scholarly journals High-Resolution Observations of Emerging Magnetic Fields and Flux Tubes in Active Region Photosphere

1990 ◽  
Vol 138 ◽  
pp. 147-152 ◽  
Author(s):  
T. Tarbell ◽  
S. Ferguson ◽  
Z. Frank ◽  
R. Shine ◽  
A. Title ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Observatory ◽  
Disk Center ◽  
Line Center ◽  
Solar Photosphere ◽  
Flux Tubes ◽  
National Solar Observatory ◽  
La Palma ◽  
The Relationship

On 29 September 1988, filtergrams of the solar photosphere with excellent resolution (0.3 to 0.5 arcsecond) were obtained at the Swedish Solar Observatory on La Palma, Canary Islands. An outstanding 2.5 hour run of digital filtergram observations was obtained, looking at a small area within an active region near disk center. On 6 August 1987, an 80 minute run of similar observations was obtained at the Vacuum Tower Telescope of the National Solar Observatory at Sacramento Peak. Digital and video movies have been made of Dopplergrams, magnetograms, line center, continuum, and white light images. Several examples of magnetic field emergence and formation of flux tubes can be studied in detail in the movies. The relationship between photospheric bright points, “filigree”, the line center brightness, and the magnetic field has been established for individual images in analysis to date.

Surges of the weak magnetic field in the photosphere of the Sun

2021 ◽  
Author(s):  
Dmitrii Baranov ◽  
Elena Vernova ◽  
Marta Tyasto
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Summation Method ◽  
Solar Observatory ◽  
Primary Data ◽  
Solar Photosphere ◽  
The Sun ◽  
National Solar Observatory ◽  
Weak Magnetic Fields ◽  
One Year

<p>The properties of the magnetic fields of the solar photosphere are investigated, in particular, the distribution of fields of different polarity over the solar surface. As primary data, synoptic maps of the photospheric magnetic field of the Kitt Peak National Solar Observatory for 1978-2016 were used. Using the vector summation method, the non-axisymmetric component of the magnetic field is determined. It was found that the nonaxisymmetric component of weak magnetic fields B < 5 G changes in antiphase with the flux of these fields. Magnetic fields of B < 5 G constitute a significant part of the total magnetic field of the Sun, since they occupy more than 60% of the area of the photosphere. The fine structure of the distribution of weak fields can  be observed by setting the upper limit to the strength of the  fields  included in the time–latitude diagram. This allows to eliminate the contribution of the strong fields of sunspots.</p><p>On the time-latitude diagram for weak magnetic fields (B < 5 G), bands of differing colors correspond to the streams of the magnetic fields moving in the direction to the Sun’s poles.. These streams or surges show the alternation of the dominant polarity - positive or negative - which is clearly seen in all four cycles. The slopes of the bands indicate the velocity of the fields movement towards the poles. The surges can be divided into two groups. The surges of the first group belong to the so-called Rush-to-the-Poles. These are bands with the width of about three years, which begin at approximately 40° of latitude and have the same polarity as the trailing sunspots. They reach high latitudes and cause the polarity reversal of the polar field. However, in addition to these surges, for most of the solar  cycle (the descending phase, the minimum and the ascending phase), there are narrower surges of both polarities (with the width less than one year), which extend from the equator almost to the poles. These surges are most clearly visible in the southern hemisphere when the southern pole is positive. Consideration of the latitude-time diagrams separately for positive and negative polarities showed that the alternating dominance of one of the polarities is associated with the antiphase development  of the positive and negative fields of the surges. The widths of surges and the periodicity of their appearance vary significantly for the two hemispheres and from one solar cycle to the other. The mean period of the polarity alternation is about 1.5 years.</p>

Synoptic Magnetic Fields Measurements of the Solar Chromosphere from SOLIS/VSM at NSO

2018 ◽  
Vol 13 (S340) ◽  
pp. 91-92
Author(s):  
Sanjay Gosain ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind Speed ◽  
Active Regions ◽  
Field Measurements ◽  
Solar Observatory ◽  
Solar Chromosphere ◽  
Polar Regions ◽  
National Solar Observatory ◽  
Perspective Effect ◽  
Stokes Polarimetry

