Photospheric Magnetic Reconnection and Canceling Magnetic Features on the Sun

1999 ◽  
Vol 515 (1) ◽  
pp. 435-440 ◽  
Author(s):  
Yuri E. Litvinenko
Keyword(s):  
Magnetic Reconnection ◽  
The Sun ◽  
Magnetic Features

scholarly journals Multispacecraft recovery of a magnetic cloud and its origin from magnetic reconnection on the Sun

2009 ◽  
Vol 114 (A4) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. Möstl ◽  
C. J. Farrugia ◽  
C. Miklenic ◽  
M. Temmer ◽  
A. B. Galvin ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Magnetic Cloud ◽  
The Sun

scholarly journals Relationships Between Sequential Chromospheric Brightening and the Corona

2016 ◽  
Vol 12 (S327) ◽  
pp. 117-127
Author(s):  
M. S. Kirk ◽  
K. S. Balasubramaniam ◽  
J. Jackiewicz ◽  
H. R. Gilbert
Keyword(s):  
Magnetic Flux ◽  
Coronal Mass Ejection ◽  
Fast Moving ◽  
Atmospheric Environment ◽  
The Sun ◽  
Flux Emergence ◽  
Complex Region ◽  
Magnetic Features ◽  
Mass Ejection ◽  
Early Indication

AbstractThe chromosphere is a complex region that acts as an intermediary between the magnetic flux emergence in the photosphere and the magnetic features seen in the corona. Large eruptions in the chromosphere of flares and filaments are often accompanied by ejections of coronal mass off the sun. Several studies have observed fast-moving progressive trains of compact bright points (called Sequential Chromospheric Brightenings or SCBs) streaming away from chromospheric flares that also produce a coronal mass ejection (CME). In this work, we review studies of SCBs and search for commonalties between them. We place these findings into a larger context with contemporary chromospheric and coronal observations. SCBs are fleeting indicators of the solar atmospheric environment as it existed before their associated eruption. Since they appear at the very outset of a flare eruption, SCBs are good early indication of a CME measured in the chromosphere.

scholarly journals Complexity of magnetic fields on red dwarfs

2019 ◽  
Vol 629 ◽  
pp. A83 ◽  
Author(s):  
N. Afram ◽  
S. V. Berdyugina
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Circular Polarization ◽  
Large Fraction ◽  
The Sun ◽  
M Dwarfs ◽  
Magnetic Studies ◽  
Molecular Lines ◽  
Magnetic Features ◽  
M Dwarf

Context. Magnetic fields in cool stars can be investigated by measuring Zeeman line broadening and polarization in atomic and molecular lines. Similar to the Sun, these fields are complex and height-dependent. Many molecular lines dominating M-dwarf spectra (e.g., FeH, CaH, MgH, and TiO) are temperature- and Zeeman-sensitive and form at different atmospheric heights, which makes them excellent probes of magnetic fields on M dwarfs. Aims. Our goal is to analyze the complexity of magnetic fields in M dwarfs. We investigate how magnetic fields vary with the stellar temperature and how “surface” inhomogeneities are distributed in height – the dimension that is usually neglected in stellar magnetic studies. Methods. We have determined effective temperatures of the photosphere and of magnetic features, magnetic field strengths and filling factors for nine M dwarfs (M1–M7). Our χ2 analysis is based on a comparison of observed and synthetic intensity and circular polarization profiles. Stokes profiles were calculated by solving polarized radiative transfer equations. Results. Properties of magnetic structures depend on the analyzed atomic or molecular species and their formation heights. Two types of magnetic features similar to those on the Sun have been found: a cooler (starspots) and a hotter (network) one. The magnetic field strength in both starspots and network is within 3–6 kG, on average it is 5 kG. These fields occupy a large fraction of M dwarf atmospheres at all heights, up to 100%. The plasma β is less than one, implying highly magnetized stars. Conclusions. A combination of molecular and atomic species and a simultaneous analysis of intensity and circular polarization spectra have allowed us to better decipher the complexity of magnetic fields on M dwarfs, including their dependence on the atmospheric height. This work provides an opportunity to investigate a larger sample of M dwarfs and L-type brown dwarfs.

scholarly journals The influence of solar wind turbulence on geomagnetic activity

2008 ◽  
Vol 15 (1) ◽  
pp. 53-59 ◽  
Author(s):  
D. Jankovičovà ◽  
Z. Vörös ◽  
J. Šimkanin
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Interplanetary Magnetic Field ◽  
Space Weather ◽  
Coupled System ◽  
Statistical Moment ◽  
The Sun ◽  
H Index ◽  
Magnetic Turbulence

Abstract. The importance of space weather and its forecasting is growing as interest in studying geoeffective processes in the Sun – solar wind – magnetosphere – ionosphere coupled system is increasing. In this paper higher order statistical moments of interplanetary magnetic field and geomagnetic SYM-H index fluctuations are compared. The proper description of fluctuations in the solar wind can elucidate important aspects of the geoeffectivity of upstream turbulence and contribute to our understanding of space weather. Our results indicate that quasi-stationary intervals during both quiet and stormy periods have to be investigated in order to find correlations between upstream and geomagnetic conditions. We found that the fourth statistical moment (kurtosis), which was not considered in previous studies, appears to be a new geoeffective parameter. Intermittency of the magnetic turbulence in the solar wind can influence the efficiency of the solar wind – magnetosphere coupling through affecting magnetic reconnection at the Earth's magnetopause.

