Magnetic Flux Emergence into the Solar Corona. I. Its Role for the Reversal of Global Coronal Magnetic Fields

2001 ◽  
Vol 561 (1) ◽  
pp. 406-419 ◽  
Author(s):  
M. Zhang ◽  
B. C. Low
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Solar Corona ◽  
Flux Emergence ◽  
Coronal Magnetic Fields

scholarly journals Photospheric and coronal magnetic fields in six magnetographs

2019 ◽  
Vol 626 ◽  
pp. A67 ◽  
Author(s):  
Ilpo Virtanen ◽  
Kalevi Mursula
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Solar Corona ◽  
Source Surface ◽  
Scaling Factors ◽  
Solar Cycle Variation ◽  
Coronal Magnetic Fields ◽  
Resolution Data

Context. Solar photospheric magnetic fields have been observed since the 1950s and calibrated digital data are available from the 1970s onwards. Synoptic maps of the photospheric magnetic field are widely used in solar research, especially in the modeling of the solar corona and solar wind, and in studies of space weather and space climate. Magnetic flux density of the solar corona is a key parameter for heliospheric physics. Aims. The observed photospheric magnetic flux depends on the instrument and data processing used, which is a major problem for long-term studies. Here we scale the different observations of the photospheric field to the same absolute level and form a uniform record of coronal magnetic flux since the 1970s. Methods. We use a recently suggested method of harmonic scaling, which scales any pair of synoptic observations of any resolution to the same level. After scaling, we use the Potential Field Source Surface (PFSS) model to calculate the scaled magnetic field at various altitudes from photosphere to coronal source surface. Results. Harmonic scaling gives effective, latitudinally dependent scaling factors, which vary over the solar cycle. When scaling low-resolution data to high-resolution data, effective scaling factors are typically largest at low latitudes in the ascending phase of solar cycle and smallest for unipolar polar fields around solar minima. The harmonic scaling method used here allows for the observations of the different data sets to be scaled to the same level and the scaled unsigned coronal flux densities agree very well with each other. We also find that scaled coronal magnetic fields show a slightly different solar cycle variation from that of the nonscaled fields.

scholarly journals Relating magnetic reconnection to coronal heating

2015 ◽  
Vol 373 (2042) ◽  
pp. 20140263 ◽  
Author(s):  
D. W. Longcope ◽  
L. A. Tarr
Keyword(s):  
Energy Dissipation ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
Active Regions ◽  
Coronal Heating ◽  
Flux Emergence ◽  
Coronal Magnetic Fields ◽  
Field Lines ◽  
A Current

It is clear that the solar corona is being heated and that coronal magnetic fields undergo reconnection all the time. Here we attempt to show that these two facts are related—i.e. coronal reconnection generates heat. This attempt must address the fact that topological change of field lines does not automatically generate heat. We present one case of flux emergence where we have measured the rate of coronal magnetic reconnection and the rate of energy dissipation in the corona. The ratio of these two, , is a current comparable to the amount of current expected to flow along the boundary separating the emerged flux from the pre-existing flux overlying it. We can generalize this relation to the overall corona in quiet Sun or in active regions. Doing so yields estimates for the contribution to coronal heating from magnetic reconnection. These estimated rates are comparable to the amount required to maintain the corona at its observed temperature.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

scholarly journals The physical mechanisms that initiate and drive solar eruptions

2013 ◽  
Vol 8 (S300) ◽  
pp. 184-196 ◽  
Author(s):  
Guillaume Aulanier
Keyword(s):  
Magnetic Fields ◽  
Long Range ◽  
Large Scale ◽  
State Of The Art ◽  
Flux Emergence ◽  
Physical Mechanisms ◽  
Driving Mechanisms ◽  
Coronal Magnetic Fields ◽  
Solar Eruptions

AbstractSolar eruptions are due to a sudden destabilization of force-free coronal magnetic fields. But the detailed mechanisms which can bring the corona towards an eruptive stage, then trigger and drive the eruption, and finally make it explosive, are not fully understood. A large variety of storage-and-release models have been developed and opposed to each other since 40 years. For example, photospheric flux emergence vs. flux cancellation, localized coronal reconnection vs. large-scale ideal instabilities and loss of equilibria, tether-cutting vs. breakout reconnection, and so on. The competition between all these approaches has led to a tremendous drive in developing and testing all these concepts, by coupling state-of-the-art models and observations. Thanks to these developments, it now becomes possible to compare all these models with one another, and to revisit their interpretation in light of their common and their different behaviors. This approach leads me to argue that no more than two distinct physical mechanisms can actually initiate and drive prominence eruptions: the magnetic breakout and the torus instability. In this view, all other processes (including flux emergence, flux cancellation, flare reconnection and long-range couplings) should be considered as various ways that lead to, or that strengthen, one of the aforementioned driving mechanisms.

