scholarly journals The Evolution of the Solar Magnetic Field

2012 ◽  
Vol 10 (H16) ◽  
pp. 86-89 ◽  
Author(s):  
J. Todd Hoeksema
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Magnetic Field ◽  
Coronal Holes ◽  
Active Regions ◽  
Statistical Characteristics ◽  
Field Pattern ◽  
Small Scale ◽  
Polar Caps ◽  
Magnetic Elements

AbstractThe almost stately evolution of the global heliospheric magnetic field pattern during most of the solar cycle belies the intense dynamic interplay of photospheric and coronal flux concentrations on scales both large and small. The statistical characteristics of emerging bipoles and active regions lead to development of systematic magnetic patterns. Diffusion and flows impel features to interact constructively and destructively, and on longer time scales they may help drive the creation of new flux. Peculiar properties of the components in each solar cycle determine the specific details and provide additional clues about their sources. The interactions of complex developing features with the existing global magnetic environment drive impulsive events on all scales. Predominantly new-polarity surges originating in active regions at low latitudes can reach the poles in a year or two. Coronal holes and polar caps composed of short-lived, small-scale magnetic elements can persist for months and years. Advanced models coupled with comprehensive measurements of the visible solar surface, as well as the interior, corona, and heliosphere promise to revolutionize our understanding of the hierarchy we call the solar magnetic field.

scholarly journals Source-region characteristics of anemone active regions in the ascending phase of solar cycle 24

2020 ◽  
Vol 642 ◽  
pp. A233
Author(s):  
R. Sharma ◽  
C. Cid
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Minimum Distance ◽  
Source Region ◽  
Coronal Holes ◽  
Active Regions ◽  
Yearly Average ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Rise Phase

Context. Active regions in close proximity to coronal holes, also known as anemone regions, are the best candidates for studying the interaction between closed and open magnetic field topologies at the Sun. Statistical investigation of their source-region characteristics can provide vital clues regarding their possible association with energetic events, relevant from space weather perspectives. Aims. The main goal of our study is to understand the distinct properties of flaring and non-flaring anemone active regions and their host coronal holes, by examining spatial and magnetic field distributions during the rise phase of the solar cycle, in the years 2011–2014. Methods. Anemone regions were identified from the minimum-distance threshold, estimated using the data available in the online catalogs for on-disk active regions and coronal holes. Along with the source-region area and magnetic field characteristics, associated filament and flare cases were also located. Regions with and without flare events were further selected for a detailed statistical examination to understand the major properties of the energetic events, both eruptive and confined, at the anemone-type active regions. Results. Identified anemone regions showed weak asymmetry in their spatial distribution over the solar disk, with yearly average independent from mean sunspot number trend, during the rise phase of solar cycle 24. With the progression in solar cycle, the area and minimum-distance parameters indicated a decreasing trend in their magnitudes, while the magnetic field characteristics indicated an increase in their estimated magnitudes. More than half of the regions in our database had an association with a filament structure, and nearly a third were linked with a magnetic reconnection (flare) event. Anemone regions with and without flares had clear distinctions in their source-region characteristics evident from the distribution of their properties and density analysis. The key differences included larger area and magnetic field magnitudes for flaring anemone regions, along with smaller distances between the centers of the active region and its host coronal hole.

scholarly journals Variations of the Coronal Radiation in X-ray Related to Coronal Holes, Active Region Loop Systems, Bright Points

1994 ◽  
Vol 143 ◽  
pp. 159-171
Author(s):  
Ester Antonucci
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Large Scale ◽  
Coronal Holes ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Small Scale ◽  
X Ray ◽  
Coronal Structures

The coronal features observed in X-ray emission, varying from the small-scale, short-lived bright points to the large-scale, long-lived coronal holes, are closely associated with the coronal magnetic field and its topology, and their variability depends strongly on the solar cycle. Here we discuss the spatial distribution of the coronal structures, the frequency distribution of the brightness variations in active regions, and the role of magnetic reconnection in determining the variability of the coronal features, on the basis of the new observations of the soft X-ray emission recently obtained with the Yohkoh satellite and the NIXT experiment.

IV. Small Scale Magnetic Fields

1988 ◽  
Vol 20 (1) ◽  
pp. 97-100
Author(s):  
S.K. Solanki
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Empirical Investigation ◽  
Solar Magnetic Field ◽  
Considerable Progress ◽  
Small Scale ◽  
Free Medium ◽  
Magnetic Elements

Considerable progress has been made during the last four years in the theoretical and empirical investigation of the small scale solar magnetic field and associated phenomena. Although the basic outlines established in the 1970s of the structure of the field, namely small fluxtubes or magnetic elements with kllogauss fields embedded in a relatively field free medium have survived, many of the details have changed and some of the large gaps in our knowlegde of these captivating structures have been filled. In the following we briefly outline some of the highlights.