High-resolution observations of changing magnetic features on the sun

1986 ◽  
Vol 306 ◽  
pp. 304 ◽  
Author(s):  
K. P. Topka ◽  
T. D. Tarbell ◽  
A. M. Title
Keyword(s):  
High Resolution ◽  
The Sun ◽  
Magnetic Features

scholarly journals OBSERVATIONS OF AN X-SHAPED RIBBON FLARE IN THE SUN AND ITS THREE-DIMENSIONAL MAGNETIC RECONNECTION

2016 ◽  
Vol 823 (1) ◽  
pp. L13 ◽  
Author(s):  
Y. Li ◽  
J. Qiu ◽  
D. W. Longcope ◽  
M. D. Ding ◽  
K. Yang
Keyword(s):  
Magnetic Reconnection ◽  
Three Dimensional ◽  
The Sun

scholarly journals Magnetic reconnection and energy release on the Sun and solar-like stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 191-200
Author(s):  
Lidia van Driel-Gesztelyi
Keyword(s):  
Free Energy ◽  
Magnetic Reconnection ◽  
Energy Release ◽  
Energy Content ◽  
Magnetic Flux Density ◽  
The Sun ◽  
X Rays ◽  
Stellar Flares ◽  
Wide Wavelength Range ◽  
Hot Corona

AbstractMagnetic reconnection is thought to play an important role in liberating free energy stored in stressed magnetic fields. The consequences vary from undetectable nanoflares to huge flares, which have signatures over a wide wavelength range, depending on e.g. magnetic topology, free energy content, total flux, and magnetic flux density of the structures involved. Events of small energy release, which are thought to be the most numerous, are one of the key factors in the existence of a hot corona in the Sun and solar-like stars. The majority of large flares are ejective, i.e. involve the expulsion of large quantities of mass and magnetic field from the star. Since magnetic reconnection requires small length-scales, which are well below the spatial resolution limits of even the solar observations, we cannot directly observe magnetic reconnection happening. However, there is a plethora of indirect evidences from X-rays to radio observations of magnetic reconnection. I discuss key observational signatures of flares on the Sun and solar-paradigm stellar flares and describe models emphasizing synergy between observations and theory.

Possible Generation Mechanism for Alfvenic Velocity Spikes and Magnetic Field Switchbacks as Observed by PSP

2020 ◽  
Author(s):  
Xingyu Zhu ◽  
Jiansen He ◽  
Die Duan ◽  
Lei Zhang ◽  
Liping Yang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Field Line ◽  
Magnetic Field Line ◽  
Small Scale ◽  
The Sun ◽  
Internal Temperature ◽  
External Temperature ◽  
Pulse Type ◽  
The Magnetic Field

<div>According to Parker's theory in the 1950s, the magnetic lines of force extending from the sun to the interplanetary appear to be Archimedean spirals. From 1960 to 1970, it was found that the interplanetary magnetic field not only follows the Archimedes spiral structure, but also has the characteristics of Alfvenic turbulence. How do these Alfvenic turbulence occur? What will be the characteristics when getting close to the Sun? Parker Solar Probe at 0.17au has found that there are often intermittent Alfvenic pulses (or called Alfvenic velocity spikes) in the solar wind. These pulses are high enough that the disturbed magnetic lines may even turn back. What's more interesting is that there is always a compressibility disturbance along with the Alfven pulse: the temperature and density inside and outside the Alfven pulse are different, the internal temperature is often higher than the external temperature, some of the internal density is higher than the external and some is lower than the external. The Alfven pulse often shows asymmetry on both sides: the magnetic field and velocity on one side are "clean" jumps, while on the other side are multiple small-scale disturbances of variables in the transition boundary layer. In view of this new phenomenon of magnetic field line switch back with compressed Alfven pulse, how it is generated is raising a hot debate. It is thought that the exchange magnetic reconnection of the solar atmosphere may be the underlying physical mechanism. But in the traditional exchange magnetic reconnection image, after reconnection, the zigzag magnetic field line can easily become smooth, which can not maintain the distortion of the magnetic field line, and may not be able to explain the observed Alfven pulses. In this work, we propose a new model called "Excitation of Alfven Pulses by Continuous Intermittent Interchange Reconnection with Guide Field Discontinuity" (EAP-CIIR-GFD). By analyzing and comparing the simulation results and observation results, we find that the model can explain the following observation features: (1) Alfven disturbance is pulse type and asymmetric; (2) Alfven pulse is compressible with the enhancement of internal temperature and the increase or decrease of the internal density; (3) Alfven pulse can cause serious distortion of the magnetic field line. Improvements to the model will also be discussed in the report.</div>

Magnetic reconnection as the origin of X-ray jets and Hα surges on the Sun

Nature ◽  
1995 ◽  
Vol 375 (6526) ◽  
pp. 42-44 ◽  
Author(s):  
Takaaki Yokoyama ◽  
Kazunari Shibata
Keyword(s):  
Magnetic Reconnection ◽  
The Sun ◽  
X Ray
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