Why Does the Torsional Oscillation Precede the Sunspot Cycle?

2009 ◽  
pp. 500-501
Author(s):  
P. Chatterjee ◽  
S. Chakraborty ◽  
A. R. Choudhuri
Keyword(s):  
Torsional Oscillation ◽  
Sunspot Cycle

scholarly journals A theoretical model of torsional oscillations from a flux transport dynamo model

2010 ◽  
Vol 6 (S273) ◽  
pp. 366-368
Author(s):  
Piyali Chatterjee ◽  
Sagar Chakraborty ◽  
Arnab Rai Choudhuri
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Lorentz Force ◽  
High Latitude ◽  
Torsional Oscillation ◽  
Sunspot Cycle ◽  
Dynamo Model ◽  
Flux Transport ◽  
Torsional Oscillations ◽  
The Magnetic Field

AbstractAssuming that the torsional oscillation is driven by the Lorentz force of the magnetic field associated with the sunspot cycle, we use a flux transport dynamo to model it and explain its initiation at a high latitude before the beginning of the sunspot cycle.

scholarly journals The Sunspot Cycle and Solar Magnetic Fields. I. The Mechanism as Inferred from Observation

1985 ◽  
Vol 38 (6) ◽  
pp. 1045 ◽  
Author(s):  
Ronald G Giovanelli
Keyword(s):  
Magnetic Fields ◽  
Differential Rotation ◽  
Torsional Oscillation ◽  
Sunspot Cycle ◽  
Polar Field ◽  
Lower Latitude ◽  
Polar Regions ◽  
Sunspot Maximum ◽  
Field Reversal ◽  
Opposite Hemisphere

Observations of solar magnetic and velocity fields can be used to derive the course of events involved in the solar cycle. These differ in three important respects from those of conventional dynamo theories: (i) Polar field reversal. Following the outbreak of a new cycle, magnetic flux released by sunspots diffuses initially by Leighton's random-walk process, but this is soon dominated by the observed poleward flow of about 20 m s - 1 which carries flux to polar regions in about 12 months. Since follower spots lie about 2� higher in latitude than leaders, follower flux arrives in polar regions some two weeks ahead of leader flux, providing a net inflow of follower polarity there until sunspot maximum, reversing the polar field from the previous sunspot cycle and building it up to a maximum. After sunspot maximum, the flux arriving in polar regions is predominantly of follower polarity until or unless spots occur at latitudes so low that flux can diffuse towards and across the equator, predominantly from the lower latitude leader; the effect is doubled by a complementary migration from the opposite hemisphere. This prevents the change in polar flux over the cycle from dropping to zero, and leaves the polarity there reversed at the end of the cycle. (ii) The sunspot cycle. A slow, deeper counterflow, essential for continuity, carries flux strands down in the polar zones and then equatorwards. The concentration of strands is increased continually by differential rotation, and they are dragged continually into contact. Reconnection occurs rapidly except between tubes that are inclined at very small angles. This results in the formation of ropes of flux strands twisted very gently. At some stage they are large enough to float, forming sunspots. The mean sunspot latitude decreases continuously as the flux is carried equatorwards, dying out as the flux ropes become exhausted. The whole process repeats, once again reversing the polar and spot group magnetic fields. Hale's polarity laws follow immediately, and Sporer's law requires only minor adjustments to the predicted velocity of the deep equatorward counterflow. The estimated velocity of this flow is compatible with the observed sunspot and magnetic cycles of 11 and 22 years. (iii) The torsional oscillation. Shear by differential rotation increases the concentration of flux strands; the reaction to strongly sheared flux strands is a tendency to reduce differential rotation. This results in cyclic variations of differential rotation, the phase with respect to sunspot formation being in good agreement with the torsional oscillation observations of Howard and LaBonte (1981) at all latitudes up to 50-55�.

Asymmetry in Solar Torsional Oscillation

2018 ◽  
Vol 13 (S340) ◽  
pp. 11-12
Author(s):  
B Lekshmi ◽  
Dibyendu Nandy ◽  
H M Antia
Keyword(s):  
Torsional Oscillation ◽  
Sunspot Cycle ◽  
Zonal Flow ◽  
Spatial And Temporal Variation ◽  
Near Surface ◽  
Global Oscillation Network Group ◽  
Long Term Study ◽  
Ring Diagram ◽  
Oscillation Velocity ◽  
Average Rotation

AbstractSolar torsional oscillations are migrating bands of slower and faster than average rotation, which are thought to be related to the Sun’s magnetic cycle. We perform the first long-term study (16 years) of hemispherical asymmetry in solar torsional oscillation velocity using helioseismic data. We explore the spatial and temporal variation of North-South asymmetry using zonal flow velocities obtained from ring diagram analysis of the Global Oscillation Network Group (GONG) Doppler images. We find a strong correlation between the asymmetries of near-surface torsional oscillation with magnetic flux and sunspot number, with the velocity asymmetry preceding in both the cases. We speculate that the asymmetry in torsional oscillation velocity may help in predicting the hemispherical asymmetry in the sunspot cycle.

