scholarly journals On the extended 23rd solar cycle

2012 ◽  
Vol 8 (S294) ◽  
pp. 69-70 ◽  
Author(s):  
Valery N. Krivodubskij
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Toroidal Field ◽  
Toroidal Magnetic Field ◽  
Dynamo Model ◽  
Linear Regime ◽  
23Rd Solar Cycle ◽  
23Rd Cycle ◽  
Inverse Proportion ◽  
Non Linear

AbstractAn explanation of the mystery of the extended 23rd solar cycle duration about 13 years in the frame of non-linear regime of the αΩ- dynamo model is proposed. The calculated dynamo-period of the solar cycle, T, depends (in the inverse proportion) on the intensity of the α- effect in the solar convection zone (SCZ). As well, the intensity of the α- effect in non-linear regime depends (also in the inverse proportion) on the value of toroidal magnetic field, BT (magnetic alpha-quenching). Thus, the calculated period is in direct proportion to the value of toroidal magnetic field: the stronger toroidal field BT in certain cycle, the longer dynamo-period T of this cycle. Since the toroidal field is hidden in the deep layers of the SCZ, it is necessary to know some other magnetic experimental evidence that reflects something like information about inner toroidal field. In this connection we allow for that the strong toroidal field is transported by magnetic buoyancy to the solar surface and produces here the sunspots, so they carry indirect information on BT. In this connection we took into account up-to-date observed data on the essential increase of the averaged annual module of the magnetic field of the large-scale sunspots, Bsp, in the 23rd cycle; and then we made calculation of the alpha-quenching which depends on these referred data. It is important to know only relative variations of magnetic index Bsp for calculation of the dynamo-period variation. Our estimations showed that the average solar period, which is about 11 years, must increase by a factor of 1,2; so the calculated 23rd cycle dynamo-period would be about 13 years.

scholarly journals Observing and modeling the poloidal and toroidal fields of the solar dynamo

2018 ◽  
Vol 609 ◽  
pp. A56 ◽  
Author(s):  
R. H. Cameron ◽  
T. L. Duvall ◽  
M. Schüssler ◽  
H. Schunker
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Time Lag ◽  
Solar Observatory ◽  
Toroidal Field ◽  
Solar Dynamo ◽  
Dynamo Model ◽  
Flux Emergence ◽  
Poloidal Field ◽  
Poloidal Magnetic Field

Context. The solar dynamo consists of a process that converts poloidal magnetic field to toroidal magnetic field followed by a process that creates new poloidal field from the toroidal field. Aims. Our aim is to observe the poloidal and toroidal fields relevant to the global solar dynamo and to see if their evolution is captured by a Babcock-Leighton dynamo. Methods. We used synoptic maps of the surface radial field from the KPNSO/VT and SOLIS observatories, to construct the poloidal field as a function of time and latitude; we also used full disk images from Wilcox Solar Observatory and SOHO/MDI to infer the longitudinally averaged surface azimuthal field. We show that the latter is consistent with an estimate of the longitudinally averaged surface azimuthal field due to flux emergence and therefore is closely related to the subsurface toroidal field. Results. We present maps of the poloidal and toroidal magnetic fields of the global solar dynamo. The longitude-averaged azimuthal field observed at the surface results from flux emergence. At high latitudes this component follows the radial component of the polar fields with a short time lag of between 1−3 years. The lag increases at lower latitudes. The observed evolution of the poloidal and toroidal magnetic fields is described by the (updated) Babcock-Leighton dynamo model.

scholarly journals High Resolution 3D Relativistic MHD Simulations of Jets

2009 ◽  
Vol 5 (H15) ◽  
pp. 254-255
Author(s):  
A. Ferrari ◽  
A. Mignone ◽  
P. Rossi ◽  
G. Bodo ◽  
S. Massaglia
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Full Length ◽  
Toroidal Field ◽  
Toroidal Magnetic Field ◽  
Mhd Simulations ◽  
Strong Current

AbstractWe performed high-resolution three dimensional numerical simulations of relativistic MHD jets carrying an initially toroidal magnetic field responsible for the process of jet acceleration and collimation. We find that in the 3D case the toroidal field gives rise to strong current driven kink instabilities leading to jet wiggling. However, it appears to be able to maintain an highly relativistic spine along its full length.

scholarly journals Stellar dynamos with solar and antisolar differential rotations: Implications to magnetic cycles of slowly rotating stars

2019 ◽  
Vol 491 (3) ◽  
pp. 3155-3164 ◽  
Author(s):  
Bidya Binay Karak ◽  
Aparna Tomar ◽  
Vindya Vashishth
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Mean Field ◽  
Rotation Period ◽  
Toroidal Field ◽  
Dynamo Model ◽  
Cycle Period ◽  
Rotating Stars ◽  
Magnetic Cycles

ABSTRACT Simulations of magnetohydrodynamics convection in slowly rotating stars predict antisolar differential rotation (DR) in which the equator rotates slower than poles. This antisolar DR in the usual αΩ dynamo model does not produce polarity reversal. Thus, the features of large-scale magnetic fields in slowly rotating stars are expected to be different than stars having solar-like DR. In this study, we perform mean-field kinematic dynamo modelling of different stars at different rotation periods. We consider antisolar DR for the stars having rotation period larger than 30 d and solar-like DR otherwise. We show that with particular α profiles, the dynamo model produces magnetic cycles with polarity reversals even with the antisolar DR provided, the DR is quenched when the toroidal field grows considerably high and there is a sufficiently strong α for the generation of toroidal field. Due to the antisolar DR, the model produces an abrupt increase of magnetic field exactly when the DR profile is changed from solar-like to antisolar. This enhancement of magnetic field is in good agreement with the stellar observational data as well as some global convection simulations. In the solar-like DR branch, with the decreasing rotation period, we find the magnetic field strength increases while the cycle period shortens. Both of these trends are in general agreement with observations. Our study provides additional support for the possible existence of antisolar DR in slowly rotating stars and the presence of unusually enhanced magnetic fields and possibly cycles that are prone to production of superflare.