Possible Influence of Large Structures of Coronal Magnetic Fields on the Propagation of Solar Cosmic Rays

1994 ◽  
Vol 144 ◽  
pp. 107-109 ◽  
Author(s):  
S. Fischer ◽  
M. Vandas ◽  
E. V. Vashenyuk
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Neutral Line ◽  
Cosmic Ray ◽  
Heliospheric Current Sheet ◽  
Solar Cosmic Rays ◽  
Large Structures ◽  
The Earth ◽  
Coronal Magnetic Fields

AbstractAn investigation of mutual positions of footpoints of the Earth in the solar corona and the heliospheric current sheet (for both relativistic and nonrelativistic solar cosmic ray events) has not revealed any apparent dependence of observed SCR increases on the coronal distance of footpoints from the neutral line.

scholarly journals Magnetic flux emergence and associated dynamic phenomena in the Sun

2012 ◽  
Vol 370 (1970) ◽  
pp. 3088-3113 ◽  
Author(s):  
Vasilis Archontis
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Numerical Experiments ◽  
Solar Interior ◽  
The Sun ◽  
Flux Emergence ◽  
Dynamic Events ◽  
Comprehensive Picture ◽  
Potential Applications ◽  
Dynamic Phenomena

We present a review of the process of magnetic flux emergence in the Sun. We focus on observations and numerical experiments that explore the dynamical rise of magnetic fields from the solar interior to the corona. We describe the response of the highly stratified solar atmosphere on flux emergence and, consequently, we present a comprehensive picture of the coupling between solar dynamic events and flux emergence. We discuss potential applications of this process in other astrophysical environments.

scholarly journals Interpreting magnetic helicity flux in solar flux emergence

2019 ◽  
Vol 85 (2) ◽  
Author(s):  
C. Prior ◽  
D. MacTaggart
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Solar Physics ◽  
Standard Form ◽  
Solar Flux ◽  
Magnetic Helicity ◽  
Flux Emergence ◽  
Topological Information ◽  
Solar Observations ◽  
Mhd Simulations

Magnetic helicity flux gives information about the topology of a magnetic field passing through a boundary. In solar physics applications, this boundary is the photosphere and magnetic helicity flux has become an important quantity in analysing magnetic fields emerging into the solar atmosphere. In this work we investigate the evolution of magnetic helicity flux in magnetohydrodynamic (MHD) simulations of solar flux emergence. We consider emerging magnetic fields with different topologies and investigate how the magnetic helicity flux patterns correspond to the dynamics of emergence. To investigate how the helicity input is connected to the emergence process, we consider two forms of the helicity flux. The first is the standard form giving topological information weighted by magnetic flux. The second form represents the net winding and can be interpreted as the standard helicity flux less the magnetic flux. Both quantities provide important and distinct information about the structure of the emerging field and these quantities differ significantly for mixed sign helicity fields. A novel aspect of this study is that we account for the varying morphology of the photosphere due to the motion of the dense plasma lifted into the chromosphere. Our results will prove useful for the interpretation of magnetic helicity flux maps in solar observations.

Atomic Structure Calculations of Landé g Factors of Astrophysical Interest with Direct Applications for Solar Coronal Magnetometry

2021 ◽  
Vol 923 (2) ◽  
pp. 186
Author(s):  
Sacha Schiffmann ◽  
Tomas Brage ◽  
Philip Gordon Judge ◽  
Alin Razvan Paraschiv ◽  
Kai Wang
Keyword(s):  
Magnetic Fields ◽  
Solar Corona ◽  
Atomic Structure ◽  
Theoretical Study ◽  
Solar Telescope ◽  
Coronal Magnetic Fields ◽  
Infrared Wavelengths ◽  
Atomic Structure Calculations ◽  
New Instruments ◽  
Structure Calculations

Abstract We perform a detailed theoretical study of the atomic structure of ions with ns 2 np m ground configurations and focus on departures from LS coupling, which directly affect the Landé g factors of magnetic dipole lines between levels of the ground terms. Particular emphasis is given to astrophysically abundant ions formed in the solar corona (those with n = 2,3) with M1 transitions spanning a broad range of wavelengths. Accurate Landé g factors are needed to diagnose coronal magnetic fields using measurements from new instruments operating at visible and infrared wavelengths, such as the Daniel K. Inouye Solar Telescope. We emphasize an explanation of the dynamics of atomic structure effects for nonspecialists.

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