REVIEW 3 major objections 6 minor 68 references
On the Origin of Solar Torsional Oscillations and Extended Solar Cycle
T0 review · 3 major / 6 minor · reviewed 2026-08-14 · deepseek-v4-flash
Pith's one-line read The extended 22-year pattern of the Sun's torsional oscillations arises from overlapping dynamo waves plus magnetic quenching of convective heat transport.
desk verdict First self-consistent mean-field model of the 22-year extended torsional oscillation pattern; the mechanism is plausible but hinges on an unvalidated heat-transport closure and needs a cleaner ablation. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The carrier of the argument is a coupled system of mean-field equations for the large-scale magnetic field, angular momentum, and heat transport in the solar convection zone, with the magnetically induced Lambda-effect component H(0,rho), a non-dissipative angular-momentum flux arising from density stratification, and the magnetic quenching functions in the eddy heat-conductivity tensor. The key mechanism is the magnetic shadow: the large-scale toroidal magnetic field suppresses the convective energy flux, changing the mean entropy gradient; this perturbs the Taylor-Proudman balance and drives the meridional circulation variations that, combined with the overlapping dynamo waves, produce the 22-year extended torsional oscillation pattern.
What would settle it
A helioseismic measurement that resolved the solar-cycle variations of the meridional circulation in the latitude band 10 to 60 degrees and found no approximately one meter per second converging flow into the activity belts, or found such variations decoupled from the zonal flow pattern, would falsify the proposed mechanism.
Extended reading notes
Core claim
The central discovery is that the extended 22-year pattern of the solar torsional oscillations emerges in a nonlinear mean-field dynamo model when two ingredients are present together: (i) a dynamo wave pattern whose successive 11-year cycles overlap in the time-latitude diagram, so that the high-latitude start of the next cycle begins before the previous cycle's equatorial branch has faded, and (ii) magnetic quenching of the eddy heat conductivity, which creates cyclic variations of the convective energy flux, the magnetic shadow, perturbs the Taylor-Proudman balance, and thereby drives cyclic variations of the meridional circulation. The meridional circulation variations act as a coherent transport term that moves the torsional wave equatorward over the full 22-year cycle. The model also shows that different parts of the observed zonal-acceleration pattern are controlled by different forces: the polar branch by the large-scale Lorentz force and meridional flow, mid-latitudes by the Lorentz force and the magnetically induced Lambda-effect, and the equatorial region by the meridional circulation variations.
Load-bearing premise
The whole explanation depends on the assumption that the mathematical formulas used for the magnetic suppression of turbulent heat transport and angular-momentum transport in the convection zone match what really happens in the Sun.
Editorial extensions
If this is right
- The extended solar cycle is a natural output of distributed dynamo models, not requiring a flux-transport dynamo with a separate tachocline storage region.
- Both identified conditions are necessary: reducing the cycle overlap (as in model M3) or removing the heat-transport quenching (as in model M7) eliminates the extended torsional mode.
- Different latitude bands of the zonal acceleration pattern are forced by different physical agents, so helioseismic maps of acceleration can be used to infer which force dominates in each region.
- The model reproduces the observed phase relation between flow deceleration and active regions, and the observed zonal acceleration amplitude of about 2 to 4 times ten to the minus eight meters per second squared.
- The extended mode appears for both single-cell and double-cell meridional circulation structures, making the result insensitive to that unresolved aspect of the deep flow.
Reading between the lines
- If this mechanism operates on the Sun, it should also leave a trace in other solar-type stars: the duration and visibility of an extended 22-year (or longer) torsional pattern should correlate with how strongly successive magnetic cycles overlap, a quantity that asteroseismic or activity-cycle observations might constrain.
- The magnetic shadow effect implies a specific phase relation between photospheric luminosity variations and the toroidal magnetic field strength; high-precision broadband photometry of the Sun could be checked against the model's predicted convective-flux variations.
- Long, deep minima such as the Maunder minimum, where cycle overlap is weak or absent, should show a disrupted or missing extended torsional pattern, a prediction testable by reconstructing zonal flows from historical sunspot or coronal data.
