Large-Scale Coronal Magnetic Structure and Its Variations during an 11-year Solar Cycle

1994 ◽  
Vol 144 ◽  
pp. 35-39
Author(s):  
E. V. Ivanov
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Large Scale ◽  
Heliospheric Current Sheet ◽  
Reference Points ◽  
Source Surface ◽  
Solar Cycles ◽  
Dipole Component ◽  
Global Magnetic Field ◽  
Main Components

AbstractMaps of coronal magnetic fields at different heights calculated under potential approximation, have been used to reconstruct the corona shape in different phases of solar cycles 21 and 22. The shape of the solar corona depends on the maximum heliolatitudes and the structure of the heliospheric current sheet (HCS) that, in turn, are determined by space-time variations of the 3 main components of the global magnetic field of the Sun: 1) the axial dipole component; 2) the inclined dipole component; and 3) the quadrupole component. Variations of theHCSmaximum heliolatitudes and the width of the corona at 2.5R⊙during a solar cycle are compared with variations of the global magnetic field indices in the photosphere and at the source surface. The role of the solar cycle reference points and the global magnetic field indices in the corona shape variations over a solar cycle are discussed.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

scholarly journals Unusual migration of the prominence activities in recent solar cycles

2013 ◽  
Vol 8 (S300) ◽  
pp. 161-167 ◽  
Author(s):  
Masumi Shimojo
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Radial Velocity ◽  
Northern Hemisphere ◽  
Solar Maximum ◽  
The Other ◽  
Occurrence Rate ◽  
Solar Cycles ◽  
Global Magnetic Field ◽  
Cycle 24

AbstractWe investigated the prominence eruptions and disappearances observed with the Nobeyama Radioheliograph during over 20 years for studying the anomaly of the recent solar cycle. Although the sunspot number of Cycle 24 is smaller than the previous one dramatically, the occurrence rate, size and radial velocity of the prominence activities are not changed significantly. We also found that the occurrence of the prominence activities in the northern hemisphere is normal from the duration of the cycle and the migration of the producing region of the prominence activities. On the other hand, the migration in the southern hemisphere significantly differs from that in the northern hemisphere and the previous cycles. Our results suggest that the anomalies of the global magnetic field distribution started at the solar maximum of Cycle 23.

scholarly journals Global magnetic field cycle evolution and prominence eruptions

2013 ◽  
Vol 8 (S300) ◽  
pp. 168-171
Author(s):  
Irina A. Bilenko
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Rossby Waves ◽  
Field Structure ◽  
Solar Cycles ◽  
Magnetic Field Structure ◽  
Structure Changes ◽  
Global Magnetic Field ◽  
The Mean

AbstractA comparison of changes in the structure of the global solar magnetic field and that in the prominence parameters, in solar cycles 21–23, are presented. It is proposed that the observed global magnetic field structure changes and periodicities in the mean solar magnetic field are the result of the excitation of large-scale Rossby waves. The changes in the prominence parameters are assumed to be the result of the global magnetic field structure changes, which may be triggered or modulated quasi-periodically by large-scale Rossby waves.

scholarly journals Explaining the Hemispheric Pattern of Filament Chirality

2013 ◽  
Vol 8 (S300) ◽  
pp. 172-175
Author(s):  
Duncan H. Mackay ◽  
Anthony R. Yeates
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Southern Hemisphere ◽  
Large Scale ◽  
Detailed Comparison ◽  
Data Driven ◽  
Temporal Dependence ◽  
Large Scale Magnetic Field ◽  
Solar Filaments ◽  
Global Magnetic Field

AbstractSolar filaments are known to exhibit a hemispheric pattern in their chirality, where dextral/sinistral filaments dominate in the northern/southern hemisphere. We show that this pattern may be explained through data driven 3D global magnetic field simulations of the Sun's large-scale magnetic field. Through a detailed comparison with 109 filaments over a 6 month period, the model correctly reproduces the filament chirality and helicity with a 96% agreement. The data driven simulation is extended to run over a full solar cycle, where predictions are made for the spatial and temporal dependence of the hemispheric pattern over the solar cycle.

scholarly journals On the origin of variable structures in the winds of hot luminous stars

2013 ◽  
Vol 440 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Yannick J. L. Michaux ◽  
Anthony F. J. Moffat ◽  
André-Nicolas Chené ◽  
Nicole St-Louis
Keyword(s):  
Magnetic Field ◽  
Empirical Evidence ◽  
Temporal Variability ◽  
Large Scale ◽  
Small Scale ◽  
Ionization Zone ◽  
Corotating Interaction Regions ◽  
Wind Variability ◽  
Global Magnetic Field ◽  
Interaction Regions

Abstract Examination of the temporal variability properties of several strong optical recombination lines in a large sample of Galactic Wolf–Rayet (WR) stars reveals possible trends, especially in the more homogeneous WC than the diverse WN subtypes, of increasing wind variability with cooler subtypes. This could imply that a serious contender for the driver of the variations is stochastic, magnetic subsurface convection associated with the 170 kK partial-ionization zone of iron, which should occupy a deeper and larger zone of greater mass in cooler WR subtypes. This empirical evidence suggests that the heretofore proposed ubiquitous driver of wind variability, radiative instabilities, may not be the only mechanism playing a role in the stochastic multiple small-scaled structures seen in the winds of hot luminous stars. In addition to small-scale stochastic behaviour, subsurface convection guided by a global magnetic field with localized emerging loops may also be at the origin of the large-scale corotating interaction regions as seen frequently in O stars and occasionally in the winds of their descendant WR stars.

