The reconnection of magnetic field lines in the solar corona

1975 ◽  
Vol 196 ◽  
pp. L129 ◽  
Author(s):  
N. R., Jr. Sheeley ◽  
J. D. Bohlin ◽  
G. E. Brueckner ◽  
J. D. Purcell ◽  
V. E. Scherrer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Field Lines

Reconstruction of the magnetic connection from Mercury to the solar corona

2020 ◽  
Author(s):  
Alessandro Ippolito ◽  
Christina Plainaki ◽  
Gaetano Zimbardo ◽  
Stefano Massetti ◽  
Anna Milillo
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Magnetic Data ◽  
Monte Carlo Code ◽  
Correlation Lengths ◽  
Magnetic Fluctuation ◽  
Magnetic Field Model ◽  
Field Lines ◽  
Field Correlation ◽  
Accelerated Particles

<p>The magnetic foot point of Mercury on the solar disk has been reconstructed for selected case studies, in order to better understand the interaction between the solar corona and the planet. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that gives a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a “local” diffusion coefficient, which is a function of the fluctuation level and magnetic field correlation lengths. The simulation is tailored to specific events by using the observed values of solar wind velocity and magnetic fluctuation levels. Magnetic data from MAG/MESSENGER have been considered to compute the magnetic fluctuation level, while, concerning proton fluxes, FIPS/MESSENGER data has been taken into account. A number of SEP events observed on Mercury during 2011 and 2012 have been analysed, studying, for each event, the magnetic connection from Mercury to the solar corona, and the position of the active region possibly source of the accelerated particles observed.</p>

Reconstruction of the magnetic connection from Mercury to the solar corona, during events in the solar proton fluxes observed by MESSENGER

2021 ◽  
Author(s):  
Alessandro Ippolito ◽  
Christina Plainaki ◽  
Gaetano Zimbardo ◽  
Tommaso Alberti ◽  
Stefano Massetti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Solar Proton ◽  
Source Surface ◽  
Monte Carlo Code ◽  
Correlation Lengths ◽  
Magnetic Turbulence ◽  
Proton Fluxes ◽  
Magnetic Field Model ◽  
Field Lines

<p>We present a study conducted on a number of selected events characterised by a significant increase in the solar proton fluxes measured by FIPS-MESSENGER during the period 2011-2013. For each of them, the magnetic connection between Mercury and the solar corona (Source Surface Field @2.5 R<sub>S</sub>) has been reconstructed, in order to identify the possible source of the accelerated particles on the solar surface. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that computes a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a “local” diffusion coefficient, which is a function of the fluctuation level and magnetic turbulence correlation lengths. The simulation is tailored to the specific events by using the observed values of solar wind velocity and magnetic fluctuation levels.</p>

Relation between the magnetic free energy and relative magnetic helicity in the MHD extreme state of solar corona

2020 ◽  
Author(s):  
Shangbin Yang ◽  
Joerg Buechner ◽  
Hongqi Zhang
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Solar Activity ◽  
Solar Corona ◽  
Solar Flares ◽  
Magnetic Helicity ◽  
Magnetic Free Energy ◽  
Helicity Conservation ◽  
Field Lines ◽  
Extreme State

<p>Magnetic helicity is a quantity describing the twist, writhe, and torsion of magnetic field lines and magnetic configurations . The concept of magnetic helicity has successfully been applied to characterize solar coronal processes. A conjecture about one approximation relation between free magnetic free energy and relative magnetic helicity in the MHD extreme state of solar corona has been proposed by using the concept of magnetic helicity conservation and Lie-Poisson mechanical structure of MHD. We use constant α force-free filed extrapolation to check out this relation. We also apply this relation to analyze the results from the simulations and observations. Such relation may be helpful to predict the solar activity like the solar flares and CMEs</p>

scholarly journals The Evolution of a Sheared Potential Magnetic Field in the Solar Corona

1990 ◽  
Vol 142 ◽  
pp. 309-312
Author(s):  
J. T. Karpen ◽  
S. K. Antiochos ◽  
C. R. DeVore
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Boundary Surface ◽  
Null Point ◽  
Current Sheets ◽  
Field Lines ◽  
Line Tying ◽  
Analytic Models ◽  
Coronal Field ◽  
A Current

Several theoretical studies have proposed that, in response to photospheric foot-point motions, current sheets can be generated in the solar corona without the presence of a null point in the initial potential magnetic field. In these analytic models, current sheets form wherever the coronal field dips down and is parallel to the photosphere. A fundamental assumption in these analyses — commonly referred to as the line-tying assumption — is that all coronal field lines are anchored to a boundary surface representing the top of the dense, gas-pressure-dominated photosphere. In theoretical arguments presented elsewhere (Karpen, Antiochos, and DeVore 1989), however, we show that line-tying is not valid for “dipped” coronal fields, and hence that the conclusions of the line-tied models are incorrect. We contend that current sheets will not form if the photosphere-corona interface is represented by a physically valid model. Here we summarize a numerical investigation of the response of a “dipped” potential magnetic field in a hydrostatic-equilibrium atmosphere to shearing motions of the foot points. Our results show that, in the absence of artificial line-tying conditions, a current sheet indeed does not form at the location of the dip. Rather, the dipped magnetic field rises, causing upflows of photospheric and chromospheric plasma.

