scholarly journals Changes in the Near-surface Shear Layer of the Sun

2022 ◽  
Vol 924 (1) ◽  
pp. 19
Author(s):  
H. M. Antia ◽  
Sarbani Basu
Keyword(s):  
Solar Cycle ◽  
Shear Layer ◽  
Solar Rotation ◽  
High Latitudes ◽  
Solar Cycles ◽  
Surface Shear ◽  
Near Surface ◽  
Radial Gradient ◽  
Cycle Dependence ◽  
Solar Rotation Rate

Abstract We use helioseismic data obtained over two solar cycles to determine whether there are changes in the near-surface shear layer (NSSL). We examine this by determining the radial gradient of the solar rotation rate. The radial gradient itself shows a solar-cycle dependence, and the changes are more pronounced in the active latitudes than at adjoining higher latitudes; results at the highest latitudes (≳70°) are unreliable. The pattern changes with depth, even within the NSSL. We find that the near-surface shear layer is deeper at lower latitudes than at high latitudes and that the extent of the layer also shows a small solar-cycle-related change.

scholarly journals The radial gradient of the near-surface shear layer of the Sun

2014 ◽  
Vol 570 ◽  
pp. L12 ◽  
Author(s):  
A. Barekat ◽  
J. Schou ◽  
L. Gizon
Keyword(s):  
Shear Layer ◽  
The Sun ◽  
Surface Shear ◽  
Near Surface ◽  
Radial Gradient

scholarly journals Hemispheric injection of magnetic helicity by surface flux transport

2019 ◽  
Vol 631 ◽  
pp. A138 ◽  
Author(s):  
G. Hawkes ◽  
A. R. Yeates
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Rotation ◽  
Surface Flux ◽  
Magnetic Helicity ◽  
Solar Cycles ◽  
Flux Transport ◽  
Transport Models ◽  
Radial Magnetic Field ◽  
Helicity Injection

Aims. We estimate the injection of relative magnetic helicity into the solar atmosphere by surface flux transport over 27 solar cycles (1700–2009). Methods. We determine the radial magnetic field evolution using two separate surface flux transport models: one driven by magnetogram inputs and another by statistical active region insertion guided by the sunspot number record. The injection of relative magnetic helicity is then computed from this radial magnetic field together with the known electric field in the flux transport models. Results. Neglecting flux emergence, solar rotation is the dominant contributor to the helicity injection. At high latitudes, the injection is always negative/positive in the northern/southern hemisphere, while at low latitudes the injection tends to have the opposite sign when integrated over the full solar cycle. The overall helicity injection in a given solar cycle depends on the balance between these two contributions. This net injected helicity correlates well with the end-of-cycle axial dipole moment.

scholarly journals The 22-year cycle in the geomagnetic 27-day recurrences reflecting on the F2-layer ionization

2004 ◽  
Vol 22 (4) ◽  
pp. 1171-1176 ◽  
Author(s):  
E. M. Apostolov ◽  
D. Altadill ◽  
M. Todorova
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Solar Rotation ◽  
Rotation Period ◽  
Sunspot Cycle ◽  
Solar Cycles ◽  
Solar Radio Flux ◽  
Critical Frequency Fof2 ◽  
Northern And Southern Hemispheres

Abstract. Solar cycle variations of the amplitudes of the 27-day solar rotation period reflected in the geomagnetic activity index Ap, solar radio flux F10.7cm and critical frequency foF2 for mid-latitude ionosonde station Moscow from the maximum of sunspot cycle 18 to the maximum of cycle 23 are examined. The analysis shows that there are distinct enhancements of the 27-day amplitudes for foF2 and Ap in the late declining phase of each solar cycle while the amplitudes for F10.7cm decrease gradually, and the foF2 and Ap amplitude peaks are much larger for even-numbered solar cycles than for the odd ones. Additionally, we found the same even-high and odd-low pattern of foF2 for other mid-latitude ionosonde stations in Northern and Southern Hemispheres. This property suggests that there exists a 22-year cycle in the F2-layer variability coupled with the 22-year cycle in the 27-day recurrence of geomagnetic activity. Key words. Ionosphere (mid-latitude ionosphere; ionosphere- magnetosphere interactions) – Magnetospheric physics (solar wind-magnetosphere interactions)

scholarly journals GYROSCOPIC PUMPING IN THE SOLAR NEAR-SURFACE SHEAR LAYER

2011 ◽  
Vol 743 (1) ◽  
pp. 79 ◽  
Author(s):  
Mark S. Miesch ◽  
Bradley W. Hindman
Keyword(s):  
Shear Layer ◽  
Surface Shear ◽  
Near Surface

scholarly journals Effect on Doppler Resonance From a Near-Surface Shear Layer

2017 ◽  
Author(s):  
Benjamin K. Smeltzer ◽  
Yan Li ◽  
Simen Å. Ellingsen
Keyword(s):  
Shear Layer ◽  
Finite Depth ◽  
Gravitational Acceleration ◽  
Surface Shear ◽  
Constant Frequency ◽  
Wave Source ◽  
Near Surface ◽  
Strong Shear ◽  
Uniform Current ◽  
Source Velocity

For waves generated by a wave source which is simultaneously moving and oscillating at a constant frequency ω, a resonance is well known to occur at a particular value τres of the nondimensional frequency τ = ωV/g (V: source velocity relative to the surface, g: gravitational acceleration). For quiescent, deep water, it is well known that τres = 1/4. We study the effect on τres from the presence of a shear flow in a layer near the surface, such as may be generated by wind or tidal currents. Assuming the vorticity is constant within the shear layer, we find that the effects on the resonant frequency can be significant even for sources corresponding to moderate shear and relatively long waves, while for stronger shear and shorter waves the effect is stronger. Even for a situation where the resonant waves have wavelengths about 20 times the width of the shear layer, the resonance frequency can change by ∼ 25% for even a moderately strong shear VS/g = 0.3 (S: vorticity in surface shear layer). Intuition for the problem is built by first considering two simpler geometries: uniform current with finite depth, and Couette flow of finite depth.

scholarly journals Modeling the solar cycles 12-20 with a Babcock-Leighton flux transport dynamo

2012 ◽  
Vol 8 (S294) ◽  
pp. 67-68
Author(s):  
Jie Jiang
Keyword(s):  
Solar Cycle ◽  
Sunspot Group ◽  
Correlation Coefficients ◽  
Strongly Correlated ◽  
Solar Cycles ◽  
Poloidal Field ◽  
Flux Transport ◽  
Field Generation ◽  
Cycle Dependence

AbstractWe use a Babcock-Leighton-type of dynamo with the poloidal source based as closely as possible on the observations to model the solar cycle irregularities during the cycles 12-20. The nonlinearities in the poloidal field generation, i.e., the cycle dependence of the sunspot group tilt angles and the latitudes are included. The convective pumping dominates the transport of the surface poloidal field to the tachocline. Our results show that the modeled polar fields have a good correlation with the observed next cycle strength and the build-up of the toroidal flux at the tachocline is strongly correlated with the observed cycle strength as well. Both correlation coefficients are above 0.8. The success of the model indicates that they are the nonlinearities in the poloidal field generation which cause the solar cycle irregularities.

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