Sun's Convection Research Articles

SOLAR ACTIVITY AS A RESULT OF TWO-WAVE MAGNETIC FLUX GENERATION

Solar activity has been studied by using the time series of the yearly mean Wolf sunspot numbers. It was shown that the long-term variation of solar activity could be interpreted both as a beat between the two wave magnetic flux with 21.5-yr and 19.3-yr periods and the epochs of low solar activity after the phase failure. This magnetic flux is likely to be generated by the torsional oscillations of the ‘transition layer’ located at the bottom of the Sun's convection zone. The periodicities of solar cycles obtained allow us to predict the Sun's activity in the 21st century with high probability. In particular, cycle 23 is predicted to start in 1999 and its maximum to occur between mid-2005 and mid-2006, the Wolf number being in the interval 50–65.

On the Inference of the Solar Internal Rotation Profile from Frequency-splitting Data

view Abstract Citations (14) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Inference of the Solar Internal Rotation Profile from Frequency-splitting Data Wilson, P. R. ; Burtonclay, D. ; Li, Y. Abstract From the earliest helioseismology data it was inferred that the internal angular velocity of the Sun is invariant across the convection zone (i.e., it mimics the surface differential rotation). This result caused some concern to theoreticians since many dynamo and dynamical models of the convection zone require that the angular velocity be approximately constant on cylinders concentric about the rotation axis. Stark and others have argued that in order to test models of the angular velocity against frequency- splitting data the uncertainties in these data must be magnified, and it is shown here that within these uncertainties it is indeed difficult to exclude some models in which the angular velocity is independent of radius across a region including the convection zone and some depths below it. Further, Gough and his colleagues have recently claimed that the currently available data are not inconsistent with some models for which the angular velocity is constant on cylinders within the Sun's convection zone. Thus, inferences from frequency-splitting data regarding the internal angular velocity of the Sun would seem to be somewhat uncertain. In this paper, these uncertainties are discussed and an alternative approach is proposed in which a forward method is used to find the simplest model for the angular velocity (i.e., with the least positional variations) consistent with the data, including the quoted uncertainties. While it is not claimed that such a model represents the true angular velocity, its features may be said to "characterize" the essential properties of a particular data set. Publication: The Astrophysical Journal Pub Date: October 1996 DOI: 10.1086/177893 Bibcode: 1996ApJ...470..621W Keywords: CONVECTION; MAGNETOHYDRODYNAMICS: MHD; SUN: INTERIOR; SUN: OSCILLATIONS full text sources ADS |

‘Asteroseismology’ Offers a New Probe of Stellar Interiors

Just as the study of seismic waves lets us look into the bowels of the Earth, helioseismology has for more than 20 years been a rich source of information about the interior of the Sun. Apparently driven by internal convective motion, the Sun rings like a great spherical bell. Many thousands of resonant pressure‐wave modes with periods on the order of 5 minutes have been painstakingly decoded from complex surface motions of dauntingly small amplitude. From the pattern of resonant frequencies one learns much about the composition, density and structure of the Sun. We now know, for example, that the Sun's convection zone is twice as deep as solar modelers believed before these oscillation modes were measured.

An Early Solar Dynamo Prediction: Cycle 23 ∼ Cycle 22

In this paper, we briefly review the “dynamo” and “geomagnetic precursor” methods of long‐term solar activity forecasting. These methods depend upon the most basic aspect of dynamo theory to predict future activity, future magnetic field arises directly from the magnification of pre‐existing magnetic field. We then generalize the dynamo technique, allowing the method to be used at any phase of the solar cycle, through the development of the “Solar Dynamo Amplitude” (SODA) index. This index is sensitive to the magnetic flux trapped within the Sun's convection zone but insensitive to the phase of the solar cycle. Since magnetic fields inside the Sun can become buoyant, one may think of the acronym SODA as describing the amount of buoyant flux. Using the present value of the SODA index, we estimate that the next cycle's smoothed peak activity will be about 210 ± 30 solar flux units for the 10.7 cm radio flux and a sunspot number of 170 ± 25. This suggests that solar cycle #23 will be large, comparable to cycle #22. The estimated peak is expected to occur near 1999.7 ± 1 year. Since the current approach is novel (using data prior to solar minimum), these estimates may improve when the upcoming solar minimum is reached.

The source of solar high-frequency acoustic modes - Theoretical expectations

The source exciting the solar p-modes is likely to be acoustic noise generated in the top part of the sun's convection zone. If so, then simple arguments suggest that most of the emitted energy may come from rare localized events that are well separated from one another in space and time. This note describes the acoustic emission that would be expected from such events, based on a ray-theory analysis. Most of the acoustic energy is found to emerge very close to the source, so that observations to identify emission events will require high spatial resolution.

Are variations in the 37Cl experiment interpretable as solar matter exclusions?

It has been suggested that variations in the solar neutrino rate measured by the 37Cl experiment that appear to be anti-correlated with the solar cycle phenomena could be explained in terms of an MSW mechanism by solar matter displacement. These matter displacements might be brought about by magnetic fields in the sun's convection zone. However, such inside displacements result in solar surface displacements. The observed limits of solar radius variations constrain the inside changes. Using these constraints together with calculations based on the MSW mechanism, we show that the corresponding neutrino rate variations are very much too small to explain any experimental observations.