- The predicted near-surface meridional circulation variations, converging toward the activity belts with an amplitude of order one meter per second, provide a concrete target for local helioseismology with current and future instruments.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents a nonlinear mean-field model of the solar convection zone that couples a distributed dynamo, angular momentum transport, and heat transport. The model reproduces cyclic magnetic activity, differential rotation, and meridional circulation, and produces zonal flow variations. The central claim is that the extended 22-year pattern of solar torsional oscillations is explained by two necessary conditions: (a) overlap of successive dynamo waves in the time-latitude diagram, and (b) cyclic variations of the meridional circulation caused by magnetic quenching of convective heat transport (the magnetic shadow effect). The claim is supported by ablation runs: M3 (increased anisotropic diffusivity reducing cycle overlap) loses the extended mode, M7 (no magnetic quenching of heat conductivity) loses it, while M8 (only heat-transport quenching active) retains it. The paper also decomposes the zonal forces and shows that different parts of the torsional oscillation pattern are driven by different forces. The extended pattern is an emergent output, not an imposed boundary condition.
Significance. If correct, the paper provides the first self-consistent mean-field explanation of the extended 22-year torsional oscillation mode, tying it to the overlap of dynamo cycles and the magnetic shadow effect in the bulk of the convection zone. The model is ambitious in its coupling of the dynamo, differential rotation, meridional circulation, and heat transport, and the ablation tests are a genuine strength: they demonstrate that the two conditions are individually necessary in the model. The force decomposition into Lorentz force, turbulent-stress quenching, dynamo-induced Lambda effect, meridional-circulation torque, and inertial force is informative and gives a concrete physical narrative. The main weakness is that the two conditions rest on unvalidated mean-field closures and partly undocumented control runs; nevertheless, the central claim is currently defensible and the missing documentation is fixable within the manuscript's scope.
major comments (3)
- [Appendix A, Eq. (A13)] The central condition (b) rests on the magnetic quenching functions phi_chi^(I),(||)(beta) in Eq. (A13), which are analytic SOCA-style closures for a homogeneous mean field. The model evaluates beta using the volume-averaged axisymmetric B, which reaches about 5 kG near the tachocline and about 1 kG at 0.9R, whereas the real convective turbulence is intermittent; if the small-scale field is much stronger than the mean, the 'magnetic shadow' and the associated Taylor-Proudman balance and meridional-circulation perturbations could be overestimated. No independent validation of Eq. (A13) by DNS or observations is given. Please provide a sensitivity study (e.g., varying the quenching amplitude) or direct numerical validation to show that the mechanism is not an artifact of the closure.
- [Sec. 3.3, Table 1] The paper mentions 'a special run, in which we suppressed the variations' of the meridional circulation and states it gives results 'similar to model M7,' but this run is not listed in Table 1 and its zonal-acceleration diagram is not shown. This is load-bearing because M7 itself removes all beta-quenching in chi_ij, which changes the mean thermodynamic state and the dynamo cycle period (25 yr and 1.8 yr delay vs 22.9 yr and 1.2 yr in M1), so the disappearance of the extended mode in M7 could be due to the altered background state or cycle overlap rather than to the suppression of cyclic meridional circulation variations. Please document the special run (parameters, table entry, figure) so that condition (b) is genuinely causally isolated.
- [Sec. 4, Fig. 1] The comparison with observations is qualitative: the paper admits that the tachocline shear is about twice too high, the subsurface shear about twice too small, the latitudinal width of the zonal acceleration pattern narrower than observed, and the pattern inclination different. Since the torsional oscillations are driven by the force balance derived from this background, it is not clear that the extended mode would survive with a closer match to the helioseismic rotation profile. A quantitative comparison (e.g., normalized cross-correlation of the observed and modeled time-latitude acceleration maps over a common window) would establish that the model's extended mode is the same phenomenon as the observed one.
minor comments (6)
- [Abstract] The phrase 'a combinations of magnetic field effects' should be 'a combination of magnetic field effects'.
- [Table 1] The entries '-/-' in the M2 row are ambiguous; the caption should state explicitly that '-/-' denotes the same full nonlinear treatment as in M1, or should list each effect.
- [Fig. 5 caption] The last two panels are both labeled 'e)'; the panel showing the Taylor-Proudman balance and delta F_c/F_sun should be labeled 'f)'.