scholarly journals The Sunspot Cycle and Solar Magnetic Fields. II. The Interaction of Flux Tubes with the Convection Zone

1985 ◽  
Vol 38 (6) ◽  
pp. 1067 ◽  
Author(s):  
Ronald G Giovanelli
Keyword(s):  
Convection Zone ◽  
Torsional Oscillation ◽  
Sunspot Cycle ◽  
Solar Magnetic Fields ◽  
Field Reversal ◽  
Flux Tubes ◽  
Dynamo Mechanism ◽  
Floating Criteria ◽  
New Type ◽  
Major Cycle

Mechanisms of interaction between flux tubes or ropes and the convection zone are examined insofar as they are relevant to the sunspot cycle. These include floating, transport, and the penetration of gas from outside the tubes. It is found that all previous studies contain one or more major errors of physics which render their conclusions invalid. The errors include invariably the assumption that Archimedes' principle is applicable to flux ropes, that gas entry can be disregarded, and usually that floating criteria depend solely or primarily on local phenomena. Some of the results presented here are explanations of (i) the transport of flux tubes by the slow observed poleward motions and the even slower systems which carry extensions of these tubes downwards to depths of ~ 150 Mm and then equatorwards; (ii) their magnetic field strengths ( ~ 104 G at a depth 10 Mm to (6-12) x 104 G at ~ 150 Mm); and (iii) the amplitudes of the torsional oscillation. Taken in conjunction with Part I, where the mechanism of polar field reversal is described and the variation of the phase of the torsional oscillation explained, all major cycle observations are accounted for in what turns out to be a new type of dynamo mechanism.

scholarly journals Why Does the Sun’s Torsional Oscillation Begin before the Sunspot Cycle?

2009 ◽  
Vol 102 (4) ◽  
Author(s):  
Sagar Chakraborty ◽  
Arnab Rai Choudhuri ◽  
Piyali Chatterjee
Keyword(s):  
Torsional Oscillation ◽  
Sunspot Cycle

scholarly journals Asymmetry in Solar Torsional Oscillation and the Sunspot Cycle

2018 ◽  
Vol 861 (2) ◽  
pp. 121 ◽  
Author(s):  
Lekshmi B ◽  
Dibyendu Nandy ◽  
H. M. Antia
Keyword(s):  
Torsional Oscillation ◽  
Sunspot Cycle

The LDE-Type Flare Occurrence (1969-1993)

1994 ◽  
Vol 144 ◽  
pp. 279-282
Author(s):  
A. Antalová
Keyword(s):  
Time Series ◽  
Fourier Analysis ◽  
Sunspot Cycle ◽  
List Type ◽  
Type Number ◽  
Solar Cycles ◽  
Type Iv ◽  
Long Duration ◽  
Cycle Maximum ◽  
Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

Cyclic Evolution of Sunspots: Gleaning New Results from Old Data

2000 ◽  
Vol 179 ◽  
pp. 163-165
Author(s):  
S. K. Solanki ◽  
M. Fligge ◽  
P. Pulkkinen ◽  
P. Hoyng
Keyword(s):  
Sunspot Number ◽  
Sunspot Cycle ◽  
Preliminary Results ◽  
Butterfly Diagram

AbstractThe records of sunspot number, sunspot areas and sunspot locations gathered over the centuries by various observatories are reanalysed with the aim of finding as yet undiscovered connections between the different parameters of the sunspot cycle and the butterfly diagram. Preliminary results of such interrelationships are presented.

Fore-Aft Forces in Tire-Wheel Assemblies Generated by Unbalances and the Influence of Balancing

1991 ◽  
Vol 19 (3) ◽  
pp. 142-162 ◽  
Author(s):  
D. S. Stutts ◽  
W. Soedel ◽  
S. K. Jha
Keyword(s):  
Mathematical Model ◽  
Elastic Foundation ◽  
Torsional Oscillation ◽  
Vertical Direction ◽  
Torsional Stiffness ◽  
Rolling Motion ◽  
Vertical Force ◽  
Horizontal Force ◽  
Wheel Rim ◽  
Open Question

Abstract When measuring bearing forces of the tire-wheel assembly during drum tests, it was found that beyond certain speeds, the horizontal force variations or so-called fore-aft forces were larger than the force variations in the vertical direction. The explanation of this phenomenon is still somewhat an open question. One of the hypothetical models argues in favor of torsional oscillations caused by a changing rolling radius. But it appears that there is a simpler answer. In this paper, a mathematical model of a tire consisting of a rigid tread ring connected to a freely rotating wheel or hub through an elastic foundation which has radial and torsional stiffness was developed. This model shows that an unbalanced mass on the tread ring will cause an oscillatory rolling motion of the tread ring on the drum which is superimposed on the nominal rolling. This will indeed result in larger fore-aft than vertical force variations beyond certain speeds, which are a function of run-out. The rolling motion is in a certain sense a torsional oscillation, but postulation of a changing rolling radius is not necessary for its creation. The model also shows the limitation on balancing the tire-wheel assembly at the wheel rim if the unbalance occurs at the tread band.

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