scholarly journals Solar Coronal Loop Dynamics Near the Null Point Above Active Region NOAA 2666

2018 ◽  
Vol 35 ◽  
Author(s):  
B. Filippov
Keyword(s):  
Magnetic Field ◽  
Vertical Direction ◽  
Coronal Magnetic Field ◽  
Null Point ◽  
Coronal Loops ◽  
Active Region Noaa ◽  
Reconnection Region ◽  
Loop Dynamics ◽  
Field Lines ◽  
Western Limb

AbstractWe analyse observations of a saddle-like structure in the corona above the western limb of the Sun on 2017 July 18. The structure was clearly outlined by coronal loops with typical coronal temperature no more than 1 MK. The dynamics of loops showed convergence towards the centre of the saddle in the vertical direction and divergence in the horizontal direction. The event is a clear example of smooth coronal magnetic field reconnection. No heating manifestations in the reconnection region or magnetically connected areas were observed. Potential magnetic field calculations, which use as the boundary condition the SDO/HMI magnetogram taken on July 14, showed the presence of a null point at the height of 122 arcsec above the photosphere just at the centre of the saddle structure. The shape of field lines fits the fan-spine magnetic configuration above NOAA 2666.

scholarly journals Reconstruction of the Coronal Magnetic Field for Active Region NOAA 8151

2001 ◽  
Vol 203 ◽  
pp. 441-443
Author(s):  
S. Régnier ◽  
T. Amari
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Energy ◽  
Coronal Magnetic Field ◽  
X Rays ◽  
Active Region Noaa ◽  
Filament Eruption ◽  
Linear Force ◽  
Region Noaa ◽  
Field Lines

The active region NOAA 8151 observed between February 11–13, 1998 exhibits a filament eruption linked to the disappearance of a sigmoidal structure. Using vector magnetograms from IVM (Mees Observatory, Hawaii), we perform a non linear force-free reconstruction of the coronal magnetic field above this active region. This reconstruction allows to determine the distribution of electric currents, the magnetic energy and the relative magnetic helicity. The reconstructed magnetic field lines are compared to the soft X-rays (SXT, Yohkoh) observations.

scholarly journals A three-dimensional velocity of an erupting prominence prior to a coronal mass ejection

2021 ◽  
Vol 73 (2) ◽  
pp. 394-404
Author(s):  
Maria V Gutierrez ◽  
Kenichi Otsuji ◽  
Ayumi Asai ◽  
Raul Terrazas ◽  
Mutsumi Ishitsuka ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Extreme Ultraviolet ◽  
Three Dimensional ◽  
Coronal Magnetic Field ◽  
Coronal Loops ◽  
Active Region Noaa ◽  
Loop Expansion ◽  
Mass Ejection ◽  
Multiple Interactions ◽  
Full Disk

Abstract We present a detailed three-dimensional (3D) view of a prominence eruption, coronal loop expansion, and coronal mass ejections (CMEs) associated with an M4.4 flare that occurred on 2011 March 8 in the active region NOAA 11165. Full-disk Hα images of the flare and filament ejection were successfully obtained by the Flare Monitoring Telescope (FMT) following its relocation to Ica University, Peru. Multiwavelength observation around the Hα line enabled us to derive the 3D velocity field of the Hα prominence eruption. Features in extreme ultraviolet were also obtained by the Atmospheric Imager Assembly onboard the Solar Dynamic Observatory and the Extreme Ultraviolet Imager on board the Solar Terrestrial Relations Observatory - Ahead satellite. We found that, following collision of the erupted filament with the coronal magnetic field, some coronal loops began to expand, leading to the growth of a clear CME. We also discuss the succeeding activities of CME driven by multiple interactions between the expanding loops and the surrounding coronal magnetic field.

scholarly journals Solar stereoscopy – where are we and what developments do we require to progress?