AbstractFull disk magnetic field measurements of the photosphere and chromosphere have been performed at National Solar Observatory (NSO), USA for many decades. Here we briefly describe recent upgrades made to this synoptic observing program. In particular, we present the full Stokes polarimetry observations made using the chromospheric Ca II 854.2 nm spectral line. These new observations have the potential to probe vector nature of magnetic field in the chromosphere above the active regions and provide improved estimates of magnetic free-energy, which is released during flares and coronal mass ejections (CMEs). We emphasize that these observations could improve estimates of polar fields, as compared to photospheric observations, due to magnetic field expansion in higher layers and perspective effect near the polar regions. The global coronal potential field models and solar wind speed estimates depend critically on polar field measurements.

scholarly journals Study of magnetic field topology of active region 12192 using an extrapolated non-force-free magnetic field

2018 ◽  
Vol 13 (S340) ◽  
pp. 81-82
Author(s):  
A. Prasad ◽  
R. Bhattacharyya ◽  
Q. Hu ◽  
S. S. Nayak ◽  
Sanjay Kumar
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Free Field ◽  
Coronal Magnetic Field ◽  
Solar Photosphere ◽  
Magnetic Field Topology ◽  
Cycle 24 ◽  
Magnetic Null ◽  
The Magnetic Field ◽  
Force Free Field

AbstractThe solar active region (AR) 12192 was one of the most flare productive region of solar cycle 24, which produced many X-class flares; the most energetic being an X3.1 flare on October 24, 2014 at 21:10 UT. Customarily, such events are believed to be triggered by magnetic reconnection in coronal magnetic fields. Here we use the vector magnetograms from solar photosphere, obtained from Heliospheric Magnetic Imager (HMI) to investigate the magnetic field topology prior to the X3.1 event, and ascertain the conditions that might have caused the flare. To infer the coronal magnetic field, a novel non-force-free field (NFFF) extrapolation technique of the photospheric field is used, which suitably mimics the Lorentz forces present in the photospheric plasma. We also highlight the presence of magnetic null points and quasi-separatrix layers (QSLs) in the magnetic field topology, which are preferred sites for magnetic reconnections and discuss the probable reconnection scenarios.

scholarly journals Active Region Evolution Through Coordinated Observations

1993 ◽  
Vol 141 ◽  
pp. 63-66 ◽  
Author(s):  
N. Mein ◽  
P. Mein ◽  
B. Schmieder ◽  
O. Engvold ◽  
R. Molowny ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Active Region ◽  
White Light ◽  
Imaging Spectroscopy ◽  
Solar Telescope ◽  
La Palma ◽  
Rocket Experiment ◽  
Region Evolution

On May 7, 1991, several ground-based instruments have been coordinated to observe AR 6615 (S10-W26), before and during the flight of the SERTS rocket experiment (Schmieder et al.,1992):– Imaging spectroscopy (MSDP) at the VTT telescope of Tenerife (collaboration Paris-Meudon and KIS Freiburg). Hα and NaD1 are observed simultaneously in 2D fields, with 9 and 11 wavelengths respectively (Mein, 1991).– High resolution “white light” pictures (around 4686Å) at the Swedish Vacuum Solar Telescope (SVST) of La Palma (Scharmer et al., 1985).We present below some data from both instruments. Magnetic field maps are also available from the Huairou magnetograph (China), and from the GCT telescope (KIS/Tenerife).

scholarly journals Of Tilt and Twist

2005 ◽  
Vol 13 ◽  
pp. 135-135
Author(s):  
Zachary A. Holder ◽  
Richard C. Canfield ◽  
Rebecca A. McMullen ◽  
Robert F. Howard ◽  
Alexei A. Pevtsov
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Active Regions ◽  
Solar Observatory ◽  
Flux Tubes ◽  
Vector Magnetograms ◽  
Full Disk

AbstractUsing Mees Solar Observatory active-region vector magnetograms and Mt. Wilson Observatory full-disk longitudinal magnetograms, we measure both the twist and tilt of the magnetic fields of 368 active regions. This dataset clearly shows two well-known phenomena, Joy’s law and the hemispheric helicity rule, as well as a lesser-known twist-tilt relationship, which is the point of this work. Those regions that closely follow Joy’s law show no twist-tilt relationship, which is a predicted consequence of convective buffeting of initially untwisted and unwrithed flux tubes through the Σ effect. Those regions that strongly depart from Joy’s law show significantly larger than average twist and a very strong twist-tilt relationship. These properties suggest that the twist-tilt relationship in these regions is due to kinking of flux tubes that are highly twisted but not strongly writhed.

