Jesper Schou,H. M. Antia,Sarbani Basu,R. S. Bogart,R. I. Bush,S. M. Chitre,Joergen Christensen-Dalsgaard,M. Di Mauro,W. A. Dziembowski,Antonio Eff-Darwich,Douglas Gough,Deborah A. Haber,J. T. Hoeksema,R. Howe,S. G. Korzennik,Alexander G. Kosovichev,R. M. Larsen,R. M. Larsen,Frank P. Pijpers,Philip H. Scherrer,Takashi Sekii,Theodore D. Tarbell,Alan M. Title,Michael Thompson,Juri Toomre +24 more
TL;DR: In this article, the authors report on joint helioseismic analyses of solar rotation in the convection zone and in the outer part of the radiative core using the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) spacecraft.
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