scholarly journals Direct evidence that twisted flux tube emergence creates solar active regions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
D. MacTaggart ◽  
C. Prior ◽  
B. Raphaldini ◽  
P. Romano ◽  
S. L. Guglielmino
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Active Regions ◽  
Basic Structure ◽  
Flux Tubes ◽  
Solar Observations ◽  
Solar Active Regions ◽  
Solar Eruptions ◽  
Magnetic Flux Tubes ◽  
Magnetic Nature

AbstractThe magnetic nature of the formation of solar active regions lies at the heart of understanding solar activity and, in particular, solar eruptions. A widespread model, used in many theoretical studies, simulations and the interpretation of observations, is that the basic structure of an active region is created by the emergence of a large tube of pre-twisted magnetic field. Despite plausible reasons and the availability of various proxies suggesting the accuracy of this model, there has not yet been a methodology that can clearly and directly identify the emergence of large pre-twisted magnetic flux tubes. Here, we present a clear signature of the emergence of pre-twisted magnetic flux tubes by investigating a robust topological quantity, called magnetic winding, in solar observations. This quantity detects the emerging magnetic topology despite the significant deformation experienced by the emerging magnetic field. Magnetic winding complements existing measures, such as magnetic helicity, by providing distinct information about field line topology, thus allowing for the direct identification of emerging twisted magnetic flux tubes.

scholarly journals ON THE AREA EXPANSION OF MAGNETIC FLUX TUBES IN SOLAR ACTIVE REGIONS

2014 ◽  
Vol 796 (1) ◽  
pp. 20 ◽  
Author(s):  
Jaroslav Dudík ◽  
Elena Dzifčáková ◽  
Jonathan W. Cirtain
Keyword(s):  
Magnetic Flux ◽  
Active Regions ◽  
Flux Tubes ◽  
Solar Active Regions ◽  
Magnetic Flux Tubes ◽  
Area Expansion

scholarly journals Investigation of Spatially Unresolved Magnetic Field Outside Sunspots Using Hinode/SOT Observations

2016 ◽  
Vol 12 (S325) ◽  
pp. 59-62
Author(s):  
Olga Botygina ◽  
Mykola Gordovskyy ◽  
Vsevolod Lozitsky
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Zeeman Effect ◽  
Active Regions ◽  
Line Ratio ◽  
Optical Telescope ◽  
Flux Tubes ◽  
Magnetic Flux Tubes ◽  
The Magnetic Field

AbstractThe structure of photospheric magnetic fields outside sunspots is investigated in three active regions using Hinode/Solar Optical Telescope(SOT) observations. We analyze Zeeman effect in FeI 6301.5 and FeI 6302.5 lines and determine the observed magnetic field value Beff for each of them. We find that the line ratio Beff(6301)/Beff(6302) is close to 1.3 in the range Beff < 0.2 kG, and close to 1.0 for 0.8 kG < Beff < 1.2 kG. We find that the observed magnetic field is formed by flux tubes with the magnetic field strengths 1.3 − 2.3 kG even in places with weak observed magnetic field fluxes. We also estimate the diameters of smallest magnetic flux tubes to be 15 − 20 km.

scholarly journals Study of helicity properties of peculiar active regions

2009 ◽  
Vol 5 (S264) ◽  
pp. 102-104 ◽  
Author(s):  
M. C. López Fuentes ◽  
C. H. Mandrini ◽  
P. Démoulin
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Active Regions ◽  
Solar Interior ◽  
Magnetic Helicity ◽  
Flux Tubes ◽  
Origin And Evolution ◽  
Magnetic Structures ◽  
Magnetic Flux Tubes ◽  
The Magnetic Field

AbstractPeculiar solar active regions (ARs), such as δ-islands and other high tilt bipoles, are commonly associated with the emergence of severely deformed magnetic flux tubes. Therefore, the study of these ARs provides valuable information on the origin and evolution of magnetic structures in the solar interior. Here, we infer the magnetic helicity properties of the flux tubes associated to a set of peculiar ARs by studying the evolution of photospheric magnetograms (SOHO/MDI) and coronal observations (SOHO/EIT and TRACE) in combination with force-free models of the magnetic field. We discuss how our results relate to different models of the evolution of emerging magnetic flux tubes.

scholarly journals Magnetic field evolution of active regions and sunspots in connection with chromospheric and coronal activities

2010 ◽  
Vol 6 (S273) ◽  
pp. 157-163
Author(s):  
Toshifumi Shimizu
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Active Regions ◽  
Vector Magnetic Field ◽  
Optical Telescope ◽  
Magnetic Field Data ◽  
Flux Tubes ◽  
X Ray ◽  
Magnetic Flux Tubes

