Comparative Analysis of Terrestrial and Satellite Observations of Photospheric Magnetic Field in an Appendix to Simulation of Parameters of Coronal Holes and Solar Wind

Coronal holes are regions of depressed density and temperature in the inner corona that coincide with open magnetic field lines. They were recognized for many years on eclipse photographs, but real understanding of their importance began to emerge only after data from rocket and satellite observations were analyzed. Wilson (1976) has summarized the early history of research on coronal holes.

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Plasma Flow and Solar Wind Acceleration in Non-Radial Coronal Magnetic Fields

Symposium - International Astronomical Union ◽

10.1017/s0074180900030151 ◽

1983 ◽

Vol 102 ◽

pp. 473-477

Author(s):

H. Biernat ◽

N. Kömle ◽

H. Rucker

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Plasma Flow ◽

Coronal Holes ◽

Expansion Velocity ◽

The Sun ◽

Solar Wind Acceleration ◽

Coronal Magnetic Fields ◽

Field Lines ◽

The Magnetic Field

In the vicinity of the Sun — especially above coronal holes — the magnetic field lines show strong non-radial divergence and considerable curvature (see e.g. Kopp and Holzer, 1976; Munro and Jackson, 1977; Ripken, 1977). In the following we study the influence of these characteristics on the expansion velocity of the solar wind.

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Formation of current sheets and plasmoids within corotating/stream interaction regions

10.5194/egusphere-egu2020-2102 ◽

2020 ◽

Author(s):

Timofey Sagitov ◽

Roman Kislov

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Coronal Hole ◽

High Speed ◽

Solar Rotation ◽

Coronal Holes ◽

Rotation Period ◽

The Sun ◽

Current Sheets ◽

Interaction Regions

High speed streams originating from coronal holes are long-lived plasma structures that form corotating interaction regions (CIRs) or stream interface regions (SIRs) in the solar wind. The term CIR is used for streams existing for at least one solar rotation period, and the SIR stands for streams with a shorter lifetime. Since the plasma flows from coronal holes quasi-continuously, CIRs/SIRs simultaneously expand and rotate around the Sun, approximately following the Parker spiral shape up to the Earth&#8217;s orbit.Coronal hole streams rotate not only around the Sun but also around their own axis of simmetry, resembling a screw. This effect may occur because of the following mechanisms: (1) the existence of a difference between the solar wind speed at different sides of the stream, (2) twisting of the magnetic field frozen into the plasma, and&#160; (3) a vortex-like motion of the edge of the mothering coronal hole at the Sun. The screw type of the rotation of a CIR/SIR can lead to centrifugal instability if CIR/SIR inner layers have a larger angular velocity than the outer. Furthermore, the rotational plasma movement and the stream distortion can twist magnetic field lines. The latter contributes to the pinch effect in accordance with a well-known criterion of Suydam instability (Newcomb, 1960, doi: 10.1016/0003-4916(60)90023-3). Owing to the presence of a cylindrical current sheet at the boundary of a coronal hole, conditions for tearing instability can also appear at the CIR/SIR boundary. Regardless of their geometry, large scale current sheets are subject to various instabilities generating plasmoids. Altogether, these effects can lead to the formation of a turbulent region within CIRs/SIRs, making them filled with current sheets and plasmoids.&#160;We study a substructure of CIRs/SIRs, characteristics of their rotation in the solar wind, and give qualitative estimations of possible mechanisms which lead to splitting of the leading edge a coronal hole flow and consequent formation of current sheets within CIRs/SIRs.

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Analysis of the distribution, rotation and scale characteristics of solar wind switchbacks: comparison between the first and second encounters of Parker Solar Probe

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/ac49e4 ◽

2022 ◽

Author(s):