scholarly journals Generation of Strong Toroidal Magnetic Field Near the Bottom of the Solar Convective Zone

1993 ◽  
Vol 137 ◽  
pp. 78-80
Author(s):  
V.N. Krivodubskij
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Magnetic Induction ◽  
Convective Zone ◽  
Generation Mechanism ◽  
Toroidal Field ◽  
Toroidal Magnetic Field ◽  
Poloidal Magnetic Field ◽  
Radial Gradient ◽  
Magnetic Buoyancy

AbstractThe generation mechanism of the toroidal magnetic field by the angular velocity radial gradient acting on the relict poloidal magnetic field on the boundary between the con-vective and radiative zones is proposed. The magnetic induction magnitude of the toroidal field reaches about 2×10σ G, the limiting effect of the magnetic buoyancy being taking into account. This value conforms to the estimation of toroidal field obtained from helioseismological data.

scholarly journals On a relationship between magnetohydrodynamic planetary eigenmodes and second-class inertial elgenmodes

1974 ◽  
Vol 18 (2) ◽  
pp. 205-215
Author(s):  
J. A. Rickard
Keyword(s):  
Magnetic Field ◽  
Spherical Shell ◽  
Toroidal Field ◽  
Toroidal Magnetic Field

AbstractStewartson [5] considered second class oscillations in a spherical shell in the presence of a toroidal magnetic field. He followed Hide [2] and supposed the toroidal field to be uniform.

scholarly journals An Insight into the Solar Dynamo Theory

2017 ◽  
Vol 3 (1) ◽  
pp. 27-36
Author(s):  
Babu Ram Tiwari ◽  
Mukul Kumar
Keyword(s):  
Magnetic Field ◽  
Toroidal Field ◽  
Solar Dynamo ◽  
Dynamo Model ◽  
The Sun ◽  
Poloidal Field ◽  
Dynamo Theory ◽  
Dynamo Action ◽  
Flux Transport ◽  
Alpha Omega

The Sun manifests its magnetic field in form of the solar activities, being observed on the surface of the Sun. The dynamo action is responsible for the evolution of the magnetic field in the Sun. The present article aims to present an overview of the studies have been carried on the theory and modelling of the solar dynamo. The article describes the alpha-omega dynamo model. Generally, the dynamo model involves the cyclic conversion between the poloidal field and the toroidal field. In case of alpha-omega dynamo model, the strong differential rotation generates a toroidal field near the base of the convection zone. On the other hand, the turbulent helicity leads to the generation of the poloidal field near the surface. The turbulent diffusion and the meridional circulation are considered as the two important flux transport agents in this model. The article briefly describes the theory of solar dynamo and mean field dynamo model.

scholarly journals The Statistical Analysis of Characteristics of Coronal Mass Ejection During the Descending Phase of Solar Cycle 23 and 24

2021 ◽  
Vol 16 (2) ◽  
Author(s):  
Hemlata Dharmashaktu ◽  
N.K. Lohani
Keyword(s):  
Solar Cycle ◽  
Angular Width ◽  
Maximum Speed ◽  
Solar Cycles ◽  
Linear Speed ◽  
23Rd Solar Cycle ◽  
23Rd Cycle ◽  
Solar Cycle 23 ◽  
Solar Cycle 24 ◽  
Cycle 24

The characteristics of CMEs we studied are angular width, linear speed, and acceleration for all categories of CMEs such as narrow (W ≤20°), intermediate (20°< W<200°), wide (W ≥ 200°) and linear speed <500 km/s during the descending phase of solar cycle 23 and 24 and compared them. We have found that there are 1951 narrow CMEs during solar cycle 23 that is 1.9 times greater than in solar cycle 24 (1047). On the other side, the number of intermediate CMEs during solar cycle 24 (1571) is 1.14 times more than solar cycle 23 (1162). We observed no noticeable difference between the number of wide CMEs of solar cycle 23 (29) and 24 (36). The angular width of CMEs during the descending phase of solar cycle 23 and solar cycle 24, predominately distributed around 100-600. The fascinating result is that the angular width distributions for the descending phase of solar cycles are approximately identical. On comparing the results of linear speed of both solar cycle, we can say that, (i) 93.7% (1729) and 87.7% (908) of narrow CMEs, (ii) 97% (1328) and 94% (1479) of intermediate CMEs and (iii) 44% (13) and 42% (15) of wide CMEs have speed of <500 km s-1, respectively. Mostly the fractions of narrow and intermediate CMEs decline sharply at the speeds greater than 500 km s-1. The maximum speed observed during the 23rd cycle is 1994 km/s (wide CME) and the 24th cycle is 3163 km/s (wide CME) respectively. It was noticed that the speed of the 24th solar cycle CME is higher than the 23rd solar cycle CME. The major fraction of CMEs has acceleration in the range of -20 to 20 km s-2, all types of CMEs. The narrow and intermediate CMEs mostly show acceleration while wide CMEs show deceleration.

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