- [Sec. 2.1, Eq. (1)] The term E dot (nabla x B) in the energy equation should have its sign and physical meaning as the Joule-heating-like term clarified, since it is not discussed elsewhere in the text.
- [Sec. 3.1] The statement that the model agrees well with helioseismology is qualified by factor-of-two mismatches; it would be helpful to quote the rms difference in the convection zone rather than only the maximum difference.
- [References] The reference list contains inconsistencies (e.g., 'Kitchatinov et al. 1994' appears twice with different author orders); please unify the entries.
Circularity Check
No significant circularity: the extended 22-year torsional pattern is a model output, not an input, and the control runs provide independent ablation support.
full rationale
The paper's derivation chain is self-contained with respect to the claimed prediction. The torsional oscillations are obtained by solving the coupled mean-field equations for angular momentum (Eq. 4), meridional circulation/vorticity (Eq. 5), heat transport (Eq. 1), and induction (Eq. 8); the observed 22-year extended pattern does not appear as a boundary condition, source term, or fitted target. Model parameters in Table 1 are carried over from previous work or varied for sensitivity runs, and no helioseismic zonal-flow data are inverted to produce the predicted acceleration. The two necessary conditions are tested by ablation: model M3 reduces dynamo-cycle overlap via anisotropic diffusivity and loses the extended pattern; model M7 suppresses magnetic quenching of the eddy heat conductivity and also loses it; model M8 isolates the heat-flux-quenching channel. These are numerical experiments whose outcomes differ from the full model, so the mechanism is not equivalent to its inputs by construction. The analytic closures used for the Lambda-effect and heat conductivity (Appendix A, Eqs. A8 and A13) are imported from prior mean-field papers, some coauthored by the present authors, but this is provenance rather than load-bearing circularity: the central claim would fail or survive on the model-data comparison, which is externally falsifiable. The paper does contain a missing-evidence caveat: the 'special run' suppressing meridional-circulation variations is mentioned in Sec. 3.3 but not listed in Table 1 or shown, so the causal isolation of condition (b) is asserted more strongly than documented; and the correctness of the Eq. (A13) quenching functions is an assumption rather than a validated result. These are accuracy and reproducibility risks, not circular reduction, and they do not change the verdict of no significant circularity.
Assumptions & free parameters
free parameters (7)
- C_alpha (alpha-effect coefficient) =
0.04
- Pm_T (turbulent magnetic Prandtl number) =
10
- Rm (magnetic Reynolds number) =
10^6
- l_min (mixing-length saturation parameter) =
0.02R (M1, M3), 0.01R (M2)
- eta_A (anisotropic eddy-diffusivity parameter) =
0 (most models), 2 sigma_T (M3)
- a (turbulence anisotropy parameter) =
2
- Pr_T (turbulent Prandtl number) =
0.75
assumptions (4)
- domain assumption Mean-field closure expressions for the Lambda effect, eddy heat conductivity, and their magnetic quenching (Eqs. A6-A13) accurately describe turbulent transport in the solar convection zone.
- domain assumption The solar dynamo is a distributed dynamo operating in the bulk of the convection zone, with the tachocline acting as a storage region.
- domain assumption Mixing-length theory with a MESA reference state provides the background stratification and convective turnover time.
- domain assumption Magnetic helicity conservation for small-scale magnetic field governs alpha quenching.
Cite this review
Pith. "Pith review of On the Origin of Solar Torsional Oscillations and Extended Solar Cycle." pith.science (2026). https://pith.science/paper/5WBJPXJ2
@misc{pith2026190804525,
author = {Pith},
title = {Pith review of: On the Origin of Solar Torsional Oscillations and Extended Solar Cycle},
year = {2026},
howpublished = {\url{https://pith.science/paper/5WBJPXJ2}},
note = {Machine review of arXiv:1908.04525}
}
read the original abstract
We present a nonlinear mean-field model of the solar interior dynamics and dynamo, which reproduces the observed cyclic variations of the global magnetic field of the Sun, as well as the differential rotation and meridional circulation. Using this model, we explain, for the first time, the extended 22-year pattern of the solar torsional oscillations, observed as propagation of zonal variations of the angular velocity from high latitudes to the equator during the time equal to the full dynamo cycle. In the literature, this effect is usually attributed to the so-called "extended solar cycle". In agreement with the commonly accepted idea our model shows that the torsional oscillations can be driven by a combinations of magnetic field effects acting on turbulent angular momentum transport, and the large-scale Lorentz force. We find that the 22-year pattern of the torsional oscillations can result from a combined effect of an overlap of subsequent magnetic cycles and magnetic quenching of the convective heat transport. The latter effect results in cyclic variations of the meridional circulation in the sunspot formation zone, in agreement with helioseismology results. The variations of the meridional circulation together with other drivers of the torsional oscillations maintain their migration to the equator during the 22-year magnetic cycle, resulting in the observed extended pattern of the torsional oscillations.