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.

Analysis of the He i chromosphere in relation to the magnetic field activity over solar cycle time periods

2020 ◽  
Vol 497 (1) ◽  
pp. 969-975
Author(s):  
K J Li ◽  
W Feng
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Active Regions ◽  
Solar Observatory ◽  
Small Scale ◽  
Large Magnetic Field ◽  
National Solar Observatory ◽  
Magnetic Elements ◽  
The Magnetic Field

ABSTRACT Solar synoptic maps of both He i 10 830 Å intensity and the magnetic field, which are observed by the Vacuum Telescope at National Solar Observatory/Kitt Peak from 2005 July to 2013 March are utilized to study relationship of He i intensity of the weakly magnetized chromosphere with the respective magnetic field strength. Strong absorption in He i intensity presents the butterfly-pattern latitude migration zone as active regions do, indicating that strong magnetic field corresponds to high-temperature structures of the active chromosphere. For He i intensity and magnetic field strength, their distribution at the time-latitude coordinate and their time series at each of the 180 measurement latitude are found to be significantly negatively correlated with each other in most cases. When a solar hemisphere is divided into three latitude bands: low, middle, and high latitude bands, and even after large magnetic field values not taken into account, they are still negatively correlated in most cases, and further when large magnetic field values are subtracted He i intensity varies more sensitively with magnetic field strength than the corresponding cases when large magnetic field values are not subtracted. He i intensity in the quiet chromosphere thus mainly presents a negative correlation with the magnetic field, and the heating of the quiet chromosphere is inferred to be caused mainly by small-scale magnetic elements.

II. Spots and Intense Flux Tubes

1988 ◽  
Vol 20 (1) ◽  
pp. 58-63
Author(s):  
J.C. Henoux
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
High Resolution ◽  
Solar Magnetic Field ◽  
Solar Physics ◽  
Small Scale ◽  
The Sun ◽  
Flux Tubes ◽  
Flux Concentration ◽  
Scientific Meetings

The development of research on starspots, stellar activity, and the suspected relationship between coronal heating and magnetic field have reenforced the interest of the study of the solar magnetic field and the study of the associated thermodynamic structures. Several proceedings of scientific meetings appeared from 1984 to 1987 (Measurements of Solar Vector Magnetic Fields, 1985 (I); The Hydrodynamics of the Sun, 1984 (II); High Resolution in Solar Physics, 1985 (III); Theoritical Problems in High Resolution Solar Physics, 1985 (IV); Small Scale Magnetic Flux Concentration in the Solar Atmosphere, 1986 (V)). The finding that the solar irradiance in affected by solar activity has renewed interest in photometry of sunspots and faculae. Sunspots have been used for investigating solar differential and meridional motions. Some results are also found in Section III.

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 Photospheric magnetic structure of coronal holes

2019 ◽  
Vol 629 ◽  
pp. A22 ◽  
Author(s):  
Stefan J. Hofmeister ◽  
Dominik Utz ◽  
Stephan G. Heinemann ◽  
Astrid Veronig ◽  
Manuela Temmer
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Coronal Hole ◽  
Magnetic Structure ◽  
Coronal Holes ◽  
Line Of Sight ◽  
Magnetic Elements ◽  
Background Magnetic Field ◽  
The Individual ◽  
The Magnetic Field

In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at ±25 G. We find that the number of magnetic bright points in magnetic elements is well correlated with the area of the magnetic elements (cc = 0.83 ± 0.01). Further, the magnetic flux of the individual magnetic elements inside coronal holes is related to their area by a power law with an exponent of 1.261 ± 0.004 (cc = 0.984 ± 0.001). Relating the magnetic elements to the overall structure of coronal holes, we find that on average (69 ± 8)% of the overall unbalanced magnetic flux of the coronal holes arises from long-lived magnetic elements with lifetimes > 40 h. About (22 ± 4)% of the unbalanced magnetic flux arises from a very weak background magnetic field in the quiet coronal hole regions with a mean magnetic field density of about 0.2−1.2 G. This background magnetic field is correlated to the flux of the magnetic elements with lifetimes of > 40 h (cc = 0.88 ± 0.02). The remaining flux arises from magnetic elements with lifetimes < 40 h. By relating the properties of the magnetic elements to the overall properties of the coronal holes, we find that the unbalanced magnetic flux of the coronal holes is completely determined by the total area that the long-lived magnetic elements cover (cc = 0.994 ± 0.001).

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.

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