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 Reconstruction of Sun-as-Star Magnetic Field Structure and Evolution Using Filament Observations

1998 ◽  
Vol 167 ◽  
pp. 493-496
Author(s):  
Dmitri I. Ponyavin
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Close Association ◽  
Field Structure ◽  
The Sun ◽  
Magnetic Field Structure ◽  
Large Scale Magnetic Field ◽  
Field Organization

AbstractA technique is used to restore the magnetic field of the Sun viewed as star from the filament distribution seen on Hα photographs. For this purpose synoptic charts of the large-scale magnetic field reconstructed by the McIntosh method have been compared with the Sun-asstar solar magnetic field observed at Stanford. We have established a close association between the Sun-as-star magnetic field and the mean magnetic field inferred from synoptic magnetic field maps. A filtering technique was applied to find correlations between the Sun-as-star and large-scale magnetic field distributions during the course of a solar cycle. The correlations found were then used to restore the Sun-as-star magnetic field and its evolution in the late 1950s and 1960s, when such measurements of the field were not being made. A stackplot display of the inferred data reveals large-scale magnetic field organization and evolution. Patterns of the Sun-as-star magnetic field during solar cycle 19 were obtained. The proposed technique can be useful for studying the solar magnetic field structure and evolution during times with no direct observations.

scholarly journals Beyond sunspots: Studies using the McIntosh Archive of global solar magnetic field patterns

2016 ◽  
Vol 12 (S328) ◽  
pp. 93-100 ◽  
Author(s):  
Sarah E. Gibson ◽  
David Webb ◽  
Ian M. Hewins ◽  
Robert H. McFadden ◽  
Barbara A. Emery ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Coronal Holes ◽  
Magnetic Polarity ◽  
Solar Cycles ◽  
Polarity Inversion ◽  
Magnetic Structures ◽  
Field Patterns ◽  
Global Evolution

AbstractIn 1964 (Solar Cycle 20; SC 20), Patrick McIntosh began creating hand-drawn synoptic maps of solar magnetic features, based on Hα images. These synoptic maps were unique in that they traced magnetic polarity inversion lines, and connected widely separated filaments, fibril patterns, and plage corridors to reveal the large-scale organization of the solar magnetic field. Coronal hole boundaries were later added to the maps, which were produced, more or less continuously, into 2009 (i.e., the start of SC 24). The result was a record of ~45 years (~570 Carrington rotations), or nearly four complete solar cycles of synoptic maps. We are currently scanning, digitizing and archiving these maps, with the final, searchable versions publicly available at NOAA's National Centers for Environmental Information. In this paper we present preliminary scientific studies using the archived maps from SC 23. We show the global evolution of closed magnetic structures (e.g., sunspots, plage, and filaments) in relation to open magnetic structures (e.g., coronal holes), and examine how both relate to the shifting patterns of large-scale positive and negative polarity regions.

A Picture of Solar Minimum and the Onset of Solar Cycle 23. I. Global Magnetic Field Evolution

2000 ◽  
Vol 529 (2) ◽  
pp. 1101-1114 ◽  
Author(s):  
Giuliana de Toma ◽  
Oran R. White ◽  
Karen L. Harvey
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Field Evolution ◽  
Solar Cycle 23 ◽  
Global Magnetic Field

Solar Irradiance: Instrument-Based Advances

2018 ◽  
Vol 14 (A30) ◽  
pp. 354-357
Author(s):  
Greg Kopp
Keyword(s):  
Solar Cycle ◽  
Solar Flares ◽  
Solar Irradiance ◽  
Large Scale ◽  
Total Solar Irradiance ◽  
Climate Forcing ◽  
Solar Cycles ◽  
Climate Stability ◽  
Measurement Results ◽  
Measuring Space

AbstractVariations of the total solar irradiance (TSI) over long periods of time provide natural Earth-climate forcing and are thus important to monitor. Variations over a solar cycle are at the 0.1 % level. Variations on multi-decadal to century timescales are (fortunately for our climate stability) very small, which drives the need for highly-accurate and stable measurements over correspondingly long periods of time to discern any such irradiance changes. Advances to TSI-measuring space-borne instruments are approaching the desired climate-driven measurement accuracies and on-orbit stabilities. I present a summary of the modern-instrument improvements enabling these measurements and present some of the solar-variability measurement results from recent space-borne instruments, including TSI variations on timescales from solar flares and large-scale convection to solar cycles.

Sign in / Sign up

Export Citation Format

Share Document