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Solar activity is a process driven by many independent but interconnected phenomena. Although the 11-year cycle is the result of operation of the dynamo mechanism, the cause of longer secular variations is not clear. In search of such a…

Solar and Stellar Astrophysics · Physics 2025-11-07 M. M. Katsova , V. N. Obridko , D. D. Sokoloff , N. V. Emelianov

Recent analyses of helioseismological observations seem to suggest the presence of two new phenomena connected with the dynamics of the solar convective zone. Firstly, there are present torsional oscillations with periods of about 11 years,…

Astrophysics · Physics 2009-10-31 Eurico Covas , Reza Tavakol , David Moss

We describe systematic changes in the centroid frequencies and the splitting coefficients as found using data from MDI on board SOHO, covering cycle 23. The data allow us to construct a seismic map of the evolving solar activity -- covering…

Astrophysics · Physics 2007-05-23 W. A. Dziembowski , Philip R. Goode

Solar activity has significantly changed over the last two Schwabe cycles. After a long and deep minimum at the end of Cycle 23, the weaker activity of Cycle 24 contrasts with the previous cycles. In this work, the response of the solar…

Solar and Stellar Astrophysics · Physics 2015-06-24 D. Salabert , R. A. Garcia , S. Turck-Chieze

The 11-year cycle of solar activity follows Hale's law by reversing the magnetic polarity of leading and following sunspots in bipolar regions during the minima of activity. In the 1996-97 solar minimum, most solar activity emerged in…

Astrophysics · Physics 2009-10-31 E. E. Benevolenskaya , J. T. Hoeksema , A. G. Kosovichev , P. H. Scherrer

Using full-disk observations obtained with the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) spacecraft, we present variations of the solar acoustic mode frequencies caused by the solar activity…

Astrophysics · Physics 2008-11-26 M. C. Rabello-Soares , S. G. Korzennik , J. Schou

The study of the global structure of the large-scale magnetic field of the Sun is extremely important for creating a theoretical model of the dynamics of the Sun and predictions of the real situation in the helio- and geomagnetosphere. The…

Solar and Stellar Astrophysics · Physics 2023-02-13 Elena Gavryuseva

Analysis of synoptic data from the Vector Stokes Magnetograph (VSM) of the Synoptic Optical Long-term Investigations of the Sun (SOLIS) and the NASA/NSO Spectromagnetograph (SPM) at the NSO/Kitt Peak Vacuum Telescope facility shows that the…

Solar and Stellar Astrophysics · Physics 2016-02-09 Alexander V. Mordvinov , Alexei A. Pevtsov , Luca Bertello , Gordon J. D. Petrie

The dynamics of the solar radiative interior are still poorly constrained by comparison to the convective zone. This disparity is even more marked when we attempt to derive meaningful temporal variations. Many data sets contain a small…

Solar and Stellar Astrophysics · Physics 2015-06-05 Antonio Eff-Darwich , Sylain G. Korzennik

Although the energetic phenomena of the Sun (flares, coronal mass injections etc.) exhibit intermittent stochastic behavior in their rate of occurrence, they are well correlated to the variations of the solar cycle. In this work we study…

Solar and Stellar Astrophysics · Physics 2010-09-23 E. Gini , J. Polygiannakis , A. Hillaris , P. Preka-Papadema , X. Moussas

Solar differential rotation exhibits a prominent feature: its cyclic variations over the solar cycle, referred to as zonal flows or torsional oscillations, are observed throughout the convection zone. Given the challenge of measuring…

Solar and Stellar Astrophysics · Physics 2024-02-27 Krishnendu Mandal , Alexander G. Kosovichev , Valery V. Pipin

In this paper, I present the results on large-scale evolution of density turbulence of solar wind in the inner heliosphere during 1985 - 2009. At a given distance from the Sun, the density turbulence is maximum around the maximum phase of…

Solar and Stellar Astrophysics · Physics 2011-04-04 P. K. Manoharan

Analysis of over 36 years of time series data from the NSO/AFRL/Sac Peak K-line monitoring program elucidates five components of the variation of the seven measured chromospheric parameters: (a) the solar cycle (period ~ 11 years), (b)…

Solar and Stellar Astrophysics · Physics 2015-06-15 Jeffrey Scargle , Stephen Keil , Pete Worden

Detailed study of the solar magnetic field is crucial to understand its generation, transport and reversals. The timing of the reversals may have implications on space weather and thus identification of the temporal behavior of the critical…

We use rotation splittings derived from very long and long time series, namely 25.2, 12.6 and 6.3 year long, computed by Korzennik (2023) independent methodology to characterize the solar tachocline and its variation with latitude and time.…

Solar and Stellar Astrophysics · Physics 2026-02-04 Sylvain G. Korzennik , Antonio Eff-Darwich

Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI), we characterize both short-term (solar rotation) and long-term (solar cycle) changes of the solar spectral irradiance (SSI) between 265-500 nm during the on-going…

Solar and Stellar Astrophysics · Physics 2016-10-26 S. V. Marchenko , M. T. DeLand , J. L. Lean

After decades of effort, the solar activity cycle is exceptionally well characterized but it remains poorly understood. Pioneering work at the Mount Wilson Observatory demonstrated that other sun-like stars also show regular activity…

Solar and Stellar Astrophysics · Physics 2017-09-01 Travis S. Metcalfe , Jennifer van Saders

Recently, Rozelot & Eren pointed out that the first solar gravitational moment (J2) might exhibit a temporal variation. The suggested explanation is through the temporal variation of the solar rotation with latitude. This issue is deeper…

Solar and Stellar Astrophysics · Physics 2023-01-19 Saliha Eren , Jean-Pierre Rozelot

The discovery of the solar activity cycle was linked from the outset to the observation of the temporal variability of sunspots, which we know to be the result of complex processes associated with the dynamics of inner layers. Numerous…

Solar and Stellar Astrophysics · Physics 2025-03-04 Jean-Pierre Rozelot , Alexander Kosovichev , Irina Kitiashvili

We studied the presence and spatiotemporal evolution of the quasi-biennial oscillations (QBOs) in the rotation rate residuals at target depths of 0.90$R_{\odot}$, 0.95$R_{\odot}$, and 0.99$R_{\odot}$ and at low (0 -- 30$^{\circ}$), mid (30…

Solar and Stellar Astrophysics · Physics 2021-10-20 Fadil Inceoglu , Rachel Howe , Paul T. M. Loto'aniu