Inferring the sun's internal angular velocity from observed p-mode frequency splittings

view Abstract Citations (337) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Inferring the Sun's Internal Angular Velocity from Observed p-Mode Frequency Splittings Brown, Timothy M. ; Christensen-Dalsgaard, Jorgen ; Dziembowski, Wojciech A. ; Goode, Philip ; Gough, Douglas O. ; Morrow, Cherilynn A. Abstract The sun's internal solar velocity Omega is studied as a function of latitude and radius using the solar oscillation data of Brown and Morrow (1987). An attempt is made to separate robust inferences about the sun from artifacts of the analysis. It is found that a latitudinal variation of Omega similar to that observed at the solar surface exists throughout the sun's convection zone and that the variation of Omega with latitude persists to some extent even beneath the convection zone. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167727 Bibcode: 1989ApJ...343..526B Keywords: Angular Velocity; Solar Interior; Solar Oscillations; Solar Rotation; Error Analysis; Forward Scattering; Integral Equations; Inverse Scattering; Kernel Functions; Tachometers; Solar Physics; SUN: INTERIOR; SUN: OSCILLATIONS; SUN: ROTATION full text sources ADS |

Solar Irradiance Change and Special Longitudes Due to r -Modes

Sluggish global oscillations, having a periodicity of months and trapped in the sun's convection zone, modulate the amount of energy reaching Earth and seem to impose some large-scale order on the distribution of solar surface features. These recently recognized oscillations (r-modes) increase the predictability of solar changes and may improve understanding of rotation and variability in other stars. Most of the 13 periodicities ranging from 13 to 85 days that are caused by r-modes can be detected in Nimbus 7 observations of solar irradiance during 3 years at solar maximum. These modes may also bear on the classical question of persistent longitudes of high solar activity.

Convection zone origins of solar atmospheric heating

view Abstract Citations (3) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Convection Zone Origins of Solar Atmospheric Heating Schatten, Kenneth H. ; Mayr, Hans G. Abstract Spicules are examined as a means for supplying the corona with mass, energy, and magnetic field. It is suggested that spicules form from the supersonic upward expansion of material on nearly evacuated network flux tubes embedded within the sun's convection zone. This allows supersonic but subescape velocities to be attained by the material as it flows outward through the photosphere. Although supersonic, the kinetic energy (subescape) of the spicule material, as observed, is insufficient for coronal heating. It is suggested that, through buoyancy changes on evacuated flux tubes, the magnetic field first 'wicks' material flow into the solar atmosphere. Subsequently, the magnetic field energizes the gaseous material to form the conventional hot, dynamically expanding, solar corona. This occurs through momentum and energy transport by Alfven waves and associated Maxwell stresses concurrently flowing upward on these 'geysers' (spicules). The vertical momentum equation governing fluid flow is examined, and a particular equipartition solution is presented for the flow velocity along a simple field geometry. Publication: The Astrophysical Journal Pub Date: October 1986 DOI: 10.1086/164655 Bibcode: 1986ApJ...309..864S Keywords: Convection Currents; Coronas; Solar Atmosphere; Solar Heating; Spicules; Atmospheric Circulation; Flow Equations; Magnetohydrodynamic Waves; Solar Energy; Solar Magnetic Field; Solar Physics; CONVECTION; SUN: ATMOSPHERE; SUN: ATMOSPHERIC MOTIONS full text sources ADS |

Tones of the Oscillating Sun

Tones of the Oscillating Sun

The influence of the angular velocity distribution on the energy transport in the Sun's convection zone

This contribution is a purely exploratory search to investigate the way the distribution of angular velocity inside the Sun's convection zone affects the energy transport. This is related with problems concerning the magnetic activity, whose appearance at the Sun's surface depends on the shape of the isorotation surfaces, and the latitudinal variations in flux. The proposed model is non-linear and axisymmetric.

Momentum and energy transport in the Sun's convection zone under the observational constraint of flux and temperature homogeneity at the surface

A previous authors' non-Boussinesq model of solar differential rotation (BPCM) is used to determine the angular velocity distribution within the convection zone, when the momentum and energy equations are solved with boundary conditions expressing the homogeneity of flux and temperature at the Sun's surface.

Convection in a rotating deep compressible spherical shell: Application to the Sun

In this paper we study the interaction of rotation with convection in a deep compressible spherical shell as the Sun's convection zone. We examine how the energy transport and the large scale motions can be affected by rotation. In particular we study how a large scale meridional circulation can give rise to variations of angular velocity with latitude and depth.

A comparison of the meridional flows in the sun's convection zone, predicted by theories of the solar dynamo and differential rotation

view Abstract Citations (6) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A comparison of the meridional flows in the sun's convection zone, predicted by theories of the solar dynamo and differential rotation. Durney, B. R. Abstract Recently Yoshimura has evaluated the gradient of the Sun's angular velocity (d /Jr) necessary to give a good fit to the observed solar activity cycle. We estimate the meridional velocities in the convection zone, implied by this value of . These meridional velocities are in good agreement with those necessary to explain the Sun's surface differential rotation. Subject headings: hydromagnetics - interiors, solar - rotation, solar Publication: The Astrophysical Journal Pub Date: August 1975 DOI: 10.1086/153749 Bibcode: 1975ApJ...199..761D Keywords: Angular Velocity; Convective Flow; Dynamo Theory; Meridional Flow; Solar Cycles; Solar Rotation; Equations Of Motion; Solar Gravitation; Solar Magnetic Field; Solar Physics full text sources ADS |

Thermally Driven Rossby-Mode Dynamo for Solar Magnetic-Field Reversals

There is increasing interest in the possible existence of large eddies or "Rossby waves" in Sun's convection zone and photosphere. It is shown that many flows of this type, driven by an equator-pole temperature diffrence, act as hydromagnetic dynamos to produce magnetic fields that periodically reverse. The periods and field amplitudes agree with solar phenomena within an order of magnitude.