2009 ◽  
Vol 27 (7) ◽  
pp. 2925-2936 ◽  
Author(s):  
T. Wiegelmann ◽  
B. Inhester ◽  
L. Feng
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Coronal Magnetic Field ◽  
Reconstruction Error ◽  
Physical Parameters ◽  
Coronal Loops ◽  
Reconstruction Problem ◽  
Temperature Plasma ◽  
Solid Objects ◽  
Polar Plumes

Abstract. Observations from the two STEREO-spacecraft give us for the first time the possibility to use stereoscopic methods to reconstruct the 3-D solar corona. Classical stereoscopy works best for solid objects with clear edges. Consequently an application of classical stereoscopic methods to the faint structures visible in the optically thin coronal plasma is by no means straight forward and several problems have to be treated adequately: 1) First there is the problem of identifying one-dimensional structures – e.g. active region coronal loops or polar plumes- from the two individual EUV-images observed with STEREO/EUVI. 2) As a next step one has the association problem to find corresponding structures in both images. This becomes more difficult as the angle between STEREO-A and B increases. 3) Within the reconstruction problem stereoscopic methods are used to compute the 3-D-geometry of the identified structures. Without any prior assumptions, e.g., regarding the footpoints of coronal loops, the reconstruction problem has not one unique solution. 4) One has to estimate the reconstruction error or accuracy of the reconstructed 3-D-structure, which depends on the accuracy of the identified structures in 2-D, the separation angle between the spacecraft, but also on the location, e.g., for east-west directed coronal loops the reconstruction error is highest close to the loop top. 5) Eventually we are not only interested in the 3-D-geometry of loops or plumes, but also in physical parameters like density, temperature, plasma flow, magnetic field strength etc. Helpful for treating some of these problems are coronal magnetic field models extrapolated from photospheric measurements, because observed EUV-loops outline the magnetic field. This feature has been used for a new method dubbed "magnetic stereoscopy". As examples we show recent application to active region loops.

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

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.

scholarly journals The exceptional aspects of the confined X-class flares of solar active region 2192

2015 ◽  
Vol 11 (S320) ◽  
pp. 60-63
Author(s):  
Julia K. Thalmann ◽  
Yang Su ◽  
Manuela Temmer ◽  
Astrid M. Veronig
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Active Region Noaa ◽  
High Energies ◽  
The Past ◽  
Large Scale Magnetic Field ◽  
High Level ◽  
Mass Ejection

AbstractDuring late October 2014, active region NOAA 2192 caused an unusual high level of solar activity, within an otherwise weak solar cycle. While crossing the solar disk, during a period of 11 days, it was the source of 114 flares of GOES class C1.0 and larger, including 29 M- and 6 X-flares. Surprisingly, none of the major flares (GOES class M5.0 and larger) was accompanied by a coronal mass ejection, contrary to statistical tendencies found in the past. From modeling the coronal magnetic field of NOAA 2192 and its surrounding, we suspect that the cause of the confined character of the flares is the strong surrounding and overlying large-scale magnetic field. Furthermore, we find evidence for multiple magnetic reconnection processes within a single flare, during which electrons were accelerated to unusual high energies.

Proton acceleration in three-dimensional non-null magnetic reconnection

2016 ◽  
Vol 82 (5) ◽  
Author(s):  
Z. Akbari ◽  
M. Hosseinpour ◽  
M. A. Mohammadi
Keyword(s):  
Magnetic Field ◽  
Energy Distribution ◽  
Magnetic Reconnection ◽  
Electric Fields ◽  
Three Dimensional ◽  
Null Point ◽  
Proton Acceleration ◽  
Electric And Magnetic Fields ◽  
Field Lines ◽  
The Magnetic Field

In a three-dimensional non-null magnetic reconnection, the process of magnetic reconnection takes place in the absence of a null point where the magnetic field vanishes. By randomly injecting a population of 10 000 protons, the trajectory and energy distribution of accelerated protons are investigated in the presence of magnetic and electric fields of a particular model of non-null magnetic reconnection with the typical parameters for the solar corona. The results show that protons are accelerated along the magnetic field lines away from the non-null point only at azimuthal angles where the magnitude of the electric field is strongest and therefore particles obtain kinetic energies of the order of thousands of MeV and even higher. Moreover, the energy distribution of the population depends strongly on the amplitude of the electric and magnetic fields. Comparison shows that a non-null magnetic reconnection is more efficient in accelerating protons to very high GeV energies than a null-point reconnection.

