scholarly journals Observations of the Latitudinal Variation of the Solar Radiance of Non Active Regions of the Sun

1998 ◽  
Vol 185 ◽  
pp. 111-112
Author(s):  
V. Domingo ◽  
L. Sanchez ◽  
T. Appourchaux
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Convection Zone ◽  
Active Regions ◽  
Latitudinal Variation ◽  
The Sun ◽  
Independent Mechanism ◽  
Photospheric Temperature

Kuhn et al. (1988) have found that there are variations in the photospheric temperature with the solar cycle that depend on solar latitude. This would be an independent mechanism, other than the effects of sunspots and faculae, contributing to the change in solar irradiance (Kuhn 1991). It is important to pursue this investigation as such variations would be related to the transport of energy through the convection zone, and thus give a good indication of its structure and evolution.

scholarly journals The Rotational Modulation of Ca II K in the Sun

1991 ◽  
Vol 130 ◽  
pp. 266-267
Author(s):  
I. Sattarov ◽  
A. Hojaev
Keyword(s):  
Solar Cycle ◽  
Active Regions ◽  
Magnetic Activity ◽  
Astronomical Observatory ◽  
Rigid Rotation ◽  
Longitudinal Distribution ◽  
The Sun ◽  
K Index ◽  
Rotational Modulation ◽  
Line Core

The most widely used indicator of the stellar magnetic activity is the flux in the CaII K-line core (K-index) (Baliunas and Vaughan, 1985). The K-index data have also been used for measuring the rotation of stars. But using the method for the Sun gives different results (Keil and Worden, 1984; Singh and Livingston, 1987). The reason for the observed differences, besides those indicated by Singh and Livingston, may be the character of the distribution of active regions. This study is based on observations made at Tashkent Astronomical Observatory and the data published in SGD for solar cycle 21. We study the longitudional distribution of sunspots and plages. Some intervals of active longitudes (IAL) were selected and the evolution of them was studied. Active regions were found to concentrate in certain longitude intervals which are in nearly rigid rotation. Fig. 1 shows the longitudinal distribution of sunspots areas for 1983-84, as an example.

scholarly journals The future of helioseismology

2009 ◽  
Vol 5 (H15) ◽  
pp. 352-353
Author(s):  
Alexander G. Kosovichev
Keyword(s):  
Solar Cycle ◽  
Physical Properties ◽  
Active Regions ◽  
Magnetic Activity ◽  
Solar Dynamo ◽  
Current Status ◽  
The Sun ◽  
Interior Structure ◽  
Structure And Dynamics ◽  
Solar Magnetic Activity

AbstractHelioseismology has provided us with the unique knowledge of the interior structure and dynamics of the Sun, and the variations with the solar cycle. However, the basic mechanisms of solar magnetic activity, formation of sunspots and active regions are still unknown. Determining the physical properties of the solar dynamo, detecting emerging active regions and observing the subsurface dynamics of sunspots are among the most important and challenging problems. The current status and perspectives of helioseismology are briefly discussed.

scholarly journals Magnetic Helicity Propagation from Inside the Sun

2005 ◽  
Vol 13 ◽  
pp. 97-100
Author(s):  
Dana Longcope
Keyword(s):  
Active Region ◽  
Flux Tube ◽  
Convection Zone ◽  
Active Regions ◽  
Magnetic Helicity ◽  
The Sun ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Region Emergence

AbstractModels of twisted flux tube evolution provide a picture of how magnetic helicity is propagated through the solar convection zone into the corona. According to the models, helicity tends toward an approximately uniform length-density along a tube, rather than concentrating at wider portions. Coronal fields lengthen rapidly during active region emergence, requiring additional helicity to propagate from the submerged flux tube. Recent observations of emerging active regions show an evolution consistent with this prediction, and no evidence of helicity concentrating in wider sections.

Latitudinal dependence of supergranular Area and Fractal dimension

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Paniveni Udayashankar
Keyword(s):  
Fractal Dimension ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Convection Zone ◽  
Magnetic Activity ◽  
The Sun ◽  
Physical Conditions ◽  
Quiet Region ◽  
Latitudinal Dependence ◽  
Shed Light

Abstract: A dependence of the area of supergranular cells with respect to the Latitude is studied and it is found that the cells are situated symmetrically about the ±250 latitude.Fractal dimension of the supergranular cells also shows a marginal latitudinal dependence, variation being in the range 1.6–1.7 in the latitudinal limits of ±300. Fractal dimension D for supergranulation is obtained according to the relation P ∝ AD/2 where ‘A is the area and ‘P’ is the perimeter of the supergranular cells. A difference in the fractal dimension between the active and quiet region cells is noted which is conjectured to be due to the magnetic activity level.Supergranular cells are essentially a manifestation of convective phenomena. They can shed light on the physical conditions in the convection zone of the Sun. Moreover, supergranules play a key role in the transport and dispersal of magnetic fields as it is an important step in our quest to understand the solar cycle.