Mingming Meng ◽

Ying Liu ◽

Chong Chen ◽

Rui Wang

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Coronal Holes ◽

Minimum Variance ◽

Tangential Component ◽

Magnetic Field Rotation ◽

Anticlockwise Rotation ◽

Scale Characteristics ◽

Field Lines ◽

The Magnetic Field

Abstract The S-shaped magnetic structure in the solar wind formed by the twisting of magnetic field lines is called a switchback, whose main characteristics are the reversal of the magnetic field and the significant increase in the solar wind radial velocity. We identify 242 switchbacks during the first two encounters of Parker Solar Probe (PSP). Statistics methods are applied to analyze the distribution and the rotation angle and direction of the magnetic field rotation of the switchbacks. The diameter of switchbacks is estimated with a minimum variance analysis (MVA) method based on the assumption of a cylindrical magnetic tube. We also make a comparison between switchbacks from inside and the boundary of coronal holes. The main conclusions are as follows: (1) the rotation angles of switchbacks observed during the first encounter seem larger than those of the switchbacks observed during the second encounter in general; (2) the tangential component of the velocity inside the switchbacks tends to be more positive (westward) than in the ambient solar wind; (3) switchbacks are more likely to rotate clockwise than anticlockwise, and the number of switchbacks with clockwise rotation is 1.48 and 2.65 times of those with anticlockwise rotation during the first and second encounters, respectively; (4) the diameter of switchbacks is about 10^5 km on average and across five orders of magnitude (10^3 – 10^7 km).

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The dynamo-wind feedback loop : Assessing their non-linear interplay

Proceedings of the International Astronomical Union ◽

10.1017/s174392132000037x ◽

2019 ◽

Vol 15 (S354) ◽

pp. 215-223

Author(s):

Barbara Perri ◽

Allan Sacha Brun ◽

Antoine Strugarek ◽

Victor Réville

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Coronal Holes ◽

Coronal Magnetic Field ◽

Space Environment ◽

Cycle Phase ◽

Activity Cycles ◽

Spatio Temporal ◽

Field Lines ◽

The Impact

AbstractThough generated deep inside the convection zone, the solar magnetic field has a direct impact on the Earth space environment via the Parker spiral. It strongly modulates the solar wind in the whole heliosphere, especially its latitudinal and longitudinal speed distribution over the years. However the wind also influences the topology of the coronal magnetic field by opening the magnetic field lines in the coronal holes, which can affect the inner magnetic field of the star by altering the dynamo boundary conditions. This coupling is especially difficult to model because it covers a large variety of spatio-temporal scales. Quasi-static studies have begun to help us unveil how the dynamo-generated magnetic field shapes the wind, but the full interplay between the solar dynamo and the solar wind still eludes our understanding.We use the compressible magnetohydrodynamical (MHD) code PLUTO to compute simultaneously in 2.5D the generation and evolution of magnetic field inside the star via an α-Ω dynamo process and the corresponding evolution of a polytropic coronal wind over several activity cycles for a young Sun. A multi-layered boundary condition at the surface of the star connects the inner and outer stellar layers, allowing both to adapt dynamically. Our continuously coupled dynamo-wind model allows us to characterize how the solar wind conditions change as a function of the cycle phase, and also to quantify the evolution of integrated quantities such as the Alfvén radius. We further assess the impact of the solar wind on the dynamo itself by comparing our results with and without wind feedback.

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Origin of the Solar Wind and Open Coronal Magnetic Structures

Symposium - International Astronomical Union ◽

10.1017/s0074180900182622 ◽

2004 ◽

Vol 219 ◽

pp. 587-598

Author(s):

Shadia Rifai Habbal ◽

Richard Woo

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Mass Loss ◽

Loss Rate ◽

Interplanetary Space ◽

Mass Loss Rate ◽

Coronal Holes ◽

Significant Fraction ◽

Unexpected Result ◽

Magnetic Structures

Identifying the regions of open magnetic structures in the corona, namely regions where field lines expand outwards into interplanetary space, is equivalent to establishing the origin of the solar wind at the Sun. A review of recent studies, based on the comparison of the distribution, as a function of latitude, of density and velocity in the inner corona and in interplanetary space, is presented. It is shown how, at solar minimum, this comparison leads to the unexpected result that the fast solar wind expands indiscriminately from a significant fraction of the solar surface, not limited to polar coronal holes, as has been believed for the past three decades. It is also shown how polarization measurements of coronal forbidden lines, which yield the direction of the coronal magnetic field, lend further support to this result. The implications of these findings are that a significant fraction of the solar magnetic field is primarily open, expanding almost radially into interplanetary space, carrying with it the imprint of the distribution of density in the corona, while the ‘closed’ structures contribute a small fraction to the overall filling factor of coronal density structures. Furthermore, the solar wind particle flux is found to be correlated with density, implying a higher mass loss rate from the higher density quiet Sun regions, and the likelihood of a solar cycle dependence in the mass loss rate, as the are of polar coronal holes decreases with increased solar activity.

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