scholarly journals TWIST AND CONNECTIVITY OF MAGNETIC FIELD LINES IN THE SOLAR ACTIVE REGION NOAA 10930

2011 ◽  
Vol 738 (2) ◽  
pp. 161 ◽  
Author(s):  
S. Inoue ◽  
K. Kusano ◽  
T. Magara ◽  
D. Shiota ◽  
T. T. Yamamoto
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Active Region ◽  
Active Region Noaa ◽  
Region Noaa ◽  
Field Lines

A physical description of magnetic helicity evolution in the presence of reconnection lines

1991 ◽  
Vol 46 (1) ◽  
pp. 179-199 ◽  
Author(s):  
Andrew N. Wright ◽  
Mitchell A. Berger
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Magnetic Reynolds Number ◽  
Magnetic Helicity ◽  
Two Dimensional ◽  
Flux Tubes ◽  
Physical Description ◽  
Reconnection Region ◽  
Field Geometry ◽  
Field Lines

The dissipation of relative magnetic helicity due to the presence of a resistive reconnection region is considered. We show that when the reconnection region has a vanishing cross-section, helicity is conserved, in agreement with previous studies. It is also shown that in two-dimensional systems reconnection can produce highly twisted reconnected flux tubes. Reconnection at a high magnetic Reynolds number generally conserves helicity to a good approximation. However, reconnection with a small Reynolds number can produce significant dissipation of helicity. We prove that helicity dissipation in two-dimensional configurations is associated with the retention of some of the inflowing magnetic flux by the reconnection region, vr. When the reconnection site is a simple Ohmic conductor, all of the magnetic field parallel to the reconnection line that is swept into vr is retained. (In contrast, the inflowing magnetic field perpendicular to the line is annihilated.) We are able to relate the amount of helicity dissipation to the retained flux. A physical interpretation of helicity dissipation is developed by considering the diffusion of magnetic field lines through vr. When compared with helicity-conserving reconnection, the two halves of a reconnected flux sheet appear to have slipped relative to each other parallel to the reconnection line. This provides a useful method by which the reconnected field geometry can be constructed: the incoming flux sheets are ‘cut’ where they encounter vr, allowed to slip relative to each other, and then ‘pasted’ together to form the reconnected flux sheets. This simple model yields estimates for helicity dissipation and the flux retained by vr in terms of the amount of slippage. These estimates are in agreement with those expected from the governing laws.

scholarly journals Particle Acceleration in the Process of Eruptive Opening and Reconnection of Magnetic Fields

1980 ◽  
Vol 91 ◽  
pp. 217-221 ◽  
Author(s):  
Z. Švestka ◽  
S. F. Martin ◽  
R. A. Kopp
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Particle Acceleration ◽  
Magnetic Fields ◽  
Magnetic Loop ◽  
Coronal Loops ◽  
X Rays ◽  
Flare Loops ◽  
Field Lines ◽  
The Magnetic Field

In a series of papers on the flare of 29 July 1973 (Nolte et al., 1979; Martin, 1979; Švestka et al., 1979) it has been shown that Hα “post-flare” loops are the cooled aftermath of previously hot coronal loops which were visible in x-rays in the same position earlier in the flare. Kopp and Pneuman (1976) have proposed that these post-flare loops are formed by a process of successive magnetic field reconnections of previously distended magnetic field lines as illustrated in Figure 1. Each successive reconnection of the magnetic field yields a closed magnetic loop that forms above and concentric with previously formed loops. A shock wave created during each sudden reconnection travels down both legs of each loop and provides energy for ionizing chromospheric mass at the footpoints of the loop. Subsequent condensation of the ionized mass at the tops of the loops renders them visible as this mass falls to the chromosphere.

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