scholarly journals The balance of magnetic fluxes in active regions

1968 ◽  
Vol 35 ◽  
pp. 47-49 ◽  
Author(s):  
Jan Olof Stenflo
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Active Region ◽  
Solar Surface ◽  
Active Regions ◽  
Basic Feature ◽  
The Sun ◽  
Magnetic Disturbance ◽  
The Magnetic Field

According to modern theories of the solar cycle, active regions on the Sun are caused by a magnetic disturbance penetrating the solar surface from below. Sunspots, filaments, flares and other conspicuous events in an active region seem to be only secondary phenomena, the basic feature being the magnetic field itself.

scholarly journals Introducing the Sun and SEPs

2021 ◽  
pp. 1-18
Author(s):  
Donald V. Reames
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Solar Cycle ◽  
Differential Rotation ◽  
Coronal Mass Ejections ◽  
Energetic Particle ◽  
Solar Magnetic Field ◽  
Solar Energetic Particle ◽  
Active Regions ◽  
The Sun

AbstractThe structure of the Sun, with its energy generation and heating, creates convection and differential rotation of the outer solar plasma. This convection and rotation of the ionized plasma generates the solar magnetic field. This field and its variation spawn all of the solar activity: solar active regions, flares, jets, and coronal mass ejections (CMEs). Solar activity provides the origin and environment for both the impulsive and gradual solar energetic particle (SEP) events. This chapter introduces the background environment and basic properties of SEP events, time durations, abundances, and solar cycle variations.

scholarly journals Interior Solar-Cycle Changes Detected by Helioseismology

2001 ◽  
Vol 203 ◽  
pp. 40-42 ◽  
Author(s):  
R. Howe ◽  
F. Hill ◽  
R. W. Komm ◽  
J. Christensen-Dalsgaard ◽  
R. Munk Larsen ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Rotation Rate ◽  
Convection Zone ◽  
The Sun

Helioseismic measurements with the MDI instrument aboard SOHO, and complementary measurements from the GONG network, are revealing changes deep within the Sun as the solar cycle progresses. We present results based on recent data from both experiments, including variations in the rotation rate deep inside the convection zone.

scholarly journals The need for active region disconnection in 3D kinematic dynamo simulations

2019 ◽  
Vol 627 ◽  
pp. A168 ◽  
Author(s):  
T. Whitbread ◽  
A. R. Yeates ◽  
A. Muñoz-Jaramillo
Keyword(s):  
Solar Cycle ◽  
Active Region ◽  
Convection Zone ◽  
Transport Model ◽  
Active Regions ◽  
Surface Flux ◽  
Dynamo Model ◽  
Flux Transport ◽  
Kinematic Dynamo ◽  
The Difference

In this paper we address a discrepancy between the surface flux evolution in a 3D kinematic dynamo model and a 2D surface flux transport model that has been closely calibrated to the real Sun. We demonstrate that the difference is due to the connectivity of active regions to the toroidal field at the base of the convection zone, which is not accounted for in the surface-only model. Initially, we consider the decay of a single active region, firstly in a simplified Cartesian 2D model and subsequently the full 3D model. By varying the turbulent diffusivity profile in the convection zone, we find that increasing the diffusivity – so that active regions are more rapidly disconnected from the base of the convection zone – improves the evolution of the surface field. However, if we simulate a full solar cycle, we find that the dynamo is unable to sustain itself under such an enhanced diffusivity. This suggests that in order to accurately model the solar cycle, we must find an alternative way to disconnect emerging active regions, whilst conserving magnetic flux.

scholarly journals Is there more global solar activity on the Sun?

2009 ◽  
Vol 5 (S264) ◽  
pp. 251-256
Author(s):  
J. X. Wang ◽  
Y. Z. Zhang ◽  
G. P. Zhou ◽  
Y. Y. Wen ◽  
J. Jiang
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Magnetic Flux ◽  
Active Regions ◽  
Global Scale ◽  
The Sun ◽  
X Rays ◽  
Wide Spread ◽  
Flux Emergence ◽  
Global Activity

AbstractThere appear indications of more global activity on the Sun which is larger, much beyond the scale of solar active regions (ARs). These indications include formation, flaring and eruption of the trans-equatorial loops seen in EUV and X-rays, formation and eruption of trans-equatorial filaments, global magnetic connectivity in EUV dimming associated with halo-coronal mass ejections, wide spread of radio burst sources in meter wavelength in the solar corona, and quasi-simultaneous magnetic flux emergence in both hemispheres seen during some major solar events. With examples of a few major events in the last solar cycle we discuss the possibility that there is large or global-scale activity on the Sun. Its spatial scale is many times larger than that of AR and temporal scale is over 10 hours. The exemplified trans-equatorial loops are anchored in ARs and their activity is temporally associated with flares in ARs too. In some sense the flares in ARs appear either as a part of or a precursor of the more global activity. It is likely that the combination of the flares in ARs and the associated global activity is responsible to the major solar-terrestrial events. More efforts in understanding the global activity are undertaken.

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