scholarly journals Modeling static magnetic field structures in solar corona

2005 ◽  
pp. 1-10
Author(s):  
V.M. Cadez
Keyword(s):  
Magnetic Field ◽  
Boundary Conditions ◽  
Solar Corona ◽  
Static Magnetic Field ◽  
Boundary Data ◽  
Active Regions ◽  
Magnetic Structures ◽  
Photospheric Level ◽  
Field Lines ◽  
Set Up

We give an overview of procedures to recover and simulate typical coronal static magnetic field topologies from given boundary data on the photosphere. Relatively simple analytical treatments allow for solutions representing magnetic structures that are invariant in one coordinate, and satisfying prescribed boundary conditions. Starting from elementary active regions in a form of localized sources/sinks of magnetic field lines on the photospheric level, we set up various composed boundary conditions which yield complex magnetic structures in the corona above.

Energetic Electron Acceleration in Unconfined Reconnection Jets

2020 ◽  
Author(s):  
Guo Chen ◽  
Huishan Fu ◽  
Ying Zhang ◽  
Xiaocan Li ◽  
Yasong Ge ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
Energetic Electron ◽  
Electron Acceleration ◽  
The Earth ◽  
Field Lines

<p>Magnetic reconnection in astronomical objects such as solar corona and the Earth’s magnetotail theoretically produces a fast jet toward the object (known as a confined jet as it connects to the object through magnetic field lines) and a fast jet departing the object (known as an unconfined jet as it propagates freely in space). So far, energetic electron acceleration has been observed in the confined jet but never in the unconfined jet, arousing a controversy about whether or not reconnection jets can intrinsically accelerate electrons. Our study is focused on the electron acceleration in unconfined reconnection jet based on Cluster observations and VPIC simulations.</p>

Probing the solar corona magnetic field with sungrazing comets

2021 ◽  
Author(s):  
Giuseppe Nisticò ◽  
Valery M. Nakariakov ◽  
Timothy Duckenfield ◽  
Miloslav Druckmüller ◽  
Gaetano Zimbardo
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Space Telescopes ◽  
Cometary Plasma ◽  
Physical Conditions ◽  
Structure And Dynamics ◽  
Field Lines ◽  
Sungrazing Comets ◽  
The Magnetic Field

<p>Space telescopes of the SoHO, STEREO and SDO missions have occasionally acquired observations of comets, providing an interesting opportunity to investigate the structure and dynamics of the heliospheric plasma.  Cometary plasma tails exhibit a wave-like motion, which is believed to be a response to the physical conditions of the local interplanetary medium. Furthermore, sungrazing comets diving in the solar atmosphere provide us with an unprecedented way to diagnose the coronal plasma at distances which are unaccessible from the current spacecraft. Here, we present observations of Comet Lovejoy C/2011 W3 from SDO/AIA, which was seen to cross the EUV solar corona in December 2011. The cometary ions produced by the sublimation of the comet nucleus were channelled along the magnetic field lines forming some filamented structures. Such structures appear to show small amplitude kink oscillations, which are used to determine the magnitude of the coronal magnetic field by coronal seismology.</p>

scholarly journals Mode Coupling in the Solar Corona. III. Alfvén and Magnetoacoustic Waves

1977 ◽  
Vol 30 (4) ◽  
pp. 495 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Acoustic Waves ◽  
Mode Coupling ◽  
Stratified Medium ◽  
Magnetoacoustic Waves ◽  
Field Lines ◽  
Hydromagnetic Waves ◽  
Special Case ◽  
The Magnetic Field

Coupling between Alfven waves and fast mode waves obliquely incident on a stratified medium is treated using the method of Clemmow and Heading (1954) within the framework of the cold plasma approximation. A result due to Frisch (1964) is rederived in the special case of vertical incidence. The coupling is strongest for nearly parallel (to the magnetic field lines) propagation, and the coupling ratio may be approximated by Q = (00 /0)" where 0 is the angle between the wave vector and the magnetic field lines, while og = A/L, with A the wavelength and L the scalelength of the inhomogeneity. This result may be of significance in connection with the heating of the solar corona by the dissipation of waves generated initially as acoustic waves in the photosphere, and perhaps with the propagation of hydromagnetic waves in the interplanetary medium.

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.

Faint Hα Emission in the Corona and Its Relation to the Prominences

1994 ◽  
Vol 144 ◽  
pp. 339-342
Author(s):  
V. N. Dermendjiev ◽  
Z. Mouradian ◽  
J.- L. Leroy ◽  
P. Duchlev
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Essential Role ◽  
Hα Emission

AbstractThe relation between episodically observed in the solar corona faint Hαemission structures and the long lived prominences was studied. Particular consideration was given for cases in which the corresponding prominences had undergone DB process. An MHD interpretation of the phenomenon “emissions froides” (cool emission) is proposed in which an essential role plays the prominence supporting magnetic field.

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