AbstractCa II H imaging observations by the Hinode Solar Optical Telescope (SOT) have revealed that the chromosphere is extremely dynamic and that ejections and jets are well observed in moat region around sunspots. X-ray and EUV observations show frequent occurrence of microflaring activities around sunspots; small emerging flux or moving magnetic features approaching opposite pre-existing magnetic flux can be identified on the footpoints for half of microflares studied, while no encounters of opposite polarities are observed at footpoints for the others even with SOT high spatial magnetorams (Kano et al. 2010). Another observations tell the involvement of twisted magnetic fields in the microflares accompanied by no polarity encounters at the footpoints. Some type of sunspot light bridges shows recurrent occurrence of chromospheric ejections, and photospheric vector magnetic field data suggests that twsited magnetic flux tubes lying along light bridge play vital roles in producing such ejections (Shimizu et al. 2009). This presentation reviewed observational findings from these studies. We will need to understand the 3D configuration of magnetic fields for better understanding of activity triggers in the solar atmosphere.

scholarly journals Ion velocity distributions within the LLBL and their possible implication to multiple reconnections

2004 ◽  
Vol 22 (1) ◽  
pp. 213-236 ◽  
Author(s):  
O. L. Vaisberg ◽  
L. A. Avanov ◽  
T. E. Moore ◽  
V. N. Smirnov
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Tube ◽  
Magnetic Flux Tube ◽  
Flux Tubes ◽  
Different Types ◽  
Subsolar Point ◽  
Magnetic Flux Tubes ◽  
Ion Velocity ◽  
Field Lines

Abstract. We analyze two LLBL crossings made by the Interball-Tail satellite under a southward or variable magnetosheath magnetic field: one crossing on the flank of the magnetosphere, and another one closer to the subsolar point. Three different types of ion velocity distributions within the LLBL are observed: (a) D-shaped distributions, (b) ion velocity distributions consisting of two counter-streaming components of magnetosheath-type, and (c) distributions with three components, one of which has nearly zero parallel velocity and two counter-streaming components. Only the (a) type fits to the single magnetic flux tube formed by reconnection between the magnetospheric and magnetosheath magnetic fields. We argue that two counter-streaming magnetosheath-like ion components observed by Interball within the LLBL cannot be explained by the reflection of the ions from the magnetic mirror deeper within the magnetosphere. Types (b) and (c) ion velocity distributions would form within spiral magnetic flux tubes consisting of a mixture of alternating segments originating from the magnetosheath and from magnetospheric plasma. The shapes of ion velocity distributions and their evolution with decreasing number density in the LLBL indicate that a significant part of the LLBL is located on magnetic field lines of long spiral flux tube islands at the magnetopause, as has been proposed and found to occur in magnetopause simulations. We consider these observations as evidence for multiple reconnection Χ-lines between magnetosheath and magnetospheric flux tubes. Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; solar wind-magnetosphere interactions)

scholarly journals Linking Thin Flux Tube MHD Models to Apparent Stellar Surface Activity

2004 ◽  
Vol 219 ◽  
pp. 546-551
Author(s):  
T. Granzer ◽  
K. G. Strassmeier
Keyword(s):  
Magnetic Flux ◽  
Surface Activity ◽  
Flux Tube ◽  
Convection Zone ◽  
Active Regions ◽  
Similar Model ◽  
Flux Tubes ◽  
Stellar Convection ◽  
Magnetic Flux Tubes ◽  
Spot Formation

We model thin magnetic flux tubes as they rise from the bottom of a stellar convection zone to the photosphere. On emergence they form active regions, i.e. star spots. This model was very successfully applied to the solar case, where the simulations where in agreement with the butterfly diagram, Joy's law, and Hale's law. We propose the use of a similar model to describe stellar activity in the more extreme form found on active stars. A comparison between Doppler-images of well-observed pre-MS stars and a theoretically derived probability of star-spot formation as a function of latitude is presented.

scholarly journals The Small-Scale Photospheric Magnetic Field as an Indicator of the Dynamo

1993 ◽  
Vol 141 ◽  
pp. 143-146
Author(s):  
K. Petrovay ◽  
G. Szakály
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Observational Data ◽  
Convective Zone ◽  
Small Scale ◽  
Dynamo Theory ◽  
Flux Tubes ◽  
Magnetic Flux Tubes ◽  
Surface Fields

AbstractThe presently widely accepted view that the solar dynamo operates near the base of the convective zone makes it difficult to relate the magnetic fields observed in the solar atmosphere to the fields in the dynamo layer. The large amount of observational data concerning photospheric magnetic fields could in principle be used to impose constraints on dynamo theory, but in order to infer these constraints the above mentioned “missing link” between the dynamo and surface fields should be found. This paper proposes such a link by modeling the passive vertical transport of thin magnetic flux tubes through the convective zone.

Rising magnetic flux tubes as a source of IR-variability of the accretion disks of young stars

2018 ◽  
Vol 14 (S345) ◽  
pp. 295-296
Author(s):  
Sergey A. Khaibrakhmanov ◽  
Alexander E. Dudorov ◽  
Andrey M. Sobolev
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Accretion Disks ◽  
Young Stars ◽  
Flux Tubes ◽  
Magnetic Flux Tubes

AbstractWe investigate dynamics of slender magnetic flux tubes (MFT) in the accretion disks of young stars. Simulations show that MFT rise from the disk and can accelerate to 20-30 km/s causing periodic outflows. Magnetic field of the disk counteracts the buoyancy, and the MFT oscillate near the disk’s surface with periods of 10-100 days. We demonstrate that rising and oscillating MFT can cause the IR-variability of the accretion disks of young stars.

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