Reference graph
Works this paper leans on
-
[1]
2008, in Astronomical Society of the Pacific Conference Series, Vol
Altrock , R., Howe , R., & Ulrich , R. 2008, in Astronomical Society of the Pacific Conference Series, Vol. 383, Subsurface and Atmospheric Influences on Solar Activity, ed. R. Howe , R. W. Komm , K. S. Balasubramaniam , & G. J. D. Petrie , 335
work page 2008
-
[2]
Altrock , R. C. 1997, , 170, 411, 10.1023/A:1004958900477
-
[3]
Beaudoin , P., Charbonneau , P., Racine , E., & Smolarkiewicz , P. K. 2013, , 282, 335, 10.1007/s11207-012-0150-2
-
[4]
2017, , 835, 9, 10.3847/1538-4357/835/1/9
Bekki , Y., & Yokoyama , T. 2017, , 835, 9, 10.3847/1538-4357/835/1/9
-
[5]
B \"o ning , V. G. A., Roth , M., Jackiewicz , J., & Kholikov , S. 2017, , 845, 2, 10.3847/1538-4357/aa7af0
- [6]
-
[7]
1991, Geophysical & Astrophysical Fluid Dynamics, 61, 179, 10.1080/03091929108229043
Brandenburg, A., Moss, D., R \" u diger, G., & Tuominen, I. 1991, Geophysical & Astrophysical Fluid Dynamics, 61, 179, 10.1080/03091929108229043
- [8]
Show all 68 references
-
[9]
H., & Sch \"u ssler , M
Cameron , R. H., & Sch \"u ssler , M. 2017, , 599, A52, 10.1051/0004-6361/201629746
2017 doi
-
[10]
R., & Dikpati , M
Choudhuri , A. R., & Dikpati , M. 1999, , 184, 61
1999
-
[11]
2000, , 360, L21
Covas , E., Tavakol , R., Moss , D., & Tworkowski , A. 2000, , 360, L21
2000
-
[12]
1999, , 518, 508, 10.1086/307269
Dikpati , M., & Charbonneau , P. 1999, , 518, 508, 10.1086/307269
1999 doi
-
[13]
Durney , B. R. 1999, , 511, 945, 10.1086/306696
1999 doi
-
[14]
K., de Gouveia Dal Pino , E
Guerrero , G., Smolarkiewicz , P. K., de Gouveia Dal Pino , E. M., Kosovichev , A. G., & Mansour , N. N. 2016 a , , 828, L3, 10.3847/2041-8205/828/1/L3
2016 doi
-
[15]
2016 b , , 819, 104, 10.3847/0004-637X/819/2/104
---. 2016 b , , 819, 104, 10.3847/0004-637X/819/2/104
2016 doi
-
[16]
2018, , 862, L5, 10.3847/2041-8213/aad1ed
Howe , R., Hill , F., Komm , R., et al. 2018, , 862, L5, 10.3847/2041-8213/aad1ed
2018 doi
-
[17]
2011, Journal of Physics Conference Series, 271, 012074, 10.1088/1742-6596/271/1/012074
---. 2011, Journal of Physics Conference Series, 271, 012074, 10.1088/1742-6596/271/1/012074
2011 doi
-
[18]
S., Arlt , R., et al
Jouve , L., Brun , A. S., Arlt , R., et al. 2008, , 483, 949, 10.1051/0004-6361:20078351
2008 doi
-
[19]
a pyl \"a , M. J., K \
K \"a pyl \"a , M. J., K \"a pyl \"a , P. J., Olspert , N., et al. 2016, , 589, A56, 10.1051/0004-6361/201527002
2016 doi
-
[20]
K \"a pyl \"a , P. J. 2019, , 622, A195, 10.1051/0004-6361/201732519
2019 doi
-
[21]
Kichatinov , L. L. 1988, Issledovaniia Geomagnetizmu Aeronomii i Fizike Solntsa, 82, 127
1988
-
[22]
L., & Nepomnyashchikh , A