scholarly journals Formation and evolution of an active region filament

2013 ◽  
Vol 8 (S300) ◽  
pp. 40-43
Author(s):  
Christoph Kuckein ◽  
Rebeca Centeno ◽  
Valentín Martínez Pillet
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Structure ◽  
Disk Center ◽  
Line Of Sight ◽  
Filament Formation ◽  
Vector Magnetic Field ◽  
Current Filament ◽  
Formation And Evolution

AbstractSeveral scenarios explaining how filaments are formed can be found in literature. In this paper, we analyzed the observations of an active region filament and critically evaluated the observed properties in the context of current filament formation models. This study is based on multi-height spectropolarimetric observations. The inferred vector magnetic field has been extrapolated starting either from the photosphere or from the chromosphere. The line-of-sight motions of the filament, which was located near disk center, have been analyzed inferring the Doppler velocities. We conclude that a part of the magnetic structure emerged from below the photosphere.

scholarly journals Twisting flux tubes as a cause of micro-flaring activity

2007 ◽  
Vol 3 (S247) ◽  
pp. 360-363
Author(s):  
D. B. Jess ◽  
R. T. J. McAteer ◽  
M. Mathioudakis ◽  
F. P. Keenan ◽  
A. Andic ◽  
...  
Keyword(s):  
Solar Observatory ◽  
Optical Observations ◽  
Bright Point ◽  
Solar Telescope ◽  
Camera System ◽  
Flux Tubes ◽  
National Solar Observatory ◽  
Blue Wing ◽  
Significance Levels ◽  
High Cadence

AbstractHigh-cadence optical observations of an H-α blue-wing bright point near solar AR NOAA 10794 are presented. The data were obtained with the Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly developed camera system, the rapid dual imager. Wavelet analysis is undertaken to search for intensity-related oscillatory signatures, and periodicities ranging from 15 to 370 s are found with significance levels exceeding 95%. During two separate microflaring events, oscillation sites surrounding the bright point are observed to twist. We relate the twisting of the oscillation sites to the twisting of physical flux tubes, thus giving rise to reconnection phenomena. We derive an average twist velocity of 8.1 km/s and detect a peak in the emitted flux between twist angles of 180° and 230°.

scholarly journals Signature of collision of magnetic flux tubes in the quiet solar photosphere

2010 ◽  
Vol 6 (S273) ◽  
pp. 399-402
Author(s):  
Aleksandra Andic
Keyword(s):  
Magnetic Flux ◽  
Spectral Line ◽  
Solar Observatory ◽  
Bright Point ◽  
Solar Photosphere ◽  
Solar Telescope ◽  
Weak Current ◽  
Flux Tubes ◽  
Oscillatory Power ◽  
Magnetic Flux Tubes

AbstractCollision of the magnetic flux tubes in the Quiet Sun was proposed as one of the possible sources for the heating of the solar atmosphere (Furusawa and Sakai, 2000). The solar photosphere was observed using the New Solar Telescope ad Big Bear Solar Observatory. In TiO spectral line at 705.68 nm we approached resolution of 0.1″. The horizontal plasma wave was observed spreading from the larger bright point. Shorty after this wave an increase in the oscillatory power appeared at the same location as the observed bright point. This behavior matches some of the results from the simulation of the collision of the two flux tubes with a weak current.

scholarly journals Generation of Magnetic Fields and Electric Currents in the Solar Photosphere

1990 ◽  
Vol 138 ◽  
pp. 273-277
Author(s):  
J.C. Henoux ◽  
B.V. Somov
Keyword(s):  
Magnetic Field ◽  
Radial Dependence ◽  
Field Energy ◽  
Solar Photosphere ◽  
Fluid Approximation ◽  
Flux Tubes ◽  
Magnetic Field Energy ◽  
Field Energy Density ◽  
Dc Current ◽  
The Magnetic Field

Velocities of electrons, ions and neutrals are computed in the three-fluid approximation for an axisymmetrical magnetic field. By prescribing a radial dependence of the velocity of neutrals in agreement with a downflow, the radial dependence of the magnetic field energy density is derived for a given set of values of the magnetic field at the central and external boundaries. Flux-tube cooling by advection of ionization energy is found to be significant. Vortices in the low photosphere could produce significant electric power and DC current intensity along the coronal magnetic lines of forces. The velocities of neutrals, the size and the number of flux-tubes required to power flares in plage regions, are estimated.

Sign in / Sign up

Export Citation Format

Share Document