Kitchatinov , L. L., & Nepomnyashchikh , A. A. 2017, Astronomy Letters, 43, 332, 10.1134/S106377371704003X
2017 doi
-
[23]
L., & Olemskoy , S
Kitchatinov , L. L., & Olemskoy , S. V. 2011, Astronomy Letters, 37, 286, 10.1134/S1063773711040037
2011 doi
-
[24]
L., Pipin , V
Kitchatinov , L. L., Pipin , V. V., & Ruediger , G. 1994, Astronomische Nachrichten, 315, 157
1994
-
[25]
L., R\"udiger, G., & Kueker, M
Kitchatinov, L. L., R\"udiger, G., & Kueker, M. 1994, , 292, 125
1994
-
[26]
2012, , 177, 10.1007/s11207-012-0073-y
Komm , R., Gonz \'a lez Hern \'a ndez , I., Hill , F., et al. 2012, , 177, 10.1007/s11207-012-0073-y
2012 doi
-
[27]
G., & Pipin , V
Kosovichev , A. G., & Pipin , V. V. 2019, , 871, L20, 10.3847/2041-8213/aafe82
2019 doi
-
[28]
G., Pipin , V
Kosovichev , A. G., Pipin , V. V., & Zhao , J. 2013, in Astronomical Society of the Pacific Conference Series, Vol. 479, Progress in Physics of the Sun and Stars: A New Era in Helio- and Asteroseismology, ed. H. Shibahashi & A. E. Lynas-Gray , 395
2013
-
[29]
G., & Zhao , J
Kosovichev , A. G., & Zhao , J. 2016, in Lecture Notes in Physics, Berlin Springer Verlag, Vol. 914, Lecture Notes in Physics, Berlin Springer Verlag, ed. J.-P. Rozelot & C. Neiner , 25
2016
-
[30]
G., Schou , J., Scherrer , P
Kosovichev , A. G., Schou , J., Scherrer , P. H., et al. 1997, , 170, 43, 10.1023/A:1004949311268
1997 doi
-
[31]
1980, Mean-Field Magnetohydrodynamics and Dynamo Theory (Berlin: Akademie-Verlag), 271
Krause, F., & R\"adler, K.-H. 1980, Mean-Field Magnetohydrodynamics and Dynamo Theory (Berlin: Akademie-Verlag), 271
1980
-
[32]
Kueker , M., Ruediger , G., & Pipin , V. V. 1996, , 312, 615
1996
-
[33]
u ker , M., Arlt , R., & R \
K \"u ker , M., Arlt , R., & R \"u diger , G. 1999, , 343, 977
1999
- [34]
-
[35]
1999, , 346, 111
Ludwig , H.-G., Freytag , B., & Steffen , M. 1999, , 346, 111
1999
-
[36]
Malkus , W. V. R., & Proctor , M. R. E. 1975, Journal of Fluid Mechanics, 67, 417, 10.1017/S0022112075000390
1975 doi
-
[37]
S., Brown , B
Miesch , M. S., Brown , B. P., Browning , M. K., Brun , A. S., & Toomre , J. 2011, in IAU Symposium, Vol. 271, IAU Symposium, ed. N. H. Brummell , A. S. Brun , M. S. Miesch , & Y. Ponty , 261--269
2011
-
[38]
1992, , 256, 371
Moss , D., & Brandenburg , A. 1992, , 256, 371
1992
-
[39]
1955, Astrophys
Parker, E. 1955, Astrophys. J., 122, 293
1955
-
[40]
2011, , 192, 3, 10.1088/0067-0049/192/1/3
Paxton , B., Bildsten , L., Dotter , A., et al. 2011, , 192, 3, 10.1088/0067-0049/192/1/3
2011 doi
-
[41]
2013, , 208, 4, 10.1088/0067-0049/208/1/4
Paxton , B., Cantiello , M., Arras , P., et al. 2013, , 208, 4, 10.1088/0067-0049/208/1/4
2013 doi
-
[42]
Pipin , V. V. 1999, , 346, 295
1999
-
[43]
2003, Geophysical and Astrophysical Fluid Dynamics, 97, 25, 10.1080/0309192021000053366
---. 2003, Geophysical and Astrophysical Fluid Dynamics, 97, 25, 10.1080/0309192021000053366
2003 doi
-
[44]
2004, Astronomy Reports, 48, 418, 10.1134/1.1744942
---. 2004, Astronomy Reports, 48, 418, 10.1134/1.1744942
2004 doi
-
[45]
2008, Geophysical and Astrophysical Fluid Dynamics, 102, 21
---. 2008, Geophysical and Astrophysical Fluid Dynamics, 102, 21
2008
-
[46]
2018, Journal of Atmospheric and Solar-Terrestrial Physics, 179, 185, 10.1016/j.jastp.2018.07.010
---. 2018, Journal of Atmospheric and Solar-Terrestrial Physics, 179, 185, 10.1016/j.jastp.2018.07.010
2018 doi
-
[47]
V., & Kitchatinov , L
Pipin , V. V., & Kitchatinov , L. L. 2000, Astronomy Reports, 44, 771, 10.1134/1.1320504
2000 doi
-
[48]
V., & Kosovichev , A
Pipin , V. V., & Kosovichev , A. G. 2011 a , ApJL, 727, L45, 10.1088/2041-8205/727/2/L45
2011 doi
-
[49]
2011 b , ApJ, 741, 1, 10.1088/0004-637X/741/1/1
---. 2011 b , ApJ, 741, 1, 10.1088/0004-637X/741/1/1
2011 doi
-
[50]
2014, , 785, 49, 10.1088/0004-637X/785/1/49
---. 2014, , 785, 49, 10.1088/0004-637X/785/1/49
2014 doi
- [51]
-
[52]
V., Sokoloff , D
Pipin , V. V., Sokoloff , D. D., & Usoskin , I. G. 2012, , 542, A26, 10.1051/0004-6361/201118733
2012 doi
-
[53]
P., & Antia , H
Rajaguru , S. P., & Antia , H. M. 2015, , 813, 114, 10.1088/0004-637X/813/2/114
2015 doi
- [54]
- [55]
-
[56]
2018, Journal of Plasma Physics, 84, 735840201, 10.1017/S0022377818000272
Rogachevskii , I., & Kleeorin , N. 2018, Journal of Plasma Physics, 84, 735840201, 10.1017/S0022377818000272
2018 doi
-
[57]
1989, Differential rotation and stellar convection
Ruediger , G. 1989, Differential rotation and stellar convection. Sun and the solar stars (Akademie-Verlag, Berlin)
1989
-
[58]
1995, , 296, 557
Ruediger , G., & Brandenburg , A. 1995, , 296, 557
1995
- [59]
-
[60]
Spruit , H. C. 2003, , 213, 1, 10.1023/A:1023202605379
2003 doi
-
[61]
Stenflo , J. O. 1992, in Astronomical Society of the Pacific Conference Series, Vol. 27, The Solar Cycle, ed. K. L. Harvey , 421
1992
-
[62]
O., & Guedel , M
Stenflo , J. O., & Guedel , M. 1988, , 191, 137
1988
-
[63]
2002, The sun: an introduction, 2nd edn
Stix , M. 2002, The sun: an introduction, 2nd edn. (Berlin : Springer), 521
2002
-
[64]
Ulrich , R. K. 2001, , 560, 466, 10.1086/322524
2001 doi
-
[65]
R., Altrocki , R
Wilson , P. R., Altrocki , R. C., Harvey , K. L., Martin , S. F., & Snodgrass , H. B. 1988, , 333, 748, 10.1038/333748a0
1988 doi
- [66]
- [67]
-
[68]
G., & Bogart , R
Zhao , J., Kosovichev , A. G., & Bogart , R. S. 2014, , 789, L7, 10.1088/2041-8205/789/1/L7
2014 doi
Reviewed August 14, 2026 · model on record